Internet DRAFT - draft-cel-fedfs-security-addendum

draft-cel-fedfs-security-addendum






NFSv4                                                           C. Lever
Internet-Draft                                                    Oracle
Intended status: Standards Track                           July 11, 2013
Expires: January 12, 2014


                 Federated Filesystem Security Addendum
                  draft-cel-fedfs-security-addendum-01

Abstract

   This document addresses critical security-related items that are
   missing from existing FedFS proposed standards.






































Lever                   Expires January 12, 2014                [Page 1]

Internet-Draft           FedFS Security Addendum               July 2013


Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 12, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.














Lever                   Expires January 12, 2014                [Page 2]

Internet-Draft           FedFS Security Addendum               July 2013


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Problem Statement: GSSAPI service name for ADMIN . . . . .  4
     1.2.  Problem Statement: Compromised NSDBs . . . . . . . . . . .  4
     1.3.  Scope Of This Document . . . . . . . . . . . . . . . . . .  6
   2.  GSSAPI Service Name for the FedFS ADMIN protocol . . . . . . .  7
   3.  Fencing Compromised NSDBs  . . . . . . . . . . . . . . . . . .  8
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 12
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13




































Lever                   Expires January 12, 2014                [Page 3]

Internet-Draft           FedFS Security Addendum               July 2013


1.  Introduction

   Requirements for federated filesystems are described in [RFC5716].
   Specification of the protocol used by administrators to configure
   fileservers and construct namespaces is provided in [FEDFS-ADMIN].
   Specification of the protocol allowing fileservers to store namespace
   information is provided in [FEDFS-NSDB].

   These documents are now immutable.  However, some security-related
   concerns have arisen that should be addressed immediately rather than
   waiting for another version of these protocols to be ratified.

1.1.  Problem Statement: GSSAPI service name for ADMIN

   After IESG review, the Security Considerations chapter of
   [FEDFS-ADMIN] now specifically requires that implementations of this
   protocol support GSSAPI security mechanisms.

   ADMIN protocol clients must use a service principal to establish a
   GSS context shared with an ADMIN server.  To construct the service
   principal, clients need to know a priori the protocol's GSSAPI
   service name.  The form of that service name is described in chapter
   4 of [RFC2724].

   According to [RFC2743], requesting an addition to the "GSSAPI/
   Kerberos/SASL Service Names" registry requires a specification.
   Because [FEDFS-ADMIN] cannot be changed, a new specification must be
   provided.

1.2.  Problem Statement: Compromised NSDBs

   The FedFS ADMIN RPC protocol provides a mechanism for provisioning
   NSDBs on remote fileservers.  The operations it provides are
   FEDFS_SET_NSDB_PARAMS, FEDFS_GET_NSDB_PARAMS, and
   FEDFS_GET_LIMITED_NSDB_PARAMS.

   FEDFS_SET_NSDB_PARAMS specifies the name of an NSDB and the security
   mode to use when connecting to this NSDB.  The fileserver connects to
   an NSDB in order to resolve a FedFS junction.  The ADMIN protocol
   specification further says:

      On success, this operation returns FEDFS_OK.  When the operation
      returns, the new connection parameters SHOULD be used for all
      subsequent LDAP connections to the given NSDB.  Existing
      connections MAY be terminated and re-established using the new
      connection parameters.  The connection parameters SHOULD be
      durable across fileserver reboots.




Lever                   Expires January 12, 2014                [Page 4]

Internet-Draft           FedFS Security Addendum               July 2013


   There are two security modes defined in the protocol specification:
   FEDFS_SEC_NONE, which does not authenticate the LDAP server; and
   FEDFS_SEC_TLS, which uses START_TLS (RFC 4513) to authenticate the
   LDAP server.

   When FEDFS_SEC_TLS is specified with the FEDFS_SET_NSDB_PARAMS
   operation, an x.509v3 certificate chain is also provided to the
   fileserver.  The fileserver uses the provided certificate to
   authenticate subsequent connections to this NSDB.  The
   FEDFS_SET_NSDB_PARAMS operation can change the connection security
   used by a fileserver to connect to a particular NSDB from NONE to TLS
   or TLS to NONE.

   Over time, domain administrators add NSDB connection parameters to
   each of their fileservers to enable FedFS junction resolution.  The
   specified NSDB may be the domain's own, or it might be an NSDB in a
   foreign domain.

   Many junctions on multiple fileservers can be created that use a
   particular NSDB.  There is no way to find such junctions without an
   exhaustive search.  Since filesystem namespace topology can evolve
   arbitrarily over time, a recorded pathname of any junction is almost
   guaranteed to become stale.

   Now suppose we have two FedFS domains: example.net and
   university.edu.  Suppose university.edu fileservers have a number of
   junctions that refer to locations maintained by example.net, and thus
   university.net's fileservers are configured to resolve junctions on
   example.net's NSDB.

   One day Mallory compromises example.net's NSDB, but the domain
   administrator there is on a long vacation.  The administrator at
   university.net discovers the compromise immediately, but has no
   control over the foreign NSDB and cannot create a fresh x.509
   certificate or verify that the contents of the NSDB are unmolested.
   The only choice is to find and remove every junction in the
   university.edu domain that contains the compromised NSDB.

   If university.edu is using a good implementation of FedFS, the
   administrative tools it provides might allow an administrator to
   simply visit each of its fileservers and mark the example.net NSDB as
   compromised.  Any junction resolution that attempts to use that NSDB
   would fail, but all junctions remain in place.  When example.net's
   administrator gets back from holiday and cleans up the mess, the
   university.edu administrator can then update each of her fileservers
   with fresh connection parameters for that NSDB.

   However, none of this can be done remotely using the FedFS ADMIN



Lever                   Expires January 12, 2014                [Page 5]

Internet-Draft           FedFS Security Addendum               July 2013


   protocol.  It does not have a mechanism for removing NSDB connection
   parameters or for fencing a compromised NSDB.

1.3.  Scope Of This Document

   This document specifies additional requirements for the FedFS ADMIN
   protocol specified in [FEDFS-ADMIN], which is a standards track
   specification.











































Lever                   Expires January 12, 2014                [Page 6]

Internet-Draft           FedFS Security Addendum               July 2013


2.  GSSAPI Service Name for the FedFS ADMIN protocol

   Section 6 of [FEDFS-ADMIN] requires a FedFS ADMIN server to support
   the RPCSEC_GSS framework [RFC2203].  The present document specifies
   the GSSAPI service name, as described in Section 4.1 of [RFC2743], to
   be used for the FedFS ADMIN protocol.

   Regardless of what security mechanism under RPCSEC_GSS is in use, a
   FedFS ADMIN server MUST identify itself in GSSAPI via a
   GSS_C_NT_HOSTBASED_SERVICE name type.  GSS_C_NT_HOSTBASED_SERVICE
   names are of the form:

         service@hostname

   For the ADMIN protocol, the "service" element is

         fedfs-admin

   Implementations of security mechanisms will convert
   fedfs-admin@hostname to various different forms.  For Kerberos V5,
   the following form is RECOMMENDED:

         fedfs-admin/hostname

   This service name SHOULD NOT be used to authenticate other GSSAPI
   services.

























Lever                   Expires January 12, 2014                [Page 7]

Internet-Draft           FedFS Security Addendum               July 2013


3.  Fencing Compromised NSDBs

   An NSDB is considered "foreign" relative to a particular FedFS domain
   if that domain's administrator has no administrative access to that
   NSDB.

   When a FedFS domain administrator is faced with a foreign NSDB that
   is compromised or otherwise unusable, and in the absense of an
   implementation-provided mechanism for fencing an NSDB, the
   administrator can fence that NSDB using the following technique.

   1.  The administrator locally generates a new certificate for the
       compromised foreign NSDB.  The certificate can be self-signed, or
       signed by the administrator's local certificate authority.

   2.  The administrator distributes this certificate to all of her
       domain's fileservers using the FedFS ADMIN protocol or some other
       secure means.  The connection security for the foreign NSDB is
       set to FEDFS_SEC_TLS on each of the local domain's fileservers.

   3.  The administrator requests fresh certificate material from the
       administrator of the foreign NSDB.

   4.  When the threat has passed and the foreign NSDB is safe to use
       again, the administrator can distribute the new valid certificate
       material to her domain's fileservers.

   No change to the ADMIN protocol as specified in [FEDFS-ADMIN] is
   required to fence a compromised NSDB.  Step 2 guarantees that, on
   fileservers in the administrator's local FedFS domain, resolving a
   junction that references the compromised foreign NSDB will fail until
   updated certificate material is provided.



















Lever                   Expires January 12, 2014                [Page 8]

Internet-Draft           FedFS Security Addendum               July 2013


4.  Security Considerations

   There are no additional security considerations.
















































Lever                   Expires January 12, 2014                [Page 9]

Internet-Draft           FedFS Security Addendum               July 2013


5.  IANA Considerations

   In accordance with Section 4.1 of [RFC2743], the service name "fedfs-
   admin" will be registered in the GSSAPI Service Name registry at
   http://www.iana.org/assignments/gssapi-service-names/ gssapi-service-
   names.xml

   The new entry should reference the present document as the
   specification.










































Lever                   Expires January 12, 2014               [Page 10]

Internet-Draft           FedFS Security Addendum               July 2013


6.  Acknowledgements

   The author of this document gratefully acknowledges the contributions
   of Nico Williams, Spencer Shepler, Tom Haynes, and David Noveck.















































Lever                   Expires January 12, 2014               [Page 11]

Internet-Draft           FedFS Security Addendum               July 2013


7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2203]  Eisler, M., Chiu, A., and L. Ling, "RPCSEC_GSS Protocol
              Specification", RFC 2203, September 1997.

   [RFC2743]  Linn, J., "Generic Security Service Application Program
              Interface Version 2, Update 1", RFC 2743, January 2000.

7.2.  Informative References

   [FEDFS-ADMIN]
              Lentini, J., Everhart, C., Ellard, D., Tewari, R., and M.
              Naik, "Administration Protocol for Federated Filesystems",
              draft-ietf-nfsv4-federated-fs-admin (Work In Progress),
              2010.

   [FEDFS-NSDB]
              Lentini, J., Everhart, C., Ellard, D., Tewari, R., and M.
              Naik, "NSDB Protocol for Federated Filesystems",
              draft-ietf-nfsv4-federated-fs-protocol (Work In Progress),
              2010.

   [RFC2724]  Handelman, S., Stibler, S., Brownlee, N., and G. Ruth,
              "RTFM: New Attributes for Traffic Flow Measurement",
              RFC 2724, October 1999.

   [RFC5716]  Lentini, J., Everhart, C., Ellard, D., Tewari, R., and M.
              Naik, "Requirements for Federated File Systems", RFC 5716,
              January 2010.

















Lever                   Expires January 12, 2014               [Page 12]

Internet-Draft           FedFS Security Addendum               July 2013


Author's Address

   Charles Lever
   Oracle Corporation
   1015 Granger Avenue
   Ann Arbor, MI  48104
   US

   Phone: +1 734 274 2396
   Email: chuck.lever@oracle.com









































Lever                   Expires January 12, 2014               [Page 13]