idnits 2.17.1 draft-ietf-appsawg-webfinger-10.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (February 8, 2013) is 4095 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Unused Reference: '15' is defined on line 992, but no explicit reference was found in the text ** Obsolete normative reference: RFC 2616 (ref. '2') (Obsoleted by RFC 7230, RFC 7231, RFC 7232, RFC 7233, RFC 7234, RFC 7235) ** Obsolete normative reference: RFC 5785 (ref. '3') (Obsoleted by RFC 8615) ** Obsolete normative reference: RFC 5988 (ref. '4') (Obsoleted by RFC 8288) ** Obsolete normative reference: RFC 4627 (ref. '5') (Obsoleted by RFC 7158, RFC 7159) == Outdated reference: A later version (-07) exists of draft-ietf-appsawg-acct-uri-02 -- Possible downref: Non-RFC (?) normative reference: ref. '9' -- Possible downref: Non-RFC (?) normative reference: ref. '10' -- Possible downref: Non-RFC (?) normative reference: ref. '11' ** Obsolete normative reference: RFC 2818 (ref. '14') (Obsoleted by RFC 9110) Summary: 5 errors (**), 0 flaws (~~), 3 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Paul E. Jones 3 Internet Draft Gonzalo Salgueiro 4 Intended status: Standards Track Cisco Systems 5 Expires: August 8, 2013 Joseph Smarr 6 Google 7 February 8, 2013 9 WebFinger 10 draft-ietf-appsawg-webfinger-10.txt 12 Abstract 14 This specification defines the WebFinger protocol, which can be used 15 to discover information about people or other entities on the 16 Internet using standard HTTP methods. WebFinger discovers 17 information for a URI that might not be usable as a locator 18 otherwise, such as account or email URIs. 20 Status of this Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on August 8, 2013. 37 Copyright Notice 39 Copyright (c) 2013 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction...................................................2 55 2. Terminology....................................................3 56 3. Example Uses of WebFinger......................................3 57 3.1. Locating a User's Blog....................................3 58 3.2. Identity Provider Discovery for OpenID Connect............5 59 3.3. Auto-Configuration of Email Clients.......................6 60 3.4. Retrieving Device Information.............................7 61 4. WebFinger Protocol.............................................8 62 4.1. Constructing a WebFinger Request URI......................8 63 4.2. Performing a WebFinger Query..............................9 64 4.3. The "rel" Parameter.......................................9 65 4.4. The JSON Resource Descriptor (JRD).......................11 66 4.4.1. subject.............................................11 67 4.4.2. aliases.............................................12 68 4.4.3. properties..........................................12 69 4.4.4. links...............................................12 70 4.5. WebFinger and URIs.......................................14 71 5. Cross-Origin Resource Sharing (CORS)..........................14 72 6. Access Control................................................15 73 7. Hosted WebFinger Services.....................................15 74 8. Security Considerations.......................................16 75 9. IANA Considerations...........................................18 76 9.1. Well-Known URI...........................................18 77 9.2. JSON Resource Descriptor (JRD) Media Type................18 78 10. Acknowledgments..............................................20 79 11. References...................................................20 80 11.1. Normative References....................................20 81 11.2. Informative References..................................21 82 Author's Addresses...............................................22 84 1. Introduction 86 WebFinger is used to discover information about people or other 87 entities on the Internet that are identified by a URI [6] or IRI [7] 88 using standard Hypertext Transfer Protocol (HTTP) [2] methods over a 89 secure transport [14]. A WebFinger resource returns a JavaScript 90 Object Notation (JSON) [5] object describing the entity that is 91 queried. The JSON object is referred to as the JSON Resource 92 Descriptor (JRD). 94 For a person, the kinds of information that might be discoverable via 95 WebFinger include a personal profile address, identity service, 96 telephone number, or preferred avatar. For other entities on the 97 Internet, a WebFinger resource might return JRDs containing link 98 relations [10] that enable a client to discover, for example, the 99 amount of toner in a printer or the physical location of a server. 101 Information returned via WebFinger might be for direct human 102 consumption (e.g., looking up someone's phone number), or it might be 103 used by systems to help carry out some operation (e.g., facilitate 104 logging into a web site by determining a user's identity service). 106 Use of WebFinger is illustrated in the examples in Section 3 and 107 described more formally in Section 4. 109 2. Terminology 111 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 112 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 113 document are to be interpreted as described in RFC 2119 [1]. 115 WebFinger makes heavy use of "Link Relations". A Link Relation is an 116 attribute-and-value pair in which the attribute identifies the type 117 of relationship between the linked entity or resource and the 118 information specified in the value. In Web Linking [4], the link 119 relation is represented using an HTTP entity-header of "Link", where 120 the "rel" attribute specifies the type of relationship and the "href" 121 attribute specifies the information that is linked to the entity or 122 resource. In WebFinger, the same concept is represented using a JSON 123 array of "links" objects, where each member named "rel" specifies the 124 type of relationship and each member named "href" specifies the 125 information that is linked to the entity or resource. Note that 126 WebFinger narrows the scope of a link relation beyond what is defined 127 for Web Linking by stipulating that the value of the "rel" member 128 needs to be either a single IANA-registered link relation type [10] 129 or a URI [6]. 131 3. Example Uses of WebFinger 133 This non-normative section shows a few sample uses of WebFinger. 135 3.1. Locating a User's Blog 137 Assume you receive an email from Bob and he refers to something he 138 posted on his blog, but you do not know where Bob's blog is located. 139 It would be simple to discover the address of Bob's blog if he made 140 that information available via WebFinger. 142 Assume your email client can discover the blog for you. After 143 receiving the message from Bob (bob@example.com), your email client 144 performs a WebFinger query either automatically or at your command. 145 It does so by issuing the following HTTPS [14] query to example.com: 147 GET /.well-known/webfinger? 148 resource=acct%3Abob%40example.com HTTP/1.1 149 Host: example.com 151 The server might then respond with a message like this: 153 HTTP/1.1 200 OK 154 Access-Control-Allow-Origin: * 155 Content-Type: application/jrd+json 157 { 158 "subject" : "acct:bob@example.com", 159 "aliases" : 160 [ 161 "http://www.example.com/~bob/" 162 ], 163 "properties" : 164 { 165 "http://example.com/ns/role/" : "employee" 166 }, 167 "links" : 168 [ 169 { 170 "rel" : "http://webfinger.example/rel/avatar", 171 "type" : "image/jpeg", 172 "href" : "http://www.example.com/~bob/bob.jpg" 173 }, 174 { 175 "rel" : "http://webfinger.example/rel/profile-page", 176 "href" : "http://www.example.com/~bob/" 177 }, 178 { 179 "rel" : "http://webfinger.example/rel/blog", 180 "type" : "text/html", 181 "href" : "http://blogs.example.com/bob/", 182 "titles" : 183 { 184 "en-us" : "The Magical World of Bob", 185 "fr" : "Le Monde Magique de Bob" 186 } 187 }, 188 { 189 "rel" : "http://webfinger.example/rel/businesscard", 190 "href" : "https://www.example.com/~bob/bob.vcf" 191 } 192 ] 193 } 195 The email client would take note of the link relation in the above 196 JRD that refers to Bob's blog. The blog's URI would then be 197 presented to you so that you could then visit his blog. The email 198 client might also note that Bob has published an avatar link relation 199 and use that picture to represent Bob inside the email client. 200 Lastly, the client might automatically retrieve the data located at 201 the URI specified by the "businesscard" link relation (which might be 202 a vcard [16]) to update the information about Bob in its internal 203 address book. 205 In the above example, an "acct" URI [8] is used in the query, though 206 any valid alias for the user might also be used. See Section 4.5 for 207 more information on WebFinger and URIs. 209 An alias is a URI that is different from the "subject" URI, yet 210 identifies the same entity. In the above example, there is one 211 "http" alias returned, though there might have been more than one. 212 Had the "http:" URI shown as an alias been used to query for 213 information about Bob, the query would have appeared as: 215 GET /.well-known/webfinger? 216 resource=http%3A%2F%2Fwww.example.com%2F~bob%2F HTTP/1.1 217 Host: www.example.com 219 Note that the host queried in this example is different than for the 220 acct URI example, since the URI refers to a different host. Either 221 this host would provide a response, or it would redirect the client 222 to another host (e.g., redirect back to example.com). Either way, 223 the response would have been substantially the same, with the subject 224 and alias information changed as necessary. 226 3.2. Identity Provider Discovery for OpenID Connect 228 Suppose Carol wishes to authenticate with a web site she visits using 229 OpenID Connect [18]. She would provide the web site with her OpenID 230 Connect identifier, say carol@example.com. The visited web site 231 would perform a WebFinger query looking for the OpenID Connect 232 Provider. Since the site is interested in only one particular link 233 relation, the WebFinger resource might utilize the "rel" parameter as 234 described in Section 4.3: 236 GET /.well-known/webfinger? 237 resource=acct%3Acarol%40example.com& 238 rel=http%3A%2F%2Fopenid.net%2Fspecs%2Fconnect%2F1.0%2Fissuer 239 HTTP/1.1 240 Host: example.com 242 The server might respond like this: 244 HTTP/1.1 200 OK 245 Access-Control-Allow-Origin: * 246 Content-Type: application/jrd+json 248 { 249 "subject" : "acct:carol@example.com", 250 "links" : 251 [ 252 { 253 "rel" : "http://openid.net/specs/connect/1.0/issuer", 254 "href" : "https://openid.example.com" 255 } 256 ] 257 } 259 Since the "rel" parameter only serves to filter the link relations 260 returned by the resource, other name/value pairs in the response, 261 including any aliases or properties, would be returned. Also, since 262 support for the "rel" parameter is OPTIONAL, the client must not 263 assume the "links" array will contain only the requested link 264 relation. 266 3.3. Auto-Configuration of Email Clients 268 WebFinger could be used to auto-provision an email client with basic 269 configuration data. Suppose that sue@example.com wants to configure 270 her email client. Her email client might issue the following query: 272 GET /.well-known/webfinger? 273 resource=mailto%3Asue%40example.com HTTP/1.1 274 Host: example.com 276 The returned resource representation would contain entries for the 277 various protocols, transport options, and security options. If there 278 are multiple options, the resource representation might include a 279 link relation for each of the valid options, and the client or Sue 280 might select which option to choose. Since JRDs list link relations 281 in a specific order, then the most-preferred choices could be 282 presented first. Consider this response: 284 HTTP/1.1 200 OK 285 Access-Control-Allow-Origin: * 286 Content-Type: application/jrd+json 288 { 289 "subject" : "mailto:sue@example.com", 290 "links" : 291 [ 292 { 293 "rel" : "http://webfinger.example/rel/smtp-server", 294 "properties" : 295 { 296 "http://webfinger.example/email/host" : "smtp.example.com", 297 "http://webfinger.example/email/port" : "587", 298 "http://webfinger.example/email/login-required" : "yes", 299 "http://webfinger.example/email/transport" : "starttls" 300 } 301 }, 302 { 303 "rel" : "http://webfinger.example/rel/imap-server", 304 "properties" : 305 { 306 "http://webfinger.example/email/host" : "imap.example.com", 307 "http://webfinger.example/email/port" : "993", 308 "http://webfinger.example/email/transport" : "ssl" 309 } 310 } 311 ] 312 } 314 In this example, you can see that the WebFinger resource 315 representation advertises an SMTP service and an IMAP service. In 316 this example, the "href" entries associated with the link relation 317 are absent. This is valid when there is no additional reference that 318 needs to be made. 320 3.4. Retrieving Device Information 322 As another example, suppose there are printers on the network and you 323 would like to check the current toner level for a particular printer 324 identified via the URI device:p1.example.com. While the "device" URI 325 scheme is not presently specified, we use it here for illustrative 326 purposes. 328 Following the procedures similar to those above, a query may be 329 issued to get link relations specific to this URI like this: 331 GET /.well-known/webfinger? 332 resource=device%3Ap1.example.com HTTP/1.1 333 Host: p1.example.com 335 The link relations that are returned for a device may be quite 336 different than those for user accounts. Perhaps we may see a 337 response like this: 339 HTTP/1.1 200 OK 340 Access-Control-Allow-Origin: * 341 Content-Type: application/jrd+json 342 { 343 "subject" : "device:p1.example.com", 344 "links" : 345 [ 346 { 347 "rel" : "http://webfinger.example/rel/tipsi", 348 "href" : "http://192.168.1.5/npap/" 349 } 350 ] 351 } 353 While this example is fictitious, you can imagine that perhaps the 354 Transport Independent, Printer/System Interface [17] may be enhanced 355 with a web interface enabling a device that understands the TIP/SI 356 web interface specification to query the printer for toner levels. 358 4. WebFinger Protocol 360 A WebFinger resource is a well-known URI [3] using the HTTPS scheme. 361 WebFinger resources MUST NOT be served with any other URI scheme 362 (such as HTTP). 364 GET requests to a WebFinger resource convey the URI to perform the 365 query upon in the URI's query string; see Section 4.1 for details. 367 The WebFinger resource returns a JSON Resource Descriptor (JRD) as 368 the resource representation to convey information about an entity on 369 the Internet. Also, the Cross-Origin Resource Sharing (CORS) [9] 370 specification is utilized to facilitate queries made via a web 371 browser. 373 4.1. Constructing a WebFinger Request URI 375 This specification defines parameters that can be passed from the 376 client to the WebFinger resource when issuing a request. These 377 parameters, "resource" and "rel", and the parameter values are 378 included in the query component of the URI (see Section 3.4 of RFC 379 3986). To construct the query component, the client performs the 380 following steps. First, each parameter value is percent-encoded, as 381 per Section 2.1 of RFC 3986, so that it conforms to the query 382 production in Section 3.4 of that specification, and additionally any 383 instances of the "=" and "&" characters are also percent-encoded. 384 Next, the client constructs a string to be placed in the query 385 component by concatenating the name of the first parameter together 386 with an equal sign ("=") and the percent-encoded parameter value. 387 For any subsequent parameters, the client appends an ampersand ("&") 388 to the string, the name of the next parameter, an equal sign, and the 389 parameter value. The client MUST NOT insert any spaces while 390 constructing the string. The order in which the client places each 391 attribute-and-value pair within the query component is unspecified. 393 4.2. Performing a WebFinger Query 395 A WebFinger client issues a query to the well-known [3] resource 396 identified by the URI whose path component begins with "/.well- 397 known/webfinger" and whose query component MUST include the 398 "resource" parameter exactly once and set to the value of the URI for 399 which information is being sought. If the "resource" parameter is 400 absent or malformed, the WebFinger resource MUST indicate that the 401 request is bad as per Section 10.4.1 of RFC 2616 [2]. 403 A client MUST query the WebFinger resource using HTTPS only. If the 404 client determines that the resource has an invalid certificate, the 405 resource returns a 4xx or 5xx status code, or the HTTPS connection 406 cannot be established for any reason, then the client MUST accept 407 that the WebFinger query has failed and MUST NOT attempt to reissue 408 the WebFinger request using HTTP over a non-secure connection. 410 A WebFinger resource MUST return a JRD as the representation for the 411 resource if the client requests no other supported format explicitly 412 via the HTTP "Accept" header. The client MAY include the "Accept" 413 header to indicate a desired representation, though no other 414 representation than JRD is defined in this specification. The media 415 type used for the JSON Resource Descriptor (JRD) is 416 "application/jrd+json" (see Section 9.2). 418 A WebFinger resource MAY redirect the client, but MUST only redirect 419 the client to an HTTPS URI. 421 A WebFinger resource can include cache validators in a response to 422 enable conditional requests by the client and/or expiration times as 423 per Section 13 of RFC 2616. 425 4.3. The "rel" Parameter 427 When issuing a request to a WebFinger resource, the client MAY 428 utilize the "rel" parameter to request only a subset of the 429 information that would otherwise be returned without the "rel" 430 parameter. When the "rel" parameter is used, only the link relations 431 that match the link relations provided via the "rel" parameter are 432 included in the array of links returned in the JRD. All other 433 information present in a resource descriptor remains present, even 434 when "rel" is employed. 436 The "rel" parameter MAY be transmitted to the WebFinger resource 437 multiple times in order to request multiple types of link relations. 439 The purpose of the "rel" parameter is to return a subset of "link 440 relation objects" (see Section 4.4.4) that would otherwise be 441 returned in the resource descriptor. Use of the parameter might 442 reduce processing requirements on either the client or server, and it 443 might also reduce the bandwidth required to convey the partial 444 resource descriptor, especially if there are numerous link relation 445 values to convey for a given "resource" value. 447 WebFinger resources SHOULD support the "rel" parameter. If the 448 resource does not support the "rel" parameter, it MUST ignore the 449 parameter and process the request as if no "rel" parameter values 450 were present. 452 The following example presents the same example as found in Section 453 3.1, but uses the "rel" parameter to select two link relations: 455 GET /.well-known/webfinger? 456 resource=acct%3Abob%40example.com& 457 rel=http%3A%2F%2Fwebfinger.example%2Frel%2Fprofile-page& 458 rel=http://webfinger.example/rel/businesscard HTTP/1.1 459 Host: example.com 461 In this example, the client requests the link relations of type 462 "http://webfinger.example/rel/profile-page" and 463 "http://webfinger.example/rel/businesscard". The server then 464 responds with a message like this: 466 HTTP/1.1 200 OK 467 Access-Control-Allow-Origin: * 468 Content-Type: application/jrd+json 470 { 471 "subject" : "acct:bob@example.com", 472 "aliases" : 473 [ 474 "http://www.example.com/~bob/" 475 ], 476 "properties" : 477 { 478 "http://example.com/ns/role/" : "employee" 479 }, 480 "links" : 481 [ 482 { 483 "rel" : "http://webfinger.example/rel/profile-page", 484 "href" : "http://www.example.com/~bob/" 485 }, 486 { 487 "rel" : "http://webfinger.example/rel/businesscard", 488 "href" : "http://www.example.com/~bob/bob.vcf" 489 } 490 ] 491 } 493 As you can see in the response, the resource representation contains 494 only the link relations requested by the client, but the other parts 495 of the JRD are still present. 497 In the event that a client requests link relation types that are not 498 defined for the specified "resource", a resource descriptor MUST be 499 returned. In the returned JRD, the "links" array MAY be absent, 500 empty, or contain only links that did match a provided "rel" value. 502 4.4. The JSON Resource Descriptor (JRD) 504 The JSON Resource Descriptor (JRD), originally introduced in RFC 6415 505 [19] and based on the Extensible Resource Descriptor (XRD) format 506 [20], is a JSON object that is comprised of the following name/value 507 pairs: 509 o subject 510 o aliases 511 o properties 512 o links 514 The member "subject" is a name/value pair whose value is a string, 515 "aliases" is an array of strings, "properties" is an object comprised 516 of name/value pairs whose values are strings, and "links" is an array 517 of objects that contain link relation information. 519 When processing a JRD, the client MUST ignore any unknown member and 520 not treat the presence of an unknown member as an error. 522 Below, each of these members of the JRD is described in more detail. 524 4.4.1. subject 526 The value of the "subject" member is a URI that identifies the entity 527 that the JRD describes. 529 The "subject" value returned by a WebFinger resource MAY differ from 530 the value of the "resource" parameter used in the client's request. 531 This might happen, for example, when the subject's identity changes 532 (e.g., a user moves his or her account to another service) or when 533 the resource prefers to express URIs in canonical form. 535 The "subject" member MUST be present in the JRD. 537 4.4.2. aliases 539 The "aliases" array is an array of zero or more URI strings that 540 identify the same entity as the "subject" URI. Each URI must be an 541 absolute URI. 543 The "aliases" array is OPTIONAL in the JRD. 545 4.4.3. properties 547 The "properties" object is comprised of zero or more name/value pairs 548 whose names are absolute URIs and whose values are strings or null. 549 Properties are used to convey additional information about the 550 subject of the JRD. As an example, consider this use of 551 "properties": 553 "properties" : { "http://webfinger.example/ns/name" : "Bob Smith" } 555 The "properties" member is OPTIONAL in the JRD. 557 4.4.4. links 559 The "links" array has any number of member objects, each of which 560 represents a link [4]. Each of these link objects can have the 561 following members: 563 o rel 564 o type 565 o href 566 o titles 567 o properties 569 The "rel" and "href" members are strings representing the link's 570 relation type and the target IRI, respectively. The context of the 571 link is the "subject" (see Section 4.4.1). 573 The "type" member is a string indicating what the media type of the 574 result of dereferencing the link ought to be. 576 The order of elements in the "links" array indicates an order of 577 preference. Thus, if there are two or more link relations having the 578 same "rel" value, the first link relation would indicate the user's 579 preferred link. 581 The "links" array is OPTIONAL in the JRD. 583 Below, each of the members of the objects found in the "links" array 584 is described in more detail. Each object in the "links" array, 585 referred to as a "link relation object", is completely independent 586 from any other object in the array; any requirement to include a 587 given member in the link relation object refers only to that 588 particular object. 590 4.4.4.1. rel 592 The value of the "rel" member is a string that is either an absolute 593 URI or a registered relation type [10] (see RFC 5988 [4]). The value 594 of the "rel" member MUST contain exactly one URI or registered 595 relation type. The URI or registered relation type identifies the 596 type of the link relation. The other members of the object have 597 meaning only once the type of link relation is understood. In some 598 instances, the link relation will have associated semantics enabling 599 the client to query for other resources on the Internet. In other 600 instances, the link relation will have associated semantics enabling 601 the client to utilize the other members of the link relation object 602 without fetching additional external resources. 604 The "rel" member MUST be present in the link relation object. 606 4.4.4.2. type 608 The value of the "type" member is a string that indicates the media 609 type [11] of the target resource (see RFC 6838 [12]). 611 The "type" member is OPTIONAL in the link relation object. 613 4.4.4.3. href 615 The value of the "href" member is a string that contains a URI 616 pointing to the target resource. 618 The "href" member is OPTIONAL in the link relation object. 620 4.4.4.4. titles 622 The "titles" object is comprised of zero or more name/value pairs 623 whose name is a language tag [13] or the string "default". The 624 string is human-readable and describes the link relation. More than 625 one title for the link relation MAY be provided for the benefit of 626 users who utilize the link relation and, if used, a language 627 identifier SHOULD be duly used as the name. If the language is 628 unknown or unspecified, then the name is "default". 630 A JRD SHOULD NOT include more than one title identified with the same 631 language tag (or "default") within the link relation object. Meaning 632 is undefined if a link relation object includes more than one title 633 named with the same language tag (or "default"), though this MUST NOT 634 be treated as an error. A client MAY select whichever title or 635 titles it wishes to utilize. 637 Here is an example of the titles object: 639 "titles" : 640 { 641 "en-us" : "The Magical World of Bob", 642 "fr" : "Le Monde Magique de Bob" 643 } 645 The "titles" member is OPTIONAL in the link relation object. 647 4.4.4.5. properties 649 The "properties" object within the link relation object is comprised 650 of zero or more name/value pairs whose names are absolute URIs and 651 whose values are strings or null. Properties are used to convey 652 additional information about the link relation. As an example, 653 consider this use of "properties": 655 "properties" : { "http://webfinger.example/mail/port" : "993" } 657 The "properties" member is OPTIONAL in the link relation object. 659 4.5. WebFinger and URIs 661 WebFinger requests can include a "resource" parameter (see Section 662 4.1) specifying the URI of an account, device, or other entity. 663 WebFinger is neutral regarding the scheme of such a URI: it could be 664 an "acct" URI [7], an "http" or "https" URI, a "mailto" URI [21], or 665 some other scheme. 667 To perform a WebFinger lookup on an account specific to the host 668 being queried, use of the "acct" URI scheme is RECOMMENDED, since it 669 explicitly identifies an account accessible via WebFinger. Further, 670 the "acct" URI scheme is not associated with other protocols as, by 671 way of example, the "mailto" URI scheme is associated with email. 672 Since not every host offers email service, using the "mailto" URI 673 scheme is not ideal for identifying user accounts on all hosts. That 674 said, use of the "mailto" URI scheme would be ideal for use with 675 WebFinger to discover mail server configuration information for a 676 user. 678 5. Cross-Origin Resource Sharing (CORS) 680 WebFinger resources might not be accessible from a web browser due to 681 "Same-Origin" policies. The current best practice is to make 682 resources available to browsers through Cross-Origin Resource Sharing 683 (CORS) [9], and servers MUST include the Access-Control-Allow-Origin 684 HTTP header in responses. Servers SHOULD support the least 685 restrictive setting by allowing any domain access to the WebFinger 686 resource: 688 Access-Control-Allow-Origin: * 690 There are cases where defaulting to the least restrictive setting is 691 not appropriate, for example a server on an intranet that provides 692 sensitive company information SHOULD NOT allow CORS requests from any 693 domain, as that could allow leaking of that sensitive information. A 694 server that wishes to restrict access to information from external 695 entities SHOULD use a more restrictive Access-Control-Allow-Origin 696 header. 698 6. Access Control 700 As with all web resources, access to the WebFinger resource MAY 701 require authentication. Further, failure to provide required 702 credentials MAY result in the server forbidding access or providing a 703 different response than had the client authenticated with the server. 705 Likewise, a WebFinger resource MAY provide different responses to 706 different clients based on other factors, such as whether the client 707 is inside or outside a corporate network. As a concrete example, a 708 query performed on the internal corporate network might return link 709 relations to employee pictures, whereas link relations for employee 710 pictures might not be provided to external entities. 712 Further, link relations provided in a WebFinger resource 713 representation MAY point to web resources that impose access 714 restrictions. For example, the aforementioned corporate server may 715 provide both internal and external entities with URIs to employee 716 pictures, but further authentication might be required in order for 717 the client to access the picture resources if the request comes from 718 outside the corporate network. 720 The decisions made with respect to what set of link relations a 721 WebFinger resource provides to one client versus another and what 722 resources require further authentication, as well as the specific 723 authentication mechanisms employed, are outside the scope of this 724 document. 726 7. Hosted WebFinger Services 728 As with most services provided on the Internet, it is possible for a 729 domain owner to utilize "hosted" WebFinger services. By way of 730 example, a domain owner might control most aspects of their domain, 731 but use a third-party hosting service for email. In the case of 732 email, MX records identify mail servers for a domain. An MX record 733 points to the mail server to which mail for the domain should be 734 delivered. It does not matter to the sending mail server whether 735 those MX records point to a server in the destination domain or a 736 different domain. 738 Likewise, a domain owner might utilize the services of a third party 739 to provide WebFinger services on behalf of its users. Just as a 740 domain owner was required to insert MX records into DNS to allow for 741 hosted email serves, the domain owner is required to redirect HTTP 742 queries to its domain to allow for hosted WebFinger services. 744 When a query is issued to the WebFinger resource, the web server MUST 745 return a response with a redirection status code that includes a 746 Location header pointing to the location of the hosted WebFinger 747 service URI. This WebFinger service URI does not need to point to 748 the well-known WebFinger location on the hosting service provider 749 server. 751 As an example, assume that example.com's WebFinger services are 752 hosted by wf.example.net. Suppose a client issues a query for 753 acct:alice@example.com like this: 755 GET /.well-known/webfinger? 756 resource=acct%3Aalice%40example.com HTTP/1.1 757 Host: example.com 759 The server might respond with this: 761 HTTP/1.1 307 Temporary Redirect 762 Access-Control-Allow-Origin: * 763 Location: https://wf.example.net/example.com/webfinger? 764 resource=acct%3Aalice%40example.com HTTP/1.1 766 The client can then follow the redirection, re-issuing the request to 767 the URI provided in the Location header. Note that the server will 768 include any required URI parameters in the Location header value, 769 which could be different than the URI parameters the client 770 originally used. 772 8. Security Considerations 774 Since this specification utilizes Cross-Origin Resource Sharing 775 (CORS) [9], all of the security considerations applicable to CORS are 776 also applicable to this specification. 778 The use of HTTPS is REQUIRED to ensure that information is not 779 modified during transit. It should be appreciated that in 780 environments where a web server is normally available, there exists 781 the possibility that a compromised network might have its WebFinger 782 resource operating on HTTPS replaced with one operating only over 783 HTTP. As such, clients MUST NOT issue queries over a non-secure 784 connection. 786 Clients MUST verify that the certificate used on an HTTPS connection 787 is valid (as defined in [14]) and accept a response only if the 788 certificate is valid. 790 Service providers and users should be aware that placing information 791 on the Internet means that any user can access that information and 792 WebFinger can be used to make it even easier to discover that 793 information. While WebFinger can be an extremely useful tool for 794 discovering one's avatar, blog, or other personal information, users 795 should understand the risks, too. If one does not wish to share 796 certain information with the world, do not allow that information to 797 be freely accessible on the Internet or discoverable via WebFinger. 798 Further, WebFinger MUST NOT be used to provide any personal 799 information to any party unless explicitly or implicitly authorized 800 by the person whose information is being shared. 802 The aforementioned word of caution is perhaps worth emphasizing again 803 with respect to information that might reveal a user's current 804 context (e.g., the user's location). The power of WebFinger comes 805 from providing a single place where others can find pointers to 806 information about a person, but service providers and users should be 807 mindful of the nature of that information shared and the fact that it 808 might be available for the entire world to see. Sharing location 809 information, for example, would potentially put a person in danger 810 from any individual who might seek to inflict harm on that person. 812 The easy access to user information via WebFinger was a design goal 813 of the protocol, not a limitation. If one wishes to limit access to 814 information available via WebFinger, such as WebFinger resources for 815 use inside a corporate network, the network administrator needs to 816 take necessary measures to limit access from outside the network. 817 Using standard methods for securing web resources, network 818 administrators do have the ability to control access to resources 819 that might return sensitive information. Further, a server can be 820 employed in such a way as to require authentication and prevent 821 disclosure of information to unauthorized entities. 823 Finally, a WebFinger resource has no means of ensuring that 824 information provided by a user is accurate. Likewise, neither the 825 resource nor the client can be absolutely guaranteed that information 826 has not been manipulated either at the server or along the 827 communication path between the client and server. Use of HTTPS helps 828 to address some concerns with manipulation of information along the 829 communication path, but it clearly cannot address issues where the 830 resource provided incorrect information, either due to being provided 831 false information or due to malicious behavior on the part of the 832 server administrator. As with any information service available on 833 the Internet, users should be wary of information received from 834 untrusted sources. 836 9. IANA Considerations 838 9.1. Well-Known URI 840 This specification registers the "webfinger" well-known URI in the 841 Well-Known URI Registry as defined by [3]. 843 URI suffix: webfinger 845 Change controller: IETF 847 Specification document(s): RFC XXXX 849 Related information: The response representation returned by a 850 WebFinger resource will be a JSON Resource Descriptor (JRD) as 851 described in Section 4.4 of RFC XXXX. 853 [RFC EDITOR: Please replace "XXXX" references in this section and the 854 following section with the number for this RFC.] 856 9.2. JSON Resource Descriptor (JRD) Media Type 858 This specification registers the media type application/jrd+json for 859 use with WebFinger in accordance with media type registration 860 procedures defined in [12]. 862 Type name: application 864 Subtype name: jrd+json 866 Required parameters: N/A 868 Optional parameters: N/A 870 In particular, because RFC 4627 already defines the character 871 encoding for JSON, no "charset" parameter is used. 873 Encoding considerations: See RFC 6839, section 3.1. 875 Security considerations: 877 The JSON Resource Descriptor (JRD) is a JavaScript Object Notation 878 (JSON) object. It is a text format that must be parsed by entities 879 that wish to utilize the format. Depending on the language and 880 mechanism used to parse a JSON object, it is possible for an 881 attacker to inject behavior into a running program. Therefore, 882 care must be taken to properly parse a received JRD to ensure that 883 only a valid JSON object is present and that no JavaScript or other 884 code is injected or executed unexpectedly. 886 Interoperability considerations: 888 This media type is a JavaScript Object Notation (JSON) object and 889 can be consumed by any software application that can consume JSON 890 objects. 892 Published specification: RFC XXXX 894 Applications that use this media type: 896 The JSON Resource Descriptor (JRD) is used by the WebFinger 897 protocol (RFC XXXX) to enable the exchange of information between a 898 client and a WebFinger resource over HTTPS. 900 Fragment identifier considerations: 902 The syntax and semantics of fragment identifiers SHOULD be as 903 specified for "application/json". (At publication of this 904 document, there is no fragment identification syntax defined for 905 "application/json".) 907 Additional information: 909 Deprecated alias names for this type: N/A 911 Magic number(s): N/A 913 File extension(s): jrd 915 Macintosh file type code(s): N/A 917 Person & email address to contact for further information: 919 Paul E. Jones 921 Intended usage: COMMON 923 Restrictions on usage: N/A 925 Author: Paul E. Jones 927 Change controller: 929 IESG has change control over this registration. 931 Provisional registration? (standards tree only): N/A 933 10. Acknowledgments 935 This document has benefited from extensive discussion and review of 936 many of the members of the APPSAWG working group. The authors would 937 like to especially acknowledge the invaluable input of Eran Hammer- 938 Lahav, Blaine Cook, Brad Fitzpatrick, Laurent-Walter Goix, Joe 939 Clarke, Michael B. Jones, Peter Saint-Andre, Dick Hardt, Tim Bray, 940 James Snell, Melvin Carvalho, Evan Prodromou, Mark Nottingham, Barry 941 Leiba, Elf Pavlik, Bjoern Hoehrmann, SM, Joe Gregorio and others that 942 we have undoubtedly, but inadvertently, missed. Special thanks go to 943 the chairs of APPSAWG, especially Salvatore Loreto for his assistance 944 in shepherding this document. 946 11. References 948 11.1. Normative References 950 [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement 951 Levels", BCP 14, RFC 2119, March 1997. 953 [2] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., 954 Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol -- 955 HTTP/1.1", RFC 2616, June 1999. 957 [3] Nottingham, M., Hammer-Lahav, E., "Defining Well-Known Uniform 958 Resource Identifiers (URIs)", RFC 5785, April 2010. 960 [4] Nottingham, M., "Web Linking", RFC 5988, October 2010. 962 [5] Crockford, D., "The application/json Media Type for JavaScript 963 Object Notation (JSON)", RFC 4627, July 2006. 965 [6] Berners-Lee, T., Fielding, R., and Masinter, L., "Uniform 966 Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, 967 January 2005. 969 [7] Duerst, M., "Internationalized Resource Identifiers (IRIs)", 970 RFC 3987, January 2005. 972 [8] Saint-Andre, P., "The 'acct' URI Scheme", draft-ietf-appsawg- 973 acct-uri-02, December 2012. 975 [9] Van Kesteren, A., "Cross-Origin Resource Sharing", W3C CORS 976 http://www.w3.org/TR/cors/, July 2010. 978 [10] IANA, "Link Relations", http://www.iana.org/assignments/link- 979 relations/. 981 [11] IANA, "MIME Media Types", 982 http://www.iana.org/assignments/media-types/index.html. 984 [12] Freed, N., Klensin, J., Hansen, T., "Media Type Specifications 985 and Registration Procedures", RFC 6838, January 2013. 987 [13] Phillips, A., Davis, M., "Tags for Identifying Languages", RFC 988 5646, January 2001. 990 [14] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. 992 [15] Klyne, G., Newman, C., "Date and Time on the Internet: 993 Timestamps", RFC 3339, July 2002. 995 11.2. Informative References 997 [16] Perreault, S., "vCard Format Specification", RFC 6350, August 998 2011. 1000 [17] "Transport Independent, Printer/System Interface", IEEE Std 1001 1284.1-1997, 1997. 1003 [18] Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., 1004 Mortimore, C., and E. Jay, "OpenID Connect Messages 1.0", 1005 January 2013, http://openid.net/specs/openid-connect-messages- 1006 1_0.html. 1008 [19] Hammer-Lahav, E. and Cook, B., "Web Host Metadata", RFC 6415, 1009 October 2011. 1011 [20] Hammer-Lahav, E. and W. Norris, "Extensible Resource Descriptor 1012 (XRD) Version 1.0", http://docs.oasis- 1013 open.org/xri/xrd/v1.0/xrd-1.0.html. 1015 [21] Duerst, M., Masinter, L., and J. Zawinski, "The 'mailto' URI 1016 Scheme", RFC 6068, October 2010. 1018 Author's Addresses 1020 Paul E. Jones 1021 Cisco Systems, Inc. 1022 7025 Kit Creek Rd. 1023 Research Triangle Park, NC 27709 1024 USA 1026 Phone: +1 919 476 2048 1027 Email: paulej@packetizer.com 1028 IM: xmpp:paulej@packetizer.com 1030 Gonzalo Salgueiro 1031 Cisco Systems, Inc. 1032 7025 Kit Creek Rd. 1033 Research Triangle Park, NC 27709 1034 USA 1036 Phone: +1 919 392 3266 1037 Email: gsalguei@cisco.com 1038 IM: xmpp:gsalguei@cisco.com 1040 Joseph Smarr 1041 Google 1043 Email: jsmarr@google.com