Re: authoritative vs. restrictive

From: Stephen Smalley (sdsat_private)
Date: Tue Sep 04 2001 - 06:32:10 PDT

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    On Tue, 4 Sep 2001, David Wheeler wrote:
    
    > So far, no one's shown a way for SGI to meet their needs using
    > restrictive-only hooks.  jmjones' desires aren't met either.
    
    That isn't entirely true.  I've previously noted that SGI (or anyone else)
    is free to use the existing capable hook to override the kernel DAC logic
    and can then implement any arbitrary logic it wants using the restrictive
    hooks.  In particular, for SGI, the restrictive hook could perform the MAC
    check first and return a MAC error code if it fails, then recompute and
    return (and optionally audit) the DAC decision.  Chris Wright has even
    suggested that SGI may be able to avoid recomputing the DAC decision by
    saving state when the capable hook is called, since it is only called when
    DAC fails.  So, strictly speaking, the authoritative hooks don't provide
    any greater generality than the current hooks.  And they do impose a cost
    in terms of the complexity and size of the patch, with potential
    ramifications for the acceptance of the patch by the kernel developers.
    
    --
    Stephen D. Smalley, NAI Labs
    ssmalleyat_private
    
    
    
    
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