Krakatau
jadx
Krakatau | jadx | |
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10 | 40 | |
1,931 | 39,130 | |
- | - | |
2.9 | 9.2 | |
26 days ago | 7 days ago | |
Rust | Java | |
GNU General Public License v3.0 only | Apache License 2.0 |
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Krakatau
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How to Create a UTF-16 Surrogate Pair by Hand, with Python
Since Java bytecode uses MUTF-8, which encodes astral characters as surrogate pairs, I've had to implement this conversion in Python multiple times, in Krakatau and Enjarify.
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How hard is interop with Java?
Not sure how applicable this is for your project since my compiler was written in Python, but I used Krakatau.
- Where do I get started on AoH modding?
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learn jvm bytecode
Here is one that disassembles the bytecodes and reassembles them https://github.com/Storyyeller/Krakatau .
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100 Languages Speedrun: Episode 77: JVM Assembly with Jasmin
There's an additional problem that unlike regular assembly or LLVM assembly where there's some fully supported standard format, Jasmin is a third party program and different JVM assemblers and disassemblers disagree on so many things. There are also some newer assemblers and disassemblers like Krakatau you could try instead. Krakatau has different syntax than Jasmin or javap.
- GitHub - Storyyeller/Krakatau: Java decompiler, assembler, and disassembler
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Awesome CTF : Top Learning Resource Labs
Krakatau - Java decompiler and disassembler.
- Krakatau: An assembler and disassembler for [obfuscated] Java bytecode
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Chocopy -> JVM Compiler, implemented in Python
The compiler outputs bytecode in a text format, which can be assembled into .class files using the Krakatau assembler. Figuring out how to translate features like nested functions and nonlocals to JVM was pretty interesting, and having access to Java’s standard library made the whole thing much easier than expected.
- Can you tell an assembly language when you see one?
jadx
- Apktool in kali
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A popular Bluetooth car battery monitor that siphons up all your location data
The best way is to just start practicing. I would say pick some simple apps on your (Android) phone and dig straight in.
The great thing about Android applications is that often they generally decompile quite nice into human readable Java soo the barrier of entry can be quite low to start reversing.
Grab a copy of JADX[1] - it will decompress and decompile the APK files. If you don't have an Android handset, use an emulator and/or grab APKs from apkpure[2]
Dynamic analysis is a bit more challenging. In my blog post I use Frida[3] extensively.
If you get started on something and get stuck/looking for support, feel free to DM me on Twitter[4], more then happy to help.
[1] https://github.com/skylot/jadx
[2] https://frida.re/docs/android/
[3] https://m.apkpure.com/
[4] https://twitter.com/haxrob
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Hardware Question
This may be overkill but you can use an oscilloscope to manually calculate the baudrate, i.e. like this. It looks like it could be UART serial data, but this is a good resource to reference. Sometimes http is used as a means for communicating, and not necessarily directly to a browser see here. This is pretty common in embedded applications actually. You can try using dirbuster to see what hidden endpoints there are that may be used for video. If there's an RC, you can try and do what you were doing before on the drone for that (see what dmesg says when plugged in, check any open ports, etc). If it's a phone you connect to, you can RE the mobile app. I like using jadx for APKs to get a lay of the land. If you don't want to pop the SPI flash like i suggested earlier (and I suggest don't do that except for last resort), you can grep for firmware urls in the mobile app to see if it does OTA updates, and see if you can directly download it and analyze it with a disassembler like Ghidra. Since it's WiFi, you can also MiTM the traffic from an AP you control like your computer. I'm guessing video is probably going to be something like RTSP at an IP address, so you can grep in the mobile app for that, and that might be good enough to get your video feed honestly.
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improved nintype
Jadx - skylot/jadx: Dex to Java decompiler (github.com) - Used for decompiling the apk - make the code readable
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How to securely set end point url and encryption keys in CN1 app
I realized when app is decompiled using JADX class names are recreated as shown in this screenshot of sample app
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Reverse Engineering the Facebook Messenger API
Not sure. I started reverse engineering Java apps very early in my life — initially it was J2ME games. Decompilers of the time sucked but that didn't stop me from modding Gravity Defied :P
I honestly don't know what's a good way of getting started on reverse engineering. There's a bunch of everything about Windows executables in particular, including "crackmes", but native machine code is a level up from JVM bytecode. Java classes and Android dex files can be decompiled back to sensible source with a good chance that you get something that can be compiled again. No such luck for native code — C/C++ compilation is a lossy process by its nature, especially the optimizations. Ghidra does a decent job but still requires a non-zero amount of manual assistance. Flash games also were good to hone one's reverse engineering skills since ActionScript decompilers did a pretty darn good job.
Anyway. To decompile dex to Java source, there's jadx: https://github.com/skylot/jadx
Since decompilation is sometimes lossy, there's apktool for when you want to put the app back together after tinkering with it: https://github.com/iBotPeaches/Apktool
It goes without saying that you also need a JDK and the Android SDK. In particular, you need apksigner form the SDK to sign the unsigned apks generated by apktool. You can also automate things a bit and use adb to deploy them to your device.
What I usually do is get a high-level overview of the app in jadx, and then modify the smali (dalvik bytecode in text form, very assembly-like) files generated by apktool.
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What Happens When Your Phone Is Spying on You
A week ago I purchased a bluetooth device that takes some measurements. You require an Android or iOS application. The first thing the iOS app did was request permission for your location. Immediate fired up MITMproxy [1] running in transparent `--mode wireguard` and installed it's certificate in the iOS trust store. It was sending a whole bunch of data to China and HK. Since I don't have a jailbroken iPhone, it's off to Android.
For BLE scanning, Android does require permissions for location, but this application is using a Chinese branded tracking SDK and sending encrypted (within already encrypted TLS). So it's time to start reversing and instrumenting the runtime.
Well - not so easy, they used a commercial packer that encrypts their compiled bytecode and decrypts and runs it within a C++ library. I managed to bull the Dalvik out of memory using Frida[2], covert it to java bytecode with dex2jar[3] then into decompiled java with jadx [3].
Since the developer relied on the packer to hide/obfuscate their software, it's quite easy to follow. The libraries that do the location tracking on the otherhand are obfuscated so now I'm at the stage of identifying where to hook before the encrypted blobs are sent to servers in China.
I've sunk about 8 hours into this so far. The message here is that to understand what some applications on your phone does you need to really invest time and effort. The developers increase the cost to the consumer to know what their application is doing by obfuscation, encryption and packing. It's asymmetric.
[1] https://mitmproxy.org/posts/wireguard-mode/
[2] https://frida.re/docs/android/
[3] https://github.com/skylot/jadx
[3] https://github.com/pxb1988/dex2jar
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Any legit cracking tutorial?
jadx: View the generated Java code for an app. This tool tries to recreate Java code from the smali bytecode, but keep in mind that sometimes it may not work because Java -> Smali conversion is not fully backwards compatible.
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Apk.sh is a Bash script that makes reverse engineering Android apps easier
If you haven't tried Jadx [1], give it a shot. It's by far the easiest way to reverse Android APKs. I doesn't do patching or reassembly, but I used it for reversing the Delong'hi APK for longshot [2][3] and the quality of output was fantastic.
[1] https://github.com/skylot/jadx
[2] https://github.com/mmastrac/longshot
[3] https://grack.com/blog/2022/12/02/hacking-bluetooth-to-brew-...
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Potentially OT: Any guides/crash course/cheatsheet on how to modify or perhaps reverse engineer an open source program to your preference?
Smali is a low level language for Dalvik bytecode and it can be quite a headache to interpret it correctly and achieve what you want. That's why I recommend another tool called jadx which can mostly recover Java code from a dex file, but unfortunately the conversion is not 100% possible. Also, editing is not possible with jadx.
What are some alternatives?
chocopy-python-compiler - Ahead-of-time compiler for Chocopy, a statically typed subset of Python 3, built in Python 3.
Apktool - A tool for reverse engineering Android apk files
CyberChef - The Cyber Swiss Army Knife - a web app for encryption, encoding, compression and data analysis
enjarify
linux - Linux kernel source tree
android-classyshark - Android and Java bytecode viewer
bettercap - The Swiss Army knife for 802.11, BLE, IPv4 and IPv6 networks reconnaissance and MITM attacks.
apk2gold - CLI tool for decompiling Android apps to Java. It does resources! It does Java! Its real easy!
Mak_Writing_Compilers_and_Interpreters - Source for the books from Ronald Mak - Writing Compilers and Interpreters.
procyon
simplify - Android virtual machine and deobfuscator
backdoor-apk - backdoor-apk is a shell script that simplifies the process of adding a backdoor to any Android APK file. Users of this shell script should have working knowledge of Linux, Bash, Metasploit, Apktool, the Android SDK, smali, etc. This shell script is provided as-is without warranty of any kind and is intended for educational purposes only.