Aldhard Oswine

NtGlobalFlag

2 posts in this topic

Posted (edited)

I'm learning Anti-RE techniques and I have simple problem with NtGlobalFlag :)
 

void PEBglobalflags() {
	BOOL f = FALSE;
	__asm {
		xor eax, eax
		mov eax, fs:[0x30]
		movzx eax, [eax+0x68]
		mov f, eax
	}
	if (f) {
		MessageBox(nullptr, L"Dbg", L"", 0);
		exit(1);
	}
}


Using this method can not detect dbgr.
eax is always 0, instead of 0x70.

Image: https://ibb.co/b89vYv

Windows 10 - 86_64, application x86, MSVC 2017, 

Edited by Aldhard Oswine

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Posted (edited)

+0x068 NtGlobalFlag     : Uint4B

 

its a dword... so your movzx is probably the issue...

try mov eax, dword ptr fs:[0x68]

the compiler should have bitched at you anyway for the asm being 'wrong'

and its a shitty antidebug method nehows.. theres much better out there..

next time, to fix it yourself, try puting in a DebugBreak() at the start of the function, compile, load it up in olly and trace then you'll see the problem...

Edited by evlncrn8

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