From: Richard Levitte <levitte@openssl.org>
Date: Wed, 1 Feb 2017 01:29:46 +0000 (+0100)
Subject: bn: fix occurance of negative zero in BN_rshift1()
X-Git-Tag: OpenSSL_1_1_0e~37
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=dfb109c522a450af7f387d66ad32afeee87f9805;p=openssl

bn: fix occurance of negative zero in BN_rshift1()

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit 0a2dcb6990dacc94337f746f4f4a6dfac1fbeac4)
---

diff --git a/crypto/bn/bn_shift.c b/crypto/bn/bn_shift.c
index b320602871..6a1eec80af 100644
--- a/crypto/bn/bn_shift.c
+++ b/crypto/bn/bn_shift.c
@@ -74,6 +74,8 @@ int BN_rshift1(BIGNUM *r, const BIGNUM *a)
         c = (t & 1) ? BN_TBIT : 0;
     }
     r->top = j;
+    if (!r->top)
+        r->neg = 0; /* don't allow negative zero */
     bn_check_top(r);
     return (1);
 }