Network Working Group T. Henderson Internet-Draft The Boeing Company Expires: August 14, 2005 February 13, 2005 Using HIP with Legacy Applications draft-henderson-hip-applications-00 Status of this Memo This document is an Internet-Draft and is subject to all provisions of section 3 of RFC 3667. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 14, 2005. Copyright Notice Copyright (C) The Internet Society (2005). Abstract The Host Identity Protocol and architecture (HIP) proposes to add a cryptographic name space for network stack names. From an application viewpoint, HIP-enabled systems support a new address family (e.g., AF_HOST), but it may be a long time until such HIP-aware applications are widely deployed even if host systems are upgraded. This informational document discusses implementation and API issues relating to using HIP in situations in which the system is Henderson Expires August 14, 2005 [Page 1] Internet-Draft Using HIP with Legacy Applications February 2005 HIP-aware but the applications are not. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Approaches for supporting legacy applications . . . . . . . . 5 3.1 Using IP addresses in applications . . . . . . . . . . . . 5 3.2 Using DNS . . . . . . . . . . . . . . . . . . . . . . . . 6 3.3 Connecting directly to a HIT . . . . . . . . . . . . . . . 7 4. Security Considerations . . . . . . . . . . . . . . . . . . . 8 5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 8 Intellectual Property and Copyright Statements . . . . . . . . 9 Henderson Expires August 14, 2005 [Page 2] Internet-Draft Using HIP with Legacy Applications February 2005 1. Introduction The Host Identity Protocol (HIP) [1] is an experimental effort in the IETF and IRTF to study a new public-key-based name space for use as host identifiers in Internet protocols. Fully deployed, the HIP architecture will permit applications to explicitly request the system to connect to another named host by expressing the name of the host when the system call to connect is performed. However, there will be a transition period during which systems become HIP-enabled but applications are not. When applications and systems are both HIP-aware, the coordination between the application and the system can be straightforward. For example, using the terminology of the widely used sockets API, the application can issue a system call to connect to another host by naming it explicitly, and the system can perform the necessary name-to-address mapping to assign appropriate routable addresses to the packets. To enable this, a new address family (e.g., AF_HOST) could be defined, and additional API extensions could be defined (such as allowing IP addresses to be passed in the system call, along with the host name, as hints of where to initially try to reach the host). This draft does not define a native HIP API such as described above. Rather, this draft is concerned with the scenario in which the application is not HIP-aware and a traditional (sockets) API is used by the application. To use HIP in such a situation, there are a few basic possibilities: i) allow applications to use IP addresses as before, and provide a mapping from IP address to host name (and back to IP address) within the system, ii) take advantage of domain name resolution to provide the application with either an alias for the host identifier or (in the case of IPv6) the host identity tag (HIT) itself, and iii) support the use of HITs directly (without prior DNS resolution) in place of IPv6 addresses. This draft describes several variations of the above strategies and suggests some pros and cons to each approach. Henderson Expires August 14, 2005 [Page 3] Internet-Draft Using HIP with Legacy Applications February 2005 2. Terminology Referral: When the application passes what it believes to be an IP address to another application instance on another host, within its application data stream. An example is the FTP PORT command. Resolver: The system function used by applications to resolve domain names to IP addresses. Henderson Expires August 14, 2005 [Page 4] Internet-Draft Using HIP with Legacy Applications February 2005 3. Approaches for supporting legacy applications This section provides examples of how legacy applications, using legacy APIs, can operate over a HIP-enabled system and use HIP. The examples are organized by the name used by an application (or application user) to name the peer system: an IP address, a domain name, or a HIT. 3.1 Using IP addresses in applications Consider the case in which an application issues a "connect(ip)" system call to connect to a system named by address "ip", but for which we would like to enable HIP to protect the communications. Since the application or user does not (can not) in this case indicate a desire to use HIP by using the standard sockets API, the decision to invoke HIP must be done on the basis of policy. For example, if an IPsec-like implementation of HIP is being used, a policy may be entered into the security policy database that mandates to use or try HIP based on a match on the source or destination IP address, or other factors. There are a number of ways that HIP could be used in such a scenario. Manual configuration: Pre-existing SAs may be available due to previous administrative action. Opportunistically: The system could send an I1 to the Responder with an empty value for Responder HIT. Using DNS: If the responder has host identities registered in the forward DNS zone and has a PTR record in the reverse zone, the initiating system could perform a reverse+forward lookup to learn the HIT associated with the address. These types of solutions have the benefit of naturally supporting application-level referrals, since the applications always use IP addresses. They have weaker security properties than full HIP, however, because the binding between host identity and address is weak. In fact, the semantics of the application's "connect(ip)" call may be interpreted as "connect me to the system reachable at IP address ip" but perhaps no stronger semantics than that. HIP can be used in this case to provide perfect forward secrecy and authentication, but not to strongly authenticate the peer at the onset of communications. DNS, if trusted, may be able to provide some additional initial authentication, but at a cost of initial Henderson Expires August 14, 2005 [Page 5] Internet-Draft Using HIP with Legacy Applications February 2005 resolution latency. 3.2 Using DNS In the previous section, it was pointed out that a HIP-enabled system might make use of DNS to transparently fetch host identifiers prior to the onset of communication. For applications that make use of DNS, the name resolution process is another opportunity to use HIP. If host identities are bound to domain names, with a trusted DNS, the following are possible: Return HIP LSIs instead of IP addresses: The system resolver could be configured to return a Local Scope Identifier (LSI) rather than an IP address, if HIP information is available in the DNS that binds a particular domain name to a host identity, and to otherwise return an IP address. The system can then maintain a mapping between LSI and host identity and perform the appropriate conversion in the transport layer and below. The application uses the LSI as it would an IP address. Locally use a HIP-specific domain name suffix: One drawback to spoofing the DNS resolution is that some applications actually may want to fetch IP addresses (e.g., diagnostic applications such as ping). One way to provide finer granularity on whether the resolver returns an IP address or an LSI is to distinguish by the presence of a domain name suffix. Specifically, if the application requests to resolve "www.ietf.org.hip" (or some similar suffix), then the system returns an LSI, while if the application requests to resolve "www.ietf.org", IP address(es) are returned as usual. If the LSI is non-routable, a couple of potential hazards arise. First, applications that perform referrals may pass the LSI to another system that has no system context to resolve the LSI back to a host identity or an IP address. Note that these are the same type of applications that will likely break if used over certain types of NATs. Second, applications may cache the results of DNS queries for a long time, and it may be hard for a HIP system to determine when to perform garbage collection on the LSI bindings. It may be possible for an LSI to be routable, but such a case may not have the level of security in the binding to host identity that a HIT has with the host identity. For example, a special IP address that have some location invariance is the identifier-address discussed in [2]. In general, LSIs considered to date for HIP have been non-routable. Henderson Expires August 14, 2005 [Page 6] Internet-Draft Using HIP with Legacy Applications February 2005 3.3 Connecting directly to a HIT The previous two sections describe the use of IP addresses and and LSIs as "handles" to a host identity. A third approach, for IPv6 applications, is to configure the application to connect directly to a HIT (e.g., "connect(HIT)" as a socket call). Although more cumbersome for human users (due to the flat HIT name space) than using either IPv6 addresses or domain names, this scenario has stronger security semantics, because the application is asking the system to connect specifically to the named peer system. It may be hard in this case for a system to distinguish between a HIT and a routable IPv6 address. Elsewhere it has been proposed that HITs be precluded (temporarily) from using highest-ordered bits that correspond to IPv6 addresses, so that at least in the near term, a system could differentiate between a HIT and an IPv6 address by inspection. Another challenge with this approach is in actually finding the IP addresses to use, based on the HIT. Some type of HIT resolution service would be needed in this case. A third challenge of this approach is in supporting referrals to possibly non-HIP-aware hosts. However, since most communications in this case would likely be to other HIP-aware hosts (else the initial connect() would fail), the problem may be instead if the peer host supports HIP but is not able to perform HIT resolution for some reason. Henderson Expires August 14, 2005 [Page 7] Internet-Draft Using HIP with Legacy Applications February 2005 4. Security Considerations To be completed. 5 References [1] Moskowitz, R., "Host Identity Protocol", draft-ietf-hip-base-01 (work in progress), October 2004. [2] Nordmark, E. and M. Bagnulo, "Multihoming L3 Shim Approach", draft-ietf-multi6-l3shim-00 (work in progress), January 2005. Author's Address Tom Henderson The Boeing Company P.O. Box 3707 Seattle, WA USA EMail: thomas.r.henderson@boeing.com Henderson Expires August 14, 2005 [Page 8] Internet-Draft Using HIP with Legacy Applications February 2005 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. 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Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2005). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Henderson Expires August 14, 2005 [Page 9]