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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Security Events Working Group A. Backman, Ed. 3 Internet-Draft Amazon 4 Intended status: Standards Track M. Jones, Ed. 5 Expires: December 26, 2020 Microsoft 6 M. Scurtescu 7 Coinbase 8 M. Ansari 9 Cisco 10 A. Nadalin 11 Microsoft 12 June 24, 2020 14 Poll-Based Security Event Token (SET) Delivery Using HTTP 15 draft-ietf-secevent-http-poll-12 17 Abstract 19 This specification defines how a series of Security Event Tokens 20 (SETs) can 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 December 26, 2020. 42 Copyright Notice 44 Copyright (c) 2020 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 . . . . . . . . . . . . . . . . . . 5 65 2.3. Polling HTTP Response . . . . . . . . . . . . . . . . . . 6 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 . . . . . . . . . . . . . . 9 70 2.4.4. Poll with Acknowledgement and Errors . . . . . . . . 10 71 2.5. Poll Response . . . . . . . . . . . . . . . . . . . . . . 10 72 2.5.1. Poll Error Response . . . . . . . . . . . . . . . . . 12 73 2.6. Error Response Handling . . . . . . . . . . . . . . . . . 12 74 3. Authentication and Authorization . . . . . . . . . . . . . . 13 75 4. Security Considerations . . . . . . . . . . . . . . . . . . . 13 76 4.1. Authentication Using Signed SETs . . . . . . . . . . . . 14 77 4.2. HTTP Considerations . . . . . . . . . . . . . . . . . . . 14 78 4.3. Confidentiality of SETs . . . . . . . . . . . . . . . . . 14 79 4.4. Access Token Considerations . . . . . . . . . . . . . . . 14 80 4.4.1. Bearer Token Considerations . . . . . . . . . . . . . 14 81 5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 15 82 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 83 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 84 7.1. Normative References . . . . . . . . . . . . . . . . . . 15 85 7.2. Informative References . . . . . . . . . . . . . . . . . 17 86 Appendix A. Unencrypted Transport Considerations . . . . . . . . 18 87 Appendix B. Other Streaming Specifications . . . . . . . . . . . 18 88 Appendix C. Acknowledgments . . . . . . . . . . . . . . . . . . 18 89 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 19 90 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 92 1. Introduction and Overview 94 This specification defines how a stream of Security Event Tokens 95 (SETs) [RFC8417] can be transmitted to an intended SET Recipient 96 using HTTP [RFC7231] over TLS. The specification defines a method to 97 poll for SETs using HTTP POST. This is an alternative SET delivery 98 method to the one defined in [I-D.ietf-secevent-http-push]. 100 Poll-based SET delivery is intended for scenarios where all of the 101 following apply: 103 o The recipient of the SET is capable of making outbound HTTP 104 requests. 106 o The transmitter is capable of hosting a TLS-enabled HTTP endpoint 107 that is accessible to the recipient. 109 o The transmitter and recipient are willing to exchange data with 110 one another. 112 In some scenarios, either push-based or poll-based delivery could be 113 used, and in others, only one of them would be applicable. 115 A mechanism for exchanging configuration metadata such as endpoint 116 URLs, cryptographic keys, and possible implementation constraints 117 such as buffer size limitations between the transmitter and recipient 118 is out of scope for this specification. How SETs are defined and the 119 process by which security events are identified for SET Recipients 120 are specified in [RFC8417]. 122 1.1. Notational Conventions 124 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 125 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 126 "OPTIONAL" in this document are to be interpreted as described in BCP 127 14 [RFC2119] [RFC8174] when, and only when, they appear in all 128 capitals, as shown here. 130 Throughout this document, all figures may contain spaces and extra 131 line wrapping for readability and due to space limitations. 133 1.2. Definitions 135 This specification utilizes terminology defined in [RFC8417] and 136 [I-D.ietf-secevent-http-push]. 138 2. SET Delivery 140 When a SET is available for a SET Recipient, the SET Transmitter 141 queues the SET in a buffer so that a SET Recipient can poll for SETs 142 using HTTP POST. 144 In poll-based SET delivery using HTTP over TLS, zero or more SETs are 145 delivered in a JSON [RFC8259] document to a SET Recipient in response 146 to an HTTP POST request to the SET Transmitter. Then in a following 147 request, the SET Recipient acknowledges received SETs and can poll 148 for more. All requests and responses are JSON documents and use a 149 "Content-Type" of "application/json", as described in Section 2.1. 151 After successful (acknowledged) SET delivery, SET Transmitters are 152 not required to retain or record SETs for retransmission. Once a SET 153 is acknowledged, the SET Recipient SHALL be responsible for 154 retention, if needed. Transmitters may also discard undelivered SETs 155 under deployment-specific conditions, such as if they have not been 156 polled for over too long a period of time or if an excessive amount 157 of storage is needed to retain them. 159 Upon receiving a SET, the SET Recipient reads the SET and validates 160 it in the manner described in Section 2 of 161 [I-D.ietf-secevent-http-push]. The SET Recipient MUST acknowledge 162 receipt to the SET Transmitter, and SHOULD do so in a timely fashion, 163 as described in Section 2.4. The SET Recipient SHALL NOT use the 164 event acknowledgement mechanism to report event errors other than 165 those relating to the parsing and validation of the SET. 167 2.1. Polling Delivery using HTTP 169 This method allows a SET Recipient to use HTTP POST (Section 4.3.3 of 170 [RFC7231]) to acknowledge SETs and to check for and receive zero or 171 more SETs. Requests MAY be made at a periodic interval (short 172 polling) or requests MAY wait, pending availability of new SETs using 173 long polling, per Section 2 of [RFC6202]. Note that short polling 174 will result in retrieving zero or more SETs whereas long polling will 175 typically result in retrieving one or more SETs unless a timeout 176 occurs. 178 The delivery of SETs in this method is facilitated by HTTP POST 179 requests initiated by the SET Recipient in which: 181 o The SET Recipient makes a request for available SETs using an HTTP 182 POST to a pre-arranged endpoint provided by the SET Transmitter 183 or, 185 o after validating previously received SETs, the SET Recipient 186 initiates another poll request using HTTP POST that includes 187 acknowledgement of previous SETs and requests the next batch of 188 SETs. 190 The purpose of the acknowledgement is to inform the SET Transmitter 191 that delivery has succeeded and redelivery is no longer required. 193 Before acknowledgement, SET Recipients validate the received SETs and 194 retain them in a manner appropriate to the recipient's requirements. 195 The level and method of retention of SETs by SET Recipients is out of 196 scope of this specification. 198 2.2. Polling HTTP Request 200 When initiating a poll request, the SET Recipient constructs a JSON 201 document that consists of polling request parameters and SET 202 acknowledgement parameters in the form of JSON objects. 204 When making a request, the HTTP "Content-Type" header field is set to 205 "application/json". 207 The following JSON object members are used in a polling request: 209 Request Processing Parameters 211 maxEvents 212 An OPTIONAL integer value indicating the maximum number of 213 unacknowledged SETs to be returned. The SET Transmitter SHOULD 214 NOT send more SETs than the specified maximum. If more than 215 the maximum number of SETs are available, the SET Transmitter 216 determines which to return first; the oldest SETs available MAY 217 returned first, or another selection algorithm MAY be used, 218 such as prioritizing SETs in some manner that makes sense for 219 the use case. first. A value of "0" MAY be used by SET 220 Recipients that would like to perform an acknowledge-only 221 request. This enables the Recipient to use separate HTTP 222 requests for acknowledgement and reception of SETs. If this 223 parameter is omitted, no limit is placed on the number of SETs 224 to be returned. 226 returnImmediately 227 An OPTIONAL JSON boolean value that indicates the SET 228 Transmitter SHOULD return an immediate response even if no 229 results are available (short polling). The default value is 230 "false", which indicates the request is to be treated as an 231 HTTP Long Poll, per Section 2 of [RFC6202]. The timeout for 232 the request is part of the configuration between the 233 participants, which is out of scope of this specification. 235 SET Acknowledgment Parameters 237 ack 238 A JSON array of strings whose values are the "jti" [RFC7519] 239 values of successfully received SETs that are being 240 acknowledged. If there are no outstanding SETs to acknowledge, 241 this member is omitted or contains an empty array. Once a SET 242 has been acknowledged, the SET Transmitter is released from any 243 obligation to retain the SET. 245 setErrs 246 A JSON object with one or more members whose keys are the "jti" 247 values of invalid SETs received. The values of these objects 248 are themselves JSON objects that describe the errors detected 249 using the "err" and "description" values specified in 250 Section 2.6. If there are no outstanding SETs with errors to 251 report, this member is omitted or contains an empty JSON 252 object. 254 2.3. Polling HTTP Response 256 In response to a poll request, the SET Transmitter checks for 257 available SETs and responds with a JSON document containing the 258 following JSON object members: 260 sets 261 A JSON object containing zero or more SETs being returned. Each 262 member name is the "jti" of a SET to be delivered and its value is 263 a JSON string representing the corresponding SET. If there are no 264 outstanding SETs to be transmitted, the JSON object SHALL be 265 empty. Note that both SETs being transmitted for the first time 266 and SETs that are being re-transmitted after not having been 267 acknowledged are communicated here. 269 moreAvailable 270 A JSON boolean value that indicates if more unacknowledged SETs 271 are available to be returned. This member MAY be omitted, with 272 the meaning being the same as including it with the boolean value 273 "false". 275 When making a response, the HTTP "Content-Type" header field is set 276 to "application/json". 278 2.4. Poll Request 280 The SET Recipient performs an HTTP POST (see Section 4.3.4 of 281 [RFC7231]) to a pre-arranged polling endpoint URI to check for SETs 282 that are available. Because the SET Recipient has no prior SETs to 283 acknowledge, the "ack" and "setErrs" request parameters are omitted. 285 After a period of time configured in an out-of-band manner between 286 the SET Transmitter and Recipient, a SET Transmitter MAY redeliver 287 SETs it has previously delivered. The SET Recipient SHOULD accept 288 repeat SETs and acknowledge the SETs regardless of whether the 289 Recipient believes it has already acknowledged the SETs previously. 290 A SET Transmitter MAY limit the number of times it attempts to 291 deliver a SET. 293 If the SET Recipient has received SETs from the SET Transmitter, the 294 SET Recipient parses and validates that received SETs meet its own 295 requirements and SHOULD acknowledge receipt in a timely fashion 296 (e.g., seconds or minutes) so that the SET Transmitter can mark the 297 SETs as received. SET Recipients SHOULD acknowledge receipt before 298 taking any local actions based on the SETs to avoid unnecessary delay 299 in acknowledgement, where possible. 301 Poll requests have three variations: 303 Poll-Only 304 In which a SET Recipient asks for the next set of events where no 305 previous SET deliveries are acknowledged (such as in the initial 306 poll request). 308 Acknowledge-Only 309 In which a SET Recipient sets the "maxEvents" value to "0" along 310 with "ack" and "setErrs" members indicating the SET Recipient is 311 acknowledging previously received SETs and does not want to 312 receive any new SETs in response to the request. 314 Combined Acknowledge and Poll 315 In which a SET Recipient is both acknowledging previously received 316 SETs using the "ack" and "setErrs" members and will wait for the 317 next group of SETs in the SET Transmitters response. 319 2.4.1. Poll-Only Request 321 In the case where no SETs were received in a previous poll (see 322 Figure 7), the SET Recipient simply polls without acknowledgement 323 parameters ("ack" and "setErrs"). 325 The following is a non-normative example request made by a SET 326 Recipient that has no outstanding SETs to acknowledge and is polling 327 for available SETs at the endpoint "https://notify.idp.example.com/ 328 Events": 330 POST /Events HTTP/1.1 331 Host: notify.idp.example.com 332 Content-Type: application/json 334 { 335 "returnImmediately": true 336 } 338 Figure 1: Example Initial Poll Request 340 A SET Recipient can poll using default parameter values by passing an 341 empty JSON object. 343 The following is a non-normative example default poll request to the 344 endpoint "https://notify.idp.example.com/Events": 346 POST /Events HTTP/1.1 347 Host: notify.idp.example.com 348 Content-Type: application/json 350 {} 352 Figure 2: Example Default Poll Request 354 2.4.2. Acknowledge-Only Request 356 In this variation, the SET Recipient acknowledges previously received 357 SETs and indicates it does not want to receive SETs in response by 358 setting the "maxEvents" value to "0". This variation might be used, 359 for instance, when a SET Recipient needs to acknowledge received SETs 360 independently (e.g., on separate threads) from the process of 361 receiving SETs. 363 If the poll needs to return immediately, then "returnImmediately" 364 MUST also be present with the value "true". If it is "false", then a 365 long poll will still occur until an event is ready to be returned, 366 even though no events will be returned. 368 The following is a non-normative example poll request with 369 acknowledgement of SETs received (for example as shown in Figure 6): 371 POST /Events HTTP/1.1 372 Host: notify.idp.example.com 373 Content-Type: application/json 375 { 376 "ack": [ 377 "4d3559ec67504aaba65d40b0363faad8", 378 "3d0c3cf797584bd193bd0fb1bd4e7d30" 379 ], 380 "maxEvents": 0, 381 "returnImmediately": true 382 } 384 Figure 3: Example Acknowledge-Only Request 386 2.4.3. Poll with Acknowledgement 388 This variation allows a recipient thread to simultaneously 389 acknowledge previously received SETs and wait for the next group of 390 SETs in a single request. 392 The following is a non-normative example poll with acknowledgement of 393 the SETs received in Figure 6: 395 POST /Events HTTP/1.1 396 Host: notify.idp.example.com 397 Content-Type: application/json 399 { 400 "ack": [ 401 "4d3559ec67504aaba65d40b0363faad8", 402 "3d0c3cf797584bd193bd0fb1bd4e7d30" 403 ], 404 "returnImmediately": false 405 } 407 Figure 4: Example Poll with Acknowledgement and No Errors 409 In the above acknowledgement, the SET Recipient has acknowledged 410 receipt of two SETs and has indicated it wants to wait until the next 411 SET is available. 413 2.4.4. Poll with Acknowledgement and Errors 415 In the case where errors were detected in previously delivered SETs, 416 the SET Recipient MAY use the "setErrs" member to communicate the 417 errors in the following poll request. 419 The following is a non-normative example of a response acknowledging 420 one successfully received SET and one SET with an error from the two 421 SETs received in Figure 6: 423 POST /Events HTTP/1.1 424 Host: notify.idp.example.com 425 Content-Language: en-US 426 Content-Type: application/json 428 { 429 "ack": ["3d0c3cf797584bd193bd0fb1bd4e7d30"], 430 "setErrs": { 431 "4d3559ec67504aaba65d40b0363faad8": { 432 "err": "authentication_failed", 433 "description": "The SET could not be authenticated" 434 } 435 }, 436 "returnImmediately": true 437 } 439 Figure 5: Example Poll Acknowledgement with Error 441 2.5. Poll Response 443 In response to a valid poll request, the service provider MAY respond 444 immediately if SETs are available to be delivered. If no SETs are 445 available at the time of the request, the SET Transmitter SHALL delay 446 responding until a SET is available or the timeout interval has 447 elapsed unless the poll request parameter "returnImmediately" is 448 present with the value "true". 450 As described in Section 2.3, a JSON document is returned containing 451 members including "sets", which SHALL contain zero or more SETs. 453 The following is a non-normative example response to the request 454 shown in Section 2.4. This example shows two SETs being returned: 456 HTTP/1.1 200 OK 457 Content-Type: application/json 459 { 460 "sets": { 461 "4d3559ec67504aaba65d40b0363faad8": 462 "eyJhbGciOiJub25lIn0. 463 eyJqdGkiOiI0ZDM1NTllYzY3NTA0YWFiYTY1ZDQwYjAzNjNmYWFkOCIsImlhdCI6MTQ 464 1ODQ5NjQwNCwiaXNzIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tIiwiYXVkIjpbIm 465 h0dHBzOi8vc2NpbS5leGFtcGxlLmNvbS9GZWVkcy85OGQ1MjQ2MWZhNWJiYzg3OTU5M 466 2I3NzU0IiwiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tL0ZlZWRzLzVkNzYwNDUxNmIx 467 ZDA4NjQxZDc2NzZlZTciXSwiZXZlbnRzIjp7InVybjppZXRmOnBhcmFtczpzY2ltOmV 468 2ZW50OmNyZWF0ZSI6eyJyZWYiOiJodHRwczovL3NjaW0uZXhhbXBsZS5jb20vVXNlcn 469 MvNDRmNjE0MmRmOTZiZDZhYjYxZTc1MjFkOSIsImF0dHJpYnV0ZXMiOlsiaWQiLCJuY 470 W1lIiwidXNlck5hbWUiLCJwYXNzd29yZCIsImVtYWlscyJdfX19.", 471 "3d0c3cf797584bd193bd0fb1bd4e7d30": 472 "eyJhbGciOiJub25lIn0. 473 eyJqdGkiOiIzZDBjM2NmNzk3NTg0YmQxOTNiZDBmYjFiZDRlN2QzMCIsImlhdCI6MTQ 474 1ODQ5NjAyNSwiaXNzIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tIiwiYXVkIjpbIm 475 h0dHBzOi8vamh1Yi5leGFtcGxlLmNvbS9GZWVkcy85OGQ1MjQ2MWZhNWJiYzg3OTU5M 476 2I3NzU0IiwiaHR0cHM6Ly9qaHViLmV4YW1wbGUuY29tL0ZlZWRzLzVkNzYwNDUxNmIx 477 ZDA4NjQxZDc2NzZlZTciXSwic3ViIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tL1V 478 zZXJzLzQ0ZjYxNDJkZjk2YmQ2YWI2MWU3NTIxZDkiLCJldmVudHMiOnsidXJuOmlldG 479 Y6cGFyYW1zOnNjaW06ZXZlbnQ6cGFzc3dvcmRSZXNldCI6eyJpZCI6IjQ0ZjYxNDJkZ 480 jk2YmQ2YWI2MWU3NTIxZDkifSwiaHR0cHM6Ly9leGFtcGxlLmNvbS9zY2ltL2V2ZW50 481 L3Bhc3N3b3JkUmVzZXRFeHQiOnsicmVzZXRBdHRlbXB0cyI6NX19fQ." 482 } 483 } 485 Figure 6: Example Poll Response 487 In the above example, two SETs whose "jti" values are 488 "4d3559ec67504aaba65d40b0363faad8" and 489 "3d0c3cf797584bd193bd0fb1bd4e7d30" are delivered. 491 The following is a non-normative example response to the request 492 shown in Section 2.4.1, which indicates that no new SETs or 493 unacknowledged SETs are available: 495 HTTP/1.1 200 OK 496 Content-Type: application/json 498 { 499 "sets": {} 500 } 502 Figure 7: Example No SETs Poll Response 504 Upon receiving the JSON document (e.g., as shown in Figure 6), the 505 SET Recipient parses and verifies the received SETs and notifies the 506 SET Transmitter of successfully received SETs and SETs with errors 507 via the next poll request to the SET Transmitter, as described in 508 Section 2.4.3 or Section 2.4.4. 510 2.5.1. Poll Error Response 512 In the event of a general HTTP error condition in the context of 513 processing a poll request, the service provider responds with the 514 applicable HTTP Response Status Code, as defined in Section 6 of 515 [RFC7231]. 517 Service providers MAY respond to any invalid poll request with an 518 HTTP Response Status Code of 400 (Bad Request) even when a more 519 specific code might apply, for example if the service provider deemed 520 that a more specific code presented an information disclosure risk. 521 When no more specific code might apply, the service provider SHALL 522 respond to an invalid poll request with an HTTP Status Code of 400. 524 The response body for responses to invalid poll requests is left 525 undefined, and its contents SHOULD be ignored. 527 The following is a non-normative example of a response to an invalid 528 poll request: 530 HTTP/1.1 400 Bad Request 532 Example Poll Error Response 534 2.6. Error Response Handling 536 If a SET is invalid, error codes from the IANA "Security Event Token 537 Delivery Error Codes" registry established by 538 [I-D.ietf-secevent-http-push] are used in error responses. As 539 described in Section 2.3 of [I-D.ietf-secevent-http-push], an error 540 response is a JSON object providing details about the error that 541 includes the following name/value pairs: 543 err 544 A value from the IANA "Security Event Token Delivery Error Codes" 545 registry that identifies the error. 547 description 548 A human-readable string that provides additional diagnostic 549 information. 551 When included as part of a batch of SETs, the above JSON is included 552 as part of the "setErrs" member, as defined in Section 2.2 and 553 Section 2.4.4. 555 When the SET Recipient includes one or more error responses in a 556 request to the SET Transmitter, it must also include in the request a 557 "Content-Language" header field whose value indicates the language of 558 the error descriptions included in the request. The method of 559 language selection in the case when the SET Recipient can provide 560 error messages in multiple languages is out of scope for this 561 specification. 563 3. Authentication and Authorization 565 The SET delivery method described in this specification is based upon 566 HTTP over TLS [RFC2818] and standard HTTP authentication and 567 authorization schemes, as per [RFC7235]. The TLS server certificate 568 MUST be validated using DNS-ID [RFC6125] and/or DANE [RFC6698]. As 569 per Section 4.1 of [RFC7235], a SET delivery endpoint SHALL indicate 570 supported HTTP authentication schemes via the "WWW-Authenticate" 571 header field when using HTTP authentication. 573 Authorization for the eligibility to provide actionable SETs can be 574 determined by using the identity of the SET Issuer, validating the 575 identity of the SET Transmitter, or via other employed authentication 576 methods. Likewise, the SET Transmitter may choose to validate the 577 identity of the SET Recipient, perhaps using mutual TLS. Because 578 SETs are not commands, SET Recipients are free to ignore SETs that 579 are not of interest after acknowledging their receipt. 581 4. Security Considerations 582 4.1. Authentication Using Signed SETs 584 JWS signed SETs can be used (see [RFC7515] and Section 5 of 585 [RFC8417]) to enable the SET Recipient to validate that the SET 586 Issuer is authorized to provide actionable SETs. 588 4.2. HTTP Considerations 590 SET delivery depends on the use of Hypertext Transfer Protocol and is 591 thus subject to the security considerations of HTTP Section 9 of 592 [RFC7230] and its related specifications. 594 4.3. Confidentiality of SETs 596 SETs may contain sensitive information, including Personally 597 Identifiable Information (PII), or be distributed through third 598 parties. In such cases, SET Transmitters and SET Recipients MUST 599 protect the confidentiality of the SET contents. In some use cases, 600 using TLS to secure the transmitted SETs will be sufficient. In 601 other use cases, encrypting the SET as described in JWE [RFC7516] 602 will also be required. The Event delivery endpoint MUST support at 603 least TLS version 1.2 [RFC5246] and SHOULD support the newest version 604 of TLS that meets its security requirements, which as of the time of 605 this publication is TLS 1.3 [RFC8446]. The client MUST perform a 606 TLS/SSL server certificate check using DNS-ID [RFC6125] and/or DANE 607 [RFC6698]. How a SET Recipient determines the expected service 608 identity to match the SET Transmitter's server certificate against is 609 out of scope for this document. The implementation security 610 considerations for TLS in "Recommendations for Secure Use of TLS and 611 DTLS" [RFC7525] MUST be followed. 613 4.4. Access Token Considerations 615 If HTTP Authentication is performed using OAuth access tokens 616 [RFC6749], implementers MUST take into account the threats and 617 countermeasures documented in Section 8 of [RFC7521]. 619 4.4.1. Bearer Token Considerations 621 Transmitting Bearer tokens [RFC6750] using TLS helps prevent their 622 interception. 624 Bearer tokens SHOULD have a limited lifetime that can be determined 625 directly or indirectly (e.g., by checking with a validation service) 626 by the service provider. By expiring tokens, clients are forced to 627 obtain a new token (which usually involves re-authentication) for 628 continued authorized access. For example, in OAuth 2.0, a client MAY 629 use an OAuth refresh token to obtain a new bearer token after 630 authenticating to an authorization server, per Section 6 of 631 [RFC6749]. 633 Implementations supporting OAuth bearer tokens need to factor in 634 security considerations of this authorization method [RFC7521]. 635 Since security is only as good as the weakest link, implementers also 636 need to consider authentication choices coupled with OAuth bearer 637 tokens. The security considerations of the default authentication 638 method for OAuth bearer tokens, HTTP Basic, are well documented in 639 [RFC7617], therefore implementers are encouraged to prefer stronger 640 authentication methods. 642 5. Privacy Considerations 644 SET Transmitters should attempt to deliver SETs that are targeted to 645 the specific business and protocol needs of subscribers. 647 When sharing personally identifiable information or information that 648 is otherwise considered confidential to affected users, SET 649 Transmitters and Recipients MUST have the appropriate legal 650 agreements and user consent or terms of service in place. 651 Furthermore, data that needs confidentiality protection MUST be 652 encrypted, at least with TLS and sometimes also using JSON Web 653 Encryption (JWE) [RFC7516]. 655 In some cases, subject identifiers themselves may be considered 656 sensitive information, such that their inclusion within a SET may be 657 considered a violation of privacy. SET Issuers and SET Transmitters 658 should consider the ramifications of sharing a particular subject 659 identifier with a SET Recipient (e.g., whether doing so could enable 660 correlation and/or de-anonymization of data) and choose appropriate 661 subject identifiers for their use cases. 663 6. IANA Considerations 665 This specification requires no IANA actions. 667 7. References 669 7.1. Normative References 671 [I-D.ietf-secevent-http-push] 672 Backman, A., Jones, M., Scurtescu, M., Ansari, M., and A. 673 Nadalin, "Push-Based Security Event Token (SET) Delivery 674 Using HTTP", draft-ietf-secevent-http-push-12 (work in 675 progress), June 2020. 677 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 678 Requirement Levels", BCP 14, RFC 2119, 679 DOI 10.17487/RFC2119, March 1997, 680 . 682 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, 683 DOI 10.17487/RFC2818, May 2000, 684 . 686 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 687 (TLS) Protocol Version 1.2", RFC 5246, 688 DOI 10.17487/RFC5246, August 2008, 689 . 691 [RFC6125] Saint-Andre, P. and J. Hodges, "Representation and 692 Verification of Domain-Based Application Service Identity 693 within Internet Public Key Infrastructure Using X.509 694 (PKIX) Certificates in the Context of Transport Layer 695 Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March 696 2011, . 698 [RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication 699 of Named Entities (DANE) Transport Layer Security (TLS) 700 Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August 701 2012, . 703 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 704 Protocol (HTTP/1.1): Semantics and Content", RFC 7231, 705 DOI 10.17487/RFC7231, June 2014, 706 . 708 [RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web 709 Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May 710 2015, . 712 [RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)", 713 RFC 7516, DOI 10.17487/RFC7516, May 2015, 714 . 716 [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token 717 (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, 718 . 720 [RFC7521] Campbell, B., Mortimore, C., Jones, M., and Y. Goland, 721 "Assertion Framework for OAuth 2.0 Client Authentication 722 and Authorization Grants", RFC 7521, DOI 10.17487/RFC7521, 723 May 2015, . 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 [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol 746 Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, 747 . 749 7.2. Informative References 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 [RFC7617] Reschke, J., "The 'Basic' HTTP Authentication Scheme", 777 RFC 7617, DOI 10.17487/RFC7617, September 2015, 778 . 780 Appendix A. Unencrypted Transport Considerations 782 Earlier versions of this specification made the use of TLS optional 783 and described security and privacy considerations resulting from use 784 of unencrypted HTTP as the underlying transport. When the working 785 group decided to mandate usage HTTP over TLS, it also decided to 786 preserve the description of these considerations in a non-normative 787 manner. 789 The considerations for using unencrypted HTTP with this protocol are 790 the same as those described in Appendix A of 791 [I-D.ietf-secevent-http-push], and are therefore not repeated here. 793 Appendix B. Other Streaming Specifications 795 [[ NOTE TO THE RFC EDITOR: This section to be removed prior to 796 publication ]] 798 A number of pub/sub, queuing, and streaming systems were reviewed as 799 possible solutions or as input to the current draft. These are 800 listed in Appendix B of [I-D.ietf-secevent-http-push], and are 801 therefore not repeated here. 803 Appendix C. Acknowledgments 805 The editors would like to thank the members of the SCIM working 806 group, which began discussions of provisioning events starting with 807 draft-hunt-scim-notify-00 in 2015. We would like to thank Phil Hunt 808 and the other the authors of draft-ietf-secevent-delivery-02, upon 809 which this specification is based. We would like to thank the 810 participants in the SecEvents working group for their contributions 811 to this specification. 813 Additionally, we would like to thank the following individuals for 814 their reviews of the specification: Roman Danyliw, Martin Duke, 815 Benjamin Kaduk, Erik Kline, Murray Kucherawy, Warren Kumari, Barry 816 Leiba, Mark Nottingham, Alvaro Retana, Yaron Sheffer, Valery Smyslov, 817 Robert Sparks, Eric Vyncke, and Robert Wilton. 819 Appendix D. Change Log 821 [[ to be removed by the RFC Editor before publication as an RFC ]] 823 Draft 00 - AB - Based on draft-ietf-secevent-delivery-02 with the 824 following additions: 826 o Renamed to "Poll-Based SET Token Delivery Using HTTP" 828 o Removed references to the HTTP Push delivery method. 830 Draft 01 - mbj: 832 o Addressed problems identified in my 18-Jul-18 review message 833 titled "Issues for both the Push and Poll Specs". 835 o Changes to align terminology with RFC 8417, for instance, by using 836 the already defined term SET Recipient rather than SET Receiver. 838 o Applied editorial and minor normative corrections. 840 o Updated Marius' contact information. 842 o Begun eliminating redundancies between this specification and 843 "Push-Based Security Event Token (SET) Delivery Using HTTP" 844 [I-D.ietf-secevent-http-push], referencing, rather that 845 duplicating common normative text. 847 Draft 02 - mbj: 849 o Removed vestigial language remaining from when the push and poll 850 delivery methods were defined in a common specification. 852 o Replaced remaining uses of the terms Event Transmitter and Event 853 Recipient with the correct terms SET Transmitter and SET 854 Recipient. 856 o Removed uses of the unnecessary term "Event Stream". 858 o Removed dependencies between the semantics of "maxEvents" and 859 "returnImmediately". 861 o Said that PII in SETs is to be encrypted with TLS, JWE, or both. 863 o Corrected grammar and spelling errors. 865 Draft 03 - mbj: 867 o Corrected uses of "attribute" to "member" when describing JSON 868 objects. 870 o Further alignment with the push draft. 872 Draft 04 - AB + mbj 874 o Referenced SET Transmitter definition in http-push. 876 o Removed incorrect normative text regarding SET construction. 878 o Consolidated general out-of-scope items under Introduction. 880 o Removed unnecessary HTTP headers in examples and added Content- 881 Type. 883 o Added Content-Language requirement for error descriptions, 884 aligning with http-push. 886 o Stated that bearer tokens SHOULD have a limited lifetime. 888 o Minor editorial fixes. 890 Draft 05 - AB + mbj 892 o Added normative text defining how to respond to invalid poll 893 requests. 895 o Addressed shepherd comments by Yaron Sheffer. 897 Draft 06 - mbj 899 o Addressed nits identified by the idnits tool. 901 Draft 07 - mbj 903 o Addressed area director review comments by Benjamin Kaduk. 905 Draft 08 - mbj + AB 907 o Corrected editorial nits. 909 Draft 09 - AB 911 o Addressed area director review comments by Benjamin Kaduk: 913 * Added text clarifying that determining the SET Recipient's 914 service identity is out of scope. 916 * Removed unelaborated reference to use of authentication to 917 prevent DoS attacks. 919 Draft 10 - mbj 921 o Addressed SecDir review comments by Valery Smyslov on draft-ietf- 922 secevent-http-push-10 that also applied here. 924 o Addressed IETF last call comments by Mark Nottingham. 926 o Addressed GenArt review comments by Robert Sparks. 928 Draft 11 - mbj 930 o Revised to unambiguously require the use of TLS, while preserving 931 descriptions of precautions needed for non-TLS use in an appendix. 933 Draft 12 - mbj 935 o Addressed IESG comments. 937 Authors' Addresses 939 Annabelle Backman (editor) 940 Amazon 942 Email: richanna@amazon.com 944 Michael B. Jones (editor) 945 Microsoft 947 Email: mbj@microsoft.com 948 URI: https://self-issued.info/ 950 Marius Scurtescu 951 Coinbase 953 Email: marius.scurtescu@coinbase.com 955 Morteza Ansari 956 Cisco 958 Email: morteza.ansari@cisco.com 959 Anthony Nadalin 960 Microsoft 962 Email: tonynad@microsoft.com