niklashigi / apk-mitm

apk-mitm > A CLI application that automatically prepares Android APK files for HTTPS inspection Inspecting a mobile app's HTTPS traffic using a proxy is probably the easiest way to figure out how it works. However, with the [Network Security Configuration][network-security-config] introduced in Android 7 and app developers trying to prevent MITM attacks using [certificate pinning][certificate-pinning], getting an app to work with an HTTPS proxy has become quite tedious. automates the entire process. All you have to do is give it an APK file and will: • decode the APK file using [Apktool][apktool] • replace the app's [Network Security Configuration][network-security-config] to allow user-added certificates • modify the source code to disable various [certificate pinning][certificate-pinning] implementations • encode the patched APK file using [Apktool][apktool] • sign the patched APK file using [uber-apk-signer][uber-apk-signer] You can also use to patch apps using Android App Bundle and rooting your phone is **not** required. ⚠️ Limitations & alternatives Modifying the regular behavior of an app to work around security features like certificate pinning requires either modifying the app's source code _before_ running it or ["hooking"][hooking] the app _while_ it is running to intercept function calls. is currently taking the former approach of modifying the app's code by first "disassembling" the app using [Apktool][apktool], making changes to several files, and then assembling it back together (again using Apktool). This approach has the benefit that it doesn't require a rooted device but it also has several drawbacks. The biggest problem is that apps aren't really _meant_ to be disassembled. Apktool tries to achieve that anyway but, especially with big and complex apps, it often runs into problems. Another issue with this approach is that some certificate pinning methods, like checks performed within native binaries (as is the case for frameworks like Flutter), are either very hard or impossible to circumvent. For this reason, it can be beneficial to try out other approaches for more tricky apps. Specifically, I'd like to highlight [mitmproxy's project][android-unpinner] and [the underlying scripts by HTTP Toolkit][frida-interception-and-unpinning]. Their approach applies patches at runtime using [Frida][frida], which is a lot more powerful but also means that it either can't be used or is more difficult to use without a rooted device. Installation If you have an up-to-date version of [Node.js][node] (14+) and [Java][java] (8+), you can install by running: Usage Once installed, you can run this command to patch an app: Patching an APK file called might look like this: You can now install the file on your Android device and use a proxy like [Charles][charles] or [mitmproxy][mitmproxy] to look at the app's traffic. Patching App Bundles You can also patch apps using Android App Bundle with by providing it with a file (for example from [APKPure][apkpure]) or a file (which you can export yourself using [SAI][sai]). If you're doing this on Linux, make sure that both and are installed. Making manual changes Sometimes you'll need to make manual changes to an app in order to get it to work. In these cases the option is what you need. Enabling it will make wait before re-enconding the app, allowing you to make changes to the files in the temporary directory. If you want to experiment with different changes to an APK, then using is probably not the most convenient option as it forces you to start from scratch every time you use it. In this case you might want to take a look at [APKLab][apklab]. It's an Android reverse engineering workbench built on top of VS Code that comes with [ support][apklab-mitm] and should allow you to iterate much more quickly. Allowing specific certificates On some devices (like Android TVs) you might not be able to add a new certificate to the system's root certificates. In those cases you can still add your proxy's certificate [directly to the app's Network Security Config][network-security-config-custom-ca] since that will work on any device. You can accomplish this by running with the flag set to the path of the certificate ( or file) used by your proxy. Caveats • If the app uses Google Maps and the map is broken after patching, then the app's API key is probably [restricted to the developer's certificate][google-api-key-restrictions]. You'll have to [create your own API key][google-maps-android] without restrictions and run with the option to be able to replace the value in the app's file. • If crashes while decoding or encoding the issue is probably related to [Apktool][apktool]. Check [their issues on GitHub][apktool-issues] to find possible workarounds. If you happen to find an Apktool version that's not affected by the issue, you can instruct to use it by specifying the path of its JAR file through the option. Thanks • Connor Tumbleson for making [an awesome APK decompiler][apktool] • Patrick Favre-Bulle for making [a very simple tool for signing APKs][uber-apk-signer] • Ryan Welton for inspiring most of the certificate pinning removal code License MIT © Niklas Higi [network-security-config]: https://developer.android.com/training/articles/security-config [network-security-config-custom-ca]: https://developer.android.com/training/articles/security-config#ConfigCustom [certificate-pinning]: https://owasp.org/www-community/controls/Certificate_and_Public_Key_Pinning#what-is-pinning [hooking]: https://en.wikipedia.org/wiki/Hooking [android-unpinner]: https://github.com/mitmproxy/android-unpinner [frida-interception-and-unpinning]: https://github.com/httptoolkit/frida-interception-and-unpinning [frida]: https://frida.re/ [node]: https://nodejs.org/en/download/ [java]: https://www.oracle.com/technetwork/java/javase/downloads/index.html [apklab]: https://github.com/Surendrajat/APKLab [apklab-mitm]: https://github.com/Surendrajat/APKLab#app…