GEOPRIV M. Thomson Internet-Draft J. Winterbottom Intended status: Standards Track Andrew Expires:
June 20,August 8, 2009 February 4, 2009 December 17, 2008Discovering the Local Location Information Server (LIS) draft-ietf-geopriv-lis-discovery-05draft-ietf-geopriv-lis-discovery-06 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or sheThis Internet-Draft is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed,submitted to IETF in accordancefull conformance with Section 6the provisions of BCP 78 and BCP 79. 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 June 20,August 8, 2009. Copyright Notice Copyright (c) 2009 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. Abstract A method is described for the discovery of a Location Information Server. The method uses a Dynamic Host Configuration Protocol (DHCP) option. DHCP options are defined for both IPv4 and IPv6 DHCP. A URI-enabled NAPTR (U-NAPTR) method is described for use where the DHCP option is unsuccessful. This document defines a U-NAPTR Application Service for a LIS, with a specific Application Protocol for the HTTP Enabled Location Delivery (HELD) protocol. Table of Contents 1. Introduction and Overview . . . . . . . . . . . . . . . . . . 3 1.1. DHCP Discovery . . . . . . . . . . . . . . . . . . . . . . 3 1.2. U-NAPTR Discovery . . . . . . . . . . . . . . . . . . . . 3 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 2. LIS Discovery Using DHCP . . . . . . . . . . . . . . . . . . . 5 2.1. DHCPv4 Option for a LIS Authentication . . . . . . .Address . . . . . . . . . . . . . 5 2.2. DHCPv4DHCPv6 Option for a LIS Address . . . . . . . . . . . . . 65 2.3. DHCPv6 Option for aLIS AddressAuthentication . . . . . . . . . . . . . . . . . . . . 6 2.3.1. DHCPv4 Option for a LIS Certificate Fingerprints . . . 7 2.3.2. DHCPv6 Option for a LIS Certificate Fingerprints . . . 9 3. U-NAPTR for LIS Discovery . . . . . . . . . . . . . . . . . . 910 3.1. Determining a Domain Name . . . . . . . . . . . . . . . . 1011 4. Overall Discovery Procedure . . . . . . . . . . . . . . . . . 1112 4.1. Virtual Private Networks (VPNs) . . . . . . . . . . . . . 1213 5. Security Considerations . . . . . . . . . . . . . . . . . . . 1314 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 1415 6.1. Registration of DHCPv4 and DHCPv6 LIS URI Option Codes . . 15 6.2. Registration of DHCPv4 and DHCPv6 LIS Certificate Fingerprints Option Codes . . . . . . 14 6.2.. . . . . . . . . . 15 6.3. Registration of a Location Server Application Service Tag . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 6.3.15 6.4. Registration of a Location Server Application Protocol Tag for HELD . . . . . . . . . . . . . . . . . . . . . . . 1415 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 1617 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 1718 8.1. Normative References . . . . . . . . . . . . . . . . . . . 1718 8.2. Informative References . . . . . . . . . . . . . . . . . . 17 Appendix A. DHCP LIS URI Option Examples . . . . . . . . . . . . 19 A.1. LIS URI Only . . . . . . . . . . . . . . . . . . . . . . . 19 A.2. LIS URI with Fingerprint . . . . . . . . . . . . . . . . . 1918 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21 Intellectual Property and Copyright Statements . . . . . . . . . . 2220 1. Introduction and Overview The location of a device is a useful and sometimes necessary part of many services. A Location Information Server (LIS) is responsible for providing that location information to devices with an access network. The LIS uses knowledge of the access network and its physical topology to generate and serve location information to devices. Each access network requires specific knowledge about topology. Therefore, it is important to discover the LIS that has the specific knowledge necessary to locate a device. That is, the LIS that serves the current access network. Automatic discovery is important where there is any chance of movement outside a single access network. Reliance on static configuration can lead to unexpected errors if a device moves between access networks. This document describes DHCP options and DNS records that a device can use to discover a LIS. The product of a discovery process, such as the one described in this document, is the address of the service. In this document, the result is an http: or https: URI, which identifies a LIS. The URI result from the discovery process is suitable for location configuration only; that is, the client MUST dereference the URI using the process described in HELD [I-D.ietf-geopriv-http-location-delivery]. URIs discovered in this way are not "location by reference" URIs; dereferencing one of them provides the location of the requester only. Clients MUST NOT embed these URIs in fields in other protocols designed to carry the location of the client. 1.1. DHCP Discovery DHCP ([RFC2131], [RFC3315]) is a commonly used mechanism for providing bootstrap configuration information allowing a device to operate in a specific network environment. The bulk of DHCP information is largely static; consisting of configuration information that does not change over the period that the device is attached to the network. Physical location information might change over this time, however the address of the LIS does not. Thus, DHCP is suitable for configuring a device with the address of a LIS. 1.2. U-NAPTR Discovery Where DHCP is not available, the DNS might be able to provide a URI. This document describes a method that uses URI-enabled NAPTR (U-NAPTR) [RFC4848], a Dynamic Delegation Discovery Service (DDDS) profile that supports URI results. For the LIS discovery DDDS application, an Application Service tag "LIS" and an Application Protocol tag "HELD" are created and registered with the IANA. Taking a domain name, this U-NAPTR application uses the two tags to determine the LIS URI. A domain name is the crucial input to the U-NAPTR resolution process. Section 3.1 of this document describes several methods for deriving an appropriate domain name. 1.3. Terminology 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 [RFC2119]. This document also uses the term "device" to refer to an end host, or client consistent with its use in HELD. In HELD and RFC3693 [RFC3693] parlance, the Device is also the Target. The terms "access network" refers to the network that a device connects to for Internet access. The "access network provider" is the entity that operates the access network. This is consistent with the definition in [I-D.ietf-geopriv-l7-lcp-ps] which combines the Internet Access Provider (IAP) and Internet Service Provider (ISP). The access network provider is responsible for allocating the device a public IP address and for directly or indirectly providing a LIS service. 2. LIS Discovery Using DHCP DHCP allows the access network provider to specify the address of a LIS as part of network configuration. If the device is able to acquire a LIS URI using DHCP then this URI is used directly; the U-NAPTR process is not necessary if this option is provided. This document registers DHCP options for a LIS addressURI for both IPv4 and IPv6. A second option for both DHCP versions is also registered to convey a fingerprint of the certificate expected to be used by the LIS. 2.1. DHCPv4 Option for a LIS Authentication TheAddress This section defines a DHCP LIS URIfor IPv4 (DHCPv4) option includes an optional authentication methodfor the address of a LIS. If an https:0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LIS_URI | Length | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | . . . LIS URI is provided for. . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: DHCPv4 LIS URI Option Example LIS_URI: The IANA assigned option number (TBD). [[IANA/RFC-Editor Note: Please replace TBD with the LIS,assigned DHCPv4 option code.]] Length: The length of the entire LIS URI option can optionally includein octets. LIS URI: The address of the LIS. The URI MUST NOT be terminated by a fingerprintzero octet. The DHCPv4 version of this URI SHOULD NOT exceed 255 octets in length, but MAY be extended by concatenating multiple option values, as described in [RFC3396]. 2.2. DHCPv6 Option for a LIS Address This section defines a DHCP for IPv6 (DHCPv6) option for the server certificate.address of a LIS. The device can useDHCPv6 option for this fingerprintparameter is similarly formatted to authenticatethe server.DHCPv4 option. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPTION_LIS_URI | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . LIS URI . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: DHCPv6 LIS URI Option OPTION_LIS_URI: The IANA assigned option number (TBD). [[IANA/ RFC-Editor Note: Please replace TBD with the assigned DHCPv6 option code.]] Length: The length of the LIS URI option in octets. The semantics and format of the remainder of the LIS URI option are identical to the DHCPv4 option, except for the larger allowance for URI length granted by the 16 bit length field. DHCPv6 prohibits concatenation of option values. 2.3. LIS Authentication HTTP over TLS [RFC2818] describes how a host can beis authenticated based on an expected domain name.name using public key infrastructure. Relying exclusively on a domain name for authentication is not appropriate for a LIS, since the domain name associated with the access network might not be known. Indeed, it is often innapropriateinappropriate to attempt to assign any particular domain name to an access network. This specification defines an alternative means of establishing an expected identity for the server that uses a certificate fingerprint. The DHCP option includes a fingerprintcertificate fingerprint. One or more fingerprints for the server certificate that is offeredused by the LIS when the associated URI is accessed. An access network operator is still able to nominate authentication based on a domain name. If no fingerprint informationis included, the device MUST authenticate the server using the method describedincluded in Section 3.1 of RFC 2818 [RFC2818]. If a fingerprint exists, the domain name method MUST NOT be used. The certificate fingerprint can be ignored if the LIS URI doesn't indicatea protocol that supports exchange of certificates (such as http:).second DHCP option. The LIS MUST be considered unauthenticated. Note: Whether the device goes on to useclient uses the fingerprint information provided by an unauthenticated LIS depends on device policy. A device might choose to continue with alternative methods of discovery before falling back to an unauthenticated LIS. The mechanismthe DHCP server to generateauthenticate the LIS when it establishes a TLS session. A fingerprint is to take thegenerated by applying a cryptographic hash offunction to the DER-encoded certificate using a cryptographically strong algorithm.certificate. The hash algorithm used for generating the fingerprint is identified by a textual name taken from the IANA registry "Hash Function Textual Names" definedestablished in [RFC4572]. Implementations MUST support SHA-1 asthe hash algorithm and useSHA-1 algorithm, using the label "sha-1" to identify the SHA-1 algorithm. Multiple fingerprints"sha-1". The output of multiple hash functions MAY be included. This provides a means to upgrade hash functions without affecting backward compatibility. If a hash algorithm is indicated, but not supported by a device, it MUST chooseuse the first fingerprint that is produced by an algorithm that the device supports. Other fingerprint values MAY be checked. If any supported fingerprint does not match, the LIS MUST be considered unauthenticated. If none of the specified hash algorithms are supported by the device, it MUST consider the LIS to be unauthenticated. A client SHOULD request the LIS certificate fingerprint option at the same time as the LIS URI option. Without the LIS certificate fingerprint option a client cannot authenticate the LIS. The certificate fingerprint can be ignored if the first algorithmLIS URI doesn't indicate a protocol that it supports. If any supportedsupports exchange of certificates (such as http:). Unless the information used in the certificate fingerprint does not match,option is used, the LIS MUST be considered asunauthenticated. If no hash algorithmNote: Whether the device goes on to use the information provided by an unauthenticated LIS depends on device policy. A device might choose to continue with alternative methods of discovery before falling back to an unauthenticated LIS. An access network operator is supportedable to nominate authentication based on a domain name by omitting fingerprints. If a zero-length fingerprint option is provided, the device, itdevice MUST considerauthenticate the LIS toserver using the method described in Section 3.1 of RFC 2818 [RFC2818]. If a fingerprint exists, the domain name method MUST NOT be unauthenticated. 2.2.used. 2.3.1. DHCPv4 Option for a LIS AddressCertificate Fingerprints This section defines a DHCP for IPv4 (DHCPv4) option for the address of a LIS.LIS certificate fingerprints. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LIS_URILIS_CERT_FP | Length | F-Code(1) | F-LengthHash-Type-Len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| Hash-Type-Len+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | . Hash-Type .... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Fingerprint-Value ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+F'print-Len | F-Code(0)| URI . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+ | URI (cont.) .... . . Fingerprint-Value . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: DHCPv4 LIS URI Option Example LIS_URI: The IANA assigned option number (TBD). [[IANA/RFC-Editor Note: Please replace TBD with the assigned DHCPv4 option code.]] Length: The length of the entire LIS URI option in octets. F-Code: A single octet indicates the type of data that follows: fingerprint or URI. A value of 1 indicates that the following data includes a certificate fingerprint. A value of 0 indicates that no more supplementary data is included and the URI follows. An "F-Code" with a value of 0 MUST be included. Values other than zero or one MAY be ignored. Any other value MUST be specified in a standards track RFC that SHOULD establish an. (Hash-Type-Len through Fingerprint-Value Repeated) . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: DHCPv4 LIS Certificate Fingerprints Option Example LIS_CERT_FP: The IANA registry. F-Length: If the "F-Code" is non-zero, it MUST be followed by an octet that indicatesassigned option number (TBD). [[IANA/ RFC-Editor Note: Please replace TBD with the length, in octets,assigned DHCPv4 option code.]] Length: The length of the data.entire LIS certificate fingerprints option in octets. This value includesoption MAY be zero length, indicating the sumabsence of the lengths of: "Hash-Type-Len", "Hash-Type", and "Fingerprint-Value".fingerprint information. Hash-Type-Len: The length, in octets, of the "Hash-Type" field. Hash-Type: A text tag that identifies the hash algorithm used to generate the fingerprint. The set of values are defined in the "Hash Function Textual Names" IANA registry [RFC4572]. F'print-Len: The length, in octets of the "Fingerprint-Value" field. Fingerprint-Value: The octet values of the certificate fingerprint. The length of this field is defined by the hash algorithm and MUST match the remainder of the fingerprint data. If this does not equal the value of "F-Length" less the length "Hash-Type-Len" and "Hash-Type", the fingerprint MUST be considered invalid. Note:An invalid fingerprint is not equivalent to no fingerprint. URI: The address of the LIS. The URI takesIf this value is not the remainderexpected length of the DHCP option. The URIhash function output, the fingerprint MUST NOTbe NULL terminated.considered invalid. The DHCPv4 version of this URI SHOULD NOT exceed 225 octets in length, butfour fields, "Hash-Type-Len", "Hash-Type", "F'print-Len" and "Fingerprint-Value" MAY be extended by concatenating multiple option values, as described in [RFC3396]. 2.3.repeated. Each repetition includes a different hash type, except for hashes that produce values longer than 2040 bits (255 octets), for which the "Fingerprint-Value" is concatenated to derive the value. 2.3.2. DHCPv6 Option for a LIS AddressCertificate Fingerprints This section defines a DHCP for IPv6 (DHCPv6) option for the address of a LIS.LIS certificate fingerprints. The DHCPv6 option for this parameter is similarly formatted to the DHCPv4 option. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPTION_LIS_URIOPTION_LIS_CERT_FP | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | F-Code(1)Hash-Type-Len | F-Length| Hash-Type-Len+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | . Hash-Type .... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Fingerprint-Value ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+F'print-Len | F-Code(0)| URI+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | . . . Fingerprint-Value . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | URI (cont.) .... (Hash-Type-Len through Fingerprint-Value Repeated) . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2:4: DHCPv6 LIS URICertificate Fingerprints Option OPTION_LIS_URI:OPTION_LIS_CERT_FP: The IANA assigned option number (TBD). [[IANA/ RFC-Editor Note: Please replace TBD with the assigned DHCPv6 option code.]] Length: The length of the LIS URIcertificate fingerprints option in octets. The formatsemantics of remainder of the LIS URI option isare identical to the DHCPv4 option. As shown, length fields are extended to 16 bits, removing the need for concatenation to accomodate values longer than 255 octets in length. DHCPv6 prohibits concatenation of option values. 3. U-NAPTR for LIS Discovery U-NAPTR resolution for a LIS takes a domain name as input and produces a URI that identifies the LIS. This process also requires an Application Service tag and an Application Protocol tag, which differentiate LIS-related NAPTR records from other records for that domain. Section 6.26.3 defines an Application Service tag of "LIS", which is used to identify the location service for a particular domain. The Application Protocol tag "HELD", defined in Section 6.3,6.4, is used to identify a LIS that understands the HELD protocol [I-D.ietf-geopriv-http-location-delivery]. The NAPTR records in the following example demonstrate the use of the Application Service and Protocol tags. Iterative NAPTR resolution is used to delegate responsibility for the LIS service from "zonea.example.net." and "zoneb.example.net." to "outsource.example.com.". zonea.example.net. ;; order pref flags IN NAPTR 100 10 "" "LIS:HELD" ( ; service "" ; regex outsource.example.com. ; replacement ) zoneb.example.net. ;; order pref flags IN NAPTR 100 10 "" "LIS:HELD" ( ; service "" ; regex outsource.example.com. ; replacement ) outsource.example.com. ;; order pref flags IN NAPTR 100 10 "u" "LIS:HELD" ( ; service "!*.!https://lis.example.org:4802/?c=ex!" ; regex . ; replacement ) Figure 3:5: Sample LIS:HELD Service NAPTR Records Details for the "LIS" Application Service tag and the "HELD" Application Protocol tag are included in Section 6. U-NAPTR MUST only be used if the DHCP LIS URI option is not available. An https: LIS URI that is a product of U-NAPTR MUST be authenticated using the domain name method described in Section 3.1 of RFC 2818 [RFC2818]. 3.1. Determining a Domain Name The U-NAPTR discovery method described requires a domain name as input. This document does not specify how that domain name is acquired by a device. If a device knows one or more of the domain names assigned to it, it MAY attempt to use each domain name as input. Static configuration of a device is possible if a domain name is known to work for this purpose. A fully qualified domain name (FQDN) for the device might be provided by a DHCP server ([RFC4702] for DHCPv4, [RFC4704] for DHCPv6). DHCPv4 option 15 [RFC2131] could also be used as a source of a domain name suffix for the device. If DHCP and any of these options are available, these values could be used as input the U-NAPTR procedure; however, implementers need to be aware that many DHCP servers do not provide a sensible value for these options. 4. Overall Discovery Procedure The individual components of discovery are combined into a single discovery procedure. Some networks maintain a topology analogous to an onion and are comprised of layers, or segments, separating hosts from the Internet through intermediate networks. Applying the individual discovery methods in an order that favours a physically proximate LIS over a remote LIS is preferred. A host MUST support DHCP discovery and MAY support U-NAPTR discovery. The process described in this document is known to not work in a very common deployment scenario, namely the fixed wired environment described in Section 3.1 of [I-D.ietf-geopriv-l7-lcp-ps]. Alternative methods of discovery to address this limitation are likely. The following process ensures a greater likelihood of a LIS in close physical proximity being discovered: 1. Request the DHCP LIS URI Option for each network interface. 2. Use U-NAPTR to discover a LIS URI using all known domain names. 3. Use a statically configured LIS URI. A host that has multiple network interfaces could potentially be served by a different access network on each interface, each with a different LIS. The host SHOULD attempt to discover the LIS applicable to each network interface, stopping when a LIS is successfully discovered on any interface. A host that discovers a LIS URI MUST attempt to verify that the LIS is able to provide location information. For the HELD protocol, the host MUST make a location request to the LIS. If the LIS responds to this request with the "notLocatable" error code (see Section 4.3.2 of [I-D.ietf-geopriv-http-location-delivery]), the host MUST continue the discovery process and not make further requests to that LIS on that network interface. DHCP discovery MUST be attempted before any other discovery method. This allows the network access provider a direct and explicit means of configuring a LIS address. Alternative methods are only specified as a means to discover a LIS where the DHCP infrastructure does not support the LIS URI option. This document does not mandate any particular source for the domain name that is used as input to U-NAPTR. Alternative methods for determining the domain name MAY be used. Static configuration MAY be used if all other discovery methods fail. Note however, that if a host has moved from its customary location, static configuration might indicate a LIS that is unable to provide a location. The product of the LIS discovery process is an http: or https: URI. Nothing distinguishes this URI from other URIs with the same scheme, aside from the fact that it is the product of this process. Only URIs produced by the discovery process can be used for location configuration using HELD. URIs that are not a product of LIS discovery MUST NOT be used for location configuration. 4.1. Virtual Private Networks (VPNs) LIS discovery over a VPN network interface SHOULD NOT be performed. A LIS discovered in this way is unlikely to have the information necessary to determine an accurate location. Since not all interfaces connected to a VPN can be detected by hosts, a LIS SHOULD NOT provide location information in response to requests that it can identify as originating from a VPN pool. This ensures that even if a host discovers a LIS over the VPN, it does not rely on a LIS that is unable to provide accurate location information. The exception to this is where the LIS and host are able to determine a location without access network support. 5. Security Considerations The primary attack against the methods described in this document is one that would lead to impersonation of a LIS. The LIS is responsible for providing location information and this information is critical to a number of network services; furthermore, a host does not necessarily have a prior relationship with a LIS. Several methods are described here that can limit the probablity of, or provide some protection against, such an attack. The address of a LIS is usually well-known within an access network; therefore, interception of messages does not introduce any specific concerns. If DHCP is used, theThe integrity of DHCP options is limited by the security of the channel over which they are provided. Physical security and separation of DHCP messages from other packets are commonplace methods that can reduce the possibility of attack within an access network; alternatively, DHCP authentication [RFC3118] can provide a degree of protection against modification.degree of protection against modification. Section 2.3 describes how a LIS is authenticated by clients, using either certificate fingerprints or a domain name certificate. An attacker could attempt to compromise the U-NAPTR resolution. A more thorough description of the security considerations for U-NAPTR applications is included in [RFC4848]. In addition to considerations related to U-NAPTR, it is important to recognize that the output of this is entirely dependent on its input. An attacker who can control the domain name is therefore able to control the final URI. Any mechanism for automatically determining such a domain name MUST consider such attacks.6. IANA Considerations 6.1. Registration of DHCPv4 and DHCPv6 LIS URI Option Codes The IANA is requested to assignhas assigned an option code of (TBD) for the DHCPv4 option for a LIS address,URI, as described in Section 2.22.1 of this document. The IANA is requested to assignhas assigned an option code of (TBD) for the DHCPv6 option for a LIS address,URI, as described in Section 2.32.2 of this document. 6.2. Registration of DHCPv4 and DHCPv6 LIS Certificate Fingerprints Option Codes The IANA has assigned an option code of (TBD) for the DHCPv4 option for a LIS certificate fingerprints, as described in Section 2.3.1 of this document. The IANA has assigned an option code of (TBD) for the DHCPv6 option for a LIS certificate fingerprints, as described in Section 2.3.2 of this document. 6.3. Registration of a Location Server Application Service Tag This section registers a new S-NAPTR/U-NAPTR Application Service tag for a LIS, as mandated by [RFC3958]. Application Service Tag: LIS Intended usage: Identifies a service that provides a host with its location information. Defining publication: RFCXXXX Related publications: HELD [I-D.ietf-geopriv-http-location-delivery] Contact information: The authors of this document Author/Change controller: The IESG 184.108.40.206. Registration of a Location Server Application Protocol Tag for HELD This section registers a new S-NAPTR/U-NAPTR Application Protocol tag for the HELD [I-D.ietf-geopriv-http-location-delivery] protocol, as mandated by [RFC3958]. Application Service Tag: HELD Intended Usage: Identifies the HELD protocol. Applicable Service Tag(s): LIS Terminal NAPTR Record Type(s): U Defining Publication: RFCXXXX Related Publications: HELD [I-D.ietf-geopriv-http-location-delivery] Contact Information: The authors of this document Author/Change Controller: The IESG 7. Acknowledgements The authors would like to thank Leslie Daigle for her work on U-NAPTR; Peter Koch for hisfeedback on thehow not to use DNS aspects of this document;for discovery; Andy Newton for constructive suggestions with regards to document direction; Hannes Tschofenig and Richard Barnes for input and reviews; Dean Willis for constructive feedback; Pasi Eronen for the certificate fingerprint concept.concept; Ralph Droms, David W. Hankins, Damien Neil, and Bernie Volz for DHCP option format. 8. References 8.1. Normative References [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997. [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. [RFC3396] Lemon, T. and S. Cheshire, "Encoding Long Options in the Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396, November 2002. [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the Transport Layer Security (TLS) Protocol in the Session Description Protocol (SDP)", RFC 4572, July 2006. [RFC4702] Stapp, M., Volz, B., and Y. Rekhter, "The Dynamic Host Configuration Protocol (DHCP) Client Fully Qualified Domain Name (FQDN) Option", RFC 4702, October 2006. [RFC4704] Volz, B., "The Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Client Fully Qualified Domain Name (FQDN) Option", RFC 4704, October 2006. [RFC4848] Daigle, L., "Domain-Based Application Service Location Using URIs and the Dynamic Delegation Discovery Service (DDDS)", RFC 4848, April 2007. [I-D.ietf-geopriv-http-location-delivery] Barnes, M., Winterbottom, J., Thomson, M., and B. Stark, "HTTP Enabled Location Delivery (HELD)", draft-ietf-geopriv-http-location-delivery-10draft-ietf-geopriv-http-location-delivery-12 (work in progress), October 2008.January 2009. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 8.2. Informative References [RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP Messages", RFC 3118, June 2001. [RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J. Polk, "Geopriv Requirements", RFC 3693, February 2004. [RFC3958] Daigle, L. and A. Newton, "Domain-Based Application Service Location Using SRV RRs and the Dynamic Delegation Discovery Service (DDDS)", RFC 3958, January 2005. [I-D.ietf-geopriv-l7-lcp-ps] Tschofenig, H. and H. Schulzrinne, "GEOPRIV Layer 7 Location Configuration Protocol; Problem Statement and Requirements", draft-ietf-geopriv-l7-lcp-ps-08 (work in progress), June 2008. Appendix A. DHCP LIS URI Option Examples A.1. LIS URI Only Figure 4 shows an example LIS URI option for DHCPv6 in hexadecimal form. This example is the simplest form, with an http: URI and no fingerprint information. Hexadecimal representation of LIS option, including the leading DHCPv4 option code and length octets: [[IANA/RFC-Editor Note: Please replace instances of "??:??" in the following example with the hexadecimal representation of the IANA allocated DHCPv6 option code; replace "???" with the decimal representation of the IANA allocated DHCPv6 option code.]] ??:??:00:1d:00:68:74:74:70:3a:2f:2f:6c:69:73:2e:65:78:61:6d: 70:6c:65:2e:6f:72:67:3a:34:38:30:31:2f Octet Value Description ------- ------- -------------------------------------------------- 00-01 ??:?? LIS URI Option Code (???) 02 00:1d Option Length = 29 03 00 F-Code = 0 (URI) 04- 68:74:74:70:3a:2f:2f:6c:69:73:2e:65:78:61:6d:70: -1f 6c:65:2e:6f:72:67:3a:34:38:30:31:2f - LIS URI = "http://lis.example.org:4801/" Figure 4: Example of a Simple LIS URI Option A.2. LIS URI with Fingerprint Figure 5 shows an example LIS URI option for DHCPv4 in hexadecimal form. This example shows the inclusion of two fingerprints, the first based on SHA-256,RRs and the second based on SHA-1. Hexadecimal representation of LIS option, including the leading DHCPv4 option codeDynamic Delegation Discovery Service (DDDS)", RFC 3958, January 2005. [I-D.ietf-geopriv-l7-lcp-ps] Tschofenig, H. and length octets: [[IANA/RFC-Editor Note: Please replace two instances of "??" in the following example with the hexadecimal representation of the IANA allocated DHCPv4 option code; replace "???" with the decimal representation of the IANA allocated DHCPv4 option code.]] ??:69:01:28:07:73:68:61:2d:32:35:36:49:20:77:6f:6e:64:65:72: 20:69:66:74:68:69:73:20:77:69:6c:6c:20:62:65:20:6e:6f:74:69: 63:65:64:3f:01:1a:07:73:68:61:2d:31:39:39:62:6f:74:74:6c:65: 73:6f:66:62:65:65:72:6f:6e:74:68:65:00:68:74:74:70:73:3a:2f: 2f:6c:69:73:2e:65:78:61:6d:70:6c:65:2e:6f:72:67:3a:34:38:30: 32:2f:3f:63:3d:65:78 Octet Value Description ------- ------- -------------------------------------------------- 00 ?? LIS URI Option Code (???) 01 6a Option Length = 106 02 01 F-Code = 1 (Fingerprint) 03 28 F-Length = 40 04 07 Hash-Type-Len =H. Schulzrinne, "GEOPRIV Layer 7 05-0b 73:68:61:2d:32:35:36 - Hash-Type = "sha-256" 0c- 49:20:77:6f:6e:64:65:72:20:69:66:74:68:69:73:20: -2b 77:69:6c:6c:20:62:65:20:6e:6f:74:69:63:65:64:3f - Fingerprint-Value (SHA-256 output) 2c 01 F-Code = 1 (Fingerprint) 2d 1a F-Length = 26 2e 07 Hash-Type-Len = 5 2f-33 73:68:61:2d:31 - Hash-Type = "sha-1" 34- 39:39:62:6f:74:74:6c:65:73:6f: -47 66:62:65:65:72:6f:6e:74:68:65 - Fingerprint-Value (SHA-1 output) 48 00 F-Code = 0 (URI) 49- 68:74:74:70:73:3a:2f:2f:6c:69:73:2e:65:78:61:6d:70: -6a 6c:65:2e:6f:72:67:3a:34:38:30:32:2f:3f:63:3d:65:78 - LIS URI = "https://lis.example.org:4802/?c=ex" Figure 5: Example LIS URI Option with Fingerprint DataLocation Configuration Protocol; Problem Statement and Requirements", draft-ietf-geopriv-l7-lcp-ps-08 (work in progress), June 2008. Authors' Addresses Martin Thomson Andrew PO Box U40 Wollongong University Campus, NSW 2500 AU Phone: +61 2 4221 2915 Email: email@example.com URI: http://www.andrew.com/ James Winterbottom Andrew PO Box U40 Wollongong University Campus, NSW 2500 AU Phone: +61 2 4221 2938 Email: firstname.lastname@example.org URI: http://www.andrew.com/ Full Copyright Statement Copyright (C) The IETF Trust (2008). 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. 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