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Allow |RSA_FLAG_NO_BLINDING| to be set with |e| set.

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This change allows blinding to be disabled without also having to remove
|e|, which would disable the CRT and the glitch checks. This is to
support disabling blinding in the FIPS power-on tests.

(Note: the case where |e| isn't set is tested by RSATest.OnlyDGiven.)

Change-Id: I28f18beda33b1687bf145f4cbdfd37ce262dd70f
Reviewed-on: https://boringssl-review.googlesource.com/17146
Commit-Queue: Adam Langley <alangley@gmail.com>
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>
This commit is contained in:
Adam Langley 2017-06-13 13:00:25 -07:00 committed by Adam Langley
parent 0a3663a64f
commit 8379978bc8
2 changed files with 34 additions and 16 deletions
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32
crypto/fipsmodule/rsa/rsa_impl.c
View File

@ -567,20 +567,18 @@ int rsa_default_private_transform(RSA *rsa, uint8_t *out, const uint8_t *in,
goto err;
}
/* We cannot do blinding or verification without |e|, and continuing without
* those countermeasures is dangerous. However, the Java/Android RSA API
* requires support for keys where only |d| and |n| (and not |e|) are known.
* The callers that require that bad behavior set |RSA_FLAG_NO_BLINDING|. */
int disable_security = (rsa->flags & RSA_FLAG_NO_BLINDING) && rsa->e == NULL;
const int do_blinding = (rsa->flags & RSA_FLAG_NO_BLINDING) == 0;
if (!disable_security) {
/* Keys without public exponents must have blinding explicitly disabled to
* be used. */
if (rsa->e == NULL) {
OPENSSL_PUT_ERROR(RSA, RSA_R_NO_PUBLIC_EXPONENT);
goto err;
}
if (rsa->e == NULL && do_blinding) {
/* We cannot do blinding or verification without |e|, and continuing without
* those countermeasures is dangerous. However, the Java/Android RSA API
* requires support for keys where only |d| and |n| (and not |e|) are known.
* The callers that require that bad behavior set |RSA_FLAG_NO_BLINDING|. */
OPENSSL_PUT_ERROR(RSA, RSA_R_NO_PUBLIC_EXPONENT);
goto err;
}
if (do_blinding) {
blinding = rsa_blinding_get(rsa, &blinding_index, ctx);
if (blinding == NULL) {
OPENSSL_PUT_ERROR(RSA, ERR_R_INTERNAL_ERROR);
@ -610,7 +608,7 @@ int rsa_default_private_transform(RSA *rsa, uint8_t *out, const uint8_t *in,
* than the CRT attack, but there have likely been improvements since 1997.
*
* This check is cheap assuming |e| is small; it almost always is. */
if (!disable_security) {
if (rsa->e != NULL) {
BIGNUM *vrfy = BN_CTX_get(ctx);
if (vrfy == NULL ||
!BN_mod_exp_mont(vrfy, result, rsa->e, rsa->n, ctx, rsa->mont_n) ||
@ -619,9 +617,11 @@ int rsa_default_private_transform(RSA *rsa, uint8_t *out, const uint8_t *in,
goto err;
}
if (!BN_BLINDING_invert(result, blinding, rsa->mont_n, ctx)) {
goto err;
}
}
if (do_blinding &&
!BN_BLINDING_invert(result, blinding, rsa->mont_n, ctx)) {
goto err;
}
if (!BN_bn2bin_padded(out, len, result)) {

18
crypto/rsa_extra/rsa_test.cc
View File

@ -679,6 +679,24 @@ TEST(RSATest, RoundKeyLengths) {
EXPECT_EQ(1152u, BN_num_bits(rsa->n));
}
TEST(RSATest, BlindingDisabled) {
bssl::UniquePtr<RSA> rsa(
RSA_private_key_from_bytes(kTwoPrimeKey, sizeof(kTwoPrimeKey) - 1));
ASSERT_TRUE(rsa);
rsa->flags |= RSA_FLAG_NO_BLINDING;
uint8_t sig[256];
ASSERT_GE(sizeof(sig), RSA_size(rsa.get()));
static const uint8_t kZeros[32] = {0};
unsigned sig_len;
ASSERT_TRUE(
RSA_sign(NID_sha256, kZeros, sizeof(kZeros), sig, &sig_len, rsa.get()));
EXPECT_TRUE(
RSA_verify(NID_sha256, kZeros, sizeof(kZeros), sig, sig_len, rsa.get()));
}
#if !defined(BORINGSSL_SHARED_LIBRARY)
TEST(RSATest, SqrtTwo) {
bssl::UniquePtr<BIGNUM> sqrt(BN_new()), pow2(BN_new());