FEATURED VIDEO

Sponsored By:


SLIDE SHOWS
A Cisco commissioned study questioned 2,000 IT professionals and employees about risky behavior that could result in corporate data leaks. From losing laptops to letting strangers wander around their building, this is what was found.
Check out these new and improved enterprise IT management tools from CA.
The best multi-function printers (MFP), also known as all-in-ones, offer a slew of great features designed to streamline production and reduce costs. Here are a few of the market's best and brightest to come out recently.
INSIDE CHANNELWEB
techcareers logo Search Jobs:


  

Post Resume|Employers

Recent Post:


Automotive Market Segment Director
Silicon Labs seeking Automotive Market Segment Director in Austin, TX
spacer

BLOGS
The Linux Channel
May 14, 2008
A security warning posted yesterday on Debian's security list warned of a critical vulnerability in the way SSH keys are generated. This issue applies to Debian systems and Debian-based machines, including Ubuntu, its variants, and Knoppix.

SSH, or Secure Shell, is an encrypted protocol (using SSL) to connect to another machine. SSH also supports X11 forwarding to get graphical programs running on one machine to display on another. It is much more secure than telnet or other protocols to get to the shell prompt on a remote machine. A key generated by the server verifies that the user is connecting to the correct machine, and had not been diverted to a different (malicious) machine. Some systems assign a user-level key as its only authentication method -- no password required.

Discovered by security expert Luciano Bello, Debian's OpenSSL library was generating predictable random number sequences. This means that content encryption and authentication mechanisms using SSH were all weak, as anyone with free time could use brute-force tactics to break the keys.

The problem extends as far back as 2006, when Debian patched the OpenSSL library to fit the distribution better. The change removed the logic that seeded the OpenSSL random number generator. Without seeding, the random number generator was no longer random.

This isn't limited to only SSH, however, as the vulnerability extends to OpenVPN keys, DNSSEC keys, and key material used in X.509 certificates, and session keys used in SSL/TLS connections. All previously generated keys using OpenSSL versions starting with 0.9.8c-1 should be considered compromised.

The testing and current (etch) Debian versions are affected, but not the old stable (sarge) distribution. For Ubuntu, versions 7.04 (Feisty Fawn), 7.10 (Gutsy Gibbon), and 8.04 LTS (Hardy Heron) are all impacted.

To fix the vulnerability, all systems should download the patch to fix the OpenSSL library. Once the update is applied, weak user keys will be automatically rejected where possible so that new keys can be regenerated.

The known_hosts files should be updated with regenerated keys and old keys deleted. The update contains a ssh-vulnkey tool which can check for vulnerable keys. Unless there is a high degree of confidence that the key was generated on a safe machine (old Debian version), all keys should be regenerated regardless.

Posted by Fahmida Y. Rashid at 4:45 PM
CHANNELWEB MARKETSPACE >> (Sponsored Links)
ADVERTISEMENT




CHANNEL SERVICES >>