On Wed, 21 Jul 2021 at 22:19, Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> wrote:
>
> The two existing trusted key sources don't make use of the kernel RNG,
> but instead let the hardware that does the sealing/unsealing also
> generate the random key material. While a previous change offers users
> the choice to use the kernel RNG instead for both, new trust sources
> may want to unconditionally use the kernel RNG for generating key
> material, like it's done elsewhere in the kernel.
>
> This is especially prudent for hardware that has proven-in-production
> HWRNG drivers implemented, as otherwise code would have to be duplicated
> only to arrive at a possibly worse result.
>
> Make this possible by turning struct trusted_key_ops::get_random
> into an optional member. If a driver leaves it NULL, kernel RNG
> will be used instead.
>
> Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
> ---
> To: James Bottomley <jejb@xxxxxxxxxxxxx>
> To: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
> To: Mimi Zohar <zohar@xxxxxxxxxxxxx>
> To: David Howells <dhowells@xxxxxxxxxx>
> Cc: James Morris <jmorris@xxxxxxxxx>
> Cc: "Serge E. Hallyn" <serge@xxxxxxxxxx>
> Cc: "Horia Geantă" <horia.geanta@xxxxxxx>
> Cc: Aymen Sghaier <aymen.sghaier@xxxxxxx>
> Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Udit Agarwal <udit.agarwal@xxxxxxx>
> Cc: Eric Biggers <ebiggers@xxxxxxxxxx>
> Cc: Jan Luebbe <j.luebbe@xxxxxxxxxxxxxx>
> Cc: David Gstir <david@xxxxxxxxxxxxx>
> Cc: Richard Weinberger <richard@xxxxxx>
> Cc: Franck LENORMAND <franck.lenormand@xxxxxxx>
> Cc: Sumit Garg <sumit.garg@xxxxxxxxxx>
> Cc: keyrings@xxxxxxxxxxxxxxx
> Cc: linux-crypto@xxxxxxxxxxxxxxx
> Cc: linux-integrity@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: linux-security-module@xxxxxxxxxxxxxxx
> ---
> include/keys/trusted-type.h | 2 +-
> security/keys/trusted-keys/trusted_core.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
> index d89fa2579ac0..4eb64548a74f 100644
> --- a/include/keys/trusted-type.h
> +++ b/include/keys/trusted-type.h
> @@ -64,7 +64,7 @@ struct trusted_key_ops {
> /* Unseal a key. */
> int (*unseal)(struct trusted_key_payload *p, char *datablob);
>
> - /* Get a randomized key. */
> + /* Optional: Get a randomized key. */
> int (*get_random)(unsigned char *key, size_t key_len);
>
> /* Exit key interface. */
> diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c
> index 569af9af8df0..d2b7626cde8b 100644
> --- a/security/keys/trusted-keys/trusted_core.c
> +++ b/security/keys/trusted-keys/trusted_core.c
> @@ -334,7 +334,7 @@ static int __init init_trusted(void)
> continue;
>
> get_random = trusted_key_sources[i].ops->get_random;
> - if (trusted_kernel_rng)
> + if (trusted_kernel_rng || !get_random)
> get_random = kernel_get_random;
>
For ease of understanding, I would prefer to write it as:
get_random = trusted_key_sources[i].ops->get_random ?:
kernel_get_random;
if (trusted_kernel_rng)
get_random = kernel_get_random;
With that:
Acked-by: Sumit Garg <sumit.garg@xxxxxxxxxx>
-Sumit
> static_call_update(trusted_key_init,
> --
> git-series 0.9.1
