The Tcpdump Group git mirrors - tcpdump/blob - print-tcp.c

   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                 rev = 0;
 298                 if (ip6) {
 299                         src = &ip6->ip6_src;
 300                         dst = &ip6->ip6_dst;
 301                         if (sport > dport)
 302                                 rev = 1;
 303                         else if (sport == dport) {
 304                                 if (memcmp(src, dst, sizeof ip6->ip6_dst) > 0)
 305                                         rev = 1;
 306                         }
 307                         if (rev) {
 308                                 memcpy(&tha.src, dst, sizeof ip6->ip6_dst);
 309                                 memcpy(&tha.dst, src, sizeof ip6->ip6_src);
 310                                 tha.port = dport << 16 | sport;
 311                         } else {
 312                                 memcpy(&tha.dst, dst, sizeof ip6->ip6_dst);
 313                                 memcpy(&tha.src, src, sizeof ip6->ip6_src);
 314                                 tha.port = sport << 16 | dport;
 315                         }
 316                 } else {
 317                         /*
 318                          * Zero out the tha structure; the src and dst
 319                          * fields are big enough to hold an IPv6
 320                          * address, but we only have IPv4 addresses
 321                          * and thus must clear out the remaining 124
 322                          * bits.
 323                          *
 324                          * XXX - should we just clear those bytes after
 325                          * copying the IPv4 addresses, rather than
 326                          * zeroing out the entire structure and then
 327                          * overwriting some of the zeroes?
 328                          *
 329                          * XXX - this could fail if we see TCP packets
 330                          * with an IPv6 address with the lower 124 bits
 331                          * all zero and also see TCP packes with an
 332                          * IPv4 address with the same 32 bits as the
 333                          * upper 32 bits of the IPv6 address in question.
 334                          * Can that happen?  Is it likely enough to be
 335                          * an issue?
 336                          */
 337                         memset(&tha, 0, sizeof(tha));
 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                 }
 356 #else
 357                 rev = 0;
 358                 src = &ip->ip_src;
 359                 dst = &ip->ip_dst;
 360                 if (sport > dport)
 361                         rev = 1;
 362                 else if (sport == dport) {
 363                         if (memcmp(src, dst, sizeof ip->ip_dst) > 0)
 364                                 rev = 1;
 365                 }
 366                 if (rev) {
 367                         memcpy(&tha.src, dst, sizeof ip->ip_dst);
 368                         memcpy(&tha.dst, src, sizeof ip->ip_src);
 369                         tha.port = dport << 16 | sport;
 370                 } else {
 371                         memcpy(&tha.dst, dst, sizeof ip->ip_dst);
 372                         memcpy(&tha.src, src, sizeof ip->ip_src);
 373                         tha.port = sport << 16 | dport;
 374                 }
 375 #endif
 376
 377                 threv = rev;
 378                 for (th = &tcp_seq_hash[tha.port % TSEQ_HASHSIZE];
 379                      th->nxt; th = th->nxt)
 380                         if (memcmp((char *)&tha, (char *)&th->addr,
 381                                    sizeof(th->addr)) == 0)
 382                                 break;
 383
 384                 if (!th->nxt || (flags & TH_SYN)) {
 385                         /* didn't find it or new conversation */
 386                         if (th->nxt == NULL) {
 387                                 th->nxt = (struct tcp_seq_hash *)
 388                                         calloc(1, sizeof(*th));
 389                                 if (th->nxt == NULL)
 390                                         error("tcp_print: calloc");
 391                         }
 392                         th->addr = tha;
 393                         if (rev)
 394                                 th->ack = seq, th->seq = ack - 1;
 395                         else
 396                                 th->seq = seq, th->ack = ack - 1;
 397                 } else {
 398                         if (rev)
 399                                 seq -= th->ack, ack -= th->seq;
 400                         else
 401                                 seq -= th->seq, ack -= th->ack;
 402                 }
 403
 404                 thseq = th->seq;
 405                 thack = th->ack;
 406         } else {
 407                 /*fool gcc*/
 408                 thseq = thack = threv = 0;
 409         }
 410         if (hlen > length) {
 411                 (void)printf(" [bad hdr length %u - too long, > %u]",
 412                              hlen, length);
 413                 return;
 414         }
 415
 416         if (IP_V(ip) == 4 && vflag && !Kflag && !fragmented) {
 417                 u_int16_t sum, tcp_sum;
 418                 if (TTEST2(tp->th_sport, length)) {
 419                         sum = tcp_cksum(ip, tp, length);
 420
 421                         (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum));
 422                         if (sum != 0) {
 423                                 tcp_sum = EXTRACT_16BITS(&tp->th_sum);
 424                                 (void)printf(" (incorrect -> 0x%04x)",in_cksum_shouldbe(tcp_sum, sum));
 425                         } else
 426                                 (void)printf(" (correct)");
 427                 }
 428         }
 429 #ifdef INET6
 430         if (IP_V(ip) == 6 && ip6->ip6_plen && vflag && !Kflag && !fragmented) {
 431                 u_int16_t sum,tcp_sum;
 432                 if (TTEST2(tp->th_sport, length)) {
 433                         sum = nextproto6_cksum(ip6, (u_short *)tp, length, IPPROTO_TCP);
 434                         (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum));
 435                         if (sum != 0) {
 436                                 tcp_sum = EXTRACT_16BITS(&tp->th_sum);
 437                                 (void)printf(" (incorrect -> 0x%04x)",in_cksum_shouldbe(tcp_sum, sum));
 438                         } else
 439                                 (void)printf(" (correct)");
 440
 441                 }
 442         }
 443 #endif
 444
 445         length -= hlen;
 446         if (vflag > 1 || length > 0 || flags & (TH_SYN | TH_FIN | TH_RST)) {
 447                 (void)printf(", seq %u", seq);
 448
 449                 if (length > 0) {
 450                         (void)printf(":%u", seq + length);
 451                 }
 452         }
 453
 454         if (flags & TH_ACK) {
 455                 (void)printf(", ack %u", ack);
 456         }
 457
 458         (void)printf(", win %d", win);
 459
 460         if (flags & TH_URG)
 461                 (void)printf(", urg %d", urp);
 462         /*
 463          * Handle any options.
 464          */
 465         if (hlen > sizeof(*tp)) {
 466                 register const u_char *cp;
 467                 register u_int i, opt, datalen;
 468                 register u_int len;
 469
 470                 hlen -= sizeof(*tp);
 471                 cp = (const u_char *)tp + sizeof(*tp);
 472                 printf(", options [");
 473                 while (hlen > 0) {
 474                         if (ch != '\0')
 475                                 putchar(ch);
 476                         TCHECK(*cp);
 477                         opt = *cp++;
 478                         if (ZEROLENOPT(opt))
 479                                 len = 1;
 480                         else {
 481                                 TCHECK(*cp);
 482                                 len = *cp++;    /* total including type, len */
 483                                 if (len < 2 || len > hlen)
 484                                         goto bad;
 485                                 --hlen;         /* account for length byte */
 486                         }
 487                         --hlen;                 /* account for type byte */
 488                         datalen = 0;
 489
 490 /* Bail if "l" bytes of data are not left or were not captured  */
 491 #define LENCHECK(l) { if ((l) > hlen) goto bad; TCHECK2(*cp, l); }
 492
 493
 494                         printf("%s", tok2str(tcp_option_values, "Unknown Option %u", opt));
 495
 496                         switch (opt) {
 497
 498                         case TCPOPT_MAXSEG:
 499                                 datalen = 2;
 500                                 LENCHECK(datalen);
 501                                 (void)printf(" %u", EXTRACT_16BITS(cp));
 502                                 break;
 503
 504                         case TCPOPT_WSCALE:
 505                                 datalen = 1;
 506                                 LENCHECK(datalen);
 507                                 (void)printf(" %u", *cp);
 508                                 break;
 509
 510                         case TCPOPT_SACK:
 511                                 datalen = len - 2;
 512                                 if (datalen % 8 != 0) {
 513                                         (void)printf("malformed sack");
 514                                 } else {
 515                                         u_int32_t s, e;
 516
 517                                         (void)printf(" %d ", datalen / 8);
 518                                         for (i = 0; i < datalen; i += 8) {
 519                                                 LENCHECK(i + 4);
 520                                                 s = EXTRACT_32BITS(cp + i);
 521                                                 LENCHECK(i + 8);
 522                                                 e = EXTRACT_32BITS(cp + i + 4);
 523                                                 if (threv) {
 524                                                         s -= thseq;
 525                                                         e -= thseq;
 526                                                 } else {
 527                                                         s -= thack;
 528                                                         e -= thack;
 529                                                 }
 530                                                 (void)printf("{%u:%u}", s, e);
 531                                         }
 532                                 }
 533                                 break;
 534
 535                         case TCPOPT_CC:
 536                         case TCPOPT_CCNEW:
 537                         case TCPOPT_CCECHO:
 538                         case TCPOPT_ECHO:
 539                         case TCPOPT_ECHOREPLY:
 540
 541                                 /*
 542                                  * those options share their semantics.
 543                                  * fall through
 544                                  */
 545                                 datalen = 4;
 546                                 LENCHECK(datalen);
 547                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 548                                 break;
 549
 550                         case TCPOPT_TIMESTAMP:
 551                                 datalen = 8;
 552                                 LENCHECK(datalen);
 553                                 (void)printf(" val %u ecr %u",
 554                                              EXTRACT_32BITS(cp),
 555                                              EXTRACT_32BITS(cp + 4));
 556                                 break;
 557
 558                         case TCPOPT_SIGNATURE:
 559                                 datalen = TCP_SIGLEN;
 560                                 LENCHECK(datalen);
 561 #ifdef HAVE_LIBCRYPTO
 562                                 switch (tcp_verify_signature(ip, tp,
 563                                                              bp + TH_OFF(tp) * 4, length, cp)) {
 564
 565                                 case SIGNATURE_VALID:
 566                                         (void)printf("valid");
 567                                         break;
 568
 569                                 case SIGNATURE_INVALID:
 570                                         (void)printf("invalid");
 571                                         break;
 572
 573                                 case CANT_CHECK_SIGNATURE:
 574                                         (void)printf("can't check - ");
 575                                         for (i = 0; i < TCP_SIGLEN; ++i)
 576                                                 (void)printf("%02x", cp[i]);
 577                                         break;
 578                                 }
 579 #else
 580                                 for (i = 0; i < TCP_SIGLEN; ++i)
 581                                         (void)printf("%02x", cp[i]);
 582 #endif
 583                                 break;
 584
 585                         case TCPOPT_AUTH:
 586                                 (void)printf("keyid %d", *cp++);
 587                                 datalen = len - 3;
 588                                 for (i = 0; i < datalen; ++i) {
 589                                         LENCHECK(i);
 590                                         (void)printf("%02x", cp[i]);
 591                                 }
 592                                 break;
 593
 594
 595                         case TCPOPT_EOL:
 596                         case TCPOPT_NOP:
 597                         case TCPOPT_SACKOK:
 598                                 /*
 599                                  * Nothing interesting.
 600                                  * fall through
 601                                  */
 602                                 break;
 603
 604                         case TCPOPT_UTO:
 605                                 datalen = 2;
 606                                 LENCHECK(datalen);
 607                                 utoval = EXTRACT_16BITS(cp);
 608                                 (void)printf("0x%x", utoval);
 609                                 if (utoval & 0x0001)
 610                                         utoval = (utoval >> 1) * 60;
 611                                 else
 612                                         utoval >>= 1;
 613                                 (void)printf(" %u", utoval);
 614                                 break;
 615
 616                         default:
 617                                 datalen = len - 2;
 618                                 for (i = 0; i < datalen; ++i) {
 619                                         LENCHECK(i);
 620                                         (void)printf("%02x", cp[i]);
 621                                 }
 622                                 break;
 623                         }
 624
 625                         /* Account for data printed */
 626                         cp += datalen;
 627                         hlen -= datalen;
 628
 629                         /* Check specification against observed length */
 630                         ++datalen;                      /* option octet */
 631                         if (!ZEROLENOPT(opt))
 632                                 ++datalen;              /* size octet */
 633                         if (datalen != len)
 634                                 (void)printf("[len %d]", len);
 635                         ch = ',';
 636                         if (opt == TCPOPT_EOL)
 637                                 break;
 638                 }
 639                 putchar(']');
 640         }
 641
 642         /*
 643          * Print length field before crawling down the stack.
 644          */
 645         printf(", length %u", length);
 646
 647         if (length <= 0)
 648                 return;
 649
 650         /*
 651          * Decode payload if necessary.
 652          */
 653         bp += TH_OFF(tp) * 4;
 654         if ((flags & TH_RST) && vflag) {
 655                 print_tcp_rst_data(bp, length);
 656                 return;
 657         }
 658
 659         if (sport == TELNET_PORT || dport == TELNET_PORT) {
 660                 if (!qflag && vflag)
 661                         telnet_print(bp, length);
 662         } else if (sport == BGP_PORT || dport == BGP_PORT)
 663                 bgp_print(bp, length);
 664         else if (sport == PPTP_PORT || dport == PPTP_PORT)
 665                 pptp_print(bp);
 666 #ifdef TCPDUMP_DO_SMB
 667         else if (sport == NETBIOS_SSN_PORT || dport == NETBIOS_SSN_PORT)
 668                 nbt_tcp_print(bp, length);
 669         else if (sport == SMB_PORT || dport == SMB_PORT)
 670                 smb_tcp_print(bp, length);
 671 #endif
 672         else if (sport == BEEP_PORT || dport == BEEP_PORT)
 673                 beep_print(bp, length);
 674         else if (length > 2 &&
 675                  (sport == NAMESERVER_PORT || dport == NAMESERVER_PORT ||
 676                   sport == MULTICASTDNS_PORT || dport == MULTICASTDNS_PORT)) {
 677                 /*
 678                  * TCP DNS query has 2byte length at the head.
 679                  * XXX packet could be unaligned, it can go strange
 680                  */
 681                 ns_print(bp + 2, length - 2, 0);
 682         } else if (sport == MSDP_PORT || dport == MSDP_PORT) {
 683                 msdp_print(bp, length);
 684         }
 685         else if (length > 0 && (sport == LDP_PORT || dport == LDP_PORT)) {
 686                 ldp_print(bp, length);
 687         }
 688
 689         return;
 690  bad:
 691         fputs("[bad opt]", stdout);
 692         if (ch != '\0')
 693                 putchar('>');
 694         return;
 695  trunc:
 696         fputs("[|tcp]", stdout);
 697         if (ch != '\0')
 698                 putchar('>');
 699 }
 700
 701 /*
 702  * RFC1122 says the following on data in RST segments:
 703  *
 704  *         4.2.2.12  RST Segment: RFC-793 Section 3.4
 705  *
 706  *            A TCP SHOULD allow a received RST segment to include data.
 707  *
 708  *            DISCUSSION
 709  *                 It has been suggested that a RST segment could contain
 710  *                 ASCII text that encoded and explained the cause of the
 711  *                 RST.  No standard has yet been established for such
 712  *                 data.
 713  *
 714  */
 715
 716 static void
 717 print_tcp_rst_data(register const u_char *sp, u_int length)
 718 {
 719         int c;
 720
 721         if (TTEST2(*sp, length))
 722                 printf(" [RST");
 723         else
 724                 printf(" [!RST");
 725         if (length > MAX_RST_DATA_LEN) {
 726                 length = MAX_RST_DATA_LEN;      /* can use -X for longer */
 727                 putchar('+');                   /* indicate we truncate */
 728         }
 729         putchar(' ');
 730         while (length-- && sp <= snapend) {
 731                 c = *sp++;
 732                 safeputchar(c);
 733         }
 734         putchar(']');
 735 }
 736
 737 #ifdef HAVE_LIBCRYPTO
 738 static int
 739 tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp,
 740                      const u_char *data, int length, const u_char *rcvsig)
 741 {
 742         struct tcphdr tp1;
 743         u_char sig[TCP_SIGLEN];
 744         char zero_proto = 0;
 745         MD5_CTX ctx;
 746         u_int16_t savecsum, tlen;
 747 #ifdef INET6
 748         struct ip6_hdr *ip6;
 749         u_int32_t len32;
 750         u_int8_t nxt;
 751 #endif
 752
 753         if (data + length > snapend) {
 754                 printf("snaplen too short, ");
 755                 return (CANT_CHECK_SIGNATURE);
 756         }
 757
 758         tp1 = *tp;
 759
 760         if (sigsecret == NULL) {
 761                 printf("shared secret not supplied with -M, ");
 762                 return (CANT_CHECK_SIGNATURE);
 763         }
 764
 765         MD5_Init(&ctx);
 766         /*
 767          * Step 1: Update MD5 hash with IP pseudo-header.
 768          */
 769         if (IP_V(ip) == 4) {
 770                 MD5_Update(&ctx, (char *)&ip->ip_src, sizeof(ip->ip_src));
 771                 MD5_Update(&ctx, (char *)&ip->ip_dst, sizeof(ip->ip_dst));
 772                 MD5_Update(&ctx, (char *)&zero_proto, sizeof(zero_proto));
 773                 MD5_Update(&ctx, (char *)&ip->ip_p, sizeof(ip->ip_p));
 774                 tlen = EXTRACT_16BITS(&ip->ip_len) - IP_HL(ip) * 4;
 775                 tlen = htons(tlen);
 776                 MD5_Update(&ctx, (char *)&tlen, sizeof(tlen));
 777 #ifdef INET6
 778         } else if (IP_V(ip) == 6) {
 779                 ip6 = (struct ip6_hdr *)ip;
 780                 MD5_Update(&ctx, (char *)&ip6->ip6_src, sizeof(ip6->ip6_src));
 781                 MD5_Update(&ctx, (char *)&ip6->ip6_dst, sizeof(ip6->ip6_dst));
 782                 len32 = htonl(EXTRACT_16BITS(&ip6->ip6_plen));
 783                 MD5_Update(&ctx, (char *)&len32, sizeof(len32));
 784                 nxt = 0;
 785                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 786                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 787                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 788                 nxt = IPPROTO_TCP;
 789                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 790 #endif
 791         } else {
 792 #ifdef INET6
 793                 printf("IP version not 4 or 6, ");
 794 #else
 795                 printf("IP version not 4, ");
 796 #endif
 797                 return (CANT_CHECK_SIGNATURE);
 798         }
 799
 800         /*
 801          * Step 2: Update MD5 hash with TCP header, excluding options.
 802          * The TCP checksum must be set to zero.
 803          */
 804         savecsum = tp1.th_sum;
 805         tp1.th_sum = 0;
 806         MD5_Update(&ctx, (char *)&tp1, sizeof(struct tcphdr));
 807         tp1.th_sum = savecsum;
 808         /*
 809          * Step 3: Update MD5 hash with TCP segment data, if present.
 810          */
 811         if (length > 0)
 812                 MD5_Update(&ctx, data, length);
 813         /*
 814          * Step 4: Update MD5 hash with shared secret.
 815          */
 816         MD5_Update(&ctx, sigsecret, strlen(sigsecret));
 817         MD5_Final(sig, &ctx);
 818
 819         if (memcmp(rcvsig, sig, TCP_SIGLEN) == 0)
 820                 return (SIGNATURE_VALID);
 821         else
 822                 return (SIGNATURE_INVALID);
 823 }
 824 #endif /* HAVE_LIBCRYPTO */
 825
 826 /*
 827  * Local Variables:
 828  * c-style: whitesmith
 829  * c-basic-offset: 8
 830  * End:
 831  */