| Internet-Draft | Groupings for SSH Clients and Servers | July 2020 |
| Watsen & Wu | Expires 9 January 2021 | [Page] |
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 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.¶
Artwork in this document contains shorthand references to drafts in progress. Please apply the following replacements:¶
AAAA --> the assigned RFC value for draft-ietf-netconf-crypto-types¶
BBBB --> the assigned RFC value for draft-ietf-netconf-trust-anchors¶
CCCC --> the assigned RFC value for draft-ietf-netconf-keystore¶
DDDD --> the assigned RFC value for draft-ietf-netconf-tcp-client-server¶
EEEE --> the assigned RFC value for this draft¶
Artwork in this document contains placeholder values for the date of publication of this draft. Please apply the following replacement:¶
2020-07-08 --> the publication date of this draft¶
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 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 9 January 2021.¶
Copyright (c) 2020 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.¶
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.¶
The modules defined in this document use 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.¶
This document presents one or more YANG modules [RFC7950] that are part of a collection of RFCs that work together to define configuration modules for clients and servers of both the NETCONF [RFC6241] and RESTCONF [RFC8040] protocols.¶
The modules have been defined in a modular fashion to enable their use by other efforts, some of which are known to be in progress at the time of this writing, with many more expected to be defined in time.¶
The relationship between the various RFCs in the collection is presented in the below diagram. The labels in the diagram represent the primary purpose provided by each RFC. Links the each RFC are provided below the diagram.¶
crypto-types
^ ^
/ \
/ \
truststore keystore
^ ^ ^ ^
| +---------+ | |
| | | |
| +------------+ |
tcp-client-server | / | |
^ ^ ssh-client-server | |
| | ^ tls-client-server
| | | ^ ^ http-client-server
| | | | | ^
| | | +-----+ +---------+ |
| | | | | |
| +-----------|--------|--------------+ | |
| | | | | |
+-----------+ | | | | |
| | | | | |
| | | | | |
netconf-client-server restconf-client-server
¶
| Label in Diagram | Originating RFC |
|---|---|
| crypto-types | [I-D.ietf-netconf-crypto-types] |
| truststore | [I-D.ietf-netconf-trust-anchors] |
| keystore | [I-D.ietf-netconf-keystore] |
| tcp-client-server | [I-D.ietf-netconf-tcp-client-server] |
| ssh-client-server | [I-D.ietf-netconf-ssh-client-server] |
| tls-client-server | [I-D.ietf-netconf-tls-client-server] |
| http-client-server | [I-D.ietf-netconf-http-client-server] |
| netconf-client-server | [I-D.ietf-netconf-netconf-client-server] |
| restconf-client-server | [I-D.ietf-netconf-restconf-client-server] |
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.¶
This document in compliant with the Network Management Datastore Architecture (NMDA) [RFC8342]. For instance, as described in [I-D.ietf-netconf-trust-anchors] and [I-D.ietf-netconf-keystore], trust anchors and keys installed during manufacturing are expected to appear in <operational>.¶
The SSH common model presented in this section contains identities and groupings common to both SSH clients and SSH servers. The "transport-params-grouping" 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 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 diagram lists all the "feature" statements defined in the "ietf-ssh-common" module:¶
Features: +-- ssh-ecc +-- ssh-x509-certs +-- ssh-dh-group-exchange +-- ssh-ctr +-- ssh-sha2¶
The following diagram illustrates the relationship amongst the "identity" statements defined in the "ietf-ssh-common" module:¶
Identities:
+-- public-key-alg-base
| +-- ssh-dss
| +-- ssh-rsa
| +-- ecdsa-sha2-nistp256
| +-- ecdsa-sha2-nistp384
| +-- ecdsa-sha2-nistp521
| +-- x509v3-ssh-rsa
| +-- x509v3-rsa2048-sha256
| +-- x509v3-ecdsa-sha2-nistp256
| +-- x509v3-ecdsa-sha2-nistp384
| +-- x509v3-ecdsa-sha2-nistp521
+-- key-exchange-alg-base
| +-- diffie-hellman-group14-sha1
| +-- diffie-hellman-group-exchange-sha1
| +-- diffie-hellman-group-exchange-sha256
| +-- ecdh-sha2-nistp256
| +-- ecdh-sha2-nistp384
| +-- ecdh-sha2-nistp521
+-- encryption-alg-base
| +-- triple-des-cbc
| +-- aes128-cbc
| +-- aes192-cbc
| +-- aes256-cbc
| +-- aes128-ctr
| +-- aes192-ctr
| +-- aes256-ctr
+-- mac-alg-base
+-- hmac-sha1
+-- hmac-sha2-256
+-- hmac-sha2-512
¶
Comments:¶
The following diagram lists all the "grouping" statements defined in the "ietf-ssh-common" module:¶
Groupings: +-- transport-params-grouping¶
Each of these groupings are presented in the following subsections.¶
The following tree diagram [RFC8340] illustrates the "transport-params-grouping" grouping:¶
grouping transport-params-grouping
+-- host-key
| +-- host-key-alg* identityref
+-- key-exchange
| +-- key-exchange-alg* identityref
+-- encryption
| +-- encryption-alg* identityref
+-- mac
+-- mac-alg* identityref
¶
Comments:¶
The "ietf-ssh-common" module does not contain any protocol-accessible nodes, but the module needs to be "implemented", as described in Section 5.6.5 of [RFC7950], in order for the identities in Section 2.1.2 to be defined.¶
This following example illustrates how the "transport-params-grouping' grouping appears when populated with some data.¶
<transport-params
xmlns="urn:ietf:params:xml:ns:yang:ietf-ssh-common"
xmlns:algs="urn:ietf:params:xml:ns:yang:ietf-ssh-common">
<host-key>
<host-key-alg>algs:x509v3-rsa2048-sha256</host-key-alg>
<host-key-alg>algs:ssh-rsa</host-key-alg>
</host-key>
<key-exchange>
<key-exchange-alg>
algs:diffie-hellman-group-exchange-sha256
</key-exchange-alg>
</key-exchange>
<encryption>
<encryption-alg>algs:aes256-ctr</encryption-alg>
<encryption-alg>algs:aes192-ctr</encryption-alg>
<encryption-alg>algs:aes128-ctr</encryption-alg>
<encryption-alg>algs:aes256-cbc</encryption-alg>
<encryption-alg>algs:aes192-cbc</encryption-alg>
<encryption-alg>algs:aes128-cbc</encryption-alg>
</encryption>
<mac>
<mac-alg>algs:hmac-sha2-256</mac-alg>
<mac-alg>algs:hmac-sha2-512</mac-alg>
</mac>
</transport-params>
¶
This YANG module has normative references to [RFC4253], [RFC4344], [RFC4419], [RFC5656], [RFC6187], and [RFC6668].¶
<CODE BEGINS> file "ietf-ssh-common@2020-07-08.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: <http://datatracker.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
Author: Kent Watsen <mailto:kent+ietf@watsen.net>
Author: Gary Wu <mailto:garywu@cisco.com>";
description
"This module defines a common features, identities, and
groupings for Secure Shell (SSH).
Copyright (c) 2020 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
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC EEEE
(https://www.rfc-editor.org/info/rfcEEEE); see the RFC
itself for full legal notices.;
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 (RFC 2119)
(RFC 8174) when, and only when, they appear in all
capitals, as shown here.";
revision 2020-07-08 {
description
"Initial version";
reference
"RFC EEEE: 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";
}
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.";
reference
"RFC 4253:
The Secure Shell (SSH) Transport Layer Protocol";
}
identity ecdsa-sha2-nistp256 {
if-feature "ssh-ecc and ssh-sha2";
base public-key-alg-base;
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 {
if-feature "ssh-ecc and ssh-sha2";
base public-key-alg-base;
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 {
if-feature "ssh-ecc and ssh-sha2";
base public-key-alg-base;
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 {
if-feature "ssh-x509-certs";
base public-key-alg-base;
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 {
if-feature "ssh-x509-certs and ssh-sha2";
base public-key-alg-base;
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 {
if-feature "ssh-ecc and ssh-x509-certs and ssh-sha2";
base public-key-alg-base;
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 {
if-feature "ssh-ecc and ssh-x509-certs and ssh-sha2";
base public-key-alg-base;
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 {
if-feature "ssh-ecc and ssh-x509-certs and ssh-sha2";
base public-key-alg-base;
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 {
if-feature "ssh-dh-group-exchange";
base key-exchange-alg-base;
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 {
if-feature "ssh-dh-group-exchange and ssh-sha2";
base key-exchange-alg-base;
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 {
if-feature "ssh-ecc and ssh-sha2";
base key-exchange-alg-base;
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 {
if-feature "ssh-ecc and ssh-sha2";
base key-exchange-alg-base;
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 {
if-feature "ssh-ecc and ssh-sha2";
base key-exchange-alg-base;
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 {
if-feature "ssh-ctr";
base encryption-alg-base;
description
"AES in SDCTR mode, with 128-bit key.";
reference
"RFC 4344: The Secure Shell (SSH) Transport Layer Encryption
Modes";
}
identity aes192-ctr {
if-feature "ssh-ctr";
base encryption-alg-base;
description
"AES in SDCTR mode, with 192-bit key.";
reference
"RFC 4344: The Secure Shell (SSH) Transport Layer Encryption
Modes";
}
identity aes256-ctr {
if-feature "ssh-ctr";
base encryption-alg-base;
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 {
if-feature "ssh-sha2";
base mac-alg-base;
description
"HMAC-SHA2-256";
reference
"RFC 6668: SHA-2 Data Integrity Verification for the
Secure Shell (SSH) Transport Layer Protocol";
}
identity hmac-sha2-512 {
if-feature "ssh-sha2";
base mac-alg-base;
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
be compatible with the algorithm used by the configured
private key. Please see Section 5 of RFC EEEE for
valid combinations.
If this leaf-list is not configured (has zero elements)
the acceptable host key algorithms are implementation-
defined.";
reference
"RFC EEEE: 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).";
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.";
}
}
}
}
¶
<CODE ENDS>¶
The following diagram lists all the "feature" statements defined in the "ietf-ssh-client" module:¶
Features: +-- ssh-client-transport-params-config +-- ssh-client-keepalives +-- client-identity-password +-- client-identity-publickey +-- client-identity-hostbased +-- client-identity-none¶
The following diagram lists all the "grouping" statements defined in the "ietf-ssh-client" module:¶
Groupings: +-- ssh-client-grouping¶
Each of these groupings are presented in the following subsections.¶
The following tree diagram [RFC8340] illustrates the "ssh-client-grouping" grouping:¶
=============== NOTE: '\' line wrapping per RFC 8792 ================
grouping ssh-client-grouping
+-- client-identity
| +-- username? string
| +-- public-key! {client-identity-publickey}?
| | +---u ks:local-or-keystore-asymmetric-key-grouping
| +-- password? string {client-identity-password}?
| +-- hostbased! {client-identity-hostbased}?
| | +---u ks:local-or-keystore-asymmetric-key-grouping
| +-- none? empty {client-identity-none}?
| +-- certificate! {sshcmn:ssh-x509-certs}?
| +---u ks:local-or-keystore-end-entity-cert-with-key-groupi\
ng
+-- server-authentication
| +-- ssh-host-keys!
| | +---u ts:local-or-truststore-public-keys-grouping
| +-- ca-certs! {sshcmn:ssh-x509-certs}?
| | +---u ts:local-or-truststore-certs-grouping
| +-- ee-certs! {sshcmn:ssh-x509-certs}?
| +---u ts:local-or-truststore-certs-grouping
+-- transport-params {ssh-client-transport-params-config}?
| +---u sshcmn:transport-params-grouping
+-- keepalives! {ssh-client-keepalives}?
+-- max-wait? uint16
+-- max-attempts? uint8
¶
Comments:¶
For the referenced grouping statement(s):¶
This section presents two examples showing the "ssh-client-grouping" 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 2 of [I-D.ietf-netconf-trust-anchors] and Section 3.2 of [I-D.ietf-netconf-keystore].¶
The following configuration example uses local-definitions for the client identity and server authentication:¶
=============== NOTE: '\\' line wrapping per RFC 8792 ===============
<ssh-client
xmlns="urn:ietf:params:xml:ns:yang:ietf-ssh-client"
xmlns:ct="urn:ietf:params:xml:ns:yang:ietf-crypto-types"
xmlns:algs="urn:ietf:params:xml:ns:yang:ietf-ssh-common">
<!-- how this client will authenticate itself to the server -->
<client-identity>
<username>foobar</username>
<public-key>
<local-definition>
<public-key-format>ct:ssh-public-key-format</public-key-form\
\at>
<public-key>base64encodedvalue==</public-key>
<private-key-format>ct:rsa-private-key-format</private-key-f\
\ormat>
<private-key>base64encodedvalue==</private-key>
</local-definition>
</public-key>
</client-identity>
<!-- which host keys will this client trust -->
<server-authentication>
<ssh-host-keys>
<local-definition> <!-- FIXME: float 'local-def' down to each?\
\ -->
<!--<ssh-public-key>-->
<public-key>
<name>corp-fw1</name>
<public-key-format>ct:ssh-public-key-format</public-key-fo\
\rmat>
<public-key>base64encodedvalue==</public-key>
<!--
</ssh-public-key>
<ssh-public-key>
-->
</public-key>
<public-key>
<name>corp-fw2</name>
<public-key-format>ct:ssh-public-key-format</public-key-fo\
\rmat>
<public-key>base64encodedvalue==</public-key>
<!--</ssh-public-key>-->
</public-key>
</local-definition>
</ssh-host-keys>
<ca-certs>
<local-definition>
<certificate>
<name>Server Cert Issuer #1</name>
<cert-data>base64encodedvalue==</cert-data>
</certificate>
<certificate>
<name>Server Cert Issuer #2</name>
<cert-data>base64encodedvalue==</cert-data>
</certificate>
</local-definition>
</ca-certs>
<ee-certs>
<local-definition>
<certificate>
<name>My Application #1</name>
<cert-data>base64encodedvalue==</cert-data>
</certificate>
<certificate>
<name>My Application #2</name>
<cert-data>base64encodedvalue==</cert-data>
</certificate>
</local-definition>
</ee-certs>
</server-authentication>
<keepalives>
<max-wait>30</max-wait>
<max-attempts>3</max-attempts>
</keepalives>
</ssh-client>
¶
The following configuration example uses keystore-references for the client identity and truststore-references for server authentication: from the keystore:¶
=============== NOTE: '\' line wrapping per RFC 8792 ================
<ssh-client
xmlns="urn:ietf:params:xml:ns:yang:ietf-ssh-client"
xmlns:algs="urn:ietf:params:xml:ns:yang:ietf-ssh-common">
<!-- how this client will authenticate itself to the server -->
<client-identity>
<username>foobar</username>
<!-- can an SSH client have move than one key?
<public-key>
<keystore-reference>ssh-rsa-key</keystore-reference>
</public-key>
-->
<certificate>
<keystore-reference>
<asymmetric-key>ssh-rsa-key-with-cert</asymmetric-key>
<certificate>ex-rsa-cert2</certificate>
</keystore-reference>
</certificate>
</client-identity>
<!-- which host-keys will this client trust -->
<server-authentication>
<ssh-host-keys> <!-- FIXME: should 'ts-ref' be to bag or each ke\
y? -->
<truststore-reference>trusted-ssh-public-keys</truststore-refe\
rence>
</ssh-host-keys>
<ca-certs> <!-- FIXME: should 'ts-ref' be to bag or each key? -->
<truststore-reference>trusted-server-ca-certs</truststore-refe\
rence>
</ca-certs>
<ee-certs> <!-- FIXME: should 'ts-ref' be to bag or each key? -->
<truststore-reference>trusted-server-ee-certs</truststore-refe\
rence>
</ee-certs>
</server-authentication>
<keepalives>
<max-wait>30</max-wait>
<max-attempts>3</max-attempts>
</keepalives>
</ssh-client>
¶
This YANG module has normative references to [I-D.ietf-netconf-trust-anchors], and [I-D.ietf-netconf-keystore].¶
<CODE BEGINS> file "ietf-ssh-client@2020-07-08.yang"¶
module ietf-ssh-client {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-ssh-client";
prefix sshc;
import ietf-netconf-acm {
prefix nacm;
reference
"RFC 8341: Network Configuration Access Control Model";
}
import ietf-crypto-types {
prefix ct;
reference
"RFC AAAA: YANG Data Types and Groupings for Cryptography";
}
import ietf-truststore {
prefix ts;
reference
"RFC BBBB: A YANG Data Model for a Truststore";
}
import ietf-keystore {
prefix ks;
reference
"RFC CCCC: A YANG Data Model for a Keystore";
}
import ietf-ssh-common {
prefix sshcmn;
revision-date 2020-07-08; // stable grouping definitions
reference
"RFC EEEE: YANG Groupings for SSH Clients and SSH Servers";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <http://datatracker.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
Author: Kent Watsen <mailto:kent+ietf@watsen.net>
Author: Gary Wu <mailto:garywu@cisco.com>";
description
"This module defines reusable groupings for SSH clients that
can be used as a basis for specific SSH client instances.
Copyright (c) 2020 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
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC EEEE
(https://www.rfc-editor.org/info/rfcEEEE); see the RFC
itself for full legal notices.;
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 (RFC 2119)
(RFC 8174) when, and only when, they appear in all
capitals, as shown here.";
revision 2020-07-08 {
description
"Initial version";
reference
"RFC EEEE: 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.";
}
feature ssh-client-keepalives {
description
"Per socket SSH keepalive parameters are configurable for
SSH clients on the server implementing this feature.";
}
feature client-identity-password {
description
"Indicates that the 'password' authentication type
is supported for client identification.";
}
feature client-identity-publickey {
description
"Indicates that the 'publickey' authentication type
is supported for client identification.
The 'publickey' authentication type is required by
RFC 4252, but common implementations enable it to
be disabled.";
}
feature client-identity-hostbased {
description
"Indicates that the 'hostbased' authentication type
is supported for client identification.";
}
feature client-identity-none {
description
"Indicates that the 'none' authentication type is
supported for client identification.";
}
// 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.
Note that this grouping uses fairly typical descendent
node names such that a stack of 'uses' statements will
have name conflicts. It is intended that the consuming
data model will resolve the issue (e.g., by wrapping
the 'uses' statement in a container called
'ssh-client-parameters'). This model purposely does
not do this itself so as to provide maximum flexibility
to consuming models.";
container client-identity {
nacm:default-deny-write;
must
'public-key or password or hostbased or none or certificate';
description
"The credentials that the client may use, pending
the SSH server's requirements, by the SSH 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.";
}
container public-key {
if-feature client-identity-publickey;
presence
"Indicates that publickey-based authentication
is configured";
description
"A locally-defined or referenced asymmetric key
pair to be used for client identification.";
reference
"RFC CCCC: A YANG Data Model for a Keystore";
uses ks:local-or-keystore-asymmetric-key-grouping {
refine "local-or-keystore/local/local-definition" {
must 'public-key-format = "ct:ssh-public-key-format"';
}
refine "local-or-keystore/keystore/keystore-reference" {
must 'deref(.)/../ks:public-key-format'
+ ' = "ct:ssh-public-key-format"';
}
}
}
leaf password {
if-feature client-identity-password;
nacm:default-deny-all;
type string;
description
"A password to be used for client identification.";
}
container hostbased {
if-feature client-identity-hostbased;
presence
"Indicates that hostbased authentication is configured";
description
"A locally-defined or referenced asymmetric key
pair to be used for host identification.";
reference
"RFC CCCC: A YANG Data Model for a Keystore";
uses ks:local-or-keystore-asymmetric-key-grouping {
refine "local-or-keystore/local/local-definition" {
must 'public-key-format = "ct:ssh-public-key-format"';
}
refine "local-or-keystore/keystore/keystore-reference" {
must 'deref(.)/../ks:public-key-format'
+ ' = "ct:ssh-public-key-format"';
}
}
}
leaf none {
if-feature client-identity-none;
type empty;
description
"Indicates that 'none' algorithm is used for client
identification.";
}
container certificate {
if-feature "sshcmn:ssh-x509-certs";
presence
"Indicates that certificate-based authentication
is configured";
description
"A locally-defined or referenced certificate
to be used for client identification.";
reference
"RFC CCCC: A YANG Data Model for a Keystore";
uses
ks:local-or-keystore-end-entity-cert-with-key-grouping {
refine "local-or-keystore/local/local-definition" {
must
'public-key-format'
+ ' = "ct:subject-public-key-info-format"';
}
refine "local-or-keystore/keystore/keystore-reference"
+ "/asymmetric-key" {
must 'deref(.)/../ks:public-key-format'
+ ' = "ct:subject-public-key-info-format"';
}
}
}
} // container client-identity
container server-authentication {
nacm:default-deny-write;
must 'ssh-host-keys or ca-certs or ee-certs';
description
"Specifies how the SSH client can authenticate SSH servers.
Any combination of credentials is additive and unordered.";
container ssh-host-keys {
presence
"Indicates that the client can authenticate servers
using the configured SSH host keys.";
description
"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 BBBB: A YANG Data Model for a Truststore";
uses ts:local-or-truststore-public-keys-grouping {
refine
"local-or-truststore/local/local-definition/public-key" {
must 'public-key-format = "ct:ssh-public-key-format"';
}
refine
"local-or-truststore/truststore/truststore-reference" {
must 'deref(.)/../*/ts:public-key-format'
+ ' = "ct:ssh-public-key-format"';
}
}
}
container ca-certs {
if-feature "sshcmn:ssh-x509-certs";
presence
"Indicates that the client can authenticate servers
using the configured trust anchor certificates.";
description
"A set of certificate authority (CA) certificates used by
the SSH client to authenticate SSH servers. A server
is authenticated if its certificate has a valid chain
of trust to a configured CA certificate.";
reference
"RFC BBBB: A YANG Data Model for a Truststore";
uses ts:local-or-truststore-certs-grouping;
}
container ee-certs {
if-feature "sshcmn:ssh-x509-certs";
presence
"Indicates that the client can authenticate servers
using the configured end-entity certificates.";
description
"A set of end-entity certificates used by the SSH client
to authenticate SSH servers. A server is authenticated
if its certificate is an exact match to a configured
end-entity certificate.";
reference
"RFC BBBB: A YANG Data Model for a Truststore";
uses ts:local-or-truststore-certs-grouping;
}
} // container server-authentication
container transport-params {
nacm:default-deny-write;
if-feature "ssh-client-transport-params-config";
description
"Configurable parameters of the SSH transport layer.";
uses sshcmn:transport-params-grouping;
} // container transport-parameters
container keepalives {
nacm:default-deny-write;
if-feature "ssh-client-keepalives";
presence
"Indicates that the SSH client proactively tests the
aliveness of the remote SSH server.";
description
"Configures the keep-alive policy, to proactively test
the aliveness of the SSH server. An unresponsive TLS
server is dropped after approximately max-wait *
max-attempts seconds. Per Section 4 of RFC 4254,
the SSH client SHOULD send an SSH_MSG_GLOBAL_REQUEST
message with a purposely nonexistent 'request name'
value (e.g., keepalive@ietf.org) and the 'want reply'
value set to '1'.";
reference
"RFC 4254: The Secure Shell (SSH) Connection Protocol";
leaf max-wait {
type uint16 {
range "1..max";
}
units "seconds";
default "30";
description
"Sets the amount of time in seconds after which if
no data has been received from the SSH server, a
TLS-level message will be sent to test the
aliveness of the SSH server.";
}
leaf max-attempts {
type uint8;
default "3";
description
"Sets the maximum number of sequential keep-alive
messages that can fail to obtain a response from
the SSH server before assuming the SSH server is
no longer alive.";
}
} // container keepalives
} // grouping ssh-client-grouping
} // module ietf-ssh-client
¶
<CODE ENDS>¶
The following diagram lists all the "feature" statements defined in the "ietf-ssh-server" module:¶
Features: +-- ssh-server-transport-params-config +-- ssh-server-keepalives +-- client-auth-config-supported +-- client-auth-publickey +-- client-auth-password +-- client-auth-hostbased +-- client-auth-none¶
The following diagram lists all the "grouping" statements defined in the "ietf-ssh-server" module:¶
Groupings: +-- ssh-server-grouping¶
Each of these groupings are presented in the following subsections.¶
The following tree diagram [RFC8340] illustrates the "ssh-server-grouping" grouping:¶
=============== NOTE: '\' line wrapping per RFC 8792 ================
grouping ssh-server-grouping
+-- server-identity
| +-- host-key* [name]
| +-- name? string
| +-- (host-key-type)
| +--:(public-key)
| | +-- public-key
| | +---u ks:local-or-keystore-asymmetric-key-grouping
| +--:(certificate)
| +-- certificate {sshcmn:ssh-x509-certs}?
| +---u ks:local-or-keystore-end-entity-cert-with-k\
ey-grouping
+-- client-authentication
| +-- supported-authentication-methods
| | +-- publickey? empty
| | +-- password? empty {client-auth-password}?
| | +-- hostbased? empty {client-auth-hostbased}?
| | +-- none? empty {client-auth-none}?
| +-- users {client-auth-config-supported}?
| | +-- user* [name]
| | +-- name? string
| | +-- public-keys! {client-auth-publickey}?
| | | +---u ts:local-or-truststore-public-keys-grouping
| | +-- password? ianach:crypt-hash
| | | {client-auth-password}?
| | +-- hostbased! {client-auth-hostbased}?
| | | +---u ts:local-or-truststore-public-keys-grouping
| | +-- none? empty {client-auth-none}?
| +-- ca-certs!
| | {client-auth-config-supported,sshcmn:ssh-x509-certs}?
| | +---u ts:local-or-truststore-certs-grouping
| +-- ee-certs!
| {client-auth-config-supported,sshcmn:ssh-x509-certs}?
| +---u ts:local-or-truststore-certs-grouping
+-- transport-params {ssh-server-transport-params-config}?
| +---u sshcmn:transport-params-grouping
+-- keepalives! {ssh-server-keepalives}?
+-- max-wait? uint16
+-- max-attempts? uint8
¶
Comments:¶
For the referenced grouping statement(s):¶
This section presents two examples showing the "ssh-server-grouping" 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 2 of [I-D.ietf-netconf-trust-anchors] and Section 3.2 of [I-D.ietf-netconf-keystore].¶
The following configuration example uses local-definitions for the server identity and client authentication:¶
=============== NOTE: '\' line wrapping per RFC 8792 ================
<ssh-server
xmlns="urn:ietf:params:xml:ns:yang:ietf-ssh-server"
xmlns:ct="urn:ietf:params:xml:ns:yang:ietf-crypto-types"
xmlns:algs="urn:ietf:params:xml:ns:yang:ietf-ssh-common">
<!-- the host-key this SSH server will present -->
<server-identity>
<host-key>
<name>my-pubkey-based-host-key</name>
<public-key>
<local-definition>
<public-key-format>ct:ssh-public-key-format</public-key-fo\
rmat>
<public-key>base64encodedvalue==</public-key>
<private-key-format>ct:rsa-private-key-format</private-key\
-format>
<private-key>base64encodedvalue==</private-key>
</local-definition>
</public-key>
</host-key>
<host-key>
<name>my-cert-based-host-key</name>
<certificate>
<local-definition>
<public-key-format>ct:subject-public-key-info-format</publ\
ic-key-format>
<public-key>base64encodedvalue==</public-key>
<private-key-format>ct:rsa-private-key-format</private-key\
-format>
<private-key>base64encodedvalue==</private-key>
<cert-data>base64encodedvalue==</cert-data>
</local-definition>
</certificate>
</host-key>
</server-identity>
<!-- the client credentials this SSH server will trust -->
<client-authentication>
<supported-authentication-methods>
<publickey/>
</supported-authentication-methods>
<users>
<user>
<name>mary</name>
<password>$0$secret</password>
<public-keys>
<local-definition>
<!--<ssh-public-key>-->
<public-key>
<name>User A</name>
<public-key-format>ct:ssh-public-key-format</public-ke\
y-format>
<public-key>base64encodedvalue==</public-key>
<!--</ssh-public-key>
<ssh-public-key>-->
</public-key>
<public-key>
<name>User B</name>
<public-key-format>ct:ssh-public-key-format</public-ke\
y-format>
<public-key>base64encodedvalue==</public-key>
</public-key>
<!--</ssh-public-key>-->
</local-definition>
</public-keys>
</user>
</users>
<ca-certs>
<local-definition>
<certificate>
<name>Identity Cert Issuer #1</name>
<cert-data>base64encodedvalue==</cert-data>
</certificate>
<certificate>
<name>Identity Cert Issuer #2</name>
<cert-data>base64encodedvalue==</cert-data>
</certificate>
</local-definition>
</ca-certs>
<ee-certs>
<local-definition>
<certificate>
<name>Application #1</name>
<cert-data>base64encodedvalue==</cert-data>
</certificate>
<certificate>
<name>Application #2</name>
<cert-data>base64encodedvalue==</cert-data>
</certificate>
</local-definition>
</ee-certs>
</client-authentication>
<keepalives>
<max-wait>30</max-wait>
<max-attempts>3</max-attempts>
</keepalives>
</ssh-server>
¶
The following configuration example uses keystore-references for the server identity and truststore-references for client authentication: from the keystore:¶
=============== NOTE: '\' line wrapping per RFC 8792 ================
<ssh-server
xmlns="urn:ietf:params:xml:ns:yang:ietf-ssh-server"
xmlns:algs="urn:ietf:params:xml:ns:yang:ietf-ssh-common">
<!-- the host-key this SSH server will present -->
<server-identity>
<host-key>
<name>my-pubkey-based-host-key</name>
<public-key>
<keystore-reference>ssh-rsa-key</keystore-reference>
</public-key>
</host-key>
<host-key>
<name>my-cert-based-host-key</name>
<certificate>
<keystore-reference>
<asymmetric-key>ssh-rsa-key-with-cert</asymmetric-key>
<certificate>ex-rsa-cert2</certificate>
</keystore-reference>
</certificate>
</host-key>
</server-identity>
<!-- the client credentials this SSH server will trust -->
<client-authentication>
<supported-authentication-methods>
<publickey/>
</supported-authentication-methods>
<users>
<user>
<name>mary</name>
<password>$0$secret</password>
<public-keys>
<truststore-reference>SSH Public Keys for Application A</t\
ruststore-reference>
</public-keys>
</user>
</users>
<ca-certs>
<truststore-reference>trusted-client-ca-certs</truststore-refe\
rence>
</ca-certs>
<ee-certs>
<truststore-reference>trusted-client-ee-certs</truststore-refe\
rence>
</ee-certs>
</client-authentication>
<keepalives>
<max-wait>30</max-wait>
<max-attempts>3</max-attempts>
</keepalives>
</ssh-server>
¶
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].¶
<CODE BEGINS> file "ietf-ssh-server@2020-07-08.yang"¶
module ietf-ssh-server {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-ssh-server";
prefix sshs;
import iana-crypt-hash {
prefix ianach;
reference
"RFC 7317: A YANG Data Model for System Management";
}
import ietf-netconf-acm {
prefix nacm;
reference
"RFC 8341: Network Configuration Access Control Model";
}
import ietf-crypto-types {
prefix ct;
reference
"RFC AAAA: YANG Data Types and Groupings for Cryptography";
}
import ietf-truststore {
prefix ts;
reference
"RFC BBBB: A YANG Data Model for a Truststore";
}
import ietf-keystore {
prefix ks;
reference
"RFC CCCC: A YANG Data Model for a Keystore";
}
import ietf-ssh-common {
prefix sshcmn;
revision-date 2020-07-08; // stable grouping definitions
reference
"RFC EEEE: YANG Groupings for SSH Clients and SSH Servers";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <http://datatracker.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
Author: Kent Watsen <mailto:kent+ietf@watsen.net>
Author: Gary Wu <mailto:garywu@cisco.com>";
description
"This module defines reusable groupings for SSH servers that
can be used as a basis for specific SSH server instances.
Copyright (c) 2020 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
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC EEEE
(https://www.rfc-editor.org/info/rfcEEEE); see the RFC
itself for full legal notices.;
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 (RFC 2119)
(RFC 8174) when, and only when, they appear in all
capitals, as shown here.";
revision 2020-07-08 {
description
"Initial version";
reference
"RFC EEEE: 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.";
}
feature ssh-server-keepalives {
description
"Per socket SSH keepalive parameters are configurable for
SSH servers on the server implementing this feature.";
}
feature client-auth-config-supported {
description
"Indicates that the configuration for how to authenticate
clients can be configured herein, as opposed to in an
application specific location. That is, to support the
consuming data models that prefer to place client
authentication with client definitions, rather then
in a data model principally concerned with configuring
the transport.";
}
feature client-auth-publickey {
description
"Indicates that the 'publickey' authentication type
is supported.
The 'publickey' authentication type is required by
RFC 4252, but common implementations enable it to
be disabled.";
reference
"RFC 4252:
The Secure Shell (SSH) Authentication Protocol";
}
feature client-auth-password {
description
"Indicates that the 'password' authentication type
is supported.";
}
feature client-auth-hostbased {
description
"Indicates that the 'hostbased' authentication type
is supported.";
}
feature client-auth-none {
description
"Indicates that the 'none' authentication type is
supported.";
}
// Groupings
grouping ssh-server-grouping {
description
"A reusable grouping for configuring a SSH server without
any consideration for how underlying TCP sessions are
established.
Note that this grouping uses fairly typical descendent
node names such that a stack of 'uses' statements will
have name conflicts. It is intended that the consuming
data model will resolve the issue (e.g., by wrapping
the 'uses' statement in a container called
'ssh-server-parameters'). This model purposely does
not do this itself so as to provide maximum flexibility
to consuming models.";
container server-identity {
nacm:default-deny-write;
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";
container public-key {
description
"A locally-defined or referenced asymmetric key pair
to be used for the SSH server's host key.";
reference
"RFC CCCC: A YANG Data Model for a Keystore";
uses ks:local-or-keystore-asymmetric-key-grouping {
refine "local-or-keystore/local/local-definition" {
must
'public-key-format = "ct:ssh-public-key-format"';
}
refine "local-or-keystore/keystore/"
+ "keystore-reference" {
must 'deref(.)/../ks:public-key-format'
+ ' = "ct:ssh-public-key-format"';
}
}
}
container certificate {
if-feature "sshcmn:ssh-x509-certs";
description
"A locally-defined or referenced end-entity
certificate to be used for the SSH server's
host key.";
reference
"RFC CCCC: A YANG Data Model for a Keystore";
uses
ks:local-or-keystore-end-entity-cert-with-key-grouping {
refine "local-or-keystore/local/local-definition" {
must
'public-key-format'
+ ' = "ct:subject-public-key-info-format"';
}
refine "local-or-keystore/keystore/keystore-reference"
+ "/asymmetric-key" {
must 'deref(.)/../ks:public-key-format'
+ ' = "ct:subject-public-key-info-format"';
}
}
}
}
}
} // container server-identity
container client-authentication {
nacm:default-deny-write;
description
"Specifies how the SSH server can authenticate SSH clients.";
container supported-authentication-methods {
description
"Indicates which authentication methods the server
supports.";
leaf publickey {
type empty;
description
"Indicates that the 'publickey' method is supported.
Note that RFC 6187 X.509v3 Certificates for SSH uses
the 'publickey' method name.";
reference
"RFC 4252: The Secure Shell (SSH) Authentication
Protocol.
RFC 6187: X.509v3 Certificates for Secure Shell
Authentication.";
}
leaf password {
if-feature client-auth-password;
type empty;
description
"Indicates that the 'password' method is supported.";
reference
"RFC 4252: The Secure Shell (SSH) Authentication
Protocol.";
}
leaf hostbased {
if-feature client-auth-hostbased;
type empty;
description
"Indicates that the 'hostbased' method is supported.";
reference
"RFC 4252: The Secure Shell (SSH) Authentication
Protocol.";
}
leaf none {
if-feature client-auth-none;
type empty;
description
"Indicates that the 'none' method is supported.";
reference
"RFC 4252: The Secure Shell (SSH) Authentication
Protocol.";
}
}
container users {
if-feature "client-auth-config-supported";
description
"A list of locally configured users.";
list user {
key name;
description
"The list of local users configured on this device.";
leaf name {
type string;
description
"The user name string identifying this entry.";
}
container public-keys {
if-feature client-auth-publickey;
presence
"Indicates that the server can authenticate this
user using any of the configured SSH public keys.";
description
"A set of SSH public keys may be used by the SSH
server to authenticate this user. A user is
authenticated if its public key is an exact
match to a configured public key.";
reference
"RFC BBBB: A YANG Data Model for a Truststore";
uses ts:local-or-truststore-public-keys-grouping {
refine "local-or-truststore/local/local-definition"
+ "/public-key" {
must 'public-key-format'
+ ' = "ct:ssh-public-key-format"';
}
refine "local-or-truststore/truststore/"
+ "truststore-reference" {
must 'deref(.)/../*/ts:public-key-format'
+ ' = "ct:ssh-public-key-format"';
}
}
}
leaf password {
if-feature client-auth-password;
type ianach:crypt-hash;
description
"The password for this user.";
}
container hostbased {
if-feature client-auth-hostbased;
presence
"Indicates that the server can authenticate this
user's 'host' using any of the configured SSH
host keys.";
description
"A set of SSH host keys may be used by the SSH
server to authenticate this user's host. A
user's host is authenticated if its host key
is an exact match to a configured host key.";
reference
"RFC 4253: The Secure Shell (SSH) Transport Layer
RFC BBBB: A YANG Data Model for a Truststore";
uses ts:local-or-truststore-public-keys-grouping {
refine "local-or-truststore/local/local-definition"
+ "/public-key" {
must 'public-key-format'
+ ' = "ct:ssh-public-key-format"';
}
refine "local-or-truststore/truststore"
+ "/truststore-reference" {
must 'deref(.)/../*/ts:public-key-format'
+ ' = "ct:ssh-public-key-format"';
}
}
}
leaf none {
if-feature client-auth-none;
type empty;
description
"Indicates that the 'none' method is supported.";
reference
"RFC 4252: The Secure Shell (SSH) Authentication
Protocol.";
}
}
}
container ca-certs {
if-feature "client-auth-config-supported";
if-feature "sshcmn:ssh-x509-certs";
presence
"Indicates that the SSH server can authenticate SSH
clients using configured certificate authority (CA)
certificates.";
description
"A set 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 CA certificate.";
reference
"RFC BBBB: A YANG Data Model for a Truststore";
uses ts:local-or-truststore-certs-grouping;
}
container ee-certs {
if-feature "client-auth-config-supported";
if-feature "sshcmn:ssh-x509-certs";
presence
"Indicates that the SSH server can authenticate SSH
clients using configured end-entity certificates.";
description
"A set of client certificates (i.e., end entity
certificates) used by the SSH server to authenticate
the certificates presented by SSH clients. A client
certificate is authenticated if it is an exact match
to a configured end-entity certificate.";
reference
"RFC BBBB: A YANG Data Model for a Truststore";
uses ts:local-or-truststore-certs-grouping;
}
} // container client-authentication
container transport-params {
nacm:default-deny-write;
if-feature "ssh-server-transport-params-config";
description
"Configurable parameters of the SSH transport layer.";
uses sshcmn:transport-params-grouping;
} // container transport-params
container keepalives {
nacm:default-deny-write;
if-feature "ssh-server-keepalives";
presence
"Indicates that the SSH server proactively tests the
aliveness of the remote SSH client.";
description
"Configures the keep-alive policy, to proactively test
the aliveness of the SSL client. An unresponsive SSL
client is dropped after approximately max-wait *
max-attempts seconds. Per Section 4 of RFC 4254,
the SSH server SHOULD send an SSH_MSG_GLOBAL_REQUEST
message with a purposely nonexistent 'request name'
value (e.g., keepalive@ietf.org) and the 'want reply'
value set to '1'.";
reference
"RFC 4254: The Secure Shell (SSH) Connection Protocol";
leaf max-wait {
type uint16 {
range "1..max";
}
units "seconds";
default "30";
description
"Sets the amount of time in seconds after which
if no data has been received from the SSL client,
a SSL-level message will be sent to test the
aliveness of the SSL client.";
}
leaf max-attempts {
type uint8;
default "3";
description
"Sets the maximum number of sequential keep-alive
messages that can fail to obtain a response from
the SSL client before assuming the SSL client is
no longer alive.";
}
}
} // grouping ssh-server-grouping
} // module ietf-ssh-server
¶
<CODE ENDS>¶
The "ietf-ssh-common" YANG module defines "grouping" statements that 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 module in this document only define groupings, these considerations are primarily for the designers of other modules that use these groupings.¶
None of the readable data nodes defined in this YANG module are considered sensitive or vulnerable in network environments. The NACM "default-deny-all" extension has not been set for any data nodes defined in this module.¶
None of the writable data nodes defined in this YANG module are considered sensitive or vulnerable in network environments. The NACM "default-deny-write" extension has not been set for any data nodes defined in this module.¶
This module does not define any RPCs, actions, or notifications, and thus the security consideration for such is not provided here.¶
The "ietf-ssh-client" YANG module defines "grouping" statements that 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 module in this document only define groupings, these considerations are primarily for the designers of other modules that use these groupings.¶
One readable data node defined in this YANG module may be considered sensitive or vulnerable in some network environments. This node is as follows:¶
The "client-identity/password" node:¶
All of the writable data nodes defined by this module may be considered sensitive or vulnerable in some network environments. For instance, any modification to a key or reference to a key may dramatically alter the implemented security policy. For this reason, the NACM extension "default-deny-write" has been set for all data nodes defined in this module.¶
This module does not define any RPCs, actions, or notifications, and thus the security consideration for such is not provided here.¶
The "ietf-ssh-server" YANG module defines "grouping" statements that 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 module in this document only define groupings, these considerations are primarily for the designers of other modules that use these groupings.¶
None of the readable data nodes defined in this YANG module are considered sensitive or vulnerable in network environments. The NACM "default-deny-all" extension has not been set for any data nodes defined in this module.¶
All of the writable data nodes defined by this module may be considered sensitive or vulnerable in some network environments. For instance, the addition or removal of references to keys, certificates, trusted anchors, etc., or even the modification of transport or keepalive parameters can dramatically alter the implemented security policy. For this reason, the NACM extension "default-deny-write" has been set for all data nodes defined in this module.¶
This module does not define any RPCs, actions, or notifications, and thus the security consideration for such is not provided here.¶
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-common 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-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 three YANG modules in the YANG Module Names registry [RFC6020]. Following the format in [RFC6020], the following registrations are requested:¶
name: ietf-ssh-common namespace: urn:ietf:params:xml:ns:yang:ietf-ssh-common prefix: sshcmn reference: RFC EEEE name: ietf-ssh-client namespace: urn:ietf:params:xml:ns:yang:ietf-ssh-client prefix: sshc reference: RFC EEEE name: ietf-ssh-server namespace: urn:ietf:params:xml:ns:yang:ietf-ssh-server prefix: sshs reference: RFC EEEE¶
This section is to be removed before publishing as an RFC.¶
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, Radek Krejci, David Lamparter, Ladislav Lhotka, Alan Luchuk, Tom Petch, Juergen Schoenwaelder, Phil Shafer, Sean Turner, Michal Vasko, Bert Wijnen, and Liang Xia.¶