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>
(cherry picked from commit
b7d0f2834e139a20560d64c73e2565e93715ce2b)
do
if (!BN_rand_range(&k, dsa->q))
goto err;
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,
if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
if (!BN_copy(&kq, &k))
goto err;
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
/*
* 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
-
- BN_set_flags(K, BN_FLG_CONSTTIME);