draft-ietf-isms-tmsm-02.txt   draft-ietf-isms-tmsm-03.txt 
Network Working Group D. Harrington Network Working Group D. Harrington
Internet-Draft Futurewei Technologies Internet-Draft Huawei Technologies (USA)
Expires: November 4, 2006 J. Schoenwaelder Intended status: Informational J. Schoenwaelder
International University Bremen Expires: December 25, 2006 International University Bremen
May 3, 2006 June 23, 2006
Transport Mapping Security Model (TMSM) Architectural Extension for the Transport Mapping Security Model (TMSM) Architectural Extension for the
Simple Network Management Protocol (SNMP) Simple Network Management Protocol (SNMP)
draft-ietf-isms-tmsm-02.txt draft-ietf-isms-tmsm-03.txt
Status of This Memo Status of This Memo
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aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
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This Internet-Draft will expire on November 4, 2006. This Internet-Draft will expire on December 25, 2006.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2006). Copyright (C) The Internet Society (2006).
Abstract Abstract
This document describes a Transport Mapping Security Model (TMSM) This document describes a Transport Mapping Security Model (TMSM)
extension for the Simple Network Management Protocol (SNMP) extension for the Simple Network Management Protocol (SNMP)
architecture defined in RFC 3411. This document identifies and architecture defined in RFC 3411. This document identifies and
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2.2.1. Architectural Modularity Requirements . . . . . . . . 7 2.2.1. Architectural Modularity Requirements . . . . . . . . 7
2.2.2. Access Control Requirements . . . . . . . . . . . . . 14 2.2.2. Access Control Requirements . . . . . . . . . . . . . 14
2.2.3. Security Parameter Passing Requirements . . . . . . . 16 2.2.3. Security Parameter Passing Requirements . . . . . . . 16
2.3. Session Requirements . . . . . . . . . . . . . . . . . . . 17 2.3. Session Requirements . . . . . . . . . . . . . . . . . . . 17
2.3.1. Session Establishment Requirements . . . . . . . . . . 18 2.3.1. Session Establishment Requirements . . . . . . . . . . 18
2.3.2. Session Maintenance Requirements . . . . . . . . . . . 19 2.3.2. Session Maintenance Requirements . . . . . . . . . . . 19
2.3.3. Message security versus session security . . . . . . . 19 2.3.3. Message security versus session security . . . . . . . 19
3. Scenario Diagrams for TMSM . . . . . . . . . . . . . . . . . . 21 3. Scenario Diagrams for TMSM . . . . . . . . . . . . . . . . . . 21
3.1. Command Generator or Notification Originator . . . . . . . 21 3.1. Command Generator or Notification Originator . . . . . . . 21
3.2. Command Responder . . . . . . . . . . . . . . . . . . . . 22 3.2. Command Responder . . . . . . . . . . . . . . . . . . . . 22
4. Abstract Service Interfaces for TMSM . . . . . . . . . . . . . 23 4. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 23
4.1. Existing Abstract Service Interfaces . . . . . . . . . . . 24 4.1. SNMPv3 Message Fields . . . . . . . . . . . . . . . . . . 24
4.2. TMSM Abstract Service Interfaces . . . . . . . . . . . . . 24 4.1.1. msgGlobalData . . . . . . . . . . . . . . . . . . . . 26
5. Cached Information and References . . . . . . . . . . . . . . 26 4.1.2. msgSecurityParameters . . . . . . . . . . . . . . . . 27
5.1. securityStateReference Cached Security Data . . . . . . . 26 5. Cached Information and References . . . . . . . . . . . . . . 27
5.2. tmStateReference Cached Security Data . . . . . . . . . . 27 5.1. tmSessionReference Cached Session Data . . . . . . . . . . 27
6. Integration with the SNMPv3 Message Format . . . . . . . . . . 28 5.2. securityStateReference Cached Security Data . . . . . . . 27
6.1. msgVersion . . . . . . . . . . . . . . . . . . . . . . . . 28 6. Abstract Service Interfaces for TMSM . . . . . . . . . . . . . 28
6.2. msgGlobalData . . . . . . . . . . . . . . . . . . . . . . 28 6.1. Generating an Outgoing SNMP Message . . . . . . . . . . . 29
6.3. securityLevel and msgFlags . . . . . . . . . . . . . . . . 29 6.2. TMSP for an Outgoing Message . . . . . . . . . . . . . . . 30
7. Prepare an Outgoing SNMP Message . . . . . . . . . . . . . . . 29 6.3. Processing an Incoming SNMP Message . . . . . . . . . . . 30
8. Prepare Data Elements from an Incoming SNMP Message . . . . . 30 6.3.1. TMSP for an Incoming Message . . . . . . . . . . . . . 30
9. Notifications . . . . . . . . . . . . . . . . . . . . . . . . 30 6.3.2. Prepare Data Elements from Incoming Messages . . . . . 31
10. The TMSM MIB Module . . . . . . . . . . . . . . . . . . . . . 31 6.3.3. MPSP for an Incoming Message . . . . . . . . . . . . . 32
10.1. Structure of the MIB Module . . . . . . . . . . . . . . . 31 7. The TMSM MIB Module . . . . . . . . . . . . . . . . . . . . . 33
10.1.1. The tmsmNotifications Subtree . . . . . . . . . . . . 31 7.1. Structure of the MIB Module . . . . . . . . . . . . . . . 33
10.1.2. The tmsmStats Subtree . . . . . . . . . . . . . . . . 31 7.1.1. The tmsmStats Subtree . . . . . . . . . . . . . . . . 33
10.1.3. The tmsmSession Subtree . . . . . . . . . . . . . . . 31 7.2. Relationship to Other MIB Modules . . . . . . . . . . . . 33
10.2. Relationship to Other MIB Modules . . . . . . . . . . . . 31 7.2.1. Textual Conventions . . . . . . . . . . . . . . . . . 33
10.2.1. Textual Conventions . . . . . . . . . . . . . . . . . 32 7.2.2. MIB Modules Required for IMPORTS . . . . . . . . . . . 33
10.2.2. MIB Modules Required for IMPORTS . . . . . . . . . . . 32 7.3. Definitions . . . . . . . . . . . . . . . . . . . . . . . 33
11. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 32 8. Security Considerations . . . . . . . . . . . . . . . . . . . 38
12. Security Considerations . . . . . . . . . . . . . . . . . . . 39 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 40 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 39
14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 41 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 39
15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 41 11.1. Normative References . . . . . . . . . . . . . . . . . . . 39
15.1. Normative References . . . . . . . . . . . . . . . . . . . 41 11.2. Informative References . . . . . . . . . . . . . . . . . . 40
15.2. Informative References . . . . . . . . . . . . . . . . . . 42 Appendix A. Parameter Table . . . . . . . . . . . . . . . . . . . 41
Appendix A. Parameter Table . . . . . . . . . . . . . . . . . . . 42 A.1. ParameterList.csv . . . . . . . . . . . . . . . . . . . . 41
A.1. ParameterList.csv . . . . . . . . . . . . . . . . . . . . 43 Appendix B. Why tmSessionReference? . . . . . . . . . . . . . . . 42
Appendix B. Why tmSecurityReference? . . . . . . . . . . . . . . 44 B.1. Define an Abstract Service Interface . . . . . . . . . . . 43
B.1. Define an Abstract Service Interface . . . . . . . . . . . 44 B.2. Using an Encapsulating Header . . . . . . . . . . . . . . 43
B.2. Using an Encapsulating Header . . . . . . . . . . . . . . 45 B.3. Modifying Existing Fields in an SNMP Message . . . . . . . 43
B.3. Modifying Existing Fields in an SNMP Message . . . . . . . 45 B.4. Using a Cache . . . . . . . . . . . . . . . . . . . . . . 44
B.4. Using a Cache . . . . . . . . . . . . . . . . . . . . . . 45 Appendix C. Open Issues . . . . . . . . . . . . . . . . . . . . . 44
Appendix C. Open Issues . . . . . . . . . . . . . . . . . . . . . 45 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 44
Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 46
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 46
Intellectual Property and Copyright Statements . . . . . . . . . . 47
1. Introduction 1. Introduction
This document describes a Transport Mapping Security Model (TMSM) This document describes a Transport Mapping Security Model (TMSM)
extension for the Simple Network Management Protocol (SNMP) extension for the Simple Network Management Protocol (SNMP)
architecture defined in [RFC3411]. This document identifies and architecture defined in [RFC3411]. This document identifies and
discusses some key aspects that need to be considered for any discusses some key aspects that need to be considered for any
transport-mapping-based security model for SNMP. transport-mapping-based security model for SNMP.
1.1. The Internet-Standard Management Framework 1.1. The Internet-Standard Management Framework
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Some points requiring further WG research and discussion are Some points requiring further WG research and discussion are
identified by [discuss] markers in the text. Some points requiring identified by [discuss] markers in the text. Some points requiring
further editing by the editors are marked [todo] in the text. further editing by the editors are marked [todo] in the text.
1.3. Acronyms 1.3. Acronyms
This section contains a list of acronyms used with the document and This section contains a list of acronyms used within the document and
references to where in the document the acronym is defined, for easy references to where in the document the acronym is defined, for easy
lookup. lookup.
o TMSM - a Transport Mapping Security Model o TMSM - a Transport Mapping Security Model
o MPSP - s Messaging Processing Security Processor, the portion of a o SMSP - a Security Model Security Processor, the portion of a TMSM
TMSM security model that resides in the Message Processing security model that resides in the Message Processing subsystem of
subsytem of an SNMPv3 engine. See Section 2.2.1 an SNMPv3 engine. See Section 2.2.1
o TMSP - the Transport Mapping Security Processor, the portion of a o TMSP - the Transport Mapping Security Processor, the portion of a
TMSM security model that resides in the Transport Mapping section TMSM security model that resides in the Transport Mapping section
of the Dispatcher of an SNMPv3 engine. See Section 2.2.1 of the Dispatcher of an SNMPv3 engine. See Section 2.2.1
1.4. Motivation 1.4. Motivation
There are multiple ways to secure one's home or business, but they There are multiple ways to secure one's home or business, in a
largely boil down to a continuum of alternatives. Let's consider continuum of alternatives. Let's consider three general approaches.
three general approaches. In the first approach, an individual could In the first approach, an individual could buy a gun, learn to use
buy a gun, learn to use it, and sit on your front porch waiting for it, and sit on your front porch waiting for intruders. In the second
intruders. In the second approach, one could hire an employee with a approach, one could hire an employee with a gun, schedule the
gun, schedule the employee, position the employee to guard what you employee, position the employee to guard what you want protected,
want protected, hire a second guard to cover if the first gets sick, hire a second guard to cover if the first gets sick, and so on. In
and so on. In the third approach, you could hire a security company, the third approach, you could hire a security company, tell them what
tell them what you want protected, and they could hire employees, you want protected, and they could hire employees, train them, buy
train them, buy the guns, position the guards, schedule the guards, the guns, position the guards, schedule the guards, send a
send a replacement when a guard cannot make it, etc., thus providing replacement when a guard cannot make it, etc., thus providing the
the security you want, with no significant effort on your part other security you want, with no significant effort on your part other than
than identifying requirements and verifying the quality of the identifying requirements and verifying the quality of the service
service being provided. being provided.
The User-based Security Model (USM) as defined in [RFC3414] largely The User-based Security Model (USM) as defined in [RFC3414] largely
uses the first approach - it provides its own security. It utilizes uses the first approach - it provides its own security. It utilizes
existing mechanisms (MD5=the gun), but provides all the coordination. existing mechanisms (MD5=the gun), but provides all the coordination.
USM provides for the authentication of a principal, message USM provides for the authentication of a principal, message
encryption, data integrity checking, timeliness checking, etc. encryption, data integrity checking, timeliness checking, etc.
USM was designed to be independent of other existing security USM was designed to be independent of other existing security
infrastructures. USM therefore requires a separate user and key infrastructures. USM therefore requires a separate principal and key
management infrastructure. Operators have reported that deploying management infrastructure. Operators have reported that deploying
another user and key management infrastructure in order to use SNMPv3 another principal and key management infrastructure in order to use
is a deterrent to deploying SNMPv3. It is possible but difficult to SNMPv3 is a deterrent to deploying SNMPv3. It is possible but
define external mechanisms that handle the distribution of keys for difficult to define external mechanisms that handle the distribution
use by the USM approach. of keys for use by the USM approach.
A solution based on the second approach might use a USM-compliant A solution based on the second approach might use a USM-compliant
architecture, but combine the authentication mechanism with an architecture, but combine the authentication mechanism with an
external mechanism, such as RADIUS [RFC2865], to provide the external mechanism, such as RADIUS [RFC2865], to provide the
authentication service. It might be possible to utilize an external authentication service. It might be possible to utilize an external
protocol to encrypt a message, to check timeliness, to check data protocol to encrypt a message, to check timeliness, to check data
integrity, etc. It is difficult to cobble together a number of integrity, etc. It is difficult to cobble together a number of
subcontracted services and coordinate them however, because it is subcontracted services and coordinate them however, because it is
difficult to build solid security bindings between the various difficult to build solid security bindings between the various
services, and potential for gaps in the security is significant. services, and potential for gaps in the security is significant.
A solution based on the third approach might utilize one or more A solution based on the third approach might utilize one or more
lower-layer security mechanisms to provide the message-oriented lower-layer security mechanisms to provide the message-oriented
security services required. These would include authentication of security services required. These would include authentication of
the sender, encryption, timeliness checking, and data integrity the sender, encryption, timeliness checking, and data integrity
checking. There are a number of IETF standards available or in checking. There are a number of IETF standards available or in
development to address these problems through security layers at the development to address these problems through security layers at the
transport layer or application layer, among them TLS [RFC4366], SASL transport layer or application layer, among them TLS [RFC4366], SASL
[RFC2222], and SSH [RFC4251]. [RFC4422], and SSH [RFC4251].
From an operational perspective, it is highly desirable to use From an operational perspective, it is highly desirable to use
security mechanisms that can unify the administrative security security mechanisms that can unify the administrative security
management for SNMPv3, command line interfaces (CLIs) and other management for SNMPv3, command line interfaces (CLIs) and other
management interfaces. The use of security services provided by management interfaces. The use of security services provided by
lower layers is the approach commonly used for the CLI, and is also lower layers is the approach commonly used for the CLI, and is also
the approach being proposed for NETCONF [I-D.ietf-netconf-ssh]. the approach being proposed for NETCONF [I-D.ietf-netconf-ssh].
This document proposes a Transport Mapping Security Model (TMSM) This document proposes a Transport Mapping Security Model (TMSM)
extension to the RFC3411 architecture, that allows security to be extension to the RFC3411 architecture, that allows security to be
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which is plugged into the RFC3411 architecture between the transport which is plugged into the RFC3411 architecture between the transport
layer and the message dispatcher. Conceptually, transport mapping layer and the message dispatcher. Conceptually, transport mapping
security processing will be called from within the Transport Mapping security processing will be called from within the Transport Mapping
functionality of an SNMP engine dispatcher to perform the translation functionality of an SNMP engine dispatcher to perform the translation
of transport security parameters to/from security-model-independent of transport security parameters to/from security-model-independent
parameters. This transport mapping security processor will be parameters. This transport mapping security processor will be
referred to in this document as TMSP. referred to in this document as TMSP.
Additional functionality may be performed as part of the message Additional functionality may be performed as part of the message
processing function, i.e., in the security subsystem of the RFC3411 processing function, i.e., in the security subsystem of the RFC3411
architecture. This document will refer to message processor's architecture. This document will refer to security model's security
security processor as the MPSP. processor as the SMSP.
Thus a TMSM is composed of both a TMSP and an MPSP. Thus a TMSM is composed of both a TMSP and an SMSP.
+------------------------------+ +------------------------------+
| Network | | Network |
+------------------------------+ +------------------------------+
^ ^ ^ ^ ^ ^
| | | | | |
v v v v v v
+-----+ +-----+ +-------+ +-----+ +-----+ +-------+
| UDP | | TCP | . . . | other | | UDP | | TCP | . . . | other |
+-----+ +-----+ +-------+ +-----+ +-----+ +-------+
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| | | | Message Processing | | Security | | | | | | Message Processing | | Security | |
| | | | Subsystem | | Subsystem | | | | | | Subsystem | | Subsystem | |
| | | | +------------+ | | | | | | | | +------------+ | | | |
| | | | +->| v1MP * |<--->| +------------+ | | | | | | +->| v1MP * |<--->| +------------+ | |
| | | | | +------------+ | | | Other | | | | | | | | +------------+ | | | Other | | |
| | | | | +------------+ | | | Security | | | | | | | | +------------+ | | | Security | | |
| | | | +->| v2cMP * |<--->| | Model | | | | | | | +->| v2cMP * |<--->| | Model | | |
| | Message | | | +------------+ | | +------------+ | | | | Message | | | +------------+ | | +------------+ | |
| | Dispatcher <--------->| +------------+ | | +------------+ | | | | Dispatcher <--------->| +------------+ | | +------------+ | |
| | | | +->| v3MP * |<--->| | TMSM | | | | | | | +->| v3MP * |<--->| | TMSM | | |
| | | | | +------------+ | | | MPSP | | | | | | | | +------------+ | | | SMSP | | |
| | PDU Dispatcher | | | +------------+ | | | | | | | | PDU Dispatcher | | | +------------+ | | | | | |
| +-------------------+ | +->| otherMP * |<--->| +------------+ | | | +-------------------+ | +->| otherMP * |<--->| +------------+ | |
| ^ | +------------+ | | | | | ^ | +------------+ | | | |
| | +---------------------+ +----------------+ | | | +---------------------+ +----------------+ |
| v | | v |
| +-------+-------------------------+---------------+ | | +-------+-------------------------+---------------+ |
| ^ ^ ^ | | ^ ^ ^ |
| | | | | | | | | |
| v v v | | v v v |
| +-------------+ +---------+ +--------------+ +-------------+ | | +-------------+ +---------+ +--------------+ +-------------+ |
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must establish a securityModel identifier, a securityLevel, and a must establish a securityModel identifier, a securityLevel, and a
securityName, which is the security model independent identifier for securityName, which is the security model independent identifier for
a principal. The SNMPv3 message processing architecture subsystem a principal. The SNMPv3 message processing architecture subsystem
relies on a security model, such as USM, to play a role in security relies on a security model, such as USM, to play a role in security
that goes beyond protecting the message - it provides a mapping that goes beyond protecting the message - it provides a mapping
between the USM-specific principal to a security-model independent between the USM-specific principal to a security-model independent
securityName which can be used for subsequent processing, such as for securityName which can be used for subsequent processing, such as for
access control. access control.
The TMSM is a two-stage security model, with a transport mapping The TMSM is a two-stage security model, with a transport mapping
security process (TMSP) and a message processing security process security process (TMSP) and a security model security process (SMSP).
(MPSP). Depending on the design of the specific TMSM model, i.e., Depending on the design of the specific TMSM model, i.e., which
which transport layer protocol is used, different features might be transport layer protocol is used, different features might be
provided by the TMSP or by the MPSP. For example, the translation provided by the TMSP or by the SMSP. For example, the translation
from a mechanism-specific authenticated identity to a securityName from a mechanism-specific authenticated identity to a securityName
might be done by the TMSP or by the MPSP. might be done by the TMSP or by the SMSP.
The securityName MUST be bound to the mechanism-specific The securityName MUST be bound to the mechanism-specific
authenticated identity, and this mapping MUST be done before the MPSP authenticated identity, and this mapping MUST be done before the SMSP
portion of the model passes securityName to the message processing portion of the model passes securityName to the message processing
model via the processIncoming() ASI. model via the processIncoming() ASI.
The SNMP architecture distinguishes between messages with no The SNMP architecture distinguishes between messages with no
authentication and no privacy (noAuthNoPriv), authentication without authentication and no privacy (noAuthNoPriv), authentication without
privacy (authNoPriv) and authentication with privacy (authPriv). privacy (authNoPriv) and authentication with privacy (authPriv).
Hence, the authentication of a transport layer identity plays an Hence, the authentication of a transport layer identity plays an
important role and must be considered by any TMSM, and user important role and must be considered by any TMSM, and principal
authentication must be available via the transport layer security authentication must be available via the transport layer security
protocol. protocol.
If the type of authentication provided by the transport layer (e.g. If the type of authentication provided by the transport layer (e.g.
TLS) is considered adequate to secure and/or encrypt the message, but TLS) is considered adequate to secure and/or encrypt the message, but
inadequate to provide the desired granularity of access control (e.g. inadequate to provide the desired granularity of access control (e.g.
user-based), then a second authentication (e.g., one provided by a user-based), then a second authentication (e.g., one provided by a
RADIUS server) may be used to provide the authentication identity RADIUS server) may be used to provide the authentication identity
which is bound to the securityName. This approach would require a which is bound to the securityName. This approach would require a
good analysis of the potential for man-in-the-middle attacks or good analysis of the potential for man-in-the-middle attacks or
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To provide support for protocols which simultaneously send To provide support for protocols which simultaneously send
information for authentication and authorization, such as RADIUS information for authentication and authorization, such as RADIUS
[RFC2865], model-specific authorization information MAY be cached or [RFC2865], model-specific authorization information MAY be cached or
otherwise made available to the access control subsystem, e.g., via a otherwise made available to the access control subsystem, e.g., via a
MIB table similar to the vacmSecurityToGroupTable, so the access MIB table similar to the vacmSecurityToGroupTable, so the access
control subsystem can create an appropriate binding between the control subsystem can create an appropriate binding between the
model-independent securityModel and securityName and a model-specific model-independent securityModel and securityName and a model-specific
access control policy. This may be highly undesirable, however, if access control policy. This may be highly undesirable, however, if
it creates a dependency between a security model and an access it creates a dependency between a security model and an access
control model, just as it is undesirable that the TMSM approach control model, just as it is undesirable that the TMSM approach
creates a dependency between a TMSP and an MPSP. creates a dependency between an SNMP message version and the security
provided by a transport mapping.
2.2.3. Security Parameter Passing Requirements 2.2.3. Security Parameter Passing Requirements
RFC3411 section 4 describes primitives to describe the abstract data RFC3411 section 4 describes primitives to describe the abstract data
flows between the various subsystems, models and applications within flows between the various subsystems, models and applications within
the architecture. Abstract Service Interfaces describe the flow of the architecture. Abstract Service Interfaces describe the flow of
data between subsystems within an engine. The ASIs generally pass data between subsystems within an engine. The ASIs generally pass
model-independent information. model-independent information.
Within an engine using a TMSM-based security model, outgoing SNMP Within an engine using a TMSM-based security model, outgoing SNMP
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perform integrity checking, and translate model-specific security perform integrity checking, and translate model-specific security
parameters into model-independent parameters. parameters into model-independent parameters.
In the TMSM approach, the security-model specific parameters are not In the TMSM approach, the security-model specific parameters are not
carried in the SNMP message. The parameters are provided by SNMP carried in the SNMP message. The parameters are provided by SNMP
applications for outgoing messages, and the parameters for incoming applications for outgoing messages, and the parameters for incoming
messages are extracted from the transport layer by the security- messages are extracted from the transport layer by the security-
model-specific transport mapping before the message is passed to the model-specific transport mapping before the message is passed to the
message processing subsystem. message processing subsystem.
For outgoing messages, it is necessary to have an MPSP because it is For outgoing messages, it is necessary to have an SMSP because it is
the MPSP that actually creates the message from its component parts. the SMSP that actually creates the message from its component parts.
Whether there are any security services provided by the MPSP for an Whether there are any security services provided by the SMSP for an
outgoing message is model-dependent. outgoing message is model-dependent.
For incoming messages, there might be security functionality that can For incoming messages, there might be security functionality that can
only be handled after the message version is known. The message only be handled after the message version is known. The message
version is determined by the Message Processing model and passed to version is determined by the Message Processing model and passed to
the MPSP via the processIncoming() ASI. the SMSP via the processIncoming() ASI.
The RFC3411 architecture has no ASI parameters for passing security The RFC3411 architecture has no ASI parameters for passing security
information between the transport mapping and the dispatcher, and information between the transport mapping and the dispatcher, and
between the dispatcher and the message processing model. If there is between the dispatcher and the message processing model. If there is
a need to have an MPSP called from the message processing model to, a need to have an SMSP called from the message processing model to,
for example, verify that msgFlags and the transport security are for example, verify that msgFlags and the transport security are
consistent, then it will be necessary to pass the model-dependent consistent, then it will be necessary to pass the model-dependent
security parameters from the TMSP through to the MPSP. security parameters from the TMSP through to the SMSP.
This document describes a cache, into which the TMSP puts information This document describes a cache, into which the TMSP puts information
about the security applied to an incoming message, and an MPSP about the security applied to an incoming message, and an SMSP
extracts that information from the cache. Given that there may be extracts that information from the cache. Given that there may be
multiple TM-security caches, a tmStateReference is passed as an extra multiple TM-security caches, a tmSessionReference is passed as an
parameter in the ASIs between the transport mapping and the messaging extra parameter in the ASIs between the transport mapping and the
security model.so the MPSP knows which cache of information to messaging security model, so the SMSP knows which cache of
consult. information to consult.
This approach does create dependencies between a model-specific TMSP This approach does create dependencies between a model-specific TMSP
and a corresponding specific MPSP. This approach of passing a model- and a corresponding specific SMSP. This approach of passing a model-
independent reference is consistent with the securityStateReference independent reference is consistent with the securityStateReference
cache already being passed around in the RFC3411 ASIs. cache already being passed around in the RFC3411 ASIs.
2.3. Session Requirements 2.3. Session Requirements
Throughout this document, the term session is used. Some underlying Throughout this document, the term session is used. Some underlying
secure transports will have a notion of session. Some underlying secure transports will have a notion of session. Some underlying
secure transports might enable the use of channels or other session- secure transports might enable the use of channels or other session-
like thing. In this document the term session refers to an like thing. In this document the term session refers to an
association between two SNMP engines that permits the secure association between two SNMP engines that permits the secure
skipping to change at page 17, line 38 skipping to change at page 17, line 38
maintained is specific to a particular security model. maintained is specific to a particular security model.
Sessions are not part of the SNMP architecture described in Sessions are not part of the SNMP architecture described in
[RFC3411], but are considered desirable because the cost of [RFC3411], but are considered desirable because the cost of
authentication can be amortized over potentially many transactions. authentication can be amortized over potentially many transactions.
It is important to note that the architecture described in [RFC3411] It is important to note that the architecture described in [RFC3411]
does not include a session selector in the Abstract Service does not include a session selector in the Abstract Service
Interfaces, and neither is that done for this architectural Interfaces, and neither is that done for this architectural
extension, so an SNMP application cannot select the session except by extension, so an SNMP application cannot select the session except by
passing a unique combination of securityName, securityModel, and passing a unique combination of transport address, securityName,
securityLevel. securityModel, and securityLevel.
All TMSM-based security models should discuss the impact of sessions All TMSM-based security models should discuss the impact of sessions
on SNMP usage, including how to establish/open a TMSM session (i.e., on SNMP usage, including how to establish/open a TMSM session (i.e.,
how it maps to the concepts of session-like things of the underlying how it maps to the concepts of session-like things of the underlying
protocol), how to behave when a TMSM session cannot be established, protocol), how to behave when a TMSM session cannot be established,
how to close a TMSM session (and the underlying protocol equivalent) how to close a TMSM session (and the underlying protocol equivalent)
properly, how to behave when a TMSM session is closed improperly, the properly, how to behave when a TMSM session is closed improperly, the
session security properties, session establishment overhead, and session security properties, session establishment overhead, and
session maintenance overhead. session maintenance overhead.
skipping to change at page 18, line 17 skipping to change at page 18, line 17
SNMP applications must provide the transport address, securityName, SNMP applications must provide the transport address, securityName,
securityModel, and securityLevel to be used for a session. securityModel, and securityLevel to be used for a session.
SNMP Applications typically have no knowledge of whether the session SNMP Applications typically have no knowledge of whether the session
that will be used to carry commands was initially established as a that will be used to carry commands was initially established as a
notification session, or a request-response session, and SHOULD NOT notification session, or a request-response session, and SHOULD NOT
make any assumptions based on knowing the direction of the session. make any assumptions based on knowing the direction of the session.
If an administrator or security model designer wants to differentiate If an administrator or security model designer wants to differentiate
a session established for different purposes, such as a notification a session established for different purposes, such as a notification
session versus a request-response session, the application can use session versus a request-response session, the application can use
different securityNames or transport addresses (e.g., port 161 vs different securityNames or transport addresses (e.g., port 161 vs.
port 162) for different purposes. port 162) for different purposes.
An SNMP engine containing an application that initiates An SNMP engine containing an application that initiates
communication, e.g., a Command Generator or Notification Originator, communication, e.g., a Command Generator or Notification Originator,
MUST be able to attempt to establish a session for delivery if a MUST be able to attempt to establish a session for delivery if a
session does not yet exist. If a session cannot be established then session does not yet exist. If a session cannot be established then
the message is discarded. the message is discarded.
Sessions are usually established by the transport mapping security Sessions are usually established by the transport mapping security
processor when no appropriate session is found for an outgoing processor when no appropriate session is found for an outgoing
skipping to change at page 23, line 47 skipping to change at page 23, line 47
: | |<-------------------| : | |<-------------------|
: | | | : | | |
: |<-------------------| | : |<-------------------| |
: | | | : | | |
: |--------------+ | | : |--------------+ | |
: | Send SNMP | | | : | Send SNMP | | |
: | Message | | | : | Message | | |
: | to Network | | | : | to Network | | |
: | v | | : | v | |
4. Abstract Service Interfaces for TMSM 4. Message Formats
4.1. Existing Abstract Service Interfaces The syntax of an SNMP message using this Security Model adheres to
the message format defined in the version-specific Message Processing
Model document (for example [RFC3412]). At the time of this writing,
there are three defined message formats - SNMPv1, SNMPv2c, and
SNMPv3. SNMPv1 and SNMPv2c have been declared Historic, so this memo
only deals with SNMPv3 messages.
The OUT parameters of the prepareOutgoingMessage() ASI are used to The processing is compatible with the RFC 3412 primitives,
pass information from the message processing model to the dispatcher generateRequestMsg() and processIncomingMsg(), that show the data
and on to the transport mapping: flow between the Message Processor and the SMSP.
statusInformation = -- success or errorIndication 4.1. SNMPv3 Message Fields
prepareOutgoingMessage(
IN transportDomain -- transport domain to be used
IN transportAddress -- transport address to be used
IN messageProcessingModel -- typically, SNMP version
IN securityModel -- Security Model to use
IN securityName -- on behalf of this principal
IN securityLevel -- Level of Security requested
IN contextEngineID -- data from/at this entity
IN contextName -- data from/in this context
IN pduVersion -- the version of the PDU
IN PDU -- SNMP Protocol Data Unit
IN expectResponse -- TRUE or FALSE
IN sendPduHandle -- the handle for matching
incoming responses
OUT destTransportDomain -- destination transport domain
OUT destTransportAddress -- destination transport address
OUT outgoingMessage -- the message to send
OUT outgoingMessageLength -- its length
)
4.2. TMSM Abstract Service Interfaces The SNMPv3Message SEQUENCE is defined in [RFC3412] and [RFC3416].
A set of abstract service interfaces have been defined within this SNMPv3MessageSyntax DEFINITIONS IMPLICIT TAGS ::= BEGIN
document to describe the conceptual data flows between the Transport
Mapping Security Models and adjacent components in the system.
The sendMessage ASI is used to pass a message from the Dispatcher to SNMPv3Message ::= SEQUENCE {
the transport mapping for sending. -- identify the layout of the SNMPv3Message
-- this element is in same position as in SNMPv1
-- and SNMPv2c, allowing recognition
-- the value 3 is used for snmpv3
msgVersion INTEGER ( 0 .. 2147483647 ),
-- administrative parameters
msgGlobalData HeaderData,
-- security model-specific parameters
-- format defined by Security Model
msgSecurityParameters OCTET STRING,
msgData ScopedPduData
}
statusInformation = HeaderData ::= SEQUENCE {
sendMessage( msgID INTEGER (0..2147483647),
IN destTransportDomain -- transport domain to be used msgMaxSize INTEGER (484..2147483647),
IN destTransportAddress -- transport address to be used
IN outgoingMessage -- the message to send
IN outgoingMessageLength -- its length
IN tmStateReference
OUT sessionID
)
The recvMessage ASI is used to pass a message from the transport msgFlags OCTET STRING (SIZE(1)),
mapping to the Dispatcher. -- .... ...1 authFlag
-- .... ..1. privFlag
-- .... .1.. reportableFlag
-- Please observe:
-- .... ..00 is OK, means noAuthNoPriv
-- .... ..01 is OK, means authNoPriv
-- .... ..10 reserved, MUST NOT be used.
-- .... ..11 is OK, means authPriv
statusInformation = msgSecurityModel INTEGER (1..2147483647)
recvMessage( }
IN destTransportDomain -- transport domain to be used
IN destTransportAddress -- transport address to be used
IN incomingMessage -- the message received
IN incomingMessageLength -- its length
OUT tmStateReference
OUT sessionID
)
The Transport Mapping Security Model provides the following ScopedPduData ::= CHOICE {
primitives to pass data back and forth between the TMSM and specific plaintext ScopedPDU,
TMSM-based security models, which provide the interface to the encryptedPDU OCTET STRING -- encrypted scopedPDU value
underlying secure transport service. Each TMSM-based security model }
should define the security-model-specific elements of procedure for
the openSession(), closeSession(), txMessage(), and rxMessage()
interfaces.
statusInformation = ScopedPDU ::= SEQUENCE {
txMessage( contextEngineID OCTET STRING,
IN destTransportDomain -- transport domain to be used contextName OCTET STRING,
IN destTransportAddress -- transport address to be used data ANY -- e.g., PDUs as defined in [RFC3416]
IN outgoingMessage -- the message to send }
IN outgoingMessageLength -- its length END
IN tmStateReference
OUT sessionID
)
statusInformation = The following describes how any TMSM model SHOULD treat certain
rxMessage( fields in the message:
IN destTransportDomain -- transport domain to be used
IN destTransportAddress -- transport address to be used
IN incomingMessage -- the message to send
IN incomingMessageLength -- its length
OUT tmStateReference
)
statusInformation = 4.1.1. msgGlobalData
openSession(
IN transportDomain -- transport domain to be used
IN transportAddress -- transport address to be used
IN tmStateReference
OUT sessionID
)
statusInformation = msgGlobalData is opaque to a TMSM security model. The values are set
closeSession( by the Message Processing model (e.g., SNMPv3 Message Processing),
IN sessionID and SHOULD NOT be modified by a TMSM security model.
)
The msgSecurityModel field should be set by the Message Processing
model to a value from the SnmpSecurityModel enumeration [RFC3411] to
identify the specific TMSM model. Each standards-track TMSM model
should have an enumeration assigned by IANA. Each enterprise-
specific security model should have an enumeration assigned following
instructions in the description of the SnmpSecurityModel TEXTUAL-
CONVENTION from RFC3411.
The msgFlags have the same values for a TMSM model as for the USM
model.
4.1.1.1. securityLevel and msgFlags
For an outgoing message, msgFlags is the requested security for the
message; if a TMSM cannot provide the requested securityLevel, the
model MUST describe a standard behavior that is followed for that
situation. If the TMSM cannot provide at least the requested level
of security, the TMSM MUST discard the request and SHOULD notify the
message processing model that the request failed.
For an outgoing message, if the TMSM is able to provide stronger than
requested security, that may be acceptable. The transport layer
protocol would need to indicate to the receiver what security has
been applied to the actual message. To avoid the need to mess with
the ASN.1 encoding, the SNMPv3 message carries the requested
msgFlags, not the actual securityLevel applied to the message. If a
message format other than SNMPv3 is used, then the new message may
carry the more accurate securityLevel in the SNMP message.
For an incoming message, the receiving TMSM knows what must be done
to process the message based on the transport layer mechanisms. If
the underlying transport security mechanisms for the receiver cannot
provide the matching securityLevel, then the message should follow
the standard behaviors for the transport security mechanism, or be
discarded silently.
Part of the responsibility of the TMSM is to ensure that the actual
security provided by the underlying transport layer security
mechanisms is configured to meet or exceed the securityLevel required
by the msgFlags in the SNMP message. When the SMSP processes the
incoming message, it should compare the msgFlags field to the
securityLevel actually provided for the message by the transport
layer security. If they differ, the SMSP should determine whether
the changed securityLevel is acceptable. If not, it should discard
the message. Depending on the model, the SMSP may issue a reportPDU
with a model-specific counter.
4.1.2. msgSecurityParameters
The field msgSecurityParameters carries model-dependent security
information between engines. When a security model does not utilize
this field, its value MUST be the BER serialization of a zero-length
OCTET STRING, to prevent its being used in a manner that could be
damaging, such as for carrying a virus or worm.
RFC3412 defines two primitives, generateRequestMsg() and
processIncomingMsg() which require the specification of an
authoritative SNMP entity. The meaning of authoritative is model
dependent.
5. Cached Information and References 5. Cached Information and References
The RFC3411 architecture uses caches to store dynamic model-specific he RFC3411 architecture uses caches to store dynamic model-specific
information, and uses references in the ASIs to indicate in a model- information, and uses references in the ASIs to indicate in a model-
independent manner which cached information must flow between independent manner which cached information must flow between
subsytems. subsystems. For most TMSM models, there are two levels of state that
need to be maintained: the session state, and the message security
state.
5.1. securityStateReference Cached Security Data 5.1. tmSessionReference Cached Session Data
The tmSessionReference is used to pass references to the appropriate
session information between the TMSP and SMSP through the ASIs.
The TMSP may provide only some aspects of security, and leave some
aspects to the SMSP. tmSessionReference should be used to pass any
parameters, in a model- and mechanism-specific format, that will be
needed to coordinate the activities of the TMSP and SMSP, plus the
parameters subsequently passed in securityStateReference.
The security model has the responsibility for explicitly releasing
the complete tmSessionReference and possibly deleting the associated
LCD information when the session is destroyed.
5.2. securityStateReference Cached Security Data
From RFC3411: "For each message received, the Security Model caches From RFC3411: "For each message received, the Security Model caches
the state information such that a Response message can be generated the state information such that a Response message can be generated
using the same security information, even if the Local Configuration using the same security information, even if the Local Configuration
Datastore is altered between the time of the incoming request and the Datastore is altered between the time of the incoming request and the
outgoing response. outgoing response.
A Message Processing Model has the responsibility for explicitly A Message Processing Model has the responsibility for explicitly
releasing the cached data if such data is no longer needed. To releasing the cached data if such data is no longer needed. To
enable this, an abstract securityStateReference data element is enable this, an abstract securityStateReference data element is
passed from the Security Model to the Message Processing Model. The passed from the Security Model to the Message Processing Model. The
cached security data may be implicitly released via the generation of cached security data may be implicitly released via the generation of
a response, or explicitly released by using the stateRelease a response, or explicitly released by using the stateRelease
primitive, as described in RFC3411 section 4.5.1." primitive, as described in RFC3411 section 4.5.1."
For the TMSM approach, the TMSP may need to provide the information For the TMSM approach, the TMSP may need to provide the information
to be stored in the securityStateReference to the message processing to be stored in the securityStateReference to the message processing
model. such as the security-model-independent securityName, model. such as the security-model-independent securityName,
securityLevel, and securityModel parameters. For responses, the securityLevel, and securityModel parameters, and the transport
messaging model may need to pass the parameters back to the TMSP. address, and transport type. For responses, the messaging model may
need to pass the parameters back to the TMSP.
This document will differentiate the tmStateReference provided by the This document will differentiate the tmSessionReference provided by
TMSP to the MPSP, from the securityStateReference provided by the the TMSP to the SMSP, from the securityStateReference provided by the
MPSP to the Dispatcher. This document does not specify an SMSP to the Dispatcher. This document does not specify an
implementation strategy, only an abstract discussion of the data that implementation strategy, only an abstract discussion of the data that
must flow between subsystems. An implementation MAY use one cache must flow between subsystems. An implementation MAY use one cache
and one reference to serve both functions, but an implementer must be and one reference to serve both functions, but an implementer must be
aware of the cache-release issues to prevent the cache from being aware of the cache-release issues to prevent the cache from being
released before the transport mapping has had an opportunity to released before the transport mapping has had an opportunity to
extract the information it needs. extract the information it needs.
5.2. tmStateReference Cached Security Data 6. Abstract Service Interfaces for TMSM
A tmStateReference is used to pass data between the TMSP and the Abstract service interfaces have been defined by RFC 3411 to describe
MPSP, similar to the securityStateReference described in RFC3412. A the conceptual data flows between the various subsystems within an
reference to this cache can be envisioned as being appended to the SNMP entity. TMSM security models use some of these conceptual data
ASIs between the TM and the MP. flows when communicating between subsystems, such as the dispatcher
and the Message Processing Subsystem.
The TMSP may provide only some aspects of security, and leave some To simplify the elements of procedure, the release of state
aspects to the MPSP. tmStateReference should be used to pass any information is not always explicitly specified. As a general rule,
parameters, in a model- and mechanism-specific format, that will be if state information is available when a message gets discarded, the
needed to coordinate the activities of the TMSP and MPSP, plus the message-state information should also be released, and if state
parameters subsequently passed in securityStateReference. For information is available when a session is closed, the session state
example, the TMSP may provide privacy and data integrity and information should also be released.
authentication and authorization policy retrievals, or some subset of
these features, depending on the features available in the transport
mechanisms. A field in tmStateReference should identify which
services were provided for each received message by the TMSP, the
securityLevel applied to the received message, the model-specific
security identity, the session identifier for session based transport
security, and so on.
6. Integration with the SNMPv3 Message Format An error indication may return an OID and value for an incremented
counter and a value for securityLevel, and values for contextEngineID
and contextName for the counter, and the securityStateReference if
the information is available at the point where the error is
detected.
TMSM proposals can use the SNMPv3 message format, defined in RFC3412, 6.1. Generating an Outgoing SNMP Message
section 6. This section discusses how the fields could be reused.
6.1. msgVersion This section describes the procedure followed by an RFC3411-
compatible system whenever it generates a message containing a
management operation (such as a request, a response, a notification,
or a report) on behalf of a user.
For proposals that reuse the SNMPv3 message format, this field should statusInformation = -- success or errorIndication
contain the value 3. prepareOutgoingMessage(
IN transportDomain -- transport domain to be used
IN transportAddress -- transport address to be used
IN messageProcessingModel -- typically, SNMP version
IN securityModel -- Security Model to use
IN securityName -- on behalf of this principal
IN securityLevel -- Level of Security requested
IN contextEngineID -- data from/at this entity
IN contextName -- data from/in this context
IN pduVersion -- the version of the PDU
IN PDU -- SNMP Protocol Data Unit
IN expectResponse -- TRUE or FALSE
IN sendPduHandle -- the handle for matching
incoming responses
OUT destTransportDomain -- destination transport domain
OUT destTransportAddress -- destination transport address
OUT outgoingMessage -- the message to send
OUT outgoingMessageLength -- its length
OUT tmSessionReference
)
6.2. msgGlobalData Note that tmSessionReference has been added to this ASI.
The fields msgID and msgMaxSize are used identically for the TMSM The IN parameters of the prepareOutgoingMessage() ASI are used to
models as for the USM model. pass information from the dispatcher (for the application subsystem)
to the message processing subsystem.
The msgSecurityModel field should be set to a value from the The abstract service primitive from a Message Processing Model to a
SnmpSecurityModel enumeration [RFC3411] to identify the specific TMSM Security Model to generate the components of a Request message is
model. Each standards-track TMSM model should have an enumeration generateRequestMsg().
assigned by IANA. Each enterprise-specific security model should
have an enumeration assigned following instructions in the
description of the SnmpSecurityModel TEXTUAL-CONVENTION from RFC3411.
The msgSecurityParameters field would carry security information The abstract service primitive from a Message Processing Model to a
required for message security processing. It is unclear whether this Security Model to generate the components of a Response message is
field would be useful or what parameters would be carried to support generateResponseMsg().
security, since message security is provided by an external process,
and msgSecurityParameters are not used by the access control
subsystem.
RFC3412 defines two primitives, generateRequestMsg() and Upon completion of the SMSP processing, the Security model returns
processIncomingMsg() which require the specification of an statusInformation. If the process was successful, the completed
authoritative SNMP entity. [discuss] We need to discuss what the message is returned. If the process was not successful, then an
meaning of authoritative would be in a TMSM environment, whether the errorIndication is returned.
specific services provided in USM security from msgSecurityParameters
still are needed, and how the Message Processing model provides this
information to the security model via generateRequestMsg() and
processIncomingMsg() primitives. RFC3412 specifies that "The data in
the msgSecurityParameters field is used exclusively by the Security
Model, and the contents and format of the data is defined by the
Security Model. This OCTET STRING is not interpreted by the v3MP,
but is passed to the local implementation of the Security Model
indicated by the msgSecurityModel field in the message."
The msgFlags have the same values for the TMSM models as for the USM The OUT parameters of the prepareOutgoingMessage() ASI are used to
model. "The authFlag and privFlag fields indicate the securityLevel pass information from the message processing model to the dispatcher
that was applied to the message before it was sent on the wire." and on to the transport mapping:
6.3. securityLevel and msgFlags 6.2. TMSP for an Outgoing Message
For an outgoing message, msgFlags is the requested security for the The sendMessage ASI is used to pass a message from the Dispatcher to
message; if a TMSM cannot provide the requested securityLevel, the the appropriate transport mapping for sending.
model MUST describe a standard behavior that is followed for that
situation. If the TMSM cannot provide at least the requested level
of security, the TMSM MUST discard the request and SHOULD notify the
message processing model that the request failed.
[discuss] how is yet to be determined, and may be model-specific or statusInformation =
implementation-specific. sendMessage(
IN destTransportDomain -- transport domain to be used
IN destTransportAddress -- transport address to be used
IN outgoingMessage -- the message to send
IN outgoingMessageLength -- its length
IN tmSessionReference
)
For an outgoing message, if the TMSM is able to provide stronger than The Transport Mapping Security Model provides the following
requested security, that may be acceptable. The transport layer primitives to pass data back and forth between the TMSM and specific
protocol would need to indicate to the receiver what security has TMSM-based security models, which provide the interface to the
been applied to the actual message. To avoid the need to mess with underlying secure transport service. Each TMSM-based security model
the ASN.1 encoding, the SNMPv3 message carries the requested should define the security-model-specific elements of procedure for
msgFlags, not the actual securityLevel applied to the message. If a the openSession() and closeSession() interfaces.
message format other than SNMPv3 is used, then the new message may
carry the more accurate securityLevel in the SNMP message.
For an incoming message, the receiving TMSM knows what must be done statusInformation =
to process the message based on the transport layer mechanisms. If openSession(
the underlying transport security mechanisms for the receiver cannot IN transportDomain -- transport domain to be used
provide the matching securityLevel, then the message should follow IN transportAddress -- transport address to be used
the standard behaviors for the transport security mechanism, or be IN tmSessionReference
discarded silently. )
Part of the responsibility of the TMSM is to ensure that the actual statusInformation =
security provided by the underlying transport layer security closeSession(
mechanisms is configured to meet or exceed the securityLevel required IN tmSessionReference
by the msgFlags in the SNMP message. When the MPSP processes the )
incoming message, it should compare the msgFlags field to the
securityLevel actually provided for the message by the transport
layer security. If they differ, the MPSP should determine whether
the changed securityLevel is acceptable. If not, it should discard
the message. Depending on the model, the MPSP may issue a reportPDU
with the XXXXXXX model-specific counter.
7. Prepare an Outgoing SNMP Message 6.3. Processing an Incoming SNMP Message
Following RFC3412, section 7.1, the SNMPv3 message processing model 6.3.1. TMSP for an Incoming Message
uses the generateResponseMsg() or generateRequestMsg() primitives, to
call the MPSP. The message processing model, or the MPSP it calls,
may need to put information into the tmStateReference cache for use
by the TMSP, such as:
tmSecurityStateReference - the unique identifier for the cached If one does not exist, the TMSP will need to create an entry in a
information Local Configuration Datastore referenced by tmSessionReference. This
tmTransportDomain information will include transportDomain, transportAddress, the
tmTransportAddress securityModel, the securityLevel, and the securityName, plus any
tmSecurityModel - an indicator of which mechanisms to use model or mechanism-specific details. How this information is
tmSecurityName - a model-specific identifier of the security determined is model-specific.
principal
tmSecurityLevel - an indicator of which security services are
requested
A tmStateReference cache may contain additional information such as
tmSessionID
tmSessionKey
tmSessionMsgID
8. Prepare Data Elements from an Incoming SNMP Message The recvMessage ASI is used to pass a message from the transport
mapping to the Dispatcher.
For an incoming message, the TMSP will need to put information from statusInformation =
the transport mechanisms used into the tmStateReference so the MPSP recvMessage(
can extract the information and add it conceptually to the IN destTransportDomain -- transport domain to be used
securityStateReference. IN destTransportAddress -- transport address to be used
IN incomingMessage -- the message received
IN incomingMessageLength -- its length
IN tmSessionReference
)
The tmStateReference cache will likely contain at least the following 6.3.2. Prepare Data Elements from Incoming Messages
information:
tmStateReference - a unique identifier for the cached information
tmSecurityStateReference - the unique identifier for the cached
information
tmTransportDomain
tmTransportAddress
tmSecurityModel - an indicator of which mechanisms to use
tmSecurityName - a model-specific identifier of the security
principal
tmSecurityLevel - an indicator of which security services are
requested
tmAuthProtocol
tmPrivProtocol
and may contain additional information such as
tmSessionID
tmSessionKey
tmSessionMsgID
9. Notifications The abstract service primitive from the Dispatcher to a Message
Processing Model for a received message is:
For notifications, if the cache has been released and then session result = -- SUCCESS or errorIndication
closed, then the MPSP will request the TMSP to establish a session, prepareDataElements(
populate the cache, and pass the securityStateReference to the MPSP. IN transportDomain -- origin transport domain
IN transportAddress -- origin transport address
IN wholeMsg -- as received from the network
IN wholeMsgLength -- as received from the network
IN tmSessionReference -- from the transport mapping
OUT messageProcessingModel -- typically, SNMP version
OUT securityModel -- Security Model to use
OUT securityName -- on behalf of this principal
OUT securityLevel -- Level of Security requested
OUT contextEngineID -- data from/at this entity
OUT contextName -- data from/in this context
OUT pduVersion -- the version of the PDU
OUT PDU -- SNMP Protocol Data Unit
OUT pduType -- SNMP PDU type
OUT sendPduHandle -- handle for matched request
OUT maxSizeResponseScopedPDU -- maximum size sender can accept
OUT statusInformation -- success or errorIndication
-- error counter OID/value if error
OUT stateReference -- reference to state information
-- to be used for possible Response
)
[discuss] We need to determine what state needs to be saved here. Note that tmSessionReference has been added to this ASI.
10. The TMSM MIB Module 6.3.3. MPSP for an Incoming Message
This section describes the procedure followed by the SMSP whenever it
receives an incoming message containing a management operation on
behalf of a user from a Message Processing model.
The Message Processing Model extracts some information from the
wholeMsg. The abstract service primitive from a Message Processing
Model to the Security Subsystem for a received message is::
statusInformation = -- errorIndication or success
-- error counter OID/value if error
processIncomingMsg(
IN messageProcessingModel -- typically, SNMP version
IN maxMessageSize -- of the sending SNMP entity
IN securityParameters -- for the received message
IN securityModel -- for the received message
IN securityLevel -- Level of Security
IN wholeMsg -- as received on the wire
IN wholeMsgLength -- length as received on the wire
IN tmSessionReference -- from the transport mapping
OUT securityEngineID -- authoritative SNMP entity
OUT securityName -- identification of the principal
OUT scopedPDU, -- message (plaintext) payload
OUT maxSizeResponseScopedPDU -- maximum size sender can handle
OUT securityStateReference -- reference to security state
) -- information, needed for response
1) The securityEngineID is set to a value in a model-specific manner.
If the securityEngineID is not utilized by the specific model, then
it should be set to the local snmpEngineID, to satisfy the SNMPv3
message processing model in RFC 3412 section 7.2 13a).
2) Extract the value of securityName from the Local Configuration
Datastore entry referenced by tmSessionReference.
3) The scopedPDU component is extracted from the wholeMsg.
4) The maxSizeResponseScopedPDU is calculated. This is the maximum
size allowed for a scopedPDU for a possible Response message.
5)The security data is cached as cachedSecurityData, so that a
possible response to this message can and will use the same security
parameters. Then securityStateReference is set for subsequent
reference to this cached data.
4) The statusInformation is set to success and a return is made to
the calling module passing back the OUT parameters as specified in
the processIncomingMsg primitive.
7. The TMSM MIB Module
This memo defines a portion of the Management Information Base (MIB) This memo defines a portion of the Management Information Base (MIB)
for managing sessions in the Transport Mapping Security Model for statistics in the Transport Mapping Security Model extension.
extension.
10.1. Structure of the MIB Module 7.1. Structure of the MIB Module
Objects in this MIB module are arranged into subtrees. Each subtree Objects in this MIB module are arranged into subtrees. Each subtree
is organized as a set of related objects. The overall structure and is organized as a set of related objects. The overall structure and
assignment of objects to their subtrees, and the intended purpose of assignment of objects to their subtrees, and the intended purpose of
each subtree, is shown below. each subtree, is shown below.
10.1.1. The tmsmNotifications Subtree 7.1.1. The tmsmStats Subtree
This subtree contains notifications to alert other entities to events
that are applicable to all security models based on the Transport
Mapping Security Model extension.
10.1.2. The tmsmStats Subtree
This subtree contains security-model-independent counters which are This subtree contains security-model-independent counters which are
applicable to all security models based on the .Transport Mapping applicable to all security models based on the .Transport Mapping
Security Model extension. This subtree provides information for Security Model extension. This subtree provides information for
identifying fault conditions and performance degradation. identifying fault conditions and performance degradation.
10.1.3. The tmsmSession Subtree 7.2. Relationship to Other MIB Modules
This subtree contains security-model-independent information about
sessions which are applicable to all security models based on the
Transport Mapping Security Model extension.
10.2. Relationship to Other MIB Modules
Some management objects defined in other MIB modules are applicable Some management objects defined in other MIB modules are applicable
to an entity implementing this MIB. In particular, it is assumed to an entity implementing this MIB. In particular, it is assumed
that an entity implementing the TMSM-MIB module will also implement that an entity implementing the TMSM-MIB module will also implement
the SNMPv2-MIB [RFC3418]. the SNMPv2-MIB [RFC3418].
This MIB module is expected to be used with the MIB modules defined This MIB module is expected to be used with the MIB modules defined
for managing specific security models that are based on the TMSM for managing specific security models that are based on the TMSM
extension. This MIB module is designed to be security-model extension. This MIB module is designed to be security-model
independent, and contains objects useful for managing common aspects independent, and contains objects useful for managing common aspects
of any TMSM-based security model. Specific security models may of any TMSM-based security model. Specific security models may
define a MIB module to contain security-model-dependent information. define a MIB module to contain security-model-dependent information.
10.2.1. Textual Conventions 7.2.1. Textual Conventions
Generic and Common Textual Conventions used in this document can be Generic and Common Textual Conventions used in this document can be
found summarized at http://www.ops.ietf.org/mib-common-tcs.html found summarized at http://www.ops.ietf.org/mib-common-tcs.html
10.2.2. MIB Modules Required for IMPORTS 7.2.2. MIB Modules Required for IMPORTS
The following MIB module imports items from [RFC2578], [RFC2579], The. following MIB module imports items from [RFC2578], [RFC2579],
[RFC2580], [RFC3411], and [RFC3419] [RFC2580], [RFC3411], and [RFC3419]
11. Definitions 7.3. Definitions
TMSM-MIB DEFINITIONS ::= BEGIN TMSM-MIB DEFINITIONS ::= BEGIN
IMPORTS IMPORTS
MODULE-IDENTITY, OBJECT-TYPE, MODULE-IDENTITY, OBJECT-TYPE,
mib-2, Integer32, Unsigned32, Gauge32 mib-2, Integer32, Unsigned32, Gauge32
FROM SNMPv2-SMI FROM SNMPv2-SMI
TestAndIncr, StorageType, RowStatus TestAndIncr, StorageType, RowStatus
FROM SNMPv2-TC FROM SNMPv2-TC
MODULE-COMPLIANCE, OBJECT-GROUP MODULE-COMPLIANCE, OBJECT-GROUP
FROM SNMPv2-CONF FROM SNMPv2-CONF
SnmpSecurityModel, SnmpSecurityModel,
SnmpAdminString, SnmpSecurityLevel, SnmpEngineID SnmpAdminString, SnmpSecurityLevel, SnmpEngineID
skipping to change at page 33, line 20 skipping to change at page 35, line 5
Editor: Editor:
David Harrington David Harrington
FutureWei Technologies FutureWei Technologies
1700 Alma Drive, Suite 100 1700 Alma Drive, Suite 100
Plano, Texas 75075 Plano, Texas 75075
USA USA
+1 603-436-8634 +1 603-436-8634
dharrington@huawei.com dharrington@huawei.com
" "
DESCRIPTION "The Transport Mapping Security Model DESCRIPTION "The Transport Mapping Security Model
MIB MIB Module
Copyright (C) The Internet Society (2006). This Copyright (C) The Internet Society (2006). This
version of this MIB module is part of RFC XXXX; version of this MIB module is part of RFC XXXX;
see the RFC itself for full legal notices. see the RFC itself for full legal notices.
-- NOTE to RFC editor: replace XXXX with actual RFC number -- NOTE to RFC editor: replace XXXX with actual RFC number
-- for this document and remove this note -- for this document and remove this note
" "
DESCRIPTION "The initial version, published in RFC XXXX. DESCRIPTION "The initial version, published in RFC XXXX.
-- NOTE to RFC editor: replace XXXX with actual RFC number -- NOTE to RFC editor: replace XXXX with actual RFC number
-- for this document and remove this note -- for this document and remove this note
skipping to change at page 34, line 4 skipping to change at page 35, line 35
tmsmNotifications OBJECT IDENTIFIER ::= { tmsmMIB 0 } tmsmNotifications OBJECT IDENTIFIER ::= { tmsmMIB 0 }
tmsmObjects OBJECT IDENTIFIER ::= { tmsmMIB 1 } tmsmObjects OBJECT IDENTIFIER ::= { tmsmMIB 1 }
tmsmConformance OBJECT IDENTIFIER ::= { tmsmMIB 2 } tmsmConformance OBJECT IDENTIFIER ::= { tmsmMIB 2 }
-- ------------------------------------------------------------- -- -------------------------------------------------------------
-- Objects -- Objects
-- ------------------------------------------------------------- -- -------------------------------------------------------------
-- Textual Conventions -- Textual Conventions
SessionIndex ::= TEXTUAL-CONVENTION
DISPLAY-HINT "d"
STATUS current
DESCRIPTION
"A unique value, greater than zero, identifying a transport
mapping security model session. The value must remain
constant for the duration of a session. New values should
be assigned in such a way that reuse of recently used
values is avoided."
SYNTAX Integer (1..2147483647)
SessionIndexOrZero TEXTUAL-CONVENTION
DISPLAY-HINT "d"
STATUS current
DESCRIPTION
"This extension of the TmsmSessionId permits the additional
value zero. The meaning of the value zero is object-specific
and must therefore be defined as part of the description of
any object which uses this syntax. Examples of the usage of
zero might include situations where a session was unknown
or where none or all sessions need to be referenced."
SYNTAX Integer (0..2147483647)
-- Notifications for the Transport Model Security Model extension -- Notifications for the Transport Model Security Model extension
-- Statistics for the Transport Model Security Model extension -- Statistics for the Transport Model Security Model extension
tmsmStats OBJECT IDENTIFIER ::= { tmsmObjects 1 } tmsmStats OBJECT IDENTIFIER ::= { tmsmObjects 1 }
tmsmSessionOpenErrors OBJECT-TYPE tmsmSessionOpenErrors OBJECT-TYPE
SYNTAX Counter32 SYNTAX Counter32
MAX-ACCESS read-only MAX-ACCESS read-only
STATUS current STATUS current
DESCRIPTION "The number of times an openSession() request DESCRIPTION "The number of times an openSession() request
failed to open a Session. failed to open a Session.
" "
::= { tmsmStats 1 } ::= { tmsmStats 1 }
tmsmSessionNoAvailableSessions OBJECT-TYPE
SYNTAX Counter32
MAX-ACCESS read-only
STATUS current
DESCRIPTION "The number of times a Response message
was dropped because the corresponding
session was no longer available.
"
::= { tmsmStats 2 }
-- The tmsmSession Group -- The tmsmSession Group
tmsmSession OBJECT IDENTIFIER ::= { tmsmObjects 2 } tmsmSession OBJECT IDENTIFIER ::= { tmsmObjects 2 }
tmsmSessionSpinLock OBJECT-TYPE
SYNTAX TestAndIncr
MAX-ACCESS read-write
STATUS current
DESCRIPTION "An advisory lock used to allow several cooperating
TMSM security models to coordinate their
use of facilities to create sessions in the
tmsmSessionTable.
"
::= { tmsmSession 1 }
tmsmSessionCurrent OBJECT-TYPE tmsmSessionCurrent OBJECT-TYPE
SYNTAX Gauge32 SYNTAX Gauge32
MAX-ACCESS read-only MAX-ACCESS read-only
STATUS current STATUS current
DESCRIPTION "The current number of open sessions. DESCRIPTION "The current number of open sessions.
" "
::= { tmsmSession 2 } ::= { tmsmSession 1 }
tmsmSessionMaxSupported OBJECT-TYPE tmsmSessionMaxSupported OBJECT-TYPE
SYNTAX Unsigned32 SYNTAX Unsigned32
MAX-ACCESS read-only MAX-ACCESS read-only
STATUS current STATUS current
DESCRIPTION "The maximum number of open sessions supported. DESCRIPTION "The maximum number of open sessions supported.
The value zero indicates the maximum is dynamic. The value zero indicates the maximum is dynamic.
" "
::= { tmsmSession 3 } ::= { tmsmSession 2 }
tmsmSessionOpenErrors OBJECT-TYPE tmsmSessionOpenErrors OBJECT-TYPE
SYNTAX Counter32 SYNTAX Counter32
MAX-ACCESS read-only MAX-ACCESS read-only
STATUS current STATUS current
DESCRIPTION "The number of times an openSession() request DESCRIPTION "The number of times an openSession() request
failed to open a Session. failed to open a Session.
" "
::= { tmsmSession 4 } ::= { tmsmSession 3 }
tmsmSessionSecurityLevelNotAvailableErrors OBJECT-TYPE tmsmSessionSecurityLevelNotAvailableErrors OBJECT-TYPE
SYNTAX Counter32 SYNTAX Counter32
MAX-ACCESS read-only MAX-ACCESS read-only
STATUS current STATUS current
DESCRIPTION "The number of times an outgoing message was DESCRIPTION "The number of times an outgoing message was
discarded because a requested securityLevel could not discarded because a requested securityLevel could not
provided. provided.
" "
::= { tmsmSession 5 } ::= { tmsmSession 4 }
tmsmSessionTable OBJECT-TYPE
SYNTAX SEQUENCE OF TmsmSessionEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "The table of currently available sessions configured
in the SNMP engine's Local Configuration Datastore
(LCD).
Sessions are created as needed, and do not persist
across network management system reboots.
"
::= { tmsmSession 6 }
tmsmSessionEntry OBJECT-TYPE
SYNTAX TmsmSessionEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "A session configured in the SNMP engine's Local
Configuration Datastore (LCD) for Transport Mapping
Security Models.
"
INDEX { tmsmSessionID }
::= { tmsmSessionTable 1 }
TmsmSessionEntry ::= SEQUENCE
{
tmsmSessionID SessionIndex,
tmsmSessionTransport TransportAddressType,
tmsmSessionAddress TransportAddress,
tmsmSessionSecurityModel SnmpSecurityModel,
tmsmSessionSecurityName SnmpAdminString,
tmsmSessionSecurityLevel SnmpSecurityLevel,
tmsmSessionEngineID SnmpEngineID
}
tmsmSessionID OBJECT-TYPE
SYNTAX SessionIndex
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "A locally-unique identifier for a session.
"
::= { tmsmSessionEntry 1 }
tmsmSessionTransport OBJECT-TYPE
SYNTAX TransportAddressType
MAX-ACCESS read-only
STATUS current
DESCRIPTION "The transport domain associated with this session.
"
::= { tmsmSessionEntry 2 }
tmsmSessionAddress OBJECT-TYPE
SYNTAX TransportAddress
MAX-ACCESS read-only
STATUS current
DESCRIPTION "The transport address associated with this session.
"
::= { tmsmSessionEntry 3 }
tmsmSessionSecurityModel OBJECT-TYPE
SYNTAX SnmpSecurityModel
MAX-ACCESS read-only
STATUS current
DESCRIPTION "The Security Model associated with this session."
::= { tmsmSessionEntry 4 }
tmsmSessionSecurityName OBJECT-TYPE
SYNTAX SnmpAdminString
MAX-ACCESS read-only
STATUS current
DESCRIPTION "A human readable string representing the principal
in Security Model independent format.
"
::= { tmsmSessionEntry 5 }
tmsmSessionSecurityLevel OBJECT-TYPE
SYNTAX SnmpSecurityLevel
MAX-ACCESS read-only
STATUS current
DESCRIPTION "The Level of Security at which SNMP messages can be
sent using this session, in particular, one of:
noAuthNoPriv - without authentication and
without privacy,
authNoPriv - with authentication but
without privacy,
authPriv - with authentication and
with privacy.
"
DEFVAL { authPriv }
::= { tmsmSessionEntry 6 }
tmsmSessionEngineID OBJECT-TYPE
SYNTAX SnmpEngineID
MAX-ACCESS read-only
STATUS current
DESCRIPTION "The administratively-unique identifier for the
remote SNMP engine associated with this session.
"
::= { tmsmSessionEntry 7 }
-- ------------------------------------------------------------- -- -------------------------------------------------------------
-- tmsmMIB - Conformance Information -- tmsmMIB - Conformance Information
-- ------------------------------------------------------------- -- -------------------------------------------------------------
tmsmGroups OBJECT IDENTIFIER ::= { tmsmConformance 1 } tmsmGroups OBJECT IDENTIFIER ::= { tmsmConformance 1 }
tmsmCompliances OBJECT IDENTIFIER ::= { tmsmConformance 2 } tmsmCompliances OBJECT IDENTIFIER ::= { tmsmConformance 2 }
-- ------------------------------------------------------------- -- -------------------------------------------------------------
-- Units of conformance -- Units of conformance
-- ------------------------------------------------------------- -- -------------------------------------------------------------
tmsmGroup OBJECT-GROUP tmsmGroup OBJECT-GROUP
OBJECTS { OBJECTS {
tmsmSessionOpenErrors, tmsmSessionOpenErrors,
tmsmSessionSecurityLevelNotAvailableErrors, tmsmSessionSecurityLevelNotAvailableErrors,
tmsmSessionCurrent, tmsmSessionCurrent,
tmsmSessionMaxSupported, tmsmSessionMaxSupported,
tmsmSessionTransport,
tmsmSessionAddress,
tmsmSessionSecurityModel,
tmsmSessionSecurityName,
tmsmSessionSecurityLevel,
tmsmSessionEngineID,
tmsmSessionSpinLock
} }
STATUS current STATUS current
DESCRIPTION "A collection of objects for maintaining session DESCRIPTION "A collection of objects for maintaining session
information of an SNMP engine which implements the information of an SNMP engine which implements the
TMSM architectural extension. TMSM architectural extension.
" "
::= { tmsmGroups 2 } ::= { tmsmGroups 2 }
-- ------------------------------------------------------------- -- -------------------------------------------------------------
skipping to change at page 39, line 4 skipping to change at page 37, line 46
-- ------------------------------------------------------------- -- -------------------------------------------------------------
tmsmCompliance MODULE-COMPLIANCE tmsmCompliance MODULE-COMPLIANCE
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"The compliance statement for SNMP engines that support the "The compliance statement for SNMP engines that support the
TMSM-MIB" TMSM-MIB"
MODULE MODULE
MANDATORY-GROUPS { tmsmGroup } MANDATORY-GROUPS { tmsmGroup }
::= { tmsmCompliances 1 } ::= { tmsmCompliances 1 }
END END
12. Security Considerations 8. Security Considerations
This document describes an architectural approach and multiple This document describes an architectural approach and multiple
proposed configurations that would permit SNMP to utilize transport proposed configurations that would permit SNMP to utilize transport
layer security services. Each section containing a proposal should layer security services. Each section containing a proposal should
discuss the security considerations of that approach. discuss the security considerations of that approach.
It is considered desirable by some industry segments that SNMP It is considered desirable by some industry segments that SNMP
security models should utilize transport layer security that security models should utilize transport layer security that
addresses perfect forward secrecy at least for encryption keys. addresses perfect forward secrecy at least for encryption keys.
Perfect forward secrecy guarantees that compromise of long term Perfect forward secrecy guarantees that compromise of long term
secret keys does not result in disclosure of past session keys. secret keys does not result in disclosure of past session keys.
There are a number of management objects defined in this MIB module
with a MAX-ACCESS clause of read-write and/or read-create. Such
objects may be considered sensitive or vulnerable in some network
environments. The support for SET operations in a non-secure
environment without proper protection can have a negative effect on
network operations. These are the tables and objects and their
sensitivity/vulnerability:
o [discuss] Should it be possible for a manager to create or modify
rows in the session table? If so, then we may need the rowstatus
object. If the session table is read-only then we can probably
eliminate the rowstatus. If the tabel is not read-only, then we
need to list the tables and objects and state why they are
sensitive.
There are no management objects defined in this MIB module that have 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 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 MIB module is implemented correctly, then there is no risk that an
intruder can alter or create any management objects of this MIB intruder can alter or create any management objects of this MIB
module via direct SNMP SET operations. module via direct SNMP SET operations.
Some of the readable objects in this MIB module (i.e., objects with a Some of the readable objects in this MIB module (i.e., objects with a
MAX-ACCESS other than not-accessible) may be considered sensitive or MAX-ACCESS other than not-accessible) may be considered sensitive or
vulnerable in some network environments. It is thus important to vulnerable in some network environments. It is thus important to
control even GET and/or NOTIFY access to these objects and possibly control even GET and/or NOTIFY access to these objects and possibly
skipping to change at page 40, line 4 skipping to change at page 38, line 31
intruder can alter or create any management objects of this MIB intruder can alter or create any management objects of this MIB
module via direct SNMP SET operations. module via direct SNMP SET operations.
Some of the readable objects in this MIB module (i.e., objects with a Some of the readable objects in this MIB module (i.e., objects with a
MAX-ACCESS other than not-accessible) may be considered sensitive or MAX-ACCESS other than not-accessible) may be considered sensitive or
vulnerable in some network environments. It is thus important to vulnerable in some network environments. It is thus important to
control even GET and/or NOTIFY access to these objects and possibly control even GET and/or NOTIFY access to these objects and possibly
to even encrypt the values of these objects when sending them over to even encrypt the values of these objects when sending them over
the network via SNMP. These are the tables and objects and their the network via SNMP. These are the tables and objects and their
sensitivity/vulnerability: sensitivity/vulnerability:
o [todo] list the tables and objects and state why they are o [todo] list the tables and objects and state why they are
sensitive. sensitive.
[discuss] how do we modify this section for an SNMP/SSH or other
transport mapping security model? If the security model provides for
securityName/Level/Model then some of the normal boilerplate is not
true.
SNMP versions prior to SNMPv3 did not include adequate security. SNMP versions prior to SNMPv3 did not include adequate security.
Even if the network itself is secure (for example by using IPSec), 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 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 allowed to access and GET/SET (read/change/create/delete) the objects
in this MIB module. in this MIB module.
It is RECOMMENDED that implementers consider the security features as It is RECOMMENDED that implementers consider the security features as
provided by the SNMPv3 framework (see [RFC3410], section 8), provided by the SNMPv3 framework (see [RFC3410], section 8),
including full support for the SNMPv3 cryptographic mechanisms (for including full support for the SNMPv3 cryptographic mechanisms (for
authentication and privacy). authentication and privacy).
Further, deployment of SNMP versions prior to SNMPv3 is NOT Further, deployment of SNMP versions prior to SNMPv3 is NOT
RECOMMENDED. Instead, it is RECOMMENDED to deploy SNMPv3 and to RECOMMENDED. Instead, it is RECOMMENDED to deploy SNMPv3 and to
enable cryptographic security. It is then a customer/operator enable cryptographic security. It is then a customer/operator
responsibility to ensure that the SNMP entity giving access to an responsibility to ensure that the SNMP entity giving access to an
instance of this MIB module is properly configured to give access to instance of this MIB module is properly configured to give access to
the objects only to those principals (users) that have legitimate the objects only to those principals (users) that have legitimate
rights to indeed GET or SET (change/create/delete) them. rights to indeed GET or SET (change/create/delete) them.
13. IANA Considerations 9. IANA Considerations
The MIB module in this document uses the following IANA-assigned The MIB module in this document uses the following IANA-assigned
OBJECT IDENTIFIER values recorded in the SMI Numbers registry: OBJECT IDENTIFIER values recorded in the SMI Numbers registry:
Descriptor OBJECT IDENTIFIER value Descriptor OBJECT IDENTIFIER value
---------- ----------------------- ---------- -----------------------
tmsmMIB { mib-2 XXXX } tmsmMIB { mib-2 XXXX }
Editor's Note (to be removed prior to publication): the IANA is Editor's Note (to be removed prior to publication): the IANA is
requested to assign a value for "XXXX" under the 'mib-2' subtree requested to assign a value for "XXXX" under the 'mib-2' subtree
and to record the assignment in the SMI Numbers registry. When and to record the assignment in the SMI Numbers registry. When
the assignment has been made, the RFC Editor is asked to replace the assignment has been made, the RFC Editor is asked to replace
"XXXX" (here and in the MIB module) with the assigned value and to "XXXX" (here and in the MIB module) with the assigned value and to
remove this note. remove this note.
[discuss] How do we add a new TransportType? 10. Acknowledgments
14. Acknowledgments
The Integrated Security for SNMP WG would like to thank the following The Integrated Security for SNMP WG would like to thank the following
people for their contributions to the process: people for their contributions to the process:
The authors of submitted security model proposals: Chris Elliot, Wes The authors of submitted security model proposals: Chris Elliot, Wes
Hardaker, Dave Harrington, Keith McCloghrie, Kaushik Narayan, Dave Hardaker, Dave Harrington, Keith McCloghrie, Kaushik Narayan, Dave
Perkins, Joseph Salowey, and Juergen Schoenwaelder. Perkins, Joseph Salowey, and Juergen Schoenwaelder.
The members of the Protocol Evaluation Team: Uri Blumenthal, The members of the Protocol Evaluation Team: Uri Blumenthal,
Lakshminath Dondeti, Randy Presuhn, and Eric Rescorla. Lakshminath Dondeti, Randy Presuhn, and Eric Rescorla.
WG members who committed to and performed detailed reviews: Jeffrey WG members who committed to and performed detailed reviews: Jeffrey
Hutzelman Hutzelman
15. References 11. References
15.1. Normative References 11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2222] Myers, J., "Simple Authentication and Security Layer
(SASL)", RFC 2222, October 1997.
[RFC4366] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., [RFC4366] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J.,
and T. Wright, "Transport Layer Security (TLS) and T. Wright, "Transport Layer Security (TLS)
Extensions", RFC 4366, April 2006. Extensions", RFC 4366, April 2006.
[RFC2578] McCloghrie, K., Ed., Perkins, D., Ed., and J. [RFC2578] McCloghrie, K., Ed., Perkins, D., Ed., and J.
Schoenwaelder, Ed., "Structure of Management Information Schoenwaelder, Ed., "Structure of Management Information
Version 2 (SMIv2)", STD 58, RFC 2578, April 1999. Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.
[RFC2579] McCloghrie, K., Ed., Perkins, D., Ed., and J. [RFC2579] McCloghrie, K., Ed., Perkins, D., Ed., and J.
Schoenwaelder, Ed., "Textual Conventions for SMIv2", Schoenwaelder, Ed., "Textual Conventions for SMIv2",
skipping to change at page 42, line 16 skipping to change at page 40, line 31
[RFC3412] Case, J., Harrington, D., Presuhn, R., and B. Wijnen, [RFC3412] Case, J., Harrington, D., Presuhn, R., and B. Wijnen,
"Message Processing and Dispatching for the Simple Network "Message Processing and Dispatching for the Simple Network
Management Protocol (SNMP)", STD 62, RFC 3412, Management Protocol (SNMP)", STD 62, RFC 3412,
December 2002. December 2002.
[RFC3414] Blumenthal, U. and B. Wijnen, "User-based Security Model [RFC3414] Blumenthal, U. and B. Wijnen, "User-based Security Model
(USM) for version 3 of the Simple Network Management (USM) for version 3 of the Simple Network Management
Protocol (SNMPv3)", STD 62, RFC 3414, December 2002. Protocol (SNMPv3)", STD 62, RFC 3414, December 2002.
[RFC3416] Presuhn, R., "Version 2 of the Protocol Operations for the
Simple Network Management Protocol (SNMP)", STD 62,
RFC 3416, December 2002.
[RFC3417] Presuhn, R., "Transport Mappings for the Simple Network [RFC3417] Presuhn, R., "Transport Mappings for the Simple Network
Management Protocol (SNMP)", STD 62, RFC 3417, Management Protocol (SNMP)", STD 62, RFC 3417,
December 2002. December 2002.
[RFC3418] Presuhn, R., "Management Information Base (MIB) for the [RFC3418] Presuhn, R., "Management Information Base (MIB) for the
Simple Network Management Protocol (SNMP)", STD 62, Simple Network Management Protocol (SNMP)", STD 62,
RFC 3418, December 2002. RFC 3418, December 2002.
[RFC3419] Daniele, M. and J. Schoenwaelder, "Textual Conventions for [RFC3419] Daniele, M. and J. Schoenwaelder, "Textual Conventions for
Transport Addresses", RFC 3419, December 2002. Transport Addresses", RFC 3419, December 2002.
[RFC4251] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH) [RFC4251] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
Protocol Architecture", RFC 4251, January 2006. Protocol Architecture", RFC 4251, January 2006.
15.2. Informative References 11.2. Informative References
[RFC3410] Case, J., Mundy, R., Partain, D., and B. Stewart, [RFC3410] Case, J., Mundy, R., Partain, D., and B.
"Introduction and Applicability Statements for Internet- Stewart, "Introduction and Applicability
Standard Management Framework", RFC 3410, December 2002. Statements for Internet-Standard Management
Framework", RFC 3410, December 2002.
[RFC3413] Levi, D., Meyer, P., and B. Stewart, "Simple Network [RFC3413] Levi, D., Meyer, P., and B. Stewart, "Simple
Management Protocol (SNMP) Applications", STD 62, Network Management Protocol (SNMP)
RFC 3413, December 2002. Applications", STD 62, RFC 3413,
December 2002.
[I-D.ietf-netconf-ssh] [RFC4422] Melnikov, A. and K. Zeilenga, "Simple
Wasserman, M. and T. Goddard, "Using the NETCONF Authentication and Security Layer (SASL)",
Configuration Protocol over Secure Shell (SSH)", RFC 4422, June 2006.
draft-ietf-netconf-ssh-06 (work in progress), March 2006.
[I-D.ietf-netconf-ssh] Wasserman, M. and T. Goddard, "Using the
NETCONF Configuration Protocol over Secure
Shell (SSH)", draft-ietf-netconf-ssh-06 (work
in progress), March 2006.
Appendix A. Parameter Table Appendix A. Parameter Table
Following is a CSV formatted matrix useful for tracking data flows Following is a CSV formatted matrix useful for tracking data flows
into and out of the dispatcher, message, and security subsystems. into and out of the dispatcher, message, and security subsystems.
Import this into your favorite spreadsheet or other CSV compatible Import this into your favorite spreadsheet or other CSV compatible
application. You will need to remove lines feeds from the second and application. You will need to remove lines feeds from the second and
third lines, which needed to be wrapped to fit into RFC limits. third lines, which needed to be wrapped to fit into RFC limits.
A.1. ParameterList.csv A.1. ParameterList.csv
skipping to change at page 44, line 20 skipping to change at page 42, line 42
securityEngineID,,,,,,,,In,Out,In securityEngineID,,,,,,,,In,Out,In
scopedPDU,,,,,,,,In,Out,In scopedPDU,,,,,,,,In,Out,In
securityParameters,,,,,,,,Out,,Out securityParameters,,,,,,,,Out,,Out
securityStateReference,,,,,,,,,Out,In securityStateReference,,,,,,,,,Out,In
pduType,,,,,,,Out,,, pduType,,,,,,,Out,,,
tmStateReference,,,,,,Out,In,,In, tmSessionReference,,,,,,Out,In,,In,
Appendix B. Why tmSecurityReference? Appendix B. Why tmSessionReference?
This appendix considers why a cache-based approach was selected for This appendix considers why a cache-based approach was selected for
passing parameters. This section may be removed from subsequent passing parameters. This section may be removed from subsequent
revisions fo the document. revisions of the document.
There are four approaches that could be used for passing information There are four approaches that could be used for passing information
between the TMSP and an MPSP. between the TMSP and an SMSP.
1. one could define an ASI to supplement the existing ASIs, or 1. one could define an ASI to supplement the existing ASIs, or
2. the TMSM could add a header to encapsulate the SNMP message, 2. the TMSM could add a header to encapsulate the SNMP message,
3. the TMSM could utilize fields already defined in the existing 3. the TMSM could utilize fields already defined in the existing
SNMPv3 message, or SNMPv3 message, or
4. the TMSM could pass the information in an implementation-specific 4. the TMSM could pass the information in an implementation-specific
cache or via a MIB module. cache or via a MIB module.
B.1. Define an Abstract Service Interface B.1. Define an Abstract Service Interface
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B.2. Using an Encapsulating Header B.2. Using an Encapsulating Header
A header could encapsulate the SNMP message to pass necessary A header could encapsulate the SNMP message to pass necessary
information from the TMSP to the dispatcher and then to a messaging information from the TMSP to the dispatcher and then to a messaging
security model. The message header would be included in the security model. The message header would be included in the
wholeMessage ASI parameter, and would be removed by a corresponding wholeMessage ASI parameter, and would be removed by a corresponding
messaging model. This would imply the (one and only) messaging messaging model. This would imply the (one and only) messaging
dispatcher would need to be modified to determine which SNMP message dispatcher would need to be modified to determine which SNMP message
version was involved, and a new message processing model would need version was involved, and a new message processing model would need
to be developed that knew how to extract the header from the message to be developed that knew how to extract the header from the message
and pass it to the MPSP. and pass it to the SMSP.
B.3. Modifying Existing Fields in an SNMP Message B.3. Modifying Existing Fields in an SNMP Message
[RFC3412] describes the SNMPv3 message, which contains fields to pass [RFC3412] describes the SNMPv3 message, which contains fields to pass
security related parameters. The TMSM could use these fields in an security related parameters. The TMSM could use these fields in an
SNMPv3 message, or comparable fields in other message formats to pass SNMPv3 message, or comparable fields in other message formats to pass
information between transport mapping security models in different information between transport mapping security models in different
SNMP engines, and to pass information between a transport mapping SNMP engines, and to pass information between a transport mapping
security model and a corresponding messaging security model. security model and a corresponding messaging security model.
If the fields in an incoming SNMPv3 message are changed by the TMSP If the fields in an incoming SNMPv3 message are changed by the TMSP
before passing it to the MPSP, then the TMSP will need to decode the before passing it to the SMSP, then the TMSP will need to decode the
ASN.1 message, modify the fields, and re-encode the message in ASN.1 ASN.1 message, modify the fields, and re-encode the message in ASN.1
before passing the message on to the message dispatcher or to the before passing the message on to the message dispatcher or to the
transport layer. This would require an intimate knowledge of the transport layer. This would require an intimate knowledge of the
message format and message versions so the TMSP knew which fields message format and message versions so the TMSP knew which fields
could be modified. This would seriously violate the modularity of could be modified. This would seriously violate the modularity of
the architecture. the architecture.
B.4. Using a Cache B.4. Using a Cache
This document describes a cache, into which the TMSP puts information This document describes a cache, into which the TMSP puts information
about the security applied to an incoming message, and an MPSP about the security applied to an incoming message, and an SMSP
extracts that information from the cache. Given that there may be extracts that information from the cache. Given that there may be
multiple TM-security caches, a tmStateReference is passed as an extra multiple TM-security caches, a tmSessionReference is passed as an
parameter in the ASIs between the transport mapping and the messaging extra parameter in the ASIs between the transport mapping and the
security model.so the MPSP knows which cache of information to messaging security model, so the SMSP knows which cache of
consult. information to consult.
This approach does create dependencies between a model-specific TMSP This approach does create dependencies between a model-specific TMSP
and a corresponding specific MPSP. This approach of passing a model- and a corresponding specific SMSP. This approach of passing a model-
independent reference is consistent with the securityStateReference independent reference is consistent with the securityStateReference
cache already being passed around in the RFC3411 ASIs. cache already being passed around in the RFC3411 ASIs.
Appendix C. Open Issues Appendix C. Open Issues
Appendix D. Change Log Appendix D. Change Log
NOTE to RFC editor: Please remove this change log before publishing NOTE to RFC editor: Please remove this change log before publishing
this document as an RFC. this document as an RFC.
Changes from revision -02- to -03-
o removed session table from MIB module
o removed sessionID from ASIs
o reorganized to put ASI discussions in EOP section, as was done in
SSHSM
o changed user auth to client auth
o changed tmStateReference to tmSessionReference
o modified document to meet consensus positions published by JS
o
* authoritative is model-specific
* msgSecurityParameters usage is model-specific
* msgFlags vs. securityLevel is model/implementation-specific
* notifications must be able to cause creation of a session
* security considerations must be model-specific
* TDomain and TAddress are model-specific
* MPSP changed to SMSP (Security model security processing)
Changes from revision -01- to -02- Changes from revision -01- to -02-
o wrote text for session establishment requirements section. o wrote text for session establishment requirements section.
o wrote text for session maintenance requirements section. o wrote text for session maintenance requirements section.
o removed section on relation to SNMPv2-MIB o removed section on relation to SNMPv2-MIB
o updated MIB module to pass smilint o updated MIB module to pass smilint
o Added Structure of the MIB module, and other expected MIB-related o Added Structure of the MIB module, and other expected MIB-related
sections. sections.
o updated author address o updated author address
o corrected spelling o corrected spelling
o removed msgFlags appendix o removed msgFlags appendix
o Removed section on implementation considerations. o Removed section on implementation considerations.
o started modifying the security boilerplate to address TMSM and MIB o started modifying the security boilerplate to address TMSM and MIB
security issues security issues
skipping to change at page 46, line 26 skipping to change at page 45, line 17
o Added Structure of the MIB module, and other expected MIB-related o Added Structure of the MIB module, and other expected MIB-related
sections. sections.
o updated author address o updated author address
o corrected spelling o corrected spelling
o removed msgFlags appendix o removed msgFlags appendix
o Removed section on implementation considerations. o Removed section on implementation considerations.
o started modifying the security boilerplate to address TMSM and MIB o started modifying the security boilerplate to address TMSM and MIB
security issues security issues
o reorganized slightly to better separate requirements from proposed o reorganized slightly to better separate requirements from proposed
solution. This probably needs additional work. solution. This probably needs additional work.
o removed section with sample protocols and sample tmStateReference. o removed section with sample protocols and sample
tmSessionReference.
o Added section for acronyms o Added section for acronyms
o moved section comparing parameter passing techniques to appendix. o moved section comparing parameter passing techniques to appendix.
o Removed section on notification requirements. o Removed section on notification requirements.
Changes from revision -00- Changes from revision -00-
o changed SSH references from I-Ds to RFCs o changed SSH references from I-Ds to RFCs
o removed parameters from tmStateReference for DTLS that revealed o removed parameters from tmSessionReference for DTLS that revealed
lower layer info. lower layer info.
o Added TMSM-MIB module o Added TMSM-MIB module
o Added Internet-Standard Management Framework boilerplate o Added Internet-Standard Management Framework boilerplate
o Added Structure of the MIB Module o Added Structure of the MIB Module
o Added MIB security considerations boilerplate (to be completed) o Added MIB security considerations boilerplate (to be completed)
o Added IANA Considerations o Added IANA Considerations
o Added ASI Parameter table o Added ASI Parameter table
o Added discussion of Sessions o Added discussion of Sessions
o Added Open issues and Change Log o Added Open issues and Change Log
o Rearranged sections o Rearranged sections
Authors' Addresses Authors' Addresses
David Harrington David Harrington
Futurewei Technologies Huawei Technologies (USA)
1700 Alma Dr. Suite 100 1700 Alma Dr. Suite 100
Plano, TX 75075 Plano, TX 75075
USA USA
Phone: +1 603 436 8634 Phone: +1 603 436 8634
EMail: dharrington@huawei.com EMail: dharrington@huawei.com
Juergen Schoenwaelder Juergen Schoenwaelder
International University Bremen International University Bremen
Campus Ring 1 Campus Ring 1
28725 Bremen 28725 Bremen
Germany Germany
Phone: +49 421 200-3587 Phone: +49 421 200-3587
EMail: j.schoenwaelder@iu-bremen.de EMail: j.schoenwaelder@iu-bremen.de
Full Copyright Statement Full Copyright Statement
skipping to change at page 48, line 21 skipping to change at page 47, line 47
http://www.ietf.org/ipr. http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at this standard. Please address the information to the IETF at
ietf-ipr@ietf.org. ietf-ipr@ietf.org.
Acknowledgement Acknowledgement
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is provided by the IETF
Internet Society. Administrative Support Activity (IASA).
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