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

From: Serge E. Hallyn (serue@private)
Date: Thu Nov 17 2005 - 06:46:38 PST


Quoting Stephen Smalley (sds@private):
> Another obvious question:  since slim directly makes calls to evm and
> look at its data structures, and is placed under evm in the tree, what
> does any of this have to do with the stacker?  You could just as easily
> have the slim hooks call evm in all cases where needed,

My impression in the past was that SLIM is just an example module,
and they expect others to be written on top of EVM.  However it does
look like SLIM requires evm always be loaded.  Still I think the reason
to stack is so that you can load multiple modules on top of EVM.

> and likewise
> couple other LSMs with evm as desired through direct calls rather than
> using the stacker.  The composition isn't truly transparent in any
> event.

Here I disagree - evm independantly verifies the integrity of files and
xattrs.  Seems useful when stacked with several modules.  For digsig, it
can ensure that the kernel, modules, and digsig keys are ok.  For
selinux, it can verify the types.  There seems to be absolutely no
reason to require selinux to directly control evm.

-serge



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