draft-ietf-nfsv4-labreqs-03.txt   draft-ietf-nfsv4-labreqs-04.txt 
NFSv4 T. Haynes, Ed. NFSv4 T. Haynes
Internet-Draft NetApp Internet-Draft NetApp
Intended status: Standards Track May 18, 2012 Intended status: Informational August 04, 2013
Expires: November 19, 2012 Expires: February 5, 2014
Requirements for Labeled NFS Requirements for Labeled NFS
draft-ietf-nfsv4-labreqs-03.txt draft-ietf-nfsv4-labreqs-04.txt
Abstract Abstract
This Internet-Draft outlines high-level requirements for the This memo outlines high-level requirements for the integration of
integration of flexible Mandatory Access Control (MAC) functionality flexible Mandatory Access Control (MAC) functionality into the
into NFSv4.2. It describes the level of protections that should be Network File System (NFS) version 4.2 (NFSv4.2). It describes the
provided over protocol components and the basic structure of the level of protections that should be provided over protocol components
proposed system. It also gives a brief explanation of what kinds of and the basic structure of the proposed system. The intent here is
protections MAC systems offer. not to present the protocol changes, but to describe the environment
in which they reside.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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
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
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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 November 19, 2012. This Internet-Draft will expire on February 5, 2014.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Portability & Interoperability . . . . . . . . . . . . . . 5 3.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Performance & Scalability . . . . . . . . . . . . . . . . 6 3.2. Security Services . . . . . . . . . . . . . . . . . . . . 6
3.3. Security Services . . . . . . . . . . . . . . . . . . . . 6 3.3. Label Encoding, Label Format Specifiers, and Label
3.4. Label Encoding, Label Format Specifiers, and Label Checking Authorities . . . . . . . . . . . . . . . . . . . 6
Checking Authorities . . . . . . . . . . . . . . . . . . . 7 3.4. Labeling . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.5. Modes of Operation . . . . . . . . . . . . . . . . . . . . 8 3.4.1. Client Labeling . . . . . . . . . . . . . . . . . . . 7
3.5.1. Full Mode . . . . . . . . . . . . . . . . . . . . . . 8 3.4.2. Server Labeling . . . . . . . . . . . . . . . . . . . 8
3.5.2. Limited Server Mode . . . . . . . . . . . . . . . . . 9 3.5. Policy Enforcement . . . . . . . . . . . . . . . . . . . . 8
3.5.3. Guest Mode . . . . . . . . . . . . . . . . . . . . . . 9 3.5.1. Client Enforcement . . . . . . . . . . . . . . . . . . 8
3.6. Labeling . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.5.2. Server Enforcement . . . . . . . . . . . . . . . . . . 9
3.6.1. Client Labeling . . . . . . . . . . . . . . . . . . . 10 3.6. Namespace Access . . . . . . . . . . . . . . . . . . . . . 9
3.6.2. Server Labeling . . . . . . . . . . . . . . . . . . . 10 3.7. Upgrading Existing Server . . . . . . . . . . . . . . . . 9
3.7. Policy Enforcement . . . . . . . . . . . . . . . . . . . . 10 4. Modes of Operation . . . . . . . . . . . . . . . . . . . . . . 10
3.7.1. Client Enforcement . . . . . . . . . . . . . . . . . . 11 4.1. Full Mode . . . . . . . . . . . . . . . . . . . . . . . . 10
3.7.2. Server Enforcement . . . . . . . . . . . . . . . . . . 11 4.2. Limited Server Mode . . . . . . . . . . . . . . . . . . . 11
3.8. Namespace Access . . . . . . . . . . . . . . . . . . . . . 11 4.3. Guest Mode . . . . . . . . . . . . . . . . . . . . . . . . 11
3.9. Upgrading Existing Server . . . . . . . . . . . . . . . . 12 5. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.1. Full MAC labeling support for remotely mounted
4.1. Full MAC labeling support for remotely mounted
filesystems . . . . . . . . . . . . . . . . . . . . . . . 12 filesystems . . . . . . . . . . . . . . . . . . . . . . . 12
4.2. MAC labeling of virtual machine images stored on the 5.2. MAC labeling of virtual machine images stored on the
network . . . . . . . . . . . . . . . . . . . . . . . . . 12 network . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.3. International Traffic in Arms Regulations (ITAR) . . . . . 13 5.3. International Traffic in Arms Regulations (ITAR) . . . . . 12
4.4. Legal Hold/eDiscovery . . . . . . . . . . . . . . . . . . 13 5.4. Legal Hold/eDiscovery . . . . . . . . . . . . . . . . . . 13
4.5. Simple security label storage . . . . . . . . . . . . . . 14 5.5. Simple security label storage . . . . . . . . . . . . . . 13
4.6. Diskless Linux . . . . . . . . . . . . . . . . . . . . . . 14 5.6. Diskless Linux . . . . . . . . . . . . . . . . . . . . . . 14
4.7. Multi-Level Security . . . . . . . . . . . . . . . . . . . 15 5.7. Multi-Level Security . . . . . . . . . . . . . . . . . . . 14
4.7.1. Full Mode - MAC-functional Client and Server . . . . . 15 5.7.1. Full Mode - MAC-functional Client and Server . . . . . 15
4.7.2. MAC-Functional Client . . . . . . . . . . . . . . . . 16 5.7.2. MAC-Functional Client . . . . . . . . . . . . . . . . 15
4.7.3. MAC-Functional Server . . . . . . . . . . . . . . . . 16 5.7.3. MAC-Functional Server . . . . . . . . . . . . . . . . 16
5. Security Considerations . . . . . . . . . . . . . . . . . . . 17 6. Security Considerations . . . . . . . . . . . . . . . . . . . 16
5.1. Trust Needed for a Community . . . . . . . . . . . . . . . 17 6.1. Trust Needed for a Community . . . . . . . . . . . . . . . 16
5.2. Guest Modes . . . . . . . . . . . . . . . . . . . . . . . 17 6.2. Guest Modes . . . . . . . . . . . . . . . . . . . . . . . 17
5.3. MAC-Functional Client Configuration . . . . . . . . . . . 17 6.3. MAC-Functional Client Configuration . . . . . . . . . . . 17
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7.1. Normative References . . . . . . . . . . . . . . . . . . . 18 7.1. Normative References . . . . . . . . . . . . . . . . . . . 18
7.2. Informative References . . . . . . . . . . . . . . . . . . 18 7.2. Informative References . . . . . . . . . . . . . . . . . . 18
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 19 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 18
Appendix B. RFC Editor Notes . . . . . . . . . . . . . . . . . . 19 Appendix B. RFC Editor Notes . . . . . . . . . . . . . . . . . . 19
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 19 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction 1. Introduction
Mandatory Access Control (MAC) systems have been mainstreamed in Mandatory Access Control (MAC) systems have been mainstreamed in
modern operating systems such as Linux (R), FreeBSD (R), and Solaris modern operating systems such as Linux, FreeBSD, and Solaris. MAC
(TM). MAC systems bind security attributes to subjects (processes) systems bind security attributes to subjects (processes) and objects
and objects within a system. These attributes are used with other within a system. These attributes are used with other information in
information in the system to make access control decisions. the system to make access control decisions.
Access control models such as Unix permissions or Access Control Access control models such as Unix permissions or Access Control
Lists are commonly referred to as Discretionary Access Control (DAC) Lists are commonly referred to as Discretionary Access Control (DAC)
models. These systems base their access decisions on user identity models. These systems base their access decisions on user identity
and resource ownership. In contrast MAC models base their access and resource ownership. In contrast MAC models base their access
control decisions on the label on the subject (usually a process) and control decisions on the label on the subject (usually a process) and
the object it wishes to access. These labels may contain user the object it wishes to access. These labels may contain user
identity information but usually contain additional information. In identity information but usually contain additional information. In
DAC systems users are free to specify the access rules for resources DAC systems users are free to specify the access rules for resources
that they own. MAC models base their security decisions on a system that they own. MAC models base their security decisions on a system
wide policy established by an administrator or organization which the wide policy established by an administrator or organization which the
users do not have the ability to override. DAC systems offer no real users do not have the ability to override. DAC systems offer no real
protection against malicious or flawed software due to each program protection against malicious or flawed software due to each program
running with the full permissions of the user executing it. running with the full permissions of the user executing it.
Inversely MAC models can confine malicious or flawed software and Inversely MAC models can confine malicious or flawed software and
usually act at a finer granularity than their DAC counterparts. usually act at a finer granularity than their DAC counterparts.
People desire to use NFSv4 with these systems. A mechanism is Besides describing the requirements, this document records the
required to provide security attribute information to NFSv4 clients functional requirements for the client imposed by the pre-existing
and servers. This mechanism has the following requirements: security models on the client. This document may help those outside
the NFS community understand those issues.
(1) Clients MUST be able to convey to the server the security
attribute of the subject making the access request. The server
may provide a mechanism to enforce MAC policy based on the
requesting subject's security attribute.
(2) Servers MUST be able to store and retrieve the security
attribute of exported files as requested by the client.
(3) Servers MUST provide a mechanism for notifying clients of
attribute changes of files on the server.
(4) Clients and Servers MUST be able to negotiate Label Formats and
provide a mechanism to translate between them as needed.
2. Definitions 2. Definitions
Label Format Specifier (LFS): is an identifier used by the client to Label Format Specifier (LFS): is an identifier used by the client to
establish the syntactic format of the security label and the establish the syntactic format of the security label and the
semantic meaning of its components. semantic meaning of its components.
Label Format Registry: is the IANA registry (see [2]) containing all Label Format Registry: is the IANA registry (see [lfsreg])
registered LFS along with references to the documents that containing all registered LFS along with references to the
describe the syntactic format and semantics of the security label. documents that describe the syntactic format and semantics of the
security label.
Policy Identifier (PI): is an optional part of the definition of a Policy Identifier (PI): is an optional part of the definition of a
Label Format Specifier which allows for clients and server to Label Format Specifier which allows for clients and server to
identify specific security policies. identify specific security policies.
Object: is a passive resource within the system that we wish to be Object: is a passive resource within the system that we wish to be
protected. Objects can be entities such as files, directories, protected. Objects can be entities such as files, directories,
pipes, sockets, and many other system resources relevant to the pipes, sockets, and many other system resources relevant to the
protection of the system state. protection of the system state.
skipping to change at page 5, line 32 skipping to change at page 5, line 21
access to an object. access to an object.
MAC-Aware: is a server which can transmit and store object labels. MAC-Aware: is a server which can transmit and store object labels.
MAC-Functional: is a client or server which is Labeled NFS enabled. MAC-Functional: is a client or server which is Labeled NFS enabled.
Such a system can interpret labels and apply policies based on the Such a system can interpret labels and apply policies based on the
security system. security system.
Multi-Level Security (MLS): is a traditional model where objects are Multi-Level Security (MLS): is a traditional model where objects are
given a sensitivity level (Unclassified, Secret, Top Secret, etc) given a sensitivity level (Unclassified, Secret, Top Secret, etc)
and a category set [5]. and a category set [RH_MLS].
2.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Requirements 3. Requirements
The following initial requirements have been gathered from users, The following initial requirements have been gathered from users,
developers, and from previous development efforts in this area such developers, and from previous development efforts in this area such
as DTOS [6] and NSA's experimental NFSv3 enhancements [7]. as DTOS [DTOS] and NSA's experimental NFSv3 enhancements [SENFSV3].
3.1. Portability & Interoperability
Labeled NFS MUST be designed with portability in mind, to facilitate
implementations on any operating system that supports mandatory
access controls.
Labeled NFS MUST be designed and developed to facilitate 3.1. General
interoperability between different Labeled NFS implementations.
Labeled NFS modifications to standard NFSv4.2 [3] implementations A mechanism is required to provide security attribute information to
MUST not adversely impact any existing interoperability of those NFSv4 clients and servers. This mechanism has the following
implementations. requirements:
3.2. Performance & Scalability (1) Clients MUST be able to convey to the server the security
attribute of the subject making the access request. The server
may provide a mechanism to enforce MAC policy based on the
requesting subject's security attribute.
Security mechanisms often impact on system performance. Labeled NFS (2) Servers MUST be able to store and retrieve the security
SHOULD be designed and implemented in a way which avoids significant attribute of exported files as requested by the client.
performance impact where possible.
As NFSv4.2 is designed for large-scale distributed networking, (3) Servers MUST provide a mechanism for notifying clients of
Labeled NFS SHOULD also be capable of scaling in a similar manner to attribute changes of files on the server.
underlying implementations where possible.
Labeled NFS SHOULD respond in a robust manner to system and network (4) Clients and Servers MUST be able to negotiate Label Formats and
outages associated with typical enterprise and Internet environments. provide a mechanism to translate between them as needed.
At the very least, Labeled NFS SHOULD always operate in a fail-safe
manner, so that service disruptions do not cause or facilitate
security vulnerabilities.
3.3. Security Services 3.2. Security Services
Labeled NFS SHOULD ensure that the following security services are Labeled NFS SHOULD support that the following security services are
provided for all NFSv4.2 messaging. These services may be provided provided for all NFSv4.2 messaging. These services may be provided
by lower layers even if NFS has to be aware of and leverage them: by lower layers even if NFS has to be aware of and leverage them:
o Authentication o Authentication
o Integrity o Integrity
o Privacy o Privacy
Mechanisms and algorithms used in the provision of security services Mechanisms and algorithms used in the provision of security services
MUST be configurable, so that appropriate levels of protection may be MUST be configurable, so that appropriate levels of protection may be
flexibly specified per mandatory security policy. flexibly specified per mandatory security policy.
Strong mutual authentication will be required between the server and Strong mutual authentication will be required between the server and
the client for Full Mode operation Section 3.5.1. the client for Full Mode operation Section 4.1.
MAC security labels and any related security state SHOULD always be MAC security labels and any related security state SHOULD always be
protected by these security services when transferred over the protected by these security services when transferred over the
network; as SHOULD the binding of labels and state to associated network; as SHOULD the binding of labels and state to associated
objects and subjects. objects and subjects.
Labeled NFS SHOULD support authentication on a context granularity so Labeled NFS SHOULD support authentication on a context granularity so
that different contexts running on a client can use different that different contexts running on a client can use different
cryptographic keys and facilities. cryptographic keys and facilities.
3.4. Label Encoding, Label Format Specifiers, and Label Checking 3.3. Label Encoding, Label Format Specifiers, and Label Checking
Authorities Authorities
Encoding of MAC labels and attributes passed over the network MUST be Encoding of MAC labels and attributes passed over the network MUST be
specified in a complete and unambiguous manner while maintaining the specified in a complete and unambiguous manner while maintaining the
flexibility of MAC implementations. To accomplish this the labels flexibility of MAC implementations. To accomplish this the labels
MUST consist of an opaque component bound with a Label Format MUST consist of an opaque component bound with a Label Format
Specifier (LFS). The LFS component provides a mechanism for Specifier (LFS). The LFS component provides a mechanism for
identifying the structure and semantics of the opaque component. identifying the structure and semantics of the opaque component.
Meanwhile, the opaque component is the security label which will be Meanwhile, the opaque component is the security label which will be
interpreted by the MAC models. interpreted by the MAC models.
MAC models base access decisions on security attributes bound to MAC models base access decisions on security attributes bound to
subjects and objects. With a given MAC model, all systems have subjects and objects. With a given MAC model, all systems have
semantically coherent labeling - a security label MUST always mean semantically coherent labeling - a security label MUST always mean
exactly the same thing on every system. While this may not be exactly the same thing on every system. While this may not be
necessary for simple MAC models it is recommended that most label necessary for simple MAC models it is recommended that most label
formats assigned an LFS incorporate this concept into their label formats assigned an LFS incorporate this concept into their label
format. format.
Labeled NFS SHOULD define an initial negotiation scheme with the
primary aims of simplicity and completeness. This is to facilitate
practical deployment of systems without being weighed down by complex
and over-generalized global schemes. Future extensibility SHOULD
also be taken into consideration.
Labeled NFS MUST provide a means for servers and clients to identify Labeled NFS MUST provide a means for servers and clients to identify
their LFS for the purposes of authorization, security service their LFS for the purposes of authorization, security service
selection, and security label interpretation. selection, and security label interpretation.
Labeled NFS MUST provide a means for servers and clients to identify
their mode of operation (see Section 4).
A negotiation scheme SHOULD be provided, allowing systems from A negotiation scheme SHOULD be provided, allowing systems from
different label formats to agree on how they will interpret or different label formats to agree on how they will interpret or
translate each others labels. Multiple concurrent agreements may be translate each others foreign labels. Multiple concurrent agreements
current between a server and a client. may be current between a server and a client.
All security labels and related security state transferred across the All security labels and related security state transferred across the
network MUST be tagged with a valid LFS. network MUST be tagged with a valid LFS.
If the LFS supported on a system changes, it SHOULD renegotiate If the LFS supported on a system changes, the system SHOULD
agreements to reflect these changes. renegotiate agreements to reflect these changes.
If a system receives any security label or security state tagged with If a system receives any security label or security state tagged with
an LFS it does not recognize or cannot interpret, it MUST reject that an LFS it does not recognize or cannot interpret, it MUST reject that
label or state. label or state.
NFSv4.2 includes features which may cause a client to cross an LFS NFSv4.2 includes features which may cause a client to cross an LFS
boundary when accessing what appears to be a single file system. If boundary when accessing what appears to be a single file system. If
LFS negotiation is supported by the client and the server, the server LFS negotiation is supported by the client and the server, the server
SHOULD negotiate a new, concurrent agreement with the client, acting SHOULD negotiate a new, concurrent agreement with the client, acting
on behalf of the externally located source of the files. on behalf of the externally located source of the files.
Labeled NFS SHOULD define an initial negotiation scheme with the 3.4. Labeling
primary aims of simplicity and completeness. This is to facilitate
practical deployment of systems without being weighed down by complex
and over-generalized global schemes. Future extensibility SHOULD
also be taken into consideration.
3.5. Modes of Operation
In a Labeled NFS client and server interaction, we can describe three
modes of operation:
1. Full
2. Limited Server
3. Guest
These modes arise from the level of MAC functionality in the clients
and servers. The clients can be non-MAC-Functional and MAC-
Functional. The servers can be non-MAC-Functional, MAC-Aware, and
MAC-Functional.
A MAC-Functional client MUST be able to determine the level of MAC
functionality in the server. Likewise, a MAC-Functional server MUST
be able to determine whether or not a client is MAC-Functional.
3.5.1. Full Mode
The server and the client have mutually recognized MAC functionality
enabled, and full Labeled NFS functionality is extended over the
network between both client and server.
An example of an operation in full mode is as follows. On the
initial lookup, the client requests access to an object on the
server. It sends its process security context over to the server.
The server checks all relevant policies to determine if that process
context from that client is allowed to access the resource. Once
this has succeeded the object with its associated security
information is released to the client. Once the client receives the
object it determines if its policies allow the process running on the
client access to the object.
On subsequent operations where the client already has a handle for
the file, the order of enforcement is reversed. Since the client
already has the security context it may make an access decision
against its policy first. This enables the client to avoid sending
requests to the server that it knows will fail regardless of the
server's policy. If the client passes its policy checks then it
sends the request to the server where the client's process context is
used to determine if the server will release that resource to the
client. If both checks pass, the client is given the resource and
everything succeeds.
In the event that the client does not trust the server, it may opt to
use an alternate labeling mechanism regardless of the server's
ability to return security information.
3.5.2. Limited Server Mode
The server is MAC-Aware and the clients are MAC-Functional. The
server can store and transmit labels. It cannot enforce labels. The
server MUST inform clients when an object label changes for a file
the client has open.
In this mode, the server may not be aware of the format of any its
object labels. Indeed, it may service several different security
models at the same time. A client MUST process foreign labels as
discussed in Section 3.4. As with the Guest Mode, this mode's level
of trust can be degraded if non-MAC-functional clients have access to
the server.
3.5.3. Guest Mode
Only one of the server or client is MAC-Functional enabled.
In the case of the server only being MAC-Functional, the server
enforces its policy, and may selectively provide standard NFS
services to clients based on their authentication credentials and/or
associated network attributes (e.g., IP address, network interface)
according to security policy. The level of trust and access extended
to a client in this mode is configuration-specific.
In the case of the client only being MAC-Functional, the client MUST
operate as a standard NFSv4.2 client, and SHOULD selectively provide
processes access to servers based upon the security attributes of the
local process, and network attributes of the server, according to
policy. The client may also override default labeling of the remote
file system based upon these security attributes, or other labeling
methods such as mount point labeling.
In other words, Guest Mode is standard NFSv4.2 over the wire, with
the MAC-Functional system mapping the non-MAC-Functional system's
processes or objects to security labels based on other
characteristics in order to preserve its MAC guarantees.
3.6. Labeling
Implementations MUST validate security labels supplied over the Implementations MUST validate security labels supplied over the
network to ensure that they are within a set of labels permitted from network to ensure that they are within a set of labels permitted from
a specific peer, and if not, reject them. Note that a system may a specific peer, and if not, reject them. Note that a system may
permit a different set of labels to be accepted from each peer. permit a different set of labels to be accepted from each peer.
3.6.1. Client Labeling 3.4.1. Client Labeling
At the client, labeling semantics for NFS mounted file systems MUST At the client, labeling semantics for NFS mounted file systems MUST
remain consistent with those for locally mounted file systems. In remain consistent with those for locally mounted file systems. In
particular, user-level labeling operations local to the client MUST particular, user-level labeling operations local to the client MUST
be enacted locally via existing APIs, to ensure compatibility and be enacted locally via existing APIs, to ensure compatibility and
consistency for applications and libraries. consistency for applications and libraries.
Note that this does not imply any specific mechanism for conveying Note that this does not imply any specific mechanism for conveying
labels over the network. labels over the network.
When an object is newly created by the client, it will calculate the When an object is newly created by the client, it will calculate the
label for the object based on its policy. Once that is done it will label for the object based on its policy. Once that is done it will
send the request to the server which has the ability to deny the send the request to the server which has the ability to deny the
creation of the object with that label based on the server's policy. creation of the object with that label based on the server's policy.
In creating the file the server MUST ensure that the label is bound In creating the file the server MUST ensure that the label is bound
to the object before the object becomes visible to the rest of the to the object before the object becomes visible to the rest of the
system. This ensures that any access control or further labeling system. This ensures that any access control or further labeling
decisions are correct for the object. decisions are correct for the object.
3.6.2. Server Labeling 3.4.2. Server Labeling
The server MUST provide the capability for clients to retrieve The server MUST provide the capability for clients to retrieve
security labels on all exported file system objects where possible. security labels on all exported file system objects where possible.
This includes cases where only in-core and/or read-only security This includes cases where only in-core and/or read-only security
labels are available at the server for any of its exported file labels are available at the server for any of its exported file
systems. systems.
The server MUST honor the ability for a client to specify the label The server MUST honor the ability for a client to specify the label
of an object on creation. If the server is MAC enabled it may choose of an object on creation. If the server is MAC enabled it may choose
to reject the label specified by the client due to restrictions in to reject the label specified by the client due to restrictions in
the server policy. The server SHOULD not attempt to find a suitable the server policy. The server SHOULD NOT attempt to find a suitable
label for an object in event of different labeling rules on its end. label for an object in event of different labeling rules on its end.
The server is allowed to translate the label but SHOULD not change The server is allowed to translate the label but SHOULD NOT change
the semantic meaning of the label. the semantic meaning of the label.
3.7. Policy Enforcement 3.5. Policy Enforcement
The MAC-Functional client determines if a process request is sent to The MAC-Functional client determines if a process request is sent to
the remote server. Upon a successful response from the server, it the remote server. Upon a successful response from the server, it
must use its own policies on the object's security labels to must use its own policies on the object's security labels to
determine if the process can be given access. The client SHOULD not determine if the process can be given access. The client SHOULD NOT
need to be cognizant if the server is either a Limited Server or need to be cognizant if the server is either a Limited Server or
fully MAC-Functional. fully MAC-Functional.
3.7.1. Client Enforcement 3.5.1. Client Enforcement
The client MUST apply its own policy to remotely located objects, The client MUST apply its own policy to remotely located objects,
using security labels for the objects obtained from the server. It using security labels for the objects obtained from the server. It
MUST be possible to configure the maximum length of time a client may MUST be possible to configure the maximum length of time a client may
cache state regarding remote labels before re-validating that state cache state regarding remote labels before re-validating that state
with the server. with the server.
If the server's policy changes, the client MUST flush all object If the server's policy changes, the client MUST flush all object
state back to the server. The server MUST ensure that any flushed state back to the server. The server MUST ensure that any flushed
state received is consistent with current policy before committing it state received is consistent with current policy before committing it
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Any local security state associated with cached or delegated objects Any local security state associated with cached or delegated objects
MUST also be flushed back to the server when any other state of the MUST also be flushed back to the server when any other state of the
objects is required to be flushed back. objects is required to be flushed back.
The implication here is that if the client holds a delegation on an The implication here is that if the client holds a delegation on an
object, then it enforces policy to local changes based on the object object, then it enforces policy to local changes based on the object
label it got from the server. When it tries to commit those changes label it got from the server. When it tries to commit those changes
to the server, it SHOULD be prepared for the server to reject those to the server, it SHOULD be prepared for the server to reject those
changes based on the policies of the server. changes based on the policies of the server.
3.7.2. Server Enforcement 3.5.2. Server Enforcement
A MAC-Functional server MUST enforce its security policy over all A MAC-Functional server MUST enforce its security policy over all
exported objects, for operations which originate both locally and exported objects, for operations which originate both locally and
remotely. remotely.
Requests from authenticated clients MUST be processed using security Requests from authenticated clients MUST be processed using security
labels and credentials supplied by the client as if they originated labels and credentials supplied by the client as if they originated
locally. locally.
As with labeling, the system MUST also take into account any other As with labeling, the system MUST also take into account any other
volatile client security state, such as a change in process security volatile client security state, such as a change in process security
context via dynamic transition. Access decisions SHOULD also be made context via dynamic transition. Access decisions SHOULD also be made
based upon the current client security label accessing the object, based upon the current client security label accessing the object,
rather than the security label which opened it, if different. rather than the security label which opened it, if different.
The server SHOULD recall delegation of an object if the object's The server SHOULD recall delegation of an object if the object's
security label changes. security label changes.
3.8. Namespace Access 3.6. Namespace Access
The server SHOULD provide a means to authorize selective access to The server SHOULD provide a means to authorize selective access to
the exported file system namespace based upon client credentials and the exported file system namespace based upon client credentials and
according to security policy. according to security policy.
This is a common requirement of MLS-enabled systems, which often need This is a common requirement of MLS-enabled systems, which often need
to present selective views of namespaces based upon the clearances of to present selective views of namespaces based upon the clearances of
the subjects. the subjects.
3.9. Upgrading Existing Server 3.7. Upgrading Existing Server
Note that under the MAC model, all objects MUST have labels. Note that under the MAC model, all objects MUST have labels.
Therefore, if an existing server is upgraded to include Labeled NFS Therefore, if an existing server is upgraded to include Labeled NFS
support, then it is the responsibility of the security system to support, then it is the responsibility of the security system to
define the behavior for existing objects. define the behavior for existing objects.
4. Use Cases 4. Modes of Operation
In a Labeled NFS client and server interaction, we can describe three
modes of operation:
1. Full
2. Limited Server
3. Guest
These modes arise from the level of MAC functionality in the clients
and servers. The clients can be non-MAC-Functional and MAC-
Functional. The servers can be non-MAC-Functional, MAC-Aware, and
MAC-Functional.
A MAC-Functional client MUST be able to determine the level of MAC
functionality in the server. Likewise, a MAC-Functional server MUST
be able to determine whether or not a client is MAC-Functional. As
discussed in Section 3.3, the protocol MUST provide for the client
and server to make those determinations.
4.1. Full Mode
The server and the client have mutually recognized MAC functionality
enabled, and full Labeled NFS functionality is extended over the
network between both client and server.
An example of an operation in full mode is as follows. On the
initial lookup, the client requests access to an object on the
server. It sends its process security context over to the server.
The server checks all relevant policies to determine if that process
context from that client is allowed to access the resource. Once
this has succeeded the object with its associated security
information is released to the client. Once the client receives the
object it determines if its policies allow the process running on the
client access to the object.
On subsequent operations where the client already has a handle for
the file, the order of enforcement is reversed. Since the client
already has the security context it may make an access decision
against its policy first. This enables the client to avoid sending
requests to the server that it knows will fail regardless of the
server's policy. If the client passes its policy checks then it
sends the request to the server where the client's process context is
used to determine if the server will release that resource to the
client. If both checks pass, the client is given the resource and
everything succeeds.
In the event that the client does not trust the server, it may opt to
use an alternate labeling mechanism regardless of the server's
ability to return security information.
4.2. Limited Server Mode
The server is MAC-Aware and the clients are MAC-Functional. The
server can store and transmit labels. It cannot enforce labels. The
server MUST inform clients when an object label changes for a file
the client has open.
In this mode, the server may not be aware of the format of any its
object labels. Indeed, it may service several different security
models at the same time. A client MUST process foreign labels as
discussed in Section 3.3. As with the Guest Mode, this mode's level
of trust can be degraded if non-MAC-functional clients have access to
the server.
4.3. Guest Mode
Only one of the server or client is MAC-Functional enabled.
In the case of the server only being MAC-Functional, the server
enforces its policy, and may selectively provide standard NFS
services to clients based on their authentication credentials and/or
associated network attributes (e.g., IP address, network interface)
according to security policy. The level of trust and access extended
to a client in this mode is configuration-specific.
In the case of the client only being MAC-Functional, the client MUST
operate as a standard NFSv4.2 (see [I-D.ietf-nfsv4-minorversion2])
client, and SHOULD selectively provide processes access to servers
based upon the security attributes of the local process, and network
attributes of the server, according to policy. The client may also
override default labeling of the remote file system based upon these
security attributes, or other labeling methods such as mount point
labeling.
In other words, Guest Mode is standard NFSv4.2 over the wire, with
the MAC-Functional system mapping the non-MAC-Functional system's
processes or objects to security labels based on other
characteristics in order to preserve its MAC guarantees.
5. Use Cases
MAC labeling is meant to allow NFSv4.2 to be deployed in site MAC labeling is meant to allow NFSv4.2 to be deployed in site
configurable security schemes. The LFS and opaque data scheme allows configurable security schemes. The LFS and opaque data scheme allows
for flexibility to meet these different implementations. In this for flexibility to meet these different implementations. In this
section, we provide some examples of how NFSv4.2 could be deployed to section, we provide some examples of how NFSv4.2 could be deployed to
meet existing needs. This is not an exhaustive listing. meet existing needs. This is not an exhaustive listing.
4.1. Full MAC labeling support for remotely mounted filesystems 5.1. Full MAC labeling support for remotely mounted filesystems
In this case, we assume a local networked environment where the In this case, we assume a local networked environment where the
servers and clients are under common administrative control. All servers and clients are under common administrative control. All
systems in this network have the same MAC implementation and systems in this network have the same MAC implementation and
semantically identical MAC security labels for objects (i.e. labels semantically identical MAC security labels for objects (i.e. labels
mean the same thing on different systems, even if the policies on mean the same thing on different systems, even if the policies on
each system may differ to some extent). Clients will be able to each system may differ to some extent). Clients will be able to
apply fine-grained MAC policy to objects accessed via NFS mounts, and apply fine-grained MAC policy to objects accessed via NFS mounts, and
thus improve the overall consistency of MAC policy application within thus improve the overall consistency of MAC policy application within
this environment. this environment.
An example of this case would be where user home directories are An example of this case would be where user home directories are
remotely mounted, and fine-grained MAC policy is implemented to remotely mounted, and fine-grained MAC policy is implemented to
protect, for example, private user data from being read by malicious protect, for example, private user data from being read by malicious
web scripts running in the user's browser. With Labeled NFS, fine- web scripts running in the user's browser. With Labeled NFS, fine-
grained MAC labeling of the user's files will allow the MAC policy to grained MAC labeling of the user's files will allow the MAC policy to
be implemented and provide the desired protection. be implemented and provide the desired protection.
4.2. MAC labeling of virtual machine images stored on the network 5.2. MAC labeling of virtual machine images stored on the network
Virtualization is now a commonly implemented feature of modern Virtualization is now a commonly implemented feature of modern
operating systems, and there is a need to ensure that MAC security operating systems, and there is a need to ensure that MAC security
policy is able to protect virtualized resources. A common policy is able to protect virtualized resources. A common
implementation scheme involves storing virtualized guest filesystems implementation scheme involves storing virtualized guest filesystems
on a networked server, which are then mounted remotely by guests upon on a networked server, which are then mounted remotely by guests upon
instantiation. In this case, there is a need to ensure that the instantiation. In this case, there is a need to ensure that the
local guest kernel is able to access fine-grained MAC labels on the local guest kernel is able to access fine-grained MAC labels on the
remotely mounted filesystem so that its MAC security policy can be remotely mounted filesystem so that its MAC security policy can be
applied. applied.
4.3. International Traffic in Arms Regulations (ITAR) 5.3. International Traffic in Arms Regulations (ITAR)
The International Traffic in Arms Regulations (ITAR) is put forth by The International Traffic in Arms Regulations (ITAR) is put forth by
the United States Department of State, Directorate of Defense and the United States Department of State, Directorate of Defense and
Trade Controls. ITAR places strict requirements on the export and Trade Controls. ITAR places strict requirements on the export and
thus access of defense articles and defense services. Organizations thus access of defense articles and defense services. Organizations
that manage projects with articles and services deemed as within the that manage projects with articles and services deemed as within the
scope of ITAR must ensure the regulations are met. The regulations scope of ITAR must ensure the regulations are met. The regulations
require an assurance that ITAR information is accessed on a need-to- require an assurance that ITAR information is accessed on a need-to-
know basis, thus requiring strict, centrally managed access controls know basis, thus requiring strict, centrally managed access controls
on items labeled as ITAR. Additionally, organizations must be able on items labeled as ITAR. Additionally, organizations must be able
to prove that the controls were adequately maintained and that to prove that the controls were adequately maintained and that
foreign nationals were not permitted access to these defense articles foreign nationals were not permitted access to these defense articles
or service. ITAR control applicability may be dynamic; information or service. ITAR control applicability may be dynamic; information
may become subject to ITAR after creation (e.g., when the defense may become subject to ITAR after creation (e.g., when the defense
implications of technology are recognized). implications of technology are recognized).
4.4. Legal Hold/eDiscovery 5.4. Legal Hold/eDiscovery
Increased cases of legal holds on electronic sources of information Increased cases of legal holds on electronic sources of information
(ESI) have resulted in organizations taking a pro-active approach to (ESI) have resulted in organizations taking a pro-active approach to
reduce the scope and thus costs associated with these activities. reduce the scope and thus costs associated with these activities.
ESI Data Maps are increasing in use and require support in operating ESI Data Maps are increasing in use and require support in operating
systems to strictly manage access controls in the case of a legal systems to strictly manage access controls in the case of a legal
hold. The sizeable quantity of information involved in a legal hold. The sizeable quantity of information involved in a legal
discovery request may preclude making a copy of the information to a discovery request may preclude making a copy of the information to a
separate system that manages the legal hold on the copies; this separate system that manages the legal hold on the copies; this
results in a need to enforce the legal hold on the original results in a need to enforce the legal hold on the original
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data map exercise is conducted with controls being applied at the data map exercise is conducted with controls being applied at the
time of a hold or labels may be applied to data sets during an time of a hold or labels may be applied to data sets during an
eDiscovery exercise to ensure the data protections are adequate eDiscovery exercise to ensure the data protections are adequate
during the legal hold period. during the legal hold period.
Note that this use case requires multi-attribute labels, as both Note that this use case requires multi-attribute labels, as both
information sensitivity (e.g., to disclosure) and information information sensitivity (e.g., to disclosure) and information
criticality (e.g., to continued business operations) need to be criticality (e.g., to continued business operations) need to be
captured. captured.
4.5. Simple security label storage 5.5. Simple security label storage
In this case, a mixed and loosely administered network is assumed, In this case, a mixed and loosely administered network is assumed,
where nodes may be running a variety of operating systems with where nodes may be running a variety of operating systems with
different security mechanisms and security policies. It is desired different security mechanisms and security policies. It is desired
that network file servers be simply capable of storing and retrieving that network file servers be simply capable of storing and retrieving
MAC security labels for clients which use such labels. The Labeled MAC security labels for clients which use such labels. The Labeled
NFS protocol would be implemented here solely to enable transport of NFS protocol would be implemented here solely to enable transport of
MAC security labels across the network. It should be noted that in MAC security labels across the network. It should be noted that in
such an environment, overall security cannot be as strongly enforced such an environment, overall security cannot be as strongly enforced
as when the server is also enforcing, and that this scheme is aimed as when the server is also enforcing, and that this scheme is aimed
at allowing MAC-capable clients to function with its MAC security at allowing MAC-capable clients to function with its MAC security
policy enabled rather than perhaps disabling it entirely. policy enabled rather than perhaps disabling it entirely.
4.6. Diskless Linux 5.6. Diskless Linux
A number of popular operating system distributions depend on a A number of popular operating system distributions depend on a
mandatory access control (MAC) model to implement a kernel-enforced mandatory access control (MAC) model to implement a kernel-enforced
security policy. Typically, such models assign particular roles to security policy. Typically, such models assign particular roles to
individual processes, which limit or permit performing certain individual processes, which limit or permit performing certain
operations on a set of files, directories, sockets, or other objects. operations on a set of files, directories, sockets, or other objects.
While the enforcing of the policy is typically a matter for the While the enforcing of the policy is typically a matter for the
diskless NFS client itself, the filesystem objects in such models diskless NFS client itself, the filesystem objects in such models
will typically carry MAC labels that are used to define policy on will typically carry MAC labels that are used to define policy on
access. These policies may, for instance, describe privilege access. These policies may, for instance, describe privilege
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For instance on a SYSV compatible system, if the 'init' process For instance on a SYSV compatible system, if the 'init' process
spawns a process that attempts to start the 'NetworkManager' spawns a process that attempts to start the 'NetworkManager'
executable, there may be a policy that sets up a role transition if executable, there may be a policy that sets up a role transition if
the 'init' process and 'NetworkManager' file labels match a the 'init' process and 'NetworkManager' file labels match a
particular rule. Without this role transition, the process may find particular rule. Without this role transition, the process may find
itself having insufficient privileges to perform its primary job of itself having insufficient privileges to perform its primary job of
configuring network interfaces. configuring network interfaces.
In setups of this type, a lot of the policy targets (such as sockets In setups of this type, a lot of the policy targets (such as sockets
or privileged system calls) are entirely local to the client. The or privileged system calls) are entirely local to the client. The
use of RPCSEC_GSSv3 ([4]) for enforcing compliance at the server use of RPCSEC_GSSv3 ([rpcsecgssv3]) for enforcing compliance at the
level is therefore of limited value. The ability to permanently server level is therefore of limited value. The ability to
label files and have those labels read back by the client is, permanently label files and have those labels read back by the client
however, crucial to the ability to enforce that policy. is, however, crucial to the ability to enforce that policy.
4.7. Multi-Level Security 5.7. Multi-Level Security
In a MLS system objects are generally assigned a sensitivity level In a MLS system objects are generally assigned a sensitivity level
and a set of compartments. The sensitivity levels within the system and a set of compartments. The sensitivity levels within the system
are given an order ranging from lowest to highest classification are given an order ranging from lowest to highest classification
level. Read access to an object is allowed when the sensitivity level. Read access to an object is allowed when the sensitivity
level of the subject "dominates" the object it wants to access. This level of the subject "dominates" the object it wants to access. This
means that the sensitivity level of the subject is higher than that means that the sensitivity level of the subject is higher than that
of the object it wishes to access and that its set of compartments is of the object it wishes to access and that its set of compartments is
a super-set of the compartments on the object. a super-set of the compartments on the object.
The rest of the section will just use sensitivity levels. In general The rest of the section will just use sensitivity levels. In general
the example is a client that wishes to list the contents of a the example is a client that wishes to list the contents of a
directory. The system defines the sensitivity levels as Unclassified directory. The system defines the sensitivity levels as Unclassified
(U), Secret (S), and Top Secret (TS). The directory to be searched (U), Secret (S), and Top Secret (TS). The directory to be searched
is labeled Top Secret which means access to read the directory will is labeled Top Secret which means access to read the directory will
only be granted if the subject making the request is also labeled Top only be granted if the subject making the request is also labeled Top
Secret. Secret.
4.7.1. Full Mode - MAC-functional Client and Server 5.7.1. Full Mode - MAC-functional Client and Server
In the first part of this example a process on the client is running In the first part of this example a process on the client is running
at the Secret level. The process issues a readdir() system call at the Secret level. The process issues a readdir() system call
which enters the kernel. Before translating the readdir() system which enters the kernel. Before translating the readdir() system
call into a request to the NFSv4.2 server the host operating system call into a request to the NFSv4.2 server the host operating system
will consult the MAC module to see if the operation is allowed. will consult the MAC module to see if the operation is allowed.
Since the process is operating at Secret and the directory to be Since the process is operating at Secret and the directory to be
accessed is labeled Top Secret the MAC module will deny the request accessed is labeled Top Secret the MAC module will deny the request
and an error code is returned to user space. and an error code is returned to user space.
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same. In the event that they were running different policies a same. In the event that they were running different policies a
translation of the labels might be needed. In this case it could be translation of the labels might be needed. In this case it could be
possible for a check to pass on the client and fail on the server. possible for a check to pass on the client and fail on the server.
The server may consider additional information when making its policy The server may consider additional information when making its policy
decisions. For example the server could determine that a certain decisions. For example the server could determine that a certain
subnet is only cleared for data up to Secret classification. If that subnet is only cleared for data up to Secret classification. If that
constraint was in place for the example above the client would still constraint was in place for the example above the client would still
succeed, but the server would fail since the client is asserting a succeed, but the server would fail since the client is asserting a
label that it is not able to use (Top Secret on a Secret network). label that it is not able to use (Top Secret on a Secret network).
4.7.2. MAC-Functional Client 5.7.2. MAC-Functional Client
In these scenarios, the server is either non-MAC-Aware or MAC-Aware. In these scenarios, the server is either non-MAC-Aware or MAC-Aware.
The actions of the client will depend whether it is configured to The actions of the client will depend whether it is configured to
treat the MAC-Aware server in the same manner as the non-MAC-Aware treat the MAC-Aware server in the same manner as the non-MAC-Aware
one. I.e., does it utilize the approach presented in Section 3.5.3 one. I.e., does it utilize the approach presented in Section 4.3 or
or does it allow the MAC-Aware server to return labels? does it allow the MAC-Aware server to return labels?
With a client that is MAC-Functional and using the example in the With a client that is MAC-Functional and using the example in the
previous section, the result should be the same. The one difference previous section, the result should be the same. The one difference
is that all decisions are made on the client. is that all decisions are made on the client.
4.7.2.1. MAC-Aware Server 5.7.2.1. MAC-Aware Server
A process on the client labeled Secret wishes to access a directory A process on the client labeled Secret wishes to access a directory
labeled Top Secret on the server. This is denied since Secret does labeled Top Secret on the server. This is denied since Secret does
not dominate Top Secret. Note that there will be NFSv4.2 operations not dominate Top Secret. Note that there will be NFSv4.2 operations
issued that return an object label for the client to process. issued that return an object label for the client to process.
Note that in this scenario, all of the clients must be MAC- Note that in this scenario, all of the clients must be MAC-
Functional. A single client which does not do its access control Functional. A single client which does not do its access control
checks would violate the model. checks would violate the model.
4.7.2.2. Non-MAC-Aware Server 5.7.2.2. Non-MAC-Aware Server
A process on the client labeled Secret wishes to access a directory A process on the client labeled Secret wishes to access a directory
which the client's policies label as Top Secret on the server. This which the client's policies label as Top Secret on the server. This
is denied since Secret does not dominate Top Secret. Note that there is denied since Secret does not dominate Top Secret. Note that there
will not be NFSv4.2 operations issued. If the process had instead a will not be NFSv4.2 operations issued. If the process had instead a
Top Secret process label, the client would issue NFSv4.2 operations Top Secret process label, the client would issue NFSv4.2 operations
to access the directory on the server. to access the directory on the server.
4.7.3. MAC-Functional Server 5.7.3. MAC-Functional Server
With a MAC-Functional server and a client which is not, the client With a MAC-Functional server and a client which is not, the client
behaves as if it were in a normal NFSv4.2 environment. Since the behaves as if it were in a normal NFSv4.2 environment. Since the
process on the client does not provide a security attribute the process on the client does not provide a security attribute the
server must define a mechanism for labeling all requests from a server must define a mechanism for labeling all requests from a
client. Assume that the server is using the same criteria used in client. Assume that the server is using the same criteria used in
the first example. The server sees the request as coming from a the first example. The server sees the request as coming from a
subnet that is a Secret network. The server determines that all subnet that is a Secret network. The server determines that all
clients on that subnet will have their requests labeled with Secret. clients on that subnet will have their requests labeled with Secret.
Since the directory on the server is labeled Top Secret and Secret Since the directory on the server is labeled Top Secret and Secret
does not dominate Top Secret the server would fail the request with does not dominate Top Secret the server would fail the request with
NFS4ERR_ACCESS. NFS4ERR_ACCESS.
5. Security Considerations 6. Security Considerations
5.1. Trust Needed for a Community 6.1. Trust Needed for a Community
Labeled NFS is a transport mechanism for labels, a storage Labeled NFS is a transport mechanism for labels, a storage
requirement for labels, and a definition of how to interpret labels. requirement for labels, and a definition of how to interpret labels.
It defines the responsibilities of the client and the server in the It defines the responsibilities of the client and the server in the
various permutations of being MAC-Functional. It does not however various permutations of being MAC-Functional. It does not however
dictate in any manner whether assumptions can be made about other dictate in any manner whether assumptions can be made about other
entities in the relationship. For example, it does not define entities in the relationship. For example, it does not define
whether a MAC-Functional client can demand that a MAC-Aware server whether a MAC-Functional client can demand that a MAC-Aware server
only accept requests from other MAC-Functional clients. That is a only accept requests from other MAC-Functional clients. That is a
policy based in a MAC model and this document does not impose policy based in a MAC model and this document does not impose
policies on systems. policies on systems.
As the requirement is a policy, it can be met with the use of a MAC As the requirement is a policy, it can be met with the use of a MAC
model. Let L be a LFS which implements the Limited Server mode, model. Let L be a LFS which implements the Limited Server mode,
i.e., a MAC-Aware server connected to MAC-Functional clients. Then a i.e., a MAC-Aware server connected to MAC-Functional clients. Then a
new LFS L' can be created which has the additional policy that the new LFS L' can be created which has the additional policy that the
MAC-Aware server MUST not accept any requests from a non-MAC- MAC-Aware server MUST NOT accept any requests from a non-MAC-
Functional client. Functional client.
5.2. Guest Modes 6.2. Guest Modes
When either the client or server is operating in guest mode it is When either the client or server is operating in guest mode it is
important to realize that one side is not enforcing MAC protections. important to realize that one side is not enforcing MAC protections.
Alternate methods are being used to handle the lack of MAC support Alternate methods are being used to handle the lack of MAC support
and care should be taken to identify and mitigate threats from and care should be taken to identify and mitigate threats from
possible tampering outside of these methods. possible tampering outside of these methods.
5.3. MAC-Functional Client Configuration 6.3. MAC-Functional Client Configuration
We defined a MAC model as a access control decision made on a system We defined a MAC model as a access control decision made on a system
which normal users do not have the ability to override policies (see which normal users do not have the ability to override policies (see
Section 1). If the process labels are created solely on the client, Section 1). If the process labels are created solely on the client,
then if a malicious user has sufficient access on that client, the then if a malicious user has sufficient access on that client, the
Labeled NFS model is compromised. Note that this is no different Labeled NFS model is compromised. Note that this is no different
from: from:
o current implementations in which the server uses policies to o current implementations in which the server uses policies to
effectively determine the object label for requests from the effectively determine the object label for requests from the
client, or client, or
o local decisions made on the client by the MAC security system. o local decisions made on the client by the MAC security system.
The server must either explicitly trust the client (as in [7]) or the The server must either explicitly trust the client (as in [SENFSV3])
MAC model should enforce that users cannot override policies, perhaps or the MAC model should enforce that users cannot override policies,
via a externally managed source. perhaps via a externally managed source.
Once the labels leave the client, they can be protected by the Once the labels leave the client, they can be protected by the
transport mechanism as described in Section 3.3. transport mechanism as described in Section 3.2.
6. IANA Considerations
It is requested that IANA creates a registry of Label Formats to
describe the syntactic format and semantics of the security label
(see [2]).
7. References 7. References
7.1. Normative References 7.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Levels", March 1997. Requirement Levels", March 1997.
[2] Quigley, D. and J. Lu, "Registry Specification for MAC Security 7.2. Informative References
Label Formats", draft-quigley-label-format-registry (work in
progress), 2011.
[3] Haynes, T., "NFS Version 4 Minor Version 2", [DTOS] Smalley, S., "The Distributed Trusted Operating System
draft-ietf-nfsv4-minorversion2-08 (Work In Progress), (DTOS) Home Page", <http://www.cs.utah.edu/flux/fluke/
March 2011. html/dtos/HTML/dtos.html>.
[4] Haynes, T. and N. Williams, "Remote Procedure Call (RPC) [I-D.ietf-nfsv4-minorversion2]
Security Version 3", draft-williams-rpcsecgssv3 (work in Haynes, T. and D. Noveck, "NFS Version 4 Minor Version 2",
progress), 2011. draft-ietf-nfsv4-minorversion2-19 (Work In Progress),
March 2013.
7.2. Informative References [RH_MLS] "Section 46.6. Multi-Level Security (MLS) of Deployment
Guide: Deployment, configuration and administration of Red
Hat Enterprise Linux 5, Edition 6", 2011.
[5] "Section 46.6. Multi-Level Security (MLS) of Deployment Guide: [SENFSV3] Carter, J., "Implementing SELinux Support for NFS", <http:
Deployment, configuration and administration of Red Hat //www.nsa.gov/research/_files/selinux/papers/nfsv3.pdf>.
Enterprise Linux 5, Edition 6", 2011.
[6] Smalley, S., "The Distributed Trusted Operating System (DTOS) [lfsreg] Quigley, D. and J. Lu, "Registry Specification for MAC
Home Page", Security Label Formats",
<http://www.cs.utah.edu/flux/fluke/html/dtos/HTML/dtos.html>. draft-quigley-label-format-registry (work in progress),
2011.
[7] Carter, J., "Implementing SELinux Support for NFS", [rpcsecgssv3]
<http://www.nsa.gov/research/_files/selinux/papers/nfsv3.pdf>. Haynes, T. and N. Williams, "Remote Procedure Call (RPC)
Security Version 3", draft-williams-rpcsecgssv3 (work in
progress), 2011.
Appendix A. Acknowledgments Appendix A. Acknowledgments
David Quigley was the early energy in motivating the entire Labeled David Quigley was the early energy in motivating the entire Labeled
NFS effort. NFS effort.
James Morris, Jarrett Lu, and Stephen Smalley all were key James Morris, Jarrett Lu, and Stephen Smalley all were key
contributors to both early versions of this document and to many contributors to both early versions of this document and to many
conference calls. conference calls.
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[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]
Author's Address Author's Address
Thomas Haynes (editor) Thomas Haynes
NetApp NetApp
9110 E 66th St 495 E Java Dr
Tulsa, OK 74133 Sunnyvale, CA 95054
USA USA
Phone: +1 918 307 1415 Phone: +1 408 419 3018
Email: thomas@netapp.com Email: thomas@netapp.com
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