Commit message: CVE-2017-13037/IP: Add bounds checks when printing time stamp options.

This fixes a buffer over-read discovered by Bhargava Shastry,
SecT/TU Berlin.

Add a test using the capture file supplied by the reporter(s), modified
so the capture file won't be rejected as an invalid capture.
CVE: CVE-2017-13037
CWE: CWE-125
Vulnerability description: The IP parser in tcpdump before 4.9.2 has a buffer over-read in print-ip.c:ip_printts().

Project: tcpdump
File: print-ip.c

ipN_print(netdissect_options *ndo, register const u_char *bp, register u_int length)
{
	if (length < 1) {
		ND_PRINT((ndo, "truncated-ip %d", length));
		return;
	}

	ND_TCHECK(*bp);
	switch (*bp & 0xF0) {
	case 0x40:
		ip_print (ndo, bp, length);
		break;
	case 0x60:
		ip6_print (ndo, bp, length);
		break;
	default:
		ND_PRINT((ndo, "unknown ip %d", (*bp & 0xF0) >> 4));
		break;
	}
	return;

trunc:
	ND_PRINT((ndo, "%s", tstr));
	return;
}

Project: tcpdump
File: print-ip.c

ip_finddst(netdissect_options *ndo,
           const struct ip *ip)
{
	int length;
	int len;
	const u_char *cp;
	uint32_t retval;

	cp = (const u_char *)(ip + 1);
	length = (IP_HL(ip) << 2) - sizeof(struct ip);

	for (; length > 0; cp += len, length -= len) {
		int tt;

		ND_TCHECK(*cp);
		tt = *cp;
		if (tt == IPOPT_EOL)
			break;
		else if (tt == IPOPT_NOP)
			len = 1;
		else {
			ND_TCHECK(cp[1]);
			len = cp[1];
			if (len < 2)
				break;
		}
		ND_TCHECK2(*cp, len);
		switch (tt) {

		case IPOPT_SSRR:
		case IPOPT_LSRR:
			if (len < 7)
				break;
			UNALIGNED_MEMCPY(&retval, cp + len - 4, 4);
			return retval;
		}
	}
trunc:
	UNALIGNED_MEMCPY(&retval, &ip->ip_dst, sizeof(uint32_t));
	return retval;
}

Project: tcpdump
File: print-ip.c

ip_print(netdissect_options *ndo,
	 const u_char *bp,
	 u_int length)
{
	struct ip_print_demux_state  ipd;
	struct ip_print_demux_state *ipds=&ipd;
	const u_char *ipend;
	u_int hlen;
	struct cksum_vec vec[1];
	uint16_t sum, ip_sum;
	const char *p_name;

	ipds->ip = (const struct ip *)bp;
	ND_TCHECK(ipds->ip->ip_vhl);
	if (IP_V(ipds->ip) != 4) { /* print version and fail if != 4 */
	    if (IP_V(ipds->ip) == 6)
	      ND_PRINT((ndo, "IP6, wrong link-layer encapsulation "));
	    else
	      ND_PRINT((ndo, "IP%u ", IP_V(ipds->ip)));
	    return;
	}
	if (!ndo->ndo_eflag)
		ND_PRINT((ndo, "IP "));

	ND_TCHECK(*ipds->ip);
	if (length < sizeof (struct ip)) {
		ND_PRINT((ndo, "truncated-ip %u", length));
		return;
	}
	hlen = IP_HL(ipds->ip) * 4;
	if (hlen < sizeof (struct ip)) {
		ND_PRINT((ndo, "bad-hlen %u", hlen));
		return;
	}

	ipds->len = EXTRACT_16BITS(&ipds->ip->ip_len);
	if (length < ipds->len)
		ND_PRINT((ndo, "truncated-ip - %u bytes missing! ",
			ipds->len - length));
	if (ipds->len < hlen) {
#ifdef GUESS_TSO
            if (ipds->len) {
                ND_PRINT((ndo, "bad-len %u", ipds->len));
                return;
            }
            else {
                /* we guess that it is a TSO send */
                ipds->len = length;
            }
#else
            ND_PRINT((ndo, "bad-len %u", ipds->len));
            return;
#endif /* GUESS_TSO */
	}

	/*
	 * Cut off the snapshot length to the end of the IP payload.
	 */
	ipend = bp + ipds->len;
	if (ipend < ndo->ndo_snapend)
		ndo->ndo_snapend = ipend;

	ipds->len -= hlen;

	ipds->off = EXTRACT_16BITS(&ipds->ip->ip_off);

        if (ndo->ndo_vflag) {
            ND_PRINT((ndo, "(tos 0x%x", (int)ipds->ip->ip_tos));
            /* ECN bits */
            switch (ipds->ip->ip_tos & 0x03) {

            case 0:
                break;

            case 1:
                ND_PRINT((ndo, ",ECT(1)"));
                break;

            case 2:
                ND_PRINT((ndo, ",ECT(0)"));
                break;

            case 3:
                ND_PRINT((ndo, ",CE"));
                break;
            }

            if (ipds->ip->ip_ttl >= 1)
                ND_PRINT((ndo, ", ttl %u", ipds->ip->ip_ttl));

	    /*
	     * for the firewall guys, print id, offset.
             * On all but the last stick a "+" in the flags portion.
	     * For unfragmented datagrams, note the don't fragment flag.
	     */

	    ND_PRINT((ndo, ", id %u, offset %u, flags [%s], proto %s (%u)",
                         EXTRACT_16BITS(&ipds->ip->ip_id),
                         (ipds->off & 0x1fff) * 8,
                         bittok2str(ip_frag_values, "none", ipds->off&0xe000),
                         tok2str(ipproto_values,"unknown",ipds->ip->ip_p),
                         ipds->ip->ip_p));

            ND_PRINT((ndo, ", length %u", EXTRACT_16BITS(&ipds->ip->ip_len)));

            if ((hlen - sizeof(struct ip)) > 0) {
                ND_PRINT((ndo, ", options ("));
                ip_optprint(ndo, (const u_char *)(ipds->ip + 1), hlen - sizeof(struct ip));
                ND_PRINT((ndo, ")"));
            }

	    if (!ndo->ndo_Kflag && (const u_char *)ipds->ip + hlen <= ndo->ndo_snapend) {
	        vec[0].ptr = (const uint8_t *)(const void *)ipds->ip;
	        vec[0].len = hlen;
	        sum = in_cksum(vec, 1);
		if (sum != 0) {
		    ip_sum = EXTRACT_16BITS(&ipds->ip->ip_sum);
		    ND_PRINT((ndo, ", bad cksum %x (->%x)!", ip_sum,
			     in_cksum_shouldbe(ip_sum, sum)));
		}
	    }

		ND_PRINT((ndo, ")\n    "));
	}

	/*
	 * If this is fragment zero, hand it to the next higher
	 * level protocol.
	 */
	if ((ipds->off & 0x1fff) == 0) {
		ipds->cp = (const u_char *)ipds->ip + hlen;
		ipds->nh = ipds->ip->ip_p;

		if (ipds->nh != IPPROTO_TCP && ipds->nh != IPPROTO_UDP &&
		    ipds->nh != IPPROTO_SCTP && ipds->nh != IPPROTO_DCCP) {
			ND_PRINT((ndo, "%s > %s: ",
				     ipaddr_string(ndo, &ipds->ip->ip_src),
				     ipaddr_string(ndo, &ipds->ip->ip_dst)));
		}
		ip_print_demux(ndo, ipds);
	} else {
		/*
		 * Ultra quiet now means that all this stuff should be
		 * suppressed.
		 */
		if (ndo->ndo_qflag > 1)
			return;

		/*
		 * This isn't the first frag, so we're missing the
		 * next level protocol header.  print the ip addr
		 * and the protocol.
		 */
		ND_PRINT((ndo, "%s > %s:", ipaddr_string(ndo, &ipds->ip->ip_src),
		          ipaddr_string(ndo, &ipds->ip->ip_dst)));
		if (!ndo->ndo_nflag && (p_name = netdb_protoname(ipds->ip->ip_p)) != NULL)
			ND_PRINT((ndo, " %s", p_name));
		else
			ND_PRINT((ndo, " ip-proto-%d", ipds->ip->ip_p));
	}
	return;

trunc:
	ND_PRINT((ndo, "%s", tstr));
	return;
}

Project: tcpdump
File: print-ip.c

ip_print_demux(netdissect_options *ndo,
	       struct ip_print_demux_state *ipds)
{
	const char *p_name;

again:
	switch (ipds->nh) {

	case IPPROTO_AH:
		if (!ND_TTEST(*ipds->cp)) {
			ND_PRINT((ndo, "[|AH]"));
			break;
		}
		ipds->nh = *ipds->cp;
		ipds->advance = ah_print(ndo, ipds->cp);
		if (ipds->advance <= 0)
			break;
		ipds->cp += ipds->advance;
		ipds->len -= ipds->advance;
		goto again;

	case IPPROTO_ESP:
	{
		int enh, padlen;
		ipds->advance = esp_print(ndo, ipds->cp, ipds->len,
				    (const u_char *)ipds->ip,
				    &enh, &padlen);
		if (ipds->advance <= 0)
			break;
		ipds->cp += ipds->advance;
		ipds->len -= ipds->advance + padlen;
		ipds->nh = enh & 0xff;
		goto again;
	}

	case IPPROTO_IPCOMP:
	{
		ipcomp_print(ndo, ipds->cp);
		/*
		 * Either this has decompressed the payload and
		 * printed it, in which case there's nothing more
		 * to do, or it hasn't, in which case there's
		 * nothing more to do.
		 */
		break;
	}

	case IPPROTO_SCTP:
		sctp_print(ndo, ipds->cp, (const u_char *)ipds->ip, ipds->len);
		break;

	case IPPROTO_DCCP:
		dccp_print(ndo, ipds->cp, (const u_char *)ipds->ip, ipds->len);
		break;

	case IPPROTO_TCP:
		/* pass on the MF bit plus the offset to detect fragments */
		tcp_print(ndo, ipds->cp, ipds->len, (const u_char *)ipds->ip,
			  ipds->off & (IP_MF|IP_OFFMASK));
		break;

	case IPPROTO_UDP:
		/* pass on the MF bit plus the offset to detect fragments */
		udp_print(ndo, ipds->cp, ipds->len, (const u_char *)ipds->ip,
			  ipds->off & (IP_MF|IP_OFFMASK));
		break;

	case IPPROTO_ICMP:
		/* pass on the MF bit plus the offset to detect fragments */
		icmp_print(ndo, ipds->cp, ipds->len, (const u_char *)ipds->ip,
			   ipds->off & (IP_MF|IP_OFFMASK));
		break;

	case IPPROTO_PIGP:
		/*
		 * XXX - the current IANA protocol number assignments
		 * page lists 9 as "any private interior gateway
		 * (used by Cisco for their IGRP)" and 88 as
		 * "EIGRP" from Cisco.
		 *
		 * Recent BSD <netinet/in.h> headers define
		 * IP_PROTO_PIGP as 9 and IP_PROTO_IGRP as 88.
		 * We define IP_PROTO_PIGP as 9 and
		 * IP_PROTO_EIGRP as 88; those names better
		 * match was the current protocol number
		 * assignments say.
		 */
		igrp_print(ndo, ipds->cp, ipds->len);
		break;

	case IPPROTO_EIGRP:
		eigrp_print(ndo, ipds->cp, ipds->len);
		break;

	case IPPROTO_ND:
		ND_PRINT((ndo, " nd %d", ipds->len));
		break;

	case IPPROTO_EGP:
		egp_print(ndo, ipds->cp, ipds->len);
		break;

	case IPPROTO_OSPF:
		ospf_print(ndo, ipds->cp, ipds->len, (const u_char *)ipds->ip);
		break;

	case IPPROTO_IGMP:
		igmp_print(ndo, ipds->cp, ipds->len);
		break;

	case IPPROTO_IPV4:
		/* DVMRP multicast tunnel (ip-in-ip encapsulation) */
		ip_print(ndo, ipds->cp, ipds->len);
		if (! ndo->ndo_vflag) {
			ND_PRINT((ndo, " (ipip-proto-4)"));
			return;
		}
		break;

	case IPPROTO_IPV6:
		/* ip6-in-ip encapsulation */
		ip6_print(ndo, ipds->cp, ipds->len);
		break;

	case IPPROTO_RSVP:
		rsvp_print(ndo, ipds->cp, ipds->len);
		break;

	case IPPROTO_GRE:
		/* do it */
		gre_print(ndo, ipds->cp, ipds->len);
		break;

	case IPPROTO_MOBILE:
		mobile_print(ndo, ipds->cp, ipds->len);
		break;

	case IPPROTO_PIM:
		pim_print(ndo, ipds->cp, ipds->len, (const u_char *)ipds->ip);
		break;

	case IPPROTO_VRRP:
		if (ndo->ndo_packettype == PT_CARP) {
			if (ndo->ndo_vflag)
				ND_PRINT((ndo, "carp %s > %s: ",
					     ipaddr_string(ndo, &ipds->ip->ip_src),
					     ipaddr_string(ndo, &ipds->ip->ip_dst)));
			carp_print(ndo, ipds->cp, ipds->len, ipds->ip->ip_ttl);
		} else {
			if (ndo->ndo_vflag)
				ND_PRINT((ndo, "vrrp %s > %s: ",
					     ipaddr_string(ndo, &ipds->ip->ip_src),
					     ipaddr_string(ndo, &ipds->ip->ip_dst)));
			vrrp_print(ndo, ipds->cp, ipds->len,
				(const u_char *)ipds->ip, ipds->ip->ip_ttl);
		}
		break;

	case IPPROTO_PGM:
		pgm_print(ndo, ipds->cp, ipds->len, (const u_char *)ipds->ip);
		break;

	default:
		if (ndo->ndo_nflag==0 && (p_name = netdb_protoname(ipds->nh)) != NULL)
			ND_PRINT((ndo, " %s", p_name));
		else
			ND_PRINT((ndo, " ip-proto-%d", ipds->nh));
		ND_PRINT((ndo, " %d", ipds->len));
		break;
	}
}

Project: tcpdump
File: print-ip.c

ip_print_inner(netdissect_options *ndo,
	       const u_char *bp,
	       u_int length, u_int nh,
	       const u_char *bp2)
{
	struct ip_print_demux_state  ipd;

	ipd.ip = (const struct ip *)bp2;
	ipd.cp = bp;
	ipd.len  = length;
	ipd.off  = 0;
	ipd.nh   = nh;
	ipd.advance = 0;

	ip_print_demux(ndo, &ipd);
}

Project: tcpdump
File: print-ip.c

nextproto4_cksum(netdissect_options *ndo,
                 const struct ip *ip, const uint8_t *data,
                 u_int len, u_int covlen, u_int next_proto)
{
	struct phdr {
		uint32_t src;
		uint32_t dst;
		u_char mbz;
		u_char proto;
		uint16_t len;
	} ph;
	struct cksum_vec vec[2];

	/* pseudo-header.. */
	ph.len = htons((uint16_t)len);
	ph.mbz = 0;
	ph.proto = next_proto;
	UNALIGNED_MEMCPY(&ph.src, &ip->ip_src, sizeof(uint32_t));
	if (IP_HL(ip) == 5)
		UNALIGNED_MEMCPY(&ph.dst, &ip->ip_dst, sizeof(uint32_t));
	else
		ph.dst = ip_finddst(ndo, ip);

	vec[0].ptr = (const uint8_t *)(void *)&ph;
	vec[0].len = sizeof(ph);
	vec[1].ptr = data;
	vec[1].len = covlen;
 	return (in_cksum(vec, 2));
 }