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SecurityPkg/RngDxe: Use GetRngGuid() when probing RngLib

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BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4151

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 was added in a previous patch.

The EFI_RNG_PROTOCOL can advertise multiple algorithms through
Guids. The PcdCpuRngSupportedAlgorithm is currently used to
advertise the RngLib in the Arm implementation.

The issues of doing that are:
- the RngLib implementation might not use CPU instructions,
  cf. the BaseRngLibTimerLib
- most platforms don't set PcdCpuRngSupportedAlgorithm

A GetRngGuid() was added to the RngLib in a previous patch,
allowing to identify the algorithm implemented by the RngLib.
Make use of this function and place the unsage algorithm
at the last position in the mAvailableAlgoArray.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Jiewen Yao <Jiewen.yao@intel.com>
Tested-by: Kun Qin <kun.qin@microsoft.com>
This commit is contained in:
Pierre Gondois
2023-08-11 16:33:09 +02:00
committed by mergify[bot]
parent 5443c2dc31
commit 19438cff97
3 changed files with 44 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
SecurityPkg/RandomNumberGenerator/RngDxe/RngDxe.inf
View File

@@ -75,13 +75,11 @@
gEfiRngAlgorithmX9313DesGuid ## SOMETIMES_PRODUCES ## GUID # Unique ID of the algorithm for RNG
gEfiRngAlgorithmX931AesGuid ## SOMETIMES_PRODUCES ## GUID # Unique ID of the algorithm for RNG
gEfiRngAlgorithmRaw ## SOMETIMES_PRODUCES ## GUID # Unique ID of the algorithm for RNG
gEdkiiRngAlgorithmUnSafe ## SOMETIMES_PRODUCES ## GUID # Unique ID of the algorithm for RNG
[Protocols]
gEfiRngProtocolGuid ## PRODUCES
[Pcd.AARCH64]
gEfiMdePkgTokenSpaceGuid.PcdCpuRngSupportedAlgorithm ## CONSUMES
[Depex]
TRUE