2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * This file contains code implementing the packet protocol and communication
6 * with the other side. This same code is used both on client and server side.
8 * As far as I am concerned, the code I have written for this software
9 * can be used freely for any purpose. Any derived versions of this
10 * software must be clearly marked as such, and if the derived work is
11 * incompatible with the protocol description in the RFC file, it must be
12 * called by a name other than "ssh" or "Secure Shell".
15 * SSH2 packet format added by Markus Friedl.
16 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
18 * Redistribution and use in source and binary forms, with or without
19 * modification, are permitted provided that the following conditions
21 * 1. Redistributions of source code must retain the above copyright
22 * notice, this list of conditions and the following disclaimer.
23 * 2. Redistributions in binary form must reproduce the above copyright
24 * notice, this list of conditions and the following disclaimer in the
25 * documentation and/or other materials provided with the distribution.
27 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
28 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
29 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
30 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
31 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
32 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
33 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
34 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
36 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
41 #include "openbsd-compat/sys-queue.h"
42 #include <netinet/in_systm.h>
43 #include <netinet/ip.h>
75 * This variable contains the file descriptors used for communicating with
76 * the other side. connection_in is used for reading; connection_out for
77 * writing. These can be the same descriptor, in which case it is assumed to
80 static int connection_in = -1;
81 static int connection_out = -1;
83 /* Protocol flags for the remote side. */
84 static u_int remote_protocol_flags = 0;
86 /* Encryption context for receiving data. This is only used for decryption. */
87 static CipherContext receive_context;
89 /* Encryption context for sending data. This is only used for encryption. */
90 static CipherContext send_context;
92 /* Buffer for raw input data from the socket. */
95 /* Buffer for raw output data going to the socket. */
98 /* Buffer for the partial outgoing packet being constructed. */
99 static Buffer outgoing_packet;
101 /* Buffer for the incoming packet currently being processed. */
102 static Buffer incoming_packet;
104 /* Scratch buffer for packet compression/decompression. */
105 static Buffer compression_buffer;
106 static int compression_buffer_ready = 0;
108 /* Flag indicating whether packet compression/decompression is enabled. */
109 static int packet_compression = 0;
111 /* default maximum packet size */
112 u_int max_packet_size = 32768;
114 /* Flag indicating whether this module has been initialized. */
115 static int initialized = 0;
117 /* Set to true if the connection is interactive. */
118 static int interactive_mode = 0;
120 /* Set to true if we are the server side. */
121 static int server_side = 0;
123 /* Set to true if we are authenticated. */
124 static int after_authentication = 0;
126 /* Session key information for Encryption and MAC */
127 Newkeys *newkeys[MODE_MAX];
128 static struct packet_state {
134 static u_int64_t max_blocks_in, max_blocks_out;
135 static u_int32_t rekey_limit;
137 /* Session key for protocol v1 */
138 static u_char ssh1_key[SSH_SESSION_KEY_LENGTH];
139 static u_int ssh1_keylen;
141 /* roundup current message to extra_pad bytes */
142 static u_char extra_pad = 0;
145 TAILQ_ENTRY(packet) next;
149 TAILQ_HEAD(, packet) outgoing;
152 * Sets the descriptors used for communication. Disables encryption until
153 * packet_set_encryption_key is called.
156 packet_set_connection(int fd_in, int fd_out)
158 Cipher *none = cipher_by_name("none");
161 fatal("packet_set_connection: cannot load cipher 'none'");
162 connection_in = fd_in;
163 connection_out = fd_out;
164 cipher_init(&send_context, none, (const u_char *)"",
165 0, NULL, 0, CIPHER_ENCRYPT);
166 cipher_init(&receive_context, none, (const u_char *)"",
167 0, NULL, 0, CIPHER_DECRYPT);
168 newkeys[MODE_IN] = newkeys[MODE_OUT] = NULL;
172 buffer_init(&output);
173 buffer_init(&outgoing_packet);
174 buffer_init(&incoming_packet);
175 TAILQ_INIT(&outgoing);
179 /* Returns 1 if remote host is connected via socket, 0 if not. */
182 packet_connection_is_on_socket(void)
184 struct sockaddr_storage from, to;
185 socklen_t fromlen, tolen;
187 /* filedescriptors in and out are the same, so it's a socket */
188 if (connection_in == connection_out)
190 fromlen = sizeof(from);
191 memset(&from, 0, sizeof(from));
192 if (getpeername(connection_in, (struct sockaddr *)&from, &fromlen) < 0)
195 memset(&to, 0, sizeof(to));
196 if (getpeername(connection_out, (struct sockaddr *)&to, &tolen) < 0)
198 if (fromlen != tolen || memcmp(&from, &to, fromlen) != 0)
200 if (from.ss_family != AF_INET && from.ss_family != AF_INET6)
206 * Exports an IV from the CipherContext required to export the key
207 * state back from the unprivileged child to the privileged parent
212 packet_get_keyiv(int mode, u_char *iv, u_int len)
216 if (mode == MODE_OUT)
219 cc = &receive_context;
221 cipher_get_keyiv(cc, iv, len);
225 packet_get_keycontext(int mode, u_char *dat)
229 if (mode == MODE_OUT)
232 cc = &receive_context;
234 return (cipher_get_keycontext(cc, dat));
238 packet_set_keycontext(int mode, u_char *dat)
242 if (mode == MODE_OUT)
245 cc = &receive_context;
247 cipher_set_keycontext(cc, dat);
251 packet_get_keyiv_len(int mode)
255 if (mode == MODE_OUT)
258 cc = &receive_context;
260 return (cipher_get_keyiv_len(cc));
263 packet_set_iv(int mode, u_char *dat)
267 if (mode == MODE_OUT)
270 cc = &receive_context;
272 cipher_set_keyiv(cc, dat);
275 packet_get_ssh1_cipher(void)
277 return (cipher_get_number(receive_context.cipher));
281 packet_get_state(int mode, u_int32_t *seqnr, u_int64_t *blocks, u_int32_t *packets)
283 struct packet_state *state;
285 state = (mode == MODE_IN) ? &p_read : &p_send;
286 *seqnr = state->seqnr;
287 *blocks = state->blocks;
288 *packets = state->packets;
292 packet_set_state(int mode, u_int32_t seqnr, u_int64_t blocks, u_int32_t packets)
294 struct packet_state *state;
296 state = (mode == MODE_IN) ? &p_read : &p_send;
297 state->seqnr = seqnr;
298 state->blocks = blocks;
299 state->packets = packets;
302 /* returns 1 if connection is via ipv4 */
305 packet_connection_is_ipv4(void)
307 struct sockaddr_storage to;
308 socklen_t tolen = sizeof(to);
310 memset(&to, 0, sizeof(to));
311 if (getsockname(connection_out, (struct sockaddr *)&to, &tolen) < 0)
313 if (to.ss_family == AF_INET)
316 if (to.ss_family == AF_INET6 &&
317 IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)&to)->sin6_addr))
323 /* Sets the connection into non-blocking mode. */
326 packet_set_nonblocking(void)
328 /* Set the socket into non-blocking mode. */
329 set_nonblock(connection_in);
331 if (connection_out != connection_in)
332 set_nonblock(connection_out);
335 /* Returns the socket used for reading. */
338 packet_get_connection_in(void)
340 return connection_in;
343 /* Returns the descriptor used for writing. */
346 packet_get_connection_out(void)
348 return connection_out;
351 /* Closes the connection and clears and frees internal data structures. */
359 if (connection_in == connection_out) {
360 shutdown(connection_out, SHUT_RDWR);
361 close(connection_out);
363 close(connection_in);
364 close(connection_out);
367 buffer_free(&output);
368 buffer_free(&outgoing_packet);
369 buffer_free(&incoming_packet);
370 if (compression_buffer_ready) {
371 buffer_free(&compression_buffer);
372 buffer_compress_uninit();
374 cipher_cleanup(&send_context);
375 cipher_cleanup(&receive_context);
378 /* Sets remote side protocol flags. */
381 packet_set_protocol_flags(u_int protocol_flags)
383 remote_protocol_flags = protocol_flags;
386 /* Returns the remote protocol flags set earlier by the above function. */
389 packet_get_protocol_flags(void)
391 return remote_protocol_flags;
395 * Starts packet compression from the next packet on in both directions.
396 * Level is compression level 1 (fastest) - 9 (slow, best) as in gzip.
400 packet_init_compression(void)
402 if (compression_buffer_ready == 1)
404 compression_buffer_ready = 1;
405 buffer_init(&compression_buffer);
409 packet_start_compression(int level)
411 if (packet_compression && !compat20)
412 fatal("Compression already enabled.");
413 packet_compression = 1;
414 packet_init_compression();
415 buffer_compress_init_send(level);
416 buffer_compress_init_recv();
420 * Causes any further packets to be encrypted using the given key. The same
421 * key is used for both sending and reception. However, both directions are
422 * encrypted independently of each other.
426 packet_set_encryption_key(const u_char *key, u_int keylen,
429 Cipher *cipher = cipher_by_number(number);
432 fatal("packet_set_encryption_key: unknown cipher number %d", number);
434 fatal("packet_set_encryption_key: keylen too small: %d", keylen);
435 if (keylen > SSH_SESSION_KEY_LENGTH)
436 fatal("packet_set_encryption_key: keylen too big: %d", keylen);
437 memcpy(ssh1_key, key, keylen);
438 ssh1_keylen = keylen;
439 cipher_init(&send_context, cipher, key, keylen, NULL, 0, CIPHER_ENCRYPT);
440 cipher_init(&receive_context, cipher, key, keylen, NULL, 0, CIPHER_DECRYPT);
444 packet_get_encryption_key(u_char *key)
447 return (ssh1_keylen);
448 memcpy(key, ssh1_key, ssh1_keylen);
449 return (ssh1_keylen);
452 /* Start constructing a packet to send. */
454 packet_start(u_char type)
459 DBG(debug("packet_start[%d]", type));
460 len = compat20 ? 6 : 9;
461 memset(buf, 0, len - 1);
463 buffer_clear(&outgoing_packet);
464 buffer_append(&outgoing_packet, buf, len);
467 /* Append payload. */
469 packet_put_char(int value)
473 buffer_append(&outgoing_packet, &ch, 1);
476 packet_put_int(u_int value)
478 buffer_put_int(&outgoing_packet, value);
481 packet_put_string(const void *buf, u_int len)
483 buffer_put_string(&outgoing_packet, buf, len);
486 packet_put_cstring(const char *str)
488 buffer_put_cstring(&outgoing_packet, str);
491 packet_put_raw(const void *buf, u_int len)
493 buffer_append(&outgoing_packet, buf, len);
496 packet_put_bignum(BIGNUM * value)
498 buffer_put_bignum(&outgoing_packet, value);
501 packet_put_bignum2(BIGNUM * value)
503 buffer_put_bignum2(&outgoing_packet, value);
507 * Finalizes and sends the packet. If the encryption key has been set,
508 * encrypts the packet before sending.
520 * If using packet compression, compress the payload of the outgoing
523 if (packet_compression) {
524 buffer_clear(&compression_buffer);
526 buffer_consume(&outgoing_packet, 8);
528 buffer_append(&compression_buffer, "\0\0\0\0\0\0\0\0", 8);
529 buffer_compress(&outgoing_packet, &compression_buffer);
530 buffer_clear(&outgoing_packet);
531 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
532 buffer_len(&compression_buffer));
534 /* Compute packet length without padding (add checksum, remove padding). */
535 len = buffer_len(&outgoing_packet) + 4 - 8;
537 /* Insert padding. Initialized to zero in packet_start1() */
538 padding = 8 - len % 8;
539 if (!send_context.plaintext) {
540 cp = buffer_ptr(&outgoing_packet);
541 for (i = 0; i < padding; i++) {
544 cp[7 - i] = rnd & 0xff;
548 buffer_consume(&outgoing_packet, 8 - padding);
550 /* Add check bytes. */
551 checksum = ssh_crc32(buffer_ptr(&outgoing_packet),
552 buffer_len(&outgoing_packet));
553 PUT_32BIT(buf, checksum);
554 buffer_append(&outgoing_packet, buf, 4);
557 fprintf(stderr, "packet_send plain: ");
558 buffer_dump(&outgoing_packet);
561 /* Append to output. */
563 buffer_append(&output, buf, 4);
564 cp = buffer_append_space(&output, buffer_len(&outgoing_packet));
565 cipher_crypt(&send_context, cp, buffer_ptr(&outgoing_packet),
566 buffer_len(&outgoing_packet));
569 fprintf(stderr, "encrypted: ");
570 buffer_dump(&output);
573 buffer_clear(&outgoing_packet);
576 * Note that the packet is now only buffered in output. It won't be
577 * actually sent until packet_write_wait or packet_write_poll is
583 set_newkeys(int mode)
589 u_int64_t *max_blocks;
592 debug2("set_newkeys: mode %d", mode);
594 if (mode == MODE_OUT) {
596 crypt_type = CIPHER_ENCRYPT;
597 p_send.packets = p_send.blocks = 0;
598 max_blocks = &max_blocks_out;
600 cc = &receive_context;
601 crypt_type = CIPHER_DECRYPT;
602 p_read.packets = p_read.blocks = 0;
603 max_blocks = &max_blocks_in;
605 if (newkeys[mode] != NULL) {
606 debug("set_newkeys: rekeying");
608 enc = &newkeys[mode]->enc;
609 mac = &newkeys[mode]->mac;
610 comp = &newkeys[mode]->comp;
611 memset(mac->key, 0, mac->key_len);
618 xfree(newkeys[mode]);
620 newkeys[mode] = kex_get_newkeys(mode);
621 if (newkeys[mode] == NULL)
622 fatal("newkeys: no keys for mode %d", mode);
623 enc = &newkeys[mode]->enc;
624 mac = &newkeys[mode]->mac;
625 comp = &newkeys[mode]->comp;
628 DBG(debug("cipher_init_context: %d", mode));
629 cipher_init(cc, enc->cipher, enc->key, enc->key_len,
630 enc->iv, enc->block_size, crypt_type);
631 /* Deleting the keys does not gain extra security */
632 /* memset(enc->iv, 0, enc->block_size);
633 memset(enc->key, 0, enc->key_len); */
634 if ((comp->type == COMP_ZLIB ||
635 (comp->type == COMP_DELAYED && after_authentication)) &&
636 comp->enabled == 0) {
637 packet_init_compression();
638 if (mode == MODE_OUT)
639 buffer_compress_init_send(6);
641 buffer_compress_init_recv();
645 * The 2^(blocksize*2) limit is too expensive for 3DES,
646 * blowfish, etc, so enforce a 1GB limit for small blocksizes.
648 if (enc->block_size >= 16)
649 *max_blocks = (u_int64_t)1 << (enc->block_size*2);
651 *max_blocks = ((u_int64_t)1 << 30) / enc->block_size;
653 *max_blocks = MIN(*max_blocks, rekey_limit / enc->block_size);
657 * Delayed compression for SSH2 is enabled after authentication:
658 * This happans on the server side after a SSH2_MSG_USERAUTH_SUCCESS is sent,
659 * and on the client side after a SSH2_MSG_USERAUTH_SUCCESS is received.
662 packet_enable_delayed_compress(void)
668 * Remember that we are past the authentication step, so rekeying
669 * with COMP_DELAYED will turn on compression immediately.
671 after_authentication = 1;
672 for (mode = 0; mode < MODE_MAX; mode++) {
673 comp = &newkeys[mode]->comp;
674 if (comp && !comp->enabled && comp->type == COMP_DELAYED) {
675 packet_init_compression();
676 if (mode == MODE_OUT)
677 buffer_compress_init_send(6);
679 buffer_compress_init_recv();
686 * Finalize packet in SSH2 format (compress, mac, encrypt, enqueue)
689 packet_send2_wrapped(void)
691 u_char type, *cp, *macbuf = NULL;
693 u_int packet_length = 0;
701 if (newkeys[MODE_OUT] != NULL) {
702 enc = &newkeys[MODE_OUT]->enc;
703 mac = &newkeys[MODE_OUT]->mac;
704 comp = &newkeys[MODE_OUT]->comp;
706 block_size = enc ? enc->block_size : 8;
708 cp = buffer_ptr(&outgoing_packet);
712 fprintf(stderr, "plain: ");
713 buffer_dump(&outgoing_packet);
716 if (comp && comp->enabled) {
717 len = buffer_len(&outgoing_packet);
718 /* skip header, compress only payload */
719 buffer_consume(&outgoing_packet, 5);
720 buffer_clear(&compression_buffer);
721 buffer_compress(&outgoing_packet, &compression_buffer);
722 buffer_clear(&outgoing_packet);
723 buffer_append(&outgoing_packet, "\0\0\0\0\0", 5);
724 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
725 buffer_len(&compression_buffer));
726 DBG(debug("compression: raw %d compressed %d", len,
727 buffer_len(&outgoing_packet)));
730 /* sizeof (packet_len + pad_len + payload) */
731 len = buffer_len(&outgoing_packet);
734 * calc size of padding, alloc space, get random data,
735 * minimum padding is 4 bytes
737 padlen = block_size - (len % block_size);
739 padlen += block_size;
741 /* will wrap if extra_pad+padlen > 255 */
742 extra_pad = roundup(extra_pad, block_size);
743 pad = extra_pad - ((len + padlen) % extra_pad);
744 debug3("packet_send2: adding %d (len %d padlen %d extra_pad %d)",
745 pad, len, padlen, extra_pad);
749 cp = buffer_append_space(&outgoing_packet, padlen);
750 if (enc && !send_context.plaintext) {
752 for (i = 0; i < padlen; i++) {
760 memset(cp, 0, padlen);
762 /* packet_length includes payload, padding and padding length field */
763 packet_length = buffer_len(&outgoing_packet) - 4;
764 cp = buffer_ptr(&outgoing_packet);
765 PUT_32BIT(cp, packet_length);
767 DBG(debug("send: len %d (includes padlen %d)", packet_length+4, padlen));
769 /* compute MAC over seqnr and packet(length fields, payload, padding) */
770 if (mac && mac->enabled) {
771 macbuf = mac_compute(mac, p_send.seqnr,
772 buffer_ptr(&outgoing_packet),
773 buffer_len(&outgoing_packet));
774 DBG(debug("done calc MAC out #%d", p_send.seqnr));
776 /* encrypt packet and append to output buffer. */
777 cp = buffer_append_space(&output, buffer_len(&outgoing_packet));
778 cipher_crypt(&send_context, cp, buffer_ptr(&outgoing_packet),
779 buffer_len(&outgoing_packet));
780 /* append unencrypted MAC */
781 if (mac && mac->enabled)
782 buffer_append(&output, (char *)macbuf, mac->mac_len);
784 fprintf(stderr, "encrypted: ");
785 buffer_dump(&output);
787 /* increment sequence number for outgoing packets */
788 if (++p_send.seqnr == 0)
789 logit("outgoing seqnr wraps around");
790 if (++p_send.packets == 0)
791 if (!(datafellows & SSH_BUG_NOREKEY))
792 fatal("XXX too many packets with same key");
793 p_send.blocks += (packet_length + 4) / block_size;
794 buffer_clear(&outgoing_packet);
796 if (type == SSH2_MSG_NEWKEYS)
797 set_newkeys(MODE_OUT);
798 else if (type == SSH2_MSG_USERAUTH_SUCCESS && server_side)
799 packet_enable_delayed_compress();
805 static int rekeying = 0;
809 cp = buffer_ptr(&outgoing_packet);
812 /* during rekeying we can only send key exchange messages */
814 if (!((type >= SSH2_MSG_TRANSPORT_MIN) &&
815 (type <= SSH2_MSG_TRANSPORT_MAX))) {
816 debug("enqueue packet: %u", type);
817 p = xmalloc(sizeof(*p));
819 memcpy(&p->payload, &outgoing_packet, sizeof(Buffer));
820 buffer_init(&outgoing_packet);
821 TAILQ_INSERT_TAIL(&outgoing, p, next);
826 /* rekeying starts with sending KEXINIT */
827 if (type == SSH2_MSG_KEXINIT)
830 packet_send2_wrapped();
832 /* after a NEWKEYS message we can send the complete queue */
833 if (type == SSH2_MSG_NEWKEYS) {
835 while ((p = TAILQ_FIRST(&outgoing))) {
837 debug("dequeue packet: %u", type);
838 buffer_free(&outgoing_packet);
839 memcpy(&outgoing_packet, &p->payload,
841 TAILQ_REMOVE(&outgoing, p, next);
843 packet_send2_wrapped();
855 DBG(debug("packet_send done"));
859 * Waits until a packet has been received, and returns its type. Note that
860 * no other data is processed until this returns, so this function should not
861 * be used during the interactive session.
865 packet_read_seqnr(u_int32_t *seqnr_p)
870 DBG(debug("packet_read()"));
872 setp = (fd_set *)xmalloc(howmany(connection_in+1, NFDBITS) *
875 /* Since we are blocking, ensure that all written packets have been sent. */
878 /* Stay in the loop until we have received a complete packet. */
880 /* Try to read a packet from the buffer. */
881 type = packet_read_poll_seqnr(seqnr_p);
883 type == SSH_SMSG_SUCCESS
884 || type == SSH_SMSG_FAILURE
885 || type == SSH_CMSG_EOF
886 || type == SSH_CMSG_EXIT_CONFIRMATION))
888 /* If we got a packet, return it. */
889 if (type != SSH_MSG_NONE) {
894 * Otherwise, wait for some data to arrive, add it to the
895 * buffer, and try again.
897 memset(setp, 0, howmany(connection_in + 1, NFDBITS) *
899 FD_SET(connection_in, setp);
901 /* Wait for some data to arrive. */
902 while (select(connection_in + 1, setp, NULL, NULL, NULL) == -1 &&
903 (errno == EAGAIN || errno == EINTR))
906 /* Read data from the socket. */
907 len = read(connection_in, buf, sizeof(buf));
909 logit("Connection closed by %.200s", get_remote_ipaddr());
913 fatal("Read from socket failed: %.100s", strerror(errno));
914 /* Append it to the buffer. */
915 packet_process_incoming(buf, len);
923 return packet_read_seqnr(NULL);
927 * Waits until a packet has been received, verifies that its type matches
928 * that given, and gives a fatal error and exits if there is a mismatch.
932 packet_read_expect(int expected_type)
936 type = packet_read();
937 if (type != expected_type)
938 packet_disconnect("Protocol error: expected packet type %d, got %d",
939 expected_type, type);
942 /* Checks if a full packet is available in the data received so far via
943 * packet_process_incoming. If so, reads the packet; otherwise returns
944 * SSH_MSG_NONE. This does not wait for data from the connection.
946 * SSH_MSG_DISCONNECT is handled specially here. Also,
947 * SSH_MSG_IGNORE messages are skipped by this function and are never returned
952 packet_read_poll1(void)
954 u_int len, padded_len;
956 u_int checksum, stored_checksum;
958 /* Check if input size is less than minimum packet size. */
959 if (buffer_len(&input) < 4 + 8)
961 /* Get length of incoming packet. */
962 cp = buffer_ptr(&input);
964 if (len < 1 + 2 + 2 || len > 256 * 1024)
965 packet_disconnect("Bad packet length %u.", len);
966 padded_len = (len + 8) & ~7;
968 /* Check if the packet has been entirely received. */
969 if (buffer_len(&input) < 4 + padded_len)
972 /* The entire packet is in buffer. */
974 /* Consume packet length. */
975 buffer_consume(&input, 4);
978 * Cryptographic attack detector for ssh
979 * (C)1998 CORE-SDI, Buenos Aires Argentina
980 * Ariel Futoransky(futo@core-sdi.com)
982 if (!receive_context.plaintext &&
983 detect_attack(buffer_ptr(&input), padded_len, NULL) == DEATTACK_DETECTED)
984 packet_disconnect("crc32 compensation attack: network attack detected");
986 /* Decrypt data to incoming_packet. */
987 buffer_clear(&incoming_packet);
988 cp = buffer_append_space(&incoming_packet, padded_len);
989 cipher_crypt(&receive_context, cp, buffer_ptr(&input), padded_len);
991 buffer_consume(&input, padded_len);
994 fprintf(stderr, "read_poll plain: ");
995 buffer_dump(&incoming_packet);
998 /* Compute packet checksum. */
999 checksum = ssh_crc32(buffer_ptr(&incoming_packet),
1000 buffer_len(&incoming_packet) - 4);
1003 buffer_consume(&incoming_packet, 8 - len % 8);
1005 /* Test check bytes. */
1006 if (len != buffer_len(&incoming_packet))
1007 packet_disconnect("packet_read_poll1: len %d != buffer_len %d.",
1008 len, buffer_len(&incoming_packet));
1010 cp = (u_char *)buffer_ptr(&incoming_packet) + len - 4;
1011 stored_checksum = GET_32BIT(cp);
1012 if (checksum != stored_checksum)
1013 packet_disconnect("Corrupted check bytes on input.");
1014 buffer_consume_end(&incoming_packet, 4);
1016 if (packet_compression) {
1017 buffer_clear(&compression_buffer);
1018 buffer_uncompress(&incoming_packet, &compression_buffer);
1019 buffer_clear(&incoming_packet);
1020 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
1021 buffer_len(&compression_buffer));
1023 type = buffer_get_char(&incoming_packet);
1024 if (type < SSH_MSG_MIN || type > SSH_MSG_MAX)
1025 packet_disconnect("Invalid ssh1 packet type: %d", type);
1030 packet_read_poll2(u_int32_t *seqnr_p)
1032 static u_int packet_length = 0;
1034 u_char *macbuf, *cp, type;
1035 u_int maclen, block_size;
1040 if (newkeys[MODE_IN] != NULL) {
1041 enc = &newkeys[MODE_IN]->enc;
1042 mac = &newkeys[MODE_IN]->mac;
1043 comp = &newkeys[MODE_IN]->comp;
1045 maclen = mac && mac->enabled ? mac->mac_len : 0;
1046 block_size = enc ? enc->block_size : 8;
1048 if (packet_length == 0) {
1050 * check if input size is less than the cipher block size,
1051 * decrypt first block and extract length of incoming packet
1053 if (buffer_len(&input) < block_size)
1054 return SSH_MSG_NONE;
1055 buffer_clear(&incoming_packet);
1056 cp = buffer_append_space(&incoming_packet, block_size);
1057 cipher_crypt(&receive_context, cp, buffer_ptr(&input),
1059 cp = buffer_ptr(&incoming_packet);
1060 packet_length = GET_32BIT(cp);
1061 if (packet_length < 1 + 4 || packet_length > 256 * 1024) {
1063 buffer_dump(&incoming_packet);
1065 packet_disconnect("Bad packet length %u.", packet_length);
1067 DBG(debug("input: packet len %u", packet_length+4));
1068 buffer_consume(&input, block_size);
1070 /* we have a partial packet of block_size bytes */
1071 need = 4 + packet_length - block_size;
1072 DBG(debug("partial packet %d, need %d, maclen %d", block_size,
1074 if (need % block_size != 0)
1075 fatal("padding error: need %d block %d mod %d",
1076 need, block_size, need % block_size);
1078 * check if the entire packet has been received and
1079 * decrypt into incoming_packet
1081 if (buffer_len(&input) < need + maclen)
1082 return SSH_MSG_NONE;
1084 fprintf(stderr, "read_poll enc/full: ");
1085 buffer_dump(&input);
1087 cp = buffer_append_space(&incoming_packet, need);
1088 cipher_crypt(&receive_context, cp, buffer_ptr(&input), need);
1089 buffer_consume(&input, need);
1091 * compute MAC over seqnr and packet,
1092 * increment sequence number for incoming packet
1094 if (mac && mac->enabled) {
1095 macbuf = mac_compute(mac, p_read.seqnr,
1096 buffer_ptr(&incoming_packet),
1097 buffer_len(&incoming_packet));
1098 if (memcmp(macbuf, buffer_ptr(&input), mac->mac_len) != 0)
1099 packet_disconnect("Corrupted MAC on input.");
1100 DBG(debug("MAC #%d ok", p_read.seqnr));
1101 buffer_consume(&input, mac->mac_len);
1103 if (seqnr_p != NULL)
1104 *seqnr_p = p_read.seqnr;
1105 if (++p_read.seqnr == 0)
1106 logit("incoming seqnr wraps around");
1107 if (++p_read.packets == 0)
1108 if (!(datafellows & SSH_BUG_NOREKEY))
1109 fatal("XXX too many packets with same key");
1110 p_read.blocks += (packet_length + 4) / block_size;
1113 cp = buffer_ptr(&incoming_packet);
1115 DBG(debug("input: padlen %d", padlen));
1117 packet_disconnect("Corrupted padlen %d on input.", padlen);
1119 /* skip packet size + padlen, discard padding */
1120 buffer_consume(&incoming_packet, 4 + 1);
1121 buffer_consume_end(&incoming_packet, padlen);
1123 DBG(debug("input: len before de-compress %d", buffer_len(&incoming_packet)));
1124 if (comp && comp->enabled) {
1125 buffer_clear(&compression_buffer);
1126 buffer_uncompress(&incoming_packet, &compression_buffer);
1127 buffer_clear(&incoming_packet);
1128 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
1129 buffer_len(&compression_buffer));
1130 DBG(debug("input: len after de-compress %d",
1131 buffer_len(&incoming_packet)));
1134 * get packet type, implies consume.
1135 * return length of payload (without type field)
1137 type = buffer_get_char(&incoming_packet);
1138 if (type < SSH2_MSG_MIN || type >= SSH2_MSG_LOCAL_MIN)
1139 packet_disconnect("Invalid ssh2 packet type: %d", type);
1140 if (type == SSH2_MSG_NEWKEYS)
1141 set_newkeys(MODE_IN);
1142 else if (type == SSH2_MSG_USERAUTH_SUCCESS && !server_side)
1143 packet_enable_delayed_compress();
1145 fprintf(stderr, "read/plain[%d]:\r\n", type);
1146 buffer_dump(&incoming_packet);
1148 /* reset for next packet */
1154 packet_read_poll_seqnr(u_int32_t *seqnr_p)
1156 u_int reason, seqnr;
1162 type = packet_read_poll2(seqnr_p);
1164 DBG(debug("received packet type %d", type));
1166 case SSH2_MSG_IGNORE:
1168 case SSH2_MSG_DEBUG:
1170 msg = packet_get_string(NULL);
1171 debug("Remote: %.900s", msg);
1173 msg = packet_get_string(NULL);
1176 case SSH2_MSG_DISCONNECT:
1177 reason = packet_get_int();
1178 msg = packet_get_string(NULL);
1179 logit("Received disconnect from %s: %u: %.400s",
1180 get_remote_ipaddr(), reason, msg);
1184 case SSH2_MSG_UNIMPLEMENTED:
1185 seqnr = packet_get_int();
1186 debug("Received SSH2_MSG_UNIMPLEMENTED for %u",
1193 type = packet_read_poll1();
1195 case SSH_MSG_IGNORE:
1198 msg = packet_get_string(NULL);
1199 debug("Remote: %.900s", msg);
1202 case SSH_MSG_DISCONNECT:
1203 msg = packet_get_string(NULL);
1204 logit("Received disconnect from %s: %.400s",
1205 get_remote_ipaddr(), msg);
1211 DBG(debug("received packet type %d", type));
1219 packet_read_poll(void)
1221 return packet_read_poll_seqnr(NULL);
1225 * Buffers the given amount of input characters. This is intended to be used
1226 * together with packet_read_poll.
1230 packet_process_incoming(const char *buf, u_int len)
1232 buffer_append(&input, buf, len);
1235 /* Returns a character from the packet. */
1238 packet_get_char(void)
1242 buffer_get(&incoming_packet, &ch, 1);
1246 /* Returns an integer from the packet data. */
1249 packet_get_int(void)
1251 return buffer_get_int(&incoming_packet);
1255 * Returns an arbitrary precision integer from the packet data. The integer
1256 * must have been initialized before this call.
1260 packet_get_bignum(BIGNUM * value)
1262 buffer_get_bignum(&incoming_packet, value);
1266 packet_get_bignum2(BIGNUM * value)
1268 buffer_get_bignum2(&incoming_packet, value);
1272 packet_get_raw(u_int *length_ptr)
1274 u_int bytes = buffer_len(&incoming_packet);
1276 if (length_ptr != NULL)
1277 *length_ptr = bytes;
1278 return buffer_ptr(&incoming_packet);
1282 packet_remaining(void)
1284 return buffer_len(&incoming_packet);
1288 * Returns a string from the packet data. The string is allocated using
1289 * xmalloc; it is the responsibility of the calling program to free it when
1290 * no longer needed. The length_ptr argument may be NULL, or point to an
1291 * integer into which the length of the string is stored.
1295 packet_get_string(u_int *length_ptr)
1297 return buffer_get_string(&incoming_packet, length_ptr);
1301 * Sends a diagnostic message from the server to the client. This message
1302 * can be sent at any time (but not while constructing another message). The
1303 * message is printed immediately, but only if the client is being executed
1304 * in verbose mode. These messages are primarily intended to ease debugging
1305 * authentication problems. The length of the formatted message must not
1306 * exceed 1024 bytes. This will automatically call packet_write_wait.
1310 packet_send_debug(const char *fmt,...)
1315 if (compat20 && (datafellows & SSH_BUG_DEBUG))
1318 va_start(args, fmt);
1319 vsnprintf(buf, sizeof(buf), fmt, args);
1323 packet_start(SSH2_MSG_DEBUG);
1324 packet_put_char(0); /* bool: always display */
1325 packet_put_cstring(buf);
1326 packet_put_cstring("");
1328 packet_start(SSH_MSG_DEBUG);
1329 packet_put_cstring(buf);
1332 packet_write_wait();
1336 * Logs the error plus constructs and sends a disconnect packet, closes the
1337 * connection, and exits. This function never returns. The error message
1338 * should not contain a newline. The length of the formatted message must
1339 * not exceed 1024 bytes.
1343 packet_disconnect(const char *fmt,...)
1347 static int disconnecting = 0;
1349 if (disconnecting) /* Guard against recursive invocations. */
1350 fatal("packet_disconnect called recursively.");
1354 * Format the message. Note that the caller must make sure the
1355 * message is of limited size.
1357 va_start(args, fmt);
1358 vsnprintf(buf, sizeof(buf), fmt, args);
1361 /* Display the error locally */
1362 logit("Disconnecting: %.100s", buf);
1364 /* Send the disconnect message to the other side, and wait for it to get sent. */
1366 packet_start(SSH2_MSG_DISCONNECT);
1367 packet_put_int(SSH2_DISCONNECT_PROTOCOL_ERROR);
1368 packet_put_cstring(buf);
1369 packet_put_cstring("");
1371 packet_start(SSH_MSG_DISCONNECT);
1372 packet_put_cstring(buf);
1375 packet_write_wait();
1377 /* Stop listening for connections. */
1378 channel_close_all();
1380 /* Close the connection. */
1385 /* Checks if there is any buffered output, and tries to write some of the output. */
1388 packet_write_poll(void)
1390 int len = buffer_len(&output);
1393 len = write(connection_out, buffer_ptr(&output), len);
1395 if (errno == EAGAIN)
1398 fatal("Write failed: %.100s", strerror(errno));
1400 buffer_consume(&output, len);
1405 * Calls packet_write_poll repeatedly until all pending output data has been
1410 packet_write_wait(void)
1414 setp = (fd_set *)xmalloc(howmany(connection_out + 1, NFDBITS) *
1416 packet_write_poll();
1417 while (packet_have_data_to_write()) {
1418 memset(setp, 0, howmany(connection_out + 1, NFDBITS) *
1420 FD_SET(connection_out, setp);
1421 while (select(connection_out + 1, NULL, setp, NULL, NULL) == -1 &&
1422 (errno == EAGAIN || errno == EINTR))
1424 packet_write_poll();
1429 /* Returns true if there is buffered data to write to the connection. */
1432 packet_have_data_to_write(void)
1434 return buffer_len(&output) != 0;
1437 /* Returns true if there is not too much data to write to the connection. */
1440 packet_not_very_much_data_to_write(void)
1442 if (interactive_mode)
1443 return buffer_len(&output) < 16384;
1445 return buffer_len(&output) < 128 * 1024;
1450 packet_set_tos(int interactive)
1452 #if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN)
1453 int tos = interactive ? IPTOS_LOWDELAY : IPTOS_THROUGHPUT;
1455 if (!packet_connection_is_on_socket() ||
1456 !packet_connection_is_ipv4())
1458 if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, &tos,
1460 error("setsockopt IP_TOS %d: %.100s:",
1461 tos, strerror(errno));
1465 /* Informs that the current session is interactive. Sets IP flags for that. */
1468 packet_set_interactive(int interactive)
1470 static int called = 0;
1476 /* Record that we are in interactive mode. */
1477 interactive_mode = interactive;
1479 /* Only set socket options if using a socket. */
1480 if (!packet_connection_is_on_socket())
1482 set_nodelay(connection_in);
1483 packet_set_tos(interactive);
1486 /* Returns true if the current connection is interactive. */
1489 packet_is_interactive(void)
1491 return interactive_mode;
1495 packet_set_maxsize(u_int s)
1497 static int called = 0;
1500 logit("packet_set_maxsize: called twice: old %d new %d",
1501 max_packet_size, s);
1504 if (s < 4 * 1024 || s > 1024 * 1024) {
1505 logit("packet_set_maxsize: bad size %d", s);
1509 debug("packet_set_maxsize: setting to %d", s);
1510 max_packet_size = s;
1514 /* roundup current message to pad bytes */
1516 packet_add_padding(u_char pad)
1522 * 9.2. Ignored Data Message
1524 * byte SSH_MSG_IGNORE
1527 * All implementations MUST understand (and ignore) this message at any
1528 * time (after receiving the protocol version). No implementation is
1529 * required to send them. This message can be used as an additional
1530 * protection measure against advanced traffic analysis techniques.
1533 packet_send_ignore(int nbytes)
1538 packet_start(compat20 ? SSH2_MSG_IGNORE : SSH_MSG_IGNORE);
1539 packet_put_int(nbytes);
1540 for (i = 0; i < nbytes; i++) {
1543 packet_put_char(rnd & 0xff);
1548 #define MAX_PACKETS (1U<<31)
1550 packet_need_rekeying(void)
1552 if (datafellows & SSH_BUG_NOREKEY)
1555 (p_send.packets > MAX_PACKETS) ||
1556 (p_read.packets > MAX_PACKETS) ||
1557 (max_blocks_out && (p_send.blocks > max_blocks_out)) ||
1558 (max_blocks_in && (p_read.blocks > max_blocks_in));
1562 packet_set_rekey_limit(u_int32_t bytes)
1564 rekey_limit = bytes;
1568 packet_set_server(void)
1574 packet_set_authenticated(void)
1576 after_authentication = 1;