1 files changed, 71 insertions, 0 deletions
diff --git a/SecurityPkg/RandomNumberGenerator/RngDxe/ArmTrng.c b/SecurityPkg/RandomNumberGenerator/RngDxe/ArmTrng.c
new file mode 100644
index 0000000000..ffe557b692
--- /dev/null
+++ b/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;
+}