NETCONF Working Group | K. Watsen |
Internet-Draft | Juniper Networks |
Intended status: Standards Track | October 30, 2017 |
Expires: May 3, 2018 |
YANG Data Model for a "Keystore" Mechanism
draft-ietf-netconf-keystore-04
This document defines a YANG module called a "keystore", containing pinned certificates and pinned SSH host-keys. The module also defines a grouping for configuring public key pairs and a grouping for configuring certificates. The module also defines a notification that a system can use when one of its configured certificates is about to expire.
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Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved.
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This document defines a YANG [RFC7950] module for a system-level mechanism, herein called a "keystore". The keystore provides a centralized location for security sensitive data, as described below.
This module has the following characteristics:
Special consideration has been given for systems that have Trusted Protection Modules (TPMs). These systems are unique in that the TPM must be directed to generate new keys (it is not possible to load a key into a TPM) and it is not possible to backup/restore the TPM's private keys as configuration.
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.
The following tree diagram [I-D.ietf-netmod-yang-tree-diagrams] provides an overview of the data model for the "ietf-keystore" module.
module: ietf-keystore +--rw keystore +--rw pinned-certificates* [name] | +--rw name string | +--rw description? string | +--rw pinned-certificate* [name] | +--rw name string | +--rw data binary +--rw pinned-host-keys* [name] +--rw name string +--rw description? string +--rw pinned-host-key* [name] +--rw name string +--rw data binary notifications: +---n certificate-expiration +--ro certificate instance-identifier +--ro expiration-date yang:date-and-time grouping certificate-grouping +---- certificates | +---- certificate* [name] | +---- name? string | +---- value? binary +---x generate-certificate-signing-request +---w input | +---w subject binary | +---w attributes? binary +--ro output +--ro certificate-signing-request binary grouping private-key-grouping +---- algorithm? identityref +---- private-key? union +---- public-key? binary +---x generate-private-key +---w input +---w algorithm identityref
The following example illustrates what a configured keystore might look like.
<keystore xmlns="urn:ietf:params:xml:ns:yang:ietf-keystore"> <!-- Manufacturer's trust root CA certs --> <pinned-certificates> <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> <pinned-certificate> <name>Manufacturer Root CA cert 1</name> <data>base64encodedvalue==</data> </pinned-certificate> <pinned-certificate> <name>Manufacturer Root CA cert 2</name> <data>base64encodedvalue==</data> </pinned-certificate> </pinned-certificates> <!-- pinned netconf/restconf client certificates --> <pinned-certificates> <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 pinned CA. </description> <pinned-certificate> <name>George Jetson</name> <data>base64encodedvalue==</data> </pinned-certificate> </pinned-certificates> <!-- pinned netconf/restconf server certificates --> <pinned-certificates> <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 pinned CA. </description> <pinned-certificate> <name>Fred Flintstone</name> <data>base64encodedvalue==</data> </pinned-certificate> </pinned-certificates> <!-- trust anchors (CA certs) for authenticating clients --> <pinned-certificates> <name>deployment-specific-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 configured CA certificates. </description> <pinned-certificate> <name>ca.example.com</name> <data>base64encodedvalue==</data> </pinned-certificate> </pinned-certificates> <!-- trust anchors for random HTTPS servers on Internet --> <pinned-certificates> <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> <pinned-certificate> <name>ex-certificate-authority</name> <data>base64encodedvalue==</data> </pinned-certificate> </pinned-certificates> <!-- pinned SSH host keys --> <pinned-host-keys> <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> <pinned-host-key> <name>corp-fw1</name> <data>base64encodedvalue==</data> </pinned-host-key> </pinned-host-keys> </keystore>
The following example illustrates the "certificate-expiration" notification in use with the NETCONF protocol.
[ note: '\' line wrapping for formatting only] <notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0"> <eventTime>2016-07-08T00:01:00Z</eventTime> <certificate-expiration xmlns="urn:ietf:params:xml:ns:yang:ietf-keystore"> <certificate xmlns:ks="urn:ietf:params:xml:ns:yang:ietf-keystore\ "> /ks:keystore/ks:keys/ks:key[ks:name='ex-rsa-key']/ks:certifica\ tes/ks:certificate[ks:name='ex-rsa-cert'] </certificate> <expiration-date>2016-08-08T14:18:53-05:00</expiration-date> </certificate-expiration> </notification>
The following example module has been constructed to illustrate the groupings 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 "IETF NETCONF (Network Configuration) Working Group"; contact "WG Web: <http://tools.ietf.org/wg/netconf/> WG List: <mailto:netconf@ietf.org> Author: Kent Watsen <mailto:kwatsen@juniper.net>"; description "This module uses the groupings defines the keystore draft for illustration."; revision "YYYY-MM-DD" { description "Initial version"; } container key { uses ks:private-key-grouping; uses ks:certificate-grouping; description "A container of certificates, and an action to generate a certificate signing request."; } }
The following example illustrates what a configured key might look like. This example uses the "ex-keystore-usage" module above.
[ note: '\' line wrapping for formatting only] <key xmlns="http://example.com/ns/example-keystore-usage"> <algorithm xmlns:ks="urn:ietf:params:xml:ns:yang:ietf-keystore">ks:\ secp521r1</algorithm> <private-key>base64encodedvalue==</private-key> <public-key>base64encodedvalue==</public-key> <certificates> <certificate> <name>domain certificate</name> <value>base64encodedvalue==</value> </certificate> </certificates> </key>
The following example illustrates the "generate-certificate-signing-request" action in use with the NETCONF protocol. This example uses the "ex-keystore-usage" module above.
REQUEST ------- <rpc message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"> <action xmlns="urn:ietf:params:xml:ns:yang:1"> <key xmlns="http://example.com/ns/example-keystore-usage"> <generate-certificate-signing-request> <subject>base64encodedvalue==</subject> <attributes>base64encodedvalue==</attributes> </generate-certificate-signing-request> </key> </action> </rpc> RESPONSE -------- <rpc-reply message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"> <certificate-signing-request xmlns="http://example.com/ns/example-keystore-usage"> base64encodedvalue== </certificate-signing-request> </rpc-reply>
The following example illustrates the "generate-private-key" action in use with the NETCONF protocol. This example uses the "ex-keystore-usage" module above.
REQUEST ------- [ note: '\' line wrapping for formatting only] <rpc message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0\ "> <action xmlns="urn:ietf:params:xml:ns:yang:1"> <key xmlns="http://example.com/ns/example-keystore-usage"> <generate-private-key> <algorithm xmlns:ks="urn:ietf:params:xml:ns:yang:ietf-keysto\ re">ks:secp521r1</algorithm> </generate-private-key> </key> </action> </rpc> RESPONSE -------- <rpc-reply message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"> <ok/> </rpc-reply>
This YANG module imports modules defined in [RFC6536] and [RFC6991]. This module uses data types defined in [RFC2315], [RFC2986], [RFC3447], [RFC4253], [RFC5280], [RFC5915], and [ITU.X690.1994]. This module uses algorithms defined in [RFC3447] and [RFC5480].
<CODE BEGINS> file "ietf-keystore@2017-10-30.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-netconf-acm { prefix nacm; reference "RFC 6536: Network Configuration Protocol (NETCONF) Access Control Model"; } organization "IETF NETCONF (Network Configuration) Working Group"; contact "WG Web: <http://tools.ietf.org/wg/netconf/> WG List: <mailto:netconf@ietf.org> Author: Kent Watsen <mailto:kwatsen@juniper.net>"; description "This module defines a keystore to centralize management of security credentials. 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 VVVV; see the RFC itself for full legal notices."; revision "2017-10-30" { description "Initial version"; reference "RFC VVVV: YANG Data Model for a 'Keystore' Mechanism"; } // Identities identity key-algorithm { description "Base identity from which all key-algorithms are derived."; } identity rsa1024 { base key-algorithm; description "The RSA algorithm using a 1024-bit key."; reference "RFC3447: Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1."; } identity rsa2048 { base key-algorithm; description "The RSA algorithm using a 2048-bit key."; reference "RFC3447: Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1."; } identity rsa3072 { base key-algorithm; description "The RSA algorithm using a 3072-bit key."; reference "RFC3447: Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1."; } identity rsa4096 { base key-algorithm; description "The RSA algorithm using a 4096-bit key."; reference "RFC3447: Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1."; } identity rsa7680 { base key-algorithm; description "The RSA algorithm using a 7680-bit key."; reference "RFC3447: Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1."; } identity rsa15360 { base key-algorithm; description "The RSA algorithm using a 15360-bit key."; reference "RFC3447: Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1."; } identity secp192r1 { base key-algorithm; description "The secp192r1 algorithm."; reference "RFC5480: Elliptic Curve Cryptography Subject Public Key Information."; } identity secp256r1 { base key-algorithm; description "The secp256r1 algorithm."; reference "RFC5480: Elliptic Curve Cryptography Subject Public Key Information."; } identity secp384r1 { base key-algorithm; description "The secp384r1 algorithm."; reference "RFC5480: Elliptic Curve Cryptography Subject Public Key Information."; } identity secp521r1 { base key-algorithm; description "The secp521r1 algorithm."; reference "RFC5480: Elliptic Curve Cryptography Subject Public Key Information."; } // typedefs typedef pinned-certificates { type leafref { path "/ks:keystore/ks:pinned-certificates/ks:name"; } description "This typedef enables importing modules to easily define a reference to pinned-certificates. Use of this type also impacts the YANG tree diagram output."; reference "I-D.ietf-netmod-yang-tree-diagrams: YANG Tree Diagrams"; } typedef pinned-host-keys { type leafref { path "/ks:keystore/ks:pinned-host-keys/ks:name"; } description "This typedef enables importing modules to easily define a reference to pinned-host-keys. Use of this type also impacts the YANG tree diagram output."; reference "I-D.ietf-netmod-yang-tree-diagrams: YANG Tree Diagrams"; } // groupings grouping private-key-grouping { description "A private/public key pair, and an action to request the system to generate a private key."; leaf algorithm { type identityref { base "key-algorithm"; } description "Identifies the key's algorithm. More specifically, this leaf specifies how the 'private-key' and 'public-key' binary leafs are encoded."; } leaf private-key { nacm:default-deny-all; 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)."; } } } must "../algorithm"; 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 [RFC3447], and an Elliptic Curve Cryptography (ECC) key is represented as ECPrivateKey as defined in [RFC5915]"; reference "RFC 3447: Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1. RFC 5915: Elliptic Curve Private Key Structure."; } leaf public-key { type binary; must "../algorithm"; must "../private-key"; 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 [RFC3447], and an Elliptic Curve Cryptography (ECC) key is represented using the 'publicKey' described in [RFC5915]"; reference "RFC 3447: Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1. RFC 5915: Elliptic Curve Private Key Structure."; } action generate-private-key { description "Requests the device to generate a private key using the specified key algorithm. This action is primarily to support cryptographic processors that must generate the private key themselves. The resulting key is considered operational state and hence only present in the <operational>."; input { leaf algorithm { type identityref { base "key-algorithm"; } mandatory true; description "The algorithm to be used when generating the key."; } } } // end generate-private-key } grouping certificate-grouping { description "A container of certificates, and an action to generate a certificate signing request."; container certificates { description "Certificates associated with this key. More than one certificate supports, for instance, a TPM-protected key that has both IDevID and LDevID certificates associated."; list certificate { key name; description "A certificate for this private key."; leaf name { type string; description "An arbitrary name for the certificate."; } leaf value { type binary; description "A PKCS #7 SignedData structure, as specified by Section 9.1 in RFC 2315, containing just certificates (no content, signatures, or CRLs), encoded using ASN.1 distinguished encoding rules (DER), as specified in ITU-T X.690. This structure contains the certificate itself as well as any intermediate certificates leading up to a trust anchor certificate. The trust anchor certificate MAY be included as well."; reference "RFC 2315: PKCS #7: Cryptographic Message Syntax Version 1.5. 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)."; } } } action generate-certificate-signing-request { description "Generates a certificate signing request structure for the associated private 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 from 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 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)."; } leaf attributes { type binary; description "The 'attributes' field from 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 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 4.1 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)."; } } } } // protocol accessible nodes container keystore { nacm:default-deny-write; description "The keystore contains X.509 certificates and SSH host keys."; list pinned-certificates { key name; description "A list of pinned certificates. These certificates can be used by a server to authenticate clients, or by clients to authenticate servers. Each list of pinned certificates SHOULD be specific to a purpose, as the list as a whole may be referenced by other modules. For instance, a NETCONF server's configuration might use a specific list of pinned certificates for when authenticating NETCONF client connections."; leaf name { type string; description "An arbitrary name for this list of pinned certificates."; } leaf description { type string; description "An arbitrary description for this list of pinned certificates."; } list pinned-certificate { key name; description "A pinned certificate."; leaf name { type string; description "An arbitrary name for this pinned certificate. The name must be unique across all lists of pinned certificates (not just this list) so that leafrefs from another module can resolve to unique values."; } leaf data { type binary; mandatory true; description "An X.509 v3 certificate structure as specified by RFC 5280, Section 4 encoded using the ASN.1 distinguished encoding rules (DER), as specified in ITU-T X.690."; reference "RFC 5280: Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile. 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)."; } } } list pinned-host-keys { key name; description "A list of pinned host keys. These pinned host-keys can be used by clients to authenticate SSH servers. Each list of pinned host keys SHOULD be specific to a purpose, so the list as a whole may be referenced by other modules. For instance, a NETCONF client's configuration might point to a specific list of pinned host keys for when authenticating specific SSH servers."; leaf name { type string; description "An arbitrary name for this list of pinned SSH host keys."; } leaf description { type string; description "An arbitrary description for this list of pinned SSH host keys."; } list pinned-host-key { key name; description "A pinned host key."; leaf name { type string; description "An arbitrary name for this pinned host-key. Must be unique across all lists of pinned host-keys (not just this list) so that a leafref to it from another module can resolve to unique values."; } leaf data { type binary; mandatory true; description "The binary public key data for this SSH key, as specified by RFC 4253, Section 6.6, i.e.: string certificate or public key format identifier byte[n] key/certificate data."; reference "RFC 4253: The Secure Shell (SSH) Transport Layer Protocol"; } } } } notification certificate-expiration { description "A notification indicating that a 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."; leaf certificate { type instance-identifier; mandatory true; description "Identifies which certificate is expiring or is expired."; } leaf expiration-date { type yang:date-and-time; mandatory true; description "Identifies the expiration date on the certificate."; } } } <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 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, Radek Krejci, Tom Petch, Juergen Schoenwaelder; Phil Shafer, Sean Turner, and Bert Wijnen.
[I-D.ietf-netmod-yang-tree-diagrams] | Bjorklund, M. and L. Berger, "YANG Tree Diagrams", Internet-Draft draft-ietf-netmod-yang-tree-diagrams-02, October 2017. |
[RFC3688] | Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004. |
[RFC4211] | Schaad, J., "Internet X.509 Public Key Infrastructure Certificate Request Message Format (CRMF)", RFC 4211, DOI 10.17487/RFC4211, September 2005. |
[RFC5056] | Williams, N., "On the Use of Channel Bindings to Secure Channels", RFC 5056, DOI 10.17487/RFC5056, November 2007. |
[RFC5914] | Housley, R., Ashmore, S. and C. Wallace, "Trust Anchor Format", RFC 5914, DOI 10.17487/RFC5914, June 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. |
[RFC8174] | Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017. |
[Std-802.1AR-2009] | IEEE SA-Standards Board, "IEEE Standard for Local and metropolitan area networks - Secure Device Identity", December 2009. |