PPLinject V2

The recent 'Redux' upgrade to PPLFault by Gabriel Landau from Elastic Security has allowed PPL injection into all Windows 10 versions (22H2+) and into Windows 11 up to 23H2:

https://www.elastic.co/security-labs/immutable-illusion https://github.com/gabriellandau/Redux

Thank you to Gabriel Landau for this work, and to James Forshaw (@tyranid) for the underlying techniques, as well as @itm4n for PPLdump code which is extended here to create fake Knowndlls directory object to bypass dll signature enforcement à la Forshaw.

PPLinject

This tool is derived from PPLdump by @itm4n (https://github.com/itm4n/PPLdump), described in two blog posts. The first part is about Protected Processes concepts while the second one discusses the bypass technique itself.

• Blog post part #1: Do You Really Know About LSA Protection (RunAsPPL)?
• Blog post part #2: Bypassing LSA Protection in Userland

PPLinject implements a userland exploit that was initially discussed by James Forshaw (a.k.a. @tiraniddo) - in this blog post - to allow injection of an arbitrary unsigned Dll into a PPL as an administrator.

Usage

Simply run the executable without any argument and you will get a detailed help/usage.

c:\Temp>PPLinject64.exe

Description:
  Inject an unsigned DLL into a Protected Process Light (PPL) with a *userland* exploit

Usage:
  PPLinject.exe [-v] [-d] [-f] <PROC_ID> <DLL>

Arguments:
  PROC_ID    The ID of a Process to inject
  DLL        The path of the Dll to inject

Options:
  -v         (Verbose) Enable verbose mode
  -d         (Debug) Enable debug mode (implies verbose)
  -f         (Force) Bypass DefineDosDevice error check

Examples:
  PPLinject.exe -d 684 C:\Users\Rebecca\AppData\Local\Temp\capemon_x64.dll

FAQ

Does it work on all versions of Windows?

First of all, PPLs were introduced with Windows 8.1 so older versions of Windows are obviously not supported. This project mainly targets Windows 10 (and its server editions) but I also tested it on older versions. You will find a summary table of the tests I did in the eponymous section.

How is it different from other tools?

Other PPL bypass tools usually execute arbitrary code in the Kernel through a digitally signed driver. This one is different as it involves only userland tricks and is (almost) fileless.

"Userland", you say?!

This tool leverages a very clever trick that was initially discussed by James Forshaw in 2018 (see Credits). It involves the use of the DefineDosDevice API function to trick the system into creating an arbitrary Known DLL entry. Since PPLs do not check the digital signature of Known DLLs, this can be later used to perform a DLL hijacking attack and execute arbitrary code inside a PPL.

Is it really "fileless"?

Although this tool performs a DLL hijacking attack as a second stage, it does not create a new DLL file on disk. Instead, it makes use of an NTFS transaction to virtually replace the content of an existing one, a technique directly inspired by the work of @_ForrestOrr (see Credits).

Can this tool cause a DoS?

Ths short answer is "no". First, it does not involve any direct Kernel access so there is no risk of causing a BSOD from this standpoint. In the worst case scenario, the tool might fail to remove the created Known DLL entry but, this will not cause a Denial of Service. It will just stay there until the next machine reboot. As the created entry would just be a symbolic link pointing to a non-existent section, the system would eventually fall back to the default location (i.e. the System32 folder) so it will not impact other programs running on the machine.

Tests

Windows version	Build	Edition	Arch	Admin	SYSTEM
Windows 10 20H2	19042	Pro	x64	✔️	✔️
Windows 10 20H2	19042	Pro	x86	✔️	✔️
Windows 10 1909	18363	Pro	x64	✔️	✔️
Windows 10 1507	10240	Educational	x64	✔️	✔️
Windows 10 1507	10240	Home	x64	✔️	✔️
Windows 10 1507	10240	Pro	x64	✔️	✔️
Windows Server 2019	17763	Standard	x64	✔️	✔️
Windows Server 2019	17763	Essentials	x64	✔️	✔️
Windows 8.1	9600	Pro	x64	⚠️	⚠️
Windows Server 2012 R2	9600	Standard	x64	⚠️	⚠️

⚠️ The exploit fails on fully updated Windows 8.1 / Server 2012 R2 machines. I have yet to figure out which patch caused the error.

[-] DefineDosDevice failed with error code 6 - The handle is invalid.

⚠️ On Windows 8.1 / Server 2012 R2, you might also have to compile the binary statically (see "Build instructions" below).

Build instructions

This Visual Studio Solution comprises two projects (the executable and a payload DLL) that need to be compiled in a specific order. Everything is pre-configured, so you just have to follow these simple instructions. The compiled payload DLL is automatically embedded into the final executable.

1. Open the Solution with Visual Studio 2017.
2. Select Release / x64 or Release / x86 depending on the architecture of the target machine.
3. Build > Build Solution.

On Windows 8.1 / Server 2012 R2, you might have to compile the binary statically.

1. Right-click on the PPLinject project.
2. Go to Configuration Properties > C/C++ > Code Generation.
3. Select Multi-threaded (/MT) as the Runtime Library option.
4. Build the Solution.

Credits

• @gabriellandau (Elastic Security) - PPLFault & Redux
• @itm4n - Original PPLdump tool [https://github.com/itm4n/PPLdump]
• @tiraniddo - Windows Exploitation Tricks: Exploiting Arbitrary Object Directory Creation for Local Elevation of Privilege
  https://googleprojectzero.blogspot.com/2018/08/windows-exploitation-tricks-exploiting.html
• @_ForrestOrr - Masking Malicious Memory Artifacts – Part I: Phantom DLL Hollowing
  https://www.forrest-orr.net/post/malicious-memory-artifacts-part-i-dll-hollowing
• @kevoreilly - This derivative tool