Re: LSM stacker update

From: Casey Schaufler (casey@schaufler-ca.com)
Date: Wed Feb 02 2005 - 08:42:25 PST


--- Stephen Smalley <sds@private> wrote:

> On Wed, 2005-02-02 at 08:50, Stephen Smalley wrote:
> > Actually, on second thought, I wonder if
> selinux_netlink_recv should be
> > calling avc_audit() upon a denial, as otherwise we
> will see no audit
> > message for a denial even it is caused by the
> SELinux computation in
> > selinux_netlink_send.  Similar issue for the audit
> subsystem's
> > capability checks on the receiver side.
> 
> Hmmm...except that we won't have the sender's SID
> available to us in
> selinux_netlink_recv(), so auditing would just occur
> in the receiver's
> context, possibly incorrectly.

Auditing BSDIPC is an adventure, to be sure.
Generating audit records for failed delivery
on the receiver side is, as y'all point out,
of questionable value without the information
about the sender. The issue has been addressed
successfully in past evaluations.

For UNICOS (anyone remember Cray Reseasrch?)
the evaluation was done under the Red Book
model, which treated the computer as a network
component and all network connections as
login sessions. Since each connection was a
login and authenticated (for some value thereof)
the information to put in the audit trail was
available, albiet not always was it all that
useful. The set of services available was pretty
limited so as to avoid excessive debate regarding
the strength of authentication.

For Trusted Irix (and later Irix) the evaluation
was done under the Orange Book model and a
collection of computers were treated as a single
system, what we would today call a cluster.
While auditing is done on the receiver side it
is only useful in conjunction with records
generated on the sender. The sender side records
contain all required information, while receiver
side records include what they can. The
assumption that all senders are audited makes
this work.

The UNICOS scheme is more in tune with modern
deployment, hence providing better guidence.
If you expect to allow a system to provide network
services you need to include an argument as to
how it is all the services are login sessions,
and how it is the user information is provided,
even if that means that you have to make it up.


=====
Casey Schaufler
casey@schaufler-ca.com

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