1 /* $OpenBSD: packet.c,v 1.151 2008/02/22 20:44:02 dtucker Exp $ */
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 * This file contains code implementing the packet protocol and communication
7 * with the other side. This same code is used both on client and server side.
9 * As far as I am concerned, the code I have written for this software
10 * can be used freely for any purpose. Any derived versions of this
11 * software must be clearly marked as such, and if the derived work is
12 * incompatible with the protocol description in the RFC file, it must be
13 * called by a name other than "ssh" or "Secure Shell".
16 * SSH2 packet format added by Markus Friedl.
17 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
19 * Redistribution and use in source and binary forms, with or without
20 * modification, are permitted provided that the following conditions
22 * 1. Redistributions of source code must retain the above copyright
23 * notice, this list of conditions and the following disclaimer.
24 * 2. Redistributions in binary form must reproduce the above copyright
25 * notice, this list of conditions and the following disclaimer in the
26 * documentation and/or other materials provided with the distribution.
28 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
29 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
30 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
31 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
33 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
34 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
35 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
36 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
37 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42 #include <sys/types.h>
43 #include "openbsd-compat/sys-queue.h"
44 #include <sys/param.h>
45 #include <sys/socket.h>
46 #ifdef HAVE_SYS_TIME_H
47 # include <sys/time.h>
50 #include <netinet/in.h>
51 #include <netinet/ip.h>
52 #include <arpa/inet.h>
88 * This variable contains the file descriptors used for communicating with
89 * the other side. connection_in is used for reading; connection_out for
90 * writing. These can be the same descriptor, in which case it is assumed to
93 static int connection_in = -1;
94 static int connection_out = -1;
96 /* Protocol flags for the remote side. */
97 static u_int remote_protocol_flags = 0;
99 /* Encryption context for receiving data. This is only used for decryption. */
100 static CipherContext receive_context;
102 /* Encryption context for sending data. This is only used for encryption. */
103 static CipherContext send_context;
105 /* Buffer for raw input data from the socket. */
108 /* Buffer for raw output data going to the socket. */
111 /* Buffer for the partial outgoing packet being constructed. */
112 static Buffer outgoing_packet;
114 /* Buffer for the incoming packet currently being processed. */
115 static Buffer incoming_packet;
117 /* Scratch buffer for packet compression/decompression. */
118 static Buffer compression_buffer;
119 static int compression_buffer_ready = 0;
121 /* Flag indicating whether packet compression/decompression is enabled. */
122 static int packet_compression = 0;
124 /* default maximum packet size */
125 u_int max_packet_size = 32768;
127 /* Flag indicating whether this module has been initialized. */
128 static int initialized = 0;
130 /* Set to true if the connection is interactive. */
131 static int interactive_mode = 0;
133 /* Set to true if we are the server side. */
134 static int server_side = 0;
136 /* Set to true if we are authenticated. */
137 static int after_authentication = 0;
139 int keep_alive_timeouts = 0;
141 /* Session key information for Encryption and MAC */
142 Newkeys *newkeys[MODE_MAX];
143 static struct packet_state {
149 static u_int64_t max_blocks_in, max_blocks_out;
150 static u_int32_t rekey_limit;
152 /* Session key for protocol v1 */
153 static u_char ssh1_key[SSH_SESSION_KEY_LENGTH];
154 static u_int ssh1_keylen;
156 /* roundup current message to extra_pad bytes */
157 static u_char extra_pad = 0;
160 TAILQ_ENTRY(packet) next;
164 TAILQ_HEAD(, packet) outgoing;
167 * Sets the descriptors used for communication. Disables encryption until
168 * packet_set_encryption_key is called.
171 packet_set_connection(int fd_in, int fd_out)
173 Cipher *none = cipher_by_name("none");
176 fatal("packet_set_connection: cannot load cipher 'none'");
177 connection_in = fd_in;
178 connection_out = fd_out;
179 cipher_init(&send_context, none, (const u_char *)"",
180 0, NULL, 0, CIPHER_ENCRYPT);
181 cipher_init(&receive_context, none, (const u_char *)"",
182 0, NULL, 0, CIPHER_DECRYPT);
183 newkeys[MODE_IN] = newkeys[MODE_OUT] = NULL;
187 buffer_init(&output);
188 buffer_init(&outgoing_packet);
189 buffer_init(&incoming_packet);
190 TAILQ_INIT(&outgoing);
194 /* Returns 1 if remote host is connected via socket, 0 if not. */
197 packet_connection_is_on_socket(void)
199 struct sockaddr_storage from, to;
200 socklen_t fromlen, tolen;
202 /* filedescriptors in and out are the same, so it's a socket */
203 if (connection_in == connection_out)
205 fromlen = sizeof(from);
206 memset(&from, 0, sizeof(from));
207 if (getpeername(connection_in, (struct sockaddr *)&from, &fromlen) < 0)
210 memset(&to, 0, sizeof(to));
211 if (getpeername(connection_out, (struct sockaddr *)&to, &tolen) < 0)
213 if (fromlen != tolen || memcmp(&from, &to, fromlen) != 0)
215 if (from.ss_family != AF_INET && from.ss_family != AF_INET6)
221 * Exports an IV from the CipherContext required to export the key
222 * state back from the unprivileged child to the privileged parent
227 packet_get_keyiv(int mode, u_char *iv, u_int len)
231 if (mode == MODE_OUT)
234 cc = &receive_context;
236 cipher_get_keyiv(cc, iv, len);
240 packet_get_keycontext(int mode, u_char *dat)
244 if (mode == MODE_OUT)
247 cc = &receive_context;
249 return (cipher_get_keycontext(cc, dat));
253 packet_set_keycontext(int mode, u_char *dat)
257 if (mode == MODE_OUT)
260 cc = &receive_context;
262 cipher_set_keycontext(cc, dat);
266 packet_get_keyiv_len(int mode)
270 if (mode == MODE_OUT)
273 cc = &receive_context;
275 return (cipher_get_keyiv_len(cc));
279 packet_set_iv(int mode, u_char *dat)
283 if (mode == MODE_OUT)
286 cc = &receive_context;
288 cipher_set_keyiv(cc, dat);
292 packet_get_ssh1_cipher(void)
294 return (cipher_get_number(receive_context.cipher));
298 packet_get_state(int mode, u_int32_t *seqnr, u_int64_t *blocks, u_int32_t *packets)
300 struct packet_state *state;
302 state = (mode == MODE_IN) ? &p_read : &p_send;
303 *seqnr = state->seqnr;
304 *blocks = state->blocks;
305 *packets = state->packets;
309 packet_set_state(int mode, u_int32_t seqnr, u_int64_t blocks, u_int32_t packets)
311 struct packet_state *state;
313 state = (mode == MODE_IN) ? &p_read : &p_send;
314 state->seqnr = seqnr;
315 state->blocks = blocks;
316 state->packets = packets;
319 /* returns 1 if connection is via ipv4 */
322 packet_connection_is_ipv4(void)
324 struct sockaddr_storage to;
325 socklen_t tolen = sizeof(to);
327 memset(&to, 0, sizeof(to));
328 if (getsockname(connection_out, (struct sockaddr *)&to, &tolen) < 0)
330 if (to.ss_family == AF_INET)
333 if (to.ss_family == AF_INET6 &&
334 IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)&to)->sin6_addr))
340 /* Sets the connection into non-blocking mode. */
343 packet_set_nonblocking(void)
345 /* Set the socket into non-blocking mode. */
346 set_nonblock(connection_in);
348 if (connection_out != connection_in)
349 set_nonblock(connection_out);
352 /* Returns the socket used for reading. */
355 packet_get_connection_in(void)
357 return connection_in;
360 /* Returns the descriptor used for writing. */
363 packet_get_connection_out(void)
365 return connection_out;
368 /* Closes the connection and clears and frees internal data structures. */
376 if (connection_in == connection_out) {
377 shutdown(connection_out, SHUT_RDWR);
378 close(connection_out);
380 close(connection_in);
381 close(connection_out);
384 buffer_free(&output);
385 buffer_free(&outgoing_packet);
386 buffer_free(&incoming_packet);
387 if (compression_buffer_ready) {
388 buffer_free(&compression_buffer);
389 buffer_compress_uninit();
391 cipher_cleanup(&send_context);
392 cipher_cleanup(&receive_context);
395 /* Sets remote side protocol flags. */
398 packet_set_protocol_flags(u_int protocol_flags)
400 remote_protocol_flags = protocol_flags;
403 /* Returns the remote protocol flags set earlier by the above function. */
406 packet_get_protocol_flags(void)
408 return remote_protocol_flags;
412 * Starts packet compression from the next packet on in both directions.
413 * Level is compression level 1 (fastest) - 9 (slow, best) as in gzip.
417 packet_init_compression(void)
419 if (compression_buffer_ready == 1)
421 compression_buffer_ready = 1;
422 buffer_init(&compression_buffer);
426 packet_start_compression(int level)
428 if (packet_compression && !compat20)
429 fatal("Compression already enabled.");
430 packet_compression = 1;
431 packet_init_compression();
432 buffer_compress_init_send(level);
433 buffer_compress_init_recv();
437 * Causes any further packets to be encrypted using the given key. The same
438 * key is used for both sending and reception. However, both directions are
439 * encrypted independently of each other.
443 packet_set_encryption_key(const u_char *key, u_int keylen,
446 Cipher *cipher = cipher_by_number(number);
449 fatal("packet_set_encryption_key: unknown cipher number %d", number);
451 fatal("packet_set_encryption_key: keylen too small: %d", keylen);
452 if (keylen > SSH_SESSION_KEY_LENGTH)
453 fatal("packet_set_encryption_key: keylen too big: %d", keylen);
454 memcpy(ssh1_key, key, keylen);
455 ssh1_keylen = keylen;
456 cipher_init(&send_context, cipher, key, keylen, NULL, 0, CIPHER_ENCRYPT);
457 cipher_init(&receive_context, cipher, key, keylen, NULL, 0, CIPHER_DECRYPT);
461 packet_get_encryption_key(u_char *key)
464 return (ssh1_keylen);
465 memcpy(key, ssh1_key, ssh1_keylen);
466 return (ssh1_keylen);
469 /* Start constructing a packet to send. */
471 packet_start(u_char type)
476 DBG(debug("packet_start[%d]", type));
477 len = compat20 ? 6 : 9;
478 memset(buf, 0, len - 1);
480 buffer_clear(&outgoing_packet);
481 buffer_append(&outgoing_packet, buf, len);
484 /* Append payload. */
486 packet_put_char(int value)
490 buffer_append(&outgoing_packet, &ch, 1);
494 packet_put_int(u_int value)
496 buffer_put_int(&outgoing_packet, value);
500 packet_put_string(const void *buf, u_int len)
502 buffer_put_string(&outgoing_packet, buf, len);
506 packet_put_cstring(const char *str)
508 buffer_put_cstring(&outgoing_packet, str);
512 packet_put_raw(const void *buf, u_int len)
514 buffer_append(&outgoing_packet, buf, len);
518 packet_put_bignum(BIGNUM * value)
520 buffer_put_bignum(&outgoing_packet, value);
524 packet_put_bignum2(BIGNUM * value)
526 buffer_put_bignum2(&outgoing_packet, value);
530 * Finalizes and sends the packet. If the encryption key has been set,
531 * encrypts the packet before sending.
543 * If using packet compression, compress the payload of the outgoing
546 if (packet_compression) {
547 buffer_clear(&compression_buffer);
549 buffer_consume(&outgoing_packet, 8);
551 buffer_append(&compression_buffer, "\0\0\0\0\0\0\0\0", 8);
552 buffer_compress(&outgoing_packet, &compression_buffer);
553 buffer_clear(&outgoing_packet);
554 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
555 buffer_len(&compression_buffer));
557 /* Compute packet length without padding (add checksum, remove padding). */
558 len = buffer_len(&outgoing_packet) + 4 - 8;
560 /* Insert padding. Initialized to zero in packet_start1() */
561 padding = 8 - len % 8;
562 if (!send_context.plaintext) {
563 cp = buffer_ptr(&outgoing_packet);
564 for (i = 0; i < padding; i++) {
567 cp[7 - i] = rnd & 0xff;
571 buffer_consume(&outgoing_packet, 8 - padding);
573 /* Add check bytes. */
574 checksum = ssh_crc32(buffer_ptr(&outgoing_packet),
575 buffer_len(&outgoing_packet));
576 put_u32(buf, checksum);
577 buffer_append(&outgoing_packet, buf, 4);
580 fprintf(stderr, "packet_send plain: ");
581 buffer_dump(&outgoing_packet);
584 /* Append to output. */
586 buffer_append(&output, buf, 4);
587 cp = buffer_append_space(&output, buffer_len(&outgoing_packet));
588 cipher_crypt(&send_context, cp, buffer_ptr(&outgoing_packet),
589 buffer_len(&outgoing_packet));
592 fprintf(stderr, "encrypted: ");
593 buffer_dump(&output);
596 buffer_clear(&outgoing_packet);
599 * Note that the packet is now only buffered in output. It won't be
600 * actually sent until packet_write_wait or packet_write_poll is
606 set_newkeys(int mode)
612 u_int64_t *max_blocks;
615 debug2("set_newkeys: mode %d", mode);
617 if (mode == MODE_OUT) {
619 crypt_type = CIPHER_ENCRYPT;
620 p_send.packets = p_send.blocks = 0;
621 max_blocks = &max_blocks_out;
623 cc = &receive_context;
624 crypt_type = CIPHER_DECRYPT;
625 p_read.packets = p_read.blocks = 0;
626 max_blocks = &max_blocks_in;
628 if (newkeys[mode] != NULL) {
629 debug("set_newkeys: rekeying");
631 enc = &newkeys[mode]->enc;
632 mac = &newkeys[mode]->mac;
633 comp = &newkeys[mode]->comp;
641 xfree(newkeys[mode]);
643 newkeys[mode] = kex_get_newkeys(mode);
644 if (newkeys[mode] == NULL)
645 fatal("newkeys: no keys for mode %d", mode);
646 enc = &newkeys[mode]->enc;
647 mac = &newkeys[mode]->mac;
648 comp = &newkeys[mode]->comp;
649 if (mac_init(mac) == 0)
651 DBG(debug("cipher_init_context: %d", mode));
652 cipher_init(cc, enc->cipher, enc->key, enc->key_len,
653 enc->iv, enc->block_size, crypt_type);
654 /* Deleting the keys does not gain extra security */
655 /* memset(enc->iv, 0, enc->block_size);
656 memset(enc->key, 0, enc->key_len);
657 memset(mac->key, 0, mac->key_len); */
658 if ((comp->type == COMP_ZLIB ||
659 (comp->type == COMP_DELAYED && after_authentication)) &&
660 comp->enabled == 0) {
661 packet_init_compression();
662 if (mode == MODE_OUT)
663 buffer_compress_init_send(6);
665 buffer_compress_init_recv();
669 * The 2^(blocksize*2) limit is too expensive for 3DES,
670 * blowfish, etc, so enforce a 1GB limit for small blocksizes.
672 if (enc->block_size >= 16)
673 *max_blocks = (u_int64_t)1 << (enc->block_size*2);
675 *max_blocks = ((u_int64_t)1 << 30) / enc->block_size;
677 *max_blocks = MIN(*max_blocks, rekey_limit / enc->block_size);
681 * Delayed compression for SSH2 is enabled after authentication:
682 * This happens on the server side after a SSH2_MSG_USERAUTH_SUCCESS is sent,
683 * and on the client side after a SSH2_MSG_USERAUTH_SUCCESS is received.
686 packet_enable_delayed_compress(void)
692 * Remember that we are past the authentication step, so rekeying
693 * with COMP_DELAYED will turn on compression immediately.
695 after_authentication = 1;
696 for (mode = 0; mode < MODE_MAX; mode++) {
697 /* protocol error: USERAUTH_SUCCESS received before NEWKEYS */
698 if (newkeys[mode] == NULL)
700 comp = &newkeys[mode]->comp;
701 if (comp && !comp->enabled && comp->type == COMP_DELAYED) {
702 packet_init_compression();
703 if (mode == MODE_OUT)
704 buffer_compress_init_send(6);
706 buffer_compress_init_recv();
713 * Finalize packet in SSH2 format (compress, mac, encrypt, enqueue)
716 packet_send2_wrapped(void)
718 u_char type, *cp, *macbuf = NULL;
720 u_int packet_length = 0;
728 if (newkeys[MODE_OUT] != NULL) {
729 enc = &newkeys[MODE_OUT]->enc;
730 mac = &newkeys[MODE_OUT]->mac;
731 comp = &newkeys[MODE_OUT]->comp;
733 block_size = enc ? enc->block_size : 8;
735 cp = buffer_ptr(&outgoing_packet);
739 fprintf(stderr, "plain: ");
740 buffer_dump(&outgoing_packet);
743 if (comp && comp->enabled) {
744 len = buffer_len(&outgoing_packet);
745 /* skip header, compress only payload */
746 buffer_consume(&outgoing_packet, 5);
747 buffer_clear(&compression_buffer);
748 buffer_compress(&outgoing_packet, &compression_buffer);
749 buffer_clear(&outgoing_packet);
750 buffer_append(&outgoing_packet, "\0\0\0\0\0", 5);
751 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
752 buffer_len(&compression_buffer));
753 DBG(debug("compression: raw %d compressed %d", len,
754 buffer_len(&outgoing_packet)));
757 /* sizeof (packet_len + pad_len + payload) */
758 len = buffer_len(&outgoing_packet);
761 * calc size of padding, alloc space, get random data,
762 * minimum padding is 4 bytes
764 padlen = block_size - (len % block_size);
766 padlen += block_size;
768 /* will wrap if extra_pad+padlen > 255 */
769 extra_pad = roundup(extra_pad, block_size);
770 pad = extra_pad - ((len + padlen) % extra_pad);
771 debug3("packet_send2: adding %d (len %d padlen %d extra_pad %d)",
772 pad, len, padlen, extra_pad);
776 cp = buffer_append_space(&outgoing_packet, padlen);
777 if (enc && !send_context.plaintext) {
779 for (i = 0; i < padlen; i++) {
787 memset(cp, 0, padlen);
789 /* packet_length includes payload, padding and padding length field */
790 packet_length = buffer_len(&outgoing_packet) - 4;
791 cp = buffer_ptr(&outgoing_packet);
792 put_u32(cp, packet_length);
794 DBG(debug("send: len %d (includes padlen %d)", packet_length+4, padlen));
796 /* compute MAC over seqnr and packet(length fields, payload, padding) */
797 if (mac && mac->enabled) {
798 macbuf = mac_compute(mac, p_send.seqnr,
799 buffer_ptr(&outgoing_packet),
800 buffer_len(&outgoing_packet));
801 DBG(debug("done calc MAC out #%d", p_send.seqnr));
803 /* encrypt packet and append to output buffer. */
804 cp = buffer_append_space(&output, buffer_len(&outgoing_packet));
805 cipher_crypt(&send_context, cp, buffer_ptr(&outgoing_packet),
806 buffer_len(&outgoing_packet));
807 /* append unencrypted MAC */
808 if (mac && mac->enabled)
809 buffer_append(&output, macbuf, mac->mac_len);
811 fprintf(stderr, "encrypted: ");
812 buffer_dump(&output);
814 /* increment sequence number for outgoing packets */
815 if (++p_send.seqnr == 0)
816 logit("outgoing seqnr wraps around");
817 if (++p_send.packets == 0)
818 if (!(datafellows & SSH_BUG_NOREKEY))
819 fatal("XXX too many packets with same key");
820 p_send.blocks += (packet_length + 4) / block_size;
821 buffer_clear(&outgoing_packet);
823 if (type == SSH2_MSG_NEWKEYS)
824 set_newkeys(MODE_OUT);
825 else if (type == SSH2_MSG_USERAUTH_SUCCESS && server_side)
826 packet_enable_delayed_compress();
832 static int rekeying = 0;
836 cp = buffer_ptr(&outgoing_packet);
839 /* during rekeying we can only send key exchange messages */
841 if (!((type >= SSH2_MSG_TRANSPORT_MIN) &&
842 (type <= SSH2_MSG_TRANSPORT_MAX))) {
843 debug("enqueue packet: %u", type);
844 p = xmalloc(sizeof(*p));
846 memcpy(&p->payload, &outgoing_packet, sizeof(Buffer));
847 buffer_init(&outgoing_packet);
848 TAILQ_INSERT_TAIL(&outgoing, p, next);
853 /* rekeying starts with sending KEXINIT */
854 if (type == SSH2_MSG_KEXINIT)
857 packet_send2_wrapped();
859 /* after a NEWKEYS message we can send the complete queue */
860 if (type == SSH2_MSG_NEWKEYS) {
862 while ((p = TAILQ_FIRST(&outgoing))) {
864 debug("dequeue packet: %u", type);
865 buffer_free(&outgoing_packet);
866 memcpy(&outgoing_packet, &p->payload,
868 TAILQ_REMOVE(&outgoing, p, next);
870 packet_send2_wrapped();
882 DBG(debug("packet_send done"));
886 * Waits until a packet has been received, and returns its type. Note that
887 * no other data is processed until this returns, so this function should not
888 * be used during the interactive session.
892 packet_read_seqnr(u_int32_t *seqnr_p)
897 DBG(debug("packet_read()"));
899 setp = (fd_set *)xcalloc(howmany(connection_in+1, NFDBITS),
902 /* Since we are blocking, ensure that all written packets have been sent. */
905 /* Stay in the loop until we have received a complete packet. */
907 /* Try to read a packet from the buffer. */
908 type = packet_read_poll_seqnr(seqnr_p);
910 type == SSH_SMSG_SUCCESS
911 || type == SSH_SMSG_FAILURE
912 || type == SSH_CMSG_EOF
913 || type == SSH_CMSG_EXIT_CONFIRMATION))
915 /* If we got a packet, return it. */
916 if (type != SSH_MSG_NONE) {
921 * Otherwise, wait for some data to arrive, add it to the
922 * buffer, and try again.
924 memset(setp, 0, howmany(connection_in + 1, NFDBITS) *
926 FD_SET(connection_in, setp);
928 /* Wait for some data to arrive. */
929 while (select(connection_in + 1, setp, NULL, NULL, NULL) == -1 &&
930 (errno == EAGAIN || errno == EINTR))
933 /* Read data from the socket. */
934 len = read(connection_in, buf, sizeof(buf));
936 logit("Connection closed by %.200s", get_remote_ipaddr());
940 fatal("Read from socket failed: %.100s", strerror(errno));
941 /* Append it to the buffer. */
942 packet_process_incoming(buf, len);
950 return packet_read_seqnr(NULL);
954 * Waits until a packet has been received, verifies that its type matches
955 * that given, and gives a fatal error and exits if there is a mismatch.
959 packet_read_expect(int expected_type)
963 type = packet_read();
964 if (type != expected_type)
965 packet_disconnect("Protocol error: expected packet type %d, got %d",
966 expected_type, type);
969 /* Checks if a full packet is available in the data received so far via
970 * packet_process_incoming. If so, reads the packet; otherwise returns
971 * SSH_MSG_NONE. This does not wait for data from the connection.
973 * SSH_MSG_DISCONNECT is handled specially here. Also,
974 * SSH_MSG_IGNORE messages are skipped by this function and are never returned
979 packet_read_poll1(void)
981 u_int len, padded_len;
983 u_int checksum, stored_checksum;
985 /* Check if input size is less than minimum packet size. */
986 if (buffer_len(&input) < 4 + 8)
988 /* Get length of incoming packet. */
989 cp = buffer_ptr(&input);
991 if (len < 1 + 2 + 2 || len > 256 * 1024)
992 packet_disconnect("Bad packet length %u.", len);
993 padded_len = (len + 8) & ~7;
995 /* Check if the packet has been entirely received. */
996 if (buffer_len(&input) < 4 + padded_len)
999 /* The entire packet is in buffer. */
1001 /* Consume packet length. */
1002 buffer_consume(&input, 4);
1005 * Cryptographic attack detector for ssh
1006 * (C)1998 CORE-SDI, Buenos Aires Argentina
1007 * Ariel Futoransky(futo@core-sdi.com)
1009 if (!receive_context.plaintext) {
1010 switch (detect_attack(buffer_ptr(&input), padded_len)) {
1011 case DEATTACK_DETECTED:
1012 packet_disconnect("crc32 compensation attack: "
1013 "network attack detected");
1014 case DEATTACK_DOS_DETECTED:
1015 packet_disconnect("deattack denial of "
1016 "service detected");
1020 /* Decrypt data to incoming_packet. */
1021 buffer_clear(&incoming_packet);
1022 cp = buffer_append_space(&incoming_packet, padded_len);
1023 cipher_crypt(&receive_context, cp, buffer_ptr(&input), padded_len);
1025 buffer_consume(&input, padded_len);
1028 fprintf(stderr, "read_poll plain: ");
1029 buffer_dump(&incoming_packet);
1032 /* Compute packet checksum. */
1033 checksum = ssh_crc32(buffer_ptr(&incoming_packet),
1034 buffer_len(&incoming_packet) - 4);
1037 buffer_consume(&incoming_packet, 8 - len % 8);
1039 /* Test check bytes. */
1040 if (len != buffer_len(&incoming_packet))
1041 packet_disconnect("packet_read_poll1: len %d != buffer_len %d.",
1042 len, buffer_len(&incoming_packet));
1044 cp = (u_char *)buffer_ptr(&incoming_packet) + len - 4;
1045 stored_checksum = get_u32(cp);
1046 if (checksum != stored_checksum)
1047 packet_disconnect("Corrupted check bytes on input.");
1048 buffer_consume_end(&incoming_packet, 4);
1050 if (packet_compression) {
1051 buffer_clear(&compression_buffer);
1052 buffer_uncompress(&incoming_packet, &compression_buffer);
1053 buffer_clear(&incoming_packet);
1054 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
1055 buffer_len(&compression_buffer));
1057 type = buffer_get_char(&incoming_packet);
1058 if (type < SSH_MSG_MIN || type > SSH_MSG_MAX)
1059 packet_disconnect("Invalid ssh1 packet type: %d", type);
1064 packet_read_poll2(u_int32_t *seqnr_p)
1066 static u_int packet_length = 0;
1068 u_char *macbuf, *cp, type;
1069 u_int maclen, block_size;
1074 if (newkeys[MODE_IN] != NULL) {
1075 enc = &newkeys[MODE_IN]->enc;
1076 mac = &newkeys[MODE_IN]->mac;
1077 comp = &newkeys[MODE_IN]->comp;
1079 maclen = mac && mac->enabled ? mac->mac_len : 0;
1080 block_size = enc ? enc->block_size : 8;
1082 if (packet_length == 0) {
1084 * check if input size is less than the cipher block size,
1085 * decrypt first block and extract length of incoming packet
1087 if (buffer_len(&input) < block_size)
1088 return SSH_MSG_NONE;
1089 buffer_clear(&incoming_packet);
1090 cp = buffer_append_space(&incoming_packet, block_size);
1091 cipher_crypt(&receive_context, cp, buffer_ptr(&input),
1093 cp = buffer_ptr(&incoming_packet);
1094 packet_length = get_u32(cp);
1095 if (packet_length < 1 + 4 || packet_length > 256 * 1024) {
1097 buffer_dump(&incoming_packet);
1099 packet_disconnect("Bad packet length %u.", packet_length);
1101 DBG(debug("input: packet len %u", packet_length+4));
1102 buffer_consume(&input, block_size);
1104 /* we have a partial packet of block_size bytes */
1105 need = 4 + packet_length - block_size;
1106 DBG(debug("partial packet %d, need %d, maclen %d", block_size,
1108 if (need % block_size != 0)
1109 fatal("padding error: need %d block %d mod %d",
1110 need, block_size, need % block_size);
1112 * check if the entire packet has been received and
1113 * decrypt into incoming_packet
1115 if (buffer_len(&input) < need + maclen)
1116 return SSH_MSG_NONE;
1118 fprintf(stderr, "read_poll enc/full: ");
1119 buffer_dump(&input);
1121 cp = buffer_append_space(&incoming_packet, need);
1122 cipher_crypt(&receive_context, cp, buffer_ptr(&input), need);
1123 buffer_consume(&input, need);
1125 * compute MAC over seqnr and packet,
1126 * increment sequence number for incoming packet
1128 if (mac && mac->enabled) {
1129 macbuf = mac_compute(mac, p_read.seqnr,
1130 buffer_ptr(&incoming_packet),
1131 buffer_len(&incoming_packet));
1132 if (memcmp(macbuf, buffer_ptr(&input), mac->mac_len) != 0)
1133 packet_disconnect("Corrupted MAC on input.");
1134 DBG(debug("MAC #%d ok", p_read.seqnr));
1135 buffer_consume(&input, mac->mac_len);
1137 if (seqnr_p != NULL)
1138 *seqnr_p = p_read.seqnr;
1139 if (++p_read.seqnr == 0)
1140 logit("incoming seqnr wraps around");
1141 if (++p_read.packets == 0)
1142 if (!(datafellows & SSH_BUG_NOREKEY))
1143 fatal("XXX too many packets with same key");
1144 p_read.blocks += (packet_length + 4) / block_size;
1147 cp = buffer_ptr(&incoming_packet);
1149 DBG(debug("input: padlen %d", padlen));
1151 packet_disconnect("Corrupted padlen %d on input.", padlen);
1153 /* skip packet size + padlen, discard padding */
1154 buffer_consume(&incoming_packet, 4 + 1);
1155 buffer_consume_end(&incoming_packet, padlen);
1157 DBG(debug("input: len before de-compress %d", buffer_len(&incoming_packet)));
1158 if (comp && comp->enabled) {
1159 buffer_clear(&compression_buffer);
1160 buffer_uncompress(&incoming_packet, &compression_buffer);
1161 buffer_clear(&incoming_packet);
1162 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
1163 buffer_len(&compression_buffer));
1164 DBG(debug("input: len after de-compress %d",
1165 buffer_len(&incoming_packet)));
1168 * get packet type, implies consume.
1169 * return length of payload (without type field)
1171 type = buffer_get_char(&incoming_packet);
1172 if (type < SSH2_MSG_MIN || type >= SSH2_MSG_LOCAL_MIN)
1173 packet_disconnect("Invalid ssh2 packet type: %d", type);
1174 if (type == SSH2_MSG_NEWKEYS)
1175 set_newkeys(MODE_IN);
1176 else if (type == SSH2_MSG_USERAUTH_SUCCESS && !server_side)
1177 packet_enable_delayed_compress();
1179 fprintf(stderr, "read/plain[%d]:\r\n", type);
1180 buffer_dump(&incoming_packet);
1182 /* reset for next packet */
1188 packet_read_poll_seqnr(u_int32_t *seqnr_p)
1190 u_int reason, seqnr;
1196 type = packet_read_poll2(seqnr_p);
1197 keep_alive_timeouts = 0;
1199 DBG(debug("received packet type %d", type));
1201 case SSH2_MSG_IGNORE:
1202 debug3("Received SSH2_MSG_IGNORE");
1204 case SSH2_MSG_DEBUG:
1206 msg = packet_get_string(NULL);
1207 debug("Remote: %.900s", msg);
1209 msg = packet_get_string(NULL);
1212 case SSH2_MSG_DISCONNECT:
1213 reason = packet_get_int();
1214 msg = packet_get_string(NULL);
1215 logit("Received disconnect from %s: %u: %.400s",
1216 get_remote_ipaddr(), reason, msg);
1220 case SSH2_MSG_UNIMPLEMENTED:
1221 seqnr = packet_get_int();
1222 debug("Received SSH2_MSG_UNIMPLEMENTED for %u",
1229 type = packet_read_poll1();
1231 case SSH_MSG_IGNORE:
1234 msg = packet_get_string(NULL);
1235 debug("Remote: %.900s", msg);
1238 case SSH_MSG_DISCONNECT:
1239 msg = packet_get_string(NULL);
1240 logit("Received disconnect from %s: %.400s",
1241 get_remote_ipaddr(), msg);
1246 DBG(debug("received packet type %d", type));
1254 packet_read_poll(void)
1256 return packet_read_poll_seqnr(NULL);
1260 * Buffers the given amount of input characters. This is intended to be used
1261 * together with packet_read_poll.
1265 packet_process_incoming(const char *buf, u_int len)
1267 buffer_append(&input, buf, len);
1270 /* Returns a character from the packet. */
1273 packet_get_char(void)
1277 buffer_get(&incoming_packet, &ch, 1);
1281 /* Returns an integer from the packet data. */
1284 packet_get_int(void)
1286 return buffer_get_int(&incoming_packet);
1290 * Returns an arbitrary precision integer from the packet data. The integer
1291 * must have been initialized before this call.
1295 packet_get_bignum(BIGNUM * value)
1297 buffer_get_bignum(&incoming_packet, value);
1301 packet_get_bignum2(BIGNUM * value)
1303 buffer_get_bignum2(&incoming_packet, value);
1307 packet_get_raw(u_int *length_ptr)
1309 u_int bytes = buffer_len(&incoming_packet);
1311 if (length_ptr != NULL)
1312 *length_ptr = bytes;
1313 return buffer_ptr(&incoming_packet);
1317 packet_remaining(void)
1319 return buffer_len(&incoming_packet);
1323 * Returns a string from the packet data. The string is allocated using
1324 * xmalloc; it is the responsibility of the calling program to free it when
1325 * no longer needed. The length_ptr argument may be NULL, or point to an
1326 * integer into which the length of the string is stored.
1330 packet_get_string(u_int *length_ptr)
1332 return buffer_get_string(&incoming_packet, length_ptr);
1336 * Sends a diagnostic message from the server to the client. This message
1337 * can be sent at any time (but not while constructing another message). The
1338 * message is printed immediately, but only if the client is being executed
1339 * in verbose mode. These messages are primarily intended to ease debugging
1340 * authentication problems. The length of the formatted message must not
1341 * exceed 1024 bytes. This will automatically call packet_write_wait.
1345 packet_send_debug(const char *fmt,...)
1350 if (compat20 && (datafellows & SSH_BUG_DEBUG))
1353 va_start(args, fmt);
1354 vsnprintf(buf, sizeof(buf), fmt, args);
1358 packet_start(SSH2_MSG_DEBUG);
1359 packet_put_char(0); /* bool: always display */
1360 packet_put_cstring(buf);
1361 packet_put_cstring("");
1363 packet_start(SSH_MSG_DEBUG);
1364 packet_put_cstring(buf);
1367 packet_write_wait();
1371 * Logs the error plus constructs and sends a disconnect packet, closes the
1372 * connection, and exits. This function never returns. The error message
1373 * should not contain a newline. The length of the formatted message must
1374 * not exceed 1024 bytes.
1378 packet_disconnect(const char *fmt,...)
1382 static int disconnecting = 0;
1384 if (disconnecting) /* Guard against recursive invocations. */
1385 fatal("packet_disconnect called recursively.");
1389 * Format the message. Note that the caller must make sure the
1390 * message is of limited size.
1392 va_start(args, fmt);
1393 vsnprintf(buf, sizeof(buf), fmt, args);
1396 /* Display the error locally */
1397 logit("Disconnecting: %.100s", buf);
1399 /* Send the disconnect message to the other side, and wait for it to get sent. */
1401 packet_start(SSH2_MSG_DISCONNECT);
1402 packet_put_int(SSH2_DISCONNECT_PROTOCOL_ERROR);
1403 packet_put_cstring(buf);
1404 packet_put_cstring("");
1406 packet_start(SSH_MSG_DISCONNECT);
1407 packet_put_cstring(buf);
1410 packet_write_wait();
1412 /* Stop listening for connections. */
1413 channel_close_all();
1415 /* Close the connection. */
1420 /* Checks if there is any buffered output, and tries to write some of the output. */
1423 packet_write_poll(void)
1425 int len = buffer_len(&output);
1428 len = write(connection_out, buffer_ptr(&output), len);
1430 if (errno == EAGAIN)
1433 fatal("Write failed: %.100s", strerror(errno));
1435 buffer_consume(&output, len);
1440 * Calls packet_write_poll repeatedly until all pending output data has been
1445 packet_write_wait(void)
1449 setp = (fd_set *)xcalloc(howmany(connection_out + 1, NFDBITS),
1451 packet_write_poll();
1452 while (packet_have_data_to_write()) {
1453 memset(setp, 0, howmany(connection_out + 1, NFDBITS) *
1455 FD_SET(connection_out, setp);
1456 while (select(connection_out + 1, NULL, setp, NULL, NULL) == -1 &&
1457 (errno == EAGAIN || errno == EINTR))
1459 packet_write_poll();
1464 /* Returns true if there is buffered data to write to the connection. */
1467 packet_have_data_to_write(void)
1469 return buffer_len(&output) != 0;
1472 /* Returns true if there is not too much data to write to the connection. */
1475 packet_not_very_much_data_to_write(void)
1477 if (interactive_mode)
1478 return buffer_len(&output) < 16384;
1480 return buffer_len(&output) < 128 * 1024;
1485 packet_set_tos(int interactive)
1487 #if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN)
1488 int tos = interactive ? IPTOS_LOWDELAY : IPTOS_THROUGHPUT;
1490 if (!packet_connection_is_on_socket() ||
1491 !packet_connection_is_ipv4())
1493 if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, &tos,
1495 error("setsockopt IP_TOS %d: %.100s:",
1496 tos, strerror(errno));
1500 /* Informs that the current session is interactive. Sets IP flags for that. */
1503 packet_set_interactive(int interactive)
1505 static int called = 0;
1511 /* Record that we are in interactive mode. */
1512 interactive_mode = interactive;
1514 /* Only set socket options if using a socket. */
1515 if (!packet_connection_is_on_socket())
1517 set_nodelay(connection_in);
1518 packet_set_tos(interactive);
1521 /* Returns true if the current connection is interactive. */
1524 packet_is_interactive(void)
1526 return interactive_mode;
1530 packet_set_maxsize(u_int s)
1532 static int called = 0;
1535 logit("packet_set_maxsize: called twice: old %d new %d",
1536 max_packet_size, s);
1539 if (s < 4 * 1024 || s > 1024 * 1024) {
1540 logit("packet_set_maxsize: bad size %d", s);
1544 debug("packet_set_maxsize: setting to %d", s);
1545 max_packet_size = s;
1549 /* roundup current message to pad bytes */
1551 packet_add_padding(u_char pad)
1557 * 9.2. Ignored Data Message
1559 * byte SSH_MSG_IGNORE
1562 * All implementations MUST understand (and ignore) this message at any
1563 * time (after receiving the protocol version). No implementation is
1564 * required to send them. This message can be used as an additional
1565 * protection measure against advanced traffic analysis techniques.
1568 packet_send_ignore(int nbytes)
1573 packet_start(compat20 ? SSH2_MSG_IGNORE : SSH_MSG_IGNORE);
1574 packet_put_int(nbytes);
1575 for (i = 0; i < nbytes; i++) {
1578 packet_put_char((u_char)rnd & 0xff);
1583 #define MAX_PACKETS (1U<<31)
1585 packet_need_rekeying(void)
1587 if (datafellows & SSH_BUG_NOREKEY)
1590 (p_send.packets > MAX_PACKETS) ||
1591 (p_read.packets > MAX_PACKETS) ||
1592 (max_blocks_out && (p_send.blocks > max_blocks_out)) ||
1593 (max_blocks_in && (p_read.blocks > max_blocks_in));
1597 packet_set_rekey_limit(u_int32_t bytes)
1599 rekey_limit = bytes;
1603 packet_set_server(void)
1609 packet_set_authenticated(void)
1611 after_authentication = 1;