Avoid signed integer overflow.

Fixes oss-fuzz issue #13843.

ok tb@

1 files changed, 2 insertions, 2 deletions

diff --git a/src/lib/libcrypto/asn1/x_long.c b/src/lib/libcrypto/asn1/x_long.c
index 61685c31a3..8b11f14217 100644
--- a/src/lib/libcrypto/asn1/x_long.c
+++ b/src/lib/libcrypto/asn1/x_long.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: x_long.c,v 1.14 2019/04/01 15:48:50 jsing Exp $ */
+/* $OpenBSD: x_long.c,v 1.15 2019/04/15 17:46:02 jsing Exp $ */
 /* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
  * project 2000.
  */
@@ -195,8 +195,8 @@ long_c2i(ASN1_VALUE **pval, const unsigned char *cont, int len, int utype,
         }
         ltmp = (long)utmp;
         if (neg) {
-                ltmp++;
                 ltmp = -ltmp;
+                ltmp--;
         }
         if (ltmp == it->size) {
                 ASN1error(ASN1_R_INTEGER_TOO_LARGE_FOR_LONG);