NetSPI Blog

Binrev- Automate Reversing Windows Binaries for Pentesters

Khai Tran
September 9th, 2013

I made a script to chain together some common tools to reverse-engineer Windows applications. It has come in handy for me in several situations when an application contains hundreds of assemblies written in native C, .NET or Java.

What you can do with this?

  • Static analysis: you can do a basic manual code review for decompiled sources to discover hidden communication channels, search for hard-coded passwords, or SQL injection vulnerabilities.
  • Import decompiled projects to an IDE to reconstruct and modify the original source code
  • Call hidden native exported functions with rundll32

Here is a rough description of what it does, and what tools it is using:

  • For exe, dll files:
    • Detect and de-obfuscate for .NET libraries with de4dot 
    • Decompile .NET libraries with JustDecompile 
    • Zip decompiled source code to netsources.zip 
    • Run strings against native libraries
    • Export call-able functions with dllexp. You can then try to run those functions with command Rundll32 <dll>,<function name> 
    • Export dependencies with depends 
    • Extract native resources with resourcesextract 
  • For jar files: 
    • Extract and combine java classes into a single zip file
    • Decompile java sources with procyon 
    • Zip decompiled source code to javasources.zip

Requirements

Usage

1. Configure the correct path to the  installed tools in the script:

set justdecompile="JustDecompileJustDecompile" set dllexp="dllexpdllexp"
set peverify=”peverify”
set zip="7-Zip7z"
set strings="strings"
set de4dot=" de4dot-2.0.3de4dot"
set java7="C:Program Files (x86)Javajre7binjava"
set procyon="procyon-decompiler-0.5.7.jar"

2. Run

Binrev [Source folder] [Output folder]
Output
/java/decompiled: decompiled Java class files
/native: native win32 libraries
/native/resextract: native win32 resource files
/net/decompiled: decompiled .NET projects
/net/bin: .NET libraries and executables
/net/deobs: deobfuscated .NET libraries
/logs: strings on native libraries, exportable functions, dependencies, list of decompiled and native dlls
/other: unhandled file extensions

The script is available at https://github.com/NetSPI/binrev

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