Clément Labro – SCRT Team Blog

Exploiting KsecDD through Server Silos

Earlier this year, an intriguing admin-to-kernel technique was published by @floesen_ in the form of a proof-of-concept (PoC) on GitHub. The author mentioned a strong limitation involving LSASS and Server Silos, without providing much details about it. This piqued our interest, so we decided to give it a second look…

Ghost in the PPL Part 3: LSASS Memory Dump

Following my failed attempt to achieve arbitrary code execution within a protected LSASS process using the BYOVDLL technique and an N-day exploit in the KeyIso service, I took a step back, and ~~reconsidered my life choices~~ opted for a less ambitious solution: a (not so) simple memory dump. After all, when it comes to LSASS, we are mostly interested in extracting credentials stored in memory.

Ghost in the PPL Part 2: From BYOVDLL to Arbitrary Code Execution in LSASS

In the previous part, I showed how a technique called “Bring Your Own Vulnerable DLL” (BYOVDLL) could be used to reintroduce known vulnerabilities in LSASS, even when it’s protected. In this second part, I’m going to discuss the strategies I considered and explored to improve my proof-of-concept, and hopefully achieve arbitrary code execution.

Ghost in the PPL Part 1: BYOVDLL

In this series of blog posts, I will explore yet another avenue for bypassing LSA Protection in Userland. I will also detail the biggest challenges I faced while developing a proof-of-concept, and discuss some novel techniques and tricks to load an arbitrary DLL in LSASS, or even dump its memory.

A Deep Dive into TPM-based BitLocker Drive Encryption

When I investigated CVE-2022-41099, a BitLocker Drive Encryption bypass through the Windows Recovery Environment (WinRE), the fact that the latter was able to transparently access an encrypted drive without requiring the recovery password struck me. My initial thought was that there had to be a way to reproduce this behavior and obtain the master key from the Recovery Environment (WinRE). The outcome of a generic BitLocker bypass was too tempting not to explore this idea…

CVE-2022-41099 – Analysis of a BitLocker Drive Encryption Bypass

In November 2022, an advisory was published by Microsoft about a BitLocker bypass. This vulnerability caught my attention because the fix required a manual operation by users and system administrators, even after installing all the security updates. Couple this with the fact that the procedure was not well documented initially, and you have the perfect recipe for disaster.

This is typically the kind of vulnerability you do not want to deal with when you are in charge of a large fleet of workstations and laptops. However, on the other side of things, hard to patch vulnerabilities such as this one usually offer the best opportunities for red teamers and the like. This is where my journey investigating this bug and learning more about TPM-based BitLocker Drive Encryption began.

Bypassing PPL in Userland (again)

This post is a sequel to Bypassing LSA Protection in Userland and The End of PPLdump. Here, I will discuss how I was able to bypass the latest mitigation implemented by Microsoft and develop a new Userland exploit for injecting arbitrary code in a PPL with the highest signer type.

Bypassing LSA Protection in Userland

In 2018, James Forshaw published an article in which he briefly mentioned a trick that could be used to inject arbitrary code into a PPL as an administrator. However, I feel like this post did not get the attention it deserved as it literally described a potential Userland exploit for bypassing PPL (which includes LSA Protection).