By bjackson2115
Microsoft will soon be releasing a new security mitigation for the Common Log File System (CLFS) to the Windows Insiders Canary channel. In the past five years, 24 CVEs impacting CLFS have been identified and mitigated, making it one of the largest targets for vulnerability research in Windows. Rather than continuing to address single issues as they are discovered, the Microsoft Offensive Research & Security Engineering (MORSE) team has worked to add a new verification step to parsing CLFS logfiles, which aims to address a class of vulnerabilities all at once. This work will help protect our customers across the Windows ecosystem before they are impacted by potential security issues.
CLFS Overview
CLFS is a general-purpose logging service that can be used by software clients running in user-mode or kernel-mode. This service provides the transaction functionality for the Kernel Transaction Manager of the Windows kernel, which Transactional Registry (TxR) and Transactional NTFS (TxF) are built upon. While used in multiple places in the Windows kernel, a public user-mode API is also offered and can be utilized for any application wanting to store log records on the file system.
CLFS stores all log information and log records in a set of files, referred to as a “logfile”, which persists at a user-defined location on the file system. While the logfile is comprised of multiple files, the CLFS driver manages them as a single unit by creating a file handle for the whole set. The logfile is made up of one “Base Log File” (BLF), which holds the necessary metadata for the log, and two or more “container files”, which is where user-supplied log records are stored.
Read the full post here: Security mitigation for the Common Log Filesystem (CLFS)