Commit e7d2b41e authored Jul 20, 2020 by Stephan Müller Committed by Herbert Xu Jul 31, 2020

crypto: ecdh - check validity of Z before export



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>

parent ef19f826

crypto/ecc.c

+8 −3

Original line number	Diff line number	Diff line
		@@ -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);

		ecc_swap_digits(product->x, secret, ndigits);

		if (ecc_point_is_zero(product))
		if (ecc_point_is_zero(product)) {
		ret = -EFAULT;
		goto err_validity;
		}

		ecc_swap_digits(product->x, secret, ndigits);

		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);

Admin message