Re: [PATCH v3 4/5] machine/nitro-enclave: Add built-in Nitro Secure Module device

[Alexander Graf <graf@amazon.com>]

On 10.08.24 18:45, Dorjoy Chowdhury wrote:
> AWS Nitro Enclaves have built-in Nitro Secure Module (NSM) device which
> is used for stripped down TPM functionality like attestation. This commit
> adds the built-in NSM device in the nitro-enclave machine type.
>
> In Nitro Enclaves, all the PCRs start in a known zero state and the first
> 16 PCRs are locked from boot and reserved. The PCR0, PCR1, PCR2 and PCR8
> contain the SHA384 hashes related to the EIF file used to boot the
> VM for validation.
>
> A new optional nitro-enclave machine option 'id' has been added which will
> be the enclave identifier reflected in the module-id of the NSM device.
> Otherwise, the device will have a default id set.
>
> Signed-off-by: Dorjoy Chowdhury <dorjoychy111@gmail.com>
> ---
>   hw/core/eif.c                   | 205 +++++++++++++++++++++++++++++++-
>   hw/core/eif.h                   |   5 +-
>   hw/core/meson.build             |   4 +-
>   hw/i386/Kconfig                 |   1 +
>   hw/i386/nitro_enclave.c         |  85 ++++++++++++-
>   include/hw/i386/nitro_enclave.h |  19 +++
>   6 files changed, 310 insertions(+), 9 deletions(-)
>

[...]


> @@ -87,10 +106,46 @@ static void nitro_enclave_machine_state_init(MachineState *machine)
>       nitro_enclave_devices_init(ne_state);
>   }
>
> +static void nitro_enclave_machine_reset(MachineState *machine,
> +                                        ShutdownCause reason)
> +{
> +    NitroEnclaveMachineClass *ne_class =
> +        NITRO_ENCLAVE_MACHINE_GET_CLASS(machine);
> +    NitroEnclaveMachineState *ne_state = NITRO_ENCLAVE_MACHINE(machine);
> +
> +    ne_class->parent_reset(machine, reason);
> +
> +    memset(ne_state->vnsm->pcrs, 0, sizeof(ne_state->vnsm->pcrs));
> +
> +    /* PCR0 */
> +    ne_state->vnsm->extend_pcr(ne_state->vnsm, 0, ne_state->image_sha384,
> +                               SHA384_BYTE_LEN);
> +    /* PCR1 */
> +    ne_state->vnsm->extend_pcr(ne_state->vnsm, 1, ne_state->bootstrap_sha384,
> +                               SHA384_BYTE_LEN);
> +    /* PCR2 */
> +    ne_state->vnsm->extend_pcr(ne_state->vnsm, 2, ne_state->app_sha384,
> +                               SHA384_BYTE_LEN);


What about PCR3 and PCR4? Both are just sha384 values of input 
strings[1]. Can you make these input strings NSM device as well as 
machine properties as well?

[1] https://docs.aws.amazon.com/enclaves/latest/user/set-up-attestation.html



Alex




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