Sometimes Linux users can be smug about their system’s security. And sometimes a major hole that’s been hiding in Linux since about version 2.6 opens up and in you fall.
The security hole this time is with how almost all Linux distributions implement Linux Unified Key Setup-on-disk-format (LUKS). LUKS is the standard mechanism for implementing Linux hard disk encryption. LUKS is often put into action with Cryptsetup. It’s in Cryptsetup default configuration file that the problem lies and it’s a nasty one. Known Linux distributions with this bug include Debian, Ubuntu, Fedora, Red Hat Enterpise Linux (RHEL), and SUSE Linux Enterprise Server (SLES).
As described in the security report, CVE-2016-4484, the hole allows attackers “to obtain a root initramfs [initial RAM file system] shell on affected systems. The vulnerability is very reliable because it doesn’t depend on specific systems or configurations. Attackers can copy, modify, or destroy the hard disc as well as set up the network to exflitrate data. This vulnerability is specially serious in environments like libraries, ATMs, airport machines, labs, etc, where the whole boot process is protected (password in BIOS and GRUB) and we only have a keyboard or/and a mouse.”
Now for the really embarrassing part. Want to know how to activate it? Boot the system and then hold down the enter key. Wait. After about a minute and a half, you’ll find yourself in a BusyBox root shell. You now control the horizontal, you now control the vertical, and whoever owns the system is not going to be happy with you.