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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force P. Hallam-Baker 3 Internet-Draft Comodo Group Inc. 4 Intended status: Standards Track R. Stradling 5 Expires: October 23, 2012 Comodo CA Ltd. 6 April 21, 2012 8 DNS Certification Authority Authorization (CAA) Resource Record 9 draft-ietf-pkix-caa-06 11 Abstract 13 The Certification Authority Authorization (CAA) DNS Resource Record 14 allows a DNS domain name holder to specify the certificate signing 15 certificate(s) authorized to issue certificates for that domain. CAA 16 resource records allow a public Certification Authority to implement 17 additional controls to reduce the risk of unintended certificate mis- 18 issue. 20 Status of this Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on October 23, 2012. 37 Copyright Notice 39 Copyright (c) 2012 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 56 1.2. Defined Terms . . . . . . . . . . . . . . . . . . . . . . 3 57 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 58 2.1. The CAA RR type . . . . . . . . . . . . . . . . . . . . . 5 59 3. Certification Authority Processing . . . . . . . . . . . . . . 7 60 3.1. Canonical Domain Name . . . . . . . . . . . . . . . . . . 8 61 3.2. Use of DNS Security . . . . . . . . . . . . . . . . . . . 8 62 3.3. Archive . . . . . . . . . . . . . . . . . . . . . . . . . 8 63 4. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . 8 64 4.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 8 65 4.1.1. Canonical Presentation Format . . . . . . . . . . . . 10 66 4.2. CAA issue Property . . . . . . . . . . . . . . . . . . . . 10 67 4.3. CAA iodef Property . . . . . . . . . . . . . . . . . . . . 11 68 5. Security Considerations . . . . . . . . . . . . . . . . . . . 12 69 5.1. Mis-Issue by Authorized Certification Authority . . . . . 12 70 5.2. Suppression or spoofing of CAA records . . . . . . . . . . 13 71 5.2.1. Certification Authorities . . . . . . . . . . . . . . 13 72 5.3. Denial of Service . . . . . . . . . . . . . . . . . . . . 13 73 5.3.1. Issuer . . . . . . . . . . . . . . . . . . . . . . . . 13 74 5.4. Abuse of the Critical Flag . . . . . . . . . . . . . . . . 14 75 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 76 6.1. Registration of the CAA Resource Record Type . . . . . . . 14 77 6.2. Certification Authority Authorization Properties . . . . . 14 78 7. Normative References . . . . . . . . . . . . . . . . . . . . . 15 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 81 1. Definitions 83 1.1. Requirements Language 85 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 86 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 87 document are to be interpreted as described in RFC 2119 [RFC2119]. 89 1.2. Defined Terms 91 The following terms are used in this document: 93 Authorization Entry An authorization assertion that grants or denies 94 a specific set of permissions to a specific group of entities. 96 Canonical Domain Name A Domain Name that is not an alias. 98 Canonical Domain Name Value The value of a Canonical Domain Name. 99 The value resulting from applying alias transformations to a 100 Domain Name that is not canonical. 102 Certificate An X.509 Certificate, as specified in RFC 5280 103 [RFC5280]. 105 Certificate Evaluator A party other than a Relying Party that 106 evaluates the trustworthiness of certificates issued by 107 Certification Authorities. 109 Certification Authority (CA) An Issuer that issues Certificates in 110 accordance with a specified Certification Policy. 112 Certification Policy (CP) Specifies the criteria that a 113 Certification Authority undertakes to meet in its issue of 114 certificates. 116 Certification Practices Statement (CPS) Specifies the means by which 117 the criteria of the Certification Policy are met. In most cases 118 this will be the document against which the operations of the 119 Certification Authority are audited. 121 Domain The set of resources associated with a DNS Domain Name. 123 Domain Name A DNS Domain name as specified in RFC 1035 [RFC1035] and 124 revisions. 126 Domain Name System (DNS) The Internet naming system specified in RFC 127 1035 [RFC1035] and revisions. 129 DNS Security (DNSSEC) Extensions to the DNS that provide 130 authentication services as specified in RFC 4033 [RFC4033] and 131 revisions. 133 Issuer An entity that issues Certificates. 135 Extended Issuer Authorization Set The most specific Issuer 136 Authorization Set that is active for a domain. This is either the 137 Issuer Authorization Set for the domain itself, or if that is 138 empty, the Issuer Authorization Set for the corresponding Public 139 Delegation Point. 141 Issuer Authorization Set The set of Authorization Entries for a 142 domain name that are flagged for use by Issuers. Analogous to an 143 Access Control List but with no ordering specified. 145 Public Delegation Point The Domain Name suffix under which DNS names 146 are delegated by a public DNS registry such as a Top Level 147 Directory. 149 Public Key Infrastructure X.509 (PKIX) Standards and specifications 150 issued by the IETF that apply the X.509 [X.509] certificate 151 standards specified by the ITU to Internet applications as 152 specified in RFC 5280 [RFC5280] and related documents. 154 Resource Record (RR) A set of attributes bound to a Domain Name. 156 Relying Party A party that makes use of an application whose 157 operation depends on use of a Certificate for making a security 158 decision. 160 Relying Application An application whose operation depends on use of 161 a Certificate for making a security decision. 163 2. Introduction 165 The Certification Authority Authorization (CAA) DNS Resource Record 166 allows a DNS domain name holder to specify the Certification 167 Authorities authorized to issue certificates for that domain. 168 Publication of CAA resource records allow a public Certification 169 Authority (CA) to implement additional controls to reduce the risk of 170 unintended certificate mis-issue. 172 Conformance with a published CAA record is a necessary but not 173 sufficient condition for issue of a certificate. Before issuing a 174 certificate, a PKIX CA is required to validate the request according 175 to the policies set out in its Certificate Policy Statement. In the 176 case of a public CA that validates certificate requests as a third 177 party, the certificate will be typically issued under a public root 178 certificate embedded in one or more relevant Relying Applications. 180 Criteria for inclusion of embedded root certificates in applications 181 are outside the scope of this document but typically require the CA 182 to publish a Certificate Practices Statement (CPS) that specifies how 183 the requirements of the Certificate Policy (CP) are achieved and 184 provide an annual audit statement of their performance against their 185 CPS performed by an independent third party auditor. 187 Verification of certificate requests against CAA records published in 188 the corresponding domain is currently under consideration by the CA- 189 Browser Forum as a required element of the Basic Requirements for 190 Certificate issue. 192 CAA records only describe the current state of Certification 193 Authority certificate issue authority. Since a certificate is 194 typically valid for at least a year, it is possible that a 195 certificate that is not conformant with the CAA records currently 196 published was conformant with the CAA records published at the time 197 that it was issued. Thus Relying Applications MUST NOT use failure 198 to conform to currently published CAA records specifying issue 199 authorization as a certificate validity criteria. 201 CAA Records MAY be used by Certificate Evaluators as a possible 202 indicator of a security policy violation. Such use SHOULD take 203 account of the possibility that the published CAA records changed 204 between the time the certificate was issued and the time that they 205 were observed by the Certificate Evaluator. 207 2.1. The CAA RR type 209 A CAA RR publishes a CAA property entry that corresponds to the 210 specified domain name. Multiple property entries MAY be associated 211 with the same domain name by publishing multiple CAA RRs at that 212 domain name. Each property entry MAY be tagged with one or more of 213 the following flag values: 215 Critical If set, indicates that the corresponding property entry tag 216 MUST be understood if the semantics of the CAA record are to be 217 correctly understood by the specified audience. 219 Issuers MUST NOT issue certificates for a domain if the Extended 220 Issuer Authorization Set contains unknown property entry tags that 221 have both the Issuer and Critical bits set. 223 The following properties are defined: 225 issue [; ]* The issue property entry 226 declares an authorization entry granting authorization to issue to 227 the holder of the specified domain name or a party acting under 228 the express written authority of the holder of the domain name. 230 iodef Specifies a URL to which an issuer MAY report 231 certificate issue requests that are inconsistent with the issuer's 232 Certification Practices or Certification Policy or that a 233 certificate evaluator may use to report observation of a possible 234 policy violation. The IODEF format is used. [RFC5070] 236 The following example informs CAs that certificates MUST NOT be 237 issued except by the holder of the domain name 'ca.example.net' or an 238 authorized agent thereof. Since the policy is published at the 239 Public Delegation Point, the policy applies to all subordinate 240 domains under example.com. 242 $ORIGIN example.com 243 . CAA 0 issue "ca.example.net" 245 If the domain name holder specifies one or more iodef properties, a 246 certificate issuer MAY report invalid certificate requests to that 247 address. In the following example the domain name holder specifies 248 that reports MAY be made by means of email with the IODEF data as an 249 attachment or a Web service or both: 251 $ORIGIN example.com 252 . CAA 0 issue "ca.example.net" 253 . CAA 0 iodef "mailto:security@example.com" 254 . CAA 0 iodef "http://iodef.example.com/" 256 A certificate issuer MAY specify additional parameters that allow 257 customers to specify additional parameters governing certificate 258 issue. For example, the Certification Policy under which the 259 certificate is to be issued or the authentication process to be used. 261 $ORIGIN example.com 262 . CAA 0 issue "ca.example.net; account=230123" 264 The syntax and semantics of such parameters is left to site policy 265 and is outside the scope of this document. 267 Future versions of this specification MAY use the critical flag to 268 introduce new semantics that MUST be understood for correct 269 processing of the record, preventing Certification Authorities that 270 do not recognize the record from issuing certificates. 272 In the following example, the property 'tbs' is flagged as critical. 273 Neither the example.net CA, nor any other issuer is authorized to 274 issue under either policy unless the processing rules for the 'tbs' 275 property tag are understood. 277 $ORIGIN example.com 278 . CAA 0 issue "ca.example.net; policy=ev" 279 . CAA 128 tbs "Unknown" 281 Note that the above restrictions only apply to issue of certificates. 282 Since the validity of an end entity certificate is typically a year 283 or more it is quite possible that the CAA records published at a 284 domain will change between the issue of the certificate and 285 verification by a relying party. 287 3. Certification Authority Processing 289 Before issue of a certificate, a compliant CA MUST check for 290 publication of a relevant CAA Resource Record(s) and if such 291 record(s) are published, that the certificate requested is consistent 292 with them. If the certificate requested is not consistent with the 293 relevant CAA RRs, the CA MUST NOT issue the certificate. 295 The Issuer Authorization Set for a domain name consists of the set of 296 all CAA Authorization Entries declared for the canonical form of the 297 specified domain. 299 The Extended Issuer Authorization Set for a domain name is determined 300 as follows: 302 o If the Issuer Authorization Set for the domain is empty, the 303 Extended Issuer Authorization Set is empty. 305 o If the immediately superior node in the DNS hierarchy is a Public 306 Delegation Point, the Extended Issuer Authorization Set is empty. 308 o Otherwise the Extended Issuer Authorization Set is that of the 309 immediately superior node in the DNS hierarchy. 311 For example, if the zone example.com has a CAA record defined for 312 caa.example.com and no other domain in the zone, the Issuer 313 Authorization Set is empty for all domains other than 314 caa.example.com. The Extended Issuer Authorization Set is empty for 315 example.com (because .com is a Public Delegation Point) and for 316 x.example.com. The Extended Issuer set for x.caa.example.com, 317 x.x.caa.example.com, etc. is the Issuer Authorization Set for 318 caa.example.com. 320 If the Extended Issuer Authorization Set for a domain name is not 321 empty, a Certification Authority MUST NOT issue a certificate unless 322 it conforms to at least one authorization entry in the Extended 323 Issuer Authorization Set. 325 3.1. Canonical Domain Name 327 The DNS defines the CNAME and DNAME mechanisms for specifying domain 328 name aliases. The canonical name of a DNS name is the name that 329 results from performing all DNS alias operations. 331 An issuer MUST perform CNAME and DNAME processing as defined in the 332 DNS specifications 1035 [RFC1035] to resolve CAA records. 334 3.2. Use of DNS Security 336 Use of DNSSEC to authenticate CAA RRs is strongly recommended but not 337 required. An issuer MUST NOT issue certificates if doing so would 338 conflict with the corresponding extended issuer authorization set 339 whether the corresponding DNS records are signed or not. 341 Use of DNSSEC allows an issuer to acquire and archive a non- 342 repudiable proof that they were authorized to issue certificates for 343 the domain. 345 3.3. Archive 347 A compliant issuer SHOULD maintain an archive of the DNS transactions 348 used to verify CAA eligibility. 350 In particular an issuer SHOULD ensure that where DNSSEC data is 351 available that the corresponding signature and NSEC/NSEC3 records are 352 preserved so as to enable later compliance audits. 354 4. Mechanism 356 4.1. Syntax 358 A CAA RR contains a single property entry consisting of a tag value 359 pair. Each tag represents a property of the CAA record. The value 360 of a CAA property is that specified in the corresponding value field. 362 A domain name MAY have multiple CAA RRs associated with it and a 363 given property MAY be specified more than once. 365 The CAA data field contains one property entry. A property entry 366 consists of the following data fields: 368 +0-1-2-3-4-5-6-7-|0-1-2-3-4-5-6-7-| 369 | Flags | Tag Length = n | 370 +----------------+----------------+...+---------------+ 371 | Tag char 0 | Tag Char 1 |...| Tag Char n-1 | 372 +----------------+----------------+...+---------------+ 373 +----------------+----------------+.....+---------------+ 374 | Data byte 0 | Data byte 1 |.....| Data byte m-1 | 375 +----------------+----------------+.....+---------------+ 377 Where n is the length specified in the tag length field and m is the 378 remaining octets in the data field (m = d - n - 2) where d is the 379 length of the data section. 381 The data fields are defined as follows: 383 Flags One octet containing the following fields: 385 Bit 0: Issuer Critical Flag If the value is set (1), the critical 386 flag is asserted and the property MUST be understood if the CAA 387 record is to be correctly processed by a certificate issuer. 389 A Certification Authority MUST NOT issue certificates for any 390 Domain that contains a CAA critical property for an unknown or 391 unsupported property type that has the issuer bit set. 393 Note that according to the conventions set out in RFC 1035 394 [RFC1035] Bit 0 is the Most Significant Bit and Bit 7 is the Least 395 Significant. Thus the flags value 1 means that bit 7 is set while 396 a value of 128 means that bit 0 is set according to this 397 convention. 399 All other bit positions are reserved for future use. 401 To ensure compatibility with futuree extensions to CAA, DNS 402 records compliant with this version of the CAA specification MUST 403 clear (0) all reserved flags bits. Applications that interpret 404 CAA records MUST ignore the value of all reserved flag bits. 406 Tag Length A single octet containing an unsigned integer specifying 407 the tag length in octets. The tag length MUST be at least 1 and 408 SHOULD be no more than 15. 410 Tag The property identifier, a sequence of ASCII characters. 412 Tag values MAY contain ASCII characters a through z and the 413 numbers 0 through 9. Tag values MUST NOT contain any other 414 characters. Matching of tag values is case insensitive. 416 Value A sequence of octets representing the property value. 417 Property values are encoded as binary values and MAY employ sub- 418 formats. 420 The length of the value field is specified implicitly as the 421 remaining length of the enclosing Resource Record data field. 423 4.1.1. Canonical Presentation Format 425 The canonical presentation format of the CAA record is as follows: 427 CAA 429 Where: 431 flags Is an unsigned integer between 0 and 255. 433 tag Is a non-zero sequence of ASCII letter and numbers in lower 434 case. 436 data Is the ascii text Encoding of the value field 438 4.2. CAA issue Property 440 The issue property is used to request that certificate issuers 441 perform CAA issue restriction processing for the domain and to grant 442 authorization to specific certificate issuers. 444 The CAA issue property value has the following sub-syntax (specified 445 in ABNF as per [RFC4234]). 447 Property = space [domain] * (space ";" parameter) space 449 domain = label *("." label) 450 label = 1* (ALPHA / DIGIT / "_" / "-" ) 452 space = *(SP / HTAB) 454 parameter = / space tag "=" value 456 tag = 1* (ALPHA / DIGIT) 457 value = *VCHAR | DQUOTE *(%x20-21 / %x23-7E) DQUOTE 459 A CAA record with an issue parameter tag that does not specify a 460 domain name is a request that certificate issuers perform CAA issue 461 restriction processing for the corresponding domain without granting 462 authorization to any certificate issuer. 464 This form of issue restriction would be appropriate for use with a 465 domain that the domain name owner does not intend to be used. 467 For example, the following CAA record set requests that no 468 certificates be issued for the domain 'nocerts.example.com' by any 469 certificate issuer. 471 nocerts.example.com CAA 0 issue ";" 473 A CAA record with an issue parameter tag that specifies a domain name 474 is a request that certificate issuers perform CAA issue restriction 475 processing for the corresponding domain and grants authorization to 476 the certificate issuer specified by the domain name. 478 For example, the following CAA record set requests that no 479 certificates be issued for the domain 'certs.example.com' by any 480 certificate issuer other than the example.net certificate issuer. 482 certs.example.com CAA 0 issue "example.net" 484 CAA authorizations are additive. thus the result of specifying both 485 the empty issuer and a specified issuer is the same as specifying 486 just the specified issuer alone. 488 An issuer MAY choose to specify issuer-parameters that further 489 constrain the issue of certificates by that issuer. For example 490 specifying that certificates are to be subject to specific validation 491 polices, billed to certain accounts or issued off specific roots. 493 The syntax and semantics of issuer-parameters are determined by the 494 issuer alone. 496 4.3. CAA iodef Property 498 The iodef property specifies a means of reporting certificate issue 499 requests or cases of certificate issue for the corresponding domain 500 that violate the security policy of the issuer or the domain name 501 holder. 503 The Incident Object Description Exchange Format (IODEF) [RFC5070] is 504 used to present the incident report in machine readable form. 506 The iodef property takes a URL as its parameter. The URL scheme type 507 determines the method used for reporting: 509 mailto The IODEF incident report is reported as a MIME email 510 attachment to an SMTP email that is submitted to the mail address 511 specified. The mail message sent SHOULD contain a brief text 512 message to alert the recipient to the nature of the attachment. 514 http or https The IODEF report is submitted as a Web Service request 515 to the HTTP address specified using the protocol specified in 516 [RFC6046]. 518 5. Security Considerations 520 CAA Records assert a security policy that the holder of a domain name 521 wishes to be observed by certificate issuers. The effectiveness of 522 CAA records as an access control is thus dependent on observance of 523 CAA constraints by issuers. 525 Observance of CAA records by issuers is subject to accountability 526 controls and proposed industry requirements. 528 While a Certification Authority can choose to ignore published CAA 529 records, doing so increases the both the probability that they will 530 mis-issue a certificate and the consequences of doing so. Once it is 531 known that a CA observes CAA records, malicious registration requests 532 will disproportionately target the negligent CAs that do not, and so 533 the mis-issue rate amongst the negligent CAs will increase. Since 534 the CA could clearly have avoided the mis-issue by performing CAA 535 processing, the likelihood of sanctions against the negligent CA is 536 increased. Failure to observe CAA issue restrictions provides an 537 objective criteria for excluding issuers from embedded roots of 538 trust. 540 In contrast, a Certification Authority that processes CAA records 541 correctly can reasonably claim that any residual mis-issue event 542 could have been avoided had the Domain Name holder published 543 appropriate CAA records. 545 5.1. Mis-Issue by Authorized Certification Authority 547 Use of CAA records does not provide protection against mis-issue by 548 an authorized Certification Authority. 550 Domain name holders SHOULD ensure that the CAs they authorize to 551 issue certificates for their domains employ appropriate controls to 552 ensure that certificates are only issued to authorized parties within 553 their organization. 555 Such controls are most appropriately determined by the domain name 556 holder and the authorized CA(s) directly and are thus out of scope of 557 this document. 559 5.2. Suppression or spoofing of CAA records 561 Suppression of the CAA record or insertion of a bogus CAA record 562 could enable an attacker to obtain a certificate from a CA that was 563 not authorized to issue for that domain name. 565 5.2.1. Certification Authorities 567 Since a certificate issued by a CA can be valid for several years, 568 the consequences of a spoofing or suppression attack are much greater 569 for Certification Authorities and so additional countermeasures are 570 justified. 572 A CA MUST mitigate this risk by employing DNSSEC verification 573 whenever possible and rejecting certificate requests in any case 574 where it is not possible to verify the non-existence or contents of a 575 relevant CAA record. 577 In cases where DNSSEC is not deployed in a corresponding domain, a CA 578 SHOULD attempt to mitigate this risk by employing appropriate DNS 579 security controls. For example all portions of the DNS lookup 580 process SHOULD be performed against the authoritative name server. 581 Cached data MUST NOT be relied on but MAY be used to support 582 additional anti-spoofing or anti-suppression controls. 584 5.3. Denial of Service 586 Introduction of a malformed or malicious CAA RR could in theory 587 enable a Denial of Service attack. 589 This specific threat is not considered to add significantly to the 590 risk of running an insecure DNS service. 592 5.3.1. Issuer 594 An attacker could in principle perform a Denial of Service attack 595 against an issuer by requesting a certificate with a maliciously long 596 DNS name. In practice the DNS protocol imposes a maximum name length 597 and the protocol does not exacerbate the existing need to mitigate 598 Denial of Service attacks to any meaningful degree. 600 5.4. Abuse of the Critical Flag 602 A Certification Authority could make use of the critical flag to 603 trick customers into publishing records which prevent competing 604 Certification Authorities from issuing certificates even though the 605 customer intends to authorize multiple providers. 607 In practice, such an attack would be of minimal effect since any 608 competent competitor that found itself unable to issue certificates 609 due to lack of support for a property marked critical SHOULD 610 investigate the cause and report the reason to the customer who will 611 thus discover the deception. It is thus unlikely that the attack 612 would succeed and the attempt might lay the perpetrator open to civil 613 or criminal sanctions. 615 6. IANA Considerations 617 6.1. Registration of the CAA Resource Record Type 619 [Note to IANA, the CAA resource record has already been assigned. On 620 issue of this draft as an RFC, the record should be updated to 621 reflect this document as the authoritative specificaton and this 622 paragraph (but not the following ones deleted] 624 IANA has assigned Resource Record Type 257 for the CAA Resource 625 Record Type and added the line depicted below to the registry named 626 Resource Record (RR) TYPEs and QTYPEs as defined in BCP 42 RFC 5395 627 [RFC5395] and located at 628 http://www.iana.org/assignments/dns-parameters. 630 Value and meaning Reference 631 ----------- --------------------------------------------- --------- 632 CAA 257 Certification Authority Restriction [RFC-THIS] 634 6.2. Certification Authority Authorization Properties 636 [Note to IANA, this is a new registry that needs to be created and 637 this paragraph but not the following ones deleted.] 639 IANA has created the Certification Authority Authorization Properties 640 registry with the following initial values: 642 Meaning Reference 643 ----------- ----------------------------------------------- --------- 644 issue Authorization Entry by Domain [RFC-THIS] 645 iodef Report incident by means of IODEF format report [RFC-THIS] 646 auth Reserved 647 path Reserved 648 policy Reserved 650 Addition of tag identifiers requires a public specification and 651 expert review as set out in RFC5395 [RFC5395] 653 7. Normative References 655 [RFC1035] Mockapetris, P., "Domain names - implementation and 656 specification", STD 13, RFC 1035, November 1987. 658 [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail 659 Extensions (MIME) Part One: Format of Internet Message 660 Bodies", RFC 2045, November 1996. 662 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 663 Requirement Levels", BCP 14, RFC 2119, March 1997. 665 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 666 Rose, "DNS Security Introduction and Requirements", 667 RFC 4033, March 2005. 669 [RFC4055] Schaad, J., Kaliski, B., and R. Housley, "Additional 670 Algorithms and Identifiers for RSA Cryptography for use in 671 the Internet X.509 Public Key Infrastructure Certificate 672 and Certificate Revocation List (CRL) Profile", RFC 4055, 673 June 2005. 675 [RFC4234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 676 Specifications: ABNF", RFC 4234, October 2005. 678 [RFC5070] Danyliw, R., Meijer, J., and Y. Demchenko, "The Incident 679 Object Description Exchange Format", RFC 5070, 680 December 2007. 682 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 683 Housley, R., and W. Polk, "Internet X.509 Public Key 684 Infrastructure Certificate and Certificate Revocation List 685 (CRL) Profile", RFC 5280, May 2008. 687 [RFC5395] Eastlake, D., "Domain Name System (DNS) IANA 688 Considerations", RFC 5395, November 2008. 690 [RFC6046] Moriarty, K. and B. Trammell, "Transport of Real-time 691 Inter-network Defense (RID) Messages", RFC 6046, 692 November 2010. 694 [X.509] International Telecommunication Union, "ITU-T 695 Recommendation X.509 (11/2008): Information technology - 696 Open systems interconnection - The Directory: Public-key 697 and attribute certificate frameworks", ITU-T 698 Recommendation X.509, November 2008. 700 Authors' Addresses 702 Phillip Hallam-Baker 703 Comodo Group Inc. 705 Email: philliph@comodo.com 707 Rob Stradling 708 Comodo CA Ltd. 710 Email: rob.stradling@comodo.com