openbsd/src/lib/libcrypto/bn/bn_add.c, branch OPENBSD_7_9

Fix previous.

2025-05-25T04:53:05+00:00

Fix handling of different length inputs in bn_sub().

2025-05-25T04:16:36+00:00

In the diff_len < 0 case, it incorrectly uses 0 - b[0], which mishandles the borrow - fix this by using bn_subw_subw(). Do the same in the diff_len > 0 case for consistency. Note that this is never currently reached since BN_usub() requires a >= b. ok beck@ tb@

Use err_local.h rather than err.h in most places

2025-05-10T05:54:39+00:00

ok jsing

Hide symbols in bn

2023-07-08T12:21:58+00:00

ok tb@

Provide and use various quad word primitives.

2023-06-12T16:17:24+00:00

This includes bn_qwaddqw(), bn_qwsubqw(), bn_qwmulw_addw() and bn_qwmulw_addqw_addw(). These can typically be optimised on architectures that have a reasonable number of general purpose registers. ok tb@

Rework bn_add()/bn_sub() to operate on word arrays.

2023-02-22T05:46:37+00:00

Rather than working on BIGNUMs, change bn_add()/bn_sub() to operate on word arrays that potentially differ in length. This matches the behaviour of s2n-bignum's bignum_add() and bignum_sub(). ok tb@

Reimplement bn_add_words() and bn_sub_words() using bignum primitives.

2023-02-16T04:42:20+00:00

This removes the effectively duplicate BN_LLONG version of bn_add_words() and simplifies the code considerably. ok tb@

Avoid negative zero.

2023-02-13T04:25:37+00:00

Whenever setting negative to one (or when it could potentially be one), always use BN_set_negative() since it checks for a zero valued bignum and will not permit negative to be set in this case. Since BN_is_zero() currently relies on top == 0, call BN_set_negative() after top has been set (or bn_correct_top() has been called). This fixes a long standing issue where -0 and +0 have been permitted, however multiple code paths (such as BN_cmp()) fail to treat these as equivalent. Prompted by Guido Vranken who is adding negative zero fuzzing to oss-fuzz. ok tb@

Refactor BN_uadd() and BN_usub().

2023-02-02T18:39:26+00:00

Unlike bn_add_words()/bn_sub_words(), the s2n-bignum bignum_add() and bignum_sub() functions correctly handle inputs with differing word lengths. This means that they can be called directly, without needing to fix up any remaining words manually. Split BN_uadd() in two - the default bn_add() implementation calls bn_add_words(), before handling the carry for any remaining words. Likewise split BN_usub() in two - the default bn_sub() implementation calls bn_sub_words(), before handling the borrow for any remaining words. On amd64, provide an implementation of bn_add() that calls s2n-bignum's bignum_add() directly, similarly with an implementation of bn_sub() that calls s2n-bignum's bignum_sub() directly. ok tb@

Correctly detect b < a in BN_usub().

2023-01-31T05:16:52+00:00

BN_usub() requires that a >= b and should return an error in the case that b < a. This is currently only detected by checking the number of words in a versus b - if they have the same number of words, the top word is not checked and b < a, which then succeeds and produces an incorrect result. Fix this by checking for the case where a and b have an equal number of words, yet there is a borrow returned from bn_sub_words(). ok miod@ tb@