It's not possible to intercept these app's traffic because they won't trust HTTP Toolkit's certificate, even after it's been injected into the device's system certificate store. (I'm focusing on certificate pinning because it's a common use case and it's convenient, but the techniques here work for all other kinds of reverse engineering & patching too, don't worry!)Ĭertificate pinning is a problem for HTTP Toolkit users, who are trying to intercept HTTPS traffic to see what messages their Android apps are sending & receiving.

I'm going to focus on the classic HTTP Toolkit user example here of certificate pinning: where security-conscious apps that send HTTPS traffic go beyond the normal HTTPS validation requirements, and actively check that the HTTPS certificates used are from a small set of specific trusted certificates, not just the standard set trusted by all Android devices.

You want to know exactly how a specific bit of behaviour works, and you want to change what it's doing. I'm assuming here that somebody else has written an Android app that you're interested in. In this article, I want to talk you through the core initial steps to look inside any Android app, give you the tools to find & understand the specific code that matters to you, and then show you how you can use that information to modify the app for yourself. There's few good guides to getting started, and even fewer guides on the advanced tricks available. There are some great tools to do this, including JADX & Frida, but using these is complicated, and every reverse engineering problem has its own unique challenges & solutions. > r20 = _ get a lot of emails from users who want to know exactly what their favourite Android app is doing, and want to tweak and change how that works for themselves. > /* Code decompiled incorrectly, please refer to instructions dump. However, JADX is generating the following errors in the output: > /* JADX WARNING: inconsistent code. I am attempting to decompile a contact duplicate remover Android app using the JADX Dex-to-Java decompiler.

Jadx gui macos