175 lines
3.5 KiB
Plaintext
Executable File
175 lines
3.5 KiB
Plaintext
Executable File
|
|
Support to pass the password via a pipe to the pppd
|
|
---------------------------------------------------
|
|
|
|
Arvin Schnell <arvin@suse.de>
|
|
2002-02-08
|
|
|
|
|
|
1. Introduction
|
|
---------------
|
|
|
|
Normally programs like wvdial or kppp read the online password from their
|
|
config file and store them in the pap- and chap-secrets before they start the
|
|
pppd and remove them afterwards. Sure they need special privileges to do so.
|
|
|
|
The passwordfd feature offers a simpler and more secure solution. The program
|
|
that starts the pppd opens a pipe and writes the password into it. The pppd
|
|
simply reads the password from that pipe.
|
|
|
|
This methods is used for quite a while on SuSE Linux by the programs wvdial,
|
|
kppp and smpppd.
|
|
|
|
|
|
2. Example
|
|
----------
|
|
|
|
Here is a short C program that uses the passwordfd feature. It starts the pppd
|
|
to buildup a pppoe connection.
|
|
|
|
|
|
--snip--
|
|
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <unistd.h>
|
|
#include <signal.h>
|
|
#include <string.h>
|
|
#include <paths.h>
|
|
|
|
#ifndef _PATH_PPPD
|
|
#define _PATH_PPPD "/usr/sbin/pppd"
|
|
#endif
|
|
|
|
|
|
// Of course these values can be read from a configuration file or
|
|
// entered in a graphical dialog.
|
|
char *device = "eth0";
|
|
char *username = "1122334455661122334455660001@t-online.de";
|
|
char *password = "hello";
|
|
|
|
pid_t pid = 0;
|
|
|
|
|
|
void
|
|
sigproc (int src)
|
|
{
|
|
fprintf (stderr, "Sending signal %d to pid %d\n", src, pid);
|
|
kill (pid, src);
|
|
exit (EXIT_SUCCESS);
|
|
}
|
|
|
|
|
|
void
|
|
sigchild (int src)
|
|
{
|
|
fprintf (stderr, "Daemon died\n");
|
|
exit (EXIT_SUCCESS);
|
|
}
|
|
|
|
|
|
int
|
|
start_pppd ()
|
|
{
|
|
signal (SIGINT, &sigproc);
|
|
signal (SIGTERM, &sigproc);
|
|
signal (SIGCHLD, &sigchild);
|
|
|
|
pid = fork ();
|
|
if (pid < 0) {
|
|
fprintf (stderr, "unable to fork() for pppd: %m\n");
|
|
return 0;
|
|
}
|
|
|
|
if (pid == 0) {
|
|
|
|
int i, pppd_argc = 0;
|
|
char *pppd_argv[20];
|
|
char buffer[32] = "";
|
|
int pppd_passwdfd[2];
|
|
|
|
for (i = 0; i < 20; i++)
|
|
pppd_argv[i] = NULL;
|
|
|
|
pppd_argv[pppd_argc++] = "pppd";
|
|
|
|
pppd_argv[pppd_argc++] = "call";
|
|
pppd_argv[pppd_argc++] = "pwfd-test";
|
|
|
|
// The device must be after the call, since the call loads the plugin.
|
|
pppd_argv[pppd_argc++] = device;
|
|
|
|
pppd_argv[pppd_argc++] = "user";
|
|
pppd_argv[pppd_argc++] = username;
|
|
|
|
// Open a pipe to pass the password to pppd.
|
|
if (pipe (pppd_passwdfd) == -1) {
|
|
fprintf (stderr, "pipe failed: %m\n");
|
|
exit (EXIT_FAILURE);
|
|
}
|
|
|
|
// Of course this only works it the password is shorter
|
|
// than the pipe buffer. Otherwise you have to fork to
|
|
// prevent that your main program blocks.
|
|
write (pppd_passwdfd[1], password, strlen (password));
|
|
close (pppd_passwdfd[1]);
|
|
|
|
// Tell the pppd to read the password from the fd.
|
|
pppd_argv[pppd_argc++] = "passwordfd";
|
|
snprintf (buffer, 32, "%d", pppd_passwdfd[0]);
|
|
pppd_argv[pppd_argc++] = buffer;
|
|
|
|
if (execv (_PATH_PPPD, (char **) pppd_argv) < 0) {
|
|
fprintf (stderr, "cannot execl %s: %m\n", _PATH_PPPD);
|
|
exit (EXIT_FAILURE);
|
|
}
|
|
}
|
|
|
|
pause ();
|
|
|
|
return 1;
|
|
}
|
|
|
|
|
|
int
|
|
main (int argc, char **argv)
|
|
{
|
|
if (start_pppd ())
|
|
exit (EXIT_SUCCESS);
|
|
|
|
exit (EXIT_FAILURE);
|
|
}
|
|
|
|
---snip---
|
|
|
|
|
|
Copy this file to /etc/ppp/peers/pwfd-test. The plugins can't be loaded on the
|
|
command line (unless you are root) since the plugin option is privileged.
|
|
|
|
|
|
---snip---
|
|
|
|
#
|
|
# PPPoE plugin for kernel 2.4
|
|
#
|
|
plugin pppoe.so
|
|
|
|
#
|
|
# This plugin enables us to pipe the password to pppd, thus we don't have
|
|
# to fiddle with pap-secrets and chap-secrets. The user is also passed
|
|
# on the command line.
|
|
#
|
|
plugin passwordfd.so
|
|
|
|
noauth
|
|
usepeerdns
|
|
defaultroute
|
|
hide-password
|
|
nodetach
|
|
nopcomp
|
|
novjccomp
|
|
noccp
|
|
|
|
---snip---
|
|
|