2020-07-20 17:12:26

by Stephan Müller

Subject: [PATCH v3 3/5] crypto: DH - check validity of Z before export

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 <[email protected]>
---
crypto/dh.c | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)

diff --git a/crypto/dh.c b/crypto/dh.c
index 566f624a2de2..f84fd50ec79b 100644
--- a/crypto/dh.c
+++ b/crypto/dh.c
@@ -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;
--
2.26.2

2020-07-24 18:03:08

by Neil Horman

Subject: Re: [PATCH v3 3/5] crypto: DH - check validity of Z before export

On Mon, Jul 20, 2020 at 07:08:32PM +0200, Stephan M?ller wrote:
> 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 <[email protected]>
> ---
> crypto/dh.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/crypto/dh.c b/crypto/dh.c
> index 566f624a2de2..f84fd50ec79b 100644
> --- a/crypto/dh.c
> +++ b/crypto/dh.c
> @@ -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;
> --
> 2.26.2
>
>
>
>
Acked-by: Neil Horman <[email protected]>