draft-ietf-nfsv4-rpcsec-gssv3-04.txt   draft-ietf-nfsv4-rpcsec-gssv3-05.txt 
NFSv4 T. Haynes, Ed. NFSv4 W. Adamson
Internet-Draft NetApp Internet-Draft NetApp
Intended status: Standards Track N. Williams Intended status: Standards Track N. Williams
Expires: May 11, 2013 Cryptonector Expires: April 20, 2014 Cryptonector
November 07, 2012 October 17, 2013
Remote Procedure Call (RPC) Security Version 3 Remote Procedure Call (RPC) Security Version 3
draft-ietf-nfsv4-rpcsec-gssv3-04.txt draft-ietf-nfsv4-rpcsec-gssv3-05.txt
Abstract Abstract
This document specifies version 3 of the Remote Procedure Call (RPC) This document specifies version 3 of the Remote Procedure Call (RPC)
security protocol (RPCSEC_GSS). This protocol provides for: compound security protocol (RPCSEC_GSS). This protocol provides for compound
authentication of client hosts and users to server (constructed by authentication of client hosts and users to server (constructed by
generic composition), channel binding, security label assertions for generic composition), security label assertions for multi-level and
multi-level and type enforcement, privilege assertions, and identity type enforcement, structured privilege assertions, and channel
assertions. bindings.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [1]. document are to be interpreted as described in RFC 2119 [1].
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
skipping to change at page 1, line 42 skipping to change at page 1, line 42
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 11, 2013. This Internet-Draft will expire on April 20, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Applications of RPCSEC_GSSv3 . . . . . . . . . . . . . . . 4
1.2. Applications of RPCSEC_GSSv3 . . . . . . . . . . . . . . . 4
2. The RPCSEC_GSSv3 protocol . . . . . . . . . . . . . . . . . . 5 2. The RPCSEC_GSSv3 protocol . . . . . . . . . . . . . . . . . . 5
2.1. Control messages . . . . . . . . . . . . . . . . . . . . . 10 2.1. New auth_stat values . . . . . . . . . . . . . . . . . . . 9
2.1.1. New auth_stat values . . . . . . . . . . . . . . . . . 10 2.2. RPC message credential and verifier . . . . . . . . . . . 10
2.1.2. Create request . . . . . . . . . . . . . . . . . . . . 11 2.3. Control Messages . . . . . . . . . . . . . . . . . . . . . 10
2.1.3. Context handle destruction . . . . . . . . . . . . . . 16 2.3.1. Create request . . . . . . . . . . . . . . . . . . . . 11
2.1.4. List request . . . . . . . . . . . . . . . . . . . . . 16 2.3.2. Destruction request . . . . . . . . . . . . . . . . . 15
2.1.5. Extensibility . . . . . . . . . . . . . . . . . . . . 17 2.3.3. List request . . . . . . . . . . . . . . . . . . . . . 16
3. Privileges and identity representation for NFSv4 . . . . . . . 17 2.3.4. Extensibility . . . . . . . . . . . . . . . . . . . . 16
4. Security Considerations . . . . . . . . . . . . . . . . . . . 19 2.4. Data Messages . . . . . . . . . . . . . . . . . . . . . . 17
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 3. Security Considerations . . . . . . . . . . . . . . . . . . . 17
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
6.1. Normative References . . . . . . . . . . . . . . . . . . . 20 5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.2. Informative References . . . . . . . . . . . . . . . . . . 21 5.1. Normative References . . . . . . . . . . . . . . . . . . . 19
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 21 5.2. Informative References . . . . . . . . . . . . . . . . . . 19
Appendix B. RFC Editor Notes . . . . . . . . . . . . . . . . . . 21 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21 Appendix B. RFC Editor Notes . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction 1. Introduction
The original RPCSEC_GSS protocol [2] provided for authentication of The original RPCSEC_GSS protocol [2] provided for authentication of
RPC clients and servers to each other using the Generic Security RPC clients and servers to each other using the Generic Security
Services Application Programming Interface (GSS-API) [3]. The second Services Application Programming Interface (GSS-API) [3]. The second
version of RPCSEC_GSS [4] added support for channel binding [5]. version of RPCSEC_GSS [4] added support for channel bindings [5].
We find that GSS-API mechanisms are insufficient for communicating We find that GSS-API mechanisms are insufficient for communicating
certain aspects of a client's identity and authority to a server. certain aspects of a client's authority to a server. The GSS-API and
The GSS-API and its mechanisms certainly could be extended to address its mechanisms certainly could be extended to address this
this shortcomming, but it seems be far simpler to address it at the shortcoming, but it seems be far simpler to address it at the
application layer, namely, in this case, RPCSEC_GSS. application layer, namely, in this case, RPCSEC_GSS.
We therefore provide a new version of RPCSEC_GSS that allows for the The motivation for RPCSEC_GSSv3 is to add support for labeled
following: security and server-side copy for NFSv4 (see [6] and [9]). Both of
these features require assertions of authority from the client.
o compound authentication of the client host and user to the server Assertions need to be verified. One party that can verify an
(done by binding of two RPCSEC_GSS handles) assertion is the client host, which can authenticate to the server
using its own credentials. We can also require users to verify an
assertion as well. This calls for compound authentication.
o channel binding (even though RPCSEC_GSSv2 provides this also; see Because the design of RPCSEC_GSSv3 relies on either RPCSEC_GSS
below) 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.
o client-side assertions of authority: We therefore describe a new version of RPCSEC_GSS that allows for the
following:
* security labels (for multi-level, type enforcement, and other o Client-side assertions of authority:
labeled security models) (see [9], [10], and [11])
* application-specific privileges * Security labels for multi-level, type enforcement, and other
labeled security models. See [10], [11], [12], [6] and [9].
o client-side assertions of identity: * Application-specific structured privileges. For an example see
server-side copy [6].
* primary client/user identity * Compound authentication of the client host and user to the
server done by binding two RPCSEC_GSS handles.
* supplementary group memberships of the client/user, including * Simplified channel binding.
support for specifying deltas to the membership list as seen on
the server
Assertions of labels, privilege and identity are evaluated by the Assertions of labels and privileges are evaluated by the server,
server, which may then map the asserted values to other values, all which may then map the asserted values to other values, all according
according to server-side policy. to server-side policy.
We also add an option for enumerating server-side domains of We also add an option for enumerating active server-side privileges
interpretation (DOI), [[Comment.1: No DOI in the LFS, why here? and supported label format specifiers (LFS). The LFS and Label
Adapt with the new format! --TH]] Format Registry are described in detail in [13].
RPCSEC_GSSv3 is patterned as follows: RPCSEC_GSSv3 is patterned as follows:
o a client uses an existing RPCSEC_GSS context handle (of any o A client uses an existing RPCSEC_GSSv1 (or RPCSEC_GSSv2) context
RPCSEC_GSS version) to protect RPCSEC_GSSv3 exchanges (this will handle to protect RPCSEC_GSSv3 exchanges (this will be termed the
be termed the "parent" or "outer" handle) "parent" handle)
o the server issues a "child" RPCSEC_GSSv3 handle, but the o The server issues a "child" RPCSEC_GSSv3 handle, but the
underlying GSS-API security context for the parent handle is used underlying GSS-API security context for the parent handle is used
in all subsequent exchanges using the child handle (this works in all subsequent exchanges using the child handle. This works
because the RPCSEC_GSS handle is included in the integrity because the RPCSEC_GSS handle is included in the integrity
protected RPCSEC_GSS auth/verifier header for all versions of protected RPCSEC_GSS auth/verifier header for all versions of
RPCSEC_GSS). 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 This means that RPCSEC_GSSv3 depends on RPCSEC_GSS versions 1 and/or
2 for actual GSS-API security context establishment. This keeps the 2 for actual GSS-API security context establishment. This keeps the
specification of RPCSEC_GSSv3 simple by avoiding the need to specification of RPCSEC_GSSv3 simple by avoiding the need to
duplicate the core functionality of RPCSEC_GSS version 1. duplicate the core functionality of RPCSEC_GSS version 1.
1.1. Motivation 1.1. Applications of RPCSEC_GSSv3
The initial motivation for RPCSEC_GSSv3 is to add support for labeled
security for NFSv4 (see [12]). We also realized that the assertion
of security label is conceptually equivalent, protocol-wise, to
assertions of privilege and identity.
Additionally, assertions need to be verified, and in this case the
one party that can verify an assertion is the client host, which can
authenticate to the server using its own credentials. Yet we want to
continue authenticating users as well. This calls for compound
authentication.
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 The common uses of RPCSEC_GSSv3, particularly for NFSv4 [6], are
expected to be: expected to be:
a. labeled security: client-side process label assertion [+ a. labeled security: client-side process label assertion [+
privilege assertion] + compound client host & user privilege assertion] + compound client host & user
authentication; authentication;
b. compound client host & user authentication [+ privilege b. compound client host & user authentication [+ critical structured
assertion]; privilege assertions] used in inter-server server-side copy;
c. client-side process credentials assertion [+ privilege assertion]
as a replacement for AUTH_SYS that is more secure than AUTH_SYS
while not requiring per-user credentials.
A traditional file copy entails the client gaining access to a file
on the source, reading it, and writing it to a file on the
destination. In Server-side Copy (see Section 2 of [6]), the client
first secures access to both source and destination and then
authorizes the destination and source to copy the file. RPCSEC_GSSv3
is used to allow the destination authentication with the source.
Labeled NFS (see Section 7 of [6] uses the subject label provided by Labeled NFS (see Section 8 of [6]) uses the subject label provided by
the client via the RPCSEC_GSSv3 layer to enforce MAC access to the client via the RPCSEC_GSSv3 layer to enforce MAC access to
objects owned by the server. objects owned by the server to enable server guest mode or full mode
labeled NFS.
[[Comment.2: check that 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 user gaining access
to a file on the source, reading it, and writing it to a file on the
destination. In secure NFSv4 inter-server server-side copy (see
Section 3.4.1 of [6]), the user first secures access to both source
and destination files, and then uses RPCSEC_GSSv3 compound
authentication and structured privileges to authorize the destination
to copy the file from the source on behalf of the user.
2. The RPCSEC_GSSv3 protocol 2. The RPCSEC_GSSv3 protocol
This document contains the External Data Representation (XDR) ([7]) This document contains the External Data Representation (XDR) ([7])
definitions for the RPCSEC_GSSv3 protocol. definitions for the RPCSEC_GSSv3 protocol.
The XDR description is provided in this document in a way that makes 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 it simple for the reader to extract into ready to compile form. The
reader can feed this document in the following shell script to reader can feed this document in the following shell script to
produce the machine readable XDR description of RPCSEC_GSSv3: produce the machine readable XDR description of RPCSEC_GSSv3:
skipping to change at page 5, line 44 skipping to change at page 5, line 36
this document is in a file called "spec.txt", then the reader can do: this document is in a file called "spec.txt", then the reader can do:
sh extract.sh < spec.txt > rpcsec_gss_v3.x sh extract.sh < spec.txt > rpcsec_gss_v3.x
The effect of the script is to remove leading white space from each The effect of the script is to remove leading white space from each
line, plus a sentinel sequence of "///". line, plus a sentinel sequence of "///".
The XDR description, with the sentinel sequence follows: The XDR description, with the sentinel sequence follows:
/// /* /// /*
/// * Copyright (c) 2011 IETF Trust and the persons /// * Copyright (c) 2013 IETF Trust and the persons
/// * identified as the document authors. All rights /// * identified as the document authors. All rights
/// * reserved. /// * reserved.
/// * /// *
/// * The document authors are identified in [RFC2203], /// * The document authors are identified in [RFC2203],
/// * [RFC5403], and [RFCxxxx]. /// * [RFC5403], and [RFCxxxx].
/// * /// *
/// * Redistribution and use in source and binary forms, /// * Redistribution and use in source and binary forms,
/// * with or without modification, are permitted /// * with or without modification, are permitted
/// * provided that the following conditions are met: /// * provided that the following conditions are met:
/// * /// *
skipping to change at page 7, line 35 skipping to change at page 7, line 28
/// RPCSEC_GSS3_LIST = 5, /// RPCSEC_GSS3_LIST = 5,
/// RPCSEC_GSS3_CREATE = 6, /// RPCSEC_GSS3_CREATE = 6,
/// RPCSEC_GSS3_DESTROY = 7 /// RPCSEC_GSS3_DESTROY = 7
/// }; /// };
/// ///
/// struct rpc_gss_cred_vers_3_t { /// struct rpc_gss_cred_vers_3_t {
/// rpc_gss3_proc_t gss_proc; /// rpc_gss3_proc_t gss_proc;
/// unsigned int seq_num; /// unsigned int seq_num;
/// rpc_gss_service_t service; /// rpc_gss_service_t service;
/// opaque handle<>; /// opaque handle<>;
/// unsigned int handle_version;
/// }; /// };
/// ///
/// const RPCSEC_GSS_VERS_1 = 1; /// const RPCSEC_GSS_VERS_1 = 1;
/// const RPCSEC_GSS_VERS_2 = 2; /// const RPCSEC_GSS_VERS_2 = 2;
/// const RPCSEC_GSS_VERS_3 = 3; /* new */ /// const RPCSEC_GSS_VERS_3 = 3; /* new */
/// ///
/// union rpc_gss_cred_t switch (unsigned int rgc_version) { /// union rpc_gss_cred_t switch (unsigned int rgc_version) {
/// case RPCSEC_GSS_VERS_1: /// case RPCSEC_GSS_VERS_1:
/// case RPCSEC_GSS_VERS_2: /// case RPCSEC_GSS_VERS_2:
/// rpc_gss_cred_vers_1_t rgc_cred_v1; /// rpc_gss_cred_vers_1_t rgc_cred_v1;
skipping to change at page 8, line 19 skipping to change at page 8, line 11
/// ///
/// struct rpc_gss3_gss_binding { /// struct rpc_gss3_gss_binding {
/// unsigned int vers; /// unsigned int vers;
/// opaque handle<>; /// opaque handle<>;
/// opaque nonce<>; /// opaque nonce<>;
/// opaque mic<>; /// opaque mic<>;
/// }; /// };
/// ///
/// typedef opaque rpc_gss3_chan_binding<>; /// typedef opaque rpc_gss3_chan_binding<>;
/// ///
/// typedef opaque rpc_gss3_doi<>; /// struct rpc_gss3_lfs {
/// unsigned int lfs_id;
/// unsigned int pi_id;
/// };
///
/// struct rpc_gss3_label { /// struct rpc_gss3_label {
/// rpc_gss3_doi doi; /// rpc_gss3_lfs lfs;
/// opaque label<>; /// opaque label<>;
/// }; /// };
/// ///
/// typedef opaque rpc_gss3_privs<>; /// typedef string rpc_gss3_list_name<>;
/// /// struct rpc_gss3_privs {
/// typedef opaque rpc_gss3_name<>; /// rpc_gss3_list_name listname;
/// /// opaque privilege<>;
/// typedef rpc_gss3_name rpc_gss3_group_list<>;
/// struct rpc_gss3_id {
/// rpc_gss3_name *username;
/// rpc_gss3_group_list *groups;
/// rpc_gss3_group_list groups_add;
/// rpc_gss3_group_list groups_remove;
/// }; /// };
/// ///
/// enum rpc_gss3_assertion_type { /// enum rpc_gss3_assertion_type {
/// LABEL = 0, /// LABEL = 0,
/// PRIVS = 1, /// PRIVS = 1
/// IDENTITY = 2
/// }; /// };
/// ///
/// union rpc_gss3_assertion_u /// union rpc_gss3_assertion_u
/// switch (rpc_gss3_assertion_type atype) { /// switch (rpc_gss3_assertion_type atype) {
/// case LABEL: /// case LABEL:
/// rpc_gss3_label label; /// rpc_gss3_label label;
/// case PRIVILEGES: /// case PRIVILEGES:
/// rpc_gss3_privs privs; /// rpc_gss3_privs privs;
/// case IDENTITY:
/// rpc_gss3_id id;
/// default: /// default:
/// opaque ext<>; /// opaque ext<>;
/// }; /// };
/// ///
/// struct rpc_gss3_assertion { /// struct rpc_gss3_assertion {
/// bool critical; /// bool critical;
/// rpc_gss3_assertion_u assertion; /// rpc_gss3_assertion_u assertion;
/// }; /// };
/// ///
/// struct rpc_gss3_create_args { /// struct rpc_gss3_create_args {
/// rpc_gss3_gss_binding *compound_binding; /// rpc_gss3_gss_binding *compound_binding;
skipping to change at page 9, line 24 skipping to change at page 9, line 10
/// rpc_gss3_gss_binding *compound_binding; /// rpc_gss3_gss_binding *compound_binding;
/// rpc_gss3_chan_binding *chan_binding_mic; /// rpc_gss3_chan_binding *chan_binding_mic;
/// rpc_gss3_assertion assertions<>; /// rpc_gss3_assertion assertions<>;
/// rpc_gss3_extension extensions<>; /// rpc_gss3_extension extensions<>;
/// }; /// };
/// ///
/// struct rpc_gss3_create_res { /// struct rpc_gss3_create_res {
/// opaque handle<>; /// opaque handle<>;
/// rpc_gss3_chan_binding *chan_binding_mic; /// rpc_gss3_chan_binding *chan_binding_mic;
/// rpc_gss3_assertion granted_assertions<>; /// rpc_gss3_assertion granted_assertions<>;
/// rpc_gss3_assertion assertions_denied<>; /// rpc_gss3_extension granted_extensions<>;
/// rpc_gss3_assertion assertions_not_understood<>;
/// rpc_gss3_assertion server_assertions<>;
/// rpc_gss3_extension extensions<>;
/// }; /// };
/// ///
/// enum rpc_gss3_list_item { /// enum rpc_gss3_list_item {
/// DOI = 0, /// LABEL = 0,
/// PRIV = 1, /// PRIV = 1,
/// PRIV_GROUP = 2
/// }; /// };
/// ///
/// struct rpc_gss3_list_args { /// struct rpc_gss3_list_args {
/// rpc_gss3_list_item list_what<>; /// rpc_gss3_list_item list_what<>;
/// }; /// };
/// ///
/// union rpc_gss3_list_item_u /// union rpc_gss3_list_item_u
/// switch (rpc_gss3_list_item itype) { /// switch (rpc_gss3_list_item itype) {
/// case DOI: /// case LABEL:
/// rpc_gss3_doi dois<>; /// rpc_gss3_lable labels<>;
/// case PRIV: /// case PRIV:
/// string privs<>; /// rpc_gss3_list_name privs<>;
/// case PRIV_GROUP:
/// string priv_groups<>;
/// default: /// default:
/// opaque ext<>; /// opaque ext<>;
/// }; /// };
/// ///
/// typedef rpc_gss3_list_item_u rpc_gss3_list_res<>; /// typedef rpc_gss3_list_item_u rpc_gss3_list_res<>;
2.1. New auth_stat values
RPCSEC_GSSv3 requires the 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 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 rpc_gss_cred_vers_1_t is used in RPCSEC_GSSv1, that is: as the arm of
the rpc_gss_cred_t discriminated union corresponding to version 3 the rpc_gss_cred_t discriminated union in the RPC message header
(RPCSEC_GSS_VERS_3). It differs from rpc_gss_cred_vers_1_t in that: 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 a. the values for gss_proc corresponding to control messages are
different, different.
b. the presence of a field indicating the version of RPCSEC_GSS used b. the handle field is the RPCSEC_GSSv3 (child) handle, except for
to established the context handle used, if any. the RPCSEC_GSS3_CREATE control message where it is set to the
parent context handle.
RPC data messages using RPCSEC_GSSv3 context handles differ from For all RPCSEC_GSSv3 data and control messages, the verifier field in
RPCSEC_GSSv1 only in that the version number used MUST be '3' instead the RPC message header is constructed in the RPCSEC_GSSv1 manner
of '1' and, as described above, in that there is one more field in using the parent GSS-API security context.
the RPCSEC_GSS header to name the version of RPCSEC_GSS used to
establish the context handle used to protect this message. All other
protocol elements from RPCSEC_GSSv1-protected RPC data messages MUST
remain the same in v3 as in v1.
RPCSEC_GSSv3 control messages are the same as RPCSEC_GSSv3 data 2.3. Control Messages
messages, but with a gss_proc value that indicates a control message
is contained in the data payload.
2.1. Control messages There are three RPCSEC_GSSv3 control messages: RPCSEC_GSS3_CREATE,
RPCSEC_GSS3_DESTROY, and RPCSEC_GSS3_LIST.
There are two RPCSEC_GSSv3 control messages: RPCSEC_GSS3_CREATE and RPCSEC_GSSv3 control messages are similar to the RPCSEC_GSSv1
RPCSEC_GSS3_LIST. RPCSEC_GSS_DESTROY control message (see section 5.4 [2]) in that the
sequence number in the request must be valid, and the header checksum
in the verifier must be valid. In other words, they look a lot like
an RPCSEC_GSSv3 data message with the header procedure set to
NULLPROC.
As in RPCSEC_GSSv1, the RPCSEC_GSSv3 control messages may contain
information following the verifier in the body of the NULLPROC
procedure.
The client MUST use one of the following security services to protect The client MUST use one of the following security services to protect
any RPCSEC_GSSv3 control message: any RPCSEC_GSSv3 control message:
o rpc_gss_svc_channel_prot (see RPCSEC_GSSv2) o rpc_gss_svc_channel_prot (see RPCSEC_GSSv2)
o rpc_gss_svc_integrity o rpc_gss_svc_integrity
o rpc_gss_svc_privacy o rpc_gss_svc_privacy
Specifically the client MUST NOT use rpc_gss_svc_none. Specifically the client MUST NOT use rpc_gss_svc_none.
2.1.1. New auth_stat values For RPCSEC_GSSv3 control messages the rpc_gss_cred_vers_3_t in the
RPC message opaque_auth structure is encoded as follows:
RPCSEC_GSSv3 requires the addition of several values to the auth_stat 1. the union rpc_gss_cred_t version is set to 3 with the value being
enumerated type definition: of type rpc_gss_cred_vers_3_t instead of rpc_gss_cred_vers_1_t.
enum auth_stat { 2. the gss_proc is set to one of RPCSEC_GSS3_CREATE,
... RPCSEC_GSS3_DESTROY, or RPCSEC_GSS3_LIST.
/*
* 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... 3. the seq_num is a valid sequence number for the context in the
--NW]] handle field.
2.1.2. Create request 4. the rpc_gss_service_t is one of rpc_gss_svc_integrity,
rpc_gss_svc_privacy, or rpc_gss_svc_channel_prot.
The RPCSEC_GSS3_CREATE call message consists of inputs to bind into a 5. the rpc_gss_cred_vers_3_t handle field is either set to the
new RPCSEC_GSSv3 handle. The context handle used to protect the parent context handle for RPCSEC_GSS3_CREATE, or to the GSS3
RPCSEC_GSS3_CREATE call message is termed the "parent" (or "outer") child handle for RPCSEC_GSS3_LIST and RPCSEC_GSS3_DESTROY.
handle. The reply to this message consists of either an error or a
new RPCSEC_GSSv3 handle, termed the "child" handle.
All uses of a child context handle MUST use the GSS-API security 2.3.1. Create request
context associated with the parent context handle of the
RPCSEC_GSS3_CREATE request that produced the child context handle.
The child context, however, has its own sequence number space and
window, distinct from that of the parent.
As described in the introduction, the RPCSEC_GSS3_CREATE call message As noted in the introduction, RPCSEC_GSSv3 relies on the RPCSEC_GSS
binds one or more items of several kinds into a new RPCSEC_GSSv3 version 1 parent context (though version 2 can be used) secure
context handle: connection to do the actual GSS-API GSS3 security context
establishment. As such, the rpc_gss_cred_vers_3_t fields in the RPC
Call opaque_auth use the parent context handle and seq_num stream.
o another RPCSEC_GSS (version 1, 2, or 3) context handle 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
authentication)
o a channel binding o a channel binding
o authorization assertions (label, privileges) o authorization assertions (labels, privileges)
o identity assertions o extensions (see Section 2.3.4 )
Servers MUST either ignore, reject or apply policy to the The reply to this message consists of either an error or an
authorization and identity assertions. Policies should take into rpc_gss3_create_res structure which includes a new RPCSEC_GSSv3
account the identity of the client and/or user as authenticated via handle, termed the "child" which is used for subsequent control and
the GSS-API. Server implementation and policy MAY result in labels, data messages.
privileges, and identities being mapped to concepts and values that
are local to the server.
2.1.2.1. Compound authentication 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.
2.3.1.1. Compound authentication
RPCSEC_GSSv3 allows for compound authentication of client hosts and RPCSEC_GSSv3 allows for compound authentication of client hosts and
users to servers. This is done by using an integrity protected users to servers. As in non-compound authentication, there is a
RPCSEC_GSSv3 message of RPCSEC_GSS3_CREATE type which includes a parent handle used to protect the RPCSEC_GSS3_CREATE call message,
reference to the context handle to bind, a nonce and a MIC of that and a resultant RPCSEC_GSSv3 child handle. In addition to the parent
nonce using the GSS-API security context associated with the named handle, the compound authentication create control message has a
context handle. We'll term the two context handles "parent" (or handle referenced via the compound_binding field of the
"outer") and "inner," and the resulting context handle the "child" RPCSEC_GSS3_CREATE arguments structure (rpc_gss3_create_args) termed
handle, where the outer context handle is the context handle the "inner" handle, as well as a nonce and a MIC of that nounce
providing integrity protection to the RPCSEC_GSS3_CREATE message, and created using the GSS-API security context associated with the
the inner context handle is the one referenced via the "inner" handle.
compound_binding field of the RPCSEC_GSS3_CREATE arguments structure
(rpc_gss3_create_args).
All uses of a child context handle that is bound to an inner context 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 MUST be treated as speaking for the initiator principal (as modified
by any assertions in the RPCSEC_GSS3_CREATE message) of the inner by any assertions in the RPCSEC_GSS3_CREATE message) of the inner
context handle's GSS-API security context. context handle's GSS-API security context.
This feature is needed, for example, when a client wishes to use 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 authority assertions that the server may only grant if a user and a
client are authenticated together to the server. Thus a server may client are authenticated together to the server. Thus a server may
refuse to grant requested authority to a user acting alone (e.g., via refuse to grant requested authority to a user acting alone (e.g., via
an unprivileged user-space program), but may grant requested an unprivileged user-space program), or to a client acting alone
authority to a client acting on behalf of a user if the server trusts (e.g. when a client is acting on behalf of a user) but may grant
the client. 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 It is assumed that an unprivileged user-space program would not have
access to client host credentials needed to establish a GSS-API access to client host credentials needed to establish a GSS-API
security context authenticating the client to the server, therefore security context authenticating the client to the server, therefore
an unprivileged user-space program could not create an RPCSEC_GSSv3 an unprivileged user-space program could not create an RPCSEC_GSSv3
RPCSEC_GSS3_CREATE message that successfully binds a client and a RPCSEC_GSS3_CREATE message that successfully binds a client and a
user security context. user security context.
Clients using RPCSEC_GSS context binding MUST use, as the outer Clients using RPCSEC_GSS context binding MUST use, as the parent
context handle, an RPCSEC_GSS context handle that corresponds to a context handle, an RPCSEC_GSS context handle that corresponds to a
GSS-API security context that authenticates the client host, and for GSS-API security context that authenticates the client host, and for
the inner context handle it SHOULD use a context handle to the inner context handle it SHOULD use a context handle to
authenticates a user. The reverse (outer handle authenticates user, authenticate a user. The reverse (parent handle authenticates user,
inner authenticates client) MUST NOT be used. Other compounds might inner authenticates client) MUST NOT be used. Other compounds might
eventually make sense. eventually make sense.
An RPCSEC_GSSv3 context handle that is bound to another RPCSEC_GSS An RPCSEC_GSSv3 context handle that is bound to another RPCSEC_GSS
context MUST be treated by servers as authenticating the GSS-API context MUST be treated by servers as authenticating the GSS-API
initiator principal authenticated by the inner context handle's GSS- initiator principal authenticated by the inner context handle's GSS-
API security context. This principal may be mapped to a server-side API security context. This principal may be mapped to a server-side
notion of user or principal as modified by any identity assertions by notion of user or principal as modified by any identity assertions by
the client in the same RPCSEC_GSS3_CREATE request that the server the client in the same RPCSEC_GSS3_CREATE request that the server
accepts. accepts.
2.1.2.2. Channel binding 2.3.1.2. Channel binding
RPCSEC_GSSv3 provides a different way to do channel binding than RPCSEC_GSSv3 provides a different way to do channel binding than
RPCSEC_GSSv2. Specifically: RPCSEC_GSSv2. Specifically:
a. RPCSEC_GSSv3 builds on RPCSEC_GSSv1 by reusing existing, a. RPCSEC_GSSv3 builds on RPCSEC_GSSv1 by reusing existing,
established context handles rather than providing a different RPC established context handles rather than providing a different RPC
security flavor for establishing context handles, security flavor for establishing context handles,
b. channel bindings data are not hashed because the community now b. channel bindings data are not hashed because the community now
agrees that it is the secure channel's responsibility to produce agrees that it is the secure channel's responsibility to produce
channel bindings data of manageable size. channel bindings data of manageable size.
(a) is useful in keeping RPCSEC_GSSv3 simple in general, not just for (a) is useful in keeping RPCSEC_GSSv3 simple in general, not just for
channel binding. (b) is useful in keeping RPCSEC_GSSv3 simple channel binding. (b) is useful in keeping RPCSEC_GSSv3 simple
specifically for channel binding. specifically for channel binding.
Channel binding is accomplished as follows. The client prefixes the Channel binding is accomplished as follows. The client prefixes the
channel bindings data octet string with the channel type as described 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 in [5], then the client calls GSS_GetMIC() to get a MIC of resulting
octet string, using the outer RPCSEC_GSS context handle's GSS-API octet string, using the parent RPCSEC_GSS context handle's GSS-API
security context. The MIC is then placed in the chan_binding_mic security context. The MIC is then placed in the chan_binding_mic
field of RPCSEC_GSS3_CREATE arguments (rpc_gss3_create_args). field of RPCSEC_GSS3_CREATE arguments (rpc_gss3_create_args).
If the chan_binding_mic field of the arguments of a If the chan_binding_mic field of the arguments of a
RPCSEC_GSS3_CREATE control message is set, then the server MUST RPCSEC_GSS3_CREATE control message is set, then the server MUST
verify the client's channel binding MIC if the server supports this verify the client's channel binding MIC if the server supports this
feature. If channel binding verification succeeds then the server feature. If channel binding verification succeeds then the server
MUST generate a new MIC of the same channel bindings and place it in 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 the chan_binding_mic field of the RPCSEC_GSS3_CREATE results. If
channel binding verification fails or the server doesn't support channel binding verification fails or the server doesn't support
skipping to change at page 14, line 5 skipping to change at page 14, line 12
server included it, by calling GSS_VerifyMIC() with the given MIC and server included it, by calling GSS_VerifyMIC() with the given MIC and
the channel bindings data (including the channel type prefix). If the channel bindings data (including the channel type prefix). If
client-side channel binding verification fails then the client MUST client-side channel binding verification fails then the client MUST
call RPCSEC_GSS3_DESTROY. If the client requested channel binding call RPCSEC_GSS3_DESTROY. If the client requested channel binding
but the server did not include a chan_binding_mic field in the but the server did not include a chan_binding_mic field in the
results, then the client MAY continue to use the resulting context results, then the client MAY continue to use the resulting context
handle as though channel binding had never been requested, otherwise handle as though channel binding had never been requested, otherwise
(if the client really wanted channel binding) it MUST call (if the client really wanted channel binding) it MUST call
RPCSEC_GSS3_DESTROY. RPCSEC_GSS3_DESTROY.
As per-RPCSEC_GSSv2: As per-RPCSEC_GSSv2 [4]:
o "Once a successful [channel binding] procedure has been performed "Once a successful [channel binding] procedure has been performed
on an [RPCSEC_GSSv3] context handle, the initiator's on an [RPCSEC_GSSv3] context handle, the initiator's
implementation may map application requests for rpc_gss_svc_none implementation may map application requests for rpc_gss_svc_none
and rpc_gss_svc_integrity to rpc_gss_svc_channel_prot credentials. and rpc_gss_svc_integrity to rpc_gss_svc_channel_prot credentials.
And if the secure channel has privacy enabled, requests for And if the secure channel has privacy enabled, requests for
rpc_gss_svc_privacy can also be mapped to rpc_gss_svc_privacy can also be mapped to
rpc_gss_svc_channel_prot." rpc_gss_svc_channel_prot."
o ...
[[Comment.3: ...? --TH]]
Any RPCSEC_GSSv3 context handle that has been bound to a secure Any RPCSEC_GSSv3 context handle that has been bound to a secure
channel in this way SHOULD be used only with the channel in this way SHOULD be used only with the
rpc_gss_svc_channel_prot, and SHOULD NOT be used with rpc_gss_svc_channel_prot, and SHOULD NOT be used with
rpc_gss_svc_none nor rpc_gss_svc_integrity -- if the secure channel rpc_gss_svc_none nor rpc_gss_svc_integrity -- if the secure channel
does not provide privacy protection then the client MAY use does not provide privacy protection then the client MAY use
rpc_gss_svc_privacy where privacy protection is needed or desired. rpc_gss_svc_privacy where privacy protection is needed or desired.
2.1.2.3. Label assertions 2.3.1.3. Label assertions
RPCSEC_GSSv3 clients MAY assert a security label in some DOI by RPCSEC_GSSv3 clients MAY assert a security label in some LSF by
binding this assertion into an RPCSEC_GSSv3 context handle. This is binding this assertion into an RPCSEC_GSSv3 context handle. This is
done by including an assertion of type rpc_gss3_label in the done by including an assertion of type rpc_gss3_label in the
'assertions' field (discriminant: 'LABEL') of the RPCSEC_GSS3_CREATE 'assertions' field (discriminant: 'LABEL') of the RPCSEC_GSS3_CREATE
arguments to the desired DOI and label. arguments to the desired LSF and label.
Label encoding is specific to each DOI and not described herein. DOI Label encoding is specified to mirror the NFSv4 sec_label attribute
encoding is TBD. [[Comment.4: [fill in... Solaris uses integers to described in Section 12.2.2 of [6]. The label format specifier (LFS)
name DOIs, and there is an IANA registry of DOIs as 32-bit integers, is an identifier used by the client to establish the syntactic format
and IPsec (whence the IANA registry) and CALIPSO use 32-bit integers of the security label and the semantic meaning of its components.
for DOIs as well. So a 32-bit unsinged integer seems to be the way The policy identifier (PI) is an optional part of the definition of
to go. Add references... -Nico] --NW]] [[Comment.5: This is just the an LFS which allows for clients and server to identify specific
LNFS format, so update it. --TH]] security policies. The opaque label field of rpc_gss3_label is
dependent on the MAC model to interpret and enforce.
[[Comment.5: Check that this Label definition provides all the
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 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 can assert that label is a secret) then the client MUST use the
rpc_gss_svc_privacy protection service for the RPCSEC_GSS3_CREATE rpc_gss_svc_privacy protection service for the RPCSEC_GSS3_CREATE
request or, if the parent handle is bound to a secure channel that request or, if the parent handle is bound to a secure channel that
provides privacy protection, rpc_gss_svc_channel_prot. provides privacy protection, rpc_gss_svc_channel_prot.
If a client wants to ensure that the server understands the asserted 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 label then it MUST set the 'critical' field of the label assertion to
TRUE, otherwise it MUST set it to FALSE. TRUE, otherwise it MUST set it to FALSE.
Servers that do not support labeling MUST ignore non-critical label Servers that do not support labeling MUST ignore non-critical label
assertions. Servers that do not support the requested DOI MUST assertions. Servers that do not support the requested LFS MUST
either ignore non-critical label assertions or map them to a suitable either ignore non-critical label assertions or map them to a suitable
label in a supported DOI. Servers that do not support labeling or do label in a supported LFS. Servers that do not support labeling or do
not support the requested DOI MUST return an error if the label not support the requested LFS MUST return an error if the label
request is critical. Servers that support labeling in the requested request is critical. Servers that support labeling in the requested
DOI MAY map the requested label to different label as a result of LFS MAY map the requested label to different label as a result of
server-side policy evaluation. server-side policy evaluation.
2.1.2.4. Privilege assertions 2.3.1.4. Structured privilege assertions
Privilege assertions are similar to label assertions, except that
there is no DOI, and the privileges supported are specified 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 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 to use this facility must define the set
of known privileges, and must specify which privileges are in the
"basic" privilege group. For example, NFSv4 might specify privileges
for reading, writing, chowning, linking, etc.
2.1.2.5. Identity assertions
Identity assertions can be used either to modify the set of groups
assigned on the server-side to a given user (authenticated by the
GSS-API) or to implement an AUTH_SYS-like [4]. In the latter case
the client specifies at least a user-name and possibly groups that it
thinks the user belongs to.
Clients may set a username, a group list, and/or lists of groups to
be added or removed from the group list that the server 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
understood"
o "accept identity assertions ... only from trusted clients" (where
the identity of 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 A structured privilege is an RPC application defined structure that
case the server MUST respond with an error if the server does not is opaque, and is encoded in the rpc_gss3_privs privilege field.
accept the identity assertion as-is. Encoding, server verification and any server policies for structured
privileges are described by the RPC application definition. The
listname field of rpc_gss3_privs is a description string used to list
the privilege.
The representation of users and groups is not given here, but is left A successful structured privilege assertion RPCSEC_GSS3_CREATE call
to the application. It is expected that RPCSEC_GSSv3 identity must return all accepted privileges in the rpc_gss3_privs
assertions in the context of the NFSv4 application would consist of granted_assertions field.
NFSv4 user and group representations as used on the wire in NFSv4
access control lists (ACLs).
2.1.2.6. Server assertions Section 3.4.1.2. "Inter-Server Copy with RPCSEC_GSSv3" of [6] shows
an example of structured privilege definition and use.
Servers MAY inform clients of assertions were granted by setting the 2.3.2. Destruction request
'granted_assertions' field of the RPCSEC_GSS3_CREATE reply.
The protocol provides a field ('server_assertions') for servers to The RPCSEC_GSS3_DESTROY control message is the same as the
make assertions about themselves. At this time there is not much use RPCSEC_GSSv1 RPCSEC_GSS_DESTROY control message, but with the version
for this field, though servers MAY assert a single security label, 3 header. Specifically, the rpc_gss_cred_vers_3_t fields in the RPC
indicating that all contents on the server is at that label. The Call opaque_auth use the GSS3 context handle and seq_num stream. As
client MUST, of course, either evaluate or ignore any server-side with all RPCSEC_GSSv3 messages, the header checksum uses the parent
assertions. context, and needs to be valid.
2.1.3. Context handle destruction The server sends a response as it would to a data request. The
client and server must then destroy the context for the session.
The RPCSEC_GSS3_DESTROY procedure is the same as for RPCSEC_GSSv1, 2.3.3. List request
but with the version 3 header.
2.1.4. List request The RPCSEC_GSS3_LIST control message is similar to
RPCSEC_GSS3_DESTROY message. Specifically, the rpc_gss_cred_vers_3_t
fields in the RPC Call opaque_auth use the GSS3 context handle and
seq_num stream. As with all RPCSEC_GSSv3 messages, the header
checksum uses the parent context, and needs to be valid.
The RPCSEC_GSS3_LIST call message consists of a single integer The RPCSEC_GSS3_LIST control message consists of a single integer
indicating what should be listed, and the reply consists of an error indicating what should be listed, and the reply consists of an error
or the requested list. or the requested list. The client may list LFSs or structured
privilege listnames.
The client may list DOIs, privilege names, or privilege group names.
The result is an opaque octet string containing a list of DOIs
[encoding TBD] or a US-ASCII string containing a comma-separated list
of privilege names or privilege group names.
2.1.5. Extensibility The result is an opaque octet string containing a list of LFSs
[encoding TBD] or a list of active structured privileges [encoding
TBD].
Assertion types may be added in the future by adding arms to the 2.3.4. Extensibility
'rpc_gss3_assertion_u' union. Every assertion has a 'critical' flag
that can be used to indicate criticality.
New fields may be added through the 'extensions' typed hole. All New fields may be added through the 'extensions' typed hole. All
such extensions have a 'critical' flag. such extensions have a 'critical' flag.
New message types may be added. [[Comment.6: Should we keep the extensions types hole? I think
not... --AA]]
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
in RPCSEC_GSSv3 SHALL be the same as the user and group
representations 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 Assertion types may be added in the future by adding arms to the
regardless of who owns the file. 'rpc_gss3_assertion_u' union. Every assertion has a 'critical' flag
that can be used to indicate criticality. Other assertion types are
described elsewhere and include:
file_chown_self Generally allows the caller to change the owner of a o Client-side assertions of identity:
file it owns.
file_dac_execute Generally allows the caller to read any file for * Primary client/user identity
execution.
file_dac_read Generally allows the caller to read any file or * Supplementary group memberships of the client/user, including
directory. support for specifying deltas to the membership list as seen on
the server.
file_dac_search Generally allows the caller to search any directory. New control message types may be added.
file_dac_write Generally allows the caller to write to any file (or Servers receiving unknown critical client assertions or unknown
create/delete/link objects in directories). RPCSEC_GSS_v3 extensions MUST return an error.
file_link_any Generally allows the caller to create hardlinks to There is no IANA or other registry for RPCSEC_GSSv3 extensions. All
files not owned by the caller. extensions MUST be done by IETF Protocol Action.
file_owner Generally allows the caller to modify the access, 2.4. Data Messages
modification and other timestamps of a filesystem object, as well
as its permissions and ACL.
file_setid Generally allows the caller to set the set-user-ID and RPCSEC_GSS3_DATA messages differ from from RPCSEC_GSSv1 data messages
set-group-ID bits of a file. in that the version number used MUST be '3' instead of '1'. As noted
in Section 2.2 the RPCSEC_GSSv3 context handle is used along with
it's sequence number stream.
file_downgrade_sl Generally allows the caller to downgrade the For RPCSEC_GSSv3 data messages the rpc_gss_cred_vers_3_t in the RPC
security label of a filesystem object. message opaque_auth structure is encoded as follows:
file_update_sl Generally allows the caller to upgrade the security 1. the union rpc_gss_cred_t version is set to 3 with the value being
label of a filesystem object. of type rpc_gss_cred_vers_3_t instead of rpc_gss_cred_vers_1_t.
[[Comment.6: [What about NFSv3? The representation of privs would be 2. the gss_proc is set to RPCSEC_GSS3_DATA
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 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 is derived from Solaris' notion of 3. the seq_num is a valid GSS3 context (child context) sequence
privileges. We should look at how well this scheme relates to other number.
operating systems as NFSv4 clients and servers. -Nico] --NW]]
[[Comment.9: On the radar. --TH]]
The contents of the 'basic' privilege set is not defined herein. 4. just as in RPCSEC_GSSv1, the rpc_gss_service_t is one of
Note that 'file_link_any' and 'file_chown_self' may be present in the rpc_gss_svc_none, rpc_gss_svc_integrity, rpc_gss_svc_privacy, or
server's notion of the basic privilege set. rpc_gss_svc_channel_prot.
The NFSv4-specific privileges may be limited by the server in ways 5. the handle field is set to the (child) RPCSEC_GSSv3 context
not specified above. For example, the server may deny access for handle
certain operations that would normally be granted given the granted
assertion of a given privilege (e.g., "no one may write to files
owned by such and such user"), or 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 to files owned by such and such user, not just
file_dac_write").
4. Security Considerations 3. Security Considerations
This entire document deals with security issues. This entire document deals with security issues.
The RPCSEC_GSSv3 protocol allows for client-side assertions of data The RPCSEC_GSSv3 protocol allows for client-side assertions of data
that is relevant to server-side authorization decisions. These that is relevant to server-side authorization decisions. These
assertions must be evaludated by the server in the context of whether assertions must be evaludated by the server in the context of whether
the client and/or user are authenticated, whether compound the client and/or user are authenticated, whether compound
authentication was used, whether the client is trusted, what ranges authentication was used, whether the client is trusted, what ranges
of assertions are allowed for the client and the user (separately or of assertions are allowed for the client and the user (separately or
together), and any relevant server-side policy. together), and any relevant server-side policy.
skipping to change at page 19, line 29 skipping to change at page 18, line 6
RPCSEC_GSSv3 supports a notion of critical assertions (and RPCSEC_GSSv3 supports a notion of critical assertions (and
extensions), but there's no need for peers to tell each other what extensions), but there's no need for peers to tell each other what
assertions were granted, or what they were mapped to. assertions were granted, or what they were mapped to.
Note that RPSEC_GSSv3 is not a complete solution for labeling: it Note that RPSEC_GSSv3 is not a complete solution for labeling: it
conveys the labels of actors, but not the labels of objects. RPC conveys the labels of actors, but not the labels of objects. RPC
application protocols may require extending in order to carry object application protocols may require extending in order to carry object
label information. 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 There may be interactions with NFSv4's callback security scheme and
NFSv4.1's GSS-API "SSV" mechanisms. Specifically, the NFSv4 callback NFSv4.1's GSS-API "SSV" mechanisms. Specifically, the NFSv4 callback
scheme requires that the server initiate GSS-API security contexts, scheme requires that the server initiate GSS-API security contexts,
which does not work well in practice, and in the context of client- which does not work well in practice, and in the context of client-
side processes running as the same user but with different privileges side processes running as the same user but with different privileges
and security labels the NFSv4 callback security scheme seems and security labels the NFSv4 callback security scheme seems
particularly unlikely to work well. NFSv4.1 has the server use an particularly unlikely to work well. NFSv4.1 has the server use an
existing, client-initiated RPCSEC_GSS context handle to protect existing, client-initiated RPCSEC_GSS context handle to protect
server-initiated callback RPCs. The NFSv4.1 callback security scheme server-initiated callback RPCs. The NFSv4.1 callback security scheme
lacks all the problems of the NFSv4 scheme, however, it is important lacks all the problems of the NFSv4 scheme, however, it is important
that the server pick an appropriate RPCSEC_GSS context handle to that the server pick an appropriate RPCSEC_GSS context handle to
protect any callbacks. Specifically, it is important that the server protect any callbacks. Specifically, it is important that the server
use RPCSEC_GSS context handles which authenticate the client to use RPCSEC_GSS context handles which authenticate the client to
protect any callbacks relating to server state initiated by RPCs protect any callbacks relating to server state initiated by RPCs
protected by RPCSEC_GSSv3 contexts. [[Comment.10: [Add text about protected by RPCSEC_GSSv3 contexts.
interaction with GSS-SSV...] --NW]]
5. IANA Considerations [[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
written.]]
[[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]. This section uses terms that are defined in [8].
There are no IANA considerations in this document. TBDs in this There are no IANA considerations in this document. TBDs in this
document will be assigned by the ONC RPC registrart (which is not document will be assigned by the ONC RPC registrar (which is not
IANA, XXX: verify). IANA, XXX: verify).
6. References 5. References
5.1. Normative References
6.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", March 1997. Levels", March 1997.
[2] Eisler, M., Chiu, A., and L. Ling, "RPCSEC_GSS Protocol [2] Eisler, M., Chiu, A., and L. Ling, "RPCSEC_GSS Protocol
Specification", RFC 2203, September 1997. Specification", RFC 2203, September 1997.
[3] Linn, J., "Generic Security Service Application Program [3] Linn, J., "Generic Security Service Application Program
Interface Version 2, Update 1", RFC 2743, January 2000. Interface Version 2, Update 1", RFC 2743, January 2000.
[4] Srinivasan, R., "RPC: Remote Procedure Call Protocol [4] Srinivasan, R., "RPC: Remote Procedure Call Protocol
Specification Version 2", RFC 1831, August 1995. Specification Version 2", RFC 1831, August 1995.
[5] Williams, N., "On the Use of Channel Bindings to Secure [5] Williams, N., "On the Use of Channel Bindings to Secure
Channels", RFC 5056, November 2007. Channels", RFC 5056, November 2007.
[6] Haynes, T., "NFS Version 4 Minor Version 2", [6] Haynes, T., "NFS Version 4 Minor Version 2",
draft-ietf-nfsv4-minorversion2-16 (Work In Progress), draft-ietf-nfsv4-minorversion2-19 (Work In Progress),
October 2012. March 2013.
[7] Eisler, M., "XDR: External Data Representation Standard", [7] Eisler, M., "XDR: External Data Representation Standard",
RFC 4506, May 2006. RFC 4506, May 2006.
[8] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA [8] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.
6.2. Informative References 5.2. Informative References
[9] "Section 46.6. Multi-Level Security (MLS) of Deployment Guide: [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 Deployment, configuration and administration of Red Hat
Enterprise Linux 5, Edition 6", 2011. Enterprise Linux 5, Edition 6", 2011.
[10] Smalley, S., "The Distributed Trusted Operating System (DTOS) [11] Smalley, S., "The Distributed Trusted Operating System (DTOS)
Home Page", Home Page",
<http://www.cs.utah.edu/flux/fluke/html/dtos/HTML/dtos.html>. <http://www.cs.utah.edu/flux/fluke/html/dtos/HTML/dtos.html>.
[11] Carter, J., "Implementing SELinux Support for NFS", [12] Carter, J., "Implementing SELinux Support for NFS",
<http://www.nsa.gov/research/_files/selinux/papers/nfsv3.pdf>. <http://www.nsa.gov/research/_files/selinux/papers/nfsv3.pdf>.
[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 [13] Quigley, D. and J. Lu, "Registry Specification for MAC Security
Label Formats", draft-quigley-label-format-registry (work in Label Formats", draft-quigley-label-format-registry (work in
progress), 2011. progress), 2011.
Appendix A. Acknowledgments Appendix A. Acknowledgments
Appendix B. RFC Editor Notes Appendix B. RFC Editor Notes
[RFC Editor: please remove this section prior to publishing this [RFC Editor: please remove this section prior to publishing this
document as an RFC] document as an RFC]
[RFC Editor: prior to publishing this document as an RFC, please [RFC Editor: prior to publishing this document as an RFC, please
replace all occurrences of RFCTBD10 with RFCxxxx where xxxx is the replace all occurrences of RFCTBD10 with RFCxxxx where xxxx is the
RFC number of this document] RFC number of this document]
Authors' Addresses Authors' Addresses
Thomas Haynes (editor) William A. (Andy) Adamson
NetApp NetApp
9110 E 66th St 3629 Wagner Ridge Ctt
Tulsa, OK 74133 Ann Arbor, MI 48103
USA USA
Phone: +1 918 307 1415 Phone: +1 734 665 1204
Email: thomas@netapp.com Email: andros@netapp.com
Nico Williams Nico Williams
cryptonector.com cryptonector.com
13115 Tamayo Dr 13115 Tamayo Dr
Austin, TX 78729 Austin, TX 78729
USA USA
Email: nico@cryptonector.com Email: nico@cryptonector.com
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