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If these are example addresses, they should be changed. ** The document seems to lack a both a reference to RFC 2119 and the recommended RFC 2119 boilerplate, even if it appears to use RFC 2119 keywords. RFC 2119 keyword, line 114: '... } OPTIONAL,...' RFC 2119 keyword, line 116: '... } OPTIONAL,...' RFC 2119 keyword, line 171: '...certificate that MUST be ignored for t...' RFC 2119 keyword, line 174: '... list of X.509 extensions that MUST be...' RFC 2119 keyword, line 177: '...st of the CA-provided checks that MUST...' (12 more instances...) Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (November 25, 2017) is 2334 days in the past. Is this intentional? Checking references for intended status: Experimental ---------------------------------------------------------------------------- -- Missing reference section? '1' on line 362 looks like a reference -- Missing reference section? '2' on line 365 looks like a reference -- Missing reference section? '3' on line 367 looks like a reference -- Missing reference section? '0' on line 284 looks like a reference Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 5 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group 3 Internet-Draft TCI 4 Intended status: Experimental November 25, 2017 5 Expires: May 29, 2018 7 Certificate Limitation Policy 8 draft-belyavskiy-certificate-limitation-policy-05 10 Abstract 12 The document provides a specification of the application-level trust 13 model. Being provided at the application level, the limitations of 14 trust can be distributed separately using cryptographically protected 15 format instead of hardcoding the checks into the application itself. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at https://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on May 29, 2018. 34 Copyright Notice 36 Copyright (c) 2017 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (https://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 1. Introduction 51 Binary trust model standardized as a set of trusted anchors and CRLs/ 52 OCSP services does not cover all corner cases in the modern crypto 53 world. There is a need in more differentiated limitations. Some of 54 them are suggested [1] by Google when it limits the usage of 55 Symantec's certificates. The CRL profile does not fit the purpose of 56 such limitations. The CRLs are issued by the same CAs that are 57 subject to be limited. 59 Currently the set of CAs trusted by OS or browsers can be used for 60 the validation purposes. In case when a large enough CA becomes 61 untrusted, it cannot be deleted from the storage of trusted CAs 62 because it may cause error of validation of many certificates. The 63 measures usually taken in such cases usually include application- 64 level limitation of certificates lifetimes, refusing to accept EV- 65 certificates in other way than DV, requirements to use Certificate 66 Transparency, etc. 68 This document suggests a cryptographically signed format dubbed 69 Certificate Limitation Profile (CLP) designed for description of such 70 limitations. This format can be used by applications that use 71 system-wide set of trust anchors for validating purposes or by 72 applications with own wide enough set of trusted anchors in case when 73 the trust anchor for the entity found misbehaving cannot be revoked. 75 Currently the only way to provide such limitations is hard coding 76 them in application itself. Using of CLPs does not allow to 77 completely avoid hard coding but allows to hard code only the minimal 78 set of rarely changing data: 80 the fact that application uses CLP 82 the certificate to verify the signature under the CLP file 84 minimal date of the CLP to be used for the current version of 85 application. 87 It will be possible to move the checks for the limitations to the 88 external cryptographical libraries, such as OpenSSL, instead of 89 checking them at the application level. 91 2. Certificate Limitations Profile 93 A proposed syntax and overall structure of CLP is very similar to the 94 one defined for CRLs [2]. 96 CertificateList ::= SEQUENCE { 97 tbsCertList TBSCertList, 98 signatureAlgorithm AlgorithmIdentifier, 99 signatureValue BIT STRING } 101 TBSCertList ::= SEQUENCE { 102 version Version, 103 signature AlgorithmIdentifier, 104 issuer Name, 105 thisUpdate Time, 106 limitedCertificates SEQUENCE OF SEQUENCE { 107 userCertificate CertificateSerialNumber, 108 certificateIssuer Name, 109 limitationDate Time, 110 limitationPropagation Enum, 111 fingerprint SEQUENCE { 112 fingerprintAlgorithm AlgorithmIdentifier, 113 fingerprintValue OCTET STRING 114 } OPTIONAL, 115 limitations Limitations, 116 } OPTIONAL, 117 }; 119 Limitations ::= SEQUENCE SIZE (1..MAX) OF Limitation 121 Limitation ::= SEQUENCE { 122 limitID OBJECT IDENTIFIER, 123 LimitationValue OCTET STRING 124 -- contains the DER encoding of an ASN.1 value 125 -- corresponding to the limitation type 126 -- identified by limitID 127 } 129 The ASN.1 format of particular limitations is provided in the 130 corresponding sections. Anywhere below the Time in ASN.1 notation is 131 treated according to RFC 5280: 133 Time ::= CHOICE { 134 utcTime UTCTime, 135 generalTime GeneralizedTime } 137 2.1. CLP fields 139 TBD 141 2.2. CLP signature 143 The key used for signing the CLP files should have a special Key 144 Usage value and/or an Extended Key Usage value. 146 2.3. CLP entry fields 148 Each entry in list contains the following fields: 150 The issuer of the certificate with limited trust. 152 The serial of the certificate with limited trust. 154 The fingerprint of the certificate with limited trust (optional). 156 limitationPropagation. This field indicates whether limitations 157 are applied to the certificate itself, to all of its descendants 158 in the chain of trust, or both. 160 and a subset of the following limitations: 162 issuedNotAfter - do not trust the certs issued after the specified 163 date 165 trustNotAfter - do not trust the certs after the specified date 167 validityPeriod, days - take minimal value from "native" validity 168 period and specified in the limitation file 170 ignoredX509Extensions - list of X.509 extensions of limited 171 certificate that MUST be ignored for the specified certificate 172 (e.g. EV-indicating extensions) 174 requiredX509extensions - list of X.509 extensions that MUST be 175 present in the certificate to be trusted. 177 requiredNativeChecking - list of the CA-provided checks that MUST 178 be applied 180 applicationNameConstraints - list of domains allowed to be issued 181 by this certificate 183 excludedIssueIntermediatory - disallow issuing of the 184 Intermediatory certificates 186 The limitations are identified by OIDs 188 2.3.1. Limitations 190 2.3.1.1. issuedNotAfter 192 When this limitation is present, any certificate matching the entry 193 and issued after the specified date MUST NOT be trusted 195 The issuedNotAfter limitation is identified by OID TBA. 197 issuedNotAfter ::= SEQUENCE { 198 IssuedNotAfter Time 199 } 201 2.3.1.2. trustNotAfter 203 When this limitation is present, any certificate matching the entry 204 MUST NOT be trusted after the specified date. 206 The trustNotAfter limitation is identified by OID TBA. 208 trustNotAfter ::= SEQUENCE { 209 TrustNotAfter Time 210 } 212 2.3.1.3. validityPeriod 214 When this limitation is present, no certificate matching the entry 215 should be treated as valid after specified period from its validFrom. 217 The validityPeriod is measured in days. 219 The validityPeriod limitation is identified by OID TBA. 221 validityPeriod ::= SEQUENCE { 222 Days INTEGER 223 } 225 2.3.1.4. ignoredX509Extensions 227 When this limitation is present, the extensions listed in this 228 element should be ignored for the matching certificate. 230 The ignoredX509Extensions limitation is identified by OID TBA. 232 ignoredX509Extensions :: = SEQUENCE SIZE (1..MAX) OF ExtenID 233 ExtenID :: = OBJECT IDENTIFIER 235 2.3.1.5. requiredX509extensions 237 When this limitation is present, the extensions listed in this 238 element should be present for the matching certificate. 240 The requiredX509extensions limitation is identified by OID TBA. 242 requiredX509extensions :: = SEQUENCE SIZE (1..MAX) OF ExtenID 243 ExtenID :: = OBJECT IDENTIFIER 245 2.3.1.6. requiredNativeChecking 247 When this limitation is present, it specifies that the certificates 248 issued by this CA SHOULD be checked against CRL and/or OCSP, 249 depending on contents of the extension. 251 The requiredNativeChecking limitation is identified by OID TBA. 253 requiredNativeChecking ::= SEQUENCE { 254 RequiredCRLChecking BOOLEAN, 255 RequiredOCSPChecking BOOLEAN 256 } 258 2.3.1.7. applicationNameConstraints 260 This limitation are applied like Name Constraints [3] limitation 261 specified in RFC 5280. 263 This section implies 2 variants of checks: 265 The list of names that are allowed for the CA to issue 266 certificates for 268 The list of names that are forbidden for the CA to issue 269 certificates for 271 The applicationNameConstraints limitation is specified according to 272 RFC 5280, 4.2.1.10 and reuses OID specified in RFC 5280. 274 id-ce-nameConstraints OBJECT IDENTIFIER ::= { id-ce 30 } 276 NameConstraints ::= SEQUENCE { 277 permittedSubtrees [0] GeneralSubtrees OPTIONAL, 278 excludedSubtrees [1] GeneralSubtrees OPTIONAL } 280 GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree 282 GeneralSubtree ::= SEQUENCE { 283 base GeneralName, 284 minimum [0] BaseDistance DEFAULT 0, 285 maximum [1] BaseDistance OPTIONAL } 287 BaseDistance ::= INTEGER (0..MAX) 289 2.3.1.7.1. excludedIssueIntermediatory 291 When this limitation is present, the intermediate certificates issued 292 by this CA MUST NOT be trusted. 294 The excludedIssueIntermediatory limitation is identified by OID TBA. 296 3. Verification of CLP 298 The verification of CLP SHOULD be performed by the application. The 299 application should check whether the provided CLP matches the 300 internal requirements and is correclty signed by the specified key. 302 4. Verification with CLP 304 In case of using CLP the checks enforced by CLP should be applied 305 after the other checks. 307 The limitation provided by CLP MUST NOT extend the trustworthy of the 308 checked certificate. 310 The limitations are applied after cryptographic validation of the 311 certificate and during building its chain of trust. If the 312 certificate or any of its ascendants in the chain of trust matches 313 any record in the CLP, the limitations are applied from the ascendant 314 to descendants. The issuedNotAfter and trustNotAfter limitations are 315 applied to find out the actual validity periods for the any 316 certificate in the chain of trust. If the CLP prescribes to have a 317 particular extension(s) and the certificate does not have it, the 318 certificate MUST NOT be trusted. 320 Application MAY use more than one CLPs (e.g. app-wide, set of system- 321 wide, user-defined). When multiple CLPs are in use, the limitations 322 are applied simultaneously. 324 In case when more than one chain of trust are valid for a 325 certificate, if any of this chains is valid after applying the 326 limitations, the certificate MUST be treated as valid. 328 5. ASN.1 notation 330 TBD 332 6. Security considerations 334 In case when an application uses CLP, it is recommended to specify 335 the minimal date of issuing of the CLP document somewhere in code. 336 It allows to avoid an attack of CLP rollback when the stale version 337 of CLP is used. 339 It is recommended to distribute CLPs using the channels that are used 340 for distribution of the applications themselves to avoid possible DoS 341 consequences. 343 7. IANA considerations 345 TBD 347 8. Acknoledgements 349 Special thanks to Rich Salz, Igor Ustinov, Vasily Dolmatov, Stanislav 350 Smyishlyaev, Patrik Faeltstroem, Alexander Venedioukhin, Artem 351 Chuprina. 353 9. References 355 The current version of the document is available on GitHub 356 https://github.com/beldmit/clp 358 10. References 360 10.1. URIs 362 [1] https://groups.google.com/a/chromium.org/forum/#!msg/blink- 363 dev/eUAKwjihhBs/rpxMXjZHCQAJ 365 [2] https://tools.ietf.org/html/rfc5280#section-5 367 [3] https://tools.ietf.org/html/rfc5280#section-4.2.1.10 369 Author's Address 371 Dmitry Belyavskiy 372 Technical Centre of Internet 373 8 Marta str., 1 bld. 12 374 Moscow 127083 375 RU 377 Email: beldmit@gmail.com