draft-ietf-nfsv4-rpcsec-gssv3-10.txt   draft-ietf-nfsv4-rpcsec-gssv3-11.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: June 11, 2015 Cryptonector Expires: July 9, 2015 Cryptonector
December 08, 2014 January 05, 2015
Remote Procedure Call (RPC) Security Version 3 Remote Procedure Call (RPC) Security Version 3
draft-ietf-nfsv4-rpcsec-gssv3-10 draft-ietf-nfsv4-rpcsec-gssv3-11
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 support for
principal authentication of client hosts and user principals to multi-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.
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 [RFC2119].
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
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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
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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 June 11, 2015. This Internet-Draft will expire on July 9, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2015 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
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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
1.1. Added Functionality . . . . . . . . . . . . . . . . . . . 3
1.2. XDR Code Extraction . . . . . . . . . . . . . . . . . . . 4
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. XDR Code Preliminaries . . . . . . . . . . . . . . . . . 6
2.5. RPCSEC_GSS_BIND_CHANNEL Operation Deprecated . . . . . . 8 2.5. RPCSEC_GSS_BIND_CHANNEL Operation . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . . . . 17 2.8. Extensibility . . . . . . . . . . . . . . . . . . . . . . 17
3. Operational Recommendation for Deployment . . . . . . . . . . 18 3. Operational Recommendation for Deployment . . . . . . . . . . 18
4. Security Considerations . . . . . . . . . . . . . . . . . . . 18 4. Security Considerations . . . . . . . . . . . . . . . . . . . 18
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.1. Normative References . . . . . . . . . . . . . . . . . . 19 6.1. Normative References . . . . . . . . . . . . . . . . . . 19
6.2. Informative References . . . . . . . . . . . . . . . . . 19 6.2. Informative References . . . . . . . . . . . . . . . . . 19
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 20 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 20
Appendix B. RFC Editor Notes . . . . . . . . . . . . . . . . . . 20 Appendix B. RFC Editor Notes . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 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 [RFC2203] provided for
RPC clients and servers to each other using the Generic Security authentication of RPC clients and servers to each other using the
Services Application Programming Interface (GSS-API) [3]. The second Generic Security Services Application Programming Interface (GSS-API)
version of RPCSEC_GSS [8] added support for channel bindings [6]. [RFC2743]. The second version of RPCSEC_GSS [RFC5403] added support
for channel bindings [RFC5056].
We find that GSS-API mechanisms are insufficient for communicating Existing 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,
namely, in this case, RPCSEC_GSS.
A major motivation for RPCSEC_GSSv3 is to add support for labeled However, here it is addressed at the application layer, i.e. in
security and server-side copy for NFSv4. RPCSEC_GSS.
Labeled NFS (see Section 8 of [4]) uses the subject label provided by A major motivation for RPCSEC_GSSv3 is to add support for multi-level
the client via the RPCSEC_GSSv3 layer to enforce MAC access to (labeled) security and server-side copy for NFSv4.
objects owned by the server to enable server guest mode.
Multi-Level Security (MLS) is a traditional model where subjects are
given a security level (Unclassified, Secret, Top Secret, etc.) and
objects are given security labels that mandate the access of the
subject to the object (see [BL73] and [RFC2401]).
Labeled NFS (see Section 8 of [NFSv4.2]) uses the MLS subject label
provided by the client via the RPCSEC_GSSv3 layer to enforce MAC
access to objects owned by the server to enable server guest mode.
RPCSEC_GSSv3 label assertions provide the means to achieve full 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 [4]), the user first secures access to both source Section 3.4.1 of [NFSv4.2]), the user first secures access to both
and destination files, and then uses NFSv4.2 defined RPCSEC_GSSv3 source and destination files, and then uses NFSv4.2 defined
structured privileges to authorize the destination to copy the file RPCSEC_GSSv3 structured privileges to authorize the destination to
from the source on behalf of the user. copy the file 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 [AFS-RXGK], multi-user machines with a single cache
can fetch and cache data on a users' behalf, and re-display it for manager can fetch and cache data on a users' behalf, and re-display
another user from the cache without re-fetching the data from the it for another user from the cache without re-fetching the data from
server. The initial data acquisition is authenticated by the first the server. The initial data acquisition is authenticated by the
user's credentials, and if only that user's credentials are used, it first user's credentials, and if only that user's credentials are
may be possible for a malicious user or users to "poison" the cache used, it may be possible for a malicious user or users to "poison"
for other users by introducing bogus data into the cache. the cache for other users by introducing bogus data into the cache.
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.
1.1. Added Functionality
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 [RFC5403], 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 security type enforcement, and
labeled security models. See [10], [11], [12], [4] and [9]. other labeled security models (See [RFC7204]).
o Application-specific structured privileges. For an example see o Application-specific structured privileges. For an example see
server-side copy [4]. server-side copy [NFSv4.2].
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. See [NFSv4.2].
We add an option for enumerating server supported label format An option for enumerating server supported label format specifiers
specifiers (LFS). The LFS and Label Format Registry are described in (LFS) is provided. See [RFC7204] for detail.
detail in [13].
This document contains the External Data Representation (XDR) ([7]) 1.2. XDR Code Extraction
definitions for the RPCSEC_GSSv3 protocol. The XDR description is
provided in this document in a way that makes it simple for the This document contains the External Data Representation (XDR)
reader to extract into ready to compile form. The reader can feed ([RFC4506]) definitions for the RPCSEC_GSSv3 protocol. The XDR
this document in the following shell script to produce the machine description is provided in this document in a way that makes it
readable XDR description of RPCSEC_GSSv3: simple for the reader to extract into ready to compile form. The
reader can feed this document in the following shell script to
produce the machine readable XDR description of RPCSEC_GSSv3:
<CODE BEGINS> <CODE BEGINS>
#!/bin/sh #!/bin/sh
grep "^ *///" | sed 's?^ */// ??' | sed 's?^ *///$??' grep "^ *///" | sed 's?^ */// ??' | sed 's?^ *///$??'
<CODE ENDS> <CODE ENDS>
I.e. if the above script is stored in a file called "extract.sh", and I.e. if the above script is stored in a file called "extract.sh", and
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:
skipping to change at page 4, line 41 skipping to change at page 4, line 50
sh extract.sh < spec.txt > rpcsec_gss_v3.x sh extract.sh < spec.txt > rpcsec_gss_v3.x
<CODE ENDS> <CODE ENDS>
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 "///".
2. The RPCSEC_GSSv3 Protocol 2. The RPCSEC_GSSv3 Protocol
RPCSEC_GSSv3 is the same as RPCSEC_GSSv2 [8], except that support for RPCSEC_GSS version 3 (RPCSEC_GSSv3) is very similar to RPCSEC_GSS
assertions has been added. The entire RPCSEC_GSSv3 protocol is not version 2 (RPCSEC_GSSv2) [RFC5403]. The differences are the addition
presented. Instead the differences between RPCSEC_GSSv3 and of support for assertions and channel bindings are supported via a
RPCSEC_GSSv2 are shown. different mechanism.
RPCSEC_GSSv3 is patterned as follows: The entire RPCSEC_GSSv3 protocol is not presented here. Only the
differences between it and RPCSEC_GSSv2 are shown.
The use of RPCSEC_GSSv3 is structured as follows:
o A client uses an existing RPCSEC_GSSv3 context handle established o A client uses an existing RPCSEC_GSSv3 context handle established
in the usual manner (See Section 5.2 [2]) to protect RPCSEC_GSSv3 in the usual manner (See Section 5.2 [RFC2203]) to protect
exchanges, this will be termed the "parent" handle. 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
The functionality of RPCSEC_GSSv2 [8] is fully supported by The functionality of RPCSEC_GSSv2 [RFC5403] is fully supported by
RPCSEC_GSSv3 with the exception of the RPCSEC_GSS_BIND_CHANNEL RPCSEC_GSSv3 with the exception of the RPCSEC_GSS_BIND_CHANNEL
operation which is deprecated (see Section 2.5). operation which is deprecated (see Section 2.5).
2.2. Version Negotiation 2.2. Version Negotiation
An initiator that supports version 3 of RPCSEC_GSS simply issues an An initiator that supports version 3 of RPCSEC_GSS simply issues an
RPCSEC_GSS request with the rgc_version field set to RPCSEC_GSS request with the rgc_version field set to
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 [RFC2203].
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: A new reply verifier is needed for RPCSEC_GSSv3 because of a
The RPCSEC_GSSv3 child handle uses the same GSS context as the parent situation that arises from the use of the same GSS context by child
handle, so a child and parent RPCSEC_GSSv3 handle could have the same and parent handles. Because the RPCSEC_GSSv3 child handle uses the
RPCSEC_GSS sequence numbers. Since the reply verifier of previous same GSS context as the parent handle, a child and parent
versions of RPCSEC_GSS computes a MIC on just the sequence number, RPCSEC_GSSv3 handle could have the same RPCSEC_GSS sequence numbers.
this provides opportunities for man in the middle attacks. Since the reply verifier of previous versions of RPCSEC_GSS computes
a MIC on just the sequence number, this provides opportunities for
man in the middle attacks.
This is easily addressed: RPCSEC_GSS version 3 changes the verifier This issue is addressed in RPCSEC_GSS version 3 by computing the
of the reply to compute the verifier using the exact same input as verifier using the exact same input as is used to compute the request
that is used for verifier of the request, except for the mtype change verifier, except for the mtype is changed from CALL to REPLY. The
from CALL to REPLY. The new reply verifier computes a MIC over the new reply verifier computes a MIC over the following RPC reply header
following RPC reply header data: 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 */
2.4. New Version Number 2.4. XDR Code Preliminaries
<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].
skipping to change at page 8, line 9 skipping to change at page 8, line 18
/// case RPCSEC_GSS_VERS_1: /// case RPCSEC_GSS_VERS_1:
/// case RPCSEC_GSS_VERS_2: /// case RPCSEC_GSS_VERS_2:
/// case RPCSEC_GSS_VERS_3: /* new */ /// case RPCSEC_GSS_VERS_3: /* new */
/// rpc_gss_cred_vers_1_t rgc_cred_v1; /// rpc_gss_cred_vers_1_t rgc_cred_v1;
/// }; /// };
/// ///
<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 [8] credential. Setting the RPCSEC_GSSv1 [RFC2203] and RPCSEC_GSSv2 [RFC5403] credential.
rgc_version field to 3 indicates that the initiator and target Setting the rgc_version field to 3 indicates that the initiator and
support the new RPCSEC_GSSv3 control procedures. target support the new RPCSEC_GSSv3 control procedures.
2.5. RPCSEC_GSS_BIND_CHANNEL Operation Deprecated 2.5. RPCSEC_GSS_BIND_CHANNEL Operation
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 these new auth_stat values is
values is explained throughout this document. 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
skipping to change at page 9, line 4 skipping to change at page 9, line 15
The RPCSEC_GSS_CREATE procedure binds any combination of assertions: The RPCSEC_GSS_CREATE procedure binds any combination of assertions:
multi-principal authentication, labels, structured privileges, or multi-principal authentication, labels, structured privileges, or
channel 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 version 2 RPCSEC_GSS_DESTROY control message (see version 1 and version 2 RPCSEC_GSS_DESTROY control message (see
section 5.4 [2]) in that the sequence number in the request must be section 5.4 [RFC2203]) in that the sequence number in the request
valid, and the header checksum in the verifier must be valid. As in must be valid, and the header checksum in the verifier must be valid.
RPCSEC_GSS version 1 and version 2, the RPCSEC_GSSv version 3 control As in RPCSEC_GSS version 1 and version 2, the RPCSEC_GSSv version 3
messages may contain call data following the verifier in the body of control messages may contain call data following the verifier in the
the NULLPROC procedure. In other words, they look a lot like an body of the NULLPROC procedure. In other words, they look a lot like
RPCSEC_GSS data message with the header procedure set to NULLPROC. an 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_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_GSS_LIST can also use rpc_gss_svc_channel_prot (see
RPCSEC_GSSv2 [8]) if the request is sent using an RPCSEC_GSSv3 child RPCSEC_GSSv2 [RFC5403]) if the request is sent using an RPCSEC_GSSv3
handle with channel bindings enabled as described in Section 2.7.1.2. 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_u rca_assertions<>; /// rgss3_assertion_u rca_assertions<>;
/// }; /// };
/// ///
skipping to change at page 12, line 44 skipping to change at page 12, line 44
On a successful verification, the rgss3_gss_mp_auth field in the On a successful verification, the rgss3_gss_mp_auth field in the
rgss3_create_res reply MUST be filled in with the inner RPCSEC_GSSv3 rgss3_create_res reply MUST be filled in with the inner RPCSEC_GSSv3
context handle as the rgmp_handle, and a MIC computed over the RPC context handle as the rgmp_handle, and a MIC computed over the RPC
reply header (see section Section 2.3) using the GSS-API security reply header (see section Section 2.3) using the GSS-API security
context associated with the inner handle. context associated with the inner handle.
On failure, the rgss3_gss_mp_auth field is not sent On failure, the rgss3_gss_mp_auth field is not sent
(rgss3_gss_mp_auth is an optional field). A MSG_DENIED reply to the (rgss3_gss_mp_auth is an optional field). A MSG_DENIED reply to the
RPCSEC_GSS_CREATE call is formulated as usual. RPCSEC_GSS_CREATE call is formulated as usual.
As described in Section 5.3.3.3 of [2] the server maintains a list of As described in Section 5.3.3.3 of [RFC2203] the server maintains a
contexts for the clients that are currently in session with it. When list of contexts for the clients that are currently in session with
a client request comes in, there may not be a context corresponding it. When a client request comes in, there may not be a context
to its handle. When this occurs on an RPCSEC_GSS3_CREATE request corresponding to its handle. When this occurs on an
processing of the parent handle, the server rejects the request with RPCSEC_GSS3_CREATE request processing of the parent handle, the
a reply status of MSG_DENIED with the reject_stat of AUTH_ERROR and server rejects the request with a reply status of MSG_DENIED with the
with an auth_stat value of RPCSEC_GSS_CREDPROBLEM. reject_stat of AUTH_ERROR and 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 sends 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.
skipping to change at page 13, line 31 skipping to change at page 13, line 31
<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
RPCSEC_GSSv2 [8]. Specifically: RPCSEC_GSSv2 [RFC5403]. 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 there is now general
agrees that it is the secure channel's responsibility to produce agreement that it is the secure channel's responsibility to
channel bindings data of manageable size. produce 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 [6], then the client calls GSS_GetMIC() to get a MIC of resulting in [RFC5056], then the client calls GSS_GetMIC() to get a MIC of
octet string, using the parent RPCSEC_GSSv3 context handle's GSS-API resulting octet string, using the parent RPCSEC_GSSv3 context
security context. The MIC is then placed in the rca_chan_bind_mic handle's GSS-API security context. The MIC is then placed in the
field of RPCSEC_GSS_CREATE arguments (rgss3_create_args). rca_chan_bind_mic field of RPCSEC_GSS_CREATE arguments
(rgss3_create_args).
If the rca_chan_bind_mic field of the arguments of a If the rca_chan_bind_mic field of the arguments of a
RPCSEC_GSS_CREATE control message is set, then the server MUST verify RPCSEC_GSS_CREATE control message is set, then the server MUST verify
the client's channel binding MIC if the server supports this feature. the client's channel binding MIC if the server supports this feature.
If channel binding verification succeeds then the server MUST If channel binding verification succeeds then the server MUST
generate a new MIC of the same channel bindings and place it in the generate a new MIC of the same channel bindings and place it in the
rcr_chan_bind_mic field of the RPCSEC_GSS_CREATE rgss3_create_res rcr_chan_bind_mic field of the RPCSEC_GSS_CREATE rgss3_create_res
results. If channel binding verification fails or the server doesn't results. If channel binding verification fails or the server doesn't
support channel binding then the server MUST indicate this in its support channel binding then the server MUST indicate this in its
reply by not including a rgss3_chan_binding value in rgss3_create_res reply by not including a rgss3_chan_binding value in rgss3_create_res
skipping to change at page 14, line 26 skipping to change at page 14, line 26
The client MUST verify the result's rcr_chan_bind_mic value by The client MUST verify the result's rcr_chan_bind_mic value by
calling GSS_VerifyMIC() with the given MIC and the channel bindings calling GSS_VerifyMIC() with the given MIC and the channel bindings
data (including the channel type prefix). If client-side channel data (including the channel type prefix). If client-side channel
binding verification fails then the client MUST call binding verification fails then the client MUST call
RPCSEC_GSS_DESTROY. If the client requested channel binding but the RPCSEC_GSS_DESTROY. If the client requested channel binding but the
server did not include an rcr_chan_binding_mic field in the results, server did not include an rcr_chan_binding_mic field in the results,
then the client MAY continue to use the resulting context handle as then the client MAY continue to use the resulting context handle as
though channel binding had never been requested. If the client though channel binding had never been requested. If the client
considers channel binding critical, it MUST call RPCSEC_GSS_DESTROY. considers channel binding critical, it MUST call RPCSEC_GSS_DESTROY.
As per-RPCSEC_GSSv2 [8]: As per-RPCSEC_GSSv2 [RFC5403]:
"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 child context handle that has been bound to a secure Any RPCSEC_GSSv3 child context handle that has been bound to a secure
skipping to change at page 15, line 24 skipping to change at page 15, line 24
<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 [4]. The label format specifier (LFS) described in Section 12.2.2 of [NFSv4.2]. The label format specifier
is an identifier used by the client to establish the syntactic format (LFS) is an identifier used by the client to establish the syntactic
of the security label and the semantic meaning of its components. format of the security label and the semantic meaning of its
The policy identifier (PI) is an optional part of the definition of components. The policy identifier (PI) is an optional part of the
an LFS which allows for clients and server to identify specific definition of an LFS which allows for clients and server to identify
security policies. The opaque label field of rgss3_label is specific 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
request. request.
RPCSEC_GSSv3 clients MAY assert a server security label in some LSF RPCSEC_GSSv3 clients MAY assert a server security label in some LSF
by binding a label assertion to the RPCSEC_GSSv3 context handle. by binding a label assertion to the RPCSEC_GSSv3 context handle.
This is done by including an assertion of type rgss3_label in the This is done by including an assertion of type rgss3_label in the
skipping to change at page 16, line 41 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 [4] shows Section 3.4.1.2. "Inter-Server Copy with RPCSEC_GSSv3" of [NFSv4.2]
an example of structured privilege definition and use. shows 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 {
skipping to change at page 18, line 7 skipping to change at page 18, line 7
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.
3. Operational Recommendation for Deployment 3. Operational Recommendation for Deployment
RPCSEC_GSSv3 is a superset of RPCSEC_GSSv2 [8] which in turn is a RPCSEC_GSSv3 is a superset of RPCSEC_GSSv2 [RFC5403] which in turn is
superset of RPCSEC_GSSv1 [2], and so can be used in all situations a superset of RPCSEC_GSSv1 [RFC2203], and so can be used in all
where RPCSEC_GSSv1 or RPCSEC_GSSv2 is used. RPCSEC_GSSv3 should be situations where RPCSEC_GSSv1 or RPCSEC_GSSv2 is used. RPCSEC_GSSv3
used when the new functionality is needed. should be used when the new functionality is needed.
4. 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 evaluated by the server in the context of whether assertions must be evaluated by the server in the context of whether
the client and/or user are authenticated, whether multi-principal 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
skipping to change at page 18, line 33 skipping to change at page 18, line 33
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 [5] GSS-API "SSV" mechanisms. Specifically, the NFSv4 NFSv4.1's [RFC5661] GSS-API "SSV" mechanisms. Specifically, the
callback scheme requires that the server initiate GSS-API security NFSv4 callback scheme requires that the server initiate GSS-API
contexts, which does not work well in practice, and in the context of security contexts, which does not work well in practice, and in the
client- side processes running as the same user but with different context of client- side processes running as the same user but with
privileges and security labels the NFSv4 callback security scheme different privileges and security labels the NFSv4 callback security
seems particularly unlikely to work well. NFSv4.1 has the server use scheme seems particularly unlikely to work well. NFSv4.1 has the
an existing, client-initiated RPCSEC_GSS context handle to protect server use an existing, client-initiated RPCSEC_GSS context handle to
server-initiated callback RPCs. The NFSv4.1 callback security scheme protect server-initiated callback RPCs. The NFSv4.1 callback
lacks all the problems of the NFSv4 scheme, however, it is important security scheme lacks all the problems of the NFSv4 scheme, however,
that the server pick an appropriate RPCSEC_GSS context handle to it is important that the server pick an appropriate RPCSEC_GSS
protect any callbacks. Specifically, it is important that the server context handle to protect any callbacks. Specifically, it is
use RPCSEC_GSS context handles which authenticate the client to important that the server use RPCSEC_GSS context handles which
protect any callbacks relating to server state initiated by RPCs authenticate the client to protect any callbacks relating to server
protected by RPCSEC_GSSv3 contexts. state initiated by RPCs protected by RPCSEC_GSSv3 contexts.
As described in Section 2.10.10 [5] the client is permitted to As described in Section 2.10.10 [RFC5661] the client is permitted to
associate multiple RPCSEC_GSS handles with a single SSV GSS context. associate multiple RPCSEC_GSS handles with a single SSV GSS context.
RPCSEC_GSSv3 handles will work well with SSV in that the man-in-the- RPCSEC_GSSv3 handles will work well with SSV in that the man-in-the-
middle attacks described in Section 2.10.10 [5] are solved by the new middle attacks described in Section 2.10.10 [RFC5661] are solved by
reply verifier (Section 2.3). Using an RPCSEC_GSSv3 handle backed by the new reply verifier (Section 2.3). Using an RPCSEC_GSSv3 handle
a GSS-SSV mechanism context as a parent handle in an backed by a GSS-SSV mechanism context as a parent handle in an
RPCSEC_GSS_CREATE call while permitted is complicated by the lifetime RPCSEC_GSS_CREATE call while permitted is complicated by the lifetime
rules of SSV contexts and their associated RPCSEC_GSS handles. rules of SSV contexts and their associated RPCSEC_GSS handles.
5. IANA Considerations 5. IANA Considerations
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 [NFSv4.2] Haynes, T., "NFS Version 4 Minor Version 2", draft-ietf-
nfsv4-minorversion2-29 (Work In Progress), December 2014.
[RFC2119] 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 [RFC2203] 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 [RFC2743] 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] Haynes, T., "NFS Version 4 Minor Version 2", draft-ietf- [RFC4506] Eisler, M., "XDR: External Data Representation Standard",
nfsv4-minorversion2-29 (Work In Progress), December 2014. RFC 4506, May 2006.
[5] Shepler, S., Eisler, M., and D. Noveck, "Network File
System (NFS) Version 4 Minor Version 1 Protocol", RFC
5661, January 2010.
[6] Williams, N., "On the Use of Channel Bindings to Secure [RFC5056] 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", [RFC5403] Eisler, M., "RPCSEC_GSS Version 2", RFC 5403, February
RFC 4506, May 2006.
[8] Eisler, M., "RPCSEC_GSS Version 2", RFC 5403, February
2009. 2009.
[9] Haynes, T., "Requirements for Labeled NFS", RFC 7204, [RFC5661] Shepler, S., Eisler, M., and D. Noveck, "Network File
System (NFS) Version 4 Minor Version 1 Protocol", RFC
5661, January 2010.
[RFC7204] Haynes, T., "Requirements for Labeled NFS", RFC 7204,
April 2014. April 2014.
6.2. Informative References 6.2. Informative References
[10] "Section 46.6. Multi-Level Security (MLS) of Deployment [AFS-RXGK]
Guide: Deployment, configuration and administration of Red Wilkinson, S. and B. Kaduk, "Integrating rxgk with AFS",
Hat Enterprise Linux 5, Edition 6", 2011.
[11] Smalley, S., "The Distributed Trusted Operating System
(DTOS) Home Page", 2000,
<http://www.cs.utah.edu/flux/fluke/html/dtos/HTML/
dtos.html>.
[12] Carter, J., "Implementing SELinux Support for NFS", 2005,
<http://www.nsa.gov/research/_files/selinux/papers/
nfsv3.pdf>.
[13] Quigley, D. and J. Lu, "Registry Specification for MAC
Security Label Formats", draft-quigley-label-format-
registry (work in progress), 2011.
[14] Wilkinson, S. and B. Kaduk, "Integrating rxgk with AFS",
draft-wilkinson-afs3-rxgk-afs (work in progress), April draft-wilkinson-afs3-rxgk-afs (work in progress), April
2014. 2014.
[BL73] Bell, D. and L. LaPadula, "Secure Computer Systems:
Mathematical Foundations and Model", Technical Report
M74-244, The MITRE Corporation Bedford, MA, May 1973.
[RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, November 1998.
Appendix A. Acknowledgments Appendix A. Acknowledgments
Andy Adamson would like to thank NetApp, Inc. for its funding of his Andy Adamson would like to thank NetApp, Inc. for its funding of his
time on this project. time on this project.
We thank Lars Eggert, Mike Eisler, Ben Kaduk, and Bruce Fields for We thank Lars Eggert, Mike Eisler, Ben Kaduk, Bruce Fields, Tom
their most helpful reviews. Haynes, and Dave Noveck 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]
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