SANS sounds alarm on Debian OpenSSL flaw
Lockpicking script prompts alarm
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The SANS Institute yesterday took the highly unusual step of issuing a yellow alert over a vulnerability in the cryptographic functions of Debian, the Linux distro that underpins Ubuntu.
Earlier this week Debian warned that the use of a cryptographically flawed pseudo random number generator in its implementation of OpenSSL meant that potentially predictable keys were generated. Versions of Debian's OpenSSL packages starting with 0.9.8c-1 (released in September 2006) are vulnerable.
Fears that the cryptographic key (including SSH, SSL session keys, OpenVPN and others) generated on affected systems may be weak were borne out by the discovery of scripts that allow brute forcing of vulnerable SSH keys. The SAN's Institute Internet Storm Centre warns that SSL certificates should also be regenerated because of the same cryptographic flaw.
Noted security researcher H D Moore, of Metasploit fame, was able to generate a table of 1024, 2048 and 4096-bit RSA keys in around two hours. Stronger keys would take longer to generate. Other security watchers also express concerns that certificate generated on vulnerable systems are wide open to exploit.
"Certificates build on affected systems may be weaker because they are generated using insufficient random data. One of the prerequisites for secure certificates is that there is a random seed for the generation of the keys, lack of randomness will make it more likely to predict or brute force the keys," Thomas Kristensen, CTO of security notification firm Secunia, explained.
"While this doesn't directly compromise any sites or communication channels it may make those who use these certificates more vulnerable to target attacks seeking to compromise the confidentiality of this communication or perhaps impersonate others. It is a very good idea to recreate any keys that has been generated on an affected system as soon as possible," he added.
Sysadmins are advised to generate new cryptographic keys after updating their software, as explained in Debian's advisory.
Debian said the flaw arises for a change it alone made in the OpenSSL package, suggesting that Linux distributions not derived from Debian are free from the bug. The flaw has been traced back to an attempt to silence a warning from a debugging tool.
One reader forwarded an excerpt from an internal discussion within the Debian Security Team that suggested the bug resides within OpenSSL itself and dates from May 2006. This pointed to possible flaws in OpenSSL 0.9.8b-1. However, the same source later told us, the flaw was later pinned down to OpenSSL 0.9.8c, as described in Debian's advisory. "They're still not revealing the full truth, particularly the fact the keyspace involved is only 215 possible permutations per architecture and thus very easily compromised if someone has a botnet at their disposal," our source said.
We ran the original post past cryptography guru Bruce Schneier who confirmed the gist of our source's concerns. "Any key generated using this system is far less random than you thought it was. This is, as they say, bad," he told El Reg. ®
COMMENTS
Debian should be truly ashamed
I'm a Linux developer, but every time I see something like this I feel more and more alienated from the Linux community. This flaw in particular baffles the mind. Think about it: The "security" people maintaining Debian's OpenSSL apparently don't understand how their own code works, to create and apply this sort of patch. Yet nobody thinks that this is a problem.
Nobody. Not at Debian. Not at Ubuntu. Not at any of the infinite (and infinitely sickening) derivatives of these two distributions. Probably not even their users, who are trusting these clearly incompetent "volunteers" with their valuable data.
If there's a moral in this, it's for the developers more than anything else. Trust upstream to do the heavy lifting -- it's their code, and they should know how it works. (I would recommend exactly the opposite to users regarding the distribution maintainers...)
Were this some little "voodoo" program -- written by someone who didn't understand the code -- I could understand patching "funky" code, or wanting to do extensive testing/debugging -- although again, that should be handled at the individual program's level, not the distribution. But OpenSSL is developed by computer security experts. If something in the code looks bizarre, but it's from a competent programmer, chances are it was done deliberately. If it ain't broke, don't fix it; if you don't know how it works, LEAVE IT ALONE.
I may be wrong, but when I googled this the other day, I'm pretty sure I saw several posts in OpenSSL's own mailing list archives about the apparent uninitialized memory "bug". At least a couple of them were well before this madness with Debian started. I think. Anyway, if that's the case, you'd think they could have at least googled the "problem" themselves before "fixing" it.
Mine's the one with the electromagnetic degausser (you can never be too sure about destroying insecure keys...) And the cattleprod, in case I ever meet any Debian people.
Patch regenerated SSL keys for me
As per title. Just running a set of upgrades on my Debian server, including this one. When the OpenSSH patch went on it regenerated my SSL keys for me automatically. Which was nice.
I'm off to regenerate my SSH keys.
Sweet
Just tried reconnecting to the server after the necessary reboot (updated the kernel image while I was at it), and PuTTY popped up a warning saying that the SSH keys had been changed. One less job for me!
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