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| author | Emilia Kasper <emilia@openssl.org> | 2015-12-14 16:38:15 +0100 |
|---|---|---|
| committer | Emilia Kasper <emilia@openssl.org> | 2015-12-14 17:39:39 +0100 |
| commit | d911097d7c93e4cfeab624b34d73fe51da158b69 (patch) | |
| tree | faf6956c8b1394033183f0e3422e42723aa6f305 /crypto/bn/bn_exp.c | |
| parent | 81eae077ce679c1d7d29e19991bf055e4888a2fc (diff) | |
| download | openssl-d911097d7c93e4cfeab624b34d73fe51da158b69.tar.gz | |
Fix a ** 0 mod 1 = 0 for real this time.
Commit 2b0180c37fa6ffc48ee40caa831ca398b828e680 attempted to do this but
only hit one of many BN_mod_exp codepaths. Fix remaining variants and add
a test for each method.
Thanks to Hanno Boeck for reporting this issue.
Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Dr. Stephen Henson <steve@openssl.org>
Diffstat (limited to 'crypto/bn/bn_exp.c')
| -rw-r--r-- | crypto/bn/bn_exp.c | 39 |
1 files changed, 31 insertions, 8 deletions
diff --git a/crypto/bn/bn_exp.c b/crypto/bn/bn_exp.c index 66feddcf96..e252593594 100644 --- a/crypto/bn/bn_exp.c +++ b/crypto/bn/bn_exp.c @@ -282,9 +282,14 @@ int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, } bits = BN_num_bits(p); - if (bits == 0) { - ret = BN_one(r); + /* x**0 mod 1 is still zero. */ + if (BN_is_one(m)) { + ret = 1; + BN_zero(r); + } else { + ret = BN_one(r); + } return ret; } @@ -418,7 +423,13 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, } bits = BN_num_bits(p); if (bits == 0) { - ret = BN_one(rr); + /* x**0 mod 1 is still zero. */ + if (BN_is_one(m)) { + ret = 1; + BN_zero(rr); + } else { + ret = BN_one(rr); + } return ret; } @@ -671,7 +682,13 @@ int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, bits = BN_num_bits(p); if (bits == 0) { - ret = BN_one(rr); + /* x**0 mod 1 is still zero. */ + if (BN_is_one(m)) { + ret = 1; + BN_zero(rr); + } else { + ret = BN_one(rr); + } return ret; } @@ -1180,8 +1197,9 @@ int BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p, if (BN_is_one(m)) { ret = 1; BN_zero(rr); - } else + } else { ret = BN_one(rr); + } return ret; } if (a == 0) { @@ -1295,9 +1313,14 @@ int BN_mod_exp_simple(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, } bits = BN_num_bits(p); - - if (bits == 0) { - ret = BN_one(r); + if (bits == 0) { + /* x**0 mod 1 is still zero. */ + if (BN_is_one(m)) { + ret = 1; + BN_zero(r); + } else { + ret = BN_one(r); + } return ret; } |