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