YANG Groupings for SSH Clients and SSH ServersJuniper Networkskwatsen@juniper.netCisco Systemsgarywu@cisco.com
Operations
NETCONF Working GroupThis 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:
I-D.ietf-netconf-keystoreArtwork in this document contains shorthand references to drafts in
progress. Please apply the following replacements:
XXXX --> the assigned RFC value for this draftYYYY --> the assigned RFC value for I-D.ietf-netconf-keystoreArtwork in this document contains placeholder values for the date of
publication of this draft. Please apply the following replacement:
2017-10-30 --> the publication date of this draftThe following Appendix section is to be removed prior to publication:
Appendix A. Change LogThis document defines three YANG
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 , , and ). It is intended
that these groupings will be used by applications using the SSH
protocol. For instance, these groupings could be used to help
define the data model for an OpenSSH
server or a NETCONF over SSH based
server.The 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
could use the grouping for the SSH parts it
provides, while adding data nodes for the TCP-level call-home
configuration.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
when, and only when, they appear in all capitals, as shown here.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 . 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 .The following tree diagram
provides an overview of the data model for the "ietf-ssh-client" module.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 .\
foobarks:secp521r1base64encodedvalue==base64encodedvalue==explicitly-trusted-ssh-host-keys
algs:ssh-rsa
algs:diffie-hellman-group-exchange-sha256
algs:aes256-ctralgs:aes192-ctralgs:aes128-ctralgs:aes256-cbcalgs:aes192-cbcalgs:aes128-cbcalgs:hmac-sha2-256algs:hmac-sha2-512algs:none
]]>This YANG module has a normative references to
and . file "ietf-ssh-client@2017-10-30.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 2017-10-30; // stable grouping definitions
reference
"RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
}
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:
WG List:
Author: Kent Watsen
Author: Gary Wu
";
description
"This module defines a reusable grouping for a SSH client that
can be used as a basis for specific SSH client instances.
Copyright (c) 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 "2017-10-30" {
description
"Initial version";
reference
"RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
}
// features
feature ssh-client-transport-params-config {
description
"SSH transport layer parameters are configurable on an SSH
client.";
}
// groupings
grouping ssh-client-grouping {
description
"A reusable grouping for configuring a SSH client without
any consideration for how an underlying TCP session is
established.";
container client-identity {
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 {
mandatory true;
description
"The authentication type.";
container certificate {
if-feature sshcom:ssh-x509-certs;
uses ks:private-key-grouping;
uses ks:certificate-grouping;
description
"A certificates to be used for client authentication.";
}
container public-key {
uses ks:private-key-grouping;
description
"A public key to be used for client authentication.";
}
leaf password {
nacm:default-deny-all;
type string;
description
"A password to be used for client authentication.";
}
}
} // end client-auth
container server-auth {
must 'pinned-ssh-host-keys or pinned-ca-certs or '
+ 'pinned-server-certs';
description
"Trusted server identities.";
leaf pinned-ssh-host-keys {
type ks:pinned-host-keys;
description
"A reference to a list of SSH host keys used by the
SSH client to authenticate SSH server host keys.
A server host key is authenticated if it is an exact
match to a configured SSH host key.";
}
leaf pinned-ca-certs {
if-feature sshcom:ssh-x509-certs;
type ks:pinned-certificates;
description
"A reference to a list of certificate authority (CA)
certificates used by the SSH client to authenticate
SSH server certificates. A server certificate is
authenticated if it has a valid chain of trust to
a configured CA certificate.";
}
leaf pinned-server-certs {
if-feature sshcom:ssh-x509-certs;
type ks:pinned-certificates;
description
"A reference to a list of server certificates used by
the SSH client to authenticate SSH server certificates.
A server certificate is authenticated if it is an
exact match to a configured server certificate.";
}
} // end server-auth
container transport-params {
if-feature ssh-client-transport-params-config;
uses sshcom:transport-params-grouping;
description
"Configurable parameters for the SSH transport layer.";
}
}
}
]]>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 .
For instance, a reference to the keystore model is made to indicate
which host key a server should present.The following tree diagram
provides an overview of the data model for the "ietf-ssh-server" module.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 .\
deployment-specific-certificateks:secp521r1base64encodedvalue==base64encodedvalue==deployment-specific-ca-certsexplicitly-trusted-client-certs
algs:ssh-rsa
algs:diffie-hellman-group-exchange-sha256
algs:aes256-ctralgs:aes192-ctralgs:aes128-ctralgs:aes256-cbcalgs:aes192-cbcalgs:aes128-cbcalgs:hmac-sha2-256algs:hmac-sha2-512algs:none
]]>This YANG module has a normative references to ,
, and . file "ietf-ssh-server@2017-10-30.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 2017-10-30; // stable grouping definitions
reference
"RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
}
import ietf-keystore {
prefix ks;
reference
"RFC YYYY: Keystore Model";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web:
WG List:
Author: Kent Watsen
Author: Gary Wu
";
description
"This module defines a reusable grouping for a SSH server that
can be used as a basis for specific SSH server instances.
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 "2017-10-30" {
description
"Initial version";
reference
"RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
}
// features
feature ssh-server-transport-params-config {
description
"SSH transport layer parameters are configurable on an SSH
server.";
}
// groupings
grouping ssh-server-grouping {
description
"A reusable grouping for configuring a SSH server without
any consideration for how underlying TCP sessions are
established.";
container server-identity {
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 {
uses ks:private-key-grouping;
description
"The SSH server uses a public-key for its host key.";
}
container certificate {
if-feature sshcom:ssh-x509-certs;
uses ks:private-key-grouping;
uses ks:certificate-grouping;
description
"The SSH server uses a certificate for its host key.";
}
}
}
}
container client-cert-auth {
if-feature sshcom:ssh-x509-certs;
description
"A reference to a list of pinned certificate authority (CA)
certificates and a reference to a list of pinned client
certificates.";
leaf pinned-ca-certs {
type ks:pinned-certificates;
description
"A reference to a list of certificate authority (CA)
certificates used by the SSH server to authenticate
SSH client certificates. A client certificate is
authenticated if it has a valid chain of trust to
a configured pinned CA certificate.";
}
leaf pinned-client-certs {
type ks:pinned-certificates;
description
"A reference to a list of client certificates used by
the SSH server to authenticate SSH client certificates.
A clients certificate is authenticated if it is an
exact match to a configured pinned client certificate.";
}
}
container transport-params {
if-feature ssh-server-transport-params-config;
uses sshcom:transport-params-grouping;
description
"Configurable parameters for the SSH transport layer.";
}
}
}
]]>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 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
provides an overview of the data model for the "ietf-ssh-common" module.This section shows how it would appear if the
transport-params-grouping were populated with some data.algs:x509v3-rsa2048-sha256algs:ssh-rsa
algs:diffie-hellman-group-exchange-sha256
algs:aes256-ctralgs:aes192-ctralgs:aes128-ctralgs:aes256-cbcalgs:aes192-cbcalgs:aes128-cbcalgs:hmac-sha2-256algs:hmac-sha2-512algs:none
]]>This YANG module has a normative references to ,
, , and . file "ietf-ssh-common@2017-10-30.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:
WG List:
Author: Kent Watsen
Author: Gary Wu
";
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 "2017-10-30" {
description
"Initial version";
reference
"RFC XXXX: YANG Groupings for SSH Clients and SSH Servers";
}
// features
feature ssh-ecc {
description
"Elliptic Curve Cryptography is supported for SSH.";
reference
"RFC 5656: Elliptic Curve Algorithm Integration in the
Secure Shell Transport Layer";
}
feature ssh-x509-certs {
description
"X.509v3 certificates are supported for SSH 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.";
}
}
}
}
]]>The YANG modules defined in this document are designed to be accessed via YANG
based management protocols, such as NETCONF and
RESTCONF . Both of these protocols have mandatory-to-implement
secure transport layers (e.g., SSH, TLS) with mutual authentication.The NETCONF access control model (NACM) provides the means
to restrict access for particular users to a pre-configured subset of all available
protocol operations and content.Since the modules defined in this document define only groupings, these
considerations are primarily for the designers of other modules that use
these groupings.There are a number of data nodes defined in the YANG modules that are
writable/creatable/deletable (i.e., config true, which is the default). These data
nodes may be considered sensitive or vulnerable in some network environments. Write
operations (e.g., edit-config) to these data nodes without proper protection can
have a negative effect on network operations. These are the subtrees and data nodes
and their sensitivity/vulnerability:
The entire data tree defined by all the modules defined in
this draft are sensitive to write operations. For instance, the addition or
removal of references to keys, certificates, trusted anchors, etc., can
dramatically alter the implemented security policy. However, no NACM
annotations are applied as the data SHOULD be editable by users other than
a designated 'recovery session'.Some of the readable data nodes in the YANG modules may be considered sensitive
or vulnerable in some network environments. It is thus important to control read
access (e.g., via get, get-config, or notification) to these data nodes. These are
the subtrees and data nodes and their sensitivity/vulnerability:
This node in the 'ietf-ssh-client' module
is additionally sensitive to read operations such that, in normal use cases, it
should never be returned to a client. The only time this node should be returned
is to support backup/restore type workflows. This being the case, this node is
marked with the NACM value 'default-deny-all'.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 . Following the format in
, the following registrations are
requested:This document registers three YANG modules in the
YANG Module Names registry .
Following the format in , the
the following registrations are requested:The authors would like to thank for following for
lively discussions on list and in the halls (ordered
by last name): Andy Bierman, Martin Bjorklund, Benoit Claise,
Mehmet Ersue, Balázs Kovács, David Lamparter, Alan Luchuk, Ladislav Lhotka,
Radek Krejci, Tom Petch, Juergen Schoenwaelder, Phil Shafer,
Sean Turner, Michal Vaško, and Bert Wijnen.OpenSSHNoted that '0.0.0.0' and '::' might have special meanings.Renamed "keychain" to "keystore".Removed the groupings 'listening-ssh-client-grouping' and
'listening-ssh-server-grouping'. Now modules only contain the
transport-independent groupings.Simplified the "client-auth" part in the ietf-ssh-client
module. It now inlines what it used to point to keystore for.Added cipher suites for various algorithms into new
'ietf-ssh-common' module.Removed 'RESTRICTED' enum from 'password' leaf type.Added a 'must' statement to container 'server-auth' asserting
that at least one of the various auth mechanisms must be specified.Fixed description statement for leaf 'trusted-ca-certs'.Change title to "YANG Groupings for SSH Clients and SSH Servers"Added reference to RFC 6668Added RFC 8174 to Requirements Language Section.Enhanced description statement for ietf-ssh-server's
"trusted-ca-certs" leaf.Added mandatory true to ietf-ssh-client's "client-auth"
'choice' statement.Now tree diagrams reference ietf-netmod-yang-tree-diagramsUpdated YANG to use typedefs around leafrefs to common keystore pathsNow inlines key and certificates (no longer a leafref to keystore)