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Internet Engineering Task Force (IETF) M. Komu Request for Comments: 6317 Aalto University Category: Experimental T. Henderson ISSN: 2070-1721 The Boeing Company July 2011 Basic Socket Interface Extensions for the Host Identity Protocol (HIP) Abstract This document defines extensions to the current sockets API for the Host Identity Protocol (HIP). The extensions focus on the use of public-key-based identifiers discovered via DNS resolution, but also define interfaces for manual bindings between Host Identity Tags (HITs) and locators. With the extensions, the application can also support more relaxed security models where communication can be non- HIP-based, according to local policies. The extensions in this document are experimental and provide basic tools for further experimentation with policies. Status of This Memo This document is not an Internet Standards Track specification; it is published for examination, experimental implementation, and evaluation. This document defines an Experimental Protocol for the Internet community. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6317. Komu & Henderson Experimental [Page 1] RFC 6317 Basic API Extensions for HIP July 2011 Copyright Notice Copyright (c) 2011 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. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Table of Contents 1. Introduction ....................................................3 2. Terminology .....................................................5 3. Name Resolution Process .........................................5 3.1. Interaction with the Resolver ..............................5 3.2. Interaction without a Resolver .............................6 4. API Syntax and Semantics ........................................7 4.1. Socket Family and Address Structure Extensions .............7 4.2. Extensions to Resolver Data Structures .....................9 4.3. The Use of getsockname() and getpeername() Functions ......12 4.4. Selection of Source HIT Type ..............................12 4.5. Verification of HIT Type ..................................13 4.6. Explicit Handling of Locators .............................14 5. Summary of New Definitions .....................................16 6. Security Considerations ........................................16 7. Contributors ...................................................17 8. Acknowledgments ................................................17 9. References .....................................................17 9.1. Normative References ......................................17 9.2. Informative References ....................................18 Komu & Henderson Experimental [Page 2] RFC 6317 Basic API Extensions for HIP July 2011 1. Introduction This document defines the C-based sockets Application Programming Interface (API) extensions for handling HIP-based identifiers explicitly in HIP-aware applications. It is up to the applications, or high-level programming languages or libraries, to manage the identifiers. The extensions in this document are mainly related to the use case in which a DNS resolution step has occurred prior to the creation of a new socket, and assumes that the system has cached or is otherwise able to resolve identifiers to locators (IP addresses). The DNS extension for HIP is described in [RFC5205]. The extensions also cover the case in which an application may want to explicitly provide suggested locators with the identifiers, including supporting the opportunistic case in which the system does not know the peer host identity. The Host Identity Protocol (HIP) [RFC4423] proposes a new cryptographic namespace by separating the roles of endpoint identifiers and locators by introducing a new namespace to the TCP/IP stack. Shim6 [RFC5533] is another protocol based on an identity- locator split. The APIs specified in this document are specific to HIP, but have been designed as much as possible to not preclude its use with other protocols. The use of these APIs with other protocols is, nevertheless, for further study. The APIs in this document are based on Host Identity Tags (HITs) that are defined as IPv6 addresses with the Overlay Routable Cryptographic Hash Identifiers (ORCHID) prefix [RFC4843]. ORCHIDs are derived from Host Identifiers using a hash and fitting the result into an IPv6 address. Such addresses are called HITs, and they can be distinguished from other IPv6 addresses via the ORCHID prefix. Note that ORCHIDs are presently an experimental allocation by IANA. If the ORCHID allocation were to expire and HIT generation were to use a different prefix in the future, most users of the API would not be impacted, unless they explicitly checked the ORCHID prefix on returned HITs. Users who check (for consistency) that HITs have a valid ORCHID prefix must monitor the IANA allocation for ORCHIDs and adapt their software in case the ORCHID allocation were to be removed at a future date. Applications can observe the HIP layer and its identifiers in the networking stacks with varying degrees of visibility. [RFC5338] discusses the lowest levels of visibility in which applications are completely unaware of the underlying HIP layer. Such HIP-unaware applications in some circumstances use HIP-based identifiers, such as Local Scope Identifiers (LSIs) or HITs, instead of IPv4 or IPv6 addresses and cannot observe the identifier-locator bindings. Komu & Henderson Experimental [Page 3] RFC 6317 Basic API Extensions for HIP July 2011 This document specifies extensions to [RFC3493] to define a new socket address family, AF_HIP. Similarly to other address families, AF_HIP can be used as an alias for PF_HIP. The extensions also describe a new socket address structure for sockets using HITs explicitly and describe how the socket calls in [RFC3493] are adapted or extended as a result. Some applications may accept incoming communications from any identifier. Other applications may initiate outgoing communications without the knowledge of the peer identifier in opportunistic mode (Section 4.1.6 of [RFC5201]) by just relying on a peer locator. This document describes how to address both situations using "wildcards" as described in Section 4.1.1. This document references one additional API document [RFC6316] that defines multihoming and explicit-locator handling. Most of the extensions defined in this document can be used independently of the above document. The identity-locator split introduced by HIP introduces some policy- related challenges with datagram-oriented sockets, opportunistic mode, and manual bindings between HITs and locators. The extensions in this document are of an experimental nature and provide basic tools for experimenting with policies. Policy-related issues are left for further experimentation. To recap, the extensions in this document have three goals. The first goal is to allow HIP-aware applications to open sockets to other hosts based on the HITs alone, presuming that the underlying system can resolve the HITs to addresses used for initial contact. The second goal is that applications can explicitly initiate communications with unknown peer identifiers. The third goal is to illustrate how HIP-aware applications can use the Shim API [RFC6316] to manually map locators to HITs. This document was published as experimental because a number of its normative references had experimental status. The success of this experiment can be evaluated by a thorough implementation of the APIs defined. Komu & Henderson Experimental [Page 4] RFC 6317 Basic API Extensions for HIP July 2011 2. Terminology The terms used in this document are summarized in Table 1. +---------+--------------------------------------------------------+ | Term | Explanation | +---------+--------------------------------------------------------+ | FQDN | Fully Qualified Domain Name | | HIP | Host Identity Protocol | | HI | Host Identifier | | HIT | Host Identity