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Constant time DH [sync with mainstream].

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Submitted by: bodo
This commit is contained in:
Andy Polyakov
2005-05-27 08:11:16 +00:00
parent 31def5ae59
commit 6b6f64da2d
1 changed files with 25 additions and 3 deletions
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28
fips/dh/fips_dh_key.c
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@@ -145,8 +145,22 @@ static int generate_key(DH *dh)
l = dh->length ? dh->length : BN_num_bits(dh->p)-1; /* secret exponent length */
if (!BN_rand(priv_key, l, 0, 0)) goto err;
}
if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, priv_key,dh->p,ctx,mont))
goto err;
{
BIGNUM local_prk;
BIGNUM *prk;
if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0)
{
prk = &local_prk;
BN_with_flags(prk, priv_key, BN_FLG_EXP_CONSTTIME);
}
else
prk = priv_key;
if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont))
goto err;
}
dh->pub_key=pub_key;
dh->priv_key=priv_key;
@@ -184,6 +198,11 @@ static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
mont = BN_MONT_CTX_set_locked(
(BN_MONT_CTX **)&dh->method_mont_p,
CRYPTO_LOCK_DH, dh->p, ctx);
if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0)
{
/* XXX */
BN_set_flags(dh->priv_key, BN_FLG_EXP_CONSTTIME);
}
if (!mont)
goto err;
}
@@ -206,7 +225,10 @@ static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
const BIGNUM *m, BN_CTX *ctx,
BN_MONT_CTX *m_ctx)
{
if (a->top == 1)
/* If a is only one word long and constant time is false, use the faster
* exponenentiation function.
*/
if (a->top == 1 && ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) != 0))
{
BN_ULONG A = a->d[0];
return BN_mod_exp_mont_word(r,A,p,m,ctx,m_ctx);