dist/tcpdump/print-tcp.c

   1 /*      $NetBSD: print-tcp.c,v 1.8 2007/07/24 11:53:48 drochner 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 1.120.2.3 2005/10/16 06:05:46 guy Exp (LBL)";
  31 #else
  32 __RCSID("$NetBSD: print-tcp.c,v 1.8 2007/07/24 11:53:48 drochner 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
  65 #define SIGNATURE_VALID         0
  66 #define SIGNATURE_INVALID       1
  67 #define CANT_CHECK_SIGNATURE    2
  68
  69 static int tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp,
  70     const u_char *data, int length, const u_char *rcvsig);
  71 #endif
  72
  73 static void print_tcp_rst_data(register const u_char *sp, u_int length);
  74
  75 #define MAX_RST_DATA_LEN        30
  76
  77
  78 struct tha {
  79 #ifndef INET6
  80         struct in_addr src;
  81         struct in_addr dst;
  82 #else
  83         struct in6_addr src;
  84         struct in6_addr dst;
  85 #endif /*INET6*/
  86         u_int port;
  87 };
  88
  89 struct tcp_seq_hash {
  90         struct tcp_seq_hash *nxt;
  91         struct tha addr;
  92         tcp_seq seq;
  93         tcp_seq ack;
  94 };
  95
  96 #define TSEQ_HASHSIZE 919
  97
  98 /* These tcp optinos do not have the size octet */
  99 #define ZEROLENOPT(o) ((o) == TCPOPT_EOL || (o) == TCPOPT_NOP)
 100
 101 static struct tcp_seq_hash tcp_seq_hash[TSEQ_HASHSIZE];
 102
 103
 104 #ifndef TELNET_PORT
 105 #define TELNET_PORT     23
 106 #endif
 107 #ifndef BGP_PORT
 108 #define BGP_PORT        179
 109 #endif
 110 #define NETBIOS_SSN_PORT 139
 111 #ifndef PPTP_PORT
 112 #define PPTP_PORT       1723
 113 #endif
 114 #define BEEP_PORT        10288
 115 #ifndef NFS_PORT
 116 #define NFS_PORT        2049
 117 #endif
 118 #define MSDP_PORT       639
 119 #define LDP_PORT        646
 120
 121 static int tcp_cksum(register const struct ip *ip,
 122                      register const struct tcphdr *tp,
 123                      register u_int len)
 124 {
 125         union phu {
 126                 struct phdr {
 127                         u_int32_t src;
 128                         u_int32_t dst;
 129                         u_char mbz;
 130                         u_char proto;
 131                         u_int16_t len;
 132                 } ph;
 133                 u_int16_t pa[6];
 134         } phu;
 135         const u_int16_t *sp;
 136
 137         /* pseudo-header.. */
 138         phu.ph.len = htons((u_int16_t)len);
 139         phu.ph.mbz = 0;
 140         phu.ph.proto = IPPROTO_TCP;
 141         memcpy(&phu.ph.src, &ip->ip_src.s_addr, sizeof(u_int32_t));
 142         if (IP_HL(ip) == 5)
 143                 memcpy(&phu.ph.dst, &ip->ip_dst.s_addr, sizeof(u_int32_t));
 144         else
 145                 phu.ph.dst = ip_finddst(ip);
 146
 147         sp = &phu.pa[0];
 148         return in_cksum((u_short *)tp, len,
 149                         sp[0]+sp[1]+sp[2]+sp[3]+sp[4]+sp[5]);
 150 }
 151
 152 #ifdef INET6
 153 static int tcp6_cksum(const struct ip6_hdr *ip6, const struct tcphdr *tp,
 154         u_int len)
 155 {
 156         size_t i;
 157         register const u_int16_t *sp;
 158         u_int32_t sum;
 159         union {
 160                 struct {
 161                         struct in6_addr ph_src;
 162                         struct in6_addr ph_dst;
 163                         u_int32_t       ph_len;
 164                         u_int8_t        ph_zero[3];
 165                         u_int8_t        ph_nxt;
 166                 } ph;
 167                 u_int16_t pa[20];
 168         } phu;
 169
 170         /* pseudo-header */
 171         memset(&phu, 0, sizeof(phu));
 172         phu.ph.ph_src = ip6->ip6_src;
 173         phu.ph.ph_dst = ip6->ip6_dst;
 174         phu.ph.ph_len = htonl(len);
 175         phu.ph.ph_nxt = IPPROTO_TCP;
 176
 177         sum = 0;
 178         for (i = 0; i < sizeof(phu.pa) / sizeof(phu.pa[0]); i++)
 179                 sum += phu.pa[i];
 180
 181         sp = (const u_int16_t *)tp;
 182
 183         for (i = 0; i < (len & ~1); i += 2)
 184                 sum += *sp++;
 185
 186         if (len & 1)
 187                 sum += htons((*(const u_int8_t *)sp) << 8);
 188
 189         while (sum > 0xffff)
 190                 sum = (sum & 0xffff) + (sum >> 16);
 191         sum = ~sum & 0xffff;
 192
 193         return (sum);
 194 }
 195 #endif
 196
 197 void
 198 tcp_print(register const u_char *bp, register u_int length,
 199           register const u_char *bp2, int fragmented)
 200 {
 201         register const struct tcphdr *tp;
 202         register const struct ip *ip;
 203         register u_char flags;
 204         register u_int hlen;
 205         register char ch;
 206         u_int16_t sport, dport, win, urp;
 207         u_int32_t seq, ack, thseq, thack;
 208         int threv;
 209 #ifdef INET6
 210         register const struct ip6_hdr *ip6;
 211 #endif
 212
 213         tp = (struct tcphdr *)bp;
 214         ip = (struct ip *)bp2;
 215 #ifdef INET6
 216         if (IP_V(ip) == 6)
 217                 ip6 = (struct ip6_hdr *)bp2;
 218         else
 219                 ip6 = NULL;
 220 #endif /*INET6*/
 221         ch = '\0';
 222         if (!TTEST(tp->th_dport)) {
 223                 (void)printf("%s > %s: [|tcp]",
 224                         ipaddr_string(&ip->ip_src),
 225                         ipaddr_string(&ip->ip_dst));
 226                 return;
 227         }
 228
 229         sport = EXTRACT_16BITS(&tp->th_sport);
 230         dport = EXTRACT_16BITS(&tp->th_dport);
 231
 232         hlen = TH_OFF(tp) * 4;
 233
 234         /*
 235          * If data present, header length valid, and NFS port used,
 236          * assume NFS.
 237          * Pass offset of data plus 4 bytes for RPC TCP msg length
 238          * to NFS print routines.
 239          */
 240         if (!qflag && hlen >= sizeof(*tp) && hlen <= length) {
 241                 if ((u_char *)tp + 4 + sizeof(struct sunrpc_msg) <= snapend &&
 242                     dport == NFS_PORT) {
 243                         nfsreq_print((u_char *)tp + hlen + 4, length - hlen,
 244                                      (u_char *)ip);
 245                         return;
 246                 } else if ((u_char *)tp + 4 + sizeof(struct sunrpc_msg)
 247                            <= snapend &&
 248                            sport == NFS_PORT) {
 249                         nfsreply_print((u_char *)tp + hlen + 4, length - hlen,
 250                                        (u_char *)ip);
 251                         return;
 252                 }
 253         }
 254 #ifdef INET6
 255         if (ip6) {
 256                 if (ip6->ip6_nxt == IPPROTO_TCP) {
 257                         (void)printf("%s.%s > %s.%s: ",
 258                                 ip6addr_string(&ip6->ip6_src),
 259                                 tcpport_string(sport),
 260                                 ip6addr_string(&ip6->ip6_dst),
 261                                 tcpport_string(dport));
 262                 } else {
 263                         (void)printf("%s > %s: ",
 264                                 tcpport_string(sport), tcpport_string(dport));
 265                 }
 266         } else
 267 #endif /*INET6*/
 268         {
 269                 if (ip->ip_p == IPPROTO_TCP) {
 270                         (void)printf("%s.%s > %s.%s: ",
 271                                 ipaddr_string(&ip->ip_src),
 272                                 tcpport_string(sport),
 273                                 ipaddr_string(&ip->ip_dst),
 274                                 tcpport_string(dport));
 275                 } else {
 276                         (void)printf("%s > %s: ",
 277                                 tcpport_string(sport), tcpport_string(dport));
 278                 }
 279         }
 280
 281         if (hlen < sizeof(*tp)) {
 282                 (void)printf(" tcp %d [bad hdr length %u - too short, < %lu]",
 283                     length - hlen, hlen, (unsigned long)sizeof(*tp));
 284                 return;
 285         }
 286
 287         TCHECK(*tp);
 288
 289         seq = EXTRACT_32BITS(&tp->th_seq);
 290         ack = EXTRACT_32BITS(&tp->th_ack);
 291         win = EXTRACT_16BITS(&tp->th_win);
 292         urp = EXTRACT_16BITS(&tp->th_urp);
 293
 294         if (qflag) {
 295                 (void)printf("tcp %d", length - hlen);
 296                 if (hlen > length) {
 297                         (void)printf(" [bad hdr length %u - too long, > %u]",
 298                             hlen, length);
 299                 }
 300                 return;
 301         }
 302         if ((flags = tp->th_flags) & (TH_SYN|TH_FIN|TH_RST|TH_PUSH|
 303                                       TH_ECNECHO|TH_CWR)) {
 304                 if (flags & TH_SYN)
 305                         putchar('S');
 306                 if (flags & TH_FIN)
 307                         putchar('F');
 308                 if (flags & TH_RST)
 309                         putchar('R');
 310                 if (flags & TH_PUSH)
 311                         putchar('P');
 312                 if (flags & TH_CWR)
 313                         putchar('W');   /* congestion _W_indow reduced (ECN) */
 314                 if (flags & TH_ECNECHO)
 315                         putchar('E');   /* ecn _E_cho sent (ECN) */
 316         } else
 317                 putchar('.');
 318
 319         if (!Sflag && (flags & TH_ACK)) {
 320                 register struct tcp_seq_hash *th;
 321                 const void *src, *dst;
 322                 register int rev;
 323                 struct tha tha;
 324                 /*
 325                  * Find (or record) the initial sequence numbers for
 326                  * this conversation.  (we pick an arbitrary
 327                  * collating order so there's only one entry for
 328                  * both directions).
 329                  */
 330 #ifdef INET6
 331                 memset(&tha, 0, sizeof(tha));
 332                 rev = 0;
 333                 if (ip6) {
 334                         src = &ip6->ip6_src;
 335                         dst = &ip6->ip6_dst;
 336                         if (sport > dport)
 337                                 rev = 1;
 338                         else if (sport == dport) {
 339                                 if (memcmp(src, dst, sizeof ip6->ip6_dst) > 0)
 340                                         rev = 1;
 341                         }
 342                         if (rev) {
 343                                 memcpy(&tha.src, dst, sizeof ip6->ip6_dst);
 344                                 memcpy(&tha.dst, src, sizeof ip6->ip6_src);
 345                                 tha.port = dport << 16 | sport;
 346                         } else {
 347                                 memcpy(&tha.dst, dst, sizeof ip6->ip6_dst);
 348                                 memcpy(&tha.src, src, sizeof ip6->ip6_src);
 349                                 tha.port = sport << 16 | dport;
 350                         }
 351                 } else {
 352                         src = &ip->ip_src;
 353                         dst = &ip->ip_dst;
 354                         if (sport > dport)
 355                                 rev = 1;
 356                         else if (sport == dport) {
 357                                 if (memcmp(src, dst, sizeof ip->ip_dst) > 0)
 358                                         rev = 1;
 359                         }
 360                         if (rev) {
 361                                 memcpy(&tha.src, dst, sizeof ip->ip_dst);
 362                                 memcpy(&tha.dst, src, sizeof ip->ip_src);
 363                                 tha.port = dport << 16 | sport;
 364                         } else {
 365                                 memcpy(&tha.dst, dst, sizeof ip->ip_dst);
 366                                 memcpy(&tha.src, src, sizeof ip->ip_src);
 367                                 tha.port = sport << 16 | dport;
 368                         }
 369                 }
 370 #else
 371                 rev = 0;
 372                 src = &ip->ip_src;
 373                 dst = &ip->ip_dst;
 374                 if (sport > dport)
 375                         rev = 1;
 376                 else if (sport == dport) {
 377                         if (memcmp(src, dst, sizeof ip->ip_dst) > 0)
 378                                 rev = 1;
 379                 }
 380                 if (rev) {
 381                         memcpy(&tha.src, dst, sizeof ip->ip_dst);
 382                         memcpy(&tha.dst, src, sizeof ip->ip_src);
 383                         tha.port = dport << 16 | sport;
 384                 } else {
 385                         memcpy(&tha.dst, dst, sizeof ip->ip_dst);
 386                         memcpy(&tha.src, src, sizeof ip->ip_src);
 387                         tha.port = sport << 16 | dport;
 388                 }
 389 #endif
 390
 391                 threv = rev;
 392                 for (th = &tcp_seq_hash[tha.port % TSEQ_HASHSIZE];
 393                      th->nxt; th = th->nxt)
 394                         if (memcmp((char *)&tha, (char *)&th->addr,
 395                                   sizeof(th->addr)) == 0)
 396                                 break;
 397
 398                 if (!th->nxt || (flags & TH_SYN)) {
 399                         /* didn't find it or new conversation */
 400                         if (th->nxt == NULL) {
 401                                 th->nxt = (struct tcp_seq_hash *)
 402                                         calloc(1, sizeof(*th));
 403                                 if (th->nxt == NULL)
 404                                         error("tcp_print: calloc");
 405                         }
 406                         th->addr = tha;
 407                         if (rev)
 408                                 th->ack = seq, th->seq = ack - 1;
 409                         else
 410                                 th->seq = seq, th->ack = ack - 1;
 411                 } else {
 412                         if (rev)
 413                                 seq -= th->ack, ack -= th->seq;
 414                         else
 415                                 seq -= th->seq, ack -= th->ack;
 416                 }
 417
 418                 thseq = th->seq;
 419                 thack = th->ack;
 420         } else {
 421                 /*fool gcc*/
 422                 thseq = thack = threv = 0;
 423         }
 424         if (hlen > length) {
 425                 (void)printf(" [bad hdr length %u - too long, > %u]",
 426                     hlen, length);
 427                 return;
 428         }
 429
 430         if (IP_V(ip) == 4 && vflag && !fragmented) {
 431                 u_int16_t sum, tcp_sum;
 432                 if (TTEST2(tp->th_sport, length)) {
 433                         sum = tcp_cksum(ip, tp, length);
 434
 435                         (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum));
 436                         if (sum != 0) {
 437                                 tcp_sum = EXTRACT_16BITS(&tp->th_sum);
 438                                 (void)printf(" (incorrect (-> 0x%04x),",in_cksum_shouldbe(tcp_sum, sum));
 439                         } else
 440                                 (void)printf(" (correct),");
 441                 }
 442         }
 443 #ifdef INET6
 444         if (IP_V(ip) == 6 && ip6->ip6_plen && vflag && !fragmented) {
 445                 u_int16_t sum,tcp_sum;
 446                 if (TTEST2(tp->th_sport, length)) {
 447                         sum = tcp6_cksum(ip6, tp, length);
 448                         (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum));
 449                         if (sum != 0) {
 450                                 tcp_sum = EXTRACT_16BITS(&tp->th_sum);
 451                                 (void)printf(" (incorrect (-> 0x%04x),",in_cksum_shouldbe(tcp_sum, sum));
 452                         } else
 453                                 (void)printf(" (correct),");
 454
 455                 }
 456         }
 457 #endif
 458
 459         length -= hlen;
 460         if (vflag > 1 || length > 0 || flags & (TH_SYN | TH_FIN | TH_RST))
 461                 (void)printf(" %u:%u(%u)", seq, seq + length, length);
 462         if (flags & TH_ACK)
 463                 (void)printf(" ack %u", ack);
 464
 465         (void)printf(" win %d", win);
 466
 467         if (flags & TH_URG)
 468                 (void)printf(" urg %d", urp);
 469         /*
 470          * Handle any options.
 471          */
 472         if (hlen > sizeof(*tp)) {
 473                 register const u_char *cp;
 474                 register u_int i, opt, datalen;
 475                 register u_int len;
 476
 477                 hlen -= sizeof(*tp);
 478                 cp = (const u_char *)tp + sizeof(*tp);
 479                 putchar(' ');
 480                 ch = '<';
 481                 while (hlen > 0) {
 482                         putchar(ch);
 483                         TCHECK(*cp);
 484                         opt = *cp++;
 485                         if (ZEROLENOPT(opt))
 486                                 len = 1;
 487                         else {
 488                                 TCHECK(*cp);
 489                                 len = *cp++;    /* total including type, len */
 490                                 if (len < 2 || len > hlen)
 491                                         goto bad;
 492                                 --hlen;         /* account for length byte */
 493                         }
 494                         --hlen;                 /* account for type byte */
 495                         datalen = 0;
 496
 497 /* Bail if "l" bytes of data are not left or were not captured  */
 498 #define LENCHECK(l) { if ((l) > hlen) goto bad; TCHECK2(*cp, l); }
 499
 500                         switch (opt) {
 501
 502                         case TCPOPT_MAXSEG:
 503                                 (void)printf("mss");
 504                                 datalen = 2;
 505                                 LENCHECK(datalen);
 506                                 (void)printf(" %u", EXTRACT_16BITS(cp));
 507
 508                                 break;
 509
 510                         case TCPOPT_EOL:
 511                                 (void)printf("eol");
 512                                 break;
 513
 514                         case TCPOPT_NOP:
 515                                 (void)printf("nop");
 516                                 break;
 517
 518                         case TCPOPT_WSCALE:
 519                                 (void)printf("wscale");
 520                                 datalen = 1;
 521                                 LENCHECK(datalen);
 522                                 (void)printf(" %u", *cp);
 523                                 break;
 524
 525                         case TCPOPT_SACKOK:
 526                                 (void)printf("sackOK");
 527                                 break;
 528
 529                         case TCPOPT_SACK:
 530                                 datalen = len - 2;
 531                                 if (datalen % 8 != 0) {
 532                                         (void)printf("malformed sack");
 533                                 } else {
 534                                         u_int32_t s, e;
 535
 536                                         (void)printf("sack %d ", datalen / 8);
 537                                         for (i = 0; i < datalen; i += 8) {
 538                                                 LENCHECK(i + 4);
 539                                                 s = EXTRACT_32BITS(cp + i);
 540                                                 LENCHECK(i + 8);
 541                                                 e = EXTRACT_32BITS(cp + i + 4);
 542                                                 if (threv) {
 543                                                         s -= thseq;
 544                                                         e -= thseq;
 545                                                 } else {
 546                                                         s -= thack;
 547                                                         e -= thack;
 548                                                 }
 549                                                 (void)printf("{%u:%u}", s, e);
 550                                         }
 551                                 }
 552                                 break;
 553
 554                         case TCPOPT_ECHO:
 555                                 (void)printf("echo");
 556                                 datalen = 4;
 557                                 LENCHECK(datalen);
 558                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 559                                 break;
 560
 561                         case TCPOPT_ECHOREPLY:
 562                                 (void)printf("echoreply");
 563                                 datalen = 4;
 564                                 LENCHECK(datalen);
 565                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 566                                 break;
 567
 568                         case TCPOPT_TIMESTAMP:
 569                                 (void)printf("timestamp");
 570                                 datalen = 8;
 571                                 LENCHECK(4);
 572                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 573                                 LENCHECK(datalen);
 574                                 (void)printf(" %u", EXTRACT_32BITS(cp + 4));
 575                                 break;
 576
 577                         case TCPOPT_CC:
 578                                 (void)printf("cc");
 579                                 datalen = 4;
 580                                 LENCHECK(datalen);
 581                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 582                                 break;
 583
 584                         case TCPOPT_CCNEW:
 585                                 (void)printf("ccnew");
 586                                 datalen = 4;
 587                                 LENCHECK(datalen);
 588                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 589                                 break;
 590
 591                         case TCPOPT_CCECHO:
 592                                 (void)printf("ccecho");
 593                                 datalen = 4;
 594                                 LENCHECK(datalen);
 595                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 596                                 break;
 597
 598                         case TCPOPT_SIGNATURE:
 599                                 (void)printf("md5:");
 600                                 datalen = TCP_SIGLEN;
 601                                 LENCHECK(datalen);
 602 #ifdef HAVE_LIBCRYPTO
 603                                 switch (tcp_verify_signature(ip, tp,
 604                                     bp + TH_OFF(tp) * 4, length, cp)) {
 605
 606                                 case SIGNATURE_VALID:
 607                                         (void)printf("valid");
 608                                         break;
 609
 610                                 case SIGNATURE_INVALID:
 611                                         (void)printf("invalid");
 612                                         break;
 613
 614                                 case CANT_CHECK_SIGNATURE:
 615                                         (void)printf("can't check - ");
 616                                         for (i = 0; i < TCP_SIGLEN; ++i)
 617                                                 (void)printf("%02x", cp[i]);
 618                                         break;
 619                                 }
 620 #else
 621                                 for (i = 0; i < TCP_SIGLEN; ++i)
 622                                         (void)printf("%02x", cp[i]);
 623 #endif
 624                                 break;
 625
 626                         default:
 627                                 (void)printf("opt-%u:", opt);
 628                                 datalen = len - 2;
 629                                 for (i = 0; i < datalen; ++i) {
 630                                         LENCHECK(i);
 631                                         (void)printf("%02x", cp[i]);
 632                                 }
 633                                 break;
 634                         }
 635
 636                         /* Account for data printed */
 637                         cp += datalen;
 638                         hlen -= datalen;
 639
 640                         /* Check specification against observed length */
 641                         ++datalen;                      /* option octet */
 642                         if (!ZEROLENOPT(opt))
 643                                 ++datalen;              /* size octet */
 644                         if (datalen != len)
 645                                 (void)printf("[len %d]", len);
 646                         ch = ',';
 647                         if (opt == TCPOPT_EOL)
 648                                 break;
 649                 }
 650                 putchar('>');
 651         }
 652
 653         if (length <= 0)
 654                 return;
 655
 656         /*
 657          * Decode payload if necessary.
 658          */
 659         bp += TH_OFF(tp) * 4;
 660         if (flags & TH_RST) {
 661                 if (vflag)
 662                         print_tcp_rst_data(bp, length);
 663         } else {
 664                 if (sport == TELNET_PORT || dport == TELNET_PORT) {
 665                         if (!qflag && vflag)
 666                                 telnet_print(bp, length);
 667                 } else if (sport == BGP_PORT || dport == BGP_PORT)
 668                         bgp_print(bp, length);
 669                 else if (sport == PPTP_PORT || dport == PPTP_PORT)
 670                         pptp_print(bp);
 671 #ifdef TCPDUMP_DO_SMB
 672                 else if (sport == NETBIOS_SSN_PORT || dport == NETBIOS_SSN_PORT)
 673                         nbt_tcp_print(bp, length);
 674 #endif
 675                 else if (sport == BEEP_PORT || dport == BEEP_PORT)
 676                         beep_print(bp, length);
 677                 else if (length > 2 &&
 678                     (sport == NAMESERVER_PORT || dport == NAMESERVER_PORT ||
 679                      sport == MULTICASTDNS_PORT || dport == MULTICASTDNS_PORT)) {
 680                         /*
 681                          * TCP DNS query has 2byte length at the head.
 682                          * XXX packet could be unaligned, it can go strange
 683                          */
 684                         ns_print(bp + 2, length - 2, 0);
 685                 } else if (sport == MSDP_PORT || dport == MSDP_PORT) {
 686                         msdp_print(bp, length);
 687                 }
 688                 else if (length > 0 && (sport == LDP_PORT || dport == LDP_PORT)) {
 689                         ldp_print(bp, length);
 690                 }
 691         }
 692         return;
 693 bad:
 694         fputs("[bad opt]", stdout);
 695         if (ch != '\0')
 696                 putchar('>');
 697         return;
 698 trunc:
 699         fputs("[|tcp]", stdout);
 700         if (ch != '\0')
 701                 putchar('>');
 702 }
 703
 704 /*
 705  * RFC1122 says the following on data in RST segments:
 706  *
 707  *         4.2.2.12  RST Segment: RFC-793 Section 3.4
 708  *
 709  *            A TCP SHOULD allow a received RST segment to include data.
 710  *
 711  *            DISCUSSION
 712  *                 It has been suggested that a RST segment could contain
 713  *                 ASCII text that encoded and explained the cause of the
 714  *                 RST.  No standard has yet been established for such
 715  *                 data.
 716  *
 717  */
 718
 719 static void
 720 print_tcp_rst_data(register const u_char *sp, u_int length)
 721 {
 722         int c;
 723
 724         if (TTEST2(*sp, length))
 725                 printf(" [RST");
 726         else
 727                 printf(" [!RST");
 728         if (length > MAX_RST_DATA_LEN) {
 729                 length = MAX_RST_DATA_LEN;      /* can use -X for longer */
 730                 putchar('+');                   /* indicate we truncate */
 731         }
 732         putchar(' ');
 733         while (length-- && sp <= snapend) {
 734                 c = *sp++;
 735                 safeputchar(c);
 736         }
 737         putchar(']');
 738 }
 739
 740 #ifdef HAVE_LIBCRYPTO
 741 static int
 742 tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp,
 743     const u_char *data, int length, const u_char *rcvsig)
 744 {
 745         struct tcphdr tp1;
 746         u_char sig[TCP_SIGLEN];
 747         char zero_proto = 0;
 748         MD5_CTX ctx;
 749         u_int16_t savecsum, tlen;
 750 #ifdef INET6
 751         struct ip6_hdr *ip6;
 752         u_int32_t len32;
 753         u_int8_t nxt;
 754 #endif
 755
 756         tp1 = *tp;
 757
 758         if (tcpmd5secret == NULL)
 759                 return (CANT_CHECK_SIGNATURE);
 760
 761         MD5_Init(&ctx);
 762         /*
 763          * Step 1: Update MD5 hash with IP pseudo-header.
 764          */
 765         if (IP_V(ip) == 4) {
 766                 MD5_Update(&ctx, (char *)&ip->ip_src, sizeof(ip->ip_src));
 767                 MD5_Update(&ctx, (char *)&ip->ip_dst, sizeof(ip->ip_dst));
 768                 MD5_Update(&ctx, (char *)&zero_proto, sizeof(zero_proto));
 769                 MD5_Update(&ctx, (char *)&ip->ip_p, sizeof(ip->ip_p));
 770                 tlen = EXTRACT_16BITS(&ip->ip_len) - IP_HL(ip) * 4;
 771                 tlen = htons(tlen);
 772                 MD5_Update(&ctx, (char *)&tlen, sizeof(tlen));
 773 #ifdef INET6
 774         } else if (IP_V(ip) == 6) {
 775                 ip6 = (struct ip6_hdr *)ip;
 776                 MD5_Update(&ctx, (char *)&ip6->ip6_src, sizeof(ip6->ip6_src));
 777                 MD5_Update(&ctx, (char *)&ip6->ip6_dst, sizeof(ip6->ip6_dst));
 778                 len32 = htonl(ntohs(ip6->ip6_plen));
 779                 MD5_Update(&ctx, (char *)&len32, sizeof(len32));
 780                 nxt = 0;
 781                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 782                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 783                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 784                 nxt = IPPROTO_TCP;
 785                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 786 #endif
 787         } else
 788                 return (CANT_CHECK_SIGNATURE);
 789
 790         /*
 791          * Step 2: Update MD5 hash with TCP header, excluding options.
 792          * The TCP checksum must be set to zero.
 793          */
 794         savecsum = tp1.th_sum;
 795         tp1.th_sum = 0;
 796         MD5_Update(&ctx, (char *)&tp1, sizeof(struct tcphdr));
 797         tp1.th_sum = savecsum;
 798         /*
 799          * Step 3: Update MD5 hash with TCP segment data, if present.
 800          */
 801         if (length > 0)
 802                 MD5_Update(&ctx, data, length);
 803         /*
 804          * Step 4: Update MD5 hash with shared secret.
 805          */
 806         MD5_Update(&ctx, tcpmd5secret, strlen(tcpmd5secret));
 807         MD5_Final(sig, &ctx);
 808
 809         if (memcmp(rcvsig, sig, TCP_SIGLEN) == 0)
 810                 return (SIGNATURE_VALID);
 811         else
 812                 return (SIGNATURE_INVALID);
 813 }
 814 #endif /* HAVE_LIBCRYPTO */