Re: [saag] Common labeled security (comment on CALIPSO, labeled NFSv4)

Russ Housley <housley@vigilsec.com> Sat, 04 April 2009 19:42 UTC

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Date: Sat, 04 Apr 2009 14:39:29 -0400
To: "Santosh Chokhani" <SChokhani@cygnacom.com>,<saag@ietf.org>
From: Russ Housley <housley@vigilsec.com>
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Cc: labeled-nfs@linux-nfs.org, nfsv4@ietf.org, nfs-discuss@opensolaris.org
Subject: Re: [saag] Common labeled security (comment on CALIPSO, labeled NFSv4)
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Santosh:

There may be things that can be kept for this environment, especially 
if all of the clients of a particular file system are probably 
operating under a single security policy.  If you can eliminate 
policy mapping and markings that must be hidden from some clients, 
then a subset of the SPIF may be useful.

Russ

At 01:36 PM 4/3/2009, Santosh Chokhani wrote:
>Russ,
>
>My thinking was that the features of SPIF that are not needed could be
>discarded.
>
>I was hoping that we could help the group save the baby and throw out
>the bath water.
>
> > -----Original Message-----
> > From: Russ Housley [mailto:housley@vigilsec.com]
> > Sent: Friday, April 03, 2009 12:45 PM
> > To: Santosh Chokhani; saag@ietf.org
> > Cc: labeled-nfs@linux-nfs.org; nfs-discuss@opensolaris.org;
> > nfsv4@ietf.org; selinux@tycho.nsa.gov
> > Subject: Re: [saag] Common labeled security (comment on
> > CALIPSO, labeled NFSv4)
> >
> > I really do not have time to write about all of my concerns.
> > However, once you get beyond the basic classifications, the
> > SPIF model breaks.  They are markings that are only to be
> > known to people that have the clearance for those markings,
> > this leads to a SPIF distribution nightmare, as a subset of
> > the real SPIF must be given out based on access (or not) to
> > various compartments and such.  It just does not scale.
> >
> > Russ
> >
> > At 11:22 AM 4/3/2009, Santosh Chokhani wrote:
> > >As part of MISSI and DMS, in mid to late 90's we did work on
> > something
> > >called Security Policy Information File (SPIF).
> > >
> > >At high level SPIF entailed the following:
> > >
> > >1.  It was ASN.1 based.
> > >2.  It permitted you to convert the machine representation to human
> > >readable representation.
> > >3.  It permitted you to convert the human readable input to machine
> > >representation.
> > >4.  It mapped labels (hierarchical sensitivity levels and
> > >non-hierarchical categories) from one labeling policy to
> > another (i.e.,
> > >establish equivalency mapping) 5.  It allowed you to
> > constrain labels
> > >since for some policies, existence of a category may mean some
> > >categories, levels, may be included and/or excluded.
> > >
> > >Different labeling policies were indicated by different policy OID.
> > >
> > >Some of the concept from that work may be applicable here.
> > >
> > > > -----Original Message-----
> > > > From: saag-bounces@ietf.org
> > [mailto:saag-bounces@ietf.org] On Behalf
> > > > Of Nicolas Williams
> > > > Sent: Thursday, April 02, 2009 11:44 AM
> > > > To: saag@ietf.org
> > > > Cc: labeled-nfs@linux-nfs.org; selinux@tycho.nsa.gov;
> > > > nfsv4@ietf.org; nfs-discuss@opensolaris.org
> > > > Subject: [saag] Common labeled security (comment on
> > CALIPSO, labeled
> > > > NFSv4)
> > > >
> > > > Over at the NFSv4 WG we've been having a discussion of a labeled
> > > > NFSv4 proposal.  [Note: NFSv4 WG and others cc'ed,
> > > > Reply-To: set to SAAG.]
> > > >
> > > > An interop issue has arisen that we believe applies equally to
> > > > CALIPSO (draft-stjohns-sipso-11.txt)and requires input
> > from the IETF
> > > > security area.
> > > >
> > > > The issue is: how do do nodes in a labeled
> > network/application know
> > > > if they agree on a common labeled security policy for a given DOI?
> > > >
> > > > Agreeing on a DOI is accomplished easily enough -- that's not an
> > > > issue.
> > > > Agreeing on what a given numeric sensitivity level or compartment
> > > > bit means in a given DOI is quite another.
> > > > Without a solution to this we're left with out-of-band agreement,
> > > > which leaves interop in a lurch.
> > > >
> > > > I think we need a generic MLS and DTE labeled security policy
> > > > document format that allows a DOI to define the names and numeric
> > > > assignments of sensitivity levels, compartments, etcetera.
> > > >
> > > > We also need a way for nodes to agree that they have the
> > same policy
> > > > for a given DOI, or that they agree on a common subset of a DOI's
> > > > policy.
> > > >
> > > > This last problem can be solved by use of a labeled
> > security policy
> > > > URI scheme that includes a version number (+ a requirement that
> > > > changes be in the form of additions and obsolescence of old
> > > > assignments, but not removals).
> > > >
> > > > To recap: I think we need a) a common MLS and DTE labeled
> > security
> > > > policy document format, b) a labeled security policy URI
> > scheme to
> > > > refer to such documents by.
> > > >
> > > > Given (a) and (b) NFSv4.x clients and servers would only have to
> > > > exchange {DOI #, policy URI} tuples to determine whether
> > they agree
> > > > on a common policy.
> > > >
> > > > Note that CALIPSO describes how to encode and compare MLS
> > labels on
> > > > the wire, but it does not describe how nodes agree on the
> > meaning of
> > > > particular sensitivity levels or compartments.  Therefore
> > CALIPSO is
> > > > going to have much the same problem as NFSv4.
> > > >
> > > > Nico
> > > > --
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