Use a dynamic curve enumerator to list/convert TLS named curves

src/libtls/tls_crypto.c

@@ -839,17 +839,53 @@ METHOD(tls_crypto_t, get_signature_algorithms, void,
 	supported->destroy(supported);
 }
 
-METHOD(tls_crypto_t, get_curves, void,
+/**
-	private_tls_crypto_t *this, tls_writer_t *writer)
+ * Mapping groups to TLS named curves
+ */
+static struct {
+	diffie_hellman_group_t group;
+	tls_named_curve_t curve;
+} curves[] = {
+	{ ECP_256_BIT, TLS_SECP256R1},
+	{ ECP_384_BIT, TLS_SECP384R1},
+	{ ECP_521_BIT, TLS_SECP521R1},
+	{ ECP_224_BIT, TLS_SECP224R1},
+	{ ECP_192_BIT, TLS_SECP192R1},
+};
+
+/**
+ * Filter EC groups, add TLS curve
+ */
+static bool group_filter(void *null,
+						diffie_hellman_group_t *in, diffie_hellman_group_t *out,
+						void* dummy1, tls_named_curve_t *curve)
 {
-	u_int16_t curves[] = {
+	int i;
-		htons(TLS_SECP256R1),
+
-		htons(TLS_SECP384R1),
+	for (i = 0; i < countof(curves); i++)
-		htons(TLS_SECP521R1),
+	{
-		htons(TLS_SECP192R1),
+		if (curves[i].group == *in)
-		htons(TLS_SECP224R1),
+		{
-	};
+			if (out)
-	writer->write_data16(writer, chunk_from_thing(curves));
+			{
+				*out = curves[i].group;
+			}
+			if (curve)
+			{
+				*curve = curves[i].curve;
+			}
+			return TRUE;
+		}
+	}
+	return FALSE;
+}
+
+METHOD(tls_crypto_t, create_ec_enumerator, enumerator_t*,
+	private_tls_crypto_t *this)
+{
+	return enumerator_create_filter(
+					lib->crypto->create_dh_enumerator(lib->crypto),
+					(void*)group_filter, NULL, NULL);
 }
 
 METHOD(tls_crypto_t, set_protection, void,
@@ -1310,7 +1346,7 @@ tls_crypto_t *tls_crypto_create(tls_t *tls)
 			.select_cipher_suite = _select_cipher_suite,
 			.get_dh_group = _get_dh_group,
 			.get_signature_algorithms = _get_signature_algorithms,
-			.get_curves = _get_curves,
+			.create_ec_enumerator = _create_ec_enumerator,
 			.set_protection = _set_protection,
 			.append_handshake = _append_handshake,
 			.sign = _sign,

src/libtls/tls_crypto.h

@@ -398,11 +398,13 @@ struct tls_crypto_t {
 	void (*get_signature_algorithms)(tls_crypto_t *this, tls_writer_t *writer);
 
 	/**
-	 * Write the list of supported elliptic curves to writer.
+	 * Create an enumerator over supported ECDH groups.
 	 *
-	 * @param writer		writer to write elliptic curves to
+	 * Enumerates over (diffie_hellman_group_t, tls_named_curve_t)
+	 *
+	 * @return				enumerator
 	 */
-	void (*get_curves)(tls_crypto_t *this, tls_writer_t *writer);
+	enumerator_t* (*create_ec_enumerator)(tls_crypto_t *this);
 
 	/**
 	 * Set the protection layer of the TLS stack to control it.

src/libtls/tls_peer.c

@@ -352,6 +352,28 @@ static status_t process_modp_key_exchange(private_tls_peer_t *this,
 	return NEED_MORE;
 }
 
+/**
+ * Get the EC group for a TLS named curve
+ */
+static diffie_hellman_group_t curve_to_ec_group(private_tls_peer_t *this,
+												tls_named_curve_t curve)
+{
+	diffie_hellman_group_t group;
+	tls_named_curve_t current;
+	enumerator_t *enumerator;
+
+	enumerator = this->crypto->create_ec_enumerator(this->crypto);
+	while (enumerator->enumerate(enumerator, &group, &current))
+	{
+		if (current == curve)
+		{
+			enumerator->destroy(enumerator);
+			return group;
+		}
+	}
+	enumerator->destroy(enumerator);
+	return 0;
+}
 
 /**
  * Process a Key Exchange message using EC Diffie Hellman
@@ -386,28 +408,14 @@ static status_t process_ec_key_exchange(private_tls_peer_t *this,
 		this->alert->add(this->alert, TLS_FATAL, TLS_DECODE_ERROR);
 		return NEED_MORE;
 	}
-	switch (curve)
+
+	group = curve_to_ec_group(this, curve);
+	if (!group)
 	{
-		case TLS_SECP256R1:
+		DBG1(DBG_TLS, "ECDH curve %N not supported",
-			group = ECP_256_BIT;
+			 tls_named_curve_names, curve);
-			break;
+		this->alert->add(this->alert, TLS_FATAL, TLS_HANDSHAKE_FAILURE);
-		case TLS_SECP384R1:
+		return NEED_MORE;
-			group = ECP_384_BIT;
-			break;
-		case TLS_SECP521R1:
-			group = ECP_521_BIT;
-			break;
-		case TLS_SECP192R1:
-			group = ECP_192_BIT;
-			break;
-		case TLS_SECP224R1:
-			group = ECP_224_BIT;
-			break;
-		default:
-			DBG1(DBG_TLS, "ECDH curve %N not supported",
-				 tls_named_curve_names, curve);
-			this->alert->add(this->alert, TLS_FATAL, TLS_HANDSHAKE_FAILURE);
-			return NEED_MORE;
 	}
 
 	public = find_public_key(this);
@@ -656,8 +664,10 @@ static status_t send_client_hello(private_tls_peer_t *this,
 							tls_handshake_type_t *type, tls_writer_t *writer)
 {
 	tls_cipher_suite_t *suites;
-	tls_writer_t *extensions;
+	tls_writer_t *extensions, *curves = NULL;
 	tls_version_t version;
+	tls_named_curve_t curve;
+	enumerator_t *enumerator;
 	int count, i;
 	rng_t *rng;
 
@@ -697,8 +707,23 @@ static status_t send_client_hello(private_tls_peer_t *this,
 	extensions->write_uint16(extensions, TLS_EXT_SIGNATURE_ALGORITHMS);
 	this->crypto->get_signature_algorithms(this->crypto, extensions);
 
-	extensions->write_uint16(extensions, TLS_EXT_ELLIPTIC_CURVES);
+	/* add supported Elliptic Curves, if any */
-	this->crypto->get_curves(this->crypto, extensions);
+	enumerator = this->crypto->create_ec_enumerator(this->crypto);
+	while (enumerator->enumerate(enumerator, NULL, &curve))
+	{
+		if (!curves)
+		{
+			extensions->write_uint16(extensions, TLS_EXT_ELLIPTIC_CURVES);
+			curves = tls_writer_create(16);
+		}
+		curves->write_uint16(curves, curve);
+	}
+	enumerator->destroy(enumerator);
+	if (curves)
+	{
+		extensions->write_data16(extensions, curves->get_buf(curves));
+		curves->destroy(curves);
+	}
 
 	writer->write_data16(writer, extensions->get_buf(extensions));
 	extensions->destroy(extensions);

src/libtls/tls_server.c

@@ -730,39 +730,38 @@ static status_t send_certificate_request(private_tls_server_t *this,
 /**
  * Get the TLS curve of a given EC DH group
  */
-static tls_named_curve_t ec_group_to_curve(diffie_hellman_group_t group)
+static tls_named_curve_t ec_group_to_curve(private_tls_server_t *this,
+										   diffie_hellman_group_t group)
 {
-	switch (group)
+	diffie_hellman_group_t current;
+	tls_named_curve_t curve;
+	enumerator_t *enumerator;
+
+	enumerator = this->crypto->create_ec_enumerator(this->crypto);
+	while (enumerator->enumerate(enumerator, &current, &curve))
 	{
-		case ECP_256_BIT:
+		if (current == group)
-			return TLS_SECP256R1;
+		{
-		case ECP_384_BIT:
+			enumerator->destroy(enumerator);
-			return TLS_SECP384R1;
+			return curve;
-		case ECP_521_BIT:
+		}
-			return TLS_SECP521R1;
-		case ECP_192_BIT:
-			return TLS_SECP192R1;
-		case ECP_224_BIT:
-			return TLS_SECP224R1;
-		default:
-			return 0;
 	}
+	enumerator->destroy(enumerator);
+	return 0;
 }
 
 /**
- * Check if the peer supports a given TLS EC group
+ * Check if the peer supports a given TLS curve
  */
-bool peer_supports_ec_group(private_tls_server_t *this,
+bool peer_supports_curve(private_tls_server_t *this, tls_named_curve_t curve)
-							diffie_hellman_group_t group)
 {
 	tls_reader_t *reader;
-	u_int16_t curve, current;
+	u_int16_t current;
 
 	if (!this->curves_received)
 	{	/* none received, assume yes */
 		return TRUE;
 	}
-	curve = ec_group_to_curve(group);
 	reader = tls_reader_create(this->curves);
 	while (reader->remaining(reader) && reader->read_uint16(reader, &current))
 	{
@@ -777,28 +776,25 @@ bool peer_supports_ec_group(private_tls_server_t *this,
 }
 
 /**
- * Try to find a group supported by both, client and server
+ * Try to find a curve supported by both, client and server
  */
-static bool find_supported_group(private_tls_server_t *this,
+static bool find_supported_curve(private_tls_server_t *this,
-							diffie_hellman_group_t *group)
+								 tls_named_curve_t *curve)
 {
-	diffie_hellman_group_t groups[] = {
+	tls_named_curve_t current;
-		ECP_256_BIT,
+	enumerator_t *enumerator;
-		ECP_384_BIT,
-		ECP_521_BIT,
-		ECP_224_BIT,
-		ECP_192_BIT,
-	};
-	int i;
 
-	for (i = 0; i < countof(groups); i++)
+	enumerator = this->crypto->create_ec_enumerator(this->crypto);
+	while (enumerator->enumerate(enumerator, NULL, &current))
 	{
-		if (peer_supports_ec_group(this, groups[i]))
+		if (peer_supports_curve(this, current))
 		{
-			*group = groups[i];
+			*curve = current;
+			enumerator->destroy(enumerator);
 			return TRUE;
 		}
 	}
+	enumerator->destroy(enumerator);
 	return FALSE;
 }
 
@@ -810,19 +806,21 @@ static status_t send_server_key_exchange(private_tls_server_t *this,
 							diffie_hellman_group_t group)
 {
 	diffie_hellman_params_t *params = NULL;
+	tls_named_curve_t curve;
 	chunk_t chunk;
 
 	if (diffie_hellman_group_is_ec(group))
 	{
-		if (!peer_supports_ec_group(this, group) &&
+		curve = ec_group_to_curve(this, group);
-			!find_supported_group(this, &group))
+		if (!curve || (!peer_supports_curve(this, curve) &&
+					   !find_supported_curve(this, &curve)))
 		{
 			DBG1(DBG_TLS, "no EC group supported by client and server");
 			this->alert->add(this->alert, TLS_FATAL, TLS_HANDSHAKE_FAILURE);
 			return NEED_MORE;
 		}
 		writer->write_uint8(writer, TLS_ECC_NAMED_CURVE);
-		writer->write_uint16(writer, ec_group_to_curve(group));
+		writer->write_uint16(writer, curve);
 	}
 	else
 	{