1 /* $NetBSD: print-tcp.c,v 1.9 2007/07/26 18:15:12 plunky Exp $ */ 2 3 /* 4 * Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Copyright (c) 1999-2004 The tcpdump.org project 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that: (1) source code distributions 11 * retain the above copyright notice and this paragraph in its entirety, (2) 12 * distributions including binary code include the above copyright notice and 13 * this paragraph in its entirety in the documentation or other materials 14 * provided with the distribution, and (3) all advertising materials mentioning 15 * features or use of this software display the following acknowledgement: 16 * ``This product includes software developed by the University of California, 17 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of 18 * the University nor the names of its contributors may be used to endorse 19 * or promote products derived from this software without specific prior 20 * written permission. 21 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED 22 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF 23 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. 24 */ 25 26 #ifndef lint 27 static const char rcsid[] _U_ = 28 "@(#) $Header: /tcpdump/master/tcpdump/print-tcp.c,v 1.135 2008-11-09 23:35:03 mcr Exp $ (LBL)"; 29 #else 30 __RCSID("$NetBSD: print-tcp.c,v 1.8 2007/07/24 11:53:48 drochner Exp $"); 31 #endif 32 33 #ifdef HAVE_CONFIG_H 34 #include "config.h" 35 #endif 36 37 #include <tcpdump-stdinc.h> 38 39 #include <stdio.h> 40 #include <stdlib.h> 41 #include <string.h> 42 43 #include "interface.h" 44 #include "addrtoname.h" 45 #include "extract.h" 46 47 #include "tcp.h" 48 49 #include "ip.h" 50 #ifdef INET6 51 #include "ip6.h" 52 #endif 53 #include "ipproto.h" 54 #include "rpc_auth.h" 55 #include "rpc_msg.h" 56 57 #include "nameser.h" 58 59 #ifdef HAVE_LIBCRYPTO 60 #include <openssl/md5.h> 61 #include <signature.h> 62 63 static int tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp, 64 const u_char *data, int length, const u_char *rcvsig); 65 #endif 66 67 static void print_tcp_rst_data(register const u_char *sp, u_int length); 68 69 #define MAX_RST_DATA_LEN 30 70 71 72 struct tha { 73 #ifndef INET6 74 struct in_addr src; 75 struct in_addr dst; 76 #else 77 struct in6_addr src; 78 struct in6_addr dst; 79 #endif /*INET6*/ 80 u_int port; 81 }; 82 83 struct tcp_seq_hash { 84 struct tcp_seq_hash *nxt; 85 struct tha addr; 86 tcp_seq seq; 87 tcp_seq ack; 88 }; 89 90 #define TSEQ_HASHSIZE 919 91 92 /* These tcp optinos do not have the size octet */ 93 #define ZEROLENOPT(o) ((o) == TCPOPT_EOL || (o) == TCPOPT_NOP) 94 95 static struct tcp_seq_hash tcp_seq_hash[TSEQ_HASHSIZE]; 96 97 struct tok tcp_flag_values[] = { 98 { TH_FIN, "F" }, 99 { TH_SYN, "S" }, 100 { TH_RST, "R" }, 101 { TH_PUSH, "P" }, 102 { TH_ACK, "." }, 103 { TH_URG, "U" }, 104 { TH_ECNECHO, "E" }, 105 { TH_CWR, "W" }, 106 { 0, NULL } 107 }; 108 109 struct tok tcp_option_values[] = { 110 { TCPOPT_EOL, "eol" }, 111 { TCPOPT_NOP, "nop" }, 112 { TCPOPT_MAXSEG, "mss" }, 113 { TCPOPT_WSCALE, "wscale" }, 114 { TCPOPT_SACKOK, "sackOK" }, 115 { TCPOPT_SACK, "sack" }, 116 { TCPOPT_ECHO, "echo" }, 117 { TCPOPT_ECHOREPLY, "echoreply" }, 118 { TCPOPT_TIMESTAMP, "TS" }, 119 { TCPOPT_CC, "cc" }, 120 { TCPOPT_CCNEW, "ccnew" }, 121 { TCPOPT_CCECHO, "" }, 122 { TCPOPT_SIGNATURE, "md5" }, 123 { TCPOPT_AUTH, "enhanced auth" }, 124 { TCPOPT_UTO, "uto" }, 125 { 0, NULL } 126 }; 127 128 static int tcp_cksum(register const struct ip *ip, 129 register const struct tcphdr *tp, 130 register u_int len) 131 { 132 union phu { 133 struct phdr { 134 u_int32_t src; 135 u_int32_t dst; 136 u_char mbz; 137 u_char proto; 138 u_int16_t len; 139 } ph; 140 u_int16_t pa[6]; 141 } phu; 142 const u_int16_t *sp; 143 144 /* pseudo-header.. */ 145 phu.ph.len = htons((u_int16_t)len); 146 phu.ph.mbz = 0; 147 phu.ph.proto = IPPROTO_TCP; 148 memcpy(&phu.ph.src, &ip->ip_src.s_addr, sizeof(u_int32_t)); 149 if (IP_HL(ip) == 5) 150 memcpy(&phu.ph.dst, &ip->ip_dst.s_addr, sizeof(u_int32_t)); 151 else 152 phu.ph.dst = ip_finddst(ip); 153 154 sp = &phu.pa[0]; 155 return in_cksum((u_short *)tp, len, 156 sp[0]+sp[1]+sp[2]+sp[3]+sp[4]+sp[5]); 157 } 158 159 void 160 tcp_print(register const u_char *bp, register u_int length, 161 register const u_char *bp2, int fragmented) 162 { 163 register const struct tcphdr *tp; 164 register const struct ip *ip; 165 register u_char flags; 166 register u_int hlen; 167 register char ch; 168 u_int16_t sport, dport, win, urp; 169 u_int32_t seq, ack, thseq, thack; 170 u_int utoval; 171 int threv; 172 #ifdef INET6 173 register const struct ip6_hdr *ip6; 174 #endif 175 176 tp = (struct tcphdr *)bp; 177 ip = (struct ip *)bp2; 178 #ifdef INET6 179 if (IP_V(ip) == 6) 180 ip6 = (struct ip6_hdr *)bp2; 181 else 182 ip6 = NULL; 183 #endif /*INET6*/ 184 ch = '\0'; 185 if (!TTEST(tp->th_dport)) { 186 (void)printf("%s > %s: [|tcp]", 187 ipaddr_string(&ip->ip_src), 188 ipaddr_string(&ip->ip_dst)); 189 return; 190 } 191 192 sport = EXTRACT_16BITS(&tp->th_sport); 193 dport = EXTRACT_16BITS(&tp->th_dport); 194 195 hlen = TH_OFF(tp) * 4; 196 197 /* 198 * If data present, header length valid, and NFS port used, 199 * assume NFS. 200 * Pass offset of data plus 4 bytes for RPC TCP msg length 201 * to NFS print routines. 202 */ 203 if (!qflag && hlen >= sizeof(*tp) && hlen <= length && 204 (length - hlen) >= 4) { 205 u_char *fraglenp; 206 u_int32_t fraglen; 207 register struct sunrpc_msg *rp; 208 enum sunrpc_msg_type direction; 209 210 fraglenp = (u_char *)tp + hlen; 211 if (TTEST2(*fraglenp, 4)) { 212 fraglen = EXTRACT_32BITS(fraglenp) & 0x7FFFFFFF; 213 if (fraglen > (length - hlen) - 4) 214 fraglen = (length - hlen) - 4; 215 rp = (struct sunrpc_msg *)(fraglenp + 4); 216 if (TTEST(rp->rm_direction)) { 217 direction = (enum sunrpc_msg_type)EXTRACT_32BITS(&rp->rm_direction); 218 if (dport == NFS_PORT && 219 direction == SUNRPC_CALL) { 220 nfsreq_print((u_char *)rp, fraglen, 221 (u_char *)ip); 222 return; 223 } 224 if (sport == NFS_PORT && 225 direction == SUNRPC_REPLY) { 226 nfsreply_print((u_char *)rp, fraglen, 227 (u_char *)ip); 228 return; 229 } 230 } 231 } 232 } 233 #ifdef INET6 234 if (ip6) { 235 if (ip6->ip6_nxt == IPPROTO_TCP) { 236 (void)printf("%s.%s > %s.%s: ", 237 ip6addr_string(&ip6->ip6_src), 238 tcpport_string(sport), 239 ip6addr_string(&ip6->ip6_dst), 240 tcpport_string(dport)); 241 } else { 242 (void)printf("%s > %s: ", 243 tcpport_string(sport), tcpport_string(dport)); 244 } 245 } else 246 #endif /*INET6*/ 247 { 248 if (ip->ip_p == IPPROTO_TCP) { 249 (void)printf("%s.%s > %s.%s: ", 250 ipaddr_string(&ip->ip_src), 251 tcpport_string(sport), 252 ipaddr_string(&ip->ip_dst), 253 tcpport_string(dport)); 254 } else { 255 (void)printf("%s > %s: ", 256 tcpport_string(sport), tcpport_string(dport)); 257 } 258 } 259 260 if (hlen < sizeof(*tp)) { 261 (void)printf(" tcp %d [bad hdr length %u - too short, < %lu]", 262 length - hlen, hlen, (unsigned long)sizeof(*tp)); 263 return; 264 } 265 266 TCHECK(*tp); 267 268 seq = EXTRACT_32BITS(&tp->th_seq); 269 ack = EXTRACT_32BITS(&tp->th_ack); 270 win = EXTRACT_16BITS(&tp->th_win); 271 urp = EXTRACT_16BITS(&tp->th_urp); 272 273 if (qflag) { 274 (void)printf("tcp %d", length - hlen); 275 if (hlen > length) { 276 (void)printf(" [bad hdr length %u - too long, > %u]", 277 hlen, length); 278 } 279 return; 280 } 281 282 flags = tp->th_flags; 283 printf("Flags [%s]", bittok2str_nosep(tcp_flag_values, "none", flags)); 284 285 if (!Sflag && (flags & TH_ACK)) { 286 register struct tcp_seq_hash *th; 287 const void *src, *dst; 288 register int rev; 289 struct tha tha; 290 /* 291 * Find (or record) the initial sequence numbers for 292 * this conversation. (we pick an arbitrary 293 * collating order so there's only one entry for 294 * both directions). 295 */ 296 #ifdef INET6 297 memset(&tha, 0, sizeof(tha)); 298 rev = 0; 299 if (ip6) { 300 src = &ip6->ip6_src; 301 dst = &ip6->ip6_dst; 302 if (sport > dport) 303 rev = 1; 304 else if (sport == dport) { 305 if (memcmp(src, dst, sizeof ip6->ip6_dst) > 0) 306 rev = 1; 307 } 308 if (rev) { 309 memcpy(&tha.src, dst, sizeof ip6->ip6_dst); 310 memcpy(&tha.dst, src, sizeof ip6->ip6_src); 311 tha.port = dport << 16 | sport; 312 } else { 313 memcpy(&tha.dst, dst, sizeof ip6->ip6_dst); 314 memcpy(&tha.src, src, sizeof ip6->ip6_src); 315 tha.port = sport << 16 | dport; 316 } 317 } else { 318 src = &ip->ip_src; 319 dst = &ip->ip_dst; 320 if (sport > dport) 321 rev = 1; 322 else if (sport == dport) { 323 if (memcmp(src, dst, sizeof ip->ip_dst) > 0) 324 rev = 1; 325 } 326 if (rev) { 327 memcpy(&tha.src, dst, sizeof ip->ip_dst); 328 memcpy(&tha.dst, src, sizeof ip->ip_src); 329 tha.port = dport << 16 | sport; 330 } else { 331 memcpy(&tha.dst, dst, sizeof ip->ip_dst); 332 memcpy(&tha.src, src, sizeof ip->ip_src); 333 tha.port = sport << 16 | dport; 334 } 335 } 336 #else 337 rev = 0; 338 src = &ip->ip_src; 339 dst = &ip->ip_dst; 340 if (sport > dport) 341 rev = 1; 342 else if (sport == dport) { 343 if (memcmp(src, dst, sizeof ip->ip_dst) > 0) 344 rev = 1; 345 } 346 if (rev) { 347 memcpy(&tha.src, dst, sizeof ip->ip_dst); 348 memcpy(&tha.dst, src, sizeof ip->ip_src); 349 tha.port = dport << 16 | sport; 350 } else { 351 memcpy(&tha.dst, dst, sizeof ip->ip_dst); 352 memcpy(&tha.src, src, sizeof ip->ip_src); 353 tha.port = sport << 16 | dport; 354 } 355 #endif 356 357 threv = rev; 358 for (th = &tcp_seq_hash[tha.port % TSEQ_HASHSIZE]; 359 th->nxt; th = th->nxt) 360 if (memcmp((char *)&tha, (char *)&th->addr, 361 sizeof(th->addr)) == 0) 362 break; 363 364 if (!th->nxt || (flags & TH_SYN)) { 365 /* didn't find it or new conversation */ 366 if (th->nxt == NULL) { 367 th->nxt = (struct tcp_seq_hash *) 368 calloc(1, sizeof(*th)); 369 if (th->nxt == NULL) 370 error("tcp_print: calloc"); 371 } 372 th->addr = tha; 373 if (rev) 374 th->ack = seq, th->seq = ack - 1; 375 else 376 th->seq = seq, th->ack = ack - 1; 377 } else { 378 if (rev) 379 seq -= th->ack, ack -= th->seq; 380 else 381 seq -= th->seq, ack -= th->ack; 382 } 383 384 thseq = th->seq; 385 thack = th->ack; 386 } else { 387 /*fool gcc*/ 388 thseq = thack = threv = 0; 389 } 390 if (hlen > length) { 391 (void)printf(" [bad hdr length %u - too long, > %u]", 392 hlen, length); 393 return; 394 } 395 396 if (IP_V(ip) == 4 && vflag && !Kflag && !fragmented) { 397 u_int16_t sum, tcp_sum; 398 if (TTEST2(tp->th_sport, length)) { 399 sum = tcp_cksum(ip, tp, length); 400 401 (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum)); 402 if (sum != 0) { 403 tcp_sum = EXTRACT_16BITS(&tp->th_sum); 404 (void)printf(" (incorrect -> 0x%04x)",in_cksum_shouldbe(tcp_sum, sum)); 405 } else 406 (void)printf(" (correct)"); 407 } 408 } 409 #ifdef INET6 410 if (IP_V(ip) == 6 && ip6->ip6_plen && vflag && !Kflag && !fragmented) { 411 u_int16_t sum,tcp_sum; 412 if (TTEST2(tp->th_sport, length)) { 413 sum = nextproto6_cksum(ip6, (u_short *)tp, length, IPPROTO_TCP); 414 (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum)); 415 if (sum != 0) { 416 tcp_sum = EXTRACT_16BITS(&tp->th_sum); 417 (void)printf(" (incorrect -> 0x%04x)",in_cksum_shouldbe(tcp_sum, sum)); 418 } else 419 (void)printf(" (correct)"); 420 421 } 422 } 423 #endif 424 425 length -= hlen; 426 if (vflag > 1 || length > 0 || flags & (TH_SYN | TH_FIN | TH_RST)) { 427 (void)printf(", seq %u", seq); 428 429 if (length > 0) { 430 (void)printf(":%u", seq + length); 431 } 432 } 433 434 if (flags & TH_ACK) { 435 (void)printf(", ack %u", ack); 436 } 437 438 (void)printf(", win %d", win); 439 440 if (flags & TH_URG) 441 (void)printf(", urg %d", urp); 442 /* 443 * Handle any options. 444 */ 445 if (hlen > sizeof(*tp)) { 446 register const u_char *cp; 447 register u_int i, opt, datalen; 448 register u_int len; 449 450 hlen -= sizeof(*tp); 451 cp = (const u_char *)tp + sizeof(*tp); 452 printf(", options ["); 453 while (hlen > 0) { 454 if (ch != '\0') 455 putchar(ch); 456 TCHECK(*cp); 457 opt = *cp++; 458 if (ZEROLENOPT(opt)) 459 len = 1; 460 else { 461 TCHECK(*cp); 462 len = *cp++; /* total including type, len */ 463 if (len < 2 || len > hlen) 464 goto bad; 465 --hlen; /* account for length byte */ 466 } 467 --hlen; /* account for type byte */ 468 datalen = 0; 469 470 /* Bail if "l" bytes of data are not left or were not captured */ 471 #define LENCHECK(l) { if ((l) > hlen) goto bad; TCHECK2(*cp, l); } 472 473 474 printf("%s", tok2str(tcp_option_values, "Unknown Option %u", opt)); 475 476 switch (opt) { 477 478 case TCPOPT_MAXSEG: 479 datalen = 2; 480 LENCHECK(datalen); 481 (void)printf(" %u", EXTRACT_16BITS(cp)); 482 break; 483 484 case TCPOPT_WSCALE: 485 datalen = 1; 486 LENCHECK(datalen); 487 (void)printf(" %u", *cp); 488 break; 489 490 case TCPOPT_SACK: 491 datalen = len - 2; 492 if (datalen % 8 != 0) { 493 (void)printf("malformed sack"); 494 } else { 495 u_int32_t s, e; 496 497 (void)printf(" %d ", datalen / 8); 498 for (i = 0; i < datalen; i += 8) { 499 LENCHECK(i + 4); 500 s = EXTRACT_32BITS(cp + i); 501 LENCHECK(i + 8); 502 e = EXTRACT_32BITS(cp + i + 4); 503 if (threv) { 504 s -= thseq; 505 e -= thseq; 506 } else { 507 s -= thack; 508 e -= thack; 509 } 510 (void)printf("{%u:%u}", s, e); 511 } 512 } 513 break; 514 515 case TCPOPT_CC: 516 case TCPOPT_CCNEW: 517 case TCPOPT_CCECHO: 518 case TCPOPT_ECHO: 519 case TCPOPT_ECHOREPLY: 520 521 /* 522 * those options share their semantics. 523 * fall through 524 */ 525 datalen = 4; 526 LENCHECK(datalen); 527 (void)printf(" %u", EXTRACT_32BITS(cp)); 528 break; 529 530 case TCPOPT_TIMESTAMP: 531 datalen = 8; 532 LENCHECK(datalen); 533 (void)printf(" val %u ecr %u", 534 EXTRACT_32BITS(cp), 535 EXTRACT_32BITS(cp + 4)); 536 break; 537 538 case TCPOPT_SIGNATURE: 539 datalen = TCP_SIGLEN; 540 LENCHECK(datalen); 541 #ifdef HAVE_LIBCRYPTO 542 switch (tcp_verify_signature(ip, tp, 543 bp + TH_OFF(tp) * 4, length, cp)) { 544 545 case SIGNATURE_VALID: 546 (void)printf("valid"); 547 break; 548 549 case SIGNATURE_INVALID: 550 (void)printf("invalid"); 551 break; 552 553 case CANT_CHECK_SIGNATURE: 554 (void)printf("can't check - "); 555 for (i = 0; i < TCP_SIGLEN; ++i) 556 (void)printf("%02x", cp[i]); 557 break; 558 } 559 #else 560 for (i = 0; i < TCP_SIGLEN; ++i) 561 (void)printf("%02x", cp[i]); 562 #endif 563 break; 564 565 case TCPOPT_AUTH: 566 (void)printf("keyid %d", *cp++); 567 datalen = len - 3; 568 for (i = 0; i < datalen; ++i) { 569 LENCHECK(i); 570 (void)printf("%02x", cp[i]); 571 } 572 break; 573 574 575 case TCPOPT_EOL: 576 case TCPOPT_NOP: 577 case TCPOPT_SACKOK: 578 /* 579 * Nothing interesting. 580 * fall through 581 */ 582 break; 583 584 case TCPOPT_UTO: 585 datalen = 2; 586 LENCHECK(datalen); 587 utoval = EXTRACT_16BITS(cp); 588 (void)printf("0x%x", utoval); 589 if (utoval & 0x0001) 590 utoval = (utoval >> 1) * 60; 591 else 592 utoval >>= 1; 593 (void)printf(" %u", utoval); 594 break; 595 596 default: 597 datalen = len - 2; 598 for (i = 0; i < datalen; ++i) { 599 LENCHECK(i); 600 (void)printf("%02x", cp[i]); 601 } 602 break; 603 } 604 605 /* Account for data printed */ 606 cp += datalen; 607 hlen -= datalen; 608 609 /* Check specification against observed length */ 610 ++datalen; /* option octet */ 611 if (!ZEROLENOPT(opt)) 612 ++datalen; /* size octet */ 613 if (datalen != len) 614 (void)printf("[len %d]", len); 615 ch = ','; 616 if (opt == TCPOPT_EOL) 617 break; 618 } 619 putchar(']'); 620 } 621 622 /* 623 * Print length field before crawling down the stack. 624 */ 625 printf(", length %u", length); 626 627 if (length <= 0) 628 return; 629 630 /* 631 * Decode payload if necessary. 632 */ 633 bp += TH_OFF(tp) * 4; 634 if ((flags & TH_RST) && vflag) { 635 print_tcp_rst_data(bp, length); 636 return; 637 } 638 639 if (sport == TELNET_PORT || dport == TELNET_PORT) { 640 if (!qflag && vflag) 641 telnet_print(bp, length); 642 } else if (sport == BGP_PORT || dport == BGP_PORT) 643 bgp_print(bp, length); 644 else if (sport == PPTP_PORT || dport == PPTP_PORT) 645 pptp_print(bp); 646 #ifdef TCPDUMP_DO_SMB 647 else if (sport == NETBIOS_SSN_PORT || dport == NETBIOS_SSN_PORT) 648 nbt_tcp_print(bp, length); 649 else if (sport == SMB_PORT || dport == SMB_PORT) 650 smb_tcp_print(bp, length); 651 #endif 652 else if (sport == BEEP_PORT || dport == BEEP_PORT) 653 beep_print(bp, length); 654 else if (length > 2 && 655 (sport == NAMESERVER_PORT || dport == NAMESERVER_PORT || 656 sport == MULTICASTDNS_PORT || dport == MULTICASTDNS_PORT)) { 657 /* 658 * TCP DNS query has 2byte length at the head. 659 * XXX packet could be unaligned, it can go strange 660 */ 661 ns_print(bp + 2, length - 2, 0); 662 } else if (sport == MSDP_PORT || dport == MSDP_PORT) { 663 msdp_print(bp, length); 664 } 665 else if (length > 0 && (sport == LDP_PORT || dport == LDP_PORT)) { 666 ldp_print(bp, length); 667 } 668 669 return; 670 bad: 671 fputs("[bad opt]", stdout); 672 if (ch != '\0') 673 putchar('>'); 674 return; 675 trunc: 676 fputs("[|tcp]", stdout); 677 if (ch != '\0') 678 putchar('>'); 679 } 680 681 /* 682 * RFC1122 says the following on data in RST segments: 683 * 684 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 685 * 686 * A TCP SHOULD allow a received RST segment to include data. 687 * 688 * DISCUSSION 689 * It has been suggested that a RST segment could contain 690 * ASCII text that encoded and explained the cause of the 691 * RST. No standard has yet been established for such 692 * data. 693 * 694 */ 695 696 static void 697 print_tcp_rst_data(register const u_char *sp, u_int length) 698 { 699 int c; 700 701 if (TTEST2(*sp, length)) 702 printf(" [RST"); 703 else 704 printf(" [!RST"); 705 if (length > MAX_RST_DATA_LEN) { 706 length = MAX_RST_DATA_LEN; /* can use -X for longer */ 707 putchar('+'); /* indicate we truncate */ 708 } 709 putchar(' '); 710 while (length-- && sp <= snapend) { 711 c = *sp++; 712 safeputchar(c); 713 } 714 putchar(']'); 715 } 716 717 #ifdef HAVE_LIBCRYPTO 718 static int 719 tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp, 720 const u_char *data, int length, const u_char *rcvsig) 721 { 722 struct tcphdr tp1; 723 u_char sig[TCP_SIGLEN]; 724 char zero_proto = 0; 725 MD5_CTX ctx; 726 u_int16_t savecsum, tlen; 727 #ifdef INET6 728 struct ip6_hdr *ip6; 729 u_int32_t len32; 730 u_int8_t nxt; 731 #endif 732 733 if (data + length > snapend) { 734 printf("snaplen too short, "); 735 return (CANT_CHECK_SIGNATURE); 736 } 737 738 tp1 = *tp; 739 740 if (sigsecret == NULL) { 741 printf("shared secret not supplied with -M, "); 742 return (CANT_CHECK_SIGNATURE); 743 } 744 745 MD5_Init(&ctx); 746 /* 747 * Step 1: Update MD5 hash with IP pseudo-header. 748 */ 749 if (IP_V(ip) == 4) { 750 MD5_Update(&ctx, (char *)&ip->ip_src, sizeof(ip->ip_src)); 751 MD5_Update(&ctx, (char *)&ip->ip_dst, sizeof(ip->ip_dst)); 752 MD5_Update(&ctx, (char *)&zero_proto, sizeof(zero_proto)); 753 MD5_Update(&ctx, (char *)&ip->ip_p, sizeof(ip->ip_p)); 754 tlen = EXTRACT_16BITS(&ip->ip_len) - IP_HL(ip) * 4; 755 tlen = htons(tlen); 756 MD5_Update(&ctx, (char *)&tlen, sizeof(tlen)); 757 #ifdef INET6 758 } else if (IP_V(ip) == 6) { 759 ip6 = (struct ip6_hdr *)ip; 760 MD5_Update(&ctx, (char *)&ip6->ip6_src, sizeof(ip6->ip6_src)); 761 MD5_Update(&ctx, (char *)&ip6->ip6_dst, sizeof(ip6->ip6_dst)); 762 len32 = htonl(EXTRACT_16BITS(&ip6->ip6_plen)); 763 MD5_Update(&ctx, (char *)&len32, sizeof(len32)); 764 nxt = 0; 765 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt)); 766 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt)); 767 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt)); 768 nxt = IPPROTO_TCP; 769 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt)); 770 #endif 771 } else { 772 #ifdef INET6 773 printf("IP version not 4 or 6, "); 774 #else 775 printf("IP version not 4, "); 776 #endif 777 return (CANT_CHECK_SIGNATURE); 778 } 779 780 /* 781 * Step 2: Update MD5 hash with TCP header, excluding options. 782 * The TCP checksum must be set to zero. 783 */ 784 savecsum = tp1.th_sum; 785 tp1.th_sum = 0; 786 MD5_Update(&ctx, (char *)&tp1, sizeof(struct tcphdr)); 787 tp1.th_sum = savecsum; 788 /* 789 * Step 3: Update MD5 hash with TCP segment data, if present. 790 */ 791 if (length > 0) 792 MD5_Update(&ctx, data, length); 793 /* 794 * Step 4: Update MD5 hash with shared secret. 795 */ 796 MD5_Update(&ctx, sigsecret, strlen(sigsecret)); 797 MD5_Final(sig, &ctx); 798 799 if (memcmp(rcvsig, sig, TCP_SIGLEN) == 0) 800 return (SIGNATURE_VALID); 801 else 802 return (SIGNATURE_INVALID); 803 } 804 #endif /* HAVE_LIBCRYPTO */ 805 806 /* 807 * Local Variables: 808 * c-style: whitesmith 809 * c-basic-offset: 8 810 * End: 811 */ 812