Re: [edk2-devel] [PATCH v3 1/6] OvmfPkg/TPM: Import PeiDxeTpmPlatformHierarchyLib.c from edk2-platforms

["Stefan Berger" <stefanb@linux.ibm.com>]

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On 8/12/21 9:48 AM, Marc-André Lureau wrote:
> Hi On Tue, Aug 10, 2021 at 9:22 PM Stefan Berger 
> <stefanb@linux.vnet.ibm.com> wrote: Import 
> PeiDxeTpmPlatformHierarchyLib.c from edk2-platforms. Modify it so that 
> ConfigureTpmPlatformHierarchy() is the only public function provided ‍ 
> ‍ ZjQcmQRYFpfptBannerStart
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> Hi
>
> On Tue, Aug 10, 2021 at 9:22 PM Stefan Berger 
> <stefanb@linux.vnet.ibm.com <mailto:stefanb@linux.vnet.ibm.com>> wrote:
>
>     Import PeiDxeTpmPlatformHierarchyLib.c from edk2-platforms. Modify
>     it so
>     that ConfigureTpmPlatformHierarchy() is the only public function
>     provided
>     by this file.
>
>     Signed-off-by: Stefan Berger <stefanb@linux.ibm.com
>     <mailto:stefanb@linux.ibm.com>>
>     ---
>      .../Include/Library/TpmPlatformHierarchyLib.h |  27 +++
>      .../PeiDxeTpmPlatformHierarchyLib.c           | 210
>     ++++++++++++++++++
>      .../PeiDxeTpmPlatformHierarchyLib.inf         |  40 ++++
>      3 files changed, 277 insertions(+)
>      create mode 100644 OvmfPkg/Include/Library/TpmPlatformHierarchyLib.h
>      create mode 100644
>     OvmfPkg/Library/PeiDxeTpmPlatformHierarchyLib/PeiDxeTpmPlatformHierarchyLib.c
>      create mode 100644
>     OvmfPkg/Library/PeiDxeTpmPlatformHierarchyLib/PeiDxeTpmPlatformHierarchyLib.inf
>
>     diff --git a/OvmfPkg/Include/Library/TpmPlatformHierarchyLib.h
>     b/OvmfPkg/Include/Library/TpmPlatformHierarchyLib.h
>     new file mode 100644
>     index 0000000000..a872fa09dc
>     --- /dev/null
>     +++ b/OvmfPkg/Include/Library/TpmPlatformHierarchyLib.h
>     @@ -0,0 +1,27 @@
>     +/** @file
>     +    TPM Platform Hierarchy configuration library.
>     +
>     +    This library provides functions for customizing the TPM's
>     Platform Hierarchy
>     +    Authorization Value (platformAuth) and Platform Hierarchy
>     Authorization
>     +    Policy (platformPolicy) can be defined through this function.
>     +
>     +Copyright (c) 2019, Intel Corporation. All rights reserved.<BR>
>     +Copyright (c) Microsoft Corporation.<BR>
>     +SPDX-License-Identifier: BSD-2-Clause-Patent
>     +
>     +**/
>     +
>     +#ifndef _TPM_PLATFORM_HIERARCHY_LIB_H_
>     +#define _TPM_PLATFORM_HIERARCHY_LIB_H_
>     +
>     +/**
>     +   This service will perform the TPM Platform Hierarchy
>     configuration at the SmmReadyToLock event.
>     +
>     +**/
>     +VOID
>     +EFIAPI
>     +ConfigureTpmPlatformHierarchy (
>     +  VOID
>     +  );
>     +
>     +#endif
>     diff --git
>     a/OvmfPkg/Library/PeiDxeTpmPlatformHierarchyLib/PeiDxeTpmPlatformHierarchyLib.c
>     b/OvmfPkg/Library/PeiDxeTpmPlatformHierarchyLib/PeiDxeTpmPlatformHierarchyLib.c
>     new file mode 100644
>     index 0000000000..ba2d99bb53
>     --- /dev/null
>     +++
>     b/OvmfPkg/Library/PeiDxeTpmPlatformHierarchyLib/PeiDxeTpmPlatformHierarchyLib.c
>     @@ -0,0 +1,210 @@
>     +/** @file
>     +    TPM Platform Hierarchy configuration library.
>     +
>     +    This library provides functions for customizing the TPM's
>     Platform Hierarchy
>     +    Authorization Value (platformAuth) and Platform Hierarchy
>     Authorization
>     +    Policy (platformPolicy) can be defined through this function.
>     +
>     +    Copyright (c) 2019, Intel Corporation. All rights reserved.<BR>
>     +    Copyright (c) Microsoft Corporation.<BR>
>     +    SPDX-License-Identifier: BSD-2-Clause-Patent
>     +
>     +    @par Specification Reference:
>     +
>     https://trustedcomputinggroup.org/resource/tcg-tpm-v2-0-provisioning-guidance/
>     <https://trustedcomputinggroup.org/resource/tcg-tpm-v2-0-provisioning-guidance/>
>     +**/
>     +
>     +#include <Uefi.h>
>     +
>     +#include <Library/BaseMemoryLib.h>
>     +#include <Library/DebugLib.h>
>     +#include <Library/MemoryAllocationLib.h>
>     +#include <Library/RngLib.h>
>     +#include <Library/Tpm2CommandLib.h>
>     +#include <Library/Tpm2DeviceLib.h>
>     +
>     +//
>     +// The authorization value may be no larger than the digest
>     produced by the hash
>     +//   algorithm used for context integrity.
>     +//
>     +#define      MAX_NEW_AUTHORIZATION_SIZE SHA512_DIGEST_SIZE
>     +
>     +UINT16       mAuthSize;
>     +
>     +/**
>     +  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;
>     +  UINT64      Seed[2];
>     +  UINT8       *Ptr;
>     +
>     +  Status = EFI_NOT_READY;
>     +  BlockCount = Length / 64;
>     +  Ptr = (UINT8 *)Entropy;
>     +
>     +  //
>     +  // Generate high-quality seed for DRBG Entropy
>     +  //
>     +  while (BlockCount > 0) {
>     +    Status = GetRandomNumber128 (Seed);
>     +    if (EFI_ERROR (Status)) {
>     +      return Status;
>     +    }
>     +    CopyMem (Ptr, Seed, 64);
>
>
> This looks like it's copying past the Seed buffer, which is 2 * 
> sizeof(u64) = 16.

Ha! Thanks for looking at this. Those seem to be the pitfalls of blindly 
importing code from edk2-platforms. Now the question is whether to leave 
it broken in edk2-platforms or fix it there first before trying to 
import it to edk2. In the interest of time I'd rather fix it here. 
Obviously the BlockCount is also wrong.


>
>     +
>     +    BlockCount--;
>     +    Ptr = Ptr + 64;
>     +  }
>     +
>     +  //
>     +  // Populate the remained data as request.
>     +  //
>     +  Status = GetRandomNumber128 (Seed);
>     +  if (EFI_ERROR (Status)) {
>     +    return Status;
>     +  }
>     +  CopyMem (Ptr, Seed, (Length % 64));
>
>
> And then again.
>
> Isn't there a better way to fill a buffer with random data in edk2?

I don't know. On ARM it *looks like* the path goes down to an assembly 
instruction getting 64bit random number from the hardware: 
MdePkg/Library/BaseRngLib/AArch64/ArmRng.asm

On x86 it will end up calling GenerateRandomNumberViaNist800Algorithm: 
MdePkg/Library/DxeRngLib/DxeRngLib.c


CryptoPkg/Drvier/Crypto.c has this here:

BOOLEAN
EFIAPI
CryptoServiceRandomSeed (
   IN  CONST  UINT8  *Seed  OPTIONAL,
   IN  UINTN         SeedSize
   )
{
   return CALL_BASECRYPTLIB (Random.Services.Seed, RandomSeed, (Seed, 
SeedSize)
}

and this one:

BOOLEAN
EFIAPI
CryptoServiceRandomBytes (
   OUT  UINT8  *Output,
   IN   UINTN  Size
   )
{
   return CALL_BASECRYPTLIB (Random.Services.Bytes, RandomBytes, 
(Output, Size)
}


Those are pseudorandom numbers. I don't know about others.


>
>     +
>     +  return Status;
>     +}
>     +
>     +/**
>     +  This function returns the maximum size of TPM2B_AUTH; this
>     structure is used for an authorization value
>     +  and limits an authValue to being no larger than the largest
>     digest produced by a TPM.
>     +
>     +  @param[out] AuthSize                 Tpm2 Auth size
>     +
>     +  @retval EFI_SUCCESS                  Auth size returned.
>     +  @retval EFI_DEVICE_ERROR             Can not return platform
>     auth due to device error.
>     +
>     +**/
>     +EFI_STATUS
>     +EFIAPI
>     +GetAuthSize (
>     +  OUT UINT16            *AuthSize
>     +  )
>     +{
>     +  EFI_STATUS            Status;
>     +  TPML_PCR_SELECTION    Pcrs;
>     +  UINTN                 Index;
>     +  UINT16                DigestSize;
>     +
>     +  Status = EFI_SUCCESS;
>     +
>     +  while (mAuthSize == 0) {
>
>
> This is a bit odd, but ok.
>
>     +
>     +    mAuthSize = SHA1_DIGEST_SIZE;
>     +    ZeroMem (&Pcrs, sizeof (TPML_PCR_SELECTION));
>     +    Status = Tpm2GetCapabilityPcrs (&Pcrs);
>     +
>     +    if (EFI_ERROR (Status)) {
>     +      DEBUG ((DEBUG_ERROR, "Tpm2GetCapabilityPcrs fail!\n"));
>     +      break;
>     +    }
>     +
>     +    DEBUG ((DEBUG_ERROR, "Tpm2GetCapabilityPcrs - %08x\n",
>     Pcrs.count));
>     +
>     +    for (Index = 0; Index < Pcrs.count; Index++) {
>     +      DEBUG ((DEBUG_ERROR, "alg - %x\n",
>     Pcrs.pcrSelections[Index].hash));
>     +
>     +      switch (Pcrs.pcrSelections[Index].hash) {
>     +      case TPM_ALG_SHA1:
>     +        DigestSize = SHA1_DIGEST_SIZE;
>     +        break;
>     +      case TPM_ALG_SHA256:
>     +        DigestSize = SHA256_DIGEST_SIZE;
>     +        break;
>     +      case TPM_ALG_SHA384:
>     +        DigestSize = SHA384_DIGEST_SIZE;
>     +        break;
>     +      case TPM_ALG_SHA512:
>     +        DigestSize = SHA512_DIGEST_SIZE;
>     +        break;
>     +      case TPM_ALG_SM3_256:
>     +        DigestSize = SM3_256_DIGEST_SIZE;
>     +        break;
>     +      default:
>     +        DigestSize = SHA1_DIGEST_SIZE;
>     +        break;
>     +      }
>     +
>     +      if (DigestSize > mAuthSize) {
>     +        mAuthSize = DigestSize;
>     +      }
>     +    }
>     +    break;
>     +  }
>     +
>     +  *AuthSize = mAuthSize;
>     +  return Status;
>     +}
>     +
>     +/**
>     +  Set PlatformAuth to random value.
>     +**/
>     +VOID
>     +RandomizePlatformAuth (
>     +  VOID
>     +  )
>     +{
>     +  EFI_STATUS                        Status;
>     +  UINT16                            AuthSize;
>     +  UINT8                             *Rand;
>     +  UINTN                             RandSize;
>     +  TPM2B_AUTH                        NewPlatformAuth;
>     +
>     +  //
>     +  // Send Tpm2HierarchyChange Auth with random value to avoid
>     PlatformAuth being null
>     +  //
>     +
>     +  GetAuthSize (&AuthSize);
>     +
>     +  ZeroMem (NewPlatformAuth.buffer, AuthSize);
>     +  NewPlatformAuth.size = AuthSize;
>     +
>     +  //
>     +  // Allocate one buffer to store random data.
>     +  //
>     +  RandSize = MAX_NEW_AUTHORIZATION_SIZE;
>     +  Rand = AllocatePool (RandSize);
>     +
>     +  RdRandGenerateEntropy (RandSize, Rand);
>     +  CopyMem (NewPlatformAuth.buffer, Rand, AuthSize);
>
>
> Why generate random data for MAX_NEW_AUTHORIZATION to only copy a 
> subset after?
>
>     +
>     +  FreePool (Rand);
>     +
>     +  //
>     +  // Send Tpm2HierarchyChangeAuth command with the new Auth value
>     +  //
>     +  Status = Tpm2HierarchyChangeAuth (TPM_RH_PLATFORM, NULL,
>     &NewPlatformAuth);
>     +  DEBUG ((DEBUG_INFO, "Tpm2HierarchyChangeAuth Result: - %r\n",
>     Status));
>     +  ZeroMem (NewPlatformAuth.buffer, AuthSize);
>     +  ZeroMem (Rand, RandSize);
>
>
> Isn't Rand free at this point?


Indeed!


>
>     +}
>     +
>     +/**
>     +   This service defines the configuration of the Platform
>     Hierarchy Authorization Value (platformAuth)
>     +   and Platform Hierarchy Authorization Policy (platformPolicy)
>     +
>     +**/
>     +VOID
>     +EFIAPI
>     +ConfigureTpmPlatformHierarchy (
>     +  )
>     +{
>     +  RandomizePlatformAuth ();
>     +}
>     diff --git
>     a/OvmfPkg/Library/PeiDxeTpmPlatformHierarchyLib/PeiDxeTpmPlatformHierarchyLib.inf
>     b/OvmfPkg/Library/PeiDxeTpmPlatformHierarchyLib/PeiDxeTpmPlatformHierarchyLib.inf
>     new file mode 100644
>     index 0000000000..a413e02302
>     --- /dev/null
>     +++
>     b/OvmfPkg/Library/PeiDxeTpmPlatformHierarchyLib/PeiDxeTpmPlatformHierarchyLib.inf
>     @@ -0,0 +1,40 @@
>     +### @file
>     +#
>     +#   TPM Platform Hierarchy configuration library.
>     +#
>     +#   This library provides functions for customizing the TPM's
>     Platform Hierarchy
>     +#   Authorization Value (platformAuth) and Platform Hierarchy
>     Authorization
>     +#   Policy (platformPolicy) can be defined through this function.
>     +#
>     +# Copyright (c) 2019, Intel Corporation. All rights reserved.<BR>
>     +# Copyright (c) Microsoft Corporation.<BR>
>     +#
>     +# SPDX-License-Identifier: BSD-2-Clause-Patent
>     +#
>     +###
>     +
>     +[Defines]
>     +  INF_VERSION                    = 0x00010005
>     +  BASE_NAME                      = PeiDxeTpmPlatformHierarchyLib
>     +  FILE_GUID                      =
>     7794F92C-4E8E-4E57-9E4A-49A0764C7D73
>     +  MODULE_TYPE                    = PEIM
>     +  VERSION_STRING                 = 1.0
>     +  LIBRARY_CLASS                  = TpmPlatformHierarchyLib|PEIM
>     DXE_DRIVER
>     +
>     +[LibraryClasses]
>     +  BaseLib
>     +  BaseMemoryLib
>     +  DebugLib
>     +  MemoryAllocationLib
>     +  RngLib
>     +  Tpm2CommandLib
>     +  Tpm2DeviceLib
>     +
>     +[Packages]
>     +  MdePkg/MdePkg.dec
>     +  MdeModulePkg/MdeModulePkg.dec
>     +  SecurityPkg/SecurityPkg.dec
>     +  CryptoPkg/CryptoPkg.dec
>     +
>     +[Sources]
>     +  PeiDxeTpmPlatformHierarchyLib.c
>     -- 
>     2.31.1
>
> 

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