Certificate Authority (CA) DigiCert on Wednesday announced the en-masse revocation of more than 23,000 HTTPS certificates after certificate reseller Trustico sent over the private keys for those certificates.
The keys are supposed to be secret and only in the possession of certificate owners, not in the hands of the certificate authority, the reseller or any other third party. With the private keys exposed, DigiCert was forced to revoke impacted certificates within 24 hours, thus affecting a large number of customers.
The revocation appears to be the result of a one-month feud between Trustico and DigiCert and might evolve into an even larger number of certificates being axed.
This all apparently started on February 2, 2018, when Trustico sent a request to DigiCert “to mass revoke all certificates that had been ordered by end users through Trustico,” Jeremy Rowley, Executive VP of Product at DigiCert, explains. The CA refused, given the large number of certificates it was asked to revoke at once (50,000).
In August last year, DigiCert announced plans to buy Symantec’s website security and related public key infrastructure (PKI) solutions, after Symantec ended up in the crosshairs for wrongfully issuing TLS certificates on several occasions. Since December 1, 2017, Symantec SSL certificates have been issued by DigiCert.
With major browsers already announcing plans to distrust older Symantec certificates, Trustico too decided to abandon those certificates, and announced in mid-February that it would cease to offer Symantec branded SSL Certificates: Symantec, GeoTrust, Thawte and RapidSSL.
“As a valued partner of Comodo, Trustico have updated their systems to minimize disruption to customers with their API and ordering processes by enabling the automatic selection and ordering of equivalent products from the Comodo range,” Trustico said at the time.
A couple of weeks later, on February 27, Trustico sent DigiCert a file with 23,000 private keys matching certificates issued to reseller’s customers, which triggered a 24-hour revocation process.
“Trustico’s CEO indicated that Trustico held the private keys for those certificates, and then emailed us approximately 20,000 certificate private keys. When he sent us those keys, his action gave us no choice but to act in accordance with the CA/Browser Forum Baseline Requirements, which mandate that we revoke a compromised certificate within 24 hours,” DigiCert said in a Wednesday statement.
Because of these actions, starting today, visitors of impacted websites will see in their browsers that the connection to the domain is untrusted, unless the revoked certificates have been replaced in the meantime.
Since the beginning of February, DigiCert and Trustico have been communicating with each other over this, but each company has a different side of the story.
According to DigiCert, Trustico informed them that the certificates had been compromised and that it was in the possession of said private keys. Thus, DigiCert requested proof of compromise and received said keys.
“At this time, Trustico has not provided any information about how these certificates were compromised or how they acquired the private keys. As is standard practice for a Certificate Authority, DigiCert never had possession of these private keys,” Rowley says.
In addition to revoking the certificates, DigiCert decided to email all impacted customers to inform them on its action: “Following our standard revocation process, we gave notice via email to each certificate holder whose private keys had been exposed to us by Trustico, so they could have time to get a replacement certificate.”
Trustico, on the other hand, claims that it never said the certificates had been compromised, but that it informed DigiCert that it believed “Symantec to have operated our account in a manner whereby it had been compromised.”
The reseller also says that it doesn’t believe it to be “ideal to have any active SSL Certificates on the Symantec systems,” especially with Chrome set to distrust of all Symantec SSL certificates.
“The same management team responsible for that situation is duly employed at DigiCert and are fully managing our account, causing grave concern on our part as it appears to be business as usual with a new name. We were also a victim whereby Symantec mis-issued SSL Certificates owned by us, subsequently we were asked to keep the matter quiet, under a confidentially notice,” the company claims.
Moreover, Trustico points out that it never authorized DigiCert to email its customers about the revocation, but adds that it too sent a notice to the impacted clients.
The bottom line here, however, is the fact that DigiCert ended up revoking 23,000 HTTPS certificates because their private keys were compromised. Even if the keys hadn’t been compromised when the spat started, the fact that the reseller sent those keys in an email represented a compromise in itself.
“In communications today, Trustico has suggested that this revocation is due to the upcoming Google Chrome distrust of Symantec roots. That is incorrect. We want to make it clear that the certificates needed to be revoked because Trustico sent us the private keys; this has nothing to do with future potential distrust dates,” DigiCert points out.
The fact that Trustico kept those private keys on their platform is also worrisome.
Both Trustico and DigiCert said they would be working with the impacted customers to replace the axed certificates and that free replacement certificates are available for those clients.
Related: DigiCert Addresses Mozilla’s Concerns on Symantec CA Acquisition