[cap-talk] Mandatory Access Control (was: What's "Discretionary Security")

[Ka-Ping Yee]

On Wed, 3 Jan 2007, Jonathan S. Shapiro wrote:
> Mandatory control advocates almost universally state that capabilities
> are purely discretionary controls. This is absolutely correct.

It may be almost universally stated, but it is also inconsistent.
The definition in the glossary of the Orange Book is

    Discretionary Access Control - A means of restricting
    access to objects based on the identity of subjects
    and/or groups to which they belong. The controls are
    discretionary in the sense that a subject with a certain
    access permission is capable of passing that permission
    (perhaps indirectly) on to any other subject (unless
    restrained by mandatory access control).

Capability systems do not permit subjects to pass on permission
to just "any other subject", so they do not meet the TCSEC
definition of DAC.

(I'll edit the Wikipedia article now to quote the above definition.)


-- ?!ng