system76-edk2/SecurityPkg/Tcg/MemoryOverwriteRequestControlLock/TcgMorLock.c

/** @file
  TCG MOR (Memory Overwrite Request) Lock Control Driver.

  This driver initilize MemoryOverwriteRequestControlLock variable.
  This module will add Variable Hook and allow MemoryOverwriteRequestControlLock variable set only once.

Copyright (c) 2015, Intel Corporation. All rights reserved.<BR>
This program and the accompanying materials 
are licensed and made available under the terms and conditions of the BSD License 
which accompanies this distribution.  The full text of the license may be found at 
http://opensource.org/licenses/bsd-license.php

THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, 
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

**/

#include <PiDxe.h>
#include <Guid/MemoryOverwriteControl.h>
#include <IndustryStandard/MemoryOverwriteRequestControlLock.h>
#include <Library/DebugLib.h>
#include <Library/BaseLib.h>
#include <Library/BaseMemoryLib.h>
#include "TcgMorLock.h"

typedef struct {
  CHAR16                                 *VariableName;
  EFI_GUID                               *VendorGuid;
} VARIABLE_TYPE;

VARIABLE_TYPE  mMorVariableType[] = {
  {MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,      &gEfiMemoryOverwriteControlDataGuid},
  {MEMORY_OVERWRITE_REQUEST_CONTROL_LOCK_NAME,  &gEfiMemoryOverwriteRequestControlLockGuid},
};

/**
  Returns if this is MOR related variable.

  @param  VariableName the name of the vendor's variable, it's a Null-Terminated Unicode String
  @param  VendorGuid   Unify identifier for vendor.

  @retval  TRUE            The variable is MOR related.
  @retval  FALSE           The variable is NOT MOR related.
**/
BOOLEAN
IsAnyMorVariable (
  IN CHAR16                                 *VariableName,
  IN EFI_GUID                               *VendorGuid
  )
{
  UINTN   Index;

  for (Index = 0; Index < sizeof(mMorVariableType)/sizeof(mMorVariableType[0]); Index++) {
    if ((StrCmp (VariableName, mMorVariableType[Index].VariableName) == 0) && 
        (CompareGuid (VendorGuid, mMorVariableType[Index].VendorGuid))) {
      return TRUE;
    }
  }
  return FALSE;
}

/**
  Returns if this is MOR lock variable.

  @param  VariableName the name of the vendor's variable, it's a Null-Terminated Unicode String
  @param  VendorGuid   Unify identifier for vendor.

  @retval  TRUE            The variable is MOR lock variable.
  @retval  FALSE           The variable is NOT MOR lock variable.
**/
BOOLEAN
IsMorLockVariable (
  IN CHAR16                                 *VariableName,
  IN EFI_GUID                               *VendorGuid
  )
{
  if ((StrCmp (VariableName, MEMORY_OVERWRITE_REQUEST_CONTROL_LOCK_NAME) == 0) && 
      (CompareGuid (VendorGuid, &gEfiMemoryOverwriteRequestControlLockGuid))) {
    return TRUE;
  }
  return FALSE;
}

/**
  This service is a checker handler for the UEFI Runtime Service SetVariable()

  @param  VariableName the name of the vendor's variable, as a
                       Null-Terminated Unicode String
  @param  VendorGuid   Unify identifier for vendor.
  @param  Attributes   Point to memory location to return the attributes of variable. If the point
                       is NULL, the parameter would be ignored.
  @param  DataSize     The size in bytes of Data-Buffer.
  @param  Data         Point to the content of the variable.

  @retval  EFI_SUCCESS            The firmware has successfully stored the variable and its data as
                                  defined by the Attributes.
  @retval  EFI_INVALID_PARAMETER  An invalid combination of attribute bits was supplied, or the
                                  DataSize exceeds the maximum allowed.
  @retval  EFI_INVALID_PARAMETER  VariableName is an empty Unicode string.
  @retval  EFI_OUT_OF_RESOURCES   Not enough storage is available to hold the variable and its data.
  @retval  EFI_DEVICE_ERROR       The variable could not be saved due to a hardware failure.
  @retval  EFI_WRITE_PROTECTED    The variable in question is read-only.
  @retval  EFI_WRITE_PROTECTED    The variable in question cannot be deleted.
  @retval  EFI_SECURITY_VIOLATION The variable could not be written due to EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS
                                  set but the AuthInfo does NOT pass the validation check carried
                                  out by the firmware.
  @retval  EFI_NOT_FOUND          The variable trying to be updated or deleted was not found.

**/
EFI_STATUS
EFIAPI
SetVariableCheckHandlerMor (
  IN CHAR16     *VariableName,
  IN EFI_GUID   *VendorGuid,
  IN UINT32     Attributes,
  IN UINTN      DataSize,
  IN VOID       *Data
  )
{
  UINTN       MorLockDataSize;
  BOOLEAN     MorLock;
  EFI_STATUS  Status;

  //
  // do not handle non-MOR variable
  //
  if (!IsAnyMorVariable (VariableName, VendorGuid)) {
    return EFI_SUCCESS;
  }

  MorLockDataSize = sizeof(MorLock);
  Status = InternalGetVariable (
             MEMORY_OVERWRITE_REQUEST_CONTROL_LOCK_NAME,
             &gEfiMemoryOverwriteRequestControlLockGuid,
             NULL,
             &MorLockDataSize,
             &MorLock
             );
  if (!EFI_ERROR (Status) && MorLock) {
    //
    // If lock, deny access
    //
    return EFI_INVALID_PARAMETER;
  }
  
  //
  // Delete not OK
  //
  if ((DataSize != sizeof(UINT8)) || (Data == NULL) || (Attributes == 0)) {
    return EFI_INVALID_PARAMETER;
  }

  //
  // check format
  //
  if (IsMorLockVariable(VariableName, VendorGuid)) {
    //
    // set to any other value not OK
    //
    if ((*(UINT8 *)Data != 1) && (*(UINT8 *)Data != 0)) {
      return EFI_INVALID_PARAMETER;
    }
  }
  //
  // Or grant access
  //
  return EFI_SUCCESS;
}

/**
  Entry Point for MOR Lock Control driver.

  @param[in] ImageHandle  Image handle of this driver.
  @param[in] SystemTable  A Pointer to the EFI System Table.

  @retval EFI_SUCEESS     
  @return Others          Some error occurs.
**/
EFI_STATUS
EFIAPI
MorLockDriverInit (
  VOID
  )
{
  EFI_STATUS  Status;
  UINT8       Data;

  Data = 0;
  Status = InternalSetVariable (
             MEMORY_OVERWRITE_REQUEST_CONTROL_LOCK_NAME,
             &gEfiMemoryOverwriteRequestControlLockGuid,
             EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
             1,
             &Data
             );
  return Status;
}