Blog
Random insights of our daily work
Filesystem Vulnerabilities in Bootloaders: A Hidden Risk for Verified Boot Mechanisms
Filesystem vulnerabilities in bootloaders like U-Boot and Barebox represent a critical yet often overlooked risk to the verified boot process in Linux-embedded IoT systems. While verified boot mechanisms authenticate file contents, weaknesses in the handling of filesystem metadata can enable attackers to bypass the chain of trust, exposing devices to arbitrary code execution and compromising system security.
sigma-star-sa-2024-001: CHAP authentication bypass in user-space Linux target framework (tgt) up to v1.0.92 (CVE-2024-45751)
The user-space iSCSI target daemon of the Linux target framework (tgt) uses an insecure random number generator to generate CHAP authentication callenges. This results in predictable challenges which an attacker capable of recording network traffic between iSCSI target and initiator can abuse to bypass CHAP authentication by replaying previous responses.
Thoughts on Linux CNA's Approach and the Resulting CVE Flood
Recently, the Linux Kernel Project attained the status of a CNA (CVE Numbering Authority), granting it the capability to independently issue CVEs (Common Vulnerabilities and Exposures). While this development may not appear groundbreaking on its own, the substantial increase in the number of newly assigned CVEs has captured the attention of many individuals. I've received numerous inquiries from people seeking clarification on the situation surrounding the Linux CNA and expressing concern about the apparent surge in the issuance of CVE numbers for almost every non-trivial patch applied to the maintained stable kernel trees.
Pseudo Graceful Process Termination through Code Injection
This blog post outlines the utilization of code injection to create a tool capable of gracefully terminating any program, setting its exit code to 0.
A Time Consuming Pitfall for 32-bit Applications on AArch64
When running legacy applications on AArch64, an interesting pitfall can arise.
Investigating Paranormal Shell Activities
Recently, while attending a conference, I observed an unusual occurrence in my terminal emulator: terminal tab windows were getting highlighted without any apparent notification within the shell session. Time to unpack our trusty debugging tools to uncover the mystery of these activities.
Analyzing Packet Drops Without Tooling: Or ftrace the Pure Way
Linux offers a lot of tools to understand internals, today we'll analyze the network stack with zero tools installed.
No Love for Negative Permissions
Negative permissions have always been bad practice, with the help of container tooling they can be bypassed too.
CVE-2023-31147: Insufficient randomness for DNS query identifiers in c-ares
We've been part of a team that audited c-ares. This is a writeup of how we discovered that DNS query identifiers generated by c-ares are not always properly random which lead to CVE-2023-31147.
Let's Embed a Go Program into the Linux Kernel
Today, we would like to present a lesser-known feature of the Linux kernel. Instead of launching a program from a file system, regardless of whether it's virtual or not, it is also possible to embed a user-space program directly into the kernel image itself and start it from there.
Embedded Open Source Summit 2023 in Prague
The Embedded Open Source Summit in Prague offered valuable insights and connections for our company, focusing on Linux and security, as our first major conference since the pandemic.
Who's your canary?
Stack canaries are a common security feature to mitigate buffer-overflows. However, it's value is generated differently in every libc-implementation, which has security implications.
Restricting network access using Linux Network Namespaces
Our last blog post on Linux mount namespaces explored ways to restrict access to the file system. In this post we'll show how to restrict access to the network.
Too many CPUs to build
Lately we've been facing strange build errors on one of our build servers. The root cause was quite surprising.
Restricting file system access using Linux Mount Namespaces
Linux offers a variety of mechanisms to confine a process, one of them are namespaces. Today they are mostly used as foundation for Linux containers. In this blog post we'll demonstrate how namespaces can be used to restrict access to the file system for a given process and all its children.
Training: Kernel Internals for Linux Admins
Understanding certain kernel internals is not only useful for persons that intend developing kernel related software.
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