| NETCONF Working Group | K. Watsen |
| Internet-Draft | Juniper Networks |
| Intended status: Standards Track | G. Wu |
| Expires: January 10, 2017 | Cisco Networks |
| July 9, 2016 |
SSH Client and Server Models
draft-ietf-netconf-ssh-client-server-00
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:
Artwork in this document contains shorthand references to drafts in progress. Please apply the following replacements:
Artwork in this document contains placeholder values for the date of publication of this draft. Please apply the following replacement:
The following two Appendix sections are to be removed prior to publication:
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 January 10, 2017.
Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
This document defines two YANG [RFC6020] modules, one defines groupings for a generic SSH client and the other defines groupings for a generic SSH server (SSH is defined in [RFC4252], [RFC4253], and [RFC4254]). 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 [OPENSSH] server or a NETCONF over SSH [RFC6242] 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 [RFC793] 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 [draft-ietf-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 [RFC2119].
A simplified graphical representation of the data models is used in this document. The meaning of the symbols in these diagrams is as follows:
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 [draft-ietf-netconf-system-keychain]. 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 [RFC6187].
The following tree diagram presents the data model for the two groupings defined in the ietf-ssh-client module.
module: ietf-ssh-client
groupings:
initiating-ssh-client-grouping
+---- 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
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 [draft-ietf-netconf-system-keychain].
FIXME (how to do an example for a module that only has groupings?)
This YANG module has a normative references to [RFC6991] and [draft-ietf-netconf-system-keychain].
<CODE BEGINS> 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: <http://tools.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
WG Chair: Mehmet Ersue
<mailto:mehmet.ersue@nsn.com>
WG Chair: Mahesh Jethanandani
<mailto:mjethanandani@gmail.com>
Author: Kent Watsen
<mailto:kwatsen@juniper.net>
Author: Gary Wu
<mailto:garywu@cisco.com>";
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;
}
}
<CODE ENDS>
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 [draft-ietf-netconf-system-keychain]. 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.
module: ietf-ssh-server
groupings:
listening-ssh-server-grouping
+---- address? inet:ip-address
+---- port? inet:port-number
+---- 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
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 [draft-ietf-netconf-system-keychain].
<listening-ssh-server
xmlns="urn:ietf:params:xml:ns:yang:ietf-ssh-server">
<port>830</port>
<host-keys>
<host-key>
<name>deployment-specific-certificate</name>
<certificate>ex-key-sect571r1-cert</certificate>
</host-key>
</host-keys>
</certificates>
<client-cert-auth>
<trusted-ca-certs>
deployment-specific-ca-certs
</trusted-ca-certs>
<trusted-client-certs>
explicitly-trusted-client-certs
</trusted-client-certs>
</client-cert-auth>
</listening-ssh-server>
This YANG module has a normative references to [RFC4253], [RFC6991], and [draft-ietf-netconf-system-keychain].
<CODE BEGINS> 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: <http://tools.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
WG Chair: Mehmet Ersue
<mailto:mehmet.ersue@nsn.com>
WG Chair: Mahesh Jethanandani
<mailto:mjethanandani@gmail.com>
Editor: Kent Watsen
<mailto:kwatsen@juniper.net>";
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;
}
}
<CODE ENDS>
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-ssh-client 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-ssh-server 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]. Following the format in [RFC6020], the the following registrations are requested:
name: ietf-ssh-client namespace: urn:ietf:params:xml:ns:yang:ietf-ssh-client prefix: sshc reference: RFC XXXX name: ietf-ssh-server namespace: urn:ietf:params:xml:ns:yang:ietf-ssh-server prefix: sshs reference: RFC XXXX
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.
| [draft-ietf-netconf-system-keychain] | Watsen, K., "System Keychain Model", Internet-Draft draft-ieft-netconf-system-keychain-00, 2016. |
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997. |
| [RFC6020] | Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010. |
| [RFC6187] | Igoe, K. and D. Stebila, "X.509v3 Certificates for Secure Shell Authentication", RFC 6187, DOI 10.17487/RFC6187, March 2011. |
| [RFC6991] | Schoenwaelder, J., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013. |
| [draft-ietf-netconf-call-home] | Watsen, K., NETCONF Call Home and RESTCONF Call Home", Internet-Draft draft-ieft-netconf-call-home-17, 2015. |
| [OPENSSH] | OpenSSH", 2016. | , "
| [RFC3688] | Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004. |
| [RFC4252] | Ylonen, T. and C. Lonvick, "The Secure Shell (SSH) Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252, January 2006. |
| [RFC4253] | Ylonen, T. and C. Lonvick, "The Secure Shell (SSH) Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253, January 2006. |
| [RFC4254] | Ylonen, T. and C. Lonvick, "The Secure Shell (SSH) Connection Protocol", RFC 4254, DOI 10.17487/RFC4254, January 2006. |
| [RFC6242] | Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011. |
| [RFC793] | Postel, J., "TRANSMISSION CONTROL PROTOCOL", STD 7, September 1981. |
Please see: https://github.com/netconf-wg/ssh-client-server/issues.