/** @file
  RNG Driver to produce the UEFI Random Number Generator protocol.

  The driver uses CPU RNG instructions to produce high-quality,
  high-performance entropy and random number.

  RNG Algorithms defined in UEFI 2.4:
   - EFI_RNG_ALGORITHM_SP800_90_CTR_256_GUID
   - 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
   - EFI_RNG_ALGORITHM_X9_31_AES_GUID

Copyright (c) 2013 - 2018, Intel Corporation. All rights reserved.<BR>
(C) Copyright 2015 Hewlett Packard Enterprise Development LP<BR>

SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include <Library/BaseLib.h>
#include <Library/BaseMemoryLib.h>
#include <Library/UefiBootServicesTableLib.h>
#include <Library/RngLib.h>
#include <Library/TimerLib.h>
#include <Protocol/Rng.h>

#include "RngDxeInternals.h"

//
// The Random Number Generator (RNG) protocol
//
EFI_RNG_PROTOCOL  mRngRdRand = {
  RngGetInfo,
  RngGetRNG
};

/**
  The user Entry Point for the Random Number Generator (RNG) driver.

  @param[in] ImageHandle    The firmware allocated handle for the EFI image.
  @param[in] SystemTable    A pointer to the EFI System Table.

  @retval EFI_SUCCESS       The entry point is executed successfully.
  @retval EFI_NOT_SUPPORTED Platform does not support RNG.
  @retval Other             Some error occurs when executing this entry point.

**/
EFI_STATUS
EFIAPI
RngDriverEntry (
  IN EFI_HANDLE        ImageHandle,
  IN EFI_SYSTEM_TABLE  *SystemTable
  )
{
  EFI_STATUS  Status;
  EFI_HANDLE  Handle;

  //
  // Install UEFI RNG (Random Number Generator) Protocol
  //
  Handle = NULL;
  Status = gBS->InstallMultipleProtocolInterfaces (
                  &Handle,
                  &gEfiRngProtocolGuid,
                  &mRngRdRand,
                  NULL
                  );

  return Status;
}

/**
  Calls RDRAND to fill a buffer of arbitrary size with random bytes.

  @param[in]   Length        Size of the buffer, in bytes,  to fill with.
  @param[out]  RandBuffer    Pointer to the buffer to store the random result.

  @retval EFI_SUCCESS        Random bytes generation succeeded.
  @retval EFI_NOT_READY      Failed to request random bytes.

**/
EFI_STATUS
EFIAPI
RngGetBytes (
  IN UINTN   Length,
  OUT UINT8  *RandBuffer
  )
{
  BOOLEAN  IsRandom;
  UINT64   TempRand[2];

  while (Length > 0) {
    IsRandom = GetRandomNumber128 (TempRand);
    if (!IsRandom) {
      return EFI_NOT_READY;
    }

    if (Length >= sizeof (TempRand)) {
      WriteUnaligned64 ((UINT64 *)RandBuffer, TempRand[0]);
      RandBuffer += sizeof (UINT64);
      WriteUnaligned64 ((UINT64 *)RandBuffer, TempRand[1]);
      RandBuffer += sizeof (UINT64);
      Length     -= sizeof (TempRand);
    } else {
      CopyMem (RandBuffer, TempRand, Length);
      Length = 0;
    }
  }

  return EFI_SUCCESS;
}