diff options
| author | Matt Caswell <matt@openssl.org> | 2016-06-07 09:12:51 +0100 |
|---|---|---|
| committer | Matt Caswell <matt@openssl.org> | 2016-06-07 09:14:32 +0100 |
| commit | b7d0f2834e139a20560d64c73e2565e93715ce2b (patch) | |
| tree | 8930600e56892e462ba6a692939455b4658afa61 /crypto/dsa | |
| parent | 621eaf49a289bfac26d4cbcdb7396e796784c534 (diff) | |
More fix DSA, preserve BN_FLG_CONSTTIME
The previous "fix" still left "k" exposed to constant time problems in
the later BN_mod_inverse() call. Ensure both k and kq have the
BN_FLG_CONSTTIME flag set at the earliest opportunity after creation.
CVE-2016-2178
Reviewed-by: Rich Salz <rsalz@openssl.org>
Diffstat (limited to 'crypto/dsa')
| -rw-r--r-- | crypto/dsa/dsa_ossl.c | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/crypto/dsa/dsa_ossl.c b/crypto/dsa/dsa_ossl.c index b29eb4bc51..58013a4a13 100644 --- a/crypto/dsa/dsa_ossl.c +++ b/crypto/dsa/dsa_ossl.c @@ -247,7 +247,12 @@ static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, do if (!BN_rand_range(&k, dsa->q)) goto err; - while (BN_is_zero(&k)) ; + while (BN_is_zero(&k)); + + if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) { + BN_set_flags(&k, BN_FLG_CONSTTIME); + } + if (dsa->flags & DSA_FLAG_CACHE_MONT_P) { if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p, @@ -261,6 +266,8 @@ static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, if (!BN_copy(&kq, &k)) goto err; + BN_set_flags(&kq, BN_FLG_CONSTTIME); + /* * We do not want timing information to leak the length of k, so we * compute g^k using an equivalent exponent of fixed length. (This @@ -276,8 +283,6 @@ static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, } K = &kq; - - BN_set_flags(K, BN_FLG_CONSTTIME); } else { K = &k; } |