Checking the validity of a PE file is a very difficult task, but checking a .NET assembly is even more complicated, since you have to check the tables integrity, the code integrity, the stack integrity etc. Ok, there’s already a tool that does that provided by the .NET framework. However, that tool isn’t perfect either and doesn’t check some other problems. When I wrote my .NET compiler I spent literally days figuring out what was wrong one time or another time in the format I produced, and the MS tools didn’t help. But let’s not go OT, I just wanted to say that this a topic on the woodmann forum triggered my interest because it was a good opportunity to test the CFF Explorer’s scripting capabilities. So, yesterday I took two hours and wrote a little script (called PE Validator Script) which checks for some of the most common problems in a PE. Since it’s a script (thus opensource) it can be expanded easily.
You can find it in the extensions repository:
http://www.woodmann.com/collaborative/tools/index.php/PE_Validator_Script
Here are the current checks:
— check CRC32 (useful for drivers)
— check number of rva and sizes
— check image size
— check sections
— check that EP is valid
— check that EP is in code
— check that the EP section is executable
— check data directories RVAs
— check whether the API IsDebuggerPresent is imported
Don’t be too serious about it, it’s just a thing I did for fun.