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[security-alerts] FYI: INFOCon yellow: update your Debian generated keys/certs ASAP

SANS     ...


INFOCon yellow: update your Debian generated keys/certs ASAP
Published: 2008-05-15,
Last Updated: 2008-05-15 14:42:52 UTC
by Bojan Zdrnja (Version: 1)
0 comment(s)

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).

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).

More information is available in our previous diaries:




Keywords: debian openssh openssl prng
0 comment(s)
Debian and Ubuntu users: fix your keys/certificates NOW
Published: 2008-05-15,
Last Updated: 2008-05-15 12:02:47 UTC
by Bojan Zdrnja (Version: 2)
1 comment(s)

Couple of days ago Swa posted a diary about a critical Debian/Ubuntu PRNG 
security vulnerability.

Today Matt wrote in to let us know that H D Moore posted a web page containing 
all SSH 1024, 2048 and 4096-bit RSA keys he brute forced.

It is obvious that this is highly critical - if you are running a Debian or 
Ubuntu system, and you are using keys for SSH authentication (ironically, 
that's something we've been recommending for a long time), and those keys were 
generated between September 2006 and May 13th 2008 then you are vulnerable. In 
other words, those secure systems can be very easily brute forced. What's even 
worse, H D Moore said that he will soon release  a brute force tool that will 
allow an attacker easy access to any SSH account that uses public key 

But this is not all - keep in mind that ANY cryptographic material created on 
vulnerable systems can be compromised. If you generated SSL keys on such Debian 
or Ubuntu systems, you will have to recreate the certificates and get them 
signed again. An attacker can even decrypt old SSH sessions now.

The Debian project guys released a tool that can detect weak keys (it is not 
100% correct though as the blacklist in the tool can be incomplete). You can 
download the tool from 

The bottom line is: this is very, very, very serious and scary. Please check 
your systems and make sure that you are both patched, and that you regenerated 
any potentially weak cryptographic material.


There have been some questions if this is related to the increase of SSH 
attacks we reported about couple of days ago (see 
http://isc.sans.org/diary.html?storyid=4408). At this point in time we think it 
is just a coincidence. In any case, you can help us by checking your logs - if 
the attackers are brute forcing password logins then the attack has nothing to 
do with this, but if you are seeing key authentication attempts then it is red 

The situation with web certificates is even worse - the public key is really 
that: public. So, for a weak key generated on Debian, an attacker could derive 
the private key and construct a Man-In-The-Middle attack without any problems 
in the browser! Very very scary. Makes one wonder how many people used Debian 
to generate their SSL keys.

As Swa said, there are basically 2 scenarios:

    * the public key is known publicly -> no brute force needed, the attackers 
walk in private key in hand
    * the public key isn't found -> brute force of some 260K keys needed.




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