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1/*
2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4 * All rights reserved
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.
7 *
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".
13 *
14 *
15 * SSH2 packet format added by Markus Friedl.
16 * Copyright (c) 2000 Markus Friedl. All rights reserved.
17 *
18 * Redistribution and use in source and binary forms, with or without
19 * modification, are permitted provided that the following conditions
20 * are met:
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.
26 *
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.
37 */
38
39#include "includes.h"
40RCSID("$OpenBSD: packet.c,v 1.61 2001/04/05 10:42:51 markus Exp $");
41
42#include "xmalloc.h"
43#include "buffer.h"
44#include "packet.h"
45#include "bufaux.h"
46#include "crc32.h"
47#include "getput.h"
48
49#include "compress.h"
50#include "deattack.h"
51#include "channels.h"
52
53#include "compat.h"
54#include "ssh1.h"
55#include "ssh2.h"
56
57#include "cipher.h"
58#include "kex.h"
59#include "mac.h"
60#include "log.h"
61#include "canohost.h"
62
63#ifdef PACKET_DEBUG
64#define DBG(x) x
65#else
66#define DBG(x)
67#endif
68
69/*
70 * This variable contains the file descriptors used for communicating with
71 * the other side. connection_in is used for reading; connection_out for
72 * writing. These can be the same descriptor, in which case it is assumed to
73 * be a socket.
74 */
75static int connection_in = -1;
76static int connection_out = -1;
77
78/*
79 * Cipher type. This value is only used to determine whether to pad the
80 * packets with zeroes or random data.
81 */
82static int cipher_type = SSH_CIPHER_NONE;
83
84/* Protocol flags for the remote side. */
85static u_int remote_protocol_flags = 0;
86
87/* Encryption context for receiving data. This is only used for decryption. */
88static CipherContext receive_context;
89
90/* Encryption context for sending data. This is only used for encryption. */
91static CipherContext send_context;
92
93/* Buffer for raw input data from the socket. */
94static Buffer input;
95
96/* Buffer for raw output data going to the socket. */
97static Buffer output;
98
99/* Buffer for the partial outgoing packet being constructed. */
100static Buffer outgoing_packet;
101
102/* Buffer for the incoming packet currently being processed. */
103static Buffer incoming_packet;
104
105/* Scratch buffer for packet compression/decompression. */
106static Buffer compression_buffer;
107static int compression_buffer_ready = 0;
108
109/* Flag indicating whether packet compression/decompression is enabled. */
110static int packet_compression = 0;
111
112/* default maximum packet size */
113int max_packet_size = 32768;
114
115/* Flag indicating whether this module has been initialized. */
116static int initialized = 0;
117
118/* Set to true if the connection is interactive. */
119static int interactive_mode = 0;
120
121/* True if SSH2 packet format is used */
122int use_ssh2_packet_format = 0;
123
124/* Session key information for Encryption and MAC */
125Newkeys *newkeys[MODE_MAX];
126
127void
128packet_set_ssh2_format(void)
129{
130 DBG(debug("use_ssh2_packet_format"));
131 use_ssh2_packet_format = 1;
132 newkeys[MODE_IN] = newkeys[MODE_OUT] = NULL;
133}
134
135/*
136 * Sets the descriptors used for communication. Disables encryption until
137 * packet_set_encryption_key is called.
138 */
139void
140packet_set_connection(int fd_in, int fd_out)
141{
142 Cipher *none = cipher_by_name("none");
143 if (none == NULL)
144 fatal("packet_set_connection: cannot load cipher 'none'");
145 connection_in = fd_in;
146 connection_out = fd_out;
147 cipher_type = SSH_CIPHER_NONE;
148 cipher_init(&send_context, none, (u_char *) "", 0, NULL, 0);
149 cipher_init(&receive_context, none, (u_char *) "", 0, NULL, 0);
150 if (!initialized) {
151 initialized = 1;
152 buffer_init(&input);
153 buffer_init(&output);
154 buffer_init(&outgoing_packet);
155 buffer_init(&incoming_packet);
156 }
157 /* Kludge: arrange the close function to be called from fatal(). */
158 fatal_add_cleanup((void (*) (void *)) packet_close, NULL);
159}
160
161/* Returns 1 if remote host is connected via socket, 0 if not. */
162
163int
164packet_connection_is_on_socket()
165{
166 struct sockaddr_storage from, to;
167 socklen_t fromlen, tolen;
168
169 /* filedescriptors in and out are the same, so it's a socket */
170 if (connection_in == connection_out)
171 return 1;
172 fromlen = sizeof(from);
173 memset(&from, 0, sizeof(from));
174 if (getpeername(connection_in, (struct sockaddr *)&from, &fromlen) < 0)
175 return 0;
176 tolen = sizeof(to);
177 memset(&to, 0, sizeof(to));
178 if (getpeername(connection_out, (struct sockaddr *)&to, &tolen) < 0)
179 return 0;
180 if (fromlen != tolen || memcmp(&from, &to, fromlen) != 0)
181 return 0;
182 if (from.ss_family != AF_INET && from.ss_family != AF_INET6)
183 return 0;
184 return 1;
185}
186
187/* returns 1 if connection is via ipv4 */
188
189int
190packet_connection_is_ipv4()
191{
192 struct sockaddr_storage to;
193 socklen_t tolen = sizeof(to);
194
195 memset(&to, 0, sizeof(to));
196 if (getsockname(connection_out, (struct sockaddr *)&to, &tolen) < 0)
197 return 0;
198 if (to.ss_family != AF_INET)
199 return 0;
200 return 1;
201}
202
203/* Sets the connection into non-blocking mode. */
204
205void
206packet_set_nonblocking()
207{
208 /* Set the socket into non-blocking mode. */
209 if (fcntl(connection_in, F_SETFL, O_NONBLOCK) < 0)
210 error("fcntl O_NONBLOCK: %.100s", strerror(errno));
211
212 if (connection_out != connection_in) {
213 if (fcntl(connection_out, F_SETFL, O_NONBLOCK) < 0)
214 error("fcntl O_NONBLOCK: %.100s", strerror(errno));
215 }
216}
217
218/* Returns the socket used for reading. */
219
220int
221packet_get_connection_in()
222{
223 return connection_in;
224}
225
226/* Returns the descriptor used for writing. */
227
228int
229packet_get_connection_out()
230{
231 return connection_out;
232}
233
234/* Closes the connection and clears and frees internal data structures. */
235
236void
237packet_close()
238{
239 if (!initialized)
240 return;
241 initialized = 0;
242 if (connection_in == connection_out) {
243 shutdown(connection_out, SHUT_RDWR);
244 close(connection_out);
245 } else {
246 close(connection_in);
247 close(connection_out);
248 }
249 buffer_free(&input);
250 buffer_free(&output);
251 buffer_free(&outgoing_packet);
252 buffer_free(&incoming_packet);
253 if (compression_buffer_ready) {
254 buffer_free(&compression_buffer);
255 buffer_compress_uninit();
256 }
257}
258
259/* Sets remote side protocol flags. */
260
261void
262packet_set_protocol_flags(u_int protocol_flags)
263{
264 remote_protocol_flags = protocol_flags;
265 channel_set_options((protocol_flags & SSH_PROTOFLAG_HOST_IN_FWD_OPEN) != 0);
266}
267
268/* Returns the remote protocol flags set earlier by the above function. */
269
270u_int
271packet_get_protocol_flags()
272{
273 return remote_protocol_flags;
274}
275
276/*
277 * Starts packet compression from the next packet on in both directions.
278 * Level is compression level 1 (fastest) - 9 (slow, best) as in gzip.
279 */
280
281void
282packet_init_compression()
283{
284 if (compression_buffer_ready == 1)
285 return;
286 compression_buffer_ready = 1;
287 buffer_init(&compression_buffer);
288}
289
290void
291packet_start_compression(int level)
292{
293 if (packet_compression && !use_ssh2_packet_format)
294 fatal("Compression already enabled.");
295 packet_compression = 1;
296 packet_init_compression();
297 buffer_compress_init_send(level);
298 buffer_compress_init_recv();
299}
300
301/*
302 * Encrypts the given number of bytes, copying from src to dest. bytes is
303 * known to be a multiple of 8.
304 */
305
306void
307packet_encrypt(CipherContext * cc, void *dest, void *src,
308 u_int bytes)
309{
310 cipher_encrypt(cc, dest, src, bytes);
311}
312
313/*
314 * Decrypts the given number of bytes, copying from src to dest. bytes is
315 * known to be a multiple of 8.
316 */
317
318void
319packet_decrypt(CipherContext *context, void *dest, void *src, u_int bytes)
320{
321 /*
322 * Cryptographic attack detector for ssh - Modifications for packet.c
323 * (C)1998 CORE-SDI, Buenos Aires Argentina Ariel Futoransky(futo@core-sdi.com)
324 */
325 if (!compat20 &&
326 context->cipher->number != SSH_CIPHER_NONE &&
327 detect_attack(src, bytes, NULL) == DEATTACK_DETECTED)
328 packet_disconnect("crc32 compensation attack: network attack detected");
329
330 cipher_decrypt(context, dest, src, bytes);
331}
332
333/*
334 * Causes any further packets to be encrypted using the given key. The same
335 * key is used for both sending and reception. However, both directions are
336 * encrypted independently of each other.
337 */
338
339void
340packet_set_encryption_key(const u_char *key, u_int keylen,
341 int number)
342{
343 Cipher *cipher = cipher_by_number(number);
344 if (cipher == NULL)
345 fatal("packet_set_encryption_key: unknown cipher number %d", number);
346 if (keylen < 20)
347 fatal("packet_set_encryption_key: keylen too small: %d", keylen);
348 cipher_init(&receive_context, cipher, key, keylen, NULL, 0);
349 cipher_init(&send_context, cipher, key, keylen, NULL, 0);
350}
351
352/* Starts constructing a packet to send. */
353
354void
355packet_start1(int type)
356{
357 char buf[9];
358
359 buffer_clear(&outgoing_packet);
360 memset(buf, 0, 8);
361 buf[8] = type;
362 buffer_append(&outgoing_packet, buf, 9);
363}
364
365void
366packet_start2(int type)
367{
368 char buf[4+1+1];
369
370 buffer_clear(&outgoing_packet);
371 memset(buf, 0, sizeof buf);
372 /* buf[0..3] = payload_len; */
373 /* buf[4] = pad_len; */
374 buf[5] = type & 0xff;
375 buffer_append(&outgoing_packet, buf, sizeof buf);
376}
377
378void
379packet_start(int type)
380{
381 DBG(debug("packet_start[%d]", type));
382 if (use_ssh2_packet_format)
383 packet_start2(type);
384 else
385 packet_start1(type);
386}
387
388/* Appends a character to the packet data. */
389
390void
391packet_put_char(int value)
392{
393 char ch = value;
394 buffer_append(&outgoing_packet, &ch, 1);
395}
396
397/* Appends an integer to the packet data. */
398
399void
400packet_put_int(u_int value)
401{
402 buffer_put_int(&outgoing_packet, value);
403}
404
405/* Appends a string to packet data. */
406
407void
408packet_put_string(const char *buf, u_int len)
409{
410 buffer_put_string(&outgoing_packet, buf, len);
411}
412void
413packet_put_cstring(const char *str)
414{
415 buffer_put_string(&outgoing_packet, str, strlen(str));
416}
417
418void
419packet_put_raw(const char *buf, u_int len)
420{
421 buffer_append(&outgoing_packet, buf, len);
422}
423
424
425/* Appends an arbitrary precision integer to packet data. */
426
427void
428packet_put_bignum(BIGNUM * value)
429{
430 buffer_put_bignum(&outgoing_packet, value);
431}
432void
433packet_put_bignum2(BIGNUM * value)
434{
435 buffer_put_bignum2(&outgoing_packet, value);
436}
437
438/*
439 * Finalizes and sends the packet. If the encryption key has been set,
440 * encrypts the packet before sending.
441 */
442
443void
444packet_send1(void)
445{
446 char buf[8], *cp;
447 int i, padding, len;
448 u_int checksum;
449 u_int32_t rand = 0;
450
451 /*
452 * If using packet compression, compress the payload of the outgoing
453 * packet.
454 */
455 if (packet_compression) {
456 buffer_clear(&compression_buffer);
457 /* Skip padding. */
458 buffer_consume(&outgoing_packet, 8);
459 /* padding */
460 buffer_append(&compression_buffer, "\0\0\0\0\0\0\0\0", 8);
461 buffer_compress(&outgoing_packet, &compression_buffer);
462 buffer_clear(&outgoing_packet);
463 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
464 buffer_len(&compression_buffer));
465 }
466 /* Compute packet length without padding (add checksum, remove padding). */
467 len = buffer_len(&outgoing_packet) + 4 - 8;
468
469 /* Insert padding. Initialized to zero in packet_start1() */
470 padding = 8 - len % 8;
471 if (cipher_type != SSH_CIPHER_NONE) {
472 cp = buffer_ptr(&outgoing_packet);
473 for (i = 0; i < padding; i++) {
474 if (i % 4 == 0)
475 rand = arc4random();
476 cp[7 - i] = rand & 0xff;
477 rand >>= 8;
478 }
479 }
480 buffer_consume(&outgoing_packet, 8 - padding);
481
482 /* Add check bytes. */
483 checksum = ssh_crc32((u_char *) buffer_ptr(&outgoing_packet),
484 buffer_len(&outgoing_packet));
485 PUT_32BIT(buf, checksum);
486 buffer_append(&outgoing_packet, buf, 4);
487
488#ifdef PACKET_DEBUG
489 fprintf(stderr, "packet_send plain: ");
490 buffer_dump(&outgoing_packet);
491#endif
492
493 /* Append to output. */
494 PUT_32BIT(buf, len);
495 buffer_append(&output, buf, 4);
496 buffer_append_space(&output, &cp, buffer_len(&outgoing_packet));
497 packet_encrypt(&send_context, cp, buffer_ptr(&outgoing_packet),
498 buffer_len(&outgoing_packet));
499
500#ifdef PACKET_DEBUG
501 fprintf(stderr, "encrypted: ");
502 buffer_dump(&output);
503#endif
504
505 buffer_clear(&outgoing_packet);
506
507 /*
508 * Note that the packet is now only buffered in output. It won\'t be
509 * actually sent until packet_write_wait or packet_write_poll is
510 * called.
511 */
512}
513
514void
515set_newkeys(int mode)
516{
517 Enc *enc;
518 Mac *mac;
519 Comp *comp;
520 CipherContext *cc;
521
522 debug("newkeys: mode %d", mode);
523
524 cc = (mode == MODE_OUT) ? &send_context : &receive_context;
525 if (newkeys[mode] != NULL) {
526 debug("newkeys: rekeying");
527 /* todo: free old keys, reset compression/cipher-ctxt; */
528 memset(cc, 0, sizeof(*cc));
529 enc = &newkeys[mode]->enc;
530 mac = &newkeys[mode]->mac;
531 comp = &newkeys[mode]->comp;
532 memset(mac->key, 0, mac->key_len);
533 xfree(enc->name);
534 xfree(enc->iv);
535 xfree(enc->key);
536 xfree(mac->name);
537 xfree(mac->key);
538 xfree(comp->name);
539 xfree(newkeys[mode]);
540 }
541 newkeys[mode] = kex_get_newkeys(mode);
542 if (newkeys[mode] == NULL)
543 fatal("newkeys: no keys for mode %d", mode);
544 enc = &newkeys[mode]->enc;
545 mac = &newkeys[mode]->mac;
546 comp = &newkeys[mode]->comp;
547 if (mac->md != NULL)
548 mac->enabled = 1;
549 DBG(debug("cipher_init_context: %d", mode));
550 cipher_init(cc, enc->cipher, enc->key, enc->cipher->key_len,
551 enc->iv, enc->cipher->block_size);
552 memset(enc->iv, 0, enc->cipher->block_size);
553 memset(enc->key, 0, enc->cipher->key_len);
554 if (comp->type != 0 && comp->enabled == 0) {
555 packet_init_compression();
556 if (mode == MODE_OUT)
557 buffer_compress_init_send(6);
558 else
559 buffer_compress_init_recv();
560 comp->enabled = 1;
561 }
562}
563
564/*
565 * Finalize packet in SSH2 format (compress, mac, encrypt, enqueue)
566 */
567void
568packet_send2(void)
569{
570 static u_int32_t seqnr = 0;
571 u_char *macbuf = NULL;
572 char *cp;
573 u_int packet_length = 0;
574 u_int i, padlen, len;
575 u_int32_t rand = 0;
576 int type;
577 Enc *enc = NULL;
578 Mac *mac = NULL;
579 Comp *comp = NULL;
580 int block_size;
581
582 if (newkeys[MODE_OUT] != NULL) {
583 enc = &newkeys[MODE_OUT]->enc;
584 mac = &newkeys[MODE_OUT]->mac;
585 comp = &newkeys[MODE_OUT]->comp;
586 }
587 block_size = enc ? enc->cipher->block_size : 8;
588
589 cp = buffer_ptr(&outgoing_packet);
590 type = cp[5] & 0xff;
591
592#ifdef PACKET_DEBUG
593 fprintf(stderr, "plain: ");
594 buffer_dump(&outgoing_packet);
595#endif
596
597 if (comp && comp->enabled) {
598 len = buffer_len(&outgoing_packet);
599 /* skip header, compress only payload */
600 buffer_consume(&outgoing_packet, 5);
601 buffer_clear(&compression_buffer);
602 buffer_compress(&outgoing_packet, &compression_buffer);
603 buffer_clear(&outgoing_packet);
604 buffer_append(&outgoing_packet, "\0\0\0\0\0", 5);
605 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
606 buffer_len(&compression_buffer));
607 DBG(debug("compression: raw %d compressed %d", len,
608 buffer_len(&outgoing_packet)));
609 }
610
611 /* sizeof (packet_len + pad_len + payload) */
612 len = buffer_len(&outgoing_packet);
613
614 /*
615 * calc size of padding, alloc space, get random data,
616 * minimum padding is 4 bytes
617 */
618 padlen = block_size - (len % block_size);
619 if (padlen < 4)
620 padlen += block_size;
621 buffer_append_space(&outgoing_packet, &cp, padlen);
622 if (enc && enc->cipher->number != SSH_CIPHER_NONE) {
623 /* random padding */
624 for (i = 0; i < padlen; i++) {
625 if (i % 4 == 0)
626 rand = arc4random();
627 cp[i] = rand & 0xff;
628 rand >>= 8;
629 }
630 } else {
631 /* clear padding */
632 memset(cp, 0, padlen);
633 }
634 /* packet_length includes payload, padding and padding length field */
635 packet_length = buffer_len(&outgoing_packet) - 4;
636 cp = buffer_ptr(&outgoing_packet);
637 PUT_32BIT(cp, packet_length);
638 cp[4] = padlen & 0xff;
639 DBG(debug("send: len %d (includes padlen %d)", packet_length+4, padlen));
640
641 /* compute MAC over seqnr and packet(length fields, payload, padding) */
642 if (mac && mac->enabled) {
643 macbuf = mac_compute(mac, seqnr,
644 (u_char *) buffer_ptr(&outgoing_packet),
645 buffer_len(&outgoing_packet));
646 DBG(debug("done calc MAC out #%d", seqnr));
647 }
648 /* encrypt packet and append to output buffer. */
649 buffer_append_space(&output, &cp, buffer_len(&outgoing_packet));
650 packet_encrypt(&send_context, cp, buffer_ptr(&outgoing_packet),
651 buffer_len(&outgoing_packet));
652 /* append unencrypted MAC */
653 if (mac && mac->enabled)
654 buffer_append(&output, (char *)macbuf, mac->mac_len);
655#ifdef PACKET_DEBUG
656 fprintf(stderr, "encrypted: ");
657 buffer_dump(&output);
658#endif
659 /* increment sequence number for outgoing packets */
660 if (++seqnr == 0)
661 log("outgoing seqnr wraps around");
662 buffer_clear(&outgoing_packet);
663
664 if (type == SSH2_MSG_NEWKEYS)
665 set_newkeys(MODE_OUT);
666}
667
668void
669packet_send()
670{
671 if (use_ssh2_packet_format)
672 packet_send2();
673 else
674 packet_send1();
675 DBG(debug("packet_send done"));
676}
677
678/*
679 * Waits until a packet has been received, and returns its type. Note that
680 * no other data is processed until this returns, so this function should not
681 * be used during the interactive session.
682 */
683
684int
685packet_read(int *payload_len_ptr)
686{
687 int type, len;
688 fd_set *setp;
689 char buf[8192];
690 DBG(debug("packet_read()"));
691
692 setp = (fd_set *)xmalloc(howmany(connection_in+1, NFDBITS) *
693 sizeof(fd_mask));
694
695 /* Since we are blocking, ensure that all written packets have been sent. */
696 packet_write_wait();
697
698 /* Stay in the loop until we have received a complete packet. */
699 for (;;) {
700 /* Try to read a packet from the buffer. */
701 type = packet_read_poll(payload_len_ptr);
702 if (!use_ssh2_packet_format && (
703 type == SSH_SMSG_SUCCESS
704 || type == SSH_SMSG_FAILURE
705 || type == SSH_CMSG_EOF
706 || type == SSH_CMSG_EXIT_CONFIRMATION))
707 packet_integrity_check(*payload_len_ptr, 0, type);
708 /* If we got a packet, return it. */
709 if (type != SSH_MSG_NONE) {
710 xfree(setp);
711 return type;
712 }
713 /*
714 * Otherwise, wait for some data to arrive, add it to the
715 * buffer, and try again.
716 */
717 memset(setp, 0, howmany(connection_in + 1, NFDBITS) *
718 sizeof(fd_mask));
719 FD_SET(connection_in, setp);
720
721 /* Wait for some data to arrive. */
722 while (select(connection_in + 1, setp, NULL, NULL, NULL) == -1 &&
723 (errno == EAGAIN || errno == EINTR))
724 ;
725
726 /* Read data from the socket. */
727 len = read(connection_in, buf, sizeof(buf));
728 if (len == 0) {
729 log("Connection closed by %.200s", get_remote_ipaddr());
730 fatal_cleanup();
731 }
732 if (len < 0)
733 fatal("Read from socket failed: %.100s", strerror(errno));
734 /* Append it to the buffer. */
735 packet_process_incoming(buf, len);
736 }
737 /* NOTREACHED */
738}
739
740/*
741 * Waits until a packet has been received, verifies that its type matches
742 * that given, and gives a fatal error and exits if there is a mismatch.
743 */
744
745void
746packet_read_expect(int *payload_len_ptr, int expected_type)
747{
748 int type;
749
750 type = packet_read(payload_len_ptr);
751 if (type != expected_type)
752 packet_disconnect("Protocol error: expected packet type %d, got %d",
753 expected_type, type);
754}
755
756/* Checks if a full packet is available in the data received so far via
757 * packet_process_incoming. If so, reads the packet; otherwise returns
758 * SSH_MSG_NONE. This does not wait for data from the connection.
759 *
760 * SSH_MSG_DISCONNECT is handled specially here. Also,
761 * SSH_MSG_IGNORE messages are skipped by this function and are never returned
762 * to higher levels.
763 *
764 * The returned payload_len does include space consumed by:
765 * Packet length
766 * Padding
767 * Packet type
768 * Check bytes
769 */
770
771int
772packet_read_poll1(int *payload_len_ptr)
773{
774 u_int len, padded_len;
775 u_char *ucp;
776 char buf[8], *cp;
777 u_int checksum, stored_checksum;
778
779 /* Check if input size is less than minimum packet size. */
780 if (buffer_len(&input) < 4 + 8)
781 return SSH_MSG_NONE;
782 /* Get length of incoming packet. */
783 ucp = (u_char *) buffer_ptr(&input);
784 len = GET_32BIT(ucp);
785 if (len < 1 + 2 + 2 || len > 256 * 1024)
786 packet_disconnect("Bad packet length %d.", len);
787 padded_len = (len + 8) & ~7;
788
789 /* Check if the packet has been entirely received. */
790 if (buffer_len(&input) < 4 + padded_len)
791 return SSH_MSG_NONE;
792
793 /* The entire packet is in buffer. */
794
795 /* Consume packet length. */
796 buffer_consume(&input, 4);
797
798 /* Copy data to incoming_packet. */
799 buffer_clear(&incoming_packet);
800 buffer_append_space(&incoming_packet, &cp, padded_len);
801 packet_decrypt(&receive_context, cp, buffer_ptr(&input), padded_len);
802 buffer_consume(&input, padded_len);
803
804#ifdef PACKET_DEBUG
805 fprintf(stderr, "read_poll plain: ");
806 buffer_dump(&incoming_packet);
807#endif
808
809 /* Compute packet checksum. */
810 checksum = ssh_crc32((u_char *) buffer_ptr(&incoming_packet),
811 buffer_len(&incoming_packet) - 4);
812
813 /* Skip padding. */
814 buffer_consume(&incoming_packet, 8 - len % 8);
815
816 /* Test check bytes. */
817
818 if (len != buffer_len(&incoming_packet))
819 packet_disconnect("packet_read_poll: len %d != buffer_len %d.",
820 len, buffer_len(&incoming_packet));
821
822 ucp = (u_char *) buffer_ptr(&incoming_packet) + len - 4;
823 stored_checksum = GET_32BIT(ucp);
824 if (checksum != stored_checksum)
825 packet_disconnect("Corrupted check bytes on input.");
826 buffer_consume_end(&incoming_packet, 4);
827
828 /* If using packet compression, decompress the packet. */
829 if (packet_compression) {
830 buffer_clear(&compression_buffer);
831 buffer_uncompress(&incoming_packet, &compression_buffer);
832 buffer_clear(&incoming_packet);
833 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
834 buffer_len(&compression_buffer));
835 }
836 /* Get packet type. */
837 buffer_get(&incoming_packet, &buf[0], 1);
838
839 /* Return length of payload (without type field). */
840 *payload_len_ptr = buffer_len(&incoming_packet);
841
842 /* Return type. */
843 return (u_char) buf[0];
844}
845
846int
847packet_read_poll2(int *payload_len_ptr)
848{
849 static u_int32_t seqnr = 0;
850 static u_int packet_length = 0;
851 u_int padlen, need;
852 u_char buf[8], *macbuf;
853 u_char *ucp;
854 char *cp;
855 int type;
856 int maclen, block_size;
857 Enc *enc = NULL;
858 Mac *mac = NULL;
859 Comp *comp = NULL;
860
861 if (newkeys[MODE_IN] != NULL) {
862 enc = &newkeys[MODE_IN]->enc;
863 mac = &newkeys[MODE_IN]->mac;
864 comp = &newkeys[MODE_IN]->comp;
865 }
866 maclen = mac && mac->enabled ? mac->mac_len : 0;
867 block_size = enc ? enc->cipher->block_size : 8;
868
869 if (packet_length == 0) {
870 /*
871 * check if input size is less than the cipher block size,
872 * decrypt first block and extract length of incoming packet
873 */
874 if (buffer_len(&input) < block_size)
875 return SSH_MSG_NONE;
876 buffer_clear(&incoming_packet);
877 buffer_append_space(&incoming_packet, &cp, block_size);
878 packet_decrypt(&receive_context, cp, buffer_ptr(&input),
879 block_size);
880 ucp = (u_char *) buffer_ptr(&incoming_packet);
881 packet_length = GET_32BIT(ucp);
882 if (packet_length < 1 + 4 || packet_length > 256 * 1024) {
883 buffer_dump(&incoming_packet);
884 packet_disconnect("Bad packet length %d.", packet_length);
885 }
886 DBG(debug("input: packet len %d", packet_length+4));
887 buffer_consume(&input, block_size);
888 }
889 /* we have a partial packet of block_size bytes */
890 need = 4 + packet_length - block_size;
891 DBG(debug("partial packet %d, need %d, maclen %d", block_size,
892 need, maclen));
893 if (need % block_size != 0)
894 fatal("padding error: need %d block %d mod %d",
895 need, block_size, need % block_size);
896 /*
897 * check if the entire packet has been received and
898 * decrypt into incoming_packet
899 */
900 if (buffer_len(&input) < need + maclen)
901 return SSH_MSG_NONE;
902#ifdef PACKET_DEBUG
903 fprintf(stderr, "read_poll enc/full: ");
904 buffer_dump(&input);
905#endif
906 buffer_append_space(&incoming_packet, &cp, need);
907 packet_decrypt(&receive_context, cp, buffer_ptr(&input), need);
908 buffer_consume(&input, need);
909 /*
910 * compute MAC over seqnr and packet,
911 * increment sequence number for incoming packet
912 */
913 if (mac && mac->enabled) {
914 macbuf = mac_compute(mac, seqnr,
915 (u_char *) buffer_ptr(&incoming_packet),
916 buffer_len(&incoming_packet));
917 if (memcmp(macbuf, buffer_ptr(&input), mac->mac_len) != 0)
918 packet_disconnect("Corrupted MAC on input.");
919 DBG(debug("MAC #%d ok", seqnr));
920 buffer_consume(&input, mac->mac_len);
921 }
922 if (++seqnr == 0)
923 log("incoming seqnr wraps around");
924
925 /* get padlen */
926 cp = buffer_ptr(&incoming_packet) + 4;
927 padlen = *cp & 0xff;
928 DBG(debug("input: padlen %d", padlen));
929 if (padlen < 4)
930 packet_disconnect("Corrupted padlen %d on input.", padlen);
931
932 /* skip packet size + padlen, discard padding */
933 buffer_consume(&incoming_packet, 4 + 1);
934 buffer_consume_end(&incoming_packet, padlen);
935
936 DBG(debug("input: len before de-compress %d", buffer_len(&incoming_packet)));
937 if (comp && comp->enabled) {
938 buffer_clear(&compression_buffer);
939 buffer_uncompress(&incoming_packet, &compression_buffer);
940 buffer_clear(&incoming_packet);
941 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
942 buffer_len(&compression_buffer));
943 DBG(debug("input: len after de-compress %d", buffer_len(&incoming_packet)));
944 }
945 /*
946 * get packet type, implies consume.
947 * return length of payload (without type field)
948 */
949 buffer_get(&incoming_packet, (char *)&buf[0], 1);
950 *payload_len_ptr = buffer_len(&incoming_packet);
951
952 /* reset for next packet */
953 packet_length = 0;
954
955 /* extract packet type */
956 type = (u_char)buf[0];
957
958 if (type == SSH2_MSG_NEWKEYS)
959 set_newkeys(MODE_IN);
960
961#ifdef PACKET_DEBUG
962 fprintf(stderr, "read/plain[%d]:\r\n", type);
963 buffer_dump(&incoming_packet);
964#endif
965 return (u_char)type;
966}
967
968int
969packet_read_poll(int *payload_len_ptr)
970{
971 char *msg;
972 for (;;) {
973 int type = use_ssh2_packet_format ?
974 packet_read_poll2(payload_len_ptr):
975 packet_read_poll1(payload_len_ptr);
976
977 if(compat20) {
978 int reason;
979 if (type != 0)
980 DBG(debug("received packet type %d", type));
981 switch(type) {
982 case SSH2_MSG_IGNORE:
983 break;
984 case SSH2_MSG_DEBUG:
985 packet_get_char();
986 msg = packet_get_string(NULL);
987 debug("Remote: %.900s", msg);
988 xfree(msg);
989 msg = packet_get_string(NULL);
990 xfree(msg);
991 break;
992 case SSH2_MSG_DISCONNECT:
993 reason = packet_get_int();
994 msg = packet_get_string(NULL);
995 log("Received disconnect from %s: %d: %.400s", get_remote_ipaddr(),
996 reason, msg);
997 xfree(msg);
998 fatal_cleanup();
999 break;
1000 default:
1001 return type;
1002 break;
1003 }
1004 } else {
1005 switch(type) {
1006 case SSH_MSG_IGNORE:
1007 break;
1008 case SSH_MSG_DEBUG:
1009 msg = packet_get_string(NULL);
1010 debug("Remote: %.900s", msg);
1011 xfree(msg);
1012 break;
1013 case SSH_MSG_DISCONNECT:
1014 msg = packet_get_string(NULL);
1015 log("Received disconnect from %s: %.400s", get_remote_ipaddr(),
1016 msg);
1017 fatal_cleanup();
1018 xfree(msg);
1019 break;
1020 default:
1021 if (type != 0)
1022 DBG(debug("received packet type %d", type));
1023 return type;
1024 break;
1025 }
1026 }
1027 }
1028}
1029
1030/*
1031 * Buffers the given amount of input characters. This is intended to be used
1032 * together with packet_read_poll.
1033 */
1034
1035void
1036packet_process_incoming(const char *buf, u_int len)
1037{
1038 buffer_append(&input, buf, len);
1039}
1040
1041/* Returns a character from the packet. */
1042
1043u_int
1044packet_get_char()
1045{
1046 char ch;
1047 buffer_get(&incoming_packet, &ch, 1);
1048 return (u_char) ch;
1049}
1050
1051/* Returns an integer from the packet data. */
1052
1053u_int
1054packet_get_int()
1055{
1056 return buffer_get_int(&incoming_packet);
1057}
1058
1059/*
1060 * Returns an arbitrary precision integer from the packet data. The integer
1061 * must have been initialized before this call.
1062 */
1063
1064void
1065packet_get_bignum(BIGNUM * value, int *length_ptr)
1066{
1067 *length_ptr = buffer_get_bignum(&incoming_packet, value);
1068}
1069
1070void
1071packet_get_bignum2(BIGNUM * value, int *length_ptr)
1072{
1073 *length_ptr = buffer_get_bignum2(&incoming_packet, value);
1074}
1075
1076char *
1077packet_get_raw(int *length_ptr)
1078{
1079 int bytes = buffer_len(&incoming_packet);
1080 if (length_ptr != NULL)
1081 *length_ptr = bytes;
1082 return buffer_ptr(&incoming_packet);
1083}
1084
1085int
1086packet_remaining(void)
1087{
1088 return buffer_len(&incoming_packet);
1089}
1090
1091/*
1092 * Returns a string from the packet data. The string is allocated using
1093 * xmalloc; it is the responsibility of the calling program to free it when
1094 * no longer needed. The length_ptr argument may be NULL, or point to an
1095 * integer into which the length of the string is stored.
1096 */
1097
1098char *
1099packet_get_string(u_int *length_ptr)
1100{
1101 return buffer_get_string(&incoming_packet, length_ptr);
1102}
1103
1104/*
1105 * Sends a diagnostic message from the server to the client. This message
1106 * can be sent at any time (but not while constructing another message). The
1107 * message is printed immediately, but only if the client is being executed
1108 * in verbose mode. These messages are primarily intended to ease debugging
1109 * authentication problems. The length of the formatted message must not
1110 * exceed 1024 bytes. This will automatically call packet_write_wait.
1111 */
1112
1113void
1114packet_send_debug(const char *fmt,...)
1115{
1116 char buf[1024];
1117 va_list args;
1118
1119 if (compat20 && (datafellows & SSH_BUG_DEBUG))
1120 return;
1121
1122 va_start(args, fmt);
1123 vsnprintf(buf, sizeof(buf), fmt, args);
1124 va_end(args);
1125
1126 if (compat20) {
1127 packet_start(SSH2_MSG_DEBUG);
1128 packet_put_char(0); /* bool: always display */
1129 packet_put_cstring(buf);
1130 packet_put_cstring("");
1131 } else {
1132 packet_start(SSH_MSG_DEBUG);
1133 packet_put_cstring(buf);
1134 }
1135 packet_send();
1136 packet_write_wait();
1137}
1138
1139/*
1140 * Logs the error plus constructs and sends a disconnect packet, closes the
1141 * connection, and exits. This function never returns. The error message
1142 * should not contain a newline. The length of the formatted message must
1143 * not exceed 1024 bytes.
1144 */
1145
1146void
1147packet_disconnect(const char *fmt,...)
1148{
1149 char buf[1024];
1150 va_list args;
1151 static int disconnecting = 0;
1152 if (disconnecting) /* Guard against recursive invocations. */
1153 fatal("packet_disconnect called recursively.");
1154 disconnecting = 1;
1155
1156 /*
1157 * Format the message. Note that the caller must make sure the
1158 * message is of limited size.
1159 */
1160 va_start(args, fmt);
1161 vsnprintf(buf, sizeof(buf), fmt, args);
1162 va_end(args);
1163
1164 /* Send the disconnect message to the other side, and wait for it to get sent. */
1165 if (compat20) {
1166 packet_start(SSH2_MSG_DISCONNECT);
1167 packet_put_int(SSH2_DISCONNECT_PROTOCOL_ERROR);
1168 packet_put_cstring(buf);
1169 packet_put_cstring("");
1170 } else {
1171 packet_start(SSH_MSG_DISCONNECT);
1172 packet_put_string(buf, strlen(buf));
1173 }
1174 packet_send();
1175 packet_write_wait();
1176
1177 /* Stop listening for connections. */
1178 channel_stop_listening();
1179
1180 /* Close the connection. */
1181 packet_close();
1182
1183 /* Display the error locally and exit. */
1184 log("Disconnecting: %.100s", buf);
1185 fatal_cleanup();
1186}
1187
1188/* Checks if there is any buffered output, and tries to write some of the output. */
1189
1190void
1191packet_write_poll()
1192{
1193 int len = buffer_len(&output);
1194 if (len > 0) {
1195 len = write(connection_out, buffer_ptr(&output), len);
1196 if (len <= 0) {
1197 if (errno == EAGAIN)
1198 return;
1199 else
1200 fatal("Write failed: %.100s", strerror(errno));
1201 }
1202 buffer_consume(&output, len);
1203 }
1204}
1205
1206/*
1207 * Calls packet_write_poll repeatedly until all pending output data has been
1208 * written.
1209 */
1210
1211void
1212packet_write_wait()
1213{
1214 fd_set *setp;
1215
1216 setp = (fd_set *)xmalloc(howmany(connection_out + 1, NFDBITS) *
1217 sizeof(fd_mask));
1218 packet_write_poll();
1219 while (packet_have_data_to_write()) {
1220 memset(setp, 0, howmany(connection_out + 1, NFDBITS) *
1221 sizeof(fd_mask));
1222 FD_SET(connection_out, setp);
1223 while (select(connection_out + 1, NULL, setp, NULL, NULL) == -1 &&
1224 (errno == EAGAIN || errno == EINTR))
1225 ;
1226 packet_write_poll();
1227 }
1228 xfree(setp);
1229}
1230
1231/* Returns true if there is buffered data to write to the connection. */
1232
1233int
1234packet_have_data_to_write()
1235{
1236 return buffer_len(&output) != 0;
1237}
1238
1239/* Returns true if there is not too much data to write to the connection. */
1240
1241int
1242packet_not_very_much_data_to_write()
1243{
1244 if (interactive_mode)
1245 return buffer_len(&output) < 16384;
1246 else
1247 return buffer_len(&output) < 128 * 1024;
1248}
1249
1250/* Informs that the current session is interactive. Sets IP flags for that. */
1251
1252void
1253packet_set_interactive(int interactive)
1254{
1255 static int called = 0;
1256#if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN)
1257 int lowdelay = IPTOS_LOWDELAY;
1258 int throughput = IPTOS_THROUGHPUT;
1259#endif
1260 int on = 1;
1261
1262 if (called)
1263 return;
1264 called = 1;
1265
1266 /* Record that we are in interactive mode. */
1267 interactive_mode = interactive;
1268
1269 /* Only set socket options if using a socket. */
1270 if (!packet_connection_is_on_socket())
1271 return;
1272 /*
1273 * IPTOS_LOWDELAY and IPTOS_THROUGHPUT are IPv4 only
1274 */
1275 if (interactive) {
1276 /*
1277 * Set IP options for an interactive connection. Use
1278 * IPTOS_LOWDELAY and TCP_NODELAY.
1279 */
1280#if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN)
1281 if (packet_connection_is_ipv4()) {
1282 if (setsockopt(connection_in, IPPROTO_IP, IP_TOS,
1283 (void *) &lowdelay, sizeof(lowdelay)) < 0)
1284 error("setsockopt IPTOS_LOWDELAY: %.100s",
1285 strerror(errno));
1286 }
1287#endif
1288 if (setsockopt(connection_in, IPPROTO_TCP, TCP_NODELAY, (void *) &on,
1289 sizeof(on)) < 0)
1290 error("setsockopt TCP_NODELAY: %.100s", strerror(errno));
1291 } else if (packet_connection_is_ipv4()) {
1292 /*
1293 * Set IP options for a non-interactive connection. Use
1294 * IPTOS_THROUGHPUT.
1295 */
1296#if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN)
1297 if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, (void *) &throughput,
1298 sizeof(throughput)) < 0)
1299 error("setsockopt IPTOS_THROUGHPUT: %.100s", strerror(errno));
1300#endif
1301 }
1302}
1303
1304/* Returns true if the current connection is interactive. */
1305
1306int
1307packet_is_interactive()
1308{
1309 return interactive_mode;
1310}
1311
1312int
1313packet_set_maxsize(int s)
1314{
1315 static int called = 0;
1316 if (called) {
1317 log("packet_set_maxsize: called twice: old %d new %d",
1318 max_packet_size, s);
1319 return -1;
1320 }
1321 if (s < 4 * 1024 || s > 1024 * 1024) {
1322 log("packet_set_maxsize: bad size %d", s);
1323 return -1;
1324 }
1325 log("packet_set_maxsize: setting to %d", s);
1326 max_packet_size = s;
1327 return s;
1328}
1329
1330/*
1331 * 9.2. Ignored Data Message
1332 *
1333 * byte SSH_MSG_IGNORE
1334 * string data
1335 *
1336 * All implementations MUST understand (and ignore) this message at any
1337 * time (after receiving the protocol version). No implementation is
1338 * required to send them. This message can be used as an additional
1339 * protection measure against advanced traffic analysis techniques.
1340 */
1341/* size of current + ignore message should be n*sumlen bytes (w/o mac) */
1342void
1343packet_inject_ignore(int sumlen)
1344{
1345 int blocksize, padlen, have, need, nb, mini, nbytes;
1346 Enc *enc = NULL;
1347
1348 if (use_ssh2_packet_format == 0)
1349 return;
1350
1351 have = buffer_len(&outgoing_packet);
1352 debug2("packet_inject_ignore: current %d", have);
1353 if (newkeys[MODE_OUT] != NULL)
1354 enc = &newkeys[MODE_OUT]->enc;
1355 blocksize = enc ? enc->cipher->block_size : 8;
1356 padlen = blocksize - (have % blocksize);
1357 if (padlen < 4)
1358 padlen += blocksize;
1359 have += padlen;
1360 have /= blocksize; /* # of blocks for current message */
1361
1362 nb = roundup(sumlen, blocksize) / blocksize; /* blocks for both */
1363 mini = roundup(5+1+4+4, blocksize) / blocksize; /* minsize ignore msg */
1364 need = nb - (have % nb); /* blocks for ignore */
1365 if (need <= mini)
1366 need += nb;
1367 nbytes = (need - mini) * blocksize; /* size of ignore payload */
1368 debug2("packet_inject_ignore: block %d have %d nb %d mini %d need %d",
1369 blocksize, have, nb, mini, need);
1370
1371 /* enqueue current message and append a ignore message */
1372 packet_send();
1373 packet_send_ignore(nbytes);
1374}
1375
1376void
1377packet_send_ignore(int nbytes)
1378{
1379 u_int32_t rand = 0;
1380 int i;
1381
1382 packet_start(compat20 ? SSH2_MSG_IGNORE : SSH_MSG_IGNORE);
1383 packet_put_int(nbytes);
1384 for(i = 0; i < nbytes; i++) {
1385 if (i % 4 == 0)
1386 rand = arc4random();
1387 packet_put_char(rand & 0xff);
1388 rand >>= 8;
1389 }
1390}