SIMPLE J. Rosenberg Internet-Draft dynamicsoft Expires: August 9, 2004 February 9, 2004 Presence Authorization Rules draft-rosenberg-simple-rules-00 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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 9, 2004. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract Authorization is a key function in presence systems. Authorization policies, also known as authorization rules, specify what presence information can be given to which watchers, and when. This specification defines an Extensible Markup Language (XML) document format for expressing presence authorization rules. Such a document can be manipulated by clients using the XML Configuration Access Protocol (XCAP), although other techniques are permitted. Rosenberg Expires August 9, 2004 [Page 1] Internet-Draft Presence Authorization February 2004 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Structure of Permission Statements . . . . . . . . . . . . . 5 3.1 Conditions . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1.1 Identity . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1.2 Anonymous . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.2 Actions . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2.1 Accept Subscription . . . . . . . . . . . . . . . . . . . . 6 3.2.2 Provide Presence . . . . . . . . . . . . . . . . . . . . . . 6 3.3 Transformations . . . . . . . . . . . . . . . . . . . . . . 6 3.3.1 Show Namespace . . . . . . . . . . . . . . . . . . . . . . . 7 3.3.2 Show Tuple . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.3.3 Show Element . . . . . . . . . . . . . . . . . . . . . . . . 8 4. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . 9 5. Example Document . . . . . . . . . . . . . . . . . . . . . . 11 6. XCAP Usage . . . . . . . . . . . . . . . . . . . . . . . . . 12 6.1 Application Unique ID . . . . . . . . . . . . . . . . . . . 12 6.2 Structure of Permission Statements . . . . . . . . . . . . . 12 6.3 Additional Constraints . . . . . . . . . . . . . . . . . . . 12 6.4 Naming Conventions . . . . . . . . . . . . . . . . . . . . . 12 6.5 Authorization Policies . . . . . . . . . . . . . . . . . . . 12 6.6 XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . 12 7. Security Considerations . . . . . . . . . . . . . . . . . . 13 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . 14 8.1 XCAP Application Usage ID . . . . . . . . . . . . . . . . . 14 8.2 URN Sub-Namespace Registration . . . . . . . . . . . . . . . 14 8.3 XML Schema Registrations . . . . . . . . . . . . . . . . . . 15 Normative References . . . . . . . . . . . . . . . . . . . . 16 Informative References . . . . . . . . . . . . . . . . . . . 18 Author's Address . . . . . . . . . . . . . . . . . . . . . . 18 Intellectual Property and Copyright Statements . . . . . . . 19 Rosenberg Expires August 9, 2004 [Page 2] Internet-Draft Presence Authorization February 2004 1. Introduction The Session Initiation Protocol (SIP) for Instant Messaging and Presence (SIMPLE) specifications allow a user, called a watcher, to subscribe to another user, called a presentity [15], in order to learn their presence information [17]. This subscription is handed by a presence agent. In order to process the subscription, the presence agent must make a determination about whether the subscription is authorized. This authorization decision includes whether or not to accept the subscription, but also includes decisions about when the watcher should receive notifications, and when it does receive them, what the content of those notifications should be. Typically, the authorization decision will be a combination of the authorization policies of the provider, combined with the authorization policies of the presentity. In order for the PA to compute the final authorization decision, it needs access to the presentity's authorization policies. [10] specifies a framework for representing such authorization policies, and is applicable to systems such as geo-location and presence. In that framework, an authorization document is a sequence of rule elements. Each rule element contains a conditions element, an actions element, and a transformations element. The conditions element specifies under what conditions the rule is to be applied to a subscription request. The actions element tells the server what actions to take against the request. The transformations element indicates how the presence data is to be manipulated before being presented to that watcher. [10] identifies a small number of specific conditions, actions and permissions common to presence and location services, and leaves it to other specifications, such as this one, to fill in usage specific details. These documents can be manipulated by clients using several means. One such mechanism is the XML Configuration Access Protocol (XCAP) [2]. This specification defines the details necessary for using XCAP to manage presence authorization documents. Rosenberg Expires August 9, 2004 [Page 3] Internet-Draft Presence Authorization February 2004 2. Terminology In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in RFC 2119 [1] and indicate requirement levels for compliant implementations. Rosenberg Expires August 9, 2004 [Page 4] Internet-Draft Presence Authorization February 2004 3. Structure of Permission Statements A permission statement is an XML document, formatted according to the schema defined in [10]. As described in [10], this document is composed of three parts - conditions, actions, and transformations. Each action or transformation, which is also called an attribute, has the property of being a positive grant of information to the watcher. As a result, there is a well-defined mechanism for combining actions and transformations obtained from several sources. This mechanism is privacy safe, since the lack of any action or transformation can only result in less information being presented to a watcher. This section defines the new conditions, actions and transformations defined by this specification. 3.1 Conditions 3.1.1 Identity Although the "identity" element is defined in [10], that specification indicates that the interpretation of the "uri" element depends on the specific protocol in use and its authentication mechanisms. This sub-section defines that interpretation for systems based on [17] [[NOTE: "uri" is a bad choice of name for this element, since its not a URI. That will be corrected in a subsequent revision of the common policy document.]] For requests that are authenticated using SIP [9] digest authentication [8], the user part of the URI is matched against the username attribute in the Authorization request header field. The domain part of the URI is matched against the realm attribute in the Authorization request header field. For requests that are authenticated using [18], the username and domain part of the URI are matched against the user and host parts of the SIP URI in the P-Asserted-Identity header field. For requests that are authenticated using [11], the username and domain part of the URI are matched against the user and host parts of the SIP URI in the From header field of the Asserted Identity Body [12]. 3.1.2 Anonymous The "anonymous" element, which is a boolean type, indicates whether or not the request was authenticated using the "anonymous" username defined in RFC 3261. It allows for the presentity to specify policies based on whether or not the requestor was anonymous. Rosenberg Expires August 9, 2004 [Page 5] Internet-Draft Presence Authorization February 2004 3.2 Actions The "confirmation" element specified in [10] applies to presence systems. When TRUE, it implies that the subscription is placed in the pending state. Confirmation is provided by modifying the rules to accept the subscription. 3.2.1 Accept Subscription The "accept-subscription" element represents a boolean action. If TRUE, it means that the subscription is to be accepted. If FALSE, it means that the subscription is to be rejected. If this element is undefined (i.e., not present in the any matching rule), it has a value of FALSE and therefore causes the subscription to be blocked. NOTE WELL: Placing a value of FALSE for this element does not guarantee that a subscription is denied! If any matching rule has a value of TRUE for "accept-subscription", the subscription will be granted due to the combining rules defined in [10]. 3.2.2 Provide Presence The "provide-presence" element is used to implement the "polite blocking" feature defined in RFC 2779 [16]. The element represents a boolean data type. When TRUE, it means that actual presence data (subject to any transformations present in the rules) is given to the watcher. If FALSE, it means that the subscription is to be politely-blocked. This implies that the subscription is accepted, but inaccurate presence data is provided to the watcher. The specific mechanism for generating inaccurate presence data is at the discretion of the implementation. Providing a single tuple [3] with a basic status of closed represents one reasonable choice. This action only applies if subscription was accepted as a result of any "accept-subscription" permissions in matching rules. If this element is not present in any matching rules, it takes on the default value of FALSE. This means that, by default, a user is politely blocked if their subscription is accepted. Actual presence information must be explicitly granted through a "provide-presence" action. 3.3 Transformations Each of the sections below defines a particular transformation that is applied to the presence document before distribution. Each of these transformations is applied to the document independently of any Rosenberg Expires August 9, 2004 [Page 6] Internet-Draft Presence Authorization February 2004 of the others, and the order of application is irrelevant. Each transformation filters the presence document based on a particular "axis" - removing tuples by class, elements by namespace, and elements by qualified name. If such a transformation results in an invalid or empty presence document, then no document is sent to the watcher. Because a particular component of the presence document can be selected by multiple axes, and because the default is to remove information, it may be necessary to include several different transformations in order to include one specific element. 3.3.1 Show Namespace This element, "show-namespace" is a "set" data type. The content of the element is either the element "all-ns", which is defined as the set of all namespaces, or else is a series of "ns" elements, each of which identifies a specific namespace that is in the set. Any namespaces identified by this element remain in the document when it is distributed to a watcher. Elements in the document from namespaces not in the set are removed. The default value for this element when not present is "urn:ietf:params:xml:ns:pidf", which is the namespace identified in [3]. As a result, if this element is omitted, the result is the namespace for the basic presence document. If the "show-namespace" element is present, it SHOULD contain "urn:ietf:params:xml:ns:pidf" as a member (either explicitly or through the "all-ns" element). If not, the filtering operation will result in an invalid presence document, and based on the rules above, no document will be passed to watchers. 3.3.2 Show Tuple This element, "show-tuple", is a "set" data type. It identifies the set of tuples, identified by value of the "class" element [13], that are passed to the watcher. The content of this element is either the element "all-tuples", which implies the set of all tuples from the unfiltered presence document, else is a series of "class" elements. Each "class" element contains a string that identifies a specific class to be included in the presence document. If a tuple contains the class element, and that class is not present in the set, that tuple is removed from the document. If a tuple does not contain a class element, it is not subject to filtration by the "show-tuple" transformation. The default value of this element is NULL, which corresponds to the Rosenberg Expires August 9, 2004 [Page 7] Internet-Draft Presence Authorization February 2004 empty set. As a result, if no matching rules contain a "show-tuple" element, all tuples containing a class element would be removed from the presence document. 3.3.3 Show Element This element, "show-element", is a "set" data type. It identifies the set of XML elements, identified by qualified element name, which are to be passed to a watcher in the presence document. The content of this element is either "all-elements", which implies the set of all elements from the unfiltered presence document, "basic-elements", which implies the set of elements defined in [3], and/or a series of "el" elements. Each "el" element contains a string that identifies an XML element, by qualified element name. Any XML element in a presence document not contained in this set is removed from the document. The default value of this element is "basic-elements", which contains the values "presence", "tuple", "note", "status", "timestamp", "contact", and "basic" from the namespace "urn:ietf:params:xml:ns:pidf". These correspond to the elements defined in the PIDF specification. As a result, if no matching rules contain the "show-element" transformation, only the basic presence information containined in [3] will be provided to watchers. If the "show-element" transformation is present, it SHOULD contain sufficient elements to result in a presence document compliant to the schema defined in [3]. This includes at least the "presence" element. Rosenberg Expires August 9, 2004 [Page 8] Internet-Draft Presence Authorization February 2004 4. XML Schema Rosenberg Expires August 9, 2004 [Page 9] Internet-Draft Presence Authorization February 2004 Rosenberg Expires August 9, 2004 [Page 10] Internet-Draft Presence Authorization February 2004 5. Example Document The example document shown below specifies authorization policy for user@example.com. That user is allowed to subscribe, and will receive information from the basic presence document, in addition to the "placetype" element defined in [13]. Notice how the document must specify both a show-namespace and show-element transformation in order for the "placetype" element to be passed to the watcher. user@example.com true true urn:ietf:params:xml:ns:rpid rpid:placetype Rosenberg Expires August 9, 2004 [Page 11] Internet-Draft Presence Authorization February 2004 6. XCAP Usage The following section defines the details necessary for clients to manipulate presence authorization documents from a server using XCAP. 6.1 Application Unique ID XCAP requires application usages to define a unique application usage ID (AUID) in either the IETF tree or a vendor tree. This specification defines the "rules" AUID within the IETF tree, via the IANA registration in Section 8. 6.2 Structure of Permission Statements The structure of permission statements is defined in Section 3. 6.3 Additional Constraints The following are additional constraints not described by the schema: o The content of an "el" element indicates the name of an XML element, and may be fully qualified (i.e., prefixed with a namespace identifier followed by a colon). o TODO: Complete this list. 6.4 Naming Conventions When a presence agent receives a subscription for some user foo within a domain, it will look for all documents within http://[xcap root services uri]/rules/users/foo, and use all documents found beneath that point to guide authorization policy. 6.5 Authorization Policies This application usage does not modify the default XCAP authorization policy, which is that only a user can read, write or modify their own documents. A server can allow priveleged users to modify documents that they don't own, but the establishment and indication of such policies is outside the scope of this document. 6.6 XML Schema The XML schema is defined in Section 4. Rosenberg Expires August 9, 2004 [Page 12] Internet-Draft Presence Authorization February 2004 7. Security Considerations Presence authorization policies contain very sensitive information. They indicate which other users are "liked" or "disliked" by a user. As such, when these documents are transported over a network, they SHOULD be encrypted. Modification of these documents by an attacker can disrupt the service seen by a user, often in subtle ways. As a result, when these documents are transported, the transport SHOULD provide authenticity and message integrity. In the case where XCAP is used to transfer the document, clients SHOULD use HTTP over TLS, and servers SHOULD define the root services URI as an https URI. The server SHOULD authenticate the client over the resulting TLS connection using HTTP digest. Rosenberg Expires August 9, 2004 [Page 13] Internet-Draft Presence Authorization February 2004 8. IANA Considerations There are several IANA considerations associated with this specification. 8.1 XCAP Application Usage ID This section registers an XCAP Application Usage ID (AUID) according to the IANA procedures defined in [2]. Name of the AUID: rules Description: Rules are documents that describe the permissions that a presentity [15] has granted to users that seek to watch their presence. 8.2 URN Sub-Namespace Registration This section registers a new XML namespace, per the guidelines in [14] URI: The URI for this namespace is urn:ietf:params:xml:ns:pres-rules. Registrant Contact: IETF, SIMPLE working group, (simple@ietf.org), Jonathan Rosenberg (jdrosen@jdrosen.net). XML: BEGIN Presence Rules Namespace

Namespace for Permission Statements

urn:ietf:params:xml:ns:pres-rules

See RFCXXXX.

END Rosenberg Expires August 9, 2004 [Page 14] Internet-Draft Presence Authorization February 2004 8.3 XML Schema Registrations This section registers an XML schema per the procedures in [14]. URI: please assign. Registrant Contact: IETF, SIMPLE working group, (simple@ietf.org), Jonathan Rosenberg (jdrosen@jdrosen.net). The XML for this schema can be found as the sole content of Section 4. Rosenberg Expires August 9, 2004 [Page 15] Internet-Draft Presence Authorization February 2004 Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Rosenberg, J., "The Extensible Markup Language (XML) Configuration Access Protocol (XCAP)", draft-ietf-simple-xcap-01 (work in progress), October 2003. [3] Sugano, H. and S. Fujimoto, "Presence Information Data Format (PIDF)", draft-ietf-impp-cpim-pidf-08 (work in progress), May 2003. [4] Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler, "Extensible Markup Language (XML) 1.0 (Second Edition)", W3C FirstEdition REC-xml-20001006, October 2000. [5] Moats, R., "URN Syntax", RFC 2141, May 1997. [6] Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC 3023, January 2001. [7] Moats, R., "A URN Namespace for IETF Documents", RFC 2648, August 1999. [8] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S., Leach, P., Luotonen, A. and L. Stewart, "HTTP Authentication: Basic and Digest Access Authentication", RFC 2617, June 1999. [9] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. [10] Schulzrinne, H., Morris, J., Tschofenig, H., Cuellar, J., Polk, J. and J. Rosenberg, "Common Policy", draft-ietf-geopriv-common-policy-00 (work in progress), February 2004. [11] Peterson, J., "Enhancements for Authenticated Identity Management in the Session Initiation Protocol (SIP)", draft-ietf-sip-identity-01 (work in progress), March 2003. [12] Peterson, J., "SIP Authenticated Identity Body (AIB) Format", draft-ietf-sip-authid-body-02 (work in progress), July 2003. [13] Schulzrinne, H., "RPID -- Rich Presence Information Data Format", draft-ietf-simple-rpid-00 (work in progress), July 2003. Rosenberg Expires August 9, 2004 [Page 16] Internet-Draft Presence Authorization February 2004 [14] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, January 2004. Rosenberg Expires August 9, 2004 [Page 17] Internet-Draft Presence Authorization February 2004 Informative References [15] Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and Instant Messaging", RFC 2778, February 2000. [16] Day, M., Aggarwal, S., Mohr, G. and J. Vincent, "Instant Messaging / Presence Protocol Requirements", RFC 2779, February 2000. [17] Rosenberg, J., "A Presence Event Package for the Session Initiation Protocol (SIP)", draft-ietf-simple-presence-10 (work in progress), January 2003. [18] Jennings, C., Peterson, J. and M. Watson, "Private Extensions to the Session Initiation Protocol (SIP) for Asserted Identity within Trusted Networks", RFC 3325, November 2002. Author's Address Jonathan Rosenberg dynamicsoft 600 Lanidex Plaza Parsippany, NJ 07054 US Phone: +1 973 952-5000 EMail: jdrosen@dynamicsoft.com URI: http://www.jdrosen.net Rosenberg Expires August 9, 2004 [Page 18] Internet-Draft Presence Authorization February 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property 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; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. 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