Security in Plan 9

The security architecture of the Plan 9(tm) operating system has recently been redesigned to address some technical shortcomings. This redesign provided an opportunity also to make the system more convenient to use securely. Plan 9 has thus improved in two ways not usually seen together: it has become more secure and easier to use.

The central component of the new architecture is a per-user self-contained agent called factotum. Factotum securely holds a copy of the user's keys and negotiates authentication protocols, on behalf of the user, with secure services around the network. Concentrating security code in a single program offers several advantages including: ease of update or repair to broken security software and protocols; the ability to run secure services at a lower privilege level; uniform management of keys for all services; and an opportunity to provide single sign on, even to unchanged legacy applications. Factotum has an unusual architecture: it is implemented as a Plan 9 file server.