SUMMARYAttackers hijacked the .gh, .sl, and .as top-level domains and used the access to create counterfeit TLS certificates for several Google domains and other major online services. Google said it updated Chrome to block the forged certificates and worked with certificate authorities so other browsers would reject them as well. The incident exposed a weakness in certificate issuance and enabled cryptographic impersonation of affected websites.
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.