edk2整体架构

关于安全校验的核心逻辑

Code\Edk2\MdeModulePkg\Universal\SecurityStubDxe\SecurityStub.c

  Status = gBS->InstallMultipleProtocolInterfaces (
                  &mSecurityArchProtocolHandle,
                  &gEfiSecurity2ArchProtocolGuid,
                  &mSecurity2Stub,
                  &gEfiSecurityArchProtocolGuid,
                  &mSecurityStub,
                  &gSecurityManagementProtocolGuid,
                  &mSecurityManagement,
                  NULL
                  );

Code\Edk2\MdeModulePkg\Core\PiSmmCore\Dispatcher.c

  if (mSecurity2 == NULL) {
    gBS->LocateProtocol (&gEfiSecurity2ArchProtocolGuid, NULL, (VOID**)&mSecurity2);
  }
  if (mSecurity == NULL) {
    gBS->LocateProtocol (&gEfiSecurityArchProtocolGuid, NULL, (VOID**)&mSecurity);
  }

Code\Edk2\MdeModulePkg\Core\PiSmmCore\Dispatcher.c

    SecurityStatus = mSecurity2->FileAuthentication (
                                  mSecurity2,
                                  OriginalFilePath,
                                  Buffer,
                                  Size,
                                  FALSE
                                  );

    SecurityStatus = mSecurity->FileAuthenticationState (
                                  mSecurity,
                                  AuthenticationStatus,
                                  OriginalFilePath
                                  );

这三段分别是注册安全句柄，获取安全句柄和使用安全句柄，所有的安全逻辑貌似都是从这里触发的。

再往核心出发就可以看到：
EFI_SECURITY_ARCH_PROTOCOL mSecurityStub = {
SecurityStubAuthenticateState
};

EFI_SECURITY2_ARCH_PROTOCOL mSecurity2Stub = {
Security2StubAuthenticate
};

以及Security2StubAuthenticate的实现：

可以发现stub 又由RegisterSecurity2Handler注册。

这边注册由较多的安全校验函数如下：

DxeImageAuthenticationStatusHandler                //未找到调用处
DxeImageVerificationHandler
DxeTpm2MeasureBootHandler
DxeTpmMeasureBootHandler                           //未找到调用处
DxePlatformImageVerificationHandler                //未找到调用处

其中Code\Build\AlderLakeIoTPkg\DEBUG_VS2017\X64\MdeModulePkg\Universal\SecurityStubDxe\SecurityStubDxe\DEBUG\AutoGen.c

VOID
EFIAPI
ProcessLibraryConstructorList (
  IN EFI_HANDLE        ImageHandle,
  IN EFI_SYSTEM_TABLE  *SystemTable
  )
{
  EFI_STATUS  Status;
......

  Status = DxeImageVerificationLibConstructor (ImageHandle, SystemTable);
  ASSERT_EFI_ERROR (Status);

  Status = DxeTpm2MeasureBootLibConstructor (ImageHandle, SystemTable);
  ASSERT_EFI_ERROR (Status);

}

再往上是_ModuleEntryPoint

FileAuthentication

所以结论是FileAuthentication 调用了DxeImageVerificationHandler / DxeTpm2MeasureBootHandler实现了镜像校验。

            Status = Tcg2MeasureGptTable (Tcg2Protocol, Handle);
            DEBUG ((EFI_D_INFO, "DxeTpm2MeasureBootHandler - Tcg2MeasureGptTable - %r\n", Status));

    DbStatus = IsSignatureFoundInDatabase (
                 EFI_IMAGE_SECURITY_DATABASE1,
                 mImageDigest,
                 &mCertType,
                 mImageDigestSize,
                 &IsFound
                 );
    if (EFI_ERROR (DbStatus) || IsFound) {
      //
      // Image Hash is in forbidden database (DBX).
      //
      DEBUG ((DEBUG_INFO, "DxeImageVerificationLib: Image is not signed and %s hash of image is forbidden by DBX.\n", mHashTypeStr));
      goto Done;
    }

调试开关和日志打印

  IN  CONST EFI_DEVICE_PATH_PROTOCOL   *File, OPTIONAL

  EFI_DEVICE_PATH_PROTOCOL            *DevicePathNode;
  EFI_DEVICE_PATH_PROTOCOL            *OrigDevicePathNode;
  OrigDevicePathNode = DuplicateDevicePath (File);

    DEBUG_CODE_BEGIN ();
      CHAR16                            *ToText;
      ToText = ConvertDevicePathToText (
                 DevicePathNode,
                 FALSE,
                 TRUE
                 );
      if (ToText != NULL) {
        DEBUG ((DEBUG_INFO, "The measured image path is %s.\n", ToText));
        FreePool (ToText);
      }
    DEBUG_CODE_END ();