From 4a2ab69ab52e5dbf006533fc509b40d22cfbdbfa Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Sat, 25 Dec 2021 21:48:38 +0100
Subject: [PATCH] gtls: check return code for gnutls_alpn_set_protocols

Closes #8181
---
 lib/vtls/gtls.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/vtls/gtls.c b/lib/vtls/gtls.c
index 2053fd439..3d7c29ebd 100644
--- a/lib/vtls/gtls.c
+++ b/lib/vtls/gtls.c
@@ -497,6 +497,7 @@ gtls_connect_step1(struct Curl_easy *data,
   /* use system ca certificate store as fallback */
   if(SSL_CONN_CONFIG(verifypeer) &&
      !(SSL_CONN_CONFIG(CAfile) || SSL_CONN_CONFIG(CApath))) {
+    /* this ignores errors on purpose */
     gnutls_certificate_set_x509_system_trust(backend->cred);
   }
 #endif
@@ -631,7 +632,10 @@ gtls_connect_step1(struct Curl_easy *data,
     cur++;
     infof(data, "ALPN, offering %s", ALPN_HTTP_1_1);
 
-    gnutls_alpn_set_protocols(session, protocols, cur, 0);
+    if(gnutls_alpn_set_protocols(session, protocols, cur, 0)) {
+      failf(data, "failed setting ALPN");
+      return CURLE_SSL_CONNECT_ERROR;
+    }
   }
 
   if(SSL_SET_OPTION(primary.clientcert)) {