SecurityPkg/RngDxe: Add AArch64 RawAlgorithm support through ArmTrngLib

Bugzilla: 3668 (https://bugzilla.tianocore.org/show_bug.cgi?id=3668)

RawAlgorithm is used to provide access to entropy that is suitable
for cryptographic applications. Therefore, add RawAlgorithm support
that provides access to entropy using the ArmTrngLib.

Also remove unused UefiBootServicesTableLib library inclusion
and Status variable.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Acked-by: Jiewen Yao <jiewen.yao@intel.com>

SecurityPkg/RandomNumberGenerator/RngDxe/AArch64/RngDxe.c

@@ -1,11 +1,13 @@
 /** @file
   RNG Driver to produce the UEFI Random Number Generator protocol.
 
-  The driver will use the RNDR instruction to produce random numbers.
+  The driver can use RNDR instruction (through the RngLib and if FEAT_RNG is
+  present) to produce random numbers. It also uses the Arm FW-TRNG interface
+  to implement EFI_RNG_ALGORITHM_RAW.
 
   RNG Algorithms defined in UEFI 2.4:
    - EFI_RNG_ALGORITHM_SP800_90_CTR_256_GUID
-   - EFI_RNG_ALGORITHM_RAW                    - Unsupported
+   - EFI_RNG_ALGORITHM_RAW
    - EFI_RNG_ALGORITHM_SP800_90_HMAC_256_GUID
    - EFI_RNG_ALGORITHM_SP800_90_HASH_256_GUID
    - EFI_RNG_ALGORITHM_X9_31_3DES_GUID        - Unsupported
@@ -26,12 +28,14 @@
 #include <Library/MemoryAllocationLib.h>
 #include <Library/UefiBootServicesTableLib.h>
 #include <Library/RngLib.h>
+#include <Library/DebugLib.h>
+#include <Library/ArmTrngLib.h>
 #include <Protocol/Rng.h>
 
 #include "RngDxeInternals.h"
 
 // Maximum number of Rng algorithms.
-#define RNG_AVAILABLE_ALGO_MAX  1
+#define RNG_AVAILABLE_ALGO_MAX  2
 
 /** Allocate and initialize mAvailableAlgoArray with the available
     Rng algorithms. Also update mAvailableAlgoArrayCount.
@@ -46,8 +50,9 @@ GetAvailableAlgorithms (
   )
 {
   UINT64  DummyRand;
+  UINT16  MajorRevision;
+  UINT16  MinorRevision;
 
-  // Allocate RNG_AVAILABLE_ALGO_MAX entries to avoid evaluating
   // Rng algorithms 2 times, one for the allocation, one to populate.
   mAvailableAlgoArray = AllocateZeroPool (RNG_AVAILABLE_ALGO_MAX);
   if (mAvailableAlgoArray == NULL) {
@@ -64,6 +69,16 @@ GetAvailableAlgorithms (
     mAvailableAlgoArrayCount++;
   }
 
+  // Raw algorithm (Trng)
+  if (!EFI_ERROR (GetArmTrngVersion (&MajorRevision, &MinorRevision))) {
+    CopyMem (
+      &mAvailableAlgoArray[mAvailableAlgoArrayCount],
+      &gEfiRngAlgorithmRaw,
+      sizeof (EFI_RNG_ALGORITHM)
+      );
+    mAvailableAlgoArrayCount++;
+  }
+
   return EFI_SUCCESS;
 }
 
@@ -141,6 +156,11 @@ FoundAlgo:
     return Status;
   }
 
+  // Raw algorithm (Trng)
+  if (CompareGuid (RNGAlgorithm, &gEfiRngAlgorithmRaw)) {
+    return GenerateEntropy (RNGValueLength, RNGValue);
+  }
+
   //
   // Other algorithms are unsupported by this driver.
   //

SecurityPkg/RandomNumberGenerator/RngDxe/ArmTrng.c

@@ -0,0 +1,71 @@
+/** @file
+  RNG Driver to produce the UEFI Random Number Generator protocol.
+
+  The driver implements the EFI_RNG_ALGORITHM_RAW using the FW-TRNG
+  interface to provide entropy.
+
+  Copyright (c) 2021 - 2022, Arm Limited. All rights reserved.<BR>
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Library/BaseLib.h>
+#include <Library/BaseMemoryLib.h>
+#include <Library/DebugLib.h>
+#include <Library/ArmTrngLib.h>
+#include <Protocol/Rng.h>
+
+#include "RngDxeInternals.h"
+
+/**
+  Generate high-quality entropy source using a TRNG or through RDRAND.
+
+  @param[in]   Length        Size of the buffer, in bytes, to fill with.
+  @param[out]  Entropy       Pointer to the buffer to store the entropy data.
+
+  @retval  RETURN_SUCCESS            The function completed successfully.
+  @retval  RETURN_INVALID_PARAMETER  Invalid parameter.
+  @retval  RETURN_UNSUPPORTED        Function not implemented.
+  @retval  RETURN_BAD_BUFFER_SIZE    Buffer size is too small.
+  @retval  RETURN_NOT_READY          No Entropy available.
+**/
+EFI_STATUS
+EFIAPI
+GenerateEntropy (
+  IN  UINTN  Length,
+  OUT UINT8  *Entropy
+  )
+{
+  EFI_STATUS  Status;
+  UINTN       CollectedEntropyBits;
+  UINTN       RequiredEntropyBits;
+  UINTN       EntropyBits;
+  UINTN       Index;
+  UINTN       MaxBits;
+
+  ZeroMem (Entropy, Length);
+
+  RequiredEntropyBits  = (Length << 3);
+  Index                = 0;
+  CollectedEntropyBits = 0;
+  MaxBits              = GetArmTrngMaxSupportedEntropyBits ();
+  while (CollectedEntropyBits < RequiredEntropyBits) {
+    EntropyBits = MIN ((RequiredEntropyBits - CollectedEntropyBits), MaxBits);
+    Status      = GetArmTrngEntropy (
+                    EntropyBits,
+                    (Length - Index),
+                    &Entropy[Index]
+                    );
+    if (EFI_ERROR (Status)) {
+      // Discard the collected bits.
+      ZeroMem (Entropy, Length);
+      return Status;
+    }
+
+    CollectedEntropyBits += EntropyBits;
+    Index                += (EntropyBits >> 3);
+  } // while
+
+  return Status;
+}

SecurityPkg/RandomNumberGenerator/RngDxe/RngDxe.inf

@@ -43,8 +43,10 @@
 
 [Sources.AARCH64]
   AArch64/RngDxe.c
+  ArmTrng.c
 
 [Packages]
+  MdeModulePkg/MdeModulePkg.dec
   MdePkg/MdePkg.dec
   SecurityPkg/SecurityPkg.dec
 
@@ -57,6 +59,9 @@
   TimerLib
   RngLib
 
+[LibraryClasses.AARCH64]
+  ArmTrngLib
+
 [Guids]
   gEfiRngAlgorithmSp80090Hash256Guid  ## SOMETIMES_PRODUCES    ## GUID        # Unique ID of the algorithm for RNG
   gEfiRngAlgorithmSp80090Hmac256Guid  ## SOMETIMES_PRODUCES    ## GUID        # Unique ID of the algorithm for RNG

SecurityPkg/SecurityPkg.dsc

@@ -4,6 +4,7 @@
 # Copyright (c) 2009 - 2021, Intel Corporation. All rights reserved.<BR>
 # (C) Copyright 2015-2020 Hewlett Packard Enterprise Development LP<BR>
 # Copyright (c) 2022, Loongson Technology Corporation Limited. All rights reserved.<BR>
+# Copyright (c) 2021 - 2022, Arm Limited. All rights reserved.<BR>
 # SPDX-License-Identifier: BSD-2-Clause-Patent
 #
 ##
@@ -89,6 +90,8 @@
 
   ArmSoftFloatLib|ArmPkg/Library/ArmSoftFloatLib/ArmSoftFloatLib.inf
 
+  ArmTrngLib|MdePkg/Library/BaseArmTrngLibNull/BaseArmTrngLibNull.inf
+
 [LibraryClasses.ARM]
   RngLib|MdePkg/Library/BaseRngLibTimerLib/BaseRngLibTimerLib.inf