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authorStephan Mueller <smueller@chronox.de>2018-06-25 13:00:18 +0300
committerHerbert Xu <herbert@gondor.apana.org.au>2018-07-08 19:26:19 +0300
commitea169a30a6bf6782a05a51d2b9cf73db151eab8b (patch)
tree448a0a4cd4213edf339e00245ff1999ad120e298 /crypto/ecc.c
parente4e4730698c9138f09ed73dadd1f35d4bb95ada5 (diff)
downloadlinux-ea169a30a6bf6782a05a51d2b9cf73db151eab8b.tar.xz
crypto: ecdh - add public key verification test
According to SP800-56A section 5.6.2.1, the public key to be processed for the ECDH operation shall be checked for appropriateness. When the public key is considered to be an ephemeral key, the partial validation test as defined in SP800-56A section 5.6.2.3.4 can be applied. The partial verification test requires the presence of the field elements of a and b. For the implemented NIST curves, b is defined in FIPS 186-4 appendix D.1.2. The element a is implicitly given with the Weierstrass equation given in D.1.2 where a = p - 3. Without the test, the NIST ACVP testing fails. After adding this check, the NIST ACVP testing passes. Signed-off-by: Stephan Mueller <smueller@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'crypto/ecc.c')
-rw-r--r--crypto/ecc.c42
1 files changed, 38 insertions, 4 deletions
diff --git a/crypto/ecc.c b/crypto/ecc.c
index 815541309a95..8facafd67802 100644
--- a/crypto/ecc.c
+++ b/crypto/ecc.c
@@ -1019,6 +1019,36 @@ out:
return ret;
}
+/* SP800-56A section 5.6.2.3.4 partial verification: ephemeral keys only */
+static int ecc_is_pubkey_valid_partial(const struct ecc_curve *curve,
+ struct ecc_point *pk)
+{
+ u64 yy[ECC_MAX_DIGITS], xxx[ECC_MAX_DIGITS], w[ECC_MAX_DIGITS];
+
+ /* Check 1: Verify key is not the zero point. */
+ if (ecc_point_is_zero(pk))
+ return -EINVAL;
+
+ /* Check 2: Verify key is in the range [1, p-1]. */
+ if (vli_cmp(curve->p, pk->x, pk->ndigits) != 1)
+ return -EINVAL;
+ if (vli_cmp(curve->p, pk->y, pk->ndigits) != 1)
+ return -EINVAL;
+
+ /* Check 3: Verify that y^2 == (x^3 + a·x + b) mod p */
+ vli_mod_square_fast(yy, pk->y, curve->p, pk->ndigits); /* y^2 */
+ vli_mod_square_fast(xxx, pk->x, curve->p, pk->ndigits); /* x^2 */
+ vli_mod_mult_fast(xxx, xxx, pk->x, curve->p, pk->ndigits); /* x^3 */
+ vli_mod_mult_fast(w, curve->a, pk->x, curve->p, pk->ndigits); /* a·x */
+ vli_mod_add(w, w, curve->b, curve->p, pk->ndigits); /* a·x + b */
+ vli_mod_add(w, w, xxx, curve->p, pk->ndigits); /* x^3 + a·x + b */
+ if (vli_cmp(yy, w, pk->ndigits) != 0) /* Equation */
+ return -EINVAL;
+
+ return 0;
+
+}
+
int crypto_ecdh_shared_secret(unsigned int curve_id, unsigned int ndigits,
const u64 *private_key, const u64 *public_key,
u64 *secret)
@@ -1046,16 +1076,20 @@ int crypto_ecdh_shared_secret(unsigned int curve_id, unsigned int ndigits,
goto out;
}
+ ecc_swap_digits(public_key, pk->x, ndigits);
+ ecc_swap_digits(&public_key[ndigits], pk->y, ndigits);
+ ret = ecc_is_pubkey_valid_partial(curve, pk);
+ if (ret)
+ goto err_alloc_product;
+
+ ecc_swap_digits(private_key, priv, ndigits);
+
product = ecc_alloc_point(ndigits);
if (!product) {
ret = -ENOMEM;
goto err_alloc_product;
}
- ecc_swap_digits(public_key, pk->x, ndigits);
- ecc_swap_digits(&public_key[ndigits], pk->y, ndigits);
- ecc_swap_digits(private_key, priv, ndigits);
-
ecc_point_mult(product, pk, priv, rand_z, curve->p, ndigits);
ecc_swap_digits(product->x, secret, ndigits);