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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 HTTPbis Working Group R. Fielding, Ed. 3 Internet-Draft Adobe 4 Obsoletes: 2616 (if approved) J. Reschke, Ed. 5 Updates: 2617 (if approved) greenbytes 6 Intended status: Standards Track February 6, 2014 7 Expires: August 10, 2014 9 Hypertext Transfer Protocol (HTTP/1.1): Authentication 10 draft-ietf-httpbis-p7-auth-26 12 Abstract 14 The Hypertext Transfer Protocol (HTTP) is a stateless application- 15 level protocol for distributed, collaborative, hypermedia information 16 systems. This document defines the HTTP Authentication framework. 18 Editorial Note (To be removed by RFC Editor) 20 Discussion of this draft takes place on the HTTPBIS working group 21 mailing list (ietf-http-wg@w3.org), which is archived at 22 . 24 The current issues list is at 25 and related 26 documents (including fancy diffs) can be found at 27 . 29 The changes in this draft are summarized in Appendix D.2. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at http://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on August 10, 2014. 48 Copyright Notice 49 Copyright (c) 2014 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (http://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 This document may contain material from IETF Documents or IETF 63 Contributions published or made publicly available before November 64 10, 2008. The person(s) controlling the copyright in some of this 65 material may not have granted the IETF Trust the right to allow 66 modifications of such material outside the IETF Standards Process. 67 Without obtaining an adequate license from the person(s) controlling 68 the copyright in such materials, this document may not be modified 69 outside the IETF Standards Process, and derivative works of it may 70 not be created outside the IETF Standards Process, except to format 71 it for publication as an RFC or to translate it into languages other 72 than English. 74 Table of Contents 76 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 77 1.1. Conformance and Error Handling . . . . . . . . . . . . . . 4 78 1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 4 79 2. Access Authentication Framework . . . . . . . . . . . . . . . 4 80 2.1. Challenge and Response . . . . . . . . . . . . . . . . . . 4 81 2.2. Protection Space (Realm) . . . . . . . . . . . . . . . . . 6 82 3. Status Code Definitions . . . . . . . . . . . . . . . . . . . 7 83 3.1. 401 Unauthorized . . . . . . . . . . . . . . . . . . . . . 7 84 3.2. 407 Proxy Authentication Required . . . . . . . . . . . . 7 85 4. Header Field Definitions . . . . . . . . . . . . . . . . . . . 7 86 4.1. WWW-Authenticate . . . . . . . . . . . . . . . . . . . . . 8 87 4.2. Authorization . . . . . . . . . . . . . . . . . . . . . . 8 88 4.3. Proxy-Authenticate . . . . . . . . . . . . . . . . . . . . 9 89 4.4. Proxy-Authorization . . . . . . . . . . . . . . . . . . . 9 90 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 91 5.1. Authentication Scheme Registry . . . . . . . . . . . . . . 10 92 5.1.1. Procedure . . . . . . . . . . . . . . . . . . . . . . 10 93 5.1.2. Considerations for New Authentication Schemes . . . . 10 94 5.2. Status Code Registration . . . . . . . . . . . . . . . . . 12 95 5.3. Header Field Registration . . . . . . . . . . . . . . . . 12 96 6. Security Considerations . . . . . . . . . . . . . . . . . . . 12 97 6.1. Confidentiality of Credentials . . . . . . . . . . . . . . 13 98 6.2. Authentication Credentials and Idle Clients . . . . . . . 13 99 6.3. Protection Spaces . . . . . . . . . . . . . . . . . . . . 14 100 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14 101 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 102 8.1. Normative References . . . . . . . . . . . . . . . . . . . 14 103 8.2. Informative References . . . . . . . . . . . . . . . . . . 15 104 Appendix A. Changes from RFCs 2616 and 2617 . . . . . . . . . . . 16 105 Appendix B. Imported ABNF . . . . . . . . . . . . . . . . . . . . 16 106 Appendix C. Collected ABNF . . . . . . . . . . . . . . . . . . . 16 107 Appendix D. Change Log (to be removed by RFC Editor before 108 publication) . . . . . . . . . . . . . . . . . . . . 17 109 D.1. Since draft-ietf-httpbis-p7-auth-24 . . . . . . . . . . . 17 110 D.2. Since draft-ietf-httpbis-p7-auth-25 . . . . . . . . . . . 18 111 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 113 1. Introduction 115 HTTP provides a general framework for access control and 116 authentication, via an extensible set of challenge-response 117 authentication schemes, which can be used by a server to challenge a 118 client request and by a client to provide authentication information. 119 This document defines HTTP/1.1 authentication in terms of the 120 architecture defined in [Part1], including the general framework 121 previously described in RFC 2617 and the related fields and status 122 codes previously defined in RFC 2616. 124 The IANA Authentication Scheme Registry (Section 5.1) lists 125 registered authentication schemes and their corresponding 126 specifications, including the "basic" and "digest" authentication 127 schemes previously defined by RFC 2617. 129 1.1. Conformance and Error Handling 131 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 132 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 133 document are to be interpreted as described in [RFC2119]. 135 Conformance criteria and considerations regarding error handling are 136 defined in Section 2.5 of [Part1]. 138 1.2. Syntax Notation 140 This specification uses the Augmented Backus-Naur Form (ABNF) 141 notation of [RFC5234] with a list extension, defined in Section 7 of 142 [Part1], that allows for compact definition of comma-separated lists 143 using a '#' operator (similar to how the '*' operator indicates 144 repetition). Appendix B describes rules imported from other 145 documents. Appendix C shows the collected grammar with all list 146 operators expanded to standard ABNF notation. 148 2. Access Authentication Framework 150 2.1. Challenge and Response 152 HTTP provides a simple challenge-response authentication framework 153 that can be used by a server to challenge a client request and by a 154 client to provide authentication information. It uses a case- 155 insensitive token as a means to identify the authentication scheme, 156 followed by additional information necessary for achieving 157 authentication via that scheme. The latter can either be a comma- 158 separated list of parameters or a single sequence of characters 159 capable of holding base64-encoded information. 161 Authentication parameters are name=value pairs, where the name token 162 is matched case-insensitively, and each parameter name MUST only 163 occur once per challenge. 165 auth-scheme = token 167 auth-param = token BWS "=" BWS ( token / quoted-string ) 169 token68 = 1*( ALPHA / DIGIT / 170 "-" / "." / "_" / "~" / "+" / "/" ) *"=" 172 The "token68" syntax allows the 66 unreserved URI characters 173 ([RFC3986]), plus a few others, so that it can hold a base64, 174 base64url (URL and filename safe alphabet), base32, or base16 (hex) 175 encoding, with or without padding, but excluding whitespace 176 ([RFC4648]). 178 A 401 (Unauthorized) response message is used by an origin server to 179 challenge the authorization of a user agent, including a WWW- 180 Authenticate header field containing at least one challenge 181 applicable to the requested resource. 183 A 407 (Proxy Authentication Required) response message is used by a 184 proxy to challenge the authorization of a client, including a Proxy- 185 Authenticate header field containing at least one challenge 186 applicable to the proxy for the requested resource. 188 challenge = auth-scheme [ 1*SP ( token68 / #auth-param ) ] 190 Note: Many clients fail to parse a challenge that contains an 191 unknown scheme. A workaround for this problem is to list well- 192 supported schemes (such as "basic") first. 194 A user agent that wishes to authenticate itself with an origin server 195 -- usually, but not necessarily, after receiving a 401 (Unauthorized) 196 -- can do so by including an Authorization header field with the 197 request. 199 A client that wishes to authenticate itself with a proxy -- usually, 200 but not necessarily, after receiving a 407 (Proxy Authentication 201 Required) -- can do so by including a Proxy-Authorization header 202 field with the request. 204 Both the Authorization field value and the Proxy-Authorization field 205 value contain the client's credentials for the realm of the resource 206 being requested, based upon a challenge received in a response 207 (possibly at some point in the past). When creating their values, 208 the user agent ought to do so by selecting the challenge with what it 209 considers to be the most secure auth-scheme that it understands, 210 obtaining credentials from the user as appropriate. Transmission of 211 credentials within header field values implies significant security 212 considerations regarding the confidentiality of the underlying 213 connection, as described in Section 6.1. 215 credentials = auth-scheme [ 1*SP ( token68 / #auth-param ) ] 217 Upon receipt of a request for a protected resource that omits 218 credentials, contains invalid credentials (e.g., a bad password) or 219 partial credentials (e.g., when the authentication scheme requires 220 more than one round trip), an origin server SHOULD send a 401 221 (Unauthorized) response that contains a WWW-Authenticate header field 222 with at least one (possibly new) challenge applicable to the 223 requested resource. 225 Likewise, upon receipt of a request that omits proxy credentials or 226 contains invalid or partial proxy credentials, a proxy that requires 227 authentication SHOULD generate a 407 (Proxy Authentication Required) 228 response that contains a Proxy-Authenticate header field with at 229 least one (possibly new) challenge applicable to the proxy. 231 A server that receives valid credentials which are not adequate to 232 gain access ought to respond with the 403 (Forbidden) status code 233 (Section 6.5.3 of [Part2]). 235 HTTP does not restrict applications to this simple challenge-response 236 framework for access authentication. Additional mechanisms can be 237 used, such as authentication at the transport level or via message 238 encapsulation, and with additional header fields specifying 239 authentication information. However, such additional mechanisms are 240 not defined by this specification. 242 2.2. Protection Space (Realm) 244 The "realm" authentication parameter is reserved for use by 245 authentication schemes that wish to indicate a scope of protection. 247 A protection space is defined by the canonical root URI (the scheme 248 and authority components of the effective request URI; see Section 249 5.5 of [Part1]) of the server being accessed, in combination with the 250 realm value if present. These realms allow the protected resources 251 on a server to be partitioned into a set of protection spaces, each 252 with its own authentication scheme and/or authorization database. 253 The realm value is a string, generally assigned by the origin server, 254 which can have additional semantics specific to the authentication 255 scheme. Note that a response can have multiple challenges with the 256 same auth-scheme but different realms. 258 The protection space determines the domain over which credentials can 259 be automatically applied. If a prior request has been authorized, 260 the user agent MAY reuse the same credentials for all other requests 261 within that protection space for a period of time determined by the 262 authentication scheme, parameters, and/or user preferences (such as a 263 configurable inactivity timeout). Unless specifically allowed by the 264 authentication scheme, a single protection space cannot extend 265 outside the scope of its server. 267 For historical reasons, a sender MUST only generate the quoted-string 268 syntax. Recipients might have to support both token and quoted- 269 string syntax for maximum interoperability with existing clients that 270 have been accepting both notations for a long time. 272 3. Status Code Definitions 274 3.1. 401 Unauthorized 276 The 401 (Unauthorized) status code indicates that the request has not 277 been applied because it lacks valid authentication credentials for 278 the target resource. The server generating a 401 response MUST send 279 a WWW-Authenticate header field (Section 4.1) containing at least one 280 challenge applicable to the target resource. 282 If the request included authentication credentials, then the 401 283 response indicates that authorization has been refused for those 284 credentials. The user agent MAY repeat the request with a new or 285 replaced Authorization header field (Section 4.2). If the 401 286 response contains the same challenge as the prior response, and the 287 user agent has already attempted authentication at least once, then 288 the user agent SHOULD present the enclosed representation to the 289 user, since it usually contains relevant diagnostic information. 291 3.2. 407 Proxy Authentication Required 293 The 407 (Proxy Authentication Required) status code is similar to 401 294 (Unauthorized), but indicates that the client needs to authenticate 295 itself in order to use a proxy. The proxy MUST send a Proxy- 296 Authenticate header field (Section 4.3) containing a challenge 297 applicable to that proxy for the target resource. The client MAY 298 repeat the request with a new or replaced Proxy-Authorization header 299 field (Section 4.4). 301 4. Header Field Definitions 303 This section defines the syntax and semantics of header fields 304 related to the HTTP authentication framework. 306 4.1. WWW-Authenticate 308 The "WWW-Authenticate" header field indicates the authentication 309 scheme(s) and parameters applicable to the target resource. 311 WWW-Authenticate = 1#challenge 313 A server generating a 401 (Unauthorized) response MUST send a WWW- 314 Authenticate header field containing at least one challenge. A 315 server MAY generate a WWW-Authenticate header field in other response 316 messages to indicate that supplying credentials (or different 317 credentials) might affect the response. 319 A proxy forwarding a response MUST NOT modify any WWW-Authenticate 320 fields in that response. 322 User agents are advised to take special care in parsing the field 323 value, as it might contain more than one challenge, and each 324 challenge can contain a comma-separated list of authentication 325 parameters. Furthermore, the header field itself can occur multiple 326 times. 328 For instance: 330 WWW-Authenticate: Newauth realm="apps", type=1, 331 title="Login to \"apps\"", Basic realm="simple" 333 This header field contains two challenges; one for the "Newauth" 334 scheme with a realm value of "apps", and two additional parameters 335 "type" and "title", and another one for the "Basic" scheme with a 336 realm value of "simple". 338 Note: The challenge grammar production uses the list syntax as 339 well. Therefore, a sequence of comma, whitespace, and comma can 340 be considered either as applying to the preceding challenge, or to 341 be an empty entry in the list of challenges. In practice, this 342 ambiguity does not affect the semantics of the header field value 343 and thus is harmless. 345 4.2. Authorization 347 The "Authorization" header field allows a user agent to authenticate 348 itself with an origin server -- usually, but not necessarily, after 349 receiving a 401 (Unauthorized) response. Its value consists of 350 credentials containing the authentication information of the user 351 agent for the realm of the resource being requested. 353 Authorization = credentials 355 If a request is authenticated and a realm specified, the same 356 credentials are presumed to be valid for all other requests within 357 this realm (assuming that the authentication scheme itself does not 358 require otherwise, such as credentials that vary according to a 359 challenge value or using synchronized clocks). 361 A proxy forwarding a request MUST NOT modify any Authorization fields 362 in that request. See Section 3.2 of [Part6] for details of and 363 requirements pertaining to handling of the Authorization field by 364 HTTP caches. 366 4.3. Proxy-Authenticate 368 The "Proxy-Authenticate" header field consists of at least one 369 challenge that indicates the authentication scheme(s) and parameters 370 applicable to the proxy for this effective request URI (Section 5.5 371 of [Part1]). A proxy MUST send at least one Proxy-Authenticate 372 header field in each 407 (Proxy Authentication Required) response 373 that it generates. 375 Proxy-Authenticate = 1#challenge 377 Unlike WWW-Authenticate, the Proxy-Authenticate header field applies 378 only to the next outbound client on the response chain. This is 379 because only the client that chose a given proxy is likely to have 380 the credentials necessary for authentication. However, when multiple 381 proxies are used within the same administrative domain, such as 382 office and regional caching proxies within a large corporate network, 383 it is common for credentials to be generated by the user agent and 384 passed through the hierarchy until consumed. Hence, in such a 385 configuration, it will appear as if Proxy-Authenticate is being 386 forwarded because each proxy will send the same challenge set. 388 Note that the parsing considerations for WWW-Authenticate apply to 389 this header field as well; see Section 4.1 for details. 391 4.4. Proxy-Authorization 393 The "Proxy-Authorization" header field allows the client to identify 394 itself (or its user) to a proxy that requires authentication. Its 395 value consists of credentials containing the authentication 396 information of the client for the proxy and/or realm of the resource 397 being requested. 399 Proxy-Authorization = credentials 401 Unlike Authorization, the Proxy-Authorization header field applies 402 only to the next inbound proxy that demanded authentication using the 403 Proxy-Authenticate field. When multiple proxies are used in a chain, 404 the Proxy-Authorization header field is consumed by the first inbound 405 proxy that was expecting to receive credentials. A proxy MAY relay 406 the credentials from the client request to the next proxy if that is 407 the mechanism by which the proxies cooperatively authenticate a given 408 request. 410 5. IANA Considerations 412 5.1. Authentication Scheme Registry 414 The HTTP Authentication Scheme Registry defines the name space for 415 the authentication schemes in challenges and credentials. It will be 416 created and maintained at (the suggested URI) 417 . 419 5.1.1. Procedure 421 Registrations MUST include the following fields: 423 o Authentication Scheme Name 425 o Pointer to specification text 427 o Notes (optional) 429 Values to be added to this name space require IETF Review (see 430 [RFC5226], Section 4.1). 432 5.1.2. Considerations for New Authentication Schemes 434 There are certain aspects of the HTTP Authentication Framework that 435 put constraints on how new authentication schemes can work: 437 o HTTP authentication is presumed to be stateless: all of the 438 information necessary to authenticate a request MUST be provided 439 in the request, rather than be dependent on the server remembering 440 prior requests. Authentication based on, or bound to, the 441 underlying connection is outside the scope of this specification 442 and inherently flawed unless steps are taken to ensure that the 443 connection cannot be used by any party other than the 444 authenticated user (see Section 2.3 of [Part1]). 446 o The authentication parameter "realm" is reserved for defining 447 Protection Spaces as defined in Section 2.2. New schemes MUST NOT 448 use it in a way incompatible with that definition. 450 o The "token68" notation was introduced for compatibility with 451 existing authentication schemes and can only be used once per 452 challenge or credential. New schemes thus ought to use the "auth- 453 param" syntax instead, because otherwise future extensions will be 454 impossible. 456 o The parsing of challenges and credentials is defined by this 457 specification, and cannot be modified by new authentication 458 schemes. When the auth-param syntax is used, all parameters ought 459 to support both token and quoted-string syntax, and syntactical 460 constraints ought to be defined on the field value after parsing 461 (i.e., quoted-string processing). This is necessary so that 462 recipients can use a generic parser that applies to all 463 authentication schemes. 465 Note: The fact that the value syntax for the "realm" parameter is 466 restricted to quoted-string was a bad design choice not to be 467 repeated for new parameters. 469 o Definitions of new schemes ought to define the treatment of 470 unknown extension parameters. In general, a "must-ignore" rule is 471 preferable over "must-understand", because otherwise it will be 472 hard to introduce new parameters in the presence of legacy 473 recipients. Furthermore, it's good to describe the policy for 474 defining new parameters (such as "update the specification", or 475 "use this registry"). 477 o Authentication schemes need to document whether they are usable in 478 origin-server authentication (i.e., using WWW-Authenticate), 479 and/or proxy authentication (i.e., using Proxy-Authenticate). 481 o The credentials carried in an Authorization header field are 482 specific to the User Agent, and therefore have the same effect on 483 HTTP caches as the "private" Cache-Control response directive 484 (Section 5.2.2.6 of [Part6]), within the scope of the request they 485 appear in. 487 Therefore, new authentication schemes that choose not to carry 488 credentials in the Authorization header field (e.g., using a newly 489 defined header field) will need to explicitly disallow caching, by 490 mandating the use of either Cache-Control request directives 491 (e.g., "no-store", Section 5.2.1.5 of [Part6]) or response 492 directives (e.g., "private"). 494 5.2. Status Code Registration 496 The HTTP Status Code Registry located at 497 shall be updated 498 with the registrations below: 500 +-------+-------------------------------+-------------+ 501 | Value | Description | Reference | 502 +-------+-------------------------------+-------------+ 503 | 401 | Unauthorized | Section 3.1 | 504 | 407 | Proxy Authentication Required | Section 3.2 | 505 +-------+-------------------------------+-------------+ 507 5.3. Header Field Registration 509 HTTP header fields are registered within the Message Header Field 510 Registry maintained at . 513 This document defines the following HTTP header fields, so their 514 associated registry entries shall be updated according to the 515 permanent registrations below (see [BCP90]): 517 +---------------------+----------+----------+-------------+ 518 | Header Field Name | Protocol | Status | Reference | 519 +---------------------+----------+----------+-------------+ 520 | Authorization | http | standard | Section 4.2 | 521 | Proxy-Authenticate | http | standard | Section 4.3 | 522 | Proxy-Authorization | http | standard | Section 4.4 | 523 | WWW-Authenticate | http | standard | Section 4.1 | 524 +---------------------+----------+----------+-------------+ 526 The change controller is: "IETF (iesg@ietf.org) - Internet 527 Engineering Task Force". 529 6. Security Considerations 531 This section is meant to inform developers, information providers, 532 and users of known security concerns specific to HTTP authentication. 533 More general security considerations are addressed in HTTP messaging 534 [Part1] and semantics [Part2]. 536 Everything about the topic of HTTP authentication is a security 537 consideration, so the list of considerations below is not exhaustive. 538 Furthermore, it is limited to security considerations regarding the 539 authentication framework, in general, rather than discussing all of 540 the potential considerations for specific authentication schemes 541 (which ought to be documented in the specifications that define those 542 schemes). Various organizations maintain topical information and 543 links to current research on Web application security (e.g., 544 [OWASP]), including common pitfalls for implementing and using the 545 authentication schemes found in practice. 547 6.1. Confidentiality of Credentials 549 The HTTP authentication framework does not define a single mechanism 550 for maintaining the confidentiality of credentials; instead, each 551 authentication scheme defines how the credentials are encoded prior 552 to transmission. While this provides flexibility for the development 553 of future authentication schemes, it is inadequate for the protection 554 of existing schemes that provide no confidentiality on their own, or 555 that do not sufficiently protect against replay attacks. 556 Furthermore, if the server expects credentials that are specific to 557 each individual user, the exchange of those credentials will have the 558 effect of identifying that user even if the content within 559 credentials remains confidential. 561 HTTP depends on the security properties of the underlying transport 562 or session-level connection to provide confidential transmission of 563 header fields. In other words, if a server limits access to 564 authenticated users using this framework, the server needs to ensure 565 that the connection is properly secured in accordance with the nature 566 of the authentication scheme used. For example, services that depend 567 on individual user authentication often require a connection to be 568 secured with TLS ("Transport Layer Security", [RFC5246]) prior to 569 exchanging any credentials. 571 6.2. Authentication Credentials and Idle Clients 573 Existing HTTP clients and user agents typically retain authentication 574 information indefinitely. HTTP does not provide a mechanism for the 575 origin server to direct clients to discard these cached credentials, 576 since the protocol has no awareness of how credentials are obtained 577 or managed by the user agent. The mechanisms for expiring or 578 revoking credentials can be specified as part of an authentication 579 scheme definition. 581 Circumstances under which credential caching can interfere with the 582 application's security model include but are not limited to: 584 o Clients that have been idle for an extended period, following 585 which the server might wish to cause the client to re-prompt the 586 user for credentials. 588 o Applications that include a session termination indication (such 589 as a "logout" or "commit" button on a page) after which the server 590 side of the application "knows" that there is no further reason 591 for the client to retain the credentials. 593 User agents that cache credentials are encouraged to provide a 594 readily accessible mechanism for discarding cached credentials under 595 user control. 597 6.3. Protection Spaces 599 Authentication schemes that solely rely on the "realm" mechanism for 600 establishing a protection space will expose credentials to all 601 resources on an origin server. Clients that have successfully made 602 authenticated requests with a resource can use the same 603 authentication credentials for other resources on the same origin 604 server. This makes it possible for a different resource to harvest 605 authentication credentials for other resources. 607 This is of particular concern when an origin server hosts resources 608 for multiple parties under the same canonical root URI (Section 2.2). 609 Possible mitigation strategies include restricting direct access to 610 authentication credentials (i.e., not making the content of the 611 Authorization request header field available), and separating 612 protection spaces by using a different host name (or port number) for 613 each party. 615 7. Acknowledgments 617 This specification takes over the definition of the HTTP 618 Authentication Framework, previously defined in RFC 2617. We thank 619 John Franks, Phillip M. Hallam-Baker, Jeffery L. Hostetler, Scott D. 620 Lawrence, Paul J. Leach, Ari Luotonen, and Lawrence C. Stewart for 621 their work on that specification. See Section 6 of [RFC2617] for 622 further acknowledgements. 624 See Section 10 of [Part1] for the Acknowledgments related to this 625 document revision. 627 8. References 629 8.1. Normative References 631 [Part1] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 632 Protocol (HTTP/1.1): Message Syntax and Routing", 633 draft-ietf-httpbis-p1-messaging-26 (work in progress), 634 February 2014. 636 [Part2] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 637 Protocol (HTTP/1.1): Semantics and Content", 638 draft-ietf-httpbis-p2-semantics-26 (work in progress), 639 February 2014. 641 [Part6] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, 642 Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching", 643 draft-ietf-httpbis-p6-cache-26 (work in progress), 644 February 2014. 646 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 647 Requirement Levels", BCP 14, RFC 2119, March 1997. 649 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 650 Specifications: ABNF", STD 68, RFC 5234, January 2008. 652 8.2. Informative References 654 [BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration 655 Procedures for Message Header Fields", BCP 90, RFC 3864, 656 September 2004. 658 [OWASP] van der Stock, A., Ed., "A Guide to Building Secure Web 659 Applications and Web Services", The Open Web Application 660 Security Project (OWASP) 2.0.1, July 2005, 661 . 663 [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., 664 Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext 665 Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. 667 [RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S., 668 Leach, P., Luotonen, A., and L. Stewart, "HTTP 669 Authentication: Basic and Digest Access Authentication", 670 RFC 2617, June 1999. 672 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 673 Resource Identifier (URI): Generic Syntax", STD 66, 674 RFC 3986, January 2005. 676 [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data 677 Encodings", RFC 4648, October 2006. 679 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 680 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 681 May 2008. 683 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 684 (TLS) Protocol Version 1.2", RFC 5246, August 2008. 686 Appendix A. Changes from RFCs 2616 and 2617 688 The framework for HTTP Authentication is now defined by this 689 document, rather than RFC 2617. 691 The "realm" parameter is no longer always required on challenges; 692 consequently, the ABNF allows challenges without any auth parameters. 693 (Section 2) 695 The "token68" alternative to auth-param lists has been added for 696 consistency with legacy authentication schemes such as "Basic". 697 (Section 2) 699 This specification introduces the Authentication Scheme Registry, 700 along with considerations for new authentication schemes. 701 (Section 5.1) 703 Appendix B. Imported ABNF 705 The following core rules are included by reference, as defined in 706 Appendix B.1 of [RFC5234]: ALPHA (letters), CR (carriage return), 707 CRLF (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double 708 quote), HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed), OCTET (any 709 8-bit sequence of data), SP (space), and VCHAR (any visible US-ASCII 710 character). 712 The rules below are defined in [Part1]: 714 BWS = 715 OWS = 716 quoted-string = 717 token = 719 Appendix C. Collected ABNF 721 In the collected ABNF below, list rules are expanded as per Section 722 1.2 of [Part1]. 724 Authorization = credentials 726 BWS = 728 OWS = 730 Proxy-Authenticate = *( "," OWS ) challenge *( OWS "," [ OWS 731 challenge ] ) 732 Proxy-Authorization = credentials 734 WWW-Authenticate = *( "," OWS ) challenge *( OWS "," [ OWS challenge 735 ] ) 737 auth-param = token BWS "=" BWS ( token / quoted-string ) 738 auth-scheme = token 740 challenge = auth-scheme [ 1*SP ( token68 / [ ( "," / auth-param ) *( 741 OWS "," [ OWS auth-param ] ) ] ) ] 742 credentials = auth-scheme [ 1*SP ( token68 / [ ( "," / auth-param ) 743 *( OWS "," [ OWS auth-param ] ) ] ) ] 745 quoted-string = 747 token = 748 token68 = 1*( ALPHA / DIGIT / "-" / "." / "_" / "~" / "+" / "/" ) 749 *"=" 751 Appendix D. Change Log (to be removed by RFC Editor before publication) 753 Changes up to the IETF Last Call draft are summarized in . 756 D.1. Since draft-ietf-httpbis-p7-auth-24 758 Closed issues: 760 o : "SECDIR review 761 of draft-ietf-httpbis-p7-auth-24" 763 o : "APPSDIR 764 review of draft-ietf-httpbis-p7-auth-24" 766 o : "note about 767 WWW-A parsing potentially misleading" 769 D.2. Since draft-ietf-httpbis-p7-auth-25 771 Closed issues: 773 o : "Gen-art 774 review of draft-ietf-httpbis-p7-auth-25" 776 o : "IESG ballot 777 on draft-ietf-httpbis-p7-auth-25" 779 o : "add 780 'stateless' to Abstract" 782 o : "mention TLS 783 vs plain text passwords or dict attacks?" 785 o : "improve 786 introduction of list rule" 788 o : "augment 789 security considerations with pointers to current research" 791 Index 793 4 794 401 Unauthorized (status code) 7 795 407 Proxy Authentication Required (status code) 7 797 A 798 Authorization header field 8 800 C 801 Canonical Root URI 6 803 G 804 Grammar 805 auth-param 5 806 auth-scheme 5 807 Authorization 8 808 challenge 5 809 credentials 6 810 Proxy-Authenticate 9 811 Proxy-Authorization 9 812 token68 5 813 WWW-Authenticate 8 815 P 816 Protection Space 6 817 Proxy-Authenticate header field 9 818 Proxy-Authorization header field 9 820 R 821 Realm 6 823 W 824 WWW-Authenticate header field 8 826 Authors' Addresses 828 Roy T. Fielding (editor) 829 Adobe Systems Incorporated 830 345 Park Ave 831 San Jose, CA 95110 832 USA 834 EMail: fielding@gbiv.com 835 URI: http://roy.gbiv.com/ 837 Julian F. Reschke (editor) 838 greenbytes GmbH 839 Hafenweg 16 840 Muenster, NW 48155 841 Germany 843 EMail: julian.reschke@greenbytes.de 844 URI: http://greenbytes.de/tech/webdav/