Authoritative hooks

Posted Aug 11, 2022 0:09 UTC (Thu) by Cyberax (✭ supporter ✭, #52523)
In reply to: Authoritative hooks by cschaufler
Parent article: Security requirements for new kernel features

> Had we adopted authoritative LSM hooks the landscape would be very different indeed. Stacking of modules would have been impossible. What would happen if module A said "yes" and module B said "no"?

Various systems (like IAM policies in AWS or ACLs in Windows) typically consider "Deny" to be a veto on any allowing ACLs/policies.

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Authoritative hooks

Posted Aug 11, 2022 17:50 UTC (Thu) by cschaufler (subscriber, #126555) [Link] (1 responses)

This is exactly the "bail on fail" model of permissive hooks that we have today. What you can't do is what you had asked for, which is to provide a mechanism for a hook to grant access instead of denying it as would occur otherwise. We could make it possible, but that would have -- wait for it -- performance impact. :)

Authoritative hooks

Posted Aug 11, 2022 18:50 UTC (Thu) by Cyberax (✭ supporter ✭, #52523) [Link]

> What you can't do is what you had asked for, which is to provide a mechanism for a hook to grant access instead of denying it as would occur otherwise.

That would actually help and make time investment into SELinux be worthwhile, as it will open up _new_ possibilities. Performance impact is another question, and it'd be interesting to see if removing the DAC entirely in favor of MAC would help.