| NETCONF Working Group | K. Watsen |
| Internet-Draft | Watsen Networks |
| Intended status: Standards Track | November 20, 2019 |
| Expires: May 23, 2020 |
A YANG Data Model for a Truststore
draft-ietf-netconf-trust-anchors-08
This document defines a YANG 1.1 data model for configuring global sets of X.509 certificates, SSH host-keys, raw public keys, and PSKs (pairwise-symmetric or pre-shared keys) that can be referenced by other data models for trust. While the SSH host-keys are uniquely for the SSH protocol, certificates, raw public keys, and PSKs may have multiple uses, including authenticating protocol peers and verifying signatures.
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.
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:
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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/.
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Copyright (c) 2019 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 a YANG 1.1 [RFC7950] data model for configuring global sets of X.509 certificates, SSH host-keys, raw public keys, and PSKs (pairwise-symmetric or pre-shared keys) that can be referenced by other data models for trust. While the SSH host-keys are uniquely for the SSH protocol, certificates, raw public keys, and PSKs may have multiple uses, including authenticating protocol peers and verifying signatures.
This document in compliant with Network Management Datastore Architecture (NMDA) [RFC8342]. For instance, trust anchors installed during manufacturing (e.g., for trusted well-known services), are expected to appear in <operational> (see Section 3).
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.
Tree diagrams used in this document follow the notation defined in [RFC8340].
The following tree diagram provides an overview of the "ietf-truststore" module.
module: ietf-truststore
+--rw truststore
+--rw certificates* [name] {x509-certificates}?
| +--rw name string
| +--rw description? string
| +--rw certificate* [name]
| +--rw name string
| +--rw cert trust-anchor-cert-cms
| +---n certificate-expiration
| +-- expiration-date yang:date-and-time
+--rw host-keys* [name] {ssh-host-keys}?
| +--rw name string
| +--rw description? string
| +--rw host-key* [name]
| +--rw name string
| +--rw host-key ct:ssh-host-key
+--rw raw-public-keys* [name] {raw-public-keys}?
+--rw name string
+--rw description? string
+--rw raw-public-key* [name]
+--rw name string
+--rw algorithm iasa:asymmetric-algorithm-type
+--rw public-key-format? identityref
+--rw public-key binary
grouping local-or-truststore-certs-grouping
+-- (local-or-truststore)
+--:(local) {local-definitions-supported}?
| +-- local-definition
| +-- cert* trust-anchor-cert-cms
| +---n certificate-expiration
| +-- expiration-date yang:date-and-time
+--:(truststore) {truststore-supported,x509-certificates}?
+-- truststore-reference? ts:certificates-ref
grouping local-or-truststore-host-keys-grouping
+-- (local-or-truststore)
+--:(local) {local-definitions-supported}?
| +-- local-definition
| +-- host-key* ct:ssh-host-key
+--:(truststore) {truststore-supported,ssh-host-keys}?
+-- truststore-reference? ts:host-keys-ref
grouping local-or-truststore-raw-pub-keys-grouping
+-- (local-or-truststore)
+--:(local) {local-definitions-supported}?
| +-- local-definition
| +-- raw-public-key* [name]
| +-- name? string
| +-- algorithm
| | iasa:asymmetric-algorithm-type
| +-- public-key-format? identityref
| +-- public-key binary
+--:(truststore) {truststore-supported,raw-public-keys}?
+-- truststore-reference? ts:raw-public-keys-ref
grouping truststore-grouping
+-- certificates* [name] {x509-certificates}?
| +-- name? string
| +-- description? string
| +-- certificate* [name]
| +-- name? string
| +-- cert trust-anchor-cert-cms
| +---n certificate-expiration
| +-- expiration-date yang:date-and-time
+-- host-keys* [name] {ssh-host-keys}?
| +-- name? string
| +-- description? string
| +-- host-key* [name]
| +-- name? string
| +-- host-key ct:ssh-host-key
+-- raw-public-keys* [name] {raw-public-keys}?
+-- name? string
+-- description? string
+-- raw-public-key* [name]
+-- name? string
+-- algorithm iasa:asymmetric-algorithm-type
+-- public-key-format? identityref
+-- public-key binary
The following example illustrates trust anchors in <intended>. Please see Section 3 for an example illustrating built-in values in <operational>.
<truststore
xmlns="urn:ietf:params:xml:ns:yang:ietf-truststore"
xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin">
<!-- Manufacturer's trusted root CA certs -->
<certificates or:origin="or:system">
<name>manufacturers-root-ca-certs</name>
<description>
Certificates built into the device for authenticating
manufacturer-signed objects, such as TLS server certificates,
vouchers, etc. Note, though listed here, these are not
configurable; any attempt to do so will be denied.
</description>
<certificate>
<name>Manufacturer Root CA cert 1</name>
<cert>base64encodedvalue==</cert>
</certificate>
<certificate>
<name>Manufacturer Root CA cert 2</name>
<cert>base64encodedvalue==</cert>
</certificate>
</certificates>
<!-- specific end-entity certs for authenticating servers -->
<certificates or:origin="or:intended">
<name>explicitly-trusted-server-certs</name>
<description>
Specific server authentication certificates for explicitly
trusted servers. These are needed for server certificates
that are not signed by a CA.
</description>
<certificate>
<name>Fred Flintstone</name>
<cert>base64encodedvalue==</cert>
</certificate>
</certificates>
<!-- trusted CA certs for authenticating servers -->
<certificates or:origin="or:intended">
<name>explicitly-trusted-server-ca-certs</name>
<description>
Trust anchors (i.e. CA certs) that are used to authenticate
server connections. Servers are authenticated if their
certificate has a chain of trust to one of these CA
certificates.
</description>
<certificate>
<name>ca.example.com</name>
<cert>base64encodedvalue==</cert>
</certificate>
</certificates>
<!-- specific end-entity certs for authenticating clients -->
<certificates or:origin="or:intended">
<name>explicitly-trusted-client-certs</name>
<description>
Specific client authentication certificates for explicitly
trusted clients. These are needed for client certificates
that are not signed by a CA.
</description>
<certificate>
<name>George Jetson</name>
<cert>base64encodedvalue==</cert>
</certificate>
</certificates>
<!-- trusted CA certs for authenticating clients -->
<certificates or:origin="or:intended">
<name>explicitly-trusted-client-ca-certs</name>
<description>
Trust anchors (i.e. CA certs) that are used to authenticate
client connections. Clients are authenticated if their
certificate has a chain of trust to one of these CA
certificates.
</description>
<certificate>
<name>ca.example.com</name>
<cert>base64encodedvalue==</cert>
</certificate>
</certificates>
<!-- trusted CA certs for random HTTPS servers on Internet -->
<certificates or:origin="or:system">
<name>common-ca-certs</name>
<description>
Trusted certificates to authenticate common HTTPS servers.
These certificates are similar to those that might be
shipped with a web browser.
</description>
<certificate>
<name>ex-certificate-authority</name>
<cert>base64encodedvalue==</cert>
</certificate>
</certificates>
<!-- specific SSH host keys for authenticating clients -->
<host-keys or:origin="or:intended">
<name>explicitly-trusted-ssh-host-keys</name>
<description>
Trusted SSH host keys used to authenticate SSH servers.
These host keys would be analogous to those stored in
a known_hosts file in OpenSSH.
</description>
<host-key>
<name>corp-fw1</name>
<host-key>base64encodedvalue==</host-key>
</host-key>
</host-keys>
</truststore>
The following example illustrates the "certificate-expiration" notification in use with the NETCONF protocol.
========== NOTE: '\' line wrapping per BCP XXX (RFC XXXX) ===========
<notification
xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
<eventTime>2018-05-25T00:01:00Z</eventTime>
<truststore xmlns="urn:ietf:params:xml:ns:yang:ietf-truststore">
<certificates>
<name>explicitly-trusted-client-certs</name>
<certificate>
<name>George Jetson</name>
<certificate-expiration>
<expiration-date>2018-08-05T14:18:53-05:00</expiration-dat\
e>
</certificate-expiration>
</certificate>
</certificates>
</truststore>
</notification>
This YANG module imports modules from [RFC8341] and [I-D.ietf-netconf-crypto-types].
<CODE BEGINS> file "ietf-truststore@2019-11-20.yang"
module ietf-truststore {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-truststore";
prefix ts;
import ietf-netconf-acm {
prefix nacm;
reference
"RFC 8341: Network Configuration Access Control Model";
}
import ietf-crypto-types {
prefix ct;
reference
"RFC YYYY: Common YANG Data Types for Cryptography";
}
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 <kent+ietf@watsen.net>
Author : Henk Birkholz <henk.birkholz@sit.fraunhofer.de>";
description
"This module defines a truststore to centralize management
of trust anchors including X.509 certificates, SSH host
keys, raw public keys, and PSKs (pairwise-symmetric or
pre-shared keys).
Copyright (c) 2019 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 XXXX
(https://www.rfc-editor.org/info/rfcXXXX); 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 2019-11-20 {
description
"Initial version";
reference
"RFC XXXX: A YANG Data Model for a Truststore";
}
/****************/
/* Features */
/****************/
feature truststore-supported {
description
"The 'truststore-supported' feature indicates that the
server supports the truststore (i.e., implements the
'ietf-truststore' module).";
}
feature local-definitions-supported {
description
"The 'local-definitions-supported' feature indicates that
the server supports locally-defined trust anchors.";
}
feature x509-certificates {
description
"The 'x509-certificates' feature indicates that the server
implements the /truststore/certificates subtree.";
}
feature ssh-host-keys {
description
"The 'ssh-host-keys' feature indicates that the server
implements the /truststore/host-keys subtree.";
}
feature raw-public-keys {
description
"The 'raw-public-keys' feature indicates that the server
implements the /truststore/raw-public-keys subtree.";
}
/****************/
/* Typedefs */
/****************/
typedef certificates-ref {
type leafref {
path "/ts:truststore/ts:certificates/ts:name";
}
description
"This typedef enables modules to easily define a reference
to a set of certificates defined in the truststore.";
}
typedef host-keys-ref {
type leafref {
path "/ts:truststore/ts:host-keys/ts:name";
}
description
"This typedef enables modules to easily define a reference
to a set of host keys defined in the truststore.";
}
typedef raw-public-keys-ref {
type leafref {
path "/ts:truststore/ts:raw-public-keys/ts:name";
}
description
"This typedef enables modules to easily define a reference
to a set of raw public keys defined in the truststore.";
}
/*****************/
/* Groupings */
/*****************/
grouping local-or-truststore-certs-grouping {
description
"A grouping that expands to allow trust anchors to be
either stored locally, within the using data model, or be
a reference to trust anchors stored in the truststore.";
choice local-or-truststore {
mandatory true;
case local {
if-feature "local-definitions-supported";
container local-definition {
description
"Container to hold the local trust anchor definitions.";
uses ct:trust-anchor-certs-grouping;
}
}
case truststore {
if-feature "truststore-supported";
if-feature "x509-certificates";
leaf truststore-reference {
type ts:certificates-ref;
description
"A reference to a set of trust anchors that exists
in the truststore.";
}
}
description
"A choice between an inlined definition and a definition
that exists in the truststore.";
}
}
grouping local-or-truststore-host-keys-grouping {
description
"A grouping that expands to allow host keys to be
either stored locally, within the using data model, or be
a reference to host keys stored in the truststore.";
choice local-or-truststore {
mandatory true;
case local {
if-feature "local-definitions-supported";
container local-definition {
description
"Container to hold local host key definitions.";
leaf-list host-key {
nacm:default-deny-write;
type ct:ssh-host-key;
description
"The binary public key data for this host key.";
reference
"RFC YYYY: Common YANG Data Types for Cryptography";
}
}
}
case truststore {
if-feature "truststore-supported";
if-feature "ssh-host-keys";
leaf truststore-reference {
type ts:host-keys-ref;
description
"A reference to a set of host keys that exist in
the truststore.";
}
}
description
"A choice between an inlined definition and a definition
that exists in the truststore.";
}
}
grouping local-or-truststore-raw-pub-keys-grouping {
description
"A grouping that expands to allow raw public keys to be
available either locally, within the using data model, or
be a reference to raw public keys stored in the truststore.";
choice local-or-truststore {
mandatory true;
case local {
if-feature "local-definitions-supported";
container local-definition {
description
"Container to hold local raw public key definitions.";
list raw-public-key {
key name;
description
"A raw public key definition.";
leaf name {
type string;
description
"An arbitrary name for this raw public key.";
}
uses ct:public-key-grouping;
}
}
}
case truststore {
if-feature "truststore-supported";
if-feature "raw-public-keys";
leaf truststore-reference {
type ts:raw-public-keys-ref;
description
"A reference to a set of raw public keys that exist
in the truststore.";
}
}
description
"A choice between an inlined definition and a definition
that exists in the truststore.";
}
}
grouping truststore-grouping {
description
"Grouping definition enables use in other contexts. If ever
done, implementations SHOULD augment new 'case' statements
into local-or-keystore 'choice' statements to supply leafrefs
to the new location.";
list certificates {
if-feature "x509-certificates";
key "name";
description
"A list of certificates. These certificates can be
used by a server to authenticate clients, or by a client
to authenticate servers. Each list of certificates
SHOULD be specific to a purpose, as the list as a whole
may be referenced by other modules. For instance, a
RESTCONF server's configuration might use a specific list
of certificates for when authenticating RESTCONF
client connections.";
leaf name {
type string;
description
"An arbitrary name for this list of certificates.";
}
leaf description {
type string;
description
"An arbitrary description for this list of
certificates.";
}
list certificate {
key "name";
description
"A certificate.";
leaf name {
type string;
description
"An arbitrary name for this certificate. The
name must be unique across all lists of
certificates (not just this list) so that leafrefs
from another module can resolve to unique values.";
}
uses ct:trust-anchor-cert-grouping {
refine "cert" {
mandatory true;
}
}
}
}
list host-keys {
if-feature "ssh-host-keys";
key "name";
description
"A list of host keys. These host-keys can be used by
clients to authenticate SSH servers. Each list of host
keys SHOULD be specific to a purpose, so the list as a
whole may be referenced by other modules. For instance,
a client's configuration might point to a specific list
of host keys for when authenticating specific SSH servers.";
leaf name {
type string;
description
"An arbitrary name for this list of SSH
host keys.";
}
leaf description {
type string;
description
"An arbitrary description for this list of SSH
host keys.";
}
list host-key {
key "name";
description
"A host key.";
leaf name {
type string;
description
"An arbitrary name for this host-key.";
}
leaf host-key {
type ct:ssh-host-key;
mandatory true;
description
"The binary public key data for this host key.";
reference
"RFC YYYY: Common YANG Data Types for Cryptography";
}
}
}
list raw-public-keys {
if-feature "raw-public-keys";
key "name";
description
"A list of raw public keys. These raw public keys can be
used by a server to authenticate clients, or by a client
to authenticate servers. Each list of raw public keys
SHOULD be specific to a purpose, so the list as a whole
may be referenced by other modules. For instance, a
client's configuration might point to a specific list
of raw public keys for when authenticating specific TLS
endpoints.";
leaf name {
type string;
description
"An arbitrary name for this list of raw public keys.";
}
leaf description {
type string;
description
"An arbitrary description for this list raw public keys.";
}
list raw-public-key {
key "name";
description
"A raw public key.";
leaf name {
type string;
description
"An arbitrary name for this raw public key.";
}
uses ct:public-key-grouping;
}
}
}
/*********************************/
/* Protocol accessible nodes */
/*********************************/
container truststore {
nacm:default-deny-write;
description
"The truststore contains sets of X.509 certificates and
SSH host keys.";
uses truststore-grouping;
}
}
<CODE ENDS>
In some implementations, the operating system a device is running, may define some built-in trust anchors. For instance, there may be built-in trust anchors enabling the device to securely connect to well-known services (e.g., an SZTP [RFC8572] bootstap server) or trust anchors to connect to arbitrary services using public PKI.
Built-in trust anchors are expected to be set by a vendor-specific process. Any ability for operators to modify built-in trust anchors is outside the scope of this docuemnt.
As built-in trust anchors are provided by the system (not configuration), they are present in <operational>. The following example illustrates bui;t-in trust anchors in <operational>.
(FIXME: add illustration with origin="system" here)
In order for the built-in trust anchors to be referenced by configuration, they must first be copied into <intended> as the example in Section 2.2 illustrates for the built-in trust anchors above. Note that this strategy is chosen, rather then setting "require-instance false" for the various leafrefs, as built-in trust anchors are relatively few in number and hence not worth relaxing the validation for.
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) [RFC8341] 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:
None of the readable data nodes in this YANG module are considered sensitive or vulnerable in network environments.
This module does not define any RPCs, actions, or notifications, and thus the security consideration for such is not provided here.
This document registers one URI in the "ns" subregistry of the IETF XML Registry [RFC3688]. Following the format in [RFC3688], the following registration is requested:
URI: urn:ietf:params:xml:ns:yang:ietf-truststore Registrant Contact: The NETCONF WG of the IETF. XML: N/A, the requested URI is an XML namespace.
This document registers one YANG module in the YANG Module Names registry [RFC6020]. Following the format in [RFC6020], the the following registration is requested:
name: ietf-truststore namespace: urn:ietf:params:xml:ns:yang:ietf-truststore prefix: ta reference: RFC XXXX
| [I-D.ietf-netconf-crypto-types] | Watsen, K. and H. Wang, "Common YANG Data Types for Cryptography", Internet-Draft draft-ietf-netconf-crypto-types-12, November 2019. |
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997. |
| [RFC7950] | Bjorklund, M., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016. |
| [RFC8174] | Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017. |
| [RFC8341] | Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018. |
| [RFC3688] | Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004. |
| [RFC6020] | Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010. |
| [RFC6241] | Enns, R., Bjorklund, M., Schoenwaelder, J. and A. Bierman, "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011. |
| [RFC8040] | Bierman, A., Bjorklund, M. and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017. |
| [RFC8340] | Bjorklund, M. and L. Berger, "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018. |
| [RFC8342] | Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K. and R. Wilton, "Network Management Datastore Architecture (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018. |
| [RFC8572] | Watsen, K., Farrer, I. and M. Abrahamsson, "Secure Zero Touch Provisioning (SZTP)", RFC 8572, DOI 10.17487/RFC8572, April 2019. |
The authors especially thank Henk Birkholz for contributing YANG to the ietf-truststore module supporting raw public keys and PSKs (pre-shared or pairwise-symmetric keys). While these contributions were eventually replaced by reusing the existing support for asymmetric and symmetric trust anchors, respectively, it was only thru Henk's initiative that the WG was able to come to that result.
The authors additionally thank the following for helping give shape to this work (ordered by last name): Martin Bjorklund, Nick Hancock, Balázs Kovács, Eric Voit, and Liang Xia.