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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Backman, Ed. 3 Internet-Draft Amazon 4 Intended status: Standards Track M. Jones, Ed. 5 Expires: September 11, 2019 Microsoft 6 M. Scurtescu 7 Coinbase 8 M. Ansari 9 Cisco 10 A. Nadalin 11 Microsoft 12 March 10, 2019 14 Poll-Based Security Event Token (SET) Delivery Using HTTP 15 draft-ietf-secevent-http-poll-02 17 Abstract 19 This specification defines how a series of Security Event Tokens 20 (SETs) may be delivered to an intended recipient using HTTP POST over 21 TLS initiated as a poll by the recipient. The specification also 22 defines how delivery can be assured, subject to the SET Recipient's 23 need for assurance. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at https://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on September 11, 2019. 42 Copyright Notice 44 Copyright (c) 2019 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (https://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction and Overview . . . . . . . . . . . . . . . . . . 2 60 1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3 61 1.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3 62 2. SET Delivery . . . . . . . . . . . . . . . . . . . . . . . . 3 63 2.1. Polling Delivery using HTTP . . . . . . . . . . . . . . . 4 64 2.2. Polling HTTP Request Attributes . . . . . . . . . . . . . 4 65 2.3. Polling HTTP Response Attributes . . . . . . . . . . . . 5 66 2.4. Poll Request . . . . . . . . . . . . . . . . . . . . . . 6 67 2.4.1. Poll Only Request . . . . . . . . . . . . . . . . . . 7 68 2.4.2. Acknowledge Only Request . . . . . . . . . . . . . . 8 69 2.4.3. Poll with Acknowledgement . . . . . . . . . . . . . . 8 70 2.4.4. Poll with Acknowledgement and Errors . . . . . . . . 9 71 2.5. Poll Response . . . . . . . . . . . . . . . . . . . . . . 10 72 2.6. Error Response Handling . . . . . . . . . . . . . . . . . 12 73 3. Authentication and Authorization . . . . . . . . . . . . . . 12 74 3.1. Use of Tokens as Authorizations . . . . . . . . . . . . . 13 75 4. Security Considerations . . . . . . . . . . . . . . . . . . . 14 76 4.1. Authentication Using Signed SETs . . . . . . . . . . . . 14 77 4.2. HTTP Considerations . . . . . . . . . . . . . . . . . . . 14 78 4.3. TLS Support Considerations . . . . . . . . . . . . . . . 14 79 4.4. Access Token Considerations . . . . . . . . . . . . . . . 15 80 4.4.1. Bearer Token Considerations . . . . . . . . . . . . . 15 81 5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 15 82 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 83 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 84 7.1. Normative References . . . . . . . . . . . . . . . . . . 16 85 7.2. Informative References . . . . . . . . . . . . . . . . . 17 86 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 18 87 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 18 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 90 1. Introduction and Overview 92 This specification defines how a stream of Security Event Tokens 93 (SETs) [RFC8417] can be transmitted to an intended SET Recipient 94 using HTTP [RFC7231] over TLS. The specification defines a method to 95 poll for SETs using HTTP POST. 97 1.1. Notational Conventions 99 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 100 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 101 "OPTIONAL" in this document are to be interpreted as described in BCP 102 14 [RFC2119] [RFC8174] when, and only when, they appear in all 103 capitals, as shown here. 105 Throughout this document, all figures MAY contain spaces and extra 106 line wrapping for readability and due to space limitations. 108 1.2. Definitions 110 This specification utilizes terminology defined in [RFC8417], as well 111 as the terms defined below: 113 SET Transmitter 114 An entity that delivers SETs in its possession to one or more SET 115 Recipients. 117 2. SET Delivery 119 When an event occurs, the SET Transmitter constructs a SET [RFC8417] 120 that describes the event. The SET Transmitter determines the SET 121 Recipients that the SET should be distributed to. 123 How SETs are defined and the process by which events are identified 124 for SET Recipients is out of scope of this specification. 126 When a SET is available for a SET Recipient, the SET Transmitter 127 attempts to deliver the SET by queueing s the SET in a buffer so that 128 a SET Recipient can poll for SETs using HTTP/1.1 POST. 130 In Poll-Based SET Delivery Using HTTP, zero or more SETs are 131 delivered in a JSON [RFC8259] document to a SET Recipient in response 132 to an HTTP POST request to the SET Transmitter. Then in a following 133 request, the SET Recipient acknowledges received SETs and can poll 134 for more. All requests and responses are JSON documents and use a 135 "Content-Type" of "application/json", as described in Section 2.1. 137 After successful (acknowledged) SET delivery, SET Transmitters are 138 not be required to retain or record SETs for recovery. Once a SET is 139 acknowledged, the SET Recipient SHALL be responsible for retention 140 and recovery. 142 Transmitted SETs SHOULD be self-validating (e.g., signed) if there is 143 a requirement to verify they were issued by the SET Transmitter at a 144 later date when de-coupled from the original delivery where 145 authenticity could be checked via the HTTP or TLS mutual 146 authentication. 148 Upon receiving a SET, the SET Recipient reads the SET and validates 149 it. The SET Recipient MUST acknowledge receipt to the SET 150 Transmitter. 152 The SET Recipient SHALL NOT use the event acknowledgement mechanism 153 to report event errors other than relating to the parsing and 154 validation of the SET. 156 2.1. Polling Delivery using HTTP 158 This method allows a SET Recipient to use HTTP POST (Section 4.3.3 of 159 [RFC7231]) to acknowledge SETs and to check for and receive zero or 160 more SETs. Requests MAY be made at a periodic interval (short 161 polling) or requests MAY wait, pending availability of new SETs using 162 long polling, per Section 2 of [RFC6202]. 164 The delivery of SETs in this method is facilitated by HTTP POST 165 requests initiated by the SET Recipient in which: 167 o The SET Recipient makes a request for available SETs using an HTTP 168 POST to a pre-arranged endpoint provided by the SET Transmitter. 169 Or, 171 o After validating previously received SETs, the SET Recipient 172 initiates another poll request using HTTP POST that includes 173 acknowledgement of previous SETs and waits for the next batch of 174 SETs. 176 The purpose of the acknowledgement is to inform the SET Transmitter 177 that delivery has succeeded and redelivery is no longer required. 178 Before acknowledgement, SET Recipients SHOULD ensure that received 179 SETs have been validated and retained in a manner appropriate to the 180 recipient's requirements. The level and method of retention of SETs 181 by SET Recipients is out of scope of this specification. 183 2.2. Polling HTTP Request Attributes 185 When initiating a poll request, the SET Recipient constructs a JSON 186 document that consists of polling request parameters and SET 187 acknowledgement parameters in the form of JSON attributes. The 188 request payloads are delivered in a JSON document, as described in 189 Section 2.4 and Section 2.5. 191 When making a request, the HTTP header "Content-Type" is set to 192 "application/json". 194 The following JSON attributes are used in a polling request: 196 Request Processing Parameters 198 maxEvents 199 An OPTIONAL JSON integer value indicating the maximum number of 200 unacknowledged SETs that SHOULD be returned. If more than the 201 maximum number of SETs are available, the oldest SETs available 202 SHOULD be returned first. A value of "0" MAY be used by SET 203 Recipients that would like to perform an acknowledge only 204 request. This enables the Recipient to use separate HTTP 205 requests for acknowledgement and reception of SETs. If this 206 parameter is omitted, no limit is placed on the number of SETs 207 to be returned. 209 returnImmediately 210 An OPTIONAL JSON boolean value that indicates the SET 211 Transmitter SHOULD return an immediate response even if no 212 results are available (short polling). The default value is 213 "false" indicates the request is to be treated as an HTTP Long 214 Poll, per Section 2 of [RFC6202]. The timeout for the request 215 is part of the configuration between the participants, which is 216 out of scope of this specification. 218 SET Acknowledgment Parameters 220 ack 221 Which is an array of Strings that each correspond to the "jti" 222 of a successfully received SET. If there are no outstanding 223 SETs to acknowledge, the attribute MAY be omitted. When 224 acknowledging a SET, the SET Transmitter is released from any 225 obligation to retain the SET (e.g., for a future retry to 226 receive). 228 setErrs 229 A JSON Object that contains one or more nested JSON attributes 230 that correspond to the "jti" of each invalid SET received. The 231 value of each is a JSON object whose contents is an "err" 232 attribute and "description" attribute whose value correspond to 233 the errors described in Section 2.6. 235 2.3. Polling HTTP Response Attributes 237 In response to a poll request, the SET Transmitter checks for 238 available SETs and responds with a JSON document containing the 239 following JSON attributes: 241 sets 242 A JSON object that contains zero or more nested JSON attributes. 243 Each nested attribute corresponds to the "jti" of a SET to be 244 delivered and whose value is a JSON String containing the value of 245 the encoded corresponding SET. If there are no outstanding SETs 246 to be transmitted, the JSON object SHALL be empty. 248 moreAvailable 249 A JSON boolean value that indicates if more unacknowledged SETs 250 are available to be returned. 252 When making a response, the HTTP header "Content-Type" is set to 253 "application/json". 255 2.4. Poll Request 257 The SET Recipient performs an HTTP POST (see Section 4.3.4 of 258 [RFC7231]) to a pre-arranged polling endpoint URI to check for SETs 259 that are available. Because the SET Recipient has no prior SETs to 260 acknowledge, the "ack" and "errs" request parameters are omitted. 262 If after a period of time, negotiated between the SET Transmitter and 263 Recipient, a SET Transmitter MAY redeliver SETs it has previously 264 delivered. The SET Recipient SHOULD accept repeat SETs and 265 acknowledge the SETs regardless of whether the Recipient believes it 266 has already acknowledged the SETs previously. A SET Transmitter MAY 267 limit the number of times it attempts to deliver a SET. 269 If the SET Recipient has received SETs from the SET Transmitter, the 270 SET Recipient SHOULD parse and validate received SETs to meet its own 271 requirements and SHOULD acknowledge receipt in a timely fashion 272 (e.g., seconds or minutes) so that the SET Transmitter can mark the 273 SETs as received. SET Recipients SHOULD acknowledge receipt before 274 taking any local actions based on the SETs to avoid unnecessary delay 275 in acknowledgement, where possible. 277 Poll requests have three variations: 279 Poll Only 280 In which a SET Recipient asks for the next set of events where no 281 previous SET deliveries are acknowledged (such as in the initial 282 poll request). 284 Acknowledge Only 285 In which a SET Recipient sets the "maxEvents" attribute to "0" 286 along with "ack" and "err" attributes indicating the SET Recipient 287 is acknowledging previously received SETs and does not want to 288 receive any new SETs in response to the request. 290 Combined Acknowledge and Poll 291 In which a SET Recipient is both acknowledging previously received 292 SETs using the "ack" and "err" attributes and will wait for the 293 next group of SETs in the SET Transmitters response. 295 2.4.1. Poll Only Request 297 In the case where no SETs were received in a previous poll (see 298 Figure 7), the SET Recipient simply polls without acknowledgement 299 parameters ("sets" and "setErrs"). 301 The following is an example request made by a SET Recipient that has 302 no outstanding SETs to acknowledge and is polling for available SETs. 304 The following is a non-normative example poll request to the 305 endpoint: "https://nofity.exampleidp.com/Events". 307 POST /Events HTTP/1.1 309 Host: notify.exampleidp.com 310 Authorization: Bearer h480djs93hd8 311 Accept: application/json 313 { 314 "returnImmediately": true 315 } 317 Figure 1: Example Initial Poll Request 319 A SET Recipient can poll using default parameter values by passing an 320 empty JSON object. 322 The following is a non-normative example default poll request to the 323 endpoint: "https://nofity.exampleidp.com/Events". 325 POST /Events HTTP/1.1 327 Host: notify.exampleidp.com 328 Authorization: Bearer h480djs93hd8 329 Accept: application/json 331 {} 333 Figure 2: Example Default Poll Request 335 2.4.2. Acknowledge Only Request 337 In this variation, the SET Recipient acknowledges previously received 338 SETs and indicates it does not want to receive SETs in response by 339 setting the "maxEvents" attribute to "0". 341 This variation might be used, for instance, when a SET Recipient 342 needs to acknowledge received SETs independently (e.g., on separate 343 threads) from the process of receiving SETs. 345 The following is a non-normative example poll with acknowledgement of 346 SETs received (for example as shown in Figure 6). 348 POST /Events HTTP/1.1 350 Host: notify.exampleidp.com 351 Authorization: Bearer h480djs93hd8 352 Content-Type: application/json 353 Authorization: Bearer h480djs93hd8 355 { 356 "ack": [ 357 "4d3559ec67504aaba65d40b0363faad8", 358 "3d0c3cf797584bd193bd0fb1bd4e7d30" 359 ], 360 "maxEvents": 0, 361 "returnImmediately": true 362 } 364 Figure 3: Example Acknowledge Only Request 366 2.4.3. Poll with Acknowledgement 368 This variation allows a recipient thread to simultaneously 369 acknowledge previously received SETs and wait for the next group of 370 SETs in a single request. 372 The following is a non-normative example poll with acknowledgement of 373 SETs received in Figure 6. 375 POST /Events HTTP/1.1 377 Host: notify.exampleidp.com 378 Authorization: Bearer h480djs93hd8 379 Content-Type: application/json 380 Authorization: Bearer h480djs93hd8 382 { 383 "ack": [ 384 "4d3559ec67504aaba65d40b0363faad8", 385 "3d0c3cf797584bd193bd0fb1bd4e7d30" 386 ], 387 "returnImmediately": false 388 } 390 Figure 4: Example Poll with Acknowledgement and No Errors 392 In the above acknowledgement, the SET Recipient has acknowledged 393 receipt of two SETs and has indicated it wants to wait until the next 394 SET is available. 396 2.4.4. Poll with Acknowledgement and Errors 398 In the case where errors were detected in previously delivered SETs, 399 the SET Recipient MAY use the "setErrs" attribute to communicate the 400 errors in the following poll request. 402 The following is a non-normative example of a response acknowledging 403 one successfully received SET and one SET with an error from the two 404 SETs received in in Figure 6. 406 POST /Events HTTP/1.1 408 Host: notify.exampleidp.com 409 Authorization: Bearer h480djs93hd8 410 Content-Type: application/json 411 Authorization: Bearer h480djs93hd8 413 { 414 "ack": ["3d0c3cf797584bd193bd0fb1bd4e7d30"], 415 "setErrs": { 416 "4d3559ec67504aaba65d40b0363faad8": { 417 "err": "jwtAud", 418 "description": "The audience value was invalid." 419 } 420 }, 421 "returnImmediately": true 422 } 424 Figure 5: Example Poll Acknowledgement with Error 426 2.5. Poll Response 428 In response to a poll request, the service provider MAY respond 429 immediately if SETs are available to be delivered. If no SETs are 430 available at the time of the request, the SET Transmitter SHALL delay 431 responding until a SET is available or the timeout interval has 432 elapsed unless the poll request parameter "returnImmediately" is 433 "true". 435 As described in Section 2.3, a JSON document is returned containing a 436 number of attributes including "sets" which SHALL contain zero or 437 more SETs. 439 The following is a non-normative example response to the request 440 shown Section 2.4. This example shows two SETs are returned. 442 HTTP/1.1 200 OK 443 Content-Type: application/json 444 Location: https://notify.exampleidp/Events 446 { 447 "sets": { 448 "4d3559ec67504aaba65d40b0363faad8": 449 "eyJhbGciOiJub25lIn0. 450 eyJqdGkiOiI0ZDM1NTllYzY3NTA0YWFiYTY1ZDQwYjAzNjNmYWFkOCIsImlhdCI6MTQ 451 1ODQ5NjQwNCwiaXNzIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tIiwiYXVkIjpbIm 452 h0dHBzOi8vc2NpbS5leGFtcGxlLmNvbS9GZWVkcy85OGQ1MjQ2MWZhNWJiYzg3OTU5M 453 2I3NzU0IiwiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tL0ZlZWRzLzVkNzYwNDUxNmIx 454 ZDA4NjQxZDc2NzZlZTciXSwiZXZlbnRzIjp7InVybjppZXRmOnBhcmFtczpzY2ltOmV 455 2ZW50OmNyZWF0ZSI6eyJyZWYiOiJodHRwczovL3NjaW0uZXhhbXBsZS5jb20vVXNlcn 456 MvNDRmNjE0MmRmOTZiZDZhYjYxZTc1MjFkOSIsImF0dHJpYnV0ZXMiOlsiaWQiLCJuY 457 W1lIiwidXNlck5hbWUiLCJwYXNzd29yZCIsImVtYWlscyJdfX19.", 458 "3d0c3cf797584bd193bd0fb1bd4e7d30": 459 "eyJhbGciOiJub25lIn0. 460 eyJqdGkiOiIzZDBjM2NmNzk3NTg0YmQxOTNiZDBmYjFiZDRlN2QzMCIsImlhdCI6MTQ 461 1ODQ5NjAyNSwiaXNzIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tIiwiYXVkIjpbIm 462 h0dHBzOi8vamh1Yi5leGFtcGxlLmNvbS9GZWVkcy85OGQ1MjQ2MWZhNWJiYzg3OTU5M 463 2I3NzU0IiwiaHR0cHM6Ly9qaHViLmV4YW1wbGUuY29tL0ZlZWRzLzVkNzYwNDUxNmIx 464 ZDA4NjQxZDc2NzZlZTciXSwic3ViIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tL1V 465 zZXJzLzQ0ZjYxNDJkZjk2YmQ2YWI2MWU3NTIxZDkiLCJldmVudHMiOnsidXJuOmlldG 466 Y6cGFyYW1zOnNjaW06ZXZlbnQ6cGFzc3dvcmRSZXNldCI6eyJpZCI6IjQ0ZjYxNDJkZ 467 jk2YmQ2YWI2MWU3NTIxZDkifSwiaHR0cHM6Ly9leGFtcGxlLmNvbS9zY2ltL2V2ZW50 468 L3Bhc3N3b3JkUmVzZXRFeHQiOnsicmVzZXRBdHRlbXB0cyI6NX19fQ." 469 } 470 } 472 Figure 6: Example Poll Response 474 In the above example, a two SETs whose "jti" are 475 "4d3559ec67504aaba65d40b0363faad8" and 476 "3d0c3cf797584bd193bd0fb1bd4e7d30" are delivered. 478 The following is a non-normative example response to the request 479 shown Section 2.4 showing no new SETs or unacknowledged SETs are 480 available. 482 HTTP/1.1 200 OK 483 Content-Type: application/json 484 Location: https://notify.exampleidp/Events 486 { 487 "sets": {} 488 } 490 Figure 7: Example No SETs Poll Response 492 Upon receiving the JSON document (e.g., as shown in Figure 6), the 493 SET Recipient parses and verifies the received SETs and notifies the 494 SET Transmitter via the next poll request to the SET Transmitter, as 495 described in Section 2.4.3 or Section 2.4.4. 497 2.6. Error Response Handling 499 If a SET is invalid, error codes from the IANA "Security Event Token 500 Delivery Error Codes" registry established by 501 [I-D.ietf-secevent-http-push] are used in error responses. An error 502 response SHALL include a JSON object that provides details about the 503 error. The JSON object includes the JSON attributes: 505 err 506 A value from the IANA "Security Event Token Delivery Error Codes" 507 registry that identifies the error. 509 description 510 A human-readable string that provides additional diagnostic 511 information. 513 When included as part of a batch of SETs, the above JSON is included 514 as part of the "setErrs" attribute, as defined in Section 2.3 and 515 Section 2.4.4. 517 3. Authentication and Authorization 519 The SET delivery method described in this specification is based upon 520 HTTP and depends on the use of TLS and/or standard HTTP 521 authentication and authorization schemes as per [RFC7235]. For 522 example, the following methodologies could be used among others: 524 TLS Client Authentication 525 Event delivery endpoints MAY request TLS mutual client 526 authentication, per Section 7.3 of [RFC5246]. 528 Bearer Tokens 529 Bearer tokens [RFC6750] MAY be used when combined with TLS and a 530 token framework such as OAuth 2.0 [RFC6749]. For security 531 considerations regarding the use of bearer tokens in SET delivery, 532 see Section 4.4.1. 534 Basic Authentication 535 Use of HTTP BASIC authentication should be avoided due to its use 536 of a single factor that is based upon a relatively static, 537 symmetric secret. When used, implementers SHOULD combine the use 538 of basic authentication with other factors. The security 539 considerations of HTTP BASIC are well documented in [RFC7617] and 540 SHOULD be considered along with using signed SETs (see SET Payload 541 Authentication below). 543 As per Section 4.1 of [RFC7235], a SET delivery endpoint SHALL 544 indicate supported HTTP authentication schemes via the "WWW- 545 Authenticate" header. 547 Because SET Delivery describes a simple function, authorization for 548 the ability to pick-up or deliver SETs can be derived by considering 549 the identity of the SET issuer, or via an authentication method 550 above. This specification considers authentication as a feature to 551 prevent denial-of-service attacks. Because SETs are not commands, 552 SET Recipients are free to ignore SETs that are not of interest after 553 acknowledging their receipt. 555 For illustrative purposes only, SET delivery examples show an OAuth2 556 bearer token value [RFC6750] in the authorization header. This is 557 not intended to imply that bearer tokens are preferred. However, the 558 use of bearer tokens in the specification does reflect common 559 practice. 561 3.1. Use of Tokens as Authorizations 563 When using bearer tokens or proof-of-possession tokens that represent 564 an authorization grant such as issued by OAuth (see [RFC6749]), 565 implementers SHOULD consider the type of authorization granted, any 566 authorized scopes (see Section 3.3 of [RFC6749]), and the security 567 subject(s) that SHOULD be mapped from the authorization when 568 considering local access control rules. Section 6 of the OAuth 569 Assertions draft [RFC7521], documents common scenarios for 570 authorization including: 572 o Clients using an assertion to authenticate and/or act on behalf of 573 itself; 575 o Clients acting on behalf of a user; and, 577 o A Client acting on behalf of an anonymous user (e.g., see next 578 section). 580 When using OAuth access tokens, implementers MUST take into account 581 the threats and countermeasures documented in the security 582 considerations for the use of client authorizations (see Section 8 of 583 [RFC7521]). When using other token formats or frameworks, 584 implementers MUST take into account similar threats and 585 countermeasures, especially those documented by the relevant 586 specifications. 588 4. Security Considerations 590 4.1. Authentication Using Signed SETs 592 In scenarios where HTTP authorization or TLS mutual authentication 593 are not used or are considered weak, JWS signed SETs SHOULD be used 594 (see [RFC7515] and Security Considerations [RFC8417]). This enables 595 the SET Recipient to validate that the SET issuer is authorized to 596 deliver the SET. 598 4.2. HTTP Considerations 600 SET delivery depends on the use of Hypertext Transfer Protocol and 601 thus subject to the security considerations of HTTP Section 9 of 602 [RFC7230] and its related specifications. 604 As stated in Section 2.7.1 of [RFC7230], an HTTP requestor MUST NOT 605 generate the "userinfo" (i.e., username and password) component (and 606 its "@" delimiter) when an "http" URI reference is generated with a 607 message as they are now disallowed in HTTP. 609 4.3. TLS Support Considerations 611 SETs may contain sensitive information that is considered PII (e.g., 612 subject claims). In such cases, SET Transmitters and SET Recipients 613 MUST encrypt the SET, either with a transport-layer security 614 mechanism, with JWE [RFC7516], or both. Event delivery endpoints 615 MUST support TLS 1.2 [RFC5246] and MAY support additional transport- 616 layer mechanisms meeting its security requirements. When using TLS, 617 the client MUST perform a TLS/SSL server certificate check, per 618 [RFC6125]. Implementation security considerations for TLS can be 619 found in "Recommendations for Secure Use of TLS and DTLS" [RFC7525]. 621 4.4. Access Token Considerations 623 When using access tokens such as those issued by OAuth 2.0 [RFC6749], 624 implementers MUST take into account threats and countermeasures 625 documented in Section 8 of [RFC7521]. 627 4.4.1. Bearer Token Considerations 629 Due to the possibility of interception, Bearer tokens MUST be 630 exchanged using TLS. 632 Bearer tokens MUST have a limited lifetime that can be determined 633 directly or indirectly (e.g., by checking with a validation service) 634 by the service provider. By expiring tokens, clients are forced to 635 obtain a new token (which usually involves re-authentication) for 636 continued authorized access. For example, in OAuth2, a client MAY 637 use an OAuth refresh token to obtain a new bearer token after 638 authenticating to an authorization server, per Section 6 of 639 [RFC6749]. 641 Implementations supporting OAuth bearer tokens need to factor in 642 security considerations of this authorization method [RFC7521]. 643 Since security is only as good as the weakest link, implementers also 644 need to consider authentication choices coupled with OAuth bearer 645 tokens. The security considerations of the default authentication 646 method for OAuth bearer tokens, HTTP BASIC, are well documented in 647 [RFC7617], therefore implementers are encouraged to prefer stronger 648 authentication methods. Designating the specific methods of 649 authentication and authorization are out of scope for the delivery of 650 SETs, however this information is provided as a resource to 651 implementers. 653 5. Privacy Considerations 655 If a SET needs to be retained for audit purposes, a JWS signature MAY 656 be used to provide verification of its authenticity. 658 SET Transmitters SHOULD attempt to deliver SETs that are targeted to 659 the specific business and protocol needs of subscribers. 661 When sharing personally identifiable information or information that 662 is otherwise considered confidential to affected users, SET 663 Transmitters and Recipients MUST have the appropriate legal 664 agreements and user consent or terms of service in place. 666 The propagation of subject identifiers can be perceived as personally 667 identifiable information. Where possible, SET Transmitters and 668 Recipients SHOULD devise approaches that prevent propagation, for 669 example, the passing of a hash value that requires the subscriber to 670 already know the subject. 672 6. IANA Considerations 674 There are no IANA considerations. 676 7. References 678 7.1. Normative References 680 [I-D.ietf-secevent-http-push] 681 Backman, A., Jones, M., Scurtescu, M., Ansari, M., and A. 682 Nadalin, "Push-Based Security Event Token (SET) Delivery 683 Using HTTP", draft-ietf-secevent-http-push-04 (work in 684 progress), January 2019. 686 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 687 Requirement Levels", BCP 14, RFC 2119, 688 DOI 10.17487/RFC2119, March 1997, 689 . 691 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 692 Resource Identifier (URI): Generic Syntax", STD 66, 693 RFC 3986, DOI 10.17487/RFC3986, January 2005, 694 . 696 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 697 (TLS) Protocol Version 1.2", RFC 5246, 698 DOI 10.17487/RFC5246, August 2008, 699 . 701 [RFC6125] Saint-Andre, P. and J. Hodges, "Representation and 702 Verification of Domain-Based Application Service Identity 703 within Internet Public Key Infrastructure Using X.509 704 (PKIX) Certificates in the Context of Transport Layer 705 Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March 706 2011, . 708 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 709 Protocol (HTTP/1.1): Semantics and Content", RFC 7231, 710 DOI 10.17487/RFC7231, June 2014, 711 . 713 [RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web 714 Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May 715 2015, . 717 [RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)", 718 RFC 7516, DOI 10.17487/RFC7516, May 2015, 719 . 721 [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token 722 (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, 723 . 725 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 726 "Recommendations for Secure Use of Transport Layer 727 Security (TLS) and Datagram Transport Layer Security 728 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 729 2015, . 731 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 732 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 733 May 2017, . 735 [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 736 Interchange Format", STD 90, RFC 8259, 737 DOI 10.17487/RFC8259, December 2017, 738 . 740 [RFC8417] Hunt, P., Ed., Jones, M., Denniss, W., and M. Ansari, 741 "Security Event Token (SET)", RFC 8417, 742 DOI 10.17487/RFC8417, July 2018, 743 . 745 7.2. Informative References 747 [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: 748 Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, 749 . 751 [RFC6202] Loreto, S., Saint-Andre, P., Salsano, S., and G. Wilkins, 752 "Known Issues and Best Practices for the Use of Long 753 Polling and Streaming in Bidirectional HTTP", RFC 6202, 754 DOI 10.17487/RFC6202, April 2011, 755 . 757 [RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework", 758 RFC 6749, DOI 10.17487/RFC6749, October 2012, 759 . 761 [RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization 762 Framework: Bearer Token Usage", RFC 6750, 763 DOI 10.17487/RFC6750, October 2012, 764 . 766 [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 767 Protocol (HTTP/1.1): Message Syntax and Routing", 768 RFC 7230, DOI 10.17487/RFC7230, June 2014, 769 . 771 [RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 772 Protocol (HTTP/1.1): Authentication", RFC 7235, 773 DOI 10.17487/RFC7235, June 2014, 774 . 776 [RFC7521] Campbell, B., Mortimore, C., Jones, M., and Y. Goland, 777 "Assertion Framework for OAuth 2.0 Client Authentication 778 and Authorization Grants", RFC 7521, DOI 10.17487/RFC7521, 779 May 2015, . 781 [RFC7617] Reschke, J., "The 'Basic' HTTP Authentication Scheme", 782 RFC 7617, DOI 10.17487/RFC7617, September 2015, 783 . 785 Appendix A. Acknowledgments 787 The editors would like to thank the members of the SCIM working 788 group, which began discussions of provisioning events starting with 789 draft-hunt-scim-notify-00 in 2015. 791 The editors would like to thank Phil Hunt and the other the authors 792 of draft-ietf-secevent-delivery-02, on which this draft is based. 794 The editors would like to thank the participants in the SecEvents 795 working group for their contributions to this specification. 797 Appendix B. Change Log 799 [[ to be removed by the RFC Editor before publication as an RFC ]] 801 Draft 00 - AB - Based on draft-ietf-secevent-delivery-02 with the 802 following additions: 804 o Renamed to "Poll-Based SET Token Delivery Using HTTP" 806 o Removed references to the HTTP Push delivery method. 808 Draft 01 - mbj: 810 o Addressed problems identified in my 18-Jul-18 review message 811 titled "Issues for both the Push and Poll Specs". 813 o Changes to align terminology with RFC 8417, for instance, by using 814 the already defined term SET Recipient rather than SET Receiver. 816 o Applied editorial and minor normative corrections. 818 o Updated Marius' contact information. 820 o Begun eliminating redundancies between this specification and 821 "Push-Based Security Event Token (SET) Delivery Using HTTP" 822 [I-D.ietf-secevent-http-push], referencing, rather that 823 duplicating common normative text. 825 Draft 02 - mbj: 827 o Removed vestigial language remaining from when the push and poll 828 delivery methods were defined in a common specification. 830 o Replaced remaining uses of the terms Event Transmitter and Event 831 Recipient with the correct terms SET Transmitter and SET 832 Recipient. 834 o Removed uses of the unnecessary term "Event Stream". 836 o Removed dependencies between the semantics of "maxEvents" and 837 "returnImmediately". 839 o Said that PII in SETs is to be encrypted with TLS, JWE, or both. 841 o Corrected grammar and spelling errors. 843 Authors' Addresses 845 Annabelle Backman (editor) 846 Amazon 848 Email: richanna@amazon.com 850 Michael B. Jones (editor) 851 Microsoft 853 Email: mbj@microsoft.com 854 URI: http://self-issued.info/ 855 Marius Scurtescu 856 Coinbase 858 Email: marius.scurtescu@coinbase.com 860 Morteza Ansari 861 Cisco 863 Email: morteza.ansari@cisco.com 865 Anthony Nadalin 866 Microsoft 868 Email: tonynad@microsoft.com