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    SubjectRe: caps in elf, next itteration (the hack get's bigger)
       Date: 	Tue, 13 Apr 1999 23:18:17 +1000
    From: Richard Gooch <rgooch@atnf.csiro.au>

    > The whole idea of capabilities is to get rid of all-powerful users, to
    > split the root powers among several people where _nobody_ has all
    > powers. Any scheme that keeps a root of some sort is broken.

    Whoever can grant caps is in effect all-powerful.

    In a pure capability model, there is no "who" can grant caps. There is
    only one or more executabes who can grant caps, and which have whatever
    auditing and access control checks are deemed necessary.

    One thing which people often don't "get" about capabilities is that by
    default capabilities are *not* inherited by child processes. If your
    shell has some large set of capabilites, child processes (such as gcc or
    gmake) do not get any of these capaibilities unless those executables
    have capabilities flags which allow them to inherit those capabilities.
    Each executable has two sets of capabilities flags: once is the set of
    capabilities which will be raised when the executable is exec'ed. The
    other set is the set of capabilities which the process is allowed to
    inherit from the parent process. By default, both sets of capaibilities
    is the null set.

    So in fact, if you want to allow a user running with a privileged shell
    process which has the ability to override filesystem discretional access
    controls, then any programs that user might want to run to modify the
    filesystem --- cp, rm, tar, mv, etc., also need capabilities set in the
    executable. So configuring a capability system is much more
    complicated.

    - Ted

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