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After Debian's epic SSL blunder, a world of hurt for security pros

Admins: Heal thy certificates

Weakened White House

Among the weak SSL certificates at time of publication is this one belonging to Whitehouse.gov. It's of little consequence, since the site doesn't conduct secure transactions, but it does show the ubiquity of the problem. The key is owned by content delivery provider Akamai Technologies and is used by about 20,000 websites. Akamai is in the process of replacing it.

Akamai has escaped relatively unscathed. All its keys involved in sensitive transactions are generated using a highly customized Debian derivative that didn't include the buggy random number generator. The single key used by Whitehouse.gov and the other Akamai customers, which was generated using a separate system running on standard Debian is the only one affected, says Andy Ellis, Akamai's senior director of information security.

"I can't imagine how painful this will be for people who are using large data centers with hundreds of certificates," Ellis said.

The unwieldy cleanup effort is akin to the aftermath of a serious Flash vulnerability found in December to be plaguing tens of thousands of websites. Three months after a patch was released, the sites - many carrying out banks financial and other sensitive transactions - remained vulnerable because they had yet to remove and regenerate an estimated 500,000 buggy flash applets. Both the Debian and Flash vulnerabilities are unusual, because applying the patch represents only the beginning of the healing process.

The Debian bug was introduced in September 2006. It vastly reduces the amount of entropy used when programs like the Apache webserver, Sendmail, Exim and some implementations of Kerberos use OpenSSL to perform basic cryptographic functions. As a result, attackers can crack SSL keys, x.509 certificate keys, SSH keys, and digital signatures in fewer than 33,000 guesses, rather than the seemingly-infinite number of tries that would normally be required.

Tools available from Ubuntu and Metasploit author HD Moore are designed to aid in the process of detecting weak keys, but Appelbaum, the independent researcher, says certain conditions will prevent even diligent searches from finding everything. For example, keys with nonstandard sizes may not be flagged even though they're vulnerable.

"What that means is you have tools that may cover large swaths of the key space, but they won't cover all of the key space," he says.

So if your organization hasn't begun a thorough audit of all the keys in its portfolio, now is the time to get to it. Like an outbreak of lice at the children's grade school, its an unpleasant task eradicating the pests, but it's got to be done.

"This is a bit of a nightmare for anybody who used Debian" or programs that relied on its OpenSSL library, says Vincent Danen, the security team manager for Mandriva, a Linux distribution that was not affected by the bug. "If you're running a Debian shop and you have 100 certificates, depending on who you've got as a certificate authority, you could be looking at big bucks to regenerate your keys and get them re-signed. It could take months or even years for all the keys to get weeded out." ®

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