[PATCH 2.4] netfilter ip_conntrack_irc parser fix

[PATCH 2.4] netfilter ip_conntrack_irc parser fix

[Harald Welte]

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Hi Dave!

This is the 3rd of a set of bugfixes (all tested against 2.4.22-pre7).
You might need to apply them incrementally (didn't test it in a
different order).  You will receive 2.6 merges of those patches soon.


Author: Harald Welte <laforge@netfilter.org>

This patch fixes a bug in the IRC DCC command parser of ip_conntrack_irc

Please apply,

--- linux/net/ipv4/netfilter/ip_conntrack_irc.c.orig	Wed May  7 12:13:55 2003
+++ linux/net/ipv4/netfilter/ip_conntrack_irc.c	Wed May  7 13:16:00 2003
@@ -59,7 +59,7 @@
 	{"TSEND ", 6},
 	{"SCHAT ", 6}
 };
-#define MAXMATCHLEN	6
+#define MINMATCHLEN	5
 
 DECLARE_LOCK(ip_irc_lock);
 struct module *ip_conntrack_irc = THIS_MODULE;
@@ -92,9 +92,11 @@
 	*ip = simple_strtoul(data, &data, 10);
 
 	/* skip blanks between ip and port */
-	while (*data == ' ')
+	while (*data == ' ') {
+		if (data >= data_end) 
+			return -1;
 		data++;
-
+	}
 
 	*port = simple_strtoul(data, &data, 10);
 	*ad_end_p = data;
@@ -153,13 +155,17 @@
 	}
 
 	data_limit = (char *) data + datalen;
-	while (data < (data_limit - (22 + MAXMATCHLEN))) {
+
+	/* strlen("\1DCC SEND 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)) {
 			data++;
 			continue;
 		}
 
 		data += 5;
+		/* we have at least (19+MINMATCHLEN)-5 bytes valid data left */
 
 		DEBUGP("DCC found in master %u.%u.%u.%u:%u %u.%u.%u.%u:%u...\n",
 			NIPQUAD(iph->saddr), ntohs(tcph->source),
@@ -174,6 +180,9 @@
 
 			DEBUGP("DCC %s detected\n", dccprotos[i].match);
 			data += dccprotos[i].matchlen;
+			/* we have at least
+			 * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid
+			 * data left (== 14/13 bytes) */
 			if (parse_dcc((char *) data, data_limit, &dcc_ip,
 				       &dcc_port, &addr_beg_p, &addr_end_p)) {
 				/* unable to parse */
-- 
- Harald Welte <laforge@netfilter.org>             http://www.netfilter.org/
============================================================================
  "Fragmentation is like classful addressing -- an interesting early
   architectural error that shows how much experimentation was going
   on while IP was being designed."                    -- Paul Vixie

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