Upx program packer

Apr 10, Dec 14, Whitespace changes. Dec 5, Initial commit from git. May 19, Apr 6, Apr 3, View code. Programs and libraries compressed by UPX are completely self-contained and run exactly as before, with no runtime or memory penalty for most of the supported formats. Full source code is available. UPX may be distributed and used freely, even with commercial applications. This means that packing, unpacking, or even testing or listing a file requires the same security considerations as actually executing the file.

Use UPX on trusted files only! For best compression results try 'upx --brute program. Interesting things here! If we look into that function which does not decompile well, to be honest , we can see that this is the primary function dispatcher for the UPX code. Guess what this is? This is the original program entry point after the code has been decompressed and is ready for execution. But this gives you an idea of how these packers work.

It has no or very few strings. It has no or very few library dependencies. And the defined functions in the executable is very small. Thanks for visiting DZone today,. Edit Profile. Sign Out View Profile. Over 2 million developers have joined DZone. A security researcher demonstrates how to get packers, specifically UPX, up and running on our system.

Read on to learn more! Like 1. Join the DZone community and get the full member experience. Join For Free. Along the way, it happens to obfuscate the intent and actual code of the program. Looking Through the Binaries See upx. Figure 1: Segments and sections of the original ls command In figure 1, we see the output from jtool-l over the original ls executable.

Messaging Not only are there very few functions defined, they are all local. Now, select the pseudo-code button at the top of the display area: Figure 4: Pseudo-code mode activated! Awards for our softwares from leading Download Sites. In this tutorial, you will learn how to unpack any UPX packed Executable file using OllyDbg UPX is a free, portable, executable packer for several different executable formats.

If you already have UPX packed binary file then proceed further. Before we begin with unpacking exercise, lets try to understand the working of UPX. Based on type and complexity of Packer, unpacking operation may vary in terms of time and difficulty.

UPX is the basic Packer and serves as great example for anyone who wants to learn Unpacking. Here is the screenshot of OllyDbg in action. Usually this is the first instruction or it will be present after first few instructions based on the UPX version. Once you set up the breakpoint, continue the execution press F9. Now start step by step tracing with F7 and soon you will encounter a JMP instruction which will take us to actual OEP in the original program.

It will automatically fix all the Import table as well. That is it, you have just unpacked UPX!!! Now launch the ImpREC tool and select the process that you are currently debugging. Now click on 'Get Imports' to retrieve all the imported functions. You will see all the import functions listed under their respective DLL names.

Now run the final fixed executable to see if everything is alright.