From: Kurt Roeckx <kurt@roeckx.be>
Date: Fri, 11 Nov 2016 20:41:50 +0000 (+0100)
Subject: Cast to an unsigned type before negating
X-Git-Tag: OpenSSL_1_1_1-pre1~3084
X-Git-Url: https://git.openssl.org/?p=openssl.git;a=commitdiff_plain;h=e80f3b6af295133107ac709329eee16ccf9af61c;hp=866e505e0d663158b0fe63a7fb7455eebacc6470

Cast to an unsigned type before negating

llvm's ubsan reported:
runtime error: negation of -9223372036854775808 cannot be represented in
type 'int64_t' (aka 'long'); cast to an unsigned type to negate this
value to itself

Found using libfuzzer

Reviewed-by: Rich Salz <rsalz@openssl.org>

GH: #1908
---

diff --git a/crypto/asn1/a_int.c b/crypto/asn1/a_int.c
index 36248df92d..833322e89b 100644
--- a/crypto/asn1/a_int.c
+++ b/crypto/asn1/a_int.c
@@ -289,7 +289,7 @@ static int asn1_get_int64(int64_t *pr, const unsigned char *b, size_t blen,
             ASN1err(ASN1_F_ASN1_GET_INT64, ASN1_R_TOO_SMALL);
             return 0;
         }
-        *pr = -(int64_t)r;
+        *pr = -(uint64_t)r;
     } else {
         if (r > INT64_MAX) {
             ASN1err(ASN1_F_ASN1_GET_INT64, ASN1_R_TOO_LARGE);