Avast Launches Open-Source Decompiler For Machine Code (techspot.com)

Greg Synek reports via TechSpot: To help with the reverse engineering of malware, Avast has released an open-source version of its machine-code decompiler, RetDec, that has been under development for over seven years. RetDec supports a variety of architectures aside from those used on traditional desktops including ARM, PIC32, PowerPC and MIPS. As Internet of Things devices proliferate throughout our homes and inside private businesses, being able to effectively analyze the code running on all of these new devices becomes a necessity to ensure security. In addition to the open-source version found on GitHub, RetDec is also being provided as a web service.

Simply upload a supported executable or machine code and get a reasonably rebuilt version of the source code. It is not possible to retrieve the exact original code of any executable compiled to machine code but obtaining a working or almost working copy of equivalent code can greatly expedite the reverse engineering of software. For any curious developers out there, a REST API is also provided to allow third-party applications to use the decompilation service. A plugin for IDA disassembler is also available for those experienced with decompiling software.

Comments

A debugger does this

[Snotnose]

Back in the late 70's I loaded TRS-80 games into my debugger, it also let me dump the results into a text file. Finding things like "jump to label_foo" helped, but was not the be-all end-all.

The killer was when I debugged my TRS-80 BASIC interpreter in ROM. You'd have some 3 byte instruction, "jump here", then somewhere else you'd have a 3 byte instruction "jump into the middle of this 3 byte instruction to do something completely different". My understanding is Bill did those, but for all the evil he did I have major respect for his coding abilities.

I beat a lot of games running my debugger on them. 90% sure it was called TRS-MON, but wouldn't bet my retirement on it.

Re:A debugger does this

[AmiMoJo]

Indeed, poking code is often the fastest way to do stuff on those older systems where memory bandwidth and CPU clocks are very limited.

We called it speedcode back in the day. Say you wanted to calculate and plot a load of points on the screen. Normally you would calculate the coordinates, store them and then later pass a reference to some plotting function. To do it faster you could turn calls to the plot function into an unrolled series of instructions, and instead of reading the coordinates every time just poke them directly into the immediate instruction op-codes.

Should crossref with github.

[shess]

Perhaps if you built a fingerprint based on the structure of calls across functions, you could map it back to source code from github. Not that malware is generally posted to github, but I'd be surprised if they didn't use a TON of third_party libraries, and factoring all of those out would make what's left easier to understand and also let you focus better.