bn: fix occurances of negative zero
authorGeoff Thorpe <geoff@openssl.org>
Thu, 6 Oct 2016 15:04:56 +0000 (10:04 -0500)
committerRichard Levitte <levitte@openssl.org>
Wed, 1 Feb 2017 01:06:39 +0000 (02:06 +0100)
commit38d1b3cc0271008b8bd130a2c4b442775b028a08
treeae79d0c8dd2fc51bda4f13da0f9d77f0da581b5d
parent2fc9b36a96ccd77cbd9ecfb3a3cdaa7ad2ca305e
bn: fix occurances of negative zero

The BIGNUM behaviour is supposed to be "consistent" when going into and
out of APIs, where "consistent" means 'top' is set minimally and that
'neg' (negative) is not set if the BIGNUM is zero (which is iff 'top' is
zero, due to the previous point).

The BN_DEBUG testing (make test) caught the cases that this patch
corrects.

Note, bn_correct_top() could have been used instead, but that is intended
for where 'top' is expected to (sometimes) require adjustment after direct
word-array manipulation, and so is heavier-weight. Here, we are just
catching the negative-zero case, so we test and correct for that
explicitly, in-place.

Change-Id: Iddefbd3c28a13d935648932beebcc765d5b85ae7
Signed-off-by: Geoff Thorpe <geoff@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1672)
crypto/bn/bn_div.c
crypto/bn/bn_mul.c
crypto/bn/bn_shift.c
crypto/bn/bn_word.c