Network Working Group D. Nelson
Internet-Draft Elbrys Networks, Inc.
Intended status: Standards Track G. Weber
Expires: January 8, 2008 Cisco Systems, Inc.
July 7, 2007
Remote Authentication Dial-In User Service (RADIUS) Authorization for
Network Access Server (NAS) Management
draft-nelson-radius-management-authorization-05.txt
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Copyright (C) The IETF Trust (2007).
Abstract
This document describes Remote Authentication Dial-In User Service
(RADIUS) attributes for the authorization and service provisioning of
local and remote management of embedded systems and other managed
entities, generally referred to as Network Access Servers (NASes).
Specific provisions are made for remote management via framed
management protocols, and for more granular levels of access rights
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and management privileges.
Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction and Rationale . . . . . . . . . . . . . . . . . . 3
3. Provisions for Framed Management . . . . . . . . . . . . . . . 3
4. Provisions for Granular Management Access Rights . . . . . . . 4
5. Provisions for Secure CLI Management Access . . . . . . . . . 4
6. New Values for Existing RADIUS Attributes . . . . . . . . . . 4
6.1. Service-Type . . . . . . . . . . . . . . . . . . . . . . . 4
7. New RADIUS Attributes . . . . . . . . . . . . . . . . . . . . 5
7.1. Framed-Management-Protocol . . . . . . . . . . . . . . . . 5
7.2. Transport-Protocol . . . . . . . . . . . . . . . . . . . . 6
7.3. Management-Policy-Id . . . . . . . . . . . . . . . . . . . 7
8. Examples of attribute groupings . . . . . . . . . . . . . . . 8
9. Diameter Translation Considerations . . . . . . . . . . . . . 9
10. Proxy Operation Considerations . . . . . . . . . . . . . . . . 10
11. Table of Attributes . . . . . . . . . . . . . . . . . . . . . 11
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
13. Security Considerations . . . . . . . . . . . . . . . . . . . 12
14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
15. Normative References . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
Intellectual Property and Copyright Statements . . . . . . . . . . 15
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1. Terminology
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 [RFC2119].
This document uses terminology from RFC 2865 [RFC2865] and RFC 2866
[RFC2866].
2. Introduction and Rationale
The remote management Service-Types defined in RFC 2865 [RFC2865]
include NAS-Prompt and Administrative. Both of these services
provide access to the interactive, ASCII-text, Command Line Interface
(CLI) of the managed entity. Current deployments of network
equipment include in the managed entity non-CLI, framed-protocol
forms of management, such as HTTP, HTTPS, and SNMP. In addition,
network devices often support more privilege levels for management
access than the two levels supported by NAS-Prompt (non-privileged)
and Administrative (privileged). To address these issues, attributes
for framed management protocols, management protocol security levels,
and management access privilege levels are described.
3. Provisions for Framed Management
Framed Management means management of an entity by means of a non-
interactive, non-CLI-style method. The management information is
typically formatted in a binary or textual protocol, such as HTTP or
SNMP. While remote management by interactive CLI sessions are
carried over protocols, such as Telnet, Rlogin, and SSH, these
protocols are primarily for the delivery of terminal, or pseudo-TTY
services. Command Line Interface, Menu Interface, or other ASCII
(UTF-8) terminal emulation interfaces are not considered to be Framed
Management protocols, as used in this document. Examples of Framed
Management protocols include HTTP, HTTPS, and SNMP.
To support the authorization and provisioning of Framed Management
access to managed entities, this document introduces a new value for
the Service-Type attribute [RFC2865], and one new attribute. The new
value for the Service-Type attribute is Framed-Management. The
definition of this service is the provisioning of remote device
management via a Framed Management protocol, as described in this
section. The new attribute is Framed-Management-Protocol, the value
of which specifies a particular protocol for use in the remote
management session.
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4. Provisions for Granular Management Access Rights
One new attribute is introduced in this document in support of
granular management access rights or command privilege levels. The
Management-Policy-Id attribute is used to contain the name of a
management access rights policy of local scope. This attribute
functions similarly to Filter-ID. It is a string variable containing
policy name of local scope. The provisioning of the rules invoked by
application of this management policy is by means outside the scope
of this document, such as by MIB objects.
The local application of the Management-Policy-Id within the managed
entity may take the form of (a) one of an enumeration of command
privilege levels, (b) a mapping into an SNMP View Based Access
Control Method (VACM) table [RFC3415], or (c) some other set of
management access policy rules that is mutually understood by the
managed entity and the remote management application. Examples are
given in Section 8.
5. Provisions for Secure CLI Management Access
To provide for the authorization and provisioning of secure Command
Line Access management methods, via a secure transport protocol, one
new attribute is introduced in this document, Transport-Protocol.
The value of this attributes is an enumeration of secure transport
protocols that may be required for the provisioning of NAS-Prompt,
Administrative or Framed-Management service.
6. New Values for Existing RADIUS Attributes
6.1. Service-Type
This document defines one new value for an existing RADIUS attribute.
The Service-Type attribute is defined in Section 5.6 of RFC 2865
[RFC2865], as follows:
This Attribute indicates the type of service the user has requested,
or the type of service to be provided. It MAY be used in both
Access-Request and Access-Accept packets.
A NAS is not required to implement all of these service types, and
MUST treat unknown or unsupported Service-Types as though an Access-
Reject had been received instead.
A summary of the Service-Type Attribute format is shown below.
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The fields are transmitted from left to right.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Value
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Value (cont) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
6 for Service-Type.
Length
6 Value
The Value field is four octets.
This document defines one new value for the Service-Type
attribute.
(TBA) Framed-Management
The semantics of the Framed-Management service are as follows:
Framed-Management A framed protocol session should be started
for a remote management user or application,
such as HTTP or SNMP.
7. New RADIUS Attributes
This document defines three new RADIUS attributes related to remote
management authorization.
7.1. Framed-Management-Protocol
The Framed-Management-Protocol attribute indicates the protocol to be
used for framed management access. It MAY be used in both Access-
Request and Access-Accept packets.
A summary of the Framed-Management-Protocol Attribute format is shown
below. The fields are transmitted from left to right.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Value
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Value (cont) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
(TBA) for Framed-Management-Protocol.
Length
6
Value
The Value field is four octets.
1 SNMP-Transport-Model
2 HTTP
3 HTTPS/TLS
4 SFTP (via SSH)
5 SCP (via SSH)
7.2. Transport-Protocol
The Transport-Protocol attribute indicates the mandated secure
transport protocol for use with framed- or non-framed management
access sessions. It MAY be used in both Access-Request and Access-
Accept packets. This attribute MAY be used in conjunction with other
managemetn access provisioning attributes.
When a secure form of Non-Framed management access is specified, for
example Telnet carried within Secure Shell (SSH), for access to the
interactive CLI prompt of the NAS, it generally means that the
terminal emulation session is encapsulated in some form of protected
application transport, or tunnel. It may also mean that an explicit
secure mode of operation is required, when the terminal emulation
access protocol contains an intrinsic secure mode of operation.
This attribute may be used with Framed access for SNMP secure
Tranport Models to specify a specific transport protocol.
A summary of the Transport-Protocol Attribute format is shown below.
The fields are transmitted from left to right.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Value
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Value (cont) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
(TBA) for Transport-Protocol.
Length
6
Value
The Value field is four octets.
1 None
2 Secure Shell (SSH)
3 Transport Layer Security (TLS)
7.3. Management-Policy-Id
The Management-Policy-Id attribute indicates the name of the
management access policy for this user. Zero or more Management-
Policy-Id attributes MAY be sent in an Access-Accept packet.
Identifying a policy by name allows the policy to be used on
different NASes without regard to implementation details.
Multiple forms of management access rules may be expressed by the
underlying named policy, the definition of which is beyond the scope
of this document. The management access policy MAY be applied
contextually, based on the nature of the management access method.
For example, some named policies may only be valid for application to
NAS-Prompt services and some other policies may only be valid for
application to SMNPv3 services.
The management access policy named in this attribute, received in an
Access-Accept packet, MUST be applied to the session authorized by
the Access-Accept. If the policy name is unknown, or the policy
rules are incorrectly formatted, the NAS SHOULD treat the packet as
if it had been an Access-Reject.
A summary of the Management-Policy-Id Attribute format is shown
below. The fields are transmitted from left to right.
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0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
| Type | Length | Text ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Type
(TBA) for Management-Policy-Id.
Length
>= 3
Text
The Text field is one or more octets, and its contents are
implementation dependent. It is intended to be human readable and
MUST NOT affect operation of the protocol. It is recommended that
the message contain UTF-8 encoded 10646 [RFC2279] characters.
8. Examples of attribute groupings
1. CLI access, via local console or telnet, to the "super-user"
access level:
* Service-Type (6) = Administrative (6)
* Transport-Protocol (xx) = None (1)
2. CLI access, via SSH/telnet, to the non-privileged user access
level:
* Service-Type (6) = NAS-Prompt (7)
* Transport-Protocol (xx) = SSH (2)
3. CLI access, via SSH/telnet, to a custom management access level,
defined by a policy:
* Service-Type (6) = NAS-Prompt (7)
* Transport-Protocol (xx) = SSH (2)
* Management-Policy-Id (xx) = "Network Administrator"
4. SNMPv3 access, using a custom VACM View, defined by a policy:
* Service-Type (6) = Framed-Management (xx)
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* Framed-Management-Protocol (xx) = SNMP-Transport-Model (3)
* Management-Policy-Id (xx) = "SNMP Network Administrator View"
5. SNMP secure Transport Model access, using the Secure Shell
Transport Model:
* Service-Type (6) = Framed-Management (xx)
* Framed-Management-Protocol (xx) = SNMP-Transport-Model (3)
* Transport-Protocol (xx) = SSH (2)
6. Web (HTTP) access:
* Service-Type (6) = Framed-Management (xx)
* Framed-Management-Protocol (xx) = HTTP (4)
7. Secure web access, using a custom management access level,
defined by a policy:
* Service-Type (6) = Framed-Management (xx)
* Framed-Management-Protocol (xx) = HTTPS (5)
* Transport-Protocol (xx) = TLS (3)
* Management-Policy-Id (xx) = "Read-only web access"
9. Diameter Translation Considerations
When used in Diameter, the attributes defined in this specification
can be used as Diameter AVPs from the Code space 1-255 (RADIUS
attribute compatibility space). No additional Diameter Code values
are therefore allocated. The data types and flag rules for the
attributes are as follows:
+---------------------+
| AVP Flag rules |
|----+-----+----+-----|----+
| | |SHLD| MUST| |
Attribute Name Value Type |MUST| MAY | NOT| NOT|Encr|
---------------------------------|----+-----+----+-----|----|
Service-Type (new value) | | | | | |
Enumerated | M | P | | V | Y |
Framed-Management-Protocol | | | | | |
Enumerated | M | P | | V | Y |
Transport-Protocol | | | | | |
Enumerated | M | P | | V | Y |
Management-Policy-Id | | | | | |
UTF8String | M | P | | V | Y |
---------------------------------|----+-----+----+-----|----|
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The attributes in this specification have no special translation
requirements for Diameter to RADIUS or RADIUS to Diameter gateways;
they are copied as is, except for changes relating to headers,
alignment, and padding. See also [RFC3588] Section 4.1 and [RFC4005]
Section 9.
What this specification says about the applicability of the
attributes for RADIUS Access-Request packets applies in Diameter to
AA-Request [RFC4005] or Diameter-EAP-Request [RFC4072]. What is said
about Access-Challenge applies in Diameter to AA-Answer [RFC4005] or
Diameter-EAP-Answer [RFC4072] with Result-Code AVP set to
DIAMETER_MULTI_ROUND_AUTH.
What is said about Access-Accept applies in Diameter to AA-Answer or
Diameter-EAP-Answer messages that indicate success. Similarly, what
is said about RADIUS Access-Reject packets applies in Diameter to AA-
Answer or Diameter-EAP-Answer messages that indicate failure.
What is said about COA-Request applies in Diameter to Re-Auth-Request
[RFC4005].
10. Proxy Operation Considerations
The device management access authorization attributes presented in
this document present certain considerations when used in proxy
environments. These considerations are not different from those that
exist in RFC 2865 [RFC2865] with respect to the Service-Type
attribute values of Administrative and NAS-Prompt.
Most proxy environments are also multi-party environments. In multi-
party proxy environments it is important to distinguish which
entities have the authority to provision management access to the
edge devices, i.e. NASes, and which entities only have authority to
provision network access services of various sorts.
It may be important that operators of the NAS are able to ensure that
access to the CLI, or other management interfaces, of the NAS are
only provisioned to their own employees or contractors. One way for
the NAS to enforce this requirement is to use only local, non-proxy
RADIUS servers for management access requests. Proxy RADIUS servers
could be used for non-management access requests, based on local
policy. This "bifurcation" of RADIUS authentication and
authorization is a simple case of separate administrative realms.
The NAS may be designed so as to maintain separate lists of RADIUS
servers for management AAA use and for non-management AAA use.
An alternate method of enforcing this requirement would be for the
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first-hop proxy server, operated by the owner of the NAS, to filter
out any RADIUS attributes that provision management access rights
that originate from "up-stream" proxy servers not operated by the NAS
owner. Access-Accept messages that provision such locally un-
authorized management access MAY be treated as if they were an
Access-Reject by the first-hop proxy server.
These issues are not of concern when all the RADIUS servers, local
and proxy, used by the NAS are under the sole administrative control
of the NAS owner.
11. Table of Attributes
The following table provides a guide to which attributes may be found
in which kinds of packets, and in what quantity.
Access-
Request Accept Reject Challenge # Attribute
---------------------------------------------------------------------
0-1 0-1 0 0 TBA Framed-Management-Protocol
0-1 0-1 0 0 TBA Transport-Protocol
0 0+ 0 0 TBA Management-Policy-Id
Accounting-
Request Response # Attribute
---------------------------------------------------------------------
0-1 0 TBA Framed-Management-Protocol
0-1 0 TBA Transport-Protocol
0+ 0 TBA Management-Policy-Id
The following table defines the meaning of the above table entries.
0 This attribute MUST NOT be present in a packet.
0+ Zero or more instances of this attribute MAY be present in
a packet.
0-1 Zero or one instance of this attribute MAY be present in
a packet.
1 Exactly one instance of this attribute MUST be present in
a packet.
12. IANA Considerations
This document contains placeholders ("TBA") for assigned numbers
within the RADIUS Attributes registry, to be assigned by IANA at the
time this document should be published as an RFC.
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13. Security Considerations
This specification describes the use of RADIUS and Diameter for
purposes of authentication, authorization and accounting for
management access to devices within local area networks. RADIUS
threats and security issues for this application are described in
[RFC3579] and [RFC3580]; security issues encountered in roaming are
described in [RFC2607]. For Diameter, the security issues relating
to this application are described in [RFC4005] and [RFC4072].
This document specifies new attributes that can be included in
existing RADIUS packets, which may be protected as described in
[RFC3579] and [RFC3576]. In Diameter, the attributes are protected
as specified in [RFC3588]. See those documents for a more detailed
description.
The security mechanisms supported in RADIUS and Diameter are focused
on preventing an attacker from spoofing packets or modifying packets
in transit. They do not prevent an authorized RADIUS/Diameter server
or proxy from inserting attributes with malicious intent.
Any of the attributes described in this memo, with the exception of
Service-Type, may not be understood by the NAS which receives it. A
legacy NAS not compliant with this specification may silently discard
these attributes while permitting the user to access the management
interface(s) of the NAS. This can lead to users improperly receiving
unauthorized management access to the NAS, or access with greater
levels of access rights than were intended. RADIUS servers SHOULD
attempt to ascertain whether or not the NAS supports these attributes
before sending them in an Access-Accept.
14. Acknowledgments
Many thanks to all reviewers, including Barney Wolff and Mauricio
Sanchez.
15. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO
10646", RFC 2279, January 1998.
[RFC2607] Aboba, B. and J. Vollbrecht, "Proxy Chaining and Policy
Implementation in Roaming", RFC 2607, June 1999.
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[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)",
RFC 2865, June 2000.
[RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.
[RFC3415] Wijnen, B., Presuhn, R., and K. McCloghrie, "View-based
Access Control Model (VACM) for the Simple Network
Management Protocol (SNMP)", STD 62, RFC 3415,
December 2002.
[RFC3576] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
Aboba, "Dynamic Authorization Extensions to Remote
Authentication Dial In User Service (RADIUS)", RFC 3576,
July 2003.
[RFC3579] Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication
Dial In User Service) Support For Extensible
Authentication Protocol (EAP)", RFC 3579, September 2003.
[RFC3580] Congdon, P., Aboba, B., Smith, A., Zorn, G., and J. Roese,
"IEEE 802.1X Remote Authentication Dial In User Service
(RADIUS) Usage Guidelines", RFC 3580, September 2003.
[RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
Arkko, "Diameter Base Protocol", RFC 3588, September 2003.
[RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton,
"Diameter Network Access Server Application", RFC 4005,
August 2005.
[RFC4072] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible
Authentication Protocol (EAP) Application", RFC 4072,
August 2005.
Authors' Addresses
David B. Nelson
Elbrys Networks, Inc.
75 Rochester Avenue, Unit 3
Portsmouth, NH 03801
USA
Email: d.b.nelson@comcast.net
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Greg Weber
Cisco Systems, Inc.
10850 Murdock Road
Knoxville, TN 37932
USA
Email: gdweber@cisco.com
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