diff options
Diffstat (limited to 'crypto/bn/bn_exp.c')
| -rw-r--r-- | crypto/bn/bn_exp.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/crypto/bn/bn_exp.c b/crypto/bn/bn_exp.c index c4b63e44ba36..40115fc72052 100644 --- a/crypto/bn/bn_exp.c +++ b/crypto/bn/bn_exp.c @@ -56,7 +56,7 @@ * [including the GNU Public Licence.] */ /* ==================================================================== - * Copyright (c) 1998-2005 The OpenSSL Project. All rights reserved. + * Copyright (c) 1998-2018 The OpenSSL Project. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions @@ -727,7 +727,11 @@ int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, top = m->top; - bits = BN_num_bits(p); + /* + * Use all bits stored in |p|, rather than |BN_num_bits|, so we do not leak + * whether the top bits are zero. + */ + bits = p->top * BN_BITS2; if (bits == 0) { /* x**0 mod 1 is still zero. */ if (BN_is_one(m)) { |