6652 lines
202 KiB
Groff
Executable File
6652 lines
202 KiB
Groff
Executable File
.\" OpenVPN -- An application to securely tunnel IP networks
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.\" over a single TCP/UDP port, with support for SSL/TLS-based
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.\" session authentication and key exchange,
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.\" packet encryption, packet authentication, and
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.\" packet compression.
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.\"
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.\" Copyright (C) 2002-2010 OpenVPN Technologies, Inc. <sales@openvpn.net>
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.\"
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.\" This program is free software; you can redistribute it and/or modify
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.\" it under the terms of the GNU General Public License version 2
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.\" as published by the Free Software Foundation.
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.\"
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.\" This program is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public License
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.\" along with this program (see the file COPYING included with this
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.\" distribution); if not, write to the Free Software Foundation, Inc.,
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.\" 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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.\"
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.\" Manual page for openvpn
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.\
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.\" SH section heading
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.\" SS subsection heading
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.\" LP paragraph
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.\" IP indented paragraph
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.\" TP hanging label
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.\
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.\" .nf -- no formatting
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.\" .fi -- resume formatting
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.\" .ft 3 -- boldface
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.\" .ft -- normal face
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.\" .in +|-{n} -- indent
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.\"
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.TH openvpn 8 "17 November 2008"
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.\"*********************************************************
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.SH NAME
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openvpn \- secure IP tunnel daemon.
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.\"*********************************************************
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.SH SYNOPSIS
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.ft 3
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openvpn [ options ... ]
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.ft
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.\"*********************************************************
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.SH INTRODUCTION
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.LP
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OpenVPN is an open source VPN daemon by James Yonan.
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Because OpenVPN tries to
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be a universal VPN tool offering a great deal of flexibility,
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there are a lot of options on this manual page.
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If you're new to OpenVPN, you might want to skip ahead to the
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examples section where you will see how to construct simple
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VPNs on the command line without even needing a configuration file.
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Also note that there's more documentation and examples on
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the OpenVPN web site:
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.I http://openvpn.net/
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And if you would like to see a shorter version of this manual,
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see the openvpn usage message which can be obtained by
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running
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.B openvpn
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without any parameters.
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.\"*********************************************************
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.SH DESCRIPTION
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.LP
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OpenVPN is a robust and highly flexible VPN daemon.
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OpenVPN supports SSL/TLS security, ethernet bridging,
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TCP or UDP tunnel transport through proxies or NAT,
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support for dynamic IP addresses and DHCP,
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scalability to hundreds or thousands of users,
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and portability to most major OS platforms.
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OpenVPN is tightly bound to the OpenSSL library, and derives much
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of its crypto capabilities from it.
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OpenVPN supports
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conventional encryption
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using a pre-shared secret key
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.B (Static Key mode)
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or
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public key security
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.B (SSL/TLS mode)
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using client & server certificates.
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OpenVPN also
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supports non-encrypted TCP/UDP tunnels.
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OpenVPN is designed to work with the
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.B TUN/TAP
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virtual networking interface that exists on most platforms.
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Overall, OpenVPN aims to offer many of the key features of IPSec but
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with a relatively lightweight footprint.
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.\"*********************************************************
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.SH OPTIONS
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OpenVPN allows any option to be placed either on the command line
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or in a configuration file. Though all command line options are preceded
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by a double-leading-dash ("\-\-"), this prefix can be removed when
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an option is placed in a configuration file.
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.\"*********************************************************
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.TP
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.B \-\-help
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Show options.
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.\"*********************************************************
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.TP
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.B \-\-config file
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Load additional config options from
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.B file
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where each line corresponds to one command line option,
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but with the leading '\-\-' removed.
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If
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.B \-\-config file
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is the only option to the openvpn command,
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the
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.B \-\-config
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can be removed, and the command can be given as
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.B openvpn file
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Note that
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configuration files can be nested to a reasonable depth.
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Double quotation or single quotation characters ("", '')
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can be used to enclose single parameters containing whitespace,
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and "#" or ";" characters in the first column
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can be used to denote comments.
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Note that OpenVPN 2.0 and higher performs backslash-based shell
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escaping for characters not in single quotations,
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so the following mappings should be observed:
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.nf
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.ft 3
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.in +4
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\\\\ Maps to a single backslash character (\\).
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\\" Pass a literal doublequote character ("), don't
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interpret it as enclosing a parameter.
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\\[SPACE] Pass a literal space or tab character, don't
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interpret it as a parameter delimiter.
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.in -4
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.ft
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.fi
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For example on Windows, use double backslashes to
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represent pathnames:
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.nf
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.ft 3
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.in +4
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secret "c:\\\\OpenVPN\\\\secret.key"
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.in -4
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.ft
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.fi
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For examples of configuration files,
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see
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.I http://openvpn.net/examples.html
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Here is an example configuration file:
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.nf
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.ft 3
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.in +4
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#
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# Sample OpenVPN configuration file for
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# using a pre-shared static key.
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#
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# '#' or ';' may be used to delimit comments.
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# Use a dynamic tun device.
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dev tun
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# Our remote peer
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remote mypeer.mydomain
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# 10.1.0.1 is our local VPN endpoint
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# 10.1.0.2 is our remote VPN endpoint
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ifconfig 10.1.0.1 10.1.0.2
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# Our pre-shared static key
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secret static.key
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.in -4
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.ft
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.fi
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.\"*********************************************************
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.SS Tunnel Options:
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.TP
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.B \-\-mode m
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Set OpenVPN major mode. By default, OpenVPN runs in
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point-to-point mode ("p2p"). OpenVPN 2.0 introduces
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a new mode ("server") which implements a multi-client
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server capability.
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.\"*********************************************************
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.TP
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.B \-\-local host
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Local host name or IP address for bind.
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If specified, OpenVPN will bind to this address only.
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If unspecified, OpenVPN will bind to all interfaces.
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.\"*********************************************************
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.TP
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.B \-\-remote host [port] [proto]
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Remote host name or IP address. On the client, multiple
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.B \-\-remote
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options may be specified for redundancy, each referring
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to a different OpenVPN server. Specifying multiple
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.B \-\-remote
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options for this purpose is a special case of the more
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general connection-profile feature. See the
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.B <connection>
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documentation below.
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The OpenVPN client will try to connect to a server at
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.B host:port
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in the order specified by the list of
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.B \-\-remote
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options.
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.B proto
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indicates the protocol to use when connecting with the
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remote, and may be "tcp" or "udp".
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The client will move on to the next host in the list,
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in the event of connection failure.
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Note that at any given time, the OpenVPN client
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will at most be connected to
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one server.
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Note that since UDP is connectionless, connection failure
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is defined by the
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.B \-\-ping
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and
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.B \-\-ping-restart
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options.
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Note the following corner case: If you use multiple
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.B \-\-remote
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options, AND you are dropping root privileges on
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the client with
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.B \-\-user
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and/or
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.B \-\-group,
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AND the client is running a non-Windows OS, if the client needs
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to switch to a different server, and that server pushes
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back different TUN/TAP or route settings, the client may lack
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the necessary privileges to close and reopen the TUN/TAP interface.
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This could cause the client to exit with a fatal error.
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If
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.B \-\-remote
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is unspecified, OpenVPN will listen
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for packets from any IP address, but will not act on those packets unless
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they pass all authentication tests. This requirement for authentication
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is binding on all potential peers, even those from known and supposedly
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trusted IP addresses (it is very easy to forge a source IP address on
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a UDP packet).
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When used in TCP mode,
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.B \-\-remote
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will act as a filter, rejecting connections from any host which does
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not match
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.B host.
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If
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.B host
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is a DNS name which resolves to multiple IP addresses,
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one will be randomly
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chosen, providing a sort of basic load-balancing and
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failover capability.
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.\"*********************************************************
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.TP
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.B \-\-remote-random-hostname
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Prepend a random string (6 bytes, 12 hex characters) to hostname to prevent
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DNS caching. For example, "foo.bar.gov" would be modified to
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"<random-chars>.foo.bar.gov".
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.\"*********************************************************
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.TP
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.B <connection>
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Define a client connection
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profile. Client connection profiles are groups of OpenVPN options that
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describe how to connect to a given OpenVPN server. Client connection
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|
profiles are specified within an OpenVPN configuration file, and
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each profile is bracketed by
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.B <connection>
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|
and
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.B </connection>.
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An OpenVPN client will try each connection profile sequentially
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until it achieves a successful connection.
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|
.B \-\-remote-random
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can be used to initially "scramble" the connection
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list.
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|
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|
Here is an example of connection profile usage:
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|
.nf
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.ft 3
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.in +4
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client
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dev tun
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<connection>
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|
remote 198.19.34.56 1194 udp
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</connection>
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<connection>
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remote 198.19.34.56 443 tcp
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</connection>
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<connection>
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remote 198.19.34.56 443 tcp
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http-proxy 192.168.0.8 8080
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http-proxy-retry
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|
</connection>
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<connection>
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remote 198.19.36.99 443 tcp
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http-proxy 192.168.0.8 8080
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http-proxy-retry
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</connection>
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|
persist-key
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|
persist-tun
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pkcs12 client.p12
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|
ns-cert-type server
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verb 3
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.in -4
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.ft
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.fi
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|
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First we try to connect to a server at 198.19.34.56:1194 using UDP.
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If that fails, we then try to connect to 198.19.34.56:443 using TCP.
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If that also fails, then try connecting through an HTTP proxy at
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192.168.0.8:8080 to 198.19.34.56:443 using TCP. Finally, try to
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connect through the same proxy to a server at 198.19.36.99:443
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using TCP.
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|
The following OpenVPN options may be used inside of
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a
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.B <connection>
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block:
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.B bind,
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.B connect-retry,
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|
.B connect-retry-max,
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|
.B connect-timeout,
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|
.B explicit-exit-notify,
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|
.B float,
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|
.B fragment,
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|
.B http-proxy,
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|
.B http-proxy-option,
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.B http-proxy-retry,
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|
.B http-proxy-timeout,
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|
.B link-mtu,
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|
.B local,
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|
.B lport,
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|
.B mssfix,
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.B mtu-disc,
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|
.B nobind,
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.B port,
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.B proto,
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.B remote,
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.B rport,
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.B socks-proxy,
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.B socks-proxy-retry,
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.B tun-mtu and
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|
.B tun-mtu-extra.
|
|
|
|
A defaulting mechanism exists for specifying options to apply to
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all
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.B <connection>
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profiles. If any of the above options (with the exception of
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.B remote
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) appear outside of a
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.B <connection>
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block, but in a configuration file which has one or more
|
|
.B <connection>
|
|
blocks, the option setting will be used as a default for
|
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.B <connection>
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|
blocks which follow it in the configuration file.
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For example, suppose the
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.B nobind
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option were placed in the sample configuration file above, near
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the top of the file, before the first
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.B <connection>
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block. The effect would be as if
|
|
.B nobind
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were declared in all
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.B <connection>
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|
blocks below it.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-proto-force p
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|
When iterating through connection profiles,
|
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only consider profiles using protocol
|
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.B p
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('tcp'|'udp').
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-remote-random
|
|
When multiple
|
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.B \-\-remote
|
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address/ports are specified, or if connection profiles are being
|
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used, initially randomize the order of the list
|
|
as a kind of basic load-balancing measure.
|
|
.\"*********************************************************
|
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.TP
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|
.B \-\-proto p
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|
Use protocol
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|
.B p
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for communicating with remote host.
|
|
.B p
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|
can be
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.B udp,
|
|
.B tcp-client,
|
|
or
|
|
.B tcp-server.
|
|
|
|
The default protocol is
|
|
.B udp
|
|
when
|
|
.B \-\-proto
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is not specified.
|
|
|
|
For UDP operation,
|
|
.B \-\-proto udp
|
|
should be specified on both peers.
|
|
|
|
For TCP operation, one peer must use
|
|
.B \-\-proto tcp-server
|
|
and the other must use
|
|
.B \-\-proto tcp-client.
|
|
A peer started with
|
|
.B tcp-server
|
|
will wait indefinitely for an incoming connection. A peer
|
|
started with
|
|
.B tcp-client
|
|
will attempt to connect, and if that fails, will sleep for 5
|
|
seconds (adjustable via the
|
|
.B \-\-connect-retry
|
|
option) and try again infinite or up to N retries (adjustable via the
|
|
.B \-\-connect-retry-max
|
|
option). Both TCP client and server will simulate
|
|
a SIGUSR1 restart signal if either side resets the connection.
|
|
|
|
OpenVPN is designed to operate optimally over UDP, but TCP capability is provided
|
|
for situations where UDP cannot be used.
|
|
In comparison with UDP, TCP will usually be
|
|
somewhat less efficient and less robust when used over unreliable or congested
|
|
networks.
|
|
|
|
This article outlines some of problems with tunneling IP over TCP:
|
|
|
|
.I http://sites.inka.de/sites/bigred/devel/tcp-tcp.html
|
|
|
|
There are certain cases, however, where using TCP may be advantageous from
|
|
a security and robustness perspective, such as tunneling non-IP or
|
|
application-level UDP protocols, or tunneling protocols which don't
|
|
possess a built-in reliability layer.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-connect-retry n
|
|
For
|
|
.B \-\-proto tcp-client,
|
|
take
|
|
.B n
|
|
as the
|
|
number of seconds to wait
|
|
between connection retries (default=5).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-connect-timeout n
|
|
For
|
|
.B \-\-proto tcp-client,
|
|
set connection timeout to
|
|
.B n
|
|
seconds (default=10).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-connect-retry-max n
|
|
For
|
|
.B \-\-proto tcp-client,
|
|
take
|
|
.B n
|
|
as the
|
|
number of retries of connection attempt (default=infinite).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-show-proxy-settings
|
|
Show sensed HTTP or SOCKS proxy settings. Currently, only Windows clients
|
|
support this option.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-http-proxy server port [authfile|'auto'|'auto-nct'] [auth-method]
|
|
Connect to remote host through an HTTP proxy at address
|
|
.B server
|
|
and port
|
|
.B port.
|
|
If HTTP Proxy-Authenticate is required,
|
|
.B authfile
|
|
is a file containing a username and password on 2 lines, or
|
|
"stdin" to prompt from console.
|
|
|
|
.B auth-method
|
|
should be one of "none", "basic", or "ntlm".
|
|
|
|
HTTP Digest authentication is supported as well, but only via
|
|
the
|
|
.B auto
|
|
or
|
|
.B auto-nct
|
|
flags (below).
|
|
|
|
The
|
|
.B auto
|
|
flag causes OpenVPN to automatically determine the
|
|
.B auth-method
|
|
and query stdin or the management interface for
|
|
username/password credentials, if required. This flag
|
|
exists on OpenVPN 2.1 or higher.
|
|
|
|
The
|
|
.B auto-nct
|
|
flag (no clear-text auth) instructs OpenVPN to automatically
|
|
determine the authentication method, but to reject weak
|
|
authentication protocols such as HTTP Basic Authentication.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-http-proxy-retry
|
|
Retry indefinitely on HTTP proxy errors. If an HTTP proxy error
|
|
occurs, simulate a SIGUSR1 reset.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-http-proxy-timeout n
|
|
Set proxy timeout to
|
|
.B n
|
|
seconds, default=5.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-http-proxy-option type [parm]
|
|
Set extended HTTP proxy options.
|
|
Repeat to set multiple options.
|
|
|
|
.B VERSION version \-\-
|
|
Set HTTP version number to
|
|
.B version
|
|
(default=1.0).
|
|
|
|
.B AGENT user-agent \-\-
|
|
Set HTTP "User-Agent" string to
|
|
.B user-agent.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-socks-proxy server [port] [authfile]
|
|
Connect to remote host through a Socks5 proxy at address
|
|
.B server
|
|
and port
|
|
.B port
|
|
(default=1080).
|
|
.B authfile
|
|
(optional) is a file containing a username and password on 2 lines, or
|
|
"stdin" to prompt from console.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-socks-proxy-retry
|
|
Retry indefinitely on Socks proxy errors. If a Socks proxy error
|
|
occurs, simulate a SIGUSR1 reset.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-resolv-retry n
|
|
If hostname resolve fails for
|
|
.B \-\-remote,
|
|
retry resolve for
|
|
.B n
|
|
seconds before failing.
|
|
|
|
Set
|
|
.B n
|
|
to "infinite" to retry indefinitely.
|
|
|
|
By default,
|
|
.B \-\-resolv-retry infinite
|
|
is enabled. You can disable by setting n=0.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-float
|
|
Allow remote peer to change its IP address and/or port number, such as due to
|
|
DHCP (this is the default if
|
|
.B \-\-remote
|
|
is not used).
|
|
.B \-\-float
|
|
when specified with
|
|
.B \-\-remote
|
|
allows an OpenVPN session to initially connect to a peer
|
|
at a known address, however if packets arrive from a new
|
|
address and pass all authentication tests, the new address
|
|
will take control of the session. This is useful when
|
|
you are connecting to a peer which holds a dynamic address
|
|
such as a dial-in user or DHCP client.
|
|
|
|
Essentially,
|
|
.B \-\-float
|
|
tells OpenVPN to accept authenticated packets
|
|
from any address, not only the address which was specified in the
|
|
.B \-\-remote
|
|
option.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ipchange cmd
|
|
Run command
|
|
.B cmd
|
|
when our remote ip-address is initially authenticated or
|
|
changes.
|
|
|
|
.B cmd
|
|
consists of a path to script (or executable program), optionally
|
|
followed by arguments. The path and arguments may be single- or double-quoted
|
|
and/or escaped using a backslash, and should be separated by one or more spaces.
|
|
|
|
When
|
|
.B cmd
|
|
is executed two arguments are appended after any arguments specified in
|
|
.B cmd
|
|
, as follows:
|
|
|
|
.B cmd ip_address port_number
|
|
|
|
Don't use
|
|
.B \-\-ipchange
|
|
in
|
|
.B \-\-mode server
|
|
mode. Use a
|
|
.B \-\-client-connect
|
|
script instead.
|
|
|
|
See the "Environmental Variables" section below for
|
|
additional parameters passed as environmental variables.
|
|
|
|
If you are running in a dynamic IP address environment where
|
|
the IP addresses of either peer could change without notice,
|
|
you can use this script, for example, to edit the
|
|
.I /etc/hosts
|
|
file with the current address of the peer. The script will
|
|
be run every time the remote peer changes its IP address.
|
|
|
|
Similarly if
|
|
.I our
|
|
IP address changes due to DHCP, we should configure
|
|
our IP address change script (see man page for
|
|
.BR dhcpcd (8)
|
|
) to deliver a
|
|
.B SIGHUP
|
|
or
|
|
.B SIGUSR1
|
|
signal to OpenVPN. OpenVPN will then
|
|
reestablish a connection with its most recently authenticated
|
|
peer on its new IP address.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-port port
|
|
TCP/UDP port number for both local and remote. The current
|
|
default of 1194 represents the official IANA port number
|
|
assignment for OpenVPN and has been used since version 2.0-beta17.
|
|
Previous versions used port 5000 as the default.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-lport port
|
|
TCP/UDP port number for bind.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-rport port
|
|
TCP/UDP port number for remote.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-bind
|
|
Bind to local address and port. This is the default unless any of
|
|
.B \-\-proto tcp-client
|
|
,
|
|
.B \-\-http-proxy
|
|
or
|
|
.B \-\-socks-proxy
|
|
are used.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-nobind
|
|
Do not bind to local address and port. The IP stack will allocate
|
|
a dynamic port for returning packets. Since the value of the dynamic port
|
|
could not be known in advance by a peer, this option is only suitable for
|
|
peers which will be initiating connections by using the
|
|
.B \-\-remote
|
|
option.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-dev tunX | tapX | null
|
|
TUN/TAP virtual network device (
|
|
.B X
|
|
can be omitted for a dynamic device.)
|
|
|
|
See examples section below
|
|
for an example on setting up a TUN device.
|
|
|
|
You must use either tun devices on both ends of the connection
|
|
or tap devices on both ends. You cannot mix them, as they
|
|
represent different underlying network layers.
|
|
|
|
.B tun
|
|
devices encapsulate IPv4 or IPv6 (OSI Layer 3) while
|
|
.B tap
|
|
devices encapsulate Ethernet 802.3 (OSI Layer 2).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-dev-type device-type
|
|
Which device type are we using?
|
|
.B device-type
|
|
should be
|
|
.B tun
|
|
(OSI Layer 3)
|
|
or
|
|
.B tap
|
|
(OSI Layer 2).
|
|
Use this option only if the TUN/TAP device used with
|
|
.B \-\-dev
|
|
does not begin with
|
|
.B tun
|
|
or
|
|
.B tap.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-topology mode
|
|
Configure virtual addressing topology when running in
|
|
.B \-\-dev tun
|
|
mode. This directive has no meaning in
|
|
.B \-\-dev tap
|
|
mode, which always uses a
|
|
.B subnet
|
|
topology.
|
|
|
|
If you set this directive on the server, the
|
|
.B \-\-server
|
|
and
|
|
.B \-\-server-bridge
|
|
directives will automatically push your chosen topology setting to clients
|
|
as well. This directive can also be manually pushed to clients. Like the
|
|
.B \-\-dev
|
|
directive, this directive must always be compatible between client and server.
|
|
|
|
.B mode
|
|
can be one of:
|
|
|
|
.B net30 \-\-
|
|
Use a point-to-point topology, by allocating one /30 subnet per client.
|
|
This is designed to allow point-to-point semantics when some
|
|
or all of the connecting clients might be Windows systems. This is the
|
|
default on OpenVPN 2.0.
|
|
|
|
.B p2p \-\-
|
|
Use a point-to-point topology where the remote endpoint of the client's
|
|
tun interface always points to the local endpoint of the server's tun interface.
|
|
This mode allocates a single IP address per connecting client.
|
|
Only use
|
|
when none of the connecting clients are Windows systems. This mode
|
|
is functionally equivalent to the
|
|
.B \-\-ifconfig-pool-linear
|
|
directive which is available in OpenVPN 2.0 and is now deprecated.
|
|
|
|
.B subnet \-\-
|
|
Use a subnet rather than a point-to-point topology by
|
|
configuring the tun interface with a local IP address and subnet mask,
|
|
similar to the topology used in
|
|
.B \-\-dev tap
|
|
and ethernet bridging mode.
|
|
This mode allocates a single IP address per connecting client and works on
|
|
Windows as well. Only available when server and clients are OpenVPN 2.1 or
|
|
higher, or OpenVPN 2.0.x which has been manually patched with the
|
|
.B \-\-topology
|
|
directive code. When used on Windows, requires version 8.2 or higher
|
|
of the TAP-Win32 driver. When used on *nix, requires that the tun
|
|
driver supports an
|
|
.BR ifconfig (8)
|
|
command which sets a subnet instead of a remote endpoint IP address.
|
|
|
|
This option exists in OpenVPN 2.1 or higher.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tun-ipv6
|
|
Build a tun link capable of forwarding IPv6 traffic.
|
|
Should be used in conjunction with
|
|
.B \-\-dev tun
|
|
or
|
|
.B \-\-dev tunX.
|
|
A warning will be displayed
|
|
if no specific IPv6 TUN support for your OS has been compiled into OpenVPN.
|
|
|
|
See below for further IPv6-related configuration options.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-dev-node node
|
|
Explicitly set the device node rather than using
|
|
/dev/net/tun, /dev/tun, /dev/tap, etc. If OpenVPN
|
|
cannot figure out whether
|
|
.B node
|
|
is a TUN or TAP device based on the name, you should
|
|
also specify
|
|
.B \-\-dev-type tun
|
|
or
|
|
.B \-\-dev-type tap.
|
|
|
|
Under Mac OS X this option can be used to specify the default tun
|
|
implementation. Using
|
|
.B \-\-dev\-node utun
|
|
forces usage of the native Darwin tun kernel support. Use
|
|
.B \-\-dev\-node utunN
|
|
to select a specific utun instance. To force using the tun.kext (/dev/tunX) use
|
|
.B \-\-dev\-node tun\fR.
|
|
When not specifying a
|
|
.B \-\-dev\-node
|
|
option openvpn will first try to open utun, and fall back to tun.kext.
|
|
|
|
On Windows systems, select the TAP-Win32 adapter which
|
|
is named
|
|
.B node
|
|
in the Network Connections Control Panel or the
|
|
raw GUID of the adapter enclosed by braces.
|
|
The
|
|
.B \-\-show-adapters
|
|
option under Windows can also be used
|
|
to enumerate all available TAP-Win32
|
|
adapters and will show both the network
|
|
connections control panel name and the GUID for
|
|
each TAP-Win32 adapter.
|
|
.TP
|
|
.B \-\-lladdr address
|
|
Specify the link layer address, more commonly known as the MAC address.
|
|
Only applied to TAP devices.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-iproute cmd
|
|
Set alternate command to execute instead of default iproute2 command.
|
|
May be used in order to execute OpenVPN in unprivileged environment.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ifconfig l rn
|
|
Set TUN/TAP adapter parameters.
|
|
.B l
|
|
is the IP address of the local VPN endpoint.
|
|
For TUN devices,
|
|
.B rn
|
|
is the IP address of the remote VPN endpoint.
|
|
For TAP devices,
|
|
.B rn
|
|
is the subnet mask of the virtual ethernet segment
|
|
which is being created or connected to.
|
|
|
|
For TUN devices, which facilitate virtual
|
|
point-to-point IP connections,
|
|
the proper usage of
|
|
.B \-\-ifconfig
|
|
is to use two private IP addresses
|
|
which are not a member of any
|
|
existing subnet which is in use.
|
|
The IP addresses may be consecutive
|
|
and should have their order reversed
|
|
on the remote peer. After the VPN
|
|
is established, by pinging
|
|
.B rn,
|
|
you will be pinging across the VPN.
|
|
|
|
For TAP devices, which provide
|
|
the ability to create virtual
|
|
ethernet segments,
|
|
.B \-\-ifconfig
|
|
is used to set an IP address and
|
|
subnet mask just as a physical
|
|
ethernet adapter would be
|
|
similarly configured. If you are
|
|
attempting to connect to a remote
|
|
ethernet bridge, the IP address
|
|
and subnet should be set to values
|
|
which would be valid on the
|
|
the bridged ethernet segment (note
|
|
also that DHCP can be used for the
|
|
same purpose).
|
|
|
|
This option, while primarily a proxy for the
|
|
.BR ifconfig (8)
|
|
command, is designed to simplify TUN/TAP
|
|
tunnel configuration by providing a
|
|
standard interface to the different
|
|
ifconfig implementations on different
|
|
platforms.
|
|
|
|
.B \-\-ifconfig
|
|
parameters which are IP addresses can
|
|
also be specified as a DNS or /etc/hosts
|
|
file resolvable name.
|
|
|
|
For TAP devices,
|
|
.B \-\-ifconfig
|
|
should not be used if the TAP interface will be
|
|
getting an IP address lease from a DHCP
|
|
server.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ifconfig-noexec
|
|
Don't actually execute ifconfig/netsh commands, instead
|
|
pass
|
|
.B \-\-ifconfig
|
|
parameters to scripts using environmental variables.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ifconfig-nowarn
|
|
Don't output an options consistency check warning
|
|
if the
|
|
.B \-\-ifconfig
|
|
option on this side of the
|
|
connection doesn't match the remote side. This is useful
|
|
when you want to retain the overall benefits of the
|
|
options consistency check (also see
|
|
.B \-\-disable-occ
|
|
option) while only disabling the ifconfig component of
|
|
the check.
|
|
|
|
For example,
|
|
if you have a configuration where the local host uses
|
|
.B \-\-ifconfig
|
|
but the remote host does not, use
|
|
.B \-\-ifconfig-nowarn
|
|
on the local host.
|
|
|
|
This option will also silence warnings about potential
|
|
address conflicts which occasionally annoy more experienced
|
|
users by triggering "false positive" warnings.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-route network/IP [netmask] [gateway] [metric]
|
|
Add route to routing table after connection is established.
|
|
Multiple routes can be specified. Routes will be
|
|
automatically torn down in reverse order prior to
|
|
TUN/TAP device close.
|
|
|
|
This option is intended as
|
|
a convenience proxy for the
|
|
.BR route (8)
|
|
shell command,
|
|
while at the same time providing portable semantics
|
|
across OpenVPN's platform space.
|
|
|
|
.B netmask
|
|
default \-\- 255.255.255.255
|
|
|
|
.B gateway
|
|
default \-\- taken from
|
|
.B \-\-route-gateway
|
|
or the second parameter to
|
|
.B \-\-ifconfig
|
|
when
|
|
.B \-\-dev tun
|
|
is specified.
|
|
|
|
.B metric
|
|
default \-\- taken from
|
|
.B \-\-route-metric
|
|
otherwise 0.
|
|
|
|
The default can be specified by leaving an option blank or setting
|
|
it to "default".
|
|
|
|
The
|
|
.B network
|
|
and
|
|
.B gateway
|
|
parameters can
|
|
also be specified as a DNS or /etc/hosts
|
|
file resolvable name, or as one of three special keywords:
|
|
|
|
.B vpn_gateway
|
|
\-\- The remote VPN endpoint address
|
|
(derived either from
|
|
.B \-\-route-gateway
|
|
or the second parameter to
|
|
.B \-\-ifconfig
|
|
when
|
|
.B \-\-dev tun
|
|
is specified).
|
|
|
|
.B net_gateway
|
|
\-\- The pre-existing IP default gateway, read from the routing
|
|
table (not supported on all OSes).
|
|
|
|
.B remote_host
|
|
\-\- The
|
|
.B \-\-remote
|
|
address if OpenVPN is being run in client mode, and is undefined in server mode.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-max-routes n
|
|
Allow a maximum number of n
|
|
.B \-\-route
|
|
options to be specified, either in the local configuration file,
|
|
or pulled from an OpenVPN server. By default, n=100.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-route-gateway gw|'dhcp'
|
|
Specify a default gateway
|
|
.B gw
|
|
for use with
|
|
.B \-\-route.
|
|
|
|
If
|
|
.B dhcp
|
|
is specified as the parameter,
|
|
the gateway address will be extracted from a DHCP
|
|
negotiation with the OpenVPN server-side LAN.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-route-metric m
|
|
Specify a default metric
|
|
.B m
|
|
for use with
|
|
.B \-\-route.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-route-delay [n] [w]
|
|
Delay
|
|
.B n
|
|
seconds (default=0) after connection
|
|
establishment, before adding routes. If
|
|
.B n
|
|
is 0, routes will be added immediately upon connection
|
|
establishment. If
|
|
.B \-\-route-delay
|
|
is omitted, routes will be added immediately after TUN/TAP device
|
|
open and
|
|
.B \-\-up
|
|
script execution, before any
|
|
.B \-\-user
|
|
or
|
|
.B \-\-group
|
|
privilege downgrade (or
|
|
.B \-\-chroot
|
|
execution.)
|
|
|
|
This option is designed to be useful in scenarios where DHCP is
|
|
used to set
|
|
tap adapter addresses. The delay will give the DHCP handshake
|
|
time to complete before routes are added.
|
|
|
|
On Windows,
|
|
.B \-\-route-delay
|
|
tries to be more intelligent by waiting
|
|
.B w
|
|
seconds (w=30 by default)
|
|
for the TAP-Win32 adapter to come up before adding routes.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-route-up cmd
|
|
Run command
|
|
.B cmd
|
|
after routes are added, subject to
|
|
.B \-\-route-delay.
|
|
|
|
.B cmd
|
|
consists of a path to script (or executable program), optionally
|
|
followed by arguments. The path and arguments may be single- or double-quoted
|
|
and/or escaped using a backslash, and should be separated by one or more spaces.
|
|
|
|
See the "Environmental Variables" section below for
|
|
additional parameters passed as environmental variables.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-route-pre-down cmd
|
|
Run command
|
|
.B cmd
|
|
before routes are removed upon disconnection.
|
|
|
|
.B cmd
|
|
consists of a path to script (or executable program), optionally
|
|
followed by arguments. The path and arguments may be single- or double-quoted
|
|
and/or escaped using a backslash, and should be separated by one or more spaces.
|
|
|
|
See the "Environmental Variables" section below for
|
|
additional parameters passed as environmental variables.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-route-noexec
|
|
Don't add or remove routes automatically. Instead pass routes to
|
|
.B \-\-route-up
|
|
script using environmental variables.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-route-nopull
|
|
When used with
|
|
.B \-\-client
|
|
or
|
|
.B \-\-pull,
|
|
accept options pushed by server EXCEPT for routes and dhcp options
|
|
like DNS servers.
|
|
|
|
When used on the client, this option effectively bars the
|
|
server from adding routes to the client's routing table,
|
|
however note that this option still allows the server
|
|
to set the TCP/IP properties of the client's TUN/TAP interface.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-allow-pull-fqdn
|
|
Allow client to pull DNS names from server (rather than being limited
|
|
to IP address) for
|
|
.B \-\-ifconfig,
|
|
.B \-\-route,
|
|
and
|
|
.B \-\-route-gateway.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-client-nat snat|dnat network netmask alias
|
|
This pushable client option sets up a stateless one-to-one NAT
|
|
rule on packet addresses (not ports), and is useful in cases
|
|
where routes or ifconfig settings pushed to the client would
|
|
create an IP numbering conflict.
|
|
|
|
.B network/netmask
|
|
(for example 192.168.0.0/255.255.0.0)
|
|
defines the local view of a resource from the client perspective, while
|
|
.B alias/netmask
|
|
(for example 10.64.0.0/255.255.0.0)
|
|
defines the remote view from the server perspective.
|
|
|
|
Use
|
|
.B snat
|
|
(source NAT) for resources owned by the client and
|
|
.B dnat
|
|
(destination NAT) for remote resources.
|
|
|
|
Set
|
|
.B \-\-verb 6
|
|
for debugging info showing the transformation of src/dest
|
|
addresses in packets.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-redirect-gateway flags...
|
|
Automatically execute routing commands to cause all outgoing IP traffic
|
|
to be redirected over the VPN. This is a client-side option.
|
|
|
|
This option performs three steps:
|
|
|
|
.B (1)
|
|
Create a static route for the
|
|
.B \-\-remote
|
|
address which forwards to the pre-existing default gateway.
|
|
This is done so that
|
|
.B (3)
|
|
will not create a routing loop.
|
|
|
|
.B (2)
|
|
Delete the default gateway route.
|
|
|
|
.B (3)
|
|
Set the new default gateway to be the VPN endpoint address (derived either from
|
|
.B \-\-route-gateway
|
|
or the second parameter to
|
|
.B \-\-ifconfig
|
|
when
|
|
.B \-\-dev tun
|
|
is specified).
|
|
|
|
When the tunnel is torn down, all of the above steps are reversed so
|
|
that the original default route is restored.
|
|
|
|
Option flags:
|
|
|
|
.B local \-\-
|
|
Add the
|
|
.B local
|
|
flag if both OpenVPN servers are directly connected via a common subnet,
|
|
such as with wireless. The
|
|
.B local
|
|
flag will cause step
|
|
.B 1
|
|
above to be omitted.
|
|
|
|
.B autolocal \-\-
|
|
Try to automatically determine whether to enable
|
|
.B local
|
|
flag above.
|
|
|
|
.B def1 \-\-
|
|
Use this flag to override
|
|
the default gateway by using 0.0.0.0/1 and 128.0.0.0/1
|
|
rather than 0.0.0.0/0. This has the benefit of overriding
|
|
but not wiping out the original default gateway.
|
|
|
|
.B bypass-dhcp \-\-
|
|
Add a direct route to the DHCP server (if it is non-local) which
|
|
bypasses the tunnel
|
|
(Available on Windows clients, may not be available
|
|
on non-Windows clients).
|
|
|
|
.B bypass-dns \-\-
|
|
Add a direct route to the DNS server(s) (if they are non-local) which
|
|
bypasses the tunnel
|
|
(Available on Windows clients, may not be available
|
|
on non-Windows clients).
|
|
|
|
.B block-local \-\-
|
|
Block access to local LAN when the tunnel is active, except for
|
|
the LAN gateway itself. This is accomplished by routing the local
|
|
LAN (except for the LAN gateway address) into the tunnel.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-link-mtu n
|
|
Sets an upper bound on the size of UDP packets which are sent
|
|
between OpenVPN peers. It's best not to set this parameter unless
|
|
you know what you're doing.
|
|
.\"*********************************************************
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-redirect-private [flags]
|
|
Like \-\-redirect-gateway, but omit actually changing the default
|
|
gateway. Useful when pushing private subnets.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tun-mtu n
|
|
Take the TUN device MTU to be
|
|
.B n
|
|
and derive the link MTU
|
|
from it (default=1500). In most cases, you will probably want to
|
|
leave this parameter set to its default value.
|
|
|
|
The MTU (Maximum Transmission Units) is
|
|
the maximum datagram size in bytes that can be sent unfragmented
|
|
over a particular network path. OpenVPN requires that packets
|
|
on the control or data channels be sent unfragmented.
|
|
|
|
MTU problems often manifest themselves as connections which
|
|
hang during periods of active usage.
|
|
|
|
It's best to use the
|
|
.B \-\-fragment
|
|
and/or
|
|
.B \-\-mssfix
|
|
options to deal with MTU sizing issues.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tun-mtu-extra n
|
|
Assume that the TUN/TAP device might return as many as
|
|
.B n
|
|
bytes more than the
|
|
.B \-\-tun-mtu
|
|
size on read. This parameter defaults to 0, which is sufficient for
|
|
most TUN devices. TAP devices may introduce additional overhead in excess
|
|
of the MTU size, and a setting of 32 is the default when TAP devices are used.
|
|
This parameter only controls internal OpenVPN buffer sizing,
|
|
so there is no transmission overhead associated with using a larger value.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-mtu-disc type
|
|
Should we do Path MTU discovery on TCP/UDP channel? Only supported on OSes such
|
|
as Linux that supports the necessary system call to set.
|
|
|
|
.B 'no'
|
|
\-\- Never send DF (Don't Fragment) frames
|
|
.br
|
|
.B 'maybe'
|
|
\-\- Use per-route hints
|
|
.br
|
|
.B 'yes'
|
|
\-\- Always DF (Don't Fragment)
|
|
.br
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-mtu-test
|
|
To empirically measure MTU on connection startup,
|
|
add the
|
|
.B \-\-mtu-test
|
|
option to your configuration.
|
|
OpenVPN will send ping packets of various sizes
|
|
to the remote peer and measure the largest packets
|
|
which were successfully received. The
|
|
.B \-\-mtu-test
|
|
process normally takes about 3 minutes to complete.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-fragment max
|
|
Enable internal datagram fragmentation so
|
|
that no UDP datagrams are sent which
|
|
are larger than
|
|
.B max
|
|
bytes.
|
|
|
|
The
|
|
.B max
|
|
parameter is interpreted in the same way as the
|
|
.B \-\-link-mtu
|
|
parameter, i.e. the UDP packet size after encapsulation
|
|
overhead has been added in, but not including
|
|
the UDP header itself.
|
|
|
|
The
|
|
.B \-\-fragment
|
|
option only makes sense when you are using the UDP protocol (
|
|
.B \-\-proto udp
|
|
).
|
|
|
|
.B \-\-fragment
|
|
adds 4 bytes of overhead per datagram.
|
|
|
|
See the
|
|
.B \-\-mssfix
|
|
option below for an important related option to
|
|
.B \-\-fragment.
|
|
|
|
It should also be noted that this option is not meant to replace
|
|
UDP fragmentation at the IP stack level. It is only meant as a
|
|
last resort when path MTU discovery is broken. Using this option
|
|
is less efficient than fixing path MTU discovery for your IP link and
|
|
using native IP fragmentation instead.
|
|
|
|
Having said that, there are circumstances where using OpenVPN's
|
|
internal fragmentation capability may be your only option, such
|
|
as tunneling a UDP multicast stream which requires fragmentation.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-mssfix max
|
|
Announce to TCP sessions running over the tunnel that they should limit
|
|
their send packet sizes such that after OpenVPN has encapsulated them,
|
|
the resulting UDP packet size that OpenVPN sends to its peer will not
|
|
exceed
|
|
.B max
|
|
bytes. The default value is
|
|
.B 1450.
|
|
|
|
The
|
|
.B max
|
|
parameter is interpreted in the same way as the
|
|
.B \-\-link-mtu
|
|
parameter, i.e. the UDP packet size after encapsulation
|
|
overhead has been added in, but not including
|
|
the UDP header itself.
|
|
|
|
The
|
|
.B \-\-mssfix
|
|
option only makes sense when you are using the UDP protocol
|
|
for OpenVPN peer-to-peer communication, i.e.
|
|
.B \-\-proto udp.
|
|
|
|
.B \-\-mssfix
|
|
and
|
|
.B \-\-fragment
|
|
can be ideally used together, where
|
|
.B \-\-mssfix
|
|
will try to keep TCP from needing
|
|
packet fragmentation in the first place,
|
|
and if big packets come through anyhow
|
|
(from protocols other than TCP),
|
|
.B \-\-fragment
|
|
will internally fragment them.
|
|
|
|
Both
|
|
.B \-\-fragment
|
|
and
|
|
.B \-\-mssfix
|
|
are designed to work around cases where Path MTU discovery
|
|
is broken on the network path between OpenVPN peers.
|
|
|
|
The usual symptom of such a breakdown is an OpenVPN
|
|
connection which successfully starts, but then stalls
|
|
during active usage.
|
|
|
|
If
|
|
.B \-\-fragment
|
|
and
|
|
.B \-\-mssfix
|
|
are used together,
|
|
.B \-\-mssfix
|
|
will take its default
|
|
.B max
|
|
parameter from the
|
|
.B \-\-fragment max
|
|
option.
|
|
|
|
Therefore, one could lower the maximum UDP packet size
|
|
to 1300 (a good first try for solving MTU-related
|
|
connection problems) with the following options:
|
|
|
|
.B \-\-tun-mtu 1500 \-\-fragment 1300 \-\-mssfix
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-sndbuf size
|
|
Set the TCP/UDP socket send buffer size.
|
|
Currently defaults to 65536 bytes.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-rcvbuf size
|
|
Set the TCP/UDP socket receive buffer size.
|
|
Currently defaults to 65536 bytes.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-mark value
|
|
Mark encrypted packets being sent with value. The mark value can be
|
|
matched in policy routing and packetfilter rules. This option is
|
|
only supported in Linux and does nothing on other operating systems.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-socket-flags flags...
|
|
Apply the given flags to the OpenVPN transport socket.
|
|
Currently, only
|
|
.B TCP_NODELAY
|
|
is supported.
|
|
|
|
The
|
|
.B TCP_NODELAY
|
|
socket flag is useful in TCP mode, and causes the kernel
|
|
to send tunnel packets immediately over the TCP connection without
|
|
trying to group several smaller packets into a larger packet.
|
|
This can result in a considerably improvement in latency.
|
|
|
|
This option is pushable from server to client, and should be used
|
|
on both client and server for maximum effect.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-txqueuelen n
|
|
(Linux only) Set the TX queue length on the TUN/TAP interface.
|
|
Currently defaults to 100.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-shaper n
|
|
Limit bandwidth of outgoing tunnel data to
|
|
.B n
|
|
bytes per second on the TCP/UDP port.
|
|
Note that this will only work if mode is set to p2p.
|
|
If you want to limit the bandwidth
|
|
in both directions, use this option on both peers.
|
|
|
|
OpenVPN uses the following algorithm to implement
|
|
traffic shaping: Given a shaper rate of
|
|
.I n
|
|
bytes per second, after a datagram write of
|
|
.I b
|
|
bytes is queued on the TCP/UDP port, wait a minimum of
|
|
.I (b / n)
|
|
seconds before queuing the next write.
|
|
|
|
It should be noted that OpenVPN supports multiple
|
|
tunnels between the same two peers, allowing you
|
|
to construct full-speed and reduced bandwidth tunnels
|
|
at the same time,
|
|
routing low-priority data such as off-site backups
|
|
over the reduced bandwidth tunnel, and other data
|
|
over the full-speed tunnel.
|
|
|
|
Also note that for low bandwidth tunnels
|
|
(under 1000 bytes per second), you should probably
|
|
use lower MTU values as well (see above), otherwise
|
|
the packet latency will grow so large as to trigger
|
|
timeouts in the TLS layer and TCP connections running
|
|
over the tunnel.
|
|
|
|
OpenVPN allows
|
|
.B n
|
|
to be between 100 bytes/sec and 100 Mbytes/sec.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-inactive n [bytes]
|
|
Causes OpenVPN to exit after
|
|
.B n
|
|
seconds of inactivity on the TUN/TAP device. The time length of
|
|
inactivity is measured since the last incoming or outgoing tunnel
|
|
packet. The default value is 0 seconds, which disables this feature.
|
|
|
|
If the optional
|
|
.B bytes
|
|
parameter is included,
|
|
exit if less than
|
|
.B bytes
|
|
of combined in/out traffic are produced on the tun/tap device
|
|
in
|
|
.B n
|
|
seconds.
|
|
|
|
In any case, OpenVPN's internal ping packets (which are just
|
|
keepalives) and TLS control packets are not considered
|
|
"activity", nor are they counted as traffic, as they are used
|
|
internally by OpenVPN and are not an indication of actual user
|
|
activity.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ping n
|
|
Ping remote over the TCP/UDP control channel
|
|
if no packets have been sent for at least
|
|
.B n
|
|
seconds (specify
|
|
.B \-\-ping
|
|
on both peers to cause ping packets to be sent in both directions since
|
|
OpenVPN ping packets are not echoed like IP ping packets).
|
|
When used in one of OpenVPN's secure modes (where
|
|
.B \-\-secret, \-\-tls-server,
|
|
or
|
|
.B \-\-tls-client
|
|
is specified), the ping packet
|
|
will be cryptographically secure.
|
|
|
|
This option has two intended uses:
|
|
|
|
(1) Compatibility
|
|
with stateful firewalls. The periodic ping will ensure that
|
|
a stateful firewall rule which allows OpenVPN UDP packets to
|
|
pass will not time out.
|
|
|
|
(2) To provide a basis for the remote to test the existence
|
|
of its peer using the
|
|
.B \-\-ping-exit
|
|
option.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ping-exit n
|
|
Causes OpenVPN to exit after
|
|
.B n
|
|
seconds pass without reception of a ping
|
|
or other packet from remote.
|
|
This option can be combined with
|
|
.B \-\-inactive, \-\-ping,
|
|
and
|
|
.B \-\-ping-exit
|
|
to create a two-tiered inactivity disconnect.
|
|
|
|
For example,
|
|
|
|
.B openvpn [options...] \-\-inactive 3600 \-\-ping 10 \-\-ping-exit 60
|
|
|
|
when used on both peers will cause OpenVPN to exit within 60
|
|
seconds if its peer disconnects, but will exit after one
|
|
hour if no actual tunnel data is exchanged.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ping-restart n
|
|
Similar to
|
|
.B \-\-ping-exit,
|
|
but trigger a
|
|
.B SIGUSR1
|
|
restart after
|
|
.B n
|
|
seconds pass without reception of a ping
|
|
or other packet from remote.
|
|
|
|
This option is useful in cases
|
|
where the remote peer has a dynamic IP address and
|
|
a low-TTL DNS name is used to track the IP address using
|
|
a service such as
|
|
.I http://dyndns.org/
|
|
+ a dynamic DNS client such
|
|
as
|
|
.B ddclient.
|
|
|
|
If the peer cannot be reached, a restart will be triggered, causing
|
|
the hostname used with
|
|
.B \-\-remote
|
|
to be re-resolved (if
|
|
.B \-\-resolv-retry
|
|
is also specified).
|
|
|
|
In server mode,
|
|
.B \-\-ping-restart, \-\-inactive,
|
|
or any other type of internally generated signal will always be
|
|
applied to
|
|
individual client instance objects, never to whole server itself.
|
|
Note also in server mode that any internally generated signal
|
|
which would normally cause a restart, will cause the deletion
|
|
of the client instance object instead.
|
|
|
|
In client mode, the
|
|
.B \-\-ping-restart
|
|
parameter is set to 120 seconds by default. This default will
|
|
hold until the client pulls a replacement value from the server, based on
|
|
the
|
|
.B \-\-keepalive
|
|
setting in the server configuration.
|
|
To disable the 120 second default, set
|
|
.B \-\-ping-restart 0
|
|
on the client.
|
|
|
|
See the signals section below for more information
|
|
on
|
|
.B SIGUSR1.
|
|
|
|
Note that the behavior of
|
|
.B SIGUSR1
|
|
can be modified by the
|
|
.B \-\-persist-tun, \-\-persist-key, \-\-persist-local-ip,
|
|
and
|
|
.B \-\-persist-remote-ip
|
|
options.
|
|
|
|
Also note that
|
|
.B \-\-ping-exit
|
|
and
|
|
.B \-\-ping-restart
|
|
are mutually exclusive and cannot be used together.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-keepalive n m
|
|
A helper directive designed to simplify the expression of
|
|
.B \-\-ping
|
|
and
|
|
.B \-\-ping-restart
|
|
in server mode configurations.
|
|
|
|
The server timeout is set twice the value of the second argument.
|
|
This ensures that a timeout is detected on client side
|
|
before the server side drops the connection.
|
|
|
|
For example,
|
|
.B \-\-keepalive 10 60
|
|
expands as follows:
|
|
|
|
.nf
|
|
.ft 3
|
|
.in +4
|
|
if mode server:
|
|
ping 10
|
|
ping-restart 120
|
|
push "ping 10"
|
|
push "ping-restart 60"
|
|
else
|
|
ping 10
|
|
ping-restart 60
|
|
.in -4
|
|
.ft
|
|
.fi
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ping-timer-rem
|
|
Run the
|
|
.B \-\-ping-exit
|
|
/
|
|
.B \-\-ping-restart
|
|
timer only if we have a remote address. Use this option if you are
|
|
starting the daemon in listen mode (i.e. without an explicit
|
|
.B \-\-remote
|
|
peer), and you don't want to start clocking timeouts until a remote
|
|
peer connects.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-persist-tun
|
|
Don't close and reopen TUN/TAP device or run up/down scripts
|
|
across
|
|
.B SIGUSR1
|
|
or
|
|
.B \-\-ping-restart
|
|
restarts.
|
|
|
|
.B SIGUSR1
|
|
is a restart signal similar to
|
|
.B SIGHUP,
|
|
but which offers finer-grained control over
|
|
reset options.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-persist-key
|
|
Don't re-read key files across
|
|
.B SIGUSR1
|
|
or
|
|
.B \-\-ping-restart.
|
|
|
|
This option can be combined with
|
|
.B \-\-user nobody
|
|
to allow restarts triggered by the
|
|
.B SIGUSR1
|
|
signal.
|
|
Normally if you drop root privileges in OpenVPN,
|
|
the daemon cannot be restarted since it will now be unable to re-read protected
|
|
key files.
|
|
|
|
This option solves the problem by persisting keys across
|
|
.B SIGUSR1
|
|
resets, so they don't need to be re-read.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-persist-local-ip
|
|
Preserve initially resolved local IP address and port number
|
|
across
|
|
.B SIGUSR1
|
|
or
|
|
.B \-\-ping-restart
|
|
restarts.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-persist-remote-ip
|
|
Preserve most recently authenticated remote IP address and port number
|
|
across
|
|
.B SIGUSR1
|
|
or
|
|
.B \-\-ping-restart
|
|
restarts.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-mlock
|
|
Disable paging by calling the POSIX mlockall function.
|
|
Requires that OpenVPN be initially run as root (though
|
|
OpenVPN can subsequently downgrade its UID using the
|
|
.B \-\-user
|
|
option).
|
|
|
|
Using this option ensures that key material and tunnel
|
|
data are never written to disk due to virtual
|
|
memory paging operations which occur under most
|
|
modern operating systems. It ensures that even if an
|
|
attacker was able to crack the box running OpenVPN, he
|
|
would not be able to scan the system swap file to
|
|
recover previously used
|
|
ephemeral keys, which are used for a period of time
|
|
governed by the
|
|
.B \-\-reneg
|
|
options (see below), then are discarded.
|
|
|
|
The downside
|
|
of using
|
|
.B \-\-mlock
|
|
is that it will reduce the amount of physical
|
|
memory available to other applications.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-up cmd
|
|
Run command
|
|
.B cmd
|
|
after successful TUN/TAP device open
|
|
(pre
|
|
.B \-\-user
|
|
UID change).
|
|
|
|
.B cmd
|
|
consists of a path to script (or executable program), optionally
|
|
followed by arguments. The path and arguments may be single- or double-quoted
|
|
and/or escaped using a backslash, and should be separated by one or more spaces.
|
|
|
|
The up command is useful for specifying route
|
|
commands which route IP traffic destined for
|
|
private subnets which exist at the other
|
|
end of the VPN connection into the tunnel.
|
|
|
|
For
|
|
.B \-\-dev tun
|
|
execute as:
|
|
|
|
.B cmd tun_dev tun_mtu link_mtu ifconfig_local_ip ifconfig_remote_ip [ init | restart ]
|
|
|
|
For
|
|
.B \-\-dev tap
|
|
execute as:
|
|
|
|
.B cmd tap_dev tap_mtu link_mtu ifconfig_local_ip ifconfig_netmask [ init | restart ]
|
|
|
|
See the "Environmental Variables" section below for
|
|
additional parameters passed as environmental variables.
|
|
|
|
Note that if
|
|
.B cmd
|
|
includes arguments, all OpenVPN-generated arguments will be appended
|
|
to them to build an argument list with which the executable will be
|
|
called.
|
|
|
|
Typically,
|
|
.B cmd
|
|
will run a script to add routes to the tunnel.
|
|
|
|
Normally the up script is called after the TUN/TAP device is opened.
|
|
In this context, the last command line parameter passed to the script
|
|
will be
|
|
.I init.
|
|
If the
|
|
.B \-\-up-restart
|
|
option is also used, the up script will be called for restarts as
|
|
well. A restart is considered to be a partial reinitialization
|
|
of OpenVPN where the TUN/TAP instance is preserved (the
|
|
.B \-\-persist-tun
|
|
option will enable such preservation). A restart
|
|
can be generated by a SIGUSR1 signal, a
|
|
.B \-\-ping-restart
|
|
timeout, or a connection reset when the TCP protocol is enabled
|
|
with the
|
|
.B \-\-proto
|
|
option. If a restart occurs, and
|
|
.B \-\-up-restart
|
|
has been specified, the up script will be called with
|
|
.I restart
|
|
as the last parameter.
|
|
|
|
The following standalone example shows how the
|
|
.B \-\-up
|
|
script can be called in both an initialization and restart context.
|
|
(NOTE: for security reasons, don't run the following example unless UDP port
|
|
9999 is blocked by your firewall. Also, the example will run indefinitely,
|
|
so you should abort with control-c).
|
|
|
|
.B openvpn \-\-dev tun \-\-port 9999 \-\-verb 4 \-\-ping-restart 10 \-\-up 'echo up' \-\-down 'echo down' \-\-persist-tun \-\-up-restart
|
|
|
|
Note that OpenVPN also provides the
|
|
.B \-\-ifconfig
|
|
option to automatically ifconfig the TUN device,
|
|
eliminating the need to define an
|
|
.B \-\-up
|
|
script, unless you also want to configure routes
|
|
in the
|
|
.B \-\-up
|
|
script.
|
|
|
|
If
|
|
.B \-\-ifconfig
|
|
is also specified, OpenVPN will pass the ifconfig local
|
|
and remote endpoints on the command line to the
|
|
.B \-\-up
|
|
script so that they can be used to configure routes such as:
|
|
|
|
.B route add -net 10.0.0.0 netmask 255.255.255.0 gw $5
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-up-delay
|
|
Delay TUN/TAP open and possible
|
|
.B \-\-up
|
|
script execution
|
|
until after TCP/UDP connection establishment with peer.
|
|
|
|
In
|
|
.B \-\-proto udp
|
|
mode, this option normally requires the use of
|
|
.B \-\-ping
|
|
to allow connection initiation to be sensed in the absence
|
|
of tunnel data, since UDP is a "connectionless" protocol.
|
|
|
|
On Windows, this option will delay the TAP-Win32 media state
|
|
transitioning to "connected" until connection establishment,
|
|
i.e. the receipt of the first authenticated packet from the peer.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-down cmd
|
|
Run command
|
|
.B cmd
|
|
after TUN/TAP device close
|
|
(post
|
|
.B \-\-user
|
|
UID change and/or
|
|
.B \-\-chroot
|
|
).
|
|
.B cmd
|
|
consists of a path to script (or executable program), optionally
|
|
followed by arguments. The path and arguments may be single- or double-quoted
|
|
and/or escaped using a backslash, and should be separated by one or more spaces.
|
|
|
|
Called with the same parameters and environmental
|
|
variables as the
|
|
.B \-\-up
|
|
option above.
|
|
|
|
Note that if you reduce privileges by using
|
|
.B \-\-user
|
|
and/or
|
|
.B \-\-group,
|
|
your
|
|
.B \-\-down
|
|
script will also run at reduced privilege.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-down-pre
|
|
Call
|
|
.B \-\-down
|
|
cmd/script before, rather than after, TUN/TAP close.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-up-restart
|
|
Enable the
|
|
.B \-\-up
|
|
and
|
|
.B \-\-down
|
|
scripts to be called for restarts as well as initial program start.
|
|
This option is described more fully above in the
|
|
.B \-\-up
|
|
option documentation.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-setenv name value
|
|
Set a custom environmental variable
|
|
.B name=value
|
|
to pass to script.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-setenv FORWARD_COMPATIBLE 1
|
|
Relax config file syntax checking so that unknown directives
|
|
will trigger a warning but not a fatal error,
|
|
on the assumption that a given unknown directive might be valid
|
|
in future OpenVPN versions.
|
|
|
|
This option should be used with caution, as there are good security
|
|
reasons for having OpenVPN fail if it detects problems in a
|
|
config file. Having said that, there are valid reasons for wanting
|
|
new software features to gracefully degrade when encountered by
|
|
older software versions.
|
|
|
|
It is also possible to tag a single directive so as not to trigger
|
|
a fatal error if the directive isn't recognized. To do this,
|
|
prepend the following before the directive:
|
|
.B setenv opt
|
|
|
|
Versions prior to OpenVPN 2.3.3 will always ignore options set with the
|
|
.B setenv opt
|
|
directive.
|
|
|
|
See also
|
|
.B \-\-ignore-unknown-option
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-setenv-safe name value
|
|
Set a custom environmental variable
|
|
.B OPENVPN_name=value
|
|
to pass to script.
|
|
|
|
This directive is designed to be pushed by the server to clients,
|
|
and the prepending of "OPENVPN_" to the environmental variable
|
|
is a safety precaution to prevent a LD_PRELOAD style attack
|
|
from a malicious or compromised server.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ignore-unknown-option opt1 opt2 opt3 ... optN
|
|
When one of options
|
|
.B opt1 ... optN
|
|
is encountered in the configuration file the configuration
|
|
file parsing does not fail if this OpenVPN version does not
|
|
support the option. Multiple
|
|
.B \-\-ignore-unknown-option
|
|
options can be given to support a larger number of options to ignore.
|
|
|
|
This option should be used with caution, as there are good security
|
|
reasons for having OpenVPN fail if it detects problems in a
|
|
config file. Having said that, there are valid reasons for wanting
|
|
new software features to gracefully degrade when encountered by
|
|
older software versions.
|
|
|
|
.B \-\-ignore-unknown-option
|
|
is available since OpenVPN 2.3.3.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-script-security level
|
|
This directive offers policy-level control over OpenVPN's usage of external programs
|
|
and scripts. Lower
|
|
.B level
|
|
values are more restrictive, higher values are more permissive. Settings for
|
|
.B level:
|
|
|
|
.B 0 \-\-
|
|
Strictly no calling of external programs.
|
|
.br
|
|
.B 1 \-\-
|
|
(Default) Only call built-in executables such as ifconfig, ip, route, or netsh.
|
|
.br
|
|
.B 2 \-\-
|
|
Allow calling of built-in executables and user-defined scripts.
|
|
.br
|
|
.B 3 \-\-
|
|
Allow passwords to be passed to scripts via environmental variables (potentially unsafe).
|
|
|
|
OpenVPN releases before v2.3 also supported a
|
|
.B method
|
|
flag which indicated how OpenVPN should call external commands and scripts. This
|
|
could be either
|
|
.B execve
|
|
or
|
|
.B system.
|
|
As of OpenVPN v2.3, this flag is no longer accepted. In most *nix environments the execve()
|
|
approach has been used without any issues.
|
|
|
|
To run scripts in Windows in earlier OpenVPN
|
|
versions you needed to either add a full path to the script interpreter which can parse the
|
|
script or use the
|
|
.B system
|
|
flag to run these scripts. As of OpenVPN v2.3 it is now a strict requirement to have
|
|
full path to the script interpreter when running non-executables files.
|
|
This is not needed for executable files, such as .exe, .com, .bat or .cmd files. For
|
|
example, if you have a Visual Basic script, you must use this syntax now:
|
|
|
|
.nf
|
|
.ft 3
|
|
.in +4
|
|
\-\-up 'C:\\\\Windows\\\\System32\\\\wscript.exe C:\\\\Program\\ Files\\\\OpenVPN\\\\config\\\\my-up-script.vbs'
|
|
.in -4
|
|
.ft
|
|
.fi
|
|
|
|
Please note the single quote marks and the escaping of the backslashes (\\) and
|
|
the space character.
|
|
|
|
The reason the support for the
|
|
.B system
|
|
flag was removed is due to the security implications with shell expansions
|
|
when executing scripts via the system() call.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-disable-occ
|
|
Don't output a warning message if option inconsistencies are detected between
|
|
peers. An example of an option inconsistency would be where one peer uses
|
|
.B \-\-dev tun
|
|
while the other peer uses
|
|
.B \-\-dev tap.
|
|
|
|
Use of this option is discouraged, but is provided as
|
|
a temporary fix in situations where a recent version of OpenVPN must
|
|
connect to an old version.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-user user
|
|
Change the user ID of the OpenVPN process to
|
|
.B user
|
|
after initialization, dropping privileges in the process.
|
|
This option is useful to protect the system
|
|
in the event that some hostile party was able to gain control of
|
|
an OpenVPN session. Though OpenVPN's security features make
|
|
this unlikely, it is provided as a second line of defense.
|
|
|
|
By setting
|
|
.B user
|
|
to
|
|
.I nobody
|
|
or somebody similarly unprivileged, the hostile party would be
|
|
limited in what damage they could cause. Of course once
|
|
you take away privileges, you cannot return them
|
|
to an OpenVPN session. This means, for example, that if
|
|
you want to reset an OpenVPN daemon with a
|
|
.B SIGUSR1
|
|
signal
|
|
(for example in response
|
|
to a DHCP reset), you should make use of one or more of the
|
|
.B \-\-persist
|
|
options to ensure that OpenVPN doesn't need to execute any privileged
|
|
operations in order to restart (such as re-reading key files
|
|
or running
|
|
.BR ifconfig
|
|
on the TUN device).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-group group
|
|
Similar to the
|
|
.B \-\-user
|
|
option,
|
|
this option changes the group ID of the OpenVPN process to
|
|
.B group
|
|
after initialization.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-cd dir
|
|
Change directory to
|
|
.B dir
|
|
prior to reading any files such as
|
|
configuration files, key files, scripts, etc.
|
|
.B dir
|
|
should be an absolute path, with a leading "/",
|
|
and without any references
|
|
to the current directory such as "." or "..".
|
|
|
|
This option is useful when you are running
|
|
OpenVPN in
|
|
.B \-\-daemon
|
|
mode, and you want to consolidate all of
|
|
your OpenVPN control files in one location.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-chroot dir
|
|
Chroot to
|
|
.B dir
|
|
after initialization.
|
|
.B \-\-chroot
|
|
essentially redefines
|
|
.B dir
|
|
as being the top
|
|
level directory tree (/). OpenVPN will therefore
|
|
be unable to access any files outside this tree.
|
|
This can be desirable from a security standpoint.
|
|
|
|
Since the chroot operation is delayed until after
|
|
initialization, most OpenVPN options that reference
|
|
files will operate in a pre-chroot context.
|
|
|
|
In many cases, the
|
|
.B dir
|
|
parameter can point to an empty directory, however
|
|
complications can result when scripts or restarts
|
|
are executed after the chroot operation.
|
|
|
|
Note: if OpenVPN is built using the PolarSSL SSL
|
|
library,
|
|
.B \-\-chroot
|
|
will only work if a /dev/urandom device node is available
|
|
inside the chroot directory
|
|
.B dir.
|
|
This is due to the way PolarSSL works (it wants to open
|
|
/dev/urandom every time randomness is needed, not just once
|
|
at startup) and nothing OpenVPN can influence.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-setcon context
|
|
Apply SELinux
|
|
.B context
|
|
after initialization. This
|
|
essentially provides the ability to restrict OpenVPN's
|
|
rights to only network I/O operations, thanks to
|
|
SELinux. This goes further than
|
|
.B \-\-user
|
|
and
|
|
.B \-\-chroot
|
|
in that those two, while being great security features,
|
|
unfortunately do not protect against privilege escalation
|
|
by exploitation of a vulnerable system call. You can of
|
|
course combine all three, but please note that since
|
|
setcon requires access to /proc you will have to provide
|
|
it inside the chroot directory (e.g. with mount \-\-bind).
|
|
|
|
Since the setcon operation is delayed until after
|
|
initialization, OpenVPN can be restricted to just
|
|
network-related system calls, whereas by applying the
|
|
context before startup (such as the OpenVPN one provided
|
|
in the SELinux Reference Policies) you will have to
|
|
allow many things required only during initialization.
|
|
|
|
Like with chroot, complications can result when scripts
|
|
or restarts are executed after the setcon operation,
|
|
which is why you should really consider using the
|
|
.B \-\-persist-key
|
|
and
|
|
.B \-\-persist-tun
|
|
options.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-daemon [progname]
|
|
Become a daemon after all initialization functions are completed.
|
|
This option will cause all message and error output to
|
|
be sent to the syslog file (such as /var/log/messages),
|
|
except for the output of scripts and
|
|
ifconfig commands,
|
|
which will go to /dev/null unless otherwise redirected.
|
|
The syslog redirection occurs immediately at the point
|
|
that
|
|
.B \-\-daemon
|
|
is parsed on the command line even though
|
|
the daemonization point occurs later. If one of the
|
|
.B \-\-log
|
|
options is present, it will supercede syslog
|
|
redirection.
|
|
|
|
The optional
|
|
.B progname
|
|
parameter will cause OpenVPN to report its program name
|
|
to the system logger as
|
|
.B progname.
|
|
This can be useful in linking OpenVPN messages
|
|
in the syslog file with specific tunnels.
|
|
When unspecified,
|
|
.B progname
|
|
defaults to "openvpn".
|
|
|
|
When OpenVPN is run with the
|
|
.B \-\-daemon
|
|
option, it will try to delay daemonization until the majority of initialization
|
|
functions which are capable of generating fatal errors are complete. This means
|
|
that initialization scripts can test the return status of the
|
|
openvpn command for a fairly reliable indication of whether the command
|
|
has correctly initialized and entered the packet forwarding event loop.
|
|
|
|
In OpenVPN, the vast majority of errors which occur after initialization are non-fatal.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-syslog [progname]
|
|
Direct log output to system logger, but do not become a daemon.
|
|
See
|
|
.B \-\-daemon
|
|
directive above for description of
|
|
.B progname
|
|
parameter.
|
|
.TP
|
|
.B \-\-errors-to-stderr
|
|
Output errors to stderr instead of stdout unless log output is redirected by one of the
|
|
.B \-\-log
|
|
options.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-passtos
|
|
Set the TOS field of the tunnel packet to what the payload's TOS is.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-inetd [wait|nowait] [progname]
|
|
Use this option when OpenVPN is being run from the inetd or
|
|
.BR xinetd(8)
|
|
server.
|
|
|
|
The
|
|
.B wait/nowait
|
|
option must match what is specified in the inetd/xinetd
|
|
config file. The
|
|
.B nowait
|
|
mode can only be used with
|
|
.B \-\-proto tcp-server.
|
|
The default is
|
|
.B wait.
|
|
The
|
|
.B nowait
|
|
mode can be used to instantiate the OpenVPN daemon as a classic TCP server,
|
|
where client connection requests are serviced on a single
|
|
port number. For additional information on this kind of configuration,
|
|
see the OpenVPN FAQ:
|
|
.I http://openvpn.net/faq.html#oneport
|
|
|
|
This option precludes the use of
|
|
.B \-\-daemon, \-\-local,
|
|
or
|
|
.B \-\-remote.
|
|
Note that this option causes message and error output to be handled in the same
|
|
way as the
|
|
.B \-\-daemon
|
|
option. The optional
|
|
.B progname
|
|
parameter is also handled exactly as in
|
|
.B \-\-daemon.
|
|
|
|
Also note that in
|
|
.B wait
|
|
mode, each OpenVPN tunnel requires a separate TCP/UDP port and
|
|
a separate inetd or xinetd entry. See the OpenVPN 1.x HOWTO for an example
|
|
on using OpenVPN with xinetd:
|
|
.I http://openvpn.net/1xhowto.html
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-log file
|
|
Output logging messages to
|
|
.B file,
|
|
including output to stdout/stderr which
|
|
is generated by called scripts.
|
|
If
|
|
.B file
|
|
already exists it will be truncated.
|
|
This option takes effect
|
|
immediately when it is parsed in the command line
|
|
and will supercede syslog output if
|
|
.B \-\-daemon
|
|
or
|
|
.B \-\-inetd
|
|
is also specified.
|
|
This option is persistent over the entire course of
|
|
an OpenVPN instantiation and will not be reset by SIGHUP,
|
|
SIGUSR1, or
|
|
.B \-\-ping-restart.
|
|
|
|
Note that on Windows, when OpenVPN is started as a service,
|
|
logging occurs by default without the need to specify
|
|
this option.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-log-append file
|
|
Append logging messages to
|
|
.B file.
|
|
If
|
|
.B file
|
|
does not exist, it will be created.
|
|
This option behaves exactly like
|
|
.B \-\-log
|
|
except that it appends to rather
|
|
than truncating the log file.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-suppress-timestamps
|
|
Avoid writing timestamps to log messages, even when they
|
|
otherwise would be prepended. In particular, this applies to
|
|
log messages sent to stdout.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-writepid file
|
|
Write OpenVPN's main process ID to
|
|
.B file.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-nice n
|
|
Change process priority after initialization
|
|
(
|
|
.B n
|
|
greater than 0 is lower priority,
|
|
.B n
|
|
less than zero is higher priority).
|
|
.\"*********************************************************
|
|
.\".TP
|
|
.\".B \-\-nice-work n
|
|
.\"Change priority of background TLS work thread. The TLS thread
|
|
.\"feature is enabled when OpenVPN is built
|
|
.\"with pthread support, and you are running OpenVPN
|
|
.\"in TLS mode (i.e. with
|
|
.\".B \-\-tls-client
|
|
.\"or
|
|
.\".B \-\-tls-server
|
|
.\"specified).
|
|
.\"
|
|
.\"Using a TLS thread offloads the CPU-intensive process of SSL/TLS-based
|
|
.\"key exchange to a background thread so that it does not become
|
|
.\"a latency bottleneck in the tunnel packet forwarding process.
|
|
.\"
|
|
.\"The parameter
|
|
.\".B n
|
|
.\"is interpreted exactly as with the
|
|
.\".B \-\-nice
|
|
.\"option above, but in relation to the work thread rather
|
|
.\"than the main thread.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-fast-io
|
|
(Experimental) Optimize TUN/TAP/UDP I/O writes by avoiding
|
|
a call to poll/epoll/select prior to the write operation. The purpose
|
|
of such a call would normally be to block until the device
|
|
or socket is ready to accept the write. Such blocking is unnecessary
|
|
on some platforms which don't support write blocking on UDP sockets
|
|
or TUN/TAP devices. In such cases, one can optimize the event loop
|
|
by avoiding the poll/epoll/select call, improving CPU efficiency
|
|
by 5% to 10%.
|
|
|
|
This option can only be used on non-Windows systems, when
|
|
.B \-\-proto udp
|
|
is specified, and when
|
|
.B \-\-shaper
|
|
is NOT specified.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-multihome
|
|
Configure a multi-homed UDP server. This option needs to be used when
|
|
a server has more than one IP address (e.g. multiple interfaces, or
|
|
secondary IP addresses), and is not using
|
|
.B \-\-local
|
|
to force binding to one specific address only. This option will
|
|
add some extra lookups to the packet path to ensure that the UDP reply
|
|
packets are always sent from the address that the client is
|
|
talking to. This is not supported on all platforms, and it adds more
|
|
processing, so it's not enabled by default.
|
|
|
|
Note: this option is only relevant for UDP servers.
|
|
|
|
Note 2: if you do an IPv6+IPv4 dual-stack bind on a Linux machine with
|
|
multiple IPv4 address, connections to IPv4 addresses will not work
|
|
right on kernels before 3.15, due to missing kernel support for the
|
|
IPv4-mapped case (some distributions have ported this to earlier kernel
|
|
versions, though).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-echo [parms...]
|
|
Echo
|
|
.B parms
|
|
to log output.
|
|
|
|
Designed to be used to send messages to a controlling application
|
|
which is receiving the OpenVPN log output.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-remap-usr1 signal
|
|
Control whether internally or externally
|
|
generated SIGUSR1 signals are remapped to
|
|
SIGHUP (restart without persisting state) or
|
|
SIGTERM (exit).
|
|
|
|
.B signal
|
|
can be set to "SIGHUP" or "SIGTERM". By default, no remapping
|
|
occurs.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-verb n
|
|
Set output verbosity to
|
|
.B n
|
|
(default=1). Each level shows all info from the previous levels.
|
|
Level 3 is recommended if you want a good summary
|
|
of what's happening without being swamped by output.
|
|
|
|
.B 0 \-\-
|
|
No output except fatal errors.
|
|
.br
|
|
.B 1 to 4 \-\-
|
|
Normal usage range.
|
|
.br
|
|
.B 5 \-\-
|
|
Output
|
|
.B R
|
|
and
|
|
.B W
|
|
characters to the console for each packet read and write, uppercase is
|
|
used for TCP/UDP packets and lowercase is used for TUN/TAP packets.
|
|
.br
|
|
.B 6 to 11 \-\-
|
|
Debug info range (see errlevel.h for additional
|
|
information on debug levels).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-status file [n]
|
|
Write operational status to
|
|
.B file
|
|
every
|
|
.B n
|
|
seconds.
|
|
|
|
Status can also be written to the syslog by sending a
|
|
.B SIGUSR2
|
|
signal.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-status-version [n]
|
|
Choose the status file format version number. Currently
|
|
.B n
|
|
can be 1, 2, or 3 and defaults to 1.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-mute n
|
|
Log at most
|
|
.B n
|
|
consecutive messages in the same category. This is useful to
|
|
limit repetitive logging of similar message types.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-comp-lzo [mode]
|
|
Use fast LZO compression \-\- may add up to 1 byte per
|
|
packet for incompressible data.
|
|
.B mode
|
|
may be "yes", "no", or "adaptive" (default).
|
|
|
|
In a server mode setup, it is possible to selectively turn
|
|
compression on or off for individual clients.
|
|
|
|
First, make sure the client-side config file enables selective
|
|
compression by having at least one
|
|
.B \-\-comp-lzo
|
|
directive, such as
|
|
.B \-\-comp-lzo no.
|
|
This will turn off compression by default,
|
|
but allow a future directive push from the server to
|
|
dynamically change the
|
|
on/off/adaptive setting.
|
|
|
|
Next in a
|
|
.B \-\-client-config-dir
|
|
file, specify the compression setting for the client,
|
|
for example:
|
|
|
|
.nf
|
|
.ft 3
|
|
.in +4
|
|
comp-lzo yes
|
|
push "comp-lzo yes"
|
|
.in -4
|
|
.ft
|
|
.fi
|
|
|
|
The first line sets the
|
|
.B comp-lzo
|
|
setting for the server
|
|
side of the link, the second sets the client side.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-comp-noadapt
|
|
When used in conjunction with
|
|
.B \-\-comp-lzo,
|
|
this option will disable OpenVPN's adaptive compression algorithm.
|
|
Normally, adaptive compression is enabled with
|
|
.B \-\-comp-lzo.
|
|
|
|
Adaptive compression tries to optimize the case where you have
|
|
compression enabled, but you are sending predominantly incompressible
|
|
(or pre-compressed) packets over the tunnel, such as an FTP or rsync transfer
|
|
of a large, compressed file. With adaptive compression,
|
|
OpenVPN will periodically sample the compression process to measure its
|
|
efficiency. If the data being sent over the tunnel is already compressed,
|
|
the compression efficiency will be very low, triggering openvpn to disable
|
|
compression for a period of time until the next re-sample test.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-management IP port [pw-file]
|
|
Enable a TCP server on
|
|
.B IP:port
|
|
to handle daemon management functions.
|
|
.B pw-file,
|
|
if specified,
|
|
is a password file (password on first line)
|
|
or "stdin" to prompt from standard input. The password
|
|
provided will set the password which TCP clients will need
|
|
to provide in order to access management functions.
|
|
|
|
The management interface can also listen on a unix domain socket,
|
|
for those platforms that support it. To use a unix domain socket, specify
|
|
the unix socket pathname in place of
|
|
.B IP
|
|
and set
|
|
.B port
|
|
to 'unix'. While the default behavior is to create a unix domain socket
|
|
that may be connected to by any process, the
|
|
.B \-\-management-client-user
|
|
and
|
|
.B \-\-management-client-group
|
|
directives can be used to restrict access.
|
|
|
|
The management interface provides a special mode where the TCP
|
|
management link can operate over the tunnel itself. To enable this mode,
|
|
set
|
|
.B IP
|
|
= "tunnel". Tunnel mode will cause the management interface
|
|
to listen for a TCP connection on the local VPN address of the
|
|
TUN/TAP interface.
|
|
|
|
While the management port is designed for programmatic control
|
|
of OpenVPN by other applications, it is possible to telnet
|
|
to the port, using a telnet client in "raw" mode. Once connected,
|
|
type "help" for a list of commands.
|
|
|
|
For detailed documentation on the management interface, see
|
|
the management-notes.txt file in the
|
|
.B management
|
|
folder of
|
|
the OpenVPN source distribution.
|
|
|
|
It is strongly recommended that
|
|
.B IP
|
|
be set to 127.0.0.1
|
|
(localhost) to restrict accessibility of the management
|
|
server to local clients.
|
|
.TP
|
|
.B \-\-management-client
|
|
Management interface will connect as a TCP/unix domain client to
|
|
.B IP:port
|
|
specified by
|
|
.B \-\-management
|
|
rather than listen as a TCP server or on a unix domain socket.
|
|
|
|
If the client connection fails to connect or is disconnected,
|
|
a SIGTERM signal will be generated causing OpenVPN to quit.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-management-query-passwords
|
|
Query management channel for private key password and
|
|
.B \-\-auth-user-pass
|
|
username/password. Only query the management channel
|
|
for inputs which ordinarily would have been queried from the
|
|
console.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-management-query-proxy
|
|
Query management channel for proxy server information for a specific
|
|
.B \-\-remote
|
|
(client-only).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-management-query-remote
|
|
Allow management interface to override
|
|
.B \-\-remote
|
|
directives (client-only).
|
|
.\"*********************************************************
|
|
.B \-\-management-external-key
|
|
Allows usage for external private key file instead of
|
|
.B \-\-key
|
|
option (client-only).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-management-forget-disconnect
|
|
Make OpenVPN forget passwords when management session
|
|
disconnects.
|
|
|
|
This directive does not affect the
|
|
.B \-\-http-proxy
|
|
username/password. It is always cached.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-management-hold
|
|
Start OpenVPN in a hibernating state, until a client
|
|
of the management interface explicitly starts it
|
|
with the
|
|
.B hold release
|
|
command.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-management-signal
|
|
Send SIGUSR1 signal to OpenVPN if management session disconnects.
|
|
This is useful when you wish to disconnect an OpenVPN session on
|
|
user logoff. For --management-client this option is not needed since
|
|
a disconnect will always generate a SIGTERM.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-management-log-cache n
|
|
Cache the most recent
|
|
.B n
|
|
lines of log file history for usage
|
|
by the management channel.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-management-up-down
|
|
Report tunnel up/down events to management interface.
|
|
.B
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-management-client-auth
|
|
Gives management interface client the responsibility
|
|
to authenticate clients after their client certificate
|
|
has been verified. See management-notes.txt in OpenVPN
|
|
distribution for detailed notes.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-management-client-pf
|
|
Management interface clients must specify a packet
|
|
filter file for each connecting client. See management-notes.txt
|
|
in OpenVPN distribution for detailed notes.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-management-client-user u
|
|
When the management interface is listening on a unix domain socket,
|
|
only allow connections from user
|
|
.B u.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-management-client-group g
|
|
When the management interface is listening on a unix domain socket,
|
|
only allow connections from group
|
|
.B g.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-plugin module-pathname [init-string]
|
|
Load plug-in module from the file
|
|
.B module-pathname,
|
|
passing
|
|
.B init-string
|
|
as an argument
|
|
to the module initialization function. Multiple
|
|
plugin modules may be loaded into one OpenVPN
|
|
process.
|
|
|
|
For more information and examples on how to build OpenVPN
|
|
plug-in modules, see the README file in the
|
|
.B plugin
|
|
folder of the OpenVPN source distribution.
|
|
|
|
If you are using an RPM install of OpenVPN, see
|
|
/usr/share/openvpn/plugin. The documentation is
|
|
in
|
|
.B doc
|
|
and the actual plugin modules are in
|
|
.B lib.
|
|
|
|
Multiple plugin modules can be cascaded, and modules can be
|
|
used in tandem with scripts. The modules will be called by
|
|
OpenVPN in the order that they are declared in the config
|
|
file. If both a plugin and script are configured for the same
|
|
callback, the script will be called last. If the
|
|
return code of the module/script controls an authentication
|
|
function (such as tls-verify, auth-user-pass-verify, or
|
|
client-connect), then
|
|
every module and script must return success (0) in order for
|
|
the connection to be authenticated.
|
|
.\"*********************************************************
|
|
.SS Server Mode
|
|
Starting with OpenVPN 2.0, a multi-client TCP/UDP server mode
|
|
is supported, and can be enabled with the
|
|
.B \-\-mode server
|
|
option. In server mode, OpenVPN will listen on a single
|
|
port for incoming client connections. All client
|
|
connections will be routed through a single tun or tap
|
|
interface. This mode is designed for scalability and should
|
|
be able to support hundreds or even thousands of clients
|
|
on sufficiently fast hardware. SSL/TLS authentication must
|
|
be used in this mode.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-server network netmask ['nopool']
|
|
A helper directive designed to simplify the configuration
|
|
of OpenVPN's server mode. This directive will set up an
|
|
OpenVPN server which will allocate addresses to clients
|
|
out of the given network/netmask. The server itself
|
|
will take the ".1" address of the given network
|
|
for use as the server-side endpoint of the local
|
|
TUN/TAP interface.
|
|
|
|
For example,
|
|
.B \-\-server 10.8.0.0 255.255.255.0
|
|
expands as follows:
|
|
|
|
.nf
|
|
.ft 3
|
|
.in +4
|
|
mode server
|
|
tls-server
|
|
push "topology [topology]"
|
|
|
|
if dev tun AND (topology == net30 OR topology == p2p):
|
|
ifconfig 10.8.0.1 10.8.0.2
|
|
if !nopool:
|
|
ifconfig-pool 10.8.0.4 10.8.0.251
|
|
route 10.8.0.0 255.255.255.0
|
|
if client-to-client:
|
|
push "route 10.8.0.0 255.255.255.0"
|
|
else if topology == net30:
|
|
push "route 10.8.0.1"
|
|
|
|
if dev tap OR (dev tun AND topology == subnet):
|
|
ifconfig 10.8.0.1 255.255.255.0
|
|
if !nopool:
|
|
ifconfig-pool 10.8.0.2 10.8.0.254 255.255.255.0
|
|
push "route-gateway 10.8.0.1"
|
|
if route-gateway unset:
|
|
route-gateway 10.8.0.2
|
|
|
|
.in -4
|
|
.ft
|
|
.fi
|
|
|
|
Don't use
|
|
.B \-\-server
|
|
if you are ethernet bridging. Use
|
|
.B \-\-server-bridge
|
|
instead.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-server-bridge gateway netmask pool-start-IP pool-end-IP
|
|
.TP
|
|
.B \-\-server-bridge ['nogw']
|
|
|
|
A helper directive similar to
|
|
.B \-\-server
|
|
which is designed to simplify the configuration
|
|
of OpenVPN's server mode in ethernet bridging configurations.
|
|
|
|
If
|
|
.B \-\-server-bridge
|
|
is used without any parameters, it will enable a DHCP-proxy
|
|
mode, where connecting OpenVPN clients will receive an IP
|
|
address for their TAP adapter from the DHCP server running
|
|
on the OpenVPN server-side LAN.
|
|
Note that only clients that support
|
|
the binding of a DHCP client with the TAP adapter (such as
|
|
Windows) can support this mode. The optional
|
|
.B nogw
|
|
flag (advanced) indicates that gateway information should not be
|
|
pushed to the client.
|
|
|
|
To configure ethernet bridging, you
|
|
must first use your OS's bridging capability
|
|
to bridge the TAP interface with the ethernet
|
|
NIC interface. For example, on Linux this is done
|
|
with the
|
|
.B brctl
|
|
tool, and with Windows XP it is done in the Network
|
|
Connections Panel by selecting the ethernet and
|
|
TAP adapters and right-clicking on "Bridge Connections".
|
|
|
|
Next you you must manually set the
|
|
IP/netmask on the bridge interface. The
|
|
.B gateway
|
|
and
|
|
.B netmask
|
|
parameters to
|
|
.B \-\-server-bridge
|
|
can be set to either the IP/netmask of the
|
|
bridge interface, or the IP/netmask of the
|
|
default gateway/router on the bridged
|
|
subnet.
|
|
|
|
Finally, set aside a IP range in the bridged
|
|
subnet,
|
|
denoted by
|
|
.B pool-start-IP
|
|
and
|
|
.B pool-end-IP,
|
|
for OpenVPN to allocate to connecting
|
|
clients.
|
|
|
|
For example,
|
|
.B server-bridge 10.8.0.4 255.255.255.0 10.8.0.128 10.8.0.254
|
|
expands as follows:
|
|
|
|
.nf
|
|
.ft 3
|
|
.in +4
|
|
mode server
|
|
tls-server
|
|
|
|
ifconfig-pool 10.8.0.128 10.8.0.254 255.255.255.0
|
|
push "route-gateway 10.8.0.4"
|
|
.in -4
|
|
.ft
|
|
.fi
|
|
|
|
In another example,
|
|
.B \-\-server-bridge
|
|
(without parameters) expands as follows:
|
|
|
|
.nf
|
|
.ft 3
|
|
.in +4
|
|
mode server
|
|
tls-server
|
|
|
|
push "route-gateway dhcp"
|
|
.in -4
|
|
.ft
|
|
.fi
|
|
|
|
Or
|
|
.B \-\-server-bridge nogw
|
|
expands as follows:
|
|
|
|
.nf
|
|
.ft 3
|
|
.in +4
|
|
mode server
|
|
tls-server
|
|
.in -4
|
|
.ft
|
|
.fi
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-push "option"
|
|
Push a config file option back to the client for remote
|
|
execution. Note that
|
|
.B
|
|
option
|
|
must be enclosed in double quotes (""). The client must specify
|
|
.B \-\-pull
|
|
in its config file. The set of options which can be
|
|
pushed is limited by both feasibility and security.
|
|
Some options such as those which would execute scripts
|
|
are banned, since they would effectively allow a compromised
|
|
server to execute arbitrary code on the client.
|
|
Other options such as TLS or MTU parameters
|
|
cannot be pushed because the client needs to know
|
|
them before the connection to the server can be initiated.
|
|
|
|
This is a partial list of options which can currently be pushed:
|
|
.B \-\-route, \-\-route-gateway, \-\-route-delay, \-\-redirect-gateway,
|
|
.B \-\-ip-win32, \-\-dhcp-option,
|
|
.B \-\-inactive, \-\-ping, \-\-ping-exit, \-\-ping-restart,
|
|
.B \-\-setenv,
|
|
.B \-\-persist-key, \-\-persist-tun, \-\-echo,
|
|
.B \-\-comp-lzo,
|
|
.B \-\-socket-flags,
|
|
.B \-\-sndbuf, \-\-rcvbuf
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-push-reset
|
|
Don't inherit the global push list for a specific client instance.
|
|
Specify this option in a client-specific context such
|
|
as with a
|
|
.B \-\-client-config-dir
|
|
configuration file. This option will ignore
|
|
.B \-\-push
|
|
options at the global config file level.
|
|
.TP
|
|
.B \-\-push-peer-info
|
|
Push additional information about the client to server. The additional information
|
|
consists of the following data:
|
|
|
|
IV_VER=<version> -- the client OpenVPN version
|
|
|
|
IV_PLAT=[linux|solaris|openbsd|mac|netbsd|freebsd|win] -- the client OS platform
|
|
|
|
IV_HWADDR=<mac address> -- the MAC address of clients default gateway
|
|
|
|
IV_LZO_STUB=1 -- if client was built with LZO stub capability
|
|
|
|
UV_<name>=<value> -- client environment variables whose names start with "UV_"
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-disable
|
|
Disable a particular client (based on the common name)
|
|
from connecting. Don't use this option to disable a client
|
|
due to key or password compromise. Use a CRL (certificate
|
|
revocation list) instead (see the
|
|
.B \-\-crl-verify
|
|
option).
|
|
|
|
This option must be associated with a specific client instance,
|
|
which means that it must be specified either in a client
|
|
instance config file using
|
|
.B \-\-client-config-dir
|
|
or dynamically generated using a
|
|
.B \-\-client-connect
|
|
script.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ifconfig-pool start-IP end-IP [netmask]
|
|
Set aside a pool of subnets to be
|
|
dynamically allocated to connecting clients, similar
|
|
to a DHCP server. For tun-style
|
|
tunnels, each client will be given a /30 subnet (for
|
|
interoperability with Windows clients). For tap-style
|
|
tunnels, individual addresses will be allocated, and the
|
|
optional
|
|
.B netmask
|
|
parameter will also be pushed to clients.
|
|
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ifconfig-pool-persist file [seconds]
|
|
Persist/unpersist ifconfig-pool
|
|
data to
|
|
.B file,
|
|
at
|
|
.B seconds
|
|
intervals (default=600), as well as on program startup and
|
|
shutdown.
|
|
|
|
The goal of this option is to provide a long-term association
|
|
between clients (denoted by their common name) and the virtual
|
|
IP address assigned to them from the ifconfig-pool.
|
|
Maintaining a long-term
|
|
association is good for clients because it allows them
|
|
to effectively use the
|
|
.B \-\-persist-tun
|
|
option.
|
|
|
|
.B file
|
|
is a comma-delimited ASCII file, formatted as
|
|
<Common-Name>,<IP-address>.
|
|
|
|
If
|
|
.B seconds
|
|
= 0,
|
|
.B file
|
|
will be treated as read-only. This is useful if
|
|
you would like to treat
|
|
.B file
|
|
as a configuration file.
|
|
|
|
Note that the entries in this file are treated by OpenVPN as
|
|
suggestions only, based on past associations between
|
|
a common name and IP address. They do not guarantee that the given common
|
|
name will always receive the given IP address. If you want guaranteed
|
|
assignment, use
|
|
.B \-\-ifconfig-push
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ifconfig-pool-linear
|
|
Modifies the
|
|
.B \-\-ifconfig-pool
|
|
directive to
|
|
allocate individual TUN interface addresses for
|
|
clients rather than /30 subnets. NOTE: This option
|
|
is incompatible with Windows clients.
|
|
|
|
This option is deprecated, and should be replaced with
|
|
.B \-\-topology p2p
|
|
which is functionally equivalent.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ifconfig-push local remote-netmask [alias]
|
|
Push virtual IP endpoints for client tunnel,
|
|
overriding the \-\-ifconfig-pool dynamic allocation.
|
|
|
|
The parameters
|
|
.B local
|
|
and
|
|
.B remote-netmask
|
|
are set according to the
|
|
.B \-\-ifconfig
|
|
directive which you want to execute on the client machine to
|
|
configure the remote end of the tunnel. Note that the parameters
|
|
.B local
|
|
and
|
|
.B remote-netmask
|
|
are from the perspective of the client, not the server. They may be
|
|
DNS names rather than IP addresses, in which case they will be resolved
|
|
on the server at the time of client connection.
|
|
|
|
The optional
|
|
.B alias
|
|
parameter may be used in cases where NAT causes the client view
|
|
of its local endpoint to differ from the server view. In this case
|
|
.B local/remote-netmask
|
|
will refer to the server view while
|
|
.B alias/remote-netmask
|
|
will refer to the client view.
|
|
|
|
This option must be associated with a specific client instance,
|
|
which means that it must be specified either in a client
|
|
instance config file using
|
|
.B \-\-client-config-dir
|
|
or dynamically generated using a
|
|
.B \-\-client-connect
|
|
script.
|
|
|
|
Remember also to include a
|
|
.B \-\-route
|
|
directive in the main OpenVPN config file which encloses
|
|
.B local,
|
|
so that the kernel will know to route it
|
|
to the server's TUN/TAP interface.
|
|
|
|
OpenVPN's internal client IP address selection algorithm works as
|
|
follows:
|
|
|
|
.B 1
|
|
\-\- Use
|
|
.B \-\-client-connect script
|
|
generated file for static IP (first choice).
|
|
.br
|
|
.B 2
|
|
\-\- Use
|
|
.B \-\-client-config-dir
|
|
file for static IP (next choice).
|
|
.br
|
|
.B 3
|
|
\-\- Use
|
|
.B \-\-ifconfig-pool
|
|
allocation for dynamic IP (last choice).
|
|
.br
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-iroute network [netmask]
|
|
Generate an internal route to a specific
|
|
client. The
|
|
.B netmask
|
|
parameter, if omitted, defaults to 255.255.255.255.
|
|
|
|
This directive can be used to route a fixed subnet from
|
|
the server to a particular client, regardless
|
|
of where the client is connecting from. Remember
|
|
that you must also add the route to the system
|
|
routing table as well (such as by using the
|
|
.B \-\-route
|
|
directive). The reason why two routes are needed
|
|
is that the
|
|
.B \-\-route
|
|
directive routes the packet from the kernel
|
|
to OpenVPN. Once in OpenVPN, the
|
|
.B \-\-iroute
|
|
directive routes to the specific client.
|
|
|
|
This option must be specified either in a client
|
|
instance config file using
|
|
.B \-\-client-config-dir
|
|
or dynamically generated using a
|
|
.B \-\-client-connect
|
|
script.
|
|
|
|
The
|
|
.B \-\-iroute
|
|
directive also has an important interaction with
|
|
.B \-\-push
|
|
"route ...".
|
|
.B \-\-iroute
|
|
essentially defines a subnet which is owned by a
|
|
particular client (we will call this client A).
|
|
If you would like other clients to be able to reach A's
|
|
subnet, you can use
|
|
.B \-\-push
|
|
"route ..."
|
|
together with
|
|
.B \-\-client-to-client
|
|
to effect this. In order for all clients to see
|
|
A's subnet, OpenVPN must push this route to all clients
|
|
EXCEPT for A, since the subnet is already owned by A.
|
|
OpenVPN accomplishes this by not
|
|
not pushing a route to a client
|
|
if it matches one of the client's iroutes.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-client-to-client
|
|
Because the OpenVPN server mode handles multiple clients
|
|
through a single tun or tap interface, it is effectively
|
|
a router. The
|
|
.B \-\-client-to-client
|
|
flag tells OpenVPN to internally route client-to-client
|
|
traffic rather than pushing all client-originating traffic
|
|
to the TUN/TAP interface.
|
|
|
|
When this option is used, each client will "see" the other
|
|
clients which are currently connected. Otherwise, each
|
|
client will only see the server. Don't use this option
|
|
if you want to firewall tunnel traffic using
|
|
custom, per-client rules.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-duplicate-cn
|
|
Allow multiple clients with the same common name to concurrently connect.
|
|
In the absence of this option, OpenVPN will disconnect a client instance
|
|
upon connection of a new client having the same common name.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-client-connect cmd
|
|
Run
|
|
.B command cmd
|
|
on client connection.
|
|
|
|
.B cmd
|
|
consists of a path to script (or executable program), optionally
|
|
followed by arguments. The path and arguments may be single- or double-quoted
|
|
and/or escaped using a backslash, and should be separated by one or more spaces.
|
|
|
|
The command is passed the common name
|
|
and IP address of the just-authenticated client
|
|
as environmental variables (see environmental variable section
|
|
below). The command is also passed
|
|
the pathname of a freshly created temporary file as the last argument
|
|
(after any arguments specified in
|
|
.B cmd
|
|
), to be used by the command
|
|
to pass dynamically generated config file directives back to OpenVPN.
|
|
|
|
If the script wants to generate a dynamic config file
|
|
to be applied on the server when the client connects,
|
|
it should write it to the file named by the last argument.
|
|
|
|
See the
|
|
.B \-\-client-config-dir
|
|
option below for options which
|
|
can be legally used in a dynamically generated config file.
|
|
|
|
Note that the return value of
|
|
.B script
|
|
is significant. If
|
|
.B script
|
|
returns a non-zero error status, it will cause the client
|
|
to be disconnected.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-client-disconnect cmd
|
|
Like
|
|
.B \-\-client-connect
|
|
but called on client instance shutdown. Will not be called
|
|
unless the
|
|
.B \-\-client-connect
|
|
script and plugins (if defined)
|
|
were previously called on this instance with
|
|
successful (0) status returns.
|
|
|
|
The exception to this rule is if the
|
|
.B \-\-client-disconnect
|
|
command or plugins are cascaded, and at least one client-connect
|
|
function succeeded, then ALL of the client-disconnect functions for
|
|
scripts and plugins will be called on client instance object deletion,
|
|
even in cases where some of the related client-connect functions returned
|
|
an error status.
|
|
|
|
The
|
|
.B \-\-client-disconnect
|
|
command is passed the same pathname as the corresponding
|
|
.B \-\-client-connect
|
|
command as its last argument. (after any arguments specified in
|
|
.B cmd
|
|
).
|
|
.B
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-client-config-dir dir
|
|
Specify a directory
|
|
.B dir
|
|
for custom client config files. After
|
|
a connecting client has been authenticated, OpenVPN will
|
|
look in this directory for a file having the same name
|
|
as the client's X509 common name. If a matching file
|
|
exists, it will be opened and parsed for client-specific
|
|
configuration options. If no matching file is found, OpenVPN
|
|
will instead try to open and parse a default file called
|
|
"DEFAULT", which may be provided but is not required. Note that
|
|
the configuration files must be readable by the OpenVPN process
|
|
after it has dropped it's root privileges.
|
|
|
|
This file can specify a fixed IP address for a given
|
|
client using
|
|
.B \-\-ifconfig-push,
|
|
as well as fixed subnets owned by the client using
|
|
.B \-\-iroute.
|
|
|
|
One of the useful properties of this option is that it
|
|
allows client configuration files to be conveniently
|
|
created, edited, or removed while the server is live,
|
|
without needing to restart the server.
|
|
|
|
The following
|
|
options are legal in a client-specific context:
|
|
.B \-\-push, \-\-push-reset, \-\-iroute, \-\-ifconfig-push,
|
|
and
|
|
.B \-\-config.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ccd-exclusive
|
|
Require, as a
|
|
condition of authentication, that a connecting client has a
|
|
.B \-\-client-config-dir
|
|
file.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tmp-dir dir
|
|
Specify a directory
|
|
.B dir
|
|
for temporary files. This directory will be used by
|
|
openvpn processes and script to communicate temporary
|
|
data with openvpn main process. Note that
|
|
the directory must be writable by the OpenVPN process
|
|
after it has dropped it's root privileges.
|
|
|
|
This directory will be used by in the following cases:
|
|
|
|
*
|
|
.B \-\-client-connect
|
|
scripts to dynamically generate client-specific
|
|
configuration files.
|
|
|
|
*
|
|
.B OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY
|
|
plugin hook to return success/failure via auth_control_file
|
|
when using deferred auth method
|
|
|
|
*
|
|
.B OPENVPN_PLUGIN_ENABLE_PF
|
|
plugin hook to pass filtering rules via pf_file
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-hash-size r v
|
|
Set the size of the real address hash table to
|
|
.B r
|
|
and the virtual address table to
|
|
.B v.
|
|
By default, both tables are sized at 256 buckets.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-bcast-buffers n
|
|
Allocate
|
|
.B n
|
|
buffers for broadcast datagrams (default=256).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tcp-queue-limit n
|
|
Maximum number of output packets queued before TCP (default=64).
|
|
|
|
When OpenVPN is tunneling data from a TUN/TAP device to a
|
|
remote client over a TCP connection, it is possible that the TUN/TAP device
|
|
might produce data at a faster rate than the TCP connection
|
|
can support. When the number of output packets queued before sending to
|
|
the TCP socket reaches this limit for a given client connection,
|
|
OpenVPN will start to drop outgoing packets directed
|
|
at this client.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tcp-nodelay
|
|
This macro sets the TCP_NODELAY socket flag on the server
|
|
as well as pushes it to connecting clients. The TCP_NODELAY
|
|
flag disables the Nagle algorithm on TCP sockets causing
|
|
packets to be transmitted immediately with low latency,
|
|
rather than waiting a short period of time in order
|
|
to aggregate several packets into a larger containing
|
|
packet. In VPN applications over TCP, TCP_NODELAY
|
|
is generally a good latency optimization.
|
|
|
|
The macro expands as follows:
|
|
|
|
.nf
|
|
.ft 3
|
|
.in +4
|
|
if mode server:
|
|
socket-flags TCP_NODELAY
|
|
push "socket-flags TCP_NODELAY"
|
|
.in -4
|
|
.ft
|
|
.fi
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-max-clients n
|
|
Limit server to a maximum of
|
|
.B n
|
|
concurrent clients.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-max-routes-per-client n
|
|
Allow a maximum of
|
|
.B n
|
|
internal routes per client (default=256).
|
|
This is designed to
|
|
help contain DoS attacks where an authenticated client floods the
|
|
server with packets appearing to come from many unique MAC addresses,
|
|
forcing the server to deplete
|
|
virtual memory as its internal routing table expands.
|
|
This directive can be used in a
|
|
.B \-\-client-config-dir
|
|
file or auto-generated by a
|
|
.B \-\-client-connect
|
|
script to override the global value for a particular client.
|
|
|
|
Note that this
|
|
directive affects OpenVPN's internal routing table, not the
|
|
kernel routing table.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-stale-routes-check n [t]
|
|
Remove routes haven't had activity for
|
|
.B n
|
|
seconds (i.e. the ageing time).
|
|
|
|
This check is ran every
|
|
.B t
|
|
seconds (i.e. check interval).
|
|
|
|
If
|
|
.B t
|
|
is not present it defaults to
|
|
.B n
|
|
|
|
This option helps to keep the dynamic routing table small.
|
|
See also
|
|
.B \-\-max-routes-per-client
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-connect-freq n sec
|
|
Allow a maximum of
|
|
.B n
|
|
new connections per
|
|
.B sec
|
|
seconds from clients. This is designed to contain DoS attacks which flood
|
|
the server with connection requests using certificates which
|
|
will ultimately fail to authenticate.
|
|
|
|
This is an imperfect solution however, because in a real
|
|
DoS scenario, legitimate connections might also be refused.
|
|
|
|
For the best protection against DoS attacks in server mode,
|
|
use
|
|
.B \-\-proto udp
|
|
and
|
|
.B \-\-tls-auth.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-learn-address cmd
|
|
Run command
|
|
.B cmd
|
|
to validate client virtual addresses or routes.
|
|
|
|
.B cmd
|
|
consists of a path to script (or executable program), optionally
|
|
followed by arguments. The path and arguments may be single- or double-quoted
|
|
and/or escaped using a backslash, and should be separated by one or more spaces.
|
|
|
|
Three arguments will be appended to any arguments in
|
|
.B cmd
|
|
as follows:
|
|
|
|
.B [1] operation \-\-
|
|
"add", "update", or "delete" based on whether or not
|
|
the address is being added to, modified, or deleted from
|
|
OpenVPN's internal routing table.
|
|
.br
|
|
.B [2] address \-\-
|
|
The address being learned or unlearned. This can be
|
|
an IPv4 address such as "198.162.10.14", an IPv4 subnet
|
|
such as "198.162.10.0/24", or an ethernet MAC address (when
|
|
.B \-\-dev tap
|
|
is being used) such as "00:FF:01:02:03:04".
|
|
.br
|
|
.B [3] common name \-\-
|
|
The common name on the certificate associated with the
|
|
client linked to this address. Only present for "add"
|
|
or "update" operations, not "delete".
|
|
|
|
On "add" or "update" methods, if the script returns
|
|
a failure code (non-zero), OpenVPN will reject the address
|
|
and will not modify its internal routing table.
|
|
|
|
Normally, the
|
|
.B cmd
|
|
script will use the information provided above to set
|
|
appropriate firewall entries on the VPN TUN/TAP interface.
|
|
Since OpenVPN provides the association between virtual IP
|
|
or MAC address and the client's authenticated common name,
|
|
it allows a user-defined script to configure firewall access
|
|
policies with regard to the client's high-level common name,
|
|
rather than the low level client virtual addresses.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-auth-user-pass-verify cmd method
|
|
Require the client to provide a username/password (possibly
|
|
in addition to a client certificate) for authentication.
|
|
|
|
OpenVPN will run
|
|
.B command cmd
|
|
to validate the username/password
|
|
provided by the client.
|
|
|
|
.B cmd
|
|
consists of a path to script (or executable program), optionally
|
|
followed by arguments. The path and arguments may be single- or double-quoted
|
|
and/or escaped using a backslash, and should be separated by one or more spaces.
|
|
|
|
If
|
|
.B method
|
|
is set to "via-env", OpenVPN will call
|
|
.B script
|
|
with the environmental variables
|
|
.B username
|
|
and
|
|
.B password
|
|
set to the username/password strings provided by the client.
|
|
Be aware that this method is insecure on some platforms which
|
|
make the environment of a process publicly visible to other
|
|
unprivileged processes.
|
|
|
|
If
|
|
.B method
|
|
is set to "via-file", OpenVPN will write the username and
|
|
password to the first two lines of a temporary file. The filename
|
|
will be passed as an argument to
|
|
.B script,
|
|
and the file will be automatically deleted by OpenVPN after
|
|
the script returns. The location of the temporary file is
|
|
controlled by the
|
|
.B \-\-tmp-dir
|
|
option, and will default to the current directory if unspecified.
|
|
For security, consider setting
|
|
.B \-\-tmp-dir
|
|
to a volatile storage medium such as
|
|
.B /dev/shm
|
|
(if available) to prevent the username/password file from touching the hard drive.
|
|
|
|
The script should examine the username
|
|
and password,
|
|
returning a success exit code (0) if the
|
|
client's authentication request is to be accepted, or a failure
|
|
code (1) to reject the client.
|
|
|
|
This directive is designed to enable a plugin-style interface
|
|
for extending OpenVPN's authentication capabilities.
|
|
|
|
To protect against a client passing a maliciously formed
|
|
username or password string, the username string must
|
|
consist only of these characters: alphanumeric, underbar
|
|
('_'), dash ('-'), dot ('.'), or at ('@'). The password
|
|
string can consist of any printable characters except for
|
|
CR or LF. Any illegal characters in either the username
|
|
or password string will be converted to underbar ('_').
|
|
|
|
Care must be taken by any user-defined scripts to avoid
|
|
creating a security vulnerability in the way that these
|
|
strings are handled. Never use these strings in such a way
|
|
that they might be escaped or evaluated by a shell interpreter.
|
|
|
|
For a sample script that performs PAM authentication, see
|
|
.B sample-scripts/auth-pam.pl
|
|
in the OpenVPN source distribution.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-opt-verify
|
|
Clients that connect with options that are incompatible
|
|
with those of the server will be disconnected.
|
|
|
|
Options that will be compared for compatibility include
|
|
dev-type, link-mtu, tun-mtu, proto, tun-ipv6, ifconfig,
|
|
comp-lzo, fragment, keydir, cipher, auth, keysize, secret,
|
|
no-replay, no-iv, tls-auth, key-method, tls-server, and tls-client.
|
|
|
|
This option requires that
|
|
.B \-\-disable-occ
|
|
NOT be used.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-auth-user-pass-optional
|
|
Allow connections by clients that do not specify a username/password.
|
|
Normally, when
|
|
.B \-\-auth-user-pass-verify
|
|
or
|
|
.B \-\-management-client-auth
|
|
is specified (or an authentication plugin module), the
|
|
OpenVPN server daemon will require connecting clients to specify a
|
|
username and password. This option makes the submission of a username/password
|
|
by clients optional, passing the responsibility to the user-defined authentication
|
|
module/script to accept or deny the client based on other factors
|
|
(such as the setting of X509 certificate fields). When this option is used,
|
|
and a connecting client does not submit a username/password, the user-defined
|
|
authentication module/script will see the username and password as being set
|
|
to empty strings (""). The authentication module/script MUST have logic
|
|
to detect this condition and respond accordingly.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-client-cert-not-required
|
|
Don't require client certificate, client will authenticate
|
|
using username/password only. Be aware that using this directive
|
|
is less secure than requiring certificates from all clients.
|
|
|
|
If you use this directive, the
|
|
entire responsibility of authentication will rest on your
|
|
.B \-\-auth-user-pass-verify
|
|
script, so keep in mind that bugs in your script
|
|
could potentially compromise the security of your VPN.
|
|
|
|
If you don't use this directive, but you also specify an
|
|
.B \-\-auth-user-pass-verify
|
|
script, then OpenVPN will perform double authentication. The
|
|
client certificate verification AND the
|
|
.B \-\-auth-user-pass-verify
|
|
script will need to succeed in order for a client to be
|
|
authenticated and accepted onto the VPN.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-username-as-common-name
|
|
For
|
|
.B \-\-auth-user-pass-verify
|
|
authentication, use
|
|
the authenticated username as the common name,
|
|
rather than the common name from the client cert.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-compat\-names [no\-remapping] (DEPRECATED)
|
|
Until OpenVPN v2.3 the format of the X.509 Subject fields was formatted
|
|
like this:
|
|
.IP
|
|
.B
|
|
/C=US/L=Somewhere/CN=John Doe/emailAddress=john@example.com
|
|
.IP
|
|
In addition the old behaviour was to remap any character other than
|
|
alphanumeric, underscore ('_'), dash ('-'), dot ('.'), and slash ('/') to
|
|
underscore ('_'). The X.509 Subject string as returned by the
|
|
.B tls_id
|
|
environmental variable, could additionally contain colon (':') or equal ('=').
|
|
.IP
|
|
When using the
|
|
.B \-\-compat\-names
|
|
option, this old formatting and remapping will be re-enabled again. This is
|
|
purely implemented for compatibility reasons when using older plug-ins or
|
|
scripts which does not handle the new formatting or UTF-8 characters.
|
|
.IP
|
|
In OpenVPN v2.3 the formatting of these fields changed into a more
|
|
standardised format. It now looks like:
|
|
.IP
|
|
.B
|
|
C=US, L=Somewhere, CN=John Doe, emailAddress=john@example.com
|
|
.IP
|
|
The new default format in OpenVPN v2.3 also does not do the character remapping
|
|
which happened earlier. This new format enables proper support for UTF\-8
|
|
characters in the usernames, X.509 Subject fields and Common Name variables and
|
|
it complies to the RFC 2253, UTF\-8 String Representation of Distinguished
|
|
Names.
|
|
|
|
The
|
|
.B no\-remapping
|
|
mode flag can be used with the
|
|
.B
|
|
\-\-compat\-names
|
|
option to be compatible with the now deprecated \-\-no\-name\-remapping option.
|
|
It is only available at the server. When this mode flag is used, the Common Name,
|
|
Subject, and username strings are allowed to include any printable character
|
|
including space, but excluding control characters such as tab, newline, and
|
|
carriage-return. no-remapping is only available on the server side.
|
|
|
|
.B Please note:
|
|
This option is immediately deprecated. It is only implemented
|
|
to make the transition to the new formatting less intrusive. It will be
|
|
removed either in OpenVPN v2.4 or v2.5. So please make sure you use the
|
|
.B \-\-verify-x509-name
|
|
option instead of
|
|
.B \-\-tls-remote
|
|
as soon as possible and update your scripts where necessary.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-no\-name\-remapping (DEPRECATED)
|
|
The
|
|
.B \-\-no\-name\-remapping
|
|
option is an alias for
|
|
.B \-\-compat\-names\ no\-remapping.
|
|
It ensures compatibility with server configurations using the
|
|
.B \-\-no\-name\-remapping
|
|
option.
|
|
|
|
.B Please note:
|
|
This option is now deprecated. It will be removed either in OpenVPN v2.4
|
|
or v2.5. So please make sure you support the new X.509 name formatting
|
|
described with the
|
|
.B \-\-compat\-names
|
|
option as soon as possible.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-port-share host port [dir]
|
|
When run in TCP server mode, share the OpenVPN port with
|
|
another application, such as an HTTPS server. If OpenVPN
|
|
senses a connection to its port which is using a non-OpenVPN
|
|
protocol, it will proxy the connection to the server at
|
|
.B host:port.
|
|
Currently only designed to work with HTTP/HTTPS,
|
|
though it would be theoretically possible to extend to
|
|
other protocols such as ssh.
|
|
|
|
.B dir
|
|
specifies an optional directory where a temporary file with name N
|
|
containing content C will be dynamically generated for each proxy
|
|
connection, where N is the source IP:port of the client connection
|
|
and C is the source IP:port of the connection to the proxy
|
|
receiver. This directory can be used as a dictionary by
|
|
the proxy receiver to determine the origin of the connection.
|
|
Each generated file will be automatically deleted when the proxied
|
|
connection is torn down.
|
|
|
|
Not implemented on Windows.
|
|
.\"*********************************************************
|
|
.SS Client Mode
|
|
Use client mode when connecting to an OpenVPN server
|
|
which has
|
|
.B \-\-server, \-\-server-bridge,
|
|
or
|
|
.B \-\-mode server
|
|
in it's configuration.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-client
|
|
A helper directive designed to simplify the configuration
|
|
of OpenVPN's client mode. This directive is equivalent to:
|
|
|
|
.nf
|
|
.ft 3
|
|
.in +4
|
|
pull
|
|
tls-client
|
|
.in -4
|
|
.ft
|
|
.fi
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-pull
|
|
This option must be used on a client which is connecting
|
|
to a multi-client server. It indicates to OpenVPN that it
|
|
should accept options pushed by the server, provided they
|
|
are part of the legal set of pushable options (note that the
|
|
.B \-\-pull
|
|
option is implied by
|
|
.B \-\-client
|
|
).
|
|
|
|
In particular,
|
|
.B \-\-pull
|
|
allows the server to push routes to the client, so you should
|
|
not use
|
|
.B \-\-pull
|
|
or
|
|
.B \-\-client
|
|
in situations where you don't trust the server to have control
|
|
over the client's routing table.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-auth-user-pass [up]
|
|
Authenticate with server using username/password.
|
|
.B up
|
|
is a file containing username/password on 2 lines (Note: OpenVPN
|
|
will only read passwords from a file if it has been built
|
|
with the \-\-enable-password-save configure option, or on Windows
|
|
by defining ENABLE_PASSWORD_SAVE in win/settings.in).
|
|
|
|
If
|
|
.B up
|
|
is omitted, username/password will be prompted from the
|
|
console.
|
|
|
|
The server configuration must specify an
|
|
.B \-\-auth-user-pass-verify
|
|
script to verify the username/password provided by
|
|
the client.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-auth-retry type
|
|
Controls how OpenVPN responds to username/password verification
|
|
errors such as the client-side response to an AUTH_FAILED message from the server
|
|
or verification failure of the private key password.
|
|
|
|
Normally used to prevent auth errors from being fatal
|
|
on the client side, and to permit username/password requeries in case
|
|
of error.
|
|
|
|
An AUTH_FAILED message is generated by the server if the client
|
|
fails
|
|
.B \-\-auth-user-pass
|
|
authentication, or if the server-side
|
|
.B \-\-client-connect
|
|
script returns an error status when the client
|
|
tries to connect.
|
|
|
|
.B type
|
|
can be one of:
|
|
|
|
.B none \-\-
|
|
Client will exit with a fatal error (this is the default).
|
|
.br
|
|
.B nointeract \-\-
|
|
Client will retry the connection without requerying for an
|
|
.B \-\-auth-user-pass
|
|
username/password. Use this option for unattended clients.
|
|
.br
|
|
.B interact \-\-
|
|
Client will requery for an
|
|
.B \-\-auth-user-pass
|
|
username/password and/or private key password before attempting a reconnection.
|
|
|
|
Note that while this option cannot be pushed, it can be controlled
|
|
from the management interface.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-static\-challenge t e
|
|
Enable static challenge/response protocol using challenge text
|
|
.B t,
|
|
with
|
|
echo flag given by
|
|
.B e
|
|
(0|1).
|
|
|
|
The echo flag indicates whether or not the user's response
|
|
to the challenge should be echoed.
|
|
|
|
See management\-notes.txt in the OpenVPN distribution for a
|
|
description of the OpenVPN challenge/response protocol.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-server-poll-timeout n
|
|
when polling possible remote servers to connect to
|
|
in a round-robin fashion, spend no more than
|
|
.B n
|
|
seconds waiting for a response before trying the next server.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-explicit-exit-notify [n]
|
|
In UDP client mode or point-to-point mode, send server/peer an exit notification
|
|
if tunnel is restarted or OpenVPN process is exited. In client mode, on
|
|
exit/restart, this
|
|
option will tell the server to immediately close its client instance object
|
|
rather than waiting for a timeout. The
|
|
.B n
|
|
parameter (default=1) controls the maximum number of attempts that the client
|
|
will try to resend the exit notification message. OpenVPN will not send any exit
|
|
notifications unless this option is enabled.
|
|
.\"*********************************************************
|
|
.SS Data Channel Encryption Options:
|
|
These options are meaningful for both Static & TLS-negotiated key modes
|
|
(must be compatible between peers).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-secret file [direction]
|
|
Enable Static Key encryption mode (non-TLS).
|
|
Use pre-shared secret
|
|
.B file
|
|
which was generated with
|
|
.B \-\-genkey.
|
|
|
|
The optional
|
|
.B direction
|
|
parameter enables the use of 4 distinct keys
|
|
(HMAC-send, cipher-encrypt, HMAC-receive, cipher-decrypt), so that
|
|
each data flow direction has a different set of HMAC and cipher keys.
|
|
This has a number of desirable security properties including
|
|
eliminating certain kinds of DoS and message replay attacks.
|
|
|
|
When the
|
|
.B direction
|
|
parameter is omitted, 2 keys are used bidirectionally, one for HMAC
|
|
and the other for encryption/decryption.
|
|
|
|
The
|
|
.B direction
|
|
parameter should always be complementary on either side of the connection,
|
|
i.e. one side should use "0" and the other should use "1", or both sides
|
|
should omit it altogether.
|
|
|
|
The
|
|
.B direction
|
|
parameter requires that
|
|
.B file
|
|
contains a 2048 bit key. While pre-1.5 versions of OpenVPN
|
|
generate 1024 bit key files, any version of OpenVPN which
|
|
supports the
|
|
.B direction
|
|
parameter, will also support 2048 bit key file generation
|
|
using the
|
|
.B \-\-genkey
|
|
option.
|
|
|
|
Static key encryption mode has certain advantages,
|
|
the primary being ease of configuration.
|
|
|
|
There are no certificates
|
|
or certificate authorities or complicated negotiation handshakes and protocols.
|
|
The only requirement is that you have a pre-existing secure channel with
|
|
your peer (such as
|
|
.B ssh
|
|
) to initially copy the key. This requirement, along with the
|
|
fact that your key never changes unless you manually generate a new one,
|
|
makes it somewhat less secure than TLS mode (see below). If an attacker
|
|
manages to steal your key, everything that was ever encrypted with
|
|
it is compromised. Contrast that to the perfect forward secrecy features of
|
|
TLS mode (using Diffie Hellman key exchange), where even if an attacker
|
|
was able to steal your private key, he would gain no information to help
|
|
him decrypt past sessions.
|
|
|
|
Another advantageous aspect of Static Key encryption mode is that
|
|
it is a handshake-free protocol
|
|
without any distinguishing signature or feature
|
|
(such as a header or protocol handshake sequence)
|
|
that would mark the ciphertext packets as being
|
|
generated by OpenVPN. Anyone eavesdropping on the wire
|
|
would see nothing
|
|
but random-looking data.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-key-direction
|
|
Alternative way of specifying the optional direction parameter for the
|
|
.B \-\-tls-auth
|
|
and
|
|
.B \-\-secret
|
|
options. Useful when using inline files (See section on inline files).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-auth alg
|
|
Authenticate packets with HMAC using message
|
|
digest algorithm
|
|
.B alg.
|
|
(The default is
|
|
.B SHA1
|
|
).
|
|
HMAC is a commonly used message authentication algorithm (MAC) that uses
|
|
a data string, a secure hash algorithm, and a key, to produce
|
|
a digital signature.
|
|
|
|
OpenVPN's usage of HMAC is to first encrypt a packet, then HMAC the resulting ciphertext.
|
|
|
|
In static-key encryption mode, the HMAC key
|
|
is included in the key file generated by
|
|
.B \-\-genkey.
|
|
In TLS mode, the HMAC key is dynamically generated and shared
|
|
between peers via the TLS control channel. If OpenVPN receives a packet with
|
|
a bad HMAC it will drop the packet.
|
|
HMAC usually adds 16 or 20 bytes per packet.
|
|
Set
|
|
.B alg=none
|
|
to disable authentication.
|
|
|
|
For more information on HMAC see
|
|
.I http://www.cs.ucsd.edu/users/mihir/papers/hmac.html
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-cipher alg
|
|
Encrypt packets with cipher algorithm
|
|
.B alg.
|
|
The default is
|
|
.B BF-CBC,
|
|
an abbreviation for Blowfish in Cipher Block Chaining mode.
|
|
Blowfish has the advantages of being fast, very secure, and allowing key sizes
|
|
of up to 448 bits. Blowfish is designed to be used in situations where
|
|
keys are changed infrequently.
|
|
|
|
For more information on blowfish, see
|
|
.I http://www.counterpane.com/blowfish.html
|
|
|
|
To see other ciphers that are available with
|
|
OpenVPN, use the
|
|
.B \-\-show-ciphers
|
|
option.
|
|
|
|
OpenVPN supports the CBC, CFB, and OFB cipher modes,
|
|
however CBC is recommended and CFB and OFB should
|
|
be considered advanced modes.
|
|
|
|
Set
|
|
.B alg=none
|
|
to disable encryption.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-keysize n
|
|
Size of cipher key in bits (optional).
|
|
If unspecified, defaults to cipher-specific default. The
|
|
.B \-\-show-ciphers
|
|
option (see below) shows all available OpenSSL ciphers,
|
|
their default key sizes, and whether the key size can
|
|
be changed. Use care in changing a cipher's default
|
|
key size. Many ciphers have not been extensively
|
|
cryptanalyzed with non-standard key lengths, and a
|
|
larger key may offer no real guarantee of greater
|
|
security, or may even reduce security.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-prng alg [nsl]
|
|
(Advanced) For PRNG (Pseudo-random number generator),
|
|
use digest algorithm
|
|
.B alg
|
|
(default=sha1), and set
|
|
.B nsl
|
|
(default=16)
|
|
to the size in bytes of the nonce secret length (between 16 and 64).
|
|
|
|
Set
|
|
.B alg=none
|
|
to disable the PRNG and use the OpenSSL RAND_bytes function
|
|
instead for all of OpenVPN's pseudo-random number needs.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-engine [engine-name]
|
|
Enable OpenSSL hardware-based crypto engine functionality.
|
|
|
|
If
|
|
.B engine-name
|
|
is specified,
|
|
use a specific crypto engine. Use the
|
|
.B \-\-show-engines
|
|
standalone option to list the crypto engines which are
|
|
supported by OpenSSL.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-no-replay
|
|
(Advanced) Disable OpenVPN's protection against replay attacks.
|
|
Don't use this option unless you are prepared to make
|
|
a tradeoff of greater efficiency in exchange for less
|
|
security.
|
|
|
|
OpenVPN provides datagram replay protection by default.
|
|
|
|
Replay protection is accomplished
|
|
by tagging each outgoing datagram with an identifier
|
|
that is guaranteed to be unique for the key being used.
|
|
The peer that receives the datagram will check for
|
|
the uniqueness of the identifier. If the identifier
|
|
was already received in a previous datagram, OpenVPN
|
|
will drop the packet. Replay protection is important
|
|
to defeat attacks such as a SYN flood attack, where
|
|
the attacker listens in the wire, intercepts a TCP
|
|
SYN packet (identifying it by the context in which
|
|
it occurs in relation to other packets), then floods
|
|
the receiving peer with copies of this packet.
|
|
|
|
OpenVPN's replay protection is implemented in slightly
|
|
different ways, depending on the key management mode
|
|
you have selected.
|
|
|
|
In Static Key mode
|
|
or when using an CFB or OFB mode cipher, OpenVPN uses a
|
|
64 bit unique identifier that combines a time stamp with
|
|
an incrementing sequence number.
|
|
|
|
When using TLS mode for key exchange and a CBC cipher
|
|
mode, OpenVPN uses only a 32 bit sequence number without
|
|
a time stamp, since OpenVPN can guarantee the uniqueness
|
|
of this value for each key. As in IPSec, if the sequence number is
|
|
close to wrapping back to zero, OpenVPN will trigger
|
|
a new key exchange.
|
|
|
|
To check for replays, OpenVPN uses
|
|
the
|
|
.I sliding window
|
|
algorithm used
|
|
by IPSec.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-replay-window n [t]
|
|
Use a replay protection sliding-window of size
|
|
.B n
|
|
and a time window of
|
|
.B t
|
|
seconds.
|
|
|
|
By default
|
|
.B n
|
|
is 64 (the IPSec default) and
|
|
.B t
|
|
is 15 seconds.
|
|
|
|
This option is only relevant in UDP mode, i.e.
|
|
when either
|
|
.B \-\-proto udp
|
|
is specifed, or no
|
|
.B \-\-proto
|
|
option is specified.
|
|
|
|
When OpenVPN tunnels IP packets over UDP, there is the possibility that
|
|
packets might be dropped or delivered out of order. Because OpenVPN, like IPSec,
|
|
is emulating the physical network layer,
|
|
it will accept an out-of-order packet sequence, and
|
|
will deliver such packets in the same order they were received to
|
|
the TCP/IP protocol stack, provided they satisfy several constraints.
|
|
|
|
.B (a)
|
|
The packet cannot be a replay (unless
|
|
.B \-\-no-replay
|
|
is specified, which disables replay protection altogether).
|
|
|
|
.B (b)
|
|
If a packet arrives out of order, it will only be accepted if the difference
|
|
between its sequence number and the highest sequence number received
|
|
so far is less than
|
|
.B n.
|
|
|
|
.B (c)
|
|
If a packet arrives out of order, it will only be accepted if it arrives no later
|
|
than
|
|
.B t
|
|
seconds after any packet containing a higher sequence number.
|
|
|
|
If you are using a network link with a large pipeline (meaning that
|
|
the product of bandwidth and latency is high), you may want to use
|
|
a larger value for
|
|
.B n.
|
|
Satellite links in particular often require this.
|
|
|
|
If you run OpenVPN at
|
|
.B \-\-verb 4,
|
|
you will see the message "Replay-window backtrack occurred [x]"
|
|
every time the maximum sequence number backtrack seen thus far
|
|
increases. This can be used to calibrate
|
|
.B n.
|
|
|
|
There is some controversy on the appropriate method of handling packet
|
|
reordering at the security layer.
|
|
|
|
Namely, to what extent should the
|
|
security layer protect the encapsulated protocol from attacks which masquerade
|
|
as the kinds of normal packet loss and reordering that occur over IP networks?
|
|
|
|
The IPSec and OpenVPN approach is to allow packet reordering within a certain
|
|
fixed sequence number window.
|
|
|
|
OpenVPN adds to the IPSec model by limiting the window size in time as well as
|
|
sequence space.
|
|
|
|
OpenVPN also adds TCP transport as an option (not offered by IPSec) in which
|
|
case OpenVPN can adopt a very strict attitude towards message deletion and
|
|
reordering: Don't allow it. Since TCP guarantees reliability, any packet
|
|
loss or reordering event can be assumed to be an attack.
|
|
|
|
In this sense, it could be argued that TCP tunnel transport is preferred when
|
|
tunneling non-IP or UDP application protocols which might be vulnerable to a
|
|
message deletion or reordering attack which falls within the normal
|
|
operational parameters of IP networks.
|
|
|
|
So I would make the statement that one should never tunnel a non-IP protocol
|
|
or UDP application protocol over UDP, if the protocol might be vulnerable to a
|
|
message deletion or reordering attack that falls within the normal operating
|
|
parameters of what is to be expected from the physical IP layer. The problem
|
|
is easily fixed by simply using TCP as the VPN transport layer.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-mute-replay-warnings
|
|
Silence the output of replay warnings, which are a common
|
|
false alarm on WiFi networks. This option preserves
|
|
the security of the replay protection code without
|
|
the verbosity associated with warnings about duplicate
|
|
packets.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-replay-persist file
|
|
Persist replay-protection state across sessions using
|
|
.B file
|
|
to save and reload the state.
|
|
|
|
This option will strengthen protection against replay attacks,
|
|
especially when you are using OpenVPN in a dynamic context (such
|
|
as with
|
|
.B \-\-inetd)
|
|
when OpenVPN sessions are frequently started and stopped.
|
|
|
|
This option will keep a disk copy of the current replay protection
|
|
state (i.e. the most recent packet timestamp and sequence number
|
|
received from the remote peer), so that if an OpenVPN session
|
|
is stopped and restarted, it will reject any replays of packets
|
|
which were already received by the prior session.
|
|
|
|
This option only makes sense when replay protection is enabled
|
|
(the default) and you are using either
|
|
.B \-\-secret
|
|
(shared-secret key mode) or TLS mode with
|
|
.B \-\-tls-auth.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-no-iv
|
|
(Advanced) Disable OpenVPN's use of IV (cipher initialization vector).
|
|
Don't use this option unless you are prepared to make
|
|
a tradeoff of greater efficiency in exchange for less
|
|
security.
|
|
|
|
OpenVPN uses an IV by default, and requires it for CFB and
|
|
OFB cipher modes (which are totally insecure without it).
|
|
Using an IV is important for security when multiple
|
|
messages are being encrypted/decrypted with the same key.
|
|
|
|
IV is implemented differently depending on the cipher mode used.
|
|
|
|
In CBC mode, OpenVPN uses a pseudo-random IV for each packet.
|
|
|
|
In CFB/OFB mode, OpenVPN uses a unique sequence number and time stamp
|
|
as the IV. In fact, in CFB/OFB mode, OpenVPN uses a datagram
|
|
space-saving optimization that uses the unique identifier for
|
|
datagram replay protection as the IV.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-use-prediction-resistance
|
|
Enable prediction resistance on PolarSSL's RNG.
|
|
|
|
Enabling prediction resistance causes the RNG to reseed in each
|
|
call for random. Reseeding this often can quickly deplete the kernel
|
|
entropy pool.
|
|
|
|
If you need this option, please consider running a daemon that adds
|
|
entropy to the kernel pool.
|
|
|
|
Note that this option only works with PolarSSL versions greater
|
|
than 1.1.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-test-crypto
|
|
Do a self-test of OpenVPN's crypto options by encrypting and
|
|
decrypting test packets using the data channel encryption options
|
|
specified above. This option does not require a peer to function,
|
|
and therefore can be specified without
|
|
.B \-\-dev
|
|
or
|
|
.B \-\-remote.
|
|
|
|
The typical usage of
|
|
.B \-\-test-crypto
|
|
would be something like this:
|
|
|
|
.B openvpn \-\-test-crypto \-\-secret key
|
|
|
|
or
|
|
|
|
.B openvpn \-\-test-crypto \-\-secret key \-\-verb 9
|
|
|
|
This option is very useful to test OpenVPN after it has been ported to
|
|
a new platform, or to isolate problems in the compiler, OpenSSL
|
|
crypto library, or OpenVPN's crypto code. Since it is a self-test mode,
|
|
problems with encryption and authentication can be debugged independently
|
|
of network and tunnel issues.
|
|
.\"*********************************************************
|
|
.SS TLS Mode Options:
|
|
TLS mode is the most powerful crypto mode of OpenVPN in both security and flexibility.
|
|
TLS mode works by establishing control and
|
|
data channels which are multiplexed over a single TCP/UDP port. OpenVPN initiates
|
|
a TLS session over the control channel and uses it to exchange cipher
|
|
and HMAC keys to protect the data channel. TLS mode uses a robust reliability
|
|
layer over the UDP connection for all control channel communication, while
|
|
the data channel, over which encrypted tunnel data passes, is forwarded without
|
|
any mediation. The result is the best of both worlds: a fast data channel
|
|
that forwards over UDP with only the overhead of encrypt,
|
|
decrypt, and HMAC functions,
|
|
and a control channel that provides all of the security features of TLS,
|
|
including certificate-based authentication and Diffie Hellman forward secrecy.
|
|
|
|
To use TLS mode, each peer that runs OpenVPN should have its own local
|
|
certificate/key pair (
|
|
.B \-\-cert
|
|
and
|
|
.B \-\-key
|
|
), signed by the root certificate which is specified
|
|
in
|
|
.B \-\-ca.
|
|
|
|
When two OpenVPN peers connect, each presents its local certificate to the
|
|
other. Each peer will then check that its partner peer presented a
|
|
certificate which was signed by the master root certificate as specified in
|
|
.B \-\-ca.
|
|
|
|
If that check on both peers succeeds, then the TLS negotiation
|
|
will succeed, both OpenVPN
|
|
peers will exchange temporary session keys, and the tunnel will begin
|
|
passing data.
|
|
|
|
The OpenVPN distribution contains a set of scripts for
|
|
managing RSA certificates & keys,
|
|
located in the
|
|
.I easy-rsa
|
|
subdirectory.
|
|
|
|
The easy-rsa package is also rendered in web form here:
|
|
.I http://openvpn.net/easyrsa.html
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tls-server
|
|
Enable TLS and assume server role during TLS handshake. Note that
|
|
OpenVPN is designed as a peer-to-peer application. The designation
|
|
of client or server is only for the purpose of negotiating the TLS
|
|
control channel.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tls-client
|
|
Enable TLS and assume client role during TLS handshake.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ca file
|
|
Certificate authority (CA) file in .pem format, also referred to as the
|
|
.I root
|
|
certificate. This file can have multiple
|
|
certificates in .pem format, concatenated together. You can construct your own
|
|
certificate authority certificate and private key by using a command such as:
|
|
|
|
.B openssl req -nodes -new -x509 -keyout ca.key -out ca.crt
|
|
|
|
Then edit your openssl.cnf file and edit the
|
|
.B certificate
|
|
variable to point to your new root certificate
|
|
.B ca.crt.
|
|
|
|
For testing purposes only, the OpenVPN distribution includes a sample
|
|
CA certificate (ca.crt).
|
|
Of course you should never use
|
|
the test certificates and test keys distributed with OpenVPN in a
|
|
production environment, since by virtue of the fact that
|
|
they are distributed with OpenVPN, they are totally insecure.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-capath dir
|
|
Directory containing trusted certificates (CAs and CRLs).
|
|
Available with OpenSSL version >= 0.9.7 dev.
|
|
Not available with PolarSSL.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-dh file
|
|
File containing Diffie Hellman parameters
|
|
in .pem format (required for
|
|
.B \-\-tls-server
|
|
only). Use
|
|
|
|
.B openssl dhparam -out dh1024.pem 1024
|
|
|
|
to generate your own, or use the existing dh1024.pem file
|
|
included with the OpenVPN distribution. Diffie Hellman parameters
|
|
may be considered public.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-cert file
|
|
Local peer's signed certificate in .pem format \-\- must be signed
|
|
by a certificate authority whose certificate is in
|
|
.B \-\-ca file.
|
|
Each peer in an OpenVPN link running in TLS mode should have its own
|
|
certificate and private key file. In addition, each certificate should
|
|
have been signed by the key of a certificate
|
|
authority whose public key resides in the
|
|
.B \-\-ca
|
|
certificate authority file.
|
|
You can easily make your own certificate authority (see above) or pay money
|
|
to use a commercial service such as thawte.com (in which case you will be
|
|
helping to finance the world's second space tourist :).
|
|
To generate a certificate,
|
|
you can use a command such as:
|
|
|
|
.B openssl req -nodes -new -keyout mycert.key -out mycert.csr
|
|
|
|
If your certificate authority private key lives on another machine, copy
|
|
the certificate signing request (mycert.csr) to this other machine (this can
|
|
be done over an insecure channel such as email). Now sign the certificate
|
|
with a command such as:
|
|
|
|
.B openssl ca -out mycert.crt -in mycert.csr
|
|
|
|
Now copy the certificate (mycert.crt)
|
|
back to the peer which initially generated the .csr file (this
|
|
can be over a public medium).
|
|
Note that the
|
|
.B openssl ca
|
|
command reads the location of the certificate authority key from its
|
|
configuration file such as
|
|
.B /usr/share/ssl/openssl.cnf
|
|
\-\- note also
|
|
that for certificate authority functions, you must set up the files
|
|
.B index.txt
|
|
(may be empty) and
|
|
.B serial
|
|
(initialize to
|
|
.B
|
|
01
|
|
).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-extra-certs file
|
|
Specify a
|
|
.B file
|
|
containing one or more PEM certs (concatenated together)
|
|
that complete the
|
|
local certificate chain.
|
|
|
|
This option is useful for "split" CAs, where the CA for server
|
|
certs is different than the CA for client certs. Putting certs
|
|
in this file allows them to be used to complete the local
|
|
certificate chain without trusting them to verify the peer-submitted
|
|
certificate, as would be the case if the certs were placed in the
|
|
.B ca
|
|
file.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-key file
|
|
Local peer's private key in .pem format. Use the private key which was generated
|
|
when you built your peer's certificate (see
|
|
.B -cert file
|
|
above).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tls-version-min version ['or-highest']
|
|
Enable TLS version negotiation, and set the minimum
|
|
TLS version we will accept from the peer (default is "1.0").
|
|
Examples for version
|
|
include "1.0", "1.1", or "1.2". If 'or-highest' is specified
|
|
and version is not recognized, we will only accept the highest TLS
|
|
version supported by the local SSL implementation.
|
|
|
|
If this options is not set, the code in OpenVPN 2.3.4 will default
|
|
to using TLS 1.0 only, without any version negotiation. This reverts
|
|
the beaviour to what OpenVPN versions up to 2.3.2 did, as it turned
|
|
out that TLS version negotiation can lead to handshake problems due
|
|
to new signature algorithms in TLS 1.2.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tls-version-max version
|
|
Set the maximum TLS version we will use (default is the highest version
|
|
supported). Examples for version include "1.0", "1.1", or "1.2".
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-pkcs12 file
|
|
Specify a PKCS #12 file containing local private key,
|
|
local certificate, and root CA certificate.
|
|
This option can be used instead of
|
|
.B \-\-ca, \-\-cert,
|
|
and
|
|
.B \-\-key.
|
|
Not available with PolarSSL.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-verify-hash hash
|
|
Specify SHA1 fingerprint for level-1 cert. The level-1 cert is the
|
|
CA (or intermediate cert) that signs the leaf certificate, and is
|
|
one removed from the leaf certificate in the direction of the root.
|
|
When accepting a connection from a peer, the level-1 cert
|
|
fingerprint must match
|
|
.B hash
|
|
or certificate verification will fail. Hash is specified
|
|
as XX:XX:... For example: AD:B0:95:D8:09:C8:36:45:12:A9:89:C8:90:09:CB:13:72:A6:AD:16
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-pkcs11-cert-private [0|1]...
|
|
Set if access to certificate object should be performed after login.
|
|
Every provider has its own setting.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-pkcs11-id name
|
|
Specify the serialized certificate id to be used. The id can be gotten
|
|
by the standalone
|
|
.B \-\-show-pkcs11-ids
|
|
option.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-pkcs11-id-management
|
|
Acquire PKCS#11 id from management interface. In this case a NEED-STR 'pkcs11-id-request'
|
|
real-time message will be triggered, application may use pkcs11-id-count command to
|
|
retrieve available number of certificates, and pkcs11-id-get command to retrieve certificate
|
|
id and certificate body.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-pkcs11-pin-cache seconds
|
|
Specify how many seconds the PIN can be cached, the default is until the token is removed.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-pkcs11-protected-authentication [0|1]...
|
|
Use PKCS#11 protected authentication path, useful for biometric and external
|
|
keypad devices.
|
|
Every provider has its own setting.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-pkcs11-providers provider...
|
|
Specify a RSA Security Inc. PKCS #11 Cryptographic Token Interface (Cryptoki) providers
|
|
to load.
|
|
This option can be used instead of
|
|
.B \-\-cert, \-\-key,
|
|
and
|
|
.B \-\-pkcs12.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-pkcs11-private-mode mode...
|
|
Specify which method to use in order to perform private key operations.
|
|
A different mode can be specified for each provider.
|
|
Mode is encoded as hex number, and can be a mask one of the following:
|
|
|
|
.B 0
|
|
(default) \-\- Try to determine automatically.
|
|
.br
|
|
.B 1
|
|
\-\- Use sign.
|
|
.br
|
|
.B 2
|
|
\-\- Use sign recover.
|
|
.br
|
|
.B 4
|
|
\-\- Use decrypt.
|
|
.br
|
|
.B 8
|
|
\-\- Use unwrap.
|
|
.br
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-cryptoapicert select-string
|
|
Load the certificate and private key from the
|
|
Windows Certificate System Store (Windows/OpenSSL Only).
|
|
|
|
Use this option instead of
|
|
.B \-\-cert
|
|
and
|
|
.B \-\-key.
|
|
|
|
This makes
|
|
it possible to use any smart card, supported by Windows, but also any
|
|
kind of certificate, residing in the Cert Store, where you have access to
|
|
the private key. This option has been tested with a couple of different
|
|
smart cards (GemSAFE, Cryptoflex, and Swedish Post Office eID) on the
|
|
client side, and also an imported PKCS12 software certificate on the
|
|
server side.
|
|
|
|
To select a certificate, based on a substring search in the
|
|
certificate's subject:
|
|
|
|
.B cryptoapicert
|
|
"SUBJ:Peter Runestig"
|
|
|
|
To select a certificate, based on certificate's thumbprint:
|
|
|
|
.B cryptoapicert
|
|
"THUMB:f6 49 24 41 01 b4 ..."
|
|
|
|
The thumbprint hex string can easily be copy-and-pasted from the Windows
|
|
Certificate Store GUI.
|
|
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-key-method m
|
|
Use data channel key negotiation method
|
|
.B m.
|
|
The key method must match on both sides of the connection.
|
|
|
|
After OpenVPN negotiates a TLS session, a new set of keys
|
|
for protecting the tunnel data channel is generated and
|
|
exchanged over the TLS session.
|
|
|
|
In method 1 (the default for OpenVPN 1.x), both sides generate
|
|
random encrypt and HMAC-send keys which are forwarded to
|
|
the other host over the TLS channel.
|
|
|
|
In method 2, (the default for OpenVPN 2.0)
|
|
the client generates a random key. Both client
|
|
and server also generate some random seed material. All key source
|
|
material is exchanged over the TLS channel. The actual
|
|
keys are generated using the TLS PRF function, taking source
|
|
entropy from both client and server. Method 2 is designed to
|
|
closely parallel the key generation process used by TLS 1.0.
|
|
|
|
Note that in TLS mode, two separate levels
|
|
of keying occur:
|
|
|
|
(1) The TLS connection is initially negotiated, with both sides
|
|
of the connection producing certificates and verifying the certificate
|
|
(or other authentication info provided) of
|
|
the other side. The
|
|
.B \-\-key-method
|
|
parameter has no effect on this process.
|
|
|
|
(2) After the TLS connection is established, the tunnel session keys are
|
|
separately negotiated over the existing secure TLS channel. Here,
|
|
.B \-\-key-method
|
|
determines the derivation of the tunnel session keys.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tls-cipher l
|
|
A list
|
|
.B l
|
|
of allowable TLS ciphers delimited by a colon (":").
|
|
If you require a high level of security,
|
|
you may want to set this parameter manually, to prevent a
|
|
version rollback attack where a man-in-the-middle attacker tries
|
|
to force two peers to negotiate to the lowest level
|
|
of security they both support.
|
|
Use
|
|
.B \-\-show-tls
|
|
to see a list of supported TLS ciphers.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tls-timeout n
|
|
Packet retransmit timeout on TLS control channel
|
|
if no acknowledgment from remote within
|
|
.B n
|
|
seconds (default=2). When OpenVPN sends a control
|
|
packet to its peer, it will expect to receive an
|
|
acknowledgement within
|
|
.B n
|
|
seconds or it will retransmit the packet, subject
|
|
to a TCP-like exponential backoff algorithm. This parameter
|
|
only applies to control channel packets. Data channel
|
|
packets (which carry encrypted tunnel data) are never
|
|
acknowledged, sequenced, or retransmitted by OpenVPN because
|
|
the higher level network protocols running on top of the tunnel
|
|
such as TCP expect this role to be left to them.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-reneg-bytes n
|
|
Renegotiate data channel key after
|
|
.B n
|
|
bytes sent or received (disabled by default).
|
|
OpenVPN allows the lifetime of a key
|
|
to be expressed as a number of bytes encrypted/decrypted, a number of packets, or
|
|
a number of seconds. A key renegotiation will be forced
|
|
if any of these three criteria are met by either peer.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-reneg-pkts n
|
|
Renegotiate data channel key after
|
|
.B n
|
|
packets sent and received (disabled by default).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-reneg-sec n
|
|
Renegotiate data channel key after
|
|
.B n
|
|
seconds (default=3600).
|
|
|
|
When using dual-factor authentication, note that this default value may
|
|
cause the end user to be challenged to reauthorize once per hour.
|
|
|
|
Also, keep in mind that this option can be used on both the client and server,
|
|
and whichever uses the lower value will be the one to trigger the renegotiation.
|
|
A common mistake is to set
|
|
.B \-\-reneg-sec
|
|
to a higher value on either the client or server, while the other side of the connection
|
|
is still using the default value of 3600 seconds, meaning that the renegotiation will
|
|
still occur once per 3600 seconds. The solution is to increase \-\-reneg-sec on both the
|
|
client and server, or set it to 0 on one side of the connection (to disable), and to
|
|
your chosen value on the other side.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-hand-window n
|
|
Handshake Window \-\- the TLS-based key exchange must finalize within
|
|
.B n
|
|
seconds
|
|
of handshake initiation by any peer (default = 60 seconds).
|
|
If the handshake fails
|
|
we will attempt to reset our connection with our peer and try again.
|
|
Even in the event of handshake failure we will still use
|
|
our expiring key for up to
|
|
.B \-\-tran-window
|
|
seconds to maintain continuity of transmission of tunnel
|
|
data.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tran-window n
|
|
Transition window \-\- our old key can live this many seconds
|
|
after a new a key renegotiation begins (default = 3600 seconds).
|
|
This feature allows for a graceful transition from old to new
|
|
key, and removes the key renegotiation sequence from the critical
|
|
path of tunnel data forwarding.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-single-session
|
|
After initially connecting to a remote peer, disallow any new connections.
|
|
Using this
|
|
option means that a remote peer cannot connect, disconnect, and then
|
|
reconnect.
|
|
|
|
If the daemon is reset by a signal or
|
|
.B \-\-ping-restart,
|
|
it will allow one new connection.
|
|
|
|
.B \-\-single-session
|
|
can be used with
|
|
.B \-\-ping-exit
|
|
or
|
|
.B \-\-inactive
|
|
to create a single dynamic session that will exit when finished.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tls-exit
|
|
Exit on TLS negotiation failure.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tls-auth file [direction]
|
|
Add an additional layer of HMAC authentication on top of the TLS
|
|
control channel to protect against DoS attacks.
|
|
|
|
In a nutshell,
|
|
.B \-\-tls-auth
|
|
enables a kind of "HMAC firewall" on OpenVPN's TCP/UDP port,
|
|
where TLS control channel packets
|
|
bearing an incorrect HMAC signature can be dropped immediately without
|
|
response.
|
|
|
|
.B file
|
|
(required) is a key file which can be in one of two formats:
|
|
|
|
.B (1)
|
|
An OpenVPN static key file generated by
|
|
.B \-\-genkey
|
|
(required if
|
|
.B direction
|
|
parameter is used).
|
|
|
|
.B (2)
|
|
A freeform passphrase file. In this case the HMAC key will
|
|
be derived by taking a secure hash of this file, similar to
|
|
the
|
|
.BR md5sum (1)
|
|
or
|
|
.BR sha1sum (1)
|
|
commands.
|
|
|
|
OpenVPN will first try format (1), and if the file fails to parse as
|
|
a static key file, format (2) will be used.
|
|
|
|
See the
|
|
.B \-\-secret
|
|
option for more information on the optional
|
|
.B direction
|
|
parameter.
|
|
|
|
.B \-\-tls-auth
|
|
is recommended when you are running OpenVPN in a mode where
|
|
it is listening for packets from any IP address, such as when
|
|
.B \-\-remote
|
|
is not specified, or
|
|
.B \-\-remote
|
|
is specified with
|
|
.B \-\-float.
|
|
|
|
The rationale for
|
|
this feature is as follows. TLS requires a multi-packet exchange
|
|
before it is able to authenticate a peer. During this time
|
|
before authentication, OpenVPN is allocating resources (memory
|
|
and CPU) to this potential peer. The potential peer is also
|
|
exposing many parts of OpenVPN and the OpenSSL library to the packets
|
|
it is sending. Most successful network attacks today seek
|
|
to either exploit bugs in programs (such as buffer overflow attacks) or
|
|
force a program to consume so many resources that it becomes unusable.
|
|
Of course the first line of defense is always to produce clean,
|
|
well-audited code. OpenVPN has been written with buffer overflow
|
|
attack prevention as a top priority.
|
|
But as history has shown, many of the most widely used
|
|
network applications have, from time to time,
|
|
fallen to buffer overflow attacks.
|
|
|
|
So as a second line of defense, OpenVPN offers
|
|
this special layer of authentication on top of the TLS control channel so that
|
|
every packet on the control channel is authenticated by an
|
|
HMAC signature and a unique ID for replay protection.
|
|
This signature will also help protect against DoS (Denial of Service) attacks.
|
|
An important rule of thumb in reducing vulnerability to DoS attacks is to
|
|
minimize the amount of resources a potential, but as yet unauthenticated,
|
|
client is able to consume.
|
|
|
|
.B \-\-tls-auth
|
|
does this by signing every TLS control channel packet with an HMAC signature,
|
|
including packets which are sent before the TLS level has had a chance
|
|
to authenticate the peer.
|
|
The result is that packets without
|
|
the correct signature can be dropped immediately upon reception,
|
|
before they have a chance to consume additional system resources
|
|
such as by initiating a TLS handshake.
|
|
.B \-\-tls-auth
|
|
can be strengthened by adding the
|
|
.B \-\-replay-persist
|
|
option which will keep OpenVPN's replay protection state
|
|
in a file so that it is not lost across restarts.
|
|
|
|
It should be emphasized that this feature is optional and that the
|
|
passphrase/key file used with
|
|
.B \-\-tls-auth
|
|
gives a peer nothing more than the power to initiate a TLS
|
|
handshake. It is not used to encrypt or authenticate any tunnel data.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-askpass [file]
|
|
Get certificate password from console or
|
|
.B file
|
|
before we daemonize.
|
|
|
|
For the extremely
|
|
security conscious, it is possible to protect your private key with
|
|
a password. Of course this means that every time the OpenVPN
|
|
daemon is started you must be there to type the password. The
|
|
.B \-\-askpass
|
|
option allows you to start OpenVPN from the command line. It will
|
|
query you for a password before it daemonizes. To protect a private
|
|
key with a password you should omit the
|
|
.B -nodes
|
|
option when you use the
|
|
.B openssl
|
|
command line tool to manage certificates and private keys.
|
|
|
|
If
|
|
.B file
|
|
is specified, read the password from the first line of
|
|
.B file.
|
|
Keep in mind that storing your password in a file
|
|
to a certain extent invalidates the extra security provided by
|
|
using an encrypted key (Note: OpenVPN
|
|
will only read passwords from a file if it has been built
|
|
with the \-\-enable-password-save configure option, or on Windows
|
|
by defining ENABLE_PASSWORD_SAVE in win/settings.in).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-auth-nocache
|
|
Don't cache
|
|
.B \-\-askpass
|
|
or
|
|
.B \-\-auth-user-pass
|
|
username/passwords in virtual memory.
|
|
|
|
If specified, this directive will cause OpenVPN to immediately
|
|
forget username/password inputs after they are used. As a result,
|
|
when OpenVPN needs a username/password, it will prompt for input
|
|
from stdin, which may be multiple times during the duration of an
|
|
OpenVPN session.
|
|
|
|
This directive does not affect the
|
|
.B \-\-http-proxy
|
|
username/password. It is always cached.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tls-verify cmd
|
|
Run command
|
|
.B cmd
|
|
to verify the X509 name of a
|
|
pending TLS connection that has otherwise passed all other
|
|
tests of certification (except for revocation via
|
|
.B \-\-crl-verify
|
|
directive; the revocation test occurs after the
|
|
.B \-\-tls-verify
|
|
test).
|
|
|
|
.B cmd
|
|
should return 0 to allow the TLS handshake to proceed, or 1 to fail.
|
|
|
|
.B cmd
|
|
consists of a path to script (or executable program), optionally
|
|
followed by arguments. The path and arguments may be single- or double-quoted
|
|
and/or escaped using a backslash, and should be separated by one or more spaces.
|
|
|
|
When
|
|
.B cmd
|
|
is executed two arguments are appended after any arguments specified in
|
|
.B cmd
|
|
, as follows:
|
|
|
|
.B cmd certificate_depth subject
|
|
|
|
These arguments are, respectively, the current certificate depth and
|
|
the X509 common name (cn) of the peer.
|
|
|
|
This feature is useful if the peer you want to trust has a certificate
|
|
which was signed by a certificate authority who also signed many
|
|
other certificates, where you don't necessarily want to trust all of them,
|
|
but rather be selective about which
|
|
peer certificate you will accept. This feature allows you to write a script
|
|
which will test the X509 name on a certificate and decide whether or
|
|
not it should be accepted. For a simple perl script which will test
|
|
the common name field on the certificate, see the file
|
|
.B verify-cn
|
|
in the OpenVPN distribution.
|
|
|
|
See the "Environmental Variables" section below for
|
|
additional parameters passed as environmental variables.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tls-export-cert directory
|
|
Store the certificates the clients uses upon connection to this
|
|
directory. This will be done before \-\-tls-verify is called. The
|
|
certificates will use a temporary name and will be deleted when
|
|
the tls-verify script returns. The file name used for the certificate
|
|
is available via the peer_cert environment variable.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-x509-username-field [ext:\]fieldname
|
|
Field in the X.509 certificate subject to be used as the username (default=CN).
|
|
Typically, this option is specified with
|
|
.B fieldname
|
|
as either of the following:
|
|
|
|
.B \-\-x509-username-field
|
|
emailAddress
|
|
.br
|
|
.B \-\-x509-username-field ext:\fRsubjectAltName
|
|
|
|
The first example uses the value of the "emailAddress" attribute in the
|
|
certificate's Subject field as the username. The second example uses
|
|
the
|
|
.B ext:
|
|
prefix to signify that the X.509 extension
|
|
.B fieldname
|
|
"subjectAltName" be searched for an rfc822Name (email) field to be used
|
|
as the username. In cases where there are multiple email addresses
|
|
in
|
|
.B ext:fieldname\fR,
|
|
the last occurrence is chosen.
|
|
|
|
When this option is used, the
|
|
.B \-\-verify-x509-name
|
|
option will match against the chosen
|
|
.B fieldname
|
|
instead of the Common Name.
|
|
|
|
.B Please note:
|
|
This option has a feature which will convert an all-lowercase
|
|
.B fieldname
|
|
to uppercase characters, e.g., ou -> OU. A mixed-case
|
|
.B fieldname
|
|
or one having the
|
|
.B ext:
|
|
prefix will be left as-is. This automatic upcasing feature
|
|
is deprecated and will be removed in a future release.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tls-remote name (DEPRECATED)
|
|
Accept connections only from a host with X509 name
|
|
or common name equal to
|
|
.B name.
|
|
The remote host must also pass all other tests
|
|
of verification.
|
|
|
|
.B NOTE:
|
|
Because tls-remote may test against a common name prefix,
|
|
only use this option when you are using OpenVPN with a custom CA
|
|
certificate that is under your control.
|
|
Never use this option when your client certificates are signed by
|
|
a third party, such as a commercial web CA.
|
|
|
|
Name can also be a common name prefix, for example if you
|
|
want a client to only accept connections to "Server-1",
|
|
"Server-2", etc., you can simply use
|
|
.B \-\-tls-remote Server
|
|
|
|
Using a common name prefix is a useful alternative to managing
|
|
a CRL (Certificate Revocation List) on the client, since it allows the client
|
|
to refuse all certificates except for those associated
|
|
with designated servers.
|
|
|
|
.B \-\-tls-remote
|
|
is a useful replacement for the
|
|
.B \-\-tls-verify
|
|
option to verify the remote host, because
|
|
.B \-\-tls-remote
|
|
works in a
|
|
.B \-\-chroot
|
|
environment too.
|
|
|
|
.B Please also note:
|
|
This option is now deprecated. It will be removed either in OpenVPN v2.4
|
|
or v2.5. So please make sure you support the new X.509 name formatting
|
|
described with the
|
|
.B \-\-compat-names
|
|
option as soon as possible by updating your configurations to use
|
|
.B \-\-verify-x509-name
|
|
instead.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-verify-x509-name name type
|
|
Accept connections only if a host's X.509 name is equal to
|
|
.B name.
|
|
The remote host must also pass all other tests of verification.
|
|
|
|
Which X.509 name is compared to
|
|
.B name
|
|
depends on the setting of type.
|
|
.B type
|
|
can be "subject" to match the complete subject DN (default),
|
|
"name" to match a subject RDN or "name-prefix" to match a subject RDN prefix.
|
|
Which RDN is verified as name depends on the
|
|
.B \-\-x509-username-field
|
|
option. But it defaults to the common name (CN), e.g. a certificate with a
|
|
subject DN "C=KG, ST=NA, L=Bishkek, CN=Server-1" would be matched by:
|
|
|
|
.B \-\-verify-x509-name 'C=KG, ST=NA, L=Bishkek, CN=Server-1'
|
|
and
|
|
.B \-\-verify-x509-name Server-1 name
|
|
or you could use
|
|
.B \-\-verify-x509-name Server- name-prefix
|
|
if you want a client to only accept connections to "Server-1", "Server-2", etc.
|
|
|
|
.B \-\-verify-x509-name
|
|
is a useful replacement for the
|
|
.B \-\-tls-verify
|
|
option to verify the remote host, because
|
|
.B \-\-verify-x509-name
|
|
works in a
|
|
.B \-\-chroot
|
|
environment without any dependencies.
|
|
|
|
Using a name prefix is a useful alternative to managing
|
|
a CRL (Certificate Revocation List) on the client, since it allows the client
|
|
to refuse all certificates except for those associated
|
|
with designated servers.
|
|
|
|
.B NOTE:
|
|
Test against a name prefix only when you are using OpenVPN with
|
|
a custom CA certificate that is under your control.
|
|
Never use this option with type "name-prefix" when your client certificates
|
|
are signed by a third party, such as a commercial web CA.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-x509-track attribute
|
|
Save peer X509
|
|
.B attribute
|
|
value in environment for use by plugins and management interface.
|
|
Prepend a '+' to
|
|
.B attribute
|
|
to save values from full cert chain. Values will be encoded
|
|
as X509_<depth>_<attribute>=<value>. Multiple
|
|
.B \-\-x509-track
|
|
options can be defined to track multiple attributes.
|
|
Not available with PolarSSL.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ns-cert-type client|server
|
|
Require that peer certificate was signed with an explicit
|
|
.B nsCertType
|
|
designation of "client" or "server".
|
|
|
|
This is a useful security option for clients, to ensure that
|
|
the host they connect with is a designated server.
|
|
|
|
See the easy-rsa/build-key-server script for an example
|
|
of how to generate a certificate with the
|
|
.B nsCertType
|
|
field set to "server".
|
|
|
|
If the server certificate's nsCertType field is set
|
|
to "server", then the clients can verify this with
|
|
.B \-\-ns-cert-type server.
|
|
|
|
This is an important security precaution to protect against
|
|
a man-in-the-middle attack where an authorized client
|
|
attempts to connect to another client by impersonating the server.
|
|
The attack is easily prevented by having clients verify
|
|
the server certificate using any one of
|
|
.B \-\-ns-cert-type, \-\-verify-x509-name,
|
|
or
|
|
.B \-\-tls-verify.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-remote-cert-ku v...
|
|
Require that peer certificate was signed with an explicit
|
|
.B key usage.
|
|
|
|
This is a useful security option for clients, to ensure that
|
|
the host they connect to is a designated server.
|
|
|
|
The key usage should be encoded in hex, more than one key
|
|
usage can be specified.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-remote-cert-eku oid
|
|
Require that peer certificate was signed with an explicit
|
|
.B extended key usage.
|
|
|
|
This is a useful security option for clients, to ensure that
|
|
the host they connect to is a designated server.
|
|
|
|
The extended key usage should be encoded in oid notation, or
|
|
OpenSSL symbolic representation.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-remote-cert-tls client|server
|
|
Require that peer certificate was signed with an explicit
|
|
.B key usage
|
|
and
|
|
.B extended key usage
|
|
based on RFC3280 TLS rules.
|
|
|
|
This is a useful security option for clients, to ensure that
|
|
the host they connect to is a designated server.
|
|
|
|
The
|
|
.B \-\-remote-cert-tls client
|
|
option is equivalent to
|
|
.B
|
|
\-\-remote-cert-ku 80 08 88 \-\-remote-cert-eku "TLS Web Client Authentication"
|
|
|
|
The key usage is digitalSignature and/or keyAgreement.
|
|
|
|
The
|
|
.B \-\-remote-cert-tls server
|
|
option is equivalent to
|
|
.B
|
|
\-\-remote-cert-ku a0 88 \-\-remote-cert-eku "TLS Web Server Authentication"
|
|
|
|
The key usage is digitalSignature and ( keyEncipherment or keyAgreement ).
|
|
|
|
This is an important security precaution to protect against
|
|
a man-in-the-middle attack where an authorized client
|
|
attempts to connect to another client by impersonating the server.
|
|
The attack is easily prevented by having clients verify
|
|
the server certificate using any one of
|
|
.B \-\-remote-cert-tls, \-\-verify-x509-name,
|
|
or
|
|
.B \-\-tls-verify.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-crl-verify crl ['dir']
|
|
Check peer certificate against the file
|
|
.B crl
|
|
in PEM format.
|
|
|
|
A CRL (certificate revocation list) is used when a particular key is
|
|
compromised but when the overall PKI is still intact.
|
|
|
|
Suppose you had a PKI consisting of a CA, root certificate, and a number of
|
|
client certificates. Suppose a laptop computer containing a client key and
|
|
certificate was stolen. By adding the stolen certificate to the CRL file,
|
|
you could reject any connection which attempts to use it, while preserving the
|
|
overall integrity of the PKI.
|
|
|
|
The only time when it would be necessary to rebuild the entire PKI from scratch would be
|
|
if the root certificate key itself was compromised.
|
|
|
|
If the optional
|
|
.B dir
|
|
flag is specified, enable a different mode where
|
|
.B crl
|
|
is a directory containing files named as revoked serial numbers
|
|
(the files may be empty, the contents are never read). If a client
|
|
requests a connection, where the client certificate serial number
|
|
(decimal string) is the name of a file present in the directory,
|
|
it will be rejected.
|
|
.\"*********************************************************
|
|
.SS SSL Library information:
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-show-ciphers
|
|
(Standalone)
|
|
Show all cipher algorithms to use with the
|
|
.B \-\-cipher
|
|
option.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-show-digests
|
|
(Standalone)
|
|
Show all message digest algorithms to use with the
|
|
.B \-\-auth
|
|
option.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-show-tls
|
|
(Standalone)
|
|
Show all TLS ciphers (TLS used only as a control channel). The TLS
|
|
ciphers will be sorted from highest preference (most secure) to
|
|
lowest.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-show-engines
|
|
(Standalone)
|
|
Show currently available hardware-based crypto acceleration
|
|
engines supported by the OpenSSL library.
|
|
.\"*********************************************************
|
|
.SS Generate a random key:
|
|
Used only for non-TLS static key encryption mode.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-genkey
|
|
(Standalone)
|
|
Generate a random key to be used as a shared secret,
|
|
for use with the
|
|
.B \-\-secret
|
|
option. This file must be shared with the
|
|
peer over a pre-existing secure channel such as
|
|
.BR scp (1)
|
|
.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-secret file
|
|
Write key to
|
|
.B file.
|
|
.\"*********************************************************
|
|
.SS TUN/TAP persistent tunnel config mode:
|
|
Available with linux 2.4.7+. These options comprise a standalone mode
|
|
of OpenVPN which can be used to create and delete persistent tunnels.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-mktun
|
|
(Standalone)
|
|
Create a persistent tunnel on platforms which support them such
|
|
as Linux. Normally TUN/TAP tunnels exist only for
|
|
the period of time that an application has them open. This option
|
|
takes advantage of the TUN/TAP driver's ability to build persistent
|
|
tunnels that live through multiple instantiations of OpenVPN and die
|
|
only when they are deleted or the machine is rebooted.
|
|
|
|
One of the advantages of persistent tunnels is that they eliminate the
|
|
need for separate
|
|
.B \-\-up
|
|
and
|
|
.B \-\-down
|
|
scripts to run the appropriate
|
|
.BR ifconfig (8)
|
|
and
|
|
.BR route (8)
|
|
commands. These commands can be placed in the the same shell script
|
|
which starts or terminates an OpenVPN session.
|
|
|
|
Another advantage is that open connections through the TUN/TAP-based tunnel
|
|
will not be reset if the OpenVPN peer restarts. This can be useful to
|
|
provide uninterrupted connectivity through the tunnel in the event of a DHCP
|
|
reset of the peer's public IP address (see the
|
|
.B \-\-ipchange
|
|
option above).
|
|
|
|
One disadvantage of persistent tunnels is that it is harder to automatically
|
|
configure their MTU value (see
|
|
.B \-\-link-mtu
|
|
and
|
|
.B \-\-tun-mtu
|
|
above).
|
|
|
|
On some platforms such as Windows, TAP-Win32 tunnels are persistent by
|
|
default.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-rmtun
|
|
(Standalone)
|
|
Remove a persistent tunnel.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-dev tunX | tapX
|
|
TUN/TAP device
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-user user
|
|
Optional user to be owner of this tunnel.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-group group
|
|
Optional group to be owner of this tunnel.
|
|
.\"*********************************************************
|
|
.SS Windows-Specific Options:
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-win-sys path
|
|
Set the Windows system directory pathname to use when looking for system
|
|
executables such as
|
|
.B route.exe
|
|
and
|
|
.B netsh.exe.
|
|
By default, if this directive is
|
|
not specified, OpenVPN will use the SystemRoot environment variable.
|
|
|
|
This option have changed behaviour in OpenVPN 2.3. Earlier you had to
|
|
define
|
|
.B --win-sys env
|
|
to use the SystemRoot environment variable, otherwise it defaulted to C:\\WINDOWS.
|
|
It is not needed to use the
|
|
.B env
|
|
keyword any more, and it will just be ignored. A warning is logged when this
|
|
is found in the configuration file.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ip-win32 method
|
|
When using
|
|
.B \-\-ifconfig
|
|
on Windows, set the TAP-Win32 adapter
|
|
IP address and netmask using
|
|
.B method.
|
|
Don't use this option unless you are also using
|
|
.B \-\-ifconfig.
|
|
|
|
.B manual \-\-
|
|
Don't set the IP address or netmask automatically.
|
|
Instead output a message
|
|
to the console telling the user to configure the
|
|
adapter manually and indicating the IP/netmask which
|
|
OpenVPN expects the adapter to be set to.
|
|
|
|
.B dynamic [offset] [lease-time] \-\-
|
|
Automatically set the IP address and netmask by replying to
|
|
DHCP query messages generated by the kernel. This mode is
|
|
probably the "cleanest" solution
|
|
for setting the TCP/IP properties since it uses the well-known
|
|
DHCP protocol. There are, however, two prerequisites for using
|
|
this mode: (1) The TCP/IP properties for the TAP-Win32
|
|
adapter must be set to "Obtain an IP address automatically," and
|
|
(2) OpenVPN needs to claim an IP address in the subnet for use
|
|
as the virtual DHCP server address. By default in
|
|
.B \-\-dev tap
|
|
mode, OpenVPN will
|
|
take the normally unused first address in the subnet. For example,
|
|
if your subnet is 192.168.4.0 netmask 255.255.255.0, then
|
|
OpenVPN will take the IP address 192.168.4.0 to use as the
|
|
virtual DHCP server address. In
|
|
.B \-\-dev tun
|
|
mode, OpenVPN will cause the DHCP server to masquerade as if it were
|
|
coming from the remote endpoint. The optional offset parameter is
|
|
an integer which is > -256 and < 256 and which defaults to 0.
|
|
If offset is positive, the DHCP server will masquerade as the IP
|
|
address at network address + offset.
|
|
If offset is negative, the DHCP server will masquerade as the IP
|
|
address at broadcast address + offset. The Windows
|
|
.B ipconfig /all
|
|
command can be used to show what Windows thinks the DHCP server
|
|
address is. OpenVPN will "claim" this address, so make sure to
|
|
use a free address. Having said that, different OpenVPN instantiations,
|
|
including different ends of the same connection, can share the same
|
|
virtual DHCP server address. The
|
|
.B lease-time
|
|
parameter controls the lease time of the DHCP assignment given to
|
|
the TAP-Win32 adapter, and is denoted in seconds.
|
|
Normally a very long lease time is preferred
|
|
because it prevents routes involving the TAP-Win32 adapter from
|
|
being lost when the system goes to sleep. The default
|
|
lease time is one year.
|
|
|
|
.B netsh \-\-
|
|
Automatically set the IP address and netmask using
|
|
the Windows command-line "netsh"
|
|
command. This method appears to work correctly on
|
|
Windows XP but not Windows 2000.
|
|
|
|
.B ipapi \-\-
|
|
Automatically set the IP address and netmask using the
|
|
Windows IP Helper API. This approach
|
|
does not have ideal semantics, though testing has indicated
|
|
that it works okay in practice. If you use this option,
|
|
it is best to leave the TCP/IP properties for the TAP-Win32
|
|
adapter in their default state, i.e. "Obtain an IP address
|
|
automatically."
|
|
|
|
.B adaptive \-\-
|
|
(Default) Try
|
|
.B dynamic
|
|
method initially and fail over to
|
|
.B netsh
|
|
if the DHCP negotiation with the TAP-Win32 adapter does
|
|
not succeed in 20 seconds. Such failures have been known
|
|
to occur when certain third-party firewall packages installed
|
|
on the client machine block the DHCP negotiation used by
|
|
the TAP-Win32 adapter.
|
|
Note that if the
|
|
.B netsh
|
|
failover occurs, the TAP-Win32 adapter
|
|
TCP/IP properties will be reset from DHCP to static, and this
|
|
will cause future OpenVPN startups using the
|
|
.B adaptive
|
|
mode to use
|
|
.B netsh
|
|
immediately, rather than trying
|
|
.B dynamic
|
|
first. To "unstick" the
|
|
.B adaptive
|
|
mode from using
|
|
.B netsh,
|
|
run OpenVPN at least once using the
|
|
.B dynamic
|
|
mode to restore the TAP-Win32 adapter TCP/IP properties
|
|
to a DHCP configuration.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-route-method m
|
|
Which method
|
|
.B m
|
|
to use for adding routes on Windows?
|
|
|
|
.B adaptive
|
|
(default) \-\- Try IP helper API first. If that fails, fall
|
|
back to the route.exe shell command.
|
|
.br
|
|
.B ipapi
|
|
\-\- Use IP helper API.
|
|
.br
|
|
.B exe
|
|
\-\- Call the route.exe shell command.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-dhcp-option type [parm]
|
|
Set extended TAP-Win32 TCP/IP properties, must
|
|
be used with
|
|
.B \-\-ip-win32 dynamic
|
|
or
|
|
.B \-\-ip-win32 adaptive.
|
|
This option can be used to set additional TCP/IP properties
|
|
on the TAP-Win32 adapter, and is particularly useful for
|
|
configuring an OpenVPN client to access a Samba server
|
|
across the VPN.
|
|
|
|
.B DOMAIN name \-\-
|
|
Set Connection-specific DNS Suffix.
|
|
|
|
.B DNS addr \-\-
|
|
Set primary domain name server address. Repeat
|
|
this option to set secondary DNS server addresses.
|
|
|
|
.B WINS addr \-\-
|
|
Set primary WINS server address (NetBIOS over TCP/IP Name Server).
|
|
Repeat this option to set secondary WINS server addresses.
|
|
|
|
.B NBDD addr \-\-
|
|
Set primary NBDD server address (NetBIOS over TCP/IP Datagram Distribution Server)
|
|
Repeat this option
|
|
to set secondary NBDD server addresses.
|
|
|
|
.B NTP addr \-\-
|
|
Set primary NTP server address (Network Time Protocol).
|
|
Repeat this option
|
|
to set secondary NTP server addresses.
|
|
|
|
.B NBT type \-\-
|
|
Set NetBIOS over TCP/IP Node type. Possible options:
|
|
.B 1
|
|
= b-node (broadcasts),
|
|
.B 2
|
|
= p-node (point-to-point
|
|
name queries to a WINS server),
|
|
.B 4
|
|
= m-node (broadcast
|
|
then query name server), and
|
|
.B 8
|
|
= h-node (query name server, then broadcast).
|
|
|
|
.B NBS scope-id \-\-
|
|
Set NetBIOS over TCP/IP Scope. A NetBIOS Scope ID provides an extended
|
|
naming service for the NetBIOS over TCP/IP (Known as NBT) module. The
|
|
primary purpose of a NetBIOS scope ID is to isolate NetBIOS traffic on
|
|
a single network to only those nodes with the same NetBIOS scope ID.
|
|
The NetBIOS scope ID is a character string that is appended to the NetBIOS
|
|
name. The NetBIOS scope ID on two hosts must match, or the two hosts
|
|
will not be able to communicate. The NetBIOS Scope ID also allows
|
|
computers to use the same computer name, as they have different
|
|
scope IDs. The Scope ID becomes a part of the NetBIOS name, making the name unique.
|
|
(This description of NetBIOS scopes courtesy of NeonSurge@abyss.com)
|
|
|
|
.B DISABLE-NBT \-\-
|
|
Disable Netbios-over-TCP/IP.
|
|
|
|
Note that if
|
|
.B \-\-dhcp-option
|
|
is pushed via
|
|
.B \-\-push
|
|
to a non-windows client, the option will be saved in the client's
|
|
environment before the up script is called, under
|
|
the name "foreign_option_{n}".
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tap-sleep n
|
|
Cause OpenVPN to sleep for
|
|
.B n
|
|
seconds immediately after the TAP-Win32 adapter state
|
|
is set to "connected".
|
|
|
|
This option is intended to be used to troubleshoot problems
|
|
with the
|
|
.B \-\-ifconfig
|
|
and
|
|
.B \-\-ip-win32
|
|
options, and is used to give
|
|
the TAP-Win32 adapter time to come up before
|
|
Windows IP Helper API operations are applied to it.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-show-net-up
|
|
Output OpenVPN's view of the system routing table and network
|
|
adapter list to the syslog or log file after the TUN/TAP adapter
|
|
has been brought up and any routes have been added.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-dhcp-renew
|
|
Ask Windows to renew the TAP adapter lease on startup.
|
|
This option is normally unnecessary, as Windows automatically
|
|
triggers a DHCP renegotiation on the TAP adapter when it
|
|
comes up, however if you set the TAP-Win32 adapter
|
|
Media Status property to "Always Connected", you may need this
|
|
flag.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-dhcp-release
|
|
Ask Windows to release the TAP adapter lease on shutdown.
|
|
This option has the same caveats as
|
|
.B \-\-dhcp-renew
|
|
above.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-register-dns
|
|
Run net stop dnscache, net start dnscache, ipconfig /flushdns
|
|
and ipconfig /registerdns on connection initiation.
|
|
This is known to kick Windows into
|
|
recognizing pushed DNS servers.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-pause-exit
|
|
Put up a "press any key to continue" message on the console prior
|
|
to OpenVPN program exit. This option is automatically used by the
|
|
Windows explorer when OpenVPN is run on a configuration
|
|
file using the right-click explorer menu.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-service exit-event [0|1]
|
|
Should be used when OpenVPN is being automatically executed by another
|
|
program in such
|
|
a context that no interaction with the user via display or keyboard
|
|
is possible. In general, end-users should never need to explicitly
|
|
use this option, as it is automatically added by the OpenVPN service wrapper
|
|
when a given OpenVPN configuration is being run as a service.
|
|
|
|
.B exit-event
|
|
is the name of a Windows global event object, and OpenVPN will continuously
|
|
monitor the state of this event object and exit when it becomes signaled.
|
|
|
|
The second parameter indicates the initial state of
|
|
.B exit-event
|
|
and normally defaults to 0.
|
|
|
|
Multiple OpenVPN processes can be simultaneously executed with the same
|
|
.B exit-event
|
|
parameter. In any case, the controlling process can signal
|
|
.B exit-event,
|
|
causing all such OpenVPN processes to exit.
|
|
|
|
When executing an OpenVPN process using the
|
|
.B \-\-service
|
|
directive, OpenVPN will probably not have a console
|
|
window to output status/error
|
|
messages, therefore it is useful to use
|
|
.B \-\-log
|
|
or
|
|
.B \-\-log-append
|
|
to write these messages to a file.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-show-adapters
|
|
(Standalone)
|
|
Show available TAP-Win32 adapters which can be selected using the
|
|
.B \-\-dev-node
|
|
option. On non-Windows systems, the
|
|
.BR ifconfig (8)
|
|
command provides similar functionality.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-allow-nonadmin [TAP-adapter]
|
|
(Standalone)
|
|
Set
|
|
.B TAP-adapter
|
|
to allow access from non-administrative accounts. If
|
|
.B TAP-adapter
|
|
is omitted, all TAP adapters on the system will be configured to allow
|
|
non-admin access.
|
|
The non-admin access setting will only persist for the length of time that
|
|
the TAP-Win32 device object and driver remain loaded, and will need
|
|
to be re-enabled after a reboot, or if the driver is unloaded
|
|
and reloaded.
|
|
This directive can only be used by an administrator.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-show-valid-subnets
|
|
(Standalone)
|
|
Show valid subnets for
|
|
.B \-\-dev tun
|
|
emulation. Since the TAP-Win32 driver
|
|
exports an ethernet interface to Windows, and since TUN devices are
|
|
point-to-point in nature, it is necessary for the TAP-Win32 driver
|
|
to impose certain constraints on TUN endpoint address selection.
|
|
|
|
Namely, the point-to-point endpoints used in TUN device emulation
|
|
must be the middle two addresses of a /30 subnet (netmask 255.255.255.252).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-show-net
|
|
(Standalone)
|
|
Show OpenVPN's view of the system routing table and network
|
|
adapter list.
|
|
.\"*********************************************************
|
|
.SS PKCS#11 Standalone Options:
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-show-pkcs11-ids provider [cert_private]
|
|
(Standalone)
|
|
Show PKCS#11 token object list. Specify cert_private as 1
|
|
if certificates are stored as private objects.
|
|
|
|
.B \-\-verb
|
|
option can be used BEFORE this option to produce debugging information.
|
|
.\"*********************************************************
|
|
.SS IPv6 Related Options
|
|
.\"*********************************************************
|
|
The following options exist to support IPv6 tunneling in peer-to-peer
|
|
and client-server mode. All options are modeled after their IPv4
|
|
counterparts, so more detailed explanations given there apply here
|
|
as well (except for
|
|
.B \-\-topology
|
|
, which has no effect on IPv6).
|
|
.TP
|
|
.B --ifconfig-ipv6 ipv6addr/bits ipv6remote
|
|
configure IPv6 address
|
|
.B ipv6addr/bits
|
|
on the ``tun'' device. The second parameter is used as route target for
|
|
.B --route-ipv6
|
|
if no gateway is specified.
|
|
.TP
|
|
.B --route-ipv6 ipv6addr/bits [gateway] [metric]
|
|
setup IPv6 routing in the system to send the specified IPv6 network
|
|
into OpenVPN's ``tun'' device
|
|
.TP
|
|
.B --server-ipv6 ipv6addr/bits
|
|
convenience-function to enable a number of IPv6 related options at
|
|
once, namely
|
|
.B --ifconfig-ipv6, --ifconfig-ipv6-pool, --tun-ipv6
|
|
and
|
|
.B --push tun-ipv6
|
|
Is only accepted if ``--mode server'' or ``--server'' is set.
|
|
.TP
|
|
.B --ifconfig-ipv6-pool ipv6addr/bits
|
|
Specify an IPv6 address pool for dynamic assignment to clients. The
|
|
pool starts at
|
|
.B ipv6addr
|
|
and increments by +1 for every new client (linear mode). The
|
|
.B /bits
|
|
setting controls the size of the pool. Due to implementation details,
|
|
the pool size must be between /64 and /112.
|
|
.TP
|
|
.B --ifconfig-ipv6-push ipv6addr/bits ipv6remote
|
|
for ccd/ per-client static IPv6 interface configuration, see
|
|
.B --client-config-dir
|
|
and
|
|
.B --ifconfig-push
|
|
for more details.
|
|
.TP
|
|
.B --iroute-ipv6 ipv6addr/bits
|
|
for ccd/ per-client static IPv6 route configuration, see
|
|
.B --iroute
|
|
for more details how to setup and use this, and how
|
|
.B --iroute
|
|
and
|
|
.B --route
|
|
interact.
|
|
|
|
.\"*********************************************************
|
|
.SH SCRIPTING AND ENVIRONMENTAL VARIABLES
|
|
OpenVPN exports a series
|
|
of environmental variables for use by user-defined scripts.
|
|
.\"*********************************************************
|
|
.SS Script Order of Execution
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-up
|
|
Executed after TCP/UDP socket bind and TUN/TAP open.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-tls-verify
|
|
Executed when we have a still untrusted remote peer.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-ipchange
|
|
Executed after connection authentication, or remote IP address change.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-client-connect
|
|
Executed in
|
|
.B \-\-mode server
|
|
mode immediately after client authentication.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-route-up
|
|
Executed after connection authentication, either
|
|
immediately after, or some number of seconds after
|
|
as defined by the
|
|
.B \-\-route-delay
|
|
option.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-route-pre-down
|
|
Executed right before the routes are removed.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-client-disconnect
|
|
Executed in
|
|
.B \-\-mode server
|
|
mode on client instance shutdown.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-down
|
|
Executed after TCP/UDP and TUN/TAP close.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-learn-address
|
|
Executed in
|
|
.B \-\-mode server
|
|
mode whenever an IPv4 address/route or MAC address is added to OpenVPN's
|
|
internal routing table.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B \-\-auth-user-pass-verify
|
|
Executed in
|
|
.B \-\-mode server
|
|
mode on new client connections, when the client is
|
|
still untrusted.
|
|
.\"*********************************************************
|
|
.SS String Types and Remapping
|
|
In certain cases, OpenVPN will perform remapping of characters
|
|
in strings. Essentially, any characters outside the set of
|
|
permitted characters for each string type will be converted
|
|
to underbar ('_').
|
|
|
|
.B Q:
|
|
Why is string remapping necessary?
|
|
|
|
.B A:
|
|
It's an important security feature to prevent the malicious coding of
|
|
strings from untrusted sources to be passed as parameters to scripts,
|
|
saved in the environment, used as a common name, translated to a filename,
|
|
etc.
|
|
|
|
.B Q:
|
|
Can string remapping be disabled?
|
|
|
|
.B A:
|
|
Yes, by using the
|
|
.B \-\-no-name-remapping
|
|
option, however this should be considered an advanced option.
|
|
|
|
Here is a brief rundown of OpenVPN's current string types and the
|
|
permitted character class for each string:
|
|
|
|
.B X509 Names:
|
|
Alphanumeric, underbar ('_'), dash ('-'), dot ('.'), at
|
|
('@'), colon (':'), slash ('/'), and equal ('='). Alphanumeric is defined
|
|
as a character which will cause the C library isalnum() function to return
|
|
true.
|
|
|
|
.B Common Names:
|
|
Alphanumeric, underbar ('_'), dash ('-'), dot ('.'), and at
|
|
('@').
|
|
|
|
.B \-\-auth-user-pass username:
|
|
Same as Common Name, with one exception: starting with OpenVPN 2.0.1,
|
|
the username is passed to the OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY plugin in its raw form,
|
|
without string remapping.
|
|
|
|
.B \-\-auth-user-pass password:
|
|
Any "printable" character except CR or LF.
|
|
Printable is defined to be a character which will cause the C library
|
|
isprint() function to return true.
|
|
|
|
.B \-\-client-config-dir filename as derived from common name or username:
|
|
Alphanumeric, underbar ('_'), dash ('-'), and dot ('.') except for "." or
|
|
".." as standalone strings. As of 2.0.1-rc6, the at ('@') character has
|
|
been added as well for compatibility with the common name character class.
|
|
|
|
.B Environmental variable names:
|
|
Alphanumeric or underbar ('_').
|
|
|
|
.B Environmental variable values:
|
|
Any printable character.
|
|
|
|
For all cases, characters in a string which are not members of the legal
|
|
character class for that string type will be remapped to underbar ('_').
|
|
.\"*********************************************************
|
|
.SS Environmental Variables
|
|
Once set, a variable is persisted
|
|
indefinitely until it is reset by a new value or a restart,
|
|
|
|
As of OpenVPN 2.0-beta12, in server mode, environmental
|
|
variables set by OpenVPN
|
|
are scoped according to the client objects
|
|
they are
|
|
associated with, so there should not be any issues with
|
|
scripts having access to stale, previously set variables
|
|
which refer to different client instances.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B bytes_received
|
|
Total number of bytes received from client during VPN session.
|
|
Set prior to execution of the
|
|
.B \-\-client-disconnect
|
|
script.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B bytes_sent
|
|
Total number of bytes sent to client during VPN session.
|
|
Set prior to execution of the
|
|
.B \-\-client-disconnect
|
|
script.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B common_name
|
|
The X509 common name of an authenticated client.
|
|
Set prior to execution of
|
|
.B \-\-client-connect, \-\-client-disconnect,
|
|
and
|
|
.B \-\-auth-user-pass-verify
|
|
scripts.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B config
|
|
Name of first
|
|
.B \-\-config
|
|
file.
|
|
Set on program initiation and reset on SIGHUP.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B daemon
|
|
Set to "1" if the
|
|
.B \-\-daemon
|
|
directive is specified, or "0" otherwise.
|
|
Set on program initiation and reset on SIGHUP.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B daemon_log_redirect
|
|
Set to "1" if the
|
|
.B \-\-log
|
|
or
|
|
.B \-\-log-append
|
|
directives are specified, or "0" otherwise.
|
|
Set on program initiation and reset on SIGHUP.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B dev
|
|
The actual name of the TUN/TAP device, including
|
|
a unit number if it exists.
|
|
Set prior to
|
|
.B \-\-up
|
|
or
|
|
.B \-\-down
|
|
script execution.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B foreign_option_{n}
|
|
An option pushed via
|
|
.B \-\-push
|
|
to a client which does not natively support it,
|
|
such as
|
|
.B \-\-dhcp-option
|
|
on a non-Windows system, will be recorded to this
|
|
environmental variable sequence prior to
|
|
.B \-\-up
|
|
script execution.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B ifconfig_broadcast
|
|
The broadcast address for the virtual
|
|
ethernet segment which is derived from the
|
|
.B \-\-ifconfig
|
|
option when
|
|
.B \-\-dev tap
|
|
is used.
|
|
Set prior to OpenVPN calling the
|
|
.I ifconfig
|
|
or
|
|
.I netsh
|
|
(windows version of ifconfig) commands which
|
|
normally occurs prior to
|
|
.B \-\-up
|
|
script execution.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B ifconfig_ipv6_local
|
|
The local VPN endpoint IPv6 address specified in the
|
|
.B \-\-ifconfig-ipv6
|
|
option (first parameter).
|
|
Set prior to OpenVPN calling the
|
|
.I ifconfig
|
|
or
|
|
.I netsh
|
|
(windows version of ifconfig) commands which
|
|
normally occurs prior to
|
|
.B \-\-up
|
|
script execution.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B ifconfig_ipv6_netbits
|
|
The prefix length of the IPv6 network on the VPN interface. Derived from
|
|
the /nnn parameter of the IPv6 address in the
|
|
.B \-\-ifconfig-ipv6
|
|
option (first parameter).
|
|
Set prior to OpenVPN calling the
|
|
.I ifconfig
|
|
or
|
|
.I netsh
|
|
(windows version of ifconfig) commands which
|
|
normally occurs prior to
|
|
.B \-\-up
|
|
script execution.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B ifconfig_ipv6_remote
|
|
The remote VPN endpoint IPv6 address specified in the
|
|
.B \-\-ifconfig-ipv6
|
|
option (second parameter).
|
|
Set prior to OpenVPN calling the
|
|
.I ifconfig
|
|
or
|
|
.I netsh
|
|
(windows version of ifconfig) commands which
|
|
normally occurs prior to
|
|
.B \-\-up
|
|
script execution.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B ifconfig_local
|
|
The local VPN endpoint IP address specified in the
|
|
.B \-\-ifconfig
|
|
option (first parameter).
|
|
Set prior to OpenVPN calling the
|
|
.I ifconfig
|
|
or
|
|
.I netsh
|
|
(windows version of ifconfig) commands which
|
|
normally occurs prior to
|
|
.B \-\-up
|
|
script execution.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B ifconfig_remote
|
|
The remote VPN endpoint IP address specified in the
|
|
.B \-\-ifconfig
|
|
option (second parameter) when
|
|
.B \-\-dev tun
|
|
is used.
|
|
Set prior to OpenVPN calling the
|
|
.I ifconfig
|
|
or
|
|
.I netsh
|
|
(windows version of ifconfig) commands which
|
|
normally occurs prior to
|
|
.B \-\-up
|
|
script execution.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B ifconfig_netmask
|
|
The subnet mask of the virtual ethernet segment
|
|
that is specified as the second parameter to
|
|
.B \-\-ifconfig
|
|
when
|
|
.B \-\-dev tap
|
|
is being used.
|
|
Set prior to OpenVPN calling the
|
|
.I ifconfig
|
|
or
|
|
.I netsh
|
|
(windows version of ifconfig) commands which
|
|
normally occurs prior to
|
|
.B \-\-up
|
|
script execution.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B ifconfig_pool_local_ip
|
|
The local
|
|
virtual IP address for the TUN/TAP tunnel taken from an
|
|
.B \-\-ifconfig-push
|
|
directive if specified, or otherwise from
|
|
the ifconfig pool (controlled by the
|
|
.B \-\-ifconfig-pool
|
|
config file directive).
|
|
Only set for
|
|
.B \-\-dev tun
|
|
tunnels.
|
|
This option is set on the server prior to execution
|
|
of the
|
|
.B \-\-client-connect
|
|
and
|
|
.B \-\-client-disconnect
|
|
scripts.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B ifconfig_pool_netmask
|
|
The
|
|
virtual IP netmask for the TUN/TAP tunnel taken from an
|
|
.B \-\-ifconfig-push
|
|
directive if specified, or otherwise from
|
|
the ifconfig pool (controlled by the
|
|
.B \-\-ifconfig-pool
|
|
config file directive).
|
|
Only set for
|
|
.B \-\-dev tap
|
|
tunnels.
|
|
This option is set on the server prior to execution
|
|
of the
|
|
.B \-\-client-connect
|
|
and
|
|
.B \-\-client-disconnect
|
|
scripts.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B ifconfig_pool_remote_ip
|
|
The remote
|
|
virtual IP address for the TUN/TAP tunnel taken from an
|
|
.B \-\-ifconfig-push
|
|
directive if specified, or otherwise from
|
|
the ifconfig pool (controlled by the
|
|
.B \-\-ifconfig-pool
|
|
config file directive).
|
|
This option is set on the server prior to execution
|
|
of the
|
|
.B \-\-client-connect
|
|
and
|
|
.B \-\-client-disconnect
|
|
scripts.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B link_mtu
|
|
The maximum packet size (not including the IP header)
|
|
of tunnel data in UDP tunnel transport mode.
|
|
Set prior to
|
|
.B \-\-up
|
|
or
|
|
.B \-\-down
|
|
script execution.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B local
|
|
The
|
|
.B \-\-local
|
|
parameter.
|
|
Set on program initiation and reset on SIGHUP.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B local_port
|
|
The local port number, specified by
|
|
.B \-\-port
|
|
or
|
|
.B \-\-lport.
|
|
Set on program initiation and reset on SIGHUP.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B password
|
|
The password provided by a connecting client.
|
|
Set prior to
|
|
.B \-\-auth-user-pass-verify
|
|
script execution only when the
|
|
.B via-env
|
|
modifier is specified, and deleted from the environment
|
|
after the script returns.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B proto
|
|
The
|
|
.B \-\-proto
|
|
parameter.
|
|
Set on program initiation and reset on SIGHUP.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B remote_{n}
|
|
The
|
|
.B \-\-remote
|
|
parameter.
|
|
Set on program initiation and reset on SIGHUP.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B remote_port_{n}
|
|
The remote port number, specified by
|
|
.B \-\-port
|
|
or
|
|
.B \-\-rport.
|
|
Set on program initiation and reset on SIGHUP.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B route_net_gateway
|
|
The pre-existing default IP gateway in the system routing
|
|
table.
|
|
Set prior to
|
|
.B \-\-up
|
|
script execution.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B route_vpn_gateway
|
|
The default gateway used by
|
|
.B \-\-route
|
|
options, as specified in either the
|
|
.B \-\-route-gateway
|
|
option or the second parameter to
|
|
.B \-\-ifconfig
|
|
when
|
|
.B \-\-dev tun
|
|
is specified.
|
|
Set prior to
|
|
.B \-\-up
|
|
script execution.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B route_{parm}_{n}
|
|
A set of variables which define each route to be added, and
|
|
are set prior to
|
|
.B \-\-up
|
|
script execution.
|
|
|
|
.B parm
|
|
will be one of "network", "netmask", "gateway", or "metric".
|
|
|
|
.B n
|
|
is the OpenVPN route number, starting from 1.
|
|
|
|
If the network or gateway are resolvable DNS names,
|
|
their IP address translations will be recorded rather
|
|
than their names as denoted on the command line
|
|
or configuration file.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B route_ipv6_{parm}_{n}
|
|
A set of variables which define each IPv6 route to be added, and
|
|
are set prior to
|
|
.B \-\-up
|
|
script execution.
|
|
|
|
.B parm
|
|
will be one of "network" or "gateway" ("netmask" is contained as "/nnn"
|
|
in the route_ipv6_network_{n}, unlike IPv4 where it is passed in a separate
|
|
environment variable).
|
|
|
|
.B n
|
|
is the OpenVPN route number, starting from 1.
|
|
|
|
If the network or gateway are resolvable DNS names,
|
|
their IP address translations will be recorded rather
|
|
than their names as denoted on the command line
|
|
or configuration file.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B peer_cert
|
|
Temporary file name containing the client certificate upon
|
|
connection. Useful in conjunction with --tls-verify
|
|
.\"*********************************************************
|
|
.TP
|
|
.B script_context
|
|
Set to "init" or "restart" prior to up/down script execution.
|
|
For more information, see
|
|
documentation for
|
|
.B \-\-up.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B script_type
|
|
Prior to execution of any script, this variable is set to the type of
|
|
script being run. It can be one of the following:
|
|
.B up, down, ipchange, route-up, tls-verify, auth-user-pass-verify,
|
|
.B client-connect, client-disconnect,
|
|
or
|
|
.B learn-address.
|
|
Set prior to execution of any script.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B signal
|
|
The reason for exit or restart. Can be one of
|
|
.B sigusr1, sighup, sigterm, sigint, inactive
|
|
(controlled by
|
|
.B \-\-inactive
|
|
option),
|
|
.B ping-exit
|
|
(controlled by
|
|
.B \-\-ping-exit
|
|
option),
|
|
.B ping-restart
|
|
(controlled by
|
|
.B \-\-ping-restart
|
|
option),
|
|
.B connection-reset
|
|
(triggered on TCP connection reset),
|
|
.B error,
|
|
or
|
|
.B unknown
|
|
(unknown signal). This variable is set just prior to down script execution.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B time_ascii
|
|
Client connection timestamp, formatted as a human-readable
|
|
time string.
|
|
Set prior to execution of the
|
|
.B \-\-client-connect
|
|
script.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B time_duration
|
|
The duration (in seconds) of the client session which is now
|
|
disconnecting.
|
|
Set prior to execution of the
|
|
.B \-\-client-disconnect
|
|
script.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B time_unix
|
|
Client connection timestamp, formatted as a unix integer
|
|
date/time value.
|
|
Set prior to execution of the
|
|
.B \-\-client-connect
|
|
script.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B tls_digest_{n}
|
|
Contains the certificate SHA1 fingerprint/digest hash value,
|
|
where
|
|
.B n
|
|
is the verification level. Only set for TLS connections. Set prior
|
|
to execution of
|
|
.B \-\-tls-verify
|
|
script.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B tls_id_{n}
|
|
A series of certificate fields from the remote peer,
|
|
where
|
|
.B n
|
|
is the verification level. Only set for TLS connections. Set prior
|
|
to execution of
|
|
.B \-\-tls-verify
|
|
script.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B tls_serial_{n}
|
|
The serial number of the certificate from the remote peer,
|
|
where
|
|
.B n
|
|
is the verification level. Only set for TLS connections. Set prior
|
|
to execution of
|
|
.B \-\-tls-verify
|
|
script. This is in the form of a decimal string like "933971680", which is
|
|
suitable for doing serial-based OCSP queries (with OpenSSL, do not
|
|
prepend "0x" to the string) If something goes wrong while reading
|
|
the value from the certificate it will be an empty string, so your
|
|
code should check that.
|
|
See the contrib/OCSP_check/OCSP_check.sh script for an example.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B tls_serial_hex_{n}
|
|
Like
|
|
.B tls_serial_{n}\fR,
|
|
but in hex form (e.g. "12:34:56:78:9A").
|
|
.\"*********************************************************
|
|
.TP
|
|
.B tun_mtu
|
|
The MTU of the TUN/TAP device.
|
|
Set prior to
|
|
.B \-\-up
|
|
or
|
|
.B \-\-down
|
|
script execution.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B trusted_ip (or trusted_ip6)
|
|
Actual IP address of connecting client or peer which has been authenticated.
|
|
Set prior to execution of
|
|
.B \-\-ipchange, \-\-client-connect,
|
|
and
|
|
.B \-\-client-disconnect
|
|
scripts.
|
|
If using ipv6 endpoints (udp6, tcp6),
|
|
.B trusted_ip6
|
|
will be set instead.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B trusted_port
|
|
Actual port number of connecting client or peer which has been authenticated.
|
|
Set prior to execution of
|
|
.B \-\-ipchange, \-\-client-connect,
|
|
and
|
|
.B \-\-client-disconnect
|
|
scripts.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B untrusted_ip (or untrusted_ip6)
|
|
Actual IP address of connecting client or peer which has not been authenticated
|
|
yet. Sometimes used to
|
|
.B nmap
|
|
the connecting host in a
|
|
.B \-\-tls-verify
|
|
script to ensure it is firewalled properly.
|
|
Set prior to execution of
|
|
.B \-\-tls-verify
|
|
and
|
|
.B \-\-auth-user-pass-verify
|
|
scripts.
|
|
If using ipv6 endpoints (udp6, tcp6),
|
|
.B untrusted_ip6
|
|
will be set instead.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B untrusted_port
|
|
Actual port number of connecting client or peer which has not been authenticated
|
|
yet.
|
|
Set prior to execution of
|
|
.B \-\-tls-verify
|
|
and
|
|
.B \-\-auth-user-pass-verify
|
|
scripts.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B username
|
|
The username provided by a connecting client.
|
|
Set prior to
|
|
.B \-\-auth-user-pass-verify
|
|
script execution only when the
|
|
.B via-env
|
|
modifier is specified.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B X509_{n}_{subject_field}
|
|
An X509 subject field from the remote peer certificate,
|
|
where
|
|
.B n
|
|
is the verification level. Only set for TLS connections. Set prior
|
|
to execution of
|
|
.B \-\-tls-verify
|
|
script. This variable is similar to
|
|
.B tls_id_{n}
|
|
except the component X509 subject fields are broken out, and
|
|
no string remapping occurs on these field values (except for remapping
|
|
of control characters to "_").
|
|
For example, the following variables would be set on the
|
|
OpenVPN server using the sample client certificate
|
|
in sample-keys (client.crt).
|
|
Note that the verification level is 0 for the client certificate
|
|
and 1 for the CA certificate.
|
|
|
|
.nf
|
|
.ft 3
|
|
.in +4
|
|
X509_0_emailAddress=me@myhost.mydomain
|
|
X509_0_CN=Test-Client
|
|
X509_0_O=OpenVPN-TEST
|
|
X509_0_ST=NA
|
|
X509_0_C=KG
|
|
X509_1_emailAddress=me@myhost.mydomain
|
|
X509_1_O=OpenVPN-TEST
|
|
X509_1_L=BISHKEK
|
|
X509_1_ST=NA
|
|
X509_1_C=KG
|
|
.in -4
|
|
.ft
|
|
.fi
|
|
.\"*********************************************************
|
|
.SH INLINE FILE SUPPORT
|
|
OpenVPN allows including files in the main configuration for the
|
|
.B \-\-ca, \-\-cert, \-\-dh, \-\-extra-certs, \-\-key, \-\-pkcs12, \-\-secret
|
|
and
|
|
.B \-\-tls-auth
|
|
options.
|
|
|
|
Each inline file started by the line
|
|
.B <option>
|
|
and ended by the line
|
|
.B </option>
|
|
|
|
Here is an example of an inline file usage
|
|
|
|
.nf
|
|
.ft 3
|
|
.in +4
|
|
<cert>
|
|
-----BEGIN CERTIFICATE-----
|
|
[...]
|
|
-----END CERTIFICATE-----
|
|
</cert>
|
|
.in -4
|
|
.ft
|
|
.fi
|
|
|
|
When using the inline file feature with
|
|
.B \-\-pkcs12
|
|
the inline file has to be base64 encoded. Encoding of a .p12 file into base64 can be done for example with OpenSSL by running
|
|
.B openssl base64 -in input.p12
|
|
|
|
.SH SIGNALS
|
|
.TP
|
|
.B SIGHUP
|
|
Cause OpenVPN to close all TUN/TAP and
|
|
network connections,
|
|
restart, re-read the configuration file (if any),
|
|
and reopen TUN/TAP and network connections.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B SIGUSR1
|
|
Like
|
|
.B SIGHUP,
|
|
except don't re-read configuration file, and possibly don't close and reopen TUN/TAP
|
|
device, re-read key files, preserve local IP address/port, or preserve most recently authenticated
|
|
remote IP address/port based on
|
|
.B \-\-persist-tun, \-\-persist-key, \-\-persist-local-ip,
|
|
and
|
|
.B \-\-persist-remote-ip
|
|
options respectively (see above).
|
|
|
|
This signal may also be internally generated by a timeout condition, governed
|
|
by the
|
|
.B \-\-ping-restart
|
|
option.
|
|
|
|
This signal, when combined with
|
|
.B \-\-persist-remote-ip,
|
|
may be
|
|
sent when the underlying parameters of the host's network interface change
|
|
such as when the host is a DHCP client and is assigned a new IP address.
|
|
See
|
|
.B \-\-ipchange
|
|
above for more information.
|
|
.\"*********************************************************
|
|
.TP
|
|
.B SIGUSR2
|
|
Causes OpenVPN to display its current statistics (to the syslog
|
|
file if
|
|
.B \-\-daemon
|
|
is used, or stdout otherwise).
|
|
.\"*********************************************************
|
|
.TP
|
|
.B SIGINT, SIGTERM
|
|
Causes OpenVPN to exit gracefully.
|
|
.\"*********************************************************
|
|
.SH TUN/TAP DRIVER SETUP
|
|
If you are running Linux 2.4.7 or higher, you probably have the TUN/TAP driver
|
|
already installed. If so, there are still a few things you need to do:
|
|
|
|
Make device:
|
|
.B mknod /dev/net/tun c 10 200
|
|
|
|
Load driver:
|
|
.B modprobe tun
|
|
.\"*********************************************************
|
|
.SH EXAMPLES
|
|
Prior to running these examples, you should have OpenVPN installed on two
|
|
machines with network connectivity between them. If you have not
|
|
yet installed OpenVPN, consult the INSTALL file included in the OpenVPN
|
|
distribution.
|
|
.\"*********************************************************
|
|
.SS TUN/TAP Setup:
|
|
If you are using Linux 2.4 or higher,
|
|
make the tun device node and load the tun module:
|
|
.IP
|
|
.B mknod /dev/net/tun c 10 200
|
|
.LP
|
|
.IP
|
|
.B modprobe tun
|
|
.LP
|
|
If you installed from RPM, the
|
|
.B mknod
|
|
step may be omitted, because the RPM install does that for you.
|
|
|
|
Only Linux 2.4 and newer are supported.
|
|
|
|
For other platforms, consult the INSTALL file at
|
|
.I http://openvpn.net/install.html
|
|
for more information.
|
|
.\"*********************************************************
|
|
.SS Firewall Setup:
|
|
If firewalls exist between
|
|
the two machines, they should be set to forward UDP port 1194
|
|
in both directions. If you do not have control over the firewalls
|
|
between the two machines, you may still be able to use OpenVPN by adding
|
|
.B \-\-ping 15
|
|
to each of the
|
|
.B openvpn
|
|
commands used below in the examples (this will cause each peer to send out
|
|
a UDP ping to its remote peer once every 15 seconds which will cause many
|
|
stateful firewalls to forward packets in both directions
|
|
without an explicit firewall rule).
|
|
|
|
If you are using a Linux iptables-based firewall, you may need to enter
|
|
the following command to allow incoming packets on the TUN device:
|
|
.IP
|
|
.B iptables -A INPUT -i tun+ -j ACCEPT
|
|
.LP
|
|
See the firewalls section below for more information on configuring firewalls
|
|
for use with OpenVPN.
|
|
.\"*********************************************************
|
|
.SS VPN Address Setup:
|
|
For purposes
|
|
of our example, our two machines will be called
|
|
.B may.kg
|
|
and
|
|
.B june.kg.
|
|
If you are constructing a VPN over the internet, then replace
|
|
.B may.kg
|
|
and
|
|
.B june.kg
|
|
with the internet hostname or IP address that each machine will use
|
|
to contact the other over the internet.
|
|
|
|
Now we will choose the tunnel endpoints. Tunnel endpoints are
|
|
private IP addresses that only have meaning in the context of
|
|
the VPN. Each machine will use the tunnel endpoint of the other
|
|
machine to access it over the VPN. In our example,
|
|
the tunnel endpoint for may.kg
|
|
will be 10.4.0.1 and for june.kg, 10.4.0.2.
|
|
|
|
Once the VPN is established, you have essentially
|
|
created a secure alternate path between the two hosts
|
|
which is addressed by using the tunnel endpoints. You can
|
|
control which network
|
|
traffic passes between the hosts
|
|
(a) over the VPN or (b) independently of the VPN, by choosing whether to use
|
|
(a) the VPN endpoint address or (b) the public internet address,
|
|
to access the remote host. For example if you are on may.kg and you wish to connect to june.kg
|
|
via
|
|
.B ssh
|
|
without using the VPN (since
|
|
.B ssh
|
|
has its own built-in security) you would use the command
|
|
.B ssh june.kg.
|
|
However in the same scenario, you could also use the command
|
|
.B telnet 10.4.0.2
|
|
to create a telnet session with june.kg over the VPN, that would
|
|
use the VPN to secure the session rather than
|
|
.B ssh.
|
|
|
|
You can use any address you wish for the
|
|
tunnel endpoints
|
|
but make sure that they are private addresses
|
|
(such as those that begin with 10 or 192.168) and that they are
|
|
not part of any existing subnet on the networks of
|
|
either peer, unless you are bridging. If you use an address that is part of
|
|
your local subnet for either of the tunnel endpoints,
|
|
you will get a weird feedback loop.
|
|
.\"*********************************************************
|
|
.SS Example 1: A simple tunnel without security
|
|
.LP
|
|
On may:
|
|
.IP
|
|
.B openvpn \-\-remote june.kg \-\-dev tun1 \-\-ifconfig 10.4.0.1 10.4.0.2 \-\-verb 9
|
|
.LP
|
|
On june:
|
|
.IP
|
|
.B openvpn \-\-remote may.kg \-\-dev tun1 \-\-ifconfig 10.4.0.2 10.4.0.1 \-\-verb 9
|
|
.LP
|
|
Now verify the tunnel is working by pinging across the tunnel.
|
|
.LP
|
|
On may:
|
|
.IP
|
|
.B ping 10.4.0.2
|
|
.LP
|
|
On june:
|
|
.IP
|
|
.B ping 10.4.0.1
|
|
.LP
|
|
The
|
|
.B \-\-verb 9
|
|
option will produce verbose output, similar to the
|
|
.BR tcpdump (8)
|
|
program. Omit the
|
|
.B \-\-verb 9
|
|
option to have OpenVPN run quietly.
|
|
.\"*********************************************************
|
|
.SS Example 2: A tunnel with static-key security (i.e. using a pre-shared secret)
|
|
First build a static key on may.
|
|
.IP
|
|
.B openvpn \-\-genkey \-\-secret key
|
|
.LP
|
|
This command will build a random key file called
|
|
.B key
|
|
(in ascii format).
|
|
Now copy
|
|
.B key
|
|
to june over a secure medium such as by
|
|
using the
|
|
.BR scp (1)
|
|
program.
|
|
.LP
|
|
On may:
|
|
.IP
|
|
.B openvpn \-\-remote june.kg \-\-dev tun1 \-\-ifconfig 10.4.0.1 10.4.0.2 \-\-verb 5 \-\-secret key
|
|
.LP
|
|
On june:
|
|
.IP
|
|
.B openvpn \-\-remote may.kg \-\-dev tun1 \-\-ifconfig 10.4.0.2 10.4.0.1 \-\-verb 5 \-\-secret key
|
|
.LP
|
|
Now verify the tunnel is working by pinging across the tunnel.
|
|
.LP
|
|
On may:
|
|
.IP
|
|
.B ping 10.4.0.2
|
|
.LP
|
|
On june:
|
|
.IP
|
|
.B ping 10.4.0.1
|
|
.\"*********************************************************
|
|
.SS Example 3: A tunnel with full TLS-based security
|
|
For this test, we will designate
|
|
.B may
|
|
as the TLS client and
|
|
.B june
|
|
as the TLS server.
|
|
.I Note that client or server designation only has meaning for the TLS subsystem. It has no bearing on OpenVPN's peer-to-peer, UDP-based communication model.
|
|
|
|
First, build a separate certificate/key pair
|
|
for both may and june (see above where
|
|
.B \-\-cert
|
|
is discussed for more info). Then construct
|
|
Diffie Hellman parameters (see above where
|
|
.B \-\-dh
|
|
is discussed for more info). You can also use the
|
|
included test files client.crt, client.key,
|
|
server.crt, server.key and ca.crt.
|
|
The .crt files are certificates/public-keys, the .key
|
|
files are private keys, and ca.crt is a certification
|
|
authority who has signed both
|
|
client.crt and server.crt. For Diffie Hellman
|
|
parameters you can use the included file dh1024.pem.
|
|
.I Note that all client, server, and certificate authority certificates and keys included in the OpenVPN distribution are totally insecure and should be used for testing only.
|
|
.LP
|
|
On may:
|
|
.IP
|
|
.B openvpn \-\-remote june.kg \-\-dev tun1 \-\-ifconfig 10.4.0.1 10.4.0.2 \-\-tls-client \-\-ca ca.crt \-\-cert client.crt \-\-key client.key \-\-reneg-sec 60 \-\-verb 5
|
|
.LP
|
|
On june:
|
|
.IP
|
|
.B openvpn \-\-remote may.kg \-\-dev tun1 \-\-ifconfig 10.4.0.2 10.4.0.1 \-\-tls-server \-\-dh dh1024.pem \-\-ca ca.crt \-\-cert server.crt \-\-key server.key \-\-reneg-sec 60 \-\-verb 5
|
|
.LP
|
|
Now verify the tunnel is working by pinging across the tunnel.
|
|
.LP
|
|
On may:
|
|
.IP
|
|
.B ping 10.4.0.2
|
|
.LP
|
|
On june:
|
|
.IP
|
|
.B ping 10.4.0.1
|
|
.LP
|
|
Notice the
|
|
.B \-\-reneg-sec 60
|
|
option we used above. That tells OpenVPN to renegotiate
|
|
the data channel keys every minute.
|
|
Since we used
|
|
.B \-\-verb 5
|
|
above, you will see status information on each new key negotiation.
|
|
|
|
For production operations, a key renegotiation interval of 60 seconds
|
|
is probably too frequent. Omit the
|
|
.B \-\-reneg-sec 60
|
|
option to use OpenVPN's default key renegotiation interval of one hour.
|
|
.\"*********************************************************
|
|
.SS Routing:
|
|
Assuming you can ping across the tunnel,
|
|
the next step is to route a real subnet over
|
|
the secure tunnel. Suppose that may and june have two network
|
|
interfaces each, one connected
|
|
to the internet, and the other to a private
|
|
network. Our goal is to securely connect
|
|
both private networks. We will assume that may's private subnet
|
|
is 10.0.0.0/24 and june's is 10.0.1.0/24.
|
|
.LP
|
|
First, ensure that IP forwarding is enabled on both peers.
|
|
On Linux, enable routing:
|
|
.IP
|
|
.B echo 1 > /proc/sys/net/ipv4/ip_forward
|
|
.LP
|
|
and enable TUN packet forwarding through the firewall:
|
|
.IP
|
|
.B iptables -A FORWARD -i tun+ -j ACCEPT
|
|
.LP
|
|
On may:
|
|
.IP
|
|
.B route add -net 10.0.1.0 netmask 255.255.255.0 gw 10.4.0.2
|
|
.LP
|
|
On june:
|
|
.IP
|
|
.B route add -net 10.0.0.0 netmask 255.255.255.0 gw 10.4.0.1
|
|
.LP
|
|
Now any machine on the 10.0.0.0/24 subnet can
|
|
access any machine on the 10.0.1.0/24 subnet
|
|
over the secure tunnel (or vice versa).
|
|
|
|
In a production environment, you could put the route command(s)
|
|
in a script and execute with the
|
|
.B \-\-up
|
|
option.
|
|
.\"*********************************************************
|
|
.SH FIREWALLS
|
|
OpenVPN's usage of a single UDP port makes it fairly firewall-friendly.
|
|
You should add an entry to your firewall rules to allow incoming OpenVPN
|
|
packets. On Linux 2.4+:
|
|
.IP
|
|
.B iptables -A INPUT -p udp -s 1.2.3.4 \-\-dport 1194 -j ACCEPT
|
|
.LP
|
|
This will allow incoming packets on UDP port 1194 (OpenVPN's default UDP port)
|
|
from an OpenVPN peer at 1.2.3.4.
|
|
|
|
If you are using HMAC-based packet authentication (the default in any of
|
|
OpenVPN's secure modes), having the firewall filter on source
|
|
address can be considered optional, since HMAC packet authentication
|
|
is a much more secure method of verifying the authenticity of
|
|
a packet source. In that case:
|
|
.IP
|
|
.B iptables -A INPUT -p udp \-\-dport 1194 -j ACCEPT
|
|
.LP
|
|
would be adequate and would not render the host inflexible with
|
|
respect to its peer having a dynamic IP address.
|
|
|
|
OpenVPN also works well on stateful firewalls. In some cases, you may
|
|
not need to add any static rules to the firewall list if you are
|
|
using a stateful firewall that knows how to track UDP connections.
|
|
If you specify
|
|
.B \-\-ping n,
|
|
OpenVPN will be guaranteed
|
|
to send a packet to its peer at least once every
|
|
.B n
|
|
seconds. If
|
|
.B n
|
|
is less than the stateful firewall connection timeout, you can
|
|
maintain an OpenVPN connection indefinitely without explicit
|
|
firewall rules.
|
|
|
|
You should also add firewall rules to allow incoming IP traffic on
|
|
TUN or TAP devices such as:
|
|
.IP
|
|
.B iptables -A INPUT -i tun+ -j ACCEPT
|
|
.LP
|
|
to allow input packets from tun devices,
|
|
.IP
|
|
.B iptables -A FORWARD -i tun+ -j ACCEPT
|
|
.LP
|
|
to allow input packets from tun devices to be forwarded to
|
|
other hosts on the local network,
|
|
.IP
|
|
.B iptables -A INPUT -i tap+ -j ACCEPT
|
|
.LP
|
|
to allow input packets from tap devices, and
|
|
.IP
|
|
.B iptables -A FORWARD -i tap+ -j ACCEPT
|
|
.LP
|
|
to allow input packets from tap devices to be forwarded to
|
|
other hosts on the local network.
|
|
|
|
These rules are secure if you use packet authentication,
|
|
since no incoming packets will arrive on a TUN or TAP
|
|
virtual device
|
|
unless they first pass an HMAC authentication test.
|
|
.\"*********************************************************
|
|
.SH FAQ
|
|
.I http://openvpn.net/faq.html
|
|
.\"*********************************************************
|
|
.SH HOWTO
|
|
For a more comprehensive guide to setting up OpenVPN
|
|
in a production setting, see the OpenVPN HOWTO at
|
|
.I http://openvpn.net/howto.html
|
|
.\"*********************************************************
|
|
.SH PROTOCOL
|
|
For a description of OpenVPN's underlying protocol,
|
|
see
|
|
.I http://openvpn.net/security.html
|
|
.\"*********************************************************
|
|
.SH WEB
|
|
OpenVPN's web site is at
|
|
.I http://openvpn.net/
|
|
|
|
Go here to download the latest version of OpenVPN, subscribe
|
|
to the mailing lists, read the mailing list
|
|
archives, or browse the SVN repository.
|
|
.\"*********************************************************
|
|
.SH BUGS
|
|
Report all bugs to the OpenVPN team <info@openvpn.net>.
|
|
.\"*********************************************************
|
|
.SH "SEE ALSO"
|
|
.BR dhcpcd (8),
|
|
.BR ifconfig (8),
|
|
.BR openssl (1),
|
|
.BR route (8),
|
|
.BR scp (1)
|
|
.BR ssh (1)
|
|
.\"*********************************************************
|
|
.SH NOTES
|
|
.LP
|
|
This product includes software developed by the
|
|
OpenSSL Project (
|
|
.I http://www.openssl.org/
|
|
)
|
|
|
|
For more information on the TLS protocol, see
|
|
.I http://www.ietf.org/rfc/rfc2246.txt
|
|
|
|
For more information on the LZO real-time compression library see
|
|
.I http://www.oberhumer.com/opensource/lzo/
|
|
.\"*********************************************************
|
|
.SH COPYRIGHT
|
|
Copyright (C) 2002-2010 OpenVPN Technologies, Inc. This program is free software;
|
|
you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License version 2
|
|
as published by the Free Software Foundation.
|
|
.\"*********************************************************
|
|
.SH AUTHORS
|
|
James Yonan <jim@yonan.net>
|