draft-ietf-nfsv4-rpcsec-gssv3-07.txt   draft-ietf-nfsv4-rpcsec-gssv3-08.txt 
NFSv4 W. Adamson NFSv4 W. Adamson
Internet-Draft NetApp Internet-Draft NetApp
Intended status: Standards Track N. Williams Intended status: Standards Track N. Williams
Expires: August 7, 2014 Cryptonector Expires: December 29, 2014 Cryptonector
February 03, 2014 June 27, 2014
Remote Procedure Call (RPC) Security Version 3 Remote Procedure Call (RPC) Security Version 3
draft-ietf-nfsv4-rpcsec-gssv3-07.txt draft-ietf-nfsv4-rpcsec-gssv3-08.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 multi-
authentication of client hosts and users to server (constructed by principal authentication of client hosts and user principals to
generic composition), security label assertions for multi-level and server (constructed by generic composition), security label
type enforcement, structured privilege assertions, and channel assertions for multi-level and type enforcement, structured privilege
bindings. assertions, and channel 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
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
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 August 7, 2014. This Internet-Draft will expire on December 29, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 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
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
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 and Motivation . . . . . . . . . . . . . . . . . 3 1. Introduction and Motivation . . . . . . . . . . . . . . . . . 3
2. The RPCSEC_GSSv3 Protocol . . . . . . . . . . . . . . . . . . 4 2. The RPCSEC_GSSv3 Protocol . . . . . . . . . . . . . . . . . . 4
2.1. Compatibility with RPCSEC_GSSv2 . . . . . . . . . . . . . 5 2.1. Compatibility with RPCSEC_GSSv2 . . . . . . . . . . . . . 5
2.2. New REPLY verifier . . . . . . . . . . . . . . . . . . . . 5 2.2. Version Negotiation . . . . . . . . . . . . . . . . . . . 5
2.3. New Version Number . . . . . . . . . . . . . . . . . . . . 5 2.3. New REPLY verifier . . . . . . . . . . . . . . . . . . . . 5
2.4. New Control Procedures . . . . . . . . . . . . . . . . . . 7 2.4. New Version Number . . . . . . . . . . . . . . . . . . . . 6
2.4.1. New Control Procedure - RPCSEC_GSS_CREATE . . . . . . 8 2.5. New auth_stat Values . . . . . . . . . . . . . . . . . . . 8
2.4.2. New Control Procedure - RPCSEC_GSS_LIST . . . . . . . 14 2.6. New Control Procedures . . . . . . . . . . . . . . . . . . 8
2.5. Extensibility . . . . . . . . . . . . . . . . . . . . . . 15 2.6.1. New Control Procedure - RPCSEC_GSS_CREATE . . . . . . 9
2.6. New auth_stat Values . . . . . . . . . . . . . . . . . . . 15 2.6.2. New Control Procedure - RPCSEC_GSS_LIST . . . . . . . 15
3. Version Negotiation . . . . . . . . . . . . . . . . . . . . . 16 2.7. Extensibility . . . . . . . . . . . . . . . . . . . . . . 16
4. Operational Recommendation for Deployment . . . . . . . . . . 16 3. Operational Recommendation for Deployment . . . . . . . . . . 17
5. Security Considerations . . . . . . . . . . . . . . . . . . . 16 4. Security Considerations . . . . . . . . . . . . . . . . . . . 17
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7.1. Normative References . . . . . . . . . . . . . . . . . . . 17 6.1. Normative References . . . . . . . . . . . . . . . . . . . 18
7.2. Informative References . . . . . . . . . . . . . . . . . . 18 6.2. Informative References . . . . . . . . . . . . . . . . . . 19
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 18 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 19
Appendix B. RFC Editor Notes . . . . . . . . . . . . . . . . . . 19 Appendix B. RFC Editor Notes . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction and Motivation 1. Introduction and Motivation
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 bindings [5]. version of RPCSEC_GSS [4] added support for channel bindings [5].
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Labeled NFS (see Section 8 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 to enable server guest mode or full mode objects owned by the server to enable server guest mode or full mode
labeled NFS. labeled NFS.
A traditional inter-server file copy entails the user gaining access 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 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 destination. In secure NFSv4 inter-server server-side copy (see
Section 3.4.1 of [6]), the user first secures access to both source Section 3.4.1 of [6]), the user first secures access to both source
and destination files, and then uses RPCSEC_GSSv3 compound and destination files, and then uses RPCSEC_GSSv3 multi-principal
authentication and structured privileges to authorize the destination authentication and structured privileges to authorize the destination
to copy the file from the source on behalf of the user. to copy the file from the source on behalf of the user.
We therefore describe RPCSEC_GSS version 3 (RPCSEC_GSSv3). We therefore describe RPCSEC_GSS version 3 (RPCSEC_GSSv3).
RPCSEC_GSSv3 is the same as RPCSEC_GSSv2 [4], except that the RPCSEC_GSSv3 is the same as RPCSEC_GSSv2 [4], except that the
following assertions of authority have been added. following assertions of authority have been added.
o Security labels for multi-level, type enforcement, and other o Security labels for multi-level, type enforcement, and other
labeled security models. See [9], [10], [11], [6] and [12]. labeled security models. See [9], [10], [11], [6] and [12].
o Application-specific structured privileges. For an example see o Application-specific structured privileges. For an example see
server-side copy [6]. server-side copy [6].
o Compound authentication of the client host and user to the server o Multi-principal authentication of the client host and user to the
done by binding two RPCSEC_GSS handles. For an example see server done by binding two RPCSEC_GSS handles. For an example see
server-side copy [6]. server-side copy [6].
o Simplified channel binding. o Simplified channel binding.
Assertions of labels and privileges are evaluated by the server, Assertions of labels and privileges are evaluated by the server,
which may then map the asserted values to other values, all according which may then map the asserted values to other values, all according
to server-side policy. to server-side policy.
We add an option for enumerating server supported label format We add an option for enumerating server supported label format
specifiers (LFS). The LFS and Label Format Registry are described in specifiers (LFS). The LFS and Label Format Registry are described in
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RPCSEC_GSSv3 is the same as RPCSEC_GSSv2 [4], except that support for RPCSEC_GSSv3 is the same as RPCSEC_GSSv2 [4], except that support for
assertions has been added. The entire RPCSEC_GSSv3 protocol is not assertions has been added. The entire RPCSEC_GSSv3 protocol is not
presented. Instead the differences between RPCSEC_GSSv3 and presented. Instead the differences between RPCSEC_GSSv3 and
RPCSEC_GSSv2 are shown. RPCSEC_GSSv2 are shown.
RPCSEC_GSSv3 is patterned as follows: RPCSEC_GSSv3 is patterned as follows:
o A client uses an existing RPCSEC_GSSv3 context handle to protect o A client uses an existing RPCSEC_GSSv3 context handle to protect
RPCSEC_GSSv3 exchanges, this will be termed the "parent" handle. RPCSEC_GSSv3 exchanges, this will be termed the "parent" handle.
[[Comment.1: CAN A CHILD handle be used as a parent? --AA]]
o The server issues a "child" RPCSEC_GSSv3 handle in the o The server issues a "child" RPCSEC_GSSv3 handle in the
RPCSEC_GSS_CREATE response which uses the underlying GSS-API RPCSEC_GSS_CREATE response which uses the underlying GSS-API
security context of the parent handle in all subsequent exchanges security context of the parent handle in all subsequent exchanges
that uses the child handle. that uses the child handle.
o An RPCSEC_GSSv3 child handle MUST NOT be used as the parent handle
in an RPCSEC_GSS3_CREATE control message.
2.1. Compatibility with RPCSEC_GSSv2 2.1. Compatibility with RPCSEC_GSSv2
The functionality of RPCSEC_GSSv2 [4] is fully supported by The functionality of RPCSEC_GSSv2 [4] is fully supported by
RPCSEC_GSSv3. RPCSEC_GSSv3.
2.2. New REPLY verifier 2.2. Version Negotiation
An initiator that supports version 3 of RPCSEC_GSS simply issues an
RPCSEC_GSS request with the rgc_version field set to
RPCSEC_GSS_VERS_3. If the target does not recognize
RPCSEC_GSS_VERS_3, the target will return an RPC error per Section
5.1 of [2].
The initiator MUST NOT attempt to use an RPCSEC_GSS handle returned
by version 3 of a target with version 1 or version 2 of the same
target. The initiator MUST NOT attempt to use an RPCSEC_GSS handle
returned by version 1 or version 2 of a target with version 3 of the
same target.
2.3. New REPLY verifier
The RPCSEC_GSSv3 child handle uses the same GSS context as the parent The RPCSEC_GSSv3 child handle uses the same GSS context as the parent
handle. Since a child and parent RPCSEC_GSSv3 handle could have the handle. Since a child and parent RPCSEC_GSSv3 handle could have the
same RPCSEC_GSS sequence numbers, and the verifier of RPCSEC_GSS same RPCSEC_GSS sequence numbers, and the verifier of RPCSEC_GSS
replies computes a MIC on just the sequence number, this provides replies computes a MIC on just the sequence number, this provides
opportunities for man in the middle attacks. opportunities for man in the middle attacks.
This is easily addressed: RPCSEC_GSS version 3 MUST change the This is easily addressed: RPCSEC_GSS version 3 MUST change the
verifier of the reply to compute the verifier using the exact same verifier of the reply to compute the verifier using the exact same
input as that is used for verifier of the request, except for the input as that is used for verifier of the request, except for the
mtype change from CALL to REPLY: mtype change from CALL to REPLY. The new reply verifier computes a
MIC over the following data:
unsigned int xid; unsigned int xid;
msg_type mtype; /* set to REPLY */ msg_type mtype; /* set to REPLY */
unsigned int rpcvers; unsigned int rpcvers;
unsigned int prog; unsigned int prog;
unsigned int vers; unsigned int vers;
unsigned int proc; unsigned int proc;
opaque_auth cred; /* captures the RPCSEC_GSS handle */ opaque_auth cred; /* captures the RPCSEC_GSS handle */
2.3. New Version Number 2.4. New Version Number
<CODE BEGINS> <CODE BEGINS>
/// /* /// /*
/// * Copyright (c) 2013 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].
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/// }; /// };
/// ///
<CODE ENDS> <CODE ENDS>
As seen above, the RPCSEC_GSSv3 credential has the same format as the As seen above, the RPCSEC_GSSv3 credential has the same format as the
RPCSEC_GSSv1 [2] and RPCSEC_GSSv2 [4] credential. Setting the RPCSEC_GSSv1 [2] and RPCSEC_GSSv2 [4] credential. Setting the
rgc_version field to 3 indicates that the initiator and target rgc_version field to 3 indicates that the initiator and target
support the new RPCSEC_GSSv3 control procedures. support the new RPCSEC_GSSv3 control procedures.
2.4. New Control Procedures 2.5. New auth_stat Values
RPCSEC_GSSv3 requires the addition of several values to the auth_stat
enumerated type definition. The use of each of these new auth_stat
values is explained later in this document.
enum auth_stat {
...
/*
* RPCSEC_GSSv3 errors
*/
RPCSEC_GSS_INNER_CREDPROBLEM = 15,
RPCSEC_GSS_LABEL_PROBLEM = 16,
RPCSEC_GSS_PRIVILEGE_PROBLEM = 17,
RPCSEC_GSS_UNKNOWN_MESSAGE = 18
};
2.6. New Control Procedures
There are two new RPCSEC_GSSv3 control procedures: RPCSEC_GSS_CREATE, There are two new RPCSEC_GSSv3 control procedures: RPCSEC_GSS_CREATE,
RPCSEC_GSS_LIST. RPCSEC_GSS_LIST.
The RPCSEC_GSS_CREATE procedure binds any combination of assertions: The RPCSEC_GSS_CREATE procedure binds any combination of assertions:
compound authentication, labels, structured privileges, or channel multi-principal authentication, labels, structured privileges, or
bindings to a new RPCSEC_GSSv3 context returned in the channel bindings to a new RPCSEC_GSSv3 context returned in the
rgss3_create_res rcr_handle field. rgss3_create_res rcr_handle field.
The RPCSEC_GSS_LIST procedure queries the target for supported The RPCSEC_GSS_LIST procedure queries the target for supported
assertions. assertions.
RPCSEC_GSS version 3 control messages are similar to the RPCSEC_GSS RPCSEC_GSS version 3 control messages are similar to the RPCSEC_GSS
version 1 and version2 RPCSEC_GSS_DESTROY control message (see version 1 and version2 RPCSEC_GSS_DESTROY control message (see
section 5.4 [2]) in that the sequence number in the request must be 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. As in valid, and the header checksum in the verifier must be valid. As in
RPCSEC_GSS version 1 and version 2, the RPCSEC_GSSv version 3 control RPCSEC_GSS version 1 and version 2, the RPCSEC_GSSv version 3 control
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RPCSEC_GSS data message with the header procedure set to NULLPROC. RPCSEC_GSS data message with the header procedure set to NULLPROC.
The client MUST use one of the following security services to protect The client MUST use one of the following security services to protect
the RPCSEC_GSS_CREATE or RPCSEC_GSS_LIST control message: the RPCSEC_GSS_CREATE or RPCSEC_GSS_LIST control message:
o rpc_gss_svc_channel_prot (see RPCSEC_GSSv2 [4]) o rpc_gss_svc_channel_prot (see RPCSEC_GSSv2 [4])
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.
2.4.1. New Control Procedure - RPCSEC_GSS_CREATE 2.6.1. New Control Procedure - RPCSEC_GSS_CREATE
<CODE BEGINS> <CODE BEGINS>
/// struct rgss3_create_args { /// struct rgss3_create_args {
/// rgss3_gss_binding *rca_comp_auth; /// rgss3_gss_mp_auth *rca_mp_auth;
/// rgss3_chan_binding *rca_chan_bind_mic; /// rgss3_chan_binding *rca_chan_bind_mic;
/// rgss3_assertion rca_assertions<>; /// rgss3_assertion rca_assertions<>;
/// }; /// };
/// ///
/// struct rgss3_create_res { /// struct rgss3_create_res {
/// opaque rcr_handle<>; /// opaque rcr_handle<>;
/// rgss3_gss_binding *rcr_comp_auth; /// rgss3_gss_mp_auth *rcr_mp_auth;
/// rgss3_chan_binding *rcr_chan_bind_mic; /// rgss3_chan_binding *rcr_chan_bind_mic;
/// rgss3_assertion rcr_assertions<>; /// rgss3_assertion rcr_assertions<>;
/// }; /// };
/// ///
/// enum rgss3_assertion_type { /// enum rgss3_assertion_type {
/// LABEL = 0, /// LABEL = 0,
/// PRIVS = 1 /// PRIVS = 1
/// }; /// };
/// ///
/// union rgss3_assertion_u /// union rgss3_assertion_u
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/// }; /// };
/// ///
<CODE ENDS> <CODE ENDS>
The call data for an RPCSEC_GSS_CREATE request consists of an The call data for an RPCSEC_GSS_CREATE request consists of an
rgss3_create_args which binds one or more items of several kinds to rgss3_create_args which binds one or more items of several kinds to
the returned rcr_handle RPCSEC_GSSv3 context handle called the the returned rcr_handle RPCSEC_GSSv3 context handle called the
"child" handle: "child" handle:
o Compound authentication: another RPCSEC_GSS context handle o Multi-principal authentication: another RPCSEC_GSS context handle
o Authorization assertions: labels and or privileges o Authorization assertions: labels and or privileges
o A channel binding o A channel binding
The reply to this message consists of either an error or an The reply to this message consists of either an error or an
rgss3_create_res structure. rgss3_create_res structure.
Upon successful RPCSEC_GSS_CREATE, both the client and the server Upon successful RPCSEC_GSS_CREATE, both the client and the server
SHOULD associate the resultant child rcr_handle context handle with SHOULD associate the resultant child rcr_handle context handle with
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able to reference the parent context given the child context handle. able to reference the parent context given the child context handle.
RPCSEC_GSSv3 child handles MUST be destroyed upon the destruction of RPCSEC_GSSv3 child handles MUST be destroyed upon the destruction of
the associated parent handle. the associated parent handle.
Server implementation and policy MAY result in labels, privileges, Server implementation and policy MAY result in labels, privileges,
and identities being mapped to concepts and values that are local to and identities being mapped to concepts and values that are local to
the server. Server policies should take into account the identity of the server. Server policies should take into account the identity of
the client and/or user as authenticated via the GSS-API. the client and/or user as authenticated via the GSS-API.
2.4.1.1. Compound Authentication 2.6.1.1. Multi-principal Authentication
<CODE BEGINS> <CODE BEGINS>
/// ///
/// struct rgss3_gss_binding { /// struct rgss3_gss_mp_auth {
/// opaque rgb_handle<>; /* inner handle */ /// opaque rgmp_handle<>; /* inner handle */
/// opaque rgb_nonce<>; /// opaque rgmp_nonce<>;
/// opaque rgb_nounc_mic<>; /// opaque rgmp_nounc_mic<>;
/// }; /// };
/// ///
<CODE ENDS> <CODE ENDS>
RPCSEC_GSSv3 clients MAY assert a compound authentication of the RPCSEC_GSSv3 clients MAY assert a multi-principal authentication of
client host and a user. This is done by including an assertion of the client host principal and a user principal. This feature is
type rgss3_gss_binding in the RPCSEC_GSS_CREATE rgss3_create_args needed, for example, when a client wishes to use authority assertions
call data. In addition to the parent handle (Section 2), the that the server may only grant if a user and a client are
compound authentication rgss3_gss_binding call data has an RPCSEC_GSS authenticated together to the server. Thus a server may refuse to
version 3 handle referenced via the rgb_handle field termed the grant requested authority to a user acting alone (e.g., via an
"inner" handle. A nonce and a MIC of that nounce created using the unprivileged user-space program), or to a client acting alone (e.g.
GSS-API security context associated with the inner handle is also when a client is acting on behalf of a user) but may grant requested
provided. authority to a client acting on behalf of a user if the server
identifies the user and trusts the client.
The target verifies the compounding by verifying the rgb_nouce_mic.
On a successful reply, the rgss3_gss_binding field in the
rgss3_create_res reply uses the parent RPCSEC_GSSv3 context as the
rgb_handle, the same rgb_nounce as was sent in the call data with the
rgb_nounce_mic created using the GSS-API security context associate
with the parent handle. Verification of the rbg_nounce_mic by the
initiator demonstrates that the target agrees to the compounding. On
failure, the rgss3_gss_binding field is not sent. (rgss3_gss_binding
is an optional field)
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 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_GSS_CREATE message that successfully binds a client and a user RPCSEC_GSS_CREATE message that successfully binds a client and a user
security context. security context.
Clients using RPCSEC_GSSv3 compound authentication MUST use an In addition to the parent handle (Section 2), the multi-principal
authentication call data has an RPCSEC_GSS version 3 handle
referenced via the rgmp_handle field termed the "inner" handle.
Clients using RPCSEC_GSSv3 multi-principal authentication MUST use an
RPCSEC_GSSv3 context handle that corresponds to a GSS-API security RPCSEC_GSSv3 context handle that corresponds to a GSS-API security
context that authenticates the client host for the outer handle. The context that authenticates the client host for the parent handle.
inner context handle it SHOULD use a context handle to authenticate a The inner context handle it SHOULD use a context handle to
user. The reverse (outer handle authenticates user, inner authenticate a user. The reverse (parent handle authenticates user,
authenticates client) MUST NOT be used. Other compounds might inner authenticates client) MUST NOT be used. Other multi-principal
eventually make sense. parent and inner context handle uses might eventually make sense.
An inner RPCSEC_GSSv3 context handle that is bound to an outer An inner RPCSEC_GSSv3 context handle that is bound to a parent
RPCSEC_GSS context MUST be treated by servers as authenticating the RPCSEC_GSS context through multi-principal authentication MUST be
GSS-API initiator principal authenticated by the inner context treated by servers as authenticating the GSS-API initiator principal
handle's GSS- API security context. This principal may be mapped to authenticated by the inner context handle's GSS-API security context.
a server-side notion of user or principal. This principal may be mapped to a server-side notion of user or
principal.
2.4.1.2. Label Assertions Multi-principal binding is done by including an assertion of type
rgss3_gss_mp_auth in the RPCSEC_GSS_CREATE rgss3_create_args call
data. The inner context handle is place in the rbmp_handle field. A
nonce and a MIC of that nounce created using the GSS-API security
context associated with the inner handle is also provided.
The target verifies the multi-principal authentication by verifying
the rgmp_nouce_mic. On a successful reply, the rgss3_gss_mp_auth
field in the rgss3_create_res reply uses the parent RPCSEC_GSSv3
context as the rgmp_handle, the same rgmp_nounce as was sent in the
call data with the rgmp_nounce_mic created using the GSS-API security
context associate with the parent handle. Verification of the
rbg_nounce_mic by the initiator demonstrates that the target agrees
to the multi-principal authentication.
On failure, the rgss3_gss_mp_auth field is not sent
(rgss3_gss_mp_auth is an optional field). A MSG_DENIED reply to an
RPCSEC_GSS_CREATE formulated as usual. A new value,
RPCSEC_GSS_INNER_CREDPROBLEM, has been added to the auth_stat type.
As described in Section 5.3.3.3 of [2] the server maintains a list of
contexts for the clients that are currently in session with it. When
a client request comes in, there may not be a context corresponding
to its handle. When this occurs on an RPCSEC_GSS3_CREATE request
processing of the parent handle, the server rejects the request with
a reply status of MSG_DENIED with the reject_stat of AUTH_ERROR and
with an auth_stat value of RPCSEC_GSS_CREDPROBLEM.
With a multi-pricipal authorization request, the server must also
have a context corresponding to the inner context handle. When the
server does not have a context handle corresponding to the inner
context handle of a multi-pricipal authorization request, the server
send a reply status of MSG_DENIED with the reject_stat of AUTH_ERROR
and with an auth_stat value of RPCSEC_GSS_INNER_CREDPROBLEM.
When processing the multi-principal authentication request, if the
GSS_VerifyMIC() call on the inner handle nouce fails to return
GSS_S_COMPLETE, the server sends a reply status of MSG_DENIED with
the reject_stat of AUTH_ERROR and with an auth_stat value of
RPCSEC_GSS_INNER_CREDPROBLEM.
2.6.1.2. Label Assertions
<CODE BEGINS> <CODE BEGINS>
/// struct rgss3_label { /// struct rgss3_label {
/// rgss3_lfs rl_lfs; /// rgss3_lfs rl_lfs;
/// opaque rl_label<>; /// opaque rl_label<>;
/// }; /// };
/// ///
/// struct rgss3_lfs { /// struct rgss3_lfs {
/// unsigned int rlf_lfs_id; /// unsigned int rlf_lfs_id;
skipping to change at page 11, line 48 skipping to change at page 13, line 15
The policy identifier (PI) is an optional part of the definition of The policy identifier (PI) is an optional part of the definition of
an LFS which allows for clients and server to identify specific an LFS which allows for clients and server to identify specific
security policies. The opaque label field of rgss3_label is security policies. The opaque label field of rgss3_label is
dependent on the MAC model to interpret and enforce. dependent on the MAC model to interpret and enforce.
Asserting a server supported label via RPCSEC_GSS_CREATE enables Asserting a server supported label via RPCSEC_GSS_CREATE enables
server guest mode labels. Full mode is enabled when an server guest mode labels. Full mode is enabled when an
RPCSEC_GSS_CREATE label assertion is combined with asserting the same RPCSEC_GSS_CREATE label assertion is combined with asserting the same
label with the NFSv4.2 sec_label attribute. label with the NFSv4.2 sec_label attribute.
[[Comment.2: Check that this Label discussion 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_GSS_CREATE rpc_gss_svc_privacy protection service for the RPCSEC_GSS_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 LFS 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 LFS. 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 LFS 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
LFS 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.
2.4.1.3. Structured Privilege Assertions 2.6.1.3. Structured Privilege Assertions
<CODE BEGINS> <CODE BEGINS>
/// ///
/// struct rgss3_privs { /// struct rgss3_privs {
/// string rp_name<>; /* human readable */ /// string rp_name<>; /* human readable */
/// opaque rp_privilege<>; /// opaque rp_privilege<>;
/// }; /// };
<CODE ENDS> <CODE ENDS>
skipping to change at page 12, line 46 skipping to change at page 14, line 9
RPCSEC_GSSv3 clients MAY assert a structured privilege by binding the RPCSEC_GSSv3 clients MAY assert a structured privilege by binding the
privilege to the RPCSEC_GSSv3 context handle. This is done by privilege to the RPCSEC_GSSv3 context handle. This is done by
including an assertion of type rgss3_privs in the RPCSEC_GSS_CREATE including an assertion of type rgss3_privs in the RPCSEC_GSS_CREATE
rgss3_create_args rca_assertions call data. Encoding, server rgss3_create_args rca_assertions call data. Encoding, server
verification and any policies for structured privileges are described verification and any policies for structured privileges are described
by the RPC application definition. by the RPC application definition.
A successful structured privilege assertion will be enumerated in the A successful structured privilege assertion will be enumerated in the
rcr_assertions field of the rgss3_create_res RPCSEC_GSS_CREATE reply. rcr_assertions field of the rgss3_create_res RPCSEC_GSS_CREATE reply.
If a server receives a structured privilege assertion that it does
not recognize the assertion is rejected with MSG_DENIED, a
reject_status of AUTH_ERROR, and an auth_stat of
RPCSEC_GSS_UNKNOWN_MESSAGE. If the server fails the RPC application
defined server verification for a structured privilege, the assertion
is rejected with MSG_DENIED, a reject_status of AUTH_ERROR, and an
auth_stat of RPCSEC_GSS_PRIVILEGE_PROBLEM.
Section 3.4.1.2. "Inter-Server Copy with RPCSEC_GSSv3" of [6] shows Section 3.4.1.2. "Inter-Server Copy with RPCSEC_GSSv3" of [6] shows
an example of structured privilege definition and use. an example of structured privilege definition and use.
2.4.1.4. Channel Binding 2.6.1.4. Channel Binding
<CODE BEGINS> <CODE BEGINS>
/// ///
/// typedef opaque rgss3_chan_binding<>; /// typedef opaque rgss3_chan_binding<>;
/// ///
<CODE ENDS> <CODE ENDS>
RPCSEC_GSSv3 provides a different way to do channel binding than RPCSEC_GSSv3 provides a different way to do channel binding than
skipping to change at page 14, line 27 skipping to change at page 15, line 44
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."
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.
2.4.2. New Control Procedure - RPCSEC_GSS_LIST 2.6.2. New Control Procedure - RPCSEC_GSS_LIST
<CODE BEGINS> <CODE BEGINS>
/// enum rgss3_list_item { /// enum rgss3_list_item {
/// LABEL = 0, /// LABEL = 0,
/// PRIVS = 1 /// PRIVS = 1
/// }; /// };
/// ///
/// struct rgss3_list_args { /// struct rgss3_list_args {
/// rgss3_list_item rla_list_what<>; /// rgss3_list_item rla_list_what<>;
/// }; /// };
/// ///
/// union rgss3_list_item_u /// union rgss3_list_item_u
skipping to change at page 15, line 11 skipping to change at page 16, line 32
/// ///
/// typedef rgss3_list_item_u rgss3_list_res<>; /// typedef rgss3_list_item_u rgss3_list_res<>;
/// ///
<CODE ENDS> <CODE ENDS>
The call data for an RPCSEC_GSS_LIST request consists of a list of The call data for an RPCSEC_GSS_LIST request consists of a list of
integers (rla_list_what<>) indicating what assertions to be listed, integers (rla_list_what<>) indicating what assertions to be listed,
and the reply consists of an error or the requested list. and the reply consists of an error or the requested list.
[[Comment.3: What good is the rli_ext field? How should we describe [[Comment.1: What good is the rli_ext field? How should we describe
it's use? --AA]] it's use? --AA]]
The result of requesting a list of rgss3_list_item LABEL is a list of The result of requesting a list of rgss3_list_item LABEL is a list of
LFSs supported by the server. The client can then use the LFS list LFSs supported by the server. The client can then use the LFS list
to assert labels via the RPCSEC_GSS_CREATE label assertions. See to assert labels via the RPCSEC_GSS_CREATE label assertions. See
Section 2.4.1.2. Section 2.6.1.2.
2.5. Extensibility 2.7. Extensibility
Assertion types may be added in the future by adding arms to the Assertion types may be added in the future by adding arms to the
'rgss3_assertion_u' union. Every assertion has a 'critical' flag 'rgss3_assertion_u' union. Every assertion has a 'critical' flag
that can be used to indicate criticality. Other assertion types are that can be used to indicate criticality. Other assertion types are
described elsewhere and include: described elsewhere and include:
o Client-side assertions of identity: o Client-side assertions of identity:
* Primary client/user identity * Primary client/user identity
* Supplementary group memberships of the client/user, including * Supplementary group memberships of the client/user, including
support for specifying deltas to the membership list as seen on support for specifying deltas to the membership list as seen on
the server. the server.
New control message types may be added. New control message types may be added.
Servers receiving unknown critical client assertions MUST return an Servers receiving unknown critical client assertions MUST return an
error. error.
2.6. New auth_stat Values 3. Operational Recommendation for Deployment
RPCSEC_GSSv3 requires the addition of several values to the auth_stat
enumerated type definition:
enum auth_stat {
...
/*
* RPCSEC_GSSv3 errors
*/
RPCSEC_GSS_COMPOUND_PROBLEM = <>,
RPCSEC_GSS_LABEL_PROBLEM = <>,
RPCSEC_GSS_UNKNOWN_PRIVILEGE = <>
RPCSEC_GSS_UNKNOWN_MESSAGE = <>
};
[[Comment.4: fix above into YYY. All the entries are TBD... --NW]]
[[Comment.5: The compound authentication problems are: can't find the
handle plus handle version on the target, or the MIC of the nounce
does not match. Both of these errors already have auth_stat entries:
RPCSEC_GSS_CREDPROBLEM for the first and "reply status of
MSG_ACCEPTED, and an acceptance status of GARBAGE_ARGS." --AA]]
3. Version Negotiation
An initiator that supports version 3 of RPCSEC_GSS simply issues an
RPCSEC_GSS request with the rgc_version field set to
RPCSEC_GSS_VERS_3. If the target does not recognize
RPCSEC_GSS_VERS_3, the target will return an RPC error per Section
5.1 of [2].
The initiator MUST NOT attempt to use an RPCSEC_GSS handle returned
by version 3 of a target with version 1 or version 2 of the same
target. The initiator MUST NOT attempt to use an RPCSEC_GSS handle
returned by version 1 or version 2 of a target with version 3 of the
same target.
4. Operational Recommendation for Deployment
RPCSEC_GSSv3 is a superset of RPCSEC_GSSv2 [4] which in turn is a RPCSEC_GSSv3 is a superset of RPCSEC_GSSv2 [4] which in turn is a
superset of RPCSEC_GSSv1 [2], and so can be used in all situations superset of RPCSEC_GSSv1 [2], and so can be used in all situations
where RPCSEC_GSSv1 or RPCSEC_GSSv2 is used. RPCSEC_GSSv3 should be where RPCSEC_GSSv1 or RPCSEC_GSSv2 is used. RPCSEC_GSSv3 should be
used when the new functionality is needed. used when the new functionality is needed.
5. Security Considerations 4. 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 multi-principal
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.
The security semantics of assertions carried by RPCSEC_GSSv3 are The security semantics of assertions carried by RPCSEC_GSSv3 are
application protocol-specific. application protocol-specific.
RPCSEC_GSSv3 supports a notion of critical assertions but there's no RPCSEC_GSSv3 supports a notion of critical assertions but there's no
need for peers to tell each other what assertions were granted, or need for peers to tell each other what assertions were granted, or
what they were mapped to. what they were mapped to.
skipping to change at page 17, line 30 skipping to change at page 18, line 14
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. protected by RPCSEC_GSSv3 contexts.
[[Comment.6: [Add text about interaction with GSS-SSV...] --NW]] [[Comment.2: [Add text about interaction with GSS-SSV...] --NW]]
[[Comment.7: AFAICS the reason to use SSV is to avoid using a client [[Comment.3: AFAICS the reason to use SSV is to avoid using a client
machine credential which means compound authentication can not be machine credential which means multi-principal authentication can not
used. --AA]] be used. --AA]]
6. IANA Considerations 5. 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 registrar (which is not document will be assigned by the ONC RPC registrar (which is not
IANA, XXX: verify). IANA, XXX: verify).
7. References 6. References
7.1. 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", RFC 2119, March 1997. Levels", RFC 2119, 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] Eisler, M., "RPCSEC_GSS Version 2", RFC 5403, February 2009. [4] Eisler, M., "RPCSEC_GSS Version 2", RFC 5403, February 2009.
[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-minorversion2-21 (Work In Progress), draft-ietf-nfsv4-minorversion2-27 (Work In Progress),
March 2013. June 2014.
[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.
7.2. Informative References 6.2. Informative References
[9] "Section 46.6. Multi-Level Security (MLS) of Deployment Guide: [9] "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) [10] 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", [11] 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", [12] Haynes, T., "Requirements for Labeled NFS",
draft-ietf-nfsv4-labreqs-05 (work in progress). draft-ietf-nfsv4-labreqs-05 (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
Andy Adamson would like to thank NetApp, Inc. for its funding of his
time on this project.
Lars Eggert and Mike Eisler for their most helpful reviews.
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
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