/* $NetBSD: print-tcp.c,v 1.9 2007/07/26 18:15:12 plunky Exp $ */

/*

* Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997

* The Regents of the University of California. All rights reserved.

*

* Copyright (c) 1999-2004 The tcpdump.org project

*

* Redistribution and use in source and binary forms, with or without

* modification, are permitted provided that: (1) source code distributions

* retain the above copyright notice and this paragraph in its entirety, (2)

* distributions including binary code include the above copyright notice and

* this paragraph in its entirety in the documentation or other materials

* provided with the distribution, and (3) all advertising materials mentioning

* features or use of this software display the following acknowledgement:

* ``This product includes software developed by the University of California,

* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of

* the University nor the names of its contributors may be used to endorse

* or promote products derived from this software without specific prior

* written permission.

* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED

* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF

* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

*/

#ifndef lint

#else

__RCSID("$NetBSD: print-tcp.c,v 1.8 2007/07/24 11:53:48 drochner Exp $");

#endif

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include <tcpdump-stdinc.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include "interface.h"

#include "addrtoname.h"

#include "extract.h"

#include "tcp.h"

#include "ip.h"

#ifdef INET6

#include "ip6.h"

#endif

#include "ipproto.h"

#include "rpc_auth.h"

#include "rpc_msg.h"

#include "nameser.h"

#ifdef HAVE_LIBCRYPTO

#include <openssl/md5.h>

#include <signature.h>

static int tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp,

const u_char *data, int length, const u_char *rcvsig);

#endif

static void print_tcp_rst_data(register const u_char *sp, u_int length);

#define MAX_RST_DATA_LEN 30

struct tha {

};

struct tcp_seq_hash {

};

#ifdef INET6

struct tha6 {

};

struct tcp_seq_hash6 {

};

#endif

#define TSEQ_HASHSIZE 919

/* These tcp optinos do not have the size octet */

#define ZEROLENOPT(o) ((o) == TCPOPT_EOL || (o) == TCPOPT_NOP)

static struct tcp_seq_hash tcp_seq_hash4[TSEQ_HASHSIZE];

#ifdef INET6

static struct tcp_seq_hash6 tcp_seq_hash6[TSEQ_HASHSIZE];

#endif

static const struct tok tcp_flag_values[] = {

{ TH_FIN, "F" },

{ TH_SYN, "S" },

{ TH_RST, "R" },

{ TH_PUSH, "P" },

{ TH_ACK, "." },

{ TH_URG, "U" },

{ TH_ECNECHO, "E" },

{ TH_CWR, "W" },

{ 0, NULL }

};

static const struct tok tcp_option_values[] = {

{ TCPOPT_EOL, "eol" },

{ TCPOPT_NOP, "nop" },

{ TCPOPT_MAXSEG, "mss" },

{ TCPOPT_WSCALE, "wscale" },

{ TCPOPT_SACKOK, "sackOK" },

{ TCPOPT_SACK, "sack" },

{ TCPOPT_ECHO, "echo" },

{ TCPOPT_ECHOREPLY, "echoreply" },

{ TCPOPT_TIMESTAMP, "TS" },

{ TCPOPT_CC, "cc" },

{ TCPOPT_CCNEW, "ccnew" },

{ TCPOPT_CCECHO, "" },

{ TCPOPT_SIGNATURE, "md5" },

{ TCPOPT_AUTH, "enhanced auth" },

{ TCPOPT_UTO, "uto" },

{ TCPOPT_MPTCP, "mptcp" },

{ TCPOPT_EXPERIMENT2, "exp" },

{ 0, NULL }

};

static int tcp_cksum(register const struct ip *ip,

register const struct tcphdr *tp,

register u_int len)

{

return nextproto4_cksum(ip, (const u_int8_t *)tp, len, len,

IPPROTO_TCP);

}

void

tcp_print(register const u_char *bp, register u_int length,

register const u_char *bp2, int fragmented)

{

register const struct tcphdr *tp;

register const struct ip *ip;

register u_char flags;

register u_int hlen;

register char ch;

u_int16_t sport, dport, win, urp;

u_int32_t seq, ack, thseq, thack;

u_int utoval;

u_int16_t magic;

register int rev;

#ifdef INET6

register const struct ip6_hdr *ip6;

#endif

tp = (struct tcphdr *)bp;

ip = (struct ip *)bp2;

#ifdef INET6

if (IP_V(ip) == 6)

ip6 = (struct ip6_hdr *)bp2;

else

ip6 = NULL;

#endif /*INET6*/

ch = '\0';

if (!TTEST(tp->th_dport)) {

(void)printf("%s > %s: [|tcp]",

ipaddr_string(&ip->ip_src),

ipaddr_string(&ip->ip_dst));

return;

}

sport = EXTRACT_16BITS(&tp->th_sport);

dport = EXTRACT_16BITS(&tp->th_dport);

hlen = TH_OFF(tp) * 4;

#ifdef INET6

if (ip6) {

if (ip6->ip6_nxt == IPPROTO_TCP) {

(void)printf("%s.%s > %s.%s: ",

ip6addr_string(&ip6->ip6_src),

tcpport_string(sport),

ip6addr_string(&ip6->ip6_dst),

tcpport_string(dport));

} else {

(void)printf("%s > %s: ",

tcpport_string(sport), tcpport_string(dport));

}

} else

#endif /*INET6*/

{

if (ip->ip_p == IPPROTO_TCP) {

(void)printf("%s.%s > %s.%s: ",

ipaddr_string(&ip->ip_src),

tcpport_string(sport),

ipaddr_string(&ip->ip_dst),

tcpport_string(dport));

} else {

(void)printf("%s > %s: ",

tcpport_string(sport), tcpport_string(dport));

}

}

if (hlen < sizeof(*tp)) {

(void)printf(" tcp %d [bad hdr length %u - too short, < %lu]",

length - hlen, hlen, (unsigned long)sizeof(*tp));

return;

}

TCHECK(*tp);

seq = EXTRACT_32BITS(&tp->th_seq);

ack = EXTRACT_32BITS(&tp->th_ack);

win = EXTRACT_16BITS(&tp->th_win);

urp = EXTRACT_16BITS(&tp->th_urp);

if (qflag) {

(void)printf("tcp %d", length - hlen);

if (hlen > length) {

(void)printf(" [bad hdr length %u - too long, > %u]",

hlen, length);

}

return;

}

flags = tp->th_flags;

printf("Flags [%s]", bittok2str_nosep(tcp_flag_values, "none", flags));

if (!Sflag && (flags & TH_ACK)) {

/*

* Find (or record) the initial sequence numbers for

* this conversation. (we pick an arbitrary

* collating order so there's only one entry for

* both directions).

*/

rev = 0;

#ifdef INET6

if (ip6) {

register struct tcp_seq_hash6 *th;

struct tcp_seq_hash6 *tcp_seq_hash;

const struct in6_addr *src, *dst;

struct tha6 tha;

tcp_seq_hash = tcp_seq_hash6;

src = &ip6->ip6_src;

dst = &ip6->ip6_dst;

if (sport > dport)

rev = 1;

else if (sport == dport) {

if (UNALIGNED_MEMCMP(src, dst, sizeof ip6->ip6_dst) > 0)

rev = 1;

}

if (rev) {

UNALIGNED_MEMCPY(&tha.src, dst, sizeof ip6->ip6_dst);

UNALIGNED_MEMCPY(&tha.dst, src, sizeof ip6->ip6_src);

tha.port = dport << 16 | sport;

} else {

UNALIGNED_MEMCPY(&tha.dst, dst, sizeof ip6->ip6_dst);

UNALIGNED_MEMCPY(&tha.src, src, sizeof ip6->ip6_src);

tha.port = sport << 16 | dport;

}

for (th = &tcp_seq_hash[tha.port % TSEQ_HASHSIZE];

th->nxt; th = th->nxt)

if (memcmp((char *)&tha, (char *)&th->addr,

sizeof(th->addr)) == 0)

break;

if (!th->nxt || (flags & TH_SYN)) {

/* didn't find it or new conversation */

if (th->nxt == NULL) {

th->nxt = (struct tcp_seq_hash6 *)

calloc(1, sizeof(*th));

if (th->nxt == NULL)

error("tcp_print: calloc");

}

th->addr = tha;

if (rev)

th->ack = seq, th->seq = ack - 1;

else

th->seq = seq, th->ack = ack - 1;

} else {

if (rev)

seq -= th->ack, ack -= th->seq;

else

seq -= th->seq, ack -= th->ack;

}

thseq = th->seq;

thack = th->ack;

} else {

#else /*INET6*/

{

#endif /*INET6*/

register struct tcp_seq_hash *th;

struct tcp_seq_hash *tcp_seq_hash;

const struct in_addr *src, *dst;

struct tha tha;

tcp_seq_hash = tcp_seq_hash4;

src = &ip->ip_src;

dst = &ip->ip_dst;

if (sport > dport)

rev = 1;

else if (sport == dport) {

if (UNALIGNED_MEMCMP(src, dst, sizeof ip->ip_dst) > 0)

rev = 1;

}

if (rev) {

UNALIGNED_MEMCPY(&tha.src, dst, sizeof ip->ip_dst);

UNALIGNED_MEMCPY(&tha.dst, src, sizeof ip->ip_src);

tha.port = dport << 16 | sport;

} else {

UNALIGNED_MEMCPY(&tha.dst, dst, sizeof ip->ip_dst);

UNALIGNED_MEMCPY(&tha.src, src, sizeof ip->ip_src);

tha.port = sport << 16 | dport;

}

for (th = &tcp_seq_hash[tha.port % TSEQ_HASHSIZE];

th->nxt; th = th->nxt)

if (memcmp((char *)&tha, (char *)&th->addr,

sizeof(th->addr)) == 0)

break;

if (!th->nxt || (flags & TH_SYN)) {

/* didn't find it or new conversation */

if (th->nxt == NULL) {

th->nxt = (struct tcp_seq_hash *)

calloc(1, sizeof(*th));

if (th->nxt == NULL)

error("tcp_print: calloc");

}

th->addr = tha;

if (rev)

th->ack = seq, th->seq = ack - 1;

else

th->seq = seq, th->ack = ack - 1;

} else {

if (rev)

seq -= th->ack, ack -= th->seq;

else

seq -= th->seq, ack -= th->ack;

}

thseq = th->seq;

thack = th->ack;

}

} else {

/*fool gcc*/

thseq = thack = rev = 0;

}

if (hlen > length) {

(void)printf(" [bad hdr length %u - too long, > %u]",

hlen, length);

return;

}

if (vflag && !Kflag && !fragmented) {

/* Check the checksum, if possible. */

u_int16_t sum, tcp_sum;

if (IP_V(ip) == 4) {

if (TTEST2(tp->th_sport, length)) {

sum = tcp_cksum(ip, tp, length);

tcp_sum = EXTRACT_16BITS(&tp->th_sum);

(void)printf(", cksum 0x%04x", tcp_sum);

if (sum != 0)

(void)printf(" (incorrect -> 0x%04x)",

in_cksum_shouldbe(tcp_sum, sum));

else

(void)printf(" (correct)");

}

}

#ifdef INET6

else if (IP_V(ip) == 6 && ip6->ip6_plen) {

if (TTEST2(tp->th_sport, length)) {

sum = nextproto6_cksum(ip6, (const u_int8_t *)tp, length, IPPROTO_TCP);

tcp_sum = EXTRACT_16BITS(&tp->th_sum);

(void)printf(", cksum 0x%04x", tcp_sum);

if (sum != 0)

(void)printf(" (incorrect -> 0x%04x)",

in_cksum_shouldbe(tcp_sum, sum));

else

(void)printf(" (correct)");

}

}

#endif

}

length -= hlen;

if (vflag > 1 || length > 0 || flags & (TH_SYN | TH_FIN | TH_RST)) {

(void)printf(", seq %u", seq);

if (length > 0) {

(void)printf(":%u", seq + length);

}

}

if (flags & TH_ACK) {

(void)printf(", ack %u", ack);

}

(void)printf(", win %d", win);

if (flags & TH_URG)

(void)printf(", urg %d", urp);

/*

* Handle any options.

*/

if (hlen > sizeof(*tp)) {

register const u_char *cp;

register u_int i, opt, datalen;

register u_int len;

hlen -= sizeof(*tp);

cp = (const u_char *)tp + sizeof(*tp);

printf(", options [");

while (hlen > 0) {

if (ch != '\0')

putchar(ch);

TCHECK(*cp);

opt = *cp++;

if (ZEROLENOPT(opt))

len = 1;

else {

TCHECK(*cp);

len = *cp++; /* total including type, len */

if (len < 2 || len > hlen)

goto bad;

--hlen; /* account for length byte */

}

--hlen; /* account for type byte */

datalen = 0;

/* Bail if "l" bytes of data are not left or were not captured */

#define LENCHECK(l) { if ((l) > hlen) goto bad; TCHECK2(*cp, l); }

printf("%s", tok2str(tcp_option_values, "unknown-%u", opt));

switch (opt) {

case TCPOPT_MAXSEG:

datalen = 2;

LENCHECK(datalen);

(void)printf(" %u", EXTRACT_16BITS(cp));

break;

case TCPOPT_WSCALE:

datalen = 1;

LENCHECK(datalen);

(void)printf(" %u", *cp);

break;

case TCPOPT_SACK:

datalen = len - 2;

if (datalen % 8 != 0) {

(void)printf("malformed sack");

} else {

u_int32_t s, e;

(void)printf(" %d ", datalen / 8);

for (i = 0; i < datalen; i += 8) {

LENCHECK(i + 4);

s = EXTRACT_32BITS(cp + i);

LENCHECK(i + 8);

e = EXTRACT_32BITS(cp + i + 4);

if (rev) {

s -= thseq;

e -= thseq;

} else {

s -= thack;

e -= thack;

}

(void)printf("{%u:%u}", s, e);

}

}

break;

case TCPOPT_CC:

case TCPOPT_CCNEW:

case TCPOPT_CCECHO:

case TCPOPT_ECHO:

case TCPOPT_ECHOREPLY:

/*

* those options share their semantics.

* fall through

*/

datalen = 4;

LENCHECK(datalen);

(void)printf(" %u", EXTRACT_32BITS(cp));

break;

case TCPOPT_TIMESTAMP:

datalen = 8;

LENCHECK(datalen);

(void)printf(" val %u ecr %u",

EXTRACT_32BITS(cp),

EXTRACT_32BITS(cp + 4));

break;

case TCPOPT_SIGNATURE:

datalen = TCP_SIGLEN;

LENCHECK(datalen);

#ifdef HAVE_LIBCRYPTO

switch (tcp_verify_signature(ip, tp,

bp + TH_OFF(tp) * 4, length, cp)) {

case SIGNATURE_VALID:

(void)printf("valid");

break;

case SIGNATURE_INVALID:

(void)printf("invalid");

break;

case CANT_CHECK_SIGNATURE:

(void)printf("can't check - ");

for (i = 0; i < TCP_SIGLEN; ++i)

(void)printf("%02x", cp[i]);

break;

}

#else

for (i = 0; i < TCP_SIGLEN; ++i)

(void)printf("%02x", cp[i]);

#endif

break;

case TCPOPT_AUTH:

(void)printf("keyid %d", *cp++);

datalen = len - 3;

for (i = 0; i < datalen; ++i) {

LENCHECK(i);

(void)printf("%02x", cp[i]);

}

break;

case TCPOPT_EOL:

case TCPOPT_NOP:

case TCPOPT_SACKOK:

/*

* Nothing interesting.

* fall through

*/

break;

case TCPOPT_UTO:

datalen = 2;

LENCHECK(datalen);

utoval = EXTRACT_16BITS(cp);

(void)printf("0x%x", utoval);

if (utoval & 0x0001)

utoval = (utoval >> 1) * 60;

else

utoval >>= 1;

(void)printf(" %u", utoval);

break;

case TCPOPT_MPTCP:

datalen = len - 2;

LENCHECK(datalen);

if (!mptcp_print(cp-2, len, flags))

goto bad;

break;

case TCPOPT_EXPERIMENT2:

datalen = len - 2;

LENCHECK(datalen);

if (datalen < 2)

goto bad;

/* RFC6994 */

magic = EXTRACT_16BITS(cp);

(void)printf("-");

switch(magic) {

case 0xf989:

/* TCP Fast Open: draft-ietf-tcpm-fastopen-04 */

if (datalen == 2) {

/* Fast Open Cookie Request */

(void)printf("tfo cookiereq");

} else {

/* Fast Open Cookie */

if (datalen % 2 != 0 || datalen < 6 || datalen > 18) {

(void)printf("tfo malformed");

} else {

(void)printf("tfo cookie ");

for (i = 2; i < datalen; ++i)

(void)printf("%02x", cp[i]);

}

}

break;

default:

/* Unknown magic number */

(void)printf("%04x", magic);

break;

}

break;

default:

datalen = len - 2;

if (datalen)

printf(" 0x");

for (i = 0; i < datalen; ++i) {

LENCHECK(i);

(void)printf("%02x", cp[i]);

}

break;

}

/* Account for data printed */

cp += datalen;

hlen -= datalen;

/* Check specification against observed length */

++datalen; /* option octet */

if (!ZEROLENOPT(opt))

++datalen; /* size octet */

if (datalen != len)

(void)printf("[len %d]", len);

ch = ',';

if (opt == TCPOPT_EOL)

break;

}

putchar(']');

}

/*

* Print length field before crawling down the stack.

*/

printf(", length %u", length);

if (length <= 0)

return;

/*

* Decode payload if necessary.

*/

bp += TH_OFF(tp) * 4;

if ((flags & TH_RST) && vflag) {

print_tcp_rst_data(bp, length);

return;

}

if (packettype) {

switch (packettype) {

case PT_ZMTP1:

zmtp1_print(bp, length);

break;

}

return;

}

if (sport == TELNET_PORT || dport == TELNET_PORT) {

if (!qflag && vflag)

telnet_print(bp, length);

} else if (sport == BGP_PORT || dport == BGP_PORT)

bgp_print(bp, length);

else if (sport == PPTP_PORT || dport == PPTP_PORT)

pptp_print(bp);

#ifdef TCPDUMP_DO_SMB

else if (sport == NETBIOS_SSN_PORT || dport == NETBIOS_SSN_PORT)

nbt_tcp_print(bp, length);

else if (sport == SMB_PORT || dport == SMB_PORT)

smb_tcp_print(bp, length);

#endif

else if (sport == BEEP_PORT || dport == BEEP_PORT)

beep_print(bp, length);

else if (sport == OPENFLOW_PORT || dport == OPENFLOW_PORT)

openflow_print(bp, length);

else if (length > 2 &&

(sport == NAMESERVER_PORT || dport == NAMESERVER_PORT ||

sport == MULTICASTDNS_PORT || dport == MULTICASTDNS_PORT)) {

/*

* TCP DNS query has 2byte length at the head.

* XXX packet could be unaligned, it can go strange

*/

ns_print(bp + 2, length - 2, 0);

} else if (sport == MSDP_PORT || dport == MSDP_PORT) {

msdp_print(bp, length);

} else if (sport == RPKI_RTR_PORT || dport == RPKI_RTR_PORT) {

rpki_rtr_print(bp, length);

}

else if (length > 0 && (sport == LDP_PORT || dport == LDP_PORT)) {

ldp_print(bp, length);

}

else if ((sport == NFS_PORT || dport == NFS_PORT) &&

length >= 4 && TTEST2(*bp, 4)) {

/*

* If data present, header length valid, and NFS port used,

* assume NFS.

* Pass offset of data plus 4 bytes for RPC TCP msg length

* to NFS print routines.

*/

u_int32_t fraglen;

register struct sunrpc_msg *rp;

enum sunrpc_msg_type direction;

fraglen = EXTRACT_32BITS(bp) & 0x7FFFFFFF;

if (fraglen > (length) - 4)

fraglen = (length) - 4;

rp = (struct sunrpc_msg *)(bp + 4);

if (TTEST(rp->rm_direction)) {

direction = (enum sunrpc_msg_type)EXTRACT_32BITS(&rp->rm_direction);

if (dport == NFS_PORT && direction == SUNRPC_CALL) {

(void)printf(": NFS request xid %u ", EXTRACT_32BITS(&rp->rm_xid));

nfsreq_print_noaddr((u_char *)rp, fraglen, (u_char *)ip);

return;

}

if (sport == NFS_PORT && direction == SUNRPC_REPLY) {

(void)printf(": NFS reply xid %u ", EXTRACT_32BITS(&rp->rm_xid));

nfsreply_print_noaddr((u_char *)rp, fraglen, (u_char *)ip);

return;

}

}

}

return;

bad:

fputs("[bad opt]", stdout);

if (ch != '\0')

putchar('>');

return;

trunc:

fputs("[|tcp]", stdout);

if (ch != '\0')

putchar('>');

}

/*

* RFC1122 says the following on data in RST segments:

*

* 4.2.2.12 RST Segment: RFC-793 Section 3.4

*

* A TCP SHOULD allow a received RST segment to include data.

*

* DISCUSSION

* It has been suggested that a RST segment could contain

* ASCII text that encoded and explained the cause of the

* RST. No standard has yet been established for such

* data.

*

*/

static void

print_tcp_rst_data(register const u_char *sp, u_int length)

{

int c;

if (TTEST2(*sp, length))

printf(" [RST");

else

printf(" [!RST");

if (length > MAX_RST_DATA_LEN) {

length = MAX_RST_DATA_LEN; /* can use -X for longer */

putchar('+'); /* indicate we truncate */

}

putchar(' ');

while (length-- && sp <= snapend) {

c = *sp++;

safeputchar(c);

}

putchar(']');

}

#ifdef HAVE_LIBCRYPTO

USES_APPLE_DEPRECATED_API

static int

tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp,

const u_char *data, int length, const u_char *rcvsig)

{

struct tcphdr tp1;

u_char sig[TCP_SIGLEN];

char zero_proto = 0;

MD5_CTX ctx;

u_int16_t savecsum, tlen;

#ifdef INET6

struct ip6_hdr *ip6;

u_int32_t len32;

u_int8_t nxt;

#endif

if (data + length > snapend) {

printf("snaplen too short, ");

return (CANT_CHECK_SIGNATURE);

}

tp1 = *tp;

if (sigsecret == NULL) {

printf("shared secret not supplied with -M, ");

return (CANT_CHECK_SIGNATURE);

}

MD5_Init(&ctx);

/*

* Step 1: Update MD5 hash with IP pseudo-header.

*/

if (IP_V(ip) == 4) {

MD5_Update(&ctx, (char *)&ip->ip_src, sizeof(ip->ip_src));

MD5_Update(&ctx, (char *)&ip->ip_dst, sizeof(ip->ip_dst));

MD5_Update(&ctx, (char *)&zero_proto, sizeof(zero_proto));

MD5_Update(&ctx, (char *)&ip->ip_p, sizeof(ip->ip_p));

tlen = EXTRACT_16BITS(&ip->ip_len) - IP_HL(ip) * 4;

tlen = htons(tlen);

MD5_Update(&ctx, (char *)&tlen, sizeof(tlen));

#ifdef INET6

} else if (IP_V(ip) == 6) {

ip6 = (struct ip6_hdr *)ip;

MD5_Update(&ctx, (char *)&ip6->ip6_src, sizeof(ip6->ip6_src));

MD5_Update(&ctx, (char *)&ip6->ip6_dst, sizeof(ip6->ip6_dst));

len32 = htonl(EXTRACT_16BITS(&ip6->ip6_plen));

MD5_Update(&ctx, (char *)&len32, sizeof(len32));

nxt = 0;

MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));

MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));

MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));

nxt = IPPROTO_TCP;

MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));

#endif

} else {

#ifdef INET6

printf("IP version not 4 or 6, ");

#else

printf("IP version not 4, ");

#endif

return (CANT_CHECK_SIGNATURE);

}

/*

* Step 2: Update MD5 hash with TCP header, excluding options.

* The TCP checksum must be set to zero.

*/

savecsum = tp1.th_sum;

tp1.th_sum = 0;

MD5_Update(&ctx, (char *)&tp1, sizeof(struct tcphdr));

tp1.th_sum = savecsum;

/*

* Step 3: Update MD5 hash with TCP segment data, if present.

*/

if (length > 0)

MD5_Update(&ctx, data, length);

/*

* Step 4: Update MD5 hash with shared secret.

*/

MD5_Update(&ctx, sigsecret, strlen(sigsecret));

MD5_Final(sig, &ctx);

if (memcmp(rcvsig, sig, TCP_SIGLEN) == 0)

return (SIGNATURE_VALID);

else

return (SIGNATURE_INVALID);

}

USES_APPLE_RST

#endif /* HAVE_LIBCRYPTO */

/*

* Local Variables:

* c-style: whitesmith

* c-basic-offset: 8

* End:

*/