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 1.97 2002/07/04 08:12:15 deraadt 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 #include "ssh.h" 64 65 #ifdef PACKET_DEBUG 66 #define DBG(x) x 67 #else 68 #define DBG(x) 69 #endif 70 71 /* 72 * This variable contains the file descriptors used for communicating with 73 * the other side. connection_in is used for reading; connection_out for 74 * writing. These can be the same descriptor, in which case it is assumed to 75 * be a socket. 76 */ 77 static int connection_in = -1; 78 static int connection_out = -1; 79 80 /* Protocol flags for the remote side. */ 81 static u_int remote_protocol_flags = 0; 82 83 /* Encryption context for receiving data. This is only used for decryption. */ 84 static CipherContext receive_context; 85 86 /* Encryption context for sending data. This is only used for encryption. */ 87 static CipherContext send_context; 88 89 /* Buffer for raw input data from the socket. */ 90 Buffer input; 91 92 /* Buffer for raw output data going to the socket. */ 93 Buffer output; 94 95 /* Buffer for the partial outgoing packet being constructed. */ 96 static Buffer outgoing_packet; 97 98 /* Buffer for the incoming packet currently being processed. */ 99 static Buffer incoming_packet; 100 101 /* Scratch buffer for packet compression/decompression. */ 102 static Buffer compression_buffer; 103 static int compression_buffer_ready = 0; 104 105 /* Flag indicating whether packet compression/decompression is enabled. */ 106 static int packet_compression = 0; 107 108 /* default maximum packet size */ 109 int max_packet_size = 32768; 110 111 /* Flag indicating whether this module has been initialized. */ 112 static int initialized = 0; 113 114 /* Set to true if the connection is interactive. */ 115 static int interactive_mode = 0; 116 117 /* Session key information for Encryption and MAC */ 118 Newkeys *newkeys[MODE_MAX]; 119 static u_int32_t read_seqnr = 0; 120 static u_int32_t send_seqnr = 0; 121 122 /* Session key for protocol v1 */ 123 static u_char ssh1_key[SSH_SESSION_KEY_LENGTH]; 124 static u_int ssh1_keylen; 125 126 /* roundup current message to extra_pad bytes */ 127 static u_char extra_pad = 0; 128 129 /* 130 * Sets the descriptors used for communication. Disables encryption until 131 * packet_set_encryption_key is called. 132 */ 133 void 134 packet_set_connection(int fd_in, int fd_out) 135 { 136 Cipher *none = cipher_by_name("none"); 137 138 if (none == NULL) 139 fatal("packet_set_connection: cannot load cipher 'none'"); 140 connection_in = fd_in; 141 connection_out = fd_out; 142 cipher_init(&send_context, none, "", 0, NULL, 0, CIPHER_ENCRYPT); 143 cipher_init(&receive_context, none, "", 0, NULL, 0, CIPHER_DECRYPT); 144 newkeys[MODE_IN] = newkeys[MODE_OUT] = NULL; 145 if (!initialized) { 146 initialized = 1; 147 buffer_init(&input); 148 buffer_init(&output); 149 buffer_init(&outgoing_packet); 150 buffer_init(&incoming_packet); 151 } 152 /* Kludge: arrange the close function to be called from fatal(). */ 153 fatal_add_cleanup((void (*) (void *)) packet_close, NULL); 154 } 155 156 /* Returns 1 if remote host is connected via socket, 0 if not. */ 157 158 int 159 packet_connection_is_on_socket(void) 160 { 161 struct sockaddr_storage from, to; 162 socklen_t fromlen, tolen; 163 164 /* filedescriptors in and out are the same, so it's a socket */ 165 if (connection_in == connection_out) 166 return 1; 167 fromlen = sizeof(from); 168 memset(&from, 0, sizeof(from)); 169 if (getpeername(connection_in, (struct sockaddr *)&from, &fromlen) < 0) 170 return 0; 171 tolen = sizeof(to); 172 memset(&to, 0, sizeof(to)); 173 if (getpeername(connection_out, (struct sockaddr *)&to, &tolen) < 0) 174 return 0; 175 if (fromlen != tolen || memcmp(&from, &to, fromlen) != 0) 176 return 0; 177 if (from.ss_family != AF_INET && from.ss_family != AF_INET6) 178 return 0; 179 return 1; 180 } 181 182 /* 183 * Exports an IV from the CipherContext required to export the key 184 * state back from the unprivileged child to the privileged parent 185 * process. 186 */ 187 188 void 189 packet_get_keyiv(int mode, u_char *iv, u_int len) 190 { 191 CipherContext *cc; 192 193 if (mode == MODE_OUT) 194 cc = &send_context; 195 else 196 cc = &receive_context; 197 198 cipher_get_keyiv(cc, iv, len); 199 } 200 201 int 202 packet_get_keycontext(int mode, u_char *dat) 203 { 204 CipherContext *cc; 205 206 if (mode == MODE_OUT) 207 cc = &send_context; 208 else 209 cc = &receive_context; 210 211 return (cipher_get_keycontext(cc, dat)); 212 } 213 214 void 215 packet_set_keycontext(int mode, u_char *dat) 216 { 217 CipherContext *cc; 218 219 if (mode == MODE_OUT) 220 cc = &send_context; 221 else 222 cc = &receive_context; 223 224 cipher_set_keycontext(cc, dat); 225 } 226 227 int 228 packet_get_keyiv_len(int mode) 229 { 230 CipherContext *cc; 231 232 if (mode == MODE_OUT) 233 cc = &send_context; 234 else 235 cc = &receive_context; 236 237 return (cipher_get_keyiv_len(cc)); 238 } 239 void 240 packet_set_iv(int mode, u_char *dat) 241 { 242 CipherContext *cc; 243 244 if (mode == MODE_OUT) 245 cc = &send_context; 246 else 247 cc = &receive_context; 248 249 cipher_set_keyiv(cc, dat); 250 } 251 int 252 packet_get_ssh1_cipher() 253 { 254 return (cipher_get_number(receive_context.cipher)); 255 } 256 257 258 u_int32_t 259 packet_get_seqnr(int mode) 260 { 261 return (mode == MODE_IN ? read_seqnr : send_seqnr); 262 } 263 264 void 265 packet_set_seqnr(int mode, u_int32_t seqnr) 266 { 267 if (mode == MODE_IN) 268 read_seqnr = seqnr; 269 else if (mode == MODE_OUT) 270 send_seqnr = seqnr; 271 else 272 fatal("packet_set_seqnr: bad mode %d", mode); 273 } 274 275 /* returns 1 if connection is via ipv4 */ 276 277 int 278 packet_connection_is_ipv4(void) 279 { 280 struct sockaddr_storage to; 281 socklen_t tolen = sizeof(to); 282 283 memset(&to, 0, sizeof(to)); 284 if (getsockname(connection_out, (struct sockaddr *)&to, &tolen) < 0) 285 return 0; 286 if (to.ss_family == AF_INET) 287 return 1; 288 #ifdef IPV4_IN_IPV6 289 if (to.ss_family == AF_INET6 && 290 IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)&to)->sin6_addr)) 291 return 1; 292 #endif 293 return 0; 294 } 295 296 /* Sets the connection into non-blocking mode. */ 297 298 void 299 packet_set_nonblocking(void) 300 { 301 /* Set the socket into non-blocking mode. */ 302 if (fcntl(connection_in, F_SETFL, O_NONBLOCK) < 0) 303 error("fcntl O_NONBLOCK: %.100s", strerror(errno)); 304 305 if (connection_out != connection_in) { 306 if (fcntl(connection_out, F_SETFL, O_NONBLOCK) < 0) 307 error("fcntl O_NONBLOCK: %.100s", strerror(errno)); 308 } 309 } 310 311 /* Returns the socket used for reading. */ 312 313 int 314 packet_get_connection_in(void) 315 { 316 return connection_in; 317 } 318 319 /* Returns the descriptor used for writing. */ 320 321 int 322 packet_get_connection_out(void) 323 { 324 return connection_out; 325 } 326 327 /* Closes the connection and clears and frees internal data structures. */ 328 329 void 330 packet_close(void) 331 { 332 if (!initialized) 333 return; 334 initialized = 0; 335 if (connection_in == connection_out) { 336 shutdown(connection_out, SHUT_RDWR); 337 close(connection_out); 338 } else { 339 close(connection_in); 340 close(connection_out); 341 } 342 buffer_free(&input); 343 buffer_free(&output); 344 buffer_free(&outgoing_packet); 345 buffer_free(&incoming_packet); 346 if (compression_buffer_ready) { 347 buffer_free(&compression_buffer); 348 buffer_compress_uninit(); 349 } 350 cipher_cleanup(&send_context); 351 cipher_cleanup(&receive_context); 352 } 353 354 /* Sets remote side protocol flags. */ 355 356 void 357 packet_set_protocol_flags(u_int protocol_flags) 358 { 359 remote_protocol_flags = protocol_flags; 360 } 361 362 /* Returns the remote protocol flags set earlier by the above function. */ 363 364 u_int 365 packet_get_protocol_flags(void) 366 { 367 return remote_protocol_flags; 368 } 369 370 /* 371 * Starts packet compression from the next packet on in both directions. 372 * Level is compression level 1 (fastest) - 9 (slow, best) as in gzip. 373 */ 374 375 static void 376 packet_init_compression(void) 377 { 378 if (compression_buffer_ready == 1) 379 return; 380 compression_buffer_ready = 1; 381 buffer_init(&compression_buffer); 382 } 383 384 void 385 packet_start_compression(int level) 386 { 387 if (packet_compression && !compat20) 388 fatal("Compression already enabled."); 389 packet_compression = 1; 390 packet_init_compression(); 391 buffer_compress_init_send(level); 392 buffer_compress_init_recv(); 393 } 394 395 /* 396 * Causes any further packets to be encrypted using the given key. The same 397 * key is used for both sending and reception. However, both directions are 398 * encrypted independently of each other. 399 */ 400 401 void 402 packet_set_encryption_key(const u_char *key, u_int keylen, 403 int number) 404 { 405 Cipher *cipher = cipher_by_number(number); 406 407 if (cipher == NULL) 408 fatal("packet_set_encryption_key: unknown cipher number %d", number); 409 if (keylen < 20) 410 fatal("packet_set_encryption_key: keylen too small: %d", keylen); 411 if (keylen > SSH_SESSION_KEY_LENGTH) 412 fatal("packet_set_encryption_key: keylen too big: %d", keylen); 413 memcpy(ssh1_key, key, keylen); 414 ssh1_keylen = keylen; 415 cipher_init(&send_context, cipher, key, keylen, NULL, 0, CIPHER_ENCRYPT); 416 cipher_init(&receive_context, cipher, key, keylen, NULL, 0, CIPHER_DECRYPT); 417 } 418 419 u_int 420 packet_get_encryption_key(u_char *key) 421 { 422 if (key == NULL) 423 return (ssh1_keylen); 424 memcpy(key, ssh1_key, ssh1_keylen); 425 return (ssh1_keylen); 426 } 427 428 /* Start constructing a packet to send. */ 429 void 430 packet_start(u_char type) 431 { 432 u_char buf[9]; 433 int len; 434 435 DBG(debug("packet_start[%d]", type)); 436 len = compat20 ? 6 : 9; 437 memset(buf, 0, len - 1); 438 buf[len - 1] = type; 439 buffer_clear(&outgoing_packet); 440 buffer_append(&outgoing_packet, buf, len); 441 } 442 443 /* Append payload. */ 444 void 445 packet_put_char(int value) 446 { 447 char ch = value; 448 449 buffer_append(&outgoing_packet, &ch, 1); 450 } 451 void 452 packet_put_int(u_int value) 453 { 454 buffer_put_int(&outgoing_packet, value); 455 } 456 void 457 packet_put_string(const void *buf, u_int len) 458 { 459 buffer_put_string(&outgoing_packet, buf, len); 460 } 461 void 462 packet_put_cstring(const char *str) 463 { 464 buffer_put_cstring(&outgoing_packet, str); 465 } 466 void 467 packet_put_raw(const void *buf, u_int len) 468 { 469 buffer_append(&outgoing_packet, buf, len); 470 } 471 void 472 packet_put_bignum(BIGNUM * value) 473 { 474 buffer_put_bignum(&outgoing_packet, value); 475 } 476 void 477 packet_put_bignum2(BIGNUM * value) 478 { 479 buffer_put_bignum2(&outgoing_packet, value); 480 } 481 482 /* 483 * Finalizes and sends the packet. If the encryption key has been set, 484 * encrypts the packet before sending. 485 */ 486 487 static void 488 packet_send1(void) 489 { 490 u_char buf[8], *cp; 491 int i, padding, len; 492 u_int checksum; 493 u_int32_t rand = 0; 494 495 /* 496 * If using packet compression, compress the payload of the outgoing 497 * packet. 498 */ 499 if (packet_compression) { 500 buffer_clear(&compression_buffer); 501 /* Skip padding. */ 502 buffer_consume(&outgoing_packet, 8); 503 /* padding */ 504 buffer_append(&compression_buffer, "\0\0\0\0\0\0\0\0", 8); 505 buffer_compress(&outgoing_packet, &compression_buffer); 506 buffer_clear(&outgoing_packet); 507 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer), 508 buffer_len(&compression_buffer)); 509 } 510 /* Compute packet length without padding (add checksum, remove padding). */ 511 len = buffer_len(&outgoing_packet) + 4 - 8; 512 513 /* Insert padding. Initialized to zero in packet_start1() */ 514 padding = 8 - len % 8; 515 if (!send_context.plaintext) { 516 cp = buffer_ptr(&outgoing_packet); 517 for (i = 0; i < padding; i++) { 518 if (i % 4 == 0) 519 rand = arc4random(); 520 cp[7 - i] = rand & 0xff; 521 rand >>= 8; 522 } 523 } 524 buffer_consume(&outgoing_packet, 8 - padding); 525 526 /* Add check bytes. */ 527 checksum = ssh_crc32(buffer_ptr(&outgoing_packet), 528 buffer_len(&outgoing_packet)); 529 PUT_32BIT(buf, checksum); 530 buffer_append(&outgoing_packet, buf, 4); 531 532 #ifdef PACKET_DEBUG 533 fprintf(stderr, "packet_send plain: "); 534 buffer_dump(&outgoing_packet); 535 #endif 536 537 /* Append to output. */ 538 PUT_32BIT(buf, len); 539 buffer_append(&output, buf, 4); 540 cp = buffer_append_space(&output, buffer_len(&outgoing_packet)); 541 cipher_crypt(&send_context, cp, buffer_ptr(&outgoing_packet), 542 buffer_len(&outgoing_packet)); 543 544 #ifdef PACKET_DEBUG 545 fprintf(stderr, "encrypted: "); 546 buffer_dump(&output); 547 #endif 548 549 buffer_clear(&outgoing_packet); 550 551 /* 552 * Note that the packet is now only buffered in output. It won\'t be 553 * actually sent until packet_write_wait or packet_write_poll is 554 * called. 555 */ 556 } 557 558 void 559 set_newkeys(int mode) 560 { 561 Enc *enc; 562 Mac *mac; 563 Comp *comp; 564 CipherContext *cc; 565 int encrypt; 566 567 debug("newkeys: mode %d", mode); 568 569 if (mode == MODE_OUT) { 570 cc = &send_context; 571 encrypt = CIPHER_ENCRYPT; 572 } else { 573 cc = &receive_context; 574 encrypt = CIPHER_DECRYPT; 575 } 576 if (newkeys[mode] != NULL) { 577 debug("newkeys: rekeying"); 578 cipher_cleanup(cc); 579 enc = &newkeys[mode]->enc; 580 mac = &newkeys[mode]->mac; 581 comp = &newkeys[mode]->comp; 582 memset(mac->key, 0, mac->key_len); 583 xfree(enc->name); 584 xfree(enc->iv); 585 xfree(enc->key); 586 xfree(mac->name); 587 xfree(mac->key); 588 xfree(comp->name); 589 xfree(newkeys[mode]); 590 } 591 newkeys[mode] = kex_get_newkeys(mode); 592 if (newkeys[mode] == NULL) 593 fatal("newkeys: no keys for mode %d", mode); 594 enc = &newkeys[mode]->enc; 595 mac = &newkeys[mode]->mac; 596 comp = &newkeys[mode]->comp; 597 if (mac->md != NULL) 598 mac->enabled = 1; 599 DBG(debug("cipher_init_context: %d", mode)); 600 cipher_init(cc, enc->cipher, enc->key, enc->key_len, 601 enc->iv, enc->block_size, encrypt); 602 /* Deleting the keys does not gain extra security */ 603 /* memset(enc->iv, 0, enc->block_size); 604 memset(enc->key, 0, enc->key_len); */ 605 if (comp->type != 0 && comp->enabled == 0) { 606 packet_init_compression(); 607 if (mode == MODE_OUT) 608 buffer_compress_init_send(6); 609 else 610 buffer_compress_init_recv(); 611 comp->enabled = 1; 612 } 613 } 614 615 /* 616 * Finalize packet in SSH2 format (compress, mac, encrypt, enqueue) 617 */ 618 static void 619 packet_send2(void) 620 { 621 u_char type, *cp, *macbuf = NULL; 622 u_char padlen, pad; 623 u_int packet_length = 0; 624 u_int i, len; 625 u_int32_t rand = 0; 626 Enc *enc = NULL; 627 Mac *mac = NULL; 628 Comp *comp = NULL; 629 int block_size; 630 631 if (newkeys[MODE_OUT] != NULL) { 632 enc = &newkeys[MODE_OUT]->enc; 633 mac = &newkeys[MODE_OUT]->mac; 634 comp = &newkeys[MODE_OUT]->comp; 635 } 636 block_size = enc ? enc->block_size : 8; 637 638 cp = buffer_ptr(&outgoing_packet); 639 type = cp[5]; 640 641 #ifdef PACKET_DEBUG 642 fprintf(stderr, "plain: "); 643 buffer_dump(&outgoing_packet); 644 #endif 645 646 if (comp && comp->enabled) { 647 len = buffer_len(&outgoing_packet); 648 /* skip header, compress only payload */ 649 buffer_consume(&outgoing_packet, 5); 650 buffer_clear(&compression_buffer); 651 buffer_compress(&outgoing_packet, &compression_buffer); 652 buffer_clear(&outgoing_packet); 653 buffer_append(&outgoing_packet, "\0\0\0\0\0", 5); 654 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer), 655 buffer_len(&compression_buffer)); 656 DBG(debug("compression: raw %d compressed %d", len, 657 buffer_len(&outgoing_packet))); 658 } 659 660 /* sizeof (packet_len + pad_len + payload) */ 661 len = buffer_len(&outgoing_packet); 662 663 /* 664 * calc size of padding, alloc space, get random data, 665 * minimum padding is 4 bytes 666 */ 667 padlen = block_size - (len % block_size); 668 if (padlen < 4) 669 padlen += block_size; 670 if (extra_pad) { 671 /* will wrap if extra_pad+padlen > 255 */ 672 extra_pad = roundup(extra_pad, block_size); 673 pad = extra_pad - ((len + padlen) % extra_pad); 674 debug3("packet_send2: adding %d (len %d padlen %d extra_pad %d)", 675 pad, len, padlen, extra_pad); 676 padlen += pad; 677 extra_pad = 0; 678 } 679 cp = buffer_append_space(&outgoing_packet, padlen); 680 if (enc && !send_context.plaintext) { 681 /* random padding */ 682 for (i = 0; i < padlen; i++) { 683 if (i % 4 == 0) 684 rand = arc4random(); 685 cp[i] = rand & 0xff; 686 rand >>= 8; 687 } 688 } else { 689 /* clear padding */ 690 memset(cp, 0, padlen); 691 } 692 /* packet_length includes payload, padding and padding length field */ 693 packet_length = buffer_len(&outgoing_packet) - 4; 694 cp = buffer_ptr(&outgoing_packet); 695 PUT_32BIT(cp, packet_length); 696 cp[4] = padlen; 697 DBG(debug("send: len %d (includes padlen %d)", packet_length+4, padlen)); 698 699 /* compute MAC over seqnr and packet(length fields, payload, padding) */ 700 if (mac && mac->enabled) { 701 macbuf = mac_compute(mac, send_seqnr, 702 buffer_ptr(&outgoing_packet), 703 buffer_len(&outgoing_packet)); 704 DBG(debug("done calc MAC out #%d", send_seqnr)); 705 } 706 /* encrypt packet and append to output buffer. */ 707 cp = buffer_append_space(&output, buffer_len(&outgoing_packet)); 708 cipher_crypt(&send_context, cp, buffer_ptr(&outgoing_packet), 709 buffer_len(&outgoing_packet)); 710 /* append unencrypted MAC */ 711 if (mac && mac->enabled) 712 buffer_append(&output, (char *)macbuf, mac->mac_len); 713 #ifdef PACKET_DEBUG 714 fprintf(stderr, "encrypted: "); 715 buffer_dump(&output); 716 #endif 717 /* increment sequence number for outgoing packets */ 718 if (++send_seqnr == 0) 719 log("outgoing seqnr wraps around"); 720 buffer_clear(&outgoing_packet); 721 722 if (type == SSH2_MSG_NEWKEYS) 723 set_newkeys(MODE_OUT); 724 } 725 726 void 727 packet_send(void) 728 { 729 if (compat20) 730 packet_send2(); 731 else 732 packet_send1(); 733 DBG(debug("packet_send done")); 734 } 735 736 /* 737 * Waits until a packet has been received, and returns its type. Note that 738 * no other data is processed until this returns, so this function should not 739 * be used during the interactive session. 740 */ 741 742 int 743 packet_read_seqnr(u_int32_t *seqnr_p) 744 { 745 int type, len; 746 fd_set *setp; 747 char buf[8192]; 748 DBG(debug("packet_read()")); 749 750 setp = (fd_set *)xmalloc(howmany(connection_in+1, NFDBITS) * 751 sizeof(fd_mask)); 752 753 /* Since we are blocking, ensure that all written packets have been sent. */ 754 packet_write_wait(); 755 756 /* Stay in the loop until we have received a complete packet. */ 757 for (;;) { 758 /* Try to read a packet from the buffer. */ 759 type = packet_read_poll_seqnr(seqnr_p); 760 if (!compat20 && ( 761 type == SSH_SMSG_SUCCESS 762 || type == SSH_SMSG_FAILURE 763 || type == SSH_CMSG_EOF 764 || type == SSH_CMSG_EXIT_CONFIRMATION)) 765 packet_check_eom(); 766 /* If we got a packet, return it. */ 767 if (type != SSH_MSG_NONE) { 768 xfree(setp); 769 return type; 770 } 771 /* 772 * Otherwise, wait for some data to arrive, add it to the 773 * buffer, and try again. 774 */ 775 memset(setp, 0, howmany(connection_in + 1, NFDBITS) * 776 sizeof(fd_mask)); 777 FD_SET(connection_in, setp); 778 779 /* Wait for some data to arrive. */ 780 while (select(connection_in + 1, setp, NULL, NULL, NULL) == -1 && 781 (errno == EAGAIN || errno == EINTR)) 782 ; 783 784 /* Read data from the socket. */ 785 len = read(connection_in, buf, sizeof(buf)); 786 if (len == 0) { 787 log("Connection closed by %.200s", get_remote_ipaddr()); 788 fatal_cleanup(); 789 } 790 if (len < 0) 791 fatal("Read from socket failed: %.100s", strerror(errno)); 792 /* Append it to the buffer. */ 793 packet_process_incoming(buf, len); 794 } 795 /* NOTREACHED */ 796 } 797 798 int 799 packet_read(void) 800 { 801 return packet_read_seqnr(NULL); 802 } 803 804 /* 805 * Waits until a packet has been received, verifies that its type matches 806 * that given, and gives a fatal error and exits if there is a mismatch. 807 */ 808 809 void 810 packet_read_expect(int expected_type) 811 { 812 int type; 813 814 type = packet_read(); 815 if (type != expected_type) 816 packet_disconnect("Protocol error: expected packet type %d, got %d", 817 expected_type, type); 818 } 819 820 /* Checks if a full packet is available in the data received so far via 821 * packet_process_incoming. If so, reads the packet; otherwise returns 822 * SSH_MSG_NONE. This does not wait for data from the connection. 823 * 824 * SSH_MSG_DISCONNECT is handled specially here. Also, 825 * SSH_MSG_IGNORE messages are skipped by this function and are never returned 826 * to higher levels. 827 */ 828 829 static int 830 packet_read_poll1(void) 831 { 832 u_int len, padded_len; 833 u_char *cp, type; 834 u_int checksum, stored_checksum; 835 836 /* Check if input size is less than minimum packet size. */ 837 if (buffer_len(&input) < 4 + 8) 838 return SSH_MSG_NONE; 839 /* Get length of incoming packet. */ 840 cp = buffer_ptr(&input); 841 len = GET_32BIT(cp); 842 if (len < 1 + 2 + 2 || len > 256 * 1024) 843 packet_disconnect("Bad packet length %d.", len); 844 padded_len = (len + 8) & ~7; 845 846 /* Check if the packet has been entirely received. */ 847 if (buffer_len(&input) < 4 + padded_len) 848 return SSH_MSG_NONE; 849 850 /* The entire packet is in buffer. */ 851 852 /* Consume packet length. */ 853 buffer_consume(&input, 4); 854 855 /* 856 * Cryptographic attack detector for ssh 857 * (C)1998 CORE-SDI, Buenos Aires Argentina 858 * Ariel Futoransky(futo@core-sdi.com) 859 */ 860 if (!receive_context.plaintext && 861 detect_attack(buffer_ptr(&input), padded_len, NULL) == DEATTACK_DETECTED) 862 packet_disconnect("crc32 compensation attack: network attack detected"); 863 864 /* Decrypt data to incoming_packet. */ 865 buffer_clear(&incoming_packet); 866 cp = buffer_append_space(&incoming_packet, padded_len); 867 cipher_crypt(&receive_context, cp, buffer_ptr(&input), padded_len); 868 869 buffer_consume(&input, padded_len); 870 871 #ifdef PACKET_DEBUG 872 fprintf(stderr, "read_poll plain: "); 873 buffer_dump(&incoming_packet); 874 #endif 875 876 /* Compute packet checksum. */ 877 checksum = ssh_crc32(buffer_ptr(&incoming_packet), 878 buffer_len(&incoming_packet) - 4); 879 880 /* Skip padding. */ 881 buffer_consume(&incoming_packet, 8 - len % 8); 882 883 /* Test check bytes. */ 884 if (len != buffer_len(&incoming_packet)) 885 packet_disconnect("packet_read_poll1: len %d != buffer_len %d.", 886 len, buffer_len(&incoming_packet)); 887 888 cp = (u_char *)buffer_ptr(&incoming_packet) + len - 4; 889 stored_checksum = GET_32BIT(cp); 890 if (checksum != stored_checksum) 891 packet_disconnect("Corrupted check bytes on input."); 892 buffer_consume_end(&incoming_packet, 4); 893 894 if (packet_compression) { 895 buffer_clear(&compression_buffer); 896 buffer_uncompress(&incoming_packet, &compression_buffer); 897 buffer_clear(&incoming_packet); 898 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer), 899 buffer_len(&compression_buffer)); 900 } 901 type = buffer_get_char(&incoming_packet); 902 return type; 903 } 904 905 static int 906 packet_read_poll2(u_int32_t *seqnr_p) 907 { 908 static u_int packet_length = 0; 909 u_int padlen, need; 910 u_char *macbuf, *cp, type; 911 int maclen, block_size; 912 Enc *enc = NULL; 913 Mac *mac = NULL; 914 Comp *comp = NULL; 915 916 if (newkeys[MODE_IN] != NULL) { 917 enc = &newkeys[MODE_IN]->enc; 918 mac = &newkeys[MODE_IN]->mac; 919 comp = &newkeys[MODE_IN]->comp; 920 } 921 maclen = mac && mac->enabled ? mac->mac_len : 0; 922 block_size = enc ? enc->block_size : 8; 923 924 if (packet_length == 0) { 925 /* 926 * check if input size is less than the cipher block size, 927 * decrypt first block and extract length of incoming packet 928 */ 929 if (buffer_len(&input) < block_size) 930 return SSH_MSG_NONE; 931 buffer_clear(&incoming_packet); 932 cp = buffer_append_space(&incoming_packet, block_size); 933 cipher_crypt(&receive_context, cp, buffer_ptr(&input), 934 block_size); 935 cp = buffer_ptr(&incoming_packet); 936 packet_length = GET_32BIT(cp); 937 if (packet_length < 1 + 4 || packet_length > 256 * 1024) { 938 buffer_dump(&incoming_packet); 939 packet_disconnect("Bad packet length %d.", packet_length); 940 } 941 DBG(debug("input: packet len %d", packet_length+4)); 942 buffer_consume(&input, block_size); 943 } 944 /* we have a partial packet of block_size bytes */ 945 need = 4 + packet_length - block_size; 946 DBG(debug("partial packet %d, need %d, maclen %d", block_size, 947 need, maclen)); 948 if (need % block_size != 0) 949 fatal("padding error: need %d block %d mod %d", 950 need, block_size, need % block_size); 951 /* 952 * check if the entire packet has been received and 953 * decrypt into incoming_packet 954 */ 955 if (buffer_len(&input) < need + maclen) 956 return SSH_MSG_NONE; 957 #ifdef PACKET_DEBUG 958 fprintf(stderr, "read_poll enc/full: "); 959 buffer_dump(&input); 960 #endif 961 cp = buffer_append_space(&incoming_packet, need); 962 cipher_crypt(&receive_context, cp, buffer_ptr(&input), need); 963 buffer_consume(&input, need); 964 /* 965 * compute MAC over seqnr and packet, 966 * increment sequence number for incoming packet 967 */ 968 if (mac && mac->enabled) { 969 macbuf = mac_compute(mac, read_seqnr, 970 buffer_ptr(&incoming_packet), 971 buffer_len(&incoming_packet)); 972 if (memcmp(macbuf, buffer_ptr(&input), mac->mac_len) != 0) 973 packet_disconnect("Corrupted MAC on input."); 974 DBG(debug("MAC #%d ok", read_seqnr)); 975 buffer_consume(&input, mac->mac_len); 976 } 977 if (seqnr_p != NULL) 978 *seqnr_p = read_seqnr; 979 if (++read_seqnr == 0) 980 log("incoming seqnr wraps around"); 981 982 /* get padlen */ 983 cp = buffer_ptr(&incoming_packet); 984 padlen = cp[4]; 985 DBG(debug("input: padlen %d", padlen)); 986 if (padlen < 4) 987 packet_disconnect("Corrupted padlen %d on input.", padlen); 988 989 /* skip packet size + padlen, discard padding */ 990 buffer_consume(&incoming_packet, 4 + 1); 991 buffer_consume_end(&incoming_packet, padlen); 992 993 DBG(debug("input: len before de-compress %d", buffer_len(&incoming_packet))); 994 if (comp && comp->enabled) { 995 buffer_clear(&compression_buffer); 996 buffer_uncompress(&incoming_packet, &compression_buffer); 997 buffer_clear(&incoming_packet); 998 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer), 999 buffer_len(&compression_buffer)); 1000 DBG(debug("input: len after de-compress %d", 1001 buffer_len(&incoming_packet))); 1002 } 1003 /* 1004 * get packet type, implies consume. 1005 * return length of payload (without type field) 1006 */ 1007 type = buffer_get_char(&incoming_packet); 1008 if (type == SSH2_MSG_NEWKEYS) 1009 set_newkeys(MODE_IN); 1010 #ifdef PACKET_DEBUG 1011 fprintf(stderr, "read/plain[%d]:\r\n", type); 1012 buffer_dump(&incoming_packet); 1013 #endif 1014 /* reset for next packet */ 1015 packet_length = 0; 1016 return type; 1017 } 1018 1019 int 1020 packet_read_poll_seqnr(u_int32_t *seqnr_p) 1021 { 1022 u_int reason, seqnr; 1023 u_char type; 1024 char *msg; 1025 1026 for (;;) { 1027 if (compat20) { 1028 type = packet_read_poll2(seqnr_p); 1029 if (type) 1030 DBG(debug("received packet type %d", type)); 1031 switch (type) { 1032 case SSH2_MSG_IGNORE: 1033 break; 1034 case SSH2_MSG_DEBUG: 1035 packet_get_char(); 1036 msg = packet_get_string(NULL); 1037 debug("Remote: %.900s", msg); 1038 xfree(msg); 1039 msg = packet_get_string(NULL); 1040 xfree(msg); 1041 break; 1042 case SSH2_MSG_DISCONNECT: 1043 reason = packet_get_int(); 1044 msg = packet_get_string(NULL); 1045 log("Received disconnect from %s: %u: %.400s", 1046 get_remote_ipaddr(), reason, msg); 1047 xfree(msg); 1048 fatal_cleanup(); 1049 break; 1050 case SSH2_MSG_UNIMPLEMENTED: 1051 seqnr = packet_get_int(); 1052 debug("Received SSH2_MSG_UNIMPLEMENTED for %u", 1053 seqnr); 1054 break; 1055 default: 1056 return type; 1057 break; 1058 } 1059 } else { 1060 type = packet_read_poll1(); 1061 switch (type) { 1062 case SSH_MSG_IGNORE: 1063 break; 1064 case SSH_MSG_DEBUG: 1065 msg = packet_get_string(NULL); 1066 debug("Remote: %.900s", msg); 1067 xfree(msg); 1068 break; 1069 case SSH_MSG_DISCONNECT: 1070 msg = packet_get_string(NULL); 1071 log("Received disconnect from %s: %.400s", 1072 get_remote_ipaddr(), msg); 1073 fatal_cleanup(); 1074 xfree(msg); 1075 break; 1076 default: 1077 if (type) 1078 DBG(debug("received packet type %d", type)); 1079 return type; 1080 break; 1081 } 1082 } 1083 } 1084 } 1085 1086 int 1087 packet_read_poll(void) 1088 { 1089 return packet_read_poll_seqnr(NULL); 1090 } 1091 1092 /* 1093 * Buffers the given amount of input characters. This is intended to be used 1094 * together with packet_read_poll. 1095 */ 1096 1097 void 1098 packet_process_incoming(const char *buf, u_int len) 1099 { 1100 buffer_append(&input, buf, len); 1101 } 1102 1103 /* Returns a character from the packet. */ 1104 1105 u_int 1106 packet_get_char(void) 1107 { 1108 char ch; 1109 1110 buffer_get(&incoming_packet, &ch, 1); 1111 return (u_char) ch; 1112 } 1113 1114 /* Returns an integer from the packet data. */ 1115 1116 u_int 1117 packet_get_int(void) 1118 { 1119 return buffer_get_int(&incoming_packet); 1120 } 1121 1122 /* 1123 * Returns an arbitrary precision integer from the packet data. The integer 1124 * must have been initialized before this call. 1125 */ 1126 1127 void 1128 packet_get_bignum(BIGNUM * value) 1129 { 1130 buffer_get_bignum(&incoming_packet, value); 1131 } 1132 1133 void 1134 packet_get_bignum2(BIGNUM * value) 1135 { 1136 buffer_get_bignum2(&incoming_packet, value); 1137 } 1138 1139 void * 1140 packet_get_raw(int *length_ptr) 1141 { 1142 int bytes = buffer_len(&incoming_packet); 1143 1144 if (length_ptr != NULL) 1145 *length_ptr = bytes; 1146 return buffer_ptr(&incoming_packet); 1147 } 1148 1149 int 1150 packet_remaining(void) 1151 { 1152 return buffer_len(&incoming_packet); 1153 } 1154 1155 /* 1156 * Returns a string from the packet data. The string is allocated using 1157 * xmalloc; it is the responsibility of the calling program to free it when 1158 * no longer needed. The length_ptr argument may be NULL, or point to an 1159 * integer into which the length of the string is stored. 1160 */ 1161 1162 void * 1163 packet_get_string(u_int *length_ptr) 1164 { 1165 return buffer_get_string(&incoming_packet, length_ptr); 1166 } 1167 1168 /* 1169 * Sends a diagnostic message from the server to the client. This message 1170 * can be sent at any time (but not while constructing another message). The 1171 * message is printed immediately, but only if the client is being executed 1172 * in verbose mode. These messages are primarily intended to ease debugging 1173 * authentication problems. The length of the formatted message must not 1174 * exceed 1024 bytes. This will automatically call packet_write_wait. 1175 */ 1176 1177 void 1178 packet_send_debug(const char *fmt,...) 1179 { 1180 char buf[1024]; 1181 va_list args; 1182 1183 if (compat20 && (datafellows & SSH_BUG_DEBUG)) 1184 return; 1185 1186 va_start(args, fmt); 1187 vsnprintf(buf, sizeof(buf), fmt, args); 1188 va_end(args); 1189 1190 if (compat20) { 1191 packet_start(SSH2_MSG_DEBUG); 1192 packet_put_char(0); /* bool: always display */ 1193 packet_put_cstring(buf); 1194 packet_put_cstring(""); 1195 } else { 1196 packet_start(SSH_MSG_DEBUG); 1197 packet_put_cstring(buf); 1198 } 1199 packet_send(); 1200 packet_write_wait(); 1201 } 1202 1203 /* 1204 * Logs the error plus constructs and sends a disconnect packet, closes the 1205 * connection, and exits. This function never returns. The error message 1206 * should not contain a newline. The length of the formatted message must 1207 * not exceed 1024 bytes. 1208 */ 1209 1210 void 1211 packet_disconnect(const char *fmt,...) 1212 { 1213 char buf[1024]; 1214 va_list args; 1215 static int disconnecting = 0; 1216 1217 if (disconnecting) /* Guard against recursive invocations. */ 1218 fatal("packet_disconnect called recursively."); 1219 disconnecting = 1; 1220 1221 /* 1222 * Format the message. Note that the caller must make sure the 1223 * message is of limited size. 1224 */ 1225 va_start(args, fmt); 1226 vsnprintf(buf, sizeof(buf), fmt, args); 1227 va_end(args); 1228 1229 /* Send the disconnect message to the other side, and wait for it to get sent. */ 1230 if (compat20) { 1231 packet_start(SSH2_MSG_DISCONNECT); 1232 packet_put_int(SSH2_DISCONNECT_PROTOCOL_ERROR); 1233 packet_put_cstring(buf); 1234 packet_put_cstring(""); 1235 } else { 1236 packet_start(SSH_MSG_DISCONNECT); 1237 packet_put_cstring(buf); 1238 } 1239 packet_send(); 1240 packet_write_wait(); 1241 1242 /* Stop listening for connections. */ 1243 channel_close_all(); 1244 1245 /* Close the connection. */ 1246 packet_close(); 1247 1248 /* Display the error locally and exit. */ 1249 log("Disconnecting: %.100s", buf); 1250 fatal_cleanup(); 1251 } 1252 1253 /* Checks if there is any buffered output, and tries to write some of the output. */ 1254 1255 void 1256 packet_write_poll(void) 1257 { 1258 int len = buffer_len(&output); 1259 1260 if (len > 0) { 1261 len = write(connection_out, buffer_ptr(&output), len); 1262 if (len <= 0) { 1263 if (errno == EAGAIN) 1264 return; 1265 else 1266 fatal("Write failed: %.100s", strerror(errno)); 1267 } 1268 buffer_consume(&output, len); 1269 } 1270 } 1271 1272 /* 1273 * Calls packet_write_poll repeatedly until all pending output data has been 1274 * written. 1275 */ 1276 1277 void 1278 packet_write_wait(void) 1279 { 1280 fd_set *setp; 1281 1282 setp = (fd_set *)xmalloc(howmany(connection_out + 1, NFDBITS) * 1283 sizeof(fd_mask)); 1284 packet_write_poll(); 1285 while (packet_have_data_to_write()) { 1286 memset(setp, 0, howmany(connection_out + 1, NFDBITS) * 1287 sizeof(fd_mask)); 1288 FD_SET(connection_out, setp); 1289 while (select(connection_out + 1, NULL, setp, NULL, NULL) == -1 && 1290 (errno == EAGAIN || errno == EINTR)) 1291 ; 1292 packet_write_poll(); 1293 } 1294 xfree(setp); 1295 } 1296 1297 /* Returns true if there is buffered data to write to the connection. */ 1298 1299 int 1300 packet_have_data_to_write(void) 1301 { 1302 return buffer_len(&output) != 0; 1303 } 1304 1305 /* Returns true if there is not too much data to write to the connection. */ 1306 1307 int 1308 packet_not_very_much_data_to_write(void) 1309 { 1310 if (interactive_mode) 1311 return buffer_len(&output) < 16384; 1312 else 1313 return buffer_len(&output) < 128 * 1024; 1314 } 1315 1316 /* Informs that the current session is interactive. Sets IP flags for that. */ 1317 1318 void 1319 packet_set_interactive(int interactive) 1320 { 1321 static int called = 0; 1322 #if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN) 1323 int lowdelay = IPTOS_LOWDELAY; 1324 int throughput = IPTOS_THROUGHPUT; 1325 #endif 1326 1327 if (called) 1328 return; 1329 called = 1; 1330 1331 /* Record that we are in interactive mode. */ 1332 interactive_mode = interactive; 1333 1334 /* Only set socket options if using a socket. */ 1335 if (!packet_connection_is_on_socket()) 1336 return; 1337 /* 1338 * IPTOS_LOWDELAY and IPTOS_THROUGHPUT are IPv4 only 1339 */ 1340 if (interactive) { 1341 /* 1342 * Set IP options for an interactive connection. Use 1343 * IPTOS_LOWDELAY and TCP_NODELAY. 1344 */ 1345 #if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN) 1346 if (packet_connection_is_ipv4()) { 1347 if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, 1348 &lowdelay, sizeof(lowdelay)) < 0) 1349 error("setsockopt IPTOS_LOWDELAY: %.100s", 1350 strerror(errno)); 1351 } 1352 #endif 1353 set_nodelay(connection_in); 1354 } else if (packet_connection_is_ipv4()) { 1355 /* 1356 * Set IP options for a non-interactive connection. Use 1357 * IPTOS_THROUGHPUT. 1358 */ 1359 #if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN) 1360 if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, &throughput, 1361 sizeof(throughput)) < 0) 1362 error("setsockopt IPTOS_THROUGHPUT: %.100s", strerror(errno)); 1363 #endif 1364 } 1365 } 1366 1367 /* Returns true if the current connection is interactive. */ 1368 1369 int 1370 packet_is_interactive(void) 1371 { 1372 return interactive_mode; 1373 } 1374 1375 int 1376 packet_set_maxsize(int s) 1377 { 1378 static int called = 0; 1379 1380 if (called) { 1381 log("packet_set_maxsize: called twice: old %d new %d", 1382 max_packet_size, s); 1383 return -1; 1384 } 1385 if (s < 4 * 1024 || s > 1024 * 1024) { 1386 log("packet_set_maxsize: bad size %d", s); 1387 return -1; 1388 } 1389 called = 1; 1390 debug("packet_set_maxsize: setting to %d", s); 1391 max_packet_size = s; 1392 return s; 1393 } 1394 1395 /* roundup current message to pad bytes */ 1396 void 1397 packet_add_padding(u_char pad) 1398 { 1399 extra_pad = pad; 1400 } 1401 1402 /* 1403 * 9.2. Ignored Data Message 1404 * 1405 * byte SSH_MSG_IGNORE 1406 * string data 1407 * 1408 * All implementations MUST understand (and ignore) this message at any 1409 * time (after receiving the protocol version). No implementation is 1410 * required to send them. This message can be used as an additional 1411 * protection measure against advanced traffic analysis techniques. 1412 */ 1413 void 1414 packet_send_ignore(int nbytes) 1415 { 1416 u_int32_t rand = 0; 1417 int i; 1418 1419 packet_start(compat20 ? SSH2_MSG_IGNORE : SSH_MSG_IGNORE); 1420 packet_put_int(nbytes); 1421 for (i = 0; i < nbytes; i++) { 1422 if (i % 4 == 0) 1423 rand = arc4random(); 1424 packet_put_char(rand & 0xff); 1425 rand >>= 8; 1426 } 1427 } 1428