NFSv4                                                     T. Haynes, Ed.                                                         W. Adamson
Internet-Draft                                                    NetApp
Intended status: Standards Track                             N. Williams
Expires: May 11, 2013 April 20, 2014                                     Cryptonector
                                                       November 07, 2012
                                                        October 17, 2013

             Remote Procedure Call (RPC) Security Version 3


   This document specifies version 3 of the Remote Procedure Call (RPC)
   security protocol (RPCSEC_GSS).  This protocol provides for: for compound
   authentication of client hosts and users to server (constructed by
   generic composition), channel binding, security label assertions for multi-level and
   type enforcement, structured privilege assertions, and identity
   assertions. channel

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [1].

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
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   Drafts is at

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   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 May 11, 2013. April 20, 2014.

Copyright Notice

   Copyright (c) 2012 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
   ( 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.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Motivation  Applications of RPCSEC_GSSv3 . . . . . . . . . . . . . . .  4
   2.  The RPCSEC_GSSv3 protocol  . . . . . . . . . . . . . .  4
     1.2.  Applications of RPCSEC_GSSv3 . . . .  5
     2.1.  New auth_stat values . . . . . . . . . . .  4
   2.  The RPCSEC_GSSv3 protocol . . . . . . . .  9
     2.2.  RPC message credential and verifier  . . . . . . . . . . .  5
     2.1. 10
     2.3.  Control messages Messages . . . . . . . . . . . . . . . . . . . . . 10
       2.1.1.  New auth_stat values
       2.3.1.  Create request . . . . . . . . . . . . . . . . . 10
       2.1.2.  Create request . . . 11
       2.3.2.  Destruction request  . . . . . . . . . . . . . . . . . 11
       2.1.3.  Context handle destruction 15
       2.3.3.  List request . . . . . . . . . . . . . . . 16
       2.1.4.  List request . . . . . . 16
       2.3.4.  Extensibility  . . . . . . . . . . . . . . . 16
       2.1.5.  Extensibility . . . . . 16
     2.4.  Data Messages  . . . . . . . . . . . . . . . 17
   3.  Privileges and identity representation for NFSv4 . . . . . . . 17
   3.  Security Considerations  . . . . . . . . . . . . . . . . . . . 19
   5. 17
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 20
   6. 18
   5.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     6.1. 19
     5.1.  Normative References . . . . . . . . . . . . . . . . . . . 20
     6.2. 19
     5.2.  Informative References . . . . . . . . . . . . . . . . . . 21 19
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 21 20
   Appendix B.  RFC Editor Notes  . . . . . . . . . . . . . . . . . . 21 20
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21 20

1.  Introduction

   The original RPCSEC_GSS protocol [2] provided for authentication of
   RPC clients and servers to each other using the Generic Security
   Services Application Programming Interface (GSS-API) [3].  The second
   version of RPCSEC_GSS [4] added support for channel binding bindings [5].

   We find that GSS-API mechanisms are insufficient for communicating
   certain aspects of a client's identity and authority to a server.  The GSS-API and
   its mechanisms certainly could be extended to address this shortcomming,
   shortcoming, but it seems be far simpler to address it at the
   application layer, namely, in this case, RPCSEC_GSS.

   The motivation for RPCSEC_GSSv3 is to add support for labeled
   security and server-side copy for NFSv4 (see [6] and [9]).  Both of
   these features require assertions of authority from the client.

   Assertions need to be verified.  One party that can verify an
   assertion is the client host, which can authenticate to the server
   using its own credentials.  We therefore can also require users to verify an
   assertion as well.  This calls for compound authentication.

   Because the design of RPCSEC_GSSv3 relies on either RPCSEC_GSS
   version 1 (though version 2 can be used) to do the actual GSS-API
   security context establishment, we add support for channel binding so
   that implementors who have implemented RPCSEC_GSS version 1 but not
   version 2 can provide a (simplified) channel binding implementation
   using RPCSEC_GSSv3.

   We therefore describe a new version of RPCSEC_GSS that allows for the

   o  compound authentication of the client host and user to the server
      (done by binding of two RPCSEC_GSS handles)

   o  channel binding (even though RPCSEC_GSSv2 provides this also; see

   o  client-side  Client-side assertions of authority:

      *  security  Security labels (for for multi-level, type enforcement, and other
         labeled security models) (see [9], models.  See [10], [11], [12], [6] and [11]) [9].

      *  application-specific privileges

   o  client-side assertions of identity:

      *  primary client/user identity  Application-specific structured privileges.  For an example see
         server-side copy [6].

      *  supplementary group memberships  Compound authentication of the client/user, including
         support for specifying deltas client host and user to the membership list as seen on
         server done by binding two RPCSEC_GSS handles.

      *  Simplified channel binding.

   Assertions of labels, privilege labels and identity privileges are evaluated by the server,
   which may then map the asserted values to other values, all according
   to server-side policy.

   We also add an option for enumerating active server-side domains of
   interpretation (DOI), [[Comment.1: No DOI privileges
   and supported label format specifiers (LFS).  The LFS and Label
   Format Registry are described in the LFS, why here?
   Adapt with the new format! --TH]] detail in [13].

   RPCSEC_GSSv3 is patterned as follows:

   o  a  A client uses an existing RPCSEC_GSS RPCSEC_GSSv1 (or RPCSEC_GSSv2) context
      handle (of any
      RPCSEC_GSS version) to protect RPCSEC_GSSv3 exchanges (this will be termed the
      "parent" or "outer" handle)

   o  the  The server issues a "child" RPCSEC_GSSv3 handle, but the
      underlying GSS-API security context for the parent handle is used
      in all subsequent exchanges using the child handle (this handle.  This works
      because the RPCSEC_GSS handle is included in the integrity
      protected RPCSEC_GSS auth/verifier header for all versions of
      RPCSEC_GSS.  The child context, however, has its own sequence
      number space and window, distinct from that of the parent.

   [[Comment.1: RFC22203 states that when data integrity is used, the
   seq_num in the rpc_gss_data_t must be the same as in the credential.
   This means that using data integrity with GSS3 context's can not
   simply construct it using the parent context as the seq_num must be
   from the GSS3 context. --AA]]

   This means that RPCSEC_GSSv3 depends on RPCSEC_GSS versions 1 and/or
   2 for actual GSS-API security context establishment.  This keeps the
   specification of RPCSEC_GSSv3 simple by avoiding the need to
   duplicate the core functionality of RPCSEC_GSS version 1.

1.1.  Motivation  Applications of RPCSEC_GSSv3

   The initial motivation common uses of RPCSEC_GSSv3, particularly for RPCSEC_GSSv3 is NFSv4 [6], are
   expected to add support for be:

   a.  labeled
   security for NFSv4 (see [12]).  We also realized that the assertion
   of security security: client-side process label is conceptually equivalent, protocol-wise, to
   assertions of assertion [+
       privilege and identity.

   Additionally, assertions need to be verified, and assertion] + compound client host & user

   b.  compound client host & user authentication [+ critical structured
       privilege assertions] used in this case inter-server server-side copy;

   Labeled NFS (see Section 8 of [6]) uses the
   one party that can verify an assertion is subject label provided by
   the client host, which can
   authenticate via the RPCSEC_GSSv3 layer to enforce MAC access to
   objects owned by the server using its own credentials.  Yet we want to
   continue authenticating users as well.  This calls for compound

   Finally, because the design of RPCSEC_GSSv3 relies on RPCSEC_GSSv1
   (though v2 can also be used) to do the actual GSS-API security
   context establishment, we add support for channel binding so that
   implementors who have implemented RPCSEC_GSSv1 but not version 2 can
   still provide channel binding without having to implement version 2.
   Channel binding is accomplished in a more simple manner in v3 also.

1.2.  Applications of RPCSEC_GSSv3

   The common uses of RPCSEC_GSSv3, particularly for NFSv4 [6], are
   expected to be:

   a. enable server guest mode or full mode
   labeled security: client-side process label assertion [+
       privilege assertion] + compound client host & user

   b.  compound client host & user authentication [+ privilege

   c.  client-side process credentials assertion [+ privilege assertion]
       as a replacement for AUTH_SYS NFS.

   [[Comment.2: check that is more secure than AUTH_SYS
       while not requiring per-user credentials. this language states what NFSv4.2 labeled NFS
   problem we are really solving. (setting labels on the server) --AA]]
   A traditional inter-server file copy entails the client user gaining access
   to a file on the source, reading it, and writing it to a file on the
   destination.  In Server-side Copy secure NFSv4 inter-server server-side copy (see
   Section 2 3.4.1 of [6]), the client user first secures access to both source
   and destination files, and then
   authorizes the destination uses RPCSEC_GSSv3 compound
   authentication and source structured privileges to copy authorize the file.  RPCSEC_GSSv3
   is used destination
   to allow copy the destination authentication with file from the source.

   Labeled NFS (see Section 7 source on behalf of [6] uses the subject label provided by
   the client via the RPCSEC_GSSv3 layer to enforce MAC access to
   objects owned by the server. user.

2.  The RPCSEC_GSSv3 protocol

   This document contains the External Data Representation (XDR) ([7])
   definitions for the RPCSEC_GSSv3 protocol.

   The XDR description is provided in this document in a way that makes
   it simple for the reader to extract into ready to compile form.  The
   reader can feed this document in the following shell script to
   produce the machine readable XDR description of RPCSEC_GSSv3:

   grep "^  *///" | sed 's?^  */// ??' | sed 's?^  *///$??'

   I.e. if the above script is stored in a file called "", and
   this document is in a file called "spec.txt", then the reader can do:

    sh < spec.txt > rpcsec_gss_v3.x

   The effect of the script is to remove leading white space from each
   line, plus a sentinel sequence of "///".

   The XDR description, with the sentinel sequence follows:

      ///  /*
      ///   * Copyright (c) 2011 2013 IETF Trust and the persons
      ///   * identified as the document authors. All rights
      ///   * reserved.
      ///   *
      ///   * The document authors are identified in [RFC2203],
      ///   * [RFC5403], and [RFCxxxx].
      ///   *
      ///   * Redistribution and use in source and binary forms,
      ///   * with or without modification, are permitted
      ///   * provided that the following conditions are met:
      ///   *
      ///   * o Redistributions of source code must retain the above
      ///   *   copyright notice, this list of conditions and the
      ///   *   following disclaimer.
      ///   *
      ///   * o Redistributions in binary form must reproduce the
      ///   *   above copyright notice, this list of
      ///   *   conditions and the following disclaimer in
      ///   *   the documentation and/or other materials
      ///   *   provided with the distribution.
      ///   *
      ///   * o Neither the name of Internet Society, IETF or IETF
      ///   *   Trust, nor the names of specific contributors, may be
      ///   *   used to endorse or promote products derived from this
      ///   *   software without specific prior written permission.
      ///   *
      ///   */
      ///  /*
      ///   * This code was derived from [RFC2203]. Please
      ///   * reproduce this note if possible.
      ///   */
      ///  /*
      ///   * rpcsec_gss_v3.x
      ///   */
      ///  enum rpc_gss_service_t {
      ///          /* Note: the enumerated value for 0 is reserved. */
      ///          rpc_gss_svc_none         = 1,
      ///          rpc_gss_svc_integrity    = 2,
      ///          rpc_gss_svc_privacy      = 3,
      ///          rpc_gss_svc_channel_prot = 4
      ///  };
      ///  enum rpc_gss_proc_t {
      ///           RPCSEC_GSS_DATA          = 0,
      ///           RPCSEC_GSS_INIT          = 1,
      ///           RPCSEC_GSS_CONTINUE_INIT = 2,
      ///           RPCSEC_GSS_DESTROY       = 3,
      ///           RPCSEC_GSS_BIND_CHANNEL  = 4
      ///  };
      ///  struct rpc_gss_cred_vers_1_t {
      ///          rpc_gss_proc_t    gss_proc; /* control procedure */
      ///          unsigned int      seq_num;  /* sequence number */
      ///          rpc_gss_service_t service;  /* service used */
      ///          opaque            handle<>; /* context handle */
      ///  };
      ///  enum rpc_gss3_proc_t {
      ///          RPCSEC_GSS3_DATA = 0,
      ///          RPCSEC_GSS3_LIST = 5,
      ///          RPCSEC_GSS3_CREATE = 6,
      ///          RPCSEC_GSS3_DESTROY = 7
      ///  };
      ///  struct rpc_gss_cred_vers_3_t {
      ///          rpc_gss3_proc_t         gss_proc;
      ///          unsigned int            seq_num;
      ///          rpc_gss_service_t       service;
      ///          opaque                  handle<>;
      ///          unsigned int            handle_version;
      ///  };
      ///  const RPCSEC_GSS_VERS_1 = 1;
      ///  const RPCSEC_GSS_VERS_2 = 2;
      ///  const RPCSEC_GSS_VERS_3 = 3; /* new */
      ///  union rpc_gss_cred_t switch (unsigned int rgc_version) {
      ///  case RPCSEC_GSS_VERS_1:
      ///  case RPCSEC_GSS_VERS_2:
      ///          rpc_gss_cred_vers_1_t rgc_cred_v1;
      ///  case RPCSEC_GSS_VERS_3: /* new */
      ///          rpc_gss_cred_vers_3_t rgc_cred_v3;
      ///  };
      ///  const MAXSEQ = 0x80000000;
      ///  struct rpc_gss3_extension {
      ///          int     type;
      ///          bool    critical;
      ///          opaque  data<>;
      ///  };
      ///  struct rpc_gss3_gss_binding {
      ///          unsigned int    vers;
      ///          opaque          handle<>;
      ///          opaque          nonce<>;
      ///          opaque          mic<>;
      ///  };
      ///  typedef opaque rpc_gss3_chan_binding<>;
      ///  typedef opaque rpc_gss3_doi<>;
      ///  struct rpc_gss3_label rpc_gss3_lfs {
      ///          rpc_gss3_doi    doi;          unsigned int lfs_id;
      ///          opaque          label<>;          unsigned int pi_id;
      ///  };
      ///  typedef opaque rpc_gss3_privs<>;  struct rpc_gss3_label {
      ///          rpc_gss3_lfs    lfs;
      ///  typedef          opaque rpc_gss3_name<>;          label<>;
      ///  };
      ///  typedef rpc_gss3_name rpc_gss3_group_list<>; string rpc_gss3_list_name<>;
      ///  struct rpc_gss3_id rpc_gss3_privs {
      ///          rpc_gss3_name         *username;
      ///          rpc_gss3_group_list   *groups;          rpc_gss3_list_name      listname;
      ///          rpc_gss3_group_list   groups_add;
      ///          rpc_gss3_group_list   groups_remove;          opaque                  privilege<>;
      ///  };
      ///  enum rpc_gss3_assertion_type {
      ///          LABEL = 0,
      ///          PRIVS = 1,
      ///          IDENTITY = 2 1
      ///  };
      ///  union rpc_gss3_assertion_u
      ///        switch (rpc_gss3_assertion_type atype) {
      ///  case LABEL:
      ///          rpc_gss3_label  label;
      ///  case PRIVILEGES:
      ///          rpc_gss3_privs  privs;
      ///  case IDENTITY:
      ///          rpc_gss3_id     id;
      ///  default:
      ///          opaque          ext<>;
      ///  };
      ///  struct rpc_gss3_assertion {
      ///          bool                    critical;
      ///          rpc_gss3_assertion_u    assertion;
      ///  };
      ///  struct rpc_gss3_create_args {
      ///          rpc_gss3_gss_binding    *compound_binding;
      ///          rpc_gss3_chan_binding   *chan_binding_mic;
      ///          rpc_gss3_assertion      assertions<>;
      ///          rpc_gss3_extension      extensions<>;
      ///  };
      ///  struct rpc_gss3_create_res {
      ///          opaque                  handle<>;
      ///          rpc_gss3_chan_binding   *chan_binding_mic;
      ///          rpc_gss3_assertion      granted_assertions<>;
      ///          rpc_gss3_assertion      assertions_denied<>;
      ///          rpc_gss3_assertion      assertions_not_understood<>;
      ///          rpc_gss3_assertion      server_assertions<>;
      ///          rpc_gss3_extension      extensions<>;      granted_extensions<>;
      ///  };
      ///  enum rpc_gss3_list_item {
      ///          DOI          LABEL = 0,
      ///          PRIV = 1,
      ///          PRIV_GROUP = 2
      ///  };
      ///  struct rpc_gss3_list_args {
      ///          rpc_gss3_list_item      list_what<>;
      ///  };
      ///  union rpc_gss3_list_item_u
      ///        switch (rpc_gss3_list_item itype) {
      ///  case DOI: LABEL:
      ///          rpc_gss3_doi    dois<>;          rpc_gss3_lable          labels<>;
      ///  case PRIV:
      ///          string          rpc_gss3_list_name      privs<>;
      ///  case PRIV_GROUP:
      ///          string          priv_groups<>;
      ///  default:
      ///          opaque                  ext<>;
      ///  };
      ///  typedef rpc_gss3_list_item_u rpc_gss3_list_res<>;

   The rpc_gss_cred_vers_3_t type is used in much

2.1.  New auth_stat values

   RPCSEC_GSSv3 requires the same way that
   rpc_gss_cred_vers_1_t is used in RPCSEC_GSSv1, that is: addition of several values to the auth_stat
   enumerated type definition:

              enum auth_stat {
                       * RPCSEC_GSS errors
                      RPCSEC_GSS3_COMPOUND_PROBEM = <>,
                      RPCSEC_GSS3_LABEL_PROBLEM = <>,
                      RPCSEC_GSS3_UNKNOWN_ASSERTION = <>
                      RPCSEC_GSS3_UNKNOWN_EXTENSION = <>
                      RPCSEC_GSS3_UNKNOWN_MESSAGE = <>

   [[Comment.3: fix above into YYY.  All the entries are TBD... --NW]]

2.2.  RPC message credential and verifier

   The rpc_gss_cred_vers_3_t type is used in much the same way that
   rpc_gss_cred_vers_1_t is used in RPCSEC_GSSv1, that is: as the arm of
   the rpc_gss_cred_t discriminated union in the RPC message header
   opaque_auth structure corresponding to version 3 (RPCSEC_GSS_VERS_3).
   It differs from rpc_gss_cred_vers_1_t in that:

   a.  the values for gss_proc corresponding to control messages are

   b.  the presence of a handle field indicating is the version of RPCSEC_GSS used RPCSEC_GSSv3 (child) handle, except for
       the RPCSEC_GSS3_CREATE control message where it is set to established the
       parent context handle used, if any.

   RPC handle.

   For all RPCSEC_GSSv3 data messages and control messages, the verifier field in
   the RPC message header is constructed in the RPCSEC_GSSv1 manner
   using the parent GSS-API security context.

2.3.  Control Messages

   There are three RPCSEC_GSSv3 context handles differ from control messages: RPCSEC_GSS3_CREATE,

   RPCSEC_GSSv3 control messages are similar to the RPCSEC_GSSv1 only
   RPCSEC_GSS_DESTROY control message (see section 5.4 [2]) in that the version
   sequence number used MUST be '3' instead
   of '1' and, as described above, in that there is one more field in the RPCSEC_GSS header to name request must be valid, and the version of RPCSEC_GSS used to
   establish header checksum
   in the context handle used to protect this message.  All verifier must be valid.  In other
   protocol elements from RPCSEC_GSSv1-protected RPC words, they look a lot like
   an RPCSEC_GSSv3 data messages MUST
   remain message with the same in v3 as header procedure set to

   As in v1. RPCSEC_GSSv1, the RPCSEC_GSSv3 control messages are may contain
   information following the same as RPCSEC_GSSv3 data
   messages, but with a gss_proc value that indicates a control message
   is contained verifier in the data payload.

2.1.  Control messages

   There are two RPCSEC_GSSv3 control messages: RPCSEC_GSS3_CREATE and

   The client MUST use one of the following security services to protect
   any RPCSEC_GSSv3 control message:

   o  rpc_gss_svc_channel_prot (see RPCSEC_GSSv2)

   o  rpc_gss_svc_integrity

   o  rpc_gss_svc_privacy

   Specifically the client MUST NOT use rpc_gss_svc_none.

2.1.1.  New auth_stat values

   For RPCSEC_GSSv3 requires control messages the addition of several values rpc_gss_cred_vers_3_t in the
   RPC message opaque_auth structure is encoded as follows:

   1.  the union rpc_gss_cred_t version is set to 3 with the auth_stat
   enumerated value being
       of type definition:

              enum auth_stat {
                       * RPCSEC_GSS errors
                      RPCSEC_GSS3_COMPOUND_PROBEM = <>,
                      RPCSEC_GSS3_LABEL_PROBLEM = <>,
                      RPCSEC_GSS3_IDENTITY_PROBLEM = <>
                      RPCSEC_GSS3_UNKNOWN_ASSERTION = <>
                      RPCSEC_GSS3_UNKNOWN_EXTENSION = <>
                      RPCSEC_GSS3_UNKNOWN_MESSAGE = <>

   [[Comment.2: XXX: fix above into YYY.  All the entries are TBD...

2.1.2.  Create request

   The RPCSEC_GSS3_CREATE call message consists rpc_gss_cred_vers_3_t instead of inputs to bind into a
   new RPCSEC_GSSv3 handle.  The context handle used to protect rpc_gss_cred_vers_1_t.

   2.  the
   RPCSEC_GSS3_CREATE call message gss_proc is termed the "parent" (or "outer")
   handle.  The reply set to this message consists one of either an error RPCSEC_GSS3_CREATE,
       RPCSEC_GSS3_DESTROY, or a
   new RPCSEC_GSSv3 handle, termed RPCSEC_GSS3_LIST.

   3.  the "child" handle.

   All uses of seq_num is a child valid sequence number for the context in the
       handle MUST use field.

   4.  the GSS-API security
   context associated with rpc_gss_service_t is one of rpc_gss_svc_integrity,
       rpc_gss_svc_privacy, or rpc_gss_svc_channel_prot.

   5.  the rpc_gss_cred_vers_3_t handle field is either set to the
       parent context handle of for RPCSEC_GSS3_CREATE, or to the
       child handle for RPCSEC_GSS3_LIST and RPCSEC_GSS3_DESTROY.

2.3.1.  Create request that produced

   As noted in the child introduction, RPCSEC_GSSv3 relies on the RPCSEC_GSS
   version 1 parent context handle.
   The child context, however, has its own sequence number space and
   window, distinct from that of (though version 2 can be used) secure
   connection to do the parent. actual GSS-API GSS3 security context
   establishment.  As described such, the rpc_gss_cred_vers_3_t fields in the introduction, RPC
   Call opaque_auth use the parent context handle and seq_num stream.

   The RPCSEC_GSS3_CREATE call message binds one or more items of
   several kinds into a new RPCSEC_GSSv3 context handle:

   o  another RPCSEC_GSS (version 1, 2, or 3) context handle (compound

   o  a channel binding

   o  authorization assertions (label, (labels, privileges)

   o  identity assertions

   Servers MUST  extensions (see Section 2.3.4 )

   The reply to this message consists of either ignore, reject an error or apply policy to an
   rpc_gss3_create_res structure which includes a new RPCSEC_GSSv3
   handle, termed the
   authorization and identity assertions.  Policies should take "child" which is used for subsequent control and
   data messages.

   Upon successful RPCSEC_GSS3_CREATE, both the client and the server
   should associate the resultant GSSv3 child context handle with the
   parent context handle in their GSS context caches so as to be able to
   reference the parent context given the child context handle.

   [[Comment.4: Destruction of the parent context => first destroy child
   handle.  IOW fail the RPCSEC_GSS_DESTROY of parent with new
   RPCSEC_GSS3_CONTEXT_EXISTS error code: What about the lifetime of the
   GSS3 context.  Is this meant to be long lived?? --AA]]

   Server policies should take into account the identity of the client
   and/or user as authenticated via the GSS-API.  Server implementation
   and policy MAY result in labels, privileges, and identities being
   mapped to concepts and values that are local to the server.  Compound authentication

   RPCSEC_GSSv3 allows for compound authentication of client hosts and
   users to servers.  This  As in non-compound authentication, there is done by using an integrity protected
   RPCSEC_GSSv3 message of a
   parent handle used to protect the RPCSEC_GSS3_CREATE type which includes call message,
   and a
   reference resultant RPCSEC_GSSv3 child handle.  In addition to the context parent
   handle, the compound authentication create control message has a
   handle to bind, referenced via the compound_binding field of the
   RPCSEC_GSS3_CREATE arguments structure (rpc_gss3_create_args) termed
   the "inner" handle, as well as a nonce and a MIC of that
   nonce nounce
   created using the GSS-API security context associated with the named
   "inner" handle.  We'll term the two context handles "parent" (or
   "outer") and "inner," and the resulting context handle the "child"
   handle, where the outer context handle is the context handle
   providing integrity protection to the RPCSEC_GSS3_CREATE message, and
   the inner context handle is the one referenced via the
   compound_binding field of the RPCSEC_GSS3_CREATE arguments structure

   All uses of a child context handle that is bound to an inner context
   MUST be treated as speaking for the initiator principal (as modified
   by any assertions in the RPCSEC_GSS3_CREATE message) of the inner
   context handle's GSS-API security context.

   This feature is needed, for example, when a client wishes to use
   authority assertions that the server may only grant if a user and a
   client are authenticated together to the server.  Thus a server may
   refuse to grant requested authority to a user acting alone (e.g., via
   an unprivileged user-space program), or to a client acting alone
   (e.g. when a client is acting on behalf of a user) but may grant
   requested authority to a client acting on behalf of a user if the
   server identifies the user and trusts the client.

   It is assumed that an unprivileged user-space program would not have
   access to client host credentials needed to establish a GSS-API
   security context authenticating the client to the server, therefore
   an unprivileged user-space program could not create an RPCSEC_GSSv3
   RPCSEC_GSS3_CREATE message that successfully binds a client and a
   user security context.

   Clients using RPCSEC_GSS context binding MUST use, as the outer parent
   context handle, an RPCSEC_GSS context handle that corresponds to a
   GSS-API security context that authenticates the client host, and for
   the inner context handle it SHOULD use a context handle to
   authenticate a user.  The reverse (outer (parent handle authenticates user,
   inner authenticates client) MUST NOT be used.  Other compounds might
   eventually make sense.

   An RPCSEC_GSSv3 context handle that is bound to another RPCSEC_GSS
   context MUST be treated by servers as authenticating the GSS-API
   initiator principal authenticated by the inner context handle's GSS-
   API security context.  This principal may be mapped to a server-side
   notion of user or principal as modified by any identity assertions by
   the client in the same RPCSEC_GSS3_CREATE request that the server
   accepts.  Channel binding

   RPCSEC_GSSv3 provides a different way to do channel binding than
   RPCSEC_GSSv2.  Specifically:

   a.  RPCSEC_GSSv3 builds on RPCSEC_GSSv1 by reusing existing,
       established context handles rather than providing a different RPC
       security flavor for establishing context handles,

   b.  channel bindings data are not hashed because the community now
       agrees that it is the secure channel's responsibility to produce
       channel bindings data of manageable size.

   (a) is useful in keeping RPCSEC_GSSv3 simple in general, not just for
   channel binding. (b) is useful in keeping RPCSEC_GSSv3 simple
   specifically for channel binding.

   Channel binding is accomplished as follows.  The client prefixes the
   channel bindings data octet string with the channel type as described
   in [5], then the client calls GSS_GetMIC() to get a MIC of resulting
   octet string, using the outer parent RPCSEC_GSS context handle's GSS-API
   security context.  The MIC is then placed in the chan_binding_mic
   field of RPCSEC_GSS3_CREATE arguments (rpc_gss3_create_args).

   If the chan_binding_mic field of the arguments of a
   RPCSEC_GSS3_CREATE control message is set, then the server MUST
   verify the client's channel binding MIC if the server supports this
   feature.  If channel binding verification succeeds then the server
   MUST generate a new MIC of the same channel bindings and place it in
   the chan_binding_mic field of the RPCSEC_GSS3_CREATE results.  If
   channel binding verification fails or the server doesn't support
   channel binding then the server MUST indicate this in its reply by
   not including a chan_binding_mic value (chan_binding_mic is an
   optional field).

   The client MUST verify the result's chan_binding_mic value, if the
   server included it, by calling GSS_VerifyMIC() with the given MIC and
   the channel bindings data (including the channel type prefix).  If
   client-side channel binding verification fails then the client MUST
   call RPCSEC_GSS3_DESTROY.  If the client requested channel binding
   but the server did not include a chan_binding_mic field in the
   results, then the client MAY continue to use the resulting context
   handle as though channel binding had never been requested, otherwise
   (if the client really wanted channel binding) it MUST call

   As per-RPCSEC_GSSv2:

   o per-RPCSEC_GSSv2 [4]:

      "Once a successful [channel binding] procedure has been performed
      on an [RPCSEC_GSSv3] context handle, the initiator's
      implementation may map application requests for rpc_gss_svc_none
      and rpc_gss_svc_integrity to rpc_gss_svc_channel_prot credentials.
      And if the secure channel has privacy enabled, requests for
      rpc_gss_svc_privacy can also be mapped to

   o  ...

   [[Comment.3: ...? --TH]]

   Any RPCSEC_GSSv3 context handle that has been bound to a secure
   channel in this way SHOULD be used only with the
   rpc_gss_svc_channel_prot, and SHOULD NOT be used with
   rpc_gss_svc_none nor rpc_gss_svc_integrity -- if the secure channel
   does not provide privacy protection then the client MAY use
   rpc_gss_svc_privacy where privacy protection is needed or desired.  Label assertions

   RPCSEC_GSSv3 clients MAY assert a security label in some DOI LSF by
   binding this assertion into an RPCSEC_GSSv3 context handle.  This is
   done by including an assertion of type rpc_gss3_label in the
   'assertions' field (discriminant: 'LABEL') of the RPCSEC_GSS3_CREATE
   arguments to the desired DOI LSF and label.

   Label encoding is specific specified to each DOI and not mirror the NFSv4 sec_label attribute
   described herein.  DOI
   encoding in Section 12.2.2 of [6].  The label format specifier (LFS)
   is TBD.  [[Comment.4: [fill in...  Solaris uses integers an identifier used by the client to
   name DOIs, establish the syntactic format
   of the security label and there the semantic meaning of its components.
   The policy identifier (PI) is an IANA registry optional part of DOIs as 32-bit integers,
   and IPsec (whence the IANA registry) and CALIPSO use 32-bit integers definition of
   an LFS which allows for DOIs as well.  So a 32-bit unsinged integer seems clients and server to be identify specific
   security policies.  The opaque label field of rpc_gss3_label is
   dependent on the way MAC model to go.  Add references... -Nico] --NW]] interpret and enforce.

   [[Comment.5: This is just Check that this Label definition provides all the
   LNFS format, so update it. --TH]]
   required pieces to enable full mode when combined with NFSv4.2 LNFS.
   Specifically, how does the client find out and respond if a server
   has changed a label. --AA]]

   If a label itself requires privacy protection (i.e., that the user
   can assert that label is a secret) then the client MUST use the
   rpc_gss_svc_privacy protection service for the RPCSEC_GSS3_CREATE
   request or, if the parent handle is bound to a secure channel that
   provides privacy protection, rpc_gss_svc_channel_prot.

   If a client wants to ensure that the server understands the asserted
   label then it MUST set the 'critical' field of the label assertion to
   TRUE, otherwise it MUST set it to FALSE.

   Servers that do not support labeling MUST ignore non-critical label
   assertions.  Servers that do not support the requested DOI LFS MUST
   either ignore non-critical label assertions or map them to a suitable
   label in a supported DOI. LFS.  Servers that do not support labeling or do
   not support the requested DOI LFS MUST return an error if the label
   request is critical.  Servers that support labeling in the requested
   LFS MAY map the requested label to different label as a result of
   server-side policy evaluation.  Privilege assertions

   Privilege  Structured privilege assertions are similar to label assertions, except

   A structured privilege is an RPC application defined structure that
   is no DOI, opaque, and is encoded in the rpc_gss3_privs privilege field.
   Encoding, server verification and any server policies for structured
   privileges supported are specified described by the RPC application.

   Privileges are encoded US-ASCII strings containing comma-separated
   privilege names, as well as up to one privilege group name and zero
   or more exclusions, where each exclusion application definition.  The
   listname field of rpc_gss3_privs is a privilege name or
   privilege group name prefixed with an exclamation point.  Two special
   privilege group names are defined here: "all" (which represents all
   possible privileges) and "basic" (which represents privileges
   normally granted to all users).

   RPC applications that wish description string used to use this facility must define list
   the set
   of known privileges, and privilege.

   A successful structured privilege assertion RPCSEC_GSS3_CREATE call
   must specify which return all accepted privileges are in the
   "basic" rpc_gss3_privs
   granted_assertions field.

   Section  "Inter-Server Copy with RPCSEC_GSSv3" of [6] shows
   an example of structured privilege group.  For example, NFSv4 might specify privileges
   for reading, writing, chowning, linking, etc.  Identity assertions

   Identity assertions can be used either to modify definition and use.

2.3.2.  Destruction request

   The RPCSEC_GSS3_DESTROY control message is the set of groups
   assigned on same as the server-side to a given user (authenticated by
   RPCSEC_GSSv1 RPCSEC_GSS_DESTROY control message, but with the
   GSS-API) or to implement an AUTH_SYS-like [4].  In version
   3 header.  Specifically, the latter case rpc_gss_cred_vers_3_t fields in the client specifies at least a user-name RPC
   Call opaque_auth use the GSS3 context handle and possibly groups that it
   thinks seq_num stream.  As
   with all RPCSEC_GSSv3 messages, the user belongs to.

   Clients may set a username, a group list, and/or lists of groups header checksum uses the parent
   context, and needs to be added or removed from the group list that the valid.

   The server sends a response as it would
   normally use for the given user.

   The server MUST decide whether to accept identity assertions by
   applying local policy.  Such policies is not described herein.
   Example policies:

   o  "always accept identity assertions"

   o  "always accept identity assertions where the identities are

   o  "accept identity assertions ... only from trusted clients" (where
      the identity of the a data request.  The
   client is taken from the initiator principal
      of the outer context handle's GSS-API security context, or from
      the network address of the client...)

   o  "accept identity assertions ... only from trusted clients where
      IPsec policy protects this application's packet flows between the
      clients and this server"

   o  "accept only removals of groups from a user's group membership
      list as determined by the server"

   o  "never accept identity assertions"

   o  etc.

   Clients may mark an identity assertion as being critical, in which
   case the server MUST respond with an error if must then destroy the server does not
   accept context for the identity assertion as-is. session.

2.3.3.  List request

   The representation of users and groups is not given here, but RPCSEC_GSS3_LIST control message is left similar to
   RPCSEC_GSS3_DESTROY message.  Specifically, the application.  It is expected that RPCSEC_GSSv3 identity
   assertions in the context of the NFSv4 application would consist of
   NFSv4 user and group representations as used on the wire rpc_gss_cred_vers_3_t
   fields in NFSv4
   access control lists (ACLs).  Server assertions

   Servers MAY inform clients of assertions were granted by setting the
   'granted_assertions' field of the RPCSEC_GSS3_CREATE reply.

   The protocol provides a field ('server_assertions') for servers to
   make assertions about themselves.  At this time there is not much RPC Call opaque_auth use
   for this field, though servers MAY assert a single security label,
   indicating that all contents on the server is at that label.  The
   client MUST, of course, either evaluate or ignore any server-side

2.1.3.  Context GSS3 context handle destruction

   The RPCSEC_GSS3_DESTROY procedure is the same as for RPCSEC_GSSv1,
   but and
   seq_num stream.  As with all RPCSEC_GSSv3 messages, the version 3 header.

2.1.4.  List request header
   checksum uses the parent context, and needs to be valid.

   The RPCSEC_GSS3_LIST call control message consists of a single integer
   indicating what should be listed, and the reply consists of an error
   or the requested list.  The client may list DOIs, privilege names, LFSs or structured
   privilege group names. listnames.

   The result is an opaque octet string containing a list of DOIs LFSs
   [encoding TBD] or a US-ASCII string containing a comma-separated list of privilege names or privilege group names.

2.1.5. active structured privileges [encoding

2.3.4.  Extensibility

   New fields may be added through the 'extensions' typed hole.  All
   such extensions have a 'critical' flag.

   [[Comment.6: Should we keep the extensions types hole?  I think
   not... --AA]]

   Assertion types may be added in the future by adding arms to the
   'rpc_gss3_assertion_u' union.  Every assertion has a 'critical' flag
   that can be used to indicate criticality.

   New fields may be added through  Other assertion types are
   described elsewhere and include:

   o  Client-side assertions of identity:

      *  Primary client/user identity

      *  Supplementary group memberships of the 'extensions' typed hole.  All
   such extensions have a 'critical' flag. client/user, including
         support for specifying deltas to the membership list as seen on
         the server.

   New control message types may be added.

   Clients receiving unknown critical server assertions MUST destroy the
   established RPCSEC_GSSv3 context handle.

   Servers receiving unknown critical client assertions or unknown
   RPCSEC_GSS_v3 extensions MUST return an error.

   There is no IANA or other registry for RPCSEC_GSSv3 extensions.  All
   extensions MUST be done by IETF Protocol Action.

3.  Privileges and identity representation for NFSv4

   The representation of users and groups for use in identity assertions

2.4.  Data Messages

   RPCSEC_GSS3_DATA messages differ from from RPCSEC_GSSv1 data messages
   in RPCSEC_GSSv3 SHALL be the same as that the user and group
   representations version number used by NFSv4 for access control list subjects on the
   wire, cast as an octet string ("opaque").

   The following privileges are defined for use with the NFSv4 protocol:

   file_chown  Generally allows the caller to change a file's owner
      regardless of who owns the file.

   file_chown_self  Generally allows the caller to change the owner MUST be '3' instead of a
      file it owns.

   file_dac_execute  Generally allows the caller to read any file for

   file_dac_read  Generally allows the caller to read any file or

   file_dac_search  Generally allows the caller to search any directory.

   file_dac_write  Generally allows the caller to write to any file (or
      create/delete/link objects '1'.  As noted
   in directories).

   file_link_any  Generally allows the caller to create hardlinks to
      files not owned by Section 2.2 the caller.

   file_owner  Generally allows RPCSEC_GSSv3 context handle is used along with
   it's sequence number stream.

   For RPCSEC_GSSv3 data messages the caller to modify rpc_gss_cred_vers_3_t in the access,
      modification and other timestamps of a filesystem object, as well RPC
   message opaque_auth structure is encoded as its permissions and ACL.

   file_setid  Generally allows follows:

   1.  the caller to union rpc_gss_cred_t version is set the set-user-ID and
      set-group-ID bits of a file.

   file_downgrade_sl  Generally allows the caller to downgrade the
      security label of a filesystem object.

   file_update_sl  Generally allows the caller to upgrade 3 with the security
      label value being
       of a filesystem object.

   [[Comment.6: [What about NFSv3?  The representation type rpc_gss_cred_vers_3_t instead of privs would be
   the same for v3 as for v4, though there'd be no privs for dealing
   with labels (file_downgrade_sl and file_update_sl).  And rpc_gss_cred_vers_1_t.

   2.  the
   representation of users/groups would NFSv3's representation thereof.
   But should we bother to specify this? -Nico] --NW]] [[Comment.7: Need
   a use case to justify v3 development. --TH]]

   [[Comment.8: [Also, this gss_proc is derived from Solaris' notion of
   privileges.  We should look at how well this scheme relates set to other
   operating systems as NFSv4 clients and servers. -Nico] --NW]]
   [[Comment.9: On the radar. --TH]]

   The contents of RPCSEC_GSS3_DATA

   3.  the 'basic' privilege set seq_num is not defined herein.
   Note that 'file_link_any' and 'file_chown_self' may be present in the
   server's notion of the basic privilege set.

   The NFSv4-specific privileges may be limited by the server a valid GSS3 context (child context) sequence

   4.  just as in ways
   not specified above.  For example, the server may deny access for
   certain operations that would normally be granted given RPCSEC_GSSv1, the granted
   assertion of a given privilege (e.g., "no one may write to files
   owned by such and such user"), rpc_gss_service_t is one of
       rpc_gss_svc_none, rpc_gss_svc_integrity, rpc_gss_svc_privacy, or

   5.  the server may require that all
   privileges be asserted (and granted, of course) in order to allow
   certain operations (e.g., "all privileges are required in order to
   write handle field is set to files owned by such and such user, not just

4. the (child) RPCSEC_GSSv3 context

3.  Security Considerations

   This entire document deals with security issues.

   The RPCSEC_GSSv3 protocol allows for client-side assertions of data
   that is relevant to server-side authorization decisions.  These
   assertions must be evaludated by the server in the context of whether
   the client and/or user are authenticated, whether compound
   authentication was used, whether the client is trusted, what ranges
   of assertions are allowed for the client and the user (separately or
   together), and any relevant server-side policy.

   The security semantics of assertions carried by RPCSEC_GSSv3 are
   application protocol-specific.

   RPCSEC_GSSv3 supports a notion of critical assertions (and
   extensions), but there's no need for peers to tell each other what
   assertions were granted, or what they were mapped to.

   Note that RPSEC_GSSv3 is not a complete solution for labeling: it
   conveys the labels of actors, but not the labels of objects.  RPC
   application protocols may require extending in order to carry object
   label information.

   The RPCSEC_GSSv3 protocol also provides for a replacement of the old
   AUTH_SYS RPC authentication flavor.  AUTH_SYS relies on "privileged
   port numbers" for "authentication," and was quite limited in what
   assertions it supported and incompatible with NFSv4 representations
   of identity.  To replace AUTH_SYS with RPCSEC_GSSv3 simply use a GSS-
   API mechanism to authenticate the client (but not the user) and let
   the client assert the user's identity.  This is more secure than
   AUTH_SYS in that at least the client can be strongly authenticated
   using GSS-API mechanisms, and it is more functional than AUTH_SYS in
   that identity representations are defined by the application layer.

   It is possible that a GSS-API mechanism that does not provide any
   security services could be created so as to make it possible to
   replace AUTH_SYS with RPCSEC_GSSv3 while retaining the same
   privileged port semantics.  Such a mechanism is out of scope for this
   document and would have its own security considerations.

   There may be interactions with NFSv4's callback security scheme and
   NFSv4.1's GSS-API "SSV" mechanisms.  Specifically, the NFSv4 callback
   scheme requires that the server initiate GSS-API security contexts,
   which does not work well in practice, and in the context of client-
   side processes running as the same user but with different privileges
   and security labels the NFSv4 callback security scheme seems
   particularly unlikely to work well.  NFSv4.1 has the server use an
   existing, client-initiated RPCSEC_GSS context handle to protect
   server-initiated callback RPCs.  The NFSv4.1 callback security scheme
   lacks all the problems of the NFSv4 scheme, however, it is important
   that the server pick an appropriate RPCSEC_GSS context handle to
   protect any callbacks.  Specifically, it is important that the server
   use RPCSEC_GSS context handles which authenticate the client to
   protect any callbacks relating to server state initiated by RPCs
   protected by RPCSEC_GSSv3 contexts.  [[Comment.10:

   [[Comment.7: [Add text about interaction with GSS-SSV...] --NW]]


   [[Comment.8: I see no reason to use RPCSEC_GSSv3 contexts for NFSv4.x
   back channel. --AA]]

   [[Comment.9: Since GSS3 requires an RPCSEC_GSSv1 or v2 context handle
   to establish a GSS3 context, SSV can not be used as this draft is

   [[Comment.10: AFAICS the reason to use SSV is to avoid using a client
   machine credential which means compound authentication can not be
   used.  Since GSS3 requires an RPCSEC_GSSv1 or v2 context handle to
   establish a GSS3 context, SSV can not be used as the parent context
   for GSSv3. --AA]]

4.  IANA Considerations

   This section uses terms that are defined in [8].

   There are no IANA considerations in this document.  TBDs in this
   document will be assigned by the ONC RPC registrart registrar (which is not
   IANA, XXX: verify).


5.  References

5.1.  Normative References

   [1]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", March 1997.

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

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

   [4]   Srinivasan, R., "RPC: Remote Procedure Call Protocol
         Specification Version 2", RFC 1831, August 1995.

   [5]   Williams, N., "On the Use of Channel Bindings to Secure
         Channels", RFC 5056, November 2007.

   [6]   Haynes, T., "NFS Version 4 Minor Version 2",
         draft-ietf-nfsv4-minorversion2-19 (Work In Progress),
         October 2012.
         March 2013.

   [7]   Eisler, M., "XDR: External Data Representation Standard",
         RFC 4506, May 2006.

   [8]   Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
         Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.


5.2.  Informative References

   [9]   Haynes, T., "Requirements for Labeled NFS",
         draft-ietf-nfsv4-labreqs-03 (work in progress).

   [10]  "Section 46.6. Multi-Level Security (MLS) of Deployment Guide:
         Deployment, configuration and administration of Red Hat
         Enterprise Linux 5, Edition 6", 2011.


   [11]  Smalley, S., "The Distributed Trusted Operating System (DTOS)
         Home Page",


   [12]  Carter, J., "Implementing SELinux Support for NFS",

   [12]  Haynes, T., "Requirements for Labeled NFS",
         draft-ietf-nfsv4-labreqs-03 (work in progress).

   [13]  Quigley, D. and J. Lu, "Registry Specification for MAC Security
         Label Formats", draft-quigley-label-format-registry (work in
         progress), 2011.

Appendix A.  Acknowledgments

Appendix B.  RFC Editor Notes

   [RFC Editor: please remove this section prior to publishing this
   document as an RFC]

   [RFC Editor: prior to publishing this document as an RFC, please
   replace all occurrences of RFCTBD10 with RFCxxxx where xxxx is the
   RFC number of this document]

Authors' Addresses

   Thomas Haynes (editor)

   William A. (Andy) Adamson
   9110 E 66th St
   Tulsa, OK  74133
   3629 Wagner Ridge Ctt
   Ann Arbor, MI  48103

   Phone: +1 918 307 1415 734 665 1204

   Nico Williams
   13115 Tamayo Dr
   Austin, TX  78729