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, 2001 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" 40 RCSID("$OpenBSD: packet.c,v 1.88 2002/02/14 23:41:01 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 #include "misc.h" 63 64 #ifdef PACKET_DEBUG 65 #define DBG(x) x 66 #else 67 #define DBG(x) 68 #endif 69 70 /* 71 * This variable contains the file descriptors used for communicating with 72 * the other side. connection_in is used for reading; connection_out for 73 * writing. These can be the same descriptor, in which case it is assumed to 74 * be a socket. 75 */ 76 static int connection_in = -1; 77 static int connection_out = -1; 78 79 /* Protocol flags for the remote side. */ 80 static u_int remote_protocol_flags = 0; 81 82 /* Encryption context for receiving data. This is only used for decryption. */ 83 static CipherContext receive_context; 84 85 /* Encryption context for sending data. This is only used for encryption. */ 86 static CipherContext send_context; 87 88 /* Buffer for raw input data from the socket. */ 89 static Buffer input; 90 91 /* Buffer for raw output data going to the socket. */ 92 static Buffer output; 93 94 /* Buffer for the partial outgoing packet being constructed. */ 95 static Buffer outgoing_packet; 96 97 /* Buffer for the incoming packet currently being processed. */ 98 static Buffer incoming_packet; 99 100 /* Scratch buffer for packet compression/decompression. */ 101 static Buffer compression_buffer; 102 static int compression_buffer_ready = 0; 103 104 /* Flag indicating whether packet compression/decompression is enabled. */ 105 static int packet_compression = 0; 106 107 /* default maximum packet size */ 108 int max_packet_size = 32768; 109 110 /* Flag indicating whether this module has been initialized. */ 111 static int initialized = 0; 112 113 /* Set to true if the connection is interactive. */ 114 static int interactive_mode = 0; 115 116 /* Session key information for Encryption and MAC */ 117 Newkeys *newkeys[MODE_MAX]; 118 119 /* roundup current message to extra_pad bytes */ 120 static u_char extra_pad = 0; 121 122 /* 123 * Sets the descriptors used for communication. Disables encryption until 124 * packet_set_encryption_key is called. 125 */ 126 void 127 packet_set_connection(int fd_in, int fd_out) 128 { 129 Cipher *none = cipher_by_name("none"); 130 if (none == NULL) 131 fatal("packet_set_connection: cannot load cipher 'none'"); 132 connection_in = fd_in; 133 connection_out = fd_out; 134 cipher_init(&send_context, none, "", 0, NULL, 0, CIPHER_ENCRYPT); 135 cipher_init(&receive_context, none, "", 0, NULL, 0, CIPHER_DECRYPT); 136 newkeys[MODE_IN] = newkeys[MODE_OUT] = NULL; 137 if (!initialized) { 138 initialized = 1; 139 buffer_init(&input); 140 buffer_init(&output); 141 buffer_init(&outgoing_packet); 142 buffer_init(&incoming_packet); 143 } 144 /* Kludge: arrange the close function to be called from fatal(). */ 145 fatal_add_cleanup((void (*) (void *)) packet_close, NULL); 146 } 147 148 /* Returns 1 if remote host is connected via socket, 0 if not. */ 149 150 int 151 packet_connection_is_on_socket(void) 152 { 153 struct sockaddr_storage from, to; 154 socklen_t fromlen, tolen; 155 156 /* filedescriptors in and out are the same, so it's a socket */ 157 if (connection_in == connection_out) 158 return 1; 159 fromlen = sizeof(from); 160 memset(&from, 0, sizeof(from)); 161 if (getpeername(connection_in, (struct sockaddr *)&from, &fromlen) < 0) 162 return 0; 163 tolen = sizeof(to); 164 memset(&to, 0, sizeof(to)); 165 if (getpeername(connection_out, (struct sockaddr *)&to, &tolen) < 0) 166 return 0; 167 if (fromlen != tolen || memcmp(&from, &to, fromlen) != 0) 168 return 0; 169 if (from.ss_family != AF_INET && from.ss_family != AF_INET6) 170 return 0; 171 return 1; 172 } 173 174 /* returns 1 if connection is via ipv4 */ 175 176 int 177 packet_connection_is_ipv4(void) 178 { 179 struct sockaddr_storage to; 180 socklen_t tolen = sizeof(to); 181 182 memset(&to, 0, sizeof(to)); 183 if (getsockname(connection_out, (struct sockaddr *)&to, &tolen) < 0) 184 return 0; 185 if (to.ss_family != AF_INET) 186 return 0; 187 return 1; 188 } 189 190 /* Sets the connection into non-blocking mode. */ 191 192 void 193 packet_set_nonblocking(void) 194 { 195 /* Set the socket into non-blocking mode. */ 196 if (fcntl(connection_in, F_SETFL, O_NONBLOCK) < 0) 197 error("fcntl O_NONBLOCK: %.100s", strerror(errno)); 198 199 if (connection_out != connection_in) { 200 if (fcntl(connection_out, F_SETFL, O_NONBLOCK) < 0) 201 error("fcntl O_NONBLOCK: %.100s", strerror(errno)); 202 } 203 } 204 205 /* Returns the socket used for reading. */ 206 207 int 208 packet_get_connection_in(void) 209 { 210 return connection_in; 211 } 212 213 /* Returns the descriptor used for writing. */ 214 215 int 216 packet_get_connection_out(void) 217 { 218 return connection_out; 219 } 220 221 /* Closes the connection and clears and frees internal data structures. */ 222 223 void 224 packet_close(void) 225 { 226 if (!initialized) 227 return; 228 initialized = 0; 229 if (connection_in == connection_out) { 230 shutdown(connection_out, SHUT_RDWR); 231 close(connection_out); 232 } else { 233 close(connection_in); 234 close(connection_out); 235 } 236 buffer_free(&input); 237 buffer_free(&output); 238 buffer_free(&outgoing_packet); 239 buffer_free(&incoming_packet); 240 if (compression_buffer_ready) { 241 buffer_free(&compression_buffer); 242 buffer_compress_uninit(); 243 } 244 cipher_cleanup(&send_context); 245 cipher_cleanup(&receive_context); 246 } 247 248 /* Sets remote side protocol flags. */ 249 250 void 251 packet_set_protocol_flags(u_int protocol_flags) 252 { 253 remote_protocol_flags = protocol_flags; 254 } 255 256 /* Returns the remote protocol flags set earlier by the above function. */ 257 258 u_int 259 packet_get_protocol_flags(void) 260 { 261 return remote_protocol_flags; 262 } 263 264 /* 265 * Starts packet compression from the next packet on in both directions. 266 * Level is compression level 1 (fastest) - 9 (slow, best) as in gzip. 267 */ 268 269 static void 270 packet_init_compression(void) 271 { 272 if (compression_buffer_ready == 1) 273 return; 274 compression_buffer_ready = 1; 275 buffer_init(&compression_buffer); 276 } 277 278 void 279 packet_start_compression(int level) 280 { 281 if (packet_compression && !compat20) 282 fatal("Compression already enabled."); 283 packet_compression = 1; 284 packet_init_compression(); 285 buffer_compress_init_send(level); 286 buffer_compress_init_recv(); 287 } 288 289 /* 290 * Causes any further packets to be encrypted using the given key. The same 291 * key is used for both sending and reception. However, both directions are 292 * encrypted independently of each other. 293 */ 294 void 295 packet_set_encryption_key(const u_char *key, u_int keylen, 296 int number) 297 { 298 Cipher *cipher = cipher_by_number(number); 299 if (cipher == NULL) 300 fatal("packet_set_encryption_key: unknown cipher number %d", number); 301 if (keylen < 20) 302 fatal("packet_set_encryption_key: keylen too small: %d", keylen); 303 cipher_init(&send_context, cipher, key, keylen, NULL, 0, CIPHER_ENCRYPT); 304 cipher_init(&receive_context, cipher, key, keylen, NULL, 0, CIPHER_DECRYPT); 305 } 306 307 /* Start constructing a packet to send. */ 308 void 309 packet_start(u_char type) 310 { 311 u_char buf[9]; 312 int len; 313 314 DBG(debug("packet_start[%d]", type)); 315 len = compat20 ? 6 : 9; 316 memset(buf, 0, len - 1); 317 buf[len - 1] = type; 318 buffer_clear(&outgoing_packet); 319 buffer_append(&outgoing_packet, buf, len); 320 } 321 322 /* Append payload. */ 323 void 324 packet_put_char(int value) 325 { 326 char ch = value; 327 buffer_append(&outgoing_packet, &ch, 1); 328 } 329 void 330 packet_put_int(u_int value) 331 { 332 buffer_put_int(&outgoing_packet, value); 333 } 334 void 335 packet_put_string(const void *buf, u_int len) 336 { 337 buffer_put_string(&outgoing_packet, buf, len); 338 } 339 void 340 packet_put_cstring(const char *str) 341 { 342 buffer_put_cstring(&outgoing_packet, str); 343 } 344 void 345 packet_put_raw(const void *buf, u_int len) 346 { 347 buffer_append(&outgoing_packet, buf, len); 348 } 349 void 350 packet_put_bignum(BIGNUM * value) 351 { 352 buffer_put_bignum(&outgoing_packet, value); 353 } 354 void 355 packet_put_bignum2(BIGNUM * value) 356 { 357 buffer_put_bignum2(&outgoing_packet, value); 358 } 359 360 /* 361 * Finalizes and sends the packet. If the encryption key has been set, 362 * encrypts the packet before sending. 363 */ 364 365 static void 366 packet_send1(void) 367 { 368 char buf[8], *cp; 369 int i, padding, len; 370 u_int checksum; 371 u_int32_t rand = 0; 372 373 /* 374 * If using packet compression, compress the payload of the outgoing 375 * packet. 376 */ 377 if (packet_compression) { 378 buffer_clear(&compression_buffer); 379 /* Skip padding. */ 380 buffer_consume(&outgoing_packet, 8); 381 /* padding */ 382 buffer_append(&compression_buffer, "\0\0\0\0\0\0\0\0", 8); 383 buffer_compress(&outgoing_packet, &compression_buffer); 384 buffer_clear(&outgoing_packet); 385 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer), 386 buffer_len(&compression_buffer)); 387 } 388 /* Compute packet length without padding (add checksum, remove padding). */ 389 len = buffer_len(&outgoing_packet) + 4 - 8; 390 391 /* Insert padding. Initialized to zero in packet_start1() */ 392 padding = 8 - len % 8; 393 if (!send_context.plaintext) { 394 cp = buffer_ptr(&outgoing_packet); 395 for (i = 0; i < padding; i++) { 396 if (i % 4 == 0) 397 rand = arc4random(); 398 cp[7 - i] = rand & 0xff; 399 rand >>= 8; 400 } 401 } 402 buffer_consume(&outgoing_packet, 8 - padding); 403 404 /* Add check bytes. */ 405 checksum = ssh_crc32(buffer_ptr(&outgoing_packet), 406 buffer_len(&outgoing_packet)); 407 PUT_32BIT(buf, checksum); 408 buffer_append(&outgoing_packet, buf, 4); 409 410 #ifdef PACKET_DEBUG 411 fprintf(stderr, "packet_send plain: "); 412 buffer_dump(&outgoing_packet); 413 #endif 414 415 /* Append to output. */ 416 PUT_32BIT(buf, len); 417 buffer_append(&output, buf, 4); 418 cp = buffer_append_space(&output, buffer_len(&outgoing_packet)); 419 cipher_crypt(&send_context, cp, buffer_ptr(&outgoing_packet), 420 buffer_len(&outgoing_packet)); 421 422 #ifdef PACKET_DEBUG 423 fprintf(stderr, "encrypted: "); 424 buffer_dump(&output); 425 #endif 426 427 buffer_clear(&outgoing_packet); 428 429 /* 430 * Note that the packet is now only buffered in output. It won\'t be 431 * actually sent until packet_write_wait or packet_write_poll is 432 * called. 433 */ 434 } 435 436 static void 437 set_newkeys(int mode) 438 { 439 Enc *enc; 440 Mac *mac; 441 Comp *comp; 442 CipherContext *cc; 443 int encrypt; 444 445 debug("newkeys: mode %d", mode); 446 447 if (mode == MODE_OUT) { 448 cc = &send_context; 449 encrypt = CIPHER_ENCRYPT; 450 } else { 451 cc = &receive_context; 452 encrypt = CIPHER_DECRYPT; 453 } 454 if (newkeys[mode] != NULL) { 455 debug("newkeys: rekeying"); 456 cipher_cleanup(cc); 457 enc = &newkeys[mode]->enc; 458 mac = &newkeys[mode]->mac; 459 comp = &newkeys[mode]->comp; 460 memset(mac->key, 0, mac->key_len); 461 xfree(enc->name); 462 xfree(enc->iv); 463 xfree(enc->key); 464 xfree(mac->name); 465 xfree(mac->key); 466 xfree(comp->name); 467 xfree(newkeys[mode]); 468 } 469 newkeys[mode] = kex_get_newkeys(mode); 470 if (newkeys[mode] == NULL) 471 fatal("newkeys: no keys for mode %d", mode); 472 enc = &newkeys[mode]->enc; 473 mac = &newkeys[mode]->mac; 474 comp = &newkeys[mode]->comp; 475 if (mac->md != NULL) 476 mac->enabled = 1; 477 DBG(debug("cipher_init_context: %d", mode)); 478 cipher_init(cc, enc->cipher, enc->key, enc->key_len, 479 enc->iv, enc->block_size, encrypt); 480 memset(enc->iv, 0, enc->block_size); 481 memset(enc->key, 0, enc->key_len); 482 if (comp->type != 0 && comp->enabled == 0) { 483 packet_init_compression(); 484 if (mode == MODE_OUT) 485 buffer_compress_init_send(6); 486 else 487 buffer_compress_init_recv(); 488 comp->enabled = 1; 489 } 490 } 491 492 /* 493 * Finalize packet in SSH2 format (compress, mac, encrypt, enqueue) 494 */ 495 static void 496 packet_send2(void) 497 { 498 static u_int32_t seqnr = 0; 499 u_char type, *ucp, *macbuf = NULL; 500 u_char padlen, pad; 501 char *cp; 502 u_int packet_length = 0; 503 u_int i, len; 504 u_int32_t rand = 0; 505 Enc *enc = NULL; 506 Mac *mac = NULL; 507 Comp *comp = NULL; 508 int block_size; 509 510 if (newkeys[MODE_OUT] != NULL) { 511 enc = &newkeys[MODE_OUT]->enc; 512 mac = &newkeys[MODE_OUT]->mac; 513 comp = &newkeys[MODE_OUT]->comp; 514 } 515 block_size = enc ? enc->block_size : 8; 516 517 ucp = buffer_ptr(&outgoing_packet); 518 type = ucp[5]; 519 520 #ifdef PACKET_DEBUG 521 fprintf(stderr, "plain: "); 522 buffer_dump(&outgoing_packet); 523 #endif 524 525 if (comp && comp->enabled) { 526 len = buffer_len(&outgoing_packet); 527 /* skip header, compress only payload */ 528 buffer_consume(&outgoing_packet, 5); 529 buffer_clear(&compression_buffer); 530 buffer_compress(&outgoing_packet, &compression_buffer); 531 buffer_clear(&outgoing_packet); 532 buffer_append(&outgoing_packet, "\0\0\0\0\0", 5); 533 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer), 534 buffer_len(&compression_buffer)); 535 DBG(debug("compression: raw %d compressed %d", len, 536 buffer_len(&outgoing_packet))); 537 } 538 539 /* sizeof (packet_len + pad_len + payload) */ 540 len = buffer_len(&outgoing_packet); 541 542 /* 543 * calc size of padding, alloc space, get random data, 544 * minimum padding is 4 bytes 545 */ 546 padlen = block_size - (len % block_size); 547 if (padlen < 4) 548 padlen += block_size; 549 if (extra_pad) { 550 /* will wrap if extra_pad+padlen > 255 */ 551 extra_pad = roundup(extra_pad, block_size); 552 pad = extra_pad - ((len + padlen) % extra_pad); 553 debug("packet_send2: adding %d (len %d padlen %d extra_pad %d)", 554 pad, len, padlen, extra_pad); 555 padlen += pad; 556 extra_pad = 0; 557 } 558 cp = buffer_append_space(&outgoing_packet, padlen); 559 if (enc && !send_context.plaintext) { 560 /* random padding */ 561 for (i = 0; i < padlen; i++) { 562 if (i % 4 == 0) 563 rand = arc4random(); 564 cp[i] = rand & 0xff; 565 rand >>= 8; 566 } 567 } else { 568 /* clear padding */ 569 memset(cp, 0, padlen); 570 } 571 /* packet_length includes payload, padding and padding length field */ 572 packet_length = buffer_len(&outgoing_packet) - 4; 573 ucp = buffer_ptr(&outgoing_packet); 574 PUT_32BIT(ucp, packet_length); 575 ucp[4] = padlen; 576 DBG(debug("send: len %d (includes padlen %d)", packet_length+4, padlen)); 577 578 /* compute MAC over seqnr and packet(length fields, payload, padding) */ 579 if (mac && mac->enabled) { 580 macbuf = mac_compute(mac, seqnr, 581 buffer_ptr(&outgoing_packet), 582 buffer_len(&outgoing_packet)); 583 DBG(debug("done calc MAC out #%d", seqnr)); 584 } 585 /* encrypt packet and append to output buffer. */ 586 cp = buffer_append_space(&output, buffer_len(&outgoing_packet)); 587 cipher_crypt(&send_context, cp, buffer_ptr(&outgoing_packet), 588 buffer_len(&outgoing_packet)); 589 /* append unencrypted MAC */ 590 if (mac && mac->enabled) 591 buffer_append(&output, (char *)macbuf, mac->mac_len); 592 #ifdef PACKET_DEBUG 593 fprintf(stderr, "encrypted: "); 594 buffer_dump(&output); 595 #endif 596 /* increment sequence number for outgoing packets */ 597 if (++seqnr == 0) 598 log("outgoing seqnr wraps around"); 599 buffer_clear(&outgoing_packet); 600 601 if (type == SSH2_MSG_NEWKEYS) 602 set_newkeys(MODE_OUT); 603 } 604 605 void 606 packet_send(void) 607 { 608 if (compat20) 609 packet_send2(); 610 else 611 packet_send1(); 612 DBG(debug("packet_send done")); 613 } 614 615 /* 616 * Waits until a packet has been received, and returns its type. Note that 617 * no other data is processed until this returns, so this function should not 618 * be used during the interactive session. 619 */ 620 621 int 622 packet_read_seqnr(u_int32_t *seqnr_p) 623 { 624 int type, len; 625 fd_set *setp; 626 char buf[8192]; 627 DBG(debug("packet_read()")); 628 629 setp = (fd_set *)xmalloc(howmany(connection_in+1, NFDBITS) * 630 sizeof(fd_mask)); 631 632 /* Since we are blocking, ensure that all written packets have been sent. */ 633 packet_write_wait(); 634 635 /* Stay in the loop until we have received a complete packet. */ 636 for (;;) { 637 /* Try to read a packet from the buffer. */ 638 type = packet_read_poll_seqnr(seqnr_p); 639 if (!compat20 && ( 640 type == SSH_SMSG_SUCCESS 641 || type == SSH_SMSG_FAILURE 642 || type == SSH_CMSG_EOF 643 || type == SSH_CMSG_EXIT_CONFIRMATION)) 644 packet_check_eom(); 645 /* If we got a packet, return it. */ 646 if (type != SSH_MSG_NONE) { 647 xfree(setp); 648 return type; 649 } 650 /* 651 * Otherwise, wait for some data to arrive, add it to the 652 * buffer, and try again. 653 */ 654 memset(setp, 0, howmany(connection_in + 1, NFDBITS) * 655 sizeof(fd_mask)); 656 FD_SET(connection_in, setp); 657 658 /* Wait for some data to arrive. */ 659 while (select(connection_in + 1, setp, NULL, NULL, NULL) == -1 && 660 (errno == EAGAIN || errno == EINTR)) 661 ; 662 663 /* Read data from the socket. */ 664 len = read(connection_in, buf, sizeof(buf)); 665 if (len == 0) { 666 log("Connection closed by %.200s", get_remote_ipaddr()); 667 fatal_cleanup(); 668 } 669 if (len < 0) 670 fatal("Read from socket failed: %.100s", strerror(errno)); 671 /* Append it to the buffer. */ 672 packet_process_incoming(buf, len); 673 } 674 /* NOTREACHED */ 675 } 676 677 int 678 packet_read(void) 679 { 680 return packet_read_seqnr(NULL); 681 } 682 683 /* 684 * Waits until a packet has been received, verifies that its type matches 685 * that given, and gives a fatal error and exits if there is a mismatch. 686 */ 687 688 void 689 packet_read_expect(int expected_type) 690 { 691 int type; 692 693 type = packet_read(); 694 if (type != expected_type) 695 packet_disconnect("Protocol error: expected packet type %d, got %d", 696 expected_type, type); 697 } 698 699 /* Checks if a full packet is available in the data received so far via 700 * packet_process_incoming. If so, reads the packet; otherwise returns 701 * SSH_MSG_NONE. This does not wait for data from the connection. 702 * 703 * SSH_MSG_DISCONNECT is handled specially here. Also, 704 * SSH_MSG_IGNORE messages are skipped by this function and are never returned 705 * to higher levels. 706 */ 707 708 static int 709 packet_read_poll1(void) 710 { 711 u_int len, padded_len; 712 u_char *ucp, type; 713 char *cp; 714 u_int checksum, stored_checksum; 715 716 /* Check if input size is less than minimum packet size. */ 717 if (buffer_len(&input) < 4 + 8) 718 return SSH_MSG_NONE; 719 /* Get length of incoming packet. */ 720 ucp = buffer_ptr(&input); 721 len = GET_32BIT(ucp); 722 if (len < 1 + 2 + 2 || len > 256 * 1024) 723 packet_disconnect("Bad packet length %d.", len); 724 padded_len = (len + 8) & ~7; 725 726 /* Check if the packet has been entirely received. */ 727 if (buffer_len(&input) < 4 + padded_len) 728 return SSH_MSG_NONE; 729 730 /* The entire packet is in buffer. */ 731 732 /* Consume packet length. */ 733 buffer_consume(&input, 4); 734 735 /* 736 * Cryptographic attack detector for ssh 737 * (C)1998 CORE-SDI, Buenos Aires Argentina 738 * Ariel Futoransky(futo@core-sdi.com) 739 */ 740 if (!receive_context.plaintext && 741 detect_attack(buffer_ptr(&input), padded_len, NULL) == DEATTACK_DETECTED) 742 packet_disconnect("crc32 compensation attack: network attack detected"); 743 744 /* Decrypt data to incoming_packet. */ 745 buffer_clear(&incoming_packet); 746 cp = buffer_append_space(&incoming_packet, padded_len); 747 cipher_crypt(&receive_context, cp, buffer_ptr(&input), padded_len); 748 749 buffer_consume(&input, padded_len); 750 751 #ifdef PACKET_DEBUG 752 fprintf(stderr, "read_poll plain: "); 753 buffer_dump(&incoming_packet); 754 #endif 755 756 /* Compute packet checksum. */ 757 checksum = ssh_crc32(buffer_ptr(&incoming_packet), 758 buffer_len(&incoming_packet) - 4); 759 760 /* Skip padding. */ 761 buffer_consume(&incoming_packet, 8 - len % 8); 762 763 /* Test check bytes. */ 764 if (len != buffer_len(&incoming_packet)) 765 packet_disconnect("packet_read_poll1: len %d != buffer_len %d.", 766 len, buffer_len(&incoming_packet)); 767 768 ucp = (u_char *)buffer_ptr(&incoming_packet) + len - 4; 769 stored_checksum = GET_32BIT(ucp); 770 if (checksum != stored_checksum) 771 packet_disconnect("Corrupted check bytes on input."); 772 buffer_consume_end(&incoming_packet, 4); 773 774 if (packet_compression) { 775 buffer_clear(&compression_buffer); 776 buffer_uncompress(&incoming_packet, &compression_buffer); 777 buffer_clear(&incoming_packet); 778 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer), 779 buffer_len(&compression_buffer)); 780 } 781 type = buffer_get_char(&incoming_packet); 782 return type; 783 } 784 785 static int 786 packet_read_poll2(u_int32_t *seqnr_p) 787 { 788 static u_int32_t seqnr = 0; 789 static u_int packet_length = 0; 790 u_int padlen, need; 791 u_char *macbuf, *ucp, type; 792 char *cp; 793 int maclen, block_size; 794 Enc *enc = NULL; 795 Mac *mac = NULL; 796 Comp *comp = NULL; 797 798 if (newkeys[MODE_IN] != NULL) { 799 enc = &newkeys[MODE_IN]->enc; 800 mac = &newkeys[MODE_IN]->mac; 801 comp = &newkeys[MODE_IN]->comp; 802 } 803 maclen = mac && mac->enabled ? mac->mac_len : 0; 804 block_size = enc ? enc->block_size : 8; 805 806 if (packet_length == 0) { 807 /* 808 * check if input size is less than the cipher block size, 809 * decrypt first block and extract length of incoming packet 810 */ 811 if (buffer_len(&input) < block_size) 812 return SSH_MSG_NONE; 813 buffer_clear(&incoming_packet); 814 cp = buffer_append_space(&incoming_packet, block_size); 815 cipher_crypt(&receive_context, cp, buffer_ptr(&input), 816 block_size); 817 ucp = buffer_ptr(&incoming_packet); 818 packet_length = GET_32BIT(ucp); 819 if (packet_length < 1 + 4 || packet_length > 256 * 1024) { 820 buffer_dump(&incoming_packet); 821 packet_disconnect("Bad packet length %d.", packet_length); 822 } 823 DBG(debug("input: packet len %d", packet_length+4)); 824 buffer_consume(&input, block_size); 825 } 826 /* we have a partial packet of block_size bytes */ 827 need = 4 + packet_length - block_size; 828 DBG(debug("partial packet %d, need %d, maclen %d", block_size, 829 need, maclen)); 830 if (need % block_size != 0) 831 fatal("padding error: need %d block %d mod %d", 832 need, block_size, need % block_size); 833 /* 834 * check if the entire packet has been received and 835 * decrypt into incoming_packet 836 */ 837 if (buffer_len(&input) < need + maclen) 838 return SSH_MSG_NONE; 839 #ifdef PACKET_DEBUG 840 fprintf(stderr, "read_poll enc/full: "); 841 buffer_dump(&input); 842 #endif 843 cp = buffer_append_space(&incoming_packet, need); 844 cipher_crypt(&receive_context, cp, buffer_ptr(&input), need); 845 buffer_consume(&input, need); 846 /* 847 * compute MAC over seqnr and packet, 848 * increment sequence number for incoming packet 849 */ 850 if (mac && mac->enabled) { 851 macbuf = mac_compute(mac, seqnr, 852 buffer_ptr(&incoming_packet), 853 buffer_len(&incoming_packet)); 854 if (memcmp(macbuf, buffer_ptr(&input), mac->mac_len) != 0) 855 packet_disconnect("Corrupted MAC on input."); 856 DBG(debug("MAC #%d ok", seqnr)); 857 buffer_consume(&input, mac->mac_len); 858 } 859 if (seqnr_p != NULL) 860 *seqnr_p = seqnr; 861 if (++seqnr == 0) 862 log("incoming seqnr wraps around"); 863 864 /* get padlen */ 865 cp = buffer_ptr(&incoming_packet); 866 cp += 4; 867 padlen = (u_char) *cp; 868 DBG(debug("input: padlen %d", padlen)); 869 if (padlen < 4) 870 packet_disconnect("Corrupted padlen %d on input.", padlen); 871 872 /* skip packet size + padlen, discard padding */ 873 buffer_consume(&incoming_packet, 4 + 1); 874 buffer_consume_end(&incoming_packet, padlen); 875 876 DBG(debug("input: len before de-compress %d", buffer_len(&incoming_packet))); 877 if (comp && comp->enabled) { 878 buffer_clear(&compression_buffer); 879 buffer_uncompress(&incoming_packet, &compression_buffer); 880 buffer_clear(&incoming_packet); 881 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer), 882 buffer_len(&compression_buffer)); 883 DBG(debug("input: len after de-compress %d", buffer_len(&incoming_packet))); 884 } 885 /* 886 * get packet type, implies consume. 887 * return length of payload (without type field) 888 */ 889 type = buffer_get_char(&incoming_packet); 890 if (type == SSH2_MSG_NEWKEYS) 891 set_newkeys(MODE_IN); 892 #ifdef PACKET_DEBUG 893 fprintf(stderr, "read/plain[%d]:\r\n", type); 894 buffer_dump(&incoming_packet); 895 #endif 896 /* reset for next packet */ 897 packet_length = 0; 898 return type; 899 } 900 901 int 902 packet_read_poll_seqnr(u_int32_t *seqnr_p) 903 { 904 int reason, seqnr; 905 u_char type; 906 char *msg; 907 908 for (;;) { 909 if (compat20) { 910 type = packet_read_poll2(seqnr_p); 911 if (type) 912 DBG(debug("received packet type %d", type)); 913 switch (type) { 914 case SSH2_MSG_IGNORE: 915 break; 916 case SSH2_MSG_DEBUG: 917 packet_get_char(); 918 msg = packet_get_string(NULL); 919 debug("Remote: %.900s", msg); 920 xfree(msg); 921 msg = packet_get_string(NULL); 922 xfree(msg); 923 break; 924 case SSH2_MSG_DISCONNECT: 925 reason = packet_get_int(); 926 msg = packet_get_string(NULL); 927 log("Received disconnect from %s: %d: %.400s", get_remote_ipaddr(), 928 reason, msg); 929 xfree(msg); 930 fatal_cleanup(); 931 break; 932 case SSH2_MSG_UNIMPLEMENTED: 933 seqnr = packet_get_int(); 934 debug("Received SSH2_MSG_UNIMPLEMENTED for %d", seqnr); 935 break; 936 default: 937 return type; 938 break; 939 } 940 } else { 941 type = packet_read_poll1(); 942 switch (type) { 943 case SSH_MSG_IGNORE: 944 break; 945 case SSH_MSG_DEBUG: 946 msg = packet_get_string(NULL); 947 debug("Remote: %.900s", msg); 948 xfree(msg); 949 break; 950 case SSH_MSG_DISCONNECT: 951 msg = packet_get_string(NULL); 952 log("Received disconnect from %s: %.400s", get_remote_ipaddr(), 953 msg); 954 fatal_cleanup(); 955 xfree(msg); 956 break; 957 default: 958 if (type) 959 DBG(debug("received packet type %d", type)); 960 return type; 961 break; 962 } 963 } 964 } 965 } 966 967 int 968 packet_read_poll(void) 969 { 970 return packet_read_poll_seqnr(NULL); 971 } 972 973 /* 974 * Buffers the given amount of input characters. This is intended to be used 975 * together with packet_read_poll. 976 */ 977 978 void 979 packet_process_incoming(const char *buf, u_int len) 980 { 981 buffer_append(&input, buf, len); 982 } 983 984 /* Returns a character from the packet. */ 985 986 u_int 987 packet_get_char(void) 988 { 989 char ch; 990 buffer_get(&incoming_packet, &ch, 1); 991 return (u_char) ch; 992 } 993 994 /* Returns an integer from the packet data. */ 995 996 u_int 997 packet_get_int(void) 998 { 999 return buffer_get_int(&incoming_packet); 1000 } 1001 1002 /* 1003 * Returns an arbitrary precision integer from the packet data. The integer 1004 * must have been initialized before this call. 1005 */ 1006 1007 void 1008 packet_get_bignum(BIGNUM * value) 1009 { 1010 buffer_get_bignum(&incoming_packet, value); 1011 } 1012 1013 void 1014 packet_get_bignum2(BIGNUM * value) 1015 { 1016 buffer_get_bignum2(&incoming_packet, value); 1017 } 1018 1019 void * 1020 packet_get_raw(int *length_ptr) 1021 { 1022 int bytes = buffer_len(&incoming_packet); 1023 if (length_ptr != NULL) 1024 *length_ptr = bytes; 1025 return buffer_ptr(&incoming_packet); 1026 } 1027 1028 int 1029 packet_remaining(void) 1030 { 1031 return buffer_len(&incoming_packet); 1032 } 1033 1034 /* 1035 * Returns a string from the packet data. The string is allocated using 1036 * xmalloc; it is the responsibility of the calling program to free it when 1037 * no longer needed. The length_ptr argument may be NULL, or point to an 1038 * integer into which the length of the string is stored. 1039 */ 1040 1041 void * 1042 packet_get_string(u_int *length_ptr) 1043 { 1044 return buffer_get_string(&incoming_packet, length_ptr); 1045 } 1046 1047 /* 1048 * Sends a diagnostic message from the server to the client. This message 1049 * can be sent at any time (but not while constructing another message). The 1050 * message is printed immediately, but only if the client is being executed 1051 * in verbose mode. These messages are primarily intended to ease debugging 1052 * authentication problems. The length of the formatted message must not 1053 * exceed 1024 bytes. This will automatically call packet_write_wait. 1054 */ 1055 1056 void 1057 packet_send_debug(const char *fmt,...) 1058 { 1059 char buf[1024]; 1060 va_list args; 1061 1062 if (compat20 && (datafellows & SSH_BUG_DEBUG)) 1063 return; 1064 1065 va_start(args, fmt); 1066 vsnprintf(buf, sizeof(buf), fmt, args); 1067 va_end(args); 1068 1069 if (compat20) { 1070 packet_start(SSH2_MSG_DEBUG); 1071 packet_put_char(0); /* bool: always display */ 1072 packet_put_cstring(buf); 1073 packet_put_cstring(""); 1074 } else { 1075 packet_start(SSH_MSG_DEBUG); 1076 packet_put_cstring(buf); 1077 } 1078 packet_send(); 1079 packet_write_wait(); 1080 } 1081 1082 /* 1083 * Logs the error plus constructs and sends a disconnect packet, closes the 1084 * connection, and exits. This function never returns. The error message 1085 * should not contain a newline. The length of the formatted message must 1086 * not exceed 1024 bytes. 1087 */ 1088 1089 void 1090 packet_disconnect(const char *fmt,...) 1091 { 1092 char buf[1024]; 1093 va_list args; 1094 static int disconnecting = 0; 1095 if (disconnecting) /* Guard against recursive invocations. */ 1096 fatal("packet_disconnect called recursively."); 1097 disconnecting = 1; 1098 1099 /* 1100 * Format the message. Note that the caller must make sure the 1101 * message is of limited size. 1102 */ 1103 va_start(args, fmt); 1104 vsnprintf(buf, sizeof(buf), fmt, args); 1105 va_end(args); 1106 1107 /* Send the disconnect message to the other side, and wait for it to get sent. */ 1108 if (compat20) { 1109 packet_start(SSH2_MSG_DISCONNECT); 1110 packet_put_int(SSH2_DISCONNECT_PROTOCOL_ERROR); 1111 packet_put_cstring(buf); 1112 packet_put_cstring(""); 1113 } else { 1114 packet_start(SSH_MSG_DISCONNECT); 1115 packet_put_cstring(buf); 1116 } 1117 packet_send(); 1118 packet_write_wait(); 1119 1120 /* Stop listening for connections. */ 1121 channel_close_all(); 1122 1123 /* Close the connection. */ 1124 packet_close(); 1125 1126 /* Display the error locally and exit. */ 1127 log("Disconnecting: %.100s", buf); 1128 fatal_cleanup(); 1129 } 1130 1131 /* Checks if there is any buffered output, and tries to write some of the output. */ 1132 1133 void 1134 packet_write_poll(void) 1135 { 1136 int len = buffer_len(&output); 1137 if (len > 0) { 1138 len = write(connection_out, buffer_ptr(&output), len); 1139 if (len <= 0) { 1140 if (errno == EAGAIN) 1141 return; 1142 else 1143 fatal("Write failed: %.100s", strerror(errno)); 1144 } 1145 buffer_consume(&output, len); 1146 } 1147 } 1148 1149 /* 1150 * Calls packet_write_poll repeatedly until all pending output data has been 1151 * written. 1152 */ 1153 1154 void 1155 packet_write_wait(void) 1156 { 1157 fd_set *setp; 1158 1159 setp = (fd_set *)xmalloc(howmany(connection_out + 1, NFDBITS) * 1160 sizeof(fd_mask)); 1161 packet_write_poll(); 1162 while (packet_have_data_to_write()) { 1163 memset(setp, 0, howmany(connection_out + 1, NFDBITS) * 1164 sizeof(fd_mask)); 1165 FD_SET(connection_out, setp); 1166 while (select(connection_out + 1, NULL, setp, NULL, NULL) == -1 && 1167 (errno == EAGAIN || errno == EINTR)) 1168 ; 1169 packet_write_poll(); 1170 } 1171 xfree(setp); 1172 } 1173 1174 /* Returns true if there is buffered data to write to the connection. */ 1175 1176 int 1177 packet_have_data_to_write(void) 1178 { 1179 return buffer_len(&output) != 0; 1180 } 1181 1182 /* Returns true if there is not too much data to write to the connection. */ 1183 1184 int 1185 packet_not_very_much_data_to_write(void) 1186 { 1187 if (interactive_mode) 1188 return buffer_len(&output) < 16384; 1189 else 1190 return buffer_len(&output) < 128 * 1024; 1191 } 1192 1193 /* Informs that the current session is interactive. Sets IP flags for that. */ 1194 1195 void 1196 packet_set_interactive(int interactive) 1197 { 1198 static int called = 0; 1199 int lowdelay = IPTOS_LOWDELAY; 1200 int throughput = IPTOS_THROUGHPUT; 1201 1202 if (called) 1203 return; 1204 called = 1; 1205 1206 /* Record that we are in interactive mode. */ 1207 interactive_mode = interactive; 1208 1209 /* Only set socket options if using a socket. */ 1210 if (!packet_connection_is_on_socket()) 1211 return; 1212 /* 1213 * IPTOS_LOWDELAY and IPTOS_THROUGHPUT are IPv4 only 1214 */ 1215 if (interactive) { 1216 /* 1217 * Set IP options for an interactive connection. Use 1218 * IPTOS_LOWDELAY and TCP_NODELAY. 1219 */ 1220 if (packet_connection_is_ipv4()) { 1221 if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, 1222 (void *) &lowdelay, sizeof(lowdelay)) < 0) 1223 error("setsockopt IPTOS_LOWDELAY: %.100s", 1224 strerror(errno)); 1225 } 1226 set_nodelay(connection_in); 1227 } else if (packet_connection_is_ipv4()) { 1228 /* 1229 * Set IP options for a non-interactive connection. Use 1230 * IPTOS_THROUGHPUT. 1231 */ 1232 if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, (void *) &throughput, 1233 sizeof(throughput)) < 0) 1234 error("setsockopt IPTOS_THROUGHPUT: %.100s", strerror(errno)); 1235 } 1236 } 1237 1238 /* Returns true if the current connection is interactive. */ 1239 1240 int 1241 packet_is_interactive(void) 1242 { 1243 return interactive_mode; 1244 } 1245 1246 int 1247 packet_set_maxsize(int s) 1248 { 1249 static int called = 0; 1250 if (called) { 1251 log("packet_set_maxsize: called twice: old %d new %d", 1252 max_packet_size, s); 1253 return -1; 1254 } 1255 if (s < 4 * 1024 || s > 1024 * 1024) { 1256 log("packet_set_maxsize: bad size %d", s); 1257 return -1; 1258 } 1259 called = 1; 1260 debug("packet_set_maxsize: setting to %d", s); 1261 max_packet_size = s; 1262 return s; 1263 } 1264 1265 /* roundup current message to pad bytes */ 1266 void 1267 packet_add_padding(u_char pad) 1268 { 1269 extra_pad = pad; 1270 } 1271 1272 /* 1273 * 9.2. Ignored Data Message 1274 * 1275 * byte SSH_MSG_IGNORE 1276 * string data 1277 * 1278 * All implementations MUST understand (and ignore) this message at any 1279 * time (after receiving the protocol version). No implementation is 1280 * required to send them. This message can be used as an additional 1281 * protection measure against advanced traffic analysis techniques. 1282 */ 1283 void 1284 packet_send_ignore(int nbytes) 1285 { 1286 u_int32_t rand = 0; 1287 int i; 1288 1289 packet_start(compat20 ? SSH2_MSG_IGNORE : SSH_MSG_IGNORE); 1290 packet_put_int(nbytes); 1291 for (i = 0; i < nbytes; i++) { 1292 if (i % 4 == 0) 1293 rand = arc4random(); 1294 packet_put_char(rand & 0xff); 1295 rand >>= 8; 1296 } 1297 } 1298