Re: lsm stacker

From: Stephen Smalley (sds@private)
Date: Wed Jun 08 2005 - 07:46:53 PDT


On Wed, 2005-06-08 at 09:05 -0400, Valdis.Kletnieks@private wrote:
>  Probably should also
> touch on the fact that while just gluing several small modules together
> probably isn't the best solution theory-wise, for many sites it's "good enough"
> - not every box that needs an LSM or three needs an SELinux-sized solution
> (which *does* add into the TCO)...  This probably won't fly on lkml unless
> you specifically use "there are different correct solutions on the cost/security
> curve" as a selling point....

As you might expect, I'd disagree with the notion that gluing several
small modules together is a good idea, and not just in theory.

Note that SELinux allows for those different correct solutions on the
cost/security curve via policy configuration and/or security server
modification.  The "size" of a SELinux solution is primarily a function
of the policy complexity.  As far as avtab memory usage is concerned,
that can certainly be optimized.

Do you really want to encourage proliferation of ad-hoc special purpose
LSMs?  That would seem to lend itself toward:
- fragmentation of already scarce security resources that could instead
be working toward a common unified solution,
- most LSMs remaining out of tree,
- no real review of how these LSMs compose (or should not compose) by
people who might be capable of evaluating them (most sysadmins won't be
able to perform such analysis on their own),
- no stable kernel security model or API due to variances in the set of
LSMs present in any given kernel and thus no effective leveraging of any
specific security model or API by upstream applications that want to be
portable.

-- 
Stephen Smalley
National Security Agency



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