OpenRCE

📚 OpenRCE is preserved as a read-only archive. Launched at RECon Montreal in 2005. Registration and posting are disabled.

About Articles Book Store Distributed RCE Downloads Event Calendar Forums Live Discussion Reference Library RSS Feeds Search Users What's New

Customize Theme

Flag: Tornado! Hurricane!

Created: Monday, October 15 2007 17:39.11 CDT

Printer Friendly ...

Semi-automatic import recovery

Author: morel

# Views: 2964

New (only?) method to automate import recovery process:
http://www.idleloop.org/?p=8

Blog Comments

sovietskicpu

Posted: Monday, October 15 2007 18:15.13 CDT

hi morel, as you referenced the AV industry with their claims about generic decryptors. You are totally wrong in that point, because analyzed files have to be worked out in a safe environement with no escape issues and the method you presented, can be applied only for reversing purposes.

And off course Generic decryptors exist for real in avs with correct implementation of CPU emulation (NOD32 ?!)

morel

Posted: Monday, October 15 2007 18:27.07 CDT

hi,

I don't claim that this technique should be used in AV engines, I see no reason to do so. It might be applicable with f.e. OllyBone, to partially recover packed files. See BlackHat presentation by Offensive Computing, they missed the import part..
By "unpacker" I mean a tool that, among many other things, can detect OEP. In this sense, it's impossible to create *generic* unpacker. AV scanners implement emulators, that's true.

jms	Posted: Tuesday, October 16 2007 12:06.56 CDT
Well what I always wanted was even a known packer, have a method to unpack (using the signature) and do the import fixing, etc. on the fly. As opposed to having to run detector -> debugger -> imprec -> etc

neox	Posted: Tuesday, October 16 2007 13:49.39 CDT
Hello, I'm afraid such technique is already talked in great detail by E Labir in a paper published at CodeBreakers-Journal, Vol. 1, No. 2 (2004) for those who do not have account there, here is the pdf http://www.plunder.com/unpacking-by-code-injection-E-Labir-download-89472.htm neox

morel

Posted: Tuesday, October 16 2007 14:42.29 CDT

I wasn't aware of this work..
E. Labir's method is similiar, but requires manual log analysis and leads nowhere in case when packer calls many fake APIs inside redirection code.
Method with magic cookie will fail when API is fully emulated, as it sometimes is with GetProcAddress and in case when there is only *one* redirection procedure and APIs are distinguished based on return address left on stack by "call redirect" (technique used in SafeCast). Calls to IAT entries, from addresses unknown to the protector code aren't recognized and redirection fails.
The other story is, that such protecting technique can lead to unstable behaviour if code was selfmodyfing at the beginning :).

There are 31,328 total registered users.

Recently Created Topics
[help] Unpacking VMP...	Mar/12
Reverse Engineering ...	Jul/06
let 'IDAPython' impo...	Sep/24
set 'IDAPython' as t...	Sep/24
GuessType return une...	Sep/20
About retrieving the...	Sep/07
How to find specific...	Aug/15
How to get data depe...	Jul/07
Identify RVA data in...	May/06
Question about memor...	Dec/12

Recent Forum Posts
Finding the procedur...	rolEYder
Question about debbu...	rolEYder
Identify RVA data in...	sohlow
let 'IDAPython' impo...	sohlow
How to find specific...	hackgreti
Problem with ollydbg	sh3dow
How can I write olly...	sh3dow
New LoadMAP plugin v...	mefisto...
Intel pin in loaded ...	djnemo
OOP_RE tool available?	Bl4ckm4n

Recent Blog Entries
	halsten	Mar/14
Breaking IonCUBE VM
	oleavr	Oct/24
Anatomy of a code tracer
	hasherezade	Sep/24
IAT Patcher - new tool for ...
	oleavr	Aug/27
CryptoShark: code tracer ba...
	oleavr	Jun/25
Build a debugger in 5 minutes
More ...

Recent Blog Comments
	nieo on:	Mar/22
IAT Patcher - new tool for ...
	djnemo on:	Nov/17
Kernel debugger vs user mod...
	acel on:	Nov/14
Kernel debugger vs user mod...
	pedram on:	Dec/21
frida.github.io: scriptable...
	capadleman on:	Jun/19
Using NtCreateThreadEx for ...
More ...

Imagery

SoySauce Blueprint
Jun 6, 2008

[+] expand

View Gallery (11) / Submit