R. Hedberg, Ed.
independent
M. Jones
Microsoft
A. Solberg
Sikt
J. Bradley
Yubico
G. De Marco
independent
June 14, 2022

OpenID Connect Federation 1.0 - draft 20
openid-connect-federation-1_0

Abstract

A federation can be expressed as an agreement between parties that trust each other. In bilateral federations, you can have direct trust between the parties. In a multilateral federation, bilateral agreements might not be practical, in which case, trust can be mediated by a third party. That is the model used in this specification.

An Entity in the federation must be able to trust that other entities it is interacting with belong to the same federation. It must also be able to trust that the information the other entities publish about themselves has not been tampered with during transport and that it adheres to the federation's policies.

This specification describes the basic components you will need to build a multilateral federation and it provides a guide on how to apply them when the underlying protocol used is OpenID Connect.


Table of Contents

1. Introduction

This specification describes how two entities that would like to interact can dynamically fetch and resolve trust and metadata for a given protocol through the use of third-party Trust Anchor. A trust anchor is an Entity whose main purpose is to issue statements about entities, such as OpenID Connect Relying Parties, OpenID Providers, and participating organizations. An identity federation can be realized using this specification using one or more levels of trust issuers. This specification does not mandate a specific way or restrict how a federation may be built. Instead, the specification provides the basic technical trust infrastructure building blocks needed to build a dynamic and distributed trust network such as a federation.

Note that this specification only concerns itself with how entities in a federation get to know about each other. Furthermore, note that a company, as with any real-world organization, MAY be represented by more than one Entity in a federation. It is also true that an Entity can be part of more than one federation.

OpenID Connect Federation Trust Chains rely on cryptographically signed JSON Web Token (JWT) documents, and the Trust Chain does not at all rely on TLS [RFC8446] to establish trust.

1.1. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].

1.2. Terminology

This specification uses the terms "Claim Name", "Claim Value", "JSON Web Token (JWT)", defined by JSON Web Token (JWT) and the terms "OpenID Provider (OP)" and "Relying Party (RP)" defined by OpenID Connect Core 1.0.

This specification also defines the following terms:

Entity

Something that has a separate and distinct existence and that can be identified in a context. All entities in an OpenID Connect federation MUST have a globally unique identifier.
Entity Identifier

A URI that is globally unique and that is bound to one Entity.
Entity Statement

Signed JWT that contains the information needed for an Entity to participate in federation(s), including metadata about itself and policies that apply to other entities that it is authoritative for.
Entity Configuration

An Entity Statement issued by an Entity about itself. It contains the entities' signing keys and further data used to control the Trust Chain resolution process, such as authority hints.
Federation Operator
An organization that is authoritative for a federation. A federation operator administers the Trust Anchor(s) for entities in its federation.
Intermediate Entity

An Entity that issues an Entity Statement that appears somewhere in between those issued by the Trust Anchor and the leaf Entity in a Trust Chain.
Leaf Entity

An Entity defined by a certain protocol, e.g., OpenID Connect Relying Party or Provider.
Trust Anchor

An Entity that represents a trusted third party.
Trust Chain

A sequence of Entity Statements that represents a chain starting at a leaf Entity and ending in a Trust Anchor.

2. Overall Architecture

The basic component is the Entity Statement, which is a cryptographically signed JSON Web Token (JWT). A set of Entity Statements can form a path from a leaf Entity to a Trust Anchor. Entity Configurations as self-signed Entity Statements issued by federation entities about themselves control the Trust Chain resolution process.

Starting with the Entity Configuration of the leaf Entity, you can find the next level of Entity Configuration by following the authority hints. And then repeat this until you hit a Trust Anchor. Using the federation APIs exposed by the intermediate entities and the Trust Anchor, you can then fetch the Entity Statements for the intermediate entities and the leaf Entity.

Once you have followed a path, you have collected a set of Entity Statements that forms a chain. You can verify that this chain has not been tampered with by verifying the signature of each statement. How this is done is described in Section 3.2.

With a verified Trust Chain in hand, you can now apply federation policy to the published metadata. How this is done is described in Section 5.

Note that this specification is only dealing with trust in that the other party is part of the same federation as you and that you can trust that the metadata you get that describes the other party is what was sent. The specification does not touch protocol operations outside those of metadata exchange. In OpenID Connect terms, these are protocol operations other than discovery and registration.

The fact that we use OpenID Connect in all the examples in this specification does not mean that the specification can only be used together with OpenID Connect. On the contrary, it can equally well be used to build an OAuth 2.0 federations or for that matter, other protocols that depend on dynamic exchange of Entity metadata.

3. Components

3.1. Entity Statement

An Entity Statement contains the information needed for the Entity that is the subject of the Entity Statement to participate in federation(s). An Entity Statement is always a signed JWT. The subject of the JWT is the Entity itself. The issuer of the JWT is the party that issued the Entity Statement, which will often be the Entity itself. All entities in a federation SHOULD be prepared to publish an Entity Statement about themselves. If they are not able to do so themselves, another issuer MUST do it for them.

An Entity Statement is composed of the following claims:

iss

REQUIRED. The Entity Identifier of the issuer of the statement. If the iss and the sub are identical, the issuer is making a statement about itself and this Entity Statement is an Entity Configuration.
sub

REQUIRED. The Entity Identifier of the subject.
iat

REQUIRED. The time the statement was issued. Its value is a JSON number representing the number of seconds from 1970-01-01T0:0:0Z as measured in UTC until the date/time. See [RFC3339] for details regarding date/times in general and UTC in particular.
exp

REQUIRED. Expiration time on or after which the statement MUST NOT be accepted for processing. Its value is a JSON number representing the number of seconds from 1970-01-01T0:0:0Z as measured in UTC until the date/time.
jwks

REQUIRED Conditional. A JSON Web Key Set (JWKS) representing the public part of the subject Entity's signing keys. The corresponding private key is used by leaf entities to sign Entity Statements about themselves, and intermediate entities to sign statements about other entities. The keys that can be found here are intended to sign Entity Statements and SHOULD NOT be used in other protocols. Keys to be used in other protocols, such as OpenID Connect, are conveyed in the metadata element of the respective Entity Statement. This claim is only OPTIONAL for the Entity Statement returned from an OP when the client is doing explicit registration. In all other cases it is REQUIRED. Every JWK in the JWK Set MUST have a Key ID (kid). It is RECOMMENDED that the Key ID be the JWK Thumbprint [RFC7638] using the SHA-256 hash function of the key.
aud

OPTIONAL. The Entity Statement MAY be specifically created for an Entity. The Entity Identifier for that Entity MUST appear in this claim.
authority_hints

OPTIONAL. Array of strings representing the Entity Identifiers of intermediate entities or Trust Anchors that MAY issue an Entity Statement about the issuer Entity. For all entities except for Trust Anchors that do not have any superiors this is REQUIRED and MUST NOT be the empty list []. This claim MUST be absent from an Entity Statement issued by a Trust Anchor with no superiors.
metadata

REQUIRED Conditional. JSON object including protocol specific metadata claims that represent the Entity's metadata. Each key of the JSON object represents a metadata type identifier, and each value MUST be a JSON object representing the metadata according to the metadata schema of that metadata type. An Entity Statement MAY contain multiple metadata statements, but only one for each metadata type. If the Entity Statement is an Entity Configuration, then the Entity Statement MUST contain a metadata claim. If iss and sub are not the same, then the Entity Statement MAY contain a metadata claim containing metadata asserted by a superior about the Entity identified by sub.
metadata_policy

REQUIRED Conditional. JSON object that describes a metadata policy. Each key of the JSON object represents a metadata type identifier, and each value MUST be a JSON object representing the metadata policy according to the metadata schema of that metadata type. An Entity Statement MAY contain multiple metadata policy statements, but only one for each metadata type. Only non-leaf entities MAY contain a metadata_policy claim. Leaf entities MUST NOT contain a metadata_policy claim.
constraints

OPTIONAL. JSON object that describes a set of Trust Chain constraints. There is more about this in Section 5.2.
crit

OPTIONAL. The crit (critical) Entity Statement claim indicates that extensions to Entity Statement claims defined by this specification are being used that MUST be understood and processed. It is used in the same way that crit is used for extension JWS header parameters that MUST be understood and processed. Its value is an array listing the Entity Statement claims present in the Entity Statement that use those extensions. If any of the listed extension Entity Statement claims are not understood and supported by the recipient, then the Entity Statement is invalid. Producers MUST NOT include Entity Statement claim names defined by this specification or names that do not occur as Entity Statement claim names in the Entity Statement in the crit list. Producers MUST NOT use the empty list [] as the crit value.
policy_language_crit

OPTIONAL. The policy_language_crit (critical) Entity Statement claim indicates that extensions to the policy language defined by this specification are being used that MUST be understood and processed. It is used in the same way that crit is used for extension JSON Web Signature (JWS) header parameters that MUST be understood and processed. Its value is an array listing the policy language extensions present in the policy language statements that use those extensions. If any of the listed extension policy language extensions are not understood and supported by the recipient, then the Entity Statement is invalid. Producers MUST NOT include policy language names defined by this specification or names that do not occur in policy language statements in the Entity Statement in the policy_language_crit list. Producers MUST NOT use the empty list [] as the policy_language_crit value.
trust_marks

OPTIONAL. A JSON array of objects, each representing a certification mark. Each object contains two claims:
id
The Trust Mark identifier
trust_mark
A signed JSON Web Token that represents a certification mark.

There is more about certification marks in

Section 5.3.
trust_marks_issuers

OPTIONAL. A Trust Anchor MAY use this claim to tell which Trust Mark identifiers and their issuers are trusted by the federation. This claim MUST be ignored if present in an Entity Statement of other entities than Trust Anchor. It is a JSON array with keys representing Trust Mark identifiers and values being an array of trusted entities representing the accreditation authority. A special value of * allows for self-signed Trust Marks. There is more about certification marks in Section 5.3.
trust_anchor_id

OPTIONAL. An OP MUST use this claim to tell the RP which Trust Anchor it chose to use when responding to an explicit client registration. The value of trust_anchor_id is the Entity Identifier of a trust anchor.

The Entity Statement is signed using the private key of the issuer Entity, in the form of a JSON Web Signature (JWS). Entities MUST support signing Entity Statements with the RSA SHA-256 algorithm (an alg value of RS256). Consequently, entities MUST support signature verification where the statement was signed using RS256.

The following is a non-normative example of a trust_marks_issuers claim value:

{
  "https://openid.net/certification/op": ["*"],
  "https://refeds.org/wp-content/uploads/2016/01/Sirtfi-1.0.pdf":
    ["https://swamid.se"]
}
              

The following is a non-normative example of an Entity Statement before serialization and adding a signature. The example contains a critical extension jti (JWT ID) to the Entity Statement and one critical extension to the policy language regexp (Regular expression).

{
  "iss": "https://feide.no",
  "sub": "https://ntnu.no",
  "iat": 1516239022,
  "exp": 1516298022,
  "crit": ["jti"],
  "jti": "7l2lncFdY6SlhNia",
  "policy_language_crit": ["regexp"],
  "metadata_policy": {
    "openid_provider": {
      "issuer": {"value": "https://ntnu.no"},
      "organization_name": {"value": "NTNU"},
      "id_token_signing_alg_values_supported":
        {"subset_of": ["RS256", "RS384", "RS512"]},
      "op_policy_uri": {
        "regexp":
          "^https:\/\/[\\w-]+\\.example\\.com\/[\\w-]+\\.html"}
    },
    "oauth_client": {
      "organization_name": {"value": "NTNU"},
      "grant_types": {
        "subset_of": ["authorization_code", "client_credentials"]},
      "scope": {
        "subset_of": ["openid", "profile", "email", "phone"]}
    }
  },
  "constraints": {
    "max_path_length": 2
  },
  "jwks": {
    "keys": [
      {
        "alg": "RS256",
        "e": "AQAB",
        "key_ops": ["verify"],
        "kid": "key1",
        "kty": "RSA",
        "n": "pnXBOusEANuug6ewezb9J_...",
        "use": "sig"
      }
    ]
  }
}

3.2. Trust Chain

In an OpenID Connect identity federation, entities that together build a Trust Chain can be categorized as:

Trust anchor

An Entity that represents a trusted third party.
Leaf

In an OpenID Connect identity federation, an RP or an OP.
Intermediate

Neither a leaf nor a Trust Anchor.

A Trust Chain begins with a leaf Entity's self-signed Entity Statement, has zero or more Entity Statements issued by intermediates about subordinates, and ends with an Entity Statement issued by the Trust Anchor about the top-most intermediate (if there are intermediates) or the leaf Entity (if there are no intermediates).

A simple example: If we have an RP that belongs to organization A that is a member of federation F, the Trust Chain for such a setup will contain the following Entity Statements:

  1. a self-signed Entity Statement about the RP published by the RP,
  2. an Entity Statement about the RP published by Organization A, and
  3. an Entity Statement about Organization A published by Federation F.

A Trust Chain MUST always be possible to order such that: If we name the Entity Statements ES[0] (the leaf Entity's self-signed Entity Statement) to ES[i] (an Entity Statement issued by the Trust Anchor), i>0 then:

The signing key that MUST be used to verify ES[i] is distributed from the Trust Anchors to any Entity that needs to verify a Trust Chain in some secure out-of-band way not described in this document.

4. Metadata

This specification does allow new metadata types to be defined, to support use cases outside OpenID Connect federations. The metadata type identifier will uniquely identify which metadata specification to utilize.

The metadata document MUST be a JSON object. Beyond that there is no restriction.

Metadata used in federations typically reuses existing metadata standards. If needed, the metadata schema is extended with additional properties relevant in a federated context. For instance, for OpenID Connect federations, this specification uses metadata values from OpenID Connect Discovery 1.0 and OpenID Connect Dynamic Client Registration 1.0 and adds additional values used for federations.

4.1. RP Metadata

The metadata type identifier is openid_relying_party.

All parameters defined in Section 2 of OpenID Connect Dynamic Client Registration 1.0 are allowed in a metadata statement.

To that list is added:

client_registration_types

REQUIRED. Array of strings specifying the client registration types the RP wants to use. Values defined by this specification are automatic and explicit.
organization_name

OPTIONAL. A human-readable name representing the organization owning the RP. If the owner is a physical person this MAY be, for example, the name of a person.
signed_jwks_uri

OPTIONAL. A URI pointing to a signed JWT having the Entity's JWK Set as its payload. The JWT is signed with a key that was included in the JWK that the Entity published in its self-signed Entity Statement. If an RP can use signed_jwks_uri, it MUST NOT use jwks or jwks_uri. A signed JWT can contain the following claims, all except keys defined in [RFC7519]:
keys

REQUIRED. List of JWKs.
iss

REQUIRED. The "iss" (issuer) claim identifies the principal that issued the JWT.
sub

REQUIRED. This claim identifies the owner of the keys. It SHOULD be the same as the issuer.
iat

OPTIONAL. This claim identifies the time at which the JWT was issued.
exp

OPTIONAL. This claim identifies the time at which the JWT is no longer valid.

There are more claims defined in

[RFC7519]; of these, aud SHOULD NOT be used, since the issuer cannot know who the audience is. nbf and jti are deemed to not be very useful in this context and are therefore to be omitted.

The following is a non-normative example of a signed JWKS before serialization and adding a signature.

{
  "keys": [
    {
      "kty": "RSA",
      "kid": "SUdtUndEWVY2cUFDeDV5NVlBWDhvOXJodVl2am1mNGNtR0pmd",
      "n": "y_Zc8rByfeRIC9fFZrDZ2MGH2ZnxLrc0ZNNwkNet5rwCPYeRF3Sv
            5nihZA9NHkDTEX97dN8hG6ACfeSo6JB2P7heJtmzM8oOBZbmQ90n
            EA_JCHszkejHaOtDDfxPH6bQLrMlItF4JSUKua301uLB7C8nzTxm
            tF3eAhGCKn8LotEseccxsmzApKRNWhfKDLpKPe9i9PZQhhJaurwD
            kMwbWTAeZbqCScU1o09piuK1JDf2PaDFevioHncZcQO74Obe4nN3
            oNPNAxrMClkZ9s9GMEd5vMqOD4huXlRpHwm9V3oJ3LRutOTxqQLV
            yPucu7eHA7her4FOFAiUk-5SieXL9Q",
      "e": "AQAB"
    },
    {
      "kty": "EC",
      "kid": "MFYycG1raTI4SkZvVDBIMF9CNGw3VEZYUmxQLVN2T21nSWlkd3",
      "crv": "P-256",
      "x": "qAOdPQROkHfZY1daGofOmSNQWpYK8c9G2m2Rbkpbd4c",
      "y": "G_7fF-T8n2vONKM15Mzj4KR_shvHBxKGjMosF6FdoPY"
    }
  ],
  "iss": "https://example.org/op",
  "iat": 1618410883
}

The following is a non-normative example of an RP's Entity Statement:

{
  "iss": "https://openid.sunet.se",
  "sub": "https://openid.sunet.se",
  "iat": 1516239022,
  "exp": 1516298022,
  "metadata": {
    "openid_relying_party": {
      "application_type": "web",
      "redirect_uris": [
        "https://openid.sunet.se/rp/callback"
      ],
      "organization_name": "SUNET",
      "logo_uri": "https://www.sunet.se/sunet/images/32x32.png",
      "grant_types": [
        "authorization_code",
        "implicit"
      ],
      "signed_jwks_uri": "https://openid.sunet.se/rp/jwks.jose"
    }
  },
  "jwks": {
    "keys": [
      {
        "alg": "RS256",
        "e": "AQAB",
        "key_ops": [
          "verify"
        ],
        "kid": "key1",
        "kty": "RSA",
        "n": "pnXBOusEANuug6ewezb9J_...",
        "use": "sig"
      }
    ]
  },
  "authority_hints": [
    "https://edugain.org/federation"
  ]
}

Note: An OpenID Connect RP MUST only use the keys published in a suitable element, such as jwks or jwks_uri or signed_jwks_uri, underneath the metadata/openid_relying_party element of the respective Entity Statement for the OpenID Connect protocol. The example above uses a signed_jwks_uri for that purpose.

4.2. OP Metadata

The metadata type identifier is openid_provider.

All parameters defined in Section 3 of OpenID Connect Discovery 1.0 are applicable.

In addition, the following parameters are defined by this specification:

client_registration_types_supported

REQUIRED. Array specifying the federation types supported. Federation type values defined by this specification are automatic and explicit.
organization_name

OPTIONAL. A human-readable name representing the organization owning the OP. It is intended to be used in the user interface, being recognized by the end users that would be using the OP to authenticate. If the owner is a physical person this MAY be, for example, the name of a person.
federation_registration_endpoint

OPTIONAL. URL of the OP's federation-specific Dynamic Client Registration Endpoint. If the OP supports explicit client registration as described in Section 10.2, then this claim is REQUIRED.
request_authentication_methods_supported

OPTIONAL. In OpenID Connect Core, no client authentication is performed at the authentication endpoint. Instead, you can say that the request itself is authenticated. What it amounts to is that the OP maps information in the request (like the redirect_uri) to information it has gained on the client, through static or dynamic registration. If the map is successful, then the request is permitted to be processed. If the RP uses automatic registration as described in this specification the OP has no prior knowledge of the RP. Therefore the OP must start by gathering information about the RP using the process outlined in Section 6. Once it has the RP's metadata, the OP can then verify the request in the same way as if it had known the RP's metadata beforehand. To make the request verification more secure we demand the use of a client authentication or verification method that proves that the RP is in possession of a key that appears in the RP's metadata.
Client authentication methods are for instance:
private_key_jwt

private_key_jwt. This authentication process is described in Section 9 of OpenID Connect Core 1.0. Note that if private_key_jwt is used, the audience of the signed JWT MUST be either the URL of the Authorization Server's Authorization Endpoint or the Authorization Server's Entity Identifier.
tls_client_auth

Section 2.1 of [RFC8705].
self_signed_tls_client_auth

Section 2.2 of [RFC8705].


A client verification method, on the other hand, is something like:
request_object

This uses a Request Object as described in OpenID Connect Core 1.0. There is more about this in Section 10.1. Here the verification is based on the fact that the request object is signed with a key the RP is in control of.


The claim value of this parameter is a JSON object with members representing authentication request methods and as values lists of client authentication/verification methods that can be used together with the authentication request method.
Examples of authentication request methods are


If AR is used, then a client verification method like request_object can be used. If PAR is used then client authentication methods like private_key_jwt, tls_client_auth and self_signed_tls_client_auth can be used.
request_authentication_signing_alg_values_supported

OPTIONAL. JSON array containing a list of the JWS signing algorithms (alg values) supported for the signature on the JWT [RFC7519] used to authenticate the request using the private_key_jwt and request_object authentication methods. This entry MUST be present if either of these authentication methods are specified in the request_authentication_methods_supported entry. No default algorithms are implied if this entry is omitted. Servers SHOULD support RS256. The value none MUST NOT be used.
signed_jwks_uri

OPTIONAL. A URI pointing to a signed JWT having the Entity's JWK Set as its payload. The JWT is signed with a key that was included in the JWK Set that the Entity published in its self-signed Entity Statement.
jwks

OPTIONAL. JSON Web Key Set document, passed by value, as defined in [RFC7517]. If an OP can use signed_jwks_uri, it MUST NOT use jwks or jwks_uri. This parameter is intended to be used by participants that, for some reason, are unable to use the signed_jwks_uri parameter. One significant downside of jwks is that it does not enable key rotation (which signed_jwks_uri and jwks_uri do).

The following is a non-normative example of an OP's Entity Statement:

{
   "iss":"https://op.umu.se",
   "sub":"https://op.umu.se",
   "exp":1568397247,
   "iat":1568310847,
   "metadata":{
      "openid_provider":{
         "issuer":"https://op.umu.se/openid",
         "signed_jwks_uri":"https://op.umu.se/openid/signed_jwks.jose",
         "authorization_endpoint":"https://op.umu.se/openid/authorization",
         "client_registration_types_supported":[
            "automatic",
            "explicit"
         ],
         "grant_types_supported":[
            "authorization_code",
            "implicit",
            "urn:ietf:params:oauth:grant-type:jwt-bearer"
         ],
         "id_token_signing_alg_values_supported":[
            "ES256",
            "RS256"
         ],
         "logo_uri":"https://www.umu.se/img/umu-logo-left-neg-SE.svg",
         "op_policy_uri":"https://www.umu.se/en/legal-information/",
         "response_types_supported":[
            "code",
            "code id_token",
            "token"
         ],
         "subject_types_supported":[
            "pairwise",
            "public"
         ],
         "token_endpoint":"https://op.umu.se/openid/token",
         "federation_registration_endpoint":"https://op.umu.se/openid/fedreg",
         "token_endpoint_auth_methods_supported":[
            "client_secret_post",
            "client_secret_basic",
            "client_secret_jwt",
            "private_key_jwt"
         ],
         "pushed_authorization_request_endpoint":"https://op.umu.se/openid/par",
         "request_authentication_methods_supported":{
            "ar":[
               "request_object"
            ],
            "par":[
               "private_key_jwt",
               "self_signed_tls_client_auth"
            ]
         }
      }
   },
   "authority_hints":[
      "https://umu.se"
   ],
   "jwks":{
      "keys":[
         {
            "e":"AQAB",
            "kid":"dEEtRjlzY3djcENuT01wOGxrZlkxb3RIQVJlMTY0...",
            "kty":"RSA",
            "n":"x97YKqc9Cs-DNtFrQ7_vhXoH9bwkDWW6En2jJ044yH..."
         }
      ]
   },
}

Note: An OpenID Connect OP MUST only use the keys published in a suitable element, such as jwks or jwks_uri or signed_jwks_uri, underneath the metadata/openid_provider element of the respective Entity Statement for the OpenID Connect protocol. The example above uses a signed_jwks_uri element for that purpose.

4.3. OAuth Authorization Server

The metadata type identifier is oauth_authorization_server.

All parameters defined in Section 2 of RFC 8414 are applicable.

4.4. OAuth Client

The metadata type identifier is oauth_client.

All parameters defined in Section 2 of RFC 7591 are applicable.

4.5. OAuth Protected Resource

The metadata type identifier is oauth_resource. There is no standard that specifies what parameters can occur in the metadata for this kind of Entity. So, for the time being, this can be regarded as a placeholder.

4.6. Federation Entity

The metadata type identifier is federation_entity.

All entities participating in a federation are of this type.

The following properties are allowed:

federation_fetch_endpoint

OPTIONAL. The fetch endpoint described in Section 7.1. Intermediate entities and Trust Anchors MUST publish a federation_fetch_endpoint. Leaf entities MUST NOT.
federation_list_endpoint

OPTIONAL. The list endpoint described in Section 7.3. Intermediate entities and Trust Anchors MUST publish a federation_list_endpoint. Leaf entities MUST NOT.
federation_resolve_endpoint

OPTIONAL. The resolve endpoint described in Section 7.2. Any federation Entity MAY publish a federation_resolve_endpoint.
federation_status_endpoint

OPTIONAL. The Trust Mark status endpoint described in Section 7.4. Trust mark issuers SHOULD publish a federation_status_endpoint.
organization_name

OPTIONAL. A human-readable name representing the organization owning the federation Entity. If the owner is a physical person this MAY be, for example, the name of a person.
contacts

OPTIONAL. JSON array with one or more strings representing contact persons at the Entity. These MAY contain names, e-mail addresses, descriptions, phone numbers, etc.
policy_uri

OPTIONAL. URL to documentation of conditions and policies relevant to this Entity.
homepage_uri

OPTIONAL. URL to a generic home page representing this Entity.

Example

"federation_entity": {
  "federation_fetch_endpoint":
    "https://example.com/federation_fetch",
  "federation_list_endpoint":
    "https://example.com/federation_list",
  "name": "The example cooperation",
  "homepage_uri": "https://www.example.com"
}

4.7. Trust Mark Issuer

The metadata type identifier is trust_mark_issuer.

All entities participating in a federation may be of this type.

The following properties are allowed:

status_endpoint

OPTIONAL. The endpoint for the status operation is described in Section 7.4. Issuers of Trust Marks MAY publish a status_endpoint.

Example

"trust_mark_issuer": {
  "status_endpoint": "https://trust_marks_are_us.example.com/status"
}

Communication with the status endpoint is described in Section 7.4.

5. Federation Policy

5.1. Metadata Policy

An Entity can publish metadata policies pertaining to entities of a specific type. Entity type identifiers specified in this document can be found in Section 4.

Each such metadata policy has the following structure:

It SHOULD be noted that claim names without language tags are different from the same claim but with language tags.

An example of a policy entry:

"id_token_signed_response_alg": {
  "default": "ES256",
  "one_of" : ["ES256", "ES384", "ES512"]
}

Which fits into a metadata policy like this:

"metadata_policy" : {
  "openid_relying_party": {
    "id_token_signed_response_alg": {
      "default": "ES256",
      "one_of" : ["ES256", "ES384", "ES512"]
    }
  }
}

5.1.1. Operators

Value modifiers are:

value

Disregarding what value the parameter had, if any, the parameter's value will be set to the operator's value.
add

Adds the value or values specified to the metadata parameter. If any of the specified values are already present as values of the parameter, they will not be added. If the parameter has no value, then the parameter is initialized with the specified value(s).
default

If no value is assigned to this parameter, then the parameter's value will be set to the operator's value(s).

Value checks are:

one_of

The value of the parameter MUST be one of the ones listed in this directive.
subset_of

The resulting value of the parameter will be the intersection of the values in the directive and the values of the parameter.
superset_of

The values of the parameter MUST contain the ones in the directive. We define superset in a mathematical way, that is, equality is included.
essential

If true, then the parameter MUST have a value.

Note that when a parameter is defined to be a space-separated list of strings like for scope in RFC7591 subset_of, superset_of and default are still expressed as lists of strings.

5.1.2. Restrictions on Policy Entries

As stated, a policy entry can contain one or more operators. Not all operators are allowed to appear together in a policy entry.

subset_of/superset_of and one_of

subset_of and superset_of applies to parameters that can have more than one value (for instance, contacts) while one_of applies to parameters that can only have one value (for instance, id_token_signed_response_alg). This means that one_of cannot appear beside subset_of/ superset_of in a policy entry.
value

value overrides everything else. So having value together with any other operator (except for essential) does not make sense.

Other restrictions are:

5.1.3. Combining Policies

If there is more than one metadata policy in a Trust Chain, then the policies MUST be combined before they are applied to the metadata statement.

Using the notation we have defined in Section 3.2, policies are combined starting with ES[i] and then adding the policies from ES[j] j=i-1,..,1 before applying the combined policy to the Entity's metadata.

After each combination, the policy for each parameter MUST adhere to the rules defined in Section 5.1.2.

5.1.3.1. Merging Operators

subset_of

The result of merging the values of two subset_of operators is the intersection of the operator values.
one_of

The result of merging the values of two one_of operators is the intersection of the operator values.
superset_of

The result of merging the values of two superset_of operators is the union of the operator values.
add

The result of merging the values of two add operators is the union of the values.
value

Merging two value operators is NOT allowed unless the two operator values are equal.
default

Merging two default operators is NOT allowed unless the two operator values are equal.
essential

If a superior has specified essential=true, then a subordinate cannot change that. If a superior has specified essential=false, then a subordinate is allowed to change that to essential=true. If a superior has not specified essential, then a subordinate can set essential to true or false.

5.1.4. Applying Policies

Once combining the Metadata policies has been accomplished, the next step is to apply the combined policy to the metadata.

Doing that, one follows these steps for each parameter in the policy.

  1. If there is a value operator in the policy, apply that and you are done.
  2. Add whatever value is specified in an add operator.
  3. If the parameter still has no value, apply the default if there is one.
  4. Do the essential check. If essential is missing as an operator, essential is to be treated as if set to false. If essential is defined to be true, then the claim MUST have a value by now. Otherwise applying the operator MUST fail.
  5. Do the other checks. Verify that the value is one_of or that the values are subset_of/superset_of. If the parameter values do not fall within the allowed boundaries, applying the operator MUST fail.

5.1.5. Policy Combination Example

A federation's policy for OAuth2 clients:

{
  "scope": {
    "subset_of": [
      "openid",
      "eduperson",
      "phone"
    ],
    "superset_of": [
      "openid"
    ],
    "default": [
      "openid",
      "eduperson"
    ]
  },
  "token_endpoint_auth_method": {
    "one_of": [
      "client_secret_post",
      "client_secret_basic"
    ]
  },
  "contacts": {
    "add": "helpdesk@federation.example.org"
  }
}

An organization's policy for OAuth2 clients:

{
  "scope": {
    "subset_of": [
      "openid",
      "eduperson",
      "address"
    ],
    "default": [
      "openid",
      "eduperson"
    ]
  },
  "token_endpoint_auth_method": {
    "one_of": [
      "client_secret_post",
      "client_secret_basic"
    ],
    "default": "client_secret_basic"
  },
  "contacts": {
    "add": "helpdesk@org.example.org"
  }
}

The combined metadata policy then becomes:

{
  "scope": {
    "subset_of": [
      "openid",
      "eduperson"
    ],
    "superset_of": [
      "openid"
    ],
    "default": [
      "openid",
      "eduperson"
    ]
  },
  "token_endpoint_auth_method": {
    "one_of": [
      "client_secret_post",
      "client_secret_basic"
    ],
    "default": "client_secret_basic"
  },
  "contacts": {
    "add": [
      "helpdesk@federation.example.org",
      "helpdesk@org.example.org"
    ]
  }
}

5.1.6. Enforcing Policy

If applying policies to a metadata statement results in incorrect metadata, then such a metadata statement MUST be regarded as broken and MUST NOT be used.

5.1.7. Extending the Policy Language

There might be parties that want to extend the policy language defined here. If that happens then the rule is that if software compliant with this specification encounters a keyword it does not understand, it MUST ignore it unless it is listed in a policy_language_crit list, as is done for JWS header parameters with the crit parameter. If the policy language extension keyword is listed in the policy_language_crit list and not understood, then the metadata MUST be rejected.

5.1.8. Policy Example

The following is a non-normative example of a set of policies being applied to an RP's metadata.

The RP's metadata:

{
  "contacts": [
    "rp_admins@cs.example.com"
  ],
  "redirect_uris": [
    "https://cs.example.com/rp1"
  ],
  "response_types": [
    "code"
  ]
}

The federation's policy for RPs:

{
  "id_token_signed_response_alg": {
    "one_of": [
      "ES256",
      "ES384"
    ],
    "default": "ES256",
  },
  "response_types": {
    "subset_of": [
      "code",
      "code id_token"
    ]
  }
}

The organization's policy for RPs:

{
  "contacts": {
    "add": "helpdesk@example.com"
  },
  "logo_uri": {
    "one_of": [
      "https://example.com/logo_small.svg",
      "https://example.com/logo_big.svg"
    ],
    "default": "https://example.com/logo_small.svg"
  },
  "policy_uri": {
    "value": "https://example.com/policy.html"
  },
  "tos_uri": {
    "value": "https://example.com/tos.html"
  }
}

The metadata for the Entity in question, after applying the policies above, would then become:

{
  "contacts": [
    "rp_admins@cs.example.com",
    "helpdesk@example.com"
  ],
  "logo_uri": "https://example.com/logo_small.svg",
  "policy_uri": "https://example.com/policy.html",
  "tos_uri": "https://example.com/tos.html",
  "id_token_signed_response_alg": "ES256",
  "response_types": [
    "code"
  ],
  "redirect_uris": [
    "https://cs.example.com/rp1"
  ]
}

5.2. Applying Constraints

A constraint specification can contain the following claims:

max_path_length

OPTIONAL. Integer. The maximum number of Entity Statements between this Entity Statement and the last Entity Statement in the Trust Chain.
naming_constraints

OPTIONAL. JSON object. Restriction on the Entity Identifiers of the entities below this Entity. The behavior of this claim mimics what is defined in Section 4.2.1.10 in [RFC5280]. Restrictions are defined in terms of permitted or excluded name subtrees.

The following is a non-normative example of such a specification:

{
  "naming_constraints": {
    "permitted": [
      "https://.example.com"
    ],
    "excluded": [
      "https://east.example.com"
    ]
  },
  "max_path_length": 2
}

If a subordinate Entity Statement contains a constraint specification that is more restrictive than the one in effect, then the more restrictive constraint is in effect from here on.

If a subordinate Entity Statement contains a constraint specification that is less restrictive than the one in effect, then it MUST be ignored.

5.2.1. Max Path Length

The max_path_length constraint specifies the maximum number of Entity Statements a Trust Chain can have between the Entity Statement that contains the constraint specification and the leaf's Entity Statement.

A max_path_length constraint of zero indicates that no Entity Statement MAY appear between this Entity Statement and the leaf Entity Statement. Where it appears, the max_path_length constraint MUST have a value that is greater than or equal to zero. Where max_path_length does not appear, no limit is imposed.

Assuming that we have a Trust Chain with four Entity Statements:

  1. Leaf Entity (LE)
  2. Intermediate 1 (I1)
  3. Intermediate 2 (I2)
  4. Trust Anchor (TA)

Then the Trust Chain fulfills the constraints if:

The Trust Chain does not fulfil the constraints if:

5.2.2. Naming Constraints

The naming_constraints member specifies a namespace within which all subject Entity Identifiers in subordinate Entity Statements in a Trust Chain MUST be located.

Restrictions are defined in terms of permitted or excluded name subtrees. Any name matching a restriction in the excluded claim is invalid regardless of information appearing in the permitted claim.

The constraint MUST be specified as a fully qualified domain name and MAY specify a host or a domain. Examples would be "host.example.com" and ".example.com". When the constraint begins with a period, it MAY be expanded with one or more labels. That is, the constraint ".example.com" is satisfied by both host.example.com and my.host.example.com. However, the constraint ".example.com" is not satisfied by "example.com". When the constraint does not begin with a period, it specifies a host.

5.3. Trust Marks

In this specification we use the US NSTIC definition: "A trustmark is used to indicate that a product or service provider has met the requirements of the Identity Ecosystem, as determined by an accreditation authority".

Technically, Trust Marks as used by this specification are signed JWTs that represent a statement of conformance to a well-scoped set of trust and/or interoperability requirements.

The Trust Marks are signed by a federation accredited authority. The validation of such a signed statement is performed in the same way that a self-signed Entity Statement is validated.

Note that a federation MAY allow an Entity to self-sign some Trust Marks.

5.3.1. Trust Mark Claims

These are the properties that can occur in a Trust Mark:

iss

REQUIRED. String. The issuer of the Trust Mark.
sub

REQUIRED. String. The Entity this Trust Mark applies to.
id

REQUIRED. String. An identifier of the Trust Mark.
iat

REQUIRED. Number. When this Trust Mark was issued. Expressed as Seconds Since the Epoch, per [RFC7519].
logo_uri

OPTIONAL. String. A URL that points to a mark/logo that the subject is allowed to display to a user of the Entity.
exp

OPTIONAL. Number. When this Trust Mark is not valid anymore. Expressed as Seconds Since the Epoch, per [RFC7519]. If not present, it means that the Trust Mark is valid forever.
ref

OPTIONAL. String. URL that points to information connected to the issuance of this Trust Mark.

Other claims MAY be used in conjunction with the claims outlined above. The claim naming recommendations outlined in Section 5.1.2 of OpenID Connect Core 1.0 apply.

5.3.2. Validating a Trust Mark

An Entity SHOULD NOT try to validate a Trust Mark until it knows which Trust Anchors it wants to use.

Validating a Trust Mark issuer follows the procedure set out in Section 8. Validating the Trust Mark itself is described in Section 7.4

Note that the Entity representing the accreditation authority SHOULD be well known and trusted for a given Trust Mark identifier. A Trust Anchor MAY publish a list of accreditation authorities of Trust Marks that SHOULD be trusted by other federation entities. A Trust Anchor uses the trust_marks_issuers claim in its Entity Statement to publish this information.

For other externally issued Trust Marks, it is an out-of-band process to define and announce accreditation authorities to other entities and it is left to the discretion of the receiving party to assign an appropriate level of trust to such Trust Marks.

5.3.3. Trust Mark Examples

A non-normative example of a Trust Mark claim inside an Entity Statement is:

{
  "iss": "https://rp.example.it/spid/",
  "sub": "https://rp.example.it/spid/",
  "iat": 1516239022,
  "exp": 1516298022,
  "trust_marks": [
    {
     "id": "https://www.spid.gov.it/certification/rp/",
     "trust_mark":
       "eyJhbGciOiJSUzI1NiIsImtpZCI6Ing0VnduN0RzRE1ib0dBOHRNV2pleVVjT0"
       "RTTVBua1luSVdJN3R6eVVnRmsifQ.eyJpc3MiOiJodHRwczovL3d3dy5hZ2lkL"
       "mdvdi5pdCIsInN1YiI6Imh0dHBzOi8vcnAuZXhhbXBsZS5pdC9zcGlkIiwiaWF"
       "0IjoxNTc5NjIxMTYwLCJpZCI6Imh0dHBzOi8vd3d3LnNwaWQuZ292Lml0L2Nlc"
       "nRpZmljYXRpb24vcnAiLCJsb2dvX3VyaSI6Imh0dHBzOi8vd3d3LmFnaWQuZ29"
       "2Lml0L3RoZW1lcy9jdXN0b20vYWdpZC9sb2dvLnN2ZyIsInJlZiI6Imh0dHBzO"
       "i8vZG9jcy5pdGFsaWEuaXQvaXRhbGlhL3NwaWQvc3BpZC1yZWdvbGUtdGVjbml"
       "jaGUtb2lkYy9pdC9zdGFiaWxlL2luZGV4Lmh0bWwifQ.vkYH4CZou-BhFRlZC3"
       "eORbPbXUf9kIcqss5N5cI6GK7JsUzvxwYk5TNm8clSpV0YZtZN4RQwEf85Q_fi"
       "FLPCPYimR-FtElWO-4Uxg44WQA1N7RbSmMNRzLfObBunMpuXcA8Trwf2d7FZ7n"
       "Zi6mXKR8B1_YDQbLiW9q1paT-RmlrwqYyHzG9yewpIj_EQEX6WOjpWj4-Jk6sT"
       "ZdCiu8r4d0Y7bpKt4GiGQTkVGdLyrLyMeX7FFcTI_yztKXbi8mV1-b1l7iOaJb"
       "FyGfpHeuFCyI3y1B00LTI5GCzuQU_hyVntTnB7Qw7csLnA6B-wwaxsQa2l9-Q8"
       "eAGXhfAlzqSqRQ"
    }
  ],
  "metadata": {
    "openid_relying_party": {
      "application_type": "web",
      "client_registration_types": ["automatic"],
      "client_name": "https://rp.example.it/spid/",
      "contacts": [
        "ops@rp.example.it"
      ],

       ... follows other claims ...

   ... follows other claims ...

An example of a decoded self-signed certification mark:

{
  "iss": "https://example.com/op",
  "sub": "https://example.com/op",
  "iat": 1579621160,
  "id": "https://openid.net/certification/op",
  "logo_uri": "http://openid.net/wordpress-content/uploads/2016/
    05/oid-l-certification-mark-l-cmyk-150dpi-90mm.svg",
  "ref": "https://openid.net/wordpress-content/uploads/2015/
    09/RolandHedberg-pyoidc-0.7.7-Basic-26-Sept-2015.zip"
}

An example of a third-party accreditation authority:

{
  "iss": "https://swamid.se",
  "sub": "https://umu.se/op",
  "iat": 1577833200,
  "exp": 1609369200,
  "id":
    "https://refeds.org/wp-content/uploads/2016/01/Sirtfi-1.0.pdf"
}

6. Obtaining Federation Entity Configuration Information

The Entity Configuration of every federation Entity SHOULD be exposed at a well-known endpoint. The configuration endpoint is found using the Well-Known URIs specification, with the suffix openid-federation. The scheme, host, and port are taken directly from the Entity Identifier combined with the following path: /.well-known/openid-federation.

If the Entity Identifier contains a path, it is concatenated after /.well-known/openid-federation in the same manner that path components are concatenated to the well-known identifier in the OAuth 2.0 Authorization Server Metadata [RFC8414] specification. Of course, in real multi-tenant deployments, in which the Entity identifier might be of the form https://multi-tenant-service.example.com/my-tenant-identifier the tenant is very likely to not have control over the path https://multi-tenant-service.example.com/.well-known/openid-federation/my-tenant-identifier whereas it is very likely to have control over the path https://multi-tenant-service.example.com/my-tenant-identifier/.well-known/openid-federation. Therefore, if using the configuration endpoint at the URL with the tenant path after the well-known part fails, it is RECOMMENDED that callers retry at the URL with the tenant path before the well-known part (even though this violates [RFC8615]).

Federation Entities SHOULD make an Entity Configuration Document available at the configuration endpoint. There is only one exception to this rule and that is for an RP that only does explicit registration. Since it posts the self-signed Entity Statement to the OP during client registration, the OP has everything it needs from the RP.

6.1. Federation Entity Configuration Request

A federation Entity Configuration Document MUST be queried using an HTTP GET request at the previously specified path. The requesting party would make the following request to the Entity https://openid.sunet.se to obtain its configuration information:


  GET /.well-known/openid-federation HTTP/1.1
  Host: openid.sunet.se

6.2. Federation Entity Configuration Response

The response is a self-signed Entity Statement, as described in Section 3.1. If the Entity is an intermediate Entity or a Trust Anchor, the response MUST contain metadata for a federation Entity.

A positive response is a signed Entity Statement, where the content type MUST be set to application/entity-statement+jwt. In case of an error, the response will be a JSON object, the content type MUST be set to application/json, and the error response uses the applicable HTTP status code value.

The following is a non-normative example response from an intermediate Entity, before serialization and adding a signature:

200 OK
Last-Modified: Thu, 29 Aug 2019 08:54:26 GMT
Content-Type: application/entity-statement+jwt

{
  "iss": "https://openid.sunet.se",
  "sub": "https://openid.sunet.se",
  "iat": 1516239022,
  "exp": 1516298022,
  "metadata": {
    "openid_provider": {
      "issuer": "https://openid.sunet.se",
      "signed_jwks_uri": "https://openid.sunet.se/jwks.jose",
      "authorization_endpoint":
        "https://openid.sunet.se/authorization",
      "client_registration_types_supported": [
        "automatic",
        "explicit"
      ],
      "grant_types_supported": [
        "authorization_code"
      ],
      "id_token_signing_alg_values_supported": [
        "ES256", "RS256"
      ],
      "logo_uri":
        "https://www.umu.se/img/umu-logo-left-neg-SE.svg",
      "op_policy_uri":
        "https://www.umu.se/en/website/legal-information/",
      "response_types_supported": [
        "code"
      ],
      "subject_types_supported": [
        "pairwise",
        "public"
      ],
      "token_endpoint": "https://openid.sunet.se/token",
      "federation_registration_endpoint":
        "https://op.umu.se/openid/fedreg",
      "token_endpoint_auth_methods_supported": [
        "private_key_jwt"
      ]

    }
  },
  "jwks": {
    "keys": [
      {
        "alg": "RS256",
        "e": "AQAB",
        "key_ops": [
          "verify"
        ],
        "kid": "key1",
        "kty": "RSA",
        "n": "pnXBOusEANuug6ewezb9J_...",
        "use": "sig"
      }
    ]
  },
  "authority_hints": [
    "https://edugain.org/federation"
  ]
}

7. Federation Endpoints

The federation endpoints of an Entity can be found in the configuration response as described in Section 6 or by other means.

7.1. Fetching Entity Statements

All entities that are expected to publish Entity Statements about other entities MUST expose a Fetch endpoint.

Fetching Entity Statements is performed to collect Entity Statements one by one to gather Trust Chains.

To fetch an Entity Statement, an Entity needs to know the identifier of the Entity to ask (the issuer), the fetch endpoint of that Entity and the identifier of the Entity that you want the statement to be about (the subject).

7.1.1. Fetch Entity Statements Request

The request MUST be an HTTP request using the GET method and the https scheme to a resolved federation endpoint with the following query string parameters:

iss

OPTIONAL. The Entity Identifier of the issuer from which you want an Entity Statement issued. Because of the normalization of the URL, multiple issuers MAY resolve to a shared fetch endpoint. This parameter makes it explicit exactly which issuer you want Entity Statements from. Without this parameter, the issuer matches to the Entity at which the request was made.
sub

OPTIONAL. The Entity Identifier of the subject for which you would like an Entity Statement issued. If this parameter is left out, it is considered to be the same as the issuer and would indicate a request for a self-signed statement.
aud

OPTIONAL. The Entity Identifier of the requester. If the aud parameter is present in the request, the aud claim SHOULD be present in the Entity Statement response and take exactly that value.

The following is a non-normative example of an API request for an Entity Statement:

GET /federation_fetch_endpoint?
iss=https%3A%2F%2Fedugain.org%2Ffederation&
sub=https%3A%2F%2Fopenid%2Esunet%2Ese HTTP/1.1
Host: edugain.org

7.1.2. Fetch Entity Statements Response

A positive response is a signed Entity Statement where the content type MUST be set to application/entity-statement+jwt. If it is a negative response, it will be a JSON object and the content type MUST be set to application/json. See more about error responses in Section 7.5.

The following is a non-normative example of a response, before serialization and adding a signature:

200 OK
Last-Modified: Mon, 17 Dec 2018 11:15:56 GMT
Content-Type: application/entity-statement+jwt

{
  "iss": "https://edugain.org/federation",
  "sub": "https://openid.sunet.se"
  "exp": 1568397247,
  "iat": 1568310847,
  "jwks": {
    "keys": [
      {
        "e": "AQAB",
        "kid": "dEEtRjlzY3djcENuT01wOGxrZlkxb3RIQVJlMTY0...",
        "kty": "RSA",
        "n": "x97YKqc9Cs-DNtFrQ7_vhXoH9bwkDWW6En2jJ044yH..."
      }
    ]
  },
  "metadata":{
    "organization_name":"SUNET"
  }
  "metadata_policy": {
    "openid_provider": {
      "subject_types_supported": {
        "value": [
          "pairwise"
        ]
      },
      "token_endpoint_auth_methods_supported": {
        "default": [
          "private_key_jwt"
        ],
        "subset_of": [
          "private_key_jwt",
          "client_secret_jwt"
        ],
        "superset_of": [
          "private_key_jwt"
        ]
      }
    }
  }
}

7.2. Resolve Entity Statement

An Entity MAY use the resolve endpoint to fetch resolved metadata and Trust Marks for an Entity as seen/trusted by the resolver. The resolver is supposed to fetch the subject's self-signed Entity Statement, collect a Trust Chain that starts with the subject's Entity Statement and ends with the specified Trust Anchor, verify the Trust Chain and then apply all the policies present in the Trust Chain to the Entity Statements metadata. The resolver is also expected to verify that the present Trust Marks are active. If it finds Trust Marks that are not active, then those should be left out of the response set.

7.2.1. Resolve Request

The request MUST be an HTTP request using the GET method and the https scheme to a resolve endpoint with the following query string parameters:

sub

REQUIRED. The Entity Identifier of the Entity whose resolved data is requested.
anchor

REQUIRED. The Trust Anchor that the remote peer MUST use when resolving the metadata. The value is an Entity identifier.
type

OPTIONAL. A specific metadata type to resolve. In this document, we use the metadata types listed in Section 4. If no value is given, then all metadata types are expected to be returned.
iss

OPTIONAL. The Entity Identifier of the Entity who is requesting the information. If this parameter is present in the request, then it MUST be present in the response in the aud/jose parameter of the signed JWT.

The following is a non-normative example of a resolve request:

GET /resolve?
sub=https%3A%2F%2Fop.example.it%2Fspid&
type=openid_provider&
anchor=https%3A%2F%2Fswamid.se HTTP/1.1
Host: openid.sunet.se

7.2.2. Resolve Response

The response is a signed JWT containing resolved metadata and verified Trust Marks. The response MAY also contain the sequence of the Entity Statements that compose the Trust Chain. The keys used by the resolver MUST be the same keys used to construct a self-signed Entity Statement.

The following is a non-normative example of a response, before serialization and adding a signature:

{
  "iss": "https://resolver.spid.gov.it/",
  "sub": "https://op.example.it/spid/",
  "iat": 1516239022,
  "exp": 1516298022,
  "metadata": {
    "openid_provider": {
      "contacts": ["legal@example.it", "technical@example.it"],
      "logo_uri":
        "https://op.example.it/static/img/op-logo.svg",
      "op_policy_uri":
        "https://op.example.it/en/about-the-website/legal-information/",
      "federation_registration_endpoint":"https://op.example.it/spid/fedreg/",
      "authorization_endpoint":
        "https://op.example.it/spid/authorization/",
      "token_endpoint": "https://op.example.it/spid/token/",
      "response_types_supported": [
        "code",
        "code id_token",
        "token"
      ],
      "grant_types_supported": [
        "authorization_code",
        "implicit",
        "urn:ietf:params:oauth:grant-type:jwt-bearer"
      ],
      "subject_types_supported": ["pairwise"],
      "id_token_signing_alg_values_supported": ["RS256"],
      "issuer": "https://op.example.it/spid/",
      "jwks": {
        "keys": [
          {
            "kty": "RSA",
            "use": "sig",
            "n": "1Ta-sE ...",
            "e": "AQAB",
            "kid": "FANFS3YnC9tjiCaivhWLVUJ3AxwGGz_98uRFaqMEEs"
          }
        ]
      }
    }
  },
  "trust_marks": [
    {"id": "https://www.spid.gov.it/certification/op/",
     "trust_mark":
       "eyJhbGciOiJSUzI1NiIsImtpZCI6ImRGRTFjMFF4UzBFdFFrWmxNRXR3ZWxOQl"
       "eyJhbGciOiJSUzI1NiIsImtpZCI6Ijh4c3VLV2lWZndTZ0hvZjFUZTRPVWRjeT"
       "RxN2RKcktmRlJsTzV4aEhJYTAifQ.eyJpc3MiOiJodHRwczovL3d3dy5hZ2lkL"
       "mdvdi5pdCIsInN1YiI6Imh0dHBzOi8vb3AuZXhhbXBsZS5pdC9zcGlkLyIsIml"
       "hdCI6MTU3OTYyMTE2MCwiaWQiOiJodHRwczovL3d3dy5zcGlkLmdvdi5pdC9jZ"
       "XJ0aWZpY2F0aW9uL29wLyIsImxvZ29fdXJpIjoiaHR0cHM6Ly93d3cuYWdpZC5"
       "nb3YuaXQvdGhlbWVzL2N1c3RvbS9hZ2lkL2xvZ28uc3ZnIiwicmVmIjoiaHR0c"
       "HM6Ly9kb2NzLml0YWxpYS5pdC9pdGFsaWEvc3BpZC9zcGlkLXJlZ29sZS10ZWN"
       "uaWNoZS1vaWRjL2l0L3N0YWJpbGUvaW5kZXguaHRtbCJ9"
    }
  ],
  "trust_chain" : [
    "eyJhbGciOiJSUzI1NiIsImtpZCI6Ims1NEhRdERpYnlHY3M5WldWTWZ2aUhm ...",
    "eyJhbGciOiJSUzI1NiIsImtpZCI6IkJYdmZybG5oQU11SFIwN2FqVW1BY0JS ...",
    "eyJhbGciOiJSUzI1NiIsImtpZCI6IkJYdmZybG5oQU11SFIwN2FqVW1BY0JS ..."
  ]
}

7.2.3. Considerations

The service provided at this endpoint goes contrary to the main parts of this specification. The basic assumption of this specification is that you should trust no one except the Trust Anchor and your own capabilities. If you use this service, you basically trust someone else to do the right thing.

Even so there are benefits from having a service like this.

7.3. Entity Listings

An Entity MAY query another Entity for a list of all the entities immediately subordinate to that Entity and about which that Entity is prepared to issue statements about. (In some cases, this MAY be a very large list.)

7.3.1. Entity Listings Request

The request MUST be an HTTP request using the GET method and the https scheme to a list endpoint.

The following is a non-normative example of an API request for a list of entities:

GET /list HTTP/1.1
Host: openid.sunet.se

7.3.2. Entity Listing Response

The response MUST contain a JSON list with the known Entity Identifiers.

The following is a non-normative example of a response:

200 OK
Last-Modified: Wed, 22 Jul 2018 19:15:56 GMT
Content-Type: application/json

[
  "https://ntnu.andreas.labs.uninett.no/",
  "https://blackboard.ntnu.no/openid/callback",
  "https://serviceprovider.andreas.labs.uninett.no/application17"
]

7.4. Trust Mark Status

This is to allow an Entity to check whether a Trust Mark is still active or not. The query MUST be sent to the Trust Mark issuer.

7.4.1. Status request

The request MUST be an HTTP request using the GET method and the https scheme to a status endpoint with the following query parameters:

sub

OPTIONAL. The ID of the Entity to which the Trust Mark was issued.
id

OPTIONAL. Identifier of the Trust Mark.
iat

OPTIONAL. When the Trust Mark was issued. If iat is not specified and the trust issuer have issued several Trust Marks with the id specified in the request to the Entity identified by sub; the last one is assumed.
trust_mark

OPTIONAL. The whole Trust Mark.

If trust_mark is used then sub and id are not needed. If trust_mark is not used, then sub and id are required.

The following is a non-normative example of a request using sub and id:

GET /federation_status_endpoint?
sub=https%3A%2F%2Fopenid.sunet.se%2FRP
&id=https%3A%2F%2Frefeds.org%2Fsirtfi
HTTP/1.1
Host: operations.swamid.se

7.4.2. Status Response

The HTTP response body MUST be a JSON object containing the claims below and the content type MUST be set to application/json.

active

REQUIRED. Boolean. Whether the Trust Mark is active or not.

The following is a non-normative example of a response:

200 OK
Last-Modified: Wed, 22 Jul 2018 19:15:56 GMT
Content-Type: application/json

{
  "active": true
}

7.5. Generic Error Response

If the request was malformed, or some error occurred during processing of the request, the following standardized error format SHOULD be used regardless of the operation specified.

The HTTP response code MUST be something in 400/500-range, giving an indication of the type of error. The response body MUST be a JSON object containing the claims below and the content type MUST be set to application/json.

operation

REQUIRED. The operation of the request.
error

REQUIRED. The error code.
error_description

REQUIRED. A human-readable short text describing the error.

The following is a non-normative example of an error response:

400 Bad request
Last-Modified: Wed, 22 Jul 2018 19:15:56 GMT
Content-Type: application/json

{
  "operation": "resolve",
  "error": "invalid_request",
  "error_description":
    "Required request parameter [sub] was missing."
}

8. Resolving Trust Chain and Metadata

An Entity (e.g., the consumer) that wants to establish trust with a remote peer MUST have the remote peer's Entity Identifier and a list of Entity Identifiers of Trust Anchors together with the public version of their signing keys. The consumer will first have to fetch sufficient Entity Statements to establish at least one chain of trust from the remote peer to one or more of the configured Trust Anchors. After that the Entity MUST validate the Trust Chains independently, and -- if there are multiple valid Trust Chains and if the application demands it -- choose one.

8.1. Fetching Entity Statements to Establish a Trust Chain

Depending on the circumstances, the consumer MAY either be handed the remote peer's Entity Configuration, or it may have to fetch it by itself. If it needs to fetch it, it will use the process described in Section 6 based on the Entity Identifier of the remote peer.

The next step is to iterate through the list of intermediates listed in authority_hints, ignoring the authority hints that end in an unknown Trust Anchor, requesting an Entity Configuration from each of the intermediates. If the received Entity Configuration contains an authority hint this process is repeated.

With the list of all intermediates and the Trust Anchor, the respective federation API (see Section 7) is used to fetch Entity Statements about the intermediates and the remote peer.

Note: The consumer SHOULD NOT attempt to fetch Entity Statements it already has fetched during this process (loop prevention).

A successful operation will return one or more lists of Entity Statements. Each of the lists terminating in a self-signed Entity Statement is issued by a Trust Anchor.

If there is no path from the remote peer to at least one of the trusted Trust Anchors, then the list will be empty and there is no way of establishing trust in the remote peer's information. How the consumer deals with this is out of scope for this specification.

8.2. Validating a Trust Chain

As described in Section 3.2, a Trust Chain consists of an ordered list of Entity Statements. So whichever way the consumer has acquired the set of Entity Statements, it MUST now verify that it is a proper Trust Chain using the rules laid out in that section.

To validate the chain, the following MUST be done:

Verifying the signature is a much more expensive operation than verifying the correctness of the statement and the timestamps. An implementer MAY therefore choose to not verify the signature until all the other checks have been done.

Consumers MAY cache Entity Statements or signature verification results for a given time until they expire, per Section 8.4.

Note that the second bullet point means that, at each step in the Trust Chain resolution, it MUST be verified that the signing JWK is also present in the jwks statement claim issued by the superior.

8.3. Choosing One of the Valid Trust Chains

If multiple valid Trust Chains are found, the consumer will need to decide on which one to use.

One simple rule would be to prefer a shorter chain over a longer one.

Consumers MAY follow other rules according to local policy.

8.4. Calculating the Expiration Time of a Trust Chain

Each Entity Statement in a Trust Chain is signed and MUST have an expiration time (exp) set. The expiration time of the whole Trust Chain is set to the minimum value of (exp) within the chain.

9. Updating Metadata, Key Rollover, and Revocation

This specification allows for a smooth process of updating metadata and public keys.

As described above in Section 8.4, each Trust Chain has an expiration time. A consumer of metadata using this specification MUST support refreshing a Trust Chain when it expires. How often a consumer SHOULD re-evaluate the Trust Chain depends on how quickly the consumer wants to find out that something has changed in the Trust Chain.

9.1. Protocol Key Rollover

If a leaf Entity publishes its public keys in the metadata part using jwks, setting an expiration time on the self-signed Entity Statement can be used to control how often the receiving Entity is fetching an updated version of the public key.

9.2. Key Rollover for a Trust Anchor

A Trust Anchor MUST publish a self-signed Entity Statement about itself. The Trust Anchor SHOULD set a reasonable expiration time on that Statement, such that the consumers will re-fetch the Entity Statement at reasonable intervals. If the Trust Anchor wants to roll over its signing keys it would have to:

  1. Add the new keys to the jwks representing the Trust Anchor's signing keys.
  2. Keep signing the Entity Statement using the old keys for a long enough time period to allow all subordinates to have gotten access to the new keys.
  3. Switch to signing with the new keys.
  4. After a reasonable time period remove the old keys. What is regarded as a reasonable time is dependent on the security profile and risk assessment of the Trust Anchor.

9.3. Redundant Retrieval of Trust Anchor Keys

It is RECOMMENDED that Federation Operators provide a means of retrieving the public keys for Trust Anchors that it administers that is independent of the Entity Statements for those Trust Anchors. This is intended to provide redundancy in the eventuality of the compromise of the Web PKI infrastructure underlying retrieval of public keys from Entity Statements.

The keys retreived via the independent mechanism specified by the Federation Operator SHOULD be be compared to those retreived via the Trust Anchor's Entity Statement. If they do not match, both SHOULD be retrieved again. If they still do not match, it is indicative of a security or configuration problem. The appropriate remediation steps in that eventuality SHOULD be specified by the Federation Operator.

9.4. Revocation

Since the consumers are expected to check the Trust Chain at regular, reasonably frequent times, this specification does not specify a standard revocation process. Specific federations MAY make a different choice and will then have to add such a process.

10. OpenID Connect Communication

This section describes how the trust framework in this specification is used to establish trust between an RP and an OP that have no explicit configuration or registration in advance.

There are two alternative approaches to establish trust between an RP and an OP, which we call automatic and explicit registration. Members of a federation or a community SHOULD agree upon which one to use. While implementations should support both methods, deployments MAY choose to disable the use of one of them.

Independent of whether the RP uses automatic or explicit registration, the way that the RP learns about the OP is the same. It will use the procedure that is described in Section 8.

10.1. Automatic Registration

Automatic registration allows an RP to send Authorization Requests to an OP without first registering with the OP. It basically works by the OP using the Client ID in the request to find the RP's metadata using the process outlined in Section 8 and then verifies that the RP is in control of a private key that is a companion to one of the public keys the RP published through its metadata.

For automatic registration to work a number of things MUST be valid:

10.1.1. Authentication Request

The Authentication Request is performed by passing a Request Object by value as described in Section 6.1 in OpenID Connect Core 1.0 or using pushed authorization as described in Pushed Authorization Requests.

10.1.1.1. Using a Request Object

In the case where a Request Object is used, the value of the request parameter is a JWT whose Claims are the request parameters specified in Section 3.1.2 in OpenID Connect Core 1.0. The JWT MUST be signed and MAY be encrypted. The following restrictions apply to the JWT:

aud

REQUIRED. The Audience (aud) MUST be the URL of the Authorization Server's Authorization Endpoint.
iss

REQUIRED. The claim iss MUST contain the client identifier.
sub

MUST NOT be present. This together with the value of aud SHOULD make reuse of the statement for private_key_jwt client authentication not feasible.
jti

REQUIRED. JWT ID. A unique identifier for the JWT, which can be used to prevent reuse of the token. These tokens MUST only be used once, unless conditions for reuse were negotiated between the parties; any such negotiation is beyond the scope of this specification.
exp

REQUIRED. Expiration time on or after which the JWT MUST NOT be accepted for processing.
iat

OPTIONAL. Time at which the JWT was issued.

The following is a non-normative example of the Claims in a Request Object before base64url encoding and signing:

{
  "aud": "https://op.example.org/authorization",
  "client_id": "https://rp.example.com",
  "exp": 1589699162,
  "iat": 1589699102,
  "iss": "https://rp.example.com",
  "jti": "4d3ec0f81f134ee9a97e0449be6d32be",
  "nonce": "4LX0mFMxdBjkGmtx7a8WIOnB",
  "redirect_uri": "https://rp.example.com/authz_cb",
  "response_type": "code",
  "scope": "openid profile email address phone",
  "state": "YmX8PM9I7WbNoMnnieKKBiptVW0sP2OZ",
  "sub": "https://rp.example.com"
}

The following is a non-normative example of an Authorization Request using the request parameter (with line wraps within values for display purposes only):

https://server.example.com/authorize?
    redirect_uri=https%3A%2F%2Frp.example.com%2Fauthz_cb
    &scope=openid+profile+email+address+phone
    &response_type=code
    &client_id=https%3A%2F%2Frp.example.com
    &request=eyJhbGciOiJSUzI1NiIsImtpZCI6ImRVTjJhMDF3Umtoa1
      NXcGxRVGh2Y1ZCSU5VSXdUVWRPVUZVMlRtVnJTbWhFUVhnelpYbHB
      UemRRTkEifQ.eyJzdWIiOiAiaHR0cHM6Ly9ycC5leGFtcGxlLmNvb
      SIsICJpc3MiOiAiaHR0cHM6Ly9ycC5leGFtcGxlLmNvbSIsICJpYX
      QiOiAxNTkzNjE1Nzk0LCAiZXhwIjogMTU5MzYxNTg1NCwgImF1ZCI
      6ICJodHRwczovL29wLmV4YW1wbGUub3JnL2F1dGhvcml6YXRpb24i
      LCAianRpIjogIjlhNDY2Njc3ZDZkOTQ5OWZiOTFjNDg4YTY1NzA0N
      TU2In0.mFq0V4KIb6eM-WV5vvQAvSSwoUyi-cy_ASMDgR1-amotjK
      6El0T1WV9-Hdrkgi_zBJtARs6VE380GmwpXXuMF1p6y-IoyIBJUSR
      w9LaeK9oi3d1stTT_J6VL8JwsNuetB6r9YLAQS-1p6mFKsv7TQSjk
      xNHfw0BTxfZftcDnooCqusC17xrz11qEY1CCtjDbbxYM1cYfzGFwS
      I0UZneQUZqa2ChOqWTguumG7XonB5NFZWieAtvyyPZaSI7AW5wCs2
      sH6kjMxOHEAIvxygZZwKpTiToccYtU7t0n2xKRr-oYDQaFjuRIemE
      xsuzVl6pbvCVYqyjxFscS9NgDB-hAAQ

10.1.1.1.1. Processing the Authentication Request

When the OP receives an incoming Authentication Request, the OP supports OpenID Connect Federation, the incoming Client ID is a valid URL, and the OP does not have the Client ID registered as a known client, then the OP SHOULD try to resolve and fetch trust chains starting with the RP's Entity Statement as described in Section 8.1.

The OP MUST then validate the possible Trust Chains, as described in Section 8.2, and resolve the RP metadata with type openid_relying_party.

The OP SHOULD furthermore consider the resolved metadata of the RP, and verify that it complies with the client metadata specification in OpenID Connect Dynamic Client Registration 1.0.

Once the OP has the RP's metadata, it can verify that the client was actually the one sending the Authorization Request by verifying the signature of the Request Object using the key material the client published through its metadata (underneath metadata/openid_relying_party).

10.1.1.2. Using Pushed Authorization

Pushed Authorization Requests provides an interoperable way to push the payload of a Request Object directly to the AS in exchange for a request_uri.

When it comes to request authentication, the applicable methods are four:

Note that if mTLS is used, TLS client authentication MUST be configured and, in case of self-signed certificates, the server must omit Trust Chain validation.

Using the example above, a request could look like this:

POST /par HTTP/1.1
Host: op.example.org
Content-Type: application/x-www-form-urlencoded

redirect_uri=https%3A%2F%2Frp.example.com%2Fauthz_cb
&scope=openid+profile+email+address+phone
&response_type=code
&nonce=4LX0mFMxdBjkGmtx7a8WIOnB
&state=YmX8PM9I7WbNoMnnieKKBiptVW0sP2OZ
&client_id=https%3A%2F%2Frp.example.com
&client_assertion_type=urn%3Aietf%3Aparams%3Aoauth%3A
  client-assertion-type%3Ajwt-bearer
&client_assertion=eyJhbGciOiJSUzI1NiIsImtpZCI6ImRVTjJ
  hMDF3Umtoa1NXcGxRVGh2Y1ZCSU5VSXdUVWRPVUZVMlRtVnJTbW
  hFUVhnelpYbHBUemRRTkEifQ.eyJzdWIiOiAiaHR0cHM6Ly9ycC
  5leGFtcGxlLmNvbSIsICJpc3MiOiAiaHR0cHM6Ly9ycC5leGFtc
  GxlLmNvbSIsICJpYXQiOiAxNTg5NzA0NzAxLCAiZXhwIjogMTU4
  OTcwNDc2MSwgImF1ZCI6ICJodHRwczovL29wLmV4YW1wbGUub3J
  nL2F1dGhvcml6YXRpb24iLCAianRpIjogIjM5ZDVhZTU1MmQ5Yz
  Q4ZjBiOTEyZGM1NTY4ZWQ1MGQ2In0.oUt9Knx_lxb4V2S0tyNFH
  CNZeP7sImBy5XDsFxv1cUpGkAojNXSy2dnU5HEzscMgNW4wguz6
  KDkC01aq5OfN04SuVItS66bsx0h4Gs7grKAp_51bClzreBVzU4g
  _-dFTgF15T9VLIgM_juFNPA_g4Lx7Eb5r37rWTUrzXdmfxeou0X
  FC2p9BIqItU3m9gmH0ojdBCUX5Up0iDsys6_npYomqitAcvaBRD
  PiuUBa5Iar9HVR-H7FMAr7aq7s-dH5gx2CHIfM3-qlc2-_Apsy0
  BrQl6VePR6j-3q6JCWvNw7l4_F2UpHeanHb31fLKQbK-1yoXDNz
  DwA7B0ZqmuSmMFQ

10.1.1.2.1. Processing the Authentication Request

There are three different paths the OP MUST follow when processing the Authentication Request, depending on which request authentication method was used. It all starts the same though. When the OP receives an incoming Authentication Request, the OP supports OpenID Connect Federation, the incoming Client ID is a valid URL, the OP does not have the Client ID registered as a known client and the OP supports the request authentication method used then the OP SHOULD try to resolve and fetch Trust Chains starting with the RP's Entity Statement as described in Section 8.1.

The OP SHOULD validate the possible Trust Chains, as described in Section 8.2, and resolve the RP metadata with type openid_relying_party.

The OP SHOULD consider the resolved metadata of the RP and verify that it complies with the client metadata specification in OpenID Connect Dynamic Client Registration 1.0.

Once the OP has the RP's metadata, it can verify the client using the keys published underneath the metadata/openid_relying_party element. This is where it diverges depending on which client authentication method was used.

private_key_jwt

If this method is used, then the OP will try to verify the signature of the signed JWT using the key material published by the RP in its metadata. If the authentication is successful, then the registration is regarded as correct.
tls_client_auth

If mTLS is used and the certificate used was not self-signed, then the Subject Alternative Name of the certificate MUST match the Entity Identifier of the RP.
self_signed_tls_client_auth

If mTLS is used and the certificate used is a self-signed certificate, then the certificate MUST be present as the value of an x5c claim for one key in the JWK Set describing the RP's keys.

10.1.2. Authentication Error Response

If the OP fails to establish trust with the RP, it SHOULD use an appropriate error code, and an error_description that aids the RP to understand what is wrong.

In addition to the error codes defined in Section 3.1.2.6 of OpenID Connect Core, this specification also defines the following error codes:

missing_trust_anchor

No trusted Trust Anchor could be found.
validation_failed

Trust chain validation failed.

The following is a non-normative example error response:

HTTP/1.1 302 Found
  Location: https://client.example.org/cb?
    error=missing_trust_anchor
    &error_description=
      Could%20not%20find%20a%20trusted%20anchor
    &state=af0ifjsldkj

10.2. Explicit Registration

This method involves performing an explicit registration of a new client the first time an RP interacts with an OP using something that basically follows the steps in OpenID Connect Dynamic Client Registration 1.0 but where the client registration request is a signed Entity Statement.

10.2.1. Client Registration

10.2.1.1. Client Registration Request

The OP MUST support OpenID Dynamic Client Registration as extended by this specification. This is signaled by having the claim federation_registration_endpoint in the OP's metadata.

Given that the OP supports explicit registration, the RP progresses as follows:

  1. Once it has the list of acceptable Trust Chains for the OP, it MUST choose the subset it wants to progress with. The subset can be as small as one Trust Chain, but it can also contain more than one.
  2. Based on the Trust Anchors referenced in the subset of Trust Chains, the RP will choose a set of authority_hints from its own set that terminate in those Trust Anchors.
  3. The RP will now construct a self-signed Entity Statement where the metadata statement chosen is influenced by the OP's metadata and the authority_hints included are picked by the process described above. Note that the aud claim in the Entity Statement is REQUIRED in this case and MUST be set to the OP issuer identifier.
  4. The Entity Statement is sent, using POST, to the federation_registration_endpoint defined in this document. The content type MUST be set to application/entity-statement+jwt.

10.2.1.2. Client Registration Response

10.2.1.2.1. OP Constructing the Response

The Trust Chains MUST be constructed using the received Entity Statement.

  1. After the OP receives the request, it collects and evaluates the Trust Chains starting with the authority_hints in the registration request. After it has verified at least one Trust Chain it MUST verify that the signature on the received registration request is correct.
  2. If it finds more than one acceptable Trust Chain, it MUST choose one Trust Anchor from those chains as the one it will proceed with.
  3. At this point, if there already exists a client registration under the same Entity Identifier then that registration MUST be regarded as invalid. Note that key material from the previous registration SHOULD be kept to enable verifying signatures or decrypting archived data.
  4. The OP will now construct a metadata policy that, if applied to the RP's metadata statement, will result in metadata that the OP finds acceptable. Note that the Client ID the OP chooses does not have to be the same as the Entity Identifier of the RP. To the Entity Statement it will add a trust_anchor_id claim, containing the Trust Anchor chosen above.
  5. It will sign and return the registration response (a signed Entity Statement) to the RP.

10.2.1.2.2. RP Parsing the Response

  1. The RP verifies the correctness of the received Entity Statement, making sure that the Trust Chains starting at the authority_hints terminate in Trust Anchors that were referenced in the Entity Statement it sent to the OP.
  2. The RP MUST NOT apply metadata policies from the trust chains that the OP provides because those are not valid for the RP's metadata. The RP MUST apply policies to the metadata using one of its own Trust Chains that ends in the Trust Anchor that the OP chose. Once it has applied those policies, it can then apply the policy returned from the OP. When it has applied all the metadata policies to its metadata statement, it then stores the result and can continue communicating with the OP using the agreed-upon metadata.
  3. At this point the RP also knows which Trust Chain it should use when evaluating the OP's metadata. It can therefore apply the metadata policies on the OP's metadata using the relevant Trust Chain and store the result as the OP's metadata.
  4. If the RP does not accept the received Entity Statement for some reason, then it has the choice to restart the registration process or to give up.

10.2.2. After Client Registration

A client registration using this specification is not expected to be valid forever. The Entity Statements exchanged all have expiration times, which means that the registration will eventually time out. An OP can also, for administrative reasons, decide that a client registration is not valid anymore. An example of this could be that the OP leaves the federation in use.

10.2.2.1. What the RP MUST Do

At regular intervals, the RP MUST:

  1. Starting with the OP's Entity Statement, resolve and verify the Trust Chains it chooses to use when constructing the registration request. If those Trust Chains do not exist anymore or do not verify, then the registration SHOULD be regarded as invalid and a new registration process SHOULD be started.
  2. If the OP's Entity Statement was properly formed the RP must now verify that the Entity Statement it received about itself from the OP is still valid. Again, if that is not the case the registration SHOULD be regarded as invalid and a new registration process SHOULD be started.

What is regarded as reasonable intervals will depend on federation policies and risk assessment by the maintainer of the RP.

10.2.2.2. What the OP MUST Do

At regular intervals, the OP MUST:

  1. If the signature on the registration request has expired, it MUST mark the registration as invalid and demand that the RP MUST re-register. Else
  2. starting with the RP's client registration request, the OP MUST verify that there still is a valid Trust Chain terminating in the Trust Anchor the OP chose during the registration process.

10.2.3. Expiration Times

An OP MUST NOT assign an expiration time to an RP's registration that is later than the trust chain's expiration time.

10.3. ID Token Validation

The RP MUST validate any ID token as defined in Section 3.1.3.7. of OpenID Connect Core 1.0. If the trust relationship between RP and OP was established using OpenID Connect Federation, the key material used for ID Token signature validation MUST be obtained from the OP's metadata the RP obtained as a result of Trust Chain validation as defined in Section 8 and combining the metadata policies from the Entity Statements of the Trust Chain as described in Section 5.1.

11. IANA Considerations

11.1. OAuth Authorization Server Metadata Registry

This specification registers the following metadata names in the IANA "OAuth Authorization Server Metadata" registry [IANA.OAuth.Parameters] established by [RFC8414].

11.1.1. Registry Contents

11.2. OAuth Dynamic Client Registration Metadata Registration

This specification registers the following client metadata definition in the IANA "OAuth Dynamic Client Registration Metadata" registry [IANA.OAuth.Parameters] established by [RFC7591].

11.2.1. Registry Contents

11.3. OAuth Extensions Error Registration

This section registers the following values in the IANA "OAuth Extensions Error Registry" registry [IANA.OAuth.Parameters] established by [RFC6749].

11.3.1. Registry Contents

11.4. Media Type Registration

This section registers the following media types [RFC2046] in the "Media Types" registry [IANA.MediaTypes] in the manner described in [RFC6838].

11.4.1. Registry Contents

12. Security Considerations

Some of the interfaces defined in this specification could be used for Denial-of-Service attacks (DOS), most notably, Entity Listings (Section 7.3) and automatic client registration (Section 10.1). If you plan to provide these interfaces as a service, you should consider applying normal defense methods, such as those described in [RFC4732].

13. References

13.1. Normative References

[OpenID.Core] Sakimura, N., Bradley, J., Jones, M., de Medeiros, B. and C. Mortimore, "OpenID Connect Discovery 1.0", August 2015.
[OpenID.Discovery] Sakimura, N., Bradley, J., Jones, M. and E. Jay, "OpenID Connect Discovery 1.0", August 2015.
[OpenID.Registration] Sakimura, N., Bradley, J. and M. Jones, "OpenID Connect Dynamic Client Registration 1.0", August 2015.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002.
[RFC4732] Handley, M., Rescorla, E. and IAB, "Internet Denial-of-Service Considerations", RFC 4732, DOI 10.17487/RFC4732, December 2006.
[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.
[RFC7515] Jones, M., Bradley, J. and N. Sakimura, "JSON Web Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May 2015.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517, DOI 10.17487/RFC7517, May 2015.
[RFC7519] Jones, M., Bradley, J. and N. Sakimura, "JSON Web Token (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015.
[RFC7591] Richer, J., Jones, M., Bradley, J., Machulak, M. and P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol", RFC 7591, DOI 10.17487/RFC7591, July 2015.
[RFC7638] Jones, M. and N. Sakimura, "JSON Web Key (JWK) Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September 2015.
[RFC8414] Jones, M., Sakimura, N. and J. Bradley, "OAuth 2.0 Authorization Server Metadata", RFC 8414, DOI 10.17487/RFC8414, June 2018.
[RFC8615] Nottingham, M., "Well-Known Uniform Resource Identifiers (URIs)", RFC 8615, DOI 10.17487/RFC8615, May 2019.
[RFC8705] Campbell, B., Bradley, J., Sakimura, N. and T. Lodderstedt, "OAuth 2.0 Mutual-TLS Client Authentication and Certificate-Bound Access Tokens", RFC 8705, DOI 10.17487/RFC8705, February 2020.
[RFC9126] Lodderstedt, T., Campbell, B., Sakimura, N., Tonge, D. and F. Skokan, "OAuth 2.0 Pushed Authorization Requests", RFC 9126, DOI 10.17487/RFC9126, September 2021.

13.2. Informative References

[IANA.MediaTypes] IANA, "Media Types"
[IANA.OAuth.Parameters] IANA, "OAuth Parameters"
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", RFC 2046, DOI 10.17487/RFC2046, November 1996.
[RFC6749] Hardt, D., "The OAuth 2.0 Authorization Framework", RFC 6749, DOI 10.17487/RFC6749, October 2012.
[RFC6838] Freed, N., Klensin, J. and T. Hansen, "Media Type Specifications and Registration Procedures", BCP 13, RFC 6838, DOI 10.17487/RFC6838, January 2013.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018.

Appendix A. Provider Information Discovery and Client Registration in a Federation

Let us assume the following: The project LIGO would like to offer access to its wiki to all OPs in EduGAIN. LIGO is registered to the InCommon federation.

The players

                       EduGAIN
                          |
       +------------------+------------------+
       |                                     |
    SWAMID                               InCommon
       |                                     |
     umu.se                                  |
       |                                     |
   op.umu.se                           wiki.ligo.org

Both SWAMID and InCommon are identity federations in their own right. They also have in common that they are both members of the EduGAIN federation.

SWAMID and InCommon are different in how they register entities. SWAMID registers organizations and lets the organizations register entities that belong to the organization, while InCommon registers all entities directly and not beneath any organization Entity. Hence the differences in depth in the federations.

Let us assume a researcher from Umeå University would like to login at the LIGO Wiki. At the Wiki, the researcher will use some kind of discovery service to find the home identity provider (op.umu.se)

Once the RP-part of the Wiki knows which OP it SHOULD talk to it has to find out a couple of things about the OP. All of those things can be found in the metadata. But finding the metadata is not enough; the RP also has to trust the metadata.

Let us make a detour and start with what it takes to build a federation.

A.1. Setting Up a Federation

These are the steps you have to go through to set up your own federation. What you minimally have to do is:

Once you have this, you can start adding entities to your federation. Adding an Entity comes down to:

Now before the federation operator starts adding entities, there have to be policies in place on who can be part of the federation and the layout of the federation. Is it supposed to be a one-layer federation like InCommon, a two-layer one like the SWAMID federation, or a multi-layer federation? The federation may also want to think about implementing other policies using the federation policy framework, as described in Section 5.

With the federation in place, things can start happening.

A.2. The LIGO Wiki Discovers the OP's Metadata

Metadata discovery is a sequence of steps that starts with the RP fetching the self-signed Entity Statement of the leaf (in this case https://op.umu.se) using the process defined in Section 6. What follows thereafter is this sequence of steps:

  1. Pick out the immediate superior entities using the authority hints
  2. Fetch the configuration for each such Entity. This uses the process defined in Section 6
  3. Using the fetch endpoint of the superiors to ask for information about the subordinate Entity Section 7.1.1.

How many times this has to be repeated depends on the depth of the federation. What follows below is the result of each step the RP has to take to find the OP's metadata using the federation setup described above.

When building the Trust Chain, the Entity Statements issued by a superior about its subordinate are used together with the self-signed Entity Statement issued by the leaf.

The self-signed Entity Statement concerning intermediates is not part of the Trust Chain.

A.2.1. Configuration Information for op.umu.se

The LIGO WIKI RP fetches the self-signed Entity Statement from the OP (op.umu.se) using the process defined in Section 6.

The result is this Entity Statement.

{
  "authority_hints": [
    "https://umu.se"
  ],
  "exp": 1568397247,
  "iat": 1568310847,
  "iss": "https://op.umu.se",
  "jwks": {
    "keys": [
      {
        "e": "AQAB",
        "kid": "dEEtRjlzY3djcENuT01wOGxrZlkxb3RIQVJlMTY0...",
        "kty": "RSA",
        "n": "x97YKqc9Cs-DNtFrQ7_vhXoH9bwkDWW6En2jJ044yH..."
      }
    ]
  },
  "metadata": {
    "openid_provider": {
      "issuer": "https://op.umu.se/openid",
      "signed_jwks_uri": "https://op.umu.se/openid/jwks.jose",
      "authorization_endpoint":
        "https://op.umu.se/openid/authorization",
      "client_registration_types_supported": [
        "automatic",
        "explicit"
      ],
      "request_parameter_supported": true,
      "grant_types_supported": [
        "authorization_code",
        "implicit",
        "urn:ietf:params:oauth:grant-type:jwt-bearer"
      ],
      "id_token_signing_alg_values_supported": [
        "ES256", "RS256"
      ],
      "logo_uri":
        "https://www.umu.se/img/umu-logo-left-neg-SE.svg",
      "op_policy_uri":
        "https://www.umu.se/en/website/legal-information/",
      "response_types_supported": [
        "code",
        "code id_token",
        "token"
      ],
      "subject_types_supported": [
        "pairwise",
        "public"
      ],
      "token_endpoint": "https://op.umu.se/openid/token",
      "federation_registration_endpoint":
        "https://op.umu.se/openid/fedreg",
      "token_endpoint_auth_methods_supported": [
        "client_secret_post",
        "client_secret_basic",
        "client_secret_jwt",
        "private_key_jwt"
      ]
    }
  },
  "sub": "https://op.umu.se"
}

The authority_hints points to the intermediate https://umu.se. So that is the next step.

This Entity Statement is the first link in the Trust Chain.

A.2.2. Configuration Information for 'https://umu.se'

The LIGO RP fetches the self-signed Entity Statement from "https://umu.se" using the process defined in Section 6.

The request will look like this:

GET /.well-known/openid-federation HTTP/1.1
Host: umu.se
            

And the GET will return:

{
  "authority_hints": [
    "https://swamid.se"
  ],
  "exp": 1568397247,
  "iat": 1568310847,
  "iss": "https://umu.se",
  "jwks": {
    "keys": [
      {
        "e": "AQAB",
        "kid": "endwNUZrNTJsX2NyQlp4bjhVcTFTTVltR2gxV2RV...",
        "kty": "RSA",
        "n": "vXdXzZwQo0hxRSmZEcDIsnpg-CMEkor50SOG-1XUlM..."
      }
    ]
  },
  "metadata": {
    "federation_entity": {
      "contacts": "ops@umu.se",
      "federation_fetch_endpoint": "https://umu.se/oidc/fedapi",
      "homepage_uri": "https://www.umu.se",
      "name": "UmU"
    }
  },
  "sub": "https://umu.se"
}

The only piece of information that is used from this Entity Statement is the federation_fetch_endpoint, which is used in the next step.

A.2.3. Entity Statement Published by 'https://umu.se' about 'https://op.umu.se'

The RP uses the fetch endpoint provided by https://umu.se as defined in Section 7.1.1 to fetch information about "https://op.umu.se".

The request will look like this:

GET /oidc/fedapi?sub=https%3A%2F%2Fop.umu.se&
iss=https%3A%2F%2Fumu.se HTTP/1.1
Host: umu.se
            

and the result is this:

{
  "exp": 1568397247,
  "iat": 1568310847,
  "iss": "https://umu.se",
  "jwks": {
    "keys": [
      {
        "e": "AQAB",
        "kid": "dEEtRjlzY3djcENuT01wOGxrZlkxb3RIQVJlMTY0...",
        "kty": "RSA",
        "n": "x97YKqc9Cs-DNtFrQ7_vhXoH9bwkDWW6En2jJ044yH..."
      }
    ]
  },
  "metadata_policy": {
    "openid_provider": {
      "contacts": {
        "add": [
          "ops@swamid.se"
        ]
      },
      "organization_name": {
        "value": "University of Ume\u00e5"
      },
      "subject_types_supported": {
        "value": [
          "pairwise"
        ]
      },
      "token_endpoint_auth_methods_supported": {
        "default": [
          "private_key_jwt"
        ],
        "subset_of": [
          "private_key_jwt",
          "client_secret_jwt"
        ],
        "superset_of": [
          "private_key_jwt"
        ]
      }
    }
  },
  "sub": "https://op.umu.se"
}

This is the second link in the Trust Chain.

Notable here is that this path leads to two Trust Anchors using the same next step ("https://swamid.se").

A.2.4. Configuration Information for 'https://swamid.se'

The LIGO Wiki RP fetches the self-signed Entity Statement from "https://swamid.se" using the process defined in Section 6.

The request will look like this:

GET /.well-known/openid-federation HTTP/1.1
Host: swamid.se
            

And the GET will return:

{
  "authority_hints": [
    "https://edugain.geant.org"
  ],
  "exp": 1568397247,
  "iat": 1568310847,
  "iss": "https://swamid.se",
  "jwks": {
    "keys": [
      {
        "e": "AQAB",
        "kid": "N1pQTzFxUXZ1RXVsUkVuMG5uMnVDSURGRVdhUzdO...",
        "kty": "RSA",
        "n": "3EQc6cR_GSBq9km9-WCHY_lWJZWkcn0M05TGtH6D9S..."
      }
    ]
  },
  "metadata": {
    "federation_entity": {
      "contacts": "ops@swamid.se",
      "federation_fetch_endpoint":
        "https://swamid.se/fedapi",
      "homepage_uri": "https://www.sunet.se/swamid/",
      "name": "SWAMID"
    }
  },
  "sub": "https://swamid.se"
}

The only piece of information that is used from this Entity Statement is the federation_fetch_endpoint, which is used in the next step.

A.2.5. Entity Statement Published by 'https://swamid.se' about 'https://umu.se'

The LIGO Wiki RP uses the fetch endpoint provided by "https://swamid.se" as defined in Section 7.1.1 to fetch information about "https://umu.se".

The request will look like this:

GET /fedapi?sub=https%3A%2F%2Fumu.se&
iss=https%3A%2F%2Fswamid.se HTTP/1.1
Host: swamid.se
            

and the result is this:

{
  "exp": 1568397247,
  "iat": 1568310847,
  "iss": "https://swamid.se",
  "jwks": {
    "keys": [
      {
        "e": "AQAB",
        "kid": "endwNUZrNTJsX2NyQlp4bjhVcTFTTVltR2gxV2RV...",
        "kty": "RSA",
        "n": "vXdXzZwQo0hxRSmZEcDIsnpg-CMEkor50SOG-1XUlM..."
      }
    ]
  },
  "metadata_policy": {
    "openid_provider": {
      "id_token_signing_alg_values_supported": {
        "subset_of": [
          "RS256",
          "ES256",
          "ES384",
          "ES512"
        ]
      },
      "token_endpoint_auth_methods_supported": {
        "subset_of": [
          "client_secret_jwt",
          "private_key_jwt"
        ]
      },
      "userinfo_signing_alg_values_supported": {
        "subset_of": [
          "ES256",
          "ES384",
          "ES512"
        ]
      }
    }
  },
  "sub": "https://umu.se"
}

This is the third link in the Trust Chain.

If we assume that the issuer of this Entity Statement is not in the list of Trust Anchors the LIGO Wiki RP has access to, we have to go one step further.

A.2.6. Configuration Information for 'https://edugain.geant.org'

RP fetches the self-signed Entity Statement from "https://edugain.geant.org" using the process defined in Section 6.

The request will look like this:

GET /.well-known/openid-federation HTTP/1.1
Host: edugain.geant.org
            

And the GET will return:

{
  "exp": 1568397247,
  "iat": 1568310847,
  "iss": "https://edugain.geant.org",
  "jwks": {
    "keys": [
      {
        "e": "AQAB",
        "kid": "Sl9DcjFxR3hrRGdabUNIR21KT3dvdWMyc2VUM2Fr...",
        "kty": "RSA",
        "n": "xKlwocDXUw-mrvDSO4oRrTRrVuTwotoBFpozvlq-1q..."
      }
    ]
  },
  "metadata": {
    "federation_entity": {
      "federation_fetch_endpoint": "https://geant.org/edugain/api"
    }
  },
  "sub": "https://edugain.geant.org"
}

Again, the only thing we need is the federation_fetch_endpoint. As described in Section 9.2, note SHOULD also be taken to jwks as the Trust Anchor MAY be performing a key rollover.

A.2.7. Entity Statement Published by 'https://edugain.geant.org' about 'https://swamid.se'

The LIGO Wiki RP uses the fetch endpoint of https://edugain.geant.org as defined in Section 7.1.1 to fetch information about "https://swamid.se".

The request will look like this:

GET /edugain/api?sub=https%3A%2F%2Fswamid.se&
iss=https%3A%2F%2Fedugain.geant.org HTTP/1.1
Host: geant.org
            

and the result is this:

{
  "exp": 1568397247,
  "iat": 1568310847,
  "iss": "https://edugain.geant.org",
  "jwks": {
    "keys": [
      {
        "e": "AQAB",
        "kid": "N1pQTzFxUXZ1RXVsUkVuMG5uMnVDSURGRVdhUzdO...",
        "kty": "RSA",
        "n": "3EQc6cR_GSBq9km9-WCHY_lWJZWkcn0M05TGtH6D9S..."
      }
    ]
  },
  "metadata_policy": {
    "openid_provider": {
      "contacts": {
        "add": "ops@edugain.geant.org"
      }
    },
    "openid_relying_party": {
      "contacts": {
        "add": "ops@edugain.geant.org"
      }
    }
  },
  "sub": "https://swamid.se"
}

If we assume that the issuer of this statement appears in the list of Trust Anchors the LIGO Wiki RP has access to this would be the fourth and final Entity Statement in the Trust Chain.

We now have the whole chain from the self-signed Entity Statement of the leaf up until the last one that is issued by a Trust Anchor. All in all, we have:

  1. Self-signed Entity Statement by the leaf (https://op.umu.se)
  2. Statement issued by https://umu.se about https://op.umu.se
  3. Statement issued by https://swamid.se about https://umu.se
  4. Statement issued by https://edugain.geant.org about https://swamid.se

We also have the self-signed Entity Statements from https://umu.se, https://swamid.se and https://edugain.geant.org about themselves but those are not used in the Trust Chain verification.

Using the public keys of the Trust Anchor that the LIGO Wiki RP has been provided with in some secure out-of-band way, it can now verify the Trust Chain as described in Section 8.2.

A.2.8. Verified Metadata for op.umu.se

Having verified the chain, the LIGO Wiki RP can proceed with the next step.

Combining the metadata policies from the tree Entity Statements we have by a superior about its subordinate and applying the combined policy to the metadata statement that the leaf Entity presented, we get:

{
  "authorization_endpoint":
    "https://op.umu.se/openid/authorization",
  "claims_parameter_supported": false,
  "contacts": [
    "ops@swamid.se"
  ],
  "federation_registration_endpoint":
    "https://op.umu.se/openid/fedreg",
  "client_registration_types_supported": [
    "automatic",
    "explicit"
  ],
  "grant_types_supported": [
    "authorization_code",
    "implicit",
    "urn:ietf:params:oauth:grant-type:jwt-bearer"
  ],
  "id_token_signing_alg_values_supported": [
    "RS256",
    "ES256"
  ],
  "issuer": "https://op.umu.se/openid",
  "signed_jwks_uri": "https://op.umu.se/openid/jwks.jose",
  "logo_uri":
    "https://www.umu.se/img/umu-logo-left-neg-SE.svg",
  "organization_name": "University of Ume\u00e5",
  "op_policy_uri":
    "https://www.umu.se/en/website/legal-information/",
  "request_parameter_supported": true,
  "request_uri_parameter_supported": true,
  "require_request_uri_registration": true,
  "response_types_supported": [
    "code",
    "code id_token",
    "token"
  ],
  "subject_types_supported": [
    "pairwise"
  ],
  "token_endpoint": "https://op.umu.se/openid/token",
  "token_endpoint_auth_methods_supported": [
    "private_key_jwt",
    "client_secret_jwt"
  ],
  "version": "3.0"
}

We have now reached the end of the Provider Discovery process.

A.3. The Two Ways of Doing Client Registration

As described in Section 10, there are two ways which can be used to do client registration:

Automatic

No negotiation between the RP and the OP is made regarding what features the client SHOULD use in future communication are done. The RP's published metadata filtered by the chosen trust chain's metadata policies defines the metadata that is to be used.
Explicit

The RP will access the federation_registration_endpoint, which provides the metadata for the RP to use. The OP MAY return a metadata policy that adds restrictions over and above what the Trust Chain already has defined.

A.3.1. RP Sends Authentication Request (Automatic Registration)

The LIGO Wiki RP does not do any registration but goes directly to sending an Authentication Request.

Here is an example of such an Authentication Request:

GET /openid/authorization?
  request=eyJhbGciOiJSUzI1NiIsImtpZCI6ImRVTjJhMDF3Umtoa1NXc
    GxRVGh2Y1ZCSU5VSXdUVWRPVUZVMlRtVnJTbWhFUVhnelpYbHBUemRR
    TkEifQ.eyJyZXNwb25zZV90eXBlIjogImNvZGUiLCAic2NvcGUiOiAi
    b3BlbmlkIHByb2ZpbGUgZW1haWwiLCAiY2xpZW50X2lkIjogImh0dHB
    zOi8vd2lraS5saWdvLm9yZyIsICJzdGF0ZSI6ICIyZmY3ZTU4OS0zOD
    Q4LTQ2ZGEtYTNkMi05NDllMTIzNWU2NzEiLCAibm9uY2UiOiAiZjU4M
    WExODYtYWNhNC00NmIzLTk0ZmMtODA0ODQwODNlYjJjIiwgInJlZGly
    ZWN0X3VyaSI6ICJodHRwczovL3dpa2kubGlnby5vcmcvb3BlbmlkL2N
    hbGxiYWNrIiwgImlzcyI6ICIiLCAiaWF0IjogMTU5MzU4ODA4NSwgIm
    F1ZCI6ICJodHRwczovL29wLnVtdS5zZSJ9.cRwSFNcDx6VsacAQDcIx
    5OAt_Pj30I_uUKRh04N4QJd6MZ0f50sETRv8uspSt9fMa-5yV3uzthX
    _v8OtQrV33gW1vzgOSRCdHgeCN40StbzjFk102seDwtU_Uzrcsy7KrX
    YSBp8U0dBDjuxC6h18L8ExjeR-NFjcrhy0wwua7Tnb4QqtN0QCia6DD
    8QBNVTL1Ga0YPmMdT25wS26wug23IgpbZB20VUosmMGgGtS5yCI5AwK
    Bhozv-oBH5KxxHzH1Oss-RkIGiQnjRnaWwEOTITmfZWra1eHP254wFF
    2se-EnWtz1q2XwsD9NSsOEJwWJPirPPJaKso8ng6qrrOSgw
  &response_type=code
  &client_id=https%3A%2F%2Fwiki.ligo.org
  &redirect_uri=https%3A%2F%2Fwiki.ligo.org/openid/callback
  &scope=openid+profile+email
  HTTP/1.1
Host: op.umu.se

The OP receiving this Authentication Request will, unless the RP is already registered, start to dynamically fetch and establish trust with the RP.

A.3.1.1. OP Fetches Entity Statements

The OP needs to establish a Trust Chain for the RP (wiki.ligo.org). The OP in this example is configured with public keys of two federations:

The OP starts to resolve metadata for the client identifier https://wiki.ligo.org by fetching the self-signed Entity Statement using the process described in Section 6.

The process is the same as described in Appendix A.2 and will result in a Trust Chain with the following Entity Statements:

  1. Self-signed Entity Statement by the leaf https://wiki.ligo.org
  2. Statement issued by https://incommon.org about https://wiki.ligo.org
  3. Statement issued by https://edugain.geant.org about https://incommon.org

A.3.1.2. OP Evaluates the RP Metadata

Using the public keys of the Trust Anchor that the LIGO Wiki RP has been provided with in some secure out-of-band way, it can now verify the Trust Chain as described in Section 8.2.

"metadata_policy": {
  "openid_provider": {
    "contacts": {
      "add": "ops@edugain.geant.org"
    }
  },
  "openid_relying_party": {
    "contacts": {
      "add": "ops@edugain.geant.org"
    }
  }
}
                

We will not list the complete Entity Statements but only the metadata and metadata_policy parts. There are two metadata policies:

edugain.geant.org

"metadata_policy": {
  "openid_relying_party": {
    "application_type": {
      "one_of": [
        "web",
        "native"
      ]
    },
    "contacts": {
      "add": "ops@incommon.org"
    },
    "grant_types": {
      "subset_of": [
        "authorization_code",
        "refresh_token"
      ]
    }
  }
}
                

incommon.org

If you combine these and apply them to the metadata for wiki.ligo.org :

"metadata": {
  "application_type": "web",
  "client_name": "LIGO Wiki",
  "contacts": [
    "ops@ligo.org"
  ],
  "grant_types": [
    "authorization_code",
    "refresh_token"
  ],
  "id_token_signed_response_alg": "RS256",
  "signed_jwks_uri": "https://wiki.ligo.org/jwks.jose",
  "redirect_uris": [
    "https://wiki.ligo.org/openid/callback"
  ],
  "response_types": [
    "code"
  ],
  "subject_type": "public"
}

You will get

{
  "application_type": "web",
  "client_name": "LIGO Wiki",
  "contacts": [
    "ops@ligo.org",
    "ops@edugain.geant.org",
    "ops@incommon.org"
  ],
  "grant_types": [
    "refresh_token",
    "authorization_code"
  ],
  "id_token_signed_response_alg": "RS256",
  "signed_jwks_uri": "https://wiki.ligo.org/jwks.jose",
  "redirect_uris": [
    "https://wiki.ligo.org/openid/callback"
  ],
  "response_types": [
    "code"
  ],
  "subject_type": "public"
}

Having that, the registration is done, and the OP MUST now use the keys found at the URL specified in signed_jwks_uri to verify the signature on the Request Object in the Authentication Request.

A.3.2. Client Starts with Registration (Explicit Client Registration)

Here the LIGO Wiki RP sends a client registration request to the federation_registration_endpoint of the OP (op.umu.se). What it sends is a self-signed Entity Statement.

Once the OP has the Entity Statement, it proceeds with the same sequence of steps as laid out in Appendix A.2.

The OP will end up with the same RP metadata as was described in Appendix A.3.1.2, but what it now can do is return a metadata policy that it wants to be applied to the RP's metadata. This metadata policy will be combined with the Trust Chain's combined metadata policy before being applied to the RP's metadata.

If we assume that the OP does not support refresh tokens, it MAY want to add a metadata policy that says:

"metadata_policy": {
  "openid_relying_party": {
    "grant_types": {
      "subset_of": [
        "authorization_code"
      ]
    }
  }
}

Thus, the Entity Statement returned by the OP to the RP MAY look like this:


{
  "trust_anchor_id": "https://edugain.geant.org",
  "metadata_policy": {
    "openid_relying_party": {
      "application_type": {
        "one_of": [
          "web",
          "native"
        ]
      },
      "contacts": {
        "add": [
          "ops@incommon.org",
          "ops@edugain.geant.org"
        ]
      },
      "grant_types": {
        "subset_of": [
          "authorization_code",
          "refresh_token"
        ]
      }
      "registration_access_token": {
        "value": "nLe19cJ5e9SXXiPqnRRuxpjyWI73bDhD"
      },
      "client_id": {
        "value": "m3GyHw"
      },
      "client_secret_expires_at": {
        "value": 1604049619
      },
      "registration_client_uri": {
        "value":
          "https://op.umu.se/openid/registration?client_id=m3GyHw"
      },
      "client_secret": {
        "value":
          "cb44eed577f3b5edf3e08362d47a0dc44630b3dc6ea99f7a79205"
      },
      "client_id_issued_at": {
        "value": 1601457619
      }
    }
  },
  "authority_hints": [
    "https://incommon.org"
  ],
  "aud": "https://wiki.ligo.org",
  "jwks": {
    "keys": [
      {
        "kty": "RSA",
        "use": "sig",
        "kid":
          "U2JTWHY0VFg0a2FEVVdTaHptVDJsNDNiSDk5MXRBVEtNSFVkeXZwb",
        "e": "AQAB",
        "n":
          "4AZjgqFwMhTVSLrpzzNcwaCyVD88C_Hb3Bmor97vH-2AzldhuVb8K..."
      },
      {
        "kty": "EC",
        "use": "sig",
        "kid": "LWtFcklLOGdrW",
        "crv": "P-256",
        "x": "X2S1dFE7zokQDST0bfHdlOWxOc8FC1l4_sG1Kwa4l4s",
        "y": "812nU6OCKxgc2ZgSPt_dkXbYldG_smHJi4wXByDHc6g"
      }
    ]
  },
  "iss": "https://op.umu.se",
  "iat": 1601457619,
  "exp": 1601544019
}

And the resulting metadata used by the RP could look like:

{
  "application_type": "web",
  "client_name": "LIGO Wiki",
  "contacts": [
    "ops@edugain.geant.org",
    "ops@incommon.org",
    "ops@ligo.org"
  ],
  "grant_types": [
    "authorization_code"
  ],
  "id_token_signed_response_alg": "RS256",
  "signed_jwks_uri": "https://wiki.ligo.org/jwks.jose",
  "redirect_uris": [
    "https://wiki.ligo.org/openid/callback"
  ],
  "response_types": [
    "code"
  ],
  "subject_type": "public"
}

Appendix B. Notices

Copyright (c) 2022 The OpenID Foundation.

The OpenID Foundation (OIDF) grants to any Contributor, developer, implementer, or other interested party a non-exclusive, royalty free, worldwide copyright license to reproduce, prepare derivative works from, distribute, perform and display, this Implementers Draft or Final Specification solely for the purposes of (i) developing specifications, and (ii) implementing Implementers Drafts and Final Specifications based on such documents, provided that attribution be made to the OIDF as the source of the material, but that such attribution does not indicate an endorsement by the OIDF.

The technology described in this specification was made available from contributions from various sources, including members of the OpenID Foundation and others. Although the OpenID Foundation has taken steps to help ensure that the technology is available for distribution, it takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this specification or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any independent effort to identify any such rights. The OpenID Foundation and the contributors to this specification make no (and hereby expressly disclaim any) warranties (express, implied, or otherwise), including implied warranties of merchantability, non-infringement, fitness for a particular purpose, or title, related to this specification, and the entire risk as to implementing this specification is assumed by the implementer. The OpenID Intellectual Property Rights policy requires contributors to offer a patent promise not to assert certain patent claims against other contributors and against implementers. The OpenID Foundation invites any interested party to bring to its attention any copyrights, patents, patent applications, or other proprietary rights that MAY cover technology that MAY be required to practice this specification.

Appendix C. Acknowledgements

The authors wish to acknowledge the contributions of the following individuals and organizations to this specification: Vladimir Dzhuvinov, Heather Flanagan, Samuel Gulliksson, Takahiko Kawasaki, Torsten Lodderstedt, Roberto Polli, Jouke Roorda, Mischa Sallé, Marcos Sanz, Peter Schober, Michael Schwartz, and the JRA3T3 task force of GEANT4-2.

Appendix D. Document History

[[ To be removed from the final specification ]]

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Authors' Addresses

Roland Hedberg (editor) independent EMail: roland@catalogix.se
Michael B. Jones Microsoft EMail: mbj@microsoft.com URI: https://self-issued.info/
Andreas Åkre Solberg Sikt EMail: Andreas.Solberg@sikt.no URI: https://www.linkedin.com/in/andreassolberg/
John Bradley Yubico EMail: ve7jtb@ve7jtb.com URI: http://www.thread-safe.com/
Giuseppe De Marco independent EMail: demarcog83@gmail.com URI: https://www.linkedin.com/in/giuseppe-de-marco-bb054245/