NETCONF Working Group K. Watsen Internet-Draft Juniper Networks Intended status: Standards Track J. Schoenwaelder Expires: March 26, 2015 Jacobs University Bremen September 22, 2014 NETCONF Server Configuration Model draft-ietf-netconf-server-model-03 Abstract This draft defines a NETCONF server configuration data model. This data model enables configuration of the NETCONF service itself, including which transports it supports, what ports they listen on, whether they support device-initiated connections, and associated parameters. 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 working documents as Internet-Drafts. The list of current Internet- Drafts is at http://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 March 26, 2015. Copyright Notice Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of Watsen & Schoenwaelder Expires March 26, 2015 [Page 1] Internet-Draft NETCONF Server Configuration Model September 2014 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Tree Diagrams . . . . . . . . . . . . . . . . . . . . . . 3 2. Objectives . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Support all NETCONF Transports . . . . . . . . . . . . . 3 2.2. Align Transport-Specific Configurations . . . . . . . . . 3 2.3. Support both Listening for Connections and Call Home . . 4 2.4. For Call Home Connections . . . . . . . . . . . . . . . . 4 2.4.1. Support More than One Application . . . . . . . . . . 4 2.4.2. Support Applications Having More than One Server . . 4 2.4.3. Support a Reconnection Strategy . . . . . . . . . . . 4 2.4.4. Support both Persistent and Periodic Connections . . 4 2.4.5. Reconnection Strategy for Periodic Connections . . . 5 2.4.6. Keep-Alives for Persistent Connections . . . . . . . 5 2.4.7. Customizations for Periodic Connections . . . . . . . 5 3. Data Model . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 8 4. Keep-Alives for SSH and TLS . . . . . . . . . . . . . . . . . 21 4.1. SSH . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 4.2. TLS . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 5. Security Considerations . . . . . . . . . . . . . . . . . . . 22 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 7. Other Considerations . . . . . . . . . . . . . . . . . . . . 23 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 23 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 9.1. Normative References . . . . . . . . . . . . . . . . . . 24 9.2. Informative References . . . . . . . . . . . . . . . . . 25 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 26 A.1. SSH Transport Configuration . . . . . . . . . . . . . . . 26 A.2. TLS Transport Configuration . . . . . . . . . . . . . . . 26 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 27 B.1. 00 to 01 . . . . . . . . . . . . . . . . . . . . . . . . 28 B.2. 01 to 02 . . . . . . . . . . . . . . . . . . . . . . . . 28 B.3. 02 to 03 . . . . . . . . . . . . . . . . . . . . . . . . 28 Appendix C. Open Issues . . . . . . . . . . . . . . . . . . . . 28 1. Introduction This draft defines a NETCONF [RFC6241] server configuration data model. This data model enables configuration of the NETCONF service itself, including which transports are supported, what ports does the Watsen & Schoenwaelder Expires March 26, 2015 [Page 2] Internet-Draft NETCONF Server Configuration Model September 2014 server listen on, whether call-home is supported, and associated parameters. 1.1. Terminology The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 1.2. Tree Diagrams A simplified graphical representation of data models is used in this document. The meaning of the symbols in these diagrams is as follows: o Brackets "[" and "]" enclose list keys. o Abbreviations before data node names: "rw" means configuration (read-write) and "ro" state data (read-only). o Symbols after data node names: "?" means an optional node, "!" means a presence container, and "*" denotes a list and leaf-list. o Parentheses enclose choice and case nodes, and case nodes are also marked with a colon (":"). 2. Objectives The primary purpose of the YANG module defined herein is to enable the configuration of the NETCONF service on the device. This scope includes the following objectives: 2.1. Support all NETCONF Transports The YANG module should support all current NETCONF transports, namely NETCONF over SSH [RFC6242] and NETCONF over TLS [rfc5539bis], and be extensible to support future transports as necessary. Since implementations may not support all transports, the module should use YANG "feature" statements so that implementations can accurately advertise which transports are supported. 2.2. Align Transport-Specific Configurations While each transport is unique in its protocol and may have some distinct configurations, there remains a significant overlap between them. Thus the YANG module should use "grouping" statements so that the common aspects can be configured similarly. Watsen & Schoenwaelder Expires March 26, 2015 [Page 3] Internet-Draft NETCONF Server Configuration Model September 2014 2.3. Support both Listening for Connections and Call Home NETCONF has always supported the server opening a port to listen for client connections. More recently the NETCONF working group defined support for call-home ([draft-ietf-netconf-call-home]). The module should configure both listening for connections and call-home. Since implementations may not support both listening for connections and call home, YANG "feature" statements should be used so that implementation can accurately advertise the connection types it supports. 2.4. For Call Home Connections The following objectives only pertain to call home connections. 2.4.1. Support More than One Application A device may be managed by more than one northbound application. For instance, a deployment may have one application for provisioning and another for fault monitoring. Therefore, when it is desired for a device to initiate call home connections, it should be able to do so for more than one application. 2.4.2. Support Applications Having More than One Server An application managing a device may implement a high-availability strategy employing a multiplicity of active and/or passive servers. Therefore, when it is desired for a device to initiate call home connections, it should be able to connect to any of the applications servers. 2.4.3. Support a Reconnection Strategy Assuming an application has more than one server, then it becomes necessary to configure how a device should reconnect to the application should it lose its connection to the application's servers. Of primary interest is if the device should start with first server defined in a user-ordered list of servers or with the last server it was connected to. Secondary settings might specify the frequency of attempts and number of attempts per server. Therefore, a reconnection strategy should be configurable. 2.4.4. Support both Persistent and Periodic Connections Applications may vary greatly on how frequently they need to interact with a device, how responsive interactions with devices need to be, and how many simultaneous connections they can support. Some Watsen & Schoenwaelder Expires March 26, 2015 [Page 4] Internet-Draft NETCONF Server Configuration Model September 2014 applications may need a persistent connection to devices to optimize real-time interactions, while others are satisfied with periodic interactions and reduced resources required. Therefore, when it is necessary for devices to initiate connections, the type of connection desired should be configured. 2.4.5. Reconnection Strategy for Periodic Connections The reconnection strategy should apply to both persistent and periodic connections. How it applies to periodic connections becomes clear when considering that a periodic "connection" is a logical connection to a single server. That is, the periods of unconnectedness are intentional as opposed to due to external reasons. A periodic "connection" should always reconnect to the same server until it is no longer able to, at which time the reconnection strategy guides how to connect to another server. 2.4.6. Keep-Alives for Persistent Connections If a persistent connection is desired, it is the responsibility of the connection-initiator to actively test the aliveness of the connection. The connection initiator must immediately work to reestablish a persistent connection as soon as the connection is lost. How often the connection should be tested is driven by applications requirements, and therefore keep-alive settings should be configurable on a per-application basis. 2.4.7. Customizations for Periodic Connections If a periodic connection is desired, it is necessary for the device to know how often it should connect. This delay essentially determines how long the application might have to wait to send data to the device. This setting does not constrain how often the device must wait to send data to the application, as the device should immediately connect to the application whenever it has data to send to it. A common communication pattern is that one data transmission is many times closely followed by another. For instance, if the device needs to send a notification message, there's a high probability that it will send another shortly thereafter. Likewise, the application may have a sequence of pending messages to send. Thus, it should be possible for a device to hold a connection open until some amount of time of no data being transmitted as transpired. Watsen & Schoenwaelder Expires March 26, 2015 [Page 5] Internet-Draft NETCONF Server Configuration Model September 2014 3. Data Model 3.1. Overview The following subtree illustrates how this YANG module enables configuration for listening for remote connections, as described in [RFC6242] and [rfc5539bis]. Feature statements are used to limit both if listening is supported at all as well as for which transports. If listening for connections is supported, then the model enables configuring a list of listening endpoints, each configured with a user-specified name (the key field), the transport to use (i.e. SSH, TLS), and the IP address and port to listen on. The port field is optional, defaulting to the transport-specific port when not configured. module: ietf-netconf-server +--rw netconf-server +--rw listen* [name] +--rw name string +--rw (transport) +--:(ssh) {ssh-listen}? | +--rw ssh | +--rw address inet:host | +--rw port? inet:port-number +--:(tls) {tls-listen}? +--rw tls +--rw address inet:host +--rw port? inet:port-number The following subtree illustrates how this YANG module enables configuration for call home, as described in [draft-ietf-netconf-call-home]. Feature statements are used to limit both if call-home is supported at all as well as for which transports, if it is. If call-home is supported, then the model supports configuring a list of applications to connect to. Each application is configured with a user-specified name (the key field), the transport to be used (i.e. SSH, TLS), and a list of remote endpoints, each having a name, an IP address, and an optional port. Additionally, the configuration for each remote application indicates the connection-type (persistent vs. periodic) and associated parameters, as well as the reconnection strategy to use. Watsen & Schoenwaelder Expires March 26, 2015 [Page 6] Internet-Draft NETCONF Server Configuration Model September 2014 module: ietf-netconf-server +--rw netconf-server +--rw call-home* [name] +--rw name string +--rw (transport) | +--:(ssh) {ssh-call-home}? | | +--rw ssh | | +--rw endpoints | | | +--rw endpoint* [name] | | | +--rw name string | | | +--rw address inet:host | | | +--rw port? inet:port-number | | +--rw host-key* [name] | | +--rw name string | +--:(tls) {tls-call-home}? | +--rw tls | +--rw endpoints | +--rw endpoint* [name] | +--rw name string | +--rw address inet:host | +--rw port? inet:port-number +--rw connection-type | +--rw (connection-type)? | +--:(persistent-connection) | | +--rw persistent | | +--rw keep-alives | | +--rw interval-secs? uint8 | | +--rw count-max? uint8 | +--:(periodic-connection) | +--rw periodic | +--rw timeout-mins? uint8 | +--rw linger-secs? uint8 +--rw reconnect-strategy +--rw start-with? enumeration +--rw interval-secs? uint8 +--rw count-max? uint8 The following subtree illustrates how this YANG module enables authentication of TLS client certificates and mapping TLS clients to NETCONF user names. More specifically, the "trusted-ca-certs" and "trusted-client-certs" containers are used to authenticate TLS client certificates, while "cert-maps" and "psk-maps" are used to map TLS clients to NETCONF user names. Watsen & Schoenwaelder Expires March 26, 2015 [Page 7] Internet-Draft NETCONF Server Configuration Model September 2014 module: ietf-netconf-server +--rw netconf-server +--rw tls-client-auth +--rw trusted-ca-certs | +--rw trusted-ca-cert* binary +--rw trusted-client-certs | +--rw trusted-client-cert* binary +--rw cert-maps {tls-map-certificates}? | +--rw cert-to-name* [id] | +--rw id uint32 | +--rw fingerprint x509c2n:tls-fingerprint | +--rw map-type identityref | +--rw name string +--rw psk-maps {tls-map-pre-shared-keys}? +--rw psk-map* [psk-identity] +--rw psk-identity string +--rw user-name nacm:user-name-type +--rw not-valid-before? yang:date-and-time +--rw not-valid-after? yang:date-and-time +--rw key yang:hex-string 3.2. YANG Module This YANG module imports YANG types from [RFC6991], [RFC6536], and [draft-ietf-netmod-snmp-cfg]. RFC Ed.: update the date below with the date of RFC publication and remove this note. file "ietf-netconf-server@YYYY-MM-DD.yang" module ietf-netconf-server { namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-server"; prefix "ncserver"; import ietf-inet-types { prefix inet; // RFC 6991 } import ietf-yang-types { prefix yang; // RFC 6991 } import ietf-netconf-acm { prefix nacm; // RFC 6536 } import ietf-x509-cert-to-name { prefix x509c2n; // draft-ietf-netmod-snmp-cfg } Watsen & Schoenwaelder Expires March 26, 2015 [Page 8] Internet-Draft NETCONF Server Configuration Model September 2014 organization "IETF NETCONF (Network Configuration) Working Group"; contact "WG Web: WG List: WG Chair: Mehmet Ersue WG Chair: Bert Wijnen Editor: Kent Watsen "; description "This module contains a collection of YANG definitions for configuring NETCONF servers. Copyright (c) 2014 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). This version of this YANG module is part of RFC XXXX; see the RFC itself for full legal notices."; // RFC Ed.: replace XXXX with actual RFC number and // remove this note // RFC Ed.: please update the date to the date of publication revision "YYYY-MM-DD" { description "Initial version"; reference "RFC XXXX: NETCONF Server Configuration Model"; } // Features Watsen & Schoenwaelder Expires March 26, 2015 [Page 9] Internet-Draft NETCONF Server Configuration Model September 2014 feature ssh-listen { description "The ssh-listen feature indicates that the NETCONF server can open a port to listen for incoming client connections."; } feature ssh-call-home { description "The ssh-call-home feature indicates that the NETCONF server can connect to a client."; reference "RFC XXXX: Reverse Secure Shell (Reverse SSH)"; } feature tls-listen { description "The tls-listen feature indicates that the NETCONF server can open a port to listen for incoming client connections."; } feature tls-call-home { description "The tls-call-home feature indicates that the NETCONF server can connect to a client."; } feature tls-map-certificates { description "The tls-map-certificates feature indicates that the NETCONF server implements mapping X.509 certificates to NETCONF usernames."; } feature tls-map-pre-shared-keys { description "The tls-map-pre-shared-keys feature indicates that the NETCONF server implements mapping TLS pre-shared keys to NETCONF usernames."; } // Module's top-level container container netconf-server { description "Top-level container for NETCONF server configuration."; list listen { key name; Watsen & Schoenwaelder Expires March 26, 2015 [Page 10] Internet-Draft NETCONF Server Configuration Model September 2014 description "List of endpoints to listen for connections on."; //if-feature "(ssh-listen or tls-listen)"; uses listen-config; } list call-home { key name; description "List of applications to call-home to."; //if-feature "(ssh-call-home or tls-call-home)"; uses call-home-config; } container tls-client-auth { //if-feature "(tls-listen or tls-call-home)"; description "Container for TLS client authentication configuration."; uses trusted-ca-certs-grouping; uses trusted-client-certs-grouping; uses cert-maps-grouping; uses psk-maps-grouping; } } // Groupings grouping listen-config { description "Grouping for listen configuration."; leaf name { type string; description "An arbitrary name for the listen endpoint."; } choice transport { mandatory true; description "Selects between SSH and TLS transports."; case ssh { if-feature ssh-listen; container ssh { description "SSH-specific listening configuration for inbound connections."; uses listen-per-transport-config { refine port { default 830; Watsen & Schoenwaelder Expires March 26, 2015 [Page 11] Internet-Draft NETCONF Server Configuration Model September 2014 } } } } case tls { if-feature tls-listen; container tls { description "TLS-specific listening configuration for inbound connections."; uses listen-per-transport-config { refine port { default 6513; } } } } } } grouping listen-per-transport-config { description "Provides the configuration of the NETCONF server to open one or more ports to listen for incoming client connections."; leaf address { type inet:host; mandatory true; description "The local IP address/name of the interface to listen on."; } leaf port { type inet:port-number; description "The local port number on this interface the NETCONF server listens on."; } } grouping call-home-config { description "Grouping for call-home configuration."; leaf name { type string; description "An arbitrary name for the remote application."; } uses call-home-transport-config; Watsen & Schoenwaelder Expires March 26, 2015 [Page 12] Internet-Draft NETCONF Server Configuration Model September 2014 uses call-home-connection-type-config; uses call-home-reconnection-strategy-config; } grouping call-home-transport-config { description "Grouping for call-home specific transport selection."; choice transport { mandatory true; description "Selects between SSH and TLS transports."; case ssh { if-feature ssh-call-home; container ssh { description "Specifies SSH-specific call-home transport configuration."; uses call-home-per-transport-config { refine endpoints/endpoint/port { default 9999; // pending IANA assignment } } list host-key { key name; min-elements 1; ordered-by user; description "User-ordered list of host-keys the SSH server should advertise."; leaf name { type string; mandatory true; description "The name of a host key the device should advertise during the SSH key exchange."; } } } } case tls { if-feature tls-call-home; container tls { description "Specifies TLS-specific call-home transport configuration."; uses call-home-per-transport-config { refine endpoints/endpoint/port { default 9999; // pending IANA assignment Watsen & Schoenwaelder Expires March 26, 2015 [Page 13] Internet-Draft NETCONF Server Configuration Model September 2014 } } } } } } grouping call-home-per-transport-config { description "Grouping for transport-specific configuration for call-home connections."; container endpoints { description "Container for the list of endpoints."; list endpoint { key name; min-elements 1; ordered-by user; description "User-ordered list of endpoints for this application. Defining more than one enables high-availability."; leaf name { type string; description "An arbitrary name for the endpoint to connect to."; } leaf address { type inet:host; mandatory true; description "The hostname or IP address of the endpoint. If a hostname is provided and DNS resolves to more than one IP address, the device SHOULD try all of the ones it can based on how its networking stack is configured (e.g. v4, v6, dual-stack)."; } leaf port { type inet:port-number; description "The IP port for this endpoint. The device will use the IANA-assigned well-known port if not specified."; } } } } Watsen & Schoenwaelder Expires March 26, 2015 [Page 14] Internet-Draft NETCONF Server Configuration Model September 2014 grouping call-home-connection-type-config { description "Grouping to define connection-type for call-home based connections."; container connection-type { description "Indicates the network manager's preference for how the device's connection is maintained."; choice connection-type { default persistent-connection; description "Selects between persistent and periodic connections."; case persistent-connection { container persistent { description "Maintain a persistent connection to the network manager. If the connection goes down, immediately start trying to reconnect to it, using the reconnection strategy. This connection type minimizes any manager-to-device data-transfer delay, albeit at the expense of holding resources longer."; container keep-alives { description "Configures keep-alive policy, to proactively detect when a persistent connection to an endpoint has dropped."; leaf interval-secs { type uint8; units seconds; default 15; description "Sets a timeout interval in seconds after which if no data has been received from the manager's endpoint, a message will be sent to request a response from the endpoint. A value of '0' indicates that no keep-alive messages should be sent."; } leaf count-max { type uint8; default 3; description "Sets the number of keep-alive messages that may be sent without receiving any data from the manager's endpoint before assuming the endpoint Watsen & Schoenwaelder Expires March 26, 2015 [Page 15] Internet-Draft NETCONF Server Configuration Model September 2014 is no longer alive. If this threshold is reached, the transport-level connection will be disconnected (thus triggering the reconnection strategy). The interval timer is reset after each transmission, thus an unresponsive endpoint will be disconnected after about count-max * interval-secs seconds."; } } } } case periodic-connection { container periodic { description "Periodically connect to network manager, using the reconnection strategy, so it can flush any pending data it may be holding. This connection type minimizes resources held open, albeit at the expense of longer manager-to-device data-transfer delay. Note that for device-to-manager data, the data should be sent immediately, connecting to network manager first if not already."; leaf timeout-mins { type uint8; units minutes; default 5; description "The maximum amount of unconnected time the device will wait until establishing a connection to the network manager again. The device MAY establish a connection before this time if it has data it needs to send to the network manager. Note: this value differs from the reconnection strategy's interval-secs value."; } leaf linger-secs { type uint8; units seconds; default 30; description "The amount of time the device should wait after last receiving data from or sending data to the network manager's endpoint before closing its connection to it. This is an optimization to prevent unnecessary connections."; } } Watsen & Schoenwaelder Expires March 26, 2015 [Page 16] Internet-Draft NETCONF Server Configuration Model September 2014 } } } } grouping call-home-reconnection-strategy-config { description "Grouping for reconnection strategy."; container reconnect-strategy { description "The reconnection strategy guides how a device reconnects to an application, after losing a connection to it, even if due to a reboot. The device starts with the specified endpoint, tries to connect to it count-max times, waiting interval-secs between each connection attempt, before trying the next endpoint in the list (round robin)."; leaf start-with { type enumeration { enum first-listed { description "Indicates that reconnections should start with the first endpoint listed."; } enum last-connected { description "Indicates that reconnections should start with the endpoint last connected to."; } } default first-listed; description "Specifies which of the application's endpoints the device should start with when trying to connect to the application. If no previous connection has ever been established, last-connected defaults to the first endpoint listed."; } leaf interval-secs { type uint8; units seconds; default 5; description "Specifies the time delay between connection attempts to the same endpoint. Note: this value differs from the periodic-connection's timeout-mins value."; } leaf count-max { Watsen & Schoenwaelder Expires March 26, 2015 [Page 17] Internet-Draft NETCONF Server Configuration Model September 2014 type uint8; default 3; description "Specifies the number times the device tries to connect to a specific endpoint before moving on to the next endpoint in the list (round robin)."; } } } grouping trusted-ca-certs-grouping { description "Grouping for trusted-ca-certs container."; container trusted-ca-certs { description "A list of Certificate Authority (CA) certificates that a NETCONF server can use to authenticate a NETCONF client's certificate. A client's certificate is authenticated if its Issuer matches one of the configured trusted CA certificates."; leaf-list trusted-ca-cert { type binary; ordered-by system; description "The binary certificate structure, as specified by RFC 5246, Section 7.4.6, i.e.,: opaque ASN.1Cert<1..2^24>; "; reference "RFC 5246: The Transport Layer Security (TLS) Protocol Version 1.2"; } } } grouping trusted-client-certs-grouping { description "Grouping for trusted-client-certs container."; container trusted-client-certs { description "A list of client certificates that a NETCONF server can use to authenticate a NETCONF client's certificate. A client's certificate is authenticated if it is an exact match to a configured trusted client certificates."; leaf-list trusted-client-cert { Watsen & Schoenwaelder Expires March 26, 2015 [Page 18] Internet-Draft NETCONF Server Configuration Model September 2014 type binary; ordered-by system; description "The binary certificate structure, as specified by RFC 5246, Section 7.4.6, i.e.,: opaque ASN.1Cert<1..2^24>; "; reference "RFC 5246: The Transport Layer Security (TLS) Protocol Version 1.2"; } } } // Objects for deriving NETCONF usernames from X.509 // certificates. grouping cert-maps-grouping { description "Grouping for cert-maps container."; container cert-maps { if-feature tls-map-certificates; uses x509c2n:cert-to-name; description "The cert-maps container is used by a NETCONF server to map the NETCONF client's presented X.509 certificate to a NETCONF username. If no matching and valid cert-to-name list entry can be found, then the NETCONF server MUST close the connection, and MUST NOT accept NETCONF messages over it."; } } // Objects for deriving NETCONF usernames from TLS // pre-shared keys. grouping psk-maps-grouping { description "Grouping for psk-maps container."; container psk-maps { if-feature tls-map-pre-shared-keys; description "During the TLS Handshake, the client indicates which key to use by including a PSK identity in the TLS ClientKeyExchange message. On the NETCONF server side, this PSK identity is used to look up an entry in the psk-map list. If such an entry is found, and the pre-shared keys Watsen & Schoenwaelder Expires March 26, 2015 [Page 19] Internet-Draft NETCONF Server Configuration Model September 2014 match, then the client is authenticated. The NETCONF server uses the value from the user-name leaf in the psk-map list as the NETCONF username. If the NETCONF server cannot find an entry in the psk-map list, or if the pre-shared keys do not match, then the NETCONF server terminates the connection."; reference "RFC 4279: Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)"; list psk-map { key psk-identity; description "List a pre-shared key mappings."; leaf psk-identity { type string; description "The PSK identity encoded as a UTF-8 string. For details how certain common PSK identity formats can be encoded in UTF-8, see section 5.1. of RFC 4279."; reference "RFC 4279: Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)"; } leaf user-name { type nacm:user-name-type; mandatory true; description "The NETCONF username associated with this PSK identity."; } leaf not-valid-before { type yang:date-and-time; description "This PSK identity is not valid before the given date and time."; } leaf not-valid-after { type yang:date-and-time; description "This PSK identity is not valid after the given date and time."; } leaf key { type yang:hex-string; mandatory true; nacm:default-deny-all; Watsen & Schoenwaelder Expires March 26, 2015 [Page 20] Internet-Draft NETCONF Server Configuration Model September 2014 description "The key associated with the PSK identity"; reference "RFC 4279: Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)"; } } } } } 4. Keep-Alives for SSH and TLS One the objectives listed above, Keep-Alives for Persistent Connections (Section 2.4.6) indicates a need for a "keep-alive" mechanism. This section specifies how the NETCONF keep-alive mechanism is to be implemented. Both SSH and TLS have the ability to support keep-alives. Using these mechanisms, the keep-alive messages are sent inside the encrypted tunnel, thus thwarting spoof attacks. 4.1. SSH The SSH keep-alive solution that is expected to be used when configured using the data model defined in this document is ubiquitous in practice, though never being explicitly defined in an RFC. The strategy used is to purposely send a malformed request message with a flag set to ensure a response. More specifically, per section 4 of [RFC4253], either SSH peer can send a SSH_MSG_GLOBAL_REQUEST message with "want reply" set to '1' and that, if there is an error, will get back a SSH_MSG_REQUEST_FAILURE response. Similarly, section 5 of [RFC4253] says that either SSH peer can send a SSH_MSG_CHANNEL_REQUEST message with "want reply" set to '1' and that, if there is an error, will get back a SSH_MSG_CHANNEL_FAILURE response. To ensure that the request will fail, current implementations send an invalid "request name" or "request type", respectively. Abiding to the extensibility guidelines specified in Section 6 of [RFC4251], these implementations use the "name@domain". For instance, when configured to send keep-alives, OpenSSH sends the string "keepalive@openssh.com". In order to remain compatible with existing Watsen & Schoenwaelder Expires March 26, 2015 [Page 21] Internet-Draft NETCONF Server Configuration Model September 2014 implementations, this draft does not require a specific "request name" or "request type" string be used. 4.2. TLS The TLS keep-alive solution is defined in [RFC6520]. This solution allows both peers to advertise if they can receive heartbeat request messages from its peer. For standard NETCONF over TLS connections, devices SHOULD advertise "peer_allowed_to_send", as per [RFC6520]. This advertisement is not a "MUST" in order to grandfather existing NETCONF over TLS implementations. For NETCONF over TLS Call Home, the network management system MUST advertise "peer_allowed_to_send" per [RFC6520]. This is a "MUST" so as to ensure devices can depend in it always being there for call home connections, which is conveniently when keep-alives are needed the most. 5. Security Considerations The YANG modules defined in this memo are designed to be accessed via the NETCONF protocol [RFC6241]. Authorization for access to specific portions of conceptual data and operations within this module is provided by the NETCONF access control model (NACM) [RFC6536]. There are a number of data nodes defined in the "ietf-netconf-server" and "ietf-system-tls-auth" YANG modules which are writable/creatable/ deletable (i.e., config true, which is the default). These data nodes may be considered sensitive or vulnerable in some network environments. Write and read operations to these data nodes can have a negative effect on network operations. It is thus important to control write and read access to these data nodes. Below are the data nodes and their sensitivity/vulnerability. ietf-netconf-server: o None. ietf-system-tls-auth: o /system/authentication/tls/psk-maps/psk-map/user-name: This leaf node contains a user name that some deployments may consider sensitive information. o /system/authentication/tls/psk-maps/psk-map/key: This leaf node contains a shared key that remote clients use to authenticate themselves to the system. This value should not be readable or writable by anyone by default. Watsen & Schoenwaelder Expires March 26, 2015 [Page 22] Internet-Draft NETCONF Server Configuration Model September 2014 6. IANA Considerations This document registers two URIs in the IETF XML registry [RFC2119]. Following the format in [RFC3688], the following registrations are requested: URI: urn:ietf:params:xml:ns:yang:ietf-netconf-server Registrant Contact: The NETCONF WG of the IETF. XML: N/A, the requested URI is an XML namespace. URI: urn:ietf:params:xml:ns:yang:ietf-system-tle-auth Registrant Contact: The NETCONF WG of the IETF. XML: N/A, the requested URI is an XML namespace. This document registers two YANG modules in the YANG Module Names registry [RFC6020]. name: ietf-netconf-server namespace: urn:ietf:params:xml:ns:yang:ietf-netconf-server prefix: ncserver reference: RFC XXXX name: ietf-system-tls-auth namespace: urn:ietf:params:xml:ns:yang:ietf-system-tls-auth prefix: sys-tls-auth reference: RFC XXXX 7. Other Considerations The YANG module define herein does not itself support virtual routing and forwarding (VRF). It is expected that external modules will augment in VRF designations when needed. 8. Acknowledgements The authors would like to thank for following for lively discussions on list and in the halls (ordered by last name): Andy Bierman, Martin Bjorklund, Benoit Claise, David Lamparter, Alan Luchuk, Ladislav Lhotka, Radek Krejci, Tom Petch, and Phil Shafer. Juergen Schoenwaelder and was partly funded by Flamingo, a Network of Excellence project (ICT-318488) supported by the European Commission under its Seventh Framework Programme. Watsen & Schoenwaelder Expires March 26, 2015 [Page 23] Internet-Draft NETCONF Server Configuration Model September 2014 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4251] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH) Protocol Architecture", RFC 4251, January 2006. [RFC4253] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH) Transport Layer Protocol", RFC 4253, January 2006. [RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, October 2010. [RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J., and A. Bierman, "Network Configuration Protocol (NETCONF)", RFC 6241, June 2011. [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, June 2011. [RFC6520] Seggelmann, R., Tuexen, M., and M. Williams, "Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) Heartbeat Extension", RFC 6520, February 2012. [RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration Protocol (NETCONF) Access Control Model", RFC 6536, March 2012. [RFC6991] Schoenwaelder, J., "Common YANG Data Types", RFC 6991, July 2013. [draft-ietf-netconf-call-home] Watsen, K., "NETCONF Call Home", draft-ieft-netconf-call- home-00 (work in progress), 2014. [draft-ietf-netmod-snmp-cfg] Bjorklund, M. and J. Schoenwaelder, "A YANG Data Model for SNMP Configuration", draft-ietf-netmod-snmp-cfg-03 (work in progress), November 2013. Watsen & Schoenwaelder Expires March 26, 2015 [Page 24] Internet-Draft NETCONF Server Configuration Model September 2014 [rfc5539bis] Badra, M., Luchuk, A., and J. Schoenwaelder, "Using the NETCONF Protocol over Transport Layer Security (TLS)", draft-ietf-netconf-rfc5539bis-04 (work in progress), October 2013. 9.2. Informative References [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, January 2004. Watsen & Schoenwaelder Expires March 26, 2015 [Page 25] Internet-Draft NETCONF Server Configuration Model September 2014 Appendix A. Examples A.1. SSH Transport Configuration foo bar 831 config-mgr east-data-center
11.22.33.44
 west-data-center
55.66.77.88
 A.2. TLS Transport Configuration foo bar 831 config-mgr east-data-center
11.22.33.44
 west-data-center
55.66.77.88
Watsen & Schoenwaelder Expires March 26, 2015 [Page 26] Internet-Draft NETCONF Server Configuration Model September 2014 QW4gRWFzdGVyIGVnZywgZm9yIHRob3NlIHdobyBtaWdodCBsb29rICA6KQo= SSBhbSB0aGUgZWdnIG1hbiwgdGhleSBhcmUgdGhlIGVnZyBtZW4uCg== SSBhbSB0aGUgd2FscnVzLCBnb28gZ29vIGcnam9vYi4K 1 11:0A:05:11:00 x509c2n:san-any 2 11:0A:05:11:00 x509c2n:specified Joe Cool a8gc8]klh59 admin 2013-01-01T00:00:00Z 2014-01-01T00:00:00Z Appendix B. Change Log Watsen & Schoenwaelder Expires March 26, 2015 [Page 27] Internet-Draft NETCONF Server Configuration Model September 2014 B.1. 00 to 01 o Restructured document so it flows better o Added trusted-ca-certs and trusted-client-certs objects into the ietf-system-tls-auth module B.2. 01 to 02 o removed the "one-to-many" construct o removed "address" as a key field o removed "network-manager" terminology o moved open issues to github issues o brought TLS client auth back into model B.3. 02 to 03 o fixed tree diagrams and surrounding text Appendix C. Open Issues Please see: https://github.com/netconf-wg/server-model/issues. Authors' Addresses Kent Watsen Juniper Networks EMail: kwatsen@juniper.net Juergen Schoenwaelder Jacobs University Bremen EMail: j.schoenwaelder@jacobs-university.de Watsen & Schoenwaelder Expires March 26, 2015 [Page 28]