Network Working Group T. Citharel Internet-Draft Framasoft Intended status: Standards Track November 30, 2018 Expires: July 3, 2019 The 'group' URI Scheme draft-tcit-group-uri-01 Abstract This document defines the 'group' Uniform Resource Identifier (URI) scheme as a way to identify a group at a service provider, irrespective of the particular protocols that can be used to interact with the group. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on July 3, 2019. Copyright Notice Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Citharel Standards Track [Page 1] RFC 7565 The 'group' URI Scheme November 2018 Table of Contents 1. Introduction ....................................................2 2. Terminology .....................................................2 3. Rationale .......................................................2 4. Definition ......................................................3 5. Security Considerations .........................................4 6. Internationalization Considerations .............................5 7. IANA Considerations .............................................5 8. References ......................................................6 8.1. Normative References .......................................6 8.2. Informative References .....................................7 Acknowledgements ...................................................8 Author's Address ...................................................8 1. Introduction Existing Uniform Resource Identifier (URI) schemes that enable interaction with, or that identify resources associated with, a user's account at a service provider are tied to particular services or application protocols. Two examples are the 'mailto' scheme (which enables interaction with a user's email account) and the 'http' scheme (which enables retrieval of web files controlled by a user or interaction with interfaces providing information about a user). The 'acct' scheme was also added with [RFC7565] to identify an account at a service provider. However, there exists no URI scheme that generically identifies a group at a service provider without specifying a particular protocol to use when interacting with the group. This specification fills that gap. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 3. Rationale With the multiplication of decentralized social networks that rely heavily on the WebFinger protocol [RFC7033] to discover users easily. The accessible form with the 'acct' URI [RFC7565] is used a lot, but it has a restriction on being used to identify something that has an account (an user, a bot, etc.). Therefore it doesn't allows quering information about a group. Even if a WebFinger query with the 'acct' URI and group name as username is done, there would be no way to identify if the returned information is about a group or an user. Citharel Standards Track [Page 2] RFC 7565 The 'group' URI Scheme November 2018 (Note that a group could be called Community.) 4. Definition The syntax of the 'group' URI scheme is defined under Section 7 of this document. Although 'group' URIs take the form "group@host", the scheme is designed for the purpose of identification instead of interaction (regarding this distinction, see Section 1.2.2 of [RFC3986]). The "Internet resource" identified by an 'group' URI is a group hosted at a service provider, where the service provider is typically associated with a DNS domain name. Thus, a particular 'group' URI is formed by setting the group portion to the group name at the service provider and by setting the "host" portion to the DNS domain name of the service provider. Consider the case of a group with an name of "foobar" on a microblogging service "status.example.net". It is taken as convention that the string "foobar@status.example.net" designates that group. This is expressed as a URI using the 'group' scheme as "group:foobar@status.example.net". A common scenario is for a person to join a group associated with a specific service provider. For example, a person sees on a public website whose domain name is "site.social" a list of groups. If she picks the group "discworld", the resulting 'group' URI would be "group:discworld@site.social". It is not assumed that an entity will necessarily be able to interact with a group using any particular application protocol, such as email; to enable such interaction, an entity would need to use the appropriate URI scheme for such a protocol, such as the 'mailto' scheme. While it might be true that the 'group' URI minus the scheme name (e.g., "mygroup@example.com" derived from "group:mygroup@example.com") can be reached via email or some other application protocol, that fact would be purely contingent and dependent upon the deployment practices of the provider. Because an 'group' URI enables abstract identification only and not interaction, this specification provides no method for dereferencing an 'group' URI on its own, e.g., as the value of the 'href' attribute of an HTML anchor element. For example, there is no behavior specified in this document for an 'group' URI used as follows: find out more Any protocol that uses 'group' URIs is responsible for specifying how an 'group' URI is employed in the context of that protocol (in particular, how it is dereferenced or resolved; see [RFC3986]). As a Citharel Standards Track [Page 3] RFC 7565 The 'group' URI Scheme November 2018 concrete example, an "Account Information" application of the WebFinger protocol [RFC7033] might take an 'group' URI, resolve the host portion to find a WebFinger server, and then pass the 'group' URI as a parameter in a WebFinger HTTP request for metadata (i.e., web links [RFC8288]) about the resource. For example: GET /.well-known/webfinger?resource=group%3Agirls%40example.com HTTP/1.1 The service retrieves the metadata associated with the group identified by that URI and then provides that metadata to the requesting entity in an HTTP response. If an application needs to compare two 'group' URIs (e.g., for purposes of authentication and authorization), it MUST do so using case normalization and percent-encoding normalization as specified in Sections 6.2.2.1 and 6.2.2.2 of [RFC3986]. 5. Security Considerations Because the 'group' URI scheme does not directly enable interaction with a group at a service provider, direct security concerns are minimized. However, a 'group' URI does provide proof of existence of the group; this implies that harvesting published 'group' URIs could prove useful to spammers and similar attackers -- for example, if they can use an 'group' URI to leverage more information about the group (e.g., via WebFinger) or if they can interact with protocol- specific URIs (such as 'mailto' URIs) whose group@host portion is the same as that of the 'group' URI. In addition, protocols that make use of 'group' URIs are responsible for defining security considerations related to such usage, e.g., the risks involved in dereferencing an 'group' URI, the authentication and authorization methods that could be used to control access to personal data associated with a group account at a service, and methods for ensuring the confidentiality of such information. The use of percent-encoding allows a wider range of characters in group names but introduces some additional risks. Implementers are advised to disallow percent-encoded characters or sequences that would (1) result in space, null, control, or other characters that are otherwise forbidden, (2) allow unauthorized access to private data, or (3) lead to other security vulnerabilities. 6. Internationalization Considerations Citharel Standards Track [Page 4] RFC 7565 The 'group' URI Scheme November 2018 As specified in [RFC3986], the 'group' URI scheme allows any character from the Unicode repertoire [Unicode] encoded as UTF-8 [RFC3629] and then percent-encoded into valid ASCII [RFC20]. Before applying any percent-encoding, an application MUST ensure the following about the string that is used as input to the URI- construction process: o The userpart consists only of Unicode code points that conform to the PRECIS IdentifierClass specified in [RFC8264]. o The host consists only of Unicode code points that conform to the rules specified in [RFC5892]. o Internationalized domain name (IDN) labels are encoded as A-labels [RFC5890]. 7. IANA Considerations In accordance with the guidelines and registration procedures for new URI schemes [RFC7595], this section provides the information needed to register the 'group' URI scheme. URI Scheme Name: group Status: permanent URI Scheme Syntax: The 'group' URI syntax is defined here in Augmented Backus-Naur Form (ABNF) [RFC5234], borrowing the 'host', 'pct-encoded', 'sub-delims', and 'unreserved' rules from [RFC3986]: groupURI = "group" ":" grouppart "@" host grouppart = unreserved / sub-delims 0*( unreserved / pct-encoded / sub-delims ) Note that additional rules regarding the strings that are used as input to construction of 'group' URIs further limit the characters that can be percent-encoded; see the Encoding Considerations as well as Section 6 of this document. URI Scheme Semantics: The 'group' URI scheme identifies groups hosted at service providers. It is used only for identification, not interaction. A protocol that employs the 'group' URI scheme is responsible for specifying how an 'group' URI is dereferenced in the context of that protocol. There is no media type associated with the 'group' URI scheme. Citharel Standards Track [Page 5] RFC 7565 The 'group' URI Scheme November 2018 Encoding Considerations: See Section 6 of this document. Applications/Protocols That Use This URI Scheme Name: At the time of this writing, only the WebFinger protocol uses the 'group' URI scheme. However, use is not restricted to the WebFinger protocol, and the scheme might be considered for use in other protocols. Interoperability Considerations: There are no known interoperability concerns related to use of the 'group' URI scheme. Security Considerations: See Section 5 of this document. Contact: Peter Saint-Andre, peter@andyet.com Author/Change Controller: This scheme is registered under the IETF tree. As such, the IETF maintains change control. References: None. 8. References 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 2003, . [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, . [RFC5234] Crocker, D., Ed., and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC5234, January 2008, . [RFC5890] Klensin, J., "Internationalized Domain Names for Applications (IDNA): Definitions and Document Framework", RFC 5890, DOI 10.17487/RFC5890, August 2010, . [RFC5892] Faltstrom, P., Ed., "The Unicode Code Points and Citharel Standards Track [Page 6] RFC 7565 The 'group' URI Scheme November 2018 Internationalized Domain Names for Applications (IDNA)", RFC 5892, DOI 10.17487/RFC5892, August 2010, . [RFC8264] Saint-Andre, P. and M. Blanchet, "PRECIS Framework: Preparation, Enforcement, and Comparison of Internationalized Strings in Application Protocols", RFC 8264, DOI 10.17487/RFC8264, October 2017, . [Unicode] The Unicode Consortium, "The Unicode Standard", . 8.2. Informative References [RFC20] Cerf, V., "ASCII format for network interchange", STD 80, RFC 20, DOI 10.17487/RFC0020, October 1969, . [RFC7595] D. Thaler, Ed., T. Hansen, T. Hardie, "Guidelines and Registration Procedures for New URI Schemes", BCP 35, RFC 7595, DOI 10.17487/RFC7595, June 2015, . [RFC8288] Nottingham, M., "Web Linking", RFC 8288, DOI 10.17487/RFC8288, October 2017, . [RFC7565] P. Saint-Andre, "The 'acct' URI Scheme", RFC 7565, DOI 10.17487/RFC7565, May 2015, . [RFC7033] Jones, P., Salgueiro, G., Jones, M., and J. Smarr, "WebFinger", RFC 7033, DOI 10.17487/RFC7033, September 2013, . Citharel Standards Track [Page 7] RFC 7565 The 'group' URI Scheme November 2018 Acknowledgements Thanks to Chocobozzz, Bat for the exchanges. Author's Address Thomas Citharel EMail: tcit@tcit.fr URI: https://tcit.fr Citharel Standards Track [Page 8]