Network Working Group K. Narayan
Internet-Draft Cisco Systems, Inc.
Intended status: Standards Track D. Nelson
Expires: August 30, 2010 Elbrys Networks, Inc.
R. Presuhn, Ed.
None
February 26, 2010
Extensions to the View-based Access Control Model for use with RADIUS
draft-ietf-isms-radius-vacm-04.txt
Abstract
This memo defines a portion of the Management Information Base (MIB)
for use with network management protocols. In particular, it
describes a backward-compatible supplement to the View-based Access
Control Model (VACM) for version 3 of the Simple Network Management
Protocol (SNMPv3) for use with the Remote Authentication Dial-In User
Service (RADIUS) and other Authentication, Authorization, and
Accounting (AAA) services to provide authorization of MIB database
access, and defines objects for managing this supplement. It is
intended to be used in conjunction with session-oriented secure SNMP
Transport Models that facilitate RADIUS authentication, such as the
Secure Shell Transport Model.
Comments are solicited and should be addressed to the working group's
mailing list at isms@ietf.org.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
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http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 30, 2010.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. The Internet-Standard Management Framework . . . . . . . . . . 4
3. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. System Block Diagram . . . . . . . . . . . . . . . . . . . 4
4.2. Using RADIUS with SNMP . . . . . . . . . . . . . . . . . . 5
4.3. Applicability . . . . . . . . . . . . . . . . . . . . . . 6
5. Structure of the MIB Module . . . . . . . . . . . . . . . . . 7
5.1. Textual Conventions . . . . . . . . . . . . . . . . . . . 7
5.2. The Table Structures . . . . . . . . . . . . . . . . . . . 7
6. Relationship to Other MIB Modules . . . . . . . . . . . . . . 7
6.1. Relationship to the VACM MIB . . . . . . . . . . . . . . . 7
6.1.1. Extended VACM for RADIUS Authorization . . . . . . . . 7
6.1.2. VACM Extension for RADIUS Authorization . . . . . . . 8
6.1.2.1. Dynamic Update of VACM and Extended VACM MIB
Module Objects . . . . . . . . . . . . . . . . . . 8
6.1.2.2. Purging Entries in the Extended VACM MIB Module . 9
6.1.3. Elements of Procedure for Extended VACM . . . . . . . 9
6.2. MIB modules required for IMPORTS . . . . . . . . . . . . . 11
7. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 11
8. Security Considerations . . . . . . . . . . . . . . . . . . . 14
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 16
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
11.1. Normative References . . . . . . . . . . . . . . . . . . . 17
11.2. Informative References . . . . . . . . . . . . . . . . . . 18
Appendix A. Open Issues . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
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1. Introduction
This memo specifies an integration of several protocols to
operationally simplify the administration of the access rights
granted to users of network management data. In this environment:
o The View-Based Access Control Model (VACM) [RFC3415] provides a
means to manage users' access rights to management information
accessed using SNMP.
o The Simple Network Management Protocol version 3 (SNMPv3) provides
message security services through the Security Subsystem.
o The Transport Subsystem for the Simple Network Management Protocol
[RFC5590] defines a Transport Subsystem.
o The Transport Security Model for SNMP [RFC5591] defines a
Transport Security Model.
o The Secure Shell Transport Model for SNMP [RFC5592] defines a
Secure Shell Transport Model and Remote Authentication Dial-In
User Service (RADIUS).
o RADIUS Usage for Simple Network Management Protocol (SNMP)
Transport Models [RFC5608] defines a method for authenticating
SNMPv3 users via RADIUS.
It is possible to authenticate SNMPv3 messages via a RADIUS when
those messages are sent over the SSH transport. As originally
envisioned, VACM authorizes a given SNMP transaction using on-device,
pre-existing authorization configuration. In order to leverage a
centralized RADIUS service to its full extent, the access control
decision in the Access Control Subsystem needs to be able to make use
of authorization information received from RADIUS as well. This
document defines an extension to the View-based Access Control Model
to obtain authorization information for an authenticated principal,
from RADIUS or equivalent AAA service supporting a Transport Security
Model.
Additional introductory material on the RADIUS operational model and
RADIUS usage with SNMP may be found in Sections 1.3 and 1.5 of
[RFC5608].
It is important to understand the SNMP architecture and the
terminology of the architecture to understand where the Extended
View-based Access Control Model described in this memo fits into the
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architecture and how it interacts with other subsystems and models
within the architecture. It is expected that reader will have also
read and understood RFC3411 [RFC3411], RFC3412 [RFC3412], RFC3413
[RFC3413], RFC3415 [RFC3415]and RFC3418 [RFC3418]. As this document
describes an extension to VACM, a thorough understanding of RFC3415
[RFC3415] is assumed.
2. The Internet-Standard Management Framework
For a detailed overview of the documents that describe the current
Internet-Standard Management Framework, please refer to section 7 of
RFC 3410 [RFC3410].
Managed objects are accessed via a virtual information store, termed
the Management Information Base or MIB. MIB objects are generally
accessed through the Simple Network Management Protocol (SNMP).
Objects in the MIB are defined using the mechanisms defined in the
Structure of Management Information (SMI). This memo specifies a MIB
module that is compliant to the SMIv2, which is described in STD 58,
RFC 2578 [RFC2578], STD 58, RFC 2579 [RFC2579] and STD 58, RFC 2580
[RFC2580].
3. Conventions
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].
4. Overview
4.1. System Block Diagram
A block diagram of the major system components referenced in this
document may be useful to understanding the text that follows.
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+--------+
+......................... |RADIUS |....+
. |Server | .
Shared +--------+ .
User | .
Credentials RADIUS | Shared
. | RADIUS
. | Secret
. | .
+-------------+ +-----------------+
| Network | | RADIUS Client / |
| Management | SNMP | SNMP Engine / |
| Application |------------------| Network Device |
+-------------+ SSH +-----------------+
Block Diagram
This diagram illustrates that a network management application
communicates with a network device, the managed entity, using, for
example, SNMP over SSH. The network device uses RADIUS to
communicate with a RADIUS Server to authenticate the network
management application (or the user whose credentials that
application provides) and to obtain authorization information related
to access via SNMP for purpose of device management. Other secure
transport protocols might be used instead of SSH, and other AAA
services might be used instead of RADIUS.
4.2. Using RADIUS with SNMP
There are two use cases for RADIUS support of management access via
SNMP. These are (a) service authorization and (b) access control
authorization. The former is discussed in detail in [RFC5608]. The
second use case is the subject of this document. This document
describes how RADIUS attributes and messages are applied to the
specific application area of SNMP Access Control Models, and VACM in
particular.
The RFC 3411 SNMP architecture maintains strong modularity and
separation of concerns, extending to separating user identity
(authentication) from user database access rights (authorization).
The former is the business of the Security Subsystem and the latter
is the business of the Access Control Subsystem. RADIUS, on the
other hand, allows for no such separation of authorization from
authentication. In order to use RADIUS with SNMP, binding of user
authentication to user authorization must be achieved, without
violating the modularity of the RFC 3411 SNMP architecture.
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RADIUS does support a limited form of Authorize-Only operations. The
RADIUS "Authorize Only" Service-Type Attribute can be specified in an
Access-Request message, but only when accompanied by a RADIUS State
Attribute, which contains an implementation specific "cookie"
representing the successful outcome of a previous authentication
transaction. For that reason, it is not possible to completely
separate the use of RADIUS by the Access Control Subsystem from the
use of RADIUS by other subsystems. This suggests that the most
straightforward approach is to leverage the existing RADIUS usage, as
documented in [RFC5608], and the tmStateReference cache, as
documented in Section 5.2 of [RFC5590].
The operative use case assumption here is that roles within an
organization, which are reflected in VACM as groups and rules, change
infrequently, while the users assigned to those roles change much
more frequently. This memo describes how the user-to-role (group)
mapping can be outsourced to the RADIUS server, avoiding the need to
re-provision managed devices as users are added, deleted, or assigned
new roles in an organization.
This memo assumes that the detailed access control policies are pre-
configued in VACM, and does not attempt to adress the question of how
the policy associated with a given role is put in place.
The only additional information obtained from the AAA service is the
mapping of the authenticated user's identifier to a specific role (or
"group" in VACM terminology) in the access control policy. Dynamic
user authorization for MIB database access control, as defined
herein, is limited to mapping the authenticated user to a group,
which in turn is mapped to the pre-existing rules.
4.3. Applicability
Though this memo was motivated to support the use of specific
Transport Security Models, it MAY be used with other Transport
Security Models whose implementations satistisfy these requirements:
o the model has a notion of "session";
o the model uses an AAA service for sign-on service authorization;
o the model provides an indication of the beginning session for a
particular user, identified using a SecurityName, and provides the
corresponding value of vacmGroupName to be used, based on
information provided by the AAA service in use;
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o the model provides an indication of the end of a session, whether
due to disconnection, termination due to timeout, or any other
reason.
Likewise, although this memo specifically refers to RADIUS, it MAY be
used with other AAA services satisfying these requirements:
o the service provides information semantically equivalent to the
RADIUS Management-Policy-ID attribute, which has been mapped
(perhaps trivially) into a GroupName;
o the service provides information semantically equivant to the
RADIUS User-Name Attribute, which has been mapped (perhaps
trivially) into a SecurityName.
5. Structure of the MIB Module
5.1. Textual Conventions
This MIB module makes use of the SnmpAdminString and
SnmpSecurityModel textual conventions.
5.2. The Table Structures
This MIB module defines a single table, the
extVacmSecurityToGroupTable. This table is indexed by the integer
assigned to each security model, the protocol-independent
SecurityName corresponding to a principal, and the unique identifier
of a transport session. This index structure was chosen to support
use cases in which a given user could potentially have multiple
concurrent sessions, and to support environments in which multiple
security models might find concurrent usage.
6. Relationship to Other MIB Modules
6.1. Relationship to the VACM MIB
The extVacmSecurityToGroupTable has a close relationship to the VACM
MIB's vacmSecurityToGroupTable.
6.1.1. Extended VACM for RADIUS Authorization
This memo relies on implementation-specific integration of the RADIUS
client for user authentication and authorization. In particular, the
implementation MUST make the RADIUS Management-Policy-Id [RFC5607]
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and User-Name Attributes (or equivalent) from the RADIUS Access-
Accept message (or equivalent) available to Extended VACM.
The design of VACM ensures that if an unknown policy (group name) is
used in the VacmSecurityToGroupTable, no access is granted.
The intended use of the content of the Management-Policy-Id attribute
is to provision a mapping between the authenticated user, associated
with the secure transport session, and an access control group pre-
provisioned in the VACM MIB module. Details of this mapping are
described in following sections.
6.1.2. VACM Extension for RADIUS Authorization
This memo describes a method by which selected MIB objects associated
with VACM [RFC3415] are dynamically provisioned based on information
received from RADIUS, or another AAA service. This method requires
no changes to the Abstract Service Interface (ASI) for the Access
Control Subsystem, nor any changes in the Elements of Procedure (EOP)
for VACM. A new MIB module that reflects the information received
from the AAA service to update the vacmSecurityToGroupTable is
defined in this document, as well as the elements of procedure for
creating, updating, and deleting entries in this module's table. Its
implementation does require that code somewhere in the NAS be able to
access (read and write) the VACM MIB module and Extended VACM MIB
Module, in immediate response to access control policy information
received from RADIUS.
6.1.2.1. Dynamic Update of VACM and Extended VACM MIB Module Objects
The implementation-dependent interface between the RADIUS Client
function and the SNMP Engine is responsible for updating the
extVacmSecurityToGroupTable and the corresponding rows of the
vacmSecurityToGroupTable table within the VACM MIB Module [RFC3415]
Specifically, the RADIUS User-Name Attribute is used as the
vacmSecurityName and the RADIUS Management-Policy-Id Attribute is
used as the vacmGroupName. The value used for vacmSecurityModel is
the registered value for the security model in use. Note that the
security model SHOULD be one which binds principal identity to access
control policy via an external AAA server, such as the Transport
Security Model. To do otherwise potentially creates a security risk.
Whenever a new session begins, a new entry is created in the
extVacmSecurityToGroupTable, indexed by the identifier of the
Security Model itself, the SecurityName (derived from, e.g., the
RADIUS User-Name Attribute), and a unique transport session
identifier.
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If no corresponding entry exists in the vacmSecurityToGroupTable,
nothing has been pre-provisioned for this particular user, so an
entry is created, with a StorageType of "volatile", and with using
the vacmGroupName supplied by the RADIUS server.
If a corresponding entry already exists in the
vacmSecurityToGroupTable, and the row's StorageType is "volatile",
the operational assumption is that this entry was probably
dynamically created by this function, since an entry created by a
security administrator would not normally be given a StorageType of
"volatile". The value being provided by RADIUS will either be the
same as what is already there, or, if it is different, the new
information is understood as a more recent role (group) assignment
for the user, which should supercede the one currently held there.
Consequently, vacmGroupName is updated with the whatever value is
supplied by the RADIUS server.
If a corresponding entry already exists in the
vacmSecurityToGroupTable, and the row's StorageType is anything other
than "volatile", a role (group) mapping for this principal has
already been administratively explicitly provisioned on this system,
and will not be overridden.
6.1.2.2. Purging Entries in the Extended VACM MIB Module
Entries in the vacmSecurityToGroupTable MUST NOT persist across
system reboots.
When the corresponding secure transport session has been terminated
for any reason, the corresponding extVacmSecurityToGroupEntry is
deleted. When no rows remain having corresponding values for
extVacmSecurityName and extVacmSecurityModel, then, if the
corresponding row in the in the vacmSecurityToGroup has a StorageType
of "volatile", that row MUST be deleted as well. The mechanism to
accomplish this task is implementation specific.
6.1.3. Elements of Procedure for Extended VACM
This section describes the Elements of Procedure for Extended VACM.
The function of the VACM extension is to manage the creation and
deletion of rows in the vacmSecurityToGroupTable, based on the
outcome of RADIUS authorization. All access control decision
functions are taken by VACM, as defined in [RFC3415]. The elements
of procedure for VACM are unchanged.
When a RADIUS (or other AAA service) authorizes SNMP data access
control for a user-authenticated secure transport session, the NAS
causes the RADIUS provisioning information to be made available to
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the Extended VACM facility, which populates the
vacmSecurityToGroupTable, as follows:
1. If the the RADIUS Management-Policy-Id Attribute is not
available, no action is taken.
2. If an existing row has a vacmSecurityName matching the RADIUS
User-Name Attribute, a vacmSecurityModel corresponding to the
security model, and an extVacmTransportSessionID matching the ID
provided by the Secure Transport, an internal logic error of some
kind has may have occurred. Recovery is implementation-specific.
3. If no additional table rows could be created, e.g. because of
resource constraints, this is an internal error. Recovery is
implementation-specific.
4. Create a new row with the columns populated as follows:
A. extVacmSecurityModel = value of SnmpSecurityModel registered
with the security model in use
B. extVacmSecurityName = RADIUS User-Name Attribute or
equivalent
C. extVacmTransportSessionID = ID provided by the Secure
Transport Model
D. extVacmGroupName = RADIUS Management-Policy-Id Attribute
5. Using the value of extVacmSecurityModel for vacmSecurityModel,
and the value of extVacmSecurityName for vacmSecurityName, if no
corresponding entry exists in the vacmSecurityToGroupTable,
create one, using extVacmGroupName to fill in vacmGroupName,
using a value of "volatile" for vacmSecurityToGroupStorageType,
and "active" for vacmSecurityToGroupStatus.
6. Otherwise (that is, if corresponding entry already exists in the
vacmSecurityToGroupTable), if vacmSecurityToGroupStorageType is
"volatile" and vacmSecurityToGroupStatus is "active", update the
value of vacmGroupName with the value from extVacmGroupName.
When a RADIUS-authenticated secure transport session is disconnected
by the remote peer, the NAS causes the Extended VACM to remove the
corresponding table row from the vacmSecurityToGroupTable. The NAS
provides an implementation dependent identifier of the session in
question to Extended VACM.
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1. Search for a row with a matching extVacmSecurityModel and
extVacmTransportSessionID.
2. If a table row exists with a matching value of
extVACMTransportSessionID, that row is deleted.
When the last row bearing a particular (extVacmSecurityModel,
extVacmSecurityName) pair is deleted from the
extVacmSecurityToGroupTable, the vacmSecurityToGroupTable is examined
for a corresponding row. If one exists, and if its StorageType is
"volatile" and its RowStatus is "active", that row is deleted as
well.
6.2. MIB modules required for IMPORTS
The MIB module employs definitions from [RFC2578], [RFC2579] and
[RFC3411].
7. Definitions
SNMP-EXT-VACM-MIB DEFINITIONS ::= BEGIN
IMPORTS
MODULE-COMPLIANCE, OBJECT-GROUP FROM SNMPv2-CONF
MODULE-IDENTITY, OBJECT-TYPE,
mib-2,
Unsigned32,
Counter32 FROM SNMPv2-SMI
SnmpAdminString,
SnmpSecurityModel FROM SNMP-FRAMEWORK-MIB;
snmpExtVacmMIB MODULE-IDENTITY
LAST-UPDATED "201002250000Z" -- 25 February, 2010
ORGANIZATION "ISMS Working Group"
CONTACT-INFO "WG-email: isms@ietf.org"
DESCRIPTION "The management and local datstore information
definitions for the Extended View-based Access
Control Model for SNMP.
Copyright (c) 2010 IETF Trust and the persons
identified as the document authors. All rights
reserved.
Redistribution and use in source and binary forms,
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with or without modification, is permitted pursuant
to, and subject to the license terms contained in,
the Simplified BSD License set forth in Section
4.c of the IETF Trust's Legal Provisions Relating
to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this MIB module is part of RFC XXXX;
see the RFC itself for full legal notices."
REVISION "201002250000Z"
DESCRIPTION "Initial version,published as RFC XXXX."
::= { mib-2 XXX }
extVacmMIBObjects OBJECT IDENTIFIER ::= { snmpExtVacmMIB 1 }
extVacmMIBConformance OBJECT IDENTIFIER ::= {snmpExtVacmMIB 2 }
extVacmSecurityToGroupTable OBJECT-TYPE
SYNTAX SEQUENCE OF ExtVacmSecurityToGroupEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "This table maps a combination of securityModel and
securityName into a groupName which is used to define
an access control policy for a group of principals."
::= { extVacmMIBObjects 1 }
extVacmSecurityToGroupEntry OBJECT-TYPE
SYNTAX ExtVacmSecurityToGroupEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "An entry in this table maps the combination of a
securityModel and securityName into a groupName.
An entry corresponds to a secure transport session.
Entries do not persist across reboots.
When the secure transport session is torn down,
disconnected, timed out (e.g. following the
RADIUS Session-Timeout Attribute), or otherwise
terminated for any reason, the corresponding
extVacmSecurityToGroupEntry is deleted."
INDEX {
extVacmSecurityModel,
extVacmSecurityName,
extVacmTransportSessionID
}
::= { extVacmSecurityToGroupTable 1 }
ExtVacmSecurityToGroupEntry ::= SEQUENCE
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{
extVacmSecurityModel SnmpSecurityModel,
extVacmSecurityName SnmpAdminString,
extVacmTransportSessionID Unsigned32,
extVacmGroupName SnmpAdminString
}
extVacmSecurityModel OBJECT-TYPE
SYNTAX SnmpSecurityModel(1..2147483647)
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "The Security Model to which the session referred
to by this entry belongs.
This object cannot take the 'any' (0) value."
::= { extVacmSecurityToGroupEntry 1 }
extVacmSecurityName OBJECT-TYPE
SYNTAX SnmpAdminString (SIZE(1..32))
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "The Security Name of the principal associated with
this session, provided by the Transport Model, and
represented in a Security Model independent format.
Transport model. which is mapped by
this entry to a groupName."
::= { extVacmSecurityToGroupEntry 2 }
extVacmTransportSessionID OBJECT-TYPE
SYNTAX Unsigned32
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "A transport model-specific identifier of the
session. This value MUST be unique among all
of a given transport model's currently open sessions.
The value has no particular significance other
to distinguish sessions. An example of a suitable
value would be tlstmSessionID."
::= { extVacmSecurityToGroupEntry 3 }
extVacmGroupName OBJECT-TYPE
SYNTAX SnmpAdminString (SIZE(1..32))
MAX-ACCESS read-only
STATUS current
DESCRIPTION "The name of the group to which this entry
is to belong. This information would have come
from, for example, the RADIUS Management-Policy-ID
attribute.
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This group name is used to set the vacmGroupName
in the corresponding vacmSecurityToGroupEntry."
::= { extVacmSecurityToGroupEntry 4 }
-- Conformance information ******************************************
extVacmMIBCompliances
OBJECT IDENTIFIER ::= {extVacmMIBConformance 1}
extVacmMIBGroups
OBJECT IDENTIFIER ::= {extVacmMIBConformance 2}
-- compliance statements
extVacmMIBBasicCompliance MODULE-COMPLIANCE
STATUS current
DESCRIPTION "The compliance statement for SNMP engines which
implement the Extensions to the View-based Access
Control Model for use with RADIUS.
"
MODULE -- this module
MANDATORY-GROUPS { extVacmGroup }
::= { extVacmMIBCompliances 1 }
-- units of conformance
extVacmGroup OBJECT-GROUP
OBJECTS {
extVacmGroupName
}
STATUS current
DESCRIPTION "A collection of objects for supporting the use
of RADIUS to provide user / group mappings for VACM.
"
::= { extVacmMIBGroups 1 }
END
8. Security Considerations
This integration strongly assumes that RADIUS (or some other AAA
service) is at least as trusted as the security administrator with
access rights to the vacmSecurityToGroupTable. It assumes that the
transport security model can be trusted to pass through the users'
security name and the group name provided by the AAA service. It
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also trusts the transport security model to enforce any session
timeouts imposed by the RADIUS server, and to provide an indicate
whenever a session ends.
The algorithms in this memo make heuristic use of the StorageType of
entries in the vacmSecurityToGroupTable to distinguish those which
have been provisioned by a security adminstrator (which would
presumably not be configured as "volatile") and those dynamically
generated. In making this distinction, it assumes that those entries
explicitly provisioned by a security administrator and given a
non-"volatile" status are not to be dynamically over-ridden. Users
of this memo need to be aware of this operational assumption, which,
while reasonable, is not necessarily universal.
There are no management objects defined in this MIB module that have
a MAX-ACCESS clause of read-write and/or read-create. So, if this
MIB module is implemented correctly, then there is no risk that an
intruder can alter or create any management objects of this MIB
module via direct SNMP SET operations.
Some of the readable objects in this MIB module (including some
objects with a MAX-ACCESS of not-accessible, whose values are exposed
as a result access to indexed objects) may be considered sensitive or
vulnerable in some network environments. It is thus important to
control even GET and/or NOTIFY access to these objects and possibly
to even encrypt the values of these objects when sending them over
the network via SNMP. These are the tables and objects and their
sensitivity/vulnerability:
o extVacmSecurityToGroupTable - the entire table is potentially
sensitive, since walking the table will reveal user names,
security models in use, transport session identifiers, and group
names.
o extVacmSecurityModel - though not-accessible, this is exposed as
an index of extVacmGroupName
o extVacmSecurityName - though not-accessible, this is exposed as an
index of extVacmGroupName
o extVacmTransportSessionID - though not-accessible, this is exposed
as an index of extVacmGroupName
o extVacmGroupName - since this identifies a security policy and
associates it with a particular user, this is potentially
sensitive.
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SNMP versions prior to SNMPv3 did not include adequate security.
Even if the network itself is secure (for example by using IPsec),
even then, there is no control as to who on the secure network is
allowed to access and GET/SET (read/change/create/delete) the objects
in this MIB module.
It is RECOMMENDED that implementers consider the security features as
provided by the SNMPv3 framework (see [RFC3410], section 8),
including full support for the SNMPv3 cryptographic mechanisms (for
authentication and privacy).
Further, deployment of SNMP versions prior to SNMPv3 is NOT
RECOMMENDED. Instead, it is RECOMMENDED to deploy SNMPv3 and to
enable cryptographic security. It is then a customer/operator
responsibility to ensure that the SNMP entity giving access to an
instance of this MIB module is properly configured to give access to
the objects only to those principals (users) that have legitimate
rights to indeed GET or SET (change/create/delete) them.
9. IANA Considerations
The MIB module in this document uses the following IANA-assigned
OBJECT IDENTIFIER values recorded in the SMI Numbers registry:
Descriptor OBJECT IDENTIFIER value
---------- -----------------------
snmpExtVacmMIB { mib-2 XXX }
Editor's Note (to be removed prior to publication): the IANA is
requested to assign a value for "XXX" under the 'mib-2' subtree and
to record the assignment in the SMI Numbers registry. When the
assignment has been made, the RFC Editor is asked to replace "XXX"
(here and in the MIB module) with the assigned value and to remove
this note.
10. Contributors
The following participants from the isms working group contributed to
the development of this document:
o David Harrington
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o Juergen Schoenwaelder
o Tom Petch
o Wes Hardaker
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2578] McCloghrie, K., Ed., Perkins, D., Ed., and J.
Schoenwaelder, Ed., "Structure of Management Information
Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.
[RFC2579] McCloghrie, K., Ed., Perkins, D., Ed., and J.
Schoenwaelder, Ed., "Textual Conventions for SMIv2",
STD 58, RFC 2579, April 1999.
[RFC2580] McCloghrie, K., Perkins, D., and J. Schoenwaelder,
"Conformance Statements for SMIv2", STD 58, RFC 2580,
April 1999.
[RFC3411] Harrington, D., Presuhn, R., and B. Wijnen, "An
Architecture for Describing Simple Network Management
Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
December 2002.
[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.
[RFC5590] Harrington, D. and J. Schoenwaelder, "Transport Subsystem
for the Simple Network Management Protocol (SNMP)",
RFC 5590, June 2009.
[RFC5591] Harrington, D. and W. Hardaker, "Transport Security Model
for the Simple Network Management Protocol (SNMP)",
RFC 5591, June 2009.
[RFC5607] Nelson, D. and G. Weber, "Remote Authentication Dial-In
User Service (RADIUS) Authorization for Network Access
Server (NAS) Management", RFC 5607, July 2009.
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[RFC5608] Narayan, K. and D. Nelson, "Remote Authentication Dial-In
User Service (RADIUS) Usage for Simple Network Management
Protocol (SNMP) Transport Models", RFC 5608, August 2009.
11.2. Informative References
[RFC3410] Case, J., Mundy, R., Partain, D., and B. Stewart,
"Introduction and Applicability Statements for Internet-
Standard Management Framework", RFC 3410, December 2002.
[RFC3412] Case, J., Harrington, D., Presuhn, R., and B. Wijnen,
"Message Processing and Dispatching for the Simple Network
Management Protocol (SNMP)", STD 62, RFC 3412,
December 2002.
[RFC3413] Levi, D., Meyer, P., and B. Stewart, "Simple Network
Management Protocol (SNMP) Applications", STD 62,
RFC 3413, December 2002.
[RFC3418] Presuhn, R., "Management Information Base (MIB) for the
Simple Network Management Protocol (SNMP)", STD 62,
RFC 3418, December 2002.
[RFC5592] Harrington, D., Salowey, J., and W. Hardaker, "Secure
Shell Transport Model for the Simple Network Management
Protocol (SNMP)", RFC 5592, June 2009.
Appendix A. Open Issues
This section identifies questions and issues that have not been
addressed in this version of this document. This section will
probably be removed prior to publication, since there will be no
questions left to address.
1. Make sure that the new Elements of Procedure make sense and cover
all the corner cases correctly.
2. Security considerations need to be filled in, specifically
concerning trust relationships to RADIUS and the interaction with
statically configured policy.
3. There's a lot of repetition / redundancy.
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Authors' Addresses
Kaushik Narayan
Cisco Systems, Inc.
10 West Tasman Drive
San Jose, CA 95134
USA
Phone: +1.408.526.8168
Email: kaushik_narayan@yahoo.com
David Nelson
Elbrys Networks, Inc.
282 Corporate Drive, Unit #1,
Portsmouth, NH 03801
USA
Phone: +1.603.570.2636
Email: d.b.nelson@comcast.net
Randy Presuhn (editor)
None
San Jose, CA 95120
USA
Email: randy_presuhn@mindspring.com
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