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 b3206028713c44d6faa31cc3460f2f308a552a82..6a1eec80af4b45522cde030dda551a82ef5b0cb2 100644 (file)
--- 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);
 }