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INFOCon yellow: update your Debian generated keys/certs ASAP

Published: 2008-05-15
Last Updated: 2008-05-15 23:16:38 UTC
by Bojan Zdrnja (Version: 3)
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As you can see, we raised the INFOCon level to yellow. The main idea behind INFOCon is to protect the Internet infrastructure at large, and the development on automated scripts exploiting key based SSH authentication looks like a real threat to SSH servers around the world (any SSH server using public keys that were generated on a vulnerable Debian machine – meaning – the keys had to be generated on a Debian machine between September 2006 and 13th of May 2008).

Note: 'Debian' in the above paragraph refers to any Debian-based Linux distribution including Ubuntu.

Scripts that allow brute forcing of vulnerable keys (see this as rainbow tables for SSH keys) are in the wild so we would like to remind all of you to regenerate SSH keys ASAP.

Please keep in mind that SSL certificates should be regenerated as well. This can be even more problematic if you had your certificates signed since you'll have to go through this process again (and possibly pay money again).

Update 2310 UTC: The new Debian package for SSH (ssh_4.3p2-9etch1) also applies a package called  "openssh-blacklist".  After this update, your  SSH server will refuse  keys from the compromised set.  The package also installs a new tool called "ssh-vulnkey" that can help in hunting down key files that contain weak keys.   Note that in combination with the existing ssh-keyscan, ssh-vulnkey can be used to easily identify servers that use weak host keys, so while these Debian patches help those who patch, they also make attacks easier against those who did not yet patch.

More information is available in our previous diaries:

http://isc.sans.org/diary.html?storyid=4420

http://isc.sans.org/diary.html?storyid=4414

 

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