From: Tobias Brunner <tobias@strongswan.org>
Date: Thu, 5 Oct 2023 08:27:18 +0000 (+0200)
Subject: tls-server: Also change DH group when selecting a different EC curve
X-Git-Tag: 5.9.12rc1~14
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b5e4bf4b6c2d5a3ac46cce78d69673c224256206;p=thirdparty%2Fstrongswan.git

tls-server: Also change DH group when selecting a different EC curve

If we initially selected a group the peer doesn't support (e.g. because
curve25519 is the first ECDH group provided by plugins), then found
a supported curve, we previously still instantiated a DH object for the
original group and might have formatted the parameters incorrectly.
---

diff --git a/src/libtls/tls_server.c b/src/libtls/tls_server.c
index e91e4e4407..3ad9fd2a5c 100644
--- a/src/libtls/tls_server.c
+++ b/src/libtls/tls_server.c
@@ -1483,20 +1483,23 @@ static status_t send_certificate_request(private_tls_server_t *this,
 }
 
 /**
- * Try to find a curve supported by both, client and server
+ * Try to find a curve/group supported by both, client and server
  */
 static bool find_supported_curve(private_tls_server_t *this,
-								 tls_named_group_t *curve)
+								 tls_named_group_t *curve,
+								 key_exchange_method_t *group)
 {
 	tls_named_group_t current;
+	key_exchange_method_t current_group;
 	enumerator_t *enumerator;
 
 	enumerator = this->crypto->create_ec_enumerator(this->crypto);
-	while (enumerator->enumerate(enumerator, NULL, &current))
+	while (enumerator->enumerate(enumerator, &current_group, &current))
 	{
 		if (peer_supports_curve(this, current))
 		{
 			*curve = current;
+			*group = current_group;
 			enumerator->destroy(enumerator);
 			return TRUE;
 		}
@@ -1520,7 +1523,7 @@ static status_t send_server_key_exchange(private_tls_server_t *this,
 	{
 		curve = tls_ec_group_to_curve(group);
 		if (!curve || (!peer_supports_curve(this, curve) &&
-					   !find_supported_curve(this, &curve)))
+					   !find_supported_curve(this, &curve, &group)))
 		{
 			DBG1(DBG_TLS, "no EC group supported by client and server");
 			this->alert->add(this->alert, TLS_FATAL, TLS_HANDSHAKE_FAILURE);