Re: Authoritative Hooks

From: Stephen Smalley (sdsat_private)
Date: Mon Nov 12 2001 - 10:38:15 PST

  • Next message: Stephen Smalley: "Re: Authoritative Hooks"

    On Fri, 9 Nov 2001, Casey Schaufler wrote:
    
    > I'm sorry if it sounds that way. I'm trying really hard to
    > come to grips with a Linux future based on restrictive hooks
    > and it's not easy. I had a vision this morning of copying the
    > entire security architecture into capable(), with historical
    > checks left in place to placate inflexible maintaners and the
    > security blob pulsing like an inflated silicon based creature
    > from a 1950's Ed Wood movie. The C+R scheme circumvents the
    > intention of the basic design, and while that would allow
    > ACLs, it does so by deceit, not design.
    
    This seems like a misunderstanding.  You aren't moving everything into
    capable - you are just using capable to enable your restrictive hooks
    (like permission) to act authoritatively.
    
    > Stephen has convinced me that C+R can be used to do ACLs.
    > I look at what it involves, and I say that I would not
    > condone such in production code. I stick by that. If we
    > have to do that to get into Linux, well, yuck, but it's
    > not like I haven't seen other schemes just as convoluted.
    
    It doesn't appear to be very difficult at all to implement POSIX ACLs via
    the C+R scheme.  In fact, I would expect the security module to be very
    similar to one implemented via authoritative hooks.  The only difference
    is that using the C+R scheme requires the module to always return success
    from its capable hook for CAP_DAC_OVERRIDE and CAP_DAC_READ_SEARCH and
    then to recompute the default logic in its permission hook.  This isn't
    so difficult.
    
    --
    Stephen D. Smalley, NAI Labs
    ssmalleyat_private
    
    
    
    
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