如何保存原始函数的地址并在以后调用它？

Question

我正在尝试在 api 挂钩中调用原始函数，以防止 LdrLoadDll() 函数注入 dll，但每次我尝试加载过滤后的不同 dll 时，应用程序崩溃并且不可能调用原始函数。似乎我什么时候会在钩子之前保存“original_function”时做错了。

我在 Windows 7 x64 上进行测试，在 32 位应用程序中注入 32 位 dll（代码如下）。

如何解决这个问题？

program Project1;

{$APPTYPE CONSOLE}
{$R *.res}

uses
  Windows,
  SysUtils;

type
  NTSTATUS = Cardinal;
  PUNICODE_STRING = ^UNICODE_STRING;

  UNICODE_STRING = packed record
    Length: Word;
    MaximumLength: Word;
    Buffer: PWideChar;
  end;

const
  STATUS_ACCESS_DENIED = NTSTATUS($C0000022);

var
  Old_LdrLoadDll: function(szcwPath: PWideChar; dwFlags: DWORD;
    pUniModuleName: PUNICODE_STRING; pResultInstance: PPointer)
    : NTSTATUS; stdcall;

function LdrLoadDll(szcwPath: PWideChar; dwFlags: DWORD;
  pUniModuleName: PUNICODE_STRING; pResultInstance: PPointer)
  : NTSTATUS; stdcall;
begin
  Result := Old_LdrLoadDll(szcwPath, dwFlags, pUniModuleName, pResultInstance);
end;

procedure PatchCode(Address: Pointer; const NewCode; Size: Integer);
var
  OldProtect: DWORD;
begin
  if VirtualProtect(Address, Size, PAGE_EXECUTE_READWRITE, OldProtect) then
  begin
    Move(NewCode, Address^, Size);
    FlushInstructionCache(GetCurrentProcess, Address, Size);
    VirtualProtect(Address, Size, OldProtect, @OldProtect);
  end;
end;

type
  PInstruction = ^TInstruction;

  TInstruction = packed record
    Opcode: Byte;
    Offset: Integer;
  end;

procedure RedirectProcedure(OldAddress, NewAddress: Pointer);
var
  NewCode: TInstruction;
begin
  NewCode.Opcode := $E9;
  NewCode.Offset := NativeInt(NewAddress) - NativeInt(OldAddress) -
    SizeOf(NewCode);
  PatchCode(OldAddress, NewCode, SizeOf(NewCode));
end;

function NewLdrLoadDll(szcwPath: PWideChar; dwFlags: DWORD;
  pUniModuleName: PUNICODE_STRING; pResultInstance: PPointer)
  : NTSTATUS; stdcall;
begin
  if (pos('111', pUniModuleName.Buffer) > 0) or
    (pos('222', pUniModuleName.Buffer) > 0) then

    Result := STATUS_ACCESS_DENIED
  else
    Result := LdrLoadDll(szcwPath, dwFlags, pUniModuleName, pResultInstance);
end;

begin
  @Old_LdrLoadDll := GetProcAddress(GetModuleHandle('ntdll.dll'), 'LdrLoadDll');
  try
    RedirectProcedure(GetProcAddress(GetModuleHandle('ntdll.dll'),
      'LdrLoadDll'), @NewLdrLoadDll);
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
  Readln;

end.

Answer 1

我建议你不要使用自制的钩子，并为此获取现有的库。

Microsoft Detours 现在是免费和开源的。当它构建为 DLL 时，您可以将它与 Delphi 一起使用。

您将需要 C++ 编译器从源代码构建它，但 Visual Studio 社区又是免费的。

Answer 2

这是遵循@GolezTrol 建议后制作的一个工作代码：

program Project1;

{$APPTYPE CONSOLE}
{$R *.res}

uses
  Windows,
  SysUtils;

type
  NTSTATUS = Cardinal;
  PUNICODE_STRING = ^UNICODE_STRING;

  UNICODE_STRING = packed record
    Length: Word;
    MaximumLength: Word;
    Buffer: PWideChar;
  end;

const
  STATUS_ACCESS_DENIED = NTSTATUS($C0000022);

var
  Old_LdrLoadDll: function(szcwPath: PWideChar; dwFlags: DWORD;
    pUniModuleName: PUNICODE_STRING; pResultInstance: PPointer)
    : NTSTATUS; stdcall;

function LdrLoadDll(szcwPath: PWideChar; dwFlags: DWORD;
  pUniModuleName: PUNICODE_STRING; pResultInstance: PPointer)
  : NTSTATUS; stdcall;
begin
  Result := Old_LdrLoadDll(szcwPath, dwFlags, pUniModuleName, pResultInstance);
end;

type
  PInstruction = ^TInstruction;

  TInstruction = packed record
    Opcode: Byte;
    Offset: Integer;
  end;

//======= Structure to store original function ======== 

type
  TSaveOriginal = packed record
    Addr: Pointer;
    Bytes: array [0 .. SizeOf(TInstruction)] of Byte;
  end;

  PSaveOriginal = ^TSaveOriginal;

var
  SaveOriginal: TSaveOriginal;

//====================================================

procedure PatchCode(Address: Pointer; const NewCode; Size: Integer;
  SaveOriginal: PSaveOriginal);
var
  OldProtect: DWORD;
begin
  if VirtualProtect(Address, Size, PAGE_EXECUTE_READWRITE, OldProtect) then
  begin
    //======== Saving original function =========
    if Assigned(SaveOriginal) then
    begin
      SaveOriginal^.Addr := Address;
      Move(Address^, SaveOriginal^.Bytes, Size);
    end;
    //===========================================
    Move(NewCode, Address^, Size);
    FlushInstructionCache(GetCurrentProcess, Address, Size);
    VirtualProtect(Address, Size, OldProtect, @OldProtect);
  end;
end;

procedure RedirectProcedure(OldAddress, NewAddress: Pointer);
var
  NewCode: TInstruction;
begin
  NewCode.Opcode := $E9;
  NewCode.Offset := NativeInt(NewAddress) - NativeInt(OldAddress) -
    SizeOf(NewCode);
  PatchCode(OldAddress, NewCode, SizeOf(NewCode), @SaveOriginal);
end;

procedure UndoRedirectProcedure(const SaveOriginal: TSaveOriginal);
var
  OldProtect: Cardinal;
begin
  if not VirtualProtect(SaveOriginal.Addr, SizeOf(TInstruction),
    PAGE_EXECUTE_READWRITE, OldProtect) then
    RaiseLastOSError;
  Move(SaveOriginal.Bytes, SaveOriginal.Addr^, SizeOf(TInstruction));
  if not VirtualProtect(SaveOriginal.Addr, SizeOf(TInstruction), OldProtect,
    OldProtect) then
    RaiseLastOSError;
end;

function NewLdrLoadDll(szcwPath: PWideChar; dwFlags: DWORD;
  pUniModuleName: PUNICODE_STRING; pResultInstance: PPointer)
  : NTSTATUS; stdcall;
begin
  if (pos('111', pUniModuleName.Buffer) > 0) or
     (pos('222', pUniModuleName.Buffer) > 0) then

    Result := STATUS_ACCESS_DENIED
  else
  begin

    UndoRedirectProcedure(SaveOriginal); // Restore original function

    @Old_LdrLoadDll := SaveOriginal.Addr;

    Result := LdrLoadDll(szcwPath, dwFlags, pUniModuleName, pResultInstance); // Call original function

    RedirectProcedure(GetProcAddress(GetModuleHandle('ntdll.dll'),
      'LdrLoadDll'), @NewLdrLoadDll); // Hook again
  end;
end;

begin
  try
    RedirectProcedure(GetProcAddress(GetModuleHandle('ntdll.dll'),
      'LdrLoadDll'), @NewLdrLoadDll); 
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
  Readln;

end.