From 0d091c8e0c645b6291f5c5aff3f154848d99e95a Mon Sep 17 00:00:00 2001
From: Jakub Jelen <jjelen@redhat.com>
Date: Wed, 23 Oct 2019 09:34:46 +0200
Subject: [PATCH] asn1: Avoid integer overflow

https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=18475
---
 src/libopensc/asn1.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libopensc/asn1.c b/src/libopensc/asn1.c
index ce95bbf2..66d4184d 100644
--- a/src/libopensc/asn1.c
+++ b/src/libopensc/asn1.c
@@ -731,7 +731,7 @@ int sc_asn1_decode_integer(const u8 * inbuf, size_t inlen, int *out)
 	}
 	if (is_negative) {
 		/* Calculate Two's complement from previously positive number */
-		a = -1 * (a + 1);
+		a = (-1 * a) - 1;
 	}
 	*out = a;
 	return 0;