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@

2 files changed, 12 insertions, 4 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)
diff --git a/src/lib/libcrypto/man/BN_CTX_start.3 b/src/lib/libcrypto/man/BN_CTX_start.3
index f4f10b8b0c..a2b62eff5c 100644
--- a/src/lib/libcrypto/man/BN_CTX_start.3
+++ b/src/lib/libcrypto/man/BN_CTX_start.3
@@ -1,5 +1,5 @@
-.\"     $OpenBSD: BN_CTX_start.3,v 1.7 2018/03/22 16:06:33 schwarze Exp $
-.\"     OpenSSL 99d63d46 Oct 26 13:56:48 2016 -0400
+.\" $OpenBSD: BN_CTX_start.3,v 1.8 2019/08/20 10:59:09 schwarze Exp $
+.\" full merge up to: OpenSSL 35fd9953 May 28 14:49:38 2019 +0200
 .\"
 .\" This file was written by Ulf Moeller <ulf@openssl.org>.
 .\" Copyright (c) 2000 The OpenSSL Project.  All rights reserved.
@@ -48,7 +48,7 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 .\" OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: March 22 2018 $
+.Dd $Mdocdate: August 20 2019 $
 .Dt BN_CTX_START 3
 .Os
 .Sh NAME
@@ -104,6 +104,11 @@ is called, the
 pointers obtained from
 .Fn BN_CTX_get
 become invalid.
+If
+.Fa ctx
+is
+.Dv NULL ,
+no action occurs.
 .Sh RETURN VALUES
 .Fn BN_CTX_get
 returns a pointer to the