NETCONF Working Group K. Watsen
Internet-Draft Juniper Networks
Intended status: Standards Track G. Wu
Expires: April 25, 2019 Cisco Systems
L. Xia
Huawei
October 22, 2018
YANG Groupings for SSH Clients and SSH Servers
draft-ietf-netconf-ssh-client-server-08
Abstract
This document defines three YANG modules: the first defines groupings
for a generic SSH client, the second defines groupings for a generic
SSH server, and the third defines common identities and groupings
used by both the client and the server. It is intended that these
groupings will be used by applications using the SSH protocol.
Editorial Note (To be removed by RFC Editor)
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:
o I-D.ietf-netconf-trust-anchors
o I-D.ietf-netconf-keystore
Artwork in this document contains shorthand references to drafts in
progress. Please apply the following replacements:
o "XXXX" --> the assigned RFC value for this draft
o "YYYY" --> the assigned RFC value for I-D.ietf-netconf-trust-
anchors
o "ZZZZ" --> the assigned RFC value for I-D.ietf-netconf-keystore
Artwork in this document contains placeholder values for the date of
publication of this draft. Please apply the following replacement:
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o "2018-10-22" --> the publication date of this draft
The following Appendix section is to be removed prior to publication:
o Appendix A. Change Log
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 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 April 25, 2019.
Copyright Notice
Copyright (c) 2018 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
(https://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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. The SSH Client Model . . . . . . . . . . . . . . . . . . . . 4
3.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Example Usage . . . . . . . . . . . . . . . . . . . . . . 5
3.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 8
4. The SSH Server Model . . . . . . . . . . . . . . . . . . . . 12
4.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 12
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4.2. Example Usage . . . . . . . . . . . . . . . . . . . . . . 12
4.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 16
5. The SSH Common Model . . . . . . . . . . . . . . . . . . . . 20
5.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 22
5.2. Example Usage . . . . . . . . . . . . . . . . . . . . . . 23
5.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 23
6. Security Considerations . . . . . . . . . . . . . . . . . . . 33
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34
7.1. The IETF XML Registry . . . . . . . . . . . . . . . . . . 34
7.2. The YANG Module Names Registry . . . . . . . . . . . . . 34
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 35
8.1. Normative References . . . . . . . . . . . . . . . . . . 35
8.2. Informative References . . . . . . . . . . . . . . . . . 36
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 38
A.1. 00 to 01 . . . . . . . . . . . . . . . . . . . . . . . . 38
A.2. 01 to 02 . . . . . . . . . . . . . . . . . . . . . . . . 38
A.3. 02 to 03 . . . . . . . . . . . . . . . . . . . . . . . . 38
A.4. 03 to 04 . . . . . . . . . . . . . . . . . . . . . . . . 38
A.5. 04 to 05 . . . . . . . . . . . . . . . . . . . . . . . . 39
A.6. 05 to 06 . . . . . . . . . . . . . . . . . . . . . . . . 39
A.7. 06 to 07 . . . . . . . . . . . . . . . . . . . . . . . . 39
A.8. 07 to 08 . . . . . . . . . . . . . . . . . . . . . . . . 39
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 39
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 40
1. Introduction
This document defines three YANG 1.1 [RFC7950] modules: the first
defines a grouping for a generic SSH client, the second defines a
grouping for a generic SSH server, and the third defines identities
and groupings common to both the client and the server. It is
intended that these groupings will be used by applications using the
SSH protocol [RFC4252], [RFC4253], and [RFC4254]. 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 client and server YANG modules in this document each define one
grouping, which is focused on just SSH-specific configuration, and
specifically avoids any transport-level configuration, such as what
ports to listen on or connect to. This affords applications the
opportunity to define their own strategy for how the underlying TCP
connection is established. For instance, applications supporting
NETCONF Call Home [RFC8071] could use the "ssh-server-grouping"
grouping for the SSH parts it provides, while adding data nodes for
the TCP-level call-home configuration.
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The modules defined in this document uses groupings defined in
[I-D.ietf-netconf-keystore] enabling keys to be either locally
defined or a reference to globally configured values.
The modules defined in this document optionally support [RFC6187]
enabling X.509v3 certificate based host keys and public keys.
2. Terminology
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 BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. The SSH Client Model
3.1. Tree Diagram
This section provides a tree diagram [RFC8340] for the "ietf-ssh-
client" module that does not have groupings expanded.
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module: ietf-ssh-client
grouping transport-params-grouping
+-- transport-params {ssh-client-transport-params-config}?
+---u transport-params-grouping
grouping client-identity-grouping
+-- client-identity
+-- username? string
+-- (auth-type)
+--:(password)
| +-- password? string
+--:(public-key)
| +-- public-key
| +---u client-identity-grouping
+--:(certificate)
+-- certificate {sshcmn:ssh-x509-certs}?
+---u client-identity-grouping
grouping ssh-client-grouping
+---u client-identity-grouping
+---u server-auth-grouping
+---u transport-params-grouping
grouping server-auth-grouping
+-- server-auth
+-- pinned-ssh-host-keys? ta:pinned-host-keys-ref
| {ta:ssh-host-keys}?
+-- pinned-ca-certs? ta:pinned-certificates-ref
| {sshcmn:ssh-x509-certs,ta:x509-certificates}?
+-- pinned-server-certs? ta:pinned-certificates-ref
{sshcmn:ssh-x509-certs,ta:x509-certificates}?
3.2. Example Usage
This section presents two examples showing the ssh-client-grouping
populated with some data. These examples are effectively the same
except the first configures the client identity using a local key
while the second uses a key configured in a keystore. Both examples
are consistent with the examples presented in Section 3 of
[I-D.ietf-netconf-trust-anchors] and Section 3.2 of
[I-D.ietf-netconf-keystore].
The following example configures the client identity using a local
key:
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[Note: '\' line wrapping for formatting only]
foobar
ct:rsa2048
base64encodedvalue==
base64encodedvalue==
explicitly-trusted-ssh-host-keys
algs:ssh-rsa
algs:diffie-hellman-group-exchange-sha256
algs:aes256-ctr
algs:aes192-ctr
algs:aes128-ctr
algs:aes256-cbc
algs:aes192-cbc
algs:aes128-cbc
algs:hmac-sha2-256
algs:hmac-sha2-512
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The following example configures the client identity using a key from
the keystore:
[Note: '\' line wrapping for formatting only]
foobar
ex-rsa-key
explicitly-trusted-ssh-host-keys
algs:ssh-rsa
algs:diffie-hellman-group-exchange-sha256
algs:aes256-ctr
algs:aes192-ctr
algs:aes128-ctr
algs:aes256-cbc
algs:aes192-cbc
algs:aes128-cbc
algs:hmac-sha2-256
algs:hmac-sha2-512
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3.3. YANG Module
This YANG module has normative references to
[I-D.ietf-netconf-trust-anchors], and [I-D.ietf-netconf-keystore].
file "ietf-ssh-client@2018-10-22.yang"
module ietf-ssh-client {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-ssh-client";
prefix "sshc";
import ietf-ssh-common {
prefix sshcmn;
revision-date 2018-10-22; // stable grouping definitions
reference
"RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
}
import ietf-trust-anchors {
prefix ta;
reference
"RFC YYYY: YANG Data Model for Global Trust Anchors";
}
import ietf-keystore {
prefix ks;
reference
"RFC ZZZZ:
YANG Data Model for a Centralized Keystore Mechanism";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web:
WG List:
Author: Kent Watsen
Author: Gary Wu
";
description
"This module defines a reusable grouping for a SSH client that
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can be used as a basis for specific SSH client instances.
Copyright (c) 2018 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 "2018-10-22" {
description
"Initial version";
reference
"RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
}
// features
feature ssh-client-transport-params-config {
description
"SSH transport layer parameters are configurable on an SSH
client.";
}
// groupings
grouping ssh-client-grouping {
description
"A reusable grouping for configuring a SSH client without
any consideration for how an underlying TCP session is
established.";
uses client-identity-grouping;
uses server-auth-grouping;
uses transport-params-grouping;
}
grouping client-identity-grouping {
description
"A reusable grouping for configuring a SSH client identity.";
container client-identity {
description
"The credentials used by the client to authenticate to
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the SSH server.";
leaf username {
type string;
description
"The username of this user. This will be the username
used, for instance, to log into an SSH server.";
}
choice auth-type {
mandatory true;
description
"The authentication type.";
leaf password {
type string;
description
"A password to be used for client authentication.";
}
container public-key {
uses ks:local-or-keystore-asymmetric-key-grouping;
description
"A locally-defined or referenced asymmetric key pair
to be used for client authentication.";
reference
"RFC ZZZZ:
YANG Data Model for a Centralized Keystore Mechanism";
}
container certificate {
if-feature sshcmn:ssh-x509-certs;
uses ks:local-or-keystore-end-entity-cert-with-key-grouping;
description
"A locally-defined or referenced certificate
to be used for client authentication.";
reference
"RFC ZZZZ
YANG Data Model for a Centralized Keystore Mechanism";
}
} // end auth-type
} // end client-identity
} // end client-identity-grouping
grouping server-auth-grouping {
description
"A reusable grouping for configuring SSH server
authentication.";
container server-auth {
must 'pinned-ssh-host-keys or pinned-ca-certs or '
+ 'pinned-server-certs';
description
"Trusted server identities.";
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leaf pinned-ssh-host-keys {
if-feature "ta:ssh-host-keys";
type ta:pinned-host-keys-ref;
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 authenticated if it is an exact
match to a configured SSH host key.";
reference
"RFC YYYY: YANG Data Model for Global Trust Anchors";
}
leaf pinned-ca-certs {
if-feature sshcmn:ssh-x509-certs;
if-feature "ta:x509-certificates";
type ta:pinned-certificates-ref;
description
"A reference to a list of certificate authority (CA)
certificates used by the SSH client to authenticate
SSH server certificates. A server certificate is
authenticated if it has a valid chain of trust to
a configured CA certificate.";
reference
"RFC YYYY: YANG Data Model for Global Trust Anchors";
}
leaf pinned-server-certs {
if-feature sshcmn:ssh-x509-certs;
if-feature "ta:x509-certificates";
type ta:pinned-certificates-ref;
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 server certificate.";
reference
"RFC YYYY: YANG Data Model for Global Trust Anchors";
}
} // end server-auth
} // end server-auth-grouping
grouping transport-params-grouping {
description
"A reusable grouping for configuring a SSH transport
parameters.";
container transport-params {
if-feature ssh-client-transport-params-config;
description
"Configurable parameters of the SSH transport layer.";
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uses sshcmn:transport-params-grouping;
}
} // end transport-params-grouping
}
4. The SSH Server Model
4.1. Tree Diagram
This section provides a tree diagram [RFC8340] for the "ietf-ssh-
server" module that does not have groupings expanded.
module: ietf-ssh-server
grouping transport-params-grouping
+-- transport-params {ssh-server-transport-params-config}?
+---u transport-params-grouping
grouping client-auth-grouping
+-- client-cert-auth {sshcmn:ssh-x509-certs}?
+-- pinned-ca-certs? ta:pinned-certificates-ref
| {ta:x509-certificates}?
+-- pinned-client-certs? ta:pinned-certificates-ref
{ta:x509-certificates}?
grouping server-identity-grouping
+-- server-identity
+-- host-key* [name]
+-- name? string
+-- (host-key-type)
+--:(public-key)
| +-- public-key
| +---u server-identity-grouping
+--:(certificate)
+-- certificate {sshcmn:ssh-x509-certs}?
+---u server-identity-grouping
grouping ssh-server-grouping
+---u server-identity-grouping
+---u client-auth-grouping
+---u transport-params-grouping
4.2. Example Usage
This section presents two examples showing the ssh-server-grouping
populated with some data. These examples are effectively the same
except the first configures the server identity using a local key
while the second uses a key configured in a keystore. Both examples
are consistent with the examples presented in Section 3 of
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[I-D.ietf-netconf-trust-anchors] and Section 3.2 of
[I-D.ietf-netconf-keystore].
The following example configures the server identity using a local
key:
[Note: '\' line wrapping for formatting only]
deployment-specific-certificate
ct:rsa2048
base64encodedvalue==
base64encodedvalue==
explicitly-trusted-client-ca-certs
explicitly-trusted-client-certs
algs:ssh-rsa
algs:diffie-hellman-group-exchange-sha256
algs:aes256-ctr
algs:aes192-ctr
algs:aes128-ctr
algs:aes256-cbc
algs:aes192-cbc
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algs:aes128-cbc
algs:hmac-sha2-256
algs:hmac-sha2-512
The following example configures the server identity using a key from
the keystore:
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[Note: '\' line wrapping for formatting only]
deployment-specific-certificate
ex-rsa-key
explicitly-trusted-client-ca-certs
explicitly-trusted-client-certs
algs:ssh-rsa
algs:diffie-hellman-group-exchange-sha256
algs:aes256-ctr
algs:aes192-ctr
algs:aes128-ctr
algs:aes256-cbc
algs:aes192-cbc
algs:aes128-cbc
algs:hmac-sha2-256
algs:hmac-sha2-512
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4.3. YANG Module
This YANG module has normative references to
[I-D.ietf-netconf-trust-anchors] and [I-D.ietf-netconf-keystore] and
informative references to [RFC4253] and [RFC7317].
file "ietf-ssh-server@2018-10-22.yang"
module ietf-ssh-server {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-ssh-server";
prefix "sshs";
import ietf-ssh-common {
prefix sshcmn;
revision-date 2018-10-22; // stable grouping definitions
reference
"RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
}
import ietf-trust-anchors {
prefix ta;
reference
"RFC YYYY: YANG Data Model for Global Trust Anchors";
}
import ietf-keystore {
prefix ks;
reference
"RFC ZZZZ:
YANG Data Model for a Centralized Keystore Mechanism";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web:
WG List:
Author: Kent Watsen
Author: Gary Wu
";
description
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"This module defines a reusable grouping for a SSH server that
can be used as a basis for specific SSH server instances.
Copyright (c) 2018 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 "2018-10-22" {
description
"Initial version";
reference
"RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
}
// features
feature ssh-server-transport-params-config {
description
"SSH transport layer parameters are configurable on an SSH
server.";
}
// groupings
grouping ssh-server-grouping {
description
"A reusable grouping for configuring a SSH server without
any consideration for how underlying TCP sessions are
established.";
uses server-identity-grouping;
uses client-auth-grouping;
uses transport-params-grouping;
}
grouping server-identity-grouping {
description
"A reusable grouping for configuring an SSH server identity.";
container server-identity {
description
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"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;
description
"An arbitrary name for this host-key";
}
choice host-key-type {
mandatory true;
description
"The type of host key being specified";
container public-key {
uses ks:local-or-keystore-asymmetric-key-grouping;
description
"A locally-defined or referenced asymmetric key pair
to be used for the SSH server's host key.";
reference
"RFC ZZZZ: YANG Data Model for a Centralized
Keystore Mechanism";
}
container certificate {
if-feature sshcmn:ssh-x509-certs;
uses
ks:local-or-keystore-end-entity-cert-with-key-grouping;
description
"A locally-defined or referenced end-entity
certificate to be used for the SSH server's
host key.";
reference
"RFC ZZZZ: YANG Data Model for a Centralized
Keystore Mechanism";
}
}
}
} // end server-identity
} // end server-identity-grouping
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grouping client-auth-grouping {
description
"A reusable grouping for configuring a SSH client
authentication.";
container client-cert-auth {
if-feature sshcmn:ssh-x509-certs;
description
"A reference to a list of pinned certificate authority (CA)
certificates and a reference to a list of pinned client
certificates.
Note: password and public-key based client authentication
are not configured in this YANG module as they are
expected to be configured by the ietf-system module
defined in RFC 7317.";
reference
"RFC 7317: A YANG Data Model for System Management";
leaf pinned-ca-certs {
if-feature "ta:x509-certificates";
type ta:pinned-certificates-ref;
description
"A reference to a list of certificate authority (CA)
certificates used by the SSH server to authenticate
SSH client certificates. A client certificate is
authenticated if it has a valid chain of trust to
a configured pinned CA certificate.";
reference
"RFC YYYY: YANG Data Model for Global Trust Anchors";
}
leaf pinned-client-certs {
if-feature "ta:x509-certificates";
type ta:pinned-certificates-ref;
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 pinned client certificate.";
reference
"RFC YYYY: YANG Data Model for Global Trust Anchors";
}
}
} // end client-auth-grouping
grouping transport-params-grouping {
description
"A reusable grouping for configuring a SSH transport
parameters.";
container transport-params {
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if-feature ssh-server-transport-params-config;
description
"Configurable parameters of the SSH transport layer.";
uses sshcmn:transport-params-grouping;
}
} // end transport-params-grouping
}
5. The SSH Common Model
The SSH common model presented in this section contains identities
and groupings common to both SSH clients and SSH servers. The
transport-params-grouping can be used to configure the list of SSH
transport algorithms permitted by the SSH client or SSH server. The
lists of algorithms are ordered such that, if multiple algorithms are
permitted by the client, the algorithm that appears first in its list
that is also permitted by the server is used for the SSH transport
layer connection. The ability to restrict the the algorithms allowed
is provided in this grouping for SSH clients and SSH servers that are
capable of doing so and may serve to make SSH clients and SSH servers
compliant with security policies.
[I-D.ietf-netconf-crypto-types] defines six categories of
cryptographic algorithms (hash-algorithm, symmetric-key-encryption-
algorithm, mac-algorithm, asymmetric-key-encryption-algorithm,
signature-algorithm, key-negotiation-algorithm) and lists several
widely accepted algorithms for each of them. The SSH client and
server models use one or more of these algorithms. The SSH common
model includes four parameters for configuring its permitted SSH
algorithms, which are: host-key-alg, key-exchange-alg, encryption-alg
and mac-alg. The following tables are provided, in part, to define
the subset of algorithms defined in the crypto-types model used by
SSH and, in part, to ensure compatibility of configured SSH
cryptographic parameters for configuring its permitted SSH algorithms
("sshcmn" representing SSH common model, and "ct" representing
crypto-types model which the SSH client/server model is based on):
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+-------------------------------+-------------------------------+
| sshcmn:host-key-alg | ct:signature-algorithm |
+-------------------------------+-------------------------------+
| dsa-sha1 | dsa-sha1 |
| rsa-pkcs1-sha1 | rsa-pkcs1-sha1 |
| rsa-pkcs1-sha256 | rsa-pkcs1-sha256 |
| rsa-pkcs1-sha512 | rsa-pkcs1-sha512 |
| ecdsa-secp256r1-sha256 | ecdsa-secp256r1-sha256 |
| ecdsa-secp384r1-sha384 | ecdsa-secp384r1-sha384 |
| ecdsa-secp521r1-sha512 | ecdsa-secp521r1-sha512 |
| x509v3-rsa-pkcs1-sha1 | x509v3-rsa-pkcs1-sha1 |
| x509v3-rsa2048-pkcs1-sha256 | x509v3-rsa2048-pkcs1-sha1 |
| x509v3-ecdsa-secp256r1-sha256 | x509v3-ecdsa-secp256r1-sha256 |
| x509v3-ecdsa-secp384r1-sha384 | x509v3-ecdsa-secp384r1-sha384 |
| x509v3-ecdsa-secp521r1-sha512 | x509v3-ecdsa-secp521r1-sha512 |
+-------------------------------+-------------------------------+
Table 1 The SSH Host-key-alg Compatibility Matrix
+-------------------------------+-------------------------------+
| sshcmn:key-exchange-alg | ct:key-negotiation-algorithm |
+-------------------------------+-------------------------------+
| diffie-hellman-group14-sha1 | diffie-hellman-group14-sha1 |
| diffie-hellman-group14-sha256 | diffie-hellman-group14-sha256 |
| diffie-hellman-group15-sha512 | diffie-hellman-group15-sha512 |
| diffie-hellman-group16-sha512 | diffie-hellman-group16-sha512 |
| diffie-hellman-group17-sha512 | diffie-hellman-group17-sha512 |
| diffie-hellman-group18-sha512 | diffie-hellman-group18-sha512 |
| ecdh-sha2-secp256r1 | ecdh-sha2-secp256r1 |
| ecdh-sha2-secp384r1 | ecdh-sha2-secp384r1 |
+-------------------------------+-------------------------------+
Table 2 The SSH Key-exchange-alg Compatibility Matrix
+-----------------------+---------------------------------------+
| sshcmn:encryption-alg | ct:symmetric-key-encryption-algorithm |
+-----------------------+---------------------------------------+
| aes-128-cbc | aes-128-cbc |
| aes-192-cbc | aes-192-cbc |
| aes-256-cbc | aes-256-cbc |
| aes-128-ctr | aes-128-ctr |
| aes-192-ctr | aes-192-ctr |
| aes-256-ctr | aes-256-ctr |
+-----------------------+---------------------------------------+
Table 3 The SSH Encryption-alg Compatibility Matrix
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+----------------+-------------------+
| sshcmn:mac-alg | ct:mac-algorithm |
+----------------+-------------------+
| hmac-sha1 | hmac-sha1 |
| hmac-sha1-96 | hmac-sha1-96 |
| hmac-sha2-256 | hmac-sha2-256 |
| hmac-sha2-512 | hmac-sha2-512 |
+----------------+-------------------+
Table 4 The SSH Mac-alg Compatibility Matrix
As is seen in the tables above, the names of the "sshcmn" algorithms
are all identical to the names of algorithms defined in
[I-D.ietf-netconf-crypto-types]. While appearing to be redundant, it
is important to realize that not all the algorithms defined in
[I-D.ietf-netconf-crypto-types] are supported by SSH. That is, the
algorithms supported by SSH are a subset of the algorithms defined in
[I-D.ietf-netconf-crypto-types]. The algorithms used by SSH are
redefined in this document in order to constrain the algorithms that
may be selected to just the ones used by SSH.
Features are defined for algorithms that are OPTIONAL or are not
widely supported by popular implementations. Note that the list of
algorithms is not exhaustive. As well, some algorithms that are
REQUIRED by [RFC4253] are missing, notably "ssh-dss" and "diffie-
hellman-group1-sha1" due to their weak security and there being
alternatives that are widely supported.
5.1. Tree Diagram
The following tree diagram [RFC8340] provides an overview of the data
model for the "ietf-ssh-common" module.
module: ietf-ssh-common
grouping transport-params-grouping
+-- host-key
| +-- host-key-alg* identityref
+-- key-exchange
| +-- key-exchange-alg* identityref
+-- encryption
| +-- encryption-alg* identityref
+-- mac
+-- mac-alg* identityref
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5.2. Example Usage
This following example illustrates how the transport-params-grouping
appears when populated with some data.
algs:x509v3-rsa2048-sha256
algs:ssh-rsa
algs:diffie-hellman-group-exchange-sha256
algs:aes256-ctr
algs:aes192-ctr
algs:aes128-ctr
algs:aes256-cbc
algs:aes192-cbc
algs:aes128-cbc
algs:hmac-sha2-256
algs:hmac-sha2-512
5.3. YANG Module
This YANG module has normative references to [RFC4253], [RFC4344],
[RFC4419], [RFC5656], [RFC6187], and [RFC6668].
file "ietf-ssh-common@2018-10-22.yang"
module ietf-ssh-common {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-ssh-common";
prefix "sshcmn";
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web:
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WG List:
Author: Kent Watsen
Author: Gary Wu
";
description
"This module defines a common features, identities, and
groupings for Secure Shell (SSH).
Copyright (c) 2018 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 "2018-10-22" {
description
"Initial version";
reference
"RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
}
// features
feature ssh-ecc {
description
"Elliptic Curve Cryptography is supported for SSH.";
reference
"RFC 5656: Elliptic Curve Algorithm Integration in the
Secure Shell Transport Layer";
}
feature ssh-x509-certs {
description
"X.509v3 certificates are supported for SSH per RFC 6187.";
reference
"RFC 6187: X.509v3 Certificates for Secure Shell
Authentication";
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}
feature ssh-dh-group-exchange {
description
"Diffie-Hellman Group Exchange is supported for SSH.";
reference
"RFC 4419: Diffie-Hellman Group Exchange for the
Secure Shell (SSH) Transport Layer Protocol";
}
feature ssh-ctr {
description
"SDCTR encryption mode is supported for SSH.";
reference
"RFC 4344: The Secure Shell (SSH) Transport Layer
Encryption Modes";
}
feature ssh-sha2 {
description
"The SHA2 family of cryptographic hash functions is
supported for SSH.";
reference
"FIPS PUB 180-4: Secure Hash Standard (SHS)";
}
// identities
identity public-key-alg-base {
description
"Base identity used to identify public key algorithms.";
}
identity ssh-dss {
base public-key-alg-base;
description
"Digital Signature Algorithm using SHA-1 as the
hashing algorithm.";
reference
"RFC 4253:
The Secure Shell (SSH) Transport Layer Protocol";
}
identity ssh-rsa {
base public-key-alg-base;
description
"RSASSA-PKCS1-v1_5 signature scheme using SHA-1 as the
hashing algorithm.";
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reference
"RFC 4253:
The Secure Shell (SSH) Transport Layer Protocol";
}
identity ecdsa-sha2-nistp256 {
base public-key-alg-base;
if-feature "ssh-ecc and ssh-sha2";
description
"Elliptic Curve Digital Signature Algorithm (ECDSA) using the
nistp256 curve and the SHA2 family of hashing algorithms.";
reference
"RFC 5656: Elliptic Curve Algorithm Integration in the
Secure Shell Transport Layer";
}
identity ecdsa-sha2-nistp384 {
base public-key-alg-base;
if-feature "ssh-ecc and ssh-sha2";
description
"Elliptic Curve Digital Signature Algorithm (ECDSA) using the
nistp384 curve and the SHA2 family of hashing algorithms.";
reference
"RFC 5656: Elliptic Curve Algorithm Integration in the
Secure Shell Transport Layer";
}
identity ecdsa-sha2-nistp521 {
base public-key-alg-base;
if-feature "ssh-ecc and ssh-sha2";
description
"Elliptic Curve Digital Signature Algorithm (ECDSA) using the
nistp521 curve and the SHA2 family of hashing algorithms.";
reference
"RFC 5656: Elliptic Curve Algorithm Integration in the
Secure Shell Transport Layer";
}
identity x509v3-ssh-rsa {
base public-key-alg-base;
if-feature ssh-x509-certs;
description
"RSASSA-PKCS1-v1_5 signature scheme using a public key stored
in an X.509v3 certificate and using SHA-1 as the hashing
algorithm.";
reference
"RFC 6187: X.509v3 Certificates for Secure Shell
Authentication";
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}
identity x509v3-rsa2048-sha256 {
base public-key-alg-base;
if-feature "ssh-x509-certs and ssh-sha2";
description
"RSASSA-PKCS1-v1_5 signature scheme using a public key stored
in an X.509v3 certificate and using SHA-256 as the hashing
algorithm. RSA keys conveyed using this format MUST have a
modulus of at least 2048 bits.";
reference
"RFC 6187: X.509v3 Certificates for Secure Shell
Authentication";
}
identity x509v3-ecdsa-sha2-nistp256 {
base public-key-alg-base;
if-feature "ssh-ecc and ssh-x509-certs and ssh-sha2";
description
"Elliptic Curve Digital Signature Algorithm (ECDSA)
using the nistp256 curve with a public key stored in
an X.509v3 certificate and using the SHA2 family of
hashing algorithms.";
reference
"RFC 6187: X.509v3 Certificates for Secure Shell
Authentication";
}
identity x509v3-ecdsa-sha2-nistp384 {
base public-key-alg-base;
if-feature "ssh-ecc and ssh-x509-certs and ssh-sha2";
description
"Elliptic Curve Digital Signature Algorithm (ECDSA)
using the nistp384 curve with a public key stored in
an X.509v3 certificate and using the SHA2 family of
hashing algorithms.";
reference
"RFC 6187: X.509v3 Certificates for Secure Shell
Authentication";
}
identity x509v3-ecdsa-sha2-nistp521 {
base public-key-alg-base;
if-feature "ssh-ecc and ssh-x509-certs and ssh-sha2";
description
"Elliptic Curve Digital Signature Algorithm (ECDSA)
using the nistp521 curve with a public key stored in
an X.509v3 certificate and using the SHA2 family of
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hashing algorithms.";
reference
"RFC 6187: X.509v3 Certificates for Secure Shell
Authentication";
}
identity key-exchange-alg-base {
description
"Base identity used to identify key exchange algorithms.";
}
identity diffie-hellman-group14-sha1 {
base key-exchange-alg-base;
description
"Diffie-Hellman key exchange with SHA-1 as HASH and
Oakley Group 14 (2048-bit MODP Group).";
reference
"RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
}
identity diffie-hellman-group-exchange-sha1 {
base key-exchange-alg-base;
if-feature ssh-dh-group-exchange;
description
"Diffie-Hellman Group and Key Exchange with SHA-1 as HASH.";
reference
"RFC 4419: Diffie-Hellman Group Exchange for the
Secure Shell (SSH) Transport Layer Protocol";
}
identity diffie-hellman-group-exchange-sha256 {
base key-exchange-alg-base;
if-feature "ssh-dh-group-exchange and ssh-sha2";
description
"Diffie-Hellman Group and Key Exchange with SHA-256 as HASH.";
reference
"RFC 4419: Diffie-Hellman Group Exchange for the
Secure Shell (SSH) Transport Layer Protocol";
}
identity ecdh-sha2-nistp256 {
base key-exchange-alg-base;
if-feature "ssh-ecc and ssh-sha2";
description
"Elliptic Curve Diffie-Hellman (ECDH) key exchange using the
nistp256 curve and the SHA2 family of hashing algorithms.";
reference
"RFC 5656: Elliptic Curve Algorithm Integration in the
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Secure Shell Transport Layer";
}
identity ecdh-sha2-nistp384 {
base key-exchange-alg-base;
if-feature "ssh-ecc and ssh-sha2";
description
"Elliptic Curve Diffie-Hellman (ECDH) key exchange using the
nistp384 curve and the SHA2 family of hashing algorithms.";
reference
"RFC 5656: Elliptic Curve Algorithm Integration in the
Secure Shell Transport Layer";
}
identity ecdh-sha2-nistp521 {
base key-exchange-alg-base;
if-feature "ssh-ecc and ssh-sha2";
description
"Elliptic Curve Diffie-Hellman (ECDH) key exchange using the
nistp521 curve and the SHA2 family of hashing algorithms.";
reference
"RFC 5656: Elliptic Curve Algorithm Integration in the
Secure Shell Transport Layer";
}
identity encryption-alg-base {
description
"Base identity used to identify encryption algorithms.";
}
identity triple-des-cbc {
base encryption-alg-base;
description
"Three-key 3DES in CBC mode.";
reference
"RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
}
identity aes128-cbc {
base encryption-alg-base;
description
"AES in CBC mode, with a 128-bit key.";
reference
"RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
}
identity aes192-cbc {
base encryption-alg-base;
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description
"AES in CBC mode, with a 192-bit key.";
reference
"RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
}
identity aes256-cbc {
base encryption-alg-base;
description
"AES in CBC mode, with a 256-bit key.";
reference
"RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
}
identity aes128-ctr {
base encryption-alg-base;
if-feature ssh-ctr;
description
"AES in SDCTR mode, with 128-bit key.";
reference
"RFC 4344: The Secure Shell (SSH) Transport Layer Encryption
Modes";
}
identity aes192-ctr {
base encryption-alg-base;
if-feature ssh-ctr;
description
"AES in SDCTR mode, with 192-bit key.";
reference
"RFC 4344: The Secure Shell (SSH) Transport Layer Encryption
Modes";
}
identity aes256-ctr {
base encryption-alg-base;
if-feature ssh-ctr;
description
"AES in SDCTR mode, with 256-bit key.";
reference
"RFC 4344: The Secure Shell (SSH) Transport Layer Encryption
Modes";
}
identity mac-alg-base {
description
"Base identity used to identify message authentication
code (MAC) algorithms.";
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}
identity hmac-sha1 {
base mac-alg-base;
description
"HMAC-SHA1";
reference
"RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
}
identity hmac-sha2-256 {
base mac-alg-base;
if-feature "ssh-sha2";
description
"HMAC-SHA2-256";
reference
"RFC 6668: SHA-2 Data Integrity Verification for the
Secure Shell (SSH) Transport Layer Protocol";
}
identity hmac-sha2-512 {
base mac-alg-base;
if-feature "ssh-sha2";
description
"HMAC-SHA2-512";
reference
"RFC 6668: SHA-2 Data Integrity Verification for the
Secure Shell (SSH) Transport Layer Protocol";
}
// groupings
grouping transport-params-grouping {
description
"A reusable grouping for SSH transport parameters.";
reference
"RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
container host-key {
description
"Parameters regarding host key.";
leaf-list host-key-alg {
type identityref {
base public-key-alg-base;
}
ordered-by user;
description
"Acceptable host key algorithms in order of descending
preference. The configured host key algorithms should
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be compatible with the algorithm used by the configured
private key. Please see Section 5 of RFC XXXX for
valid combinations.
If this leaf-list is not configured (has zero elements)
the acceptable host key algorithms are implementation-
defined.";
reference
"RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
}
}
container key-exchange {
description
"Parameters regarding key exchange.";
leaf-list key-exchange-alg {
type identityref {
base key-exchange-alg-base;
}
ordered-by user;
description
"Acceptable key exchange algorithms in order of descending
preference.
If this leaf-list is not configured (has zero elements)
the acceptable key exchange algorithms are implementation
defined.";
}
}
container encryption {
description
"Parameters regarding encryption.";
leaf-list encryption-alg {
type identityref {
base encryption-alg-base;
}
ordered-by user;
description
"Acceptable encryption algorithms in order of descending
preference.
If this leaf-list is not configured (has zero elements)
the acceptable encryption algorithms are implementation
defined.";
}
}
container mac {
description
"Parameters regarding message authentication code (MAC).";
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leaf-list mac-alg {
type identityref {
base mac-alg-base;
}
ordered-by user;
description
"Acceptable MAC algorithms in order of descending
preference.
If this leaf-list is not configured (has zero elements)
the acceptable MAC algorithms are implementation-
defined.";
}
}
} // transport-params-grouping
}
6. Security Considerations
The YANG modules defined in this document are designed to be accessed
via YANG based management protocols, such as NETCONF [RFC6241] and
RESTCONF [RFC8040]. Both of these protocols have mandatory-to-
implement secure transport layers (e.g., SSH, TLS) with mutual
authentication.
The NETCONF access control model (NACM) [RFC8341] provides the means
to restrict access for particular users to a pre-configured subset of
all available protocol operations and content.
Since the modules defined in this document define only groupings,
these considerations are primarily for the designers of other modules
that use these groupings.
There are a number of data nodes defined in the YANG modules that 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 operations (e.g., edit-config)
to these data nodes without proper protection can have a negative
effect on network operations. These are the subtrees and data nodes
and their sensitivity/vulnerability:
/: The entire data tree defined by all the modules defined in this
draft are sensitive to write operations. For instance, the
addition or removal of references to keys, certificates,
trusted anchors, etc., can dramatically alter the implemented
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security policy. However, no NACM annotations are applied as
the data SHOULD be editable by users other than a designated
'recovery session'.
Some of the readable data nodes in the YANG modules may be considered
sensitive or vulnerable in some network environments. It is thus
important to control read access (e.g., via get, get-config, or
notification) to these data nodes. These are the subtrees and data
nodes and their sensitivity/vulnerability:
/client-auth/password: This node in the 'ietf-ssh-client' module
is additionally sensitive to read operations such that, in
normal use cases, it should never be returned to a client. The
only time this node should be returned is to support backup/
restore type workflows. However, no NACM annotations are
applied as the data SHOULD be writable by users other than a
designated 'recovery session'.
Some of the RPC operations in this YANG module may be considered
sensitive or vulnerable in some network environments. It is thus
important to control access to these operations. These are the
operations and their sensitivity/vulnerability:
NONE
7. IANA Considerations
7.1. The IETF XML Registry
This document registers three URIs in the "ns" subregistry of the
IETF XML Registry [RFC3688]. 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.
URI: urn:ietf:params:xml:ns:yang:ietf-ssh-common
Registrant Contact: The NETCONF WG of the IETF.
XML: N/A, the requested URI is an XML namespace.
7.2. The YANG Module Names Registry
This document registers three YANG modules in the YANG Module Names
registry [RFC6020]. Following the format in [RFC6020], the the
following registrations are requested:
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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
name: ietf-ssh-common
namespace: urn:ietf:params:xml:ns:yang:ietf-ssh-common
prefix: sshcmn
reference: RFC XXXX
8. References
8.1. Normative References
[I-D.ietf-netconf-crypto-types]
Watsen, K., "Common YANG Data Types for Cryptography",
draft-ietf-netconf-crypto-types-01 (work in progress),
September 2018.
[I-D.ietf-netconf-keystore]
Watsen, K., "YANG Data Model for a Centralized Keystore
Mechanism", draft-ietf-netconf-keystore-06 (work in
progress), September 2018.
[I-D.ietf-netconf-trust-anchors]
Watsen, K., "YANG Data Model for Global Trust Anchors",
draft-ietf-netconf-trust-anchors-01 (work in progress),
September 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
.
[RFC4344] Bellare, M., Kohno, T., and C. Namprempre, "The Secure
Shell (SSH) Transport Layer Encryption Modes", RFC 4344,
DOI 10.17487/RFC4344, January 2006,
.
[RFC4419] Friedl, M., Provos, N., and W. Simpson, "Diffie-Hellman
Group Exchange for the Secure Shell (SSH) Transport Layer
Protocol", RFC 4419, DOI 10.17487/RFC4419, March 2006,
.
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[RFC5656] Stebila, D. and J. Green, "Elliptic Curve Algorithm
Integration in the Secure Shell Transport Layer",
RFC 5656, DOI 10.17487/RFC5656, December 2009,
.
[RFC6020] Bjorklund, M., Ed., "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, .
[RFC6668] Bider, D. and M. Baushke, "SHA-2 Data Integrity
Verification for the Secure Shell (SSH) Transport Layer
Protocol", RFC 6668, DOI 10.17487/RFC6668, July 2012,
.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, .
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
.
8.2. Informative References
[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, Ed., "The Secure Shell (SSH)
Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252,
January 2006, .
[RFC4253] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253,
January 2006, .
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[RFC4254] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Connection Protocol", RFC 4254, DOI 10.17487/RFC4254,
January 2006, .
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
.
[RFC7317] Bierman, A. and M. Bjorklund, "A YANG Data Model for
System Management", RFC 7317, DOI 10.17487/RFC7317, August
2014, .
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
.
[RFC8071] Watsen, K., "NETCONF Call Home and RESTCONF Call Home",
RFC 8071, DOI 10.17487/RFC8071, February 2017,
.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
.
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Appendix A. Change Log
A.1. 00 to 01
o Noted that '0.0.0.0' and '::' might have special meanings.
o Renamed "keychain" to "keystore".
A.2. 01 to 02
o Removed the groupings 'listening-ssh-client-grouping' and
'listening-ssh-server-grouping'. Now modules only contain the
transport-independent groupings.
o Simplified the "client-auth" part in the ietf-ssh-client module.
It now inlines what it used to point to keystore for.
o Added cipher suites for various algorithms into new 'ietf-ssh-
common' module.
A.3. 02 to 03
o Removed 'RESTRICTED' enum from 'password' leaf type.
o Added a 'must' statement to container 'server-auth' asserting that
at least one of the various auth mechanisms must be specified.
o Fixed description statement for leaf 'trusted-ca-certs'.
A.4. 03 to 04
o Change title to "YANG Groupings for SSH Clients and SSH Servers"
o Added reference to RFC 6668
o Added RFC 8174 to Requirements Language Section.
o Enhanced description statement for ietf-ssh-server's "trusted-ca-
certs" leaf.
o Added mandatory true to ietf-ssh-client's "client-auth" 'choice'
statement.
o Changed the YANG prefix for module ietf-ssh-common from 'sshcom'
to 'sshcmn'.
o Removed the compression algorithms as they are not commonly
configurable in vendors' implementations.
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o Updating descriptions in transport-params-grouping and the
servers's usage of it.
o Now tree diagrams reference ietf-netmod-yang-tree-diagrams
o Updated YANG to use typedefs around leafrefs to common keystore
paths
o Now inlines key and certificates (no longer a leafref to keystore)
A.5. 04 to 05
o Merged changes from co-author.
A.6. 05 to 06
o Updated to use trust anchors from trust-anchors draft (was
keystore draft)
o Now uses new keystore grouping enabling asymmetric key to be
either locally defined or a reference to the keystore.
A.7. 06 to 07
o factored the ssh-[client|server]-groupings into more reusable
groupings.
o added if-feature statements for the new "ssh-host-keys" and
"x509-certificates" features defined in draft-ietf-netconf-trust-
anchors.
A.8. 07 to 08
o Added a number of compatibility matricies to Section 5 (thanks
Frank!)
o Claified that any configured "host-key-alg" values need to be
compatible with the configured private key.
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, Mehmet Ersue, Balazs Kovacs, David
Lamparter, Alan Luchuk, Ladislav Lhotka, Radek Krejci, Tom Petch,
Juergen Schoenwaelder, Phil Shafer, Sean Turner, Michal Vasko, and
Bert Wijnen.
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Authors' Addresses
Kent Watsen
Juniper Networks
EMail: kwatsen@juniper.net
Gary Wu
Cisco Systems
EMail: garywu@cisco.com
Liang Xia
Huawei
EMail: frank.xialiang@huawei.com
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