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POI need help developing a polymorphism engine - instruction dependency trees
 

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  1. POI need help developing a polymorphism engine - instruction dependency trees
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    <p>I am currently trying to write a polymorphism engine in C++ to toy-around with a neat anti-hacking stay-alive checking idea I have. However, writing the polymorphism engine is proving rather difficult - I haven't even established how I should go about doing it. The idea is to stream executable code to the user (that is the application I am protecting) and occasionally send them some code that runs some checksums on the memory image and returns it to the server. The problem is that I don't want someone to simply hijack or programatically crack the stay-alive check; instead each one would be generated on the server working off of a simple stub of code and running it through a polymorphism engine. Each stay-alive check would return a value dependant on the check-sum of the data and a random algorithm sneaked inside of the stay-alive check. If the stub returns incorrectly, I know that the stay-alive check has been tampered with.</p> <p>What I have to work with:</p> <p>*The executable images PDB file. *Assembler &amp; disassembler engine of which I have implemented a interface between them which allows to to relocate code etc...</p> <p>Here are the steps I was thinking of doing and how I might do them. I am using the x86 instruction set on a windows PE executable</p> <p>Steps I plan on taking(My problem is with step 2):</p> <ol> <li><p>Expand instructions</p> <ul> <li>Find simple instructions like mov, or push and replace them with a couple instructions which achieve the same end though with more instructions. In this step I'll also add loads of junk-code.</li> <li>I plan on doing this just by using a series of translation tables in a database. This shouldn't be very difficult to do. </li> </ul></li> <li><p>Shuffling</p> <ul> <li>This is the part I have the most trouble with. I need to isolate the code in to functions. Then I need to establish a series of instruction dependancies trees, and then I need to relocate them based upon which one depend on the other. I can find functions by parsing the pdb files, but creating instruction dependancy trees is the tricky part I am totally lost on.</li> </ul></li> <li><p>Compress instructions</p> <ul> <li>Compress instructions and implement a series of uncommon &amp; obscure instructions in the process. And, like the first step, do this by using a database of code signatures.</li> </ul></li> </ol> <p>To clarify again, I need help performing step number 2 and am unsure how I should even begin. I have tried making some diagrams but they become very confusing to follow.</p> <p>OH: And obviously the protected code is not going to be very optimal - but this is just a security project I wanted to play with for school.</p>
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    1. COThis is pretty advanced, but if you look for articles regarding writing rootkits and the like, you'll find some really useful information on writing metamorphic code engines. I've seen a number of articles but I can't remember where, I would check phrack firstly.
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    2. COAlright, I'll take a look at phrack. Thanks Nawazy :)
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