contrib/tcpdump/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 1.130.2.3 2007-12-22 03:08:45 guy 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
  62 #define SIGNATURE_VALID         0
  63 #define SIGNATURE_INVALID       1
  64 #define CANT_CHECK_SIGNATURE    2
  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         { 0, NULL }
 128 };
 129
 130 static int tcp_cksum(register const struct ip *ip,
 131                      register const struct tcphdr *tp,
 132                      register u_int len)
 133 {
 134         union phu {
 135                 struct phdr {
 136                         u_int32_t src;
 137                         u_int32_t dst;
 138                         u_char mbz;
 139                         u_char proto;
 140                         u_int16_t len;
 141                 } ph;
 142                 u_int16_t pa[6];
 143         } phu;
 144         const u_int16_t *sp;
 145
 146         /* pseudo-header.. */
 147         phu.ph.len = htons((u_int16_t)len);
 148         phu.ph.mbz = 0;
 149         phu.ph.proto = IPPROTO_TCP;
 150         memcpy(&phu.ph.src, &ip->ip_src.s_addr, sizeof(u_int32_t));
 151         if (IP_HL(ip) == 5)
 152                 memcpy(&phu.ph.dst, &ip->ip_dst.s_addr, sizeof(u_int32_t));
 153         else
 154                 phu.ph.dst = ip_finddst(ip);
 155
 156         sp = &phu.pa[0];
 157         return in_cksum((u_short *)tp, len,
 158                         sp[0]+sp[1]+sp[2]+sp[3]+sp[4]+sp[5]);
 159 }
 160
 161 #ifdef INET6
 162 static int tcp6_cksum(const struct ip6_hdr *ip6, const struct tcphdr *tp,
 163                       u_int len)
 164 {
 165         size_t i;
 166         u_int32_t sum = 0;
 167         union {
 168                 struct {
 169                         struct in6_addr ph_src;
 170                         struct in6_addr ph_dst;
 171                         u_int32_t       ph_len;
 172                         u_int8_t        ph_zero[3];
 173                         u_int8_t        ph_nxt;
 174                 } ph;
 175                 u_int16_t pa[20];
 176         } phu;
 177
 178         /* pseudo-header */
 179         memset(&phu, 0, sizeof(phu));
 180         phu.ph.ph_src = ip6->ip6_src;
 181         phu.ph.ph_dst = ip6->ip6_dst;
 182         phu.ph.ph_len = htonl(len);
 183         phu.ph.ph_nxt = IPPROTO_TCP;
 184
 185         for (i = 0; i < sizeof(phu.pa) / sizeof(phu.pa[0]); i++)
 186                 sum += phu.pa[i];
 187
 188         return in_cksum((u_short *)tp, len, sum);
 189 }
 190 #endif
 191
 192 void
 193 tcp_print(register const u_char *bp, register u_int length,
 194           register const u_char *bp2, int fragmented)
 195 {
 196         register const struct tcphdr *tp;
 197         register const struct ip *ip;
 198         register u_char flags;
 199         register u_int hlen;
 200         register char ch;
 201         u_int16_t sport, dport, win, urp;
 202         u_int32_t seq, ack, thseq, thack;
 203         int threv;
 204 #ifdef INET6
 205         register const struct ip6_hdr *ip6;
 206 #endif
 207
 208         tp = (struct tcphdr *)bp;
 209         ip = (struct ip *)bp2;
 210 #ifdef INET6
 211         if (IP_V(ip) == 6)
 212                 ip6 = (struct ip6_hdr *)bp2;
 213         else
 214                 ip6 = NULL;
 215 #endif /*INET6*/
 216         ch = '\0';
 217         if (!TTEST(tp->th_dport)) {
 218                 (void)printf("%s > %s: [|tcp]",
 219                              ipaddr_string(&ip->ip_src),
 220                              ipaddr_string(&ip->ip_dst));
 221                 return;
 222         }
 223
 224         sport = EXTRACT_16BITS(&tp->th_sport);
 225         dport = EXTRACT_16BITS(&tp->th_dport);
 226
 227         hlen = TH_OFF(tp) * 4;
 228
 229         /*
 230          * If data present, header length valid, and NFS port used,
 231          * assume NFS.
 232          * Pass offset of data plus 4 bytes for RPC TCP msg length
 233          * to NFS print routines.
 234          */
 235         if (!qflag && hlen >= sizeof(*tp) && hlen <= length &&
 236             (length - hlen) >= 4) {
 237                 u_char *fraglenp;
 238                 u_int32_t fraglen;
 239                 register struct sunrpc_msg *rp;
 240                 enum sunrpc_msg_type direction;
 241
 242                 fraglenp = (u_char *)tp + hlen;
 243                 if (TTEST2(*fraglenp, 4)) {
 244                         fraglen = EXTRACT_32BITS(fraglenp) & 0x7FFFFFFF;
 245                         if (fraglen > (length - hlen) - 4)
 246                                 fraglen = (length - hlen) - 4;
 247                         rp = (struct sunrpc_msg *)(fraglenp + 4);
 248                         if (TTEST(rp->rm_direction)) {
 249                                 direction = (enum sunrpc_msg_type)EXTRACT_32BITS(&rp->rm_direction);
 250                                 if (dport == NFS_PORT &&
 251                                     direction == SUNRPC_CALL) {
 252                                         nfsreq_print((u_char *)rp, fraglen,
 253                                             (u_char *)ip);
 254                                         return;
 255                                 }
 256                                 if (sport == NFS_PORT &&
 257                                     direction == SUNRPC_REPLY) {
 258                                         nfsreply_print((u_char *)rp, fraglen,
 259                                             (u_char *)ip);
 260                                         return;
 261                                 }
 262                         }
 263                 }
 264         }
 265 #ifdef INET6
 266         if (ip6) {
 267                 if (ip6->ip6_nxt == IPPROTO_TCP) {
 268                         (void)printf("%s.%s > %s.%s: ",
 269                                      ip6addr_string(&ip6->ip6_src),
 270                                      tcpport_string(sport),
 271                                      ip6addr_string(&ip6->ip6_dst),
 272                                      tcpport_string(dport));
 273                 } else {
 274                         (void)printf("%s > %s: ",
 275                                      tcpport_string(sport), tcpport_string(dport));
 276                 }
 277         } else
 278 #endif /*INET6*/
 279         {
 280                 if (ip->ip_p == IPPROTO_TCP) {
 281                         (void)printf("%s.%s > %s.%s: ",
 282                                      ipaddr_string(&ip->ip_src),
 283                                      tcpport_string(sport),
 284                                      ipaddr_string(&ip->ip_dst),
 285                                      tcpport_string(dport));
 286                 } else {
 287                         (void)printf("%s > %s: ",
 288                                      tcpport_string(sport), tcpport_string(dport));
 289                 }
 290         }
 291
 292         if (hlen < sizeof(*tp)) {
 293                 (void)printf(" tcp %d [bad hdr length %u - too short, < %lu]",
 294                              length - hlen, hlen, (unsigned long)sizeof(*tp));
 295                 return;
 296         }
 297
 298         TCHECK(*tp);
 299
 300         seq = EXTRACT_32BITS(&tp->th_seq);
 301         ack = EXTRACT_32BITS(&tp->th_ack);
 302         win = EXTRACT_16BITS(&tp->th_win);
 303         urp = EXTRACT_16BITS(&tp->th_urp);
 304
 305         if (qflag) {
 306                 (void)printf("tcp %d", length - hlen);
 307                 if (hlen > length) {
 308                         (void)printf(" [bad hdr length %u - too long, > %u]",
 309                                      hlen, length);
 310                 }
 311                 return;
 312         }
 313
 314         flags = tp->th_flags;
 315         printf("Flags [%s]", bittok2str_nosep(tcp_flag_values, "none", flags));
 316
 317         if (!Sflag && (flags & TH_ACK)) {
 318                 register struct tcp_seq_hash *th;
 319                 const void *src, *dst;
 320                 register int rev;
 321                 struct tha tha;
 322                 /*
 323                  * Find (or record) the initial sequence numbers for
 324                  * this conversation.  (we pick an arbitrary
 325                  * collating order so there's only one entry for
 326                  * both directions).
 327                  */
 328 #ifdef INET6
 329                 memset(&tha, 0, sizeof(tha));
 330                 rev = 0;
 331                 if (ip6) {
 332                         src = &ip6->ip6_src;
 333                         dst = &ip6->ip6_dst;
 334                         if (sport > dport)
 335                                 rev = 1;
 336                         else if (sport == dport) {
 337                                 if (memcmp(src, dst, sizeof ip6->ip6_dst) > 0)
 338                                         rev = 1;
 339                         }
 340                         if (rev) {
 341                                 memcpy(&tha.src, dst, sizeof ip6->ip6_dst);
 342                                 memcpy(&tha.dst, src, sizeof ip6->ip6_src);
 343                                 tha.port = dport << 16 | sport;
 344                         } else {
 345                                 memcpy(&tha.dst, dst, sizeof ip6->ip6_dst);
 346                                 memcpy(&tha.src, src, sizeof ip6->ip6_src);
 347                                 tha.port = sport << 16 | dport;
 348                         }
 349                 } else {
 350                         src = &ip->ip_src;
 351                         dst = &ip->ip_dst;
 352                         if (sport > dport)
 353                                 rev = 1;
 354                         else if (sport == dport) {
 355                                 if (memcmp(src, dst, sizeof ip->ip_dst) > 0)
 356                                         rev = 1;
 357                         }
 358                         if (rev) {
 359                                 memcpy(&tha.src, dst, sizeof ip->ip_dst);
 360                                 memcpy(&tha.dst, src, sizeof ip->ip_src);
 361                                 tha.port = dport << 16 | sport;
 362                         } else {
 363                                 memcpy(&tha.dst, dst, sizeof ip->ip_dst);
 364                                 memcpy(&tha.src, src, sizeof ip->ip_src);
 365                                 tha.port = sport << 16 | dport;
 366                         }
 367                 }
 368 #else
 369                 rev = 0;
 370                 src = &ip->ip_src;
 371                 dst = &ip->ip_dst;
 372                 if (sport > dport)
 373                         rev = 1;
 374                 else if (sport == dport) {
 375                         if (memcmp(src, dst, sizeof ip->ip_dst) > 0)
 376                                 rev = 1;
 377                 }
 378                 if (rev) {
 379                         memcpy(&tha.src, dst, sizeof ip->ip_dst);
 380                         memcpy(&tha.dst, src, sizeof ip->ip_src);
 381                         tha.port = dport << 16 | sport;
 382                 } else {
 383                         memcpy(&tha.dst, dst, sizeof ip->ip_dst);
 384                         memcpy(&tha.src, src, sizeof ip->ip_src);
 385                         tha.port = sport << 16 | dport;
 386                 }
 387 #endif
 388
 389                 threv = rev;
 390                 for (th = &tcp_seq_hash[tha.port % TSEQ_HASHSIZE];
 391                      th->nxt; th = th->nxt)
 392                         if (memcmp((char *)&tha, (char *)&th->addr,
 393                                    sizeof(th->addr)) == 0)
 394                                 break;
 395
 396                 if (!th->nxt || (flags & TH_SYN)) {
 397                         /* didn't find it or new conversation */
 398                         if (th->nxt == NULL) {
 399                                 th->nxt = (struct tcp_seq_hash *)
 400                                         calloc(1, sizeof(*th));
 401                                 if (th->nxt == NULL)
 402                                         error("tcp_print: calloc");
 403                         }
 404                         th->addr = tha;
 405                         if (rev)
 406                                 th->ack = seq, th->seq = ack - 1;
 407                         else
 408                                 th->seq = seq, th->ack = ack - 1;
 409                 } else {
 410                         if (rev)
 411                                 seq -= th->ack, ack -= th->seq;
 412                         else
 413                                 seq -= th->seq, ack -= th->ack;
 414                 }
 415
 416                 thseq = th->seq;
 417                 thack = th->ack;
 418         } else {
 419                 /*fool gcc*/
 420                 thseq = thack = threv = 0;
 421         }
 422         if (hlen > length) {
 423                 (void)printf(" [bad hdr length %u - too long, > %u]",
 424                              hlen, length);
 425                 return;
 426         }
 427
 428         if (IP_V(ip) == 4 && vflag && !Kflag && !fragmented) {
 429                 u_int16_t sum, tcp_sum;
 430                 if (TTEST2(tp->th_sport, length)) {
 431                         sum = tcp_cksum(ip, tp, length);
 432
 433                         (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum));
 434                         if (sum != 0) {
 435                                 tcp_sum = EXTRACT_16BITS(&tp->th_sum);
 436                                 (void)printf(" (incorrect -> 0x%04x)",in_cksum_shouldbe(tcp_sum, sum));
 437                         } else
 438                                 (void)printf(" (correct)");
 439                 }
 440         }
 441 #ifdef INET6
 442         if (IP_V(ip) == 6 && ip6->ip6_plen && vflag && !Kflag && !fragmented) {
 443                 u_int16_t sum,tcp_sum;
 444                 if (TTEST2(tp->th_sport, length)) {
 445                         sum = tcp6_cksum(ip6, tp, length);
 446                         (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum));
 447                         if (sum != 0) {
 448                                 tcp_sum = EXTRACT_16BITS(&tp->th_sum);
 449                                 (void)printf(" (incorrect -> 0x%04x)",in_cksum_shouldbe(tcp_sum, sum));
 450                         } else
 451                                 (void)printf(" (correct)");
 452
 453                 }
 454         }
 455 #endif
 456
 457         length -= hlen;
 458         if (vflag > 1 || flags & (TH_SYN | TH_FIN | TH_RST)) {
 459                 (void)printf(", seq %u", seq);
 460
 461                 if (length > 0) {
 462                         (void)printf(":%u", seq + length);
 463                 }
 464         }
 465
 466         if (flags & TH_ACK) {
 467                 (void)printf(", ack %u", ack);
 468         }
 469
 470         (void)printf(", win %d", win);
 471
 472         if (flags & TH_URG)
 473                 (void)printf(", urg %d", urp);
 474         /*
 475          * Handle any options.
 476          */
 477         if (hlen > sizeof(*tp)) {
 478                 register const u_char *cp;
 479                 register u_int i, opt, datalen;
 480                 register u_int len;
 481
 482                 hlen -= sizeof(*tp);
 483                 cp = (const u_char *)tp + sizeof(*tp);
 484                 printf(", options [");
 485                 while (hlen > 0) {
 486                         if (ch != '\0')
 487                                 putchar(ch);
 488                         TCHECK(*cp);
 489                         opt = *cp++;
 490                         if (ZEROLENOPT(opt))
 491                                 len = 1;
 492                         else {
 493                                 TCHECK(*cp);
 494                                 len = *cp++;    /* total including type, len */
 495                                 if (len < 2 || len > hlen)
 496                                         goto bad;
 497                                 --hlen;         /* account for length byte */
 498                         }
 499                         --hlen;                 /* account for type byte */
 500                         datalen = 0;
 501
 502 /* Bail if "l" bytes of data are not left or were not captured  */
 503 #define LENCHECK(l) { if ((l) > hlen) goto bad; TCHECK2(*cp, l); }
 504
 505
 506                         printf("%s", tok2str(tcp_option_values, "Unknown Option %u", opt));
 507
 508                         switch (opt) {
 509
 510                         case TCPOPT_MAXSEG:
 511                                 datalen = 2;
 512                                 LENCHECK(datalen);
 513                                 (void)printf(" %u", EXTRACT_16BITS(cp));
 514                                 break;
 515
 516                         case TCPOPT_WSCALE:
 517                                 datalen = 1;
 518                                 LENCHECK(datalen);
 519                                 (void)printf(" %u", *cp);
 520                                 break;
 521
 522                         case TCPOPT_SACK:
 523                                 datalen = len - 2;
 524                                 if (datalen % 8 != 0) {
 525                                         (void)printf("malformed sack");
 526                                 } else {
 527                                         u_int32_t s, e;
 528
 529                                         (void)printf(" %d ", datalen / 8);
 530                                         for (i = 0; i < datalen; i += 8) {
 531                                                 LENCHECK(i + 4);
 532                                                 s = EXTRACT_32BITS(cp + i);
 533                                                 LENCHECK(i + 8);
 534                                                 e = EXTRACT_32BITS(cp + i + 4);
 535                                                 if (threv) {
 536                                                         s -= thseq;
 537                                                         e -= thseq;
 538                                                 } else {
 539                                                         s -= thack;
 540                                                         e -= thack;
 541                                                 }
 542                                                 (void)printf("{%u:%u}", s, e);
 543                                         }
 544                                 }
 545                                 break;
 546
 547                         case TCPOPT_CC:
 548                         case TCPOPT_CCNEW:
 549                         case TCPOPT_CCECHO:
 550                         case TCPOPT_ECHO:
 551                         case TCPOPT_ECHOREPLY:
 552
 553                                 /*
 554                                  * those options share their semantics.
 555                                  * fall through
 556                                  */
 557                                 datalen = 4;
 558                                 LENCHECK(datalen);
 559                                 (void)printf(" %u", EXTRACT_32BITS(cp));
 560                                 break;
 561
 562                         case TCPOPT_TIMESTAMP:
 563                                 datalen = 8;
 564                                 LENCHECK(datalen);
 565                                 (void)printf(" val %u ecr %u",
 566                                              EXTRACT_32BITS(cp),
 567                                              EXTRACT_32BITS(cp + 4));
 568                                 break;
 569
 570                         case TCPOPT_SIGNATURE:
 571                                 datalen = TCP_SIGLEN;
 572                                 LENCHECK(datalen);
 573 #ifdef HAVE_LIBCRYPTO
 574                                 switch (tcp_verify_signature(ip, tp,
 575                                                              bp + TH_OFF(tp) * 4, length, cp)) {
 576
 577                                 case SIGNATURE_VALID:
 578                                         (void)printf("valid");
 579                                         break;
 580
 581                                 case SIGNATURE_INVALID:
 582                                         (void)printf("invalid");
 583                                         break;
 584
 585                                 case CANT_CHECK_SIGNATURE:
 586                                         (void)printf("can't check - ");
 587                                         for (i = 0; i < TCP_SIGLEN; ++i)
 588                                                 (void)printf("%02x", cp[i]);
 589                                         break;
 590                                 }
 591 #else
 592                                 for (i = 0; i < TCP_SIGLEN; ++i)
 593                                         (void)printf("%02x", cp[i]);
 594 #endif
 595                                 break;
 596
 597                         case TCPOPT_AUTH:
 598                                 (void)printf("keyid %d", *cp++);
 599                                 datalen = len - 3;
 600                                 for (i = 0; i < datalen; ++i) {
 601                                         LENCHECK(i);
 602                                         (void)printf("%02x", cp[i]);
 603                                 }
 604                                 break;
 605
 606
 607                         case TCPOPT_EOL:
 608                         case TCPOPT_NOP:
 609                         case TCPOPT_SACKOK:
 610                                 /*
 611                                  * Nothing interesting.
 612                                  * fall through
 613                                  */
 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         tp1 = *tp;
 754
 755         if (tcpmd5secret == NULL)
 756                 return (CANT_CHECK_SIGNATURE);
 757
 758         MD5_Init(&ctx);
 759         /*
 760          * Step 1: Update MD5 hash with IP pseudo-header.
 761          */
 762         if (IP_V(ip) == 4) {
 763                 MD5_Update(&ctx, (char *)&ip->ip_src, sizeof(ip->ip_src));
 764                 MD5_Update(&ctx, (char *)&ip->ip_dst, sizeof(ip->ip_dst));
 765                 MD5_Update(&ctx, (char *)&zero_proto, sizeof(zero_proto));
 766                 MD5_Update(&ctx, (char *)&ip->ip_p, sizeof(ip->ip_p));
 767                 tlen = EXTRACT_16BITS(&ip->ip_len) - IP_HL(ip) * 4;
 768                 tlen = htons(tlen);
 769                 MD5_Update(&ctx, (char *)&tlen, sizeof(tlen));
 770 #ifdef INET6
 771         } else if (IP_V(ip) == 6) {
 772                 ip6 = (struct ip6_hdr *)ip;
 773                 MD5_Update(&ctx, (char *)&ip6->ip6_src, sizeof(ip6->ip6_src));
 774                 MD5_Update(&ctx, (char *)&ip6->ip6_dst, sizeof(ip6->ip6_dst));
 775                 len32 = htonl(ntohs(ip6->ip6_plen));
 776                 MD5_Update(&ctx, (char *)&len32, sizeof(len32));
 777                 nxt = 0;
 778                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 779                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 780                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 781                 nxt = IPPROTO_TCP;
 782                 MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
 783 #endif
 784         } else
 785                 return (CANT_CHECK_SIGNATURE);
 786
 787         /*
 788          * Step 2: Update MD5 hash with TCP header, excluding options.
 789          * The TCP checksum must be set to zero.
 790          */
 791         savecsum = tp1.th_sum;
 792         tp1.th_sum = 0;
 793         MD5_Update(&ctx, (char *)&tp1, sizeof(struct tcphdr));
 794         tp1.th_sum = savecsum;
 795         /*
 796          * Step 3: Update MD5 hash with TCP segment data, if present.
 797          */
 798         if (length > 0)
 799                 MD5_Update(&ctx, data, length);
 800         /*
 801          * Step 4: Update MD5 hash with shared secret.
 802          */
 803         MD5_Update(&ctx, tcpmd5secret, strlen(tcpmd5secret));
 804         MD5_Final(sig, &ctx);
 805
 806         if (memcmp(rcvsig, sig, TCP_SIGLEN) == 0)
 807                 return (SIGNATURE_VALID);
 808         else
 809                 return (SIGNATURE_INVALID);
 810 }
 811 #endif /* HAVE_LIBCRYPTO */
 812
 813 /*
 814  * Local Variables:
 815  * c-style: whitesmith
 816  * c-basic-offset: 8
 817  * End:
 818  */