| NETCONF Working Group | K. Watsen |
| Internet-Draft | Juniper Networks |
| Intended status: Standards Track | G. Wu |
| Expires: December 15, 2017 | Cisco Systems |
| June 13, 2017 |
SSH Client and Server Models
draft-ietf-netconf-ssh-client-server-03
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.
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 Appendix section is 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 December 15, 2017.
Copyright (c) 2017 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 three YANG [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 (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 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 enables 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 grouping for the SSH parts it provides, while adding data nodes for the TCP-level call-home configuration.
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 one YANG grouping, to just configure the SSH client omitting, for instance, any configuration for which IP address or port the client should connect to.
This grouping references data nodes defined by the keystore model [I-D.ietf-netconf-keystore]. For instance, a reference to the keystore 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 grouping defined in the ietf-ssh-client module. Please see Section 1.2 for tree diagram notation.
module: ietf-ssh-client
groupings:
ssh-client-grouping
+---- server-auth
| +---- trusted-ssh-host-keys?
| | -> /ks:keystore/trusted-host-keys/name
| +---- trusted-ca-certs?
| | -> /ks:keystore/trusted-certificates/name
| | {sshcom:ssh-x509-certs}?
| +---- trusted-server-certs?
| -> /ks:keystore/trusted-certificates/name
| {sshcom:ssh-x509-certs}?
+---- client-auth
| +---- username? string
| +---- (auth-type)?
| +--:(certificate)
| | +---- certificate? leafref {sshcom:ssh-x509-certs}?
| +--:(public-key)
| | +---- public-key? -> /ks:keystore/keys/key/name
| +--:(password)
| +---- password? string
+---- transport-params {ssh-client-transport-params-config}?
+---- host-key
| +---- host-key-alg* identityref
+---- key-exchange
| +---- key-exchange-alg* identityref
+---- encryption
| +---- encryption-alg* identityref
+---- mac
| +---- mac-alg* identityref
+---- compression
+---- compression-alg* identityref
This section shows how it would appear if the ssh-client-grouping were populated with some data. This example is consistent with the examples presented in Section 2.2 of [I-D.ietf-netconf-keystore].
<!-- hypothetical example, as groupings don't have instance data -->
<ssh-client xmlns="urn:ietf:params:xml:ns:yang:ietf-ssh-client">
<!-- which host-keys will this client trust -->
<server-auth>
<trusted-ssh-host-keys>explicitly-trusted-ssh-host-keys</trusted-ssh-host-keys>
</server-auth>
<!-- how this client will authenticate itself to the server -->
<client-auth>
<username>foobar</username>
<public-key>ex-rsa-key</public-key>
</client-auth>
</ssh-client>
This YANG module has a normative references to [RFC6991] and [I-D.ietf-netconf-keystore].
<CODE BEGINS> file "ietf-ssh-client@2017-06-13.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 sshcom;
revision-date 2017-06-13; // stable grouping definitions
reference
"RFC XXXX: SSH Client and Server Models";
}
import ietf-netconf-acm {
prefix nacm;
reference
"RFC 6536: Network Configuration Protocol (NETCONF) Access
Control Model";
}
import ietf-keystore {
prefix ks;
reference
"RFC YYYY: Keystore Model";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
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 "2017-06-13" {
description
"Initial version";
reference
"RFC XXXX: SSH Client and Server Models";
}
feature ssh-client-transport-params-config {
description
"SSH transport layer parameters are configurable on an SSH
client.";
}
grouping ssh-client-grouping {
description
"A reusable grouping for configuring a SSH client without
any consideration for how an underlying TCP session is
established.";
container server-auth {
must 'trusted-ssh-host-keys or trusted-ca-certs or trusted-server-certs';
description
"Trusted server identities.";
leaf trusted-ssh-host-keys {
type leafref {
path "/ks:keystore/ks:trusted-host-keys/ks: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 sshcom:ssh-x509-certs;
type leafref {
path "/ks:keystore/ks:trusted-certificates/ks:name";
}
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 trusted CA certificate.";
}
leaf trusted-server-certs {
if-feature sshcom:ssh-x509-certs;
type leafref {
path "/ks:keystore/ks:trusted-certificates/ks: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.";
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 {
description
"The authentication type.";
leaf certificate {
if-feature sshcom:ssh-x509-certs;
type leafref {
path "/ks:keystore/ks:keys/ks:key/ks:certificates/"
+ "ks:certificate/ks:name";
}
description
"A certificates to be used for user authentication.";
}
leaf public-key {
type leafref {
path "/ks:keystore/ks:keys/ks:key/ks:name";
}
description
"A public keys to be used for user authentication.";
}
leaf password {
nacm:default-deny-all;
type string;
description
"A password to be used for user authentication.";
}
}
} // end client-auth
container transport-params {
if-feature ssh-client-transport-params-config;
uses sshcom:transport-params-grouping;
description
"Configurable parameters for the SSH transport layer.";
}
} // ssh-client-grouping
}
<CODE ENDS>
The SSH server model presented in this section contains one YANG grouping, for just the SSH-level configuration omitting, for instance, configuration for which ports to open to listen for connections on.
This grouping references data nodes defined by the keystore model [I-D.ietf-netconf-keystore]. For instance, a reference to the keystore model is made to indicate which host key a server should present.
The following tree diagram presents the data model for the grouping defined in the ietf-ssh-server module. Please see Section 1.2 for tree diagram notation.
module: ietf-ssh-server
groupings:
ssh-server-grouping
+---- host-keys
| +---- host-key* [name]
| +---- name? string
| +---- (host-key-type)
| +--:(public-key)
| | +---- public-key? -> /ks:keystore/keys/key/name
| +--:(certificate)
| +---- certificate? leafref {sshcom:ssh-x509-certs}?
+---- client-cert-auth {sshcom:ssh-x509-certs}?
| +---- trusted-ca-certs?
| | -> /ks:keystore/trusted-certificates/name
| +---- trusted-client-certs?
| -> /ks:keystore/trusted-certificates/name
+---- transport-params {ssh-server-transport-params-config}?
+---- host-key
| +---- host-key-alg* identityref
+---- key-exchange
| +---- key-exchange-alg* identityref
+---- encryption
| +---- encryption-alg* identityref
+---- mac
| +---- mac-alg* identityref
+---- compression
+---- compression-alg* identityref
This section shows how it would appear if the ssh-server-grouping were populated with some data. This example is consistent with the examples presented in Section 2.2 of [I-D.ietf-netconf-keystore].
<!-- hypothetical example, as groupings don't have instance data -->
<ssh-server xmlns="urn:ietf:params:xml:ns:yang:ietf-ssh-server">
<!-- which host-keys will this SSH server present -->
<host-keys>
<host-key>
<name>deployment-specific-certificate</name>
<certificate>ex-rsa-cert</certificate>
</host-key>
</host-keys>
<!-- NOTE: password/public-key auth is NOT configured here, -->
<!-- as it is configured in the ietf-system (RFC 7317) -->
<!-- module instead. -->
<!-- which client-certs will this SSH server trust -->
<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>
</ssh-server>
This YANG module has a normative references to [RFC4253], [RFC6991], and [I-D.ietf-netconf-keystore].
<CODE BEGINS> file "ietf-ssh-server@2017-06-13.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 sshcom;
revision-date 2017-06-13; // stable grouping definitions
reference
"RFC XXXX: SSH Client and Server Models";
}
import ietf-keystore {
prefix ks;
reference
"RFC YYYY: Keystore Model";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
Author: 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 "2017-06-13" {
description
"Initial version";
reference
"RFC XXXX: SSH Client and Server Models";
}
// features
feature ssh-server-transport-params-config {
description
"SSH transport layer parameters are configurable on an SSH
server.";
}
// grouping
grouping ssh-server-grouping {
description
"A reusable grouping for configuring a SSH server without
any consideration for how underlying TCP sessions are
established.";
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;
description
"An arbitrary name for this host-key";
}
choice host-key-type {
mandatory true;
description
"The type of host key being specified";
leaf public-key {
type leafref {
path "/ks:keystore/ks:keys/ks:key/ks:name";
}
description
"The public key is actually identified by the name of
its cooresponding private-key in the keystore.";
}
leaf certificate {
if-feature sshcom:ssh-x509-certs;
type leafref {
path "/ks:keystore/ks:keys/ks:key/ks:certificates/"
+ "ks:certificate/ks:name";
}
description
"The name of a certificate in the keystore.";
}
}
}
}
container client-cert-auth {
if-feature sshcom: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 "/ks:keystore/ks:trusted-certificates/ks: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 "/ks:keystore/ks:trusted-certificates/ks: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.";
}
}
container transport-params {
if-feature ssh-server-transport-params-config;
uses sshcom:transport-params-grouping;
description
"Configurable parameters for the SSH transport layer.";
}
} // ssh-server-grouping
}
<CODE ENDS>
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.
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.
The following tree diagram presents the data model for the grouping defined in the ietf-ssh-common module. Please see Section 1.2 for tree diagram notation.
module: ietf-ssh-common
groupings:
transport-params-grouping
+---- host-key
| +---- host-key-alg* identityref
+---- key-exchange
| +---- key-exchange-alg* identityref
+---- encryption
| +---- encryption-alg* identityref
+---- mac
| +---- mac-alg* identityref
+---- compression
+---- compression-alg* identityref
This section shows how it would appear if the transport-params-grouping were populated with some data.
<!-- hypothetical example, as groupings don't have instance data -->
<transport-params xmlns="urn:ietf:params:xml:ns:yang:ietf-ssh-common">
<host-key>
<host-key-alg>x509v3-rsa2048-sha256</host-key-alg>
<host-key-alg>ssh-rsa</host-key-alg>
</host-key>
<key-exchange>
<key-exchange-alg>
diffie-hellman-group-exchange-sha256
</key-exchange-alg>
</key-exchange>
<encryption>
<encryption-alg>aes256-ctr</encryption-alg>
<encryption-alg>aes192-ctr</encryption-alg>
<encryption-alg>aes128-ctr</encryption-alg>
<encryption-alg>aes256-cbc</encryption-alg>
<encryption-alg>aes192-cbc</encryption-alg>
<encryption-alg>aes128-cbc</encryption-alg>
</encryption>
<mac>
<mac-alg>hmac-sha2-256</mac-alg>
<mac-alg>hmac-sha2-512</mac-alg>
</mac>
<compression>
<compression-alg>none</compression-alg>
</compression>
</transport-params>
This YANG module has a normative references to [RFC4344], [RFC4419], and [RFC5656].
<CODE BEGINS> file "ietf-ssh-common@2017-06-13.yang"
module ietf-ssh-common {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-ssh-common";
prefix "sshcom";
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
Author: Kent Watsen
<mailto:kwatsen@juniper.net>
Author: Gary Wu
<mailto:garywu@cisco.com>";
description
"This module defines a common features, identities, and groupings
for Secure Shell (SSH).
Copyright (c) 2017 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 "2017-06-13" {
description
"Initial version";
reference
"RFC XXXX: SSH Client and Server Models";
}
// 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 as per RFC 6187.";
reference
"RFC 6187: X.509v3 Certificates for Secure Shell
Authentication";
}
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)";
}
feature ssh-zlib {
description
"ZLIB (LZ77) compression is supported for SSH.";
reference
"RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
}
// 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.";
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";
}
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 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
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;
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.";
}
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";
}
identity compression-alg-base {
description
"Base identity used to identify compression algorithms.";
}
identity none {
base compression-alg-base;
description
"No compression.";
reference
"RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
}
identity zlib {
base compression-alg-base;
if-feature ssh-zlib;
description
"ZLIB (LZ77) compression.";
reference
"RFC 4253: The Secure Shell (SSH) Transport Layer Protocol";
}
// groupings
grouping transport-params-grouping {
description
"A reusable grouping for SSH transport parameters.
For configurable parameters, a zero-element leaf-list of
algorithms indicates the system default configuration for that
parameter.";
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
"Host key algorithms in order of descending preference.";
}
}
container key-exchange {
description
"Parameters regarding key exchange.";
leaf-list key-exchange-alg {
type identityref {
base key-exchange-alg-base;
}
ordered-by user;
description
"Key exchange algorithms in order of descending
preference.";
}
}
container encryption {
description
"Parameters regarding encryption.";
leaf-list encryption-alg {
type identityref {
base encryption-alg-base;
}
ordered-by user;
description
"Encryption algorithms in order of descending preference.";
}
}
container mac {
description
"Parameters regarding message authentication code (MAC).";
leaf-list mac-alg {
type identityref {
base mac-alg-base;
}
ordered-by user;
description
"MAC algorithms in order of descending preference.";
}
}
container compression {
description
"Parameters regarding compression.";
leaf-list compression-alg {
type identityref {
base compression-alg-base;
}
ordered-by user;
description
"Compression algorithms in order of descending preference.";
}
}
}
}
<CODE ENDS>
The YANG module defined in this document is 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) [RFC6536] provides the means to restrict access for particular users to a pre-configured subset of all available protocol operations and content.
There are a number of data nodes defined in this YANG module 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:
Some of the readable data nodes in this YANG module 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:
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:
This document registers three URIs in 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.
This document registers three YANG modules in the YANG Module Names registry [RFC7950]. Following the format in [RFC7950], 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 name: ietf-ssh-common namespace: urn:ietf:params:xml:ns:yang:ietf-ssh-common prefix: sshcom 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, Balázs Kovács, David Lamparter, Alan Luchuk, Ladislav Lhotka, Radek Krejci, Tom Petch, Juergen Schoenwaelder, Phil Shafer, Sean Turner, Michal Vaško, and Bert Wijnen.
| [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. |
| [RFC6241] | Enns, R., Bjorklund, M., Schoenwaelder, J. and A. Bierman, "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. |
| [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. |