gnutls_alert_send_appropriate: do not send alert to peer on all errorstmp-alerts-fix

That is, do not send alerts for success, or for errors indicating that
an alert has been received. This changes the documented function behavior
but does not break any existing caller expectations.

Relates: #672

Signed-off-by: Nikos Mavrogiannopoulos <nmav@gnutls.org>

1 files changed, 11 insertions, 7 deletions

diff --git a/lib/alert.c b/lib/alert.c
index 34d2d769be..15f5183430 100644
--- a/lib/alert.c
+++ b/lib/alert.c
@@ -184,7 +184,7 @@ gnutls_alert_send(gnutls_session_t session, gnutls_alert_level_t level,
  * renegotiation will be performed.
  *
  * If there is no mapping to a valid alert the alert to indicate
- * internal error is returned.
+ * internal error (%GNUTLS_A_INTERNAL_ERROR) is returned.
  *
  * Returns: the alert code to use for a particular error code.
  **/
@@ -340,7 +340,7 @@ int gnutls_error_to_alert(int err, int *level)
 /**
  * gnutls_alert_send_appropriate:
  * @session: is a #gnutls_session_t type.
- * @err: is an integer
+ * @err: is an error code returned by another GnuTLS function
  *
  * Sends an alert to the peer depending on the error code returned by
  * a gnutls function. This function will call gnutls_error_to_alert()
@@ -349,8 +349,11 @@ int gnutls_error_to_alert(int err, int *level)
  * This function may also return %GNUTLS_E_AGAIN, or
  * %GNUTLS_E_INTERRUPTED.
  *
- * If the return value is %GNUTLS_E_INVALID_REQUEST, then no alert has
- * been sent to the peer.
+ * This function historically was always sending an alert to the
+ * peer, even if @err was inappropriate to respond with an alert
+ * (e.g., %GNUTLS_E_SUCCESS). Since 3.6.6 this function returns
+ * success without transmitting any data on error codes that
+ * should not result to an alert.
  *
  * Returns: On success, %GNUTLS_E_SUCCESS (0) is returned, otherwise
  *   an error code is returned.
@@ -360,10 +363,11 @@ int gnutls_alert_send_appropriate(gnutls_session_t session, int err)
 	int alert;
 	int level;
 
+	if (err != GNUTLS_E_REHANDSHAKE && (!gnutls_error_is_fatal(err) ||
+	    err == GNUTLS_E_FATAL_ALERT_RECEIVED))
+		return gnutls_assert_val(0);
+
 	alert = gnutls_error_to_alert(err, &level);
-	if (alert < 0) {
-		return alert;
-	}
 
 	return gnutls_alert_send(session, (gnutls_alert_level_t)level, alert);
 }