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Certigna publishes SSL private key by mistake

SecurityNews
by Staff Writer
, 09 Jun 2011News

A French provider of SSL certificates appears to have made a bit of a boo-boo in its webserver configuration: publishing its private key for the world to see, and opening up a potentially serious security hole in the world's web browsers.

SSL certificates serve two purposes on the Internet: to encrypt information, and to verify a webserver's identity. An SSL certificate is what is used to keep the password you log in to your Internet banking site private, and also serves to ensure that you're genuinely logging in to the bank's own server.

This latter function requires that certificate providers don't issue certificates willy-nilly, instead verifying that the person requesting the certificate has some control over the domain in question. This can be as difficult as a long-winded meetings with business executives, and as simple as placing a secret file somewhere on the web server.

Certigna SSL trust in Firefox

To prevent random users from generating their own trusted certificates, each SSL certificate provider has a 'private key.' This is a piece of code which is kept completely secret, and which is used to sign each issued SSL certificate to validate that it has been issued by a trusted authority. These keys are usually closely guarded, as any certificate signed by the key from a trusted authority will be implicitly trusted by a web browser without display any warning messages.

Sadly, French SSL specialist Certigna appears to have failed to keep its secret under lock and key. A visit to the site's revocation list page - which is fully publicly accessible via a standard web browser - allows anyone and everyone to download the private key and other supposedly secret files, potentially enabling the creation of their own valid Certigna-signed SSL certificates.

Certigna server file list (private key highlighted)

Certigna isn't a small outfit, either. Its certificates are implicitly trusted in Internet Explorer, Firefox, Opera, Safari, and most other current browsers. A ne'er-do-well who downloads the key will be able to create his or her own certificates - for sites like www.yourbank.co.uk, or www.windowsupdate.com, for example - which will be seen as completely valid.

Sadly, the company's woes extend beyond the accidental publication of its private key. Because the key is likely to have been downloaded multiple times, the key must now be revoked. While this will allow the company to generate a new private key - which it will hopefully keep more secure this time around - it means that every single one of its customers certificates will suddenly become untrusted and need to be reissued.

Certigna SSL private key

It's a major security breach, and one of which the company appears unaware. We have attempted to contact Certigna to alert them to the issue, but at the time of writing have not received a response.

UPDATE 10:58
While we still haven't received a response from Certigna to our queries, the offending files have disappeared from the website.

UPDATE 11:57
Certigna has issued a response claiming that the file represented a 'test' certificate that had long since expired. "The private key available on the server corresponds to a test certificate used on our website certigna.fr," the company claimed. "It is impossible to generate new valid user certificates from this key. Moreover, it is encrypted and is an SSL certificate expired since July 2010. This key does not affect our infrastructure security. The Certigna SSL authority’s private key is stored in HSM (Hardware Security Module) and hence can never be recovered. This useless file has been removed."

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