Aladdin: Advanced .NET Payload Generation and Execution Techniques

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  Lefty @lefterispan - Nettitude Red Team - 2022 / 2023 

Aladdin is a payload generation technique based on the work of James Forshaw (@tiraniddo) that allows the deseriallization of a .NET payload and execution in memory. The original vector was documented on https://www.tiraniddo.dev/2017/07/dg-on-windows-10-s-executing-arbitrary.html.

By spawning the process AddInProcess.exe with arguments /guid:32a91b0f-30cd-4c75-be79-ccbd6345de99 and /pid:, the process will start a named pipe under \\.\pipe\32a91b0f-30cd-4c75-be79-ccbd6345de99 and will wait for a .NET Remoting object. If we generate a payload that has the appropiate packet bytes required to communicate with a .NET remoting listener we will be able to trigger the ActivitySurrogateSelector class from System.Workflow.ComponentModel. and gain code execution.

Originally, James Forshaw released a POC at https://github.com/tyranid/DeviceGuardBypasses/tree/master/CreateAddInIpcData. However this POC will fail on recent versions of Windows since Microsoft went ahead and patched the vulnerable System.Workflow.ComponentModel (https://github.com/microsoft/dotnet-framework-early-access/blob/master/release-notes/NET48/dotnet-48-changes.md).

Nick Landers (@monoxgas) however, identified a way to disable the check that Microsoft introduced and wrote a detailed article at https://www.netspi.com/blog/technical/adversary-simulation/re-animating-activitysurrogateselector/ . The bypass is documented at pwntester/ysoserial.net#41 .

Aladdin is a payload generation tool, which using the specific bypass as well as the necessary header bytes of the .NET remoting protocol is able to generate initial access payloads that abuse the AddInProcess as originally documented.

The provided templates are:

* HTA

* VBA

* JS

* CHM

Notes

In order for the attack to be successfull the .NET assembly must contain a single public class with an empty constructor to act as the entry point during deserialization. An example assembly has been included in the project.

public class EntryPoint {
    public EntryPoint() {
        MessageBox.Show("Hello");
    }
}

Usage

Usage:
  -w, --scriptType=VALUE     Set to js / hta / vba / chm.

  -o, --output=VALUE         The generated output, e.g: -o
                               C:\Users\Nettitude\Desktop\payload

  -a, --assembly=VALUE       Provided Assembly DLL, e.g: -a
                               C:\Users\Nettitude\Desktop\popcalc.dll

  -h, --help                 Help

OpSec

• The user supplied .NET binary will be executed under the AddInProcess.exe that gets spawned from the HTA / JS payload. The spawning of the processes currently happens using the 9BA05972-F6A8-11CF-A442-00A0C90A8F39 COM object (https://dl.packetstormsecurity.net/papers/general/abusing-objects.pdf) which will launch the process as a child of Explorer.exe process.
• The GUID supplied in the process parameters of AddInProcess.exe can be user controlled. At the moment the guid is hardcoded in the template and the code.
• CHM executes the JScript through XSLT transformation

Defensive Considerations

• Addinprocess.exe will always launch with /guid and /pid. Baseline your environment for legitimate uses – monitor the rest