Network Working Group A. Lindem, Ed. Internet-Draft Y. Qu Intended status: Standards Track D. Yeung Expires: April 17, 2016 Cisco Systems I. Chen Ericsson J. Zhang Juniper Networks Y. Yang Cisco Systems October 15, 2015 Key Chain YANG Data Model draft-acee-rtg-yang-key-chain-09.txt Abstract This document describes the key chain YANG data model. A key chain is a list of elements each containing a key, send lifetime, accept lifetime, and algorithm. By properly overlapping the send and accept lifetimes of multiple key chain elements, keys and algorithms may be gracefully updated. By representing them in a YANG data model, key distribution can be automated. Key chains are commonly used for routing protocol authentication and other applications. In some applications, the protocols do not use the key chain element key directly, but rather a key derivation function is used to derive a short-lived key from the key chain element key. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on April 17, 2016. Lindem, et al. Expires April 17, 2016 [Page 1] Internet-Draft YANG Key Chain October 2015 Copyright Notice Copyright (c) 2015 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 (http://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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 3 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Graceful Key Rollover using Key Chains . . . . . . . . . 3 3. Design of the Key Chain Model . . . . . . . . . . . . . . . . 4 3.1. Key Chain Operational State . . . . . . . . . . . . . . . 5 3.2. Key Chain Model Features . . . . . . . . . . . . . . . . 5 3.3. Key Chain Model Tree . . . . . . . . . . . . . . . . . . 5 4. Key Chain YANG Model . . . . . . . . . . . . . . . . . . . . 8 5. Relationship to other Work . . . . . . . . . . . . . . . . . 16 6. Security Considerations . . . . . . . . . . . . . . . . . . . 16 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 8.1. Normative References . . . . . . . . . . . . . . . . . . 17 8.2. Informative References . . . . . . . . . . . . . . . . . 17 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 18 Authors’ Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 1. Introduction This document describes the key chain YANG data model. A key chain is a list of elements each containing a key, send lifetime, accept lifetime, and algorithm. By properly overlapping the send and accept lifetimes of multiple key chain elements, keys and algorithms may be gracefully updated. By representing them in a YANG data model, key distribution can be automated. Key chains are commonly used for routing protocol authentication and other applications. In some applications, the protocols do not use the key chain element key directly, but rather a key derivation function is used to derive a short-lived key from the key chain element key. Lindem, et al. Expires April 17, 2016 [Page 2] Internet-Draft YANG Key Chain October 2015 1.1. Requirements Notation The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC-KEYWORDS]. 2. Problem Statement This document describes a YANG [YANG] data model for key chains. Key chains have been implemented and deployed by a large percentage of network equipment vendors. Providing a standard YANG model will facilitate automated key distribution and non-disruptive key rollover. This will aid in tightening the security of the core routing infrastructure as recommended in [IAB-REPORT]. A key chain is a list containing one or more elements containing a Key ID, key, send/accept lifetimes, and the associated authentication or encryption algorithm. A key chain can be used by any service or application requiring authentication or encryption. In essence, the key-chain is a reusable key policy that can be referenced where ever it is required. The key-chain construct has been implemented by most networking vendors and deployed in many networks. A conceptual representation of a crypto key table is described in [CRYPTO-KEYTABLE]. The crypto key table also includes keys as well as their corresponding lifetimes and algorithms. Additionally, the key table includes key selection criteria and envisions a deployment model where the details of the applications or services requiring authentication or encryption permeate into the key database. The YANG key-chain model described herein doesn’t include key selection criteria or support this deployment model. At the same time, it does not preclude it. The draft [YANG-CRYPTO-KEYTABLE] describes augmentations to the key chain YANG model in support of key selection criteria. 2.1. Graceful Key Rollover using Key Chains Key chains may be used to gracefully update the key and/or algorithm used by an application for authentication or encryption. This MAY be accomplished by accepting all the keys that have a valid accept lifetime and sending the key with the most recent send lifetime. One scenario for facilitating key rollover is to: 1. Distribute a key chain with a new key to all the routers or other network devices in the domain of that key chain. The new key’s accept lifetime should be such that it is accepted during the key rollover period. The send lifetime should be a time in the future when it can be assured that all the routers in the domain Lindem, et al. Expires April 17, 2016 [Page 3] Internet-Draft YANG Key Chain October 2015 of that key are upgraded. This will have no immediate impact on the keys used for transmission. 2. Assure that all the network devices have been updated with the updated key chain and that their system times are roughly synchronized. The system times of devices within an administrative domain are commonly synchronized (e.g., using Network Time Protocol (NTP) [NTP-PROTO]). This also may be automated. 3. When the send lifetime of the new key becomes valid, the network devices within the domain of key chain will start sending the new key. 4. At some point in the future, a new key chain with the old key removed may be distributed to the network devices within the domain of the key chain. However, this may be deferred until the next key rollover. If this is done, the key chain will always include two keys; either the current and future key (during key rollovers) or the current and previous keys (between key rollovers). 3. Design of the Key Chain Model The ietf-keychain module contains a list of one or more keys indexed by a Key ID. For some applications (e.g., OSPFv3 [OSPFV3-AUTH]), the Key-Id is used to identify the key chain entry to be used. In addition to the Key-ID, each key chain entry includes a key-string and a cryptographic algorithm. Optionally, the key chain entries include send/accept lifetimes. If the send/accept lifetime is unspecified, the key is always considered valid. Note that asymmetric keys, i.e., a different key value used for transmission versus acceptance, may be supported with multiple key chain elements where the accept-lifetime or send-lifetime is not valid (e.g., has an end-time equal to the start-time). Due to the differences in key chain implementations across various vendors, some of the data elements are optional. Additionally, the key-chain is made a grouping so that an implementation could support scoping other than at the global level. Finally, the crypto- algorithm-types grouping is provided for reuse when configuring legacy authentication and encryption not using key-chains. A key-chain is identified by a unique name within the scope of the network device. The "key-chain-ref" typedef SHOULD be used by other YANG modules when they need to reference a configured key-chain. Lindem, et al. Expires April 17, 2016 [Page 4] Internet-Draft YANG Key Chain October 2015 3.1. Key Chain Operational State The key chain operational state is maintained in the key-chain entries along with the configuration state. The key string itself is omitted from the operational state to minimize visibility similar to what was done with keys in SNMP MIBs. This is an area for further discussion. Additionally, the operational state includes an indication of whether or not a key chain entry is valid for sending or acceptance. 3.2. Key Chain Model Features Features are used to handle differences between vendor implementations. For example, not all vendors support configuration an acceptance tolerance or configuration of key strings in hexadecimal. They are also used to support of security requirements (e.g., TCP-AO Algorithms [TCP-AO-ALGORITHMS]) not implemented by vendors or only a single vendor. 3.3. Key Chain Model Tree +--rw key-chains +--rw key-chain-list* [name] | +--rw name string | +--ro name-state? string | +--rw accept-tolerance {accept-tolerance}? | | +--rw duration? uint32 | +--ro accept-tolerance-state | | +--ro duration? uint32 | +--rw key-chain-entry* [key-id] | +--rw key-id uint64 | +--ro key-id-state? uint64 | +--rw key-string | | +--rw (key-string-style)? | | +--:(keystring) | | | +--rw keystring? string | | +--:(hexadecimal) {hex-key-string}? | | +--rw hexadecimal-string? yang:hex-string | +--rw lifetime | | +--rw (lifetime)? | | +--:(send-and-accept-lifetime) | | | +--rw send-accept-lifetime | | | +--rw (lifetime)? | | | +--:(always) | | | | +--rw always? empty | | | +--:(start-end-time) | | | +--rw start-date-time? | | | yang:date-and-time Lindem, et al. Expires April 17, 2016 [Page 5]