Avoid memcmp() with NULL pointer and 0 length

diff --git a/regress/lib/libssl/ssl/ssltest.c b/regress/lib/libssl/ssl/ssltest.c
index f50824d..f95ea44 100644 (file)
--- a/regress/lib/libssl/ssl/ssltest.c
+++ b/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;
        }