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crypto: ecdh - check validity of Z before export

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SP800-56A rev3 section 5.7.1.2 step 2 mandates that the validity of the
calculated shared secret is verified before the data is returned to the
caller. Thus, the export function and the validity check functions are
reversed. In addition, the sensitive variables of priv and rand_z are
zeroized.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Reviewed-by: Vitaly Chikunov <vt@altlinux.org>
Acked-by: Neil Horman <nhorman@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Stephan Müller 2020-07-20 19:07:48 +02:00 committed by Herbert Xu
parent ef19f826ec
commit e7d2b41e5c
1 changed files with 8 additions and 3 deletions
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11
crypto/ecc.c
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@ -1495,11 +1495,16 @@ int crypto_ecdh_shared_secret(unsigned int curve_id, unsigned int ndigits,
ecc_point_mult(product, pk, priv, rand_z, curve, ndigits);
if (ecc_point_is_zero(product)) {
ret = -EFAULT;
goto err_validity;
}
ecc_swap_digits(product->x, secret, ndigits);
if (ecc_point_is_zero(product))
ret = -EFAULT;
err_validity:
memzero_explicit(priv, sizeof(priv));
memzero_explicit(rand_z, sizeof(rand_z));
ecc_free_point(product);
err_alloc_product:
ecc_free_point(pk);