SIMPLE J. Rosenberg Internet-Draft dynamicsoft Expires: December 22, 2003 June 23, 2003 Extensible Markup Language (XML) Configuration Access Protocol (XCAP) Usages for Setting Presence Authorization draft-ietf-simple-xcap-auth-usage-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 December 22, 2003. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract This document describes three usages of the Extensible Markup Language (XML) Configuration Access Protocol (XCAP) that allow a client to provide authorization decisions regarding watchers of their presence. The first of these usages, called permission-statements, contains statements about what permissions are to be granted to watchers of presence. The second of these usages, called compound-permissions, allows a client to define new permissions as combinations of other defined permissions. The third usage, called supported-permissions, allows a client to determine what permissions are understood by the provider. Rosenberg Expires December 22, 2003 [Page 1] Internet-Draft XCAP Usage for Authorization June 2003 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . 4 2. Structuring Presence Authorization . . . . . . . . . . . 5 3. Terminology . . . . . . . . . . . . . . . . . . . . . . 6 4. Permission Statements . . . . . . . . . . . . . . . . . 7 4.1 Application Unique ID . . . . . . . . . . . . . . . . . 7 4.2 Structure of Permission Statements . . . . . . . . . . . 7 4.2.1 Applying Statements to Watchers . . . . . . . . . . . . 7 4.2.2 Specifying Permissions . . . . . . . . . . . . . . . . . 9 4.2.2.1 Acceptance Permissions . . . . . . . . . . . . . . . . . 10 4.2.2.2 Rule Permissions . . . . . . . . . . . . . . . . . . . . 12 4.2.2.2.1 Identifying Elements and Indicating Values . . . . . . . 13 4.2.2.2.2 Examples . . . . . . . . . . . . . . . . . . . . . . . . 14 4.2.2.3 Content Permissions . . . . . . . . . . . . . . . . . . 15 4.2.2.3.1 Examples . . . . . . . . . . . . . . . . . . . . . . . . 17 4.2.2.4 Transformational Permissions . . . . . . . . . . . . . . 18 4.2.2.4.1 Examples . . . . . . . . . . . . . . . . . . . . . . . . 18 4.3 Additional Constraints . . . . . . . . . . . . . . . . . 19 4.4 Naming Conventions . . . . . . . . . . . . . . . . . . . 20 4.5 Authorization Policies . . . . . . . . . . . . . . . . . 20 4.6 XML Schema . . . . . . . . . . . . . . . . . . . . . . . 20 5. Compound Permissions . . . . . . . . . . . . . . . . . . 27 5.1 Application Unique ID . . . . . . . . . . . . . . . . . 27 5.2 Structure of Compound Permissions . . . . . . . . . . . 27 5.3 Naming Conventions . . . . . . . . . . . . . . . . . . . 27 5.4 Authorization Policies . . . . . . . . . . . . . . . . . 27 5.5 XML Schema . . . . . . . . . . . . . . . . . . . . . . . 28 5.6 Example Document . . . . . . . . . . . . . . . . . . . . 28 6. Supported Permissions . . . . . . . . . . . . . . . . . 30 6.1 Application Unique ID . . . . . . . . . . . . . . . . . 30 6.2 Structure of Supported Permissions . . . . . . . . . . . 30 6.3 Naming Conventions . . . . . . . . . . . . . . . . . . . 31 6.4 Authorization Policies . . . . . . . . . . . . . . . . . 31 6.5 XML Schema . . . . . . . . . . . . . . . . . . . . . . . 31 6.6 Example Document . . . . . . . . . . . . . . . . . . . . 32 7. IANA Considerations . . . . . . . . . . . . . . . . . . 34 7.1 XCAP Application Usage IDs . . . . . . . . . . . . . . . 34 7.1.1 Permission Statements . . . . . . . . . . . . . . . . . 34 7.1.2 Compound Permissions . . . . . . . . . . . . . . . . . . 34 7.1.3 Supported Permissions . . . . . . . . . . . . . . . . . 34 7.2 URN Sub-Namespace Registrations . . . . . . . . . . . . 34 7.2.1 urn:ietf:params:xml:ns:permission-statements . . . . . . 34 7.2.2 urn:ietf:params:xml:ns:compound-permissions . . . . . . 35 7.2.3 urn:ietf:params:xml:ns:supported-permissions . . . . . . 36 7.3 XML Schema Registrations . . . . . . . . . . . . . . . . 37 7.3.1 Permissions Statements . . . . . . . . . . . . . . . . . 37 7.3.2 Compound Permissions . . . . . . . . . . . . . . . . . . 37 Rosenberg Expires December 22, 2003 [Page 2] Internet-Draft XCAP Usage for Authorization June 2003 7.3.3 Supported Permissions . . . . . . . . . . . . . . . . . 37 Normative References . . . . . . . . . . . . . . . . . . 38 Informative References . . . . . . . . . . . . . . . . . 39 Author's Address . . . . . . . . . . . . . . . . . . . . 39 Intellectual Property and Copyright Statements . . . . . 40 Rosenberg Expires December 22, 2003 [Page 3] Internet-Draft XCAP Usage for Authorization June 2003 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 [12], in order to learn their presence information [13]. 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 policices of the presentity. In order for the PA to compute the final authorization decision, it needs access to the presentity's authorization policies. In order to provide this access, the XML Configuration Access Protocol (XCAP) [2] is used. XCAP allows a client to manipulate XML documents stored on a server. Those XML documents represent per-user provisioning data on how an application should operate. XCAP has the notion of an application usage, which is a definition of the XML schema used by a particular application, along with other relevant information. Each application usage is given a unique application usage ID (AUID) which identifies it. This specification makes use of three application usages. Rosenberg Expires December 22, 2003 [Page 4] Internet-Draft XCAP Usage for Authorization June 2003 2. Structuring Presence Authorization This specification defines three application usages (each with their own XML schema) that, put together, present a comprehensive solution for allowing clients to specify authorization policies that a PA can use when processing a subscription. The first of these application usages has the AUID of permission-statements. This usage allows a client to make statements about which permissions are granted to which watchers. Each statement contains a definition of the watchers to whom it applies, and then contains a list of permissions which are granted to those watchers. The concept of a permission is central to this specification. A permission is an atomic statement of consent or denial. A permission can indicate a condition under which a subscription is accepted or rejected, a condition under which a notification is or is not sent, or a piece of information which is or is not revealed in a presence document. The overall authorization for a watcher is represented by the union of the permissions granted to that watcher. Permissions can be classified as either primitive or compound. A primitive permission is one of the permissions defined in this specification. A compound permission is a new permission that is defined as a combination of other primitive or compound permissions. As an example, the "grant-phone" permission might be a compound permission which accepts the subscription, sends a watcher notifications when the status of the user's phone changes, and those notifications contain the status of the phone. As a result, to facilitate ease of use, a second application usage is defined, which allows a user to construct new compound permissions. This specification contains a fairly broad set of primitive permissions. It is anticipated that new ones will be standardized in the future. It is also anticipated that vendors will define proprietary permissions. In order for a client to connect to a server, and achieve interoperability, it is neccesary for the client to know what permissions are supported by the server. The third application usage, supported-permissions, allows a client to read the list of permissions understood by the server. Rosenberg Expires December 22, 2003 [Page 5] Internet-Draft XCAP Usage for Authorization June 2003 3. 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 December 22, 2003 [Page 6] Internet-Draft XCAP Usage for Authorization June 2003 4. Permission Statements 4.1 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 "permission-statements" AUID within the IETF tree, via the IANA registration in Section 7. 4.2 Structure of Permission Statements A permission statement is an XML [3] document that MUST be well-formed and SHOULD be valid. Permission statement documents MUST be based on XML 1.0 and MUST be encoded using UTF-8. This specification makes use of XML namespaces for identifying permission statement documents and document fragments. The namespace URI for elements defined for this purpose is a URN [5], using the namespace identifier 'ietf' defined by [7] and extended by [11]. This URN is: urn:ietf:params:xml:ns:permission-statements A permission statement document begins with the root element tag "permission-statements". It consists of any number of "statement" elements. Each statement element defines a set of permissions and identifies to whom they are granted. Each "statement" element has a single attribute: id: This is a string which serves as a way to uniquely identify statements in the document. The attribute MUST be unique amongst all statement elements in the document. This attribute is mandatory. Each statement is composed of a single "applies-to" element and a single "permissions" element. The "permissions" element is composed of one or more elements that grant permissions. 4.2.1 Applying Statements to Watchers The "applies-to" element defines the set of watchers to whom the statement applies. It contains one or more "uri" elements, "domain" elements, "on-list" elements or a single "any" element. The "uri" element identifies a single watcher by specifying its URI. The "domain" element says that the statement applies to all watchers from the specified domain. The "on-list" element says that the statement applies to all users on the specified presence list [16], identified with an HTTP URI that points to the list. Finally, the "any" element says that the statement applies to all watchers. Additional elements Rosenberg Expires December 22, 2003 [Page 7] Internet-Draft XCAP Usage for Authorization June 2003 can be added that express other ways of identifying the watchers to whom the statement applies. The "uri", "domain", "on-list" and "any" elements all have the following attributes: id: This is a string which serves as a way to uniquely identify an instance of this element within the enclosing "applies-to" element. The attribute MUST be unique amongst all elements of the same name within the enclosing "applies-to" element. This attribute is mandatory. display-name: This is a string that contains a display name, suitable for rendering to a human user, the identity of the user or domain implied by the element. This attribute is optional. lang: This attribute identifies the language used to represent the display name. It is imported from the XML namespace. This attribute is optional. When a subscription arrives at the PA, the PA performs an authentication operation to determine the identity of the watcher. It then uses the "applies-to" element in each statement within the presentity's document, and determines the set of statements that apply to the watcher. It is possible that multiple statements can match a single subscription. In that case, the union of the permissions across those statements is applied to the subscription. It is also possible that none of the statements match, in which case the subscription is considered "pending". OPEN ISSUE: Another model is that you take permissions for the most specific match. I think union makes more sense in the model where the entries in the statement are permissions. For example, the following XML fragment includes two statements, one that applies to the user joe@example.com, and another that applies to example.com. When Joe subscribes, both statements match. Therefore, he is granted the union of the permissions across the two statements. Rosenberg Expires December 22, 2003 [Page 8] Internet-Draft XCAP Usage for Authorization June 2003 sip:joe@example.com example.com 4.2.2 Specifying Permissions The remainder of the content of the "statement" element contains specific permissions that are granted to watchers to whom the statement applies. Each permission is represented by a single XML element. Permissions can be primitive or they can be compound. A primitive permission is one that explicitly defines the permission that is being granted. A compound permission is a collection of other permissions, both compound and primitive. Compound permissions are a useful way of grouping permissions in order to simplify the overall user interface. Primitive permissions can be grouped broadly into three categories: 1. Acceptance permissions allow the watcher to subscribe. Without an acceptance permission, a subscription is rejected outright. 2. Rule permissions indicate conditions on which a notification is sent. Whenever there is a change in the presence of a user, the presence agent will check to see if any rule permissions apply. If any of them do, a notification is sent. This of course, assumes that the subscription had an acceptance permission in the Rosenberg Expires December 22, 2003 [Page 9] Internet-Draft XCAP Usage for Authorization June 2003 first place. 3. Content permissions indicate which information the watcher is permitted to see, in the event a notification is sent in the first place (based on the rule permissions). 4. Transformational permissions indicate any changes that should be made to information sent to a watcher. This, of course, assumes that the information is to be transmitted to the watcher in the first place (based on the content permissions). 4.2.2.1 Acceptance Permissions Acceptance permissions grant the ability of the watcher to subscribe to the presentity. Without an acceptance permission, none of the other permissions make any sense. There are only two primitive acceptance permissions, each of which is an XML element. These are "accept" and "accept-if". The "accept" element has no content and no attributes. It simply grants permission to the watcher to subscribe. Only one such element can be present in any statement. The "accept-if" element also grants permission to subscribe, but the granting of this permissions is predicated on some condition. The content of the "accept-if" element is a condition element. Condition elements describe characteristics of the subscription, or of the operating environment of the server, which are either true or false. If the condition within the "accept-if" element is true, an acceptance permission is granted. The first condition element is "and". This condition evaluates to true if all of the conditions contained within it evaluate to true. The second condition element is "or". This condition evaluates to true if any of the conditions contained within it evaluate to true. The third condition element is "not". This condition evaluates to true if the single condition contained within it evaluates to false. These basic boolean types, which can themselves be composed, allow for statements of fairly complex conditions under which a subscription should be granted. The following represent the "atomic" conditions which can be checked: requested-namespace: This element has a value that contains a URI identifying an XML namespace. The condition evaluates to true if the subscription request explicitly contained a filter which requested the PA to include elements from that namespace within its notifications. Rosenberg Expires December 22, 2003 [Page 10] Internet-Draft XCAP Usage for Authorization June 2003 requested-element: This element has a value that contains a string identifying an XML element. The condition evaluates to true if the subscription request explicitly contained a filter which requested the PA to include elements of that name within its notifications. requested-tuple: This element has a value that contains a string whose value is a tuple ID [14]. The condition evaluates to true if the subscription request explicitly contained a filter which requested the PA to include tuples with that tuple ID within its notifications. duration: This element has a value that contains an integer, representing a number of seconds. The condition evaluates to true if the subscription request was for a duration less than or equal to this value. This condition is handy for allowing watchers the ability only to fetch presence documents. This is done by setting this condition to zero. auth-mechanism: This element contains an enumerated type that describes authentication mechanisms. The defined values are none, digest (referring to the HTTP digest [8] mechanism used in RFC 3261 [9]), smime (referring to SIP's S/MIME authentication), tls (meaning that the watcher authenticated themself using a client certificate in a mutual TLS exchange with the server), and p-asserted-id (as defined in RFC 3325 [15]). The condition evaluates to true if the client was authenticated using the listed algorithm. anonymous: This element contains no values. The condition evaluates to true if the watcher is anonymous. They are considered anonymous if the From header field of the request is equal to "Anonymous". Note that a user can be anonymous and also have authenticated themselves with digest. This occurs when the "anonymous" username and password, as defined in RFC 3261 [9], are used. can-encrypt: This element contains no values. The condition evaluates to true if it is possible to encrypt, using S/MIME, notifications sent to this watcher. Generally, this can be determined when the Accept header field in the subscription indicates support for the application/pkcs7-mime [10] MIME type. As an example, the following statement grants permission for watcher sip:joe@example.com to subscribe if he authenticates with digest and doesn't ask to be notified of phone state: Rosenberg Expires December 22, 2003 [Page 11] Internet-Draft XCAP Usage for Authorization June 2003 sip:joe@example.com digest urn:ietf:params:xml:ns:pidf:common-phone-state OPEN ISSUE: It is possible to eliminate the notion of "applies-to" by folding it into accept-if, and allowing conditions to be used in granting other forms of permissions. I preferred the model of a separate applies-to because it allowed us to break the XML document into sets of statements, each of which could apply to totally different watchers, and therefore manipulated independently of each other. This made it more amenable to usage with XCAP without requiring locks. In terms of allowing conditions to be used with the other permission types, that can be added in the future, but seemed to be overly complex for this specification. 4.2.2.2 Rule Permissions Rule permissions grant the watcher the ability to receive a notification when there is a state change of some sort. Each permission specifies a condition under which a state change will cause a notification to be sent. Generally, these conditions are checks on the values of the attributes that have changed. Each permission is associated with an XML element. The elements defined in this specification are: Rosenberg Expires December 22, 2003 [Page 12] Internet-Draft XCAP Usage for Authorization June 2003 any-event: This element has no attributes and no content. It grants permission for the watcher to see all presence state changes. enter-state: This element indicates that a watcher is permitted to receive notifications when a particular piece of presence information changes to the specified value. The content of this element is a "state" element. A "state" element has two parts. One identifies the particular piece of presence information, and the other specifies its value. exit-state: This element indicates that a watcher is permitted to receive notifications when a particular piece of presence information changes from the specified value. The content of this element is also a "state" element. transition: This element indicates that a watcher is permitted to receive notifications when a particular piece of presence information changes from one value to another value. The content of this element are three XML elements - one that identifies the piece of presence information (using either the "element-name" or "element-path" elements, discussed below), one (called "value") that indicates the original value, and another "value" element that indicates the value that it changed to. change-in: This element indicates that a watcher is permitted to receive notifications triggered by a change in the value of the specified piece of presence information. The value of the element is an identifier for a particular piece of presence information (using either the "element-name" or "element-path" elements). equals: This element indicates that a watcher is permitted to receive notifications while a particular piece of presence information has a particular value. As an example, a presentity can indicate that a watcher should receive notifications of changes in phone state while the basic status is open, but notifications are not sent when the value of basic status is closed. The content of this element is a "state" element. subscription-state: This element indicates that a watcher is permitted to receive notifications that convey changes in the state of the subscription itself. It has no attributes or content. 4.2.2.2.1 Identifying Elements and Indicating Values A key component of most of these rule permissions is the ability to identify a piece of presence information and indicate a value for it. This function is provided by several XML elements. Rosenberg Expires December 22, 2003 [Page 13] Internet-Draft XCAP Usage for Authorization June 2003 The first issue is to identify a piece of presence information. This specification provides two ways to identify a piece of presence information. The first is with the "element-name" element. This element, which has no attributes, contains, as a value, the name of an XML element. This is a reference to any instances in the presence document where this element would occur. It is also a reference to the ways in which that element is used as an input to the computation of other elements. For example, if the rule permission says that a watcher will receive notifications when "call-state" elements change, that implies that they are also permitted to receive notifications when there is a change in some other element, such as the PIDF "basic" element, when that change is a direct result of a change in the "call-state" element. In this regard, the "element-name" doesn't address a specific element in an XML document as much as a raw piece of presence data. The second way to address an XML element is with XPath [4]. This is done using the "element-path" element. This element has no attributes, and its content is a valid location-set XPath expression that points to components of a presence document. In this case, the expression refers to the actual XML document components, rather than the raw data they represent. The "state" element is composed of either the "element-name" or "element-path" elements, followed by the "value" element. The "value" element has no attributes, and its content is a string containing the value of the element identified by the "element-name" or "element-path". In the latter case, the XPath expression MUST refer to a single attribute or a single element with text content. 4.2.2.2.2 Examples The following XML document specifies a rule permission that specifies that a watcher should receive notifications only when the basic status changes: Rosenberg Expires December 22, 2003 [Page 14] Internet-Draft XCAP Usage for Authorization June 2003 sip:joe@example.com pidf:basic This document says that a watcher should receive notifications only when the "placetype" element is equal to "home". This is useful as a permission to apply to watchers that are friends - they will receive no notifications while you are at work, and only receive them when you are at home: sip:joe@example.com rpids:placetype home 4.2.2.3 Content Permissions Content permissions specify the information that is to be sent to a Rosenberg Expires December 22, 2003 [Page 15] Internet-Draft XCAP Usage for Authorization June 2003 watcher. Each permission specifies a piece of information that is to be sent, or to be used in general in the computation of the presence document. The defined permissions are: all-content: This permission specifies that all presence information can be sent. The element has no attributes or value. show-contact-element: This permission specifies that the contact component of the tuple can be sent. The element has no attributes or value. show-note: This permission specifies that the note component of the tuple can be sent. The element has no attributes or value. show-tuple: This permission specifies that the tuple identified by the element can be sent to the watcher. The element has not attributes. Its content is a string that matches the tuple "id" attribute in the presence document. show-element: This permission specifies that the XML element identified by "show-element" can be sent to the watcher. The content of "show-element" is either the "element-name" or "element-path" elements as defined above. If the "element-name" is used, it means that the specified element can be "presented" to the watcher, where "presented" implies that they are either present in the XML document, or used as part of the derivation of other presence data. Otherwise, if the "element-path" is used, it means that the specified element can be present in the document sent to the watcher. show-namespace: This permission specifies that elements and attributes in the presence document within the specified namespace can be presented to the watcher. Here, "presented" implies that they are either present in the XML document, or used as part of the derivation of other presence data. show-values: This permission specifies that an element of the presence document can only be "presented", per the above definition, if it has the specified value. The content of this element is an "element-name" element followed by a "value" element. encrypt: This permission specifies that the presence document should be sent to the watcher encrypted. It should never be present in a statement without the presence of an "accept-if" element which conditions acceptance of the subscription on the ability of the watcher to receive encrypted presence documents. Rosenberg Expires December 22, 2003 [Page 16] Internet-Draft XCAP Usage for Authorization June 2003 4.2.2.3.1 Examples The following example specifies that a watcher is only allowed to see baseline pidf information: sip:joe@example.com urn:ietf:params:xml:ns:pidf The following example shows that the watcher is allowed to see PIDF information along with the placetype element from RPIDS: sip:joe@example.com urn:ietf:params:xml:ns:pidf rpids:placetype Rosenberg Expires December 22, 2003 [Page 17] Internet-Draft XCAP Usage for Authorization June 2003 4.2.2.4 Transformational Permissions Transformational permissions specify explicit ways in which the presence document is changed before it is presented to a watcher. Generally, this is useful for allowing a presentity to "lie" in the information sent to a watcher. The permissions defined in this specification are: set-document: This permission indicates that the specified presence document should be sent to the watcher. The value of the element is a valid PIDF document. set-element: This permission indicates that the specified element should be set to the specified value. The value of this element is a "state" element. change-element-from: This permission indicates that the specified element, when its value is as indicated, should change to the specified value. Its content is either "element-name" or "element-path", followed by two "value" elements. When the transformations specified by these attributes overlap, the sequence of the operations is important. The "change-element-from" are done first, followed by "set-element", followed by "set-document". 4.2.2.4.1 Examples The following document specifies that the "activity" element from rpids should always be set to "active": Rosenberg Expires December 22, 2003 [Page 18] Internet-Draft XCAP Usage for Authorization June 2003 sip:joe@example.com urn:ietf:params:xml:ns:pidf urn:ietf:params:xml:ns:sip-rpids rpids:activity active 4.3 Additional Constraints The following are additional constraints not described by the schema: o The content of an "element-path" element MUST be a valid Xpath expression that contains a location-set. [[OPEN ISSUE: Is there a way to express this in the schema?]] o The content of an "element-name" 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 The value of the "domain" element MUST be compliant to the BNF for "host" as defined in RFC 3261 [9]. o The value of the "on-list" element MUST be a valid HTTP URI that represents a presence list, as defined in [16]. o TODO: Complete this list. Rosenberg Expires December 22, 2003 [Page 19] Internet-Draft XCAP Usage for Authorization June 2003 4.4 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]/permission-statements/users/foo, and use all documents found beneath that point to guide authorization policy. 4.5 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. 4.6 XML Schema Comment describing your root element Acceptance Permissions Rosenberg Expires December 22, 2003 [Page 20] Internet-Draft XCAP Usage for Authorization June 2003 Rule Permissions Rosenberg Expires December 22, 2003 [Page 21] Internet-Draft XCAP Usage for Authorization June 2003 Content Permissions Transformational Permissions Rosenberg Expires December 22, 2003 [Page 22] Internet-Draft XCAP Usage for Authorization June 2003 Compound Permissions Rosenberg Expires December 22, 2003 [Page 23] Internet-Draft XCAP Usage for Authorization June 2003 Rosenberg Expires December 22, 2003 [Page 24] Internet-Draft XCAP Usage for Authorization June 2003 Rosenberg Expires December 22, 2003 [Page 25] Internet-Draft XCAP Usage for Authorization June 2003 TODOS: need to add points of extensibility. Rosenberg Expires December 22, 2003 [Page 26] Internet-Draft XCAP Usage for Authorization June 2003 5. Compound Permissions Compound permissions allow a user to specify new permissions that are a combination of primitive and compound permissions. Compound permissions can be used within permission statements. 5.1 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 "compound-permissions" AUID within the IETF tree, via the IANA registration in Section 7. 5.2 Structure of Compound Permissions A compound permission is an XML [3] document that MUST be well-formed and SHOULD be valid. Compound permission documents MUST be based on XML 1.0 and MUST be encoded using UTF-8. This specification makes use of XML namespaces for identifying compound permission documents and document fragments. The namespace URI for elements defined for this purpose is a URN [5], using the namespace identifier 'ietf' defined by [7] and extended by [11]. This URN is: urn:ietf:params:xml:ns:compound-permissions A compound permission document begins with the root element tag "compound-permissions". It consists of any number of "compound-permission" elements. Each "compound-permission" defines a new compound permission. It is a mandatory attribute "name" which MUST be unique across all other "name" attributes within the document. It serves as a unique handle to the compound permission. A compound-permission is composed of a "permission-name" element, containing a string value, which presents the name of the compound permission. This is then followed by a "permissions" element, which contains the permissions associated with the new compound permission. 5.3 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]/compound-permissions/users/foo, and use all documents found beneath that point as definitions of valid compound permissions. 5.4 Authorization Policies This application usage does not modify the default XCAP authorization Rosenberg Expires December 22, 2003 [Page 27] Internet-Draft XCAP Usage for Authorization June 2003 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. 5.5 XML Schema A series of compound permissions 5.6 Example Document This example document defines a new compound permission, called friends, and associates some permissions with it. Rosenberg Expires December 22, 2003 [Page 28] Internet-Draft XCAP Usage for Authorization June 2003 friends rpids:placetype home Rosenberg Expires December 22, 2003 [Page 29] Internet-Draft XCAP Usage for Authorization June 2003 6. Supported Permissions Supported permissions allow a presentity to determine what the capabilities of the PA are, in terms of expressing authorization policy. This capability is expressed as a list of primitive permissions, primitive conditions, and compound permissions. When a client starts up, it reads this set of permissions from a well known URI (see Section Section 6.3). It then knows which permissions, both primitive and compound, that it can include in its permission statements. 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 "supported-permissions" AUID within the IETF tree, via the IANA registration in Section 7. 6.2 Structure of Supported Permissions A supported permission is an XML [3] document that MUST be well-formed and SHOULD be valid. Supported permission documents MUST be based on XML 1.0 and MUST be encoded using UTF-8. This specification makes use of XML namespaces for identifying supported permission documents and document fragments. The namespace URI for elements defined for this purpose is a URN [5], using the namespace identifier 'ietf' defined by [7] and extended by [11]. This URN is: urn:ietf:params:xml:ns:supported-permissions A supported permission document begins with the root element tag "supported-permissions". It consists of one "primitive-permissions" element, zero or one "conditions" elements and zero or one "compound-permissions" elements. The "primitive-permissions" element has, for its content, a "permissions" element. This element contains a valid permission statement which purposefully includes all primitive permissions that are supported by the server. All PA's which allow for xcap-based configuration of authorization MUST support, at a minimum, the "accept", "any-event" and "all-content" primitive permissions. The "conditions" element contains a sequence of conditions which can be used within the "accept-if" element. Clearly, the "conditions" element will not be present if "accept-if" is not listed as a supported permission. There is no minimum requirement for a PA in terms of the conditions that need to be supported. Rosenberg Expires December 22, 2003 [Page 30] Internet-Draft XCAP Usage for Authorization June 2003 The "compound-permissions" element is a sequence of compound permissions supported by the server. Each one, described by a "compound-permission" element, has a "name" and "description". The "name" contains the name of the permission, and "description" is a textual definition of the permission, meant for human consumption. This is helpful in cases where the compound permissions are not understood by the client. The descriptions can be rendered to the human user, so that they can make a choice in the application of a permission. 6.3 Naming Conventions When a client starts, it can fetch the permissions understood by the server in one of two places. If the server capabilities differ on a user by user basis, the supported permissions for user foo can be found in http://[xcap root services uri]/supported-permissions/users/ foo/sp.xml. A client SHOULD check this file first. If this document doesn't exist, the client should next check for the system wide permissions by checking http://[xcap root services uri]/ supported-permissions/global/sp.xml. 6.4 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. 6.5 XML Schema Rosenberg Expires December 22, 2003 [Page 31] Internet-Draft XCAP Usage for Authorization June 2003 6.6 Example Document This example document describes a PA that allows very simple primitive types. Instead, it defines several compound ones that are the preferred way for clients to express permissions. Rosenberg Expires December 22, 2003 [Page 32] Internet-Draft XCAP Usage for Authorization June 2003 low This represents low security. Use this with people you don't know. high This represents high security. Use this with people you trust. Rosenberg Expires December 22, 2003 [Page 33] Internet-Draft XCAP Usage for Authorization June 2003 7. IANA Considerations There are several IANA considerations associated with this specification. 7.1 XCAP Application Usage IDs This section registers three XCAP Application Usage IDs (AUID) according to the IANA procedures defined in [2]. 7.1.1 Permission Statements Name of the AUID: permission-statements Description: Permission-statements are documents that describe the permissions that a presentity [12] has granted to users that seek to watch their presence. 7.1.2 Compound Permissions Name of the AUID: compound-permissions Description: Compound permissions are documents that describe new types of permissions which can be granted to watchers [12] of the presence of a user. 7.1.3 Supported Permissions Name of the AUID: supported-permissions Description: Supported permissions are documents that describe the types of permissions which are supported by a presence agent [13]. These permissions specify the information that watchers [12] of presence are allowed to see. 7.2 URN Sub-Namespace Registrations This section registers several new XML namespaces, as per the guidelines in [11] 7.2.1 urn:ietf:params:xml:ns:permission-statements URI: The URI for this namespace is urn:ietf:params:xml:ns:permission-statements. Rosenberg Expires December 22, 2003 [Page 34] Internet-Draft XCAP Usage for Authorization June 2003 Registrant Contact: IETF, SIMPLE working group, (simple@ietf.org), Jonathan Rosenberg (jdrosen@jdrosen.net). XML: BEGIN Permission Statements Namespace

Namespace for Permission Statements

urn:ietf:params:xml:ns:permission-statements

See RFCXXXX.

END 7.2.2 urn:ietf:params:xml:ns:compound-permissions URI: The URI for this namespace is urn:ietf:params:xml:ns:compound-permissions. Registrant Contact: IETF, SIMPLE working group, (simple@ietf.org), Jonathan Rosenberg (jdrosen@jdrosen.net). XML: Rosenberg Expires December 22, 2003 [Page 35] Internet-Draft XCAP Usage for Authorization June 2003 BEGIN Compound Permissions Namespace

Namespace for Compound Permissions

urn:ietf:params:xml:ns:compound-permissions

See RFCXXXX.

END 7.2.3 urn:ietf:params:xml:ns:supported-permissions URI: The URI for this namespace is urn:ietf:params:xml:ns:supported-permissions. Registrant Contact: IETF, SIMPLE working group, (simple@ietf.org), Jonathan Rosenberg (jdrosen@jdrosen.net). XML: BEGIN Supported Permissions Namespace

Namespace for Supported Permissions

urn:ietf:params:xml:ns:supported-permissions

See RFCXXXX.

END Rosenberg Expires December 22, 2003 [Page 36] Internet-Draft XCAP Usage for Authorization June 2003 7.3 XML Schema Registrations This section registers three XML schemas as per the procedures in [11]. 7.3.1 Permissions Statements 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 4.6. 7.3.2 Compound Permissions 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 5.5. 7.3.3 Supported Permissions 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 6.5. Rosenberg Expires December 22, 2003 [Page 37] Internet-Draft XCAP Usage for Authorization June 2003 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-rosenberg-simple-xcap-00 (work in progress), May 2003. [3] Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler, "Extensible Markup Language (XML) 1.0 (Second Edition)", W3C REC REC-xml-20001006, October 2000. [4] Clark, J. and S. DeRose, "XML Path Language (XPath) Version 1.0", W3C REC REC-xpath-19991116, November 1999. [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] Ramsdell, B., "S/MIME Version 3 Message Specification", RFC 2633, June 1999. [11] Mealling, M., "The IETF XML Registry", draft-mealling-iana-xmlns-registry-05 (work in progress), June 2003. Rosenberg Expires December 22, 2003 [Page 38] Internet-Draft XCAP Usage for Authorization June 2003 Informative References [12] Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and Instant Messaging", RFC 2778, February 2000. [13] Rosenberg, J., "A Presence Event Package for the Session Initiation Protocol (SIP)", draft-ietf-simple-presence-10 (work in progress), January 2003. [14] Fujimoto, S. and H. Sugano, "Presence Information Data Format (PIDF)", draft-ietf-impp-cpim-pidf-08 (work in progress), May 2003. [15] 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. [16] Rosenberg, J., "An Extensible Markup Language (XML) Configuration Access Protocol (XCAP) Usage for Presence Lists", draft-rosenberg-simple-xcap-list-usage-00 (work in progress), May 2003. Author's Address Jonathan Rosenberg dynamicsoft 600 Lanidex Plaza Parsippany, NJ 07052 US Phone: +1 973 952-5000 EMail: jdrosen@dynamicsoft.com URI: http://www.jdrosen.net Rosenberg Expires December 22, 2003 [Page 39] Internet-Draft XCAP Usage for Authorization June 2003 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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This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assignees. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION Rosenberg Expires December 22, 2003 [Page 40] Internet-Draft XCAP Usage for Authorization June 2003 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Rosenberg Expires December 22, 2003 [Page 41]