SIMPLE WG J. Rosenberg Internet-Draft Dynamicsoft Expires: December 26, 2003 M. Isomaki Nokia Research Center June 27, 2003 Requirements for Manipulation of Data Elements in Session Initiation Protocol (SIP) for Instant Messaging and Presence Leveraging Extensions (SIMPLE) Systems draft-ietf-simple-data-req-03 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 26, 2003. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract In any presence application, it is frequently necessary for the user to configure a number of pieces of information. Users will need to manipulate their presentity list, adding and removing presentities, and manipulate their authorization lists, which specify the set of users that can subscribe to their presence. In this document, we provide a framework and requirements for such data manipulations. Rosenberg & Isomaki Expires December 26, 2003 [Page 1] Internet-Draft Data Manipulation Requirements June 2003 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Framework . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. Resource List Manipulation Requirements . . . . . . . . . . . 6 6. Authorization Policy Manipulation . . . . . . . . . . . . . . 8 6.1 Acceptance Policy Requirements . . . . . . . . . . . . . . . . 8 6.2 Notification Requirements . . . . . . . . . . . . . . . . . . 9 6.3 Content Requirements . . . . . . . . . . . . . . . . . . . . . 10 6.4 General Requirements . . . . . . . . . . . . . . . . . . . . . 11 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 9. Changes from version 02 . . . . . . . . . . . . . . . . . . . 13 Informative References . . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 14 Intellectual Property and Copyright Statements . . . . . . . . 15 Rosenberg & Isomaki Expires December 26, 2003 [Page 2] Internet-Draft Data Manipulation Requirements June 2003 1. Introduction Consumer-based instant messaging and presence applications typically provide a rich set of features. In addition to being able to subscribe to, and get notified of, changes in presence, users can also configure the operation of the application. Most systems allow the user to add or remove users from their 'buddy list', which we refer to here as a resource list. The resource list is the set of presentities [2] that a user is subscribed to. This list is frequently stored on the server, allowing the user to generate a single subscription to the entire list. The server then 'fans out' that subscription to all the presentities on the list. Subscription to resource lists is supported through the SIP event notification extension for resource lists [6]. However, no automated means is currently defined to create these lists, add users to them, remove users from them, or query for the set of users on the list. Similarly, most systems support user-defined authorization policies. A user can specify which watchers are (or are not) allowed to subscribe to their presence, and furthermore, what aspects of their presence a watcher is able to see. While SIMPLE [3] systems can support such authorization policies, besides human-driven techniques, such as web or voice response, there is no automated way to specify these policies. In this document, we propose a framework and a set of requirements for manipulation of resource lists and authorization policies. Further data manipulation requirements may be defined in the future, but they are out of the scope of this document. 2. Conventions 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. 3. Terminology This document uses the following terminology: Resource list: A resource list is a set of presentities, each of which is identified by a URI. The list itself is identified by a URI (for example, sip:myfriends@example.com). Using the SIP event extension for resource lists [6], a watcher can subscribe to the resource list and learn about the presence state of all the Rosenberg & Isomaki Expires December 26, 2003 [Page 3] Internet-Draft Data Manipulation Requirements June 2003 presentities in the set. Presence Authorization Policy: Presence authorization policy refers to the set of directives given to a presence agent on what subscriptions to accept, when to generate notifications for a subscription, and what information should be placed in those notifications. Acceptance Policy: The component of presence authorization policy that determines whether or not to accept a subscription from a watcher. Notification Policy: The component of presence authorization policy that determines when a notification should be sent to a watcher. Content Policy: The component of presence authorization that determines the content of the information provided to a watcher in a notification. SIMPLE Data Elements: SIMPLE data elements are user specified data that determine the behavior of a presence agent. This includes resource lists and presence authorization policy. Data Manipulation Client: A data manipulation client is a protocol agent that reads, writes, and receives notifications of changes in SIMPLE data elements. Data Manipulation Server: A data manipulation server is a protocol agent that receives reads, writes, and sends notifications of changes in SIMPLE data elements. The server is responsible for the storage of the SIMPLE data elements. 4. Framework The framework for the usage and manipulation of SIMPLE data elements are shown in Figure 1. SUBSCRIBE |--------| ------------->| |<---| //-----\\ <-------------| PA | | || || NOTIFY |--------| |---|\\-----//| | | | Storage | | | |->|---------| Rosenberg & Isomaki Expires December 26, 2003 [Page 4] Internet-Draft Data Manipulation Requirements June 2003 |--------| | | |<----| | Server | Read/Write |--------| ^ | | | RL/Auth manipulations | v |--------| | | | Client | |--------| Figure 1: Framework for Data Manipulation The data manipulation client (just referred to as the client) uses some protocol, whose requirements are specified here, to interact with the data manipulation server. Those interactions include requests to read a SIMPLE data element, write one, or receive notifications in changes to one. The data manipulation server (just referred to as the server) manages a persistent store of the SIMPLE data elements, and interacts with the client. When a Presence Agent (PA) receives a SIP SUBSCRIBE request [3], it may require access to SIMPLE data elements in order to process the request. For example, if the subscription is for a resource list, the PA will need to determine that this is the case, and secondly, 'expand' the resource list, obtaining the list of URIs for that resource list. If the SUBSCRIBE request is for a presentity, the PA will need to obtain the presence authorization policy of that presentity in order to process the SUBSCRIBE request. In both cases, the PA requires only read access to the data. As a result, it obtains it directly from the data store, rather than interacting with the server. This, of course, is just a model of the system; a real implementation might involve interaction with the server before reading the data. Between the resource list and presence authorization policy, the presence authorization policy is a far more complicated piece of data. The authorization policy can be reasonably split into three separate pieces. The first, which we call the acceptance policy, determines whether or not to grant a subscription to the subscriber. This policy results in a binary decision. The second piece, which we call the notification policy, determines when that particular Rosenberg & Isomaki Expires December 26, 2003 [Page 5] Internet-Draft Data Manipulation Requirements June 2003 subscriber should receive notifications. For example, a subscriber might only be permitted to see when I log in or log out of IM, but not receive notifications when my phone goes on hook. This is closely related to the third piece, which we call the content policy. This policy specifies the content of the information present in a notification that is sent to a subscriber. All of these policies are data that is manipulated by the data manipulation protocol. 5. Resource List Manipulation Requirements The following are the set of requirements for the protocol between the client and the server for the purposes of manipulation resource lists. It is obvious that similar requirements would apply to lists used by other applications than presence as well, but those are outside the scope of this document. REQ PC-1: It MUST be possible for the client to create resource lists and associate each of them with a distinct URI. REQ PC-2: It MUST be possible for the user to specify the URI for the resource list when one is created. If the name cannot be allocated (because it already exists, for example), it MUST be possible to inform the client of the failure, and the reason for it. REQ PC-3: It MUST be possible for the server to provide the client a URI for the list when one is created, in the case where the client does not provide it. REQ PC-4: It MUST be possible to associate a display name with a resource list. REQ PC-5: It MUST be possible to add an entry to the resource list. Each entry MUST be able to include at least a URI, and a display name. It MUST be possible for the entry to be any URI that is meaningful in the context of a resource list. Examples would include a SIP URI or pres URI [7]. REQ PC-6: It MUST be possible to extend the set of information associated with the entries in the resource list and with the list itself. An example would be a filtering document associated with the list. Rosenberg & Isomaki Expires December 26, 2003 [Page 6] Internet-Draft Data Manipulation Requirements June 2003 REQ PC-7: It MUST be possible for a resource list to contain entries which are themselves resource lists. REQ PC-8: It MUST be possible to remove an entry from the resource list. If the entry does not exist, it MUST be possible for the server to inform the client of this fact. REQ PC-9: It MUST be possible to modify an entry in the resource list. REQ PC-10: It MUST be possible to clear all entries from a resource list. REQ PC-11: It MUST be possible to query for the set of URIs and other possible information related to a particular resource list by providing the URI for the resource list. REQ PC-12: It MUST be possible to delete a resource list. In this context, deleted means that the name of the resource list is no longer defined, so that subscriptions to the list would fail. REQ PC-13: It MUST be possible for a user to retrieve the list of resource lists that they have created. REQ PC-14: It MUST be possible for the resource list to be associated with a list of authorized users who are able to query for the set of URIs and other possible information related to the list. REQ PC-15: It MUST be possible for the resource list to be associated with a list of authorized users who are the only ones permitted to manipulate the resource list. REQ PC-16: It MUST be possible for the resource list to be associated with a list of authorized users who are authorized to subscribe to the list. REQ PC-17: It MUST be possible for a client to store a cached copy of the list. It MUST be possible for the client to manipulate the local cached copy even when there is no connectivity to the server. It MUST be possible to synchronize the cached copy with the master copy on the server, when connectivity is re-established. This particular requirement is crucial for wireless systems, where a copy of the list resides on the handset. Without this requirement, a user would not be able to view the list, or add a user to it, when they go out of coverage. Rosenberg & Isomaki Expires December 26, 2003 [Page 7] Internet-Draft Data Manipulation Requirements June 2003 REQ PC-18: It MUST be possible multiple clients to manipulate a resource list without knowing of each other's actions. This implies that it MUST be possible for the server to notify each client of the changes if the client has indicated the need for the change notifications. REQ PC-19: Manipulations of the resource list MUST exhibit the ACID property; that is, they MUST be atomic, be consistent, durable, and operate independently. REQ PC-20: It SHOULD be possible for the client to batch multiple operations (add a presentity, remove a presentity) into a single request that is processed atomically. REQ PC-21: It MUST be possible for the server to authenticate the client. REQ PC-22: It SHOULD be possible to use the same database of client credentials used with SIP and SIMPLE, with the data manipulation protocol. REQ PC-23: It MUST be possible for the client to authenticate the server. REQ PC-24: It MUST be possible for message integrity to be insured between the client and the server. REQ PC-25: It MUST be possible for confidentiality to be ensured between the client and server. As a motivating example, an eavesdropper on the protocol could ascertain the set of people in my resource list, resulting in divulging private information. REQ PC-26: It MUST be possible for the protocol to operate through an intermediary, such as a proxy, to allow easier firewall traversal. 6. Authorization Policy Manipulation The following are the set of requirements for the protocol between the client and the server for the purposes of manipulating presence authorization policy. The requirements are divided between acceptance policy, notification policy, and content policy. It is obvious that these requirements would apply to other SIP event packages than presence as well, but those are outside the scope of this document. 6.1 Acceptance Policy Requirements Rosenberg & Isomaki Expires December 26, 2003 [Page 8] Internet-Draft Data Manipulation Requirements June 2003 REQ AP-1: It MUST be possible for the acceptance policy to support rejection of the subscription if the watcher is present on a specified list of 'blocked watchers'. When a list is checked in this fashion, it is referred to as a blocked list. REQ AP-2: It MUST be possible for the acceptance policy to support rejection of the subscription if the watcher is not present on a specified list of 'allowed watchers'. REQ AP-3: It MUST be possible for the acceptance policy to support making a subscription pending if the watcher is present on neither an explicit allowed or blocked list. In that case, the watcher info package [5] can be used for reactive authorization. REQ AP-4: It MUST be possible for the acceptance policy to check multiple blocked and allowed lists. REQ AP-5: It SHOULD be possible for the policy to be based on the means by which the authenticated identity of the watcher was determined (digest vs. S/MIME, for example). REQ AP-6: It SHOULD be possible for the policy to be based on whether notifications can be sent encrypted to the subscriber. REQ AP-7: It MUST be possible for authorized users to create, read, modify and delete lists that are checked by the authorization policy (e.g., the allowed and blocked lists). REQ AP-8: It MUST be possible for authorized users to read, add, remove and modify entries of the lists. REQ AP-9: It MUST be possible for the lists to contain entries with wildcards, e.g., allow everyone in a certain domain. 6.2 Notification Requirements REQ N-1: It SHOULD be possible for the user to specify that notifications are to be sent only when the value of a particular status type changes. REQ N-2: It SHOULD be possible for the user to specify that the notifications are to be sent only when a particular status type changes to a specified value or set of values. REQ N-3: It SHOULD be possible for the user to specify that the notifications are to be sent only when a particular status type changes from a specified value to a specified value (e.g., from Rosenberg & Isomaki Expires December 26, 2003 [Page 9] Internet-Draft Data Manipulation Requirements June 2003 open to closed). REQ N-4: It SHOULD be possible for the user to specify that the notifications are to be sent only when the value of the contact address changes. REQ N-5: It SHOULD be possible for the user to specify that the notifications are not, or should be sent on changes in the state of the subscription (as opposed to the state of the presentity). 6.3 Content Requirements REQ C-1: The user MUST be able to specify that the notification should only contain information for particular tuples. It SHOULD be possible to use any presence attribute within a tuple as criteria for this selection. REQ C-2: It MUST be possible for the user to specify that the notification should or should not contain a contact address. REQ C-3: It MUST be possible for the user to specify that the notification should contain only specific status types (such as basic). REQ C-4: The user MUST be able to specify the specific values of a specific status type that the notification should or should not contain. Values not permitted must result in the omission of that status type. If all status is omitted, the tuple must be omitted as well. As an example, a user can specify that the notification should include tuples with OPEN status, but suppress those with only CLOSED status. REQ C-5: It MUST be possible for the user to specify different values of the semantically identical presence information, such as status attribute, to different watchers. It MUST be possible for the user to give different level of detail of information to different watchers. The assumption is that the presentity also publishes the different values separately (e.g. in separate tuples), so that the authorization rules can simply select which (level of) information to give to each watcher. REQ C-6: It SHOULD be possible for the user to specify the specific presence document to send to a watcher. Rosenberg & Isomaki Expires December 26, 2003 [Page 10] Internet-Draft Data Manipulation Requirements June 2003 REQ C-7: It SHOULD be possible for the user to specify that the notifications should be encrypted using S/MIME. REQ C-8: It SHOULD be possible for the user to specify that a particular tuple be added, removed or modified based on the value of another tuple. As an example, a user might want to include their IM tuple when their phone is busy, but not include it when the phone is not busy. 6.4 General Requirements These requirements apply to all of the three components of the authorization policy. REQ G-1: It MUST be possible for a client to store a cached copy of the policies. It MUST be possible for the client to manipulate the local cached copy even when there is no connectivity to the server. It MUST be possible to synchronize the cached copy with the master copy on the server, when connectivity is re-established. REQ G-2: It MUST be possible for multiple clients to manipulate the same policies without knowing of each others' actions. This implies that it MUST be possible for the server to notify each client of the changes if the client has indicated the need for the change notifications. REQ G-3: Manipulations of the data MUST exhibit the ACID property; that is, they MUST be atomic, be consistent, durable, and operate independently. REQ G-4: It MUST be possible to ensure that the authorization policies are always consistent as a whole when transitioning from one policy state to another. To enable this, it MUST be possible for the client to batch multiple operations (remove a user from one list, add the same user to another list) into a single request that is processed atomically, or to otherwise ensure that the policies are never left in an inconsistent state. REQ G-5: It MUST be possible for the server to authenticate the client. REQ G-6: It SHOULD be possible to use the same database of client credentials used with SIP and SIMPLE, with the data manipulation protocol. Rosenberg & Isomaki Expires December 26, 2003 [Page 11] Internet-Draft Data Manipulation Requirements June 2003 REQ G-7: It MUST be possible for the client to authenticate the server. REQ G-8: It MUST be possible for message integrity to be ensured between the client and the server. REQ G-9: It MUST be possible for confidentiality to be ensured between the client and server. As a motivating example, an eavesdropper on the protocol could ascertain the set of people in my allowed list, resulting in divulging private information. REQ G-10: It MUST be possible to extend the authorization policies with new types of rules. REQ G-11: It MUST be possible for a client to discover the types of authorization policies the server can handle. 7. Security Considerations There are many security considerations associated with the protocol whose requirements are defined here. The protocol is used to manipulate data that has a significant impact on the operation of a service provided to a user. In particular, if an attacker manipulates the data, the attacker can: o convey information to subscribers that the presentity wishes to keep private; o launch denial of service attacks by flooding a subscriber with more presence information than they expected; o deny service to subscribers or to presentities. To prevent these attacks, the protocol has to ensure than only authorized users can manipulate the data. Requirements for authentication and authorization are defined above. Information conveyed in the protocol represents sensitive data. It can include the content of resource lists and lists of blocked users, both of which reveal personal preferences of a user that they do not wish to convey. As a result, it is necessary that the client authenticate the server, to be sure it is passing this information to a trusted entity. It is also necessary for the protocol to provide encryption services, so that eavesdroppers cannot inspect the data as it passes by. Rosenberg & Isomaki Expires December 26, 2003 [Page 12] Internet-Draft Data Manipulation Requirements June 2003 8. Acknowledgements The authors would like to thank Paul Kyzivat, Ben Campbell, Krisztian Kiss and Eva Leppanen for their input. 9. Changes from version 02 o Conventions chapter added. o To-Do list removed. o Presentity collection renamed resource list. o Ordering of requirements 'rationalized'. o References updated. o Defined the scope to be explicitly limited to only resource list and presence authorization policy requirements. o Several requirements modified based on SIMPLE WG last call comments by Ben Campbell and Krisztian Kiss. Informative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Day, M., "A model for presence and instant messaging", RFC 2778, February 2000. [3] Rosenberg, J., "Session Initiation Protocol (SIP) Extensions for Presence", draft-ietf-simple-presence-10.txt, January 2003. [4] Roach, A., "Session Initiation Protocol (SIP)-Specific Event Notification", RFC 3265, June 2002. [5] Rosenberg, J., "A Watcher Information Event Template-Package for the Session Initiation Protocol (SIP)", draft-ietf-simple-winfo-package-05.txt, January 2003. [6] Rosenberg, J., "A Session Initiation Protocol (SIP) Event Notification Extension for Resource Lists", draft-ietf-simple-event-list-03.txt, May 2003. [7] Peterson, J., "Common profile for presence (CPP)", draft-ietf-impp-pres-03.txt, May 2003. Rosenberg & Isomaki Expires December 26, 2003 [Page 13] Internet-Draft Data Manipulation Requirements June 2003 Authors' Addresses Jonathan Rosenberg Dynamicsoft 72 Eagle Rock Avenue First Floor East Hanover, NJ 07936 USA Phone: EMail: jdrosen@dynamicsoft.com Markus Isomaki Nokia Research Center Itamerenkatu 11-13 00180 Helsinki Finland Phone: EMail: markus.isomaki@nokia.com Rosenberg & Isomaki Expires December 26, 2003 [Page 14] Internet-Draft Data Manipulation Requirements 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. 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