+ * Process the supported_groups extension if present. Returns success if the
+ * extension is absent, or if it has been successfully processed.
+ *
+ * Returns 1 on success or 0 on failure
+ */
+static int tls_process_supported_groups(SSL *s, CLIENTHELLO_MSG *hello)
+{
+#ifndef OPENSSL_NO_EC
+ PACKET supported_groups_list;
+ RAW_EXTENSION *suppgroups = tls_get_extension_by_type(hello->pre_proc_exts,
+ hello->num_extensions,
+ TLSEXT_TYPE_supported_groups);
+
+ if (suppgroups == NULL)
+ return 1;
+
+ /* Each group is 2 bytes and we must have at least 1. */
+ if (!PACKET_as_length_prefixed_2(&suppgroups->data,
+ &supported_groups_list)
+ || PACKET_remaining(&supported_groups_list) == 0
+ || (PACKET_remaining(&supported_groups_list) % 2) != 0) {
+ return 0;
+ }
+
+ if (!s->hit
+ && !PACKET_memdup(&supported_groups_list,
+ &s->session->tlsext_supportedgroupslist,
+ &s->session->tlsext_supportedgroupslist_length)) {
+ return 0;
+ }
+#endif
+ return 1;
+}
+
+/*
+ * Checks a list of |groups| to determine if the |group_id| is in it. If it is
+ * and |checkallow| is 1 then additionally check if the group is allowed to be
+ * used. Returns 1 if the group is in the list (and allowed if |checkallow| is
+ * 1) or 0 otherwise.
+ */
+static int check_in_list(SSL *s, unsigned int group_id,
+ const unsigned char *groups, size_t num_groups,
+ int checkallow)
+{
+ size_t i;
+
+ if (groups == NULL || num_groups == 0)
+ return 0;
+
+ for (i = 0; i < num_groups; i++, groups += 2) {
+ unsigned int share_id = (groups[0] << 8) | (groups[1]);
+
+ if (group_id == share_id
+ && (!checkallow || tls_curve_allowed(s, groups,
+ SSL_SECOP_CURVE_CHECK))) {
+ break;
+ }
+ }
+
+ /* If i == num_groups then not in the list */
+ return i < num_groups;
+}
+
+/*
+ * Process a key_share extension received in the ClientHello. |pkt| contains
+ * the raw PACKET data for the extension. Returns 1 on success or 0 on failure.
+ * If a failure occurs then |*al| is set to an appropriate alert value.
+ */
+static int process_key_share_ext(SSL *s, PACKET *pkt, int *al)
+{
+ unsigned int group_id;
+ PACKET key_share_list, encoded_pt;
+ const unsigned char *clntcurves, *srvrcurves;
+ size_t clnt_num_curves, srvr_num_curves;
+ int group_nid, found = 0;
+ unsigned int curve_flags;
+
+ /* Sanity check */
+ if (s->s3->peer_tmp != NULL) {
+ *al = SSL_AD_INTERNAL_ERROR;
+ SSLerr(SSL_F_PROCESS_KEY_SHARE_EXT, ERR_R_INTERNAL_ERROR);
+ return 0;
+ }
+
+ if (!PACKET_as_length_prefixed_2(pkt, &key_share_list)) {
+ *al = SSL_AD_HANDSHAKE_FAILURE;
+ SSLerr(SSL_F_PROCESS_KEY_SHARE_EXT,
+ SSL_R_LENGTH_MISMATCH);
+ return 0;
+ }
+
+ /* Get our list of supported curves */
+ if (!tls1_get_curvelist(s, 0, &srvrcurves, &srvr_num_curves)) {
+ *al = SSL_AD_INTERNAL_ERROR;
+ SSLerr(SSL_F_PROCESS_KEY_SHARE_EXT,
+ ERR_R_INTERNAL_ERROR);
+ return 0;
+ }
+
+ /* Get the clients list of supported curves */
+ if (!tls1_get_curvelist(s, 1, &clntcurves, &clnt_num_curves)) {
+ *al = SSL_AD_INTERNAL_ERROR;
+ SSLerr(SSL_F_PROCESS_KEY_SHARE_EXT,
+ ERR_R_INTERNAL_ERROR);
+ return 0;
+ }
+
+ while (PACKET_remaining(&key_share_list) > 0) {
+ if (!PACKET_get_net_2(&key_share_list, &group_id)
+ || !PACKET_get_length_prefixed_2(&key_share_list, &encoded_pt)
+ || PACKET_remaining(&encoded_pt) == 0) {
+ *al = SSL_AD_HANDSHAKE_FAILURE;
+ SSLerr(SSL_F_PROCESS_KEY_SHARE_EXT,
+ SSL_R_LENGTH_MISMATCH);
+ return 0;
+ }
+
+ /*
+ * If we already found a suitable key_share we loop through the
+ * rest to verify the structure, but don't process them.
+ */
+ if (found)
+ continue;
+
+ /* Check if this share is in supported_groups sent from client */
+ if (!check_in_list(s, group_id, clntcurves, clnt_num_curves, 0)) {
+ *al = SSL_AD_HANDSHAKE_FAILURE;
+ SSLerr(SSL_F_PROCESS_KEY_SHARE_EXT,
+ SSL_R_BAD_KEY_SHARE);
+ return 0;
+ }
+
+ /* Check if this share is for a group we can use */
+ if (!check_in_list(s, group_id, srvrcurves, srvr_num_curves, 1)) {
+ /* Share not suitable */
+ continue;
+ }
+
+ group_nid = tls1_ec_curve_id2nid(group_id, &curve_flags);
+
+ if (group_nid == 0) {
+ *al = SSL_AD_INTERNAL_ERROR;
+ SSLerr(SSL_F_PROCESS_KEY_SHARE_EXT,
+ SSL_R_UNABLE_TO_FIND_ECDH_PARAMETERS);
+ return 0;
+ }
+
+ if ((curve_flags & TLS_CURVE_TYPE) == TLS_CURVE_CUSTOM) {
+ /* Can happen for some curves, e.g. X25519 */
+ EVP_PKEY *key = EVP_PKEY_new();
+
+ if (key == NULL || !EVP_PKEY_set_type(key, group_nid)) {
+ *al = SSL_AD_INTERNAL_ERROR;
+ SSLerr(SSL_F_PROCESS_KEY_SHARE_EXT, ERR_R_EVP_LIB);
+ EVP_PKEY_free(key);
+ return 0;
+ }
+ s->s3->peer_tmp = key;
+ } else {
+ /* Set up EVP_PKEY with named curve as parameters */
+ EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_EC, NULL);
+ if (pctx == NULL
+ || EVP_PKEY_paramgen_init(pctx) <= 0
+ || EVP_PKEY_CTX_set_ec_paramgen_curve_nid(pctx,
+ group_nid) <= 0
+ || EVP_PKEY_paramgen(pctx, &s->s3->peer_tmp) <= 0) {
+ *al = SSL_AD_INTERNAL_ERROR;
+ SSLerr(SSL_F_PROCESS_KEY_SHARE_EXT, ERR_R_EVP_LIB);
+ EVP_PKEY_CTX_free(pctx);
+ return 0;
+ }
+ EVP_PKEY_CTX_free(pctx);
+ pctx = NULL;
+ }
+ s->s3->group_id = group_id;
+
+ if (!EVP_PKEY_set1_tls_encodedpoint(s->s3->peer_tmp,
+ PACKET_data(&encoded_pt),
+ PACKET_remaining(&encoded_pt))) {
+ *al = SSL_AD_DECODE_ERROR;
+ SSLerr(SSL_F_PROCESS_KEY_SHARE_EXT, SSL_R_BAD_ECPOINT);
+ return 0;
+ }
+
+ found = 1;
+ }
+
+ return 1;
+}
+
+/*
+ * Loop through all remaining ClientHello extensions that we collected earlier
+ * and haven't already processed. For each one parse it and update the SSL
+ * object as required.