dns: validate IPv4 record addressesHEADmaster

Ensure the IPv4 PTR address contains exactly four numbers, and no excess
characters.

This avoids leaving ip1 potentially uninitialized for shorter prefixes.

Fixes: 2b28094 ("dns: add support for reverse address mapping queries")
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/dns.c b/dns.c
index 08515f6..6e7ec15 100644
--- a/dns.c
+++ b/dns.c
@@ -475,9 +475,13 @@ match_ipv6_addresses(char *reverse_ip, struct in6_addr *intf_ip)
 static int
 match_ip_addresses(char *reverse_ip, char *intf_ip)
 {
-	int ip1[4], ip2[4];
+	int ip1[4], ip2[4], res;
+	char c;
+
+	res = sscanf(reverse_ip, "%d.%d.%d.%d%c", &ip1[3], &ip1[2], &ip1[1], &ip1[0], &c);
+	if (res != 4)
+		return 0;
 
-	sscanf(reverse_ip, "%d.%d.%d.%d", &ip1[3], &ip1[2], &ip1[1], &ip1[0]);
 	sscanf(intf_ip, "%d.%d.%d.%d", &ip2[0], &ip2[1], &ip2[2], &ip2[3]);
 
 	int i;