draft-ietf-nfsv4-rpcsec-gssv3-09.txt   draft-ietf-nfsv4-rpcsec-gssv3-10.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: May 22, 2015 Cryptonector Expires: June 11, 2015 Cryptonector
November 18, 2014 December 08, 2014
Remote Procedure Call (RPC) Security Version 3 Remote Procedure Call (RPC) Security Version 3
draft-ietf-nfsv4-rpcsec-gssv3-09.txt draft-ietf-nfsv4-rpcsec-gssv3-10
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 multi- security protocol (RPCSEC_GSS). This protocol provides for multi-
principal authentication of client hosts and user principals to principal authentication of client hosts and user principals to
server (constructed by generic composition), security label server (constructed by generic composition), security label
assertions for multi-level and type enforcement, structured privilege assertions for multi-level and type enforcement, structured privilege
assertions, and channel bindings. assertions, and channel bindings.
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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-
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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 May 22, 2015. This Internet-Draft will expire on June 11, 2015.
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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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 . . . . . . . . . . . . . . . . . 2 1. Introduction and Motivation . . . . . . . . . . . . . . . . . 2
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. Version Negotiation . . . . . . . . . . . . . . . . . . . 5 2.2. Version Negotiation . . . . . . . . . . . . . . . . . . . 5
2.3. New REPLY verifier . . . . . . . . . . . . . . . . . . . 5 2.3. New REPLY Verifier . . . . . . . . . . . . . . . . . . . 5
2.4. New Version Number . . . . . . . . . . . . . . . . . . . 6 2.4. New Version Number . . . . . . . . . . . . . . . . . . . 6
2.5. RPCSEC_GSS_BIND_CHANNEL Operation Deprecated . . . . . . 8 2.5. RPCSEC_GSS_BIND_CHANNEL Operation Deprecated . . . . . . 8
2.6. New auth_stat Values . . . . . . . . . . . . . . . . . . 8 2.6. New auth_stat Values . . . . . . . . . . . . . . . . . . 8
2.7. New Control Procedures . . . . . . . . . . . . . . . . . 8 2.7. New Control Procedures . . . . . . . . . . . . . . . . . 8
2.7.1. New Control Procedure - RPCSEC_GSS_CREATE . . . . . . 9 2.7.1. New Control Procedure - RPCSEC_GSS_CREATE . . . . . . 9
2.7.2. New Control Procedure - RPCSEC_GSS_LIST . . . . . . . 16 2.7.2. New Control Procedure - RPCSEC_GSS_LIST . . . . . . . 16
2.8. Extensibility . . . . . . . . . . . . . . . . . . . . . . 16 2.8. Extensibility . . . . . . . . . . . . . . . . . . . . . . 17
3. Operational Recommendation for Deployment . . . . . . . . . . 17 3. Operational Recommendation for Deployment . . . . . . . . . . 18
4. Security Considerations . . . . . . . . . . . . . . . . . . . 17 4. Security Considerations . . . . . . . . . . . . . . . . . . . 18
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.1. Normative References . . . . . . . . . . . . . . . . . . 18 6.1. Normative References . . . . . . . . . . . . . . . . . . 19
6.2. Informative References . . . . . . . . . . . . . . . . . 18 6.2. Informative References . . . . . . . . . . . . . . . . . 19
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 19 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 20
Appendix B. RFC Editor Notes . . . . . . . . . . . . . . . . . . 19 Appendix B. RFC Editor Notes . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
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 [8] added support for channel bindings [6]. version of RPCSEC_GSS [8] added support for channel bindings [6].
We find that GSS-API mechanisms are insufficient for communicating We find that GSS-API mechanisms are insufficient for communicating
certain aspects of authority to a server. The GSS-API and its certain aspects of authority to a server. The GSS-API and its
mechanisms certainly could be extended to address this shortcoming, mechanisms certainly could be extended to address this shortcoming,
but it seems be far simpler to address it at the application layer, but it seems be far simpler to address it at the application layer,
namely, in this case, RPCSEC_GSS. namely, in this case, RPCSEC_GSS.
A major motivation for RPCSEC_GSSv3 is to add support for labeled A major motivation for RPCSEC_GSSv3 is to add support for labeled
security and server-side copy for NFSv4. security and server-side copy for NFSv4.
Labeled NFS (see Section 8 of [5]) uses the subject label provided by Labeled NFS (see Section 8 of [4]) 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.
RPCSEC_GSSv3 label assertions provide the means to achieve 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 [5]), the user first secures access to both source Section 3.4.1 of [4]), the user first secures access to both source
and destination files, and then uses NFSv4.2 defined RPCSEC_GSSv3 and destination files, and then uses NFSv4.2 defined RPCSEC_GSSv3
structured privileges to authorize the destination to copy the file structured privileges to authorize the destination to copy the file
from the source on behalf of the user. from the source on behalf of the user.
Multi-principal assertions can be used to address shared cache Multi-principal assertions can be used to address shared cache
poisoning attacks on the client cache by a user. As described in poisoning attacks on the client cache by a user. As described in
Section 7 of [14], multi-user machines with a single cache manager Section 7 of [14], multi-user machines with a single cache manager
can fetch and cache data on a users' behalf, and re-display it for can fetch and cache data on a users' behalf, and re-display it for
another user from the cache without re-fetching the data from the another user from the cache without re-fetching the data from the
server. The initial data acquisition is authenticated by the first server. The initial data acquisition is authenticated by the first
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Another use of the multi-principal assertion is the secure conveyance Another use of the multi-principal assertion is the secure conveyance
of privilege information for processes running with more (or even of privilege information for processes running with more (or even
with less) privilege than the user normally would be accorded. with less) privilege than the user normally would be accorded.
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 [8], except that the RPCSEC_GSSv3 is the same as RPCSEC_GSSv2 [8], 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 [10], [11], [12], [5] and [9]. labeled security models. See [10], [11], [12], [4] and [9].
o Application-specific structured privileges. For an example see o Application-specific structured privileges. For an example see
server-side copy [5]. server-side copy [4].
o Multi-principal authentication of the client host and user to the o Multi-principal authentication of the client host and user to the
server done by binding two RPCSEC_GSS handles. server done by binding two RPCSEC_GSS handles.
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.
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2. The RPCSEC_GSSv3 Protocol 2. The RPCSEC_GSSv3 Protocol
RPCSEC_GSSv3 is the same as RPCSEC_GSSv2 [8], except that support for RPCSEC_GSSv3 is the same as RPCSEC_GSSv2 [8], 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 established
RPCSEC_GSSv3 exchanges, this will be termed the "parent" handle. in the usual manner (See Section 5.2 [2]) to protect RPCSEC_GSSv3
exchanges, this will be termed the "parent" handle.
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 o An RPCSEC_GSSv3 child handle MUST NOT be used as the parent handle
in an RPCSEC_GSS3_CREATE control message. in an RPCSEC_GSS3_CREATE control message.
2.1. Compatibility with RPCSEC_GSSv2 2.1. Compatibility with RPCSEC_GSSv2
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RPCSEC_GSS_VERS_3. If the target does not recognize RPCSEC_GSS_VERS_3. If the target does not recognize
RPCSEC_GSS_VERS_3, the target will return an RPC error per RPCSEC_GSS_VERS_3, the target will return an RPC error per
Section 5.1 of [2]. Section 5.1 of [2].
The initiator MUST NOT attempt to use an RPCSEC_GSS handle returned 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 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 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 returned by version 1 or version 2 of a target with version 3 of the
same target. same target.
2.3. New REPLY verifier 2.3. New REPLY Verifier
A new reply verifier is needed for RPCSEC_GSSv3 due to the following:
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, so a child and parent RPCSEC_GSSv3 handle could have the same
same RPCSEC_GSS sequence numbers, and the verifier of RPCSEC_GSS RPCSEC_GSS sequence numbers. Since the reply verifier of previous
replies computes a MIC on just the sequence number, this provides versions of RPCSEC_GSS computes a MIC on just the sequence number,
opportunities for man in the middle attacks. this provides opportunities for man in the middle attacks.
This is easily addressed: RPCSEC_GSS version 3 changes the verifier This is easily addressed: RPCSEC_GSS version 3 changes the verifier
of the reply to compute the verifier using the exact same input as of the reply to compute the verifier using the exact same input as
that is used for verifier of the request, except for the mtype change that is used for verifier of the request, except for the mtype change
from CALL to REPLY. The new reply verifier computes a MIC over the from CALL to REPLY. The new reply verifier computes a MIC over the
following RPC reply header data: following RPC reply header 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;
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RPCSEC_GSSv3 provides a channel binding assertion that replaces the RPCSEC_GSSv3 provides a channel binding assertion that replaces the
RPCSEC_GSSv2 RPCSEC_GSS_BIND_CHANNEL operation. RPCSEC_GSSv2 RPCSEC_GSS_BIND_CHANNEL operation.
RPCSEC_GSS_BIND_CHANNEL MUST NOT be used on RPCSEC_GSS version 3 RPCSEC_GSS_BIND_CHANNEL MUST NOT be used on RPCSEC_GSS version 3
handles. handles.
2.6. New auth_stat Values 2.6. New auth_stat Values
RPCSEC_GSSv3 requires the addition of several values to the auth_stat RPCSEC_GSSv3 requires the addition of several values to the auth_stat
enumerated type definition. The use of each of these new auth_stat enumerated type definition. The use of each of these new auth_stat
values is explained later in this document. values is explained throughout this document.
enum auth_stat { enum auth_stat {
... ...
/* /*
* RPCSEC_GSSv3 errors * RPCSEC_GSSv3 errors
*/ */
RPCSEC_GSS_INNER_CREDPROBLEM = 15, RPCSEC_GSS_INNER_CREDPROBLEM = 15,
RPCSEC_GSS_LABEL_PROBLEM = 16, RPCSEC_GSS_LABEL_PROBLEM = 16,
RPCSEC_GSS_PRIVILEGE_PROBLEM = 17, RPCSEC_GSS_PRIVILEGE_PROBLEM = 17,
RPCSEC_GSS_UNKNOWN_MESSAGE = 18 RPCSEC_GSS_UNKNOWN_MESSAGE = 18
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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
messages may contain call data following the verifier in the body of messages may contain call data following the verifier in the body of
the NULLPROC procedure. In other words, they look a lot like an the NULLPROC procedure. In other words, they look a lot like an
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 [8])
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.
RPCSEC_GSS_LIST can also use rpc_gss_svc_channel_prot (see
RPCSEC_GSSv2 [8]) if the request is sent using an RPCSEC_GSSv3 child
handle with channel bindings enabled as described in Section 2.7.1.2.
2.7.1. New Control Procedure - RPCSEC_GSS_CREATE 2.7.1. New Control Procedure - RPCSEC_GSS_CREATE
<CODE BEGINS> <CODE BEGINS>
/// struct rgss3_create_args { /// struct rgss3_create_args {
/// rgss3_gss_mp_auth *rca_mp_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_u rca_assertions<>;
/// }; /// };
/// ///
/// struct rgss3_create_res { /// struct rgss3_create_res {
/// opaque rcr_handle<>; /// opaque rcr_handle<>;
/// rgss3_gss_mp_auth *rcr_mp_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_u 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
/// switch (rgss3_assertion_type atype) { /// switch (rgss3_assertion_type atype) {
/// case LABEL: /// case LABEL:
/// rgss3_label rau_label; /// rgss3_label rau_label;
/// case PRIVS: /// case PRIVS:
/// rgss3_privs rau_privs; /// rgss3_privs rau_privs;
/// default: /// default:
/// opaque rau_ext<>; /// opaque rau_ext<>;
/// }; /// };
/// ///
/// struct rgss3_assertion {
/// rgss3_assertion_u ra_assertion;
/// };
///
<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 Multi-principal authentication: another RPCSEC_GSS context handle o Multi-principal authentication: another RPCSEC_GSS context handle
o A channel binding o A channel binding
o Authorization assertions: labels and or privileges o Authorization assertions: labels and or privileges
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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 Multi-principal authentication: another RPCSEC_GSS context handle o Multi-principal authentication: another RPCSEC_GSS context handle
o A channel binding o A channel binding
o Authorization assertions: labels and or privileges o Authorization assertions: labels and or privileges
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. As noted in Section 2.7.1.3 and
Section 2.7.1.4 successful rgss3_assertions are enumerated in
rcr_assertions, and are REQUIRED be enumerated in the same order as
they appeared in the rca_assertions argument.
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
the parent context handle in their GSS context caches so as to be the parent context handle in their GSS context caches so as to be
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,
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to its handle. When this occurs on an RPCSEC_GSS3_CREATE request to its handle. When this occurs on an RPCSEC_GSS3_CREATE request
processing of the parent handle, the server rejects the request with 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 a reply status of MSG_DENIED with the reject_stat of AUTH_ERROR and
with an auth_stat value of RPCSEC_GSS_CREDPROBLEM. with an auth_stat value of RPCSEC_GSS_CREDPROBLEM.
A new value, RPCSEC_GSS_INNER_CREDPROBLEM, has been added to the A new value, RPCSEC_GSS_INNER_CREDPROBLEM, has been added to the
auth_stat type. With a multi-pricipal authorization request, the auth_stat type. With a multi-pricipal authorization request, the
server must also have a context corresponding to the inner context server must also have a context corresponding to the inner context
handle. When the server does not have a context handle corresponding handle. When the server does not have a context handle corresponding
to the inner context handle of a multi-pricipal authorization to the inner context handle of a multi-pricipal authorization
request, the server send a reply status of MSG_DENIED with the request, the server sends a reply status of MSG_DENIED with the
reject_stat of AUTH_ERROR and with an auth_stat value of reject_stat of AUTH_ERROR and with an auth_stat value of
RPCSEC_GSS_INNER_CREDPROBLEM. RPCSEC_GSS_INNER_CREDPROBLEM.
When processing the multi-principal authentication request, if the When processing the multi-principal authentication request, if the
GSS_VerifyMIC() call on the rgmp_rpcheader_mic fails to return GSS_VerifyMIC() call on the rgmp_rpcheader_mic fails to return
GSS_S_COMPLETE, the server sends a reply status of MSG_DENIED with 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 the reject_stat of AUTH_ERROR and with an auth_stat value of
RPCSEC_GSS_INNER_CREDPROBLEM. RPCSEC_GSS_INNER_CREDPROBLEM.
2.7.1.2. Channel Binding 2.7.1.2. Channel Binding
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As per-RPCSEC_GSSv2 [8]: As per-RPCSEC_GSSv2 [8]:
"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."
Any RPCSEC_GSSv3 context handle that has been bound to a secure Any RPCSEC_GSSv3 child 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.
2.7.1.3. Label Assertions 2.7.1.3. 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;
/// unsigned int rlf_pi_id; /// unsigned int rlf_pi_id;
/// }; /// };
/// ///
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<CODE ENDS> <CODE ENDS>
The client discovers which labels the server supports via the The client discovers which labels the server supports via the
RPCSEC_GSS_LIST control message. Asserting a server supported label RPCSEC_GSS_LIST control message. Asserting a server supported label
via RPCSEC_GSS_CREATE enables server guest mode labels. Full mode is via RPCSEC_GSS_CREATE enables server guest mode labels. Full mode is
enabled when an RPCSEC_GSS_CREATE label assertion is combined with enabled when an RPCSEC_GSS_CREATE label assertion is combined with
asserting the same label with the NFSv4.2 sec_label attribute. asserting the same label with the NFSv4.2 sec_label attribute.
Label encoding is specified to mirror the NFSv4.2 sec_label attribute Label encoding is specified to mirror the NFSv4.2 sec_label attribute
described in Section 12.2.2 of [5]. The label format specifier (LFS) described in Section 12.2.2 of [4]. The label format specifier (LFS)
is an identifier used by the client to establish the syntactic format is an identifier used by the client to establish the syntactic format
of the security label and the semantic meaning of its components. of the security label and the semantic meaning of its components.
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.
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
skipping to change at page 15, line 48 skipping to change at page 16, line 41
not recognize the assertion is rejected with a reply status of not recognize the assertion is rejected with a reply status of
MSG_DENIED, a reject_status of AUTH_ERROR, and an auth_stat of MSG_DENIED, a reject_status of AUTH_ERROR, and an auth_stat of
RPCSEC_GSS_UNKNOWN_MESSAGE. RPCSEC_GSS_UNKNOWN_MESSAGE.
If a server receives a structured privilege assertion that it fails If a server receives a structured privilege assertion that it fails
to verify according to the requirements of the RPC application to verify according to the requirements of the RPC application
defined behavior, the assertion is rejected with a reply status of defined behavior, the assertion is rejected with a reply status of
MSG_DENIED, a reject_status of AUTH_ERROR, and an auth_stat of MSG_DENIED, a reject_status of AUTH_ERROR, and an auth_stat of
RPCSEC_GSS_PRIVILEGE_PROBLEM. RPCSEC_GSS_PRIVILEGE_PROBLEM.
Section 3.4.1.2. "Inter-Server Copy with RPCSEC_GSSv3" of [5] shows Section 3.4.1.2. "Inter-Server Copy with RPCSEC_GSSv3" of [4] shows
an example of structured privilege definition and use. an example of structured privilege definition and use.
2.7.2. New Control Procedure - RPCSEC_GSS_LIST 2.7.2. 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
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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.
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.
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 [5] GSS-API "SSV" mechanisms. Specifically, the NFSv4
scheme requires that the server initiate GSS-API security contexts, callback scheme requires that the server initiate GSS-API security
which does not work well in practice, and in the context of client- contexts, which does not work well in practice, and in the context of
side processes running as the same user but with different privileges client- side processes running as the same user but with different
and security labels the NFSv4 callback security scheme seems privileges and security labels the NFSv4 callback security scheme
particularly unlikely to work well. NFSv4.1 has the server use an seems particularly unlikely to work well. NFSv4.1 has the server use
existing, client-initiated RPCSEC_GSS context handle to protect an 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.
[[AI6: [Add text about interaction with GSS-SSV...] --NW]] As described in Section 2.10.10 [5] the client is permitted to
associate multiple RPCSEC_GSS handles with a single SSV GSS context.
[[AI7: AFAICS the reason to use SSV is to avoid using a client RPCSEC_GSSv3 handles will work well with SSV in that the man-in-the-
machine credential which means multi-principal authentication can not middle attacks described in Section 2.10.10 [5] are solved by the new
be used. --AA]] reply verifier (Section 2.3). Using an RPCSEC_GSSv3 handle backed by
a GSS-SSV mechanism context as a parent handle in an
RPCSEC_GSS_CREATE call while permitted is complicated by the lifetime
rules of SSV contexts and their associated RPCSEC_GSS handles.
5. IANA Considerations 5. IANA Considerations
This section uses terms that are defined in [4].
There are no IANA considerations in this document. There are no IANA considerations in this document.
6. References 6. References
6.1. Normative References 6.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate [1] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997. Requirement 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] Narten, T. and H. Alvestrand, "Guidelines for Writing an [4] Haynes, T., "NFS Version 4 Minor Version 2", draft-ietf-
IANA Considerations Section in RFCs", BCP 26, RFC 5226, nfsv4-minorversion2-29 (Work In Progress), December 2014.
May 2008.
[5] Haynes, T., "NFS Version 4 Minor Version 2", draft-ietf- [5] Shepler, S., Eisler, M., and D. Noveck, "Network File
nfsv4-minorversion2-27 (Work In Progress), June 2014. System (NFS) Version 4 Minor Version 1 Protocol", RFC
5661, January 2010.
[6] Williams, N., "On the Use of Channel Bindings to Secure [6] Williams, N., "On the Use of Channel Bindings to Secure
Channels", RFC 5056, November 2007. Channels", RFC 5056, November 2007.
[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] Eisler, M., "RPCSEC_GSS Version 2", RFC 5403, February [8] Eisler, M., "RPCSEC_GSS Version 2", RFC 5403, February
2009. 2009.
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