原理和HOOK是一样的,都是通过WriteProcessMemory写入代码,但这里我们想任意位置加入代码,为了不影响原程序的执行,执行完我们的函数后,必须恢复原有程序的寄存器和堆栈的值,所以第一句话就是 pushad将所有寄存器压栈,执行完我们的函数跳回原有程序后,第一句就是pop eax,因为跳转代码是mov eax,xxx jmp eax修改了eax:
伪代码:
需要9个字节 0.pushad 1 (机器码:60) 1.mov eax, $自己的函数地址 5 2.jmp eax 2 3.pop eax 1 (机器码:58) 4..... procedure foo; begin {do your things} asm popad xxx(执行原程序代码) push eax mov eax, 3 jmp eax end; end;
根据伪代码用delphi写成的函数:
procedure WriteJmpCode(baseAddr, addrProc: dword); var Tmp : array [0..3] of Byte; jmpcode: array[0..8] of byte; sizeWritten: dword; begin Move(addrProc, Tmp, 4); {00A989B0 B8 ACAB6904 mov eax, 469ABAC 00A989B5 FFE0 jmp eax} jmpcode[0] := $60; jmpcode[1] := $B8; jmpcode[2] := tmp[0]; jmpcode[3] := tmp[1]; jmpcode[4] := tmp[2]; jmpcode[5] := tmp[3]; jmpcode[6] := $FF; jmpcode[7] := $E0; jmpcode[8] := $58; //here WriteProcessMemory(ProcessHandle, Pointer(baseAddr), @jmpcode, sizeof(jmpcode), sizeWritten); end;
我们自己的函数:
procedure OnBeforeWriteCard();//stdcall; begin recsyslog2('OnbeforeWriteCard'); asm popad push 0 push $0E0 push ebx mov eax, dword ptr [ebx] push eax mov eax, addrBeforeWriteCard jmp eax end; end;
调用方法:
addrAfterGetLocalTime := ($091A1CEC-$091A0000+p^.htmp); WriteJmpCode2(($091A1C0D-$091A0000+p^.htmp), dword(@OnAfterGetLocalTime));
说明:这里的addrBeforeWriteCard等于baseAddr+$8