VeriSign remedies massive SSL blunder (kinda, sorta)
Rolling the dice with the internet's future
Analysis After being publicly outed issuing web credentials that were vulnerable to attacks that could allow criminals to spoof the encryption certificates of any website on the internet, VeriSign has issued assurances it has neutralized any real-world threat.
Tim Callan, vice president of VeriSign's product marketing, has said that within hours of last week's news that researchers had uncovered a devastating weakness in secure sockets layer certificates issued by VeriSign subsidiary RapidSSL, the company made changes to ensure all its SSL products were immune to the attacks.
As usual, the truth is a little more complicated.
To recap, an international team of researchers discovered that RapidSSL's reliance on the MD5 algorithm to sign SSL certificates made the certification authority (CA) vulnerable to spoofing. That meant that anyone with the know-how and computing power could buy an SSL certificate from the issuer, and with the flip of a few bits, generate the credentials to issue valid SSL certificates that would be accepted by Firefox, Internet Explorer, and other browsers.
It was analogous to someone acquiring a notary's official stamp that could then be used to certify fraudulent documents.
What Callan meant was that all VeriSign SSL products issued on or after December 30 were immune to the attack. But there's nothing stopping anyone who might have used the attack before that date to masquerade as RapidSSL and issue counterfeit certificates for any website of their choosing (think Bank of America, HMRC, or any other sensitive online destination).
Callan rightly concedes that it's impossible to prove a negative, but he says it's highly unlikely anyone besides the researchers has figured out how to execute the attack.
Mainly that's because the sheer amount of brain and computing power required take the attack out of the grasp of the average internet criminal. The attack used years' worth of research into the shortcomings of MD5 and even then required more than a month of intense computational processing to generate a certificate that was vulnerable.
"Connecting all of these together, it certainly seems this would be an unprofitable and unappealing avenue for a criminal to pursue," Callan told us the other day. "With so many lucrative green fields staring at them, why are they exploiting this?"
This line of reasoning has left some in the security world a little uneasy.
"They are betting that it took specialized knowledge to perform this attack and no one has independently exploited it before these researchers," says Nate Lawson, principal of security consulting firm Root Labs. "While the odds are probably good for VeriSign in this, betting the entire internet is a pretty big bet - one I wouldn't want to have to back up."
To its credit, VeriSign has cryptographers in the process of investigating whether it's possible to run previously issued certificates through some sort of collision detector that can identify any that may have been used to forge a CA certificate. The company has also offered to replace free of charge any MD5-hashed certificates issued before December 30.
But no one is sure if such a collision detector is even possible, and even if it is, what if it comes too late?
More generally, what Callan seems to gloss over is the truism VeriSign and the rest of the security community have repeated so many times that it's become a cliche: Hacking is no longer the province of script kiddies, but rather sophisticated and well-funded criminal enterprises. It's hard to imagine these groups wouldn't spend huge amounts of money to buy the credentials that would allow them to spoof any website in the world.
If he's correct that no one else stumbled upon the weakness the online world has dodged one hell of a bullet. If he's wrong and the internet suffers a crippling blow, we'll have VeriSign to thank. ®
MD5 hased certs are not vulnerable
Why don't people get this?
It doesn't matter if sercurebanking.blobby.com has an SHA hashed certificate or not, bad guy can create a certificate which looks like it has been signed validly with the sercurebanking.blobby.com common name in it.
But this still depends on another hack;
DNS, PC compromise (host file, IP redirection etc.) or a network routing/spoofing hack, you can't merely man-in-the middle an https (transparent) proxy, obviously more complex proxies could present a different certificate (like the ISA server functions), but if you have that much control of the network you could just use IP redirects or DNS etc.
If you *only* spoof the certificate then the DNS name won't match and you'll still get a warning (which, yes people still ignore, but they'll also ignore the same unsigned warnings which make the whole hack moot).
What this is, is a lot of excitement that a mathamatical theory has been proven.
Wost case scenaro:
Bad guys duplicate some important websites (paypal?) SSL cerificate, then also have the resources to perform a global DNS hack, they get in quick and steal money - but wait! anything this big would result in sites being closed and accounts locked.
It's a catch-22; the gain would have to be large as any hack requires a huge time investment depending on multiple hacks, but any large scale attack would be detected quickly, so it would need to be small-scale, and if it's small scale then there's easier ways to get the same effect.
in summary...... meh
"an email concerning cert renewal..."
Quis custodiet ipsos custodes?
DEAD CERT! If you need more detail read it twice.