Sudo Axes Escalation Glitch
Among the important benefits of Linux's permission hierarchy is its ability to keep untrusted users from running amok. The all-or-nothing nature of root access, however, can present headaches when users are trusted, but only so far. That is a problem the sudo utility attempts to solve, and does so fairly well — except for the occasional glitch.
A glitch of this sort turned up last week, allowing less-privileged users to skirt around sudo's protections and gain the powers of other users, including the superpowers of root. A vulnerability in sudo's sudoedit pseudo-command (sudo -e) could allow arbitrary command execution by those empowered to use the command. (Users can be granted access to specific abilities like sudoedit, without being assigned full sudo access.) According to sudo's security advisory:
When sudo performs its command matching, there is a special case for pseudo-commands in the sudoers file (currently, the only pseudo-command is sudoedit). Unlike a regular command, pseudo-commands do not begin with a slash ('/'). The flaw is that sudo's the matching code would only check against the list of pseudo-commands if the user-specified command also contained no slashes. As a result, if the user ran "sudo ./sudoedit" the normal matching code path was followed, which uses stat(2) to verify that the user-specified command matches the one in sudoers. In this case, it would compare the "./sudoedit" specified by the user with "sudoedit" from the sudoers file, resulting in a positive match.
The advisory notes that impact of the vulnerability is mitigated by the utility's defaults, however. Exploiting the glitch depends on sudoedit having been enabled in /etc/sudoers — the pseudo-command is not configured by default, rendering most installs impervious to the attack. All versions of sudo from 1.6.9 to 1.7.2p3, the then-stable release, are affected — versions 1.7.2p4 (now superseded by 1.7.2p5) and 1.6.9p21 patch the vulnerability. Mandriva, Red Hat, and Ubuntu have already pushed updated versions out to users.
Interestingly enough, sudo — the creation of SUNY/Buffalo students Cliff Spencer and Bob Coggshall — celebrates its thirtieth anniversary this year. Though it is often associated with sudo-dependent distributions like Ubuntu, which disables the root account entirely, it first appeared in 1980, some eleven years before Linux development began. The utility has been consistently rewritten over its three decades, to the extent that none of its original code remains. More information about sudo and its development can be found on the sudo project website.
Justin Ryan is a Contributing Editor for Linux Journal.
|Using Salt Stack and Vagrant for Drupal Development||May 20, 2013|
|Making Linux and Android Get Along (It's Not as Hard as It Sounds)||May 16, 2013|
|Drupal Is a Framework: Why Everyone Needs to Understand This||May 15, 2013|
|Home, My Backup Data Center||May 13, 2013|
|Non-Linux FOSS: Seashore||May 10, 2013|
|Trying to Tame the Tablet||May 08, 2013|
- Using Salt Stack and Vagrant for Drupal Development
- Making Linux and Android Get Along (It's Not as Hard as It Sounds)
- New Products
- Validate an E-Mail Address with PHP, the Right Way
- Drupal Is a Framework: Why Everyone Needs to Understand This
- A Topic for Discussion - Open Source Feature-Richness?
- The Pari Package On Linux
- Home, My Backup Data Center
- New Products
- Developer Poll
- This is the easiest tutorial
4 hours 26 min ago
- Ahh, the Koolaid.
10 hours 4 min ago
- git-annex assistant
16 hours 4 min ago
- direct cable connection
16 hours 26 min ago
- Agreed on AirDroid. With my
16 hours 37 min ago
- I just learned this
16 hours 41 min ago
17 hours 11 min ago
- not living upto the mobile revolution
20 hours 2 min ago
- Deceptive Advertising and
20 hours 38 min ago
- Let\'s declare that you have
20 hours 39 min ago
Free Webinar: Linux Backup and Recovery
Most companies incorporate backup procedures for critical data, which can be restored quickly if a loss occurs. However, fewer companies are prepared for catastrophic system failures, in which they lose all data, the entire operating system, applications, settings, patches and more, reducing their system(s) to “bare metal.” After all, before data can be restored to a system, there must be a system to restore it to.
In this one hour webinar, learn how to enhance your existing backup strategies for better disaster recovery preparedness using Storix System Backup Administrator (SBAdmin), a highly flexible bare-metal recovery solution for UNIX and Linux systems.