Backport UDP validation from trunk

3 files changed, 26 insertions, 28 deletions

diff --git a/client.c b/client.c
index d14bd751..e9645662 100644
--- a/client.c
+++ b/client.c
@@ -1548,7 +1548,7 @@ handle_dhcp_packet(struct if_state *state, const struct options *options)
 		}
 		if (bytes == -1)
 			break;
-		if (valid_udp_packet(packet) == -1)
+		if (valid_udp_packet(packet, bytes) == -1)
 			continue;
 		bytes = get_udp_data(&pp, packet);
 		if ((size_t)bytes > sizeof(*dhcp)) {
diff --git a/net.c b/net.c
index fa5af103..29344f82 100644
--- a/net.c
+++ b/net.c
@@ -634,44 +634,42 @@ get_udp_data(const uint8_t **data, const uint8_t *udp)
 }
 
 int
-valid_udp_packet(const uint8_t *data)
+valid_udp_packet(const uint8_t *data, size_t data_len)
 {
 	struct udp_dhcp_packet packet;
-	uint16_t bytes;
-	uint16_t ipsum;
-	uint16_t iplen;
-	uint16_t udpsum;
-	struct in_addr source;
-	struct in_addr dest;
-	int retval = 0;
-
-	memcpy(&packet, data, sizeof(packet));
-	bytes = ntohs(packet.ip.ip_len);
-	ipsum = packet.ip.ip_sum;
-	iplen = packet.ip.ip_len;
-	udpsum = packet.udp.uh_sum;
+	uint16_t bytes, udpsum;
 
-	if (0 != checksum(&packet.ip, sizeof(packet.ip))) {
+	if (data_len > sizeof(packet)) {
+		errno = EINVAL;
+		return -1;
+	}
+	memcpy(&packet, data, data_len);
+	if (checksum(&packet.ip, sizeof(packet.ip)) != 0) {
 		errno = EINVAL;
 		return -1;
 	}
 
-	packet.ip.ip_sum = 0;
-	memcpy(&source, &packet.ip.ip_src, sizeof(packet.ip.ip_src));
-	memcpy(&dest, &packet.ip.ip_dst, sizeof(packet.ip.ip_dst));
-	memset(&packet.ip, 0, sizeof(packet.ip));
+	bytes = ntohs(packet.ip.ip_len);
+	if (data_len < bytes) {
+		errno = EINVAL;
+		return -1;
+	}
+	udpsum = packet.udp.uh_sum;
 	packet.udp.uh_sum = 0;
-
-	packet.ip.ip_p = IPPROTO_UDP;
-	memcpy(&packet.ip.ip_src, &source, sizeof(packet.ip.ip_src));
-	memcpy(&packet.ip.ip_dst, &dest, sizeof(packet.ip.ip_dst));
+	packet.ip.ip_hl = 0;
+	packet.ip.ip_v = 0;
+	packet.ip.ip_tos = 0;
 	packet.ip.ip_len = packet.udp.uh_ulen;
-	if (udpsum && udpsum != checksum(&packet, bytes)) {
+	packet.ip.ip_id = 0;
+	packet.ip.ip_off = 0;
+	packet.ip.ip_ttl = 0;
+	packet.ip.ip_sum = 0;
+	if (udpsum && checksum(&packet, bytes) != udpsum) {
 		errno = EINVAL;
-		retval = -1;
+		return -1;
 	}
 
-	return retval;
+	return 0;
 }
 
 int
diff --git a/net.h b/net.h
index e9005d02..1447aba0 100644
--- a/net.h
+++ b/net.h
@@ -160,7 +160,7 @@ const size_t udp_dhcp_len;
 ssize_t make_udp_packet(uint8_t **, const uint8_t *, size_t,
 			struct in_addr, struct in_addr);
 ssize_t get_udp_data(const uint8_t **, const uint8_t *);
-int valid_udp_packet(const uint8_t *);
+int valid_udp_packet(const uint8_t *, size_t);
 
 int open_socket(struct interface *, int);
 ssize_t send_packet(const struct interface *, struct in_addr,