USN-612-5: OpenSSH update

14 May 2008

openssh update

A security issue affects these releases of Ubuntu and its derivatives:

  • Ubuntu 8.04 LTS
  • Ubuntu 7.10
  • Ubuntu 7.04

Software Description

  • openssh

Details

Matt Zimmerman discovered that entries in ~/.ssh/authorized_keys with options (such as “no-port-forwarding” or forced commands) were ignored by the new ssh-vulnkey tool introduced in OpenSSH (see USN-612-2). This could cause some compromised keys not to be listed in ssh-vulnkey’s output.

This update also adds more information to ssh-vulnkey’s manual page.

Original advisory details:

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.

Update instructions

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

Ubuntu 8.04 LTS
openssh-client - 1:4.7p1-8ubuntu1.2
openssh-client-udeb - 1:4.7p1-8ubuntu1.2
Ubuntu 7.10
openssh-client - 1:4.6p1-5ubuntu0.5
openssh-client-udeb - 1:4.6p1-5ubuntu0.5
Ubuntu 7.04
openssh-client - 1:4.3p2-8ubuntu1.4
openssh-client-udeb - 1:4.3p2-8ubuntu1.4

To update your system, please follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.

After performing a standard system upgrade, users are encouraged to re-run ssh-vulnkey on their systems.

References