Double-click the function to jump to its address in the disassembly Window. If nothing happens, download GitHub Desktop and try again. You can use the command Java in the Frida CLI to access the Java runtime and retrieve information from the running app. In this example, we'll use the CFR decompiler. You should get an output similar to the following: The hooked function outputted the decrypted string. This also applies to applications that contain native code. Discussing all the instructions in the function is beyond the scope of this chapter, instead we will discuss only the important points needed for the analysis. This is known as DLL injection on Windows (broadly used to modify and bypass anti-cheat mechanisms in games), LD_PRELOAD on Linux and DYLD_INSERT_LIBRARIES on macOS. Afterwards retrieve a wrapper for MainActivity class and overwrite its a method. Once the breakpoint is reached, you can read the method argument with the locals command. This is the plaintext string you're looking for! Installing and running it in an emulator or Android device is optional. to learn about the search command and get a list of options. sg.vantagepoint.a.a (again, everything is called a) along with something that looks suspiciously like a hex-encoded encryption key (16 hex bytes = 128bit, a common key length). In the above output, the most relevant fields for us are: This can be extremely useful to spot unusual files when monitoring applications using obfuscation or other anti-reverse engineering techniques, without having to reverse the code. GitHub # Reverse Engineering Star The process of analyzing a subject system to identify the system's components and their interrelationships and to create representations of the system in another form or at a higher level of abstraction. Sony's Xperia series is also known for its openness. Once the file is loaded, click into the "Functions" window on the left and press Alt+t to open the search dialog. Install the tool and run the following command on your boot image: This should create the files bootimg.cfg, initrd.img, and zImage (your original kernel) in the local directory. APK files are saved in a compressed .zip format and can be opened by any zip decompression tool. Reverse engineering, also called back engineering, is the process by which a man-made object is deconstructed to reveal its designs, architecture, or to extract knowledge from the object;. You can print the arguments passed to setCancelable with the locals command (the arguments are shown incorrectly under "local variables"). At this point, libnative-lib.so has been loaded. You also have access to the /dev/kmem interface, which you can use to patch kernel memory on-the-fly. These functions are available to normal processes via the system call interface. Alternatively you can use apktool to extract and disassemble resources directly from the APK archive and disassemble Java bytecode to smali. Create a file called kmem_util.c with the following code: Beginning with Android 5.0 (API level 21), all executables must be compiled with PIE support. Remember to always type ? Pass the address from which the analysis should start. The app is now going to exit. People that are used to IDA or Hopper just load the binary, go out to make a coffee and then when the analysis is done, they start doing the manual analysis to understand what the program is doing. Also note the "This is unacceptable" message from the first method of the class, private void a. Once the breakpoint is reached, activate method tracing with the trace go methods command and resume execution. With Frida, you can prevent the app from exiting by hooking the MainActivity.a method or the callback inside it. This is the syscall that the /bin/cat program uses when accessing a file, so the call should be suitable for a demonstration. You can use its adb jdwp command to list the process IDs of all debuggable processes running on the connected device (i.e., processes hosting a JDWP transport). This takes you to the method definition. Using the lsmod command, verify that the module has been loaded successfully. The following command logs all translated blocks to a file: Unfortunately, generating a complete guest instruction trace with QEMU is impossible because code blocks are written to the log only at the time they are translated, not when they're taken from the cache. Alternatively, you might prefer to look into the imports/exports. Patching APKs to load frida-gadget.so on start. Attaching the debugger, however, causes the app to resume, which you don't want. The process of analyzing a subject system to identify the system's components and their interrelationships and to create representations of the system in another form or at a higher level of abstraction. The content will . If the system property ro.debuggable is set to "0", Android disallows both JDWP and native debugging of release builds. If you own an IDA Pro license, open the file and once in the "Load new file" dialog, choose "ELF for ARM (Shared Object)" as the file type (IDA should detect this automatically), and "ARM Little-Endian" as the processor type. In this section we've just slightly touched the surface, please refer to the section "Basic Network Monitoring/Sniffing" in the "Android Basic Security Testing" chapter and also check the test cases in the "Android Network Communication" chapter. Review the code and you'll see that the method sg.vantagepoint.uncrackable1.MainActivity.a displays the "This in unacceptable" message box. Similarly, the above approach can be used to determine where and how an application is using NFC. 65. 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. The most straightforward way to intercept system calls is to inject your own code into kernel memory, then overwrite the original function in the system call table to redirect execution. Android's implementation of JDWP also includes hooks for supporting extra features implemented by the Dalvik Debug Monitor Server (DDMS). Immediately after that, the input string is passed to a Base32 decoding function at offset 0x00001340. In this case, we will initialize the state with the first instruction of the serial validation function. How to get an APK File. You can't intercept HTTPS traffic with a proxy because the app employs SSL pinning. jnitrace is a Frida based tool similar to frida-trace which specifically targets the usage of Android's JNI API by native libraries, providing a convenient way to obtain JNI method traces including arguments and return values. ", sg.vantagepoint.helloworldjni.MainActivity., com.acme.bob.mobile.android.core.BobMobileApplication.. This happens because you're working on the decompiled code instead of the source code. The feature can be enabled with the following command: The /sys/kernel/debug/tracing directory holds all control and output files related to ftrace. Be sure that apksigner is in the path and that you run it from the folder where your repackaged APK is located. GitHub Instantly share code, notes, and snippets. After you obtain the APK of an app that you wish to peek into. Here I have created a directory called Mobile_App. Open IntelliJ and select "Android" as the project type in the left tab of the "New Project" dialog. you cannot run the Frida server on the target device). The first thing you need to know is that the first argument passed to every JNI function is a JNI interface pointer. There is a thing that is worth noticing about radare2 vs other disassemblers like e.g. In jdb, set a breakpoint at the java.lang.System.loadLibrary method and resume the process. Runtime Instrumentation encompasses adding hooks and runtime patches to observe the app's behavior. 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). The whole process is called dynamic binary translation. Many command line tools are not shipped with the Android firmware to reduce the size, but can be easily installed on a rooted device using BusyBox. Retrieving the memory map and loaded libraries. Running this script should return the following output: Now you can run the validate binary in your Android device to verify the solution as indicated here. After execution of the basic block, QEMU repeats the process for the next block of guest instructions (or loads the already translated block from the cache). The address of the string is obtained from address r11 - 0x20. Follow Google's instructions to identify the correct git repo and branch for a given device and Android version. Release builds aren't meant to be debugged, that's the purpose of debug builds. This results in the package name "sg.vantagepoint.uncrackable1", which matches the original package name. 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 For instance, in the case of an app encrypting/decrypting data and handling keys in memory instead of using the AndroidKeyStore API. This technique can prove to be very useful when dealing with applications that have a big codebase and/or are obfuscated. Seems like we're expected to find some kind of secret code! In contrast to method profiling, which tells you how frequently a method is being called, method tracing helps you to also determine its input and output values. Note: If you experience JRE compatibility issues with apksigner, you can use jarsigner instead. HelloWorld JNI APK) that should be running on your Android phone (connected per USB). To learn more about all options for advanced usage, check the documentation on the jnitrace GitHub page. 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. The remaining anti-tampering and anti-debugging controls can be defeated in similar ways so that you can finally reach the secret string verification functionality. The following shows only a subset of them: You can adjust your search by using the search settings \e~search. Decompiling APK from directory, in this case the directory is titled "ReverseEngineering": After modifications are done, to recompile folder to APK from ReverseEngineering directory use the following command with apktool: 2.2. use jar signer to sign the apk with the key signature. Right-click the class name (the first a in a.a) and select Refactor -> Rename from the drop-down menu (or press Shift-F6).
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