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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-23) exists of draft-ietf-precis-framework-13 -- Possible downref: Non-RFC (?) normative reference: ref. 'UNICODE' -- Obsolete informational reference (is this intentional?): RFC 2616 (Obsoleted by RFC 7230, RFC 7231, RFC 7232, RFC 7233, RFC 7234, RFC 7235) -- Obsolete informational reference (is this intentional?): RFC 4395 (Obsoleted by RFC 7595) -- Obsolete informational reference (is this intentional?): RFC 5988 (Obsoleted by RFC 8288) Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 5 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group P. Saint-Andre 3 Internet-Draft 4 Intended status: Standards Track January 23, 2014 5 Expires: July 27, 2014 7 The 'acct' URI Scheme 8 draft-ietf-appsawg-acct-uri-07 10 Abstract 12 This document defines the 'acct' Uniform Resource Identifier (URI) 13 scheme as a way to identify a user's account at a service provider, 14 irrespective of the particular protocols that can be used to interact 15 with the account. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at http://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on July 27, 2014. 34 Copyright Notice 36 Copyright (c) 2014 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (http://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 52 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 53 3. Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . 2 54 4. Definition . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 56 6. Internationalization Considerations . . . . . . . . . . . . . 5 57 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 58 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 59 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 8 60 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8 62 1. Introduction 64 Existing Uniform Resource Identifier (URI) schemes that enable 65 interaction with, or that identify resources associated with, a 66 user's account at a service provider are tied to particular services 67 or application protocols. Two examples are the 'mailto' scheme 68 (which enables interaction with a user's email account) and the 69 'http' scheme (which enables retrieval of web files controlled by a 70 user or interaction with interfaces providing information about a 71 user). However, there exists no URI scheme that generically 72 identifies a user's account at a service provider without specifying 73 a particular protocol to use when interacting with the account. This 74 specification fills that gap. 76 2. Terminology 78 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 79 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 80 "OPTIONAL" in this document are to be interpreted as described in 81 [RFC2119]. 83 3. Rationale 85 During formalization of the WebFinger protocol [RFC7033], much 86 discussion occurred regarding the appropriate URI scheme to include 87 when specifying a user's account as a web link [RFC5988]. Although 88 both the 'mailto' [RFC6068] and 'http' [RFC2616] schemes were 89 proposed, not all service providers offer email services or web 90 interfaces on behalf of user accounts (e.g., a microblogging or 91 instant messaging provider might not offer email services, or an 92 enterprise might not offer HTTP interfaces to information about its 93 employees). Therefore, the participants in the discussion recognized 94 that it would be helpful to define a URI scheme that could be used to 95 generically identify a user's account at a service provider, 96 irrespective of the particular application protocols used to interact 97 with the account. The result was the 'acct' URI scheme defined in 98 this document. 100 (Note that a user is not necessarily a human; it could be an 101 automated application such as a bot, a role-based alias, etc. 102 However, an 'acct' URI is always used to identify something that has 103 an account at a service, not the service itself.) 105 4. Definition 107 The syntax of the 'acct' URI scheme is defined under Section 7 of 108 this document. Although 'acct' URIs take the form "user@host", the 109 scheme is designed for the purpose of identification instead of 110 interaction (regarding this distinction, see Section 1.2.2 of 111 [RFC3986]). The "Internet resource" identified by an 'acct' URI is a 112 user's account hosted at a service provider, where the service 113 provider is typically associated with a DNS domain name. Thus a 114 particular 'acct' URI is formed by setting the "user" portion to the 115 user's account name at the service provider and by setting the "host" 116 portion to the DNS domain name of the service provider. 118 Consider the case of a user with an account name of "foobar" on a 119 microblogging service "status.example.net". It is taken as 120 convention that the string "foobar@status.example.net" designates 121 that account. This is expressed as a URI using the 'acct' scheme as 122 "acct:foobar@status.example.net". 124 A common scenario is for a user to register with a service provider 125 using an identifier (such as an email address) that is associated 126 with some other service provider. For example, a user with the email 127 address "juliet@capulet.example" might register with a commerce 128 website whose domain name is "shoppingsite.example". In order to use 129 her email address as the localpart of the 'acct' URI, the at-sign 130 character (U+0040) needs to be percent-encoded as described in 131 [RFC3986]. Thus the resulting 'acct' URI would be 132 "acct:juliet%40capulet.example@shoppingsite.example". 134 It is not assumed that an entity will necessarily be able to interact 135 with a user's account using any particular application protocol, such 136 as email; to enable such interaction, an entity would need to use the 137 appropriate URI scheme for such a protocol, such as the 'mailto' 138 scheme. While it might be true that the 'acct' URI minus the scheme 139 name (e.g., "user@example.com" derived from "acct:user@example.com") 140 can be reached via email or some other application protocol, that 141 fact would be purely contingent and dependent upon the deployment 142 practices of the provider. 144 Because an 'acct' URI enables abstract identification only and not 145 interaction, this specification provides no method for dereferencing 146 an 'acct' URI on its own, e.g., as the value of the 'href' attribute 147 of an HTML anchor element. For example, there is no behavior 148 specified in this document for an 'acct' URI used as follows: 150 find out more 152 Any protocol that uses 'acct' URIs is responsible for specifying how 153 an 'acct' URI is employed in the context of that protocol (in 154 particular, how it is dereferenced or resolved; see [RFC3986]). As a 155 concrete example, an "Account Information" application of the 156 WebFinger protocol [RFC7033] might take an 'acct' URI, resolve the 157 host portion to find a WebFinger server, and then pass the 'acct' URI 158 as a parameter in a WebFinger HTTP request for metadata (i.e., web 159 links [RFC5988]) about the resource. For example: 161 GET /.well-known/webfinger?resource=acct%3Abob%40example.com HTTP/1.1 163 The service retrieves the metadata associated with the account 164 identified by that URI and then provides that metadata to the 165 requesting entity in an HTTP response. 167 If an application needs to compare two 'acct' URIs (e.g., for 168 purposes of authentication and authorization), it MUST do so using 169 case normalization and percent-encoding normalization as specified in 170 Sections 6.2.2.1 and 6.2.2.2 of [RFC3986]. 172 5. Security Considerations 174 Because the 'acct' URI scheme does not directly enable interaction 175 with a user's account at a service provider, direct security concerns 176 are minimized. 178 However, an 'acct' URI does provide proof of existence of the 179 account; this implies that harvesting published 'acct' URIs could 180 prove useful to spammers and similar attackers, for example if they 181 can use an 'acct' URI to leverage more information about the account 182 (e.g., via WebFinger) or if they can interact with protocol-specific 183 URIs (such as 'mailto' URIs) whose user@host portion is the same as 184 that of the 'acct' URI. 186 In addition, protocols that make use of 'acct' URIs are responsible 187 for defining security considerations related to such usage, e.g., the 188 risks involved in dereferencing an 'acct' URI, the authentication and 189 authorization methods that could be used to control access to 190 personal data associated with a user's account at a service, and 191 methods for ensuring the confidentiality of such information. 193 The use of percent-encoding allows a wider range of characters in 194 account names, but introduces some additional risks. Implementers 195 are advised to disallow percent-encoded characters or sequences that 196 would (1) result in space, null, control, or other characters that 197 are otherwise forbidden, (2) allow unauthorized access to private 198 data, or (3) lead to other security vulnerabilities. 200 6. Internationalization Considerations 202 As specified in [RFC3986], the 'acct' URI scheme allows any character 203 from the Unicode repertoire [UNICODE] encoded as UTF-8 [RFC3629] and 204 then percent-encoded into valid ASCII [RFC20]. Before applying any 205 percent-encoding, an application MUST ensure the following about the 206 string that is used as input to the URI-construction process: 208 o The userpart consists only of Unicode code points that conform to 209 the PRECIS IdentifierClass specified in 210 [I-D.ietf-precis-framework]. 212 o The host consists only of Unicode code points that conform to the 213 rules specified in [RFC5892]. 215 o Internationalized domain name (IDN) labels are encoded as A-labels 216 [RFC5890]. 218 7. IANA Considerations 220 In accordance with the guidelines and registration procedures for new 221 URI schemes [RFC4395], this section provides the information needed 222 to register the 'acct' URI scheme. 224 7.1. URI Scheme Name 226 acct 228 7.2. Status 230 permanent 232 7.3. URI Scheme Syntax 234 The 'acct' URI syntax is defined here in Augmented Backus-Naur Form 235 (ABNF) [RFC5234], borrowing the 'host', 'pct-encoded', 'sub-delims', 236 'unreserved' rules from [RFC3986]: 238 acctURI = "acct" ":" userpart "@" host 239 userpart = unreserved / sub-delims 240 0*( unreserved / pct-encoded / sub-delims ) 242 Note that additional rules regarding the strings that are used as 243 input to construction of 'acct' URIs further limit the characters 244 that can be percent-encoded; see the Encoding Considerations as well 245 as Section 6 of RFC XXXX. [Note to RFC Editor: please replace XXXX 246 with the number issued to this document.] 248 7.4. URI Scheme Semantics 250 The 'acct' URI scheme identifies accounts hosted at service 251 providers. It is used only for identification, not interaction. A 252 protocol that employs the 'acct' URI scheme is responsible for 253 specifying how an 'acct' URI is dereferenced in the context of that 254 protocol. There is no media type associated with the 'acct' URI 255 scheme. 257 7.5. Encoding Considerations 259 See Section 6 of RFC XXXX. [Note to RFC Editor: please replace XXXX 260 with the number issued to this document.] 262 7.6. Applications/Protocols That Use This URI Scheme Name 264 At the time of this writing, only the WebFinger protocol uses the 265 'acct' URI scheme. However, use is not restricted to the WebFinger 266 protocol, and the scheme might be considered for use in other 267 protocols. 269 7.7. Interoperability Considerations 271 There are no known interoperability concerns related to use of the 272 'acct' URI scheme. 274 7.8. Security Considerations 276 See Section 5 of RFC XXXX. [Note to RFC Editor: please replace XXXX 277 with the number issued to this document.] 279 7.9. Contact 281 Peter Saint-Andre, psaintan@cisco.com 283 7.10. Author/Change Controller 284 This scheme is registered under the IETF tree. As such, the IETF 285 maintains change control. 287 7.11. References 289 None. 291 8. References 293 8.1. Normative References 295 [I-D.ietf-precis-framework] 296 Saint-Andre, P. and M. Blanchet, "Precis Framework: 297 Handling Internationalized Strings in Protocols", draft- 298 ietf-precis-framework-13 (work in progress), December 299 2013. 301 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 302 Requirement Levels", BCP 14, RFC 2119, March 1997. 304 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 305 10646", STD 63, RFC 3629, November 2003. 307 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 308 Resource Identifier (URI): Generic Syntax", STD 66, RFC 309 3986, January 2005. 311 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 312 Specifications: ABNF", STD 68, RFC 5234, January 2008. 314 [RFC5890] Klensin, J., "Internationalized Domain Names for 315 Applications (IDNA): Definitions and Document Framework", 316 RFC 5890, August 2010. 318 [RFC5892] Faltstrom, P., "The Unicode Code Points and 319 Internationalized Domain Names for Applications (IDNA)", 320 RFC 5892, August 2010. 322 [UNICODE] The Unicode Consortium, "The Unicode Standard, Version 323 6.1", 2012, 324 . 326 8.2. Informative References 328 [RFC20] Cerf, V., "ASCII format for network interchange", RFC 20, 329 October 1969. 331 [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., 332 Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext 333 Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. 335 [RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines and 336 Registration Procedures for New URI Schemes", BCP 35, RFC 337 4395, February 2006. 339 [RFC5988] Nottingham, M., "Web Linking", RFC 5988, October 2010. 341 [RFC6068] Duerst, M., Masinter, L., and J. Zawinski, "The 'mailto' 342 URI Scheme", RFC 6068, October 2010. 344 [RFC7033] Jones, P., Salgueiro, G., Jones, M., and J. Smarr, 345 "WebFinger", RFC 7033, September 2013. 347 Appendix A. Acknowledgements 349 The 'acct' URI scheme was originally proposed during work on the 350 WebFinger protocol; special thanks are due to Blaine Cook, Brad 351 Fitzpatrick, and Eran Hammer-Lahav for their early work on the 352 concept (which in turn was partially inspired by work on Extensible 353 Resource Indentifiers at OASIS). The scheme was first formally 354 specified in [RFC7033]; the authors of that specification (Paul 355 Jones, Gonzalo Salgueiro, and Joseph Smarr) are gratefully 356 acknowledged. Thanks are also due to Stephane Bortzmeyer, Melvin 357 Carvalho, Martin Duerst, Graham Klyne, Barry Leiba, Subramanian 358 Moonesamy, Evan Prodromou, James Snell, and various participants in 359 the IETF APPSAWG for their feedback. Meral Shirazipour completed a 360 Gen-ART review. Dave Cridland completed an AppsDir review, and is 361 gratefully acknowledged for providing proposed text that was 362 incorporated into Section 3 and Section 5. IESG comments from 363 Richard Barnes, Adrian Farrel, Stephen Farrell, Barry Leiba, Pete 364 Resnick, and Sean Turner also led to improvements in the 365 specification. 367 Author's Address 369 Peter Saint-Andre 371 Email: ietf@stpeter.im