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/** @file
Support routines for RDRAND instruction access.
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/RngLib.h>
#include "RdRand.h"
#include "AesCore.h"
/**
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
RdRandGetBytes (
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;
}
/**
Creates a 128bit random value that is fully forward and backward prediction resistant,
suitable for seeding a NIST SP800-90 Compliant, FIPS 1402-2 certifiable SW DRBG.
This function takes multiple random numbers through RDRAND without intervening
delays to ensure reseeding and performs AES-CBC-MAC over the data to compute the
seed value.
@param[out] SeedBuffer Pointer to a 128bit buffer to store the random seed.
@retval EFI_SUCCESS Random seed generation succeeded.
@retval EFI_NOT_READY Failed to request random bytes.
**/
EFI_STATUS
EFIAPI
RdRandGetSeed128 (
OUT UINT8 *SeedBuffer
)
{
EFI_STATUS Status;
UINT8 RandByte[16];
UINT8 Key[16];
UINT8 Ffv[16];
UINT8 Xored[16];
UINT32 Index;
UINT32 Index2;
//
// Chose an arbitrary key and zero the feed_forward_value (FFV)
//
for (Index = 0; Index < 16; Index++) {
Key[Index] = (UINT8) Index;
Ffv[Index] = 0;
}
//
// Perform CBC_MAC over 32 * 128 bit values, with 10us gaps between 128 bit value
// The 10us gaps will ensure multiple reseeds within the HW RNG with a large design margin.
//
for (Index = 0; Index < 32; Index++) {
MicroSecondDelay (10);
Status = RdRandGetBytes (16, RandByte);
if (EFI_ERROR (Status)) {
return Status;
}
//
// Perform XOR operations on two 128-bit value.
//
for (Index2 = 0; Index2 < 16; Index2++) {
Xored[Index2] = RandByte[Index2] ^ Ffv[Index2];
}
AesEncrypt (Key, Xored, Ffv);
}
for (Index = 0; Index < 16; Index++) {
SeedBuffer[Index] = Ffv[Index];
}
return EFI_SUCCESS;
}
/**
Generate high-quality entropy source 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 EFI_SUCCESS Entropy generation succeeded.
@retval EFI_NOT_READY Failed to request random data.
**/
EFI_STATUS
EFIAPI
RdRandGenerateEntropy (
IN UINTN Length,
OUT UINT8 *Entropy
)
{
EFI_STATUS Status;
UINTN BlockCount;
UINT8 Seed[16];
UINT8 *Ptr;
Status = EFI_NOT_READY;
BlockCount = Length / 16;
Ptr = (UINT8 *)Entropy;
//
// Generate high-quality seed for DRBG Entropy
//
while (BlockCount > 0) {
Status = RdRandGetSeed128 (Seed);
if (EFI_ERROR (Status)) {
return Status;
}
CopyMem (Ptr, Seed, 16);
BlockCount--;
Ptr = Ptr + 16;
}
//
// Populate the remained data as request.
//
Status = RdRandGetSeed128 (Seed);
if (EFI_ERROR (Status)) {
return Status;
}
CopyMem (Ptr, Seed, (Length % 16));
return Status;
}
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