make BN_CTX_end(NULL) a NOOP for compatibility with documented behaviour

in OpenSSL 1.1.1 even though in general, letting random functions
accept NULL is not advisable because it can hide programming errors;

"yes please" tb@
"unfortunately I suspect you're right" jsing@
"oh well" deraadt@

1 files changed, 4 insertions, 1 deletions

diff --git a/src/lib/libcrypto/bn/bn_ctx.c b/src/lib/libcrypto/bn/bn_ctx.c
index 1237ac1365..0d64ccab93 100644
--- a/src/lib/libcrypto/bn/bn_ctx.c
+++ b/src/lib/libcrypto/bn/bn_ctx.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_ctx.c,v 1.15 2017/01/29 17:49:22 beck Exp $ */
+/* $OpenBSD: bn_ctx.c,v 1.16 2019/08/20 10:59:09 schwarze Exp $ */
 /* Written by Ulf Moeller for the OpenSSL project. */
 /* ====================================================================
  * Copyright (c) 1998-2004 The OpenSSL Project.  All rights reserved.
@@ -283,6 +283,9 @@ BN_CTX_start(BN_CTX *ctx)
 void
 BN_CTX_end(BN_CTX *ctx)
 {
+        if (ctx == NULL)
+                return;
+
         CTXDBG_ENTRY("BN_CTX_end", ctx);
 
         if (ctx->err_stack)