Manipulate Your Way to the Root of It
One of the nice things about Linux — but by no means the most important — is the enhanced security that comes along with running it. That doesn't mean Linux never runs into security issues, though, and this week, the vulnerability in question centers around a nifty little service called udev.
According to advisories from several distributions, including Fedora, Ubuntu, and SUSE, a bug has been discovered that allows a local or remote user to exploit the udev service in order to gain root access to the system. Specially crafted Netlink messages, if sent to udev, can allow the sender to create a block device file that is globally-writable for an existing block device — that includes the root file system. The attacker can then create or manipulate files in order to gain root access to the system.
udev is a service, not a part of the kernel itself, used by most 2.6 series kernels to dynamically create files and folders — the /dev directory — for input and output from specific devices.
According to the SUSE Security Team's Sebastian Krahmer, who discovered the original bug, a further udev issue has been discovered, involving a function for decoding the path which is vulnerable to an integer overflow, and according to reports, to a heap overflow as well. At this time, it has only been confirmed that this second bug can cause udev to crash, though Fedora's security team has not ruled out the possibility that it may be exploited to obtain root access.
Fixes are in the works for the affected distributions, with some having already pushed updated packages to users while others are in the process. More information is available through security advisories from the relevant distributions, including Ubuntu Security Notice USN-758-1 and FEDORA-2009-3711.
Justin Ryan is a Contributing Editor for Linux Journal.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
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