openssl: ensure to check SSL_CTX_set_alpn_protos return values

SSL_CTX_set_alpn_protos() return 0 on success, and non-0 on failure

Signed-off-by: Jean-Philippe Menil <jpmenil@gmail.com>
Closes #6794

diff --git a/lib/vtls/openssl.c b/lib/vtls/openssl.c
index a9690383ddf89ef16a5c1623d41ac09ec072d81f..498f8b9d1d0879c9a8c7b6d3aa05441e120f70d9 100644 (file)
--- a/lib/vtls/openssl.c
+++ b/lib/vtls/openssl.c
@@ -2749,7 +2749,10 @@ static CURLcode ossl_connect_step1(struct Curl_easy *data,
     /* expects length prefixed preference ordered list of protocols in wire
      * format
      */
-    SSL_CTX_set_alpn_protos(backend->ctx, protocols, cur);
+    if(SSL_CTX_set_alpn_protos(backend->ctx, protocols, cur)) {
+      failf(data, "Error setting ALPN");
+      return CURLE_SSL_CONNECT_ERROR;
+    }
   }
 #endif