[1/2] eap-tls: Drop cached session when phase2 fails

Commit Message

Andrew Zaborowski Jan. 27, 2023, 12:31 p.m. UTC

If we used TLS session resumption successfully but the overall EAP method
failed, forget the session to improve the chances that authentication
succeeds on the next attempt considering that some authenticators
strangely allow resumption but can't handle it all the way to EAP method
success.  Logically the session resumption in the TLS layers on the
server should be transparent to the EAP layers so I guess those may be
failed attempts to further optimise phase 2 when the server thinks it can
already trust the client.
---
 src/eap-tls-common.c | 37 ++++++++++++++++++++++++++++++++-----
 1 file changed, 32 insertions(+), 5 deletions(-)

Patch

diff --git a/src/eap-tls-common.c b/src/eap-tls-common.c
index 784a57ee..b909d0cc 100644
--- a/src/eap-tls-common.c
+++ b/src/eap-tls-common.c
@@ -115,6 +115,7 @@  struct eap_tls_state {
 
 	bool expecting_frag_ack:1;
 	bool tunnel_ready:1;
+	bool tls_session_resumed:1;
 
 	struct l_queue *ca_cert;
 	struct l_certchain *client_cert;
@@ -129,8 +130,10 @@  static struct l_settings *eap_tls_session_cache;
 static eap_tls_session_cache_load_func_t eap_tls_session_cache_load;
 static eap_tls_session_cache_sync_func_t eap_tls_session_cache_sync;
 
-static void __eap_tls_common_state_reset(struct eap_tls_state *eap_tls)
+static void __eap_tls_common_state_reset(struct eap_state *eap)
 {
+	struct eap_tls_state *eap_tls = eap_get_data(eap);
+
 	eap_tls->version_negotiated = EAP_TLS_VERSION_NOT_NEGOTIATED;
 	eap_tls->method_completed = false;
 	eap_tls->phase2_failed = false;
@@ -145,6 +148,27 @@  static void __eap_tls_common_state_reset(struct eap_tls_state *eap_tls)
 	if (eap_tls->tunnel)
 		l_tls_reset(eap_tls->tunnel);
 
+	/*
+	 * If we used TLS session resumption successfully but the overall
+	 * EAP method failed, forget the session to improve the chances
+	 * that authentication succeeds on the next attempt considering
+	 * that some authenticators strangely allow resumption but can't
+	 * handle it all the way to EAP method success.  Do this even if
+	 * we have no indication that the method failed but it just didn't
+	 * succeed, to handle cases like the server getting stuck and a
+	 * timout occuring at a higher layer.  The risk is that we may
+	 * occasionally flush the session data when there was only a
+	 * momentary radio issue, invalid phase2 credentials or decision
+	 * to abort.  Those are not hot paths.
+	 *
+	 * TLS errors before the ready callback are already handled in
+	 * l_tls so we only need to look at .tls_session_resumed here.
+	 */
+	if (eap_tls->tls_session_resumed && !eap_method_is_success(eap))
+		eap_tls_forget_peer(eap_get_peer_id(eap));
+
+	eap_tls->tls_session_resumed = false;
+
 	eap_tls->tx_frag_offset = 0;
 	eap_tls->tx_frag_last_len = 0;
 
@@ -187,7 +211,7 @@  bool eap_tls_common_state_reset(struct eap_state *eap)
 {
 	struct eap_tls_state *eap_tls = eap_get_data(eap);
 
-	__eap_tls_common_state_reset(eap_tls);
+	__eap_tls_common_state_reset(eap);
 
 	if (eap_tls->variant_ops->reset)
 		eap_tls->variant_ops->reset(eap_tls->variant_data);
@@ -199,7 +223,7 @@  void eap_tls_common_state_free(struct eap_state *eap)
 {
 	struct eap_tls_state *eap_tls = eap_get_data(eap);
 
-	__eap_tls_common_state_reset(eap_tls);
+	__eap_tls_common_state_reset(eap);
 
 	eap_set_data(eap, NULL);
 
@@ -244,7 +268,9 @@  static void eap_tls_tunnel_ready(const char *peer_identity, void *user_data)
 {
 	struct eap_state *eap = user_data;
 	struct eap_tls_state *eap_tls = eap_get_data(eap);
-	bool resumed = l_tls_get_session_resumed(eap_tls->tunnel);
+
+	eap_tls->tls_session_resumed =
+		l_tls_get_session_resumed(eap_tls->tunnel);
 
 	if (eap_tls->ca_cert && !peer_identity) {
 		l_error("%s: TLS did not verify AP identity",
@@ -265,7 +291,8 @@  static void eap_tls_tunnel_ready(const char *peer_identity, void *user_data)
 	if (!eap_tls->variant_ops->tunnel_ready)
 		return;
 
-	if (!eap_tls->variant_ops->tunnel_ready(eap, peer_identity, resumed))
+	if (!eap_tls->variant_ops->tunnel_ready(eap, peer_identity,
+						eap_tls->tls_session_resumed))
 		l_tls_close(eap_tls->tunnel);
 }