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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-10) exists of draft-ietf-sidr-rpki-validation-reconsidered-08 ** Obsolete normative reference: RFC 6485 (Obsoleted by RFC 7935) ** Obsolete normative reference: RFC 6486 (Obsoleted by RFC 9286) ** Obsolete normative reference: RFC 7730 (Obsoleted by RFC 8630) Summary: 3 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 SIDR Operations O. Muravskiy 3 Internet-Draft T. Bruijnzeels 4 Intended status: Informational RIPE NCC 5 Expires: January 20, 2018 July 19, 2017 7 RPKI Certificate Tree Validation by the RIPE NCC RPKI Validator 8 draft-ietf-sidrops-rpki-tree-validation-01 10 Abstract 12 This document describes the approach to validate the content of the 13 RPKI certificate tree, as it is implemented in the RIPE NCC RPKI 14 Validator. This approach is independent of a particular object 15 retrieval mechanism. This allows it to be used with repositories 16 available over the rsync protocol, the RPKI Repository Delta 17 Protocol, and repositories that use a mix of both. 19 Status of This Memo 21 This Internet-Draft is submitted in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at http://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on January 20, 2018. 36 Copyright Notice 38 Copyright (c) 2017 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (http://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Scope of this document . . . . . . . . . . . . . . . . . . . 3 54 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 55 3. General Considerations . . . . . . . . . . . . . . . . . . . 4 56 3.1. Hash comparisons . . . . . . . . . . . . . . . . . . . . 4 57 3.2. Discovery of RPKI objects issued by a CA . . . . . . . . 4 58 3.3. Manifest entries versus repository content . . . . . . . 4 59 4. Top-down Validation of a Single Trust Anchor Certificate Tree 5 60 4.1. Fetching the Trust Anchor Certificate Using the Trust 61 Anchor Locator . . . . . . . . . . . . . . . . . . . . . 5 62 4.2. CA Certificate Validation . . . . . . . . . . . . . . . . 6 63 4.2.1. Finding the most recent valid manifest and CRL . . . 7 64 4.2.2. Manifest entries validation . . . . . . . . . . . . . 8 65 4.3. Object Store Cleanup . . . . . . . . . . . . . . . . . . 9 66 5. Remote Objects Fetcher . . . . . . . . . . . . . . . . . . . 9 67 5.1. Fetcher Operations . . . . . . . . . . . . . . . . . . . 9 68 5.1.1. Fetch repository objects . . . . . . . . . . . . . . 10 69 5.1.2. Fetch single repository object . . . . . . . . . . . 10 70 6. Local Object Store . . . . . . . . . . . . . . . . . . . . . 11 71 6.1. Store Operations . . . . . . . . . . . . . . . . . . . . 11 72 6.1.1. Store Repository Object . . . . . . . . . . . . . . . 11 73 6.1.2. Get objects by hash . . . . . . . . . . . . . . . . . 11 74 6.1.3. Get certificate objects by URI . . . . . . . . . . . 11 75 6.1.4. Get manifest objects by AKI . . . . . . . . . . . . . 11 76 6.1.5. Delete objects for a URI . . . . . . . . . . . . . . 12 77 6.1.6. Delete outdated objects . . . . . . . . . . . . . . . 12 78 6.1.7. Update object's validation time . . . . . . . . . . . 12 79 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 80 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 81 9. Security Considerations . . . . . . . . . . . . . . . . . . . 12 82 9.1. Hash collisions . . . . . . . . . . . . . . . . . . . . . 12 83 9.2. Mismatch between the expected and the actual location of 84 an object in the repository . . . . . . . . . . . . . . . 12 85 9.3. Manifest content versus publication point content . . . . 13 86 9.4. Storing of a TA certificate object before its complete 87 validation . . . . . . . . . . . . . . . . . . . . . . . 13 88 9.5. Possible denial of service . . . . . . . . . . . . . . . 14 89 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 90 10.1. Normative References . . . . . . . . . . . . . . . . . . 14 91 10.2. Informative References . . . . . . . . . . . . . . . . . 15 92 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 94 1. Scope of this document 96 This document describes how the RIPE NCC RPKI Validator version 2.23 97 has been implemented. Source code to this software can be found at 98 [github]. The purpose of this document is to provide transparency to 99 users of (and contributors to) this software tool, as well as serve 100 to be subjected to scrutiny by the SIDR Operations Working Group. It 101 is not intended as a document that describes a standard or best 102 practices on how validation should be done in general. 104 2. Introduction 106 In order to use information published in RPKI repositories, Relying 107 Parties (RP) need to retrieve and validate the content of 108 certificates, certificate revocation lists (CRLs), and other RPKI 109 signed objects. To validate a particular object, one must ensure 110 that all certificates in the certificate chain up to the Trust Anchor 111 (TA) are valid. Therefore the validation of a certificate tree is 112 performed top-down, starting from the TA certificate and descending 113 down the certificate chain, validating every encountered certificate 114 and its products. The result of this process is a list of all 115 encountered RPKI objects with a validity status attached to each of 116 them. These results may later be used by a Relying Party in taking 117 routing decisions, etc. 119 Traditionally RPKI data is made available to RPs through the 120 repositories [RFC6481] accessible over [rsync] protocol. Relying 121 parties are advised to keep a local copy of repository data, and 122 perform regular updates of this copy from the repository (Section 5 123 of [RFC6481]). The RPKI Repository Delta Protocol 124 [I-D.ietf-sidr-delta-protocol] introduces another method to fetch 125 repository data and keep the local copy up to date with the 126 repository. 128 This document describes how the RIPE NCC RPKI Validator discovers 129 RPKI objects to download, builds certificate paths, and validates 130 RPKI objects, independently from what repository access protocol is 131 used. To achieve this, it puts downloaded RPKI objects in an object 132 store, where each RPKI object can be found by its URI, the hash of 133 its content, value of its Authority Key Identifier (AKI) extension, 134 or a combination of these. It also keeps track of the download and 135 the validation time for every object, to decide which locally stored 136 objects are not used in the RPKI tree validation and could be 137 removed. 139 3. General Considerations 141 3.1. Hash comparisons 143 This algorithm relies on the properties of the file hash algorithm 144 (defined in [RFC6485]) to compute the hash of repository objects. It 145 assumes that any two objects for which the hash value is the same, 146 are identical. 148 The hash comparison is used when matching objects in the repository 149 with entries on the manifest (Section 4.2.2), and when looking up 150 objects in the object store (Section 6). 152 3.2. Discovery of RPKI objects issued by a CA 154 There are several possible ways of discovering products of a CA 155 certificate: one could use all objects located in a repository 156 directory designated as a publication point for a CA, or only objects 157 mentioned on the manifest located at that publication point (see 158 Section 6 of [RFC6486]), or use all objects whose AKI extension 159 matches the Subject Key Identifier (SKI) extension (Section 4.2.1 of 160 [RFC5280]) of a CA certificate. 162 For publication points whose content is consistent with the manifest 163 and issuing certificate all of these approaches should produce the 164 same result. For inconsistent publication points the results might 165 be different. Section 6 of [RFC6486] leaves the decision on how to 166 deal with inconsistencies to a local policy. 168 The implementation described here does not rely on content of 169 repository directories, but uses the Authority Key Identifier (AKI) 170 extension of a manifest and a certificate revocation list (CRL) to 171 find in an object store (Section 6) a manifest and a CRL issued by a 172 particular Certification Authority (CA) (see Section 4.2.1). It 173 further uses the hashes of manifest's fileList entries (Section 4.2.1 174 of [RFC6486]) to find other objects issued by the CA, as described in 175 Section 4.2.2. 177 3.3. Manifest entries versus repository content 179 Since the current set of RPKI standards requires use of the manifest 180 [RFC6486] to describe the content of a publication point, this 181 implementation requires strict consistency between the publication 182 point content and manifest content. (This is a more stringent 183 requirement than established in [RFC6486].) Therefore it will not 184 process objects that are found in the publication point but do not 185 match any of the entries of that publication point's manifest (see 186 Section 4.2.2). It will also issue warnings for all found 187 mismatches, so that the responsible operators could be made aware of 188 inconsistencies and fix them. 190 4. Top-down Validation of a Single Trust Anchor Certificate Tree 192 1. The validation of a Trust Anchor (TA) certificate tree starts 193 from its TA certificate. To retrieve the TA certificate, a Trust 194 Anchor Locator (TAL) object is used, as described in Section 4.1. 196 2. If the TA certificate is retrieved, it is validated according to 197 Section 7 of [RFC6487] and Section 2.2 of [RFC7730]. Otherwise 198 the validation of certificate tree is aborted and an error is 199 issued. 201 3. If the TA certificate is valid, then all its subordinate objects 202 are validated as described in Section 4.2. Otherwise the 203 validation of certificate tree is aborted and an error is issued. 205 4. For each repository object that was validated during this 206 validation run, its validation timestamp is updated in the object 207 store (see Section 6.1.7). 209 5. Outdated objects are removed from the store as described in 210 Section 4.3. This completes the validation of the TA certificate 211 tree. 213 4.1. Fetching the Trust Anchor Certificate Using the Trust Anchor 214 Locator 216 The following steps are performed in order to fetch a Trust Anchor 217 Certificate: 219 1. (Optional) If the Trust Anchor Locator contains a "prefetch.uris" 220 field, pass the URIs contained in that field to the fetcher (see 221 Section 5.1.1). (This field is a non-standard addition to the 222 TAL format. It helps fetching non-hierarchical rsync 223 repositories more efficiently.) 225 2. Extract the first TA certificate URI from the TAL's URI section 226 (see Section 2.1 of [RFC7730]) and pass it to the object fetcher 227 (Section 5.1.2). If the fetcher returns an error, repeat this 228 step for every URI in the URI section, until no error is 229 encountered, or no more URIs left. 231 3. Retrieve from the object store (see Section 6.1.3) all 232 certificate objects, for which the URI matches the URI extracted 233 from the TAL in the previous step, and the public key matches the 234 subjectPublicKeyInfo extension of the TAL (see Section 2.1 of 235 [RFC7730]). 237 4. If no, or more than one such objects are found, issue an error 238 and abort certificate tree validation process with an error. 239 Otherwise, use the single found object as the Trust Anchor 240 certificate. 242 4.2. CA Certificate Validation 244 The following steps describe the validation of a single CA Resource 245 certificate: 247 1. If both the caRepository (Section 4.8.8.1 of [RFC6487]), and the 248 id-ad-rpkiNotify (Section 3.2 of [I-D.ietf-sidr-delta-protocol]) 249 SIA pointers are present in the CA certificate, use a local 250 policy to determine which pointer to use. Extract the URI from 251 the selected pointer and pass it to the object fetcher (see 252 Section 5.1.1). 254 2. For the CA certificate, find the current manifest and certificate 255 revocation list (CRL), using the procedure described in 256 Section 4.2.1. If no such manifest and CRL could be found, stop 257 validation of this certificate, consider it invalid, and issue an 258 error. 260 3. Compare the URI found in the id-ad-rpkiManifest field 261 (Section 4.8.8.1 of [RFC6487]) of the SIA extension of the 262 certificate with the URI of the manifest found in the previous 263 step. If they are different, issue a warning, but continue 264 validation process using this manifest object. (This warning 265 indicates that there is a mismatch between the expected and the 266 actual location of an object in a repository. See Section 9 for 267 the explanation of this mismatch and the decision taken.) 269 4. Perform manifest entries discovery and validation as described in 270 Section 4.2.2. 272 5. Validate all resource certificate objects found on the manifest, 273 using the CRL object found on the manifest: 275 * if the strict validation option is enabled by the operator, 276 the validation is performed according to Section 7 of 277 [RFC6487], 279 * otherwise, the validation is performed according to Section 7 280 of [RFC6487], with the exception of the resource certification 281 path validation, that is performed according to 282 Section 4.2.4.4 of 283 [I-D.ietf-sidr-rpki-validation-reconsidered]. 285 (Note that this implementation uses the operator configuration to 286 decide which algorithm to use for path validation. It applies 287 selected algorithm to all resource certificates, rather than 288 applying appropriate algorithm per resource certificate, based on 289 the object identifier (OID) for the Certificate Policy found in 290 that certificate, as specified in 291 [I-D.ietf-sidr-rpki-validation-reconsidered].) 293 6. Validate all ROA objects found on the manifest, using the CRL 294 object found on the manifest, according to Section 4 of 295 [RFC6482]. 297 7. Validate all Ghostbusters Record objects found on the manifest, 298 using the CRL object found on the manifest, according to 299 Section 7 of [RFC6493]. 301 8. For every valid CA certificate object found on the manifest, 302 apply the procedure described in this section (Section 4.2), 303 recursively, provided that this CA certificate (identified by its 304 SKI) has not yet been validated during current tree validation 305 run. 307 4.2.1. Finding the most recent valid manifest and CRL 309 1. Fetch from the store (see Section 6.1.4) all objects of type 310 manifest, whose certificate's AKI extension matches the SKI of 311 the current CA certificate. If no such objects are found, stop 312 processing the current CA certificate and issue an error. 314 2. Find among found objects the manifest object with the highest 315 manifestNumber field (Section 4.2.1 of [RFC6486]), for which all 316 following conditions are met: 318 * There is only one entry in the manifest for which the store 319 contains exactly one object of type CRL, the hash of which 320 matches the hash of the entry. 322 * The manifest's certificate AKI equals the above CRL's AKI. 324 * The above CRL is a valid object according to Section 6.3 of 325 [RFC5280]. 327 * The manifest is a valid object according to Section 4.4 of 328 [RFC6486], and its EE certificates is not in the CRL found 329 above. 331 3. If there is an object that matches above criteria, consider this 332 object to be the valid manifest, and the CRL found at the 333 previous step - the valid CRL for the current CA certificate's 334 publication point. 336 4. Report an error for every other manifest with a number higher 337 than the number of the valid manifest. 339 4.2.2. Manifest entries validation 341 For every entry in the manifest object: 343 1. Construct an entry's URI by appending the entry name to the 344 current CA's publication point URI. 346 2. Get all objects from the store whose hash attribute equals 347 entry's hash (see Section 6.1.2). 349 3. If no such objects are found, issue an error for this manifest 350 entry and progress to the next entry. This case indicates that 351 the repository does not have an object at the location listed in 352 the manifest, or that the object's hash does not match the hash 353 listed in the manifest. 355 4. For every found object, compare its URI with the URI of the 356 manifest entry. 358 * For every object with a non-matching URI issue a warning. 359 This case indicates that the object from the manifest entry is 360 (also) found at a different location in a (possibly different) 361 repository. 363 * If no objects with a matching URI are found, issue a warning. 364 This case indicates that there is no object found in the 365 repository at the location listed in the manifest entry (but 366 there is at least one matching object found at a different 367 location). 369 5. Use all found objects for further validation as per Section 4.2. 371 Please note that the above steps will not reject objects whose hash 372 matches the hash listed in the manifest, but the URI does not. See 373 Section 9.2 for additional information. 375 4.3. Object Store Cleanup 377 At the end of every TA tree validation some objects are removed from 378 the store using the following rules: 380 1. Given all objects that were encountered during the current 381 validation run, remove from the store (Section 6.1.6) all objects 382 whose URI attribute matches the URI of one of the encountered 383 objects, but the content's hash is different. This removes from 384 the store objects that were replaced in the repository by their 385 newer versions with the same URIs. 387 2. Remove from the store all objects that were last encountered 388 during validation a long time ago (as specified by the local 389 policy). This removes objects that do not appear on any valid 390 manifest anymore (but possibly are still published in a 391 repository). 393 3. Remove from the store all objects that were downloaded recently 394 (as specified by the local policy), but have never been used in 395 the validation process. This removes objects that have never 396 appeared on any valid manifest. 398 Shortening the time interval used in step 2 will free more disk space 399 used by the store, at the expense of downloading removed objects 400 again if they are still published in the repository. 402 Extending the time interval used in step 3 will prevent repeated 403 downloads of repository objects, with the risk that such objects, if 404 created massively by mistake or by an adversary, will fill up local 405 disk space, if they are not cleaned up promptly. 407 5. Remote Objects Fetcher 409 The fetcher is responsible for downloading objects from remote 410 repositories (described in Section 3 of [RFC6481]) using rsync 411 protocol ([rsync]), or RPKI Repository Delta Protocol (RRDP) 412 ([I-D.ietf-sidr-delta-protocol]). 414 5.1. Fetcher Operations 416 For every visited URI the fetcher keeps track of the last time a 417 successful fetch occurred. 419 5.1.1. Fetch repository objects 421 This operation receives one parameter - a URI. For an rsync 422 repository this URI points to a directory. For an RRDP repository it 423 points to the repository's notification file. 425 The fetcher performs following steps: 427 1. If data associated with the URI has been downloaded recently (as 428 specified by the local policy), skip following steps. 430 2. Download remote objects using the URI provided (for an rsync 431 repository use recursive mode). If the URI contains schema 432 "https" and download has failed, issue a warning, replace "https" 433 schema in the URI by "http", and try to download objects again, 434 using the resulting URI. 436 3. If remote objects can not be downloaded, issue an error and skip 437 following steps. 439 4. Perform syntactic verification of fetched objects. The type of 440 every object (certificate, manifest, CRL, ROA, or Ghostbusters 441 record), is determined based on the object's filename extension 442 (.cer, .mft, .crl, .roa, and .gbr, respectively). The syntax of 443 the object is described in Section 4 of [RFC6487] for resource 444 certificates, step 1 of Section 3 of [RFC6488] for signed 445 objects, and specifically, Section 4 of [RFC6486] for manifests, 446 [RFC5280] for CRLs, Section 3 of [RFC6482] for ROAs, and 447 Section 5 of [RFC6493] for Ghostbusters records. 449 5. Put every downloaded and syntactically correct object in the 450 object store (Section 6.1.1). 452 The time interval used in the step 1 should be chosen based on the 453 acceptable delay in receiving repository updates. 455 5.1.2. Fetch single repository object 457 This operation receives one parameter - a URI that points to an 458 object in a repository. 460 The fetcher performs following operations: 462 1. Download remote object using the URI provided. If the URI 463 contains "https" schema and download failed, issue a warning, 464 replace "https" schema in the URI by "http", and try to download 465 the object using the resulting URI. 467 2. If the remote object can not be downloaded, issue an error and 468 skip following steps. 470 3. Perform syntactic verification of fetched object. The type of 471 object (certificate, manifest, CRL, ROA, or Ghostbusters record), 472 is determined based on the object's filename extension (.cer, 473 .mft, .crl, .roa, and .gbr, respectively). The syntax of the 474 object is described in Section 4 of [RFC6487] for resource 475 certificates, step 1 of Section 3 of [RFC6488] for signed 476 objects, and specifically, Section 4 of [RFC6486] for manifests, 477 [RFC5280] for CRLs, Section 3 of [RFC6482] for ROAs, and 478 Section 5 of [RFC6493] for Ghostbusters records. 480 4. If the downloaded object is not syntactically correct, issue an 481 error and skip further steps. 483 5. Delete all objects from the object store (Section 6.1.5) whose 484 URI matches the URI given. 486 6. Put the downloaded object in the object store (Section 6.1.1). 488 6. Local Object Store 490 6.1. Store Operations 492 6.1.1. Store Repository Object 494 Put given object in the store, along with its type, URI, hash, and 495 AKI, if there is no record with the same hash and URI fields. Note 496 that in the (unlikely) event of hash collision the given object will 497 not replace the object in the store. 499 6.1.2. Get objects by hash 501 Retrieve all objects from the store whose hash attribute matches the 502 given hash. 504 6.1.3. Get certificate objects by URI 506 Retrieve from the store all objects of type certificate, whose URI 507 attribute matches the given URI. 509 6.1.4. Get manifest objects by AKI 511 Retrieve from the store all objects of type manifest, whose AKI 512 attribute matches the given AKI. 514 6.1.5. Delete objects for a URI 516 For a given URI, delete all objects in the store with matching URI 517 attribute. 519 6.1.6. Delete outdated objects 521 For a given URI and a list of hashes, delete all objects in the store 522 with matching URI, whose hash attribute is not in the given list of 523 hashes. 525 6.1.7. Update object's validation time 527 For all objects in the store whose hash attribute matches the given 528 hash, set the last validation time attribute to the given timestamp. 530 7. Acknowledgements 532 This document describes the algorithm as it is implemented by the 533 software development team at the RIPE NCC. The authors would also 534 like to acknowledge contributions by Carlos Martinez, Andy Newton, 535 Rob Austein, and Stephen Kent. 537 8. IANA Considerations 539 This document has no actions for IANA. 541 9. Security Considerations 543 9.1. Hash collisions 545 This implementation will not detect possible hash collisions in the 546 hashes of repository objects (calculated using the file hash 547 algorithm specified in [RFC6485]). It considers objects with same 548 hash values as identical. 550 9.2. Mismatch between the expected and the actual location of an object 551 in the repository 553 According to Section 2 of [RFC6481], all objects issued by a 554 particular CA certificate are expected to be located in one 555 repository publication point, specified in the SIA extension of that 556 CA certificate. The manifest object issued by that CA certificate 557 enumerates all other issued objects, listing their file names and 558 content hashes. 560 However, it is possible that an object whose content hash matches the 561 hash listed in the manifest, has either a different file name, or is 562 located at a different publication point in a repository. 564 On the other hand, all RPKI objects, either explicitly or within 565 their embedded EE certificate, have an Authority Key Identifier 566 extension that contains the key identifier of their issuing CA 567 certificate. Therefore it is always possible to perform an RPKI 568 validation of the object whose expected location does not match its 569 actual location, provided that the certificate that matches the AKI 570 of the object in question is known to the system that performs 571 validation. 573 In case of a mismatch described above this implementation will not 574 exclude an object from further validation merely because it's actual 575 location or file name does not match the expected location or file 576 name. This decision was chosen because the actual location of a file 577 in a repository is taken from the repository retrieval mechanism, 578 which, in case of an rsync repository, does not provide any 579 cryptographic security, and in case of an RRDP repository, provides 580 only a transport layer security, with the fallback to unsecured 581 transport. On the other hand, the manifest is an RPKI signed object, 582 and its content could be verified in the context of the RPKI 583 validation. 585 9.3. Manifest content versus publication point content 587 This algorithm uses the content of a manifest object to determine 588 other objects issued by a CA certificate. It verifies that the 589 manifest is located in the publication point designated in the CA 590 Certificate's SIA extension. However, if there are other (not listed 591 in the manifest) objects located in the same publication point 592 directory, they are ignored, even if they might be valid and issued 593 by the same CA certificate as the manifest. (This behavior is 594 allowed, but not required, by [RFC6486].) 596 9.4. Storing of a TA certificate object before its complete validation 598 When fetching and storing a TA certificate to the object store, only 599 a syntactic validation of a downloaded object is performed before 600 newly downloaded object replaces the previously downloaded object in 601 the object store (see Section 5.1.2). If an attacker will be able to 602 replace a genuine TA certificate by a syntactically valid certificate 603 object (either by manipulating the content of a repository, or by a 604 man-in-the-middle attack), this implementation will discard 605 previously downloaded genuine object, and replace it by a false 606 object. Such false object will be detected later, but the validation 607 of the whole RPKI tree under this TA will be aborted, as described in 608 Section 4. 610 9.5. Possible denial of service 612 The store cleanup procedure described in Section 4.3 tries to 613 minimise removal and subsequent re-fetch of objects that are 614 published in a repository, but not used in the validation. Once such 615 objects are removed from the remote repository, they will be 616 discarded from the local object store after a period of time 617 specified by a local policy. By generating an excessive amount of 618 syntactically valid RPKI objects, a man-in-the-middle attack between 619 a validating tool and a repository could force an implementation to 620 fetch and store those objects in the object store before they are 621 validated and discarded, leading to an out-of-memory or out-of-disk- 622 space conditions, and, subsequently, a denial of service. 624 10. References 626 10.1. Normative References 628 [I-D.ietf-sidr-delta-protocol] 629 Bruijnzeels, T., Muravskiy, O., Weber, B., and R. Austein, 630 "RPKI Repository Delta Protocol (RRDP)", draft-ietf-sidr- 631 delta-protocol-08 (work in progress), March 2017. 633 [I-D.ietf-sidr-rpki-validation-reconsidered] 634 Huston, G., Michaelson, G., Martinez, C., Bruijnzeels, T., 635 Newton, A., and D. Shaw, "RPKI Validation Reconsidered", 636 draft-ietf-sidr-rpki-validation-reconsidered-08 (work in 637 progress), June 2017. 639 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 640 Housley, R., and W. Polk, "Internet X.509 Public Key 641 Infrastructure Certificate and Certificate Revocation List 642 (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, 643 . 645 [RFC6481] Huston, G., Loomans, R., and G. Michaelson, "A Profile for 646 Resource Certificate Repository Structure", RFC 6481, 647 DOI 10.17487/RFC6481, February 2012, 648 . 650 [RFC6482] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route 651 Origin Authorizations (ROAs)", RFC 6482, 652 DOI 10.17487/RFC6482, February 2012, 653 . 655 [RFC6485] Huston, G., "The Profile for Algorithms and Key Sizes for 656 Use in the Resource Public Key Infrastructure (RPKI)", 657 RFC 6485, DOI 10.17487/RFC6485, February 2012, 658 . 660 [RFC6486] Austein, R., Huston, G., Kent, S., and M. Lepinski, 661 "Manifests for the Resource Public Key Infrastructure 662 (RPKI)", RFC 6486, DOI 10.17487/RFC6486, February 2012, 663 . 665 [RFC6487] Huston, G., Michaelson, G., and R. Loomans, "A Profile for 666 X.509 PKIX Resource Certificates", RFC 6487, 667 DOI 10.17487/RFC6487, February 2012, 668 . 670 [RFC6488] Lepinski, M., Chi, A., and S. Kent, "Signed Object 671 Template for the Resource Public Key Infrastructure 672 (RPKI)", RFC 6488, DOI 10.17487/RFC6488, February 2012, 673 . 675 [RFC6493] Bush, R., "The Resource Public Key Infrastructure (RPKI) 676 Ghostbusters Record", RFC 6493, DOI 10.17487/RFC6493, 677 February 2012, . 679 [RFC7730] Huston, G., Weiler, S., Michaelson, G., and S. Kent, 680 "Resource Public Key Infrastructure (RPKI) Trust Anchor 681 Locator", RFC 7730, DOI 10.17487/RFC7730, January 2016, 682 . 684 10.2. Informative References 686 [github] "RIPE NCC RPKI Validator on GitHub", . 689 [rsync] "Rsync home page", . 691 Authors' Addresses 693 Oleg Muravskiy 694 RIPE NCC 696 Email: oleg@ripe.net 698 Tim Bruijnzeels 699 RIPE NCC 701 Email: tim@ripe.net