draft-ietf-sidr-rpki-tree-validation-02.txt   draft-ietf-sidr-rpki-tree-validation-03.txt 
SIDR O. Muravskiy SIDR O. Muravskiy
Internet-Draft T. Bruijnzeels Internet-Draft T. Bruijnzeels
Intended status: Informational RIPE NCC Intended status: Informational RIPE NCC
Expires: January 21, 2017 July 20, 2016 Expires: May 4, 2017 October 31, 2016
RPKI Certificate Tree Validation by a Relying Party Tool RPKI Certificate Tree Validation by the RIPE NCC RPKI Validator
draft-ietf-sidr-rpki-tree-validation-02 draft-ietf-sidr-rpki-tree-validation-03
Abstract Abstract
This document describes the approach to validate the content of the This document describes the approach to validate the content of the
RPKI certificate tree, as used by the RIPE NCC RPKI Validator. This RPKI certificate tree, as used by the RIPE NCC RPKI Validator. This
approach is independent of a particular object retrieval mechanism. approach is independent of a particular object retrieval mechanism.
This allows it to be used with repositories available over the rsync This allows it to be used with repositories available over the rsync
protocol, the RPKI Repository Delta Protocol, and repositories that protocol, the RPKI Repository Delta Protocol, and repositories that
use a mix of both. use a mix of both.
skipping to change at page 1, line 35 skipping to change at page 1, line 35
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 21, 2017. This Internet-Draft will expire on May 4, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Scope of this document . . . . . . . . . . . . . . . . . . . 3
2. General Considerations . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Hash comparisons . . . . . . . . . . . . . . . . . . . . 3 3. General Considerations . . . . . . . . . . . . . . . . . . . 4
2.2. Discovery of RPKI objects issued by a CA . . . . . . . . 3 3.1. Hash comparisons . . . . . . . . . . . . . . . . . . . . 4
2.3. Manifest entries versus repository content . . . . . . . 4 3.2. Discovery of RPKI objects issued by a CA . . . . . . . . 4
3. Top-down Validation of a Single Trust Anchor Certificate Tree 4 3.3. Manifest entries versus repository content . . . . . . . 4
3.1. Fetching the Trust Anchor Certificate Using the Trust 4. Top-down Validation of a Single Trust Anchor Certificate Tree 5
4.1. Fetching the Trust Anchor Certificate Using the Trust
Anchor Locator . . . . . . . . . . . . . . . . . . . . . 5 Anchor Locator . . . . . . . . . . . . . . . . . . . . . 5
3.2. CA Certificate Validation . . . . . . . . . . . . . . . . 5 4.2. CA Certificate Validation . . . . . . . . . . . . . . . . 6
3.2.1. Finding the most recent valid manifest and CRL . . . 6 4.2.1. Finding the most recent valid manifest and CRL . . . 7
3.2.2. Manifest entries validation . . . . . . . . . . . . . 7 4.2.2. Manifest entries validation . . . . . . . . . . . . . 7
3.3. Object Store Cleanup . . . . . . . . . . . . . . . . . . 8 4.3. Object Store Cleanup . . . . . . . . . . . . . . . . . . 8
4. Remote Objects Fetcher . . . . . . . . . . . . . . . . . . . 8 5. Remote Objects Fetcher . . . . . . . . . . . . . . . . . . . 9
4.1. Fetcher Operations . . . . . . . . . . . . . . . . . . . 8 5.1. Fetcher Operations . . . . . . . . . . . . . . . . . . . 9
4.1.1. Fetch repository objects . . . . . . . . . . . . . . 9 5.1.1. Fetch repository objects . . . . . . . . . . . . . . 9
4.1.2. Fetch single repository object . . . . . . . . . . . 9 5.1.2. Fetch single repository object . . . . . . . . . . . 10
5. Local Object Store . . . . . . . . . . . . . . . . . . . . . 10 6. Local Object Store . . . . . . . . . . . . . . . . . . . . . 11
5.1. Store Operations . . . . . . . . . . . . . . . . . . . . 10 6.1. Store Operations . . . . . . . . . . . . . . . . . . . . 11
5.1.1. Store Repository Object . . . . . . . . . . . . . . . 10 6.1.1. Store Repository Object . . . . . . . . . . . . . . . 11
5.1.2. Get objects by hash . . . . . . . . . . . . . . . . . 10 6.1.2. Get objects by hash . . . . . . . . . . . . . . . . . 11
5.1.3. Get certificate objects by URI . . . . . . . . . . . 10 6.1.3. Get certificate objects by URI . . . . . . . . . . . 11
5.1.4. Get manifest objects by AKI . . . . . . . . . . . . . 10 6.1.4. Get manifest objects by AKI . . . . . . . . . . . . . 11
5.1.5. Delete objects for a URI . . . . . . . . . . . . . . 10 6.1.5. Delete objects for a URI . . . . . . . . . . . . . . 11
5.1.6. Delete outdated objects . . . . . . . . . . . . . . . 10 6.1.6. Delete outdated objects . . . . . . . . . . . . . . . 11
5.1.7. Update object's validation time . . . . . . . . . . . 11 6.1.7. Update object's validation time . . . . . . . . . . . 11
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
8. Security Considerations . . . . . . . . . . . . . . . . . . . 11 9. Security Considerations . . . . . . . . . . . . . . . . . . . 12
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 9.1. Hash collisions . . . . . . . . . . . . . . . . . . . . . 12
9.1. Normative References . . . . . . . . . . . . . . . . . . 12 9.2. Mismatch between the expected and the actual location of
9.2. Informative References . . . . . . . . . . . . . . . . . 13 an object in the repository . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 9.3. Manifest content versus publication point content . . . . 13
9.4. Storing of a TA certificate object before its complete
validation . . . . . . . . . . . . . . . . . . . . . . . 13
9.5. Possible denial of service . . . . . . . . . . . . . . . 13
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
10.1. Normative References . . . . . . . . . . . . . . . . . . 13
10.2. Informative References . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction 1. Scope of this document
This document describes how the RIPE NCC RPKI Validator version 2.23
has been implemented. Source code to this software can be found
here: [github]. The purpose of this document is to provide
transparency to users of (and contributors to) this software tool, as
well as serve to be subjected to scrutiny by the SIDR Working Group.
It is not intended as a document that describes a standard or best
practices on how validation should be done in general.
2. Introduction
In order to use information published in RPKI repositories, Relying In order to use information published in RPKI repositories, Relying
Parties (RP) need to retrieve and validate the content of Parties (RP) need to retrieve and validate the content of
certificates, CRLs, and other RPKI signed objects. To validate a certificates, certificate revocation lists (CRLs), and other RPKI
particular object, one must ensure that all certificates in the signed objects. To validate a particular object, one must ensure
certificate chain up to the Trust Anchor (TA) are valid. Therefore that all certificates in the certificate chain up to the Trust Anchor
the validation of a certificate tree is performed top-down, starting (TA) are valid. Therefore the validation of a certificate tree is
from the TA certificate and descending down the certificate chain, performed top-down, starting from the TA certificate and descending
validating every encountered certificate and its products. The down the certificate chain, validating every encountered certificate
result of this process is a list of all encountered RPKI objects with and its products. The result of this process is a list of all
a validity status attached to each of them. These results may later encountered RPKI objects with a validity status attached to each of
be used by a Relying Party in taking routing decisions, etc. them. These results may later be used by a Relying Party in taking
routing decisions, etc.
Traditionally RPKI data is made available to RPs through the Traditionally RPKI data is made available to RPs through the
repositories [RFC6481] accessible over rsync protocol. Relying repositories [RFC6481] accessible over [rsync] protocol. Relying
parties are advised to keep a local copy of repository data, and parties are advised to keep a local copy of repository data, and
perform regular updates of this copy from the repository (Section 5 perform regular updates of this copy from the repository (Section 5
of [RFC6481]). The RPKI Repository Delta Protocol of [RFC6481]). The RPKI Repository Delta Protocol
[I-D.ietf-sidr-delta-protocol] introduces another method to fetch [I-D.ietf-sidr-delta-protocol] introduces another method to fetch
repository data and keep the local copy up to date with the repository data and keep the local copy up to date with the
repository. repository.
This document describes how the RIPE NCC RPKI Validator discovers This document describes how the RIPE NCC RPKI Validator discovers
RPKI objects to download, builds certificate paths, and validates RPKI objects to download, builds certificate paths, and validates
RPKI objects, independently from what repository access protocol is RPKI objects, independently from what repository access protocol is
used. To achieve this, it puts downloaded RPKI objects in an object used. To achieve this, it puts downloaded RPKI objects in an object
store, where each RPKI object can be found by its URI, the hash of store, where each RPKI object can be found by its URI, the hash of
its content, value of its Authority Key Identifier (AKI) extension, its content, value of its Authority Key Identifier (AKI) extension,
or a combination of these. It also keeps track of the download and or a combination of these. It also keeps track of the download and
the validation time for every object, to perform cleanups of the the validation time for every object, to decide which locally stored
local copy. objects are not used in the RPKI tree validation and could be
removed.
2. General Considerations 3. General Considerations
2.1. Hash comparisons 3.1. Hash comparisons
This algorithm relies on the properties of the file hash algorithm This algorithm relies on the properties of the file hash algorithm
(defined in [RFC6485]) to compute the hash of repository objects. It (defined in [RFC6485]) to compute the hash of repository objects. It
assumes that any two objects for which the hash value is the same, assumes that any two objects for which the hash value is the same,
are identical. are identical.
The hash comparison is used when matching objects in the repository The hash comparison is used when matching objects in the repository
with entries on the manifest, and when looking up objects in the with entries on the manifest (Section 4.2.2), and when looking up
object store (Section 5). objects in the object store (Section 6).
2.2. Discovery of RPKI objects issued by a CA 3.2. Discovery of RPKI objects issued by a CA
There are several possible ways of discovering products of a CA There are several possible ways of discovering products of a CA
certificate: one could use all objects located in a repository certificate: one could use all objects located in a repository
directory designated as a publication point for a CA, or only objects directory designated as a publication point for a CA, or only objects
mentioned on the manifest located at that publication point (see mentioned on the manifest located at that publication point (see
Section 6 of [RFC6486]), or use all objects whose AKI extension Section 6 of [RFC6486]), or use all objects whose AKI extension
matches the Subject Key Identifier (SKI) extension (Section 4.2.1 of matches the Subject Key Identifier (SKI) extension (Section 4.2.1 of
[RFC5280]) of a CA certificate. [RFC5280]) of a CA certificate.
For publication points whose content is consistent with the manifest For publication points whose content is consistent with the manifest
and issuing certificate all of these approaches should produce the and issuing certificate all of these approaches should produce the
same result. For inconsistent publication points the results might same result. For inconsistent publication points the results might
be different. Section 6 of [RFC6486] leaves the decision on how to be different. Section 6 of [RFC6486] leaves the decision on how to
deal with inconsistencies to a local policy. deal with inconsistencies to a local policy.
The implementation described here does not rely on content of The implementation described here does not rely on content of
repository directories, but uses the Authority Key Identifier (AKI) repository directories, but uses the Authority Key Identifier (AKI)
extension of a manifest and a certificate revocation list (CRL) to extension of a manifest and a certificate revocation list (CRL) to
find in an object store (Section 5) a manifest and a CRL issued by a find in an object store (Section 6) a manifest and a CRL issued by a
particular Certification Authority (CA) (see Section 3.2.1). It particular Certification Authority (CA) (see Section 4.2.1). It
further uses the hashes of manifest's fileList entries (Section 4.2.1 further uses the hashes of manifest's fileList entries (Section 4.2.1
of [RFC6486]) to find other objects issued by the CA, as described in of [RFC6486]) to find other objects issued by the CA, as described in
Section 3.2.2. Section 4.2.2.
2.3. Manifest entries versus repository content 3.3. Manifest entries versus repository content
Since the current set of RPKI standards requires use of the manifest Since the current set of RPKI standards requires use of the manifest
[RFC6486] to describe the content of a publication point, this [RFC6486] to describe the content of a publication point, this
implementation requires strict consistency between the publication implementation requires strict consistency between the publication
point content and manifest content. (This is a more stringent point content and manifest content. (This is a more stringent
requirement than established in [RFC6486].) Therefore it will not requirement than established in [RFC6486].) Therefore it will not
process objects that are found in the publication point but do not process objects that are found in the publication point but do not
match any of the entries of that publication point's manifest (see match any of the entries of that publication point's manifest (see
Section 3.2.2). It will also issue warnings for all found Section 4.2.2). It will also issue warnings for all found
mismatches, so that the responsible operators could be made aware of mismatches, so that the responsible operators could be made aware of
inconsistencies and fix them. inconsistencies and fix them.
3. Top-down Validation of a Single Trust Anchor Certificate Tree 4. Top-down Validation of a Single Trust Anchor Certificate Tree
1. The validation of a Trust Anchor (TA) certificate tree starts 1. The validation of a Trust Anchor (TA) certificate tree starts
from its TA certificate. To retrieve the TA certificate, a Trust from its TA certificate. To retrieve the TA certificate, a Trust
Anchor Locator (TAL) object is used, as described in Section 3.1. Anchor Locator (TAL) object is used, as described in Section 4.1.
2. If the TA certificate is retrieved, it is validated according to 2. If the TA certificate is retrieved, it is validated according to
Section 7 of [RFC6487] and Section 2.2 of [RFC7730]. Otherwise Section 7 of [RFC6487] and Section 2.2 of [RFC7730]. Otherwise
the validation of certificate tree is aborted and an error is the validation of certificate tree is aborted and an error is
issued. issued.
3. If the TA certificate is valid, then all its subordinate objects 3. If the TA certificate is valid, then all its subordinate objects
are validated as described in Section 3.2. Otherwise the are validated as described in Section 4.2. Otherwise the
validation of certificate tree is aborted and an error is issued. validation of certificate tree is aborted and an error is issued.
4. For each repository object that was validated during this 4. For each repository object that was validated during this
validation run, its validation timestamp is updated in the object validation run, its validation timestamp is updated in the object
store (see Section 5.1.7). store (see Section 6.1.7).
5. Outdated objects are removed from the store as described in 5. Outdated objects are removed from the store as described in
Section 3.3. This completes the validation of the TA certificate Section 4.3. This completes the validation of the TA certificate
tree. tree.
3.1. Fetching the Trust Anchor Certificate Using the Trust Anchor 4.1. Fetching the Trust Anchor Certificate Using the Trust Anchor
Locator Locator
The following steps are performed in order to fetch a Trust Anchor The following steps are performed in order to fetch a Trust Anchor
Certificate: Certificate:
1. (Optional) If the Trust Anchor Locator contains a "prefetch.uris" 1. (Optional) If the Trust Anchor Locator contains a "prefetch.uris"
field, pass the URIs contained in that field to the fetcher (see field, pass the URIs contained in that field to the fetcher (see
Section 4.1.1). (This field is a non-standard addition to the Section 5.1.1). (This field is a non-standard addition to the
TAL format. It helps fetching non-hierarchical rsync TAL format. It helps fetching non-hierarchical rsync
repositories more efficiently.) repositories more efficiently.)
2. Extract the TA certificate URI from the TAL's URI section (see 2. Extract the first TA certificate URI from the TAL's URI section
Section 2.1 of [RFC7730]) and pass it to the object fetcher (see Section 2.1 of [RFC7730]) and pass it to the object fetcher
(Section 4.1.2). (Section 5.1.2). If the fetcher returns an error, repeat this
step for every URI in the URI section, until no error is
encountered, or no more URIs left.
3. Retrieve from the object store (see Section 5.1.3) all 3. Retrieve from the object store (see Section 6.1.3) all
certificate objects, for which the URI matches the URI extracted certificate objects, for which the URI matches the URI extracted
from the TAL in the previous step, and the public key matches the from the TAL in the previous step, and the public key matches the
subjectPublicKeyInfo extension of the TAL (see Section 2.1 of subjectPublicKeyInfo extension of the TAL (see Section 2.1 of
[RFC7730]). [RFC7730]).
4. If no, or more than one such objects are found, issue an error 4. If no, or more than one such objects are found, issue an error
and abort certificate tree validation process with an error. and abort certificate tree validation process with an error.
Otherwise, use the single found object as the Trust Anchor Otherwise, use the single found object as the Trust Anchor
certificate. certificate.
3.2. CA Certificate Validation 4.2. CA Certificate Validation
The following steps describe the validation of a single CA Resource The following steps describe the validation of a single CA Resource
certificate: certificate:
1. If both the caRepository (Section 4.8.8.1 of [RFC6487]), and the 1. If both the caRepository (Section 4.8.8.1 of [RFC6487]), and the
id-ad-rpkiNotify (Section 3.2 of [I-D.ietf-sidr-delta-protocol]) id-ad-rpkiNotify (Section 3.2 of [I-D.ietf-sidr-delta-protocol])
SIA pointers are present in the CA certificate, use a local SIA pointers are present in the CA certificate, use a local
policy to determine which pointer to use. Extract the URI from policy to determine which pointer to use. Extract the URI from
the selected pointer and pass it to the object fetcher (see the selected pointer and pass it to the object fetcher (see
Section 4.1.1). Section 5.1.1).
2. For the CA certificate, find the current manifest and certificate 2. For the CA certificate, find the current manifest and certificate
revocation list (CRL), using the procedure described in revocation list (CRL), using the procedure described in
Section 3.2.1. If no such manifest and CRL could be found, stop Section 4.2.1. If no such manifest and CRL could be found, stop
validation of this certificate, consider it invalid, and issue an validation of this certificate, consider it invalid, and issue an
error. error.
3. Compare the URI found in the id-ad-rpkiManifest field 3. Compare the URI found in the id-ad-rpkiManifest field
(Section 4.8.8.1 of [RFC6487]) of the SIA extension of the (Section 4.8.8.1 of [RFC6487]) of the SIA extension of the
certificate with the URI of the manifest found in the previous certificate with the URI of the manifest found in the previous
step. If they are different, issue a warning. step. If they are different, issue a warning, but continue
validation process using this manifest object. (This warning
indicates that there is a mismatch between the expected and the
actual location of an object in a repository. See Section 9 for
the explanation of this mismatch and the decision taken.)
4. Perform manifest entries discovery and validation as described in 4. Perform manifest entries discovery and validation as described in
Section 3.2.2. Section 4.2.2.
5. Validate all resource certificate objects found on the manifest, 5. Validate all resource certificate objects found on the manifest,
using the CRL object found on the manifest, according to using the CRL object found on the manifest, according to
Section 7 of [RFC6487]. Section 7 of [RFC6487].
6. Validate all ROA objects found on the manifest, using the CRL 6. Validate all ROA objects found on the manifest, using the CRL
object found on the manifest, according to Section 4 of object found on the manifest, according to Section 4 of
[RFC6482]. [RFC6482].
7. Validate all Ghostbusters Record objects found on the manifest, 7. Validate all Ghostbusters Record objects found on the manifest,
using the CRL object found on the manifest, according to using the CRL object found on the manifest, according to
Section 7 of [RFC6493]. Section 7 of [RFC6493].
8. For every valid CA certificate object found on the manifest, 8. For every valid CA certificate object found on the manifest,
apply the procedure described in this section (Section 3.2), apply the procedure described in this section (Section 4.2),
recursively, provided that this CA certificate (identified by its recursively, provided that this CA certificate (identified by its
SKI) has not yet been validated during current tree validation SKI) has not yet been validated during current tree validation
run. run.
3.2.1. Finding the most recent valid manifest and CRL 4.2.1. Finding the most recent valid manifest and CRL
1. Fetch from the store (see Section 5.1.4) all objects of type 1. Fetch from the store (see Section 6.1.4) all objects of type
manifest, whose certificate's AKI extension matches the SKI of manifest, whose certificate's AKI extension matches the SKI of
the current CA certificate. If no such objects are found, stop the current CA certificate. If no such objects are found, stop
processing the current CA certificate and issue an error. processing the current CA certificate and issue an error.
2. Find among found objects the manifest object with the highest 2. Find among found objects the manifest object with the highest
manifestNumber field (Section 4.2.1 of [RFC6486]), for which all manifestNumber field (Section 4.2.1 of [RFC6486]), for which all
following conditions are met: following conditions are met:
* There is only one entry in the manifest for which the store * There is only one entry in the manifest for which the store
contains exactly one object of type CRL, the hash of which contains exactly one object of type CRL, the hash of which
skipping to change at page 7, line 13 skipping to change at page 7, line 47
above. above.
3. If there is an object that matches above criteria, consider this 3. If there is an object that matches above criteria, consider this
object to be the valid manifest, and the CRL found at the object to be the valid manifest, and the CRL found at the
previous step - the valid CRL for the current CA certificate's previous step - the valid CRL for the current CA certificate's
publication point. publication point.
4. Report an error for every other manifest with a number higher 4. Report an error for every other manifest with a number higher
than the number of the valid manifest. than the number of the valid manifest.
3.2.2. Manifest entries validation 4.2.2. Manifest entries validation
For every entry in the manifest object: For every entry in the manifest object:
1. Construct an entry's URI by appending the entry name to the 1. Construct an entry's URI by appending the entry name to the
current CA's publication point URI. current CA's publication point URI.
2. Get all objects from the store whose hash attribute equals 2. Get all objects from the store whose hash attribute equals
entry's hash (see Section 5.1.2). entry's hash (see Section 6.1.2).
3. If no such objects are found, issue an error for this manifest 3. If no such objects are found, issue an error for this manifest
entry and progress to the next entry. This case indicates that entry and progress to the next entry. This case indicates that
the repository does not have an object at the location listed in the repository does not have an object at the location listed in
the manifest, or that the object's hash does not match the hash the manifest, or that the object's hash does not match the hash
listed in the manifest. listed in the manifest.
4. For every found object, compare its URI with the URI of the 4. For every found object, compare its URI with the URI of the
manifest entry. manifest entry.
skipping to change at page 7, line 43 skipping to change at page 8, line 28
This case indicates that the object from the manifest entry is This case indicates that the object from the manifest entry is
(also) found at a different location in a (possibly different) (also) found at a different location in a (possibly different)
repository. repository.
* If no objects with a matching URI are found, issue a warning. * If no objects with a matching URI are found, issue a warning.
This case indicates that there is no object found in the This case indicates that there is no object found in the
repository at the location listed in the manifest entry (but repository at the location listed in the manifest entry (but
there is at least one matching object found at a different there is at least one matching object found at a different
location). location).
5. Use all found objects for further validation as per Section 3.2. 5. Use all found objects for further validation as per Section 4.2.
Please note that the above steps will not reject objects whose hash Please note that the above steps will not reject objects whose hash
matches the hash listed in the manifest, but the URI does not. The matches the hash listed in the manifest, but the URI does not. See
warning is generated in this case. It indicates that there is an Section 9.2 for additional information.
inconsistency in a repository between the content of the publication
point and its manifest. The choice has been made in favour of the
manifest, because the manifest, and the object it refers to by the
hash are both RPKI signed objects, while the repository's directory
listing is not.
3.3. Object Store Cleanup 4.3. Object Store Cleanup
At the end of every TA tree validation some objects are removed from At the end of every TA tree validation some objects are removed from
the store using the following steps: the store using the following rules:
1. Given all objects that were encountered during the current 1. Given all objects that were encountered during the current
validation run, remove from the store (Section 5.1.6) all objects validation run, remove from the store (Section 6.1.6) all objects
whose URI attribute matches the URI of one of the encountered whose URI attribute matches the URI of one of the encountered
objects, but the content's hash is different. This removes from objects, but the content's hash is different. This removes from
the store objects that were replaced in the repository by their the store objects that were replaced in the repository by their
newer versions with the same URIs. newer versions with the same URIs.
2. Remove from the store all objects that were last encountered 2. Remove from the store all objects that were last encountered
during validation a long time ago (as specified by the local during validation a long time ago (as specified by the local
policy). This removes objects that do not appear on any valid policy). This removes objects that do not appear on any valid
manifest anymore (but possibly are still published in a manifest anymore (but possibly are still published in a
repository). repository).
3. Remove from the store all objects that were downloaded recently 3. Remove from the store all objects that were downloaded recently
(as specified by the local policy), but have never been used in (as specified by the local policy), but have never been used in
the validation process. This removes objects that have never the validation process. This removes objects that have never
appeared on any valid manifest. appeared on any valid manifest.
Shortening the time interval used in step 2 will free disk space used Shortening the time interval used in step 2 will free more disk space
by the store, at the expense of downloading removed objects again if used by the store, at the expense of downloading removed objects
they are still published in the repository. again if they are still published in the repository.
Extending the time interval used in step 3 will prevent repeated Extending the time interval used in step 3 will prevent repeated
downloads of repository objects, with the risk that such objects, if downloads of repository objects, with the risk that such objects, if
created massively by mistake or by an adversary, will fill up local created massively by mistake or by an adversary, will fill up local
disk space, if they are not cleaned up promptly. disk space, if they are not cleaned up promptly.
4. Remote Objects Fetcher 5. Remote Objects Fetcher
The fetcher is responsible for downloading objects from remote The fetcher is responsible for downloading objects from remote
repositories (described in Section 3 of [RFC6481]) using rsync repositories (described in Section 3 of [RFC6481]) using rsync
protocol ([rsync]), or RPKI Repository Delta Protocol (RRDP) protocol ([rsync]), or RPKI Repository Delta Protocol (RRDP)
([I-D.ietf-sidr-delta-protocol]). ([I-D.ietf-sidr-delta-protocol]).
4.1. Fetcher Operations 5.1. Fetcher Operations
For every visited URI the fetcher keeps track of the last time a For every visited URI the fetcher keeps track of the last time a
successful fetch occurred. successful fetch occurred.
4.1.1. Fetch repository objects 5.1.1. Fetch repository objects
This operation receives one parameter - a URI. For an rsync This operation receives one parameter - a URI. For an rsync
repository this URI points to a directory. For an RRDP repository it repository this URI points to a directory. For an RRDP repository it
points to the repository's notification file. points to the repository's notification file.
The fetcher performs following steps: The fetcher performs following steps:
1. If data associated with the URI has been downloaded recently (as 1. If data associated with the URI has been downloaded recently (as
specified by the local policy), skip following steps. specified by the local policy), skip following steps.
2. Download remote objects using the URI provided (for an rsync 2. Download remote objects using the URI provided (for an rsync
repository use recursive mode). repository use recursive mode). If the URI contains schema
"https" and download has failed, issue a warning, replace "https"
schema in the URI by "http", and try to download objects again,
using the resulting URI.
3. Perform syntactic verification of fetched objects. The type of 3. If remote objects can not be downloaded, issue an error and skip
following steps.
4. Perform syntactic verification of fetched objects. The type of
every object (certificate, manifest, CRL, ROA, or Ghostbusters every object (certificate, manifest, CRL, ROA, or Ghostbusters
record), is determined based on the object's filename extension record), is determined based on the object's filename extension
(.cer, .mft, .crl, .roa, and .gbr, respectively). The syntax of (.cer, .mft, .crl, .roa, and .gbr, respectively). The syntax of
the object is described in Section 4 of [RFC6487] for resource the object is described in Section 4 of [RFC6487] for resource
certificates, step 1 of Section 3 of [RFC6488] for signed certificates, step 1 of Section 3 of [RFC6488] for signed
objects, and specifically, Section 4 of [RFC6486] for manifests, objects, and specifically, Section 4 of [RFC6486] for manifests,
[RFC5280] for CRLs, Section 3 of [RFC6482] for ROAs, and [RFC5280] for CRLs, Section 3 of [RFC6482] for ROAs, and
Section 5 of [RFC6493] for Ghostbusters records. Section 5 of [RFC6493] for Ghostbusters records.
4. Put every downloaded and syntactically correct object in the 5. Put every downloaded and syntactically correct object in the
object store (Section 5.1.1). object store (Section 6.1.1).
The time interval used in the step 1 should be chosen based on the The time interval used in the step 1 should be chosen based on the
acceptable delay in receiving repository updates. acceptable delay in receiving repository updates.
4.1.2. Fetch single repository object 5.1.2. Fetch single repository object
This operation receives one parameter - a URI that points to an This operation receives one parameter - a URI that points to an
object in a repository. object in a repository.
The fetcher performs following operations: The fetcher performs following operations:
1. If data associated with the URI has been downloaded recently (as 1. Download remote object using the URI provided. If the URI
specified by the local policy), skip all following steps. contains "https" schema and download failed, issue a warning,
replace "https" schema in the URI by "http", and try to download
the object using the resulting URI.
2. Download the remote object using the URI provided. 2. If the remote object can not be downloaded, issue an error and
skip following steps.
3. Perform syntactic verification of fetched object. The type of 3. Perform syntactic verification of fetched object. The type of
object (certificate, manifest, CRL, ROA, or Ghostbusters record), object (certificate, manifest, CRL, ROA, or Ghostbusters record),
is determined based on the object's filename extension (.cer, is determined based on the object's filename extension (.cer,
.mft, .crl, .roa, and .gbr, respectively). The syntax of the .mft, .crl, .roa, and .gbr, respectively). The syntax of the
object is described in Section 4 of [RFC6487] for resource object is described in Section 4 of [RFC6487] for resource
certificates, step 1 of Section 3 of [RFC6488] for signed certificates, step 1 of Section 3 of [RFC6488] for signed
objects, and specifically, Section 4 of [RFC6486] for manifests, objects, and specifically, Section 4 of [RFC6486] for manifests,
[RFC5280] for CRLs, Section 3 of [RFC6482] for ROAs, and [RFC5280] for CRLs, Section 3 of [RFC6482] for ROAs, and
Section 5 of [RFC6493] for Ghostbusters records. Section 5 of [RFC6493] for Ghostbusters records.
4. If the downloaded object is not syntactically correct, issue an 4. If the downloaded object is not syntactically correct, issue an
error and skip further steps. error and skip further steps.
5. Delete all objects from the object store (Section 5.1.5) whose 5. Delete all objects from the object store (Section 6.1.5) whose
URI matches the URI given. URI matches the URI given.
6. Put the downloaded object in the object store (Section 5.1.1). 6. Put the downloaded object in the object store (Section 6.1.1).
5. Local Object Store 6. Local Object Store
5.1. Store Operations 6.1. Store Operations
5.1.1. Store Repository Object 6.1.1. Store Repository Object
Put given object in the store, along with its type, URI, hash, and Put given object in the store, along with its type, URI, hash, and
AKI, if there is no record with the same hash and URI fields. Note AKI, if there is no record with the same hash and URI fields. Note
that in the (unlikely) event of hash collision the given object will that in the (unlikely) event of hash collision the given object will
not replace the object in the store. not replace the object in the store.
5.1.2. Get objects by hash 6.1.2. Get objects by hash
Retrieve all objects from the store whose hash attribute matches the Retrieve all objects from the store whose hash attribute matches the
given hash. given hash.
5.1.3. Get certificate objects by URI 6.1.3. Get certificate objects by URI
Retrieve from the store all objects of type certificate, whose URI Retrieve from the store all objects of type certificate, whose URI
attribute matches the given URI. attribute matches the given URI.
5.1.4. Get manifest objects by AKI 6.1.4. Get manifest objects by AKI
Retrieve from the store all objects of type manifest, whose AKI Retrieve from the store all objects of type manifest, whose AKI
attribute matches the given AKI. attribute matches the given AKI.
5.1.5. Delete objects for a URI 6.1.5. Delete objects for a URI
For a given URI, delete all objects in the store with matching URI For a given URI, delete all objects in the store with matching URI
attribute. attribute.
5.1.6. Delete outdated objects 6.1.6. Delete outdated objects
For a given URI and a list of hashes, delete all objects in the store For a given URI and a list of hashes, delete all objects in the store
with matching URI, whose hash attribute is not in the given list of with matching URI, whose hash attribute is not in the given list of
hashes. hashes.
5.1.7. Update object's validation time 6.1.7. Update object's validation time
For all objects in the store whose hash attribute matches the given For all objects in the store whose hash attribute matches the given
hash, set the last validation time attribute to the given timestamp. hash, set the last validation time attribute to the given timestamp.
6. Acknowledgements 7. Acknowledgements
This document describes the algorithm as it is implemented by the This document describes the algorithm as it is implemented by the
software development team at the RIPE NCC. The authors would also software development team at the RIPE NCC. The authors would also
like to acknowledge contributions by Carlos Martinez, Andy Newton, like to acknowledge contributions by Carlos Martinez, Andy Newton,
Rob Austein, and Stephen Kent. Rob Austein, and Stephen Kent.
7. IANA Considerations 8. IANA Considerations
This document has no actions for IANA. This document has no actions for IANA.
8. Security Considerations 9. Security Considerations
9.1. Hash collisions
This implementation will not detect possible hash collisions in the This implementation will not detect possible hash collisions in the
hashes of repository objects (calculated using the file hash hashes of repository objects (calculated using the file hash
algorithm specified in [RFC6485]). It considers objects with same algorithm specified in [RFC6485]). It considers objects with same
hash values as identical. hash values as identical.
This algorithm uses the content of a manifest object to discover 9.2. Mismatch between the expected and the actual location of an object
other objects issued by a specified CA. It verifies that the in the repository
According to Section 2 of [RFC6481], all objects issued by a
particular CA certificate are expected to be located in one
repository publication point, specified in the SIA extension of that
CA certificate. The manifest object issued by that CA certificate
enumerates all other issued objects, listing their file names and
content hashes.
However, it is possible that an object whose content hash matches the
hash listed in the manifest, has either a different file name, or is
located at a different publication point in a repository.
On the other hand, all RPKI objects, either explicitly or within
their embedded EE certificate, have an Authority Key Identifier
extension that contains the key identifier of their issuing CA
certificate. Therefore it is always possible to perform an RPKI
validation of the object whose expected location does not match its
actual location, provided that the certificate that matches the AKI
of the object in question is known to the system that performs
validation.
In case of a mismatch described above this implementation will not
exclude an object from further validation merely because it's actual
location or file name does not match the expected location or file
name. This decision was chosen because the actual location of a file
in a repository is taken from the repository retrieval mechanism,
which, in case of an rsync repository, does not provide any
cryptographic security, and in case of an RRDP repository, provides
only a transport layer security, with the fallback to unsecured
transport. On the other hand, the manifest is an RPKI signed object,
and its content could be verified in the context of the RPKI
validation.
9.3. Manifest content versus publication point content
This algorithm uses the content of a manifest object to determine
other objects issued by a CA certificate. It verifies that the
manifest is located in the publication point designated in the CA manifest is located in the publication point designated in the CA
Certificate. However, if there are other (not listed in the Certificate's SIA extension. However, if there are other (not listed
manifest) objects located in that publication point directory, they in the manifest) objects located in the same publication point
will be ignored, even if their content is correct and they are issued directory, they are ignored, even if they might be valid and issued
by the same CA as the manifest. (This behavior is allowed, but not by the same CA certificate as the manifest. (This behavior is
required, by [RFC6486].) allowed, but not required, by [RFC6486].)
In contrast, objects whose content hash matches the hash listed in 9.4. Storing of a TA certificate object before its complete validation
the manifest, but that are not located in the publication directory
listed in their CA certificate, will be used in the validation
process (although a warning will be issued in that case), as
explained in Section 3.2.2.
The store cleanup procedure described in Section 3.3 tries to When fetching and storing a TA certificate to the object store, only
a syntactic validation of a downloaded object is performed before
newly downloaded object replaces the previously downloaded object in
the object store (see Section 5.1.2). If an attacker will be able to
replace a genuine TA certificate by a syntactically valid certificate
object (either by manipulating the content of a repository, or by a
man-in-the-middle attack), this implementation will discard
previously downloaded genuine object, and replace it by a false
object. Such false object will be detected later, but the validation
of the whole RPKI tree under this TA will be aborted, as described in
Section 4.
9.5. Possible denial of service
The store cleanup procedure described in Section 4.3 tries to
minimise removal and subsequent re-fetch of objects that are minimise removal and subsequent re-fetch of objects that are
published in a repository, but not used in the validation. Once such published in a repository, but not used in the validation. Once such
objects are removed from the remote repository, they will be objects are removed from the remote repository, they will be
discarded from the local object store after a period of time discarded from the local object store after a period of time
specified by a local policy. By generating an excessive amount of specified by a local policy. By generating an excessive amount of
syntactically valid RPKI objects, a man-in-the-middle attack between syntactically valid RPKI objects, a man-in-the-middle attack between
a validating tool and a repository could force an implementation to a validating tool and a repository could force an implementation to
fetch and store those objects in the object store before they are fetch and store those objects in the object store before they are
validated and discarded, leading to an out-of-memory or out-of-disk- validated and discarded, leading to an out-of-memory or out-of-disk-
space conditions, and, subsequently, a denial of service. space conditions, and, subsequently, a denial of service.
9. References 10. References
9.1. Normative References 10.1. Normative References
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<http://www.rfc-editor.org/info/rfc5280>. <http://www.rfc-editor.org/info/rfc5280>.
[RFC6481] Huston, G., Loomans, R., and G. Michaelson, "A Profile for [RFC6481] Huston, G., Loomans, R., and G. Michaelson, "A Profile for
Resource Certificate Repository Structure", RFC 6481, Resource Certificate Repository Structure", RFC 6481,
DOI 10.17487/RFC6481, February 2012, DOI 10.17487/RFC6481, February 2012,
skipping to change at page 13, line 10 skipping to change at page 14, line 44
[RFC6493] Bush, R., "The Resource Public Key Infrastructure (RPKI) [RFC6493] Bush, R., "The Resource Public Key Infrastructure (RPKI)
Ghostbusters Record", RFC 6493, DOI 10.17487/RFC6493, Ghostbusters Record", RFC 6493, DOI 10.17487/RFC6493,
February 2012, <http://www.rfc-editor.org/info/rfc6493>. February 2012, <http://www.rfc-editor.org/info/rfc6493>.
[RFC7730] Huston, G., Weiler, S., Michaelson, G., and S. Kent, [RFC7730] Huston, G., Weiler, S., Michaelson, G., and S. Kent,
"Resource Public Key Infrastructure (RPKI) Trust Anchor "Resource Public Key Infrastructure (RPKI) Trust Anchor
Locator", RFC 7730, DOI 10.17487/RFC7730, January 2016, Locator", RFC 7730, DOI 10.17487/RFC7730, January 2016,
<http://www.rfc-editor.org/info/rfc7730>. <http://www.rfc-editor.org/info/rfc7730>.
9.2. Informative References 10.2. Informative References
[github] "RIPE NCC RPKI Validator on GitHub", <https://github.com/
RIPE-NCC/rpki-validator>.
[I-D.ietf-sidr-delta-protocol] [I-D.ietf-sidr-delta-protocol]
Bruijnzeels, T., Muravskiy, O., Weber, B., Austein, R., Bruijnzeels, T., Muravskiy, O., Weber, B., Austein, R.,
and D. Mandelberg, "RPKI Repository Delta Protocol", and D. Mandelberg, "RPKI Repository Delta Protocol",
draft-ietf-sidr-delta-protocol-02 (work in progress), draft-ietf-sidr-delta-protocol-02 (work in progress),
March 2016. March 2016.
[rsync] "Rsync home page", <https://rsync.samba.org>. [rsync] "Rsync home page", <https://rsync.samba.org>.
Authors' Addresses Authors' Addresses
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