Ubuntu users: You need to update your SSH keys

A bug was discovered that made the random number generator that helped create your .ssh/id_rsa key less random than it should have been. What does this mean in plain English? It means that if you created an SSH key with Ubuntu Feisty, Ubuntu Gutsy, Ubuntu Hardy or Debian Etch you need to update an important OpenSSL file and regenerate your key ASAP.

I’m going to follow Philip Newborough’s lead and reproduce the security notice in its entirety.

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Ubuntu Security Notice USN-612-1 May 13, 2008
openssl vulnerability
CVE-2008-0166
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A weakness has been discovered in the random number generator used by OpenSSL on Debian and Ubuntu systems. As a result of this weakness, certain encryption keys are much more common than they should be, such that an attacker could guess the key through a brute-force attack given minimal knowledge of the system. This particularly affects the use of encryption keys in OpenSSH, OpenVPN and SSL certificates.

This vulnerability only affects operating systems which (like Ubuntu) are based on Debian. However, other systems can be indirectly affected if weak keys are imported into them.

We consider this an extremely serious vulnerability, and urge all
users to act immediately to secure their systems .(CVE-2008-0166)

This advisory also applies to the corresponding versions of Kubuntu, Edubuntu, and Xubuntu.

== Who is affected ==

Systems which are running any of the following releases:

* Ubuntu 7.04 (Feisty)
* Ubuntu 7.10 (Gutsy)
* Ubuntu 8.04 LTS (Hardy)
* Ubuntu “Intrepid Ibex” (development): libssl <= 0.9.8g-8
* Debian 4.0 (etch) (see corresponding Debian security advisory)

and have openssh-server installed or have been used to create an OpenSSH key or X.509 (SSL) certificate.

All OpenSSH and X.509 keys generated on such systems must be considered untrustworthy, regardless of the system on which they are used, even after the update has been applied.

This includes the automatically generated host keys used by OpenSSH, which are the basis for its server spoofing and man-in-the-middle protection.

The problem can be corrected by upgrading your system to the following package versions:

Ubuntu 7.04:
libssl0.9.8 0.9.8c-4ubuntu0.3

Ubuntu 7.10:
libssl0.9.8 0.9.8e-5ubuntu3.2

Ubuntu 8.04 LTS:
libssl0.9.8 0.9.8g-4ubuntu3.1

Now’s a great time to update your SSH keys, and if you’re a member of Launchpad you’ll need to update your key there as well.

Big thanks to Philip Newborough and Steven Harms for posting this to both Planet Ubuntu Users and Planet Ubuntu itself to make sure we got this very important information. And as Zak B. Elep states in his post about the issue, this concerns you if you’ve created a key in the last couple of years. Ouch, indeed!