Hackers obtain counterfeit TLS certificates for Google and other large services

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Attackers hijacked three top-level domains and used their control to mint counterfeit TLS certificates for Google and other large organizations, Google said Tuesday.
The attackers launched a series of attacks on the .gh, .sl, and .as country code top-level domains (ccTLDs) and then modified authoritative DNS records for selected domains within those namespaces. By controlling those DNS records, the attackers were able to pass automated domain control validation checks and obtain unauthorized certificates for “several Google domains” and “several leading global brands and widely used online services.” Google said it updated Chrome to block all certificates it identified as unauthorized, and worked with the issuing certification authorities to ensure the unauthorized certificates for Google properties were revoked.
Certificate issuance: The weak link in the chain
TLS certificates are the cryptographic credentials that underpin authentication and encryption protections for websites, mail servers, and other Internet infrastructure. These x.509 certificates use a digital signature to bind a domain name such as google.com to a public key. The public key is publicly available, while the private key is held only by the website operator. When a connection shows that the keys match, the visiting party knows it’s connected to the authentic site rather than an impostor. Possession of unauthorized certificates allows attackers to cryptographically impersonate the affected infrastructure.
Google didn’t identify the affected domains it owns or name any of the other organizations whose domains were affected. While noting that Chrome users do not need to take any action to be protected, Google cautioned domain owners not to rely solely on browser-side interventions to protect their users. The company is advising domain owners to monitor certificate transparency logs for unexpected certificate issuance across their domains and to publish restrictive Certification Authority Authorization DNS records to prevent attackers from reusing cached validation data after DNS control is restored.

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