RPKI Not Identity: The 'I' in RPKI Does Not Stand for Identity
Why RPKI certificates prove who may speak for addresses and AS numbers, never who a company really is.
Bush, R. and R. Housley, "The 'I' in RPKI Does Not Stand for Identity", RFC 9255, DOI 10.17487/RFC9255, June 2022, <https://www.rfc-editor.org/info/rfc9255>.
@misc{rfc9255,
series = {Request for Comments},
number = 9255,
howpublished = {RFC 9255},
publisher = {RFC Editor},
doi = {10.17487/RFC9255},
url = {https://www.rfc-editor.org/info/rfc9255},
author = {R. Bush and R. Housley},
title = {{The 'I' in RPKI Does Not Stand for Identity}},
pagetotal = 7,
year = 2022,
month = jun,
} RFC text
Contents
Internet Engineering Task Force (IETF) R. Bush
Request for Comments: 9255 Arrcus & IIJ Research
Category: Standards Track R. Housley
ISSN: 2070-1721 Vigil Security
June 2022
The 'I' in RPKI Does Not Stand for Identity
Abstract
There is a false notion that Internet Number Resources (INRs) in the
RPKI can be associated with the real-world identity of the 'holder'
of an INR. This document specifies that RPKI does not associate to
the INR holder.
Status of This Memo
This is an Internet Standards Track document.
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). Further information on
Internet Standards is available in 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/rfc9255.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Revised BSD License text as described in Section 4.e of the
Trust Legal Provisions and are provided without warranty as described
in the Revised BSD License.
Table of Contents
1. Introduction
1.1. Requirements Language
2. The RPKI is for Authorization
3. Discussion
4. Security Considerations
5. IANA Considerations
6. References
6.1. Normative References
6.2. Informative References
Acknowledgments
Authors' Addresses
1. Introduction
The Resource Public Key Infrastructure (RPKI), see [RFC6480],
"represents the allocation hierarchy of IP address space and
Autonomous System (AS) numbers," which are collectively known as
Internet Number Resources (INRs). Since initial deployment, the RPKI
has grown to include other similar resource and routing data, e.g.,
Router Keying for BGPsec [RFC8635].
In security terms, the phrase "Public Key" implies there is also a
corresponding private key [RFC5280]. The RPKI provides strong
authority to the current holder of INRs; however, some people have a
desire to use RPKI private keys to sign arbitrary documents as the
INR 'holder' of those resources with the inappropriate expectation
that the signature will be considered an attestation to the
authenticity of the document content. But, in reality, the RPKI
certificate is only an authorization to speak for the explicitly
identified INRs; it is explicitly not intended for authentication of
the 'holders' of the INRs. This situation is emphasized in
Section 2.1 of [RFC6480].
It has been suggested that one could authenticate real-world business
transactions with the signatures of INR holders. For example, Bill's
Bait and Sushi (BB&S) could use the private key attesting to that
they are the holder of their AS in the RPKI to sign a Letter of
Authorization (LOA) for some other party to rack and stack hardware
owned by BB&S. Unfortunately, while this may be technically
possible, it is neither appropriate nor meaningful.
The 'I' in RPKI actually stands for "Infrastructure," as in Resource
Public Key Infrastructure, not for "Identity". In fact, the RPKI
does not provide any association between INRs and the real-world
holder(s) of those INRs. The RPKI provides authorization to make
assertions only regarding Internet Number Resources, such as IP
prefixes or AS numbers, and data such as Autonomous System Provider
Authorization (ASPA) records [ASPA-PROFILE].
In short, avoid the desire to use RPKI certificates for any purpose
other than the verification of authorizations associated with the
delegation of INRs or attestations related to INRs. Instead,
recognize that these authorizations and attestations take place
irrespective of the identity of an RPKI private key holder.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. The RPKI is for Authorization
The RPKI was designed and specified to sign certificates for use
within the RPKI itself and to generate Route Origin Authorizations
(ROAs) [RFC6480] for use in routing. Its design intentionally
precluded use for attesting to real-world identity as, among other
issues, it would expose the Certification Authority (CA) to
liability.
That the RPKI does not authenticate real-world identity is by design.
If it tried to do so, aside from the liability, it would end in a
world of complexity with no proof of termination.
Registries such as the Regional Internet Registries (RIRs) provide
INR to real-world identity mapping through WHOIS [RFC3912] and
similar services. They claim to be authoritative, at least for the
INRs that they allocate.
That is, RPKI-based credentials of INRs MUST NOT be used to
authenticate real-world documents or transactions. That might be
done with some formal external authentication of authority allowing
an otherwise anonymous INR holder to authenticate the particular
document or transaction. Given such external, i.e. non-RPKI,
verification of authority, the use of RPKI-based credentials adds no
authenticity.
3. Discussion
Section 2.1 of the RPKI base document [RFC6480] says explicitly "An
important property of this PKI is that certificates do not attest to
the identity of the subject."
Section 3.1 of "Template for a Certification Practice Statement (CPS)
for the Resource PKI (RPKI)" [RFC7382] states that the Subject name
in each certificate SHOULD NOT be meaningful and goes on to explain
this at some length.
Normally, the INR holder does not hold the private key attesting to
their resources; the CA does. The INR holder has a real-world
business relationship with the CA for which they have likely signed
real-world documents.
As the INR holder does not have the keying material, they rely on the
CA, to which they presumably present credentials, to manipulate their
INRs. These credentials may be user ID and password (with two-factor
authentication one hopes), a hardware token, client browser
certificates, etc.
Hence schemes such as Resource Tagged Attestations [RPKI-RTA] and
Signed Checklists [RPKI-RSC] must go to great lengths to extract the
supposedly relevant keys from the CA.
For some particular INR, say, Bill's Bait and Sushi's Autonomous
System (AS) number, someone out on the net probably has the
credentials to the CA account in which BB&S's INRs are registered.
That could be the owner of BB&S, Randy's Taco Stand, an IT vendor, or
the Government of Elbonia. One simply can not know.
In large organizations, INR management is often compartmentalized
with no authority over anything beyond dealing with INR registration.
The INR manager for Bill's Bait and Sushi is unlikely to be
authorized to conduct bank transactions for BB&S, or even to
authorize access to BB&S's servers in some colocation facility.
Then there is the temporal issue. The holder of that AS may be BB&S
today when some document was signed, and could be the Government of
Elbonia tomorrow. Or the resource could have been administratively
moved from one CA to another, likely requiring a change of keys. If
so, how does one determine if the signature on the real-world
document is still valid?
While Ghostbuster Records [RFC6493] may seem to identify real-world
entities, their semantic content is completely arbitrary and does not
attest to holding of any INRs. They are merely clues for operational
support contact in case of technical RPKI problems.
Usually, before registering INRs, CAs require proof of an INR holding
via external documentation and authorities. It is somewhat droll
that the CPS Template [RFC7382] does not mention any diligence the CA
must, or even might, conduct to assure the INRs are in fact owned by
a registrant.
That someone can provide 'proof of possession' of the private key
signing over a particular INR should not be taken to imply that they
are a valid legal representative of the organization in possession of
that INR. They could be in an INR administrative role, and not be a
formal representative of the organization.
Autonomous System Numbers do not identify real-world entities. They
are identifiers some network operators 'own' and are only used for
loop detection in routing. They have no inherent semantics other
than uniqueness.
4. Security Considerations
Attempts to use RPKI data to authenticate real-world documents or
other artifacts requiring identity, while possibly cryptographically
valid within the RPKI, are misleading as to any authenticity.
When a document is signed with the private key associated with an
RPKI certificate, the signer is speaking for the INRs (the IP address
space and AS numbers) in the certificate. This is not an identity;
this is an authorization. In schemes such as Resource Tagged
Attestations [RPKI-RTA] and Signed Checklists [RPKI-RSC], the signed
message further narrows this scope of INRs. The INRs in the message
are a subset of the INRs in the certificate. If the signature is
valid, the message content comes from a party that is authorized to
speak for that subset of INRs.
Control of INRs for an entity could be used to falsely authorize
transactions or documents for which the INR manager has no authority.
5. IANA Considerations
This document has no IANA actions.
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[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>.
[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>.
[RFC7382] Kent, S., Kong, D., and K. Seo, "Template for a
Certification Practice Statement (CPS) for the Resource
PKI (RPKI)", BCP 173, RFC 7382, DOI 10.17487/RFC7382,
April 2015, <https://www.rfc-editor.org/info/rfc7382>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8635] Bush, R., Turner, S., and K. Patel, "Router Keying for
BGPsec", RFC 8635, DOI 10.17487/RFC8635, August 2019,
<https://www.rfc-editor.org/info/rfc8635>.
6.2. Informative References
[ASPA-PROFILE]
Azimov, A., Uskov, E., Bush, R., Patel, K., Snijders, J.,
and R. Housley, "A Profile for Autonomous System Provider
Authorization", Work in Progress, Internet-Draft, draft-
ietf-sidrops-aspa-profile-07, 31 January 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-sidrops-
aspa-profile-07>.
[RFC3912] Daigle, L., "WHOIS Protocol Specification", RFC 3912,
DOI 10.17487/RFC3912, September 2004,
<https://www.rfc-editor.org/info/rfc3912>.
[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>.
[RPKI-RSC] Snijders, J., Harrison, T., and B. Maddison, "A profile
for Resource Public Key Infrastructure (RPKI) Signed
Checklists (RSC)", Work in Progress, Internet-Draft,
draft-ietf-sidrops-rpki-rsc-08, 26 May 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-sidrops-
rpki-rsc-08>.
[RPKI-RTA] Michaelson, G., Huston, G., Harrison, T., Bruijnzeels, T.,
and M. Hoffmann, "A profile for Resource Tagged
Attestations (RTAs)", Work in Progress, Internet-Draft,
draft-ietf-sidrops-rpki-rta-00, 21 January 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-sidrops-
rpki-rta-00>.
Acknowledgments
The authors thank George Michaelson and Job Snijders for lively
discussion, Geoff Huston for some more formal text, Ties de Kock for
useful suggestions, many directorate and IESG reviewers, and last but
not least, Biff for the loan of Bill's Bait and Sushi.
Authors' Addresses
Randy Bush
Arrcus & Internet Initiative Japan Research
5147 Crystal Springs
Bainbridge Island, WA 98110
United States of America
Email: randy@psg.com
Russ Housley
Vigil Security, LLC
516 Dranesville Road
Herndon, VA 20170
United States of America
Email: housley@vigilsec.com
AI ELI5
On this page
§1The Misunderstanding
The Resource Public Key Infrastructure (RPKI), described in RFC 6480, represents the allocation hierarchy of IP address space and Autonomous System (AS) numbers. Together these are called Internet Number Resources (INRs). Since its first deployment the RPKI has grown to include related data such as Router Keying for BGPsec.
A public key implies a private key. The RPKI gives strong authority to the current holder of INRs, and some people want to use the private keys to sign arbitrary documents as the INR 'holder'. They expect the signature to attest that the document is authentic. The RFC says this is inappropriate: the certificate is only an authorization to speak for the explicitly identified INRs.
Some people wanted to use a key that proves who controls some internet addresses to sign any paper. But that key was never made to say who the signer really is.
§1.1The Bait and Sushi Example
The RFC gives an example. Bill's Bait and Sushi (BB&S) could use the key that shows it holds its AS in the RPKI to sign a Letter of Authorization (LOA) letting another party rack and stack hardware that BB&S owns. The RFC says that while this may be technically possible, it is neither appropriate nor meaningful.
The 'I' in RPKI stands for "Infrastructure" (Resource Public Key Infrastructure), not for "Identity". The RPKI does not associate INRs with the real-world holders of those INRs.
A fish-and-sushi shop could sign a note with its address key, but that does not prove the note is real. The 'I' stands for infrastructure, not identity.
§2RPKI Is for Authorization
The RPKI was designed to sign certificates for use inside the RPKI itself and to generate Route Origin Authorizations (ROAs) for use in routing. Its design intentionally precluded attesting to real-world identity because, among other issues, that would expose the Certification Authority (CA) to liability. The RFC adds that trying to do so would end in a world of complexity with no proof of termination.
Registries such as the Regional Internet Registries (RIRs) provide the mapping from INR to real-world identity through WHOIS and similar services, and they claim to be authoritative for the INRs they allocate.
The core rule is stated with a requirement word: RPKI-based credentials of INRs MUST NOT be used to authenticate real-world documents or transactions. That might be done with some formal external authentication of authority allowing an otherwise anonymous INR holder to authenticate a document or transaction. Given such external verification, RPKI credentials add no authenticity.
The address keys were built to answer 'who may announce these addresses?' and nothing else. If you want to know who someone really is, ask the registry or use some other proof.
§3Why the Key Does Not Mean the Holder
The RFC lists several reasons. RFC 6480 says explicitly that certificates do not attest to the identity of the subject, and the CPS template in RFC 7382 says the Subject name in each certificate SHOULD NOT be meaningful.
- Normally the INR holder does not hold the private key; the CA does. The holder only has a business relationship with the CA, so schemes such as Resource Tagged Attestations and Signed Checklists must go to great lengths to extract the relevant keys from the CA.
- Whoever has the credentials to the CA account is unknown. It could be the owner, an IT vendor or a government.
- INR managers in large organizations often have no authority beyond INR registration, such as for bank transactions or server access.
- Holders change over time. A resource may be held by one party when a document is signed and by another later, or be moved from one CA to another, likely requiring a change of keys.
- Ghostbuster Records (RFC 6493) are arbitrary and are only clues for operational support contacts; they do not attest to holding any INRs.
- Proof of possession of a private key does not make someone a valid legal representative of the organization.
Autonomous System Numbers are only identifiers used for loop detection in routing, with no inherent semantics other than uniqueness.
The key often sits with a middleman, people change jobs, and companies change hands. So holding the key says very little about who is really behind a signature.
§4Security Considerations
Using RPKI data to authenticate real-world documents or other artifacts requiring identity may be cryptographically valid within the RPKI, but it is misleading about authenticity.
When a document is signed with the private key of an RPKI certificate, the signer is speaking for the INRs in the certificate. That is an authorization, not an identity. In schemes like Resource Tagged Attestations and Signed Checklists, the signed message narrows the scope further, so its INRs are a subset of those in the certificate. A valid signature means the content comes from a party authorized to speak for that subset.
Control of INRs could also be used to falsely authorize transactions or documents for which the INR manager has no authority. The RFC has no IANA actions.
A valid signature only says 'this person may speak for these addresses'. Trusting it for anything else could let the wrong person approve things they should not.