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Gmail Attack Highlights Web Insecurity

A man-in-the-middle attack that relied on an unauthorized Google SSL certificate has revived concern over whether any Web communication is really secure.

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A user posting to Google's Gmail Help forum under the name "Alibo" claims to have received a warning from Google's Chrome browser that the SSL certificate he received when visiting Gmail was a fake. A self-described resident of Iran, "Alibo" speculates that either his government or ISP, ParsOnline, presented the fake certificate to intercept his communications.

"Alibo" posted a copy of the certificate to PasteBin, and security researcher Moxie Marlinspike confirmed via Twitter that the certificate has a valid signature. That means that the person or entity using it could use it to intercept Gmail traffic via a man-in-the-middle (MITM) attack.

Google acknowledged the reported MITM attack and noted that the certificate authority (CA) issuing the certificate, DigiNotar, should not be issuing certificates for Google. The company also called attention to a Chrome security feature that blocked the attack.

"We're pleased that the security measures in Chrome protected the user and brought this attack to the public's attention," a spokesperson said in an email. "While we investigate, we plan to block any sites whose certificates were signed by DigiNotar."

Mozilla said it has issued updates to Firefox and other software that revoke trust in the DigiNotar root.

A separate post to PasteBin provides information about verifying the validity of the certificate's signature and condemns for possibly enabling the Iranian government to intercept communications.

"This CA should receive an Internet death sentence as [its] carelessness may have resulted in deaths in Iran--this cert was issued in JULY of 2011 and it is now just a few days before SEPTEMBER," the unattributed post said. "It is being used in the wild against real people in Iran *right* now."

Or it was. DigiNotar issued a statement Tuesday saying that on July 19, 2011 it had detected an intrusion into its systems that had resulted in the fraudulent issuance of several public key certificate requests. The company says it conducted an audit to revoke those certificates but recently discovered at least one certificate had not been revoked. It subsequently consulted the Dutch government and revoked the fake certificate.

On one level, this is a triumph for Google, which just introduced a way to ensure that only SSL certificates from a pre-approved list of CAs will be accepted for Google sites and a limited number of third-party sites like PayPal, LastPass, and a handful of others.

On another level, it's reminder that certificate authorities can be hacked, duped, or induced to surrender the keys to someone else's Web kingdom. And there really isn't any penalty for CAs that allow this to happen.

The issue was brought to the fore in March when certificate authority Comodo acknowledged that two affiliated registration authorities had been compromised, allowing a hacker to obtain certificates associated with Google, Mozilla, Skype, Windows Live, and Yahoo. As if to underscore that point, Comodo was hacked three more times in the following two months.

But as Marlinspike noted in his presentation at the Black Hat security conference, a UBM TechWeb event, this year, nothing happened to Comodo as a result of these breaches.

Christopher Soghoian, a security researcher and privacy advocate, said in phone interview that while webmail can be secured, "the certificate authority infrastructure is horribly broken." He documented the issues at length in a paper he published in March, Certified Lies: Detecting and Defeating Government Interception Attacks Against SSL.

Essentially, the U.S. government and other governments around the world, either via appliances purchased from legitimate vendors or using illegitimate means, can intercept supposedly secure SSL sessions. And anyone else who can obtain a certificate from a CA, and possesses the technical know-how and network access, can do so as well.

"I don't know how much worse it could get," said Soghoian. "You would think folks would be worried about people spying on confidential communications."

Soghoian said that none of the browser vendors wants to be the first address the issue for fear that a fix might break some websites and prompt users to switch to other browsers. He said the browser vendors should work together to resolve the issue and that if they can't, the Department of Justice or the Federal Trade Commission might have to mandate a coordinated effort to address the problem.

"This is an issue of national security," he said. "The real story is this is happening every day."

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