Questions tagged [java]

Java is an object-oriented language and runtime environment (JRE). Java programs are platform independent, because they are compiled to bytecode and their execution is handled by a Virtual Machine called the Java VM or JVM.

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75 views

Patching Jar File (2022)

Currently reversing a .jar program recreationally, and I understand the workflow proposed here: https://www.netspi.com/blog/technical/thick-application-penetration-testing/patching-java-executables-...
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<"..." is not a valid class name"> when trying to debug an android app using jdb

I am trying to reverse engineer an android app for education purpose, but I ran into an annoying problem: the android app is obfuscated and some classnames start with digits. So when I tried putting a ...
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23 views

Injecting class into the JNIEnv in android jni

void *handle = dlopen("/data/local/tmp/libnative-lib.so", RTLD_LAZY); if (!handle) { printf("\nFailed to load library\n"); } void *offset = dlsym(handle, "...
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1answer
150 views

Determine if exe is written using Java

I'm examining my Windows programs to determine which ones are written in Java, and if so, whether they import a log4j library affected by the log4shell vulnerability. Programs that are packaged as JAR ...
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1answer
51 views

Ghidra: Iterating over function's codeUnits returns only 1st instruction

public void run() throws Exception { var cp = currentProgram; var nsSymbols = ghidra.app.util.NamespaceUtils.getSymbols("myNameSpace", cp); var glNS = nsSymbols.get(0)...
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62 views

How to deobfuscate Java application

Hi i am unable to deobfuscate the Advanced String Obfuscation Jar on tryHackMe I tried dumping the classes using a dumper javaagent deobfuscate the jar with java-deobfuscator threadtear functions ...
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1answer
75 views

Java Malware Dollar Sign

I am analyzing a mobile malware sample and got a trouble. When i put sample in JADX, i see some dollar sign. I mean like this; What does these dollar signs means?
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60 views

Need help logging string in smali

I'm trying to log p1 string to logcat. This is my function. new-instance v4, Ljava/lang/StringBuilder; invoke-direct {v4}, Ljava/lang/StringBuilder;-><init>()V invoke-virtual {v4, v3}, ...
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35 views

Capturing created and deleted files from a Java file

I am new to the malware analysis field but I do have an issue, a file I am working on creates 2 vbs files, reads from them and deletes them, this all happens in around 2 seconds. Also this is a Java ...
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40 views

Checksum verification of an apk does not the same as my java program

I'm from the sysadmin side of the IT and have not much experience in programing. I have an app that lets me screen share Android apps on my car's display. Sadly there is a whitelist baked into the app,...
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91 views

Is this native code possible for further static analysis?

I was trying to reverse engineer a native lib code in an android app. the .so contains many functions. But the function sUQWWyTBEs() was referred in the Java code. I was curious how this function ...
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1answer
109 views

what do these assembly code doing?

I tried to reverse engineer an apk app, and it was loading a native code. I have observed that the app was using the native code like this public static String v = sUQWWyTBEs().toString().substring(32,...
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105 views

What tools can be appropriate to reverse engineer a (open-source) java program?

I am very new reverse engineering, and have the below mentioned tasks to achieve on a open source program called Apache Ant. What (preferably free) tools can be appropriate to achieve these. I have ...
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29 views

Java Software cleanroom implementation

I'm trying to make a cleanrooom implementation of a java written lib. What resources can I use for it. Only the official software docs? Or can I use what I get after i throw the lib into a java ide (...
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121 views

How do I decode or decompile this class It seems codes are encrypted?

I've used JD-Gui, Luyten and other couple of Java Decompilers but it's not working what is the problem in here? Thanks! It's A Mod (Minecraft) and I'm porting into different versions. Code: public ...
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1answer
561 views

How to decompile heavily obfuscated classes mixed with Arabic/Chinese/Korean characters?

I recently downloaded a jar file and was curious to see if it was malicious, so I ran it through FernFlower and it wasn't able to deobfuscate it. When I unzipped the jar, I looked inside it and saw ...
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1answer
114 views

Java Help Understanding RSA Encrypt/Decrypt file and SD card

I was directed this way from the main superuser site: I have zero experience with Java or Android apps (I have coding experience in C) and tried reverse engineering a [now defunct/unsupported] app ...
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22 views

"strings" command from *nix, but as a Java API?

Looking for the "strings" command from *nix, but as a Java API. Does such a library or JAR exist? I've automated calling the strings *nix command, but would like to explore reverse ...
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22 views

How can I find the native functions used by the Java Runtime Environment on Linux?

I am not usually a Java programmer, but I need to locate for example, which native functions (or APIs) are used in something like java.io.File.createNewFile() on Linux? Initially, I am thinking of 2 ...
3
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2answers
452 views

Frida reading files is slow

I need to read a file around 2 MB into a byte array. var fis = Java.use("java.io.FileInputStream"); var file = fis.$new("/data/local/file.txt"); var fileBytes = new Uint8Array(file....
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1answer
163 views

Making a Android Toast via JNI, i.e. calling Java methods via JNI

Concerning the outputting of an Toast, I found that there are some ways to make a Toast, that invoke calling a FindClass on JNIEnv object with the android/widget/Toast parameter, but I found no ...
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568 views

Tracing all (or most of) function calls in a specific Android app

I'm having a problem, where I'm trying to trace some function calls in an Android app, that uses JNI for about all of its work. More specifically, a function call, in JNI, that makes (IIRC Android ...
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1answer
157 views

How can I see when a library is being called in Android?

Apologies for a beginner-esque question, but I am reverse engineering an Android application, that is most probably using the libusbhost.so library to interface with USB devices via Java Native ...
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1answer
844 views

Recaf: Recompile disabled, can't edit

I've download recaf jar file and install JDK 8. When I execute it/start it, it all works fine with java -jar recaf-2.12.0-J8-jar-with-dependencies.jar. I open a class file also no problem. The issue ...
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33 views

How can I tell whether or not a given library method is being referenced by a consumer program statically in OOP languages?

Preface: This question is about source code reverse engineering and static analysis. Meaning, there is no built code available but I have access to the source code of the program. Imagine I'm looking ...
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1answer
200 views

How to deobfuscate Java application protected by Java Antidecompiler [closed]

Here is some infomation I found from MANIFEST.MF Archiver-Version: Plexus Archiver Built-By: boonb Created-By: Apache Maven Build-Jdk: 1.8.0_231 Main-Class: JavaLauncher Modified-By: 9.4 (BIS Guard &...
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1answer
109 views

Accessing Call String of CALLOTHER Pcode Instruction via Java API?

Is there a way to access the call string of a CALLOTHER Pcode instruction when iterating over the Pcode in Java? The listing below shows an example of what I mean: 048 ...
2
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1answer
378 views

How do we decompile java so easy?

I have seen a lot of videos where everyone is decompiling the jar files so easily. but I learnt that we cannot decompile any compiled file so easily. I have a little bit of experience in Gidhra. I ...
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1answer
248 views

frida - The specified child already has a parent. You must call removeView() on the child's parent first when hooking, how do you solve it?

I wanted to hook the method A1f in the below code but frida returns the following exceptions: Found instance: MyHomeFragment{9bbd8d5} (0965bca9-4838-4ca1-a835-d99639ae15f1)} java.lang....
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1answer
744 views

how to deobfuscate to java zkm?

I will have a question for you, dear forum residents. I have a .jar file encrypted with ZKM which I think will work for me. I don't know how to decrypt this, can you help me?
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1answer
349 views

Calling a method of a Java object passed as argument to hooked function in Frida

I am trying to obtain the SecretKey passed to the decryptAesCipherText function. I hooked the function in Frida to try to print out the arguments when the method is called but since SecretKey is an ...
2
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1answer
772 views

How to Launch and debug Ghidra from Eclipse with two Modules I'm developing at the same time?

Ghidra comes with its own Eclipse extensions that allows you to develop new Scripts and Modules for Ghidra. I'm working on several new Modules for Ghidra that will work together. But I've basically ...
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2answers
335 views

Working with strong obfuscated Java

I've got a jar file, that is strong obfuscated. When I tried to put it into decompilers such as bytecode-viewer and luyten I seen many lines of traps and Chinese letters. I tried to deobfuscate it ...
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1answer
428 views

Dynamic analysis (Frida) reveals instance of a class that doesn't exist in the source code (dex2jar)

I have been diving into an apk's source code, doing both static analysis with Jadx (same as dex2jar) and dynamic analysis with Frida. I am trying to replicate the method that signs HTTP requests "...
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92 views

Hashing algorithm of length 50

I have been trying to reverse-engineer an Android application using Jadx for static analysis and Frida for dynamic analysis. The end goal is to be able to re-create the request signature, sent as a "x-...
1
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1answer
264 views

Reverse Engineering Java - Deobfuscating symbols

I'm new to Java and working on cleaning up a fairly large Java .jar sample where the obfuscator has renamed symbols into invalid names. For example: import org.lib.00.0.2; public final class 90 ...
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1answer
461 views

How can I get classes from "protected" JAR file?

I'm trying to get classes from JAR file / actually running JVM machine but: When I'm trying to open JAR file using for example 7Zip I dont see any classes. After unzip Manifest file is empty too. When ...
3
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1answer
259 views

How can I retrieve the encryption key in this code?

can anyone explain the following code? is it possible to retrieve the encryption key? I think the code was heavily obfuscated in addition to obfuscation, I can recognize it is using algorithms like ...
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0answers
107 views

JEB Decompiler - Signature recognition engine

I've been playing around with the JEB decompiler and Android reverse engineering suite. One interesting feature they have is deobfuscation by library code matching in which 3rd party libraries out ...
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0answers
364 views

Some obstacles in reversing a JNI Native library

I deleted my last question (it was not still answered and none's effort was wasted) as I got back and thought to re-read JNI documentation, to find I misinterpreted some bits. Things are now clearer ...
2
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2answers
2k views

Dealing with heavily obfuscated Java, possibly on bytecode level

I've got a jarfile from a friend, he told me to put it thru an decompiler. So I did, but: JD-GUI basically spit out just the imports and didn't show any class data CFR dumped out stack trace on ...
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2answers
156 views

Load Library Android

I work as cybersecurity consultant, and now I am on mission to reverse engineering of mobile app. I always reverse it using Jadx and dex2jar... the problem that after reverse them I found some native ...
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2answers
252 views

J2ME games obfuscator - Spyro and Tekken 5

While reversing some J2ME games like Spyro or Tekken 5 Mobile I have encountered a weird obfuscation where all fields, methods and classes have names like A, a, B, b, Aa, Bb etc. It's really hard to ...
2
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0answers
161 views

Google Maps, Android serialisation format

I've come across an SQLite database (gmm_storage.db) used by Google Maps on Android, and I'm unsure as to how the data it contains is serialised. For example: I'm saying serialised, as from the ...
2
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2answers
796 views

Java reverse engineering tool [closed]

I'm getting started on Java reverse engineering but I can't find a great tool. I'm currently using JD-Gui to decompile it. I've tried PNF's JEB which is really perfect but it's only for Android stuff....
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1answer
74 views

What types are read from byte array?

I try to understand what data types are read from a byte array. These methods seem to follow a common pattern: public class Reader { static short readA(byte[] bytes, int i) { int s = ((((...
5
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1answer
4k views

How to do debug a running java process in linux?

TLDR I want to do live debugging of a java program on a linux machine, and don't how/what debugger to attach to the JVM to get this done. I expect that this is a well-solved problem, but I lack the ...
3
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1answer
100 views

DEX file referenced type is not defined in file

I am analyzing a dex file and to ease with reverse engineering, I converted it a jar so it could be decompiled. In the file android/support/v17/leanback/media/MediaControllerGlue.class, the following ...
2
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1answer
555 views

Are there any Java decompilers accurate enough that if I recompiled the result, it should be identical to the original program?

I am trying to decompile Minecraft, to see if I can analyze the code to make a few small changes, but I need a decompiler good enough so I can recompile it in a way that will work. I have tried ...
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0answers
2k views

Obfuscated Config Files: EHI Files for HTTP Injector

So I have an ehi file, which is a configuration file for an Android App called HTTP Injector. Of course when I try to see it as a simple text, I just get random characters. What tool could I use to ...