Do not take the strlen() of a NULL name. Defer the CBS_init() to later.

Found the hard way by sthen.

ok sthen

1 files changed, 3 insertions, 3 deletions

diff --git a/src/lib/libssl/s3_lib.c b/src/lib/libssl/s3_lib.c
index c4d68f654e..497dea6f08 100644
--- a/src/lib/libssl/s3_lib.c
+++ b/src/lib/libssl/s3_lib.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: s3_lib.c,v 1.218 2021/11/01 16:45:56 jsing Exp $ */
+/* $OpenBSD: s3_lib.c,v 1.219 2021/11/02 13:59:29 tb Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -1789,14 +1789,14 @@ _SSL_set_tlsext_host_name(SSL *s, const char *name)
         int is_ip;
         CBS cbs;
 
-        CBS_init(&cbs, name, strlen(name));
-
         free(s->tlsext_hostname);
         s->tlsext_hostname = NULL;
 
         if (name == NULL)
                 return 1;
 
+        CBS_init(&cbs, name, strlen(name));
+
         if (!tlsext_sni_is_valid_hostname(&cbs, &is_ip)) {
                 SSLerror(s, SSL_R_SSL3_EXT_INVALID_SERVERNAME);
                 return 0;