NETCONF Working Group | K. Watsen |
Internet-Draft | Juniper Networks |
Intended status: Standards Track | June 4, 2018 |
Expires: December 6, 2018 |
YANG Data Model for a Centralized Keystore Mechanism
draft-ietf-netconf-keystore-05
This document defines a YANG 1.1 module called "ietf-keystore" that enables centralized configuration of asymmetric keys and their associated certificates, and notification for when configured certificates are about to expire.
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This document defines a YANG 1.1 [RFC7950] module called "ietf-keystore" that enables centralized configuration of asymmetric keys and their associated certificates, and notification for when configured certificates are about to expire.
This module also defines Six groupings designed for maximum reuse. These groupings include one for the public half of an asymmetric key, one for both the public and private halves of an asymmetric key, one for both halves of an asymmetric key and a list of associated certificates, one for an asymmetric key that may be configured locally or via a reference to an asymmetric key in the keystore, one for a trust anchor certificate and, lastly, one for an end entity certificate.
Special consideration has been given for systems that have cryptographic hardware, such as a Trusted Protection Module (TPM). These systems are unique in that the cryptographic hardware completely hides the private keys and must perform all private key operations. To support such hardware, the "private-key" can be the special value "hardware-protected" and the actions "generate-private-key" and "generate-certificate-signing-request" can be used to direct these operations to the hardware .
This document in compliant with Network Management Datastore Architecture (NMDA) [RFC8342]. For instance, to support keys and associated certificates installed during manufacturing (e.g., for a IDevID [Std-802.1AR-2009] certificate), it is expected that such data may appear only in <operational>.
While only asymmetric keys are currently supported, the module has been designed to enable other key types to be introduced in the future.
The module does not support protecting the contents of the keystore (e.g., via encryption), though it could be extended to do so in the future.
It is not required that a system has an operating system level keystore utility to implement this module.
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 section provides a tree diagrams [RFC8340] for the "ietf-keystore" module that presents both the protocol-accessible "keystore" as well the all the groupings intended for external usage.
module: ietf-keystore +--rw keystore +--rw asymmetric-keys +--rw asymmetric-key* [name] | +--rw name string | +--rw algorithm | | ct:key-algorithm-ref | +--rw public-key binary | +--rw private-key union | +--rw certificates | | +--rw certificate* [name] | | +--rw name string | | +--rw cert | | | ct:end-entity-cert-cms | | +---n certificate-expiration | | +-- expiration-date? yang:date-and-time | +---x generate-certificate-signing-request | +---w input | | +---w subject binary | | +---w attributes? binary | +--ro output | +--ro certificate-signing-request binary +---x generate-asymmetric-key +---w input +---w name string +---w algorithm ct:key-algorithm-ref grouping end-entity-cert-grouping +-- cert ct:end-entity-cert-cms +---n certificate-expiration +-- expiration-date? yang:date-and-time grouping local-or-keystore-end-entity-certificate-grouping +-- (local-or-keystore) +--:(local) | +-- algorithm ct:key-algorithm-ref | +-- public-key binary | +-- private-key union | +-- cert ct:end-entity-cert-cms | +---n certificate-expiration | +-- expiration-date? yang:date-and-time +--:(keystore) {keystore-implemented}? +-- reference ks:asymmetric-key-certificate-ref grouping local-or-keystore-asymmetric-key-with-certs-grouping +-- (local-or-keystore) +--:(local) | +-- algorithm | | ct:key-algorithm-ref | +-- public-key binary | +-- private-key union | +-- certificates | | +-- certificate* [name] | | +-- name? string | | +-- cert ct:end-entity-cert-cms | | +---n certificate-expiration | | +-- expiration-date? yang:date-and-time | +---x generate-certificate-signing-request | +---w input | | +---w subject binary | | +---w attributes? binary | +--ro output | +--ro certificate-signing-request binary +--:(keystore) {keystore-implemented}? +-- reference ks:asymmetric-key-ref grouping trust-anchor-cert-grouping +-- cert ct:trust-anchor-cert-cms grouping asymmetric-key-pair-grouping +-- algorithm ct:key-algorithm-ref +-- public-key binary +-- private-key union grouping public-key-grouping +-- algorithm ct:key-algorithm-ref +-- public-key binary grouping asymmetric-key-pair-with-certs-grouping +-- algorithm ct:key-algorithm-ref +-- public-key binary +-- private-key union +-- certificates | +-- certificate* [name] | +-- name? string | +-- cert ct:end-entity-cert-cms | +---n certificate-expiration | +-- expiration-date? yang:date-and-time +---x generate-certificate-signing-request +---w input | +---w subject binary | +---w attributes? binary +--ro output +--ro certificate-signing-request binary grouping local-or-keystore-asymmetric-key-grouping +-- (local-or-keystore) +--:(local) | +-- algorithm ct:key-algorithm-ref | +-- public-key binary | +-- private-key union +--:(keystore) {keystore-implemented}? +-- reference ks:asymmetric-key-ref
The following example illustrates what a fully configured keystore might look like in <operational>, as described by Section 5.3 in [RFC8342]. This datastore view illustrates data set by the manufacturing process alongside conventional configuration. This keystore instance has three keys, two having one associated certificate and one having two associated certificates.
<keystore xmlns="urn:ietf:params:xml:ns:yang:ietf-keystore" xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin" xmlns:ct="urn:ietf:params:xml:ns:yang:ietf-crypto-types"> <asymmetric-keys> <asymmetric-key or:origin="or:intended"> <name>ex-rsa-key</name> <algorithm>ct:rsa1024</algorithm> <private-key>base64encodedvalue==</private-key> <public-key>base64encodedvalue==</public-key> <certificates> <certificate> <name>ex-rsa-cert</name> <cert>base64encodedvalue==</cert> </certificate> </certificates> </asymmetric-key> <asymmetric-key or:origin="or:intended"> <name>tls-ec-key</name> <algorithm>ct:secp256r1</algorithm> <private-key>base64encodedvalue==</private-key> <public-key>base64encodedvalue==</public-key> <certificates> <certificate> <name>tls-ec-cert</name> <cert>base64encodedvalue==</cert> </certificate> </certificates> </asymmetric-key> <asymmetric-key or:origin="or:system"> <name>tpm-protected-key</name> <algorithm>ct:rsa2048</algorithm> <private-key>hardware-protected</private-key> <public-key>base64encodedvalue==</public-key> <certificates> <certificate> <name>builtin-idevid-cert</name> <cert>base64encodedvalue==</cert> </certificate> <certificate or:origin="or:intended"> <name>my-ldevid-cert</name> <cert>base64encodedvalue==</cert> </certificate> </certificates> </asymmetric-key> </asymmetric-keys> </keystore>
The following example illustrates the "generate-private-key" action in use with the NETCONF protocol.
REQUEST ------- <rpc message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"> <action xmlns="urn:ietf:params:xml:ns:yang:1"> <keystore xmlns="urn:ietf:params:xml:ns:yang:ietf-keystore"> <asymmetric-keys> <generate-asymmetric-key> <name>ex-key-sect571r1</name> <algorithm xmlns:ct="urn:ietf:params:xml:ns:yang:ietf-crypto-types"> ct:secp521r1 </algorithm> </generate-asymmetric-key> </asymmetric-keys> </keystore> </action> </rpc> RESPONSE -------- <rpc-reply message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"> <ok/> </rpc-reply>
The following example illustrates the "generate-certificate-signing-request" action in use with the NETCONF protocol.
REQUEST ------- <rpc message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"> <action xmlns="urn:ietf:params:xml:ns:yang:1"> <keystore xmlns="urn:ietf:params:xml:ns:yang:ietf-keystore"> <asymmetric-keys> <asymmetric-key> <name>ex-key-sect571r1</name> <generate-certificate-signing-request> <subject>base64encodedvalue==</subject> <attributes>base64encodedvalue==</attributes> </generate-certificate-signing-request> </asymmetric-key> </asymmetric-keys> </keystore> </action> </rpc> RESPONSE -------- <rpc-reply message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"> <certificate-signing-request xmlns="urn:ietf:params:xml:ns:yang:ietf-keystore"> base64encodedvalue== </certificate-signing-request> </rpc-reply>
The following example illustrates the "certificate-expiration" notification in use with the NETCONF protocol.
<notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0"> <eventTime>2018-05-25T00:01:00Z</eventTime> <keystore xmlns="urn:ietf:params:xml:ns:yang:ietf-keystore"> <asymmetric-keys> <asymmetric-key> <name>tpm-protected-key</name> <certificates> <certificate> <name>my-ldevid-cert</name> <certificate-expiration> <expiration-date> 2018-08-05T14:18:53-05:00 </expiration-date> </certificate-expiration> </certificate> </certificates> </asymmetric-key> </asymmetric-keys> </keystore> </notification>
The following example module has been constructed to illustrate the "local-or-keystore-asymmetric-key-grouping" grouping defined in the "ietf-keystore" module.
module ex-keystore-usage { yang-version 1.1; namespace "http://example.com/ns/example-keystore-usage"; prefix "eku"; import ietf-keystore { prefix ks; reference "RFC VVVV: YANG Data Model for a 'Keystore' Mechanism"; } organization "Example Corporation"; contact "Author: YANG Designer <mailto:yang.designer@example.com>"; description "This module illustrates the grouping defined in the keystore draft called 'local-or-keystore-asymmetric-key-grouping'."; revision "YYYY-MM-DD" { description "Initial version"; reference "RFC XXXX: YANG Data Model for a 'Keystore' Mechanism"; } container keys { description "A container of keys."; list key { key name; leaf name { type string; description "An arbitrary name for this key."; } uses ks:local-or-keystore-asymmetric-key-grouping; description "A key which may be configured locally or be a reference to a key in the keystore."; } } }
The following example illustrates what two configured keys, one local and the other remote, might look like. This example consistent with other examples above (i.e., the referenced key is in an example above).
<keys xmlns="http://example.com/ns/example-keystore-usage"> <key> <name>locally-defined key</name> <algorithm xmlns:ct="urn:ietf:params:xml:ns:yang:ietf-crypto-types"> ct:secp521r1 </algorithm> <private-key>base64encodedvalue==</private-key> <public-key>base64encodedvalue==</public-key> </key> <key> <name>keystore-defined key</name> <reference>ex-rsa-key</reference> </key> </keys>
This YANG module imports modules defined in [RFC6536], [RFC6991], and [I-D.ietf-netconf-crypto-types]. This module uses data types defined in [RFC2986], [RFC3447], [RFC5652], [RFC5915], [RFC6125], and [ITU.X690.2015].
<CODE BEGINS> file "ietf-keystore@2018-06-04.yang" module ietf-keystore { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-keystore"; prefix "ks"; import ietf-yang-types { prefix yang; reference "RFC 6991: Common YANG Data Types"; } import ietf-crypto-types { prefix ct; reference "RFC CCCC: 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 <mailto:kwatsen@juniper.net>"; description "This module defines a keystore to centralize management of security credentials. Copyright (c) 2018 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Simplified BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info). This version of this YANG module is part of RFC VVVV; see the RFC itself for full legal notices."; revision "2018-06-04" { description "Initial version"; reference "RFC VVVV: YANG Data Model for a 'Keystore' Mechanism"; } // Features feature keystore-implemented { description "The 'keystore-implemented' feature indicates that the server implements the keystore, and therefore groupings defined in this module that reference the keystore are usable."; } // Typedefs typedef asymmetric-key-ref { type leafref { path "/ks:keystore/ks:asymmetric-keys/ks:asymmetric-key" + "/ks:name"; require-instance false; } description "This typedef enables modules to easily define a reference to an asymmetric key stored in the keystore. The require instance attribute is false to enable the referencing of asymmetric keys that exist only in <operational>."; reference "RFC 8342: Network Management Datastore Architecture (NMDA)"; } typedef asymmetric-key-certificate-ref { type leafref { path "/ks:keystore/ks:asymmetric-keys/ks:asymmetric-key" + "/ks:certificates/ks:certificate/ks:name"; require-instance false; } description "This typedef enables modules to easily define a reference to a specific certificate associated with an asymmetric key stored in the keystore. The require instance attribute is false to enable the referencing of certificates that exist only in <operational>."; reference "RFC 8342: Network Management Datastore Architecture (NMDA)"; } // Groupings // // These groupings are factored out more than needed for // reusability purposes. grouping public-key-grouping { description "A public key."; leaf algorithm { type ct:key-algorithm-ref; mandatory true; description "Identifies the key's algorithm. More specifically, this leaf specifies how the 'public-key' binary leaf is encoded."; reference "RFC CCCC: Common YANG Data Types for Cryptography"; } leaf public-key { type binary; mandatory true; description "A binary that contains the value of the public key. The interpretation of the content is defined by the key algorithm. For example, a DSA key is an integer, an RSA key is represented as RSAPublicKey as defined in RFC 3447, and an Elliptic Curve Cryptography (ECC) key is represented using the 'publicKey' described in RFC 5915."; reference "RFC 3447: Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1. RFC 5915: Elliptic Curve Private Key Structure."; } } grouping asymmetric-key-pair-grouping { description "A private/public key pair."; uses public-key-grouping; leaf private-key { type union { type binary; type enumeration { enum "hardware-protected" { description "The private key is inaccessible due to being protected by a cryptographic hardware module (e.g., a TPM)."; } } } mandatory true; description "A binary that contains the value of the private key. The interpretation of the content is defined by the key algorithm. For example, a DSA key is an integer, an RSA key is represented as RSAPrivateKey as defined in RFC 3447, and an Elliptic Curve Cryptography (ECC) key is represented as ECPrivateKey as defined in RFC 5915."; reference "RFC 3447: Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1. RFC 5915: Elliptic Curve Private Key Structure."; } } grouping trust-anchor-cert-grouping { description "A certificate, and a notification for when it might expire."; leaf cert { type ct:trust-anchor-cert-cms; mandatory true; description "The binary certificate data for this certificate."; reference "RFC YYYY: Common YANG Data Types for Cryptography"; } } grouping end-entity-cert-grouping { description "A certificate, and a notification for when it might expire."; leaf cert { type ct:end-entity-cert-cms; mandatory true; description "The binary certificate data for this certificate."; reference "RFC YYYY: Common YANG Data Types for Cryptography"; } notification certificate-expiration { description "A notification indicating that the configured certificate is either about to expire or has already expired. When to send notifications is an implementation specific decision, but it is RECOMMENDED that a notification be sent once a month for 3 months, then once a week for four weeks, and then once a day thereafter until the issue is resolved."; leaf expiration-date { type yang:date-and-time; //mandatory true; description "Identifies the expiration date on the certificate."; } } } grouping asymmetric-key-pair-with-certs-grouping { description "A private/public key pair and associated certificates."; uses asymmetric-key-pair-grouping; container certificates { description "Certificates associated with this asymmetric key. More than one certificate supports, for instance, a TPM-protected asymmetric key that has both IDevID and LDevID certificates associated."; list certificate { key name; description "A certificate for this asymmetric key."; leaf name { type string; description "An arbitrary name for the certificate."; } uses end-entity-cert-grouping; } // end certifcate } // end certificates action generate-certificate-signing-request { description "Generates a certificate signing request structure for the associated asymmetric key using the passed subject and attribute values. The specified assertions need to be appropriate for the certificate's use. For example, an entity certificate for a TLS server SHOULD have values that enable clients to satisfy RFC 6125 processing."; input { leaf subject { type binary; mandatory true; description "The 'subject' field per the CertificationRequestInfo structure as specified by RFC 2986, Section 4.1 encoded using the ASN.1 distinguished encoding rules (DER), as specified in ITU-T X.690."; reference "RFC 2986: PKCS #10: Certification Request Syntaxi Specification Version 1.7. ITU-T X.690: Information technology – ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)."; } leaf attributes { type binary; description "The 'attributes' field from the structure CertificationRequestInfo as specified by RFC 2986, Section 4.1 encoded using the ASN.1 distinguished encoding rules (DER), as specified in ITU-T X.690."; reference "RFC 2986: PKCS #10: Certification Request Syntax Specification Version 1.7. ITU-T X.690: Information technology – ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)."; } } output { leaf certificate-signing-request { type binary; mandatory true; description "A CertificationRequest structure as specified by RFC 2986, Section 4.2 encoded using the ASN.1 distinguished encoding rules (DER), as specified in ITU-T X.690."; reference "RFC 2986: PKCS #10: Certification Request Syntax Specification Version 1.7. ITU-T X.690: Information technology – ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)."; } } // end output } // end generate-certificate-signing-request } grouping local-or-keystore-asymmetric-key-grouping { description "A grouping that expands to allow the key to be either stored locally within the using data model, or be a reference to an asymmetric key stored in the keystore."; choice local-or-keystore { mandatory true; case local { uses asymmetric-key-pair-grouping; } case keystore { if-feature "keystore-implemented"; leaf reference { type ks:asymmetric-key-ref; mandatory true; description "A reference to a value that exists in the keystore."; } } description "A choice between an inlined definition and a definition that exists in the keystore."; } } grouping local-or-keystore-asymmetric-key-with-certs-grouping { description "A grouping that expands to allow the key to be either stored locally within the using data model, or be a reference to an asymmetric key stored in the keystore."; choice local-or-keystore { mandatory true; case local { uses asymmetric-key-pair-with-certs-grouping; } case keystore { if-feature "keystore-implemented"; leaf reference { type ks:asymmetric-key-ref; mandatory true; description "A reference to a value that exists in the keystore."; } } description "A choice between an inlined definition and a definition that exists in the keystore."; } } grouping local-or-keystore-end-entity-certificate-grouping { description "A grouping that expands to allow the end-entity certificate (and the associated private key) to be either stored locally within the using data model, or be a reference to a specific certificate in the keystore."; choice local-or-keystore { mandatory true; case local { uses ks:asymmetric-key-pair-grouping; uses ks:end-entity-cert-grouping; } case keystore { if-feature "keystore-implemented"; leaf reference { type ks:asymmetric-key-certificate-ref; mandatory true; description "A reference to a value that exists in the keystore."; } } description "A choice between an inlined definition and a definition that exists in the keystore."; } } // protocol accessible nodes container keystore { description "The keystore contains a list of keys."; container asymmetric-keys { description "A list of asymmetric keys."; list asymmetric-key { key name; description "An asymmetric key."; leaf name { type string; description "An arbitrary name for the asymmetric key."; } uses asymmetric-key-pair-with-certs-grouping; } // end asymmetric-key action generate-asymmetric-key { description "Requests the device to generate an asymmetric key using the specified asymmetric key algorithm. This action is primarily to support cryptographic processors that must generate the asymmetric key themselves. The resulting asymmetric key is considered operational state and hence present only in <operational>."; input { leaf name { type string; mandatory true; description "The name the asymmetric key should have when listed in /keystore/asymmetric-keys/asymmetric-key, in <operational>."; } leaf algorithm { type ct:key-algorithm-ref; mandatory true; description "The algorithm to be used when generating the asymmetric key."; reference "RFC CCCC: Common YANG Data Types for Cryptography"; } } } // end generate-asymmetric-key } // end asymmetric-keys } // end keystore } <CODE ENDS>
The YANG module defined in this document is designed to be accessed via YANG based management protocols, such as NETCONF [RFC6241] and RESTCONF [RFC8040]. Both of these protocols have mandatory-to-implement secure transport layers (e.g., SSH, TLS) with mutual authentication.
The NETCONF access control model (NACM) [RFC6536] provides the means to restrict access for particular users to a pre-configured subset of all available protocol operations and content.
There are a number of data nodes defined in this YANG module that are writable/creatable/deletable (i.e., config true, which is the default). These data nodes may be considered sensitive or vulnerable in some network environments. Write operations (e.g., edit-config) to these data nodes without proper protection can have a negative effect on network operations. These are the subtrees and data nodes and their sensitivity/vulnerability:
Some of the readable data nodes in this YANG module may be considered sensitive or vulnerable in some network environments. It is thus important to control read access (e.g., via get, get-config, or notification) to these data nodes. These are the subtrees and data nodes and their sensitivity/vulnerability:
Some of the 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 uses PKCS #10 [RFC2986] for the "generate-certificate-signing-request" action. The use of Certificate Request Message Format (CRMF) [RFC4211] was considered, but is was unclear if there was market demand for it. If it is desired to support CRMF in the future, placing a "choice" statement in both the input and output statements, along with an "if-feature" statement on the CRMF option, would enable a backwards compatible solution.
This document registers one URI in the IETF XML registry [RFC3688]. Following the format in [RFC3688], the following registration is requested:
URI: urn:ietf:params:xml:ns:yang:ietf-keystore 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-keystore namespace: urn:ietf:params:xml:ns:yang:ietf-keystore prefix: ks reference: RFC VVVV
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, Mahesh Jethanandani, Radek Krejci, Reshad Rahman, Tom Petch, Juergen Schoenwaelder, Phil Shafer, Sean Turner, Eric Voit, Bert Wijnen, and Liang Xia.