Distributed Policy Specification and Interpretation with Classified Advertisements

In a distributed system, the principle of separation of policy and mechanism provides the flexibility to revise policies without altering mechanisms and vice versa. This separation can be achieved by devising a language for specifying policy and an engine for interpreting policy. In the Condor [14] high throughput distributed system the ClassAd language [16] is used to specify resource selection policies and matchmaking algorithms are used to interpret that policy by matching jobs with available machines. We extend this framework to specify and interpret authorization policies using the SPKI/SDSI [6] public key infrastructure. SPKI/SDSI certificates are represented using the ClassAd language and certificate chain discovery is implemented using a modified matchmaking algorithm. This extension complements the resource selection policy capabilities of Condor with the authorization policy capabilities of SPKI/SDSI. Techniques for policy analysis in the context of resource selection and authorization are also presented.