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sRDI - Shellcode Reflective DLL Injection

sRDI allows for the conversion of DLL files to position independent shellcode.

Functionality is accomplished via two components:

  • C project which compiles a PE loader implementation (RDI) to shellcode
  • Conversion code which attaches the DLL, RDI, and user data together with a bootstrap

This project is comprised of the following elements:

  • ShellcodeRDI: Compiles shellcode for the DLL loader
  • NativeLoader: Converts DLL to shellcode if neccesarry, then injects into memory
  • DotNetLoader: C# implementation of NativeLoader
  • Python\ConvertToShellcode.py: Convert DLL to shellcode in place
  • Python\EncodeBlobs.py: Encodes compiled sRDI blobs for static embedding
  • PowerShell\ConvertTo-Shellcode.ps1: Convert DLL to shellcode in place
  • FunctionTest: Imports sRDI C function for debug testing
  • TestDLL: Example DLL that includes two exported functions for call on Load and after

The DLL does not need to be compiled with RDI, however the technique is cross compatiable.

Use Cases / Examples

Before use, I recommend you become familiar with Reflective DLL Injection and it's purpose.

Convert DLL to shellcode using python

from ShellcodeRDI import *

dll = open("TestDLL_x86.dll", 'rb').read()
shellcode = ConvertToShellcode(dll)

Load DLL into memory using C# loader

DotNetLoader.exe TestDLL_x64.dll

Convert DLL with python script and load with Native EXE

python ConvertToShellcode.py TestDLL_x64.dll
NativeLoader.exe TestDLL_x64.bin

Convert DLL with powershell and load with Invoke-Shellcode

Import-Module .\Invoke-Shellcode.ps1
Import-Module .\ConvertTo-Shellcode.ps1
Invoke-Shellcode -Shellcode (ConvertTo-Shellcode -File TestDLL_x64.dll)

Stealth Considerations

There are many ways to detect memory injection. The loader function implements two stealth improvments on traditional RDI:

  • Proper Permissions: When relocating sections, memory permissions are set based on the section characteristics rather than a massive RWX blob.
  • PE Header Cleaning (Optional): The DOS Header and DOS Stub for the target DLL are completley wiped with null bytes on load (Except for e_lfanew). This can be toggled with 0x1 in the flags argument for C/C#, or via command line args in Python/Powershell.

Building

This project is built using Visual Studio 2015 (v140) and Windows SDK 8.1. The python script is written using Python 3.

The Python and Powershell scripts are located at:

  • Python\ConvertToShellcode.py
  • PowerShell\ConvertTo-Shellcode.ps1

After building the project, the other binaries will be located at:

  • bin\NativeLoader.exe
  • bin\DotNetLoader.exe
  • bin\TestDLL_.dll
  • bin\ShellcodeRDI_.bin

Credits

The basis of this project is derived from "Improved Reflective DLL Injection" from Dan Staples which itself is derived from the original project by Stephen Fewer.

The project framework for compiling C code as shellcode is taken from Mathew Graeber's reasearch "PIC_BindShell"

The PEFile project is used in the python script for parsing.