Internet DRAFT - draft-ietf-oauth-jwk-thumbprint-uri
draft-ietf-oauth-jwk-thumbprint-uri
OAuth Working Group M. Jones
Internet-Draft K. Yasuda
Intended status: Standards Track Microsoft
Expires: December 3, 2022 Jun 1, 2022
JWK Thumbprint URI
draft-ietf-oauth-jwk-thumbprint-uri-03
Abstract
This specification registers a kind of URI that represents a JSON Web
Key (JWK) Thumbprint value. JWK Thumbprints are defined in RFC 7638.
This enables JWK Thumbprints to be used, for instance, as key
identifiers in contexts requiring URIs.
Status of This Memo
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This Internet-Draft will expire on December 3, 2022.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Notation and Conventions . . . . . . . . . . . . 2
3. JWK Thumbprint URI . . . . . . . . . . . . . . . . . . . . . 3
4. Hash Algorithms Identifier . . . . . . . . . . . . . . . . . 3
5. Mandatory to Implement Hash Algorithm . . . . . . . . . . . . 3
6. Example JWK Thumbprint URI . . . . . . . . . . . . . . . . . 3
7. Security Considerations . . . . . . . . . . . . . . . . . . . 3
7.1. Multiple Public Keys per Private Key . . . . . . . . . . 3
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
8.1. OAuth URI Registration . . . . . . . . . . . . . . . . . 4
8.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 4
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
9.1. Normative References . . . . . . . . . . . . . . . . . . 4
9.2. Informative References . . . . . . . . . . . . . . . . . 5
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 5
Appendix B. Document History . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
A JSON Web Key (JWK) Thumbprint [RFC7638] is a URL-safe
representation of a hash value over a JSON Web Key (JWK) [RFC7517].
This specification defines a URI prefix indicating that the portion
of the URI following the prefix is a JWK Thumbprint. This enables
JWK Thumbprints to be communicated in contexts requiring URIs,
including in specific JSON Web Token (JWT) [RFC7519] claims.
JWK Thumbprints URIs are being used in the [SIOPv2] specification as
one kind of subject identifier in a context requiring that the
identifier be a URI. In this case, the subject identifier is derived
from a public key represented as a JWK. Expressing the identifier as
JWK Thumbprint URI enables this kind of identifier to be
differentiated from other kinds of identifiers that are also URIs,
such as Decentralized Identifiers (DIDs) [DID-Core].
2. Requirements Notation and Conventions
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.
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3. JWK Thumbprint URI
The following URI prefix is defined to indicate that the portion of
the URI following the prefix is a JWK Thumbprint:
o "urn:ietf:params:oauth:jwk-thumbprint"
To make it explicit in a URI which hash algorithm is used, the prefix
is followed by a hash algorithm identifier and a JWK Thumbprint
value, each separated by a colon character to form a URI representing
a JWK Thumbprint.
4. Hash Algorithms Identifier
Hash algorithm identifiers used in JWK Thumbprint URIs MUST be values
from the "Hash Name String" column in the IANA "Named Information
Hash Algorithm" registry [IANA.Hash.Algorithms]. JWK Thumbprint URIs
with hash algorithm identifiers not found in this registry are not
considered valid and applications will need to detect and handle this
error, should it occur.
5. Mandatory to Implement Hash Algorithm
To promote interoperability among implementations, the SHA-256 hash
algorithm is mandatory to implement.
6. Example JWK Thumbprint URI
Section 3.1 of [RFC7638] contains the following example JWK
Thumbprint value:
NzbLsXh8uDCcd-6MNwXF4W_7noWXFZAfHkxZsRGC9Xs
A complete JWK Thumbprint URI using the above JWK Thumbprint and
SHA-256 hash algorithm is:
urn:ietf:params:oauth:jwk-thumbprint:sha-256:NzbLsXh8uDCcd-6MNwXF4W_7noWXFZAfHkxZsRGC9Xs
7. Security Considerations
The security considerations of [RFC7638] also apply when using this
specification.
7.1. Multiple Public Keys per Private Key
There are cryptographic algorithms for which multiple public keys
correspond to the same private key. This is described in the
security considerations of [RFC7748] as follows:
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Designers using these curves should be aware that for each public
key, there are several publicly computable public keys that are
equivalent to it, i.e., they produce the same shared secrets.
Thus using a public key as an identifier and knowledge of a shared
secret as proof of ownership (without including the public keys in
the key derivation) might lead to subtle vulnerabilities.
This consideration for public keys as identifiers equally applies to
JWK Thumbprint URIs used as identifiers. A recommended way to ensure
that the JWK Thumbprint URI corresponds to the actual public key used
is to sign a message containing the correct public key with the
private key. This signed message could also contain the JWK
Thumbprint URI (although, by definition, it could also be computed
directly from the public key).
8. IANA Considerations
8.1. OAuth URI Registration
This specification registers the following value in the IANA "OAuth
URI" registry [IANA.OAuth.Parameters] established by [RFC6755].
8.1.1. Registry Contents
o URN: urn:ietf:params:oauth:jwk-thumbprint
o Common Name: JWK Thumbprint URI
o Change controller: IESG
o Specification Document: [[ this specification ]]
9. References
9.1. Normative References
[IANA.OAuth.Parameters]
IANA, "OAuth Parameters",
<http://www.iana.org/assignments/oauth-parameters>.
[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>.
[RFC7638] Jones, M. and N. Sakimura, "JSON Web Key (JWK)
Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September
2015, <https://www.rfc-editor.org/info/rfc7638>.
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[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>.
9.2. Informative References
[DID-Core]
Sporny, M., Guy, A., Sabadello, M., and D. Reed,
"Decentralized Identifiers (DIDs) v1.0", Aug 2021,
<https://www.w3.org/TR/2021/PR-did-core-20210803/>.
[IANA.Hash.Algorithms]
IANA, "Named Information Hash Algorithm Registry",
<https://www.iana.org/assignments/named-information/named-
information.xhtml#hash-alg>.
[RFC6755] Campbell, B. and H. Tschofenig, "An IETF URN Sub-Namespace
for OAuth", RFC 6755, DOI 10.17487/RFC6755, October 2012,
<https://www.rfc-editor.org/info/rfc6755>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<https://www.rfc-editor.org/info/rfc7517>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>.
[RFC7748] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves
for Security", RFC 7748, DOI 10.17487/RFC7748, January
2016, <https://www.rfc-editor.org/info/rfc7748>.
[SIOPv2] Yasuda, K. and M. B. Jones, "Self-Issued OpenID Provider
v2", December 2021, <https://openid.net/specs/openid-
connect-self-issued-v2-1_0.html>.
Appendix A. Acknowledgements
Use cases for this specification were developed in the OpenID Connect
Working Group of the OpenID Foundation. Specifically, it is being
used a key identifier in the [SIOPv2] specification.
The following individuals also contributed to the creation of this
specification: John Bradley, Scott Bradner, Brian Campbell, Roman
Danyliw, Vladimir Dzhuvinov, Lars Eggert, Warren Kumari, Adam Lemmon,
Neil Madden, James Manger, Francesca Palombini, Aaron Parecki,
Gonzalo Salgueiro, Rifaat Shekh-Yusef, Robert Sparks, David Waite,
Robert Wilton, and Paul Wouters.
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Appendix B. Document History
[[ to be removed by the RFC Editor before publication as an RFC ]]
-03
o Addressed IESG comment by Lars Eggert on the use of inclusive
language.
-02
o Addressed IETF last call comments by clarifying the requirement to
use registered hash algorithm identifiers.
-01
o Added security considerations about multiple public keys
coresponding to the same private key.
o Added hash algorithm identifier after the JWK thumbprint URI
prefix to make it explicit in a URI which hash algorithm is used.
o Added reference to a registry for hash algorithm identifiers.
o Added SHA-256 as a mandatory to implement hash algorithm to
promote interoperability.
-00
o Created initial working group draft from draft-jones-oauth-jwk-
thumbprint-uri-01.
Authors' Addresses
Michael B. Jones
Microsoft
Email: mbj@microsoft.com
URI: https://self-issued.info/
Kristina Yasuda
Microsoft
Email: kryasuda@microsoft.com
URI: https://twitter.com/kristinayasuda
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