Windows

Yesterday, the BSI (the German Federal Office for Information Security, or Bundesamt für Sicherheit in der Informationstechnik in German) published the first result document from the “Windows dissected” (ger.: “Windows seziert”) project: our analysis of Windows Hello for Business (WHfB). If you have followed this blog over the past year, you have seen the pieces. The full 170-page report has now been published. And it can be downloaded from the project page.

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While investigating how process mitigation settings are initialized, I encountered the global variable PspSystemMitigationOptions. Tracing how this value is populated led me to the CmControlVector. In this blog post, we take a look at the Windows kernel land configuration manager, especially its global CmControlVector variable. Quick note: the kernel’s configuration manager is not related to Microsoft Intune’s Configuration Manager. In short, the configuration manager is responsible for managing and implementing the registry. However, it is also responsible for setting up parts of the system during early boot.

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Today we are releasing a new white paper that delivers a technical analysis of security weaknesses discovered in WinpMem, an open-source Windows memory acquisition driver widely used in digital forensics.

After a concise primer on relevant Windows internals (virtual vs. physical memory, page tables and PTEs, CR3 context switching, and kernel and user memory separation), the report examines how both the fundamental design of WinpMem and specific implementation choices create severe risk.

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We are back from Black Hat USA, where we presented our research on Windows Hello for Business (Slides) once more. In the last two blog posts, we have discussed the architecture of WHfB and past attacks, as well as how the database works and how to swap identities in the database.

First, a few words regarding my experience at Black Hat: for me, it was the first time attending the conference and then directly as a speaker. I thoroughly enjoyed Black Hat. It took a while to get used to the size of the conference and the vibe of Las Vegas. What was especially interesting for me was connecting with other researchers. One thing that stood out was meeting with the team from MSRC and putting faces to the team itself. It feels way more personal to know who you’re talking to when you know the people handling your cases. During TROOPERS I typically have the chance to connect with many researchers, mainly from Europe. At Black Hat US, on the other hand, it is possible to connect more with the US scene and meet people you haven’t seen in a long time! Seeing familiar faces again is always nice, as opposed to putting them into your biometric template database. One nice detail was that some international researchers are aware of the research BSI (German: “Bundesamt für Sicherheit in der Informationstechnik” – “German federal office for IT security”) is facilitating. The results of our presentation stem from the “Windows Dissected” project we are performing on behalf of the BSI.

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In the last blog post, we discussed the full authentication flow using Windows Hello for Business (WHfB) with face recognition to authenticate against an Active Directory with Kerberos and showcased existing and new vulnerabilities. In this blog post, we dive into the architectural challenges WHfB faces and explore how we can exploit them.

The majority of the work was conducted in the context of the “Windows Dissected” project. This project, funded by the BSI (German: “Bundesamt für Sicherheit in der Informationstechnik” – the German Federal Office for Information Security), has the goal to perform ” various in-depth security analyses of security-critical components and functions in Windows.” Over the next years we will discuss these results here once they are published.

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Windows Hello for Business is a key component of Microsoft’s passwordless authentication strategy. It enables user authentication not only during system sign-in but also in conjunction with new and advanced features such as Personal Data Encryption, Administrator Protection, and Recall. Rather than depending on traditional passwords, Windows Hello leverages a PIN or biometric methods – such as fingerprint or facial recognition – to unlock cryptographic keys protected by the Trusted Platform Module (TPM).

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In a recent incident response project, we had the chance to virtually look over the attackers’ shoulder and observe their activities. The attackers used the Remote Desktop Protocol (RDP) for lateral movement within the compromized environment and beyond (MITRE techniques T1570, T1021). As a matter of fact, RDP creates cache files that contain tiles of the transferred screen recording data. While this fact is well-known and there are existing tools, we found it worth reporting because of two different aspects:

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This article is about the massive BSOD triggered by CrowdStrike worldwide on July 19. Analysis and information from CrowdStrike or other sources are regularly published, completing what is expressed here. Updates may also be provided in the future.

Friday, July 19, is a day to be remembered in computing history as the day of one of the biggest BSODs (Blue Screens of Death). We have seen air traffic come to a standstill over the USA and people climbing ladders with USB sticks to update giant screens. The impact was still measurable over many days. The question on everyone’s lips is how that all happened. CrowdStrike provided, on a regular basis, an explanation for people to understand what happened. But explanations can be hard to understand, especially for one who would like to read directly within CrowdStrike’s internal wording in their publications and regarding technical driver implementation details. Also, the analysis misses some points we consider relevant for secure software development. This article discusses conclusions from this massive crash, especially the necessity to change our mindset about software. This means we should understand, document, and evaluate independently software provided by vendors to know exactly what we install on our systems and to figure out the risk that may be taken by using the software. The time of naive belief in software magic must end with a third party’s independent review of the software, analysing its reliability, security, and stability. This is an activity we have been doing at ERNW for years, especially for e.g. the German Federal Office for Information Security (BSI)¹.

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The German Federal Office for Information Security (BSI – Bundesamt für Sicherheit in der Informationstechnik) has published several papers ERNW created as part of the long-term SiSyPHuS Win10-Project. This project focuses on system analysis of selected parts of the Windows 10 operating system performed by ERNW.

Analysis of the Application Compatibility Infrastructure (ACI): In this work we present an overview of the ACI technology along with a technical analysis of the compatibility protocol which is used first to determine if a compatibility solution needs to be applied, and second, to apply said compatibility solution. Furthermore, threats and mitigation in the context of the technology are presented a long with a monitoring approach. Finally, configuration and logging capabilities are discussed.

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I’m happy to announce the release of several plugins for Volatility 3 that allow you to dig deeper into the memory analysis. One of those plugins is PteMalfind, which is essentially an improved version of malfind. Another one is PteResolve which, similarly to the WinDBG command !pte, allows you to inspect Page Table Entry (PTE) information for e.g., a given virtual address. In this blog post we will have a closer look at these and more plugins, and the PteEnumerator base class and what you can do with it. The memory dump used for this blog post is available here. Some of the injection tools used in this blog post can be gathered from here.

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