tls-crypto: Generalizing DH group to TLS group mapping

This simplifies writing the key share extension as the TLS group does
not have to be cached.

src/libtls/tls_crypto.c

@@ -2319,3 +2319,20 @@ int tls_crypto_get_supported_suites(bool null, tls_version_t version,
 	}
 	return count;
 }
+
+/**
+ * See header.
+ */
+tls_named_group_t tls_ec_group_to_curve(diffie_hellman_group_t group)
+{
+	int i;
+
+	for (i = 0; i < countof(curves); i++)
+	{
+		if (curves[i].group == group)
+		{
+			return curves[i].curve;
+		}
+	}
+	return 0;
+}

src/libtls/tls_crypto.h

@@ -669,4 +669,12 @@ tls_crypto_t *tls_crypto_create(tls_t *tls, tls_cache_t *cache);
 int tls_crypto_get_supported_suites(bool null, tls_version_t version,
 									tls_cipher_suite_t **suites);
 
+/**
+ * Get the TLS curve of a given EC DH group
+ *
+ * @param group			diffie hellman group indicator
+ * @return				TLS group indicator
+ */
+tls_named_group_t tls_ec_group_to_curve(diffie_hellman_group_t group);
+
 #endif /** TLS_CRYPTO_H_ @}*/

src/libtls/tls_peer.c

@@ -158,8 +158,7 @@ struct private_tls_peer_t {
 };
 
 /* Implemented in tls_server.c */
-bool tls_write_key_share(bio_writer_t **key_share, tls_named_group_t group,
-						 diffie_hellman_t *dh);
+bool tls_write_key_share(bio_writer_t **key_share, diffie_hellman_t *dh);
 
 /**
  * Verify the DH group/key type requested by the server is valid.
@@ -1202,7 +1201,7 @@ static status_t send_client_hello(private_tls_peer_t *this,
 	bio_writer_t *extensions, *curves = NULL, *versions, *key_share, *signatures;
 	tls_version_t version_max, version_min;
 	diffie_hellman_group_t group;
-	tls_named_group_t curve, selected_curve = 0;
+	tls_named_group_t curve;
 	enumerator_t *enumerator;
 	int count, i, v;
 	rng_t *rng;
@@ -1296,7 +1295,6 @@ static status_t send_client_hello(private_tls_peer_t *this,
 			{
 				continue;
 			}
-			selected_curve = curve;
 		}
 		curves->write_uint16(curves, curve);
 	}
@@ -1355,13 +1353,12 @@ static status_t send_client_hello(private_tls_peer_t *this,
 	extensions->write_data16(extensions, signatures->get_buf(signatures));
 	signatures->destroy(signatures);
 
-	if (this->tls->get_version_max(this->tls) >= TLS_1_3 &&
-		this->dh)
+	if (this->tls->get_version_max(this->tls) >= TLS_1_3)
 	{
 		DBG2(DBG_TLS, "sending extension: %N",
 			 tls_extension_names, TLS_EXT_KEY_SHARE);
 		extensions->write_uint16(extensions, TLS_EXT_KEY_SHARE);
-		if (!tls_write_key_share(&key_share, selected_curve, this->dh))
+		if (!tls_write_key_share(&key_share, this->dh))
 		{
 			this->alert->add(this->alert, TLS_FATAL, TLS_INTERNAL_ERROR);
 			extensions->destroy(extensions);

src/libtls/tls_server.c

@@ -954,20 +954,25 @@ METHOD(tls_handshake_t, process, status_t,
 /**
  * Write public key into key share extension
  */
-bool tls_write_key_share(bio_writer_t **key_share, tls_named_group_t group,
-						 diffie_hellman_t *dh)
+bool tls_write_key_share(bio_writer_t **key_share, diffie_hellman_t *dh)
 {
 	bio_writer_t *writer;
+	tls_named_group_t curve;
 	chunk_t pub;
 
-	if (!dh || !dh->get_my_public_value(dh, &pub))
+	if (!dh)
+	{
+		return FALSE;
+	}
+	curve = tls_ec_group_to_curve(dh->get_dh_group(dh));
+	if (!curve || !dh->get_my_public_value(dh, &pub))
 	{
 		return FALSE;
 	}
 	*key_share = writer = bio_writer_create(pub.len + 7);
-	writer->write_uint16(writer, group);
-	if (group == TLS_CURVE25519 ||
-		group == TLS_CURVE448)
+	writer->write_uint16(writer, curve);
+	if (curve == TLS_CURVE25519 ||
+		curve == TLS_CURVE448)
 	{
 		writer->write_data16(writer, pub);
 	}
@@ -1019,7 +1024,7 @@ static status_t send_server_hello(private_tls_server_t *this,
 	   		 tls_extension_names, TLS_EXT_KEY_SHARE);
 		extensions->write_uint16(extensions, TLS_EXT_KEY_SHARE);
 
-		if (!tls_write_key_share(&key_share, this->requested_curve, this->dh))
+		if (!tls_write_key_share(&key_share, this->dh))
 		{
 			this->alert->add(this->alert, TLS_FATAL, TLS_INTERNAL_ERROR);
 			extensions->destroy(extensions);
@@ -1197,29 +1202,6 @@ static status_t send_certificate_request(private_tls_server_t *this,
 	return NEED_MORE;
 }
 
-/**
- * Get the TLS curve of a given EC DH group
- */
-static tls_named_group_t ec_group_to_curve(private_tls_server_t *this,
-                                           diffie_hellman_group_t group)
-{
-	diffie_hellman_group_t current;
-	tls_named_group_t curve;
-	enumerator_t *enumerator;
-
-	enumerator = this->crypto->create_ec_enumerator(this->crypto);
-	while (enumerator->enumerate(enumerator, &current, &curve))
-	{
-		if (current == group)
-		{
-			enumerator->destroy(enumerator);
-			return curve;
-		}
-	}
-	enumerator->destroy(enumerator);
-	return 0;
-}
-
 /**
  * Try to find a curve supported by both, client and server
  */
@@ -1256,7 +1238,7 @@ static status_t send_server_key_exchange(private_tls_server_t *this,
 
 	if (diffie_hellman_group_is_ec(group))
 	{
-		curve = ec_group_to_curve(this, group);
+		curve = tls_ec_group_to_curve(group);
 		if (!curve || (!peer_supports_curve(this, curve) &&
 					   !find_supported_curve(this, &curve)))
 		{