Re: [PATCH v1 4/8] MdePkg/Rng: Add GUIDs to describe Rng algorithms

["Sami Mujawar" <sami.mujawar@arm.com>]

Hi Pierre,

Thank you for this patch.

Please find my response inline marked [SAMI].

Other than the concern mentioned below, this patch looks good to me.

Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>

Regards,

Sami Mujawar

On 09/05/2023 08:40 am, pierre.gondois@arm.com wrote:
> From: Pierre Gondois <pierre.gondois@arm.com>
>
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4441
>
> The EFI_RNG_PROTOCOL can rely on the RngLib. The RngLib has multiple
> implementations, some of them are unsafe (e.g. BaseRngLibTimerLib).
> To allow the RngDxe to detect when such implementation is used,
> a GetRngGuid() function is added in a following patch.
>
> Prepare GetRngGuid() return values and add GUIDs describing
> Rng algorithms:
> - gEfiRngAlgorithmArmRndr
> to describe a Rng algorithm accessed through Arm's RNDR instruction.
> [1] states that the implementation of this algorithm should be
> compliant to NIST SP900-80. The compliance is not guaranteed.
> - gEfiRngAlgorithmUnSafe
> to describe an unsafe implementation, cf. the BaseRngLibTimerLib.
>
> [1] Arm Architecture Reference Manual Armv8, for A-profile architecture
> sK12.1 'Properties of the generated random number'
>
> Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
> ---
>   MdePkg/Include/Protocol/Rng.h | 20 ++++++++++++++++++++
>   MdePkg/MdePkg.dec             |  2 ++
>   2 files changed, 22 insertions(+)
>
> diff --git a/MdePkg/Include/Protocol/Rng.h b/MdePkg/Include/Protocol/Rng.h
> index baf425587b3c..dfdaf36e41dc 100644
> --- a/MdePkg/Include/Protocol/Rng.h
> +++ b/MdePkg/Include/Protocol/Rng.h
> @@ -67,6 +67,24 @@ typedef EFI_GUID EFI_RNG_ALGORITHM;
>     { \
>       0xe43176d7, 0xb6e8, 0x4827, {0xb7, 0x84, 0x7f, 0xfd, 0xc4, 0xb6, 0x85, 0x61 } \
>     }
> +///
> +/// The Arm Architecture states the RNDR that the DRBG algorithm should be compliant
> +/// with NIST SP800-90A, while not mandating a particular algorithm, so as to be
> +/// inclusive of different geographies.
> +///
> +#define EFI_RNG_ALGORITHM_ARM_RNDR \
> +  { \
> +    0x43d2fde3, 0x9d4e, 0x4d79,  {0x02, 0x96, 0xa8, 0x9b, 0xca, 0x78, 0x08, 0x41} \
> +  }
> +///
> +/// The implementation of a Random Number Generator might be unsafe, when using
> +/// a dummy implementation for instance. Allow identifying such implementation
> +/// with this GUID.
> +///
> +#define EFI_RNG_ALGORITHM_UNSAFE \
> +  { \
> +    0x869f728c, 0x409d, 0x4ab4, {0xac, 0x03, 0x71, 0xd3, 0x09, 0xc1, 0xb3, 0xf4 } \
> +  }

[SAMI] Unlike the EFI_RNG_ALGORITHM_ARM_RNDR which is backed by the code 
first spec update at https://mantis.uefi.org/mantis/view.php?id=2386; 
the EFI_RNG_ALGORITHM_UNSAFE is not backed by any specification.

Although I agree that a definition of the unsafe algorithm is required 
to support some platforms, I am not sure if this file and the macro 
prefix is right for this definition.

I would defer this decision, and any advice on how to proceed to the 
MdePkg maintainers.

[/SAMI]

>   
>   /**
>     Returns information about the random number generation implementation.
> @@ -146,5 +164,7 @@ extern EFI_GUID  gEfiRngAlgorithmSp80090Ctr256Guid;
>   extern EFI_GUID  gEfiRngAlgorithmX9313DesGuid;
>   extern EFI_GUID  gEfiRngAlgorithmX931AesGuid;
>   extern EFI_GUID  gEfiRngAlgorithmRaw;
> +extern EFI_GUID  gEfiRngAlgorithmArmRndr;
> +extern EFI_GUID  gEfiRngAlgorithmUnSafe;
>   
>   #endif
> diff --git a/MdePkg/MdePkg.dec b/MdePkg/MdePkg.dec
> index 0ecfad5795e4..754085eaa55b 100644
> --- a/MdePkg/MdePkg.dec
> +++ b/MdePkg/MdePkg.dec
> @@ -633,6 +633,8 @@ [Guids]
>     gEfiRngAlgorithmX9313DesGuid       = { 0x63c4785a, 0xca34, 0x4012, {0xa3, 0xc8, 0x0b, 0x6a, 0x32, 0x4f, 0x55, 0x46 }}
>     gEfiRngAlgorithmX931AesGuid        = { 0xacd03321, 0x777e, 0x4d3d, {0xb1, 0xc8, 0x20, 0xcf, 0xd8, 0x88, 0x20, 0xc9 }}
>     gEfiRngAlgorithmRaw                = { 0xe43176d7, 0xb6e8, 0x4827, {0xb7, 0x84, 0x7f, 0xfd, 0xc4, 0xb6, 0x85, 0x61 }}
> +  gEfiRngAlgorithmArmRndr            = { 0x43d2fde3, 0x9d4e, 0x4d79, {0x02, 0x96, 0xa8, 0x9b, 0xca, 0x78, 0x08, 0x41 }}
> +  gEfiRngAlgorithmUnSafe             = { 0x869f728c, 0x409d, 0x4ab4, {0xac, 0x03, 0x71, 0xd3, 0x09, 0xc1, 0xb3, 0xf4 }}
>   
>     ## Include/Protocol/AdapterInformation.h
>     gEfiAdapterInfoMediaStateGuid       = { 0xD7C74207, 0xA831, 0x4A26, {0xB1, 0xF5, 0xD1, 0x93, 0x06, 0x5C, 0xE8, 0xB6 }}