Avoid calling memcpy with a length <= 0. Reported due to a GCC 7.3.0

compiler warning by Pavel Kraynyukhov. A similar fix was made in
OpenSSL commit 369e93398b68b8a328e6c1d766222b.

ok inoguchi

1 files changed, 6 insertions, 5 deletions

diff --git a/src/lib/libcrypto/asn1/a_bitstr.c b/src/lib/libcrypto/asn1/a_bitstr.c
index 11771bdd02..7fd40d8a8c 100644
--- a/src/lib/libcrypto/asn1/a_bitstr.c
+++ b/src/lib/libcrypto/asn1/a_bitstr.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: a_bitstr.c,v 1.28 2018/05/13 13:48:08 jsing Exp $ */
+/* $OpenBSD: a_bitstr.c,v 1.29 2018/10/20 16:07:09 tb Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -118,10 +118,11 @@ i2c_ASN1_BIT_STRING(ASN1_BIT_STRING *a, unsigned char **pp)
 
         *(p++) = (unsigned char)bits;
         d = a->data;
-        memcpy(p, d, len);
-        p += len;
-        if (len > 0)
-                p[-1]&=(0xff << bits);
+        if (len > 0) {
+                memcpy(p, d, len);
+                p += len;
+                p[-1] &= 0xff << bits;
+        }
         *pp = p;
         return (ret);
 }