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266489c6c9
tcpdump/print-tcp.c
Guy Harris ec88d36bcd CVE-2016-7975/Make sure we have the data offset field before fetching it. 
Fixes a heap overflow found with American Fuzzy Lop by Hanno Böck.
2017-01-18 09:16:36 +01:00

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34 KiB
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/* $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.
*/
/* \summary: TCP printer */
#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 <netdissect-stdinc.h>
#include <stdlib.h>
#include <string.h>
#include "netdissect.h"
#include "addrtoname.h"
#include "extract.h"
#include "tcp.h"
#include "ip.h"
#include "ip6.h"
#include "ipproto.h"
#include "rpc_auth.h"
#include "rpc_msg.h"
#ifdef HAVE_LIBCRYPTO
#include <openssl/md5.h>
#include "signature.h"
static int tcp_verify_signature(netdissect_options *ndo,
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(netdissect_options *, register const u_char *sp, u_int length);
static void print_tcp_fastopen_option(netdissect_options *ndo, register const u_char *cp,
u_int datalen, int exp);
#define MAX_RST_DATA_LEN 30
struct tha {
struct in_addr src;
struct in_addr dst;
u_int port;
};
struct tcp_seq_hash {
struct tcp_seq_hash *nxt;
struct tha addr;
tcp_seq seq;
tcp_seq ack;
};
struct tha6 {
struct in6_addr src;
struct in6_addr dst;
u_int port;
};
struct tcp_seq_hash6 {
struct tcp_seq_hash6 *nxt;
struct tha6 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_hash4[TSEQ_HASHSIZE];
static struct tcp_seq_hash6 tcp_seq_hash6[TSEQ_HASHSIZE];
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_FASTOPEN, "tfo" },
{ TCPOPT_EXPERIMENT2, "exp" },
{ 0, NULL }
};
static int
tcp_cksum(netdissect_options *ndo,
register const struct ip *ip,
register const struct tcphdr *tp,
register u_int len)
{
return nextproto4_cksum(ndo, ip, (const uint8_t *)tp, len, len,
IPPROTO_TCP);
}
static int
tcp6_cksum(netdissect_options *ndo,
register const struct ip6_hdr *ip6,
register const struct tcphdr *tp,
register u_int len)
{
return nextproto6_cksum(ndo, ip6, (const uint8_t *)tp, len, len,
IPPROTO_TCP);
}
void
tcp_print(netdissect_options *ndo,
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;
uint16_t sport, dport, win, urp;
uint32_t seq, ack, thseq, thack;
u_int utoval;
uint16_t magic;
register int rev;
register const struct ip6_hdr *ip6;
tp = (const struct tcphdr *)bp;
ip = (const struct ip *)bp2;
if (IP_V(ip) == 6)
ip6 = (const struct ip6_hdr *)bp2;
else
ip6 = NULL;
ch = '\0';
if (!ND_TTEST(tp->th_dport)) {
ND_PRINT((ndo, "%s > %s: [|tcp]",
ipaddr_string(ndo, &ip->ip_src),
ipaddr_string(ndo, &ip->ip_dst)));
return;
}
sport = EXTRACT_16BITS(&tp->th_sport);
dport = EXTRACT_16BITS(&tp->th_dport);
if (ip6) {
if (ip6->ip6_nxt == IPPROTO_TCP) {
ND_PRINT((ndo, "%s.%s > %s.%s: ",
ip6addr_string(ndo, &ip6->ip6_src),
tcpport_string(ndo, sport),
ip6addr_string(ndo, &ip6->ip6_dst),
tcpport_string(ndo, dport)));
} else {
ND_PRINT((ndo, "%s > %s: ",
tcpport_string(ndo, sport), tcpport_string(ndo, dport)));
}
} else {
if (ip->ip_p == IPPROTO_TCP) {
ND_PRINT((ndo, "%s.%s > %s.%s: ",
ipaddr_string(ndo, &ip->ip_src),
tcpport_string(ndo, sport),
ipaddr_string(ndo, &ip->ip_dst),
tcpport_string(ndo, dport)));
} else {
ND_PRINT((ndo, "%s > %s: ",
tcpport_string(ndo, sport), tcpport_string(ndo, dport)));
}
}
ND_TCHECK(*tp);
hlen = TH_OFF(tp) * 4;
if (hlen < sizeof(*tp)) {
ND_PRINT((ndo, " tcp %d [bad hdr length %u - too short, < %lu]",
length - hlen, hlen, (unsigned long)sizeof(*tp)));
return;
}
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 (ndo->ndo_qflag) {
ND_PRINT((ndo, "tcp %d", length - hlen));
if (hlen > length) {
ND_PRINT((ndo, " [bad hdr length %u - too long, > %u]",
hlen, length));
}
return;
}
flags = tp->th_flags;
ND_PRINT((ndo, "Flags [%s]", bittok2str_nosep(tcp_flag_values, "none", flags)));
if (!ndo->ndo_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;
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)
(*ndo->ndo_error)(ndo,
"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 {
register struct tcp_seq_hash *th;
struct tcp_seq_hash *tcp_seq_hash;
struct tha tha;
tcp_seq_hash = tcp_seq_hash4;
if (sport > dport)
rev = 1;
else if (sport == dport) {
if (UNALIGNED_MEMCMP(&ip->ip_src, &ip->ip_dst, sizeof ip->ip_dst) > 0)
rev = 1;
}
if (rev) {
UNALIGNED_MEMCPY(&tha.src, &ip->ip_dst, sizeof ip->ip_dst);
UNALIGNED_MEMCPY(&tha.dst, &ip->ip_src, sizeof ip->ip_src);
tha.port = dport << 16 | sport;
} else {
UNALIGNED_MEMCPY(&tha.dst, &ip->ip_dst, sizeof ip->ip_dst);
UNALIGNED_MEMCPY(&tha.src, &ip->ip_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)
(*ndo->ndo_error)(ndo,
"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) {
ND_PRINT((ndo, " [bad hdr length %u - too long, > %u]",
hlen, length));
return;
}
if (ndo->ndo_vflag && !ndo->ndo_Kflag && !fragmented) {
/* Check the checksum, if possible. */
uint16_t sum, tcp_sum;
if (IP_V(ip) == 4) {
if (ND_TTEST2(tp->th_sport, length)) {
sum = tcp_cksum(ndo, ip, tp, length);
tcp_sum = EXTRACT_16BITS(&tp->th_sum);
ND_PRINT((ndo, ", cksum 0x%04x", tcp_sum));
if (sum != 0)
ND_PRINT((ndo, " (incorrect -> 0x%04x)",
in_cksum_shouldbe(tcp_sum, sum)));
else
ND_PRINT((ndo, " (correct)"));
}
} else if (IP_V(ip) == 6 && ip6->ip6_plen) {
if (ND_TTEST2(tp->th_sport, length)) {
sum = tcp6_cksum(ndo, ip6, tp, length);
tcp_sum = EXTRACT_16BITS(&tp->th_sum);
ND_PRINT((ndo, ", cksum 0x%04x", tcp_sum));
if (sum != 0)
ND_PRINT((ndo, " (incorrect -> 0x%04x)",
in_cksum_shouldbe(tcp_sum, sum)));
else
ND_PRINT((ndo, " (correct)"));
}
}
}
length -= hlen;
if (ndo->ndo_vflag > 1 || length > 0 || flags & (TH_SYN | TH_FIN | TH_RST)) {
ND_PRINT((ndo, ", seq %u", seq));
if (length > 0) {
ND_PRINT((ndo, ":%u", seq + length));
}
}
if (flags & TH_ACK) {
ND_PRINT((ndo, ", ack %u", ack));
}
ND_PRINT((ndo, ", win %d", win));
if (flags & TH_URG)
ND_PRINT((ndo, ", 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);
ND_PRINT((ndo, ", options ["));
while (hlen > 0) {
if (ch != '\0')
ND_PRINT((ndo, "%c", ch));
ND_TCHECK(*cp);
opt = *cp++;
if (ZEROLENOPT(opt))
len = 1;
else {
ND_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; ND_TCHECK2(*cp, l); }
ND_PRINT((ndo, "%s", tok2str(tcp_option_values, "unknown-%u", opt)));
switch (opt) {
case TCPOPT_MAXSEG:
datalen = 2;
LENCHECK(datalen);
ND_PRINT((ndo, " %u", EXTRACT_16BITS(cp)));
break;
case TCPOPT_WSCALE:
datalen = 1;
LENCHECK(datalen);
ND_PRINT((ndo, " %u", *cp));
break;
case TCPOPT_SACK:
datalen = len - 2;
if (datalen % 8 != 0) {
ND_PRINT((ndo, " invalid sack"));
} else {
uint32_t s, e;
ND_PRINT((ndo, " %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;
}
ND_PRINT((ndo, "{%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);
ND_PRINT((ndo, " %u", EXTRACT_32BITS(cp)));
break;
case TCPOPT_TIMESTAMP:
datalen = 8;
LENCHECK(datalen);
ND_PRINT((ndo, " val %u ecr %u",
EXTRACT_32BITS(cp),
EXTRACT_32BITS(cp + 4)));
break;
case TCPOPT_SIGNATURE:
datalen = TCP_SIGLEN;
LENCHECK(datalen);
ND_PRINT((ndo, " "));
#ifdef HAVE_LIBCRYPTO
switch (tcp_verify_signature(ndo, ip, tp,
bp + TH_OFF(tp) * 4, length, cp)) {
case SIGNATURE_VALID:
ND_PRINT((ndo, "valid"));
break;
case SIGNATURE_INVALID:
ND_PRINT((ndo, "invalid"));
break;
case CANT_CHECK_SIGNATURE:
ND_PRINT((ndo, "can't check - "));
for (i = 0; i < TCP_SIGLEN; ++i)
ND_PRINT((ndo, "%02x", cp[i]));
break;
}
#else
for (i = 0; i < TCP_SIGLEN; ++i)
ND_PRINT((ndo, "%02x", cp[i]));
#endif
break;
case TCPOPT_AUTH:
ND_PRINT((ndo, " keyid %d", *cp++));
datalen = len - 3;
for (i = 0; i < datalen; ++i) {
LENCHECK(i + 1);
ND_PRINT((ndo, "%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);
ND_PRINT((ndo, " 0x%x", utoval));
if (utoval & 0x0001)
utoval = (utoval >> 1) * 60;
else
utoval >>= 1;
ND_PRINT((ndo, " %u", utoval));
break;
case TCPOPT_MPTCP:
datalen = len - 2;
LENCHECK(datalen);
if (!mptcp_print(ndo, cp-2, len, flags))
goto bad;
break;
case TCPOPT_FASTOPEN:
datalen = len - 2;
LENCHECK(datalen);
ND_PRINT((ndo, " "));
print_tcp_fastopen_option(ndo, cp, datalen, FALSE);
break;
case TCPOPT_EXPERIMENT2:
datalen = len - 2;
LENCHECK(datalen);
if (datalen < 2)
goto bad;
/* RFC6994 */
magic = EXTRACT_16BITS(cp);
ND_PRINT((ndo, "-"));
switch(magic) {
case 0xf989: /* TCP Fast Open RFC 7413 */
print_tcp_fastopen_option(ndo, cp + 2, datalen - 2, TRUE);
break;
default:
/* Unknown magic number */
ND_PRINT((ndo, "%04x", magic));
break;
}
break;
default:
datalen = len - 2;
if (datalen)
ND_PRINT((ndo, " 0x"));
for (i = 0; i < datalen; ++i) {
LENCHECK(i + 1);
ND_PRINT((ndo, "%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)
ND_PRINT((ndo, "[len %d]", len));
ch = ',';
if (opt == TCPOPT_EOL)
break;
}
ND_PRINT((ndo, "]"));
}
/*
* Print length field before crawling down the stack.
*/
ND_PRINT((ndo, ", length %u", length));
if (length <= 0)
return;
/*
* Decode payload if necessary.
*/
bp += TH_OFF(tp) * 4;
if ((flags & TH_RST) && ndo->ndo_vflag) {
print_tcp_rst_data(ndo, bp, length);
return;
}
if (ndo->ndo_packettype) {
switch (ndo->ndo_packettype) {
case PT_ZMTP1:
zmtp1_print(ndo, bp, length);
break;
case PT_RESP:
resp_print(ndo, bp, length);
break;
}
return;
}
if (IS_SRC_OR_DST_PORT(TELNET_PORT)) {
telnet_print(ndo, bp, length);
} else if (IS_SRC_OR_DST_PORT(SMTP_PORT)) {
ND_PRINT((ndo, ": "));
smtp_print(ndo, bp, length);
} else if (IS_SRC_OR_DST_PORT(BGP_PORT))
bgp_print(ndo, bp, length);
else if (IS_SRC_OR_DST_PORT(PPTP_PORT))
pptp_print(ndo, bp);
else if (IS_SRC_OR_DST_PORT(REDIS_PORT))
resp_print(ndo, bp, length);
#ifdef ENABLE_SMB
else if (IS_SRC_OR_DST_PORT(NETBIOS_SSN_PORT))
nbt_tcp_print(ndo, bp, length);
else if (IS_SRC_OR_DST_PORT(SMB_PORT))
smb_tcp_print(ndo, bp, length);
#endif
else if (IS_SRC_OR_DST_PORT(BEEP_PORT))
beep_print(ndo, bp, length);
else if (IS_SRC_OR_DST_PORT(OPENFLOW_PORT_OLD) || IS_SRC_OR_DST_PORT(OPENFLOW_PORT_IANA))
openflow_print(ndo, bp, length);
else if (IS_SRC_OR_DST_PORT(FTP_PORT)) {
ND_PRINT((ndo, ": "));
ftp_print(ndo, bp, length);
} else if (IS_SRC_OR_DST_PORT(HTTP_PORT) || IS_SRC_OR_DST_PORT(HTTP_PORT_ALT)) {
ND_PRINT((ndo, ": "));
http_print(ndo, bp, length);
} else if (IS_SRC_OR_DST_PORT(RTSP_PORT) || IS_SRC_OR_DST_PORT(RTSP_PORT_ALT)) {
ND_PRINT((ndo, ": "));
rtsp_print(ndo, bp, length);
} else if (length > 2 &&
(IS_SRC_OR_DST_PORT(NAMESERVER_PORT))) {
/*
* TCP DNS query has 2byte length at the head.
* XXX packet could be unaligned, it can go strange
*/
ns_print(ndo, bp + 2, length - 2, 0);
} else if (IS_SRC_OR_DST_PORT(MSDP_PORT)) {
msdp_print(ndo, bp, length);
} else if (IS_SRC_OR_DST_PORT(RPKI_RTR_PORT)) {
rpki_rtr_print(ndo, bp, length);
}
else if (length > 0 && (IS_SRC_OR_DST_PORT(LDP_PORT))) {
ldp_print(ndo, bp, length);
}
else if ((IS_SRC_OR_DST_PORT(NFS_PORT)) &&
length >= 4 && ND_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.
*/
uint32_t fraglen;
register const struct sunrpc_msg *rp;
enum sunrpc_msg_type direction;
fraglen = EXTRACT_32BITS(bp) & 0x7FFFFFFF;
if (fraglen > (length) - 4)
fraglen = (length) - 4;
rp = (const struct sunrpc_msg *)(bp + 4);
if (ND_TTEST(rp->rm_direction)) {
direction = (enum sunrpc_msg_type)EXTRACT_32BITS(&rp->rm_direction);
if (dport == NFS_PORT && direction == SUNRPC_CALL) {
ND_PRINT((ndo, ": NFS request xid %u ", EXTRACT_32BITS(&rp->rm_xid)));
nfsreq_print_noaddr(ndo, (const u_char *)rp, fraglen, (const u_char *)ip);
return;
}
if (sport == NFS_PORT && direction == SUNRPC_REPLY) {
ND_PRINT((ndo, ": NFS reply xid %u ", EXTRACT_32BITS(&rp->rm_xid)));
nfsreply_print_noaddr(ndo, (const u_char *)rp, fraglen, (const u_char *)ip);
return;
}
}
}
return;
bad:
ND_PRINT((ndo, "[bad opt]"));
if (ch != '\0')
ND_PRINT((ndo, ">"));
return;
trunc:
ND_PRINT((ndo, "[|tcp]"));
if (ch != '\0')
ND_PRINT((ndo, ">"));
}
/*
* 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(netdissect_options *ndo,
register const u_char *sp, u_int length)
{
int c;
ND_PRINT((ndo, ND_TTEST2(*sp, length) ? " [RST" : " [!RST"));
if (length > MAX_RST_DATA_LEN) {
length = MAX_RST_DATA_LEN; /* can use -X for longer */
ND_PRINT((ndo, "+")); /* indicate we truncate */
}
ND_PRINT((ndo, " "));
while (length-- && sp < ndo->ndo_snapend) {
c = *sp++;
safeputchar(ndo, c);
}
ND_PRINT((ndo, "]"));
}
static void
print_tcp_fastopen_option(netdissect_options *ndo, register const u_char *cp,
u_int datalen, int exp)
{
u_int i;
if (exp)
ND_PRINT((ndo, "tfo"));
if (datalen == 0) {
/* Fast Open Cookie Request */
ND_PRINT((ndo, " cookiereq"));
} else {
/* Fast Open Cookie */
if (datalen % 2 != 0 || datalen < 4 || datalen > 16) {
ND_PRINT((ndo, " invalid"));
} else {
ND_PRINT((ndo, " cookie "));
for (i = 0; i < datalen; ++i)
ND_PRINT((ndo, "%02x", cp[i]));
}
}
}
#ifdef HAVE_LIBCRYPTO
USES_APPLE_DEPRECATED_API
static int
tcp_verify_signature(netdissect_options *ndo,
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;
uint16_t savecsum, tlen;
const struct ip6_hdr *ip6;
uint32_t len32;
uint8_t nxt;
if (data + length > ndo->ndo_snapend) {
ND_PRINT((ndo, "snaplen too short, "));
return (CANT_CHECK_SIGNATURE);
}
tp1 = *tp;
if (ndo->ndo_sigsecret == NULL) {
ND_PRINT((ndo, "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, (const char *)&ip->ip_src, sizeof(ip->ip_src));
MD5_Update(&ctx, (const char *)&ip->ip_dst, sizeof(ip->ip_dst));
MD5_Update(&ctx, (const char *)&zero_proto, sizeof(zero_proto));
MD5_Update(&ctx, (const char *)&ip->ip_p, sizeof(ip->ip_p));
tlen = EXTRACT_16BITS(&ip->ip_len) - IP_HL(ip) * 4;
tlen = htons(tlen);
MD5_Update(&ctx, (const char *)&tlen, sizeof(tlen));
} else if (IP_V(ip) == 6) {
ip6 = (const struct ip6_hdr *)ip;
MD5_Update(&ctx, (const char *)&ip6->ip6_src, sizeof(ip6->ip6_src));
MD5_Update(&ctx, (const char *)&ip6->ip6_dst, sizeof(ip6->ip6_dst));
len32 = htonl(EXTRACT_16BITS(&ip6->ip6_plen));
MD5_Update(&ctx, (const char *)&len32, sizeof(len32));
nxt = 0;
MD5_Update(&ctx, (const char *)&nxt, sizeof(nxt));
MD5_Update(&ctx, (const char *)&nxt, sizeof(nxt));
MD5_Update(&ctx, (const char *)&nxt, sizeof(nxt));
nxt = IPPROTO_TCP;
MD5_Update(&ctx, (const char *)&nxt, sizeof(nxt));
} else {
ND_PRINT((ndo, "IP version not 4 or 6, "));
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, (const 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, ndo->ndo_sigsecret, strlen(ndo->ndo_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:
*/
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