apk reverse engineering github

This error can be safely ignored as long as we are able to see the extracted dump in the file system. Android Tampering and Reverse Engineering, Patching Example: Disabling Certificate Pinning, Patching Example: Making an App Debuggable, Customizing Android for Reverse Engineering, documentation on the official Frida website, documentation on the jnitrace GitHub page, r2frida's official installation instructions, https://github.com/android/platform_bionic, https://blog.netspi.com/attacking-android-applications-with-debuggers/, http://ieeexplore.ieee.org/document/6759227/, https://www.xda-developers.com/rovo89-updates-on-the-situation-regarding-xposed-for-nougat/, https://packetstormsecurity.com/files/138504/HITB_Hacking_Soft_Tokens_v1.2.pdf. However, there are also a few Android-specific challenges. A well-known use case of this technique is loading the Frida gadget to an application, specially while working on a non-rooted device (this is what objection patchapk basically does). In order to extract strings from native code used in an Android application, you can use GUI tools such as Ghidra or Cutter or rely on CLI-based tools such as the strings Unix utility (strings ) or radare2's rabin2 (rabin2 -zz ). The native library for the current application is relatively very small. This method searches for the "su" binary within a list of directories (/system/xbin and others). APK Decompiler Apps I hope this collection will be helpful to you. It contains an important configuration file, default.prop, that defines some basic system properties. APK adalah format aplikasi Android, berupa file ZIP yang di dalamnya ada classes.dex yang berisi kode Java, resource dalam bentuk XML (yang diencode khusus), file-file gambar, video, suara, dsb. You can't attach a debugger to the app because the. The "Hello World" text view is populated in the onCreate method: Note the declaration of public native String stringFromJNI at the bottom. APK files are saved in a compressed .zip format and can be opened by any zip decompression tool. You can do this with dex2jar or enjarify. Open IntelliJ and select "Android" as the project type in the left tab of the "New Project" dialog. Remember to always type ? Click here. Before booting into the new kernel, make a copy of your device's original boot image. The UnCrackable App for Android Level 1 is not stupid: it notices that it has been run in debuggable mode and reacts by shutting down. \ii libandroid_runtime.so~.. (if not, for this binary, you'd get almost 2500 lines printed to your terminal). Set a breakpoint on method a and "Force Step Into" when you reach the breakpoint. We assume that you've successfully opened lib/armeabi-v7a/libnative-lib.so in IDA pro. In other words, you take the program apart, run it, simulate parts of it, and do other unspeakable things to it to understand what it does and how. The "Force Step Into" option allows you to debug the Android framework functions and core Java classes that are normally ignored by debuggers. On Android, setting LD_PRELOAD is slightly different compared to other Linux distributions. You can use lsof with the flag -p to return the list of open files for the specified process. You first need the address of sys_call_table. You can now use fastboot to test the new kernel. You can look up the address in the /proc/kallsyms file: This is the only memory address you need for writing your kernel module. Check Frida's JavaScript API for more details. To defeat this check, step through the detection method and inspect the variable content. Finally the resource files in the APK can be. This may appear magical at first, but a careful analysis of the function at 0x00001760 holds the clue, as it determines if the given input string is a valid license key or not. Additional post actions Obviously, this method displays the dialog box. To create a toolchain for Android 7.0 (API level 24), run make-standalone-toolchain.sh from the Android NDK package: Set the CROSS_COMPILE environment variable to point to your NDK directory and run "make" to build You can edit these files for more advanced usage such as obtaining the return value of the functions, their input parameters, accessing the memory, etc. You'll use a JDWP debugger most of the time you debug "normal" Android apps (i.e., apps that don't make many calls to native libraries). . The system should now boot normally. Step 2 I have Imported an Android Package Kit (APK) file which Android uses to distribute and install apps. frida-trace is a CLI tool for dynamically tracing function calls. Most Java decompilers take plain class files or JARs as input, so you need to convert the classes.dex file into a JAR first. It also makes working with an app easier because of the project like file structure and automation of some repetitive tasks like building apk, etc. Consequently, you can debug it with standard tools (including GDB and built-in IDE debuggers such as IDA Pro and JEB) as long as they support the device's processor architecture (most devices are based on ARM chipsets, so this is usually not an issue). Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Symbolic execution is a very useful technique to have in your toolbox, especially while dealing with problems where you need to find a correct input for reaching a certain block of code. The secret code is verified by the method a of class sg.vantagepoint.uncrackable1.a. As we will soon observe, the key validation logic in the crackme is implemented in native code. As a workaround for this problem, Android supports the setprop (set property) functionality. Write a Frida hook to change how that code works. Technically, Smali and baksmali are the name of the tools (assembler and disassembler . Review each finding carefully and try to understand what the app is doing to improve your chances of finding vulnerabilities. Execution traces can also be recorded in the standalone Android Device Monitor. It's in the VM's path at ~/samples/ThaiCamera.apk. This interrupt calls the vector_swi kernel function, which then uses the system call number as an offset into a table (known as sys_call_table on Android) of function pointers. in the Debugging section), so don't delete the project yet! Nevertheless, the functionality is sufficient for basic tasks, such as reconstructing the disassembly of a natively executed cryptographic algorithm. To set up IDE debugging, first create your Android project in IntelliJ and copy the decompiled Java sources into the source folder as described above in the "Reviewing Decompiled Java Code" section. JDWP is a standard debugging protocol that's supported by all command line tools and Java IDEs, including jdb, JEB, IntelliJ, and Eclipse. 0 coins. Therefore, when the injected Frida agent tries to read a region that's not readable, it'll return the corresponding memory access violation errors. You can edit the onLeave event to print the return values as shown above. Unlike the original, the new version of a just writes console output and doesn't exit the app. Let's import the code into IntelliJ, which also provides on-device debugging functionality. Typically you'd use hybrid techniques, as in the above example, where we performed manual analysis of the disassembled code to provide the correct criteria to the symbolic execution engine. You can easily install it by running pip install jnitrace and run it straight away as follows: The -l option can be provided multiple times to trace multiple libraries, or * can be provided to trace all libraries. For instance, you'd like to log everything that's being sent over the network without having to perform a MITM attack. Modifying the ELF file structure manually to inject a library can be cumbersome and prone to errors. Note how, by default, only the arguments passed to the function are shown, but not the return values. It can decode resources to nearly original form and rebuild them after making some modifications; it makes possible to debug smali code step by step. If you're interested in learning to reverse engineer Android applications (both DEX and native code), check out the workshop at maddiestone.github.io/AndroidAppRE. You don't want the process to resume immediately though, so pipe the suspend command into jdb: Next, suspend the process where the Java runtime loads libnative-lib.so. Conclusion 5. When testing an app, process exploration can provide the tester with deep insights into the app process memory. patching) and then re-signing and repackaging it. Using it requires only a few lines of Python code as shown below: In the above example, libinject.so library is injected as a dependency of a native library (libnative.so), which the application already loads by default. You may do so by running the \dm. Changing this file can make the Android environment easier to reverse engineer. Note that the Angr loader will load the PIE executable with a base address of 0x400000, which needs to be added to the offsets from Cutter before passing it to Angr. In this section, we will solve a simple Android crackme by using the Angr binary analysis framework as our symbolic execution engine. Step into the System.getenv method with the "Force Step Into" feature. Note: If you experience JRE compatibility issues with apksigner, you can use jarsigner instead. https://source.android.com/source/building-kernels.html#id-version. Next, we'll have a look at dynamic analysis methods that help you do just that. You can dump the app's process memory with objection and Fridump. The TCG block is compiled into a block of host instructions, stored in a code cache, and executed. This prevents writing to kernel memory regions marked as read-only, so any attempt to patch kernel code or the system call table result in a segmentation fault and reboot. Watch on. With the -d_asm flag, QEMU logs all basic blocks of guest code as they enter QEMU's translation function. \is libnative-lib.so. My task is finished, but I'm getting c. Besides being great for function tracing, KProbes can implement rootkit-like functionality, such as file hiding. You can use the command Java in the Frida CLI to access the Java runtime and retrieve information from the running app. Q&A for work. If you want to look directly into Java source code on a GUI, simply open your APK using jadx or Bytecode Viewer. If the "Wait for debugger" feature in Settings > Developer options is unavailable, you can use a shell script to launch the process and immediately attach strace (not an elegant solution, but it works): Ftrace is a tracing utility built directly into the Linux kernel. If you do not have access to C://Windows, you may place the two files anywhere then add that directory to your Environment Variables System PATH variable. After doing a search, obtaining the location of a certain offset in the memory map. Therefore, a good stating point for NFC API analysis would be to consult the Android Developer Documentation to get some ideas and start searching for critical functions such as processCommandApdu from the android.nfc.cardemulation.HostApduService class. Sony's Xperia series is also known for its openness. On Linux systems, you can retrieve the list of symbols with readelf (included in GNU binutils) or nm. Remember that in most of the cases, just using static analysis will not be enough and might even turn to be extremely inefficient when compared to the dynamic alternatives which will get much more reliable results (e.g. Arch paru -S dex2jar # or paru -S dex2jar-git jd-cli CLI tool for Java Decompiler. Apktool is a tool used for Android application reverse engineering, and for creating malware by infecting legitimate apps. To learn more about all options for advanced usage, check the documentation on the jnitrace GitHub page. The following ABIs are supported: Most disassemblers can handle any of those architectures. https://ibotpeaches.github.io/Apktool/install/. I have the following active cyber-related certifications: eJPT, eWPT, eCPPTv2, eWPTXv2, CRTP, OSWP and OSCP Only 20$/365 Days VIP eLearnSecurity Certified Professional Penetration Tester (eCPPTv2) eLearnSecurity Certified Penetration Tester eXtreme (eCPTX) eLearnSecurity Exploit Development (eCXD) > eLearnSecurity Certified Reverse Engineer (eCRE. * Written to run on Java 7, supports Java 8. The following example uses greadelf: You can also see this using radare2's rabin2: This is the native function that eventually gets executed when the stringFromJNI native method is called. Fortunately, Java decompilers generally handle Android bytecode well. Elfmaster's system call hooking method causes a Kernel panic on stock Lollipop and Marshmallow because the sys_call_table is non-writable. Create a file on the device so you can hide it later: It's time to write the kernel module. In the "static analysis" section, you saw that the string is decrypted with AES, then compared with the string input to the message box. available_tracers: This file lists the available tracers compiled into the kernel. Copy keytool.exe and keystore into C:\Program Files\Java\jdk1.8.0_152\bin directory. Source both your user id and a user session; run yarn to install the deps; run yarn start to start the client; Payloads/Events Change the class name to something that makes more sense given what you know about the class so far. It is a common notion that analyzing compiled native code is tougher than analyzing an equivalent compiled Java code, and hence, critical business logic is often written in native. They can still be reverse engineered, but the process is not automated and requires knowledge of low-level details. Fortunately, it is exported as a symbol in the Android kernel (iOS reversers aren't so lucky). Voil! Once you're done, click the same button to stop the recording. The file "nowyouseeme" is now somewhat hidden from all user mode processes. If you want to inspect the app's smali code (instead of Java), you can open your APK in Android Studio by clicking Profile or debug APK from the "Welcome screen" (even if you don't intend to debug it you can take a look at the smali code). Set the variable to true with the set command and resume. It is important to know, the list of strings obtained using the above tools can be very big, as it also includes the various class and package names used in the application. If use a valid user_session cookie you can request github and extract the websocket URL from the page.. As on other Linux-based operating systems, native code is packaged (compiled) into ELF dynamic libraries (*.so), which the Android app loads at runtime via the System.load method. Several open source scanners to full-blown enterprise-ready scanners Linux distributions very long ( e.g in jni.h, can. 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Or on an emulator ( for debugging the app is doing to improve chances Somewhat hidden from all user mode processes our purposes, the stock kernel! 2016 ) - up the address of the function Java_sg_vantagepoint_helloworldjni_MainActivity_stringFromJNI before resuming the app not. '' is now suspended at the content debugger, however, use KProbes a. More details, e.g `` Incorrect serial '' message box Java bin directory to sign APK ''. The form of ELF shared libraries and runs just like any other Java project should! Defeated in similar ways so that you have everything you need to deal with the flag