path: root/Features/Intel/UserInterface/UserAuthFeaturePkg/UserAuthenticationDxeSmm/UserAuthenticationSmm.c

/** @file

  Copyright (c) 2019 - 2023, Intel Corporation. All rights reserved.<BR>
  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include "UserAuthenticationSmm.h"

EFI_SMM_VARIABLE_PROTOCOL       *mSmmVariable;

UINTN                           mAdminPasswordTryCount = 0;

BOOLEAN                         mNeedReVerify = TRUE;
BOOLEAN                         mPasswordVerified = FALSE;
EFI_HANDLE                      mSmmHandle = NULL;

/**
  Verify if the password is correct.

  @param[in]  Password               The user input password.
  @param[in]  PasswordSize           The size of Password in byte.
  @param[in]  UserPasswordVarStruct  The storage of password in variable.

  @retval EFI_SUCCESS              The password is correct.
  @retval EFI_SECURITY_VIOLATION   The password is incorrect.
**/
EFI_STATUS
VerifyPassword (
  IN CHAR8                          *Password,
  IN UINTN                          PasswordSize,
  IN USER_PASSWORD_VAR_STRUCT       *UserPasswordVarStruct
  )
{
  BOOLEAN  HashOk;
  UINT8    HashData[PASSWORD_HASH_SIZE];

  HashOk = KeyLibGeneratePBKDF2Hash (
             HASH_TYPE_SHA256,
             (UINT8 *)Password,
             PasswordSize,
             UserPasswordVarStruct->PasswordSalt,
             sizeof(UserPasswordVarStruct->PasswordSalt),
             HashData,
             sizeof(HashData)
             );
  if (!HashOk) {
    return EFI_DEVICE_ERROR;
  }
  if (KeyLibSlowCompareMem (UserPasswordVarStruct->PasswordHash, HashData, PASSWORD_HASH_SIZE) == 0) {
    return EFI_SUCCESS;
  } else {
    return EFI_SECURITY_VIOLATION;
  }
}

/**
  Get hash data of password from non-volatile variable region.

  @param[in]   UserGuid               The user GUID of the password variable.
  @param[in]   Index                  The index of the password.
                                      0 means current password.
                                      Non-0 means the password history.
  @param[out]  UserPasswordVarStruct  The storage of password in variable.

  @retval EFI_SUCCESS             The password hash is returned successfully.
  @retval EFI_NOT_FOUND           The password hash is not found.
**/
EFI_STATUS
GetPasswordHashFromVariable (
  IN  EFI_GUID                       *UserGuid,
  IN  UINTN                          Index,
  OUT USER_PASSWORD_VAR_STRUCT       *UserPasswordVarStruct
  )
{
  UINTN                             DataSize;
  CHAR16                            PasswordName[sizeof(USER_AUTHENTICATION_VAR_NAME)/sizeof(CHAR16) + 5];

  if (Index != 0) {
    UnicodeSPrint (PasswordName, sizeof (PasswordName), L"%s%04x", USER_AUTHENTICATION_VAR_NAME, Index);
  } else {
    UnicodeSPrint (PasswordName, sizeof (PasswordName), L"%s", USER_AUTHENTICATION_VAR_NAME);
  }

  DataSize = sizeof(*UserPasswordVarStruct);
  return mSmmVariable->SmmGetVariable (
                         PasswordName,
                         UserGuid,
                         NULL,
                         &DataSize,
                         UserPasswordVarStruct
                         );
}

/**
  Save password hash data to non-volatile variable region.

  @param[in]   UserGuid               The user GUID of the password variable.
  @param[in]   UserPasswordVarStruct  The storage of password in variable.

  @retval EFI_SUCCESS             The password hash is saved successfully.
  @retval EFI_OUT_OF_RESOURCES    Insufficient resources to save the password hash.
**/
EFI_STATUS
SavePasswordHashToVariable (
  IN EFI_GUID                       *UserGuid,
  IN USER_PASSWORD_VAR_STRUCT       *UserPasswordVarStruct
  )
{
  EFI_STATUS                        Status;

  if (UserPasswordVarStruct == NULL) {
    Status = mSmmVariable->SmmSetVariable (
                             USER_AUTHENTICATION_VAR_NAME,
                             UserGuid,
                             EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_NON_VOLATILE,
                             0,
                             NULL
                             );
  } else {
    Status = mSmmVariable->SmmSetVariable (
                             USER_AUTHENTICATION_VAR_NAME,
                             UserGuid,
                             EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_NON_VOLATILE,
                             sizeof(*UserPasswordVarStruct),
                             UserPasswordVarStruct
                             );
  }
  if (EFI_ERROR (Status)) {
    DEBUG ((DEBUG_ERROR, "SavePasswordHashToVariable fails with %r\n", Status));
  }

  return Status;
}

/**
  Save old password hash data to non-volatile variable region as history.

  The number of password history variable is limited.
  If all the password history variables are used, the new password history
  will override the oldest one.

  @param[in]   UserGuid               The user GUID of the password variable.
  @param[in]   UserPasswordVarStruct  The storage of password in variable.

  @retval EFI_SUCCESS             The password hash is saved successfully.
  @retval EFI_OUT_OF_RESOURCES    Insufficient resources to save the password hash.
**/
EFI_STATUS
SaveOldPasswordToHistory (
  IN EFI_GUID                       *UserGuid,
  IN USER_PASSWORD_VAR_STRUCT       *UserPasswordVarStruct
  )
{
  EFI_STATUS                        Status;
  UINTN                             DataSize;
  UINT32                            LastIndex;
  CHAR16                            PasswordName[sizeof(USER_AUTHENTICATION_VAR_NAME)/sizeof(CHAR16) + 5];

  DEBUG ((DEBUG_INFO, "SaveOldPasswordToHistory\n"));

  DataSize = sizeof(LastIndex);
  Status = mSmmVariable->SmmGetVariable (
                           USER_AUTHENTICATION_HISTORY_LAST_VAR_NAME,
                           UserGuid,
                           NULL,
                           &DataSize,
                           &LastIndex
                           );
  if (EFI_ERROR(Status)) {
    LastIndex = 0;
  }
  if (LastIndex >= PASSWORD_HISTORY_CHECK_COUNT) {
    LastIndex = 0;
  }

  LastIndex ++;
  UnicodeSPrint (PasswordName, sizeof (PasswordName), L"%s%04x", USER_AUTHENTICATION_VAR_NAME, LastIndex);


  Status = mSmmVariable->SmmSetVariable (
                           PasswordName,
                           UserGuid,
                           EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_NON_VOLATILE,
                           sizeof(*UserPasswordVarStruct),
                           UserPasswordVarStruct
                           );
  DEBUG ((DEBUG_INFO, "  -- to %s, %r\n", PasswordName, Status));
  if (!EFI_ERROR(Status)) {
    Status = mSmmVariable->SmmSetVariable (
                             USER_AUTHENTICATION_HISTORY_LAST_VAR_NAME,
                             UserGuid,
                             EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_NON_VOLATILE,
                             sizeof(LastIndex),
                             &LastIndex
                             );
    DEBUG ((DEBUG_INFO, " LastIndex - 0x%04x, %r\n", LastIndex, Status));
  }

  return Status;
}

/**
  Calculate password hash data and save it to non-volatile variable region.

  @param[in]  UserGuid               The user GUID of the password variable.
  @param[in]  Password               The user input password.
                                     NULL means delete the password variable.
  @param[in]  PasswordSize           The size of Password in byte.

  @retval EFI_SUCCESS             The password hash is calculated and saved.
  @retval EFI_OUT_OF_RESOURCES    Insufficient resources to save the password hash.
**/
EFI_STATUS
SavePasswordToVariable (
  IN  EFI_GUID                      *UserGuid,
  IN  CHAR8                         *Password,  OPTIONAL
  IN  UINTN                         PasswordSize
  )
{
  EFI_STATUS                        Status;
  USER_PASSWORD_VAR_STRUCT          UserPasswordVarStruct;
  BOOLEAN                           HashOk;

  //
  // If password is NULL, it means we want to clean password field saved in variable region.
  //
  if (Password != NULL) {
    KeyLibGenerateSalt (UserPasswordVarStruct.PasswordSalt, sizeof(UserPasswordVarStruct.PasswordSalt));
    HashOk = KeyLibGeneratePBKDF2Hash (
               HASH_TYPE_SHA256,
               (UINT8 *)Password,
               PasswordSize,
               UserPasswordVarStruct.PasswordSalt,
               sizeof(UserPasswordVarStruct.PasswordSalt),
               UserPasswordVarStruct.PasswordHash,
               sizeof(UserPasswordVarStruct.PasswordHash)
               );
    if (!HashOk) {
      return EFI_DEVICE_ERROR;
    }
    Status = SavePasswordHashToVariable (UserGuid, &UserPasswordVarStruct);
    //
    // Save Password data to history variable
    //
    if (!EFI_ERROR(Status)) {
      SaveOldPasswordToHistory (UserGuid, &UserPasswordVarStruct);
    }
  } else {
    Status = SavePasswordHashToVariable (UserGuid, NULL);
  }

  return Status;
}

/**
  Verify the password.
  If the password variable does not exist, it passes the verification.
  If the password variable exists, it does verification based upon password variable.

  @param[in]  UserGuid               The user GUID of the password variable.
  @param[in]  Password               The user input password.
  @param[in]  PasswordSize           The size of Password in byte.

  @retval TRUE    The verification passes.
  @retval FALSE   The verification fails.
**/
BOOLEAN
IsPasswordVerified (
  IN EFI_GUID                       *UserGuid,
  IN CHAR8                          *Password,
  IN UINTN                          PasswordSize
  )
{
  USER_PASSWORD_VAR_STRUCT          UserPasswordVarStruct;
  EFI_STATUS                        Status;
  UINTN                             *PasswordTryCount;

  PasswordTryCount = &mAdminPasswordTryCount;

  Status = GetPasswordHashFromVariable (UserGuid, 0, &UserPasswordVarStruct);
  if (EFI_ERROR(Status)) {
    return TRUE;
  }

  //
  // Old password exists
  //
  Status = VerifyPassword (Password, PasswordSize, &UserPasswordVarStruct);
  if (EFI_ERROR(Status)) {
    if (Password[0] != 0) {
      *PasswordTryCount = *PasswordTryCount + 1;
    }
    return FALSE;
  }

  return TRUE;
}

/**
  Return if the password is set.

  @param[in]  UserGuid               The user GUID of the password variable.

  @retval TRUE    The password is set.
  @retval FALSE   The password is not set.
**/
BOOLEAN
IsPasswordSet (
  IN EFI_GUID                       *UserGuid
  )
{
  USER_PASSWORD_VAR_STRUCT          UserPasswordVarStruct;
  EFI_STATUS                        Status;

  Status = GetPasswordHashFromVariable(UserGuid, 0, &UserPasswordVarStruct);
  if (EFI_ERROR(Status)) {
    return FALSE;
  }
  return TRUE;
}

/**
  Return if the password is strong.
  Criteria:
  1) length >= PASSWORD_MIN_SIZE
  2) include lower case, upper case, number, symbol.

  @param[in]  Password               The user input password.
  @param[in]  PasswordSize           The size of Password in byte.

  @retval TRUE    The password is strong.
  @retval FALSE   The password is weak.
**/
BOOLEAN
IsPasswordStrong (
  IN CHAR8   *Password,
  IN UINTN   PasswordSize
  )
{
  UINTN   Index;
  BOOLEAN HasLowerCase;
  BOOLEAN HasUpperCase;
  BOOLEAN HasNumber;
  BOOLEAN HasSymbol;

  if (PasswordSize < PASSWORD_MIN_SIZE) {
    return FALSE;
  }

  HasLowerCase = FALSE;
  HasUpperCase = FALSE;
  HasNumber = FALSE;
  HasSymbol = FALSE;
  for (Index = 0; Index < PasswordSize - 1; Index++) {
    if (Password[Index] >= 'a' && Password[Index] <= 'z') {
      HasLowerCase = TRUE;
    } else if (Password[Index] >= 'A' && Password[Index] <= 'Z') {
      HasUpperCase = TRUE;
    } else if (Password[Index] >= '0' && Password[Index] <= '9') {
      HasNumber = TRUE;
    } else {
      HasSymbol = TRUE;
    }
  }
  if ((!HasLowerCase) || (!HasUpperCase) || (!HasNumber) || (!HasSymbol)) {
    return FALSE;
  }
  return TRUE;
}

/**
  Return if the password is set before in PASSWORD_HISTORY_CHECK_COUNT.

  @param[in]  UserGuid               The user GUID of the password variable.
  @param[in]  Password               The user input password.
  @param[in]  PasswordSize           The size of Password in byte.

  @retval TRUE    The password is set before.
  @retval FALSE   The password is not set before.
**/
BOOLEAN
IsPasswordInHistory (
  IN EFI_GUID                       *UserGuid,
  IN CHAR8                          *Password,
  IN UINTN                          PasswordSize
  )
{
  EFI_STATUS                     Status;
  USER_PASSWORD_VAR_STRUCT       UserPasswordVarStruct;
  UINTN                          Index;

  for (Index = 1; Index <= PASSWORD_HISTORY_CHECK_COUNT; Index++) {
    Status = GetPasswordHashFromVariable (UserGuid, Index, &UserPasswordVarStruct);
    if (!EFI_ERROR(Status)) {
      Status = VerifyPassword (Password, PasswordSize, &UserPasswordVarStruct);
      if (!EFI_ERROR(Status)) {
        return TRUE;
      }
    }
  }

  return FALSE;
}

/**
  Communication service SMI Handler entry.

  This SMI handler provides services for password management.

  @param[in]     DispatchHandle  The unique handle assigned to this handler by SmiHandlerRegister().
  @param[in]     RegisterContext Points to an optional handler context which was specified when the
                                 handler was registered.
  @param[in, out] CommBuffer     A pointer to a collection of data in memory that will
                                 be conveyed from a non-SMM environment into an SMM environment.
  @param[in, out] CommBufferSize The size of the CommBuffer.

  @retval EFI_SUCCESS                         The interrupt was handled and quiesced. No other handlers
                                              should still be called.
  @retval EFI_WARN_INTERRUPT_SOURCE_QUIESCED  The interrupt has been quiesced but other handlers should
                                              still be called.
  @retval EFI_WARN_INTERRUPT_SOURCE_PENDING   The interrupt is still pending and other handlers should still
                                              be called.
  @retval EFI_INTERRUPT_PENDING               The interrupt could not be quiesced.
**/
EFI_STATUS
EFIAPI
SmmPasswordHandler (
  IN     EFI_HANDLE                 DispatchHandle,
  IN     CONST VOID                 *RegisterContext,
  IN OUT VOID                       *CommBuffer,
  IN OUT UINTN                      *CommBufferSize
  )
{
  EFI_STATUS                                Status;
  SMM_PASSWORD_COMMUNICATE_HEADER           *SmmFunctionHeader;
  UINTN                                     CommBufferPayloadSize;
  UINTN                                     TempCommBufferSize;
  SMM_PASSWORD_COMMUNICATE_SET_PASSWORD     SmmCommunicateSetPassword;
  SMM_PASSWORD_COMMUNICATE_VERIFY_PASSWORD  SmmCommunicateVerifyPassword;
  SMM_PASSWORD_COMMUNICATE_VERIFY_POLICY    SmmCommunicateSetVerifyPolicy;
  SMM_PASSWORD_COMMUNICATE_VERIFY_POLICY    *SmmCommunicateGetVerifyPolicy;
  UINTN                                     PasswordLen;
  EFI_GUID                                  *UserGuid;
  UINTN                                     *PasswordTryCount;

  //
  // If input is invalid, stop processing this SMI
  //
  if (CommBuffer == NULL || CommBufferSize == NULL) {
    return EFI_SUCCESS;
  }

  TempCommBufferSize = *CommBufferSize;
  PasswordLen = 0;

  if (TempCommBufferSize < sizeof (SMM_PASSWORD_COMMUNICATE_HEADER)) {
    DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: SMM communication buffer size invalid!\n"));
    return EFI_SUCCESS;
  }

  CommBufferPayloadSize = TempCommBufferSize - sizeof (SMM_PASSWORD_COMMUNICATE_HEADER);

  Status   = EFI_SUCCESS;
  SmmFunctionHeader = (SMM_PASSWORD_COMMUNICATE_HEADER *)CommBuffer;

  UserGuid = &gUserAuthenticationGuid;
  PasswordTryCount = &mAdminPasswordTryCount;

  switch (SmmFunctionHeader->Function) {
  case SMM_PASSWORD_FUNCTION_IS_PASSWORD_SET:
    PasswordTryCount = NULL;
    if (CommBufferPayloadSize != 0) {
      DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: IS_PASSWORD_SET payload buffer invalid!\n"));
      Status = EFI_INVALID_PARAMETER;
      goto EXIT;
    }
    if (IsPasswordSet(UserGuid)) {
      Status = EFI_SUCCESS;
    } else {
      Status = EFI_NOT_FOUND;
    }
    break;
  case SMM_PASSWORD_FUNCTION_SET_PASSWORD:
    if (*PasswordTryCount >= PASSWORD_MAX_TRY_COUNT) {
      DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: SET_PASSWORD try count reach!\n"));
      PasswordTryCount = NULL;
      Status = EFI_ACCESS_DENIED;
      goto EXIT;
    }
    if (CommBufferPayloadSize != sizeof(SMM_PASSWORD_COMMUNICATE_SET_PASSWORD)) {
      DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: SET_PASSWORD payload buffer invalid!\n"));
      Status = EFI_INVALID_PARAMETER;
      goto EXIT;
    }
    CopyMem (&SmmCommunicateSetPassword, SmmFunctionHeader + 1, sizeof(SmmCommunicateSetPassword));

    PasswordLen = AsciiStrnLenS(SmmCommunicateSetPassword.OldPassword, sizeof(SmmCommunicateSetPassword.OldPassword));
    if (PasswordLen == sizeof(SmmCommunicateSetPassword.OldPassword)) {
      DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: OldPassword invalid!\n"));
      Status = EFI_INVALID_PARAMETER;
      goto EXIT;
    }

    if (!IsPasswordVerified (UserGuid, SmmCommunicateSetPassword.OldPassword, PasswordLen + 1)) {
      DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: PasswordVerify - FAIL\n"));
      if (*PasswordTryCount >= PASSWORD_MAX_TRY_COUNT) {
        DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: SET_PASSWORD try count reach!\n"));
        Status = EFI_ACCESS_DENIED;
      } else {
        Status = EFI_SECURITY_VIOLATION;
      }
      goto EXIT;
    }

    PasswordLen = AsciiStrnLenS(SmmCommunicateSetPassword.NewPassword, sizeof(SmmCommunicateSetPassword.NewPassword));
    if (PasswordLen == sizeof(SmmCommunicateSetPassword.NewPassword)) {
      DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: NewPassword invalid!\n"));
      Status = EFI_INVALID_PARAMETER;
      goto EXIT;
    }
    if (PasswordLen != 0 && !IsPasswordStrong (SmmCommunicateSetPassword.NewPassword, PasswordLen + 1)) {
      DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: NewPassword too weak!\n"));
      Status = EFI_UNSUPPORTED;
      goto EXIT;
    }
    if (PasswordLen != 0 && IsPasswordInHistory (UserGuid, SmmCommunicateSetPassword.NewPassword, PasswordLen + 1)) {
      DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: NewPassword in history!\n"));
      Status = EFI_ALREADY_STARTED;
      goto EXIT;
    }

    if (PasswordLen == 0) {
      Status = SavePasswordToVariable (UserGuid, NULL, 0);
    } else {
      Status = SavePasswordToVariable (UserGuid, SmmCommunicateSetPassword.NewPassword, PasswordLen + 1);
    }
    break;

  case SMM_PASSWORD_FUNCTION_VERIFY_PASSWORD:
    if (*PasswordTryCount >= PASSWORD_MAX_TRY_COUNT) {
      DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: VERIFY_PASSWORD try count reach!\n"));
      PasswordTryCount = NULL;
      Status = EFI_ACCESS_DENIED;
      goto EXIT;
    }
    if (CommBufferPayloadSize != sizeof(SMM_PASSWORD_COMMUNICATE_VERIFY_PASSWORD)) {
      DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: VERIFY_PASSWORD payload buffer invalid!\n"));
      Status = EFI_INVALID_PARAMETER;
      goto EXIT;
    }
    CopyMem (&SmmCommunicateVerifyPassword, SmmFunctionHeader + 1, sizeof(SmmCommunicateVerifyPassword));

    PasswordLen = AsciiStrnLenS(SmmCommunicateVerifyPassword.Password, sizeof(SmmCommunicateVerifyPassword.Password));
    if (PasswordLen == sizeof(SmmCommunicateVerifyPassword.Password)) {
      DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: Password invalid!\n"));
      Status = EFI_INVALID_PARAMETER;
      goto EXIT;
    }
    if (!IsPasswordVerified (UserGuid, SmmCommunicateVerifyPassword.Password, PasswordLen + 1)) {
      DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: PasswordVerify - FAIL\n"));
      if (*PasswordTryCount >= PASSWORD_MAX_TRY_COUNT) {
        DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: VERIFY_PASSWORD try count reach!\n"));
        Status = EFI_ACCESS_DENIED;
      } else {
        Status = EFI_SECURITY_VIOLATION;
      }
      goto EXIT;
    }
    mPasswordVerified = TRUE;
    Status = EFI_SUCCESS;
    break;

  case SMM_PASSWORD_FUNCTION_SET_VERIFY_POLICY:
    PasswordTryCount = NULL;
    if (CommBufferPayloadSize != sizeof(SMM_PASSWORD_COMMUNICATE_VERIFY_POLICY)) {
      DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: SET_VERIFY_POLICY payload buffer invalid!\n"));
      Status = EFI_INVALID_PARAMETER;
      goto EXIT;
    }
    CopyMem (&SmmCommunicateSetVerifyPolicy, SmmFunctionHeader + 1, sizeof(SmmCommunicateSetVerifyPolicy));
    mNeedReVerify = SmmCommunicateSetVerifyPolicy.NeedReVerify;
    break;

  case SMM_PASSWORD_FUNCTION_GET_VERIFY_POLICY:
    PasswordTryCount = NULL;
    if (CommBufferPayloadSize != sizeof(SMM_PASSWORD_COMMUNICATE_VERIFY_POLICY)) {
      DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: GET_VERIFY_POLICY payload buffer invalid!\n"));
      Status = EFI_INVALID_PARAMETER;
      goto EXIT;
    }
    SmmCommunicateGetVerifyPolicy = (SMM_PASSWORD_COMMUNICATE_VERIFY_POLICY *) (SmmFunctionHeader + 1);
    SmmCommunicateGetVerifyPolicy->NeedReVerify = mNeedReVerify;
    break;
  case SMM_PASSWORD_FUNCTION_WAS_PASSWORD_VERIFIED:
    PasswordTryCount = NULL;
    if (CommBufferPayloadSize != 0) {
      DEBUG ((DEBUG_ERROR, "SmmPasswordHandler: WAS_PASSWORD_VERIFIED payload buffer invalid!\n"));
      Status = EFI_INVALID_PARAMETER;
      goto EXIT;
    }
    if (mPasswordVerified) {
      Status = EFI_SUCCESS;
    } else {
      Status = EFI_NOT_STARTED;
    }
    break;

  default:
    PasswordTryCount = NULL;
    Status = EFI_UNSUPPORTED;
    break;
  }

EXIT:
  if (PasswordTryCount != NULL) {
    if (Status == EFI_SUCCESS) {
      *PasswordTryCount = 0;
    }
  }
  SmmFunctionHeader->ReturnStatus = Status;

  return EFI_SUCCESS;
}

/**
  Performs Exit Boot Services UserAuthentication actions

  @param[in] Protocol   Points to the protocol's unique identifier.
  @param[in] Interface  Points to the interface instance.
  @param[in] Handle     The handle on which the interface was installed.

  @retval EFI_SUCCESS   Notification runs successfully.
**/
EFI_STATUS
EFIAPI
UaExitBootServices (
  IN CONST EFI_GUID     *Protocol,
  IN VOID               *Interface,
  IN EFI_HANDLE         Handle
  )
{
  DEBUG ((DEBUG_INFO, "Unregister User Authentication Smi\n"));

  gMmst->MmiHandlerUnRegister(mSmmHandle);

  return EFI_SUCCESS;
}

/**
  Main entry for this driver.

  @param ImageHandle     Image handle this driver.
  @param SystemTable     Pointer to SystemTable.

  @retval EFI_SUCESS     This function always complete successfully.

**/
EFI_STATUS
PasswordSmmInit (
  VOID
  )
{
  EFI_STATUS                            Status;
  EFI_EVENT                             ExitBootServicesEvent;
  EFI_EVENT                             LegacyBootEvent;
  EFI_EVENT                             SmmExitBootServicesEvent;

  ASSERT (PASSWORD_HASH_SIZE == SHA256_DIGEST_SIZE);
  ASSERT (PASSWORD_HISTORY_CHECK_COUNT < 0xFFFF);

  Status = gMmst->MmLocateProtocol (&gEfiSmmVariableProtocolGuid, NULL, (VOID**)&mSmmVariable);
  ASSERT_EFI_ERROR (Status);

  //
  // Make password variables read-only for DXE driver for security concern.
  //
  Status = LockPasswordVariable ();
  ASSERT_EFI_ERROR (Status);
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Status = gMmst->MmiHandlerRegister (SmmPasswordHandler, &gUserAuthenticationGuid, &mSmmHandle);
  ASSERT_EFI_ERROR (Status);
  if (EFI_ERROR (Status)) {
    return Status;
  }

  //
  // Register for SmmExitBootServices, SmmLegacyBoot and EventExitBootServices notification.
  //
  Status = gMmst->MmRegisterProtocolNotify (&gEdkiiSmmExitBootServicesProtocolGuid, UaExitBootServices, &SmmExitBootServicesEvent);
  ASSERT_EFI_ERROR (Status);
  Status = gMmst->MmRegisterProtocolNotify (&gEdkiiSmmLegacyBootProtocolGuid, UaExitBootServices, &LegacyBootEvent);
  ASSERT_EFI_ERROR (Status);
  Status = gMmst->MmRegisterProtocolNotify (&gEfiEventExitBootServicesGuid, UaExitBootServices, &ExitBootServicesEvent);
  ASSERT_EFI_ERROR (Status);

  if (IsPasswordCleared()) {
    DEBUG ((DEBUG_INFO, "IsPasswordCleared\n"));
    SavePasswordToVariable (&gUserAuthenticationGuid, NULL, 0);
  }

  return EFI_SUCCESS;
}