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 #include <sys/cdefs.h> 27 #ifndef lint 28 #if 0 29 static const char rcsid[] _U_ = 30 "@(#) Header: /tcpdump/master/tcpdump/print-tcp.c,v 1.135 2008-11-09 23:35:03 mcr Exp (LBL)"; 31 #else 32 __RCSID("$NetBSD: print-tcp.c,v 1.2 2010/12/05 05:11:31 christos Exp $"); 33 #endif 34 #endif 35 36 #ifdef HAVE_CONFIG_H 37 #include "config.h" 38 #endif 39 40 #include <tcpdump-stdinc.h> 41 42 #include <stdio.h> 43 #include <stdlib.h> 44 #include <string.h> 45 46 #include "interface.h" 47 #include "addrtoname.h" 48 #include "extract.h" 49 50 #include "tcp.h" 51 52 #include "ip.h" 53 #ifdef INET6 54 #include "ip6.h" 55 #endif 56 #include "ipproto.h" 57 #include "rpc_auth.h" 58 #include "rpc_msg.h" 59 60 #include "nameser.h" 61 62 #ifdef HAVE_LIBCRYPTO 63 #include <openssl/md5.h> 64 #include <signature.h> 65 66 static int tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp, 67 const u_char *data, int length, const u_char *rcvsig); 68 #endif 69 70 static void print_tcp_rst_data(register const u_char *sp, u_int length); 71 72 #define MAX_RST_DATA_LEN 30 73 74 75 struct tha { 76 #ifndef INET6 77 struct in_addr src; 78 struct in_addr dst; 79 #else 80 struct in6_addr src; 81 struct in6_addr dst; 82 #endif /*INET6*/ 83 u_int port; 84 }; 85 86 struct tcp_seq_hash { 87 struct tcp_seq_hash *nxt; 88 struct tha addr; 89 tcp_seq seq; 90 tcp_seq ack; 91 }; 92 93 #define TSEQ_HASHSIZE 919 94 95 /* These tcp optinos do not have the size octet */ 96 #define ZEROLENOPT(o) ((o) == TCPOPT_EOL || (o) == TCPOPT_NOP) 97 98 static struct tcp_seq_hash tcp_seq_hash[TSEQ_HASHSIZE]; 99 100 struct tok tcp_flag_values[] = { 101 { TH_FIN, "F" }, 102 { TH_SYN, "S" }, 103 { TH_RST, "R" }, 104 { TH_PUSH, "P" }, 105 { TH_ACK, "." }, 106 { TH_URG, "U" }, 107 { TH_ECNECHO, "E" }, 108 { TH_CWR, "W" }, 109 { 0, NULL } 110 }; 111 112 struct tok tcp_option_values[] = { 113 { TCPOPT_EOL, "eol" }, 114 { TCPOPT_NOP, "nop" }, 115 { TCPOPT_MAXSEG, "mss" }, 116 { TCPOPT_WSCALE, "wscale" }, 117 { TCPOPT_SACKOK, "sackOK" }, 118 { TCPOPT_SACK, "sack" }, 119 { TCPOPT_ECHO, "echo" }, 120 { TCPOPT_ECHOREPLY, "echoreply" }, 121 { TCPOPT_TIMESTAMP, "TS" }, 122 { TCPOPT_CC, "cc" }, 123 { TCPOPT_CCNEW, "ccnew" }, 124 { TCPOPT_CCECHO, "" }, 125 { TCPOPT_SIGNATURE, "md5" }, 126 { TCPOPT_AUTH, "enhanced auth" }, 127 { TCPOPT_UTO, "uto" }, 128 { 0, NULL } 129 }; 130 131 static int tcp_cksum(register const struct ip *ip, 132 register const struct tcphdr *tp, 133 register u_int len) 134 { 135 union phu { 136 struct phdr { 137 u_int32_t src; 138 u_int32_t dst; 139 u_char mbz; 140 u_char proto; 141 u_int16_t len; 142 } ph; 143 u_int16_t pa[6]; 144 } phu; 145 const u_int16_t *sp; 146 147 /* pseudo-header.. */ 148 phu.ph.len = htons((u_int16_t)len); 149 phu.ph.mbz = 0; 150 phu.ph.proto = IPPROTO_TCP; 151 memcpy(&phu.ph.src, &ip->ip_src.s_addr, sizeof(u_int32_t)); 152 if (IP_HL(ip) == 5) 153 memcpy(&phu.ph.dst, &ip->ip_dst.s_addr, sizeof(u_int32_t)); 154 else 155 phu.ph.dst = ip_finddst(ip); 156 157 sp = &phu.pa[0]; 158 return in_cksum((u_short *)tp, len, 159 sp[0]+sp[1]+sp[2]+sp[3]+sp[4]+sp[5]); 160 } 161 162 void 163 tcp_print(register const u_char *bp, register u_int length, 164 register const u_char *bp2, int fragmented) 165 { 166 register const struct tcphdr *tp; 167 register const struct ip *ip; 168 register u_char flags; 169 register u_int hlen; 170 register char ch; 171 u_int16_t sport, dport, win, urp; 172 u_int32_t seq, ack, thseq, thack; 173 u_int utoval; 174 int threv; 175 #ifdef INET6 176 register const struct ip6_hdr *ip6; 177 #endif 178 179 tp = (struct tcphdr *)bp; 180 ip = (struct ip *)bp2; 181 #ifdef INET6 182 if (IP_V(ip) == 6) 183 ip6 = (struct ip6_hdr *)bp2; 184 else 185 ip6 = NULL; 186 #endif /*INET6*/ 187 ch = '\0'; 188 if (!TTEST(tp->th_dport)) { 189 (void)printf("%s > %s: [|tcp]", 190 ipaddr_string(&ip->ip_src), 191 ipaddr_string(&ip->ip_dst)); 192 return; 193 } 194 195 sport = EXTRACT_16BITS(&tp->th_sport); 196 dport = EXTRACT_16BITS(&tp->th_dport); 197 198 hlen = TH_OFF(tp) * 4; 199 200 /* 201 * If data present, header length valid, and NFS port used, 202 * assume NFS. 203 * Pass offset of data plus 4 bytes for RPC TCP msg length 204 * to NFS print routines. 205 */ 206 if (!qflag && hlen >= sizeof(*tp) && hlen <= length && 207 (length - hlen) >= 4) { 208 u_char *fraglenp; 209 u_int32_t fraglen; 210 register struct sunrpc_msg *rp; 211 enum sunrpc_msg_type direction; 212 213 fraglenp = (u_char *)tp + hlen; 214 if (TTEST2(*fraglenp, 4)) { 215 fraglen = EXTRACT_32BITS(fraglenp) & 0x7FFFFFFF; 216 if (fraglen > (length - hlen) - 4) 217 fraglen = (length - hlen) - 4; 218 rp = (struct sunrpc_msg *)(fraglenp + 4); 219 if (TTEST(rp->rm_direction)) { 220 direction = (enum sunrpc_msg_type)EXTRACT_32BITS(&rp->rm_direction); 221 if (dport == NFS_PORT && 222 direction == SUNRPC_CALL) { 223 nfsreq_print((u_char *)rp, fraglen, 224 (u_char *)ip); 225 return; 226 } 227 if (sport == NFS_PORT && 228 direction == SUNRPC_REPLY) { 229 nfsreply_print((u_char *)rp, fraglen, 230 (u_char *)ip); 231 return; 232 } 233 } 234 } 235 } 236 #ifdef INET6 237 if (ip6) { 238 if (ip6->ip6_nxt == IPPROTO_TCP) { 239 (void)printf("%s.%s > %s.%s: ", 240 ip6addr_string(&ip6->ip6_src), 241 tcpport_string(sport), 242 ip6addr_string(&ip6->ip6_dst), 243 tcpport_string(dport)); 244 } else { 245 (void)printf("%s > %s: ", 246 tcpport_string(sport), tcpport_string(dport)); 247 } 248 } else 249 #endif /*INET6*/ 250 { 251 if (ip->ip_p == IPPROTO_TCP) { 252 (void)printf("%s.%s > %s.%s: ", 253 ipaddr_string(&ip->ip_src), 254 tcpport_string(sport), 255 ipaddr_string(&ip->ip_dst), 256 tcpport_string(dport)); 257 } else { 258 (void)printf("%s > %s: ", 259 tcpport_string(sport), tcpport_string(dport)); 260 } 261 } 262 263 if (hlen < sizeof(*tp)) { 264 (void)printf(" tcp %d [bad hdr length %u - too short, < %lu]", 265 length - hlen, hlen, (unsigned long)sizeof(*tp)); 266 return; 267 } 268 269 TCHECK(*tp); 270 271 seq = EXTRACT_32BITS(&tp->th_seq); 272 ack = EXTRACT_32BITS(&tp->th_ack); 273 win = EXTRACT_16BITS(&tp->th_win); 274 urp = EXTRACT_16BITS(&tp->th_urp); 275 276 if (qflag) { 277 (void)printf("tcp %d", length - hlen); 278 if (hlen > length) { 279 (void)printf(" [bad hdr length %u - too long, > %u]", 280 hlen, length); 281 } 282 return; 283 } 284 285 flags = tp->th_flags; 286 printf("Flags [%s]", bittok2str_nosep(tcp_flag_values, "none", flags)); 287 288 if (!Sflag && (flags & TH_ACK)) { 289 register struct tcp_seq_hash *th; 290 const void *src, *dst; 291 register int rev; 292 struct tha tha; 293 /* 294 * Find (or record) the initial sequence numbers for 295 * this conversation. (we pick an arbitrary 296 * collating order so there's only one entry for 297 * both directions). 298 */ 299 #ifdef INET6 300 memset(&tha, 0, sizeof(tha)); 301 rev = 0; 302 if (ip6) { 303 src = &ip6->ip6_src; 304 dst = &ip6->ip6_dst; 305 if (sport > dport) 306 rev = 1; 307 else if (sport == dport) { 308 if (memcmp(src, dst, sizeof ip6->ip6_dst) > 0) 309 rev = 1; 310 } 311 if (rev) { 312 memcpy(&tha.src, dst, sizeof ip6->ip6_dst); 313 memcpy(&tha.dst, src, sizeof ip6->ip6_src); 314 tha.port = dport << 16 | sport; 315 } else { 316 memcpy(&tha.dst, dst, sizeof ip6->ip6_dst); 317 memcpy(&tha.src, src, sizeof ip6->ip6_src); 318 tha.port = sport << 16 | dport; 319 } 320 } else { 321 src = &ip->ip_src; 322 dst = &ip->ip_dst; 323 if (sport > dport) 324 rev = 1; 325 else if (sport == dport) { 326 if (memcmp(src, dst, sizeof ip->ip_dst) > 0) 327 rev = 1; 328 } 329 if (rev) { 330 memcpy(&tha.src, dst, sizeof ip->ip_dst); 331 memcpy(&tha.dst, src, sizeof ip->ip_src); 332 tha.port = dport << 16 | sport; 333 } else { 334 memcpy(&tha.dst, dst, sizeof ip->ip_dst); 335 memcpy(&tha.src, src, sizeof ip->ip_src); 336 tha.port = sport << 16 | dport; 337 } 338 } 339 #else 340 rev = 0; 341 src = &ip->ip_src; 342 dst = &ip->ip_dst; 343 if (sport > dport) 344 rev = 1; 345 else if (sport == dport) { 346 if (memcmp(src, dst, sizeof ip->ip_dst) > 0) 347 rev = 1; 348 } 349 if (rev) { 350 memcpy(&tha.src, dst, sizeof ip->ip_dst); 351 memcpy(&tha.dst, src, sizeof ip->ip_src); 352 tha.port = dport << 16 | sport; 353 } else { 354 memcpy(&tha.dst, dst, sizeof ip->ip_dst); 355 memcpy(&tha.src, src, sizeof ip->ip_src); 356 tha.port = sport << 16 | dport; 357 } 358 #endif 359 360 threv = rev; 361 for (th = &tcp_seq_hash[tha.port % TSEQ_HASHSIZE]; 362 th->nxt; th = th->nxt) 363 if (memcmp((char *)&tha, (char *)&th->addr, 364 sizeof(th->addr)) == 0) 365 break; 366 367 if (!th->nxt || (flags & TH_SYN)) { 368 /* didn't find it or new conversation */ 369 if (th->nxt == NULL) { 370 th->nxt = (struct tcp_seq_hash *) 371 calloc(1, sizeof(*th)); 372 if (th->nxt == NULL) 373 error("tcp_print: calloc"); 374 } 375 th->addr = tha; 376 if (rev) 377 th->ack = seq, th->seq = ack - 1; 378 else 379 th->seq = seq, th->ack = ack - 1; 380 } else { 381 if (rev) 382 seq -= th->ack, ack -= th->seq; 383 else 384 seq -= th->seq, ack -= th->ack; 385 } 386 387 thseq = th->seq; 388 thack = th->ack; 389 } else { 390 /*fool gcc*/ 391 thseq = thack = threv = 0; 392 } 393 if (hlen > length) { 394 (void)printf(" [bad hdr length %u - too long, > %u]", 395 hlen, length); 396 return; 397 } 398 399 if (IP_V(ip) == 4 && vflag && !Kflag && !fragmented) { 400 u_int16_t sum, tcp_sum; 401 if (TTEST2(tp->th_sport, length)) { 402 sum = tcp_cksum(ip, tp, length); 403 404 (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum)); 405 if (sum != 0) { 406 tcp_sum = EXTRACT_16BITS(&tp->th_sum); 407 (void)printf(" (incorrect -> 0x%04x)",in_cksum_shouldbe(tcp_sum, sum)); 408 } else 409 (void)printf(" (correct)"); 410 } 411 } 412 #ifdef INET6 413 if (IP_V(ip) == 6 && ip6->ip6_plen && vflag && !Kflag && !fragmented) { 414 u_int16_t sum,tcp_sum; 415 if (TTEST2(tp->th_sport, length)) { 416 sum = nextproto6_cksum(ip6, (u_short *)tp, length, IPPROTO_TCP); 417 (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum)); 418 if (sum != 0) { 419 tcp_sum = EXTRACT_16BITS(&tp->th_sum); 420 (void)printf(" (incorrect -> 0x%04x)",in_cksum_shouldbe(tcp_sum, sum)); 421 } else 422 (void)printf(" (correct)"); 423 424 } 425 } 426 #endif 427 428 length -= hlen; 429 if (vflag > 1 || length > 0 || flags & (TH_SYN | TH_FIN | TH_RST)) { 430 (void)printf(", seq %u", seq); 431 432 if (length > 0) { 433 (void)printf(":%u", seq + length); 434 } 435 } 436 437 if (flags & TH_ACK) { 438 (void)printf(", ack %u", ack); 439 } 440 441 (void)printf(", win %d", win); 442 443 if (flags & TH_URG) 444 (void)printf(", urg %d", urp); 445 /* 446 * Handle any options. 447 */ 448 if (hlen > sizeof(*tp)) { 449 register const u_char *cp; 450 register u_int i, opt, datalen; 451 register u_int len; 452 453 hlen -= sizeof(*tp); 454 cp = (const u_char *)tp + sizeof(*tp); 455 printf(", options ["); 456 while (hlen > 0) { 457 if (ch != '\0') 458 putchar(ch); 459 TCHECK(*cp); 460 opt = *cp++; 461 if (ZEROLENOPT(opt)) 462 len = 1; 463 else { 464 TCHECK(*cp); 465 len = *cp++; /* total including type, len */ 466 if (len < 2 || len > hlen) 467 goto bad; 468 --hlen; /* account for length byte */ 469 } 470 --hlen; /* account for type byte */ 471 datalen = 0; 472 473 /* Bail if "l" bytes of data are not left or were not captured */ 474 #define LENCHECK(l) { if ((l) > hlen) goto bad; TCHECK2(*cp, l); } 475 476 477 printf("%s", tok2str(tcp_option_values, "Unknown Option %u", opt)); 478 479 switch (opt) { 480 481 case TCPOPT_MAXSEG: 482 datalen = 2; 483 LENCHECK(datalen); 484 (void)printf(" %u", EXTRACT_16BITS(cp)); 485 break; 486 487 case TCPOPT_WSCALE: 488 datalen = 1; 489 LENCHECK(datalen); 490 (void)printf(" %u", *cp); 491 break; 492 493 case TCPOPT_SACK: 494 datalen = len - 2; 495 if (datalen % 8 != 0) { 496 (void)printf("malformed sack"); 497 } else { 498 u_int32_t s, e; 499 500 (void)printf(" %d ", datalen / 8); 501 for (i = 0; i < datalen; i += 8) { 502 LENCHECK(i + 4); 503 s = EXTRACT_32BITS(cp + i); 504 LENCHECK(i + 8); 505 e = EXTRACT_32BITS(cp + i + 4); 506 if (threv) { 507 s -= thseq; 508 e -= thseq; 509 } else { 510 s -= thack; 511 e -= thack; 512 } 513 (void)printf("{%u:%u}", s, e); 514 } 515 } 516 break; 517 518 case TCPOPT_CC: 519 case TCPOPT_CCNEW: 520 case TCPOPT_CCECHO: 521 case TCPOPT_ECHO: 522 case TCPOPT_ECHOREPLY: 523 524 /* 525 * those options share their semantics. 526 * fall through 527 */ 528 datalen = 4; 529 LENCHECK(datalen); 530 (void)printf(" %u", EXTRACT_32BITS(cp)); 531 break; 532 533 case TCPOPT_TIMESTAMP: 534 datalen = 8; 535 LENCHECK(datalen); 536 (void)printf(" val %u ecr %u", 537 EXTRACT_32BITS(cp), 538 EXTRACT_32BITS(cp + 4)); 539 break; 540 541 case TCPOPT_SIGNATURE: 542 datalen = TCP_SIGLEN; 543 LENCHECK(datalen); 544 #ifdef HAVE_LIBCRYPTO 545 switch (tcp_verify_signature(ip, tp, 546 bp + TH_OFF(tp) * 4, length, cp)) { 547 548 case SIGNATURE_VALID: 549 (void)printf("valid"); 550 break; 551 552 case SIGNATURE_INVALID: 553 (void)printf("invalid"); 554 break; 555 556 case CANT_CHECK_SIGNATURE: 557 (void)printf("can't check - "); 558 for (i = 0; i < TCP_SIGLEN; ++i) 559 (void)printf("%02x", cp[i]); 560 break; 561 } 562 #else 563 for (i = 0; i < TCP_SIGLEN; ++i) 564 (void)printf("%02x", cp[i]); 565 #endif 566 break; 567 568 case TCPOPT_AUTH: 569 (void)printf("keyid %d", *cp++); 570 datalen = len - 3; 571 for (i = 0; i < datalen; ++i) { 572 LENCHECK(i); 573 (void)printf("%02x", cp[i]); 574 } 575 break; 576 577 578 case TCPOPT_EOL: 579 case TCPOPT_NOP: 580 case TCPOPT_SACKOK: 581 /* 582 * Nothing interesting. 583 * fall through 584 */ 585 break; 586 587 case TCPOPT_UTO: 588 datalen = 2; 589 LENCHECK(datalen); 590 utoval = EXTRACT_16BITS(cp); 591 (void)printf("0x%x", utoval); 592 if (utoval & 0x0001) 593 utoval = (utoval >> 1) * 60; 594 else 595 utoval >>= 1; 596 (void)printf(" %u", utoval); 597 break; 598 599 default: 600 datalen = len - 2; 601 for (i = 0; i < datalen; ++i) { 602 LENCHECK(i); 603 (void)printf("%02x", cp[i]); 604 } 605 break; 606 } 607 608 /* Account for data printed */ 609 cp += datalen; 610 hlen -= datalen; 611 612 /* Check specification against observed length */ 613 ++datalen; /* option octet */ 614 if (!ZEROLENOPT(opt)) 615 ++datalen; /* size octet */ 616 if (datalen != len) 617 (void)printf("[len %d]", len); 618 ch = ','; 619 if (opt == TCPOPT_EOL) 620 break; 621 } 622 putchar(']'); 623 } 624 625 /* 626 * Print length field before crawling down the stack. 627 */ 628 printf(", length %u", length); 629 630 if (length <= 0) 631 return; 632 633 /* 634 * Decode payload if necessary. 635 */ 636 bp += TH_OFF(tp) * 4; 637 if ((flags & TH_RST) && vflag) { 638 print_tcp_rst_data(bp, length); 639 return; 640 } 641 642 if (sport == TELNET_PORT || dport == TELNET_PORT) { 643 if (!qflag && vflag) 644 telnet_print(bp, length); 645 } else if (sport == BGP_PORT || dport == BGP_PORT) 646 bgp_print(bp, length); 647 else if (sport == PPTP_PORT || dport == PPTP_PORT) 648 pptp_print(bp); 649 #ifdef TCPDUMP_DO_SMB 650 else if (sport == NETBIOS_SSN_PORT || dport == NETBIOS_SSN_PORT) 651 nbt_tcp_print(bp, length); 652 else if (sport == SMB_PORT || dport == SMB_PORT) 653 smb_tcp_print(bp, length); 654 #endif 655 else if (sport == BEEP_PORT || dport == BEEP_PORT) 656 beep_print(bp, length); 657 else if (length > 2 && 658 (sport == NAMESERVER_PORT || dport == NAMESERVER_PORT || 659 sport == MULTICASTDNS_PORT || dport == MULTICASTDNS_PORT)) { 660 /* 661 * TCP DNS query has 2byte length at the head. 662 * XXX packet could be unaligned, it can go strange 663 */ 664 ns_print(bp + 2, length - 2, 0); 665 } else if (sport == MSDP_PORT || dport == MSDP_PORT) { 666 msdp_print(bp, length); 667 } 668 else if (length > 0 && (sport == LDP_PORT || dport == LDP_PORT)) { 669 ldp_print(bp, length); 670 } 671 672 return; 673 bad: 674 fputs("[bad opt]", stdout); 675 if (ch != '\0') 676 putchar('>'); 677 return; 678 trunc: 679 fputs("[|tcp]", stdout); 680 if (ch != '\0') 681 putchar('>'); 682 } 683 684 /* 685 * RFC1122 says the following on data in RST segments: 686 * 687 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 688 * 689 * A TCP SHOULD allow a received RST segment to include data. 690 * 691 * DISCUSSION 692 * It has been suggested that a RST segment could contain 693 * ASCII text that encoded and explained the cause of the 694 * RST. No standard has yet been established for such 695 * data. 696 * 697 */ 698 699 static void 700 print_tcp_rst_data(register const u_char *sp, u_int length) 701 { 702 int c; 703 704 if (TTEST2(*sp, length)) 705 printf(" [RST"); 706 else 707 printf(" [!RST"); 708 if (length > MAX_RST_DATA_LEN) { 709 length = MAX_RST_DATA_LEN; /* can use -X for longer */ 710 putchar('+'); /* indicate we truncate */ 711 } 712 putchar(' '); 713 while (length-- && sp <= snapend) { 714 c = *sp++; 715 safeputchar(c); 716 } 717 putchar(']'); 718 } 719 720 #ifdef HAVE_LIBCRYPTO 721 static int 722 tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp, 723 const u_char *data, int length, const u_char *rcvsig) 724 { 725 struct tcphdr tp1; 726 u_char sig[TCP_SIGLEN]; 727 char zero_proto = 0; 728 MD5_CTX ctx; 729 u_int16_t savecsum, tlen; 730 #ifdef INET6 731 struct ip6_hdr *ip6; 732 u_int32_t len32; 733 u_int8_t nxt; 734 #endif 735 736 if (data + length > snapend) { 737 printf("snaplen too short, "); 738 return (CANT_CHECK_SIGNATURE); 739 } 740 741 tp1 = *tp; 742 743 if (sigsecret == NULL) { 744 printf("shared secret not supplied with -M, "); 745 return (CANT_CHECK_SIGNATURE); 746 } 747 748 MD5_Init(&ctx); 749 /* 750 * Step 1: Update MD5 hash with IP pseudo-header. 751 */ 752 if (IP_V(ip) == 4) { 753 MD5_Update(&ctx, (char *)&ip->ip_src, sizeof(ip->ip_src)); 754 MD5_Update(&ctx, (char *)&ip->ip_dst, sizeof(ip->ip_dst)); 755 MD5_Update(&ctx, (char *)&zero_proto, sizeof(zero_proto)); 756 MD5_Update(&ctx, (char *)&ip->ip_p, sizeof(ip->ip_p)); 757 tlen = EXTRACT_16BITS(&ip->ip_len) - IP_HL(ip) * 4; 758 tlen = htons(tlen); 759 MD5_Update(&ctx, (char *)&tlen, sizeof(tlen)); 760 #ifdef INET6 761 } else if (IP_V(ip) == 6) { 762 ip6 = (struct ip6_hdr *)ip; 763 MD5_Update(&ctx, (char *)&ip6->ip6_src, sizeof(ip6->ip6_src)); 764 MD5_Update(&ctx, (char *)&ip6->ip6_dst, sizeof(ip6->ip6_dst)); 765 len32 = htonl(EXTRACT_16BITS(&ip6->ip6_plen)); 766 MD5_Update(&ctx, (char *)&len32, sizeof(len32)); 767 nxt = 0; 768 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt)); 769 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt)); 770 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt)); 771 nxt = IPPROTO_TCP; 772 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt)); 773 #endif 774 } else { 775 #ifdef INET6 776 printf("IP version not 4 or 6, "); 777 #else 778 printf("IP version not 4, "); 779 #endif 780 return (CANT_CHECK_SIGNATURE); 781 } 782 783 /* 784 * Step 2: Update MD5 hash with TCP header, excluding options. 785 * The TCP checksum must be set to zero. 786 */ 787 savecsum = tp1.th_sum; 788 tp1.th_sum = 0; 789 MD5_Update(&ctx, (char *)&tp1, sizeof(struct tcphdr)); 790 tp1.th_sum = savecsum; 791 /* 792 * Step 3: Update MD5 hash with TCP segment data, if present. 793 */ 794 if (length > 0) 795 MD5_Update(&ctx, data, length); 796 /* 797 * Step 4: Update MD5 hash with shared secret. 798 */ 799 MD5_Update(&ctx, sigsecret, strlen(sigsecret)); 800 MD5_Final(sig, &ctx); 801 802 if (memcmp(rcvsig, sig, TCP_SIGLEN) == 0) 803 return (SIGNATURE_VALID); 804 else 805 return (SIGNATURE_INVALID); 806 } 807 #endif /* HAVE_LIBCRYPTO */ 808 809 /* 810 * Local Variables: 811 * c-style: whitesmith 812 * c-basic-offset: 8 813 * End: 814 */ 815