Avoid memcmp() with NULL pointer and 0 length

1 files changed, 3 insertions, 3 deletions

diff --git a/src/regress/lib/libssl/ssl/ssltest.c b/src/regress/lib/libssl/ssl/ssltest.c
index f50824d242..f95ea44a91 100644
--- a/src/regress/lib/libssl/ssl/ssltest.c
+++ b/src/regress/lib/libssl/ssl/ssltest.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: ssltest.c,v 1.42 2023/07/27 07:08:09 tb Exp $ */
+/*      $OpenBSD: ssltest.c,v 1.43 2023/08/15 11:20:57 tb Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -281,8 +281,8 @@ verify_alpn(SSL *client, SSL *server)
         free(alpn_selected);
         alpn_selected = NULL;
 
-        if (client_proto_len != server_proto_len ||
-            memcmp(client_proto, server_proto, client_proto_len) != 0) {
+        if (client_proto_len != server_proto_len || (client_proto_len > 0 &&
+            memcmp(client_proto, server_proto, client_proto_len) != 0)) {
                 BIO_printf(bio_stdout, "ALPN selected protocols differ!\n");
                 goto err;
         }