Re: [RFC][PATCH 2/3] SLIM

From: Stephen Smalley (sds@private)
Date: Thu Nov 17 2005 - 08:48:58 PST


On Thu, 2005-11-17 at 10:36 -0500, Stephen Smalley wrote:
> Using SLIM as an example, it appears that SELinux would have to make
> direct calls to EVM regardless of whether or not we use stacker.
> Further, it appears that even tighter integration with EVM is needed in
> order to avoid the redundant processing and potential inconsistencies
> created by the current weaker coupling.  EVM can certainly serve as a
> support module to a variety of other modules (SLIM, SELinux, ...) while
> still being directly called by those modules - those modules are
> consumers of the services provided by EVM.  Using stacker for part of
> the composition while using direct calls elsewhere only seems to confuse
> the interaction.

I'm also a bit unclear as to whether we can use EVM with SELinux at all,
given that EVM seems to presently assume a modular build and insertion
after TPM activation but SELinux has to be built-in.  EVM is also
clearly written with only SLIM in mind (or at least not with SELinux in
mind), as EVM performs its attribute validation on inode_permission, not
when SELinux fetches the attribute and maps it to an incore SID (upon
d_instantiate).  EVM would require a major overhaul to be useable by
SELinux even aside from its significant implementation problems and even
aside from the question of whether stacker should be used.

-- 
Stephen Smalley
National Security Agency



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