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AggressiveGadgetToJScript

We created this aggressor script in order to automate the generation of payloads using the GadgetToJScript technique.

For the purposes of this release, we used a common injector that implements the QueueUserAPC injection method and injects to notepad.exe.

Feel free to use your own templates.

Additionally, the shellcode generated is compressed before being used in the injector template.

Usage

• Install mono framework: apt install mono-complete.
• Set the path variables inside GadgetToJScript.cna:
  • $toolpath is the absolute path of the installation directory.
  • $outpath is the directory used to output all generated artifacts.
  • $python3 is the absolute path of python3 binary.
  • $gzip is the absolute path of gzip binary.
  • $mcs is the absolute path of mcs binary.
• Load cna into CobaltStrike.
• A new menu CustomPayloads will appear. Generate the payload choosing listener, staged / stageless, architecture. Payload will be stored in your defined $outpath.
• Due to ConfigurationManager.AppSettings being readonly in Mono (https://github.com/mono/mono/issues/11751), we have to copy the generated EXE file into a windows box and execute it.
• The final GadgetToJscript payload (.js) will be generated. Currently using the reg-free template from GadgetToJscript.

Configuration:

$toolpath = "/opt/cobaltstrike/custom/AggressiveGadgetToJScript";
$outpath = "/tmp/payloads";
$python3 = "/usr/bin/python3";
$gzip = "/usr/bin/gzip";
$mcs = "/usr/bin/mcs";

Caveats

• Payload generated (.js) gets flagged by AV. Consider obfuscating /Templates/GadgetToJScript.js. As a PoC we opted using a powerful royal-like technique directly stolen from Caesar!
• Shellcode can also be encrypted by placing an encrypt function in Helper.py and a decrypt function in /Templates/Injector.cs
• Injection method can be replaced in /Templates/Injector.cs. Just make sure to place it in the constructor of the class.

Authors

• @eksperience

• @leftp

Credits

This tool is based on:

• Original code of GadgetToJScript from @med0x2e - https://github.com/med0x2e/GadgetToJScript

• Sample Injector used from @pwndizzle - https://github.com/pwndizzle/c-sharp-memory-injection/blob/master/apc-injection-new-process.cs