656 lines
18 KiB
C
Executable File
656 lines
18 KiB
C
Executable File
/*
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* Dropbear - a SSH2 server
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*
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* Copyright (c) 2002,2003 Matt Johnston
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* All rights reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE. */
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#include "includes.h"
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#include "packet.h"
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#include "session.h"
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#include "dbutil.h"
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#include "ssh.h"
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#include "algo.h"
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#include "buffer.h"
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#include "kex.h"
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#include "random.h"
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#include "service.h"
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#include "auth.h"
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#include "channel.h"
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static void read_packet_init();
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static void writemac(buffer * outputbuffer, buffer * clearwritebuf);
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static int checkmac(buffer* hashbuf, buffer* readbuf);
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#define ZLIB_COMPRESS_INCR 20 /* this is 12 bytes + 0.1% of 8000 bytes */
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#define ZLIB_DECOMPRESS_INCR 100
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#ifndef DISABLE_ZLIB
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static buffer* buf_decompress(buffer* buf, unsigned int len);
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static void buf_compress(buffer * dest, buffer * src, unsigned int len);
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#endif
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/* non-blocking function writing out a current encrypted packet */
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void write_packet() {
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int len, written;
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buffer * writebuf = NULL;
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TRACE(("enter write_packet"))
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dropbear_assert(!isempty(&ses.writequeue));
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/* Get the next buffer in the queue of encrypted packets to write*/
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writebuf = (buffer*)examine(&ses.writequeue);
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len = writebuf->len - writebuf->pos;
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dropbear_assert(len > 0);
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/* Try to write as much as possible */
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written = write(ses.sock_out, buf_getptr(writebuf, len), len);
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if (written < 0) {
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if (errno == EINTR) {
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TRACE(("leave writepacket: EINTR"))
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return;
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} else {
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dropbear_exit("error writing");
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}
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}
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ses.last_trx_packet_time = time(NULL);
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ses.last_packet_time = time(NULL);
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if (written == 0) {
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ses.remoteclosed();
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}
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if (written == len) {
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/* We've finished with the packet, free it */
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dequeue(&ses.writequeue);
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buf_free(writebuf);
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writebuf = NULL;
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} else {
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/* More packet left to write, leave it in the queue for later */
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buf_incrpos(writebuf, written);
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}
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TRACE(("leave write_packet"))
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}
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/* Non-blocking function reading available portion of a packet into the
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* ses's buffer, decrypting the length if encrypted, decrypting the
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* full portion if possible */
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void read_packet() {
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int len;
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unsigned int maxlen;
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unsigned char blocksize;
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TRACE(("enter read_packet"))
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blocksize = ses.keys->recv_algo_crypt->blocksize;
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if (ses.readbuf == NULL || ses.readbuf->len < blocksize) {
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/* In the first blocksize of a packet */
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/* Read the first blocksize of the packet, so we can decrypt it and
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* find the length of the whole packet */
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read_packet_init();
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/* If we don't have the length of decryptreadbuf, we didn't read
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* a whole blocksize and should exit */
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if (ses.decryptreadbuf->len == 0) {
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TRACE(("leave read_packet: packetinit done"))
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return;
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}
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}
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/* Attempt to read the remainder of the packet, note that there
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* mightn't be any available (EAGAIN) */
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dropbear_assert(ses.readbuf != NULL);
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maxlen = ses.readbuf->len - ses.readbuf->pos;
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len = read(ses.sock_in, buf_getptr(ses.readbuf, maxlen), maxlen);
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if (len == 0) {
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ses.remoteclosed();
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}
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if (len < 0) {
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if (errno == EINTR || errno == EAGAIN) {
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TRACE(("leave read_packet: EINTR or EAGAIN"))
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return;
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} else {
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dropbear_exit("error reading: %s", strerror(errno));
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}
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}
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buf_incrpos(ses.readbuf, len);
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if ((unsigned int)len == maxlen) {
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/* The whole packet has been read */
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decrypt_packet();
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/* The main select() loop process_packet() to
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* handle the packet contents... */
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}
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TRACE(("leave read_packet"))
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}
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/* Function used to read the initial portion of a packet, and determine the
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* length. Only called during the first BLOCKSIZE of a packet. */
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static void read_packet_init() {
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unsigned int maxlen;
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int len;
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unsigned char blocksize;
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unsigned char macsize;
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blocksize = ses.keys->recv_algo_crypt->blocksize;
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macsize = ses.keys->recv_algo_mac->hashsize;
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if (ses.readbuf == NULL) {
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/* start of a new packet */
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ses.readbuf = buf_new(INIT_READBUF);
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dropbear_assert(ses.decryptreadbuf == NULL);
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ses.decryptreadbuf = buf_new(blocksize);
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}
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maxlen = blocksize - ses.readbuf->pos;
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/* read the rest of the packet if possible */
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len = read(ses.sock_in, buf_getwriteptr(ses.readbuf, maxlen),
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maxlen);
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if (len == 0) {
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ses.remoteclosed();
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}
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if (len < 0) {
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if (errno == EINTR) {
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TRACE(("leave read_packet_init: EINTR"))
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return;
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}
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dropbear_exit("error reading: %s", strerror(errno));
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}
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buf_incrwritepos(ses.readbuf, len);
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if ((unsigned int)len != maxlen) {
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/* don't have enough bytes to determine length, get next time */
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return;
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}
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/* now we have the first block, need to get packet length, so we decrypt
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* the first block (only need first 4 bytes) */
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buf_setpos(ses.readbuf, 0);
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if (ses.keys->recv_crypt_mode->decrypt(buf_getptr(ses.readbuf, blocksize),
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buf_getwriteptr(ses.decryptreadbuf,blocksize),
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blocksize,
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&ses.keys->recv_cipher_state) != CRYPT_OK) {
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dropbear_exit("error decrypting");
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}
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buf_setlen(ses.decryptreadbuf, blocksize);
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len = buf_getint(ses.decryptreadbuf) + 4 + macsize;
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buf_setpos(ses.readbuf, blocksize);
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/* check packet length */
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if ((len > RECV_MAX_PACKET_LEN) ||
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(len < MIN_PACKET_LEN + macsize) ||
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((len - macsize) % blocksize != 0)) {
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dropbear_exit("bad packet size %d", len);
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}
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buf_resize(ses.readbuf, len);
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buf_setlen(ses.readbuf, len);
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}
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/* handle the received packet */
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void decrypt_packet() {
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unsigned char blocksize;
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unsigned char macsize;
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unsigned int padlen;
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unsigned int len;
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TRACE(("enter decrypt_packet"))
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blocksize = ses.keys->recv_algo_crypt->blocksize;
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macsize = ses.keys->recv_algo_mac->hashsize;
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ses.kexstate.datarecv += ses.readbuf->len;
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/* we've already decrypted the first blocksize in read_packet_init */
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buf_setpos(ses.readbuf, blocksize);
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buf_resize(ses.decryptreadbuf, ses.readbuf->len - macsize);
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buf_setlen(ses.decryptreadbuf, ses.decryptreadbuf->size);
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buf_setpos(ses.decryptreadbuf, blocksize);
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/* decrypt it */
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while (ses.readbuf->pos < ses.readbuf->len - macsize) {
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if (ses.keys->recv_crypt_mode->decrypt(
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buf_getptr(ses.readbuf, blocksize),
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buf_getwriteptr(ses.decryptreadbuf, blocksize),
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blocksize,
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&ses.keys->recv_cipher_state) != CRYPT_OK) {
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dropbear_exit("error decrypting");
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}
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buf_incrpos(ses.readbuf, blocksize);
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buf_incrwritepos(ses.decryptreadbuf, blocksize);
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}
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/* check the hmac */
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buf_setpos(ses.readbuf, ses.readbuf->len - macsize);
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if (checkmac(ses.readbuf, ses.decryptreadbuf) != DROPBEAR_SUCCESS) {
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dropbear_exit("Integrity error");
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}
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/* readbuf no longer required */
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buf_free(ses.readbuf);
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ses.readbuf = NULL;
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/* get padding length */
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buf_setpos(ses.decryptreadbuf, PACKET_PADDING_OFF);
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padlen = buf_getbyte(ses.decryptreadbuf);
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/* payload length */
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/* - 4 - 1 is for LEN and PADLEN values */
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len = ses.decryptreadbuf->len - padlen - 4 - 1;
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if ((len > RECV_MAX_PAYLOAD_LEN) || (len < 1)) {
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dropbear_exit("bad packet size");
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}
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buf_setpos(ses.decryptreadbuf, PACKET_PAYLOAD_OFF);
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#ifndef DISABLE_ZLIB
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if (is_compress_recv()) {
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/* decompress */
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ses.payload = buf_decompress(ses.decryptreadbuf, len);
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} else
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#endif
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{
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/* copy payload */
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ses.payload = buf_new(len);
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memcpy(ses.payload->data, buf_getptr(ses.decryptreadbuf, len), len);
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buf_incrlen(ses.payload, len);
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}
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buf_free(ses.decryptreadbuf);
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ses.decryptreadbuf = NULL;
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buf_setpos(ses.payload, 0);
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ses.recvseq++;
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TRACE(("leave decrypt_packet"))
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}
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/* Checks the mac in hashbuf, for the data in readbuf.
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* Returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE */
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static int checkmac(buffer* macbuf, buffer* sourcebuf) {
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unsigned int macsize;
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hmac_state hmac;
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unsigned char tempbuf[MAX_MAC_LEN];
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unsigned long bufsize;
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unsigned int len;
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macsize = ses.keys->recv_algo_mac->hashsize;
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if (macsize == 0) {
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return DROPBEAR_SUCCESS;
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}
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/* calculate the mac */
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if (hmac_init(&hmac,
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find_hash(ses.keys->recv_algo_mac->hashdesc->name),
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ses.keys->recvmackey,
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ses.keys->recv_algo_mac->keysize)
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!= CRYPT_OK) {
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dropbear_exit("HMAC error");
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}
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/* sequence number */
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STORE32H(ses.recvseq, tempbuf);
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if (hmac_process(&hmac, tempbuf, 4) != CRYPT_OK) {
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dropbear_exit("HMAC error");
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}
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buf_setpos(sourcebuf, 0);
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len = sourcebuf->len;
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if (hmac_process(&hmac, buf_getptr(sourcebuf, len), len) != CRYPT_OK) {
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dropbear_exit("HMAC error");
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}
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bufsize = sizeof(tempbuf);
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if (hmac_done(&hmac, tempbuf, &bufsize) != CRYPT_OK) {
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dropbear_exit("HMAC error");
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}
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/* compare the hash */
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if (memcmp(tempbuf, buf_getptr(macbuf, macsize), macsize) != 0) {
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return DROPBEAR_FAILURE;
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} else {
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return DROPBEAR_SUCCESS;
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}
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}
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#ifndef DISABLE_ZLIB
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/* returns a pointer to a newly created buffer */
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static buffer* buf_decompress(buffer* buf, unsigned int len) {
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int result;
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buffer * ret;
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z_streamp zstream;
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zstream = ses.keys->recv_zstream;
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ret = buf_new(len);
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zstream->avail_in = len;
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zstream->next_in = buf_getptr(buf, len);
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/* decompress the payload, incrementally resizing the output buffer */
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while (1) {
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zstream->avail_out = ret->size - ret->pos;
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zstream->next_out = buf_getwriteptr(ret, zstream->avail_out);
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result = inflate(zstream, Z_SYNC_FLUSH);
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buf_setlen(ret, ret->size - zstream->avail_out);
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buf_setpos(ret, ret->len);
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if (result != Z_BUF_ERROR && result != Z_OK) {
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dropbear_exit("zlib error");
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}
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if (zstream->avail_in == 0 &&
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(zstream->avail_out != 0 || result == Z_BUF_ERROR)) {
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/* we can only exit if avail_out hasn't all been used,
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* and there's no remaining input */
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return ret;
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}
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if (zstream->avail_out == 0) {
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buf_resize(ret, ret->size + ZLIB_DECOMPRESS_INCR);
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}
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}
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}
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#endif
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/* returns 1 if the packet is a valid type during kex (see 7.1 of rfc4253) */
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static int packet_is_okay_kex(unsigned char type) {
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if (type >= SSH_MSG_USERAUTH_REQUEST) {
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return 0;
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}
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if (type == SSH_MSG_SERVICE_REQUEST || type == SSH_MSG_SERVICE_ACCEPT) {
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return 0;
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}
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if (type == SSH_MSG_KEXINIT) {
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/* XXX should this die horribly if !dataallowed ?? */
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return 0;
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}
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return 1;
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}
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static void enqueue_reply_packet() {
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struct packetlist * new_item = NULL;
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new_item = m_malloc(sizeof(struct packetlist));
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new_item->next = NULL;
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new_item->payload = buf_newcopy(ses.writepayload);
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buf_setpos(ses.writepayload, 0);
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buf_setlen(ses.writepayload, 0);
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if (ses.reply_queue_tail) {
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ses.reply_queue_tail->next = new_item;
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} else {
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ses.reply_queue_head = new_item;
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}
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ses.reply_queue_tail = new_item;
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TRACE(("leave enqueue_reply_packet"))
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}
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void maybe_flush_reply_queue() {
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struct packetlist *tmp_item = NULL, *curr_item = NULL;
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if (!ses.dataallowed)
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{
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TRACE(("maybe_empty_reply_queue - no data allowed"))
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return;
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}
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for (curr_item = ses.reply_queue_head; curr_item; ) {
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CHECKCLEARTOWRITE();
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buf_putbytes(ses.writepayload,
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curr_item->payload->data, curr_item->payload->len);
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buf_free(curr_item->payload);
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tmp_item = curr_item;
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curr_item = curr_item->next;
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m_free(tmp_item);
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encrypt_packet();
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}
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ses.reply_queue_head = ses.reply_queue_tail = NULL;
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}
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/* encrypt the writepayload, putting into writebuf, ready for write_packet()
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* to put on the wire */
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void encrypt_packet() {
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unsigned char padlen;
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unsigned char blocksize, macsize;
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buffer * writebuf; /* the packet which will go on the wire */
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buffer * clearwritebuf; /* unencrypted, possibly compressed */
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unsigned char type;
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unsigned int clear_len;
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type = ses.writepayload->data[0];
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TRACE(("enter encrypt_packet()"))
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TRACE(("encrypt_packet type is %d", type))
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if (!ses.dataallowed && !packet_is_okay_kex(type)) {
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/* During key exchange only particular packets are allowed.
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Since this type isn't OK we just enqueue it to send
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after the KEX, see maybe_flush_reply_queue */
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enqueue_reply_packet();
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return;
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}
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blocksize = ses.keys->trans_algo_crypt->blocksize;
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macsize = ses.keys->trans_algo_mac->hashsize;
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/* Encrypted packet len is payload+5, then worst case is if we are 3 away
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* from a blocksize multiple. In which case we need to pad to the
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* multiple, then add another blocksize (or MIN_PACKET_LEN) */
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clear_len = (ses.writepayload->len+4+1) + MIN_PACKET_LEN + 3;
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#ifndef DISABLE_ZLIB
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clear_len += ZLIB_COMPRESS_INCR; /* bit of a kludge, but we can't know len*/
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#endif
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clearwritebuf = buf_new(clear_len);
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buf_setlen(clearwritebuf, PACKET_PAYLOAD_OFF);
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buf_setpos(clearwritebuf, PACKET_PAYLOAD_OFF);
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buf_setpos(ses.writepayload, 0);
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#ifndef DISABLE_ZLIB
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/* compression */
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if (is_compress_trans()) {
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buf_compress(clearwritebuf, ses.writepayload, ses.writepayload->len);
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} else
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#endif
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{
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memcpy(buf_getwriteptr(clearwritebuf, ses.writepayload->len),
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buf_getptr(ses.writepayload, ses.writepayload->len),
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ses.writepayload->len);
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buf_incrwritepos(clearwritebuf, ses.writepayload->len);
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}
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/* finished with payload */
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buf_setpos(ses.writepayload, 0);
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buf_setlen(ses.writepayload, 0);
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/* length of padding - packet length must be a multiple of blocksize,
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* with a minimum of 4 bytes of padding */
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padlen = blocksize - (clearwritebuf->len) % blocksize;
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if (padlen < 4) {
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padlen += blocksize;
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}
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/* check for min packet length */
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if (clearwritebuf->len + padlen < MIN_PACKET_LEN) {
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padlen += blocksize;
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}
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buf_setpos(clearwritebuf, 0);
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/* packet length excluding the packetlength uint32 */
|
|
buf_putint(clearwritebuf, clearwritebuf->len + padlen - 4);
|
|
|
|
/* padding len */
|
|
buf_putbyte(clearwritebuf, padlen);
|
|
/* actual padding */
|
|
buf_setpos(clearwritebuf, clearwritebuf->len);
|
|
buf_incrlen(clearwritebuf, padlen);
|
|
genrandom(buf_getptr(clearwritebuf, padlen), padlen);
|
|
|
|
/* do the actual encryption */
|
|
buf_setpos(clearwritebuf, 0);
|
|
/* create a new writebuffer, this is freed when it has been put on the
|
|
* wire by writepacket() */
|
|
writebuf = buf_new(clearwritebuf->len + macsize);
|
|
|
|
/* encrypt it */
|
|
while (clearwritebuf->pos < clearwritebuf->len) {
|
|
if (ses.keys->trans_crypt_mode->encrypt(
|
|
buf_getptr(clearwritebuf, blocksize),
|
|
buf_getwriteptr(writebuf, blocksize),
|
|
blocksize,
|
|
&ses.keys->trans_cipher_state) != CRYPT_OK) {
|
|
dropbear_exit("error encrypting");
|
|
}
|
|
buf_incrpos(clearwritebuf, blocksize);
|
|
buf_incrwritepos(writebuf, blocksize);
|
|
}
|
|
|
|
/* now add a hmac and we're done */
|
|
writemac(writebuf, clearwritebuf);
|
|
|
|
/* clearwritebuf is finished with */
|
|
buf_free(clearwritebuf);
|
|
clearwritebuf = NULL;
|
|
|
|
/* enqueue the packet for sending */
|
|
buf_setpos(writebuf, 0);
|
|
enqueue(&ses.writequeue, (void*)writebuf);
|
|
|
|
/* Update counts */
|
|
ses.kexstate.datatrans += writebuf->len;
|
|
ses.transseq++;
|
|
|
|
TRACE(("leave encrypt_packet()"))
|
|
}
|
|
|
|
|
|
/* Create the packet mac, and append H(seqno|clearbuf) to the output */
|
|
static void writemac(buffer * outputbuffer, buffer * clearwritebuf) {
|
|
|
|
unsigned int macsize;
|
|
unsigned char seqbuf[4];
|
|
unsigned char tempbuf[MAX_MAC_LEN];
|
|
unsigned long bufsize;
|
|
hmac_state hmac;
|
|
|
|
TRACE(("enter writemac"))
|
|
|
|
macsize = ses.keys->trans_algo_mac->hashsize;
|
|
if (macsize > 0) {
|
|
/* calculate the mac */
|
|
if (hmac_init(&hmac,
|
|
find_hash(ses.keys->trans_algo_mac->hashdesc->name),
|
|
ses.keys->transmackey,
|
|
ses.keys->trans_algo_mac->keysize) != CRYPT_OK) {
|
|
dropbear_exit("HMAC error");
|
|
}
|
|
|
|
/* sequence number */
|
|
STORE32H(ses.transseq, seqbuf);
|
|
if (hmac_process(&hmac, seqbuf, 4) != CRYPT_OK) {
|
|
dropbear_exit("HMAC error");
|
|
}
|
|
|
|
/* the actual contents */
|
|
buf_setpos(clearwritebuf, 0);
|
|
if (hmac_process(&hmac,
|
|
buf_getptr(clearwritebuf,
|
|
clearwritebuf->len),
|
|
clearwritebuf->len) != CRYPT_OK) {
|
|
dropbear_exit("HMAC error");
|
|
}
|
|
|
|
bufsize = sizeof(tempbuf);
|
|
if (hmac_done(&hmac, tempbuf, &bufsize)
|
|
!= CRYPT_OK) {
|
|
dropbear_exit("HMAC error");
|
|
}
|
|
buf_putbytes(outputbuffer, tempbuf, macsize);
|
|
}
|
|
TRACE(("leave writemac"))
|
|
}
|
|
|
|
#ifndef DISABLE_ZLIB
|
|
/* compresses len bytes from src, outputting to dest (starting from the
|
|
* respective current positions. */
|
|
static void buf_compress(buffer * dest, buffer * src, unsigned int len) {
|
|
|
|
unsigned int endpos = src->pos + len;
|
|
int result;
|
|
|
|
TRACE(("enter buf_compress"))
|
|
|
|
while (1) {
|
|
|
|
ses.keys->trans_zstream->avail_in = endpos - src->pos;
|
|
ses.keys->trans_zstream->next_in =
|
|
buf_getptr(src, ses.keys->trans_zstream->avail_in);
|
|
|
|
ses.keys->trans_zstream->avail_out = dest->size - dest->pos;
|
|
ses.keys->trans_zstream->next_out =
|
|
buf_getwriteptr(dest, ses.keys->trans_zstream->avail_out);
|
|
|
|
result = deflate(ses.keys->trans_zstream, Z_SYNC_FLUSH);
|
|
|
|
buf_setpos(src, endpos - ses.keys->trans_zstream->avail_in);
|
|
buf_setlen(dest, dest->size - ses.keys->trans_zstream->avail_out);
|
|
buf_setpos(dest, dest->len);
|
|
|
|
if (result != Z_OK) {
|
|
dropbear_exit("zlib error");
|
|
}
|
|
|
|
if (ses.keys->trans_zstream->avail_in == 0) {
|
|
break;
|
|
}
|
|
|
|
dropbear_assert(ses.keys->trans_zstream->avail_out == 0);
|
|
|
|
/* the buffer has been filled, we must extend. This only happens in
|
|
* unusual circumstances where the data grows in size after deflate(),
|
|
* but it is possible */
|
|
buf_resize(dest, dest->size + ZLIB_COMPRESS_INCR);
|
|
|
|
}
|
|
TRACE(("leave buf_compress"))
|
|
}
|
|
#endif
|