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Commit 468adf7a authored by David Leadbeater's avatar David Leadbeater Committed by Greg Kroah-Hartman
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netfilter: nf_conntrack_irc: Tighten matching on DCC message 



[ Upstream commit e8d5dfd1d8747b56077d02664a8838c71ced948e ]

CTCP messages should only be at the start of an IRC message, not
anywhere within it.

While the helper only decodes packes in the ORIGINAL direction, its
possible to make a client send a CTCP message back by empedding one into
a PING request.  As-is, thats enough to make the helper believe that it
saw a CTCP message.

Fixes: 869f37d8 ("[NETFILTER]: nf_conntrack/nf_nat: add IRC helper port")
Signed-off-by: default avatarDavid Leadbeater <dgl@dgl.cx>
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 9431ef7d

net/netfilter/nf_conntrack_irc.c

+28 −6
Original line number Diff line number Diff line
@@ -150,15 +150,37 @@ static int help(struct sk_buff *skb, unsigned int protoff, 
	data = ib_ptr;

	data_limit = ib_ptr + skb->len - dataoff;



	/* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24

	 * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */

	while (data < data_limit - (19 + MINMATCHLEN)) {

		if (memcmp(data, "\1DCC ", 5)) {

	/* Skip any whitespace */

	while (data < data_limit - 10) {

		if (*data == ' ' || *data == '\r' || *data == '\n')

			data++;

		else

			break;

	}



	/* strlen("PRIVMSG x ")=10 */

	if (data < data_limit - 10) {

		if (strncasecmp("PRIVMSG ", data, 8))

			goto out;

		data += 8;

	}



	/* strlen(" :\1DCC SENT t AAAAAAAA P\1\n")=26

	 * 7+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=26

	 */

	while (data < data_limit - (21 + MINMATCHLEN)) {

		/* Find first " :", the start of message */

		if (memcmp(data, " :", 2)) {

			data++;

			continue;

		}

		data += 2;



		/* then check that place only for the DCC command */

		if (memcmp(data, "\1DCC ", 5))

			goto out;

		data += 5;

		/* we have at least (19+MINMATCHLEN)-5 bytes valid data left */

		/* we have at least (21+MINMATCHLEN)-(2+5) bytes valid data left */



		iph = ip_hdr(skb);

		pr_debug("DCC found in master %pI4:%u %pI4:%u\n",
@@ -174,7 +196,7 @@ static int help(struct sk_buff *skb, unsigned int protoff, 
			pr_debug("DCC %s detected\n", dccprotos[i]);



			/* we have at least

			 * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid

			 * (21+MINMATCHLEN)-7-dccprotos[i].matchlen bytes valid

			 * data left (== 14/13 bytes) */

			if (parse_dcc(data, data_limit, &dcc_ip,

				       &dcc_port, &addr_beg_p, &addr_end_p)) {