Internet Engineering Task Force (IETF) D. Ma
Request for Comments: 8897 ZDNS
Category: Informational S. Kent
ISSN: 2070-1721 Independent
September 2020
Requirements for Resource Public Key Infrastructure (RPKI) Relying
Parties
Abstract
This document provides a single reference point for requirements for
Relying Party (RP) software for use in the Resource Public Key
Infrastructure (RPKI). It cites requirements that appear in several
RPKI RFCs, making it easier for implementers to become aware of these
requirements. Over time, this RFC will be updated to reflect changes
to the requirements and guidance specified in the RFCs discussed
herein.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8897.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
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described in the Simplified BSD License.
Table of Contents
1. Introduction
2. Fetching and Caching RPKI Repository Objects
2.1. TAL Configuration and Processing
2.2. Locating RPKI Objects Using Authority and Subject
Information Extensions
2.3. Dealing with Key Rollover
2.4. Dealing with Algorithm Transition
2.5. Strategies for Efficient Cache Maintenance
3. Certificate and CRL Processing
3.1. Verifying Resource Certificate and Syntax
3.2. Certificate Path Validation
3.3. CRL Processing
4. Processing RPKI Repository Signed Objects
4.1. Basic Signed Object Syntax Checks
4.2. Syntax and Validation for Each Type of Signed Object
4.2.1. Manifest
4.2.2. ROA
4.2.3. Ghostbusters
4.2.4. Verifying BGPsec Router Certificate
4.3. How to Make Use of Manifest Data
4.4. What To Do with Ghostbusters Information
5. Distributing Validated Cache
6. Local Control
7. Security Considerations
8. IANA Considerations
9. References
9.1. Normative References
9.2. Informative References
Acknowledgements
Authors' Addresses
1. Introduction
RPKI Relying Party (RP) software is used by network operators and
others to acquire and verify Internet Number Resource (INR) data
stored in the RPKI repository system. RPKI data, when verified,
allows an RP to verify assertions about which Autonomous Systems
(ASes) are authorized to originate routes for IP address prefixes.
RPKI data also establishes a binding between public keys and BGP
routers and indicates the AS numbers that each router is authorized
to represent.
The essential requirements imposed on RP software to support secure
Internet routing [RFC6480] are scattered throughout numerous
protocol-specific RFCs and Best Current Practice RFCs. The following
RFCs define these requirements:
RFC 6481 (Repository Structure)
RFC 6482 (ROA format)
RFC 6486 (Manifests)
RFC 6487 (Certificate and CRL profile)
RFC 6488 (RPKI Signed Objects)
RFC 6489 (Key Rollover)
RFC 6810 (RPKI to Router Protocol)
RFC 6916 (Algorithm Agility)
RFC 7935 (Algorithms)
RFC 8209 (Router Certificates)
RFC 8210 (RPKI to Router Protocol, Version 1)
RFC 8360 (Certificate Validation Procedure)
RFC 8630 (Trust Anchor Locator)
The distribution of RPKI RP requirements across these 13 documents
makes it hard for an implementer to be confident that he/she has
addressed all of these requirements. Additionally, good software
engineering practice may call for segmenting the RP system into
components with orthogonal functionalities so that those components
may be distributed. A taxonomy of the collected RP software
requirements can help clarify the role of the RP.
To consolidate RP software requirements in one document, with
pointers to all the relevant RFCs, this document outlines a set of
baseline requirements imposed on RPs and provides a single reference
point for requirements for RP software for use in the RPKI. The
requirements are organized into four groups:
* Fetching and Caching RPKI Repository Objects
* Processing Certificates and Certificate Revocation Lists (CRLs)
* Processing RPKI Repository Signed Objects
* Distributing Validated Cache of the RPKI Data
This document will be updated to reflect new or changed requirements
as these RFCs are updated or additional RFCs are written.
2. Fetching and Caching RPKI Repository Objects
RP software uses synchronization mechanisms supported by targeted
repositories (e.g., [rsync] or RRDP [RFC8182]) to download RPKI
signed objects from the repository system in order to update a local
cache. These mechanisms download only those objects that have been
added or replaced with new versions since the time when the RP most
recently checked the repository. RP software validates the RPKI data
and uses it to generate authenticated data identifying which ASes are
authorized to originate routes for address prefixes and which routers
are authorized to sign BGP updates on behalf of specified ASes.
2.1. TAL Configuration and Processing
In the RPKI, each RP chooses a set of trust anchors (TAs).
Consistent with the extant INR allocation hierarchy, the IANA and/or
the five Regional Internet Registries (RIRs) are obvious candidates
to be default TAs for the RP.
An RP does not retrieve TAs directly. A set of Trust Anchor Locators
(TALs) is used by RP software to retrieve and verify the authenticity
of each TA.
TAL configuration and processing are specified in Section 3 of
[RFC8630].
2.2. Locating RPKI Objects Using Authority and Subject Information
Extensions
The RPKI repository system is a distributed one, consisting of
multiple repository instances. Each repository instance contains one
or more repository publication points. RP software discovers
publication points using the Subject Information Access (SIA) and the
Authority Information Access (AIA) extensions from (validated)
certificates.
Section 5 of [RFC6481] specifies how RP software locates all RPKI
objects by using the SIA and AIA extensions. Detailed specifications
of SIA and AIA extensions in a resource certificate are described in
Sections 4.8.8 and 4.8.7 of [RFC6487], respectively.
2.3. Dealing with Key Rollover
RP software takes the key rollover period into account with regard to
its frequency of synchronization with the RPKI repository system.
RP software requirements for dealing with key rollover are described
in Section 3 of [RFC6489] and Section 3 of [RFC8634].
2.4. Dealing with Algorithm Transition
The set of cryptographic algorithms used with the RPKI is expected to
change over time. Each RP is expected to be aware of the milestones
established for the algorithm transition and what actions are
required at every juncture.
RP software requirements for dealing with algorithm transition are
specified in Section 4 of [RFC6916].
2.5. Strategies for Efficient Cache Maintenance
Each RP is expected to maintain a local cache of RPKI objects. The
cache needs to be brought up to date and made consistent with the
repository publication point data as frequently as allowed by
repository publication points and by locally selected RP processing
constraints.
The last paragraph of Section 5 of [RFC6481] provides guidance for
maintenance of a local cache.
3. Certificate and CRL Processing
The RPKI makes use of X.509 certificates and CRLs, but it profiles
the standard formats described in [RFC6487]. The major change to the
profile established in [RFC5280] is the mandatory use of a new
extension in RPKI certificates, defined in [RFC3779].
3.1. Verifying Resource Certificate and Syntax
Certificates in the RPKI are called resource certificates, and they
are required to conform to the profile described in [RFC6487]. An RP
is required to verify that a resource certificate adheres to the
profile established by Section 4 of [RFC6487]. This means that all
extensions mandated by Section 4.8 of [RFC6487] must be present and
the value of each extension must be within the range specified by
[RFC6487]. Moreover, any extension excluded by Section 4.8 of
[RFC6487] must be omitted.
Section 7.1 of [RFC6487] specifies the procedure that RP software
follows when verifying extensions described in [RFC3779].
3.2. Certificate Path Validation
Initially, the INRs in the issuer's certificate are required to
encompass the INRs in the subject's certificate. This is one of the
necessary principles of certificate path validation in addition to
cryptographic verification (i.e., verification of the signature on
each certificate using the public key of the parent certificate).
Section 7.2 of [RFC6487] specifies the procedure that RP software
should follow to perform certificate path validation.
Certification Authorities (CAs) that want to reduce aspects of
operational fragility will migrate to the new OIDs [RFC8360],
informing RP software to use an alternative RPKI validation
algorithm. An RP is expected to support the amended procedure to
handle accidental overclaiming, which is described in Section 4 of
[RFC8360].
3.3. CRL Processing
The CRL processing requirements imposed on CAs and RPs are described
in Section 5 of [RFC6487]. CRLs in the RPKI are tightly constrained;
only the AuthorityKeyIdentifier (Section 4.8.3 of [RFC6487]) and
CRLNumber (Section 5.2.3 of [RFC5280]) extensions are allowed, and
they are required to be present. No other CRL extensions are
allowed, and no CRLEntry extensions are permitted. RP software is
required to verify that these constraints have been met. Each CRL in
the RPKI must be verified using the public key from the certificate
of the CA that issued the CRL.
In the RPKI, RPs are expected to pay extra attention when dealing
with a CRL that is not consistent with the manifest associated with
the publication point associated with the CRL.
Processing of a CRL that is not consistent with a manifest is a
matter of local policy, as described in the fifth paragraph of
Section 6.6 of [RFC6486].
4. Processing RPKI Repository Signed Objects
4.1. Basic Signed Object Syntax Checks
Before an RP can use a signed object from the RPKI repository, RP
software is required to check the signed-object syntax.
Section 3 of [RFC6488] lists all the steps that RP software is
required to execute in order to validate the top-level syntax of a
repository signed object.
Note that these checks are necessary but not sufficient. Additional
validation checks must be performed based on the specific type of
signed object, as described in Section 4.2.
4.2. Syntax and Validation for Each Type of Signed Object
4.2.1. Manifest
To determine whether a manifest is valid, RP software is required to
perform manifest-specific checks in addition to the generic signed-
object checks specified in [RFC6488].
Specific checks for a manifest are described in Section 4 of
[RFC6486]. If any of these checks fail, indicating that the manifest
is invalid, then the manifest will be discarded, and RP software will
act as though no manifest were present.
4.2.2. ROA
To validate a Route Origin Authorization (ROA), RP software is
required to perform all the checks specified in [RFC6488] as well as
additional, ROA-specific validation steps. The IP Address Delegation
extension [RFC3779] present in the end-entity (EE) certificate
(contained within the ROA) must encompass each of the IP address
prefix(es) in the ROA.
More details for ROA validation are specified in Section 4 of
[RFC6482].
4.2.3. Ghostbusters
The Ghostbusters Record is optional; a publication point in the RPKI
can have zero or more associated Ghostbusters Records. If a CA has
at least one Ghostbusters Record, RP software is required to verify
that this Ghostbusters Record conforms to the syntax of signed
objects defined in [RFC6488].
The payload of this signed object is a (severely) profiled vCard. RP
software is required to verify that the payload of Ghostbusters
conforms to format as profiled in [RFC6493].
4.2.4. Verifying BGPsec Router Certificate
A BGPsec Router Certificate is a resource certificate, so it is
required to comply with [RFC6487]. Additionally, the certificate
must contain an AS Identifier Delegation extension (Section 4.8.11 of
[RFC6487]) and must not contain an IP Address Delegation extension
(Section 4.8.10 of [RFC6487]). The validation procedure used for
BGPsec Router Certificates is analogous to the validation procedure
described in Section 7 of [RFC6487], but it uses the constraints
defined in Section 3 of [RFC8209].
Note that the cryptographic algorithms used by BGPsec routers are
found in [RFC8608]. Currently, the algorithms specified in [RFC8608]
and [RFC7935] are different. BGPsec RP software will need to support
algorithms that are used to validate BGPsec signatures as well as the
algorithms that are needed to validate signatures on BGPsec
certificates, RPKI CA certificates, and RPKI CRLs.
4.3. How to Make Use of Manifest Data
For a given publication point, RP software ought to perform tests, as
specified in Section 6.1 of [RFC6486], to determine the state of the
manifest at the publication point. A manifest can be classified as
either valid or invalid, and a valid manifest is either current or
stale. An RP decides how to make use of a manifest based on its
state, according to local (RP) policy.
If there are valid objects in a publication point that are not
present on a manifest, [RFC6486] does not mandate specific RP
behavior with respect to such objects.
In the absence of a manifest, an RP is expected to accept all valid
signed objects present in the publication point (see Section 6.2 of
[RFC6486]). If a manifest is stale or invalid and an RP has no way
to acquire a more recent valid manifest, the RP is expected to
contact the repository manager via Ghostbusters Records and
thereafter make decisions according to local (RP) policy (see
Sections 6.3 and 6.4 of [RFC6486]).
4.4. What To Do with Ghostbusters Information
RP software may encounter a stale manifest or CRL, or an expired CA
certificate or ROA at a publication point. An RP is expected to use
the information from the Ghostbusters Records to contact the
maintainer of the publication point where any stale/expired objects
were encountered. The intent here is to encourage the relevant CA
and/or repository manager to update the stale or expired objects.
5. Distributing Validated Cache
On a periodic basis, BGP speakers within an AS request updated
validated origin AS data and router/ASN data from the (local)
validated cache of RPKI data. The RP may either transfer the
validated data to the BGP speakers directly, or it may transfer the
validated data to a cache server that is responsible for provisioning
such data to BGP speakers. The specifications of the protocol
designed to deliver validated cache data to a BGP Speaker are
provided in [RFC6810] and [RFC8210].
6. Local Control
ISPs may want to establish a local view of exceptions to the RPKI
data in the form of local filters and additions. For instance, a
network operator might wish to make use of a local override
capability to protect routes from adverse actions [RFC8211]. The
mechanisms developed to provide this capability to network operators
are called Simplified Local Internet Number Resource Management with
the RPKI (SLURM). If an ISP wants to implement SLURM, its RP system
can follow the instruction specified in [RFC8416].
7. Security Considerations
This document does not introduce any new security considerations; it
is a resource for implementers. The RP links the RPKI provisioning
side and the routing system, establishing a verified, local view of
global RPKI data to BGP speakers. The security of the RP is critical
for exchanging BGP messages. Each RP implementation is expected to
offer cache backup management to facilitate recovery from outages.
RP software should also support secure transport (e.g., IPsec
[RFC4301]) that can protect validated cache delivery in an unsafe
environment. This document highlights many validation actions
applied to RPKI signed objects, an essential element of secure
operation of RPKI security.
8. IANA Considerations
This document has no IANA actions.
9. References
9.1. Normative References
[RFC3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP
Addresses and AS Identifiers", RFC 3779,
DOI 10.17487/RFC3779, June 2004,
<https://www.rfc-editor.org/info/rfc3779>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[RFC6481] Huston, G., Loomans, R., and G. Michaelson, "A Profile for
Resource Certificate Repository Structure", RFC 6481,
DOI 10.17487/RFC6481, February 2012,
<https://www.rfc-editor.org/info/rfc6481>.
[RFC6482] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route
Origin Authorizations (ROAs)", RFC 6482,
DOI 10.17487/RFC6482, February 2012,
<https://www.rfc-editor.org/info/rfc6482>.
[RFC6486] Austein, R., Huston, G., Kent, S., and M. Lepinski,
"Manifests for the Resource Public Key Infrastructure
(RPKI)", RFC 6486, DOI 10.17487/RFC6486, February 2012,
<https://www.rfc-editor.org/info/rfc6486>.
[RFC6487] Huston, G., Michaelson, G., and R. Loomans, "A Profile for
X.509 PKIX Resource Certificates", RFC 6487,
DOI 10.17487/RFC6487, February 2012,
<https://www.rfc-editor.org/info/rfc6487>.
[RFC6488] Lepinski, M., Chi, A., and S. Kent, "Signed Object
Template for the Resource Public Key Infrastructure
(RPKI)", RFC 6488, DOI 10.17487/RFC6488, February 2012,
<https://www.rfc-editor.org/info/rfc6488>.
[RFC6489] Huston, G., Michaelson, G., and S. Kent, "Certification
Authority (CA) Key Rollover in the Resource Public Key
Infrastructure (RPKI)", BCP 174, RFC 6489,
DOI 10.17487/RFC6489, February 2012,
<https://www.rfc-editor.org/info/rfc6489>.
[RFC6493] Bush, R., "The Resource Public Key Infrastructure (RPKI)
Ghostbusters Record", RFC 6493, DOI 10.17487/RFC6493,
February 2012, <https://www.rfc-editor.org/info/rfc6493>.
[RFC6810] Bush, R. and R. Austein, "The Resource Public Key
Infrastructure (RPKI) to Router Protocol", RFC 6810,
DOI 10.17487/RFC6810, January 2013,
<https://www.rfc-editor.org/info/rfc6810>.
[RFC6916] Gagliano, R., Kent, S., and S. Turner, "Algorithm Agility
Procedure for the Resource Public Key Infrastructure
(RPKI)", BCP 182, RFC 6916, DOI 10.17487/RFC6916, April
2013, <https://www.rfc-editor.org/info/rfc6916>.
[RFC7935] Huston, G. and G. Michaelson, Ed., "The Profile for
Algorithms and Key Sizes for Use in the Resource Public
Key Infrastructure", RFC 7935, DOI 10.17487/RFC7935,
August 2016, <https://www.rfc-editor.org/info/rfc7935>.
[RFC8209] Reynolds, M., Turner, S., and S. Kent, "A Profile for
BGPsec Router Certificates, Certificate Revocation Lists,
and Certification Requests", RFC 8209,
DOI 10.17487/RFC8209, September 2017,
<https://www.rfc-editor.org/info/rfc8209>.
[RFC8210] Bush, R. and R. Austein, "The Resource Public Key
Infrastructure (RPKI) to Router Protocol, Version 1",
RFC 8210, DOI 10.17487/RFC8210, September 2017,
<https://www.rfc-editor.org/info/rfc8210>.
[RFC8360] Huston, G., Michaelson, G., Martinez, C., Bruijnzeels, T.,
Newton, A., and D. Shaw, "Resource Public Key
Infrastructure (RPKI) Validation Reconsidered", RFC 8360,
DOI 10.17487/RFC8360, April 2018,
<https://www.rfc-editor.org/info/rfc8360>.
[RFC8608] Turner, S. and O. Borchert, "BGPsec Algorithms, Key
Formats, and Signature Formats", RFC 8608,
DOI 10.17487/RFC8608, June 2019,
<https://www.rfc-editor.org/info/rfc8608>.
[RFC8630] Huston, G., Weiler, S., Michaelson, G., Kent, S., and T.
Bruijnzeels, "Resource Public Key Infrastructure (RPKI)
Trust Anchor Locator", RFC 8630, DOI 10.17487/RFC8630,
August 2019, <https://www.rfc-editor.org/info/rfc8630>.
[RFC8634] Weis, B., Gagliano, R., and K. Patel, "BGPsec Router
Certificate Rollover", BCP 224, RFC 8634,
DOI 10.17487/RFC8634, August 2019,
<https://www.rfc-editor.org/info/rfc8634>.
9.2. Informative References
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/info/rfc4301>.
[RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", RFC 6480, DOI 10.17487/RFC6480,
February 2012, <https://www.rfc-editor.org/info/rfc6480>.
[RFC8182] Bruijnzeels, T., Muravskiy, O., Weber, B., and R. Austein,
"The RPKI Repository Delta Protocol (RRDP)", RFC 8182,
DOI 10.17487/RFC8182, July 2017,
<https://www.rfc-editor.org/info/rfc8182>.
[RFC8211] Kent, S. and D. Ma, "Adverse Actions by a Certification
Authority (CA) or Repository Manager in the Resource
Public Key Infrastructure (RPKI)", RFC 8211,
DOI 10.17487/RFC8211, September 2017,
<https://www.rfc-editor.org/info/rfc8211>.
[RFC8416] Ma, D., Mandelberg, D., and T. Bruijnzeels, "Simplified
Local Internet Number Resource Management with the RPKI
(SLURM)", RFC 8416, DOI 10.17487/RFC8416, August 2018,
<https://www.rfc-editor.org/info/rfc8416>.
[rsync] "rsync", <http://rsync.samba.org/>.
Acknowledgements
The authors thank David Mandelberg, Wei Wang, Tim Bruijnzeels, George
Michaelson, and Oleg Muravskiy for their review, feedback, and
editorial assistance in preparing this document.
Authors' Addresses
Di Ma
ZDNS
4 South 4th St. Zhongguancun
Haidian
Beijing, 100190
China
Email: madi@zdns.cn
Stephen Kent
Independent
Email: kent@alum.mit.edu