Google, Microsoft, and Mozilla have decided to revoke trust in two digital certificates improperly issued by a Turkish certificate authority (CA).

The situation came to light Christmas Eve when Google Chrome detected and blocked an unauthorized digital certificate for the "*.google.com" domain.

"We investigated immediately and found the certificate was issued by an intermediate certificate authority (CA) linking back to TURKTRUST, a Turkish certificate authority," blogged Adam Langley, Google Software Engineer. "Intermediate CA certificates carry the full authority of the CA, so anyone who has one can use it to create a certificate for any website they wish to impersonate."

As a result of the detection of the rogue certificate, Google updated Chrome's certificate revocation metadata on Dec. 25 to block the intermediate CA, and then alerted TURKTRUST and other browser vendors.

"TURKTRUST told us that based on our information, they discovered that in August 2011 they had mistakenly issued two intermediate CA certificates to organizations that should have instead received regular SSL certificates," Langley continued. "On December 26, we pushed another Chrome metadata update to block the second mistaken CA certificate and informed the other browser vendors."

According to Microsoft, the intermediate certificate authorities TURKTRUST created were (*.EGO.GOV.TR and e-islam.kktcmerkezbankasi.org). It was the *.EGO.GOV.TR subsidiary CA then used to issue a fraudulent digital certificate to *.google.com, Microsoft notes in a customer advisory.

To address the issue, the company updated the Certificate Trust List (CTL) to remove the trust of the certificates causing the issue.

Mozilla, meanwhile, is "actively revoking trust" for the certificates in an update, blogged Michael Coates, Mozilla's director of security assurance, adding that users can expect a Firefox update Jan. 8.

"This is not a Firefox-specific issue," he explained. "Nevertheless, we are concerned that at least one of the mis-issued intermediate certificates was used for man-in-the-middle (MITM) traffic management of domain names that the customer did not legitimately own or control. We are also concerned that the private keys for these certificates were not kept as secure as would be expected for intermediate certificates."

"We have also suspended inclusion of the “TÜRKTRUST Bilgi İletişim ve Bilişim Güvenliği Hizmetleri A.Ş. (c) Aralık 2007” root certificate, pending further review," he added.

In 2011, CA security received increased attention due to a number of security incidents, including an attack on DigiNotar that led to browser vendors revoking hundreds of fraudulent SSL certificates and ultimately forced the company into bankruptcy.

In light of the most recent situation, Google announced plans to update Chrome again later this month to no longer indicate Extended Validation status for certificates issued by TURKTRUST, though connections to TURKTRUST-validated HTTPS servers may continue to be allowed, Langley blogged.

"Since our priority is the security and privacy of our users, we may also decide to take additional action after further discussion and careful consideration," he added.

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