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crypto: dh - check validity of Z before export

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SP800-56A rev3 section 5.7.1.1 step 2 mandates that the validity of the
calculated shared secret is verified before the data is returned to the
caller. This patch adds the validation check.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
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 19:08:32 +02:00 committed by Herbert Xu
parent 4278e9d99e
commit 90fa9ae51c
1 changed files with 29 additions and 0 deletions
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29
crypto/dh.c
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@ -9,6 +9,7 @@
#include <crypto/internal/kpp.h>
#include <crypto/kpp.h>
#include <crypto/dh.h>
#include <linux/fips.h>
#include <linux/mpi.h>
struct dh_ctx {
@ -179,6 +180,34 @@ static int dh_compute_value(struct kpp_request *req)
if (ret)
goto err_free_base;
/* SP800-56A rev3 5.7.1.1 check: Validation of shared secret */
if (fips_enabled && req->src) {
MPI pone;
/* z <= 1 */
if (mpi_cmp_ui(val, 1) < 1) {
ret = -EBADMSG;
goto err_free_base;
}
/* z == p - 1 */
pone = mpi_alloc(0);
if (!pone) {
ret = -ENOMEM;
goto err_free_base;
}
ret = mpi_sub_ui(pone, ctx->p, 1);
if (!ret && !mpi_cmp(pone, val))
ret = -EBADMSG;
mpi_free(pone);
if (ret)
goto err_free_base;
}
ret = mpi_write_to_sgl(val, req->dst, req->dst_len, &sign);
if (ret)
goto err_free_base;