]> Juniper Networks

kwatsen@juniper.net

Cisco Networks

garywu@cisco.com

Operations NETCONF Working Group This document defines two YANG modules, one defines groupings for a generic SSH client and the other defines groupings for a generic SSH server. It is intended that these groupings will be used by applications using the SSH protocol. This draft contains many placeholder values that need to be replaced with finalized values at the time of publication. This note summarizes all of the substitutions that are needed. No other RFC Editor instructions are specified elsewhere in this document. This document contains references to other drafts in progress, both in the Normative References section, as well as in body text throughout. Please update the following references to reflect their final RFC assignments: draft-ietf-netconf-system-keychain Artwork in this document contains shorthand references to drafts in progress. Please apply the following replacements: XXXX --> the assigned RFC value for this draft YYYY --> the assigned RFC value for draft-ietf-netconf-system-keychain Artwork in this document contains placeholder values for the date of publication of this draft. Please apply the following replacement: 2016-07-08 --> the publication date of this draft The following two Appendix sections are to be removed prior to publication: Appendix A. Change Log Appendix B. Open Issues

This document defines two YANG modules, one defines groupings for a generic SSH client and the other defines groupings for a generic SSH server (SSH is defined in , , and ). It is intended that these groupings will be used by applications using the SSH protocol. For instance, these groupings could be used to help define the data model for an OpenSSH server or a NETCONF over SSH based server. The two YANG modules in this document each define two groupings. One grouping defines everything other than what's needed for the TCP protocol layer. The other grouping uses the first grouping while adding TCP layer specifics (e.g., addresses to connect to, ports to listen on, etc.). This separation is done in order to enable applications the opportunity to define their own strategy for how the underlying TCP connection is established. For instance, applications supporting NETCONF Call Home could use the first grouping for the SSH parts it provides, while adding data nodes for the reversed TCP layer.

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 .

A simplified graphical representation of the data models is used in this document. The meaning of the symbols in these diagrams is as follows: Brackets "[" and "]" enclose list keys. Braces "{" and "}" enclose feature names, and indicate that the named feature must be present for the subtree to be present. Abbreviations before data node names: "rw" means configuration (read-write) and "ro" state data (read-only). Symbols after data node names: "?" means an optional node, "!" means a presence container, and "*" denotes a list and leaf-list. Parentheses enclose choice and case nodes, and case nodes are also marked with a colon (":"). Ellipsis ("...") stands for contents of subtrees that are not shown.

The SSH client model presented in this section contains two YANG groupings, one for a client that initiates the underlying TCP connection and another for a client that has had the TCP connection opened for it already (e.g., call home). Both of these groupings reference data nodes defined by the System Keychain model . For instance, a reference to the keychain model is made to indicate which trusted CA certificate a client should use to authenticate X.509v3 certificate based host keys .

The following tree diagram presents the data model for the two groupings defined in the ietf-ssh-client module.

/kc:keychain/trusted-ssh-host -keys/name | +---- trusted-ca-certs? -> /kc:keychain/trusted-certific ates/name {ssh-x509-certs}? | +---- trusted-server-certs? -> /kc:keychain/trusted-certific ates/name +---- client-auth +---- matches* [name] +---- name? string +---- match* [name] | +---- name? string | +---- trusted-ssh-host-keys? -> /kc:keychain/trusted-ss h-host-keys/name | +---- trusted-ca-certs? -> /kc:keychain/trusted-ce rtificates/name | +---- trusted-server-certs? -> /kc:keychain/trusted-ce rtificates/name +---- user-auth-credentials? -> /kc:keychain/user-auth-cre dentials/user-auth-credential/username listening-ssh-client-grouping +---- address? inet:ip-address +---- port? inet:port-number +---- server-auth | +---- trusted-ssh-host-keys? -> /kc:keychain/trusted-ssh-host -keys/name | +---- trusted-ca-certs? -> /kc:keychain/trusted-certific ates/name {ssh-x509-certs}? | +---- trusted-server-certs? -> /kc:keychain/trusted-certific ates/name +---- client-auth +---- matches* [name] +---- name? string +---- match* [name] | +---- name? string | +---- trusted-ssh-host-keys? -> /kc:keychain/trusted-ss h-host-keys/name | +---- trusted-ca-certs? -> /kc:keychain/trusted-ce rtificates/name | +---- trusted-server-certs? -> /kc:keychain/trusted-ce rtificates/name +---- user-auth-credentials? -> /kc:keychain/user-auth-cre dentials/user-auth-credential/username ]]>

This section shows how it would appear if the initiating-ssh-client-grouping were populated with some data. This example is consistent with the examples presented in Section 2.2 of .

This YANG module has a normative references to and .

file "ietf-ssh-client@2016-07-08.yang" module ietf-ssh-client { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-ssh-client"; prefix "sshc"; import ietf-inet-types { prefix inet; reference "RFC 6991: Common YANG Data Types"; } import ietf-system-keychain { prefix kc; reference "RFC YYYY: System Keychain Model"; } organization "IETF NETCONF (Network Configuration) Working Group"; contact "WG Web: WG List: WG Chair: Mehmet Ersue WG Chair: Mahesh Jethanandani Author: Kent Watsen Author: Gary Wu "; description "This module defines a reusable grouping for a SSH client that can be used as a basis for specific SSH client instances. 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."; revision "2016-07-08" { description "Initial version"; reference "RFC XXXX: SSH Client and Server Models"; } feature ssh-x509-certs { description "The ssh-x509-certs feature indicates that the SSH client supports RFC 6187"; reference "RFC 6187: X.509v3 Certificates for Secure Shell Authentication"; } grouping initiating-ssh-client-grouping { description "A reusable grouping for a SSH client that initiates the underlying TCP transport connection."; container server-auth { description "Trusted server identities."; leaf trusted-ssh-host-keys { type leafref { path "/kc:keychain/kc:trusted-ssh-host-keys/kc:name"; } description "A reference to a list of SSH host keys used by the SSH client to authenticate SSH server host keys. A server host key is authenticate if it is an exact match to a configured trusted SSH host key."; } leaf trusted-ca-certs { if-feature ssh-x509-certs; type leafref { path "/kc:keychain/kc:trusted-certificates/kc:name"; } description "A reference to a list of certificate authority (CA) certificates used by the SSH client to authenticate SSH server certificates."; } leaf trusted-server-certs { type leafref { path "/kc:keychain/kc:trusted-certificates/kc:name"; } description "A reference to a list of server certificates used by the SSH client to authenticate SSH server certificates. A server certificate is authenticated if it is an exact match to a configured trusted server certificate."; } } container client-auth { description "The credentials used by the client to authenticate to the SSH server."; list matches { key name; description "A matches expression, which performs like a firewall rulebase in that each matches expression is considered for a match before moving onto the next matches expression. The first matching expression terminates the search, and its 'user-auth-credentials' are used to log into the SSH server."; leaf name { type string; description "An arbitrary name for this matches expression."; } list match { key name; description "A match rule. The presented SSH server's host key is matched against possible trusted SSH host keys and certificates. If a match is found, the specified 'user-auth-credentials' is used to log into the SSH server."; leaf name { type string; description "An arbitrary name for this match rule."; } leaf trusted-ssh-host-keys { type leafref { path "/kc:keychain/kc:trusted-ssh-host-keys/kc:name"; } description "A test to see if the presented SSH host key matches any of the host keys in the specified 'trusted-ssh-host-keys' list maintained by the system-keychain module."; } leaf trusted-ca-certs { type leafref { path "/kc:keychain/kc:trusted-certificates/kc:name"; } description "A test to see if the presented SSH host key matches any of the trusted CA certificates in the specified 'trusted-certificates' list maintained by the system-keychain module."; } leaf trusted-server-certs { type leafref { path "/kc:keychain/kc:trusted-certificates/kc:name"; } description "A test to see if the presented SSH host key matches any of the trusted server certificates in the specified 'trusted-certificates' list maintained by the system-keychain module."; } } leaf user-auth-credentials { type leafref { path "/kc:keychain/kc:user-auth-credentials/" + "kc:user-auth-credential/kc:username"; } description "The specific user authentication credentials to use if all of the above 'match' expressions match."; } } } } // end initiating-ssh-client-grouping grouping listening-ssh-client-grouping { description "A reusable grouping for a SSH client that does not the underlying TCP transport connection have been established using some other mechanism."; leaf address { type inet:ip-address; description "The IP address to listen for call-home connections on."; } leaf port { type inet:port-number; description "The port number to listen for call-home connections. When this grouping is used, it is RECOMMENED that refine statement is used to either set a default port value or to set mandatory true."; } uses initiating-ssh-client-grouping; } } ]]>

The SSH server model presented in this section contains two YANG groupings, one for a server that opens a socket to accept TCP connections and another for a server that has had the TCP connection opened for it already (e.g., inetd). Both of these groupings reference data nodes defined by the System Keychain model . For instance, a reference to the keychain model is made to indicate which host key a server should present.

The following tree diagram presents the data model for the two groupings defined in the ietf-ssh-server module.

/kc:keychain/private-keys/priv ate-key/name | +--:(certificate) | +---- certificate? -> /kc:keychain/private-keys/priv ate-key/certificate-chains/certificate-chain/name {ssh-x509-certs}? +---- client-cert-auth {ssh-x509-certs}? +---- trusted-ca-certs? -> /kc:keychain/trusted-certifica tes/name +---- trusted-client-certs? -> /kc:keychain/trusted-certifica tes/name non-listening-ssh-server-grouping +---- host-keys | +---- host-key* [name] | +---- name string | +---- (type)? | +--:(public-key) | | +---- public-key? -> /kc:keychain/private-keys/priv ate-key/name | +--:(certificate) | +---- certificate? -> /kc:keychain/private-keys/priv ate-key/certificate-chains/certificate-chain/name {ssh-x509-certs}? +---- client-cert-auth {ssh-x509-certs}? +---- trusted-ca-certs? -> /kc:keychain/trusted-certifica tes/name +---- trusted-client-certs? -> /kc:keychain/trusted-certifica tes/name ]]>

This section shows how it would appear if the listening-ssh-server-grouping were populated with some data. This example is consistent with the examples presented in Section 2.2 of .

830 deployment-specific-certificate ex-key-sect571r1-cert deployment-specific-ca-certs explicitly-trusted-client-certs ]]>

This YANG module has a normative references to , , and .

file "ietf-ssh-server@2016-07-08.yang" module ietf-ssh-server { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-ssh-server"; prefix "sshs"; import ietf-inet-types { prefix inet; reference "RFC 6991: Common YANG Data Types"; } import ietf-system-keychain { prefix kc; reference "RFC YYYY: System Keychain Model"; } organization "IETF NETCONF (Network Configuration) Working Group"; contact "WG Web: WG List: WG Chair: Mehmet Ersue WG Chair: Mahesh Jethanandani Editor: Kent Watsen "; description "This module defines a reusable grouping for a SSH server that can be used as a basis for specific SSH server instances. 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."; revision "2016-07-08" { description "Initial version"; reference "RFC XXXX: SSH Client and Server Models"; } // features feature ssh-x509-certs { description "The ssh-x509-certs feature indicates that the NETCONF server supports RFC 6187"; reference "RFC 6187: X.509v3 Certificates for Secure Shell Authentication"; } // grouping grouping non-listening-ssh-server-grouping { description "A reusable grouping for a SSH server that can be used as a basis for specific SSH server instances."; container host-keys { description "The list of host-keys the SSH server will present when establishing a SSH connection."; list host-key { key name; min-elements 1; ordered-by user; description "An ordered list of host keys the SSH server will use to construct its ordered list of algorithms, when sending its SSH_MSG_KEXINIT message, as defined in Section 7.1 of RFC 4253."; reference "RFC 4253: The Secure Shell (SSH) Transport Layer Protocol"; leaf name { type string; mandatory true; description "An arbitrary name for this host-key"; } choice type { description "The type of host key being specified"; leaf public-key { type leafref { path "/kc:keychain/kc:private-keys/kc:private-key/" + "kc:name"; } description "The public key is actually identified by the name of its cooresponding private-key in the keychain."; } leaf certificate { if-feature ssh-x509-certs; type leafref { path "/kc:keychain/kc:private-keys/kc:private-key/" + "kc:certificate-chains/kc:certificate-chain/" + "kc:name"; } description "The name of a certificate in the keychain."; } } } } container client-cert-auth { if-feature ssh-x509-certs; description "A reference to a list of trusted certificate authority (CA) certificates and a reference to a list of trusted client certificates."; leaf trusted-ca-certs { type leafref { path "/kc:keychain/kc:trusted-certificates/kc:name"; } description "A reference to a list of certificate authority (CA) certificates used by the SSH server to authenticate SSH client certificates."; } leaf trusted-client-certs { type leafref { path "/kc:keychain/kc:trusted-certificates/kc:name"; } description "A reference to a list of client certificates used by the SSH server to authenticate SSH client certificates. A clients certificate is authenticated if it is an exact match to a configured trusted client certificate."; } } } grouping listening-ssh-server-grouping { description "A reusable grouping for a SSH server that can be used as a basis for specific SSH server instances."; leaf address { type inet:ip-address; description "The IP address of the interface to listen on. The SSH server will listen on all interfaces if no value is specified. Please note that some addresses have special meanings (e.g., '0.0.0.0' and '::')."; } leaf port { type inet:port-number; description "The local port number on this interface the SSH server listens on. When this grouping is used, it is RECOMMENED that refine statement is used to either set a default port value or to set mandatory true."; } uses non-listening-ssh-server-grouping; } } ]]>

This document registers two URIs in the IETF XML registry . Following the format in , the following registrations are requested:

This document registers two YANG modules in the YANG Module Names registry . Following the format in , the the following registrations are requested:

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, Mehmet Ersue, David Lamparter, Alan Luchuk, Ladislav Lhotka, Radek Krejci, Tom Petch, Juergen Schoenwaelder, Phil Shafer, Sean Turner, and Bert Wijnen.

&rfc2119; &rfc6020; &rfc6187; &rfc6991; Juniper Networks &rfc3688; &rfc4252; &rfc4253; &rfc4254; &rfc6242; Juniper Networks

This draft was split out from draft-ietf-netconf-server-model-09. Added in previously missing ietf-ssh-client module. Noted that '0.0.0.0' and '::' might have special meanings.

Please see: https://github.com/netconf-wg/ssh-client-server/issues.