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

From: Serge E. Hallyn (serue@private)
Date: Thu Nov 17 2005 - 08:52:41 PST


Quoting Stephen Smalley (sds@private):
> c) the direct integration of SLIM and IMA in patches posted by David
> yielded reduced complexity and overhead in IMA (per David's own
> description of the IMA patch) than trying to keep IMA completely
> separate and independent, and

Oh, that's not what I'd gotten from his comments - I thought he meant
the current approach resulted in reduced complexity versus ima being
a separate architecture.

> 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.

Dave, I think I see how we would cause evm to check all security.selinux
xattrs, but could you explain the simplest way that we could cause it to
halt the system in the case of a violation?

I guess ideally we would in fact have interaction, so that evm could
mark any files with corrupt selinux xattrs as type integrity_violated_t
or something.

> This isn't an argument about the merits of stacker by itself; it is an

Well, indirectly it is  :-)

> argument about whether EVM/SLIM/IMA are an effective motivating example
> for stacker.  As far as I can see, they are not.

All stacker aims to do is appropriately call each LSM's defined security
hooks, so that one LSM does not need to fully control the other LSMs.
I think that part is still valuable.  However, a separate integrity
notifier api to be exported to evm could be interesting.  So perhaps

	EVM uses LSM as it does now
	SLIM registers itself with EVM
		which events are of interest
		which data to send
	When EVM does bprm_check, for instance, it calls the
		appropriate SLIM function and sends it the
		already evaluated file and xattr properties
	SELinux registers itself with EVM
	When EVM does d_instantiate, it sends the selinux context
		integrity info to an selinux hook.

This would require a pretty standard, clean set for both the
events and sets of data of interest...  Does this seem feasible?

-serge



This archive was generated by hypermail 2.1.3 : Thu Nov 17 2005 - 08:53:18 PST