idnits 2.17.1 draft-ietf-dmarc-failure-reporting-01.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** The document seems to lack an IANA Considerations section. (See Section 2.2 of https://www.ietf.org/id-info/checklist for how to handle the case when there are no actions for IANA.) -- The draft header indicates that this document obsoletes RFC7489, but the abstract doesn't seem to mention this, which it should. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (18 February 2021) is 1162 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'CFWS' is mentioned on line 182, but not defined == Outdated reference: A later version (-30) exists of draft-ietf-dmarc-dmarcbis-00 == Outdated reference: A later version (-14) exists of draft-ietf-dmarc-aggregate-reporting-00 Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 DMARC Working Group S. M. Jones, Ed. 3 Internet-Draft DMARC.org 4 Obsoletes: 7489 (if approved) A. Vesely, Ed. 5 Intended status: Standards Track Tana 6 Expires: 22 August 2021 18 February 2021 8 Domain-based Message Authentication, Reporting, and Conformance (DMARC) 9 Failure Reporting 10 draft-ietf-dmarc-failure-reporting-01 12 Abstract 14 Domain-based Message Authentication, Reporting, and Conformance 15 (DMARC) is a scalable mechanism by which a domain owner can request 16 feedback about email messages using their domain in the From: address 17 field. This document describes "failure reports," or "failed message 18 reports," which provide details about individual messages that failed 19 to authenticate according to the DMARC mechanism. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at https://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on 22 August 2021. 38 Copyright Notice 40 Copyright (c) 2021 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 45 license-info) in effect on the date of publication of this document. 46 Please review these documents carefully, as they describe your rights 47 and restrictions with respect to this document. Code Components 48 extracted from this document must include Simplified BSD License text 49 as described in Section 4.e of the Trust Legal Provisions and are 50 provided without warranty as described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 2. Terminology and Definitions . . . . . . . . . . . . . . . . . 3 56 3. Failure Reports . . . . . . . . . . . . . . . . . . . . . . . 3 57 3.1. Reporting Format Update . . . . . . . . . . . . . . . . . 4 58 3.2. Verifying External Destinations . . . . . . . . . . . . . 5 59 3.3. Transport . . . . . . . . . . . . . . . . . . . . . . . . 5 60 4. Privacy Considerations . . . . . . . . . . . . . . . . . . . 5 61 4.1. Data Exposure Considerations . . . . . . . . . . . . . . 5 62 4.2. Report Recipients . . . . . . . . . . . . . . . . . . . . 6 63 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 64 6. Normative References . . . . . . . . . . . . . . . . . . . . 7 65 7. Informative References . . . . . . . . . . . . . . . . . . . 7 66 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 7 67 A.1. Entire Domain, Monitoring Only, Per-Message Reports . . . 8 68 A.2. Per-Message Failure Reports Directed to Third Party . . . 9 69 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 10 70 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 11 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 73 1. Introduction 75 Domain-based Message Authentication, Reporting, and Conformance 76 (DMARC) [I-D.ietf-dmarc-dmarcbis] is a scalable mechanism by which a 77 mail-originating organization can express domain-level policies and 78 preferences for message validation, disposition, and reporting, that 79 a mail-receiving organization can use to improve mail handling. This 80 document focuses on one type of reporting that can be requested under 81 DMARC. 83 Failure reports provide detailed information about the failure of a 84 single message or a group of similar messages failing for the same 85 reason. They are meant to aid in cases where a domain owner is 86 unable to detect why failures reported in aggregate form did occur. 87 It is important to note these reports can contain either the header 88 or the entire content of a failed message, which in turn may contain 89 personally identifiable information, which should be considered when 90 deciding whether to generate such reports. 92 2. Terminology and Definitions 94 This section defines terms used in the rest of the document. 96 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 97 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 98 "OPTIONAL" in this document are to be interpreted as described in BCP 99 14 [RFC2119] [RFC8174] when, and only when, they appear in all 100 capitals, as shown here. 102 Readers are expected to be familiar with the contents of 103 [I-D.ietf-dmarc-dmarcbis], specifically the terminology and 104 definitions section. 106 3. Failure Reports 108 Failure reports can supply more detailed information about messages 109 that failed to authenticate, enabling the Domain Owner to determine 110 exactly what might be causing those specific failures. 112 Failure reports are normally generated and sent almost immediately 113 after the Mail Receiver detects a DMARC failure. Rather than waiting 114 for an aggregate report, these reports are useful for quickly 115 notifying the Domain Owners when there is an authentication failure. 116 Whether the failure is due to an infrastructure problem or the 117 message is inauthentic, failure reports also provide more information 118 about the failed message than is available in an aggregate report. 120 These reports should include as much of the message header and body 121 as possible, consistent with the reporting party's privacy policies, 122 to enable the Domain Owner to diagnose the authentication failure. 124 When a Domain Owner requests failure reports for the purpose of 125 forensic analysis, and the Mail Receiver is willing to provide such 126 reports, the Mail Receiver generates and sends a message using the 127 format described in [RFC6591]; this document updates that reporting 128 format, as described in Section 3.1. 130 The destination(s) and nature of the reports are defined by the "ruf" 131 and "fo" tags as defined in Section 6.3 of [I-D.ietf-dmarc-dmarcbis]. 133 Where multiple URIs are selected to receive failure reports, the 134 report generator MUST make an attempt to deliver to each of them. 136 An obvious consideration is the denial-of-service attack that can be 137 perpetrated by an attacker who sends numerous messages purporting to 138 be from the intended victim Domain Owner but that fail both SPF and 139 DKIM; this would cause participating Mail Receivers to send failure 140 reports to the Domain Owner or its delegate in potentially huge 141 volumes. Accordingly, participating Mail Receivers are encouraged to 142 aggregate these reports as much as is practical, using the Incidents 143 field of the Abuse Reporting Format ([RFC5965]). Various aggregation 144 techniques are possible, including the following: 146 * only send a report to the first recipient of multi-recipient 147 messages; 149 * store reports for a period of time before sending them, allowing 150 detection, collection, and reporting of like incidents; 152 * apply rate limiting, such as a maximum number of reports per 153 minute that will be generated (and the remainder discarded). 155 3.1. Reporting Format Update 157 Operators implementing this specification also implement an augmented 158 version of [RFC6591] as follows: 160 1. A DMARC failure report includes the following ARF header fields, 161 with the indicated normative requirement levels: 163 * Identity-Alignment (REQUIRED; defined below) 165 * Delivery-Result (OPTIONAL) 167 * DKIM-Domain, DKIM-Identity, DKIM-Selector (REQUIRED if the 168 message was signed by DKIM) 170 * DKIM-Canonicalized-Header, DKIM-Canonicalized-Body (OPTIONAL 171 if the message was signed by DKIM) 173 * SPF-DNS (REQUIRED) 175 2. The "Identity-Alignment" field is defined to contain a comma- 176 separated list of authentication mechanism names that produced an 177 aligned identity, or the keyword "none" if none did. ABNF: 179 id-align = "Identity-Alignment:" [CFWS] 180 ( "none" / 181 dmarc-method *( [CFWS] "," [CFWS] dmarc-method ) ) 182 [CFWS] 184 dmarc-method = ( "dkim" / "spf" ) 185 ; each may appear at most once in an id-align 187 3. Authentication Failure Type "dmarc" is defined, which is to be 188 used when a failure report is generated because some or all of 189 the authentication mechanisms failed to produce aligned 190 identifiers. Note that a failure report generator MAY also 191 independently produce an AFRF message for any or all of the 192 underlying authentication methods. 194 3.2. Verifying External Destinations 196 The procedure described for aggragate reports Section 2.1 of 197 [I-D.ietf-dmarc-aggregate-reporting] applies to failure reports as 198 well. 200 3.3. Transport 202 Email streams carrying DMARC failure reports SHOULD provide DMARC- 203 based authentication, so as to produce "dmarc=pass". This 204 requirement is a MUST in case the report is sent through a host 205 having a DMARC record with a ruf= tag. Indeed, special care must be 206 taken of authentication in that case, as failure to authenticate 207 failure reports may result in mail loops. 209 Reporters SHOULD rate limit the number of failure reports sent to any 210 recipient to avoid overloading recipient systems. Again, in case the 211 reports being sent are in turn at risk of being reported for DMARC 212 authentication failure, reporters MUST make sure that possible mail 213 loop are stopped. 215 4. Privacy Considerations 217 This section discusses issues specific to private data that may be 218 included in the DMARC reporting functions. 220 4.1. Data Exposure Considerations 222 Failed-message reporting provides message-specific details pertaining 223 to authentication failures. Individual reports can contain message 224 content as well as trace header fields. Domain Owners are able to 225 analyze individual reports and attempt to determine root causes of 226 authentication mechanism failures, gain insight into 227 misconfigurations or other problems with email and network 228 infrastructure, or inspect messages for insight into abusive 229 practices. 231 These reports may expose sender and recipient identifiers (e.g., 232 RFC5322.From addresses), and although the [RFC6591] format used for 233 failed-message reporting supports redaction, failed-message reporting 234 is capable of exposing the entire message to the report recipient. 236 Domain Owners requesting reports will receive information about mail 237 claiming to be from them, which includes mail that was not, in fact, 238 from them. Information about the final destination of mail where it 239 might otherwise be obscured by intermediate systems will therefore be 240 exposed. 242 When message-forwarding arrangements exist, Domain Owners requesting 243 reports will also receive information about mail forwarded to domains 244 that were not originally part of their messages' recipient lists. 245 This means that destination domains previously unknown to the Domain 246 Owner may now become visible. 248 Disclosure of information about the messages is being requested by 249 the entity generating the email in the first place, i.e., the Domain 250 Owner and not the Mail Receiver, so this may not fit squarely within 251 existing privacy policy provisions. For some providers, failed- 252 message reporting is viewed as a function similar to complaint 253 reporting about spamming or phishing and is treated similarly under 254 the privacy policy. Report generators (i.e., Mail Receivers) are 255 encouraged to review their reporting limitations under such policies 256 before enabling DMARC reporting. 258 4.2. Report Recipients 260 A DMARC record can specify that reports should be sent to an 261 intermediary operating on behalf of the Domain Owner. This is done 262 when the Domain Owner contracts with an entity to monitor mail 263 streams for abuse and performance issues. Receipt by third parties 264 of such data may or may not be permitted by the Mail Receiver's 265 privacy policy, terms of use, or other similar governing document. 266 Domain Owners and Mail Receivers should both review and understand if 267 their own internal policies constrain the use and transmission of 268 DMARC reporting. 270 Some potential exists for report recipients to perform traffic 271 analysis, making it possible to obtain metadata about the Receiver's 272 traffic. In addition to verifying compliance with policies, 273 Receivers need to consider that before sending reports to a third 274 party. 276 5. Security Considerations 278 Considerations discussed in Section 11 of [I-D.ietf-dmarc-dmarcbis] 279 apply. 281 In addition, note that Organizational Domains are only an 282 approximation to actual domain ownership. Therefore, reports may be 283 sent to someone unrelated to the actual sender or domain owner. That 284 makes considerations in Section 4.1 all the more relevant. 286 6. Normative References 288 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 289 Requirement Levels", BCP 14, RFC 2119, 290 DOI 10.17487/RFC2119, March 1997, 291 . 293 [RFC6591] Fontana, H., "Authentication Failure Reporting Using the 294 Abuse Reporting Format", RFC 6591, DOI 10.17487/RFC6591, 295 April 2012, . 297 [I-D.ietf-dmarc-dmarcbis] 298 Gustafsson, E., Herr, T., and J. Levine, "Domain-based 299 Message Authentication, Reporting, and Conformance 300 (DMARC)", Work in Progress, Internet-Draft, draft-ietf- 301 dmarc-dmarcbis-00, 11 November 2020, 302 . 305 [I-D.ietf-dmarc-aggregate-reporting] 306 Brotman, A., "DMARC Aggregate Reporting", Work in 307 Progress, Internet-Draft, draft-ietf-dmarc-aggregate- 308 reporting-00, 12 November 2020, 309 . 312 7. Informative References 314 [RFC5965] Shafranovich, Y., Levine, J., and M. Kucherawy, "An 315 Extensible Format for Email Feedback Reports", RFC 5965, 316 DOI 10.17487/RFC5965, August 2010, 317 . 319 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 320 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 321 May 2017, . 323 Appendix A. Examples 325 This section presents some examples related to the use of DMARC 326 reporting functions. 328 A.1. Entire Domain, Monitoring Only, Per-Message Reports 330 The owners of the domain "example.com" have deployed SPF and DKIM on 331 their messaging infrastructure. As described in, Appendix B.2.1 of 332 [I-D.ietf-dmarc-aggregate-reporting] they have used the aggregate 333 reporting to discover some messaging systems that had not yet 334 implemented DKIM correctly. However, they are still seeing periodic 335 authentication failures. In order to diagnose these intermittent 336 problems, they wish to request per-message failure reports when 337 authentication failures occur. 339 Not all Receivers will honor such a request, but the Domain Owner 340 feels that any reports it does receive will be helpful enough to 341 justify publishing this record. The default per-message report 342 format ([RFC6591]) meets the Domain Owner's needs in this scenario. 344 The Domain Owner accomplishes this by adding the following to its 345 policy record: 347 * Per-message failure reports should be sent via email to the 348 address "auth-reports@example.com" ("ruf=mailto:auth- 349 reports@example.com") 351 The updated DMARC policy record might look like this when retrieved 352 using a common command-line tool (the output shown would appear on a 353 single line but is wrapped here for publication): 355 % dig +short TXT _dmarc.example.com. 356 "v=DMARC1; p=none; rua=mailto:dmarc-feedback@example.com; 357 ruf=mailto:auth-reports@example.com" 359 To publish such a record, the DNS administrator for the Domain Owner 360 might create an entry like the following in the appropriate zone file 361 (following the conventional zone file format): 363 ; DMARC record for the domain example.com 365 _dmarc IN TXT ( "v=DMARC1; p=none; " 366 "rua=mailto:dmarc-feedback@example.com; " 367 "ruf=mailto:auth-reports@example.com" ) 369 A.2. Per-Message Failure Reports Directed to Third Party 371 The Domain Owner from the previous example is maintaining the same 372 policy but now wishes to have a third party receive and process the 373 per-message failure reports. Again, not all Receivers will honor 374 this request, but those that do may implement additional checks to 375 validate that the third party wishes to receive the failure reports 376 for this domain. 378 The Domain Owner needs to alter its policy record from Appendix A.1 379 as follows: 381 * Per-message failure reports should be sent via email to the 382 address "auth-reports@thirdparty.example.net" ("ruf=mailto:auth- 383 reports@thirdparty.example.net") 385 The DMARC policy record might look like this when retrieved using a 386 common command-line tool (the output shown would appear on a single 387 line but is wrapped here for publication): 389 % dig +short TXT _dmarc.example.com. 390 "v=DMARC1; p=none; rua=mailto:dmarc-feedback@example.com; 391 ruf=mailto:auth-reports@thirdparty.example.net" 393 To publish such a record, the DNS administrator for the Domain Owner 394 might create an entry like the following in the appropriate zone file 395 (following the conventional zone file format): 397 ; DMARC record for the domain example.com 399 _dmarc IN TXT ( "v=DMARC1; p=none; " 400 "rua=mailto:dmarc-feedback@example.com; " 401 "ruf=mailto:auth-reports@thirdparty.example.net" ) 403 Because the address used in the "ruf" tag is outside the 404 Organizational Domain in which this record is published, conforming 405 Receivers will implement additional checks as described in 406 Section 3.2 of this document. In order to pass these additional 407 checks, the third party will need to publish an additional DNS record 408 as follows: 410 * Given the DMARC record published by the Domain Owner at 411 "_dmarc.example.com", the DNS administrator for the third party 412 will need to publish a TXT resource record at 413 "example.com._report._dmarc.thirdparty.example.net" with the value 414 "v=DMARC1;". 416 The resulting DNS record might look like this when retrieved using a 417 common command-line tool (the output shown would appear on a single 418 line but is wrapped here for publication): 420 % dig +short TXT example.com._report._dmarc.thirdparty.example.net 421 "v=DMARC1;" 423 To publish such a record, the DNS administrator for example.net might 424 create an entry like the following in the appropriate zone file 425 (following the conventional zone file format): 427 ; zone file for thirdparty.example.net 428 ; Accept DMARC failure reports on behalf of example.com 430 example.com._report._dmarc IN TXT "v=DMARC1;" 432 Intermediaries and other third parties should refer to Section 3.2 433 for the full details of this mechanism. 435 Appendix B. Change Log 437 [RFC Editor: Please remove this section prior to publication.] 439 00 to 01 440 * Replace references to RFC7489 with references to I-D.ietf- 441 dmarc-dmarcbis. 443 * Replace the 2nd paragraph in the Introduction with the text 444 proposed by Ned for Ticket #55, which enjoys some consensus: 445 https://mailarchive.ietf.org/arch/msg/dmarc/ 446 HptVyJ9SgrfxWRbeGwORagPrhCw 448 * Strike a spurious sentence about criticality of feedback, 449 which was meant for feedback in general, not failure reports. 450 In fact, failure reports are not critical to establishing and 451 maintaining accurate authentication deployments. Still 452 attributable to Ticket #55. 454 * Remove the content of section "Verifying External 455 Destinations" and refer to I-D.ietf-dmarc-aggregate-reporting. 457 * Remove the content of section "Security Considerations" and 458 refer to I-D.ietf-dmarc-dmarcbis. 460 * Slightly tweak the wording of the example in Appendix A.1 so 461 that it makes sense standing alone. 463 * Remove the sentence containing "must include any URI(s)", as 464 the issue arose https://mailarchive.ietf.org/arch/msg/dmarc/ 465 mFk0qiTCy8tzghRvcxus01W_Blw. 467 * Add paragraph in Security Considerations, noting that note 468 that Organizational Domains are only an approximation... 470 * Add a Transport section, mentioning DMARC conformance and 471 failure report mail loops (Ticket #28). 473 Acknowledgements 475 DMARC and the draft version of this document submitted to the 476 Independent Submission Editor were the result of lengthy efforts by 477 an informal industry consortium: DMARC.org (see http://dmarc.org 478 (http://dmarc.org)). Participating companies included Agari, 479 American Greetings, AOL, Bank of America, Cloudmark, Comcast, 480 Facebook, Fidelity Investments, Google, JPMorgan Chase & Company, 481 LinkedIn, Microsoft, Netease, PayPal, ReturnPath, The Trusted Domain 482 Project, and Yahoo!. Although the contributors and supporters are 483 too numerous to mention, notable individual contributions were made 484 by J. Trent Adams, Michael Adkins, Monica Chew, Dave Crocker, Tim 485 Draegen, Steve Jones, Franck Martin, Brett McDowell, and Paul Midgen. 486 The contributors would also like to recognize the invaluable input 487 and guidance that was provided early on by J.D. Falk. 489 Additional contributions within the IETF context were made by Kurt 490 Anderson, Michael Jack Assels, Les Barstow, Anne Bennett, Jim Fenton, 491 J. Gomez, Mike Jones, Scott Kitterman, Eliot Lear, John Levine, S. 492 Moonesamy, Rolf Sonneveld, Henry Timmes, and Stephen J. Turnbull. 494 Authors' Addresses 496 Steven M Jones (editor) 497 DMARC.org 499 Email: smj@dmarc.org 501 Alessandro Vesely (editor) 502 Tana 504 Email: vesely@tana.it