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How To - Java Importing

Java resources have no special preprocessing before you open them.
Import your Jar/Class/WAR/EAR file via the File>Open menu in Bytecode Viewer. (CTRL + O)

How To - Android Importing

Android resources have three options for preprocessing:
    1). Decode Resources
    2). Enjarify
    3). Dex2Jar (d2j)
1). Decode Resources will run APKTool to decode any packed android-specific resources
2). Enjarify will convert the dalvik specific bytecode to java bytecode
3). Dex2Jar will convert the dalvik specific bytecode to java bytecode

Import your APK/WAPK/DEX file via the File>Open menu in Bytecode Viewer. (CTRL + O)

How To - File Navigation

Using the resource list (it should say "Files" on the title bar) you can select all of the resources added into BCV.
Any archive will opened, to select a resource click + button for each folder.
Using the search pane inside of the resource list you can search by file name and extension.
For case-sensitivity enable the checkbox labeled "Exact".

Settings

• Fat Jar: {fatJar}
• Java: {java}
• Javac: {javac}
• Python 2.7 (or PyPy): {python}
• Python 3.X (or PyPy): {python3}
• RT.jar: {rt}
• Optional Lib: {lib}
• BCV Dir: {bcvDir}
• Temp Dir: {tempDir}
• Krakatau Dir: {krakatauDir}
• Enjarify Dir: {enjarifyDir}
• BCV Krakatau version: v{krakatauVersion}
• BCV Enjarify version: v{enjarifyVersion}

Command Line Interface (CLI)

• -help Displays the help menu
• -list Displays the available decompilers
• -decompiler [decompiler] Selects the decompiler, procyon by default
• -i [input file] Selects the input file (Jar, Class, APK, ZIP, DEX all work automatically)
• -o [output file] Selects the output file (Java or Java-Bytecode)
• -t [target classname] Must either be the fully qualified classname or "all" to decompile all as zip
• -nowait Doesn't wait for the user to read the CLI messages

File

• Add (Ctrl + O) - If you add a jar/zip BCV will unzip it, if you add an APK or DEX file, BCV will run dex2jar then run the jar input process.
• Reopen Recent File (Ctrl + L) - Reopens your last recent opened file.
• New Workspace (Ctrl + N) - It clears the opened jars/resources.
• Run (Ctrl + R) - Runs the classfiles you've loaded into BCV in a secure sandboxed JVM instance that you can fully debug.
• Compile (Ctrl + T) - Tries to compile all of the editable panes you've selected, if it's Java it'll compile with Ranino. Krakatau and *Smali use their own assemblers.
• Save As Jar - Export the class files and loaded resources as a runnable Jar file.
• Save As DEX - Run jar2dex and export the Classfiles as DEX.
• Save Files As - Save all the Classfiles and resources as a zip.
• Save Java File As - Save the currently opened decompiled Classfile.
• Save Java Files As - Save all of the decompiled Classfiles as a zip.
• Recent Files - Last 25 files/directories you've opened with BCV.
• About - A small information window about BCV.
• Exit - Closes BCV.

View Panes

• Editable - Defines if that viewing pane will be editable.
• None - Nothing will be displayed.
• Procyon - Decompiles with Procyon decompiler.
• CFR - Decompilers with CFR decompiler.
• FernFlower - Decompiles with FernFlower decompiler.
• JD-GUI - Decompiles with JD-GUI decompiler.
• Krakatau Java - Decompiles with Krakatau decompiler.
• Krakatau Bytecode - Disassembles with Krakatau disassembler.
• Smali - Disassembles with Smali.
• Bytecode - Decompiles the Bytecode via CFIDE. Not Editable.
• Hexcode - Shows the classfile in a hex viewer. Not Editable.

Settings

• Compile On Save - If selected whenever you do one of the File>Save * functions it will try to compile before it saves.
• Compile On Refresh - If selected whenever you press refresh it compile before it reloads the resource/class.
• Update Check - If selected it queries https://github.com/Konloch/bytecode-viewer to ensure you've got the latest version.
• Refresh On View Change - If selected whenever you change an option in the View Panes it will refresh the currently opened resources/class.
• Decode APK Resources - If selected whenever you add an APK, it will first run APKTool.jar to decode the resources.
• Set Python 2.7 Executable - Set the Python 2.7 executable if you want Krakatau decompiler/disassembler/assembler to work.
• Set JRE RT Library - Set the JRE RT library for Krakatau decompiler.

Plugins

• Open Plugin - Open a .java plugin created for BCV.
• Recent Plugins - Last 25 plugins you've opened with BCV.
• Code Sequence Diagram - Builds a crude code sequence diagram for the classfile that's currently opened.
• Malicious Code Scanner - Allows you to define what to search for, and outputs what it found.
• Show Main Methods - Detects and outputs all of the public static void main(String[]) functions.
• Show All Strings - Grabs then outputs all of the strings in every classfile.
• Replace Strings - Allows you to do a simple permanent .replace on the classfile strings, very useful for URL swapping.
• Allatori String Decrypter - Decrypts the Allatori obfuscated/encrypted strings.
• ZKM String Decrypter - Decrypts the ZKM obfuscated/encrypted strings.
• ZStringArray String Decrypter - Decrypts the ZStringArray obfuscated/encrypted strings.

Code from various projects has been used, including but not limited to

• J-RET by WaterWolf
• JHexPane by Sam Koivu
• RSynaxPane by Robert Futrell
• Commons IO by Apache
• ASM by OW2
• FernFlower by Stiver
• Procyon by Mstrobel
• CFR by Lee Benfield
• CFIDE by Bibl
• Smali by JesusFreke
• Dex2Jar by pxb1988
• Krakatau by Storyyeller
• JD-GUI + JD-Core by The Java-Decompiler Team
• Enjarify by Storyyeller

Notes

• If BCV fails to boot simply append -clean as an argument to clean the lib directory.
• Relax and take notes
• BCV was created out of love for Java Reverse engineering.
• You can join our Discord server at https://discord.gg/aexsYpfMEf!
• Bytecode Viewer's Homepage is https://bytecodeviewer.com