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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group P. Saint-Andre 3 Internet-Draft Cisco Systems, Inc. 4 Intended status: Standards Track July 2, 2013 5 Expires: January 3, 2014 7 The 'acct' URI Scheme 8 draft-ietf-appsawg-acct-uri-06 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 January 3, 2014. 34 Copyright Notice 36 Copyright (c) 2013 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 52 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 53 3. Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 54 4. Definition . . . . . . . . . . . . . . . . . . . . . . . . . . 4 55 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 56 6. Internationalization Considerations . . . . . . . . . . . . . . 6 57 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 58 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 59 8.1. Normative References . . . . . . . . . . . . . . . . . . . 8 60 8.2. Informative References . . . . . . . . . . . . . . . . . . 8 61 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . . 9 62 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9 64 1. Introduction 66 Existing Uniform Resource Identifier (URI) schemes that enable 67 interaction with, or that identify resources associated with, a 68 user's account at a service provider are tied to particular services 69 or application protocols. Two examples are the 'mailto' scheme 70 (which enables interaction with a user's email account) and the 71 'http' scheme (which enables retrieval of web files controlled by a 72 user or interaction with interfaces providing information about a 73 user). However, there exists no URI scheme that generically 74 identifies a user's account at a service provider without specifying 75 a particular protocol to use when interacting with the account. This 76 specification fills that gap. 78 2. Terminology 80 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 81 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 82 "OPTIONAL" in this document are to be interpreted as described in 83 [RFC2119]. 85 3. Rationale 87 During formalization of the WebFinger protocol 88 [I-D.ietf-appsawg-webfinger], much discussion occurred regarding the 89 appropriate URI scheme to include when specifying a user's account as 90 a web link [RFC5988]. Although both the 'mailto' [RFC6068] and 91 'http' [RFC2616] schemes were proposed, not all service providers 92 offer email services or web interfaces on behalf of user accounts 93 (e.g., a microblogging or instant messaging provider might not offer 94 email services, or an enterprise might not offer HTTP interfaces to 95 information about its employees). Therefore, the participants in the 96 discussion recognized that it would be helpful to define a URI scheme 97 that could be used to generically identify a user's account at a 98 service provider, irrespective of the particular application 99 protocols used to interact with the account. The result was the 100 'acct' URI scheme defined in this document. 102 (Note that a user is not necessarily a human; it could be an 103 automated application such as a bot, a role-based alias, etc. 104 However, an 'acct' URI is always used to identify something that has 105 an account at a service, not the service itself.) 107 4. Definition 109 The syntax of the 'acct' URI scheme is defined under Section 7 of 110 this document. Although 'acct' URIs take the form "user@host", the 111 scheme is designed for the purpose of identification instead of 112 interaction (regarding this distinction, see Section 1.2.2 of 113 [RFC3986]). The "Internet resource" identified by an 'acct' URI is a 114 user's account hosted at a service provider, where the service 115 provider is typically associated with a DNS domain name. Thus a 116 particular 'acct' URI is formed by setting the "user" portion to the 117 user's account name at the service provider and by setting the "host" 118 portion to the DNS domain name of the service provider. 120 Consider the case of a user with an account name of "foobar" on a 121 microblogging service "status.example.net". It is taken as 122 convention that the string "foobar@status.example.net" designates 123 that account. This is expressed as a URI using the 'acct' scheme as 124 "acct:foobar@status.example.net". 126 A common scenario is for a user to register with a service provider 127 using an identifier (such as an email address) that is associated 128 with some other service provider. For example, a user with the email 129 address "juliet@capulet.example" might register with a commerce 130 website whose domain name is "shoppingsite.example". In order to use 131 her email address as the localpart of the 'acct' URI, the at-sign 132 character (U+0040) needs to be percent-encoded as described in 133 [RFC3986]. Thus the resulting 'acct' URI would be 134 "juliet%40capulet.example@shoppingsite.example.com". 136 It is not assumed that an entity will necessarily be able to interact 137 with a user's account using any particular application protocol, such 138 as email; to enable such interaction, an entity would need to use the 139 appropriate URI scheme for such a protocol, such as the 'mailto' 140 scheme. While it might be true that the 'acct' URI minus the scheme 141 name (e.g., "user@example.com" derived from "acct:user@example.com") 142 can be reached via email or some other application protocol, that 143 fact would be purely contingent and dependent upon the deployment 144 practices of the provider. 146 Because an 'acct' URI enables abstract identification only and not 147 interaction, this specification provides no method for dereferencing 148 an 'acct' URI on its own, e.g., as the value of the 'href' attribute 149 of an HTML anchor element. For example, there is no behavior 150 specified in this document for an 'acct' URI used as follows: 152 find out more 154 Any protocol that uses 'acct' URIs is responsible for specifying how 155 an 'acct' URI is employed in the context of that protocol (in 156 particular, how it is dereferenced or resolved; see [RFC3986]). As a 157 concrete example, an "Account Information" application of the 158 WebFinger protocol [I-D.ietf-appsawg-webfinger] might take an 'acct' 159 URI, resolve the host portion to find a WebFinger server, and then 160 pass the 'acct' URI as a parameter in a WebFinger HTTP request for 161 metadata (i.e., web links [RFC5988]) about the resource. For 162 example: 164 GET /.well-known/webfinger?resource=acct%3Abob%40example.com HTTP/1.1 166 The service retrieves the metadata associated with the account 167 identified by that URI and then provides that metadata to the 168 requesting entity in an HTTP response. 170 If an application needs to compare two 'acct' URIs (e.g., for 171 purposes of authentication and authorization), it MUST do so using 172 case normalization and percent-encoding normalization as specified in 173 Sections 6.2.2.1 and 6.2.2.2 of [RFC3986]. 175 5. Security Considerations 177 Because the 'acct' URI scheme does not directly enable interaction 178 with a user's account at a service provider, direct security concerns 179 are minimized. 181 However, an 'acct' URI does provide proof of existence of the 182 account; this implies that harvesting published 'acct' URIs could 183 prove useful to spammers and similar attackers, for example if they 184 can use an 'acct' URI to leverage more information about the account 185 (e.g., via WebFinger) or if they can interact with protocol-specific 186 URIs (such as 'mailto' URIs) whose user@host portion is the same as 187 that of the 'acct' URI. 189 In addition, protocols that make use of 'acct' URIs are responsible 190 for defining security considerations related to such usage, e.g., the 191 risks involved in dereferencing an 'acct' URI, the authentication and 192 authorization methods that could be used to control access to 193 personal data associated with a user's account at a service, and 194 methods for ensuring the confidentiality of such information. 196 The use of percent-encoding allows a wider range of characters in 197 account names, but introduces some additional risks. Implementers 198 are advised to disallow percent-encoded characters or sequences that 199 would (1) result in space, null, control, or other characters that 200 are otherwise forbidden, (2) allow unauthorized access to private 201 data, or (3) lead to other security vulnerabilities. 203 6. Internationalization Considerations 205 As specified in [RFC3986], the 'acct' URI scheme allows any character 206 from the Unicode repertoire [UNICODE] encoded as UTF-8 [RFC3629] and 207 then percent-encoded into valid ASCII [RFC20]. Before applying any 208 percent-encoding, an application MUST ensure the following about the 209 string that is used as input to the URI-construction process: 211 o The userpart consists only of Unicode code points that conform to 212 the PRECIS IdentifierClass specified in 213 [I-D.ietf-precis-framework]. 214 o The host consists only of Unicode code points that conform to the 215 rules specified in [RFC5892]. 216 o Internationalized domain name (IDN) labels are encoded as A-labels 217 [RFC5890]. 219 7. IANA Considerations 221 In accordance with the guidelines and registration procedures for new 222 URI schemes [RFC4395], this section provides the information needed 223 to register the 'acct' URI scheme. 225 7.1. URI Scheme Name 227 acct 229 7.2. Status 231 permanent 233 7.3. URI Scheme Syntax 235 The 'acct' URI syntax is defined here in Augmented Backus-Naur Form 236 (ABNF) [RFC5234], borrowing the 'host', 'pct-encoded', 'sub-delims', 237 'unreserved' rules from [RFC3986]: 239 acctURI = "acct" ":" userpart "@" host 240 userpart = unreserved / sub-delims 241 0*( unreserved / pct-encoded / sub-delims ) 243 Note that additional rules regarding the strings that are used as 244 input to construction of 'acct' URIs further limit the characters 245 that can be percent-encoded; see the Encoding Considerations as well 246 as Section 6 of RFC XXXX. [Note to RFC Editor: please replace XXXX 247 with the number issued to this document.] 249 7.4. URI Scheme Semantics 251 The 'acct' URI scheme identifies accounts hosted at service 252 providers. It is used only for identification, not interaction. A 253 protocol that employs the 'acct' URI scheme is responsible for 254 specifying how an 'acct' URI is dereferenced in the context of that 255 protocol. There is no media type associated with the 'acct' URI 256 scheme. 258 7.5. Encoding Considerations 260 See Section 6 of RFC XXXX. [Note to RFC Editor: please replace XXXX 261 with the number issued to this document.] 263 7.6. Applications/Protocols That Use This URI Scheme Name 265 At the time of this writing, only the WebFinger protocol uses the 266 'acct' URI scheme. However, use is not restricted to the WebFinger 267 protocol, and the scheme might be considered for use in other 268 protocols. 270 7.7. Interoperability Considerations 272 There are no known interoperability concerns related to use of the 273 'acct' URI scheme. 275 7.8. Security Considerations 277 See Section 5 of RFC XXXX. [Note to RFC Editor: please replace XXXX 278 with the number issued to this document.] 280 7.9. Contact 282 Peter Saint-Andre, psaintan@cisco.com 284 7.10. Author/Change Controller 286 This scheme is registered under the IETF tree. As such, the IETF 287 maintains change control. 289 7.11. References 291 None. 293 8. References 294 8.1. Normative References 296 [I-D.ietf-precis-framework] 297 Saint-Andre, P. and M. Blanchet, "Precis Framework: 298 Handling Internationalized Strings in Protocols", 299 draft-ietf-precis-framework-08 (work in progress), 300 March 2013. 302 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 303 Requirement Levels", BCP 14, RFC 2119, March 1997. 305 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 306 10646", STD 63, RFC 3629, November 2003. 308 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 309 Resource Identifier (URI): Generic Syntax", STD 66, 310 RFC 3986, January 2005. 312 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 313 Specifications: ABNF", STD 68, RFC 5234, January 2008. 315 [RFC5890] Klensin, J., "Internationalized Domain Names for 316 Applications (IDNA): Definitions and Document Framework", 317 RFC 5890, August 2010. 319 [RFC5892] Faltstrom, P., "The Unicode Code Points and 320 Internationalized Domain Names for Applications (IDNA)", 321 RFC 5892, August 2010. 323 [UNICODE] The Unicode Consortium, "The Unicode Standard, Version 324 6.1", 2012, 325 . 327 8.2. Informative References 329 [I-D.ietf-appsawg-webfinger] 330 Jones, P., Salgueiro, G., and J. Smarr, "WebFinger", 331 draft-ietf-appsawg-webfinger-14 (work in progress), 332 May 2013. 334 [RFC20] Cerf, V., "ASCII format for network interchange", RFC 20, 335 October 1969. 337 [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., 338 Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext 339 Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. 341 [RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines and 342 Registration Procedures for New URI Schemes", BCP 35, 343 RFC 4395, February 2006. 345 [RFC5988] Nottingham, M., "Web Linking", RFC 5988, October 2010. 347 [RFC6068] Duerst, M., Masinter, L., and J. Zawinski, "The 'mailto' 348 URI Scheme", RFC 6068, October 2010. 350 Appendix A. Acknowledgements 352 The 'acct' URI scheme was originally proposed during work on the 353 WebFinger protocol; special thanks are due to Blaine Cook, Brad 354 Fitzpatrick, and Eran Hammer-Lahav for their early work on the 355 concept (which in turn was partially inspired by work on Extensible 356 Resource Indentifiers at OASIS). The scheme was first formally 357 specified in [I-D.ietf-appsawg-webfinger]; the authors of that 358 specification (Paul Jones, Gonzalo Salgueiro, and Joseph Smarr) are 359 gratefully acknowledged. Thanks are also due to Melvin Carvalho, 360 Martin Duerst, Graham Klyne, Barry Leiba, Subramanian Moonesamy, Evan 361 Prodromou, James Snell, and other participants in the IETF APPSAWG 362 for their feedback. Meral Shirazipour completed a Gen-ART review. 363 Dave Cridland completed an AppsDir review, and is gratefully 364 acknowledged for providing proposed text that was incorporated into 365 Section 3 and Section 5. IESG comments from Richard Barnes, Adrian 366 Farrel, Stephen Farrell, Barry Leiba, Pete Resnick, and Sean Turner 367 also led to improvements in the specification. 369 Author's Address 371 Peter Saint-Andre 372 Cisco Systems, Inc. 373 1899 Wynkoop Street, Suite 600 374 Denver, CO 80202 375 USA 377 Email: psaintan@cisco.com