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-rw-r--r--print-tcp.c807
1 files changed, 807 insertions, 0 deletions
diff --git a/print-tcp.c b/print-tcp.c
new file mode 100644
index 000000000000..11bd6b7ab46f
--- /dev/null
+++ b/print-tcp.c
@@ -0,0 +1,807 @@
+/*
+ * 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
+static const char rcsid[] _U_ =
+ "@(#) $Header: /tcpdump/master/tcpdump/print-tcp.c,v 1.120.2.3 2005/10/16 06:05:46 guy Exp $ (LBL)";
+#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>
+
+#define SIGNATURE_VALID 0
+#define SIGNATURE_INVALID 1
+#define CANT_CHECK_SIGNATURE 2
+
+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 {
+#ifndef INET6
+ struct in_addr src;
+ struct in_addr dst;
+#else
+ struct in6_addr src;
+ struct in6_addr dst;
+#endif /*INET6*/
+ u_int port;
+};
+
+struct tcp_seq_hash {
+ struct tcp_seq_hash *nxt;
+ struct tha addr;
+ tcp_seq seq;
+ tcp_seq ack;
+};
+
+#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_hash[TSEQ_HASHSIZE];
+
+
+#ifndef TELNET_PORT
+#define TELNET_PORT 23
+#endif
+#ifndef BGP_PORT
+#define BGP_PORT 179
+#endif
+#define NETBIOS_SSN_PORT 139
+#ifndef PPTP_PORT
+#define PPTP_PORT 1723
+#endif
+#define BEEP_PORT 10288
+#ifndef NFS_PORT
+#define NFS_PORT 2049
+#endif
+#define MSDP_PORT 639
+#define LDP_PORT 646
+
+static int tcp_cksum(register const struct ip *ip,
+ register const struct tcphdr *tp,
+ register u_int len)
+{
+ union phu {
+ struct phdr {
+ u_int32_t src;
+ u_int32_t dst;
+ u_char mbz;
+ u_char proto;
+ u_int16_t len;
+ } ph;
+ u_int16_t pa[6];
+ } phu;
+ const u_int16_t *sp;
+
+ /* pseudo-header.. */
+ phu.ph.len = htons((u_int16_t)len);
+ phu.ph.mbz = 0;
+ phu.ph.proto = IPPROTO_TCP;
+ memcpy(&phu.ph.src, &ip->ip_src.s_addr, sizeof(u_int32_t));
+ if (IP_HL(ip) == 5)
+ memcpy(&phu.ph.dst, &ip->ip_dst.s_addr, sizeof(u_int32_t));
+ else
+ phu.ph.dst = ip_finddst(ip);
+
+ sp = &phu.pa[0];
+ return in_cksum((u_short *)tp, len,
+ sp[0]+sp[1]+sp[2]+sp[3]+sp[4]+sp[5]);
+}
+
+#ifdef INET6
+static int tcp6_cksum(const struct ip6_hdr *ip6, const struct tcphdr *tp,
+ u_int len)
+{
+ size_t i;
+ register const u_int16_t *sp;
+ u_int32_t sum;
+ union {
+ struct {
+ struct in6_addr ph_src;
+ struct in6_addr ph_dst;
+ u_int32_t ph_len;
+ u_int8_t ph_zero[3];
+ u_int8_t ph_nxt;
+ } ph;
+ u_int16_t pa[20];
+ } phu;
+
+ /* pseudo-header */
+ memset(&phu, 0, sizeof(phu));
+ phu.ph.ph_src = ip6->ip6_src;
+ phu.ph.ph_dst = ip6->ip6_dst;
+ phu.ph.ph_len = htonl(len);
+ phu.ph.ph_nxt = IPPROTO_TCP;
+
+ sum = 0;
+ for (i = 0; i < sizeof(phu.pa) / sizeof(phu.pa[0]); i++)
+ sum += phu.pa[i];
+
+ sp = (const u_int16_t *)tp;
+
+ for (i = 0; i < (len & ~1); i += 2)
+ sum += *sp++;
+
+ if (len & 1)
+ sum += htons((*(const u_int8_t *)sp) << 8);
+
+ while (sum > 0xffff)
+ sum = (sum & 0xffff) + (sum >> 16);
+ sum = ~sum & 0xffff;
+
+ return (sum);
+}
+#endif
+
+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;
+ int threv;
+#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;
+
+ /*
+ * 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.
+ */
+ if (!qflag && hlen >= sizeof(*tp) && hlen <= length) {
+ if ((u_char *)tp + 4 + sizeof(struct sunrpc_msg) <= snapend &&
+ dport == NFS_PORT) {
+ nfsreq_print((u_char *)tp + hlen + 4, length - hlen,
+ (u_char *)ip);
+ return;
+ } else if ((u_char *)tp + 4 + sizeof(struct sunrpc_msg)
+ <= snapend &&
+ sport == NFS_PORT) {
+ nfsreply_print((u_char *)tp + hlen + 4, length - hlen,
+ (u_char *)ip);
+ return;
+ }
+ }
+#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;
+ }
+ if ((flags = tp->th_flags) & (TH_SYN|TH_FIN|TH_RST|TH_PUSH|
+ TH_ECNECHO|TH_CWR)) {
+ if (flags & TH_SYN)
+ putchar('S');
+ if (flags & TH_FIN)
+ putchar('F');
+ if (flags & TH_RST)
+ putchar('R');
+ if (flags & TH_PUSH)
+ putchar('P');
+ if (flags & TH_CWR)
+ putchar('W'); /* congestion _W_indow reduced (ECN) */
+ if (flags & TH_ECNECHO)
+ putchar('E'); /* ecn _E_cho sent (ECN) */
+ } else
+ putchar('.');
+
+ if (!Sflag && (flags & TH_ACK)) {
+ register struct tcp_seq_hash *th;
+ const void *src, *dst;
+ register int rev;
+ struct tha tha;
+ /*
+ * 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).
+ */
+#ifdef INET6
+ memset(&tha, 0, sizeof(tha));
+ rev = 0;
+ if (ip6) {
+ src = &ip6->ip6_src;
+ dst = &ip6->ip6_dst;
+ if (sport > dport)
+ rev = 1;
+ else if (sport == dport) {
+ if (memcmp(src, dst, sizeof ip6->ip6_dst) > 0)
+ rev = 1;
+ }
+ if (rev) {
+ memcpy(&tha.src, dst, sizeof ip6->ip6_dst);
+ memcpy(&tha.dst, src, sizeof ip6->ip6_src);
+ tha.port = dport << 16 | sport;
+ } else {
+ memcpy(&tha.dst, dst, sizeof ip6->ip6_dst);
+ memcpy(&tha.src, src, sizeof ip6->ip6_src);
+ tha.port = sport << 16 | dport;
+ }
+ } else {
+ src = &ip->ip_src;
+ dst = &ip->ip_dst;
+ if (sport > dport)
+ rev = 1;
+ else if (sport == dport) {
+ if (memcmp(src, dst, sizeof ip->ip_dst) > 0)
+ rev = 1;
+ }
+ if (rev) {
+ memcpy(&tha.src, dst, sizeof ip->ip_dst);
+ memcpy(&tha.dst, src, sizeof ip->ip_src);
+ tha.port = dport << 16 | sport;
+ } else {
+ memcpy(&tha.dst, dst, sizeof ip->ip_dst);
+ memcpy(&tha.src, src, sizeof ip->ip_src);
+ tha.port = sport << 16 | dport;
+ }
+ }
+#else
+ rev = 0;
+ src = &ip->ip_src;
+ dst = &ip->ip_dst;
+ if (sport > dport)
+ rev = 1;
+ else if (sport == dport) {
+ if (memcmp(src, dst, sizeof ip->ip_dst) > 0)
+ rev = 1;
+ }
+ if (rev) {
+ memcpy(&tha.src, dst, sizeof ip->ip_dst);
+ memcpy(&tha.dst, src, sizeof ip->ip_src);
+ tha.port = dport << 16 | sport;
+ } else {
+ memcpy(&tha.dst, dst, sizeof ip->ip_dst);
+ memcpy(&tha.src, src, sizeof ip->ip_src);
+ tha.port = sport << 16 | dport;
+ }
+#endif
+
+ threv = rev;
+ 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 = threv = 0;
+ }
+ if (hlen > length) {
+ (void)printf(" [bad hdr length %u - too long, > %u]",
+ hlen, length);
+ return;
+ }
+
+ if (IP_V(ip) == 4 && vflag && !fragmented) {
+ u_int16_t sum, tcp_sum;
+ if (TTEST2(tp->th_sport, length)) {
+ sum = tcp_cksum(ip, tp, length);
+
+ (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum));
+ if (sum != 0) {
+ tcp_sum = EXTRACT_16BITS(&tp->th_sum);
+ (void)printf(" (incorrect (-> 0x%04x),",in_cksum_shouldbe(tcp_sum, sum));
+ } else
+ (void)printf(" (correct),");
+ }
+ }
+#ifdef INET6
+ if (IP_V(ip) == 6 && ip6->ip6_plen && vflag && !fragmented) {
+ u_int16_t sum,tcp_sum;
+ if (TTEST2(tp->th_sport, length)) {
+ sum = tcp6_cksum(ip6, tp, length);
+ (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum));
+ if (sum != 0) {
+ tcp_sum = EXTRACT_16BITS(&tp->th_sum);
+ (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(" %u:%u(%u)", seq, seq + length, 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);
+ putchar(' ');
+ ch = '<';
+ while (hlen > 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); }
+
+ switch (opt) {
+
+ case TCPOPT_MAXSEG:
+ (void)printf("mss");
+ datalen = 2;
+ LENCHECK(datalen);
+ (void)printf(" %u", EXTRACT_16BITS(cp));
+
+ break;
+
+ case TCPOPT_EOL:
+ (void)printf("eol");
+ break;
+
+ case TCPOPT_NOP:
+ (void)printf("nop");
+ break;
+
+ case TCPOPT_WSCALE:
+ (void)printf("wscale");
+ datalen = 1;
+ LENCHECK(datalen);
+ (void)printf(" %u", *cp);
+ break;
+
+ case TCPOPT_SACKOK:
+ (void)printf("sackOK");
+ break;
+
+ case TCPOPT_SACK:
+ datalen = len - 2;
+ if (datalen % 8 != 0) {
+ (void)printf("malformed sack");
+ } else {
+ u_int32_t s, e;
+
+ (void)printf("sack %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 (threv) {
+ s -= thseq;
+ e -= thseq;
+ } else {
+ s -= thack;
+ e -= thack;
+ }
+ (void)printf("{%u:%u}", s, e);
+ }
+ }
+ break;
+
+ case TCPOPT_ECHO:
+ (void)printf("echo");
+ datalen = 4;
+ LENCHECK(datalen);
+ (void)printf(" %u", EXTRACT_32BITS(cp));
+ break;
+
+ case TCPOPT_ECHOREPLY:
+ (void)printf("echoreply");
+ datalen = 4;
+ LENCHECK(datalen);
+ (void)printf(" %u", EXTRACT_32BITS(cp));
+ break;
+
+ case TCPOPT_TIMESTAMP:
+ (void)printf("timestamp");
+ datalen = 8;
+ LENCHECK(4);
+ (void)printf(" %u", EXTRACT_32BITS(cp));
+ LENCHECK(datalen);
+ (void)printf(" %u", EXTRACT_32BITS(cp + 4));
+ break;
+
+ case TCPOPT_CC:
+ (void)printf("cc");
+ datalen = 4;
+ LENCHECK(datalen);
+ (void)printf(" %u", EXTRACT_32BITS(cp));
+ break;
+
+ case TCPOPT_CCNEW:
+ (void)printf("ccnew");
+ datalen = 4;
+ LENCHECK(datalen);
+ (void)printf(" %u", EXTRACT_32BITS(cp));
+ break;
+
+ case TCPOPT_CCECHO:
+ (void)printf("ccecho");
+ datalen = 4;
+ LENCHECK(datalen);
+ (void)printf(" %u", EXTRACT_32BITS(cp));
+ break;
+
+ case TCPOPT_SIGNATURE:
+ (void)printf("md5:");
+ 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;
+
+ default:
+ (void)printf("opt-%u:", opt);
+ datalen = len - 2;
+ 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('>');
+ }
+
+ if (length <= 0)
+ return;
+
+ /*
+ * Decode payload if necessary.
+ */
+ bp += TH_OFF(tp) * 4;
+ if (flags & TH_RST) {
+ if (vflag)
+ print_tcp_rst_data(bp, length);
+ } else {
+ 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);
+#endif
+ else if (sport == BEEP_PORT || dport == BEEP_PORT)
+ beep_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 (length > 0 && (sport == LDP_PORT || dport == LDP_PORT)) {
+ ldp_print(bp, length);
+ }
+ }
+ 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
+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;
+#endif
+ u_int32_t len32;
+ u_int8_t nxt;
+
+ tp1 = *tp;
+
+ if (tcpmd5secret == NULL)
+ 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(ntohs(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
+ 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, tcpmd5secret, strlen(tcpmd5secret));
+ MD5_Final(sig, &ctx);
+
+ if (memcmp(rcvsig, sig, TCP_SIGLEN) == 0)
+ return (SIGNATURE_VALID);
+ else
+ return (SIGNATURE_INVALID);
+}
+#endif /* HAVE_LIBCRYPTO */