Introduce a Revocation functionality into Kerberos eco-system.
Possible scenarios and approaches
- “Black list” on KDC: KDC stores information about jeopardized clients together with the timestamp when the accident was recorded (e. g. Client lost mobile phone with some active security-sensitive applications and informed KDC about it). The Application Server accesses this information (perhaps, through a special channel/protocol) and acts accordingly;
- Application server observes some malicious activity (e.g.from audit log analysis) and reports it to KDC. KDC acts accordingly. Ideally, the Client (person or service) is also informed that his/her credentials are jeopardized;
- KDC learns that client is jeopardized and dispatches warnings to all services that may be potentially affected by the accident. The warning is sent only if the ticket for the particular service was issued and it is still valid.
- Forensics: Application server observes the malicious action. It informs KDC about the accident, but continues to serve the hacker to allow time to track down the originator of the attack.
Lightweight approach under CAMMAC umbrella
KDC learns that client is jeopardized or his/her credentials are changed or revoked, and incorporates the revocation information into AD-CAMMAC container for every NEWLY issued ticket. Once ticket receiver processes AD-CAMMAC, it can “locally” revoke/filter all existing tickets for that particular user.