wdiff rfc8414.original rfc8414.txt

OAuth Working Group
Internet Engineering Task Force (IETF) M. Jones
Internet-Draft
Request for Comments: 8414 Microsoft
Intended status:
Category: Standards Track N. Sakimura
Expires: September 5, 2018
ISSN: 2070-1721 NRI
J. Bradley
Ping Identity
March 4,
Yubico
June 2018

OAuth 2.0 Authorization Server Metadata
draft-ietf-oauth-discovery-10

Abstract

This specification defines a metadata format that an OAuth 2.0 client
can use to obtain the information needed to interact with an OAuth
2.0 authorization server, including its endpoint locations and
authorization server capabilities.

Status of This Memo

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This Internet-Draft will expire on September 5, 2018.
https://www.rfc-editor.org/info/rfc8414.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 ....................................................2
1.1. Requirements Notation and Conventions . . . . . . . . . . 3 ......................3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 ................................................3
2. Authorization Server Metadata . . . . . . . . . . . . . . . . 4 ...................................4
2.1. Signed Authorization Server Metadata . . . . . . . . . . 7 .......................8
3. Obtaining Authorization Server Metadata . . . . . . . . . . . 8 .........................8
3.1. Authorization Server Metadata Request . . . . . . . . . . 9 ......................9
3.2. Authorization Server Metadata Response . . . . . . . . . 9 ....................10
3.3. Authorization Server Metadata Validation . . . . . . . . 10 ..................11
4. String Operations . . . . . . . . . . . . . . . . . . . . . . 11 ..............................................11
5. Compatibility Notes . . . . . . . . . . . . . . . . . . . . . 11 ............................................11
6. Security Considerations . . . . . . . . . . . . . . . . . . . 12 ........................................12
6.1. TLS Requirements . . . . . . . . . . . . . . . . . . . . 12 ..........................................12
6.2. Impersonation Attacks . . . . . . . . . . . . . . . . . . 12 .....................................12
6.3. Publishing Metadata in a Standard Format . . . . . . . . 13 ..................13
6.4. Protected Resources . . . . . . . . . . . . . . . . . . . 13 .......................................13
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 ............................................14
7.1. OAuth Authorization Server Metadata Registry . . . . . . 14 ..............14
7.1.1. Registration Template . . . . . . . . . . . . . . . . 15 ..............................15
7.1.2. Initial Registry Contents . . . . . . . . . . . . . . 15 ..........................16
7.2. Updated Registration Instructions . . . . . . . . . . . . 18 .........................19
7.3. Well-Known URI Registry . . . . . . . . . . . . . . . . . 19 ...................................19
7.3.1. Registry Contents . . . . . . . . . . . . . . . . . . 19 ..................................19
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 .....................................................20
8.1. Normative References . . . . . . . . . . . . . . . . . . 19 ......................................20
8.2. Informative References . . . . . . . . . . . . . . . . . 21
Appendix A. ....................................22
Acknowledgements . . . . . . . . . . . . . . . . . . 22
Appendix B. Document History . . . . . . . . . . . . . . . . . . 22 ..................................................23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 ................................................23

1. Introduction

This specification generalizes the metadata format defined by "OpenID
Connect Discovery 1.0" [OpenID.Discovery] in a way that is compatible
with OpenID Connect Discovery, Discovery while being applicable to a wider set
of OAuth 2.0 use cases. This is intentionally parallel to the way
that the "OAuth 2.0 Dynamic Client Registration Protocol" [RFC7591]
specification
generalized the dynamic client registration mechanisms defined by
"OpenID Connect Dynamic Client Registration 1.0"
[OpenID.Registration] in a way that was is compatible with it.

The metadata for an authorization server is retrieved from a well-
known location as a JSON [RFC7159] [RFC8259] document, which declares its
endpoint locations and authorization server capabilities. This
process is described in Section 3.

This metadata can either be communicated either in a self-asserted fashion
by the server origin via HTTPS or as a set of signed metadata values
represented as claims in a JSON Web Token (JWT) [JWT]. In the JWT
case, the issuer is vouching for the validity of the data about the
authorization server. This is analogous to the role that the
Software Statement plays in OAuth Dynamic Client Registration
[RFC7591].

The means by which the client chooses an authorization server is out
of scope. In some cases, its issuer identifier may be manually
configured into the client. In other cases, it may be dynamically
discovered, for instance, through the use of WebFinger [RFC7033], as
described in Section 2 of "OpenID Connect Discovery 1.0"
[OpenID.Discovery].

1.1. 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.

All uses of JSON Web Signature (JWS) [JWS] and JSON Web Encryption
(JWE) [JWE] data structures in this specification utilize the JWS
Compact Serialization or the JWE Compact Serialization; the JWS JSON
Serialization and the JWE JSON Serialization are not used.

1.2. Terminology

This specification uses the terms "Access Token", "Authorization
Code", "Authorization Endpoint", "Authorization Grant",
"Authorization Server", "Client", "Client Authentication", "Client
Identifier", "Client Secret", "Grant Type", "Protected Resource",
"Redirection URI", "Refresh Token", "Resource Owner", "Resource
Server", "Response Type", and "Token Endpoint" defined by OAuth 2.0
[RFC6749],
[RFC6749]; the terms "Claim Name", "Claim Value", and "JSON Web Token
(JWT)" defined by JSON Web Token (JWT) [JWT], [JWT]; and the term "Response
Mode" defined by OAuth "OAuth 2.0 Multiple Response Type Encoding Practices
Practices" [OAuth.Responses].

2. Authorization Server Metadata

Authorization servers can have metadata describing their
configuration. The following authorization server metadata values
are used by this specification and are registered in the IANA "OAuth
Authorization Server Metadata" registry established in Section 7.1:

issuer
REQUIRED. The authorization server's issuer identifier, which is
a URL that uses the "https" scheme and has no query or fragment
components. Authorization server metadata is published at a
location that is ".well-known" according to RFC 5785 [RFC5785] location
derived from this issuer identifier, as described in Section 3.
The issuer identifier is used to prevent authorization server mix-up mix-
up attacks, as described in "OAuth 2.0 Mix-Up Mitigation"
[I-D.ietf-oauth-mix-up-mitigation].
[MIX-UP].

authorization_endpoint
URL of the authorization server's authorization endpoint
[RFC6749]. This is REQUIRED unless no grant types are supported
that use the authorization endpoint.

token_endpoint
URL of the authorization server's token endpoint [RFC6749]. This
is REQUIRED unless only the implicit grant type is supported.

jwks_uri
OPTIONAL. URL of the authorization server's JWK Set [JWK]
document. The referenced document contains the signing key(s) the
client uses to validate signatures from the authorization server.
This URL MUST use the "https" scheme. The JWK Set MAY also
contain the server's encryption key(s), key or keys, which are used by
clients to encrypt requests to the server. When both signing and
encryption keys are made available, a "use" (public key use)
parameter value is REQUIRED for all keys in the referenced JWK Set
to indicate each key's intended usage.

registration_endpoint
OPTIONAL. URL of the authorization server's OAuth 2.0 Dynamic
Client Registration endpoint [RFC7591].

scopes_supported
RECOMMENDED. JSON array containing a list of the OAuth 2.0
[RFC6749] "scope" values that this authorization server supports.
Servers MAY choose not to advertise some supported scope values
even when this parameter is used.

response_types_supported
REQUIRED. JSON array containing a list of the OAuth 2.0
"response_type" values that this authorization server supports.
The array values used are the same as those used with the
"response_types" parameter defined by "OAuth 2.0 Dynamic Client
Registration Protocol" [RFC7591].

response_modes_supported
OPTIONAL. JSON array containing a list of the OAuth 2.0
"response_mode" values that this authorization server supports, as
specified in OAuth "OAuth 2.0 Multiple Response Type Encoding Practices Practices"
[OAuth.Responses]. If omitted, the default is "["query",
"fragment"]". The response mode value "form_post" is also defined
in OAuth "OAuth 2.0 Form Post Response Mode Mode" [OAuth.Post].

grant_types_supported
OPTIONAL. JSON array containing a list of the OAuth 2.0 grant
type values that this authorization server supports. The array
values used are the same as those used with the "grant_types"
parameter defined by "OAuth 2.0 Dynamic Client Registration
Protocol" [RFC7591]. If omitted, the default value is
"["authorization_code", "implicit"]".

token_endpoint_auth_methods_supported
OPTIONAL. JSON array containing a list of client authentication
methods supported by this token endpoint. Client authentication
method values are used in the "token_endpoint_auth_method"
parameter defined in Section 2 of [RFC7591]. If omitted, the
default is "client_secret_basic" -- the HTTP Basic Authentication
Scheme specified in Section 2.3.1 of OAuth 2.0 [RFC6749].

token_endpoint_auth_signing_alg_values_supported
OPTIONAL. JSON array containing a list of the JWS signing
algorithms ("alg" values) supported by the token endpoint for the
signature on the JWT [JWT] used to authenticate the client at the
token endpoint for the "private_key_jwt" and "client_secret_jwt"
authentication methods. This metadata entry MUST be present if
either of these authentication methods are specified in the
"token_endpoint_auth_methods_supported" entry. No default
algorithms are implied if this entry is omitted. Servers SHOULD
support "RS256". The value "none" MUST NOT be used.

service_documentation
OPTIONAL. URL of a page containing human-readable information
that developers might want or need to know when using the
authorization server. In particular, if the authorization server
does not support Dynamic Client Registration, then information on
how to register clients needs to be provided in this
documentation.

ui_locales_supported
OPTIONAL. Languages and scripts supported for the user interface,
represented as a JSON array of BCP47 [RFC5646] language tag
values. values from BCP 47
[RFC5646]. If omitted, the set of supported languages and scripts
is unspecified.

op_policy_uri
OPTIONAL. URL that the authorization server provides to the
person registering the client to read about the authorization
server's requirements on how the client can use the data provided
by the authorization server. The registration process SHOULD
display this URL to the person registering the client if it is
given. As described in Section 5, despite the identifier
"op_policy_uri",
"op_policy_uri" appearing to be OpenID-specific, its usage in this
specification is actually referring to a general OAuth 2.0 feature
that is not specific to OpenID Connect.

op_tos_uri
OPTIONAL. URL that the authorization server provides to the
person registering the client to read about the authorization
server's terms of service. The registration process SHOULD
display this URL to the person registering the client if it is
given. As described in Section 5, despite the identifier
"op_tos_uri", appearing to be OpenID-specific, its usage in this
specification is actually referring to a general OAuth 2.0 feature
that is not specific to OpenID Connect.

revocation_endpoint
OPTIONAL. URL of the authorization server's OAuth 2.0 revocation
endpoint [RFC7009].

revocation_endpoint_auth_methods_supported
OPTIONAL. JSON array containing a list of client authentication
methods supported by this revocation endpoint. The valid client
authentication method values are those registered in the IANA
"OAuth Token Endpoint Authentication Methods" registry
[IANA.OAuth.Parameters]. If omitted, the default is
"client_secret_basic" -- the HTTP Basic Authentication Scheme
specified in Section 2.3.1 of OAuth 2.0 [RFC6749].

revocation_endpoint_auth_signing_alg_values_supported
OPTIONAL. JSON array containing a list of the JWS signing
algorithms ("alg" values) supported by the revocation endpoint for
the signature on the JWT [JWT] used to authenticate the client at
the revocation endpoint for the "private_key_jwt" and
"client_secret_jwt" authentication methods. This metadata entry
MUST be present if either of these authentication methods are
specified in the "revocation_endpoint_auth_methods_supported"
entry. No default algorithms are implied if this entry is
omitted. The value "none" MUST NOT be used.

introspection_endpoint
OPTIONAL. URL of the authorization server's OAuth 2.0
introspection endpoint [RFC7662].

introspection_endpoint_auth_methods_supported
OPTIONAL. JSON array containing a list of client authentication
methods supported by this introspection endpoint. The valid
client authentication method values are those registered in the
IANA "OAuth Token Endpoint Authentication Methods" registry
[IANA.OAuth.Parameters] or those registered in the IANA "OAuth
Access Token Types" registry [IANA.OAuth.Parameters]. (These
values are and will remain distinct, due to Section 7.2.) If
omitted, the set of supported authentication methods MUST be
determined by other means.

introspection_endpoint_auth_signing_alg_values_supported
OPTIONAL. JSON array containing a list of the JWS signing
algorithms ("alg" values) supported by the introspection endpoint
for the signature on the JWT [JWT] used to authenticate the client
at the introspection endpoint for the "private_key_jwt" and
"client_secret_jwt" authentication methods. This metadata entry
MUST be present if either of these authentication methods are
specified in the "introspection_endpoint_auth_methods_supported"
entry. No default algorithms are implied if this entry is
omitted. The value "none" MUST NOT be used.

code_challenge_methods_supported
OPTIONAL. JSON array containing a list of PKCE Proof Key for Code
Exchange (PKCE) [RFC7636] code challenge methods supported by this
authorization server. Code challenge method values are used in
the "code_challenge_method" parameter defined in Section 4.3 of
[RFC7636]. The valid code challenge method values are those
registered in the IANA "PKCE Code Challenge Methods" registry
[IANA.OAuth.Parameters]. If omitted, the authorization server
does not support PKCE.

Additional authorization server metadata parameters MAY also be used.
Some are defined by other specifications, such as OpenID Connect
Discovery 1.0 [OpenID.Discovery].

2.1. Signed Authorization Server Metadata

In addition to JSON elements, metadata values MAY also be provided as
a "signed_metadata" value, which is a JSON Web Token (JWT) [JWT] that
asserts metadata values about the authorization server as a bundle.
A set of claims that can be used in signed metadata are is defined in
Section 2. The signed metadata MUST be digitally signed or MACed
using JSON Web Signature (JWS) [JWS] and MUST contain an "iss"
(issuer) claim denoting the party attesting to the claims in the
signed metadata. Consumers of the metadata MAY ignore the signed
metadata if they do not support this feature. If the consumer of the
metadata supports signed metadata, metadata values conveyed in the
signed metadata MUST take precedence over the corresponding values
conveyed using plain JSON elements.

Signed metadata is included in the authorization server metadata JSON
object using this OPTIONAL member:

signed_metadata
A JWT containing metadata values about the authorization server as
claims. This is a string value consisting of the entire signed
JWT. A "signed_metadata" metadata value SHOULD NOT appear as a
claim in the JWT.

3. Obtaining Authorization Server Metadata

Authorization servers supporting metadata MUST make a JSON document
containing metadata as specified in Section 2 available at a path
formed by inserting a well-known URI string into the authorization
server's issuer identifier between the host component and the path
component, if any. By default, the well-known URI string used is
"/.well-known/oauth-authorization-server". This path MUST use the
"https" scheme. The syntax and semantics of ".well-known" are
defined in RFC 5785 [RFC5785]. The well-known URI suffix used MUST
be registered in the IANA "Well-Known URIs" registry
[IANA.well-known].

Different applications utilizing OAuth authorization servers in
application-specific ways may define and register different well-
known URI suffixes used to publish authorization server metadata as
used by those applications. For instance, if the Example example application
uses an OAuth authorization server in an Example-specific example-specific way, and
there are Example-specific example-specific metadata values that it needs to publish,
then it might register and use the "example-configuration" URI suffix
and publish the metadata document at the path formed by inserting
"/.well-known/example-configuration" between the host and path
components of the authorization server's issuer identifier.
Alternatively, many such applications will use the default well-known
URI string "/.well-known/oauth-authorization-server", which is the
right choice for general-purpose OAuth authorization servers, and not
register an application-specific one.

An OAuth 2.0 application using this specification MUST specify what
well-known URI suffix it will use for this purpose. The same
authorization server MAY choose to publish its metadata at multiple
well-known locations derived from its issuer identifier, for example,
publishing metadata at both "/.well-known/example-configuration" and
"/.well-known/oauth-authorization-server".

Some OAuth applications will choose to use the well-known URI suffix
"openid-configuration". As described in Section 5, despite the
identifier "/.well-known/openid-configuration", appearing to be
OpenID-specific,
OpenID specific, its usage in this specification is actually
referring to a general OAuth 2.0 feature that is not specific to
OpenID Connect.

3.1. Authorization Server Metadata Request

An authorization server metadata document MUST be queried using an
HTTP "GET" request at the previously specified path.

The client would make the following request when the issuer
identifier is "https://example.com" and the well-known URI suffix is
"oauth-authorization-server" to obtain the metadata, since the issuer
identifier contains no path component:

GET /.well-known/oauth-authorization-server HTTP/1.1
Host: example.com

If the issuer identifier value contains a path component, any
terminating "/" MUST be removed before inserting "/.well-known/" and
the well-known URI suffix between the host component and the path
component. The client would make the following request when the
issuer identifier is "https://example.com/issuer1" and the well-known
URI suffix is "oauth-authorization-server" to obtain the metadata,
since the issuer identifier contains a path component:

GET /.well-known/oauth-authorization-server/issuer1 HTTP/1.1
Host: example.com

Using path components enables supporting multiple issuers per host.
This is required in some multi-tenant hosting configurations. This
use of ".well-known" is for supporting multiple issuers per host;
unlike its use in RFC 5785 [RFC5785], it does not provide general
information about the host.

3.2. Authorization Server Metadata Response

The response is a set of claims about the authorization server's
configuration, including all necessary endpoints and public key
location information. A successful response MUST use the 200 OK HTTP
status code and return a JSON object using the "application/json"
content type that contains a set of claims as its members that are a
subset of the metadata values defined in Section 2. Other claims MAY
also be returned.

Claims that return multiple values are represented as JSON arrays.
Claims with zero elements MUST be omitted from the response.

An error response uses the applicable HTTP status code value.

The following is a non-normative example response:

HTTP/1.1 200 OK
Content-Type: application/json

{
"issuer":
"https://server.example.com",
"authorization_endpoint":
"https://server.example.com/authorize",
"token_endpoint":
"https://server.example.com/token",
"token_endpoint_auth_methods_supported":
["client_secret_basic", "private_key_jwt"],
"token_endpoint_auth_signing_alg_values_supported":
["RS256", "ES256"],
"userinfo_endpoint":
"https://server.example.com/userinfo",
"jwks_uri":
"https://server.example.com/jwks.json",
"registration_endpoint":
"https://server.example.com/register",
"scopes_supported":
["openid", "profile", "email", "address",
"phone", "offline_access"],
"response_types_supported":
["code", "code token"],
"service_documentation":
"http://server.example.com/service_documentation.html",
"ui_locales_supported":
["en-US", "en-GB", "en-CA", "fr-FR", "fr-CA"]
}

3.3. Authorization Server Metadata Validation

The "issuer" value returned MUST be identical to the authorization
server's issuer identifier value into which the well-known URI string
was inserted to create the URL used to retrieve the metadata. If
these values are not identical, the data contained in the response
MUST NOT be used.

4. String Operations

Processing some OAuth 2.0 messages requires comparing values in the
messages to known values. For example, the member names in the
metadata response might be compared to specific member names such as
"issuer". Comparing Unicode [UNICODE] strings, however, has
significant security implications.

Therefore, comparisons between JSON strings and other Unicode strings
MUST be performed as specified below:

1. Remove any JSON applied JSON-applied escaping to produce an array of Unicode
code points.

2. Unicode Normalization [USA15] MUST NOT be applied at any point to
either the JSON string or to the string it is to be compared
against.

3. Comparisons between the two strings MUST be performed as a
Unicode code point to code point code-point-to-code-point equality comparison.

Note that this is the same equality comparison procedure described in
Section 8.3 of [RFC7159]. [RFC8259].

5. Compatibility Notes

The identifiers "/.well-known/openid-configuration", "op_policy_uri",
and "op_tos_uri" contain strings referring to the OpenID Connect
[OpenID.Core] family of specifications that were originally defined
by "OpenID Connect Discovery 1.0" [OpenID.Discovery]. Despite the
reuse of these identifiers that appear to be OpenID-specific, OpenID specific, their
usage in this specification is actually referring to general OAuth
2.0 features that are not specific to OpenID Connect.

The algorithm for transforming the issuer identifier to an
authorization server metadata location defined in Section 3 is
equivalent to the corresponding transformation defined in Section 4
of "OpenID Connect Discovery 1.0" [OpenID.Discovery], provided that
the issuer identifier contains no path component. However, they are
different when there is a path component, because OpenID Connect
Discovery 1.0 specifies that the well-known URI string is appended to
the issuer identifier (e.g., "https://example.com/issuer1/.well-
known/openid-configuration"),
"https://example.com/issuer1/.well-known/openid-configuration"),
whereas this specification specifies that the well-known URI string
is inserted before the path component of the issuer identifier (e.g., "https://example.com/.well-known/
openid-configuration/issuer1").
"https://example.com/.well-known/openid-configuration/issuer1").

Going forward, OAuth authorization server metadata locations should
use the transformation defined in this specification. However, when
deployed in legacy environments in which the OpenID Connect Discovery
1.0 transformation is already used, it may be necessary during a
transition period to publish metadata for issuer identifiers
containing a path component at both locations. During this
transition period, applications should first apply the transformation
defined in this specification and attempt to retrieve the
authorization server metadata from the resulting location; only if
the retrieval from that location fails should they fall back to
attempting to retrive retrieve it from the alternate location obtained using
the transformation defined by OpenID Connect Discovery 1.0. This
backwards-compatibility
backwards-compatible behavior should only be necessary when the
well-known well-
known URI suffix employed by the application is "openid-
configuration".

6. Security Considerations

6.1. TLS Requirements

Implementations MUST support TLS. Which version(s) ought to be
implemented will vary over time and depend on the widespread
deployment and known security vulnerabilities at the time of
implementation. The authorization server MUST support TLS version
1.2 [RFC5246] and MAY support additional transport-layer security TLS mechanisms meeting its
security requirements. When using TLS, the client MUST perform a
TLS/SSL server certificate check, per RFC 6125 [RFC6125].
Implementation security considerations can be found in
Recommendations
"Recommendations for Secure Use of TLS Transport Layer Security (TLS) and DTLS
Datagram Transport Layer Security (DTLS)" [BCP195].

To protect against information disclosure and tampering,
confidentiality protection MUST be applied using TLS with a
ciphersuite that provides confidentiality and integrity protection.

6.2. Impersonation Attacks

TLS certificate checking MUST be performed by the client, as
described in Section 6.1, when making an authorization server
metadata request. Checking that the server certificate is valid for
the issuer identifier URL prevents man-in-middle and DNS-based
attacks. These attacks could cause a client to be tricked into using
an attacker's keys and endpoints, which would enable impersonation of
the legitimate authorization server. If an attacker can accomplish
this, they can access the resources that the affected client has
access to using the authorization server that they are impersonating.

An attacker may also attempt to impersonate an authorization server
by publishing a metadata document that contains an "issuer" claim
using the issuer identifier URL of the authorization server being
impersonated, but with its own endpoints and signing keys. This
would enable it to impersonate that authorization server, if accepted
by the client. To prevent this, the client MUST ensure that the
issuer identifier URL it is using as the prefix for the metadata
request exactly matches the value of the "issuer" metadata value in
the authorization server metadata document received by the client.

6.3. Publishing Metadata in a Standard Format

Publishing information about the authorization server in a standard
format makes it easier for both legitimate clients and attackers to
use the authorization server. Whether an authorization server
publishes its metadata in an ad-hoc ad hoc manner or in the standard format
defined by this specification, the same defenses against attacks that
might be mounted that use this information should be applied.

6.4. Protected Resources

Secure determination of appropriate protected resources to use with
an authorization server for all use cases is out of scope of this
specification. This specification assumes that the client has a
means of determining appropriate protected resources to use with an
authorization server and that the client is using the correct
metadata for each authorization server. Implementers need to be
aware that if an inappropriate protected resource is used by the
client, that an attacker may be able to act as a man-in-the-middle
proxy to a valid protected resource without it being detected by the
authorization server or the client.

The ways to determine the appropriate protected resources to use with
an authorization server are are, in general, application-dependent. application dependent. For
instance, some authorization servers are used with a fixed protected
resource or set of protected resources, the locations of which may be
well known, known or which could be published as metadata values by the
authorization server. In other cases, the set of resources that can
be used with an authorization server can by be dynamically changed by
administrative actions. Many other means of determining appropriate
associations between authorization servers and protected resources
are also possible.

7. IANA Considerations

The following registration procedure is used for the registry
established by this specification.

Values are registered on a Specification Required [RFC8126] basis
after a two-week review period on the oauth-ext-review@ietf.org
mailing list, on the advice of one or more Designated Experts.
However, to allow for the allocation of values prior to publication,
the Designated Experts may approve registration once they are
satisfied that such a specification will be published.

Registration requests sent to the mailing list for review should use
an appropriate subject (e.g., "Request to register OAuth
Authorization Server Metadata: example").

Within the review period, the Designated Experts will either approve
or deny the registration request, communicating this decision to the
review list and IANA. Denials should include an explanation and, if
applicable, suggestions as to how to make the request successful.
Registration requests that are undetermined for a period longer than
21 days can be brought to the IESG's attention (using the
iesg@ietf.org mailing list) for resolution.

Criteria that should be applied by the Designated Experts includes include
determining whether the proposed registration duplicates existing
functionality, determining whether it is likely to be of general
applicability or whether it is useful only for a single application,
and whether the registration makes sense.

IANA must only accept registry updates from the Designated Experts
and should direct all requests for registration to the review mailing
list.

It is suggested that multiple Designated Experts be appointed who are
able to represent the perspectives of different applications using
this specification, in order to enable broadly-informed review of
registration decisions. In cases where a registration decision could
be perceived as creating a conflict of interest for a particular
Designated Expert, that Designated Expert should defer to the
judgment of the other Designated Experts.

7.1. OAuth Authorization Server Metadata Registry

This specification establishes the IANA "OAuth Authorization Server
Metadata" registry for OAuth 2.0 authorization server metadata names.
The registry records the authorization server metadata member and a
reference to the specification that defines it.

The Designated Experts must either:

(a) require that metadata names and values being registered use only
printable ASCII characters excluding double quote ('"') and backslash
('\') (the Unicode characters with code points U+0021, U+0023 through
U+005B, and U+005D through U+007E), or

(b) if new metadata members or values are defined that use other code
points, require that their definitions specify the exact sequences of
Unicode code
point sequences points used to represent them. Furthermore, proposed
registrations that use Unicode code points that can only be
represented in JSON strings as escaped characters must not be
accepted.

7.1.1. Registration Template

Metadata Name:
The name requested (e.g., "issuer"). This name is case-sensitive.
Names may not match other registered names in a case-insensitive
manner (one that would cause a match if the Unicode toLowerCase()
operation were applied to both strings) unless the Designated
Experts state that there is a compelling reason to allow an
exception.

Metadata Description:
Brief description of the metadata (e.g., "Issuer identifier URL").

Change Controller:
For Standards Track RFCs, list the "IESG". For others, give the
name of the responsible party. Other details (e.g., postal
address, email address, home page URI) may also be included.

Specification Document(s):
Reference to the document or documents that specify the parameter,
preferably including URIs that can be used to retrieve copies of
the documents. An indication of the relevant sections may also be
included but is not required.

7.1.2. Initial Registry Contents

o Metadata Name: "issuer" issuer
o Metadata Description: Authorization server's issuer identifier URL
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name: "authorization_endpoint" authorization_endpoint
o Metadata Description: URL of the authorization server's
authorization endpoint
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name: "token_endpoint" token_endpoint
o Metadata Description: URL of the authorization server's token
endpoint
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name: "jwks_uri" jwks_uri
o Metadata Description: URL of the authorization server's JWK Set
document
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name: "registration_endpoint" registration_endpoint
o Metadata Description: URL of the authorization server's OAuth 2.0
Dynamic Client Registration Endpoint
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name: "scopes_supported" scopes_supported
o Metadata Description: JSON array containing a list of the OAuth
2.0 "scope" values that this authorization server supports
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name: "response_types_supported" response_types_supported
o Metadata Description: JSON array containing a list of the OAuth
2.0 "response_type" values that this authorization server supports
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name: "response_modes_supported" response_modes_supported
o Metadata Description: JSON array containing a list of the OAuth
2.0 "response_mode" values that this authorization server supports
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414
o Metadata Name: "grant_types_supported" grant_types_supported
o Metadata Description: JSON array containing a list of the OAuth
2.0 grant type values that this authorization server supports
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name: "token_endpoint_auth_methods_supported" token_endpoint_auth_methods_supported
o Metadata Description: JSON array containing a list of client
authentication methods supported by this token endpoint
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name: "token_endpoint_auth_signing_alg_values_supported" token_endpoint_auth_signing_alg_values_supported
o Metadata Description: JSON array containing a list of the JWS
signing algorithms supported by the token endpoint for the
signature on the JWT used to authenticate the client at the token
endpoint
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name: "service_documentation" service_documentation
o Metadata Description: URL of a page containing human-readable
information that developers might want or need to know when using
the authorization server
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name: "ui_locales_supported" ui_locales_supported
o Metadata Description: Languages and scripts supported for the user
interface, represented as a JSON array of BCP47 language tag values from
BCP 47
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name: "op_policy_uri" op_policy_uri
o Metadata Description: URL that the authorization server provides
to the person registering the client to read about the
authorization server's requirements on how the client can use the
data provided by the authorization server
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name: "op_tos_uri" op_tos_uri
o Metadata Description: URL that the authorization server provides
to the person registering the client to read about the
authorization server's terms of service
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414
o Metadata Name: "revocation_endpoint" revocation_endpoint
o Metadata Description: URL of the authorization server's OAuth 2.0
revocation endpoint
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name: "revocation_endpoint_auth_methods_supported" revocation_endpoint_auth_methods_supported
o Metadata Description: JSON array containing a list of client
authentication methods supported by this revocation endpoint
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name:
"revocation_endpoint_auth_signing_alg_values_supported"
revocation_endpoint_auth_signing_alg_values_supported
o Metadata Description: JSON array containing a list of the JWS
signing algorithms supported by the revocation endpoint for the
signature on the JWT used to authenticate the client at the
revocation endpoint
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name: "introspection_endpoint" introspection_endpoint
o Metadata Description: URL of the authorization server's OAuth 2.0
introspection endpoint
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name: "introspection_endpoint_auth_methods_supported" introspection_endpoint_auth_methods_supported
o Metadata Description: JSON array containing a list of client
authentication methods supported by this introspection endpoint
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name:
"introspection_endpoint_auth_signing_alg_values_supported"
introspection_endpoint_auth_signing_alg_values_supported
o Metadata Description: JSON array containing a list of the JWS
signing algorithms supported by the introspection endpoint for the
signature on the JWT used to authenticate the client at the
introspection endpoint
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414

o Metadata Name: "code_challenge_methods_supported" code_challenge_methods_supported
o Metadata Description: PKCE code challenge methods supported by
this authorization server
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]] RFC 8414
o Metadata Name: signed_metadata
o Metadata Description: Signed JWT containing metadata values about
the authorization server as claims
o Change Controller: IESG
o Specification Document(s): Section 2.1 of RFC 8414

7.2. Updated Registration Instructions

This specification adds to the instructions for the Designated
Experts of the following IANA registries, both of which are in the
"OAuth Parameters" registry [IANA.OAuth.Parameters]:

o OAuth Access Token Types
o OAuth Token Endpoint Authentication Methods

IANA has added a link to this specification in the Reference sections
of these registries. [[ RFC Editor: The above sentence is written in
the past tense as it would appear in the final specification, even
though these links won't actually be created until after the IESG has
requested publication of the specification. Please delete this note
after the links are in place. ]]

For these registries, the designated experts Designated Experts must reject registration
requests in one registry for values already occurring in the other
registry. This is necessary because the
"introspection_endpoint_auth_methods_supported" parameter allows for
the use of values from either registry. That way, because the values
in the two registries will continue to be mutually exclusive, no
ambiguities will arise.

7.3. Well-Known URI Registry

This specification registers the well-known URI defined in Section 3
in the IANA "Well-Known URIs" registry [IANA.well-known] established
by RFC 5785 [RFC5785].

7.3.1. Registry Contents

o URI suffix: "oauth-authorization-server" oauth-authorization-server
o Change controller: IESG
o Specification document: Section 3 of [[ this specification ]] RFC 8414
o Related information: (none)

8. References

8.1. Normative References

[BCP195] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 2015,
<http://www.rfc-editor.org/info/bcp195>.

[IANA.OAuth.Parameters]
IANA, "OAuth Parameters",
<http://www.iana.org/assignments/oauth-parameters>.
<https://www.iana.org/assignments/oauth-parameters>.

[JWE] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
RFC 7516, DOI 10.17487/RFC7516, May 2015,
<http://tools.ietf.org/html/rfc7516>.
<https://www.rfc-editor.org/info/rfc7516>.

[JWK] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<http://tools.ietf.org/html/rfc7517>.
<https://www.rfc-editor.org/info/rfc7517>.

[JWS] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <http://tools.ietf.org/html/rfc7515>. <https://www.rfc-editor.org/info/rfc7515>.

[JWT] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<http://tools.ietf.org/html/rfc7519>.
<https://www.rfc-editor.org/info/rfc7519>.

[OAuth.Post]
Jones, M. and B. Campbell, "OAuth 2.0 Form Post Response
Mode", April 2015, <http://openid.net/specs/
oauth-v2-form-post-response-mode-1_0.html>.

[OAuth.Responses]
de Medeiros, B., Ed., Scurtescu, M., Tarjan, P., and M.
Jones, "OAuth 2.0 Multiple Response Type Encoding
Practices", February 2014, <http://openid.net/specs/
oauth-v2-multiple-response-types-1_0.html>.

[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>.

[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.

[RFC5646] Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying
Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646,
September 2009, <https://www.rfc-editor.org/info/rfc5646>.

[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
Uniform Resource Identifiers (URIs)", RFC 5785,
DOI 10.17487/RFC5785, April 2010,
<https://www.rfc-editor.org/info/rfc5785>.

[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
2011, <https://www.rfc-editor.org/info/rfc6125>.

[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<https://www.rfc-editor.org/info/rfc6749>.

[RFC7009] Lodderstedt, T., Ed., Dronia, S., and M. Scurtescu, "OAuth
2.0 Token Revocation", RFC 7009, DOI 10.17487/RFC7009,
August 2013, <https://www.rfc-editor.org/info/rfc7009>.

[RFC7033] Jones, P., Salgueiro, G., Jones, M., and J. Smarr,
"WebFinger", RFC 7033, DOI 10.17487/RFC7033, September
2013, <https://www.rfc-editor.org/info/rfc7033>.

[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <https://www.rfc-editor.org/info/rfc7159>.

[RFC7591] Richer, J., Ed., Jones, M., Bradley, J., Machulak, M., and
P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol",
RFC 7591, DOI 10.17487/RFC7591, July 2015,
<https://www.rfc-editor.org/info/rfc7591>.

[RFC7636] Sakimura, N., Ed., Bradley, J., and N. Agarwal, "Proof Key
for Code Exchange by OAuth Public Clients", RFC 7636,
DOI 10.17487/RFC7636, September 2015,
<https://www.rfc-editor.org/info/rfc7636>.

[RFC7662] Richer, J., Ed., "OAuth 2.0 Token Introspection",
RFC 7662, DOI 10.17487/RFC7662, October 2015,
<https://www.rfc-editor.org/info/rfc7662>.

[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.

[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>.

[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.

[UNICODE] The Unicode Consortium, "The Unicode Standard",
<http://www.unicode.org/versions/latest/>.

[USA15] Davis, M. M., Ed. and K. Whistler, Ed., "Unicode
Normalization Forms", Unicode Standard Annex 15, June 2015, #15, May
2018, <http://www.unicode.org/reports/tr15/>.

8.2. Informative References

[I-D.ietf-oauth-mix-up-mitigation]

[IANA.well-known]
IANA, "Well-Known URIs",
<https://www.iana.org/assignments/well-known-uris>.

[MIX-UP] Jones, M., Bradley, J., and N. Sakimura, "OAuth 2.0 Mix-Up
Mitigation", draft-ietf-oauth-mix-up-mitigation-01 (work Work in progress), Progress, draft-ietf-oauth-mix-up-
mitigation-01, July 2016.

[IANA.well-known]
IANA, "Well-Known URIs",
<http://www.iana.org/assignments/well-known-uris>.

[OpenID.Core]
Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and
C. Mortimore, "OpenID Connect Core 1.0", November 2014,
<http://openid.net/specs/openid-connect-core-1_0.html>.

[OpenID.Discovery]
Sakimura, N., Bradley, J., Jones, M., and E. Jay, "OpenID
Connect Discovery 1.0", November 2014,
<http://openid.net/specs/
openid-connect-discovery-1_0.html>.

[OpenID.Registration]
Sakimura, N., Bradley, J., and M. Jones, "OpenID Connect
Dynamic Client Registration 1.0", November 2014,
<http://openid.net/specs/
openid-connect-registration-1_0.html>.

Appendix A.

Acknowledgements

This specification is based on the OpenID Connect Discovery 1.0
specification, which was produced by the OpenID Connect working group
of the OpenID Foundation. This specification standardizes the de
facto usage of the metadata format defined by OpenID Connect
Discovery to publish OAuth authorization server metadata.

The authors would like to thank the following people for their
reviews of this specification: Shwetha Bhandari, Ben Campbell, Brian
Campbell, Brian Carpenter, William Denniss, Vladimir Dzhuvinov,
Donald Eastlake, Samuel Erdtman, George Fletcher, Dick Hardt, Phil
Hunt, Alexey Melnikov, Tony Nadalin, Mark Nottingham, Eric Rescorla,
Justin Richer, Adam Roach, Hannes Tschofenig, and Hans Zandbelt.

Appendix B. Document History

[[ to be removed by the RFC Editor before publication as an RFC ]]

-10

o Clarified the meaning of "case-insensitive", as suggested by
Alexey Melnikov.

-09
o Revised the transformation between the issuer identifier and the
authorization server metadata location to conform to BCP 190, as
suggested by Adam Roach.

o Defined the characters allowed in registered metadata names and
values, as suggested by Alexey Melnikov.

o Changed to using the RFC 8174 boilerplate instead of the RFC 2119
boilerplate, as suggested by Ben Campbell.

o Acknowledged additional reviewers.

-08

o Changed the "authorization_endpoint" to be REQUIRED only when
grant types are supported that use the authorization endpoint.

o Added the statement, to provide historical context, that this
specification standardizes the de facto usage of the metadata
format defined by OpenID Connect Discovery to publish OAuth
authorization server metadata.

o Applied clarifications suggested by Mark Nottingham about when
application-specific well-known suffixes are and are not
appropriate.

o Acknowledged additional reviewers.

-07

o Applied clarifications suggested by EKR.

-06

o Incorporated resolutions to working group last call comments.

-05

o Removed the "protected_resources" element and the reference to
draft-jones-oauth-resource-metadata.

-04

o Added the ability to list protected resources with the
"protected_resources" element.

o Added ability to provide signed metadata with the
"signed_metadata" element.

o Removed "Discovery" from the name, since this is now just about
authorization server metadata.

-03

o Changed term "issuer URL" to "issuer identifier" for terminology
consistency, paralleling the same terminology consistency change
in the mix-up mitigation spec.

-02

o Changed the title to OAuth 2.0 Authorization Server Discovery
Metadata.

o Made "jwks_uri" and "registration_endpoint" OPTIONAL.

o Defined the well-known URI string "/.well-known/oauth-
authorization-server".

o Added security considerations about publishing authorization
server discovery metadata in a standard format.

o Added security considerations about protected resources.

o Added more information to the "grant_types_supported" and
"response_types_supported" definitions.

o Referenced the working group Mix-Up Mitigation draft.

o Changed some example metadata values.

o Acknowledged individuals for their contributions to the
specification.

-01

o Removed WebFinger discovery.

o Clarified the relationship between the issuer identifier URL and
the well-known URI path relative to it at which the discovery
metadata document is located.

-00

o Created the initial working group version based on draft-jones-
oauth-discovery-01, with no normative changes.

Authors' Addresses

Michael B. Jones
Microsoft

Email: mbj@microsoft.com
URI: http://self-issued.info/

Nat Sakimura
Nomura Research Institute, Ltd.

Email: n-sakimura@nri.co.jp
URI: http://nat.sakimura.org/

John Bradley
Ping Identity
Yubico

Email: ve7jtb@ve7jtb.com RFC8414@ve7jtb.com
URI: http://www.thread-safe.com/