ghidra VS depsdev

[1] https://github.com/boricj/ghidra/tree/feature/elfrelocatebleobjectexporter

I've been working on a specific reverse-engineering technique called _unlinking_ [1] on-and-off for the past 16 months or so. I'm on my third prototype (first a set of Ghidra scripts written in Jython [2], then a fork of Ghidra [3] and now a Ghidra extension [4]) and I've started a blog in order to document it [5], which side-tracked into writing a whole series of articles on reverse-engineering to introduce the topic.

What for, you may ask? Basically I'm trying to decompile a PlayStation 1 video game and I've quickly decided that dealing alone with multiple +500 KiB executables of complete utter spaghetti code wasn't going to work. Instead, I've decided that I'd rather divide-and-conquer the problem, so I've been tooling up to split executables into relocatable object files, in order to decompile those one at a time and _Ship of Theseus_-style my way to success.

Ironically, all of that stuff is so not done that I don't even know what meaningful feedback there could be. My prototypes do work, but only for 32 bit little endian statically-linked MIPS executables. The articles on my blog are draft-quality. As for the decompilation project itself that started all of this, it hasn't seen much progress due to all of those side-quests. The overall topic is so esoteric that so far I've only managed to hear about one group of two persons that tried to do anything remotely similar and one another anecdotal account [6] that this particular skill is very uncommon among reverse engineers.

Personally, I'm starting to think that maybe I could've actually reverse-engineered and decompiled the game in the time I took to get here. I've also tried to engage with Ghidra to upstream the foundations of my modifications in my fork, but after some back-and-forth it became clear that my prototype-grade stuff wasn't industrial-grade and couldn't be merged in its current state, which is why I'm currently reworking the code in my fork as a Ghidra extension.

To those that want to provide feedback after reading all of this: beware, I've had a lot of fun going down that rabbit hole, but this is one hell of a time sink _and_ a particularly tricky mind-bender.

[1] I don't actually _know_ what's the actual name for this technique, given that there are so few resources on it out there. I do know I didn't invent it.

[2] https://github.com/boricj/ghidra-unlinker-scripts

[3] https://github.com/boricj/ghidra/tree/feature/elfrelocateble...

[4] https://github.com/boricj/ghidra-unlinker-extension

[5] https://news.ycombinator.com/item?id=36575081#36590078

[6] https://news.ycombinator.com/item?id=35729232&p=3#35740761

- The relocation synthesizer for MIPS: https://github.com/boricj/ghidra/blob/feature/elfrelocateble...

  - The Ghidra analyzer that leverages this synthesizer: https://github.com/boricj/ghidra/blob/feature/elfrelocatebleobjectexporter/Ghidra/Features/Delinker/src/main/java/ghidra/app/analyzers/RelocationTableSynthesizerAnalyzer.java

Open Source Insights by Google for the dependency graph

Something I've recently worked on is building an SQLite database of all the dependencies my organisation uses, which makes it possible to write our own queries and reports. The tool is all Open Source (https://dmd.tanna.dev) and has a CLI as well as the SQLite data.

Ive used it to look for software that's out of date (via https://endoflife.date), to find vulnerablilities (via https://osv.dev) and get license information (via https://deps.dev)

It's been hugely useful for us understanding use of internal and external dependencies, and I wish I'd built it earlier in my career so I could've had it for other companies I've worked at!

https://deps.dev/ (a Google project) repeatedly examines sites such as github.com, npmjs.com, and pkg.go.dev to find up-to-date information about open source software packages. Using that information it builds for each package the full dependency graph from scratch—not just from package lock files—connecting it to the packages it depends on and to those that depend on it. And then does it all again to keep the information fresh. This transitive dependency graph allows problems in any package to be made visible to the owners and users of any software they affect.