Re: permissive vs. restrictive issue and solutions...

From: Stephen Smalley (sdsat_private)
Date: Mon Jun 04 2001 - 08:02:30 PDT

  • Next message: Howard Holm: "Bitkeeper repository"

    On Sat, 2 Jun 2001, Crispin Cowan wrote:
    
    > So here's yet another idea:  split the LSM interface into two parts, permissive
    > and restrictive.  Designers that want purely restrictive functionality use only
    > the restrictive parts, and thus get easier/higher assurance. Those who want
    > permissive functionality can turn it on if they need it.
    
    I'll reverse myself on the question of permissive hooks.  As I mentioned
    earlier, SELinux does not currently need or use permissive hooks, but we
    would like to have them in the long term.  However, for the same reasons
    against migrating all of the logic that I cited in my reply to Howard,
    I think that trying to implement permissive hooks in our first version
    of LSM would be a mistake.
    
    With regard to capabilities, I would again suggest that we leave the
    existing capable() calls unchanged, and merely change the guts of
    the capabilities implementation to call our new hooks (i.e. the
    capable() function logic and the execve capabilities processing will be
    moved into the module, as it is currently in LSM).  In cases where
    we want the ability to check more information, like parameters, we
    can insert a new hook in addition to the existing capable() call
    rather than changing the existing call.  This will reduce the
    pervasiveness of the LSM changes, allow us to focus our work on
    directly supporting the needs of our particular security modules,
    and avoid introducing subtle bugs.  
    
    --
    Stephen D. Smalley, NAI Labs
    ssmalleyat_private
    
    
    
    
    
    
    
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