diff options
Diffstat (limited to 'crypto/bn/bn_lib.c')
| -rw-r--r-- | crypto/bn/bn_lib.c | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/crypto/bn/bn_lib.c b/crypto/bn/bn_lib.c index eb4a31849bef..cd6aa3448afd 100644 --- a/crypto/bn/bn_lib.c +++ b/crypto/bn/bn_lib.c @@ -1,5 +1,5 @@ /* - * Copyright 1995-2020 The OpenSSL Project Authors. All Rights Reserved. + * Copyright 1995-2023 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the OpenSSL license (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy @@ -1001,6 +1001,28 @@ BIGNUM *bn_wexpand(BIGNUM *a, int words) return (words <= a->dmax) ? a : bn_expand2(a, words); } +void bn_correct_top_consttime(BIGNUM *a) +{ + int j, atop; + BN_ULONG limb; + unsigned int mask; + + for (j = 0, atop = 0; j < a->dmax; j++) { + limb = a->d[j]; + limb |= 0 - limb; + limb >>= BN_BITS2 - 1; + limb = 0 - limb; + mask = (unsigned int)limb; + mask &= constant_time_msb(j - a->top); + atop = constant_time_select_int(mask, j + 1, atop); + } + + mask = constant_time_eq_int(atop, 0); + a->top = atop; + a->neg = constant_time_select_int(mask, 0, a->neg); + a->flags &= ~BN_FLG_FIXED_TOP; +} + void bn_correct_top(BIGNUM *a) { BN_ULONG *ftl; |