STUN/netsock2: Fix some valgrind uninitialized memory findings.

* netsock2.c: Test the addr->len member first as it may be the only member
initialized in the struct.

* stun.c:ast_stun_handle_packet(): The combinded[] local array could get
used uninitialized by ast_stun_request().  The uninitialized string gets
copied to another location and could overflow the destination memory
buffer.

These valgrind findings were found for ASTERISK_27150 but are not
necessarily a fix for the issue.

Change-Id: I55f8687ba4ffc0f69578fd850af006a56cbc9a57

main/netsock2.c

@@ -475,8 +475,12 @@ uint32_t ast_sockaddr_ipv4(const struct ast_sockaddr *addr)
 
 int ast_sockaddr_is_ipv4(const struct ast_sockaddr *addr)
 {
-	return addr->ss.ss_family == AF_INET &&
-	    addr->len == sizeof(struct sockaddr_in);
+	/*
+	 * Test addr->len first to be tolerant of an ast_sockaddr_setnull()
+	 * addr.  In that case addr->len might be the only value initialized.
+	 */
+	return addr->len == sizeof(struct sockaddr_in)
+		&& addr->ss.ss_family == AF_INET;
 }
 
 int ast_sockaddr_is_ipv4_mapped(const struct ast_sockaddr *addr)
@@ -498,8 +502,12 @@ int ast_sockaddr_is_ipv6_link_local(const struct ast_sockaddr *addr)
 
 int ast_sockaddr_is_ipv6(const struct ast_sockaddr *addr)
 {
-	return addr->ss.ss_family == AF_INET6 &&
-	    addr->len == sizeof(struct sockaddr_in6);
+	/*
+	 * Test addr->len first to be tolerant of an ast_sockaddr_setnull()
+	 * addr.  In that case addr->len might be the only value initialized.
+	 */
+	return addr->len == sizeof(struct sockaddr_in6)
+		&& addr->ss.ss_family == AF_INET6;
 }
 
 int ast_sockaddr_is_any(const struct ast_sockaddr *addr)

main/stun.c

@@ -343,6 +343,8 @@ int ast_stun_handle_packet(int s, struct sockaddr_in *src, unsigned char *data,
 			if (st.username) {
 				append_attr_string(&attr, STUN_USERNAME, st.username, &resplen, &respleft);
 				snprintf(combined, sizeof(combined), "%16s%16s", st.username + 16, st.username);
+			} else {
+				combined[0] = '\0';
 			}
 
 			append_attr_address(&attr, STUN_MAPPED_ADDRESS, src, &resplen, &respleft);
@@ -398,8 +400,6 @@ int ast_stun_request(int s, struct sockaddr_in *dst,
 	stun_req_id(req);
 	reqlen = 0;
 	reqleft = sizeof(req_buf) - sizeof(struct stun_header);
-	req->msgtype = 0;
-	req->msglen = 0;
 	attr = (struct stun_attr *) req->ies;
 	if (username) {
 		append_attr_string(&attr, STUN_USERNAME, username, &reqlen, &reqleft);