print-tcp.c revision 190207 
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
27static 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
66static 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
70static void print_tcp_rst_data(register const u_char *sp, u_int length);
71
72#define MAX_RST_DATA_LEN	30
73
74
75struct 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
86struct 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
98static struct tcp_seq_hash tcp_seq_hash[TSEQ_HASHSIZE];
99
100struct 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
112struct 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
130static 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
162static 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
192void
193tcp_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
716static void
717print_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
738static int
739tcp_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 */
819