Internet Engineering Task Force                           K. Vaughn, Ed.
Internet-Draft                                              Trevilon LLC
Obsoletes: 6353 (if approved)                              29 March 2021
Intended status: Standards Track
Expires: 30 September 2021


 Transport Layer Security Verion 1.3 (TLS 1.3) Transport Model for the
         Simple Network Management Protocol Version 3 (SNMPv3)
                      draft-vaughn-tlstm-update-00

Abstract

   describes a Transport Model for the Simple Network Management
   Protocol Version 3 (SNMPv3) that uses Transport Layer Security
   Version 1.3 (TLS 1.3).  TLS 1.3 provides authentication and privacy
   services for SNMPv3 applications.  This document describes how the
   TLS 1.3 Transport Model (TLSTM 1.3) implements the needed features of
   an SNMPv3 Transport Subsystem to make this protection possible in an
   interoperable way.

   This Transport Model is designed to meet the security and operational
   needs of network administrators.  It supports the sending of SNMP
   messages over TLS/TCP.  TLS integrates well into existing public key
   infrastructures.

   This document also defines a portion of the Management Information
   Base (MIB) for use with network management protocols.  In particular,
   it defines objects for managing TLSTM for SNMP.

   This document obsoletes RFC 6353 (if approved).

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 30 September 2021.



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Copyright Notice

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Conventions . . . . . . . . . . . . . . . . . . . . . . .   6
     1.2.  Changes Since RFC 6353  . . . . . . . . . . . . . . . . .   7
   2.  The Transport Layer Security Protocol . . . . . . . . . . . .   8
   3.  How the TLSTM Fits into the Transport Subsystem . . . . . . .   9
     3.1.  Security Capabilities of This Model . . . . . . . . . . .  11
       3.1.1.  Threats . . . . . . . . . . . . . . . . . . . . . . .  11
       3.1.2.  Message Protection  . . . . . . . . . . . . . . . . .  12
       3.1.3.  TLS Connections . . . . . . . . . . . . . . . . . . .  13
     3.2.  Security Parameter Passing  . . . . . . . . . . . . . . .  13
     3.3.  Notifications and Proxy . . . . . . . . . . . . . . . . .  14
   4.  Elements of the Model . . . . . . . . . . . . . . . . . . . .  15
     4.1.  X.509 Certificates  . . . . . . . . . . . . . . . . . . .  15
       4.1.1.  Provisioning for the Certificate  . . . . . . . . . .  15
     4.2.  TLS Usage . . . . . . . . . . . . . . . . . . . . . . . .  17
     4.3.  SNMP Services . . . . . . . . . . . . . . . . . . . . . .  17
       4.3.1.  SNMP Services for an Outgoing Message . . . . . . . .  17
       4.3.2.  SNMP Services for an Incoming Message . . . . . . . .  18
     4.4.  Cached Information and References . . . . . . . . . . . .  19
       4.4.1.  TLS Transport Model Cached Information  . . . . . . .  19



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         4.4.1.1.  tmSecurityName  . . . . . . . . . . . . . . . . .  19
         4.4.1.2.  tmSessionID . . . . . . . . . . . . . . . . . . .  20
         4.4.1.3.  Session State . . . . . . . . . . . . . . . . . .  20
   5.  Elements of Procedure . . . . . . . . . . . . . . . . . . . .  20
     5.1.  Procedures for an Incoming Message  . . . . . . . . . . .  21
     5.2.  Procedures for an Outgoing SNMP Message . . . . . . . . .  22
     5.3.  Establishing or Accepting a Session . . . . . . . . . . .  24
       5.3.1.  Establishing a Session as a Client  . . . . . . . . .  24
       5.3.2.  Accepting a Session as a Server . . . . . . . . . . .  26
     5.4.  Closing a Session . . . . . . . . . . . . . . . . . . . .  27
   6.  MIB Module Overview . . . . . . . . . . . . . . . . . . . . .  28
     6.1.  Structure of the MIB Module . . . . . . . . . . . . . . .  28
     6.2.  Textual Conventions . . . . . . . . . . . . . . . . . . .  28
     6.3.  Statistical Counters  . . . . . . . . . . . . . . . . . .  28
     6.4.  Configuration Tables  . . . . . . . . . . . . . . . . . .  28
       6.4.1.  Notifications . . . . . . . . . . . . . . . . . . . .  29
     6.5.  Relationship to Other MIB Modules . . . . . . . . . . . .  29
       6.5.1.  MIB Modules Required for IMPORTS  . . . . . . . . . .  29
   7.  MIB Module Definition . . . . . . . . . . . . . . . . . . . .  29
   8.  Operational Considerations  . . . . . . . . . . . . . . . . .  59
     8.1.  Sessions  . . . . . . . . . . . . . . . . . . . . . . . .  60
     8.2.  Notification Receiver Credential Selection  . . . . . . .  60
     8.3.  contextEngineID Discovery . . . . . . . . . . . . . . . .  61
     8.4.  Transport Considerations  . . . . . . . . . . . . . . . .  61
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  61
     9.1.  Certificates, Authentication, and Authorization . . . . .  61
     9.2.  TLS Security Considerations . . . . . . . . . . . . . . .  62
       9.2.1.  TLS Version Requirements  . . . . . . . . . . . . . .  62
       9.2.2.  Session Resumption  . . . . . . . . . . . . . . . . .  63
       9.2.3.  TLS Ciphersuites, Extensions and Protocol
               Invariants  . . . . . . . . . . . . . . . . . . . . .  63
     9.3.  Use with SNMPv1/SNMPv2c Messages  . . . . . . . . . . . .  63
     9.4.  MIB Module Security . . . . . . . . . . . . . . . . . . .  64
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  65
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  66
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  66
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  66
     12.2.  Informative References . . . . . . . . . . . . . . . . .  68
   Appendix A.  Target and Notification Configuration Example  . . .  68
     A.1.  Configuring a Notification Originator . . . . . . . . . .  68
     A.2.  Configuring TLSTM to Utilize a Simple Derivation of
           tmSecurityName  . . . . . . . . . . . . . . . . . . . . .  69
     A.3.  Configuring TLSTM to Utilize Table-Driven Certificate
           Mapping . . . . . . . . . . . . . . . . . . . . . . . . .  70
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  70






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1.  Introduction

   It is important to understand the modular SNMPv3 architecture
   (RFC3411) as enhanced by the Transport Subsystem [RFC5590].  It is
   also important to understand the terminology of the SNMPv3
   architecture in order to understand where the Transport Model
   described in this document fits into the architecture and how it
   interacts with the other architecture subsystems.  For a detailed
   overview of the documents that describe the current Internet-Standard
   Management Framework, please refer to Section 7 of [RFC3410].

   This document describes a Transport Model that makes use of Transport
   Layer Security Version 1.3 (TLS 1.3) [RFC8446] within a Transport
   Subsystem [RFC5590].  The Transport Model in this document is
   referred to as the Transport Layer Security 1.3 Transport Model
   (TLSTM 1.3).  TLS employs the X.509 public key infrastructure
   [RFC5280].  While TLS supports several authentication mechanisms,
   this document only discusses X.509 certificate-based authentication.
   This transport model is designed to meet the security and operational
   needs of network administrators, operating in various environments
   where data can be sent over a TCP-based stream.  TLS integrates well
   into existing public key infrastructures.

   This document supports sending of SNMP messages over TLS/TCP.  This
   document also defines a portion of the Management Information Base
   (MIB) for use with network management protocols.  In particular, it
   defines objects for managing the TLSTM 1.3.  Managed objects are
   accessed via a virtual information store, termed the Management
   Information Base or MIB.  MIB objects are generally accessed through
   the Simple Network Management Protocol Version 3 (SNMPv3).  Objects
   in the MIB are defined using the mechanisms defined in the Structure
   of Management Information (SMI).  This memo specifies a MIB module
   that is compliant to the SMIv2, which is described in [STD58].

   The diagram shown below gives a conceptual overview of two SNMP
   entities communicating using the TLS Transport Model (shown as
   "TLSTM").  One entity contains a command responder and notification
   originator application, and the other a command generator and
   notification receiver application.  This particular mix of
   application types is an example only and other combinations are
   equally valid.

   Note: this diagram shows the Transport Security Model (TSM) being
   used as the security model that is defined in [RFC5591].







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    +-----------------------------------------------------------------+
    |                            Network                              |
    +-----------------------------------------------------------------+
        ^                   |           ^              |
        |Notifications      |Commands   |Commands      |Notifications
    +---|-------------------|-------+ +--|--------------|-------------+
    |   |                   V       | |  |              V             |
    | +----------+  +----------+    | | +----------+  +----------+    |
    | | TLS      |  | TLS      |    | | | TLS      |  | TLS      |    |
    | | (Client) |  | (Server) |    | | | (Client) |  | (Server) |    |
    | +----------+  +----------+    | | +----------+  +----------+    |
    |      ^            ^           | |      ^             ^          |
    |      |            |           | |      |             |          |
    |      +------------+           | |      +-------------+          |
    | +----|-----------+            | | +-----|----------+            |
    | |    V           |            | | |     V          |            |
    | | +--------+     |  +-----+   | | | +--------+     |  +-----+   |
    | | | TLS TM |<------>|Cache|   | | | | TLS TM |<------>|Cache|   |
    | | +--------+     |  +-----+   | | | +--------+     |  +-----+   |
    | |Transport Subsys|     ^      | | |Transport Subsys|     ^      |
    | +----------------+     |      | | +----------------+     |      |
    |   ^                    |      | |    ^                   |      |
    |   |                    +---+  | |    |                   +---+  |
    |   v                        |  | |    V                       |  |
    | +-----+ +-------+ +------+ |  | | +-----+ +-------+ +------+ |  |
    | |     | |Message| |Sec.  | |  | | |     | |Message| |Sec.  | |  |
    | |Disp.| |Proc.  | |Subsys| |  | | |Disp.| |Proc.  | |Subsys| |  |
    | |     | |Subsys.| |      | |  | | |     | |Subsys.| |      | |  |
    | |     | |       | |      | |  | | |     | |       | |      | |  |
    | |     | |+----+ | |+---+ | |  | | |     | |+----+ | |+---+ | |  |
    | |    <-->|v3MP|<-->|TSM|<--+  | | |    <-->|v3MP|<-->|TSM|<--+  |
    | |     | |+----+ | |+---+ |    | | |     | |+----+ | |+---+ |    |
    | |     | |       | |      |    | | |     | |       | |      |    |
    | +-----+ +-------+ +------+    | | +-----+ +-------+ +------+    |
    |    ^                          | |    ^                          |
    |    |                          | |    |                          |
    |    +-+------------+           | |    +-+----------+             |
    |      |            |           | |      |          |             |
    |      v            v           | |      v          V             |
    | +-----------+ +-------------+ | | +-----------+ +-------------+ |
    | |  COMMAND  | | NOTIFICAT.  | | | |  COMMAND  | |  NOTIFICAT. | |
    | | RESPONDER | | ORIGINATOR  | | | | GENERATOR | |  RECEIVER   | |
    | |application| | application | | | |application| | application | |
    | +-----------+ +-------------+ | | +-----------+ +-------------+ |
    |                   SNMP entity | |                   SNMP entity |
    +-------------------------------+ +-------------------------------+

           Figure 1: Two communicating SNMP entities using TLSTM



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1.1.  Conventions

   Within this document the terms "TLS", "SNMP", and "TLSTM" mean "TLS
   1.3", "SMNPv3", and "TLSTM 1.3", respectively.  The full forms of the
   terms are generally only used when the text needs to emphasize
   version numbers, such as within the title.  When this document refers
   to any other version of these protocols, it always explicitly states
   the version intended.

   For consistency with SNMP-related specifications, this document
   favors terminology as defined in [STD62], rather than favoring
   terminology that is consistent with non-SNMP specifications.  This is
   consistent with the IESG decision to not require the SNMPv3
   terminology be modified to match the usage of other non-SNMP
   specifications when SNMPv3 was advanced to a Full Standard.
   "Authentication" in this document typically refers to the English
   meaning of "serving to prove the authenticity of" the message, not
   data source authentication or peer identity authentication.  The
   terms "manager" and "agent" are not used in this document because, in
   the RFC3411 architecture, all SNMP entities have the capability of
   acting as manager, agent, or both depending on the SNMP application
   types supported in the implementation.  Where distinction is
   necessary, the application names of command generator, command
   responder, notification originator, notification receiver, and proxy
   forwarder are used.  See "SNMP Applications" (RFC3411) for further
   information.

   Throughout this document, the terms "client" and "server" are used to
   refer to the two ends of the TLS transport connection.  The client
   actively opens the TLS connection, and the server passively listens
   for the incoming TLS connection.  An SNMP entity MAY act as a TLS
   client or server or both, depending on the SNMP applications
   supported.

   The User-Based Security Model (USM) (RFC3414) is a mandatory-to-
   implement Security Model in [STD62].  The USM derives the
   securityName and securityLevel from the SNMP message received, even
   when the message was received over a secure transport.  It is
   RECOMMENDED that deployments that support the TLSTM disable the USM,
   if it has been implemented.

   While TLS frequently refers to a user, the terminology preferred in
   RFC3411 and in this memo is "principal".  A principal is the "who" on
   whose behalf services are provided or processing takes place.  A
   principal can be, among other things, an individual acting in a
   particular role; a set of individuals, with each acting in a
   particular role; an application or a set of applications, or a
   combination of these within an administrative domain.



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   Throughout this document, the term "session" is used to refer to a
   secure association between two TLS Transport Models that permits the
   transmission of one or more SNMP messages within the lifetime of the
   session.  The TLS protocol also has an internal notion of a session
   and although these two concepts of a session are related, when the
   term "session" is used this document is referring to the TLSTM's
   specific session and not directly to the TLS protocol's session.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", NOT RECOMMENDED, "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].

1.2.  Changes Since RFC 6353

   This document obsoletes [RFC6353].  The changes from [RFC6353] are
   noted as follows:

   *  Updating the fingerprint format to reflect the two-octet TLS 1.3
      cipher suite identifier rather than the one-octet TLS 1.2 hash
      algorithm identifier

   *  Deprecating the MIB tables that rely upon the original fingerprint
      format and replacing them with similar tables using the updated
      format
      // Revising the existing tables appear to be problematic due to
      the
      // rules related to the RowStatus objects

   *  Limiting the discussion to TLS and removing any mention of DTLS
      // The removal of DTLS from this document is proposed for several
      // reasons, including: 1) CISA recommendations prefer the use of
      TLS
      // since it hides the identification of the encapsulated protocol
      // completely whereas DTLS does not (i.e., DTLS does not encrypt
      the
      // UDP port number). 2) DTLS requires more logic /complexity to
      // prevent replay and DoS attacks 3) Support for both TLS/TCP and
      // DTLS/UDP implies additional testing requirements for little
      // benefit 4) It seems likely that future versions of DTLS will
      // frequently, if not always be released years after its companion
      // TLS version; while this might not be the intent of the
      developers
      // of DTLS, the history of development cycles seem to suggest
      // otherwise.  Thus, even if there is a desire to support DTLS, it
      // might be best to address the TLS TM and DTLS TM in separate
      RFCs.
      // 5) DTLS 1.3 is not yet an approved RFC.  While it is currently



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      // before the IESG, it seems premature to include within this
      draft.
      // 6) The main advantage of cited DTLS seems to be the shorter
      // session setup time, which theoretically can be a benefit in
      // certain network environments, but a.  TLS1.3 already reduced
      the
      // setup time compared to TLS1.2, b.  these environments are not
      // typical of ITS deployments where network paths tend to be more
      // direct and controlled and so the advantage of DTLS in this
      sense
      // is even smaller.  7) While most of ITS data is elemental and
      well
      // suited for traditional SNMP operations, several ITS devices
      // support complex structures that are treated as a single element
      // and are defined as a single SNMP object.  As these can be 1500
      // octets or more, a TCP environment is often needed anyway 8)
      Within
      // ITS, there has been at least one attempt to deploy a draft
      version
      // of DTLS 1.3 and the implementer decided to drop it and use TLS
      1.3
      // instead.

   *  Removing any defined support for SNMPv1 or SNMPv2c since these
      would not be secure anyway

   *  Prohibiting the use of the User-based security model since this is
      less secure

   *  Renegotiation of sessions is not supported as it is not supported
      by TLS 1.3

   *  Prohibiting the use of the certificate's CommonName to determine a
      tmSecurityName

   *  Prohibiting use of the 0-RTT mode of session resumption of TLS 1.3

   *  Forcing all SNMPv3 opertaions to use the highest security level
      (authPriv) because all TLS 1.3 connections are authenticated and
      encrypted.

2.  The Transport Layer Security Protocol

   TLS provides authentication, data message integrity, and privacy at
   the transport layer.






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   The primary goals of the TLS Transport Model are to provide peer
   identity authentication, data integrity, and privacy between two
   communicating SNMP entities.  The TLS protocol provides a secure
   transport upon which the TLSTM is based.  Please refer to [RFC8446]
   for a complete descriptions of the TLS.

3.  How the TLSTM Fits into the Transport Subsystem

   A transport model is a component of the Transport Subsystem.  The TLS
   Transport Model thus fits between the underlying TLS transport layer
   and the Message Dispatcher RFC3411 component of the SNMP engine.

   The TLS Transport Model will establish a session between itself and
   the TLS Transport Model of another SNMP engine.  The sending
   transport model passes unencrypted and unauthenticated messages from
   the Dispatcher to TLS to be encrypted and authenticated, and the
   receiving transport model accepts decrypted and authenticated/
   integrity-checked incoming messages from TLS and passes them to the
   Dispatcher.

   After a TLS Transport Model session is established, SNMP messages can
   conceptually be sent through the session from one SNMP Message
   Dispatcher to another SNMP Message Dispatcher.  If multiple SNMP
   messages are needed to be passed between two SNMP applications they
   MAY be passed through the same session.  A TLSTM implementation
   engine MAY choose to close the session to conserve resources.

   The TLS Transport Model of an SNMP engine will perform the
   translation between TLS-specific security parameters and SNMP-
   specific, model-independent parameters.

   The diagram below depicts where the TLS Transport Model (shown as
   "TLS TM") fits into the architecture described in RFC3411 and the
   Transport Subsystem:

















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   +------------------------------+
   |    Network                   |
   +------------------------------+
      ^       ^              ^
      |       |              |
      v       v              v
   +------------------------------------------------------------------+
   | +-------------------------------------------------+              |
   | |  Transport Subsystem                            |  +--------+  |
   | |  +-------+ +-------+                 +-------+  |  |        |  |
   | |  |  SSH  | |  TLS  |      . . .      | other |<--->| Cache  |  |
   | |  |  TM   | |  TM   |                 |       |  |  |        |  |
   | |  +-------+ +-------+                 +-------+  |  +--------+  |
   | +-------------------------------------------------+         ^    |
   |              ^                                              |    |
   |              |                                              |    |
   | Dispatcher   v                                              |    |
   | +--------------+ +---------------------+  +---------------+ |    |
   | | Transport    | | Message Processing  |  | Security      | |    |
   | | Dispatcher   | | Subsystem           |  | Subsystem     | |    |
   | |              | |     +------------+  |  | +-----------+ | |    |
   | |              | |  +->| v3MP       |<--->| | Transport | | |    |
   | | Message      | |  |  +------------+  |  | | Security  |<--+    |
   | | Dispatcher  <---->|                  |  | | Model     | |      |
   | |              | |  |                  |  | +-----------+ |      |
   | |              | |  |                  |  | +-----------+ |      |
   | | PDU Dispatch | |  |  +------------+  |  | | Other     | |      |
   | +--------------+ |  +->| otherMP    |<--->| | Model(s)  | |      |
   |              ^   |     +------------+  |  | +-----------+ |      |
   |              |   +---------------------+  +---------------+      |
   |              v                                                   |
   |      +-------+-------------------------+--------------+          |
   |      ^                                 ^              ^          |
   |      |                                 |              |          |
   |      v                                 v              v          |
   | +-------------+   +---------+   +--------------+ +-------------+ |
   | |   COMMAND   |   | ACCESS  |   | NOTIFICATION | |    PROXY    | |
   | |  RESPONDER  |<->| CONTROL |<->|  ORIGINATOR  | |  FORWARDER  | |
   | | application |   |         |   | applications | | application | |
   | +-------------+   +---------+   +--------------+ +-------------+ |
   |      ^                                 ^                         |
   |      |                                 |                         |
   |      v                                 v                         |
   | +----------------------------------------------+                 |
   | |             MIB instrumentation              |     SNMP entity |
   +------------------------------------------------------------------+

          Figure 2: TLS Transport Model and the SNMP Architecture



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3.1.  Security Capabilities of This Model

3.1.1.  Threats

   The TLS Transport Model provides protection against the threats
   identified by the RFC3411 architecture and other threats:

   1.  Modification of Information - The modification threat is the
       danger that an unauthorized entity might alter in-transit SNMP
       messages generated on behalf of an authorized principal in such a
       way as to effect unauthorized management operations, including
       falsifying the value of an object.

       TLS provides integrity verification.  In other words, TLS ensures
       that the content of each received message has not been modified
       during its transmission through the network, data has not been
       altered or destroyed in an unauthorized manner, and data
       sequences have not been altered or delayed to an extent greater
       than can occur non-maliciously.  This is achieved via message
       authentication codes (MAC) for the handshake protocol and the TLS
       cipher suites, which support integrity and confidentiality
       protection for the record protocol.

   2.  Masquerade - The masquerade threat is the danger that management
       operations unauthorized for a given principal might be attempted
       by assuming the identity of another principal that has the
       appropriate authorizations.

       The TLSTM verifies the identity of the TLS server through the use
       of the TLS protocol and X.509 certificates.  A TLS Transport
       Model implementation MUST support the authentication of both the
       server and the client with X.509 certificates.

   3.  Replay - The replay threat is the danger that messages might be
       maliciously resent in order to effect unauthorized management
       operations.

       TLS replay protection in the handshake protocol is achieved
       through the server's random value and in the record protocol via
       a new random number (nonce) for each record, with the nonce being
       derived based on the record sequence number.

   4.  Disclosure - The disclosure threat is the danger of eavesdropping
       on the exchanges between SNMP engines.







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       TLS 1.3 provides protection against the disclosure of information
       to unauthorized recipients or eavesdroppers by requiring
       encryption of all traffic.  TLS 1.3 cipher suites support
       integrity and confidentiality protection for all TLS Transport
       Model exchanges.

   5.  Key compromise - The key compromise attack consists of revealing
       the secret long-term key(s) used to protect the data stream.

       TLS 1.3 provides perfect forward secrecy.  If these keys are
       compromised after the TLS handshake completes, this does not
       compromise the session key itself (see section E.1 of [RFC8446].

   6.  Denial of Service - The RFC3411 architecture states that denial-
       of-service (DoS) attacks need not be addressed by an SNMP
       security protocol.

       The cookie mechanism of TLS might help mitigate this attack.

   See Section 9 for more detail on the security considerations
   associated with the TLSTM and these security threats.

3.1.2.  Message Protection

   The RFC3411 architecture recognizes three levels of security:

   *  without authentication and without privacy (noAuthNoPriv)

   *  with authentication but without privacy (authNoPriv)

   *  with authentication and with privacy (authPriv)

   With TLS 1.3, authentication and privacy are always provided.  Hence,
   all exchanges conforming to the rules of this document will include
   authentication and privacy, regardless of the security level
   requested.
   // This is consistent with what was prescribed in RFC6353, where a
   // TLS Transport Model is expected to provide for outgoing
   // connections with a security level at least that of the requested
   // security level.

   The TLS Transport Model determines from TLS the identity of the
   authenticated principal, the transport type, and the transport
   address associated with an incoming message.  The TLS Transport Model
   provides the identity and destination type and address to TLS for
   outgoing messages.





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   When an application requests a TLS Transport Model session for a
   message, it SHOULD request a security level of authPriv.  Regardless
   of the security level requested, the TLS Transport Model MUST provide
   authentication and privacy.  How the security level is translated
   into the algorithms used to provide data integrity and privacy is
   implementation dependent.

   The authentication, integrity, and privacy algorithms used by the TLS
   protocol might vary over time as the science of cryptography
   continues to evolve and the development of TLS continues over time.
   Implementers are encouraged to plan for changes in operator trust of
   particular algorithms.

3.1.3.  TLS Connections

   TLS connections are opened by the TLS Transport Model during the
   elements of procedure for an outgoing SNMP message.  Since the sender
   of a message initiates the creation of a TLS connection if needed,
   the TLS connection will already exist for an incoming message.

   Implementations MAY choose to instantiate TLS connections in
   anticipation of outgoing messages.  This approach might be useful to
   ensure that a TLS connection to a given target can be established
   before it becomes important to send a message over the TLS
   connection.  Of course, there is no guarantee that a pre-established
   session will still be valid when needed.

   TLS connections over TCP sessions MUST provide a unique
   tlstmSessionID for referencing the session; they do not require a
   unique pairing of address and port attributes since TCP already
   provides adequate session framing.

   The tlstmSessionID MUST NOT change during the entire duration of the
   session from the TLSTM's perspective, and MUST uniquely identify a
   single session.

3.2.  Security Parameter Passing

   For the TLS server-side, TLS-specific security parameters (i.e.,
   cipher_suites, X.509 certificate fields, IP addresses, and ports) are
   translated by the TLS Transport Model into security parameters for
   the TLS Transport Model and security model (e.g., tmSecurityLevel,
   tmSecurityName, transportDomain, transportAddress).  The transport-
   related and TLS-security-related information, including the
   authenticated identity, are stored in a cache referenced by
   tmStateReference.





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   For the TLS client side, the TLS Transport Model takes input provided
   by the Dispatcher in the sendMessage() Abstract Service Interface
   (ASI) and input from the tmStateReference cache.  The TLS Transport
   Model converts that information into suitable security parameters for
   TLS and establishes sessions as needed.

   The elements of procedure in Section 5 discuss these concepts in much
   greater detail.

3.3.  Notifications and Proxy

   TLS connections might be initiated by TLS clients on behalf of SNMP
   applications that initiate communications, such as command
   generators, notification originators, proxy forwarders.  Command
   generators are frequently operated by a human, but notification
   originators and proxy forwarders are usually unmanned automated
   processes.  The targets to whom notifications and proxied requests
   are to be sent are typically determined and configured by a network
   administrator.

   The SNMP-TARGET-MIB module of RFC3413 contains objects for defining
   management targets, including transportDomain, transportAddress,
   securityName, securityModel, and securityLevel parameters, for
   notification originator, proxy forwarder, and SNMP-controllable
   command generator applications.  Transport domains and transport
   addresses are configured in the snmpTargetAddrTable, and the
   securityModel, securityName, and securityLevel parameters are
   configured in the snmpTargetParamsTable.  This document defines a MIB
   module that extends the SNMP-TARGET-MIB's snmpTargetParamsTable to
   specify a TLS client-side certificate to use for the connection.

   When configuring a TLS target, the snmpTargetAddrTDomain and
   snmpTargetAddrTAddress parameters in snmpTargetAddrTable SHOULD be
   set to the snmpTLSTCPDomain or snmpDTLSUDPDomain object and an
   appropriate snmpTLSAddress value.  When used with the SNMPv3 message
   processing model, the snmpTargetParamsMPModel column of the
   snmpTargetParamsTable SHOULD be set to a value of 3.  The
   snmpTargetParamsSecurityName SHOULD be set to an appropriate
   securityName value, and the snmpTlstmParams13ClientFingerprint
   parameter of the snmpTlstmParams13Table SHOULD be set to a value that
   refers to a locally held certificate (and the corresponding private
   key) to be used.  Other parameters, for example, cryptographic
   configuration such as which cipher_suites to use, MUST come from
   configuration mechanisms not defined in this document.

   The securityName defined in the snmpTargetParamsSecurityName column
   will be used by the access control model to authorize any
   notifications that need to be sent.



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4.  Elements of the Model

   This section contains definitions for the TLS Transport Model defined
   by this document.

4.1.  X.509 Certificates

   TLS can make use of X.509 certificates for authentication of both
   sides of the transport.  This section discusses the use of X.509
   certificates in the TLSTM.

   While TLS supports several authentication mechanisms, this document
   only discusses X.509-certificate-based authentication; other forms of
   authentication are outside the scope of this specification.  TLSTM
   implementations are REQUIRED to support X.509 certificates.

4.1.1.  Provisioning for the Certificate

   Authentication using TLS requires that SNMP entities have
   certificates, either signed by trusted Certification Authorities
   (CAs), or self-signed.  Furthermore, SNMP entities will most commonly
   need to be provisioned with root certificates that represent the list
   of trusted CAs that an SNMP entity can use for certificate
   verification.  SNMP entities SHOULD also be provisioned with an X.509
   certificate revocation mechanism which can be used to verify that a
   certificate has not been revoked.  Trusted public keys from either CA
   certificates and/or self-signed certificates MUST be installed into
   the server through a trusted out-of-band mechanism and their
   authenticity MUST be verified before access is granted.

   Having received a certificate from a connecting TLSTM client, the
   authenticated tmSecurityName of the principal is derived using the
   snmpTlstmCertToTSN13Table.  This table allows mapping of incoming
   connections to tmSecurityNames through defined transformations.  The
   transformations defined in the SNMP-TLS-TM-MIB include:

   *  Mapping a certificate's subjectAltName component to a
      tmSecurityName, or

   *  Mapping a certificate's fingerprint value to a directly specified
      tmSecurityName

   As an implementation hint: implementations MAY choose to discard any
   connections for which no potential snmpTlstmCertToTSN13Table mapping
   exists before performing certificate verification to avoid expending
   computational resources associated with certificate verification.





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   Deployments SHOULD map the "subjectAltName" component of X.509
   certificates to the TLSTM specific tmSecurityNames.  The
   authenticated identity can be obtained by the TLS Transport Model by
   extracting the subjectAltName(s) from the peer's certificate.  The
   receiving application will then have an appropriate tmSecurityName
   for use by other SNMPv3 components like an access control model.

   An example of this type of mapping setup can be found in Appendix A.

   This tmSecurityName MAY be later translated from a TLSTM specific
   tmSecurityName to an SNMP engine securityName by the security model.
   A security model, like the TSM security model [RFC5591], MAY perform
   an identity mapping or a more complex mapping to derive the
   securityName from the tmSecurityName offered by the TLS Transport
   Model.

   The standard View-Based Access Control Model (VACM) (RFC3415)
   constrains securityNames to be 32 octets or less in length.  A TLSTM
   generated tmSecurityName, possibly in combination with a messaging or
   security model that increases the length of the securityName, might
   cause the securityName length to exceed 32 octets.  For example, a
   32-octet tmSecurityName derived from an IPv6 address, paired with a
   TSM prefix, will generate a 36-octet securityName.  Such a
   securityName will not be able to be used with standard VACM or TARGET
   MIB modules.  Operators SHOULD be careful to select algorithms and
   subjectAltNames to avoid this situation.

   A pictorial view of the complete transformation process (using the
   TSM security model for the example) is shown below:

    +-------------+     +-------+                   +-----+
    | Certificate |     |       |                   |     |
    |    Path     |     | TLSTM |  tmSecurityName   | TSM |
    | Validation  | --> |       | ----------------->|     |
    +-------------+     +-------+                   +-----+
                                                        |
                                                        | securityName
                                                        V
                                                    +-------------+
                                                    | application |
                                                    +-------------+

             Figure 3: TSM Securty Model Transformation Process








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4.2.  TLS Usage

   TLS MUST negotiate a cipher_suite that uses X.509 certificates for
   authentication, and MUST authenticate both the client and the server.
   The mandatory-to-implement cipher_suite is specified in the TLS
   specification [RFC8446].

   TLSTM verifies the certificates when the connection is opened (see
   Section 5.3).  TLS renegotiation is not supported with TLS 1.3, thus
   there is no risk of a different certificate being used later in a TLS
   session.  MUST NOT be done.

4.3.  SNMP Services

   This section describes the services provided by the TLS Transport
   Model with their inputs and outputs.  The services are between the
   Transport Model and the Dispatcher.

   The services are described as primitives of an abstract service
   interface (ASI) and the inputs and outputs are described as abstract
   data elements as they are passed in these abstract service
   primitives.

4.3.1.  SNMP Services for an Outgoing Message

   The Dispatcher passes the information to the TLS Transport Model
   using the ASI defined in the Transport Subsystem:

      statusInformation =
      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   tmStateReference              -- reference to transport state
       )

   The abstract data elements returned from or passed as parameters into
   the abstract service primitives are as follows:

   statusInformation:  An indication of whether the sending of the
                       message was successful.  If not, it is an
                       indication of the problem.

   destTransportDomain:  The transport domain for the associated






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                       destTransportAddress.  The Transport Model uses
                       this parameter to determine the transport type of
                       the associated destTransportAddress.  This
                       document specifies the snmpTLSTCPDomain transport
                       domain.

   destTransportAddress:  The transport address of the destination TLS
                       Transport Model in a format specified by the
                       SnmpTLSAddress TEXTUAL-CONVENTION.

   outgoingMessage:    The outgoing message to send to TLS for
                       encapsulation and transmission.

   outgoingMessageLength:  The length of the outgoingMessage.

   tmStateReference:   A reference used to pass model-specific and
                       mechanism-specific parameters between the
                       Transport Subsystem and transport-aware Security
                       Models.

4.3.2.  SNMP Services for an Incoming Message

   The TLS Transport Model processes the received message from the
   network using the TLS service and then passes it to the Dispatcher
   using the following ASI:

      statusInformation =
      receiveMessage(
      IN   transportDomain             -- origin transport domain
      IN   transportAddress            -- origin transport address
      IN   incomingMessage             -- the message received
      IN   incomingMessageLength       -- its length
      IN   tmStateReference            -- reference to transport state
       )

   The abstract data elements returned from or passed as parameters into
   the abstract service primitives are as follows:

   statusInformation:  An indication of whether the passing of the
                       message was successful.  If not, it is an
                       indication of the problem.

   transportDomain:    The transport domain for the associated
                       transportAddress.  This document specifies the
                       snmpTLSTCPDomain transport domain.

   transportAddress:   The transport address of the source of the




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                       received message in a format specified by the
                       SnmpTLSAddress TEXTUAL-CONVENTION.

   incomingMessage:    The whole SNMP message after being processed by
                       TLS.

   incomingMessageLength:  The length of the incomingMessage.

   tmStateReference:   A reference used to pass model-specific and
                       mechanism-specific parameters between the
                       Transport Subsystem and transport-aware Security
                       Models.

4.4.  Cached Information and References

   When performing SNMP processing, there are two levels of state
   information that might need to be retained: the immediate state
   linking a request-response pair, and potentially longer-term state
   relating to transport and security.  "Transport Subsystem for the
   Simple Network Management Protocol (SNMP)" [RFC5590] defines general
   requirements for caches and references.

4.4.1.  TLS Transport Model Cached Information

   The TLS Transport Model has specific responsibilities regarding the
   cached information.  See the Elements of Procedure in Section 5 for
   detailed processing instructions on the use of the tmStateReference
   fields by the TLS Transport Model.

4.4.1.1.  tmSecurityName

   The tmSecurityName MUST be a human-readable name (in SnmpAdminString
   format as defined in RFC3411) representing the identity that has been
   set according to the procedures in Section 5.  The tmSecurityName
   MUST be constant for all traffic passing through a single TLSTM
   session.  Messages MUST NOT be sent through an existing TLS
   connection that was established using a different tmSecurityName.

   On the TLS server side of a connection, the tmSecurityName is derived
   using the procedures described in Section 5.3.2 and the SNMP- TLS-TM-
   MIB's snmpTlstmCertToTSN13Table DESCRIPTION clause.










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   On the TLS client side of a connection, the tmSecurityName is
   presented to the TLS Transport Model by the security model through
   the tmStateReference.  This tmSecurityName is typically a copy of or
   is derived from the securityName that was passed by application
   (possibly because of configuration specified in the SNMP-TARGET-MIB).
   The Security Model likely derived the tmSecurityName from the
   securityName presented to the Security Model by the application
   (possibly because of configuration specified in the SNMP-TARGET-MIB).

   Transport-Model-aware security models derive tmSecurityName from a
   securityName, possibly configured in MIB modules for notifications
   and access controls.  Transport Models SHOULD use predictable
   tmSecurityNames so operators will know what to use when configuring
   MIB modules that use securityNames derived from tmSecurityNames.  The
   TLSTM generates predictable tmSecurityNames based on the
   configuration found in the SNMP-TLS-TM-MIB's
   snmpTlstmCertToTSN13Table and relies on the network operators to have
   configured this table appropriately.

4.4.1.2.  tmSessionID

   The tmSessionID MUST be recorded per message at the time of receipt.
   When tmSameSecurity is set, the recorded tmSessionID can be used to
   determine whether the TLS connection available for sending a
   corresponding outgoing message is the same TLS connection as was used
   when receiving the incoming message (e.g., a response to a request).

4.4.1.3.  Session State

   The per-session state that is referenced by tmStateReference MAY be
   saved across multiple messages in a Local Configuration Datastore.
   Additional session/connection state information might also be stored
   in a Local Configuration Datastore (LCD).

5.  Elements of Procedure

   Abstract service interfaces have been defined by RFC3411 and further
   augmented by [RFC5590] to describe the conceptual data flows between
   the various subsystems within an SNMP entity.  The TLSTM uses some of
   these conceptual data flows when communicating between subsystems.











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   To simplify the elements of procedure, the release of state
   information is not always explicitly specified.  As a general rule,
   if state information is available when a message gets discarded, the
   message-state information SHOULD also be released.  If state
   information is available when a session is closed, the session state
   information SHOULD also be released.  Sensitive information, like
   cryptographic keys, SHOULD be overwritten appropriately prior to
   being released.

   An error indication in statusInformation will typically include the
   Object Identifier (OID) and value for an incremented error counter.
   This MAY be accompanied by the requested securityLevel and the
   tmStateReference.  Per-message context information is not accessible
   to Transport Models, so for the returned counter OID and value,
   contextEngine would be set to the local value of snmpEngineID and
   contextName to the default context for error counters.

5.1.  Procedures for an Incoming Message

   This section describes the procedures followed by the TLS Transport
   Model when it receives a TLS protected packet.  It describes the
   transport processing REQUIRED once the TLS processing has been
   completed.

   The procedures in this section describe how the TLS Transport Model
   is to process messages that have already been properly extracted from
   the TLS stream.  Implementations SHOULD verify that messages from TLS
   are complete and single.  For example, partial SNMP messages can be
   received from a TLS stream.  These steps describe the processing of a
   singular SNMP message after it has been delivered from the TLS
   stream.

   1)  Determine the tlstmSessionID for the incoming message.  The
       tlstmSessionID MUST be a unique session identifier for this TLS
       connection.  The contents and format of this identifier are
       implementation dependent as long as it is unique to the session.
       A session identifier MUST NOT be reused until all references to
       it are no longer in use.  The tmSessionID is equal to the
       tlstmSessionID. tmSessionID refers to the session identifier when
       stored in the tmStateReference and tlstmSessionID refers to the
       session identifier when stored in the LCD.  They MUST always be
       equal when processing a given session's traffic.

       If this is the first message received through this session, and
       the session does not have an assigned tlstmSessionID yet, then
       the snmpTlstmSessionAccepts counter is incremented and a
       tlstmSessionID for the session is created.  This will only happen
       on the server side of a connection because a client would have



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       already assigned a tlstmSessionID during the openSession()
       invocation.  Implementations MAY have performed the procedures
       described in Section 5.3.2 prior to this point or they MAY
       perform them now, but the procedures described in Section 5.3.2
       MUST be performed before continuing beyond this point.

   2)  Create a tmStateReference cache for the subsequent reference and
       assign the following values within it:

       tmTransportDomain  snmpTLSTCPDomain.

       tmTransportAddress  The address from which the message
                      originated.

       tmSecurityLevel  The tmSecurityLevel for the session, as
                      discussed in Sections 3.1.2 and 5.3, which will
                      always be authPriv for TLS 1.3.

       tmSecurityName  The derived tmSecurityName for the session as
                      discussed in Section 5.3.  This value MUST be
                      constant during the lifetime of the session.

       tmSessionID    The tlstmSessionID described in step 1 above.

   3)  The incomingMessage and incomingMessageLength are assigned values
       from the TLS processing.

   4)  The TLS Transport Model passes the transportDomain,
       transportAddress, incomingMessage, and incomingMessageLength to
       the Dispatcher using the receiveMessage ASI:

          statusInformation =
          receiveMessage(
          IN transportDomain         -- snmpTLSTCPDomain,
          IN transportAddress        -- address for the received message
          IN incomingMessage         -- the whole SNMP message from TLS
          IN incomingMessageLength   -- the length of the SNMP message
          IN tmStateReference        -- transport info
          )

5.2.  Procedures for an Outgoing SNMP Message

   The Dispatcher sends a message to the TLS Transport Model using the
   following ASI:







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      statusInformation =
      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   tmStateReference         -- transport info
      )

   This section describes the procedure followed by the TLS Transport
   Model whenever it is requested through this ASI to send a message.

   1)  If tmStateReference does not refer to a cache containing values
       for tmTransportDomain, tmTransportAddress, tmSecurityName, and
       tmSameSecurity, then increment the snmpTlstmSessionInvalidCaches
       counter, discard the message, and return the error indication in
       the statusInformation.  Processing of this message stops.

   2)  Extract the tmSessionID, tmTransportDomain, tmTransportAddress,
       tmSecurityName, and tmSameSecurity values from the
       tmStateReference.  Note: the tmSessionID value might be undefined
       if no session exists yet over which the message can be sent.

   3)  If tmSameSecurity is true and tmSessionID is either undefined or
       refers to a session that is no longer open, then increment the
       snmpTlstmSessionNoSessions counter, discard the message, and
       return the error indication in the statusInformation.  Processing
       of this message stops.

   4)  If tmSameSecurity is false and tmSessionID refers to a session
       that is no longer available, then an implementation SHOULD open a
       new session, using the openSession() ASI (described in greater
       detail in step 5b).  Instead of opening a new session an
       implementation MAY return an snmpTlstmSessionNoSessions error to
       the calling module and stop the processing of the message.

   5)  If tmSessionID is undefined, then use tmTransportDomain,
       tmTransportAddress, and tmSecurityName to see if there is a
       corresponding entry in the LCD suitable to send the message over.

       5a)  If there is a corresponding LCD entry, then this session
            will be used to send the message.

       5b)  If there is no corresponding LCD entry, then open a session
            using the openSession() ASI (discussed further in
            Section 5.3.1).  Implementations MAY wish to offer message
            buffering to prevent redundant openSession() calls for the
            same cache entry.  If an error is returned from



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            openSession(), then discard the message, discard the
            tmStateReference, increment the snmpTlstmSessionOpenErrors,
            return an error indication to the calling module, and stop
            the processing of the message.

   6)  Using either the session indicated by the tmSessionID (if there
       was one) or the session resulting from a previous step (4 or 5),
       pass the outgoingMessage to TLS for encapsulation and
       transmission.

5.3.  Establishing or Accepting a Session

   Establishing a TLS connection as either a client or a server requires
   slightly different processing.  The following two sections describe
   the necessary processing steps.

5.3.1.  Establishing a Session as a Client

   The TLS Transport Model provides the following primitive for use by a
   client to establish a new TLS connection:

      statusInformation =           -- errorIndication or success
      openSession(
      IN   tmStateReference         -- transport information to be used
      OUT  tmStateReference         -- transport information to be used
      IN   maxMessageSize           -- of the sending SNMP entity
      )

   The following describes the procedure to follow when establishing an
   SNMP over a TLS connection between SNMP engines for exchanging SNMP
   messages.  This process is followed by any SNMP client's engine when
   establishing a session for subsequent use.

   This procedure MAY be done automatically for an SNMP application that
   initiates a transaction, such as a command generator, a notification
   originator, or a proxy forwarder.

   1)  The snmpTlstmSessionOpens counter is incremented.


   2)  The client selects the appropriate certificate and cipher_suites
       for the key agreement based on the tmSecurityName for the
       session.  For sessions being established as a result of an SNMP-
       TARGET-MIB based operation, the certificate will potentially have
       been identified via the snmpTlstmParams13Table mapping and the
       cipher_suites will have to be taken from a system-wide or
       implementation-specific configuration.  If no row in the
       snmpTlstmParams13Table exists, then implementations MAY choose to



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       establish the connection using a default client certificate
       available to the application.  Otherwise, the certificate and
       appropriate cipher_suites will need to be passed to the
       openSession() ASI as supplemental information or configured
       through an implementation-dependent mechanism.  The security
       level of the session MUST always be authPriv and is reported in
       the tmStateReference cache as tmSecurityLevel.  For TLS to
       provide strong authentication, each principal acting as a command
       generator SHOULD have its own certificate.

   3)  Using the destTransportDomain and destTransportAddress values,
       the client will initiate the TLS handshake protocol to establish
       a session key for message integrity and encryption.  Note that
       with TLS 1.3, only one key is necessary to accomplish both
       message integrity and encryption.

       If the attempt to establish a session is unsuccessful, then
       snmpTlstmSessionOpenErrors is incremented, an error indication is
       returned, and processing stops.  If the session failed to open
       because the presented server certificate was unknown or invalid,
       then the snmpTlstmSessionUnknownServerCertificate or
       snmpTlstmSessionInvalidServerCertificates MUST be incremented and
       an snmpTlstmServerCertificateUnknown or
       snmpTlstmServerInvalidCertificate13 notification SHOULD be sent
       as appropriate.  Reasons for server certificate invalidation
       include, but are not limited to, cryptographic validation
       failures and an unexpected presented certificate identity.

   4)  The TLS client MUST then verify that the TLS server's presented
       certificate is the expected certificate.  The TLS client MUST NOT
       transmit SNMP messages until the server certificate has been
       authenticated, the client certificate has been transmitted, and
       the TLS connection has been fully established.

       If the connection is being established from a configuration based
       on SNMP-TARGET-MIB configuration, then the
       snmpTlstmAddr13Table DESCRIPTION clause describes how the
       verification is done (using either a certificate fingerprint, or
       an identity authenticated via certification path validation).












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       If the connection is being established for reasons other than
       configuration found in the SNMP-TARGET-MIB, then configuration
       and procedures outside the scope of this document SHOULD be
       followed.  Configuration mechanisms SHOULD be similar in nature
       to those defined in the snmpTlstmAddr13Table to ensure
       consistency across management configuration systems.  For
       example, a command- line tool for generating SNMP GETs might
       support specifying either the server's certificate fingerprint or
       the expected host name as a command-line argument.

   5)  TLS provides assurance that the authenticated identity in the
       certificate has been signed by a trusted configured Certification
       Authority.  If verification of the server's certificate fails in
       any way (for example, because of failures in cryptographic
       verification or the presented identity did not match the expected
       named entity), then the session establishment MUST fail, and the
       snmpTlstmSessionInvalidServerCertificates object is incremented.
       If the session cannot be opened for any reason at all, including
       cryptographic verification failures and
       snmpTlstmCertToTSN13Table lookup failures, then the
       snmpTlstmSessionOpenErrors counter is incremented and processing
       stops.

   6)  The TLSTM-specific session identifier (tlstmSessionID) is set in
       the tmSessionID of the tmStateReference passed to the TLS
       Transport Model to indicate that the session has been established
       successfully and to point to a specific TLS connection for future
       use.  The tlstmSessionID is also stored in the LCD for later
       lookup during processing of incoming messages (Section 5.1).

5.3.2.  Accepting a Session as a Server

   A TLS server SHOULD accept new session connections from any client
   for which it is able to verify the client's credentials.  This is
   done by authenticating the client's presented certificate through a
   certificate path validation process (e.g., [RFC5280]) or through
   certificate fingerprint verification using fingerprints configured in
   the snmpTlstmCertToTSN13Table.  Afterward, the server will determine
   the identity of the remote entity using the following procedures.

   The TLS server identifies the authenticated identity from the TLS
   client's principal certificate using configuration information from
   the snmpTlstmCertToTSN13Table mapping table.  The TLS server MUST
   request and expect a certificate from the client and MUST NOT accept
   SNMP messages over the TLS connection until the client has sent a
   certificate and it has been authenticated.  The resulting derived
   tmSecurityName is recorded in the tmStateReference cache as
   tmSecurityName.  The details of the lookup process are fully



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   described in the DESCRIPTION clause of the
   snmpTlstmCertToTSN13Table MIB object.  If any verification fails in
   any way (for example, because of failures in cryptographic
   verification or because of the lack of an appropriate row in the
   snmpTlstmCertToTSN13Table), then the session establishment MUST fail,
   and the snmpTlstmSessionInvalidClientCertificates object is
   incremented.  If the session cannot be opened for any reason at all,
   including cryptographic verification failures, then the
   snmpTlstmSessionOpenErrors counter is incremented and processing
   stops.

   Servers that wish to support multiple principals at a particular port
   SHOULD make use of a TLS extension that allows server-side principal
   selection like the Server Name Indication extension defined in
   Section 3 of [RFC6066].  Supporting this will allow, for example,
   sending notifications to a specific principal at a given TCP port.

5.4.  Closing a Session

   The TLS Transport Model provides the following primitive to close a
   session:

      statusInformation =
      closeSession(
      IN  tmSessionID        -- session ID of the session to be closed
      )

   The following describes the procedure to follow to close a session
   between a client and server.  This process is followed by any SNMP
   engine closing the corresponding SNMP session.

   1)  Increment either the snmpTlstmSessionClientCloses or the
       snmpTlstmSessionServerCloses counter as appropriate.

   2)  Look up the session using the tmSessionID.

   3)  If there is no open session associated with the tmSessionID, then
       closeSession processing is completed.

   4)  Have TLS close the specified connection.  This MUST include
       sending a close_notify TLS Alert to inform the other side that
       session cleanup might be performed.









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6.  MIB Module Overview

   This MIB module provides management of the TLS Transport Model.  It
   defines needed textual conventions, statistical counters,
   notifications, and configuration infrastructure necessary for session
   establishment.  Example usage of the configuration tables can be
   found in Appendix A.

6.1.  Structure of the MIB Module

   Objects in this MIB module are arranged into subtrees.  Each subtree
   is organized as a set of related objects.  The overall structure and
   assignment of objects to their subtrees, and the intended purpose of
   each subtree, is shown below.

6.2.  Textual Conventions

   Generic and Common Textual Conventions used in this module can be
   found summarized at http://www.ops.ietf.org/mib-common-tcs.html.

   This module defines the following Textual Conventions:

   *  A new TransportAddress format for describing TLS connection
      addressing requirements.

   *  A certificate fingerprint allowing MIB module objects to
      generically refer to a stored X.509 certificate using a
      cryptographic hash as a reference pointer.

6.3.  Statistical Counters

   The SNMP-TLS-TM-MIB defines counters that provide network management
   stations with information about session usage and potential errors
   that a device might be experiencing.

6.4.  Configuration Tables

   The SNMP-TLS-TM-MIB defines configuration tables that an
   administrator can use for configuring a device for sending and
   receiving SNMP messages over TLS.  In particular, there are MIB
   tables that extend the SNMP-TARGET-MIB for configuring TLS
   certificate usage and a MIB table for mapping incoming TLS client
   certificates to SNMPv3 tmSecurityNames.








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6.4.1.  Notifications

   The SNMP-TLS-TM-MIB defines notifications to alert management
   stations when a TLS connection fails because a server's presented
   certificate did not meet an expected value
   (snmpTlstmServerCertificateUnknown) or because cryptographic
   validation failed (snmpTlstmServerInvalidCertificate13).

6.5.  Relationship to Other MIB Modules

   Some management objects defined in other MIB modules are applicable
   to an entity implementing the TLS Transport Model.  In particular, it
   is assumed that an entity implementing the SNMP-TLS-TM-MIB will
   implement the SNMPv2-MIB (RFC3418), the SNMP-FRAMEWORK-MIB (RFC3411),
   the SNMP-TARGET-MIB (RFC3413), the SNMP-NOTIFICATION-MIB (RFC3413),
   and the SNMP-VIEW-BASED-ACM-MIB (RFC3415).

   The SNMP-TLS-TM-MIB module contained in this document is for managing
   TLS Transport Model information.

6.5.1.  MIB Modules Required for IMPORTS

   The SNMP-TLS-TM-MIB module imports items from SNMPv2-SMI (RFC2578),
   SNMPv2-TC (RFC2579), SNMP-FRAMEWORK-MIB (RFC3411), SNMP-TARGET-MIB
   (RFC3413), and SNMPv2-CONF (RFC2580).

7.  MIB Module Definition

   SNMP-TLS-TM-MIB DEFINITIONS ::= BEGIN
   IMPORTS
     MODULE-IDENTITY, OBJECT-TYPE,
     OBJECT-IDENTITY, mib-2, snmpDomains,
     Counter32, Unsigned32, Gauge32, NOTIFICATION-TYPE
       FROM SNMPv2-SMI                 -- RFC 2578 or any update thereof
     TEXTUAL-CONVENTION, TimeStamp, RowStatus, StorageType,
     AutonomousType
       FROM SNMPv2-TC                  -- RFC 2579 or any update thereof
     MODULE-COMPLIANCE, OBJECT-GROUP, NOTIFICATION-GROUP
       FROM SNMPv2-CONF                -- RFC 2580 or any update thereof
     SnmpAdminString
       FROM SNMP-FRAMEWORK-MIB         -- RFC 3411 or any update thereof
     snmpTargetParamsName, snmpTargetAddrName
       FROM SNMP-TARGET-MIB            -- RFC 3413 or any update thereof
       ;
   snmpTlstmMIB MODULE-IDENTITY
     LAST-UPDATED "202103280000Z"

     ORGANIZATION "ISMS Working Group"



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     CONTACT-INFO "Kenneth Vaughn
                   Trevilon LLC
                   6606 FM 1488 RD, STE 503
                   Magnolia, TX 77354
                   USA
                   kvaughn@trevilon.com
     DESCRIPTION  "
         The TLS Transport Model MIB
         Copyright (c) 2010-2021 IETF Trust and the persons identified
         as authors of the code.  All rights reserved.
         Redistribution and use in source and binary forms, with or
         without modification, is permitted pursuant to, and subject
         to the license terms contained in, the Simplified BSD License
         set forth in Section 4.c of the IETF Trust's Legal Provisions
         Relating to IETF Documents
         (http://trustee.ietf.org/license-info)."
        REVISION     "202103280000Z"
        DESCRIPTION  "This version of this MIB module is part of
                      RFC XXXX; see the RFC itself for full legal
                      notices.  This version updated the MIB to
                      support TLS 1.3."

        REVISION     "201107190000Z"
        DESCRIPTION  "This version of this MIB module is part of
                      RFC 6353; see the RFC itself for full legal
                      notices.  The only change was to introduce
                      new wording to reflect require changes for
                      IDNA addresses in the SnmpTLSAddress TC."

        REVISION     "201005070000Z"
        DESCRIPTION  "This version of this MIB module is part of
                      RFC 5953; see the RFC itself for full legal
                      notices."
     ::= { mib-2 198 }
   -- ************************************************
   -- subtrees of the SNMP-TLS-TM-MIB
   -- ************************************************
   snmpTlstmNotifications OBJECT IDENTIFIER ::= { snmpTlstmMIB 0 }
   snmpTlstmIdentities    OBJECT IDENTIFIER ::= { snmpTlstmMIB 1 }
   snmpTlstmObjects       OBJECT IDENTIFIER ::= { snmpTlstmMIB 2 }
   snmpTlstmConformance   OBJECT IDENTIFIER ::= { snmpTlstmMIB 3 }
   -- ************************************************
   -- snmpTlstmObjects - Objects
   -- ************************************************
   snmpTLSTCPDomain OBJECT-IDENTITY
     STATUS      current
     DESCRIPTION
         "The SNMP over TLS via TCP transport domain.  The



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         corresponding transport address is of type SnmpTLSAddress.
         The securityName prefix to be associated with the
         snmpTLSTCPDomain is 'tls'.  This prefix may be used by
         security models or other components to identify which secure
         transport infrastructure authenticated a securityName."
     REFERENCE
       "RFC 2579: Textual Conventions for SMIv2"
     ::= { snmpDomains 8 }
   snmpDTLSUDPDomain OBJECT-IDENTITY
     STATUS      deprecated
     DESCRIPTION
         "The SNMP over DTLS via UDP transport domain.  The
         corresponding transport address is of type SnmpTLSAddress.
         The securityName prefix to be associated with the
         snmpDTLSUDPDomain is 'dtls'.  This prefix may be used by
         security models or other components to identify which secure
         transport infrastructure authenticated a securityName."
     REFERENCE
       "RFC 2579: Textual Conventions for SMIv2"
     ::= { snmpDomains 9 }
   SnmpTLSAddress ::= TEXTUAL-CONVENTION
     DISPLAY-HINT "1a"
     STATUS       current
     DESCRIPTION
        "Represents an IPv4 address, an IPv6 address, or a
         US-ASCII-encoded hostname and port number.
         An IPv4 address must be in dotted decimal format followed by a
         colon ':' (US-ASCII character 0x3A) and a decimal port number
         in US-ASCII.
         An IPv6 address must be a colon-separated format (as described
         in RFC 5952), surrounded by square brackets ('[', US-ASCII
         character 0x5B, and ']', US-ASCII character 0x5D), followed by
         a colon ':' (US-ASCII character 0x3A) and a decimal port number
         in US-ASCII.
         A hostname is always in US-ASCII (as per RFC 1123);
         internationalized hostnames are encoded as A-labels as
         specified in  RFC 5890.  The hostname is followed by a
         colon ':' (US-ASCII character 0x3A) and a decimal port number
         in US-ASCII.  The name SHOULD be fully qualified whenever
         possible.
         Values of this textual convention may not be directly usable
         as transport-layer addressing information, and may require
         run-time resolution.  As such, applications that write them
         must be prepared for handling errors if such values are not
         supported, or cannot be resolved (if resolution occurs at the
         time of the management operation).
         The DESCRIPTION clause of TransportAddress objects that may
         have SnmpTLSAddress values must fully describe how (and



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         when) such names are to be resolved to IP addresses and vice
         versa.
         This textual convention SHOULD NOT be used directly in object
         definitions since it restricts addresses to a specific
         format.  However, if it is used, it MAY be used either on its
         own or in conjunction with TransportAddressType or
         TransportDomain as a pair.
         When this textual convention is used as a syntax of an index
         object, there may be issues with the limit of 128
         sub-identifiers specified in SMIv2 (STD 58).  It is
         RECOMMENDED that all MIB documents using this textual
         convention make explicit any limitations on index component
         lengths that management software must observe.  This may be
         done either by including SIZE constraints on the index
         components or by specifying applicable constraints in the
         conceptual row DESCRIPTION clause or in the surrounding
         documentation."
     REFERENCE
       "RFC 1123: Requirements for Internet Hosts - Application and
                  Support
        RFC 5890: Internationalized Domain Names for Applications
                  (IDNA): Definitions and Document Framework
        RFC 5952: A Recommendation for IPv6 Address Text Representation
       "
      SYNTAX       OCTET STRING (SIZE (1..255))
   SnmpTLSFingerprint ::= TEXTUAL-CONVENTION
     DISPLAY-HINT "1x:1x"
     STATUS       deprecated
     DESCRIPTION
        "A fingerprint value that can be used to uniquely reference
        other data of potentially arbitrary length.
        An SnmpTLSFingerprint value is composed of a 1-octet hashing
        algorithm identifier followed by the fingerprint value.  The
        octet value encoded is taken from the IANA TLS HashAlgorithm
        Registry (RFC 5246).  The remaining octets are filled using the
        results of the hashing algorithm.
        This TEXTUAL-CONVENTION allows for a zero-length (blank)
        SnmpTLSFingerprint value for use in tables where the
        fingerprint value may be optional.  MIB definitions or
        implementations may refuse to accept a zero-length value as
        appropriate.
        This textual convention was deprecated because TLS 1.3 uses a
        2-octet cipher suite identifier rather than a 1-octet hashing
        algorithm identifier."
     REFERENCE "RFC 5246: The Transport Layer
                Security (TLS) Protocol Version 1.2
                http://www.iana.org/assignments/tls-parameters/
     "



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     SYNTAX OCTET STRING (SIZE (0..255))
   SnmpTLS13Fingerprint ::= TEXTUAL-CONVENTION
     DISPLAY-HINT "1x,1x"
     STATUS       current
     DESCRIPTION
        "A fingerprint value that can be used to uniquely reference
        other data of potentially arbitrary length.
        An SnmpTLS13Fingerprint value is composed of a 2-octet cipher
        suite identifier followed by the fingerprint value.  The
        octet value encoded is taken from the IANA TLS Cipher Suites
        Registry(RFC 8446).  The remaining octets are filled using the
        results of the hashing algorithm, up to the first 253 octets.
        This TEXTUAL-CONVENTION allows for a zero-length (blank)
        SnmpTLS13Fingerprint value for use in tables where the
        fingerprint value may be optional.  MIB definitions or
        implementations may refuse to accept a zero-length value as
        appropriate."
     REFERENCE "RFC 8446: The Transport Layer
                Security (TLS) Protocol Version 1.3
                http://www.iana.org/assignments/tls-parameters/
     "
     SYNTAX OCTET STRING (SIZE (0..255))
   -- Identities for use in the snmpTlstmCertToTSNTable and
   -- snmpTlstmCertToTSN13Table
   snmpTlstmCertToTSNMIdentities OBJECT IDENTIFIER
     ::= { snmpTlstmIdentities 1 }
   snmpTlstmCertSpecified OBJECT-IDENTITY
     STATUS        current
     DESCRIPTION  "Directly specifies the tmSecurityName to be used for
                   this certificate.  The value of the tmSecurityName
                   to use is specified in the snmpTlstmCertToTSN13Data
                   column.  The snmpTlstmCertToTSN13Data column must
                   contain a non-zero length SnmpAdminString compliant
                   value or the mapping described in this row must be
                   considered a failure."
     ::= { snmpTlstmCertToTSNMIdentities 1 }
   snmpTlstmCertSANRFC822Name OBJECT-IDENTITY
     STATUS        current
     DESCRIPTION  "Maps a subjectAltName's rfc822Name to a
                   tmSecurityName.  The local part of the rfc822Name is
                   passed unaltered but the host-part of the name must
                   be passed in lowercase.  This mapping results in a
                   1:1 correspondence between equivalent subjectAltName
                   rfc822Name values and tmSecurityName values except
                   that the host-part of the name MUST be passed in
                   lowercase.
                   Example rfc822Name Field:  FooBar@Example.COM
                   is mapped to tmSecurityName: FooBar@example.com."



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     ::= { snmpTlstmCertToTSNMIdentities 2 }
   snmpTlstmCertSANDNSName OBJECT-IDENTITY
     STATUS        current
     DESCRIPTION  "Maps a subjectAltName's dNSName to a
                   tmSecurityName after first converting it to all
                   lowercase (RFC 5280 does not specify converting to
                   lowercase so this involves an extra step).  This
                   mapping results in a 1:1 correspondence between
                   subjectAltName dNSName values and the tmSecurityName
                   values."
     REFERENCE "RFC 5280 - Internet X.509 Public Key Infrastructure
                   Certificate and Certificate Revocation
                   List (CRL) Profile."
     ::= { snmpTlstmCertToTSNMIdentities 3 }
   snmpTlstmCertSANIpAddress OBJECT-IDENTITY
     STATUS        current
     DESCRIPTION  "Maps a subjectAltName's iPAddress to a
                   tmSecurityName by transforming the binary encoded
                   address as follows:
                   1) for IPv4, the value is converted into a
                      decimal-dotted quad address (e.g., '192.0.2.1').
                   2) for IPv6 addresses, the value is converted into a
                      32-character all lowercase hexadecimal string
                      without any colon separators.
                   This mapping results in a 1:1 correspondence between
                   subjectAltName iPAddress values and the
                   tmSecurityName values.
                   The resulting length of an encoded IPv6 address is
                   the maximum length supported by the View-Based
                   Access Control Model (VACM).  Using both the
                   Transport Security Model's support for transport
                   prefixes (see the SNMP-TSM-MIB's
                   snmpTsmConfigurationUsePrefix object for details)
                   will result in securityName lengths that exceed what
                   VACM can handle."
     ::= { snmpTlstmCertToTSNMIdentities 4 }
   snmpTlstmCertSANAny OBJECT-IDENTITY
     STATUS        current
     DESCRIPTION  "Maps any of the following fields using the
                   corresponding mapping algorithms:
                   |------------+----------------------------|
                   | Type       | Algorithm                  |
                   |------------+----------------------------|
                   | rfc822Name | snmpTlstmCertSANRFC822Name |
                   | dNSName    | snmpTlstmCertSANDNSName    |
                   | iPAddress  | snmpTlstmCertSANIpAddress  |
                   |------------+----------------------------|
                   The first matching subjectAltName value found in the



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                   certificate of the above types MUST be used when
                   deriving the tmSecurityName.  The mapping algorithm
                   specified in the 'Algorithm' column MUST be used to
                   derive the tmSecurityName.
                   This mapping results in a 1:1 correspondence between
                   subjectAltName values and tmSecurityName values.  The
                   three sub-mapping algorithms produced by this
                   combined algorithm cannot produce conflicting
                   results between themselves."
     ::= { snmpTlstmCertToTSNMIdentities 5 }
   snmpTlstmCertCommonName OBJECT-IDENTITY
     STATUS        deprecated
     DESCRIPTION  "Maps a certificate's CommonName to a tmSecurityName
                   after converting it to a UTF-8 encoding.  The usage
                   of CommonNames is deprecated and users are
                   encouraged to use subjectAltName mapping methods
                   instead.  This mapping results in a 1:1
                   correspondence between certificate CommonName values
                   and tmSecurityName values."
     ::= { snmpTlstmCertToTSNMIdentities 6 }

   -- The snmpTlstmSession Group
   snmpTlstmSession       OBJECT IDENTIFIER ::= { snmpTlstmObjects 1 }
   snmpTlstmSessionOpens  OBJECT-TYPE
     SYNTAX       Counter32
     MAX-ACCESS   read-only
     STATUS       current
     DESCRIPTION
        "The number of times an openSession() request has been executed
        as a (D)TLS client, regardless of whether it succeeded or
        failed."
     ::= { snmpTlstmSession 1 }
   snmpTlstmSessionClientCloses  OBJECT-TYPE
     SYNTAX       Counter32
     MAX-ACCESS   read-only
     STATUS       current
     DESCRIPTION
         "The number of times a closeSession() request has been
         executed as a (D)TLS client, regardless of whether it
         succeeded or failed."
     ::= { snmpTlstmSession 2 }
   snmpTlstmSessionOpenErrors  OBJECT-TYPE
     SYNTAX       Counter32
     MAX-ACCESS   read-only
     STATUS       current
     DESCRIPTION
         "The number of times an openSession() request failed to open a
         session as a (D)TLS client, for any reason."



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     ::= { snmpTlstmSession 3 }
   snmpTlstmSessionAccepts  OBJECT-TYPE
     SYNTAX       Counter32
     MAX-ACCESS   read-only
     STATUS       current
     DESCRIPTION
        "The number of times a (D)TLS server has accepted a new
        connection from a client and has received at least one SNMP
        message through it."
     ::= { snmpTlstmSession 4 }

   snmpTlstmSessionServerCloses  OBJECT-TYPE
     SYNTAX       Counter32
     MAX-ACCESS   read-only
     STATUS       current
     DESCRIPTION
         "The number of times a closeSession() request has been
         executed as a (D)TLS server, regardless of whether it
         succeeded or failed."
     ::= { snmpTlstmSession 5 }
   snmpTlstmSessionNoSessions  OBJECT-TYPE
     SYNTAX       Counter32
     MAX-ACCESS   read-only
     STATUS       current
     DESCRIPTION
         "The number of times an outgoing message was dropped because
         the session associated with the passed tmStateReference was no
         longer (or was never) available."
     ::= { snmpTlstmSession 6 }
   snmpTlstmSessionInvalidClientCertificates OBJECT-TYPE
     SYNTAX       Counter32
     MAX-ACCESS   read-only
     STATUS       current
     DESCRIPTION
         "The number of times an incoming session was not established
         on a (D)TLS server because the presented client certificate
         was invalid.  Reasons for invalidation include, but are not
         limited to, cryptographic validation failures or lack of a
         suitable mapping row in the snmpTlstmCertToTSNTable or the
         snmpTlstmCertToTSN13Table."
     ::= { snmpTlstmSession 7 }
   snmpTlstmSessionUnknownServerCertificate OBJECT-TYPE
     SYNTAX       Counter32
     MAX-ACCESS   read-only
     STATUS       current
     DESCRIPTION
         "The number of times an outgoing session was not established
          on a (D)TLS client because the server certificate presented



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          by an SNMP over (D)TLS server was invalid because no
          configured fingerprint or Certification Authority (CA) was
          acceptable to validate it.
          This may result because there was no entry in the
          snmpTlstmAddrTable (or snmpTlstmAddr13Table) or because no
          path could be found to a known CA."
     ::= { snmpTlstmSession 8 }
   snmpTlstmSessionInvalidServerCertificates OBJECT-TYPE
     SYNTAX       Counter32
     MAX-ACCESS   read-only
     STATUS       current
     DESCRIPTION
         "The number of times an outgoing session was not established
          on a (D)TLS client because the server certificate presented
          by an SNMP over (D)TLS server could not be validated even if
          the fingerprint or expected validation path was known.  That
          is, a cryptographic validation error occurred during
          certificate validation processing.
          Reasons for invalidation include, but are not
          limited to, cryptographic validation failures."
     ::= { snmpTlstmSession 9 }
   snmpTlstmSessionInvalidCaches OBJECT-TYPE
     SYNTAX       Counter32
     MAX-ACCESS   read-only
     STATUS       current
     DESCRIPTION
         "The number of outgoing messages dropped because the
         tmStateReference referred to an invalid cache."
     ::= { snmpTlstmSession 10 }
   -- Configuration Objects
   snmpTlstmConfig            OBJECT IDENTIFIER ::= {snmpTlstmObjects 2}
   -- Certificate mapping
   snmpTlstmCertificateMapping OBJECT IDENTIFIER ::= {snmpTlstmConfig 1}
   snmpTlstmCertToTSNCount OBJECT-TYPE
     SYNTAX      Gauge32
     MAX-ACCESS  read-only
     STATUS      deprecated
     DESCRIPTION
         "A count of the number of entries in the
         snmpTlstmCertToTSNTable."
     ::= { snmpTlstmCertificateMapping 1 }
   snmpTlstmCertToTSNTableLastChanged OBJECT-TYPE
     SYNTAX      TimeStamp
     MAX-ACCESS  read-only
     STATUS      deprecated
     DESCRIPTION
         "The value of sysUpTime.0 when the snmpTlstmCertToTSNTable was
         last modified through any means, or 0 if it has not been



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         modified since the command responder was started."
     ::= { snmpTlstmCertificateMapping 2 }
   snmpTlstmCertToTSNTable OBJECT-TYPE
     SYNTAX      SEQUENCE OF SnmpTlstmCertToTSNEntry
     MAX-ACCESS  not-accessible
     STATUS      deprecated
     DESCRIPTION
         "This table is used by a (D)TLS server to map the (D)TLS
         client's presented X.509 certificate to a tmSecurityName.
         On an incoming (D)TLS/SNMP connection, the client's presented
         certificate must either be validated based on an established
         trust anchor, or it must directly match a fingerprint in this
         table.  This table does not provide any mechanisms for
         configuring the trust anchors; the transfer of any needed
         trusted certificates for path validation is expected to occur
         through an out-of-band transfer.
         Once the certificate has been found acceptable (either by path
         validation or directly matching a fingerprint in this table),
         this table is consulted to determine the appropriate
         tmSecurityName to identify with the remote connection.  This
         is done by considering each active row from this table in
         prioritized order according to its snmpTlstmCertToTSNID value.
         Each row's snmpTlstmCertToTSNFingerprint value determines
         whether the row is a match for the incoming connection:
             1) If the row's snmpTlstmCertToTSNFingerprint value
                identifies the presented certificate, then consider the
                row as a successful match.
             2) If the row's snmpTlstmCertToTSNFingerprint value
                identifies a locally held copy of a trusted CA
                certificate and that CA certificate was used to
                validate the path to the presented certificate, then
                consider the row as a successful match.
         Once a matching row has been found, the
         snmpTlstmCertToTSNMapType value can be used to determine how
         the tmSecurityName to associate with the session should be
         determined.  See the snmpTlstmCertToTSNMapType column's
         DESCRIPTION for details on determining the tmSecurityName
         value.  If it is impossible to determine a tmSecurityName from
         the row's data combined with the data presented in the
         certificate, then additional rows MUST be searched looking for
         another potential match.  If a resulting tmSecurityName mapped
         from a given row is not compatible with the needed
         requirements of a tmSecurityName (e.g., VACM imposes a
         32-octet-maximum length and the certificate derived
         securityName could be longer), then it must be considered an
         invalid match and additional rows MUST be searched looking for
         another potential match.
         If no matching and valid row can be found, the connection MUST



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         be closed and SNMP messages MUST NOT be accepted over it.
         Missing values of snmpTlstmCertToTSNID are acceptable and
         implementations should continue to the next highest numbered
         row.  It is recommended that administrators skip index values
         to leave room for the insertion of future rows (for example,
         use values of 10 and 20 when creating initial rows).
         Users are encouraged to make use of certificates with
         subjectAltName fields that can be used as tmSecurityNames so
         that a single root CA certificate can allow all child
         certificate's subjectAltName to map directly to a
         tmSecurityName via a 1:1 transformation.  However, this table
         is flexible to allow for situations where existing deployed
         certificate infrastructures do not provide adequate
         subjectAltName values for use as tmSecurityNames.
         Direct mapping from each individual
         certificate fingerprint to a tmSecurityName is also possible
         but requires one entry in the table per tmSecurityName and
         requires more management operations to completely configure a
         device.
         This table and its associated objects were deprecated because
         the fingerprint format changed to support TLS 1.3. By
         deprecating (and creating an updated) table, rather than just
         the fingerprint object, an implementation is able to support
         both the original TLS and new TLS 1.3 tables while forcing some
         agents to only use TLS 1.3."
     ::= { snmpTlstmCertificateMapping 3 }
   snmpTlstmCertToTSNEntry OBJECT-TYPE
     SYNTAX      SnmpTlstmCertToTSNEntry
     MAX-ACCESS  not-accessible
     STATUS      deprecated
     DESCRIPTION
         "A row in the snmpTlstmCertToTSNTable that specifies a mapping
         for an incoming (D)TLS certificate to a tmSecurityName to use
         for a connection."
     INDEX   { snmpTlstmCertToTSNID }
     ::= { snmpTlstmCertToTSNTable 1 }
   SnmpTlstmCertToTSNEntry ::= SEQUENCE {
     snmpTlstmCertToTSNID           Unsigned32,
     snmpTlstmCertToTSNFingerprint  SnmpTLSFingerprint,
     snmpTlstmCertToTSNMapType      AutonomousType,
     snmpTlstmCertToTSNData         OCTET STRING,
     snmpTlstmCertToTSNStorageType  StorageType,
     snmpTlstmCertToTSNRowStatus    RowStatus
   }
   snmpTlstmCertToTSNID OBJECT-TYPE
     SYNTAX      Unsigned32 (1..4294967295)
     MAX-ACCESS  not-accessible
     STATUS      deprecated



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     DESCRIPTION
         "A unique, prioritized index for the given entry.  Lower
         numbers indicate a higher priority."
     ::= { snmpTlstmCertToTSNEntry 1 }
   snmpTlstmCertToTSNFingerprint OBJECT-TYPE
     SYNTAX      SnmpTLSFingerprint (SIZE(1..255))
     MAX-ACCESS  read-create
     STATUS      deprecated
     DESCRIPTION
         "A cryptographic hash of an X.509 certificate.  The results of
         a successful matching fingerprint to either the trusted CA in
         the certificate validation path or to the certificate itself
         is dictated by the snmpTlstmCertToTSNMapType column.
         This object was deprecated because TLS 1.3 uses a 2-octet
         cipher suite identifier rather than a 1-octet hashing algorithm
         identifier."
     ::= { snmpTlstmCertToTSNEntry 2 }
   snmpTlstmCertToTSNMapType OBJECT-TYPE
     SYNTAX      AutonomousType
     MAX-ACCESS  read-create
     STATUS      deprecated
     DESCRIPTION
         "Specifies the mapping type for deriving a tmSecurityName from
         a certificate.  Details for mapping of a particular type SHALL
         be specified in the DESCRIPTION clause of the OBJECT-IDENTITY
         that describes the mapping.  If a mapping succeeds it will
         return a tmSecurityName for use by the TLSTM model and
         processing stops.
         If the resulting mapped value is not compatible with the
         needed requirements of a tmSecurityName (e.g., VACM imposes a
         32-octet-maximum length and the certificate derived
         securityName could be longer), then future rows MUST be
         searched for additional snmpTlstmCertToTSNFingerprint matches
         to look for a mapping that succeeds.
         Suitable values for assigning to this object that are defined
         within the SNMP-TLS-TM-MIB can be found in the
         snmpTlstmCertToTSNMIdentities portion of the MIB tree."
     DEFVAL { snmpTlstmCertSpecified }
     ::= { snmpTlstmCertToTSNEntry 3 }
   snmpTlstmCertToTSNData OBJECT-TYPE
     SYNTAX      OCTET STRING (SIZE(0..1024))
     MAX-ACCESS  read-create
     STATUS      deprecated
     DESCRIPTION
         "Auxiliary data used as optional configuration information for
         a given mapping specified by the snmpTlstmCertToTSNMapType
         column.  Only some mapping systems will make use of this
         column.  The value in this column MUST be ignored for any



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         mapping type that does not require data present in this
         column."
     DEFVAL { "" }
     ::= { snmpTlstmCertToTSNEntry 4 }
   snmpTlstmCertToTSNStorageType OBJECT-TYPE
     SYNTAX       StorageType
     MAX-ACCESS   read-create
     STATUS       deprecated
     DESCRIPTION
         "The storage type for this conceptual row.  Conceptual rows
         having the value 'permanent' need not allow write-access to
         any columnar objects in the row."
     DEFVAL      { nonVolatile }
     ::= { snmpTlstmCertToTSNEntry 5 }
   snmpTlstmCertToTSNRowStatus OBJECT-TYPE
     SYNTAX      RowStatus
     MAX-ACCESS  read-create
     STATUS      deprecated
     DESCRIPTION
         "The status of this conceptual row.  This object may be used
         to create or remove rows from this table.
         To create a row in this table, an administrator must set this
         object to either createAndGo(4) or createAndWait(5).
         Until instances of all corresponding columns are appropriately
         configured, the value of the corresponding instance of the
         snmpTlstmParamsRowStatus column is notReady(3).
         In particular, a newly created row cannot be made active until
         the corresponding snmpTlstmCertToTSNFingerprint,
         snmpTlstmCertToTSNMapType, and snmpTlstmCertToTSNData columns
         have been set.
         The following objects may not be modified while the
         value of this object is active(1):
             - snmpTlstmCertToTSNFingerprint
             - snmpTlstmCertToTSNMapType
             - snmpTlstmCertToTSNData
         An attempt to set these objects while the value of
         snmpTlstmParamsRowStatus is active(1) will result in
         an inconsistentValue error."
     ::= { snmpTlstmCertToTSNEntry 6 }
   -- Maps tmSecurityNames to certificates for use by SNMP-TARGET-MIB
   snmpTlstmParamsCount OBJECT-TYPE
     SYNTAX      Gauge32
     MAX-ACCESS  read-only
     STATUS      deprecated
     DESCRIPTION
         "A count of the number of entries in the snmpTlstmParamsTable."
     ::= { snmpTlstmCertificateMapping 4 }
   snmpTlstmParamsTableLastChanged OBJECT-TYPE



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     SYNTAX      TimeStamp
     MAX-ACCESS  read-only
     STATUS      deprecated
     DESCRIPTION
         "The value of sysUpTime.0 when the snmpTlstmParamsTable
         was last modified through any means, or 0 if it has not been
         modified since the command responder was started."
     ::= { snmpTlstmCertificateMapping 5 }
   snmpTlstmParamsTable OBJECT-TYPE
     SYNTAX      SEQUENCE OF SnmpTlstmParamsEntry
     MAX-ACCESS  not-accessible
     STATUS      deprecated
     DESCRIPTION
         "This table is used by a (D)TLS client when a (D)TLS
         connection is being set up using an entry in the
         SNMP-TARGET-MIB.  It extends the SNMP-TARGET-MIB's
         snmpTargetParamsTable with a fingerprint of a certificate to
         use when establishing such a (D)TLS connection."
     ::= { snmpTlstmCertificateMapping 6 }
   snmpTlstmParamsEntry OBJECT-TYPE
     SYNTAX      SnmpTlstmParamsEntry
     MAX-ACCESS  not-accessible
     STATUS      deprecated
     DESCRIPTION
         "A conceptual row containing a fingerprint hash of a locally
         held certificate for a given snmpTargetParamsEntry.  The
         values in this row should be ignored if the connection that
         needs to be established, as indicated by the SNMP-TARGET-MIB
         infrastructure, is not a certificate and TLS based
         connection.  The connection SHOULD NOT be established if the
         certificate fingerprint stored in this entry does not point to
         a valid locally held certificate or if it points to an
         unusable certificate (such as might happen when the
         certificate's expiration date has been reached)."
     INDEX    { IMPLIED snmpTargetParamsName }
     ::= { snmpTlstmParamsTable 1 }
   SnmpTlstmParamsEntry ::= SEQUENCE {
     snmpTlstmParamsClientFingerprint SnmpTLSFingerprint,
     snmpTlstmParamsStorageType       StorageType,
     snmpTlstmParamsRowStatus         RowStatus
   }
   snmpTlstmParamsClientFingerprint OBJECT-TYPE
     SYNTAX      SnmpTLSFingerprint
     MAX-ACCESS  read-create
     STATUS      deprecated
     DESCRIPTION
         "This object stores the hash of the public portion of a
         locally held X.509 certificate.  The X.509 certificate, its



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         public key, and the corresponding private key will be used
         when initiating a TLS connection as a TLS client."
     ::= { snmpTlstmParamsEntry 1 }
   snmpTlstmParamsStorageType OBJECT-TYPE
     SYNTAX       StorageType
     MAX-ACCESS   read-create
     STATUS       deprecated
     DESCRIPTION
         "The storage type for this conceptual row.  Conceptual rows
         having the value 'permanent' need not allow write-access to
         any columnar objects in the row."
     DEFVAL      { nonVolatile }
     ::= { snmpTlstmParamsEntry 2 }
   snmpTlstmParamsRowStatus OBJECT-TYPE
     SYNTAX      RowStatus
     MAX-ACCESS  read-create
     STATUS      deprecated
     DESCRIPTION
         "The status of this conceptual row.  This object may be used
         to create or remove rows from this table.
         To create a row in this table, an administrator must set this
         object to either createAndGo(4) or createAndWait(5).
         Until instances of all corresponding columns are appropriately
         configured, the value of the corresponding instance of the
         snmpTlstmParamsRowStatus column is notReady(3).
         In particular, a newly created row cannot be made active until
         the corresponding snmpTlstmParamsClientFingerprint column has
         been set.
         The snmpTlstmParamsClientFingerprint object may not be modified
         while the value of this object is active(1).
         An attempt to set these objects while the value of
         snmpTlstmParamsRowStatus is active(1) will result in
         an inconsistentValue error."
     ::= { snmpTlstmParamsEntry 3 }
   mpTlstmAddrCount OBJECT-TYPE
     SYNTAX      Gauge32
     MAX-ACCESS  read-only
     STATUS      deprecated
     DESCRIPTION
         "A count of the number of entries in the snmpTlstmAddrTable."
     ::= { snmpTlstmCertificateMapping 7 }
   snmpTlstmAddrTableLastChanged OBJECT-TYPE
     SYNTAX      TimeStamp
     MAX-ACCESS  read-only
     STATUS      deprecated
     DESCRIPTION
         "The value of sysUpTime.0 when the snmpTlstmAddrTable
         was last modified through any means, or 0 if it has not been



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         modified since the command responder was started."
     ::= { snmpTlstmCertificateMapping 8 }
   snmpTlstmAddrTable OBJECT-TYPE
     SYNTAX      SEQUENCE OF SnmpTlstmAddrEntry
     MAX-ACCESS  not-accessible
     STATUS      deprecated
     DESCRIPTION
         "This table is used by a TLS client when a TLS
         connection is being set up using an entry in the
         SNMP-TARGET-MIB.  It extends the SNMP-TARGET-MIB's
         snmpTargetAddrTable so that the client can verify that the
         correct server has been reached.  This verification can use
         either a certificate fingerprint, or an identity
         authenticated via certification path validation.
         If there is an active row in this table corresponding to the
         entry in the SNMP-TARGET-MIB that was used to establish the
         connection, and the row's snmpTlstmAddrServerFingerprint
         column has non-empty value, then the server's presented
         certificate is compared with the
         snmpTlstmAddrServerFingerprint value (and the
         snmpTlstmAddrServerIdentity column is ignored).  If the
         fingerprint matches, the verification has succeeded.  If the
         fingerprint does not match, then the connection MUST be
         closed.
         If the server's presented certificate has passed
         certification path validation [RFC5280] to a configured
         trust anchor, and an active row exists with a zero-length
         snmpTlstmAddrServerFingerprint value, then the
         snmpTlstmAddrServerIdentity column contains the expected
         host name.  This expected host name is then compared against
         the server's certificate as follows:
           - Implementations MUST support matching the expected host
           name against a dNSName in the subjectAltName extension
           field
           - The '*' (ASCII 0x2a) wildcard character is allowed in the
           dNSName of the subjectAltName extension, but only as the
           left-most (least significant) DNS label in that value.
           This wildcard matches any left-most DNS label in the
           server name.  That is, the subject *.example.com matches
           the server names a.example.com and b.example.com, but does
           not match example.com or a.b.example.com.  Implementations
           MUST support wildcards in certificates as specified above,
           but MAY provide a configuration option to disable them.
           - If the locally configured name is an internationalized
           domain name, conforming implementations MUST convert it to
           the ASCII Compatible Encoding (ACE) format for performing
           comparisons, as specified in Section 7 of [RFC5280].
         If the expected host name fails these conditions then the



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         connection MUST be closed.

         If there is no row in this table corresponding to the entry
         in the SNMP-TARGET-MIB and the server can be authorized by
         another, implementation-dependent means, then the connection
         MAY still proceed."
     ::= { snmpTlstmCertificateMapping 9 }
   snmpTlstmAddrEntry OBJECT-TYPE
     SYNTAX      SnmpTlstmAddrEntry
     MAX-ACCESS  not-accessible
     STATUS      deprecated
     DESCRIPTION
         "A conceptual row containing a copy of a certificate's
         fingerprint for a given snmpTargetAddrEntry.  The values in
         this row should be ignored if the connection that needs to be
         established, as indicated by the SNMP-TARGET-MIB
         infrastructure, is not a TLS based connection.  If an
         snmpTlstmAddrEntry exists for a given snmpTargetAddrEntry, then
         the presented server certificate MUST match or the connection
         MUST NOT be established.  If a row in this table does not
         exist to match an snmpTargetAddrEntry row, then the connection
         SHOULD still proceed if some other certificate validation path
         algorithm (e.g., RFC 5280) can be used."
     INDEX    { IMPLIED snmpTargetAddrName }
     ::= { snmpTlstmAddrTable 1 }
   SnmpTlstmAddrEntry ::= SEQUENCE {
     snmpTlstmAddrServerFingerprint    SnmpTLSFingerprint,
     snmpTlstmAddrServerIdentity       SnmpAdminString,
     snmpTlstmAddrStorageType          StorageType,
     snmpTlstmAddrRowStatus            RowStatus
   }
   snmpTlstmAddrServerFingerprint OBJECT-TYPE
     SYNTAX      SnmpTLSFingerprint
     MAX-ACCESS  read-create
     STATUS      deprecated
     DESCRIPTION
         "A cryptographic hash of a public X.509 certificate.  This
         object should store the hash of the public X.509 certificate
         that the remote server should present during the TLS
         connection setup.  The fingerprint of the presented
         certificate and this hash value MUST match exactly or the
         connection MUST NOT be established."
     DEFVAL { "" }
     ::= { snmpTlstmAddrEntry 1 }
   snmpTlstmAddrServerIdentity OBJECT-TYPE
     SYNTAX      SnmpAdminString
     MAX-ACCESS  read-create
     STATUS      deprecated



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     DESCRIPTION
         "The reference identity to check against the identity
         presented by the remote system."
     DEFVAL { "" }
     ::= { snmpTlstmAddrEntry 2 }
   snmpTlstmAddrStorageType OBJECT-TYPE
     SYNTAX       StorageType
     MAX-ACCESS   read-create
     STATUS       deprecated
     DESCRIPTION
         "The storage type for this conceptual row.  Conceptual rows
         having the value 'permanent' need not allow write-access to
         any columnar objects in the row."
     DEFVAL      { nonVolatile }
     ::= { snmpTlstmAddrEntry 3 }
   snmpTlstmAddrRowStatus OBJECT-TYPE
     SYNTAX      RowStatus
     MAX-ACCESS  read-create
     STATUS      deprecated
     DESCRIPTION
         "The status of this conceptual row.  This object may be used
         to create or remove rows from this table.
         To create a row in this table, an administrator must set this
         object to either createAndGo(4) or createAndWait(5).
         Until instances of all corresponding columns are
         appropriately configured, the value of the
         corresponding instance of the snmpTlstmAddrRowStatus
         column is notReady(3).
         In particular, a newly created row cannot be made active until
         the corresponding snmpTlstmAddrServerFingerprint column has
         been set.
         Rows MUST NOT be active if the snmpTlstmAddrServerFingerprint
         column is blank and the snmpTlstmAddrServerIdentity is set to
         '*' since this would insecurely accept any presented
         certificate.

         The snmpTlstmAddrServerFingerprint object may not be modified
         while the value of this object is active(1).
         An attempt to set these objects while the value of
         snmpTlstmAddrRowStatus is active(1) will result in
         an inconsistentValue error."
     ::= { snmpTlstmAddrEntry 4 }
   snmpTlstmCertToTSN13Count OBJECT-TYPE
     SYNTAX      Gauge32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
         "A count of the number of entries in the



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         snmpTlstmCertToTSN13Table."
     ::= { snmpTlstmCertificateMapping 10 }
   snmpTlstmCertToTSN13TableLastChanged OBJECT-TYPE
     SYNTAX      TimeStamp
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
         "The value of sysUpTime.0 when the snmpTlstmCertToTSN13Table
         was last modified through any means, or 0 if it has not been
         modified since the command responder was started."
     ::= { snmpTlstmCertificateMapping 11 }
   snmpTlstmCertToTSN13Table OBJECT-TYPE
     SYNTAX      SEQUENCE OF SnmpTlstmCertToTSN13Entry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
         "This table is used by a TLS 1.3 server to map the TLS 1.3
         client's presented X.509 certificate to a tmSecurityName.
         On an incoming TLS/SNMP connection, the client's presented
         certificate must either be validated based on an established
         trust anchor, or it must directly match a fingerprint in this
         table.  This table does not provide any mechanisms for
         configuring the trust anchors; the transfer of any needed
         trusted certificates for path validation is expected to occur
         through an out-of-band transfer.
         Once the certificate has been found acceptable (either by path
         validation or directly matching a fingerprint in this table),
         this table is consulted to determine the appropriate
         tmSecurityName to identify with the remote connection.  This
         is done by considering each active row from this table in
         prioritized order according to its snmpTlstmCertToTSN13ID
         value. Each row's snmpTlstmCertToTSN13Fingerprint value
         determines whether the row is a match for the incoming
         connection:
             1) If the row's snmpTlstmCertToTSN13Fingerprint value
                identifies the presented certificate, then consider the
                row as a successful match.
             2) If the row's snmpTlstmCertToTSN13Fingerprint value
                identifies a locally held copy of a trusted CA
                certificate and that CA certificate was used to
                validate the path to the presented certificate, then
                consider the row as a successful match.
         Once a matching row has been found, the
         snmpTlstmCertToTSN13MapType value can be used to determine how
         the tmSecurityName to associate with the session should be
         determined.  See the snmpTlstmCertToTSN13MapType column's
         DESCRIPTION for details on determining the tmSecurityName
         value.  If it is impossible to determine a tmSecurityName from



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         the row's data combined with the data presented in the
         certificate, then additional rows MUST be searched looking for
         another potential match.  If a resulting tmSecurityName mapped
         from a given row is not compatible with the needed
         requirements of a tmSecurityName (e.g., VACM imposes a
         32-octet-maximum length and the certificate derived
         securityName could be longer), then it must be considered an
         invalid match and additional rows MUST be searched looking for
         another potential match.
         If no matching and valid row can be found, the connection MUST
         be closed and SNMP messages MUST NOT be accepted over it.
         Missing values of snmpTlstmCertToTSN13ID are acceptable and
         implementations should continue to the next highest numbered
         row.  It is recommended that administrators skip index values
         to leave room for the insertion of future rows (for example,
         use values of 10 and 20 when creating initial rows).
         Users are encouraged to make use of certificates with
         subjectAltName fields that can be used as tmSecurityNames so
         that a single root CA certificate can allow all child
         certificate's subjectAltName to map directly to a
         tmSecurityName via a 1:1 transformation.  However, this table
         is flexible to allow for situations where existing deployed
         certificate infrastructures do not provide adequate
         subjectAltName values for use as tmSecurityNames.
         Direct mapping from each individual certificate fingerprint to
         a tmSecurityName is possible but requires one entry in the
         table per tmSecurityName and requires more management
         operations to completely configure a device."
     ::= { snmpTlstmCertificateMapping 12 }
   snmpTlstmCertToTSN13Entry OBJECT-TYPE
     SYNTAX      SnmpTlstmCertToTSN13Entry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
         "A row in the snmpTlstmCertToTSN13Table that specifies a
         mapping for an incoming TLS certificate to a tmSecurityName
         to use for a connection."
     INDEX   { snmpTlstmCertToTSN13ID }
     ::= { snmpTlstmCertToTSN13Table 1 }
   SnmpTlstmCertToTSN13Entry ::= SEQUENCE {
     snmpTlstmCertToTSN13ID           Unsigned32,
     snmpTlstmCertToTSN13Fingerprint  SnmpTLS13Fingerprint,
     snmpTlstmCertToTSN13MapType      AutonomousType,
     snmpTlstmCertToTSN13Data         OCTET STRING,
     snmpTlstmCertToTSN13StorageType  StorageType,
     snmpTlstmCertToTSN13RowStatus    RowStatus
   }
   snmpTlstmCertToTSN13ID OBJECT-TYPE



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     SYNTAX      Unsigned32 (1..4294967295)
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
         "A unique, prioritized index for the given entry.  Lower
         numbers indicate a higher priority."
     ::= { snmpTlstmCertToTSN13Entry 1 }
   snmpTlstmCertToTSN13Fingerprint OBJECT-TYPE
     SYNTAX      SnmpTLS13Fingerprint (SIZE(2..255))
     MAX-ACCESS  read-create
     STATUS      current
     DESCRIPTION
         "A cryptographic hash of an X.509 certificate.  The results of
         a successful matching fingerprint to either the trusted CA in
         the certificate validation path or to the certificate itself
         is dictated by the snmpTlstmCertToTSN13MapType column."
     ::= { snmpTlstmCertToTSN13Entry 2 }
   snmpTlstmCertToTSN13MapType OBJECT-TYPE
     SYNTAX      AutonomousType
     MAX-ACCESS  read-create
     STATUS      current
     DESCRIPTION
         "Specifies the mapping type for deriving a tmSecurityName from
         a certificate.  Details for mapping of a particular type SHALL
         be specified in the DESCRIPTION clause of the OBJECT-IDENTITY
         that describes the mapping.  If a mapping succeeds it will
         return a tmSecurityName for use by the TLSTM model and
         processing stops.
         If the resulting mapped value is not compatible with the
         needed requirements of a tmSecurityName (e.g., VACM imposes a
         32-octet-maximum length and the certificate derived
         securityName could be longer), then future rows MUST be
         searched for additional snmpTlstmCertToTSN13Fingerprint matches
         to look for a mapping that succeeds.
         Suitable values for assigning to this object that are defined
         within the SNMP-TLS-TM-MIB can be found in the
         snmpTlstmCertToTSNMIdentities portion of the MIB tree."
     DEFVAL { snmpTlstmCertSpecified }
     ::= { snmpTlstmCertToTSN13Entry 3 }
   snmpTlstmCertToTSN13Data OBJECT-TYPE
     SYNTAX      OCTET STRING (SIZE(0..1024))
     MAX-ACCESS  read-create
     STATUS      current
     DESCRIPTION
         "Auxiliary data used as optional configuration information for
         a given mapping specified by the snmpTlstmCertToTSN13MapType
         column.  Only some mapping systems will make use of this
         column.  The value in this column MUST be ignored for any



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         mapping type that does not require data present in this
         column."
     DEFVAL { "" }
     ::= { snmpTlstmCertToTSN13Entry 4 }
   snmpTlstmCertToTSN13StorageType OBJECT-TYPE
     SYNTAX       StorageType
     MAX-ACCESS   read-create
     STATUS       current
     DESCRIPTION
         "The storage type for this conceptual row.  Conceptual rows
         having the value 'permanent' need not allow write-access to
         any columnar objects in the row."
     DEFVAL      { nonVolatile }
     ::= { snmpTlstmCertToTSN13Entry 5 }
   snmpTlstmCertToTSN13RowStatus OBJECT-TYPE
     SYNTAX      RowStatus
     MAX-ACCESS  read-create
     STATUS      current
     DESCRIPTION
         "The status of this conceptual row.  This object may be used
         to create or remove rows from this table.
         To create a row in this table, an administrator must set this
         object to either createAndGo(4) or createAndWait(5).
         Until instances of all corresponding columns are appropriately
         configured, the value of the corresponding instance of the
         snmpTlstmParams13RowStatus column is notReady(3).
         In particular, a newly created row cannot be made active until
         the corresponding snmpTlstmCertToTSN13Fingerprint,
         snmpTlstmCertToTSN13MapType, and snmpTlstmCertToTSN13Data
         columns have been set.
         The following objects may not be modified while the
         value of this object is active(1):
             - snmpTlstmCertToTSN13Fingerprint
             - snmpTlstmCertToTSN13MapType
             - snmpTlstmCertToTSN13Data
         An attempt to set these objects while the value of
         snmpTlstmParams13RowStatus is active(1) will result in
         an inconsistentValue error."
     ::= { snmpTlstmCertToTSN13Entry 6 }
   snmpTlstmParams13Count OBJECT-TYPE
     SYNTAX      Gauge32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
         "A count of the number of entries in the
         snmpTlstmParams13Table."
     ::= { snmpTlstmCertificateMapping 13 }
   snmpTlstmParams13TableLastChanged OBJECT-TYPE



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     SYNTAX      TimeStamp
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
         "The value of sysUpTime.0 when the snmpTlstmParams13Table
         was last modified through any means, or 0 if it has not been
         modified since the command responder was started."
     ::= { snmpTlstmCertificateMapping 14 }
   snmpTlstmParams13Table OBJECT-TYPE
     SYNTAX      SEQUENCE OF SnmpTlstmParams13Entry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
         "This table is used by a TLS client when a TLS
         connection is being set up using an entry in the
         SNMP-TARGET-MIB.  It extends the SNMP-TARGET-MIB's
         snmpTargetParams13Table with a fingerprint of a certificate to
         use when establishing such a TLS connection."
     ::= { snmpTlstmCertificateMapping 15 }
   snmpTlstmParams13Entry OBJECT-TYPE
     SYNTAX      SnmpTlstmParams13Entry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
         "A conceptual row containing a fingerprint hash of a locally
         held certificate for a given snmpTargetParamsEntry.  The
         values in this row should be ignored if the connection that
         needs to be established, as indicated by the SNMP-TARGET-MIB
         infrastructure, is not a certificate and TLS based
         connection.  The connection SHOULD NOT be established if the
         certificate fingerprint stored in this entry does not point to
         a valid locally held certificate or if it points to an
         unusable certificate (such as might happen when the
         certificate's expiration date has been reached)."
     INDEX    { IMPLIED snmpTargetParamsName }
     ::= { snmpTlstmParams13Table 1 }
   SnmpTlstmParams13Entry ::= SEQUENCE {
     snmpTlstmParams13ClientFingerprint SnmpTLS13Fingerprint,
     snmpTlstmParams13StorageType       StorageType,
     snmpTlstmParams13RowStatus         RowStatus
   }
   snmpTlstmParams13ClientFingerprint OBJECT-TYPE
     SYNTAX      SnmpTLS13Fingerprint
     MAX-ACCESS  read-create
     STATUS      current
     DESCRIPTION
         "This object stores the hash of the public portion of a
         locally held X.509 certificate.  The X.509 certificate, its



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         public key, and the corresponding private key will be used
         when initiating a TLS connection as a TLS client."
     ::= { snmpTlstmParams13Entry 1 }
   snmpTlstmParams13StorageType OBJECT-TYPE
     SYNTAX       StorageType
     MAX-ACCESS   read-create
     STATUS       current
     DESCRIPTION
         "The storage type for this conceptual row.  Conceptual rows
         having the value 'permanent' need not allow write-access to
         any columnar objects in the row."
     DEFVAL      { nonVolatile }
     ::= { snmpTlstmParams13Entry 2 }
   snmpTlstmParams13RowStatus OBJECT-TYPE
     SYNTAX      RowStatus
     MAX-ACCESS  read-create
     STATUS      current
     DESCRIPTION
         "The status of this conceptual row.  This object may be used
         to create or remove rows from this table.
         To create a row in this table, an administrator must set this
         object to either createAndGo(4) or createAndWait(5).
         Until instances of all corresponding columns are appropriately
         configured, the value of the corresponding instance of the
         snmpTlstmParams13RowStatus column is notReady(3).
         In particular, a newly created row cannot be made active until
         the corresponding snmpTlstmParams13ClientFingerprint column has
         been set.
         The snmpTlstmParams13ClientFingerprint object may not be
         modified while the value of this object is active(1).
         An attempt to set these objects while the value of
         snmpTlstmParams13RowStatus is active(1) will result in
         an inconsistentValue error."
     ::= { snmpTlstmParams13Entry 3 }
   snmpTlstmAddr13Count OBJECT-TYPE
     SYNTAX      Gauge32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
         "A count of the number of entries in the snmpTlstmAddr13Table."
     ::= { snmpTlstmCertificateMapping 16 }
   snmpTlstmAddr13TableLastChanged OBJECT-TYPE
     SYNTAX      TimeStamp
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
         "The value of sysUpTime.0 when the snmpTlstmAddr13Table
         was last modified through any means, or 0 if it has not been



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         modified since the command responder was started."
     ::= { snmpTlstmCertificateMapping 17 }
   snmpTlstmAddr13Table OBJECT-TYPE
     SYNTAX      SEQUENCE OF SnmpTlstmAddr13Entry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
         "This table is used by a TLS client when a TLS
         connection is being set up using an entry in the
         SNMP-TARGET-MIB.  It extends the SNMP-TARGET-MIB's
         snmpTargetAddrTable so that the client can verify that the
         correct server has been reached.  This verification can use
         either a certificate fingerprint, or an identity
         authenticated via certification path validation.
         If there is an active row in this table corresponding to the
         entry in the SNMP-TARGET-MIB that was used to establish the
         connection, and the row's snmpTlstmAddr13ServerFingerprint
         column has non-empty value, then the server's presented
         certificate is compared with the
         snmpTlstmAddr13ServerFingerprint value (and the
         snmpTlstmAddr13ServerIdentity column is ignored).  If the
         fingerprint matches, the verification has succeeded.  If the
         fingerprint does not match, then the connection MUST be
         closed.
         If the server's presented certificate has passed
         certification path validation [RFC5280] to a configured
         trust anchor, and an active row exists with a zero-length
         snmpTlstmAddr13ServerFingerprint value, then the
         snmpTlstmAddr13ServerIdentity column contains the expected
         host name.  This expected host name is then compared against
         the server's certificate as follows:
           - Implementations MUST support matching the expected host
           name against a dNSName in the subjectAltName extension
           field.
           - The '*' (ASCII 0x2a) wildcard character is allowed in the
           dNSName of the subjectAltName extension, but only as the
           left-most (least significant) DNS label in that value.
           This wildcard matches any left-most DNS label in the
           server name.  That is, the subject *.example.com matches
           the server names a.example.com and b.example.com, but does
           not match example.com or a.b.example.com.  Implementations
           MUST support wildcards in certificates as specified above,
           but MAY provide a configuration option to disable them.
           - If the locally configured name is an internationalized
           domain name, conforming implementations MUST convert it to
           the ASCII Compatible Encoding (ACE) format for performing
           comparisons, as specified in Section 7 of [RFC5280].
         If the expected host name fails these conditions then the



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         connection MUST be closed.

         If there is no row in this table corresponding to the entry
         in the SNMP-TARGET-MIB and the server can be authorized by
         another, implementation-dependent means, then the connection
         MAY still proceed."
     ::= { snmpTlstmCertificateMapping 18 }
   snmpTlstmAddr13Entry OBJECT-TYPE
     SYNTAX      SnmpTlstmAddr13Entry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
         "A conceptual row containing a copy of a certificate's
         fingerprint for a given snmpTargetAddrEntry.  The values in
         this row should be ignored if the connection that needs to be
         established, as indicated by the SNMP-TARGET-MIB
         infrastructure, is not a TLS based connection.  If an
         snmpTlstmAddr13Entry exists for a given snmpTargetAddrEntry,
         then the presented server certificate MUST match or the
         connection MUST NOT be established.  If a row in this table
         does not exist to match an snmpTargetAddrEntry row, then the
         connection SHOULD still proceed if some other certificate
         validation path algorithm (e.g., RFC 5280) can be used."
     INDEX    { IMPLIED snmpTargetAddrName }
     ::= { snmpTlstmAddr13Table 1 }
   SnmpTlstmAddr13Entry ::= SEQUENCE {
     snmpTlstmAddr13ServerFingerprint    SnmpTLS13Fingerprint,
     snmpTlstmAddr13ServerIdentity       SnmpAdminString,
     snmpTlstmAddr13StorageType          StorageType,
     snmpTlstmAddr13RowStatus            RowStatus
   }
   snmpTlstmAddr13ServerFingerprint OBJECT-TYPE
     SYNTAX      SnmpTLS13Fingerprint
     MAX-ACCESS  read-create
     STATUS      current
     DESCRIPTION
         "A cryptographic hash of a public X.509 certificate.  This
         object should store the hash of the public X.509 certificate
         that the remote server should present during the TLS
         connection setup.  The fingerprint of the presented
         certificate and this hash value MUST match exactly or the
         connection MUST NOT be established."
     DEFVAL { "" }
     ::= { snmpTlstmAddr13Entry 1 }
   snmpTlstmAddr13ServerIdentity OBJECT-TYPE
     SYNTAX      SnmpAdminString
     MAX-ACCESS  read-create
     STATUS      current



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     DESCRIPTION
         "The reference identity to check against the identity
         presented by the remote system."
     DEFVAL { "" }
     ::= { snmpTlstmAddr13Entry 2 }
   snmpTlstmAddr13StorageType OBJECT-TYPE
     SYNTAX       StorageType
     MAX-ACCESS   read-create
     STATUS       current
     DESCRIPTION
         "The storage type for this conceptual row.  Conceptual rows
         having the value 'permanent' need not allow write-access to
         any columnar objects in the row."
     DEFVAL      { nonVolatile }
     ::= { snmpTlstmAddr13Entry 3 }
   snmpTlstmAddr13RowStatus OBJECT-TYPE
     SYNTAX      RowStatus
     MAX-ACCESS  read-create
     STATUS      current
     DESCRIPTION
         "The status of this conceptual row.  This object may be used
         to create or remove rows from this table.
         To create a row in this table, an administrator must set this
         object to either createAndGo(4) or createAndWait(5).
         Until instances of all corresponding columns are
         appropriately configured, the value of the
         corresponding instance of the snmpTlstmAddr13RowStatus
         column is notReady(3).
         In particular, a newly created row cannot be made active until
         the corresponding snmpTlstmAddr13ServerFingerprint column has
         been set.
         Rows MUST NOT be active if the snmpTlstmAddr13ServerFingerprint
         column is blank and the snmpTlstmAddr13ServerIdentity is set to
         '*' since this would insecurely accept any presented
         certificate.
         The snmpTlstmAddr13ServerFingerprint object may not be modified
         while the value of this object is active(1).
         An attempt to set these objects while the value of
         snmpTlstmAddr13RowStatus is active(1) will result in
         an inconsistentValue error."
     ::= { snmpTlstmAddr13Entry 4 }
   -- ************************************************
   --  snmpTlstmNotifications - Notifications Information
   -- ************************************************
   snmpTlstmServerCertificateUnknown NOTIFICATION-TYPE
     OBJECTS { snmpTlstmSessionUnknownServerCertificate }
     STATUS  current
     DESCRIPTION



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         "Notification that the server certificate presented by an SNMP
          over (D)TLS server was invalid because no configured
          fingerprint or CA was acceptable to validate it.  This may be
          because there was no entry in the snmpTlstmAddrTable (or
          snmpTlstmAddr13Table) or
          because no path could be found to known Certification
          Authority.
          To avoid notification loops, this notification MUST NOT be
          sent to servers that themselves have triggered the
          notification."
     ::= { snmpTlstmNotifications 1 }
   snmpTlstmServerInvalidCertificate NOTIFICATION-TYPE
     OBJECTS { snmpTlstmAddrServerFingerprint,
               snmpTlstmSessionInvalidServerCertificates}
     STATUS  deprecated
     DESCRIPTION
         "Notification that the server certificate presented by an SNMP
          over (D)TLS server could not be validated even if the
          fingerprint or expected validation path was known.  That is, a
          cryptographic validation error occurred during certificate
          validation processing.
          To avoid notification loops, this notification MUST NOT be
          sent to servers that themselves have triggered the
          notification."
     ::= { snmpTlstmNotifications 2 }
   snmpTlstmServerInvalidCertificate13 NOTIFICATION-TYPE
     OBJECTS { snmpTlstmAddr13ServerFingerprint,
               snmpTlstmSessionInvalidServerCertificates}
     STATUS  current
     DESCRIPTION
         "Notification that the server certificate presented by an SNMP
          over TLS server could not be validated even if the
          fingerprint or expected validation path was known.  That is, a
          cryptographic validation error occurred during certificate
          validation processing.
          To avoid notification loops, this notification MUST NOT be
          sent to servers that themselves have triggered the
          notification."
     ::= { snmpTlstmNotifications 3 }
   -- ************************************************
   -- snmpTlstmCompliances - Conformance Information
   -- ************************************************
   snmpTlstmCompliances OBJECT IDENTIFIER ::= { snmpTlstmConformance 1 }
   snmpTlstmGroups OBJECT IDENTIFIER ::= { snmpTlstmConformance 2 }
   -- ************************************************
   -- Compliance statements
   -- ************************************************
   snmpTlstmCompliance MODULE-COMPLIANCE



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     STATUS      deprecated
     DESCRIPTION
         "The compliance statement for SNMP engines that support the
         SNMP-TLS-TM-MIB"
     MODULE
         MANDATORY-GROUPS { snmpTlstmStatsGroup,
                            snmpTlstmIncomingGroup,
                            snmpTlstmOutgoingGroup,
                            snmpTlstmNotificationGroup }
     ::= { snmpTlstmCompliances 1 }
   snmpTlstmCompliance13 MODULE-COMPLIANCE
     STATUS      current
     DESCRIPTION
         "The compliance statement for SNMP engines that support the
         SNMP-TLS-TM-MIB"
     MODULE
         MANDATORY-GROUPS { snmpTlstmStatsGroup,
                            snmpTlstmIncoming13Group,
                            snmpTlstmOutgoing13Group,
                            snmpTlstmNotification13Group }
     ::= { snmpTlstmCompliances 2 }
   -- ************************************************
   -- Units of conformance
   -- ************************************************
   snmpTlstmStatsGroup OBJECT-GROUP
     OBJECTS {
         snmpTlstmSessionOpens,
         snmpTlstmSessionClientCloses,
         snmpTlstmSessionOpenErrors,
         snmpTlstmSessionAccepts,
         snmpTlstmSessionServerCloses,
         snmpTlstmSessionNoSessions,
         snmpTlstmSessionInvalidClientCertificates,
         snmpTlstmSessionUnknownServerCertificate,
         snmpTlstmSessionInvalidServerCertificates,
         snmpTlstmSessionInvalidCaches
     }
     STATUS      current
     DESCRIPTION
         "A collection of objects for maintaining
         statistical information of an SNMP engine that
         implements the SNMP TLS Transport Model."
     ::= { snmpTlstmGroups 1 }
   snmpTlstmIncomingGroup OBJECT-GROUP
     OBJECTS {
         snmpTlstmCertToTSNCount,
         snmpTlstmCertToTSNTableLastChanged,
         snmpTlstmCertToTSNFingerprint,



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         snmpTlstmCertToTSNMapType,
         snmpTlstmCertToTSNData,
         snmpTlstmCertToTSNStorageType,
         snmpTlstmCertToTSNRowStatus
     }
     STATUS      deprecated
     DESCRIPTION
         "A collection of objects for maintaining
         incoming connection certificate mappings to
         tmSecurityNames of an SNMP engine that implements the
         SNMP TLS Transport Model."
     ::= { snmpTlstmGroups 2 }
   snmpTlstmOutgoingGroup OBJECT-GROUP
     OBJECTS {
         snmpTlstmParamsCount,
         snmpTlstmParamsTableLastChanged,
         snmpTlstmParamsClientFingerprint,
         snmpTlstmParamsStorageType,
         snmpTlstmParamsRowStatus,
         snmpTlstmAddrCount,
         snmpTlstmAddrTableLastChanged,
         snmpTlstmAddrServerFingerprint,
         snmpTlstmAddrServerIdentity,
         snmpTlstmAddrStorageType,
         snmpTlstmAddrRowStatus
     }
     STATUS      deprecated
     DESCRIPTION
         "A collection of objects for maintaining
         outgoing connection certificates to use when opening
         connections as a result of SNMP-TARGET-MIB settings."
     ::= { snmpTlstmGroups 3 }
   snmpTlstmNotificationGroup NOTIFICATION-GROUP
     NOTIFICATIONS {
         snmpTlstmServerCertificateUnknown,
         snmpTlstmServerInvalidCertificate
     }
     STATUS deprecated
     DESCRIPTION
         "Notifications"
     ::= { snmpTlstmGroups 4 }
   snmpTlstmIncoming13Group OBJECT-GROUP
     OBJECTS {
         snmpTlstmCertToTSN13Count,
         snmpTlstmCertToTSN13TableLastChanged,
         snmpTlstmCertToTSN13Fingerprint,
         snmpTlstmCertToTSN13MapType,
         snmpTlstmCertToTSN13Data,



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         snmpTlstmCertToTSN13StorageType,
         snmpTlstmCertToTSN13RowStatus
     }
     STATUS      current
     DESCRIPTION
         "A collection of objects for maintaining
         incoming connection certificate mappings to
         tmSecurityNames of an SNMP engine that implements the
         SNMP TLS 1.3 Transport Model."
     ::= { snmpTlstmGroups 5 }
   snmpTlstmOutgoing13Group OBJECT-GROUP
     OBJECTS {
         snmpTlstmParams13Count,
         snmpTlstmParams13TableLastChanged,
         snmpTlstmParams13ClientFingerprint,
         snmpTlstmParams13StorageType,
         snmpTlstmParams13RowStatus,
         snmpTlstmAddr13Count,
         snmpTlstmAddr13TableLastChanged,
         snmpTlstmAddr13ServerFingerprint,
         snmpTlstmAddr13ServerIdentity,
         snmpTlstmAddr13StorageType,
         snmpTlstmAddr13RowStatus
     }
     STATUS      current
     DESCRIPTION
         "A collection of objects for maintaining
         outgoing connection certificates to use when opening
         TLS 1.3 connections as a result of SNMP-TARGET-MIB settings."
     ::= { snmpTlstmGroups 6 }
   snmpTlstmNotification13Group NOTIFICATION-GROUP
     NOTIFICATIONS {
         snmpTlstmServerCertificateUnknown,
         snmpTlstmServerInvalidCertificate13
     }
     STATUS current
     DESCRIPTION
         "Notifications for the SNMP TLS 1.3 Transport Model"
     ::= { snmpTlstmGroups 7 }
   END

8.  Operational Considerations

   This section discusses various operational aspects of deploying
   TLSTM.






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8.1.  Sessions

   Within this document, the term "session" means a security association
   between two TLSTM instances.  State information for the sessions are
   maintained in each TLSTM implementation and this information is
   created and destroyed as sessions are opened and closed.  A "broken"
   session (one side up and one side down) can result if one side of a
   session is brought down abruptly (i.e., reboot, power outage, etc.).
   Whenever possible, implementations SHOULD provide graceful session
   termination through the use of TLS closure alert or error alert
   messages.  Implementations SHOULD also have a system in place for
   detecting "broken" sessions.

   Implementations SHOULD limit the lifetime of established sessions
   depending on the algorithms used for generation of the master session
   secret, the privacy and integrity algorithms used to protect
   messages, the environment of the session, the amount of data
   transferred, and the sensitivity of the data.

   TLS1.3 implementations for SNMPv3 MUST NOT enable the 0-RTT mode of
   session resumption (either sending or accepting) and MUST NOT
   automatically resend 0-RTT data if it is rejected by the server.  The
   reason 0-RTT is disallowed is that there are no "safe" messages that
   if replayed will be guaranteed to cause no harm at a server side: all
   incoming notification or command responses are meant to be acted upon
   only once.  See Security considerations section for further details.

8.2.  Notification Receiver Credential Selection

   When an SNMP engine needs to establish an outgoing session for
   notifications, the snmpTargetParamsTable includes an entry for the
   snmpTargetParamsSecurityName of the target.  Servers that wish to
   support multiple principals at a particular port SHOULD make use of
   the Server Name Indication extension defined in Section 3 of
   [RFC6066].  Without the Server Name Indication the receiving SNMP
   engine (server) will not know which TLS certificate to offer to the
   client so that the tmSecurityName identity-authentication will be
   successful.

   Another solution is to maintain a one-to-one mapping between
   certificates and incoming ports for notification receivers.  This can
   be handled at the notification originator by configuring the
   snmpTargetAddrTable (snmpTargetAddrTDomain and
   snmpTargetAddrTAddress) and requiring the receiving SNMP engine to
   monitor multiple incoming static ports based on which principals are
   capable of receiving notifications.





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   Implementations MAY also choose to designate a single Notification
   Receiver Principal to receive all incoming notifications or select an
   implementation specific method of selecting a server certificate to
   present to clients.

8.3.  contextEngineID Discovery

   SNMPv3 requires that an application know the identifier
   (snmpEngineID) of the remote SNMP protocol engine in order to
   retrieve or manipulate objects maintained on the remote SNMP entity.

   [RFC5343] introduces a well-known localEngineID and a discovery
   mechanism that can be used to learn the snmpEngineID of a remote SNMP
   protocol engine.  Implementations are RECOMMENDED to support and use
   the contextEngineID discovery mechanism defined in [RFC5343].

8.4.  Transport Considerations

   This document defines how SNMP messages can be transmitted over TLS,
   which is based on TCP.  Transport over DTLS and underlying UDP has
   been removed to further enhance security and due to the diminishing
   returns on the session setup efficiencies, since TLS 1.3 saves one
   roundtrip compared to TLS 1.2.

   TLS has operational considerations that SHOULD be taken into
   consideration with respect to MTU size, performance, etc.

9.  Security Considerations

   This document describes a transport model that permits SNMP to
   utilize TLS security services.  The security threats and how the TLS
   transport model mitigates these threats are covered throughout this
   document.  Security considerations for TLS are described in
   Section 10 and Appendix E of TLS 1.3 [RFC8446].

9.1.  Certificates, Authentication, and Authorization

   Implementations are responsible for providing a security certificate
   installation and configuration mechanism.  Implementations SHOULD
   support certificate revocation lists.

   TLS provides for authentication of the identity of both the TLS
   server and the TLS client.  Access to MIB objects for the
   authenticated principal MUST be enforced by an access control
   subsystem (e.g., the VACM).






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   Authentication of the command generator principal's identity is
   important for use with the SNMP access control subsystem to ensure
   that only authorized principals have access to potentially sensitive
   data.  The authenticated identity of the command generator
   principal's certificate is mapped to an SNMP model-independent
   securityName for use with SNMP access control.

   The TLS handshake only provides assurance that the certificate of the
   authenticated identity has been signed by a configured trusted
   Certification Authority.  TLS has no way to further authorize or
   reject access based on the authenticated identity.  An Access Control
   Model (such as the VACM) provides access control and authorization of
   a command generator's requests to a command responder and a
   notification receiver's authorization to receive Notifications from a
   notification originator.  However, to avoid man-in-the-middle
   attacks, both ends of the TLS-based connection MUST check the
   certificate presented by the other side against what was expected.
   For example, command generators are to check that the command
   responder presented and authenticated itself with an X.509
   certificate that was expected.  Not doing so would allow an impostor,
   at a minimum, to present false data, receive sensitive information,
   and/or provide a false belief that configuration was actually
   received and acted upon.  Authenticating and verifying the identity
   of the TLS server and the TLS client for all operations ensures the
   authenticity of the SNMP engine that provides MIB data.

   The instructions found in the DESCRIPTION clause of the
   snmpTlstmCertToTSN13Table object MUST be followed exactly.  It is
   also important that the rows of the table be searched in prioritized
   order starting with the row containing the lowest numbered
   snmpTlstmCertToTSN13ID value.

9.2.  TLS Security Considerations

   This section discusses security considerations specific to the usage
   of TLS.

9.2.1.  TLS Version Requirements

   Implementations of TLS typically support multiple versions of the
   Transport Layer Security protocol as well as the older Secure Sockets
   Layer (SSL) protocol.  Because of known security vulnerabilities,
   TLSTM clients and servers MUST NOT request, offer, or use SSL 2.0 or
   3.0, or TLS 1.0 or 1.1.  See Appendix D.5 of [RFC8446] for further
   details.  For backward compatibility issues with older TLS versions,
   see Appendix D of [RFC8446].





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9.2.2.  Session Resumption

   TLS TM clients and servers MUST NOT request, offer or use the 0-RTT
   mode of TLS1.3.  [RFC8446] removed the renegotiation supported in
   TLS1.2 [RFC5246]; for session resumption, it introduced a zero-RTT
   (0-RTT) mode, saving a round-trip at connection setup at the cost of
   increased risk of replay attacks (it is possible for servers to guard
   against this attack by keeping track of all the messages received).
   [RFC8446] requires a profile be written for any application that
   wants to use 0-RTT, specifying which messages are "safe to use" on
   this mode.  The reason 0-RTT is disallowed here is that there are no
   "safe" SNMPv3 messages that if replayed will be sure to cause no harm
   at a server side: all incoming notification or command responses have
   consequences and are to be acted upon only once.

9.2.3.  TLS Ciphersuites, Extensions and Protocol Invariants

   [RFC8446] section 9 requires that, in the absence of application
   profiles, certain cipher suites, TLS extensions, and TLS protocol
   invariants are mandatory to implement.  This document does not
   specify an application profile, hence all of the compliance
   requirements in [RFC8446] apply.

9.3.  Use with SNMPv1/SNMPv2c Messages

   The SNMPv1 and SNMPv2c message processing described in [RFC3584] (BCP
   74) always selects the SNMPv1 or SNMPv2c Security Models,
   respectively.  Both of these and the User-based Security Model of
   SNMPv3 derive the securityName and securityLevel from the SNMP
   message received, even when the message was received over a secure
   transport.  Access control decisions are therefore made based on the
   contents of the SNMP message, rather than using the authenticated
   identity and securityLevel provided by the TLS Transport Model.

   Implementations MUST only send SNMPv3 messages using the Transport
   Security Model (TSM) or another secure-transport aware security model
   over the TLSTM transport.

   Implementations MUST NOT use a non-transport-aware Security Model
   (e.g., SNMPv1, SNMPv2c, or the User-based Security Model of SNMPv3)
   with a secure Transport Model.

   It is RECOMMENDED that deployments that support the TLSTM disable or
   not support previous versions of SNMP or the User-based Security
   Model of SNMPv3.






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9.4.  MIB Module Security

   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 might 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:

   *  The snmpTlstmParams13Table can be used to change the outgoing
      X.509 certificate used to establish a TLS connection.
      Modifications to objects in this table need to be adequately
      authenticated since modifying the values in this table will have
      profound impacts to the security of outbound connections from the
      device.  Since knowledge of authorization rules and certificate
      usage mechanisms might be considered sensitive, protection from
      disclosure of the SNMP traffic via encryption is automatically
      acheived via TLS 1.3.

   *  The snmpTlstmAddr13Table can be used to change the expectations of
      the certificates presented by a remote TLS server.  Modifications
      to objects in this table need to be adequately authenticated since
      modifying the values in this table will have profound impacts to
      the security of outbound connections from the device.  Since
      knowledge of authorization rules and certificate usage mechanisms
      might be considered sensitive, protection from disclosure of the
      SNMP traffic via encryption is automatically acheived via TLS 1.3.

   *  The snmpTlstmCertToTSN13Table is used to specify the mapping of
      incoming X.509 certificates to tmSecurityNames, which eventually
      get mapped to an SNMPv3 securityName.  Modifications to objects in
      this table need to be adequately authenticated since modifying the
      values in this table will have profound impacts to the security of
      incoming connections to the device.  Since knowledge of
      authorization rules and certificate usage mechanisms might be
      considered sensitive, protection from disclosure of the SNMP
      traffic via encryption is automatically acheived via TLS 1.3.
      When this table contains a significant number of rows it might
      affect the system performance when accepting new TLS connections.

   Some of the readable objects in this MIB module (i.e., objects with a
   MAX-ACCESS other than not-accessible) might be considered sensitive
   or vulnerable in some network environments.  It is thus important to
   control even GET and/or NOTIFY access to these objects and encrypt
   the values of these objects when sending them over the network via
   SNMP.  These are the tables and objects and their sensitivity/
   vulnerability:



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   *  This MIB contains a collection of counters that monitor the TLS
      connections being established with a device.  Since knowledge of
      connection and certificate usage mechanisms might be considered
      sensitive, protection from disclosure of the SNMP traffic via
      encryption is automatically acheived via TLS 1.3.

   SNMP versions prior to SNMPv3 did not include adequate security.
   Even if the network itself is secure (for example, by using IPsec),
   even then, there is no control as to who on the secure network is
   allowed to access and GET/SET (read/change/create/delete) the objects
   in this MIB module.

   It is RECOMMENDED that implementers consider the security features as
   provided by the SNMPv3 framework (see Section 8 of [RFC3410]),
   including full support for the SNMPv3 cryptographic mechanisms (for
   authentication and privacy).

   Further, deployment of SNMP versions prior to SNMPv3 is NOT
   RECOMMENDED.  Instead, it is RECOMMENDED to deploy SNMPv3 and to
   enable cryptographic security.  It is then a customer/operator
   responsibility to ensure that the SNMP entity giving access to an
   instance of this MIB module is properly configured to give access to
   the objects only to those principals (users) that have legitimate
   rights to indeed GET or SET (change/create/delete) them.

10.  IANA Considerations

   IANA has assigned:

   1.  Two TCP/UDP port numbers from the "Registered Ports" range of the
       Port Numbers registry, with the following keywords:

     Keyword         Decimal      Description       References
     -------         -------      -----------       ----------
     snmptls         10161/tcp    SNMP-TLS          [RFC6353]
     snmptls-trap    10162/tcp    SNMP-Trap-TLS     [RFC6353]

   These are the default ports for receipt of SNMP command messages
   (snmptls and snmpdtls) and SNMP notification messages (snmptls-trap
   and snmpdtls-trap) over a TLS Transport Model as defined in this
   document.

   1.  An SMI number (8) under snmpDomains for the snmpTLSTCPDomain
       object identifier

   2.  An SMI number (198) under mib-2, for the MIB module in this
       document




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   3.  "tls" as the corresponding prefix for the snmpTLSTCPDomain in the
       SNMP Transport Domains registry

11.  Acknowledgements

   This document is based on [RFC6353].

   This document was reviewed by the following people who helped provide
   useful comments (in alphabetical order): Michaela Vanderveen.

   Work to develop and review this document was supported in part by the
   United States Department of Transportation.

12.  References

12.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3584]  Frye, R., Levi, D., Routhier, S., and B. Wijnen,
              "Coexistence between Version 1, Version 2, and Version 3
              of the Internet-standard Network Management Framework",
              BCP 74, RFC 3584, DOI 10.17487/RFC3584, August 2003,
              <https://www.rfc-editor.org/info/rfc3584>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <https://www.rfc-editor.org/info/rfc5280>.

   [RFC5590]  Harrington, D. and J. Schoenwaelder, "Transport Subsystem
              for the Simple Network Management Protocol (SNMP)",
              STD 78, RFC 5590, DOI 10.17487/RFC5590, June 2009,
              <https://www.rfc-editor.org/info/rfc5590>.

   [RFC5591]  Harrington, D. and W. Hardaker, "Transport Security Model
              for the Simple Network Management Protocol (SNMP)",
              STD 78, RFC 5591, DOI 10.17487/RFC5591, June 2009,
              <https://www.rfc-editor.org/info/rfc5591>.

   [RFC6066]  Eastlake 3rd, D., "Transport Layer Security (TLS)
              Extensions: Extension Definitions", RFC 6066,
              DOI 10.17487/RFC6066, January 2011,
              <https://www.rfc-editor.org/info/rfc6066>.



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   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [STD58]    McCloghrie, K., Ed., Perkins, D., Ed., and J.
              Schoenwaelder, Ed., "Structure of Management Information
              Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.

              McCloghrie, K., Ed., Perkins, D., Ed., and J.
              Schoenwaelder, Ed., "Textual Conventions for SMIv2",
              STD 58, RFC 2579, April 1999.

              McCloghrie, K., Ed., Perkins, D., Ed., and J.
              Schoenwaelder, Ed., "Conformance Statements for SMIv2",
              STD 58, RFC 2580, April 1999.

   [STD62]    Harrington, D., Presuhn, R., and B. Wijnen, "An
              Architecture for Describing Simple Network Management
              Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
              December 2002.

              Case, J., Harrington, D., Presuhn, R., and B. Wijnen,
              "Message Processing and Dispatching for the Simple Network
              Management Protocol (SNMP)", STD 62, RFC 3412, December
              2002.

              Levi, D., Meyer, P., and B. Stewart, "Simple Network
              Management Protocol (SNMP) Applications", STD 62,
              RFC 3413, December 2002.

              Blumenthal, U. and B. Wijnen, "User-based Security Model
              (USM) for version 3 of the Simple Network Management
              Protocol (SNMPv3)", STD 62, RFC 3414, December 2002.

              Wijnen, B., Presuhn, R., and K. McCloghrie, "View-based
              Access Control Model (VACM) for the Simple Network
              Management Protocol (SNMP)", STD 62, RFC 3415, December
              2002.

              Presuhn, R., Ed., "Version 2 of the Protocol Operations
              for the Simple Network Management Protocol (SNMP)",
              STD 62, RFC 3416, December 2002.

              Presuhn, R., Ed., "Transport Mappings for the Simple
              Network Management Protocol (SNMP)", STD 62, RFC 3417,
              December 2002.





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              Presuhn, R., Ed., "Management Information Base (MIB) for
              the Simple Network Management Protocol (SNMP)", STD 62,
              RFC 3418, December 2002.

12.2.  Informative References

   [RFC3410]  Case, J., Mundy, R., Partain, D., and B. Stewart,
              "Introduction and Applicability Statements for Internet-
              Standard Management Framework", RFC 3410,
              DOI 10.17487/RFC3410, December 2002,
              <https://www.rfc-editor.org/info/rfc3410>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

   [RFC5343]  Schoenwaelder, J., "Simple Network Management Protocol
              (SNMP) Context EngineID Discovery", STD 78, RFC 5343,
              DOI 10.17487/RFC5343, September 2008,
              <https://www.rfc-editor.org/info/rfc5343>.

   [RFC6353]  Hardaker, W., "Transport Layer Security (TLS) Transport
              Model for the Simple Network Management Protocol (SNMP)",
              STD 78, RFC 6353, DOI 10.17487/RFC6353, July 2011,
              <https://www.rfc-editor.org/info/rfc6353>.

Appendix A.  Target and Notification Configuration Example

   The following sections describe example configuration for the SNMP-
   TLS-TM-MIB, the SNMP-TARGET-MIB, the NOTIFICATION-MIB, and the SNMP-
   VIEW-BASED-ACM-MIB.

A.1.  Configuring a Notification Originator

   The following row adds the "Joe Cool" user to the "administrators"
   group:

       vacmSecurityModel              = 4 (TSM)
       vacmSecurityName               = "Joe Cool"
       vacmGroupName                  = "administrators"
       vacmSecurityToGroupStorageType = 3 (nonVolatile)
       vacmSecurityToGroupStatus      = 4 (createAndGo)

   The following row configures the snmpTlstmAddr13Table to use
   certificate path validation and to require the remote notification
   receiver to present a certificate for the "server.example.org"
   identity.



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       snmpTargetAddrName               =  "toNRAddr"
       snmpTlstmAddr13ServerFingerprint =  ""
       snmpTlstmAddr13ServerIdentity    =  "server.example.org"
       snmpTlstmAddr13StorageType       =  3         (nonVolatile)
       snmpTlstmAddr13RowStatus         =  4         (createAndGo)

   The following row configures the snmpTargetAddrTable to send
   notifications using TLS/TCP to the snmptls-trap port at 192.0.2.1:

       snmpTargetAddrName              = "toNRAddr"
       snmpTargetAddrTDomain           = snmpTLSTCPDomain
       snmpTargetAddrTAddress          = "192.0.2.1:10162"
       snmpTargetAddrTimeout           = 1500
       snmpTargetAddrRetryCount        = 3
       snmpTargetAddrTagList           = "toNRTag"
       snmpTargetAddrParams            = "toNR"     (MUST match below)
       snmpTargetAddrStorageType       = 3          (nonVolatile)
       snmpTargetAddrRowStatus         = 4          (createAndGo)

   The following row configures the snmpTargetParamsTable to send the
   notifications to "Joe Cool", using authPriv SNMPv3 notifications
   through the TransportSecurityModel [[RFC5591]]:

       snmpTargetParamsName            = "toNR"     (MUST match above)
       snmpTargetParamsMPModel         = 3 (SNMPv3)
       snmpTargetParamsSecurityModel   = 4 (TransportSecurityModel)
       snmpTargetParamsSecurityName    = "Joe Cool"
       snmpTargetParamsSecurityLevel   = 3          (authPriv)
       snmpTargetParamsStorageType     = 3          (nonVolatile)
       snmpTargetParamsRowStatus       = 4          (createAndGo)

A.2.  Configuring TLSTM to Utilize a Simple Derivation of tmSecurityName

   The following row configures the snmpTlstmCertToTSN13Table to map a
   validated client certificate, referenced by the client's public X.509
   hash fingerprint, to a tmSecurityName using the subjectAltName
   component of the certificate.

       snmpTlstmCertToTSN13ID          = 1
                                       (chosen by ordering preference)
       snmpTlstmCertToTSN13Fingerprint = HASH (appropriate fingerprint)
       snmpTlstmCertToTSN13MapType     = snmpTlstmCertSANAny
       snmpTlstmCertToTSN13Data        = ""  (not used)
       snmpTlstmCertToTSN13StorageType = 3   (nonVolatile)
       snmpTlstmCertToTSN13RowStatus   = 4   (createAndGo)






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   This type of configuration should only be used when the naming
   conventions of the (possibly multiple) Certification Authorities are
   well understood, so two different principals cannot inadvertently be
   identified by the same derived tmSecurityName.

A.3.  Configuring TLSTM to Utilize Table-Driven Certificate Mapping

   The following row configures the snmpTlstmCertToTSN13Table to map a
   validated client certificate, referenced by the client's public X.509
   hash fingerprint, to the directly specified tmSecurityName of "Joe
   Cool".

       snmpTlstmCertToTSN13ID           = 2
                                        (chosen by ordering preference)
       snmpTlstmCertToTSN13Fingerprint = HASH (appropriate fingerprint)
       snmpTlstmCertToTSN13MapType      = snmpTlstmCertSpecified
       snmpTlstmCertToTSN13SecurityName = "Joe Cool"
       snmpTlstmCertToTSN13StorageType  = 3  (nonVolatile)
       snmpTlstmCertToTSN13RowStatus    = 4  (createAndGo)

Author's Address

   Kenneth Vaughn (editor)
   Trevilon LLC
   6606 FM 1488 RD
   Suite 148-503
   Magnolia, TX 77354
   United States of America

   Phone: +1 571 331 5670
   Email: kvaughn@trevilon.com




















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