+static int compare_uint(const void *p1, const void *p2) {
+ unsigned int u1 = *((const unsigned int *)p1);
+ unsigned int u2 = *((const unsigned int *)p2);
+ if (u1 < u2)
+ return -1;
+ else if (u1 > u2)
+ return 1;
+ else
+ return 0;
+}
+
+/*
+ * Per http://tools.ietf.org/html/rfc5246#section-7.4.1.4, there may not be
+ * more than one extension of the same type in a ClientHello or ServerHello.
+ * This function does an initial scan over the extensions block to filter those
+ * out. It returns 1 if all extensions are unique, and 0 if the extensions
+ * contain duplicates, could not be successfully parsed, or an internal error
+ * occurred.
+ */
+static int tls1_check_duplicate_extensions(const PACKET *packet) {
+ PACKET extensions = *packet;
+ size_t num_extensions = 0, i = 0;
+ unsigned int *extension_types = NULL;
+ int ret = 0;
+
+ /* First pass: count the extensions. */
+ while (PACKET_remaining(&extensions) > 0) {
+ unsigned int type;
+ PACKET extension;
+ if (!PACKET_get_net_2(&extensions, &type) ||
+ !PACKET_get_length_prefixed_2(&extensions, &extension)) {
+ goto done;
+ }
+ num_extensions++;
+ }
+
+ if (num_extensions <= 1)
+ return 1;
+
+ extension_types = OPENSSL_malloc(sizeof(unsigned int) * num_extensions);
+ if (extension_types == NULL) {
+ SSLerr(SSL_F_TLS1_CHECK_DUPLICATE_EXTENSIONS, ERR_R_MALLOC_FAILURE);
+ goto done;
+ }
+
+ /* Second pass: gather the extension types. */
+ extensions = *packet;
+ for (i = 0; i < num_extensions; i++) {
+ PACKET extension;
+ if (!PACKET_get_net_2(&extensions, &extension_types[i]) ||
+ !PACKET_get_length_prefixed_2(&extensions, &extension)) {
+ /* This should not happen. */
+ SSLerr(SSL_F_TLS1_CHECK_DUPLICATE_EXTENSIONS, ERR_R_INTERNAL_ERROR);
+ goto done;
+ }
+ }
+
+ if (PACKET_remaining(&extensions) != 0) {
+ SSLerr(SSL_F_TLS1_CHECK_DUPLICATE_EXTENSIONS, ERR_R_INTERNAL_ERROR);
+ goto done;
+ }
+ /* Sort the extensions and make sure there are no duplicates. */
+ qsort(extension_types, num_extensions, sizeof(unsigned int), compare_uint);
+ for (i = 1; i < num_extensions; i++) {
+ if (extension_types[i - 1] == extension_types[i])
+ goto done;
+ }
+ ret = 1;
+ done:
+ OPENSSL_free(extension_types);
+ return ret;
+}
+