OpenID Federation 1.0

OpenID Federation 1.0 - draft 32 independent

roland@catalogix.se

Self-Issued Consulting

michael_b_jones@hotmail.com https://self-issued.info/

Sikt

Andreas.Solberg@sikt.no https://www.linkedin.com/in/andreassolberg/

Yubico

ve7jtb@ve7jtb.com http://www.thread-safe.com/

independent

demarcog83@gmail.com https://www.linkedin.com/in/giuseppe-de-marco-bb054245/

Connect2id

vladimir@connect2id.com https://twitter.com/dzhuvi

OpenID Connect Working Group OpenID Connect Federation A federation can be expressed as an agreement between parties that trust each other. In bilateral federations, direct trust can be established between two organizations belonging to the same federation. 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 interacts 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 defines basic components used to build multilateral federations and describes how to apply them when the underlying authentication protocol used is OpenID Connect or the underlying authorization protocol is OAuth 2.0.

This specification describes how two Entities that would like to interact can establish trust between them by means of a trusted third party called a Trust Anchor. A Trust Anchor is an Entity whose main purpose is to issue statements about Entities. An identity federation can be realized using this specification using one or more levels of authorities. Examples of authorities are federation operators, organizations, departments within organizations, and individual sites. This specification provides the basic technical trust infrastructure building blocks needed to create 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. An organization MAY be represented by more than one Entity in a federation. An Entity MAY also belong to more than one federation.

Below is an example of two federations rooted at two different Trust Anchors with some members in common. Every Leaf Entity is able to establish mutual trust with any other Leaf Entity by means of having at least one common Trust Anchor between them. Two Coexisting Federations with Some Members in Common

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 .

This specification uses the terms "Claim Name", "Claim Value", "JSON Web Token (JWT)", and "JWT Claims Set" 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: Something that has a separate and distinct existence and that can be identified in a context. A globally unique URI that is bound to one Entity. An Entity that represents a trusted third party. An Entity for which it is possible to construct a Trust Chain from the Entity to a Trust Anchor. A 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. An Entity Statement issued by an Entity about itself. It contains the Entity's signing keys and further data used to control the Trust Chain resolution process, such as authority hints. An Entity Statement issued by a Superior Entity about an Entity that is immediately Subordinate to it. A role and function that an Entity plays within a federation. An Entity MUST be of at least one type and MAY be of many types. For example, an Entity can be both an OpenID Provider and Relying Party at the same time. String identifier for an Entity Type. An organization that is authoritative for a federation. A federation operator administers the Trust Anchor(s) for Entities in its federation. An Entity that issues an Entity Statement appearing somewhere in between those issued by the Trust Anchor and the Leaf Entity in a Trust Chain. The terms Intermediate Entity and Intermediate are used interchangeably in this specification. An Entity with no Subordinate Entities. Leaf Entities typically play a protocol role, such as an OpenID Connect Relying Party or OpenID Provider. An Entity that is a direct descendant of a Superior Entity (a Trust Anchor or Intermediate). An Entity with one or more Entities that are Subordinate to it. A process that starts with an Entity Identifier and collects a number of Entity Statements until the chosen Trust Anchor is reached. From the collected Entity Statements, a Trust Chain is constructed and verified. The result of the Federation Entity Discovery is that the Leaf Entity's metadata is constructed from the Trust Chain. A sequence of Entity Statements that represents a chain starting at a Leaf Entity and ending in a Trust Anchor. Statement of conformance to a well-scoped set of trust and/or interoperability requirements as determined by an accreditation authority. Keys used for the cryptogaphic signatures required by the trust mechanisms defined in this specification. Every participant in a Federation publishes its Federation Entity Keys in its Entity Configuration.

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 issued by Entities about themselves control the Trust Chain resolution process. The Entity Configuration of a Leaf Entity contains one or more references to its Superiors, found in the authority_hints parameter described in . These references can be used to download the Entity Configuration of each Superior. One or more Entity Configurations are traversed during the Federation Entity Discovery until the Trust Anchor is reached. The Trust Anchor and its Intermediates issue Entity Statements about their Subordinates called Subordinate Statements. The sequence of Entity Configurations and Subordinate Statements that validate the relationship between a Superior and a Subordinate, along a path towards the Trust Anchor, forms the proof that a Leaf Entity is a member of the federation rooted at the Trust Anchor. The chain that links the statements to one another is verified with the signature of each statement, as described in . With a verified Trust Chain, the federation policy is finally applied and the metadata describing a Leaf Entity within the Federation is derived, as described in . This specification deals with trust operations; it does not cover or touch protocol operations other than metadata derivation and exchange. In OpenID Connect terms, these are the protocol operations specified in OpenID Connect Discovery 1.0 and OpenID Connect Dynamic Client Registration 1.0. OpenID Connect is used in all of the examples in this specification, however this does not mean that this specification can only be used together with OpenID Connect. On the contrary, it can also be used to build federations using any other protocols.

The objects defined by this specification that are used to establish cryptographic trust between participants are secured as signed JWTs using public key cryptography. In particular, the keys used for securing these objects are managed by the Entities controlling those objects, with the public keys securing them being distributed through those objects themselves. This kind of trust mechanism has been utilized by research and academic federations for over a decade. Note that this cryptographic trust mechanim intentionally does not rely on Web PKI / TLS certificates for signing keys. Which TLS certificates are considered trusted can vary considerably between systems depending upon which certificate authorities are considered trusted and there are have been notable examples of ostensibly trusted certificates being compromised. For those reasons, this specification explicitly eschews reliance on Web PKI in favor of self-managed public keys, in this case, keys represented as JSON Web Keys (JWKs) .

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 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. All Entities in a federation publish an Entity Statement about themselves called an Entity Configuration. Superior Entities in a federation publish Entity Statements about their immediate Subordinate Entities called Subordinate Statements. Entity Statement JWTs MUST be explicitly typed, by setting the typ header parameter to entity-statement+jwt. This prevents cross-JWT confusion, per Section 3.11 of . The Entity Statement is signed using the private key of the issuer Entity in the form of a JSON Web Signature (JWS). Implementations SHOULD support signature verification with the RSA SHA-256 algorithm because OpenID Connect Core requires support for it (alg value of RS256). Federations MAY also specify different mandatory-to-implement algorithms. An Entity Statement is composed of the following claims: REQUIRED. The Entity Identifier of the issuer of the Entity Statement. If the iss and the sub are identical, the issuer is making an Entity Statement about itself called an Entity Configuration. REQUIRED. The Entity Identifier of the subject. 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 for details regarding date/times in general and UTC in particular. REQUIRED. Expiration time 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. REQUIRED. A JSON Web Key Set (JWKS) representing the public part of the subject's Federation Entity signing keys. The corresponding private key is used by the Entity to sign the Entity Configuration about itself, and by Trust Anchors and Intermediate Entities to sign Subordinate Statements about their immediate Subordinates. The public keys are used to verify the signatures of the issued Entity Statements and Trust Marks and SHOULD NOT be used in other protocols. (Keys to be used in other protocols, such as OpenID Connect, are conveyed in the metadata elements of the respective Entity Statements.) 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 unique kid (Key ID) value. It is RECOMMENDED that the Key ID be the JWK Thumbprint using the SHA-256 hash function of the key. OPTIONAL. An array of strings representing the Entity Identifiers of Intermediate Entities or Trust Anchors that MAY issue Subordinate Statements about the Entity. This claim is REQUIRED in the Entity Configurations of the Entities that have at least one Superior above them, such as Leaf and Intermediate Entities. Its value MUST NOT be the empty array []. This claim MUST NOT be present in the Entity Configurations of Trust Anchors with no Superiors. It MUST NOT be present in Subordinate Statements. OPTIONAL. JSON object with protocol-specific claims that represent the Entity's Types within its federations and metadata for those Entity Types. Each member name of the JSON object is an Entity Type Identifier, and each value MUST be a JSON object representing metadata according to the metadata schema of that Entity Type. When an Entity participates in a federation or federations with one or more Entity Types, its Entity Configuration MUST contain a metadata claim with entries for each of the corresponding Entity Type Identifiers, even if the values for those entries are the empty JSON object {}. (The value might contain no entries when Superiors supply any needed metadata). In some cases, a Superior may want to be explicit about what metadata should be used for a Subordinate. In that case metadata MAY be used in a Subordinate Statement. If metadata is used in a Subordinate Statement, it is only valid for the subject of the Subordinate Statement and has no impact on the subject's Subordinates. If a metadata claim appears along with a metadata_policy claim in an Entity Statement, then for each Entity Type Identifier, claims that appear in metadata MUST NOT appear in metadata_policy. OPTIONAL. JSON object that defines a metadata policy. The metadata policy applies to the Entity that is the subject of this Subordinate Statement as well as to all Entities that are Subordinate to it. Applying to Subordinate Entities distinguishes metadata_policy from metadata, which only applies to the subject itself. Each member name of the JSON object is an Entity Type Identifier, and each value MUST be a JSON object representing the metadata policy according to the metadata schema of that Entity Type. A Subordinate Statement MAY contain multiple sets of metadata policy statements, but only one for each Entity Type. Entity Configurations MUST NOT contain a metadata_policy claim. OPTIONAL. JSON object that describes constraints that apply to the Trust Chain, as described in . If the claim appears in an Entity Configuration, it MUST be applied to all Subordinates of that Entity. If the claim appears in a Subordinate Statement, then it MUST be applied to the subject of the Subordinate Statement and all the subject's Subordinates. 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 claim names in the Entity Statement in the crit list. Producers MUST NOT use the empty array [] as the crit value. OPTIONAL. The metadata_policy_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 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 metadata policy statements in the Entity Statement in the metadata_policy_crit list. Producers MUST NOT use the empty array [] as the metadata_policy_crit value. OPTIONAL. An array of JSON objects, each representing a Trust Mark. Each JSON object MUST contain the following two claims and MAY contain other claims. All the claims in the JSON object MUST have the same values as those contained in the Trust Mark JWT. The Trust Mark identifier. It MUST be the same value as the id claim contained in the Trust Mark JWT. A signed JSON Web Token that represents a Trust Mark. This claim MUST NOT be present in Subordinate Statements. Trust Marks are described in . OPTIONAL. A Trust Anchor MAY use this claim to tell which combination of Trust Mark identifiers and issuers are trusted by the federation. This claim MUST be ignored if present in an Entity Configuration for an Entity that is not a Trust Anchor. It is a JSON object with member names that are Trust Mark identifiers and each corresponding value being an array of Entity Identifiers that are trusted to represent the accreditation authority for Trust Marks with that identifier. If the array following a Trust Mark identifier is empty, anyone MAY issue Trust Marks with that identifier. This claim MUST NOT be present in Subordinate Statements. Trust Marks are described in . OPTIONAL. If a Federation Operator knows that a Trust Mark identifier is owned by an Entity different from the Trust Mark issuer, then that knowledge MUST be expressed in this claim. This claim MUST be ignored if present in an Entity Configuration for an Entity that is not a Trust Anchor. It is a JSON object with member names that are Trust Mark identifiers and each corresponding value being a JSON object with these members: REQUIRED Identifier of the Trust Mark owner. REQUIRED JSON Web Key Set (JWKS) containing the owner's Federation Entity Keys used for signing. Other members MAY also be defined and used. This claim MUST NOT be present in Subordinate Statements. OPTIONAL. String containing the fetch endpoint URL from which the Entity Statement was issued, as specified in . This parameter enables an optimized refresh of the Subordinate Statements and hence the Trust Chain, by skipping the request to the Entity Configuration that is normally required to discover the federation_fetch_endpoint of the issuing authority. If an Entity Statement cannot be retrieved from the source_endpoint, which can occur if the endpoint URL has changed, the current federation_fetch_endpoint location can be determined by retrieving the Entity Configuration of the issuer. Applications and protocols utilizing Entity Statements MAY specify and use additional claims.

The following is a non-normative example of the JWT Claims Set for an Entity Statement. The example contains a critical extension jti (JWT ID) to the Entity Statement and one critical extension to the policy language regexp (Regular expression). Example Entity Statement JWT Claims Set

The following is a non-normative example of a trust_mark_owners claim value: Example trust_mark_owners Claim Value

The following is a non-normative example of a trust_mark_issuers claim value: Example trust_mark_issuers Claim Value

Entities whose statements build a Trust Chain are categorized as: An Entity that represents a trusted third party. In an OpenID Connect identity federation, an RP or an OP, or in an OAuth 2.0 federation, a Client, Authorization Server, or Protected Resource. Neither a Leaf Entity nor a Trust Anchor. A Trust Chain begins with a Leaf Entity Configuration, and has zero or more Subordinate Statements issued by Intermediates about Subordinates, and includes the Subordinate Statement issued by the Trust Anchor about the top-most Intermediate (if there are Intermediates) or the Leaf Entity (if there are no Intermediates). The Trust Chain logically always ends with the Entity Configuration of the Trust Anchor, even though it MAY be omitted from the JSON array representating the Trust Chain in some cases. The Trust Chain contains the configuration of the federation as it applies to the Leaf at the time of the evaluation of the chain. 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: an Entity Configuration about the RP published by itself, a Subordinate Statement about the RP published by Organization A, a Subordinate Statement about Organization A published by the Trust Anchor for F, an Entity Configuration about the Trust Anchor for F published by itself. Let us refer to the Entity Statements in the Trust Chain as ES[j], where j = 0,...,i, with 0 being the index of the first Entity Statement and i being the zero-based index of the last. Then: ES[0] (the Leaf's Entity Configuration in the Trust Chain) is signed using a key in ES[0]["jwks"]. The iss claim in an Entity Statement is equal to the sub claim in the next. Restating this symbolically, for each j = 0,...,i-1, ES[j]["iss"] == ES[j+1]["sub"]. An Entity Statement is signed using a key from the jwks claim in the next. Restating this symbolically, for each j = 0,...,i-1, ES[j] is signed by a key in ES[j+1]["jwks"]. ES[i] (the Trust Anchor's Entity Configuration in the Trust Chain) is signed using a key in ES[i]["jwks"]. The Trust Anchor's public keys are used to verify the signatures on ES[i] (the Trust Anchor's Entity Configuration) and ES[i-1] (the Trust Anchor's Subordinate Statement about the Entity immediately Subordinate to it in the Trust Chain). The Trust Anchor's public keys are distributed to Entities that need to verify a Trust Chain in some secure out-of-band way not described in this document.

The trust_chain JWS header parameter is a JSON array containing the sequence of the statements that proves the trust relationship between the issuer of the JWS and the selected Trust Anchor, sorted as shown in . The Trust Chain contains the public key used to verify the JWS. The issuer of the JWS SHOULD select the Trust Anchor that it has in common with the audience of the JWS. Otherwise, the issuer is free to select a Trust Anchor. All signed JWTs MAY include the trust_chain JWS header parameter, with the exception of Entity Configurations and Subordinate Statements. These MUST NOT contain the trust_chain header parameter, as they are integral components of a Trust Chain themselves. Use of this header parameter is OPTIONAL.

The following is a non-normative example of a JWS header with the trust_chain parameter. Example JWS Header with a trust_chain Parameter

This section defines how to represent and use metadata about Entities. It reuses existing OpenID Connect and OAuth 2.0 metadata standards that are applicable to each Entity Type. As described in , Entity metadata is located in the metadata claim of an Entity Statement, whose value is a JSON object. The member names of this object are Entity Type Identifiers, as specified in . The metadata data structure following each Entity Type Identifier is a JSON object; it MAY be the empty JSON object {}, which may be the case when Superiors supply any needed metadata values. Top-level JSON object members in the metadata data structures MAY use any JSON value other than null; the use of null is prohibited to prevent likely implementation errors caused by confusing members having null values with omitted members.

This specification defines Entity Type Identifiers for OpenID Connect and OAuth 2.0 objects. The Entity Type Identifier uniquely identifies the Entity Type of the participant and the format of metadata for that Entity Type. Additional Entity Type Identifiers MAY be defined to support use cases outside OpenID Connect and OAuth 2.0 federations.

The Entity Type Identifier is openid_relying_party. All parameters defined in Section 2 of OpenID Connect Dynamic Client Registration 1.0 and are applicable, as well as additional parameters registered in the IANA "OAuth Dynamic Client Registration Metadata" registry . In addition, the following RP metadata parameter is defined: REQUIRED. An array of strings specifying the client registration types the RP wants to use. Values defined by this specification are automatic and explicit.

The following is a non-normative example of the JWT Claims Set for an RP's Entity Configuration: Example Relying Party Entity Configuration JWT Claims Set

The Entity Type Identifier is openid_provider. All parameters defined in Section 3 of OpenID Connect Discovery 1.0 and are applicable, as well as additional parameters registered in the IANA "OAuth Authorization Server Metadata" registry . In addition, the following OP metadata parameters are defined: REQUIRED. Array specifying the federation types supported. Federation-type values defined by this specification are automatic and explicit. OPTIONAL. URL of the OP's federation-specific Dynamic Client Registration Endpoint. If the OP supports Explicit Client Registration Endpoint this URL MUST use the https scheme and MAY contain port, path, and query parameter components encoded in application/x-www-form-urlencoded format; it MUST NOT contain a fragment component. If the OP supports Explicit Client Registration as described in , then this claim is REQUIRED. OPTIONAL. An OP MUST be able to verify that a request comes from an RP that is a member of a federation that the OP is a member of. This is done via request authentication methods. These methods achieve this by proving that the RP is in possession of a key that appears in its metadata. This parameter declares the request authentication methods that the OP supports. The request_authentication_methods_supported value is a JSON object where the member names are names of endpoints where the request authentication occurs. This MAY be either at the OP's Authorization Endpoint or the OP's Pushed Authorization Request (PAR) endpoint. Supported endpoint identifiers are authorization_endpoint and pushed_authorization_request_endpoint. The values of the JSON object members for the endpoint names are JSON arrays containing the names of the request authentication methods used at those endpoints. Some OAuth 2.0 client authentication methods can be used at the pushed_authorization_request_endpoint to achieve request authentication. They are the subset of those listed in the IANA "OAuth Token Endpoint Authentication Methods" registry that perform client authentication by proving possession of a private key. These client authentication methods are: This client authentication method 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. Section 2.1 of . Section 2.2 of . A request authentication method that is not a client authentication method is: Use of a Request Object, as described in OpenID Connect Core 1.0. The request authentication is performed by verifying that the request object is signed with a key that the RP controls. Use of Request Objects by Automatic Registration is described at . The request_object method MAY be used at either endpoint. Other request authentication methods MAY be defined and used. OPTIONAL. JSON array containing a list of the supported JWS algorithms (alg values) for signing the JWT used in the Request Object contained in the request parameter of an authorization request or in the private_key_jwt of a pushed authorization request. 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.

The following is a non-normative example of the JWT Claims Set for an OP's Entity Configuration: Example OpenID Provider Entity Configuration JWT Claims Set

The Entity Type Identifier is oauth_authorization_server. All parameters defined in Section 2 of and are applicable, as well as additional parameters registered in the IANA "OAuth Authorization Server Metadata" registry .

The Entity Type Identifier is oauth_client. All parameters defined in Section 2 of OAuth 2.0 Dynamic Client Registration Protocol and are applicable, as well as additional parameters registered in the IANA "OAuth Dynamic Client Registration Metadata" registry .

The Entity Type Identifier is oauth_resource. The parameters defined in are applicable. In addition, while it is not yet a standard, deployments MAY use the protected resource metadata parameters defined in .

The Entity Type Identifier is federation_entity. All Entities in a federation MAY use this Entity Type. The Entities that provide federation API endpoints MUST use this Entity Type. The following Federation Entity properties are defined: OPTIONAL. The fetch endpoint described in . This URL MUST use the https scheme and MAY contain port, path, and query parameter components encoded in application/x-www-form-urlencoded format; it MUST NOT contain a fragment component. Intermediate Entities and Trust Anchors MUST publish a federation_fetch_endpoint. Leaf Entities MUST NOT. OPTIONAL. The list endpoint described in . This URL MUST use the https scheme and MAY contain port, path, and query parameter components encoded in application/x-www-form-urlencoded format; it MUST NOT contain a fragment component. Intermediate Entities and Trust Anchors MUST publish a federation_list_endpoint. Leaf Entities MUST NOT. OPTIONAL. The resolve endpoint described in . This URL MUST use the https scheme and MAY contain port, path, and query parameter components encoded in application/x-www-form-urlencoded format; it MUST NOT contain a fragment component. Any federation Entity MAY publish a federation_resolve_endpoint. OPTIONAL. The Trust Mark status endpoint described in . Trust Mark issuers SHOULD publish a federation_trust_mark_status_endpoint. This URL MUST use the https scheme and MAY contain port, path, and query parameter components encoded in application/x-www-form-urlencoded format; it MUST NOT contain a fragment component. OPTIONAL. The endpoint described in . This URL MUST use the https scheme and MAY contain port, path, and query parameter components encoded in application/x-www-form-urlencoded format; it MUST NOT contain a fragment component. Trust Mark issuers MAY publish a federation_trust_mark_list_endpoint. OPTIONAL. The endpoint described in . This URL MUST use the https scheme and MAY contain port, path, and query parameter components encoded in application/x-www-form-urlencoded format; it MUST NOT contain a fragment component. Trust Mark issuers MAY publish a federation_trust_mark_endpoint. OPTIONAL. The endpoint described in . This URL MUST use the https scheme and MAY contain port, path, and query parameter components encoded in application/x-www-form-urlencoded format; it MUST NOT contain a fragment component. All federation Entities MAY publish a historical keys endpoint. It is RECOMMENDED that each Federation Entity contain an organization_name claim, as defined in .

The following is a non-normative example of the federation_entity Entity Type: Example of federation_entity Entity Type

This section defines additional metadata properties that MAY be used with all the Entity Types above.

The following metadata properties define ways of obtaining JWK Sets for an Entity Type of the Entity. OPTIONAL. URL referencing a signed JWT having the Entity's JWK Set document for that Entity Type as its payload. The JWT MUST be signed using a Federation Entity Key. This URL MUST use the https scheme. When both signing and encryption keys are made available, a use (public key use) parameter value is REQUIRED for all keys in the referenced JWK Set to indicate each key's intended usage. The following claims are specified for use in the payload, all of which except keys are defined in : REQUIRED. Array of JWK values. REQUIRED. The "iss" (issuer) claim identifies the principal that issued the JWT. REQUIRED. This claim identifies the owner of the keys. It SHOULD be the same as the issuer. OPTIONAL. This claim identifies the time when the JWT was issued. OPTIONAL. This claim identifies the time when the JWT is no longer valid. More claims are defined in ; of these, aud SHOULD NOT be used since the issuer cannot know who the audience is. nbf and jti are not particularly useful in this context and SHOULD be omitted.

The following is a non-normative example of the JWT Claims Set for a signed JWK Set. Example JWT Claims Set for a Signed JWK Set OPTIONAL. URL referencing a JWK Set document containing the Entity's keys for that Entity Type. This URL MUST use the https scheme. When both signing and encryption keys are made available, a use (public key use) parameter value is REQUIRED for all keys in the referenced JWK Set to indicate each key's intended usage. OPTIONAL. JSON Web Key Set document, passed by value, containing the Entity's keys for that Entity Type. This parameter is intended to be used by participants that, for some reason, cannot use the signed_jwks_uri parameter. An upside of using jwks is that the Entity's keys for the Entity Type are recorded in Trust Chains.

It is RECOMMENDED that an Entity Configuration use only one of jwks, jwks_uri, and signed_jwks_uri in its OpenID Connect or OAuth 2.0 metadata. However, there may be circumstances in which is it desirable to use multiple JWK Set representations, such as when an Entity is in multiple federations and the federations have different policies about the JWK Set representation to be used. When multiple JWK Set representations are used, the keys present in each representation SHOULD be the same. Even if they are not completely the same at a given instant in time (which may be the case during key rollover operations), implementations MUST make them consistent in a timely manner.

The following metadata properties define ways of obtaining information about the Entity for an Entity Type. OPTIONAL. A human-readable name representing the organization owning this Entity. If the owner is a physical person, this MAY be, for example, the person's name. Note that this information will be publicly available. 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. OPTIONAL. String. A URL that points to the logo of this Entity. The file containing the logo SHOULD be published in a format that can be viewed via the web. OPTIONAL. URL of the documentation of conditions and policies relevant to this Entity. OPTIONAL. URL of a Web page for the organization owning this Entity. It is RECOMMENDED that, when present, these metadata properties occur in an Entity's federation_entity metadata section. They MAY also be present in the Entity's metadata for other Entity Types, particularly when the values for those Entity Types differ from those for the federation_entity metadata.

Trust Anchors and Intermediate Entities MAY publish Entity Type-specific policies that apply to the metadata of their immediate Subordinates as well as any further Subordinates along the Trust Chain. As described in , the metadata policy operators are located in the metadata_policy claim of an Entity Statement, whose value is a JSON object. Each member in this object is an Entity Type-specific metadata policy, whose member name is an Entity Type Identifier, as specified in , for example openid_relying_party. The member value is a JSON object that represents metadata policies for the Entity Type and has the following structure: It consists of one or more policy entries, each entry being represented by a JSON object. A policy entry applies to a single metadata parameter, for example id_token_signed_response_alg. A policy entry is represented by a JSON object and consists of one or more operators, to check or modify the metadata parameter, as described in . A policy entry MAY include at most one operator of each kind. Note that metadata policies MUST regard any metadata parameter with a language tag in its name, as described in , as distinct from the same metadata parameter without a language tag.

The following is a non-normative example of a policy entry providing metadata policy for an OpenID Connect RP: Example metadata_policy Claim

This specification defines the following metadata policy operators. Metadata policy operators that modify values are: The metadata parameter MUST be assigned the value that is the value of this operator. The value or values of this operator MUST be added to the metadata parameter. If any of these values are already present in the metadata parameter, they MUST NOT be added another time. If the metadata parameter is absent, the parameter MUST be initialized with the value of this operator. If the metadata parameter is absent, it MUST be set to the value of this operator. Metadata policy operators that check values are: If the value of this operator is true, then the metadata parameter MUST be present. If false the metadata parameter is voluntary and may be absent. If the essential operator is omitted, this is equivalent to including it with a value of false. If the metadata parameter is present its value MUST be one of those listed in the operator value. If the metadata parameter is present this operator computes the intersection between the values of the operator and the metadata parameter. If the intersection is non-empty, the parameter is set to the values in the intersection. If the intersection is empty, the result is determined by the essential operator: For an essential metadata parameter, the result is an error; for a voluntary metadata parameter, it MUST be removed from the metadata. Note that this behavior makes subset_of a potential value modifier in addition to it being a value check. If the metadata parameter is present its values MUST contain those specified in the operator. By mathematically defining supersets, equality is included. Applications and protocols utilizing metadata policies MAY specify and use additional policy operators. All policy operators MUST consider it an error if a metadata parameter that is being operated on has a null value. Policy operators MUST NOT output metadata parameters with a null value. A "set equals" value check can be expressed by combining a subset_of and a superset_of with identical string list values. Note that when a metadata parameter is defined as a space-separated list of strings, like scope in , the subset_of, superset_of and default operator values are still expressed as lists of strings. This language from also applies to metadata parameters for which values can be expressed as a space-separated lists of strings: "If the value contains multiple space-delimited strings, their order does not matter, and each string adds an additional access range to the requested scope." The following table is a map of the outputs produced by the combination of the essential and subset_of policy operators with different input metadata parameter values. Note, the subset_of check is ignored when the metadata parameter is absent and designated as voluntary, as shown in the last row. Examples of outputs with Combinations of essential and subset_of inputs

Policy		Metadata Parameter
essential	subset_of	input	output
true	[a,b,c]	[a,e]	[a]
false	[a,b,c]	[a,e]	[a]
true	[a,b,c]	[d,e]	error
false	[a,b,c]	[d,e]	no parameter
true	[a,b,c]	no parameter	error
false	[a,b,c]	no parameter	no parameter

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 and superset_of apply 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). Therefore, one_of cannot appear beside subset_of/ superset_of in a policy entry. value overrides everything else. So having value together with any other operator (except for essential) does not make sense. Other restrictions are: If subset_of and superset_of both appear as operators, then the list of values in subset_of MUST be a superset of the values in superset_of. If add appears in a policy entry together with subset_of then the value/values of add MUST be a subset of subset_of. If add appears in a policy entry together with superset_of then the values of add MUST be a superset of superset_of. If default appears in a policy entry together with subset_of then the values of default MUST be a subset of subset_of. If default appears in a policy entry together with superset_of then the values of default MUST be a superset of superset_of. If add appears in a policy entry together with one_of then the value of add MUST be a member of one_of. If default appears in a policy entry together with one_of then the value default MUST be a member of one_of.

If there is more than one Entity Statement with metadata policy in a Trust Chain, then the policies MUST be combined before they are applied to the metadata statement. Using the notation defined in , policies are combined by starting with ES[i] and then adding the policies from ES[j] j=i-1,..,1. When for a given metadata parameter both the combined policy at the current step and the Subordinate Entity specify a policy operator, for example subset_of, the two operators are merged, as described in . After each combination step the policy for each parameter MUST adhere to the rules in . The final combined policy is then applied to the Entity's metadata, as described in . If during the combination process an operator merge rule or a policy restriction is violated or otherwise an error is produced, the process MUST stop and the policy combination MUST be considered invalid.

The policy operators (as defined in ) for a metadata parameter MUST be merged as follows: The result of merging the values of two subset_of operators is the intersection of the operator values. The result of merging the values of two one_of operators is the intersection of the operator values. The result of merging the values of two superset_of operators is the union of the operator values. The result of merging the values of two add operators is the union of the values. Merging two value operators requires the two operator values to be equal. If the values are not equal this MUST be treated as error. Merging two default operators requires the two operator values to be equal. If the values are not equal this MUST be treated as error. 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. If those rules are not met this MUST be treated as error.

The policies that apply to the Entity's metadata are those that result from the combining of the policies from the Entity Statements that make up the Trust Chain, as specified in . For every Entity Type metadata parameter for which a policy entry is present, the policy operators MUST be applied in accordance to their definitions in and in a sequence as follows: value: If this policy operator is present, further policy operators on the metadata parameter MUST NOT be applied. add default essential: If this parameter value is false or it is absent, then any subsequent policy operators that represent a value check MUST be skipped. one_of subset_of superset_of Applications and protocols that specify additional policy operators MUST define their order relative to the above sequence of operator application.

We start with a federation's policy for OAuth 2.0 clients: Example Federation's Policy for OAuth 2.0 Clients

Next, we have an organization's policy for OAuth 2.0 clients: Example Organization's Policy for OAuth 2.0 Clients

The resulting combined metadata policy is: Combined Policies from the Previous Two Examples

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. It is the responsibility of the implementation to verify that the metadata resulting from applying the policies of a federation that it is using is supported by the implementation. For instance, the implementation needs to support any cryptographic algorithms required by the resulting metadata. Implementations may need to reevaluate their compliance when policies change.

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 metadata_policy_crit list, as is done for JWS header parameters with the crit parameter. If the policy language extension keyword is listed in the metadata_policy_crit list and not understood, then the metadata MUST be rejected.

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

The RP's metadata from its Entity Configuration is: RP's Metadata from its Entity Configuration

The federation's policy for RPs is: Federation's Policy for RPs

The organization's policy for RPs is: Organization's Policy for RPs

After applying the policies above, the metadata for the Entity in question would become: RP's Metadata After Application of Policies

Constraints define criteria applied to Trust Chains, as described in the constraints claim definition in . Constraints are applied to all Entity Statements that are subordinates of the one containing them. A set of constraints can contain the following claims: OPTIONAL. Integer. The maximum number of Entity Statements between this Entity Statement and the last Entity Statement in the Trust Chain. 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 of . Restrictions are defined in terms of permitted or excluded name subtrees. OPTIONAL. An array of strings. Each string is an Entity Type. Entity Type Identifiers defined in this specification can be found in . This constraint restricts what types of Leaf Entities MAY appear beneath the Entity described in this Entity Statement.

The following is a non-normative example of a set of constraints: Example Set of Constraints When an Entity has a constraints claim in its Entity Configuration and issues a Subordinate Statement, then if the same type of constraint, for example a max_path_length, appears in both the Entity Configuration and the Subordinate Statement, the more restrictive of the two MUST take precedence. If a Subordinate Statement contains a constraint specification that is more restrictive than the one in effect, then the more restrictive constraint MUST take effect from here on. If a Subordinate Statement contains a constraint specification that is less restrictive than the one in effect, then it MUST be ignored.

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 Intermediates MAY appear between this Entity and the Leaf Entity. Where it appears, the max_path_length constraint MUST have a value greater than or equal to zero. Not including a max_path_length constraint means that there are no additional constraints apart from those already in effect. Assuming that we have a Trust Chain with four Entity Statements: Entity Configuration of the Leaf Entity (LE) Subordinate Statement by Intermediate 1 (I1) about LE Subordinate Statement by Intermediate 2 (I2) about I1 Subordinate Statement by the Trust Anchor (TA) about I2 Then the Trust Chain fulfills the constraints if, for instance: The TA specifies a max_path_length that is greater than or equal to 2. TA specifies a max_path_length of 2, I2 specifies a max_path_length of 1, and I1 sets no max_path_length constraint. Neither TA nor I2 specifies any max_path_length constraint while I1 sets max_path_length to 0. The Trust Chain does not fulfill the constraints if, for instance, the: TA's Subordinate Statement has set the max_path_length to 1.

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 domain name subtrees. Any name matching a restriction in the excluded claim is invalid regardless of the information appearing in the permitted claim. Domain name constraints are as specified in Section 4.2.1.10 of . As stated there, a domain name constraint MUST be specified as a fully qualified domain name and MAY specify a host or a domain. Examples are "host.example.com" and ".example.com". When the domain name constraint begins with a period, it MAY be expanded with one or more labels. That is, the domain name constraint ".example.com" is satisfied by both host.example.com and my.host.example.com. However, the domain name constraint ".example.com" is not satisfied by "example.com". When the domain name constraint does not begin with a period, it specifies a host.

The allowed_leaf_entity_types constraint specifies what Entity Types are acceptable for Leaf Entities beneath an Entity. If there is no allowed_leaf_entity_types constraint, it means that any Entity Type is allowed.

Per the definition in , Trust Marks are statements of conformance to sets of criteria determined by an accreditation authority. Trust Marks used by this specification are signed JWTs. Entity Statements MAY include Trust Marks, as described in the trust_marks claim definition in . A Trust Mark issuer is a Federation Entity that issues Trust Marks. A Trust Mark owner is an Entity the owns the right to a Trust Mark identifier. Trust Marks are signed by a federation-accredited authority called a Trust Mark issuer. All Trust Mark issuers MUST be represented in the federation by an Entity. The fact that a Trust Mark issuer is accepted by the federation is expressed in the trust_mark_issuers claim of the Trust Anchor's Entity Configuration. The key used by the Trust Mark issuer to sign its Trust Marks MUST be one of the private keys related to its Federation Entity Keys. Note that a federation MAY allow an Entity to self-sign Trust Marks. Trust Mark JWTs MUST be explicitly typed by setting the typ header parameter to trust-mark+jwt. This is done to prevent cross-JWT confusion, per Section 3.11 of .

There will be cases where the owner of a Trust Mark for some reason may not match the Trust Mark issuer due to administrative or technical requirements. Take as an example vehicle inspection. Vehicle inspection is a procedure mandated by national or subnational governments in many countries, in which a vehicle is inspected to ensure that it conforms to regulations governing safety, emissions, or both. The body that mandates the inspections does not perform them; instead, there may be commercial companies performing the inspections, after which they issue the Trust Mark. The fact that a Trust Mark is issued by a Trust Mark issuer that is not the owner of the Trust Mark is expressed by including a delegation claim in the Trust Mark, whose value is a signed JWT. The format of the delegation JWT is described below. If the Federation Operator knows that Trust Marks with a certain Trust Mark identifier may legitimately be issued by Trust Mark issuers that are not the owner of the Trust Mark identifier, then information about the owner and the Trust Mark identifier MUST be included in the trust_mark_owners claim in the Trust Anchor's Entity Configuration.

These claims are used in Trust Marks: REQUIRED. String. Issuer of the Trust Mark. REQUIRED. String. Entity this Trust Mark applies to. The id (identifier) claim provides an identifier for a property of the JWT. Like the sub (subject) claim, the processing of this claim is generally application specific. The id value is a case-sensitive string containing a StringOrURI value. Use of this claim in JWTs is OPTIONAL. This claim is REQUIRED when the JWT is a Trust Mark. In this case, its value is the identifier of the Trust Mark. The Trust Mark identifier MUST be collision-resistant across multiple federations. It is RECOMMENDED that the identifier value is built using a URL that uniquely identifies the federation or the trust framework within which it was issued. This is required to prevent Trust Marks issued in different federations from having colliding identifiers. REQUIRED. Number. Time when this Trust Mark was issued. This is expressed as Seconds Since the Epoch, per . OPTIONAL. String. URL that references a logo for the Entity. The value of this field MUST point to a valid image file. OPTIONAL. Number. Time when this Trust Mark is no longer valid. This is expressed as Seconds Since the Epoch, per . If not present, it means that the Trust Mark does not expire. The ref (reference) claim provides a URI property for the JWT. Like the sub (subject) claim, the processing of this claim is generally application specific. The ref value is a case-sensitive string containing a URI value. Use of this claim in JWTs is OPTIONAL. When the JWT is a Trust Mark, its value is a URL that refers to human-readable information connected to the issuance of the Trust Mark. Use of this claim in Trust Marks is OPTIONAL. The delegation claim expresses a delegation relationship. Like the sub (subject) claim, the processing of this claim is generally application specific. The delegation value is a case-sensitive string. Use of this claim in JWTs is OPTIONAL. When the JWT is a Trust Mark, its value is a signed JWT containing information about a delegation of the right to issue Trust Marks with a particular identifier created by the owner of the Trust Mark that identifies the delegated issuer of the Trust Mark. Use of this claim in Trust Marks is OPTIONAL. Other claims MAY be defined and used in conjunction with the claims above. The recommendations for claim naming in Section 5.1.2 of OpenID Connect Core 1.0 apply.

Trust Mark delegation JWTs MUST be explicitly typed, by setting the typ header parameter to trust-mark-delegation+jwt. This prevents cross-JWT confusion, per Section 3.11 of . The delegation claims: REQUIRED. String. The owner of the Trust Mark. REQUIRED. String. The Entity this delegation applies to. REQUIRED. String. The identifier of the Trust Mark. REQUIRED. Number. Time when this delegation was issued. This is expressed as Seconds Since the Epoch, per . OPTIONAL. Number. Time when this delegation stops being valid. This is expressed as Seconds Since the Epoch, per . If not present, it means that the delegation does not expire and is valid until revoked. OPTIONAL. String. URL that points to human-readable information connected to the Trust Mark.

An Entity SHOULD NOT try to validate a Trust Mark until it knows which Trust Anchor it is using. To validate a Trust Mark issuer, follow the procedure defined in . To validate a Trust Mark: Check the signature of the signed JWT and verify that it has not expired. If the Trust Mark identifier appears in the trust_mark_owners claim, verify that the Trust Mark contains a delegation claim. The set of claims for the the Trust Mark identifier in the trust_mark_owners value are used in the following way: The signature of the delegation JWT MUST verify with a key from jwks claim. The issuer of the delegation JWT MUST match the sub value in this set of claims. Using the Trust Mark issuer status endpoint to verify that the Trust Mark is still active is described in . 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 Entities. A Trust Anchor uses the trust_mark_issuers claim in its Entity Configuration to publish this information. If a Trust Mark issuer is issuing Trust Marks on behalf of a Trust Mark owner, then the Trust Anchor MUST publish the connection between the Trust Mark identifier and the corresponding Trust Mark issuer in the trust_mark_issuers claim. This signifies that the Trust Anchor has validated the Trust Mark owner and that the Trust Mark owner has delegated the right to issue Trust Marks with a designated Trust Mark identifier to a specified Trust Mark issuer. Trust Marks that are not recognized within a federation SHOULD be ignored when evaluating trust in the Entity that presented them. Such Trust Marks can appear for various reasons, such as the Entity Configuration including Trust Marks associated with another federation, or Trust Marks intended for specific purposes or Entity audiences. An Entity MAY choose, at its own discretion, to utilize Trust Marks presented to it that are not recognized within the federation, and where the accreditation authority is established by some out-of-band mechanism.

A non-normative example of a trust_marks claim in the JWT Claims Set for an Entity Configuration is: Trust Mark in an Entity Configuration JWT Claims Set

An example of a decoded Trust Mark payload issued to an RP, attesting to conformance to a national public service profile: Trust Mark for a National Profile

An example of a decoded Trust Mark payload issued to an RP, attesting to its conformance to the rules for data management of underage users: Trust Mark Issued to an RP

An example of a decoded Trust Mark payload attesting a stipulation of an agreement between two organization's Entities: Trust Mark Attesting to an Agreement Between Entities

An example of a decoded Trust Mark payload asserting conformance to a security profile: Trust Mark Asserting Conformance to a Security Profile

An example of a decoded self-signed Trust Mark: Self-Signed Trust Mark

An example of a third-party accreditation authority for Trust Marks: Third-Party Accreditation Authority for Trust Marks

The Entity Configuration of every participant 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 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 ). 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 Entity Configuration to the OP during client registration, the OP has everything it needs from the RP.

An Entity Configuration document MUST be queried using an HTTP GET request at the previously specified path.

In this example, the requesting party would make the following request to the Entity https://openid.sunet.se to obtain its Entity Configuration: Request for Entity Configuration

The response is an Entity Configuration, as described in . If the Entity is an Intermediate Entity or a Trust Anchor, the response MUST contain metadata for a federation Entity (federation_entity). A successful response MUST use the HTTP status code 200 with the content type application/entity-statement+jwt, to make it clear that the response contains an Entity Statement. In case of an error, the response is as defined in .

The following is a non-normative example JWT Claims Set for a response from an Intermediate Entity: Entity Configuration Response JWT Claims Set

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

Fetching Entity Statements is performed to collect Entity Statements one by one to assemble Trust Chains. All Entities that publish Subordinate Statements MUST expose a fetch endpoint. The fetch endpoint location is published in the Entity's metadata for the federation_entity Entity Type in its federation_fetch_endpoint parameter. 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 is, the subject of the Entity Statement.

The request MUST be an HTTP request using the GET method to a fetch endpoint with the following query string parameters, encoded in application/x-www-form-urlencoded format. The request is made to the fetch endpoint of the specified issuer. REQUIRED. The Entity Identifier of the issuer from which the Entity Statement is 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 the Entity Statement must come from. OPTIONAL. The Entity Identifier of the subject for which the Entity Statement is being requested. If this parameter is omitted, it is considered to be the same as the issuer and indicates a request for a self-signed Entity Configuration.

The following is a non-normative example of an HTTP GET request for a Subordinate Statement from edugain.org about https://openid.sunet.se: API Request for a Subordinate Statement

A successful response MUST use the HTTP status code 200 with the content type application/entity-statement+jwt, to make it clear that the response contains an Entity Statement. If it is a negative response, it will be a JSON object and the content type MUST be application/json. See more about error responses in .

The following is a non-normative example of the JWT Claims Set for a fetch response: Fetch Response JWT Claims Set

An Entity MAY use a resolve endpoint to fetch resolved metadata and Trust Marks for an Entity. The resolver fetches the subject's Entity Configuration, assembles a Trust Chain that starts with the subject's Entity Configuration and ends with the specified Trust Anchor's Entity Configuration, verifies the Trust Chain, and then applies all the policies present in the Trust Chain to the subject's metadata. The resolver MUST verify that all present Trust Marks with identifiers recognized within the Federation are active. The response set MUST include only verified Trust Marks. The resolve endpoint location is published in the Entity's metadata for the federation_entity Entity Type in its federation_resolve_endpoint parameter.

The request MUST be an HTTP request using the GET method to a resolve endpoint with the following query string parameters, encoded in application/x-www-form-urlencoded format. REQUIRED. The Entity Identifier of the Entity whose resolved data is requested. REQUIRED. The Trust Anchor that the resolve endpoint MUST use when resolving the metadata. The value is an Entity identifier. OPTIONAL. A specific Entity Type to resolve. Its value is an Entity Type Identifier, as specified in . If this parameter is not present, then all Entity Types are returned.

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

A successful response MUST use the HTTP status code 200 with the content type application/resolve-response+jwt, containing resolved metadata and verified Trust Marks. The response is a signed JWT, explicitly typed by setting the typ header parameter to resolve-response+jwt. This is done to prevent cross-JWT confusion (see , section 3.11). The resolve response JWT MAY return the Trust Chain from the subject to the Trust Anchor in its trust_chain parameter, sorted as shown in . The key used by the resolver to sign the response MUST be one of its Federation Entity Keys. The resolve response MAY also return the Trust Chain from its issuer to the Trust Anchor in the trust_chain JWS header parameter, as specified in . When this is present, the Trust Anchor in the Trust Chain MUST match the Trust Anchor requested in the related request in the anchor parameter. An issuer that provides its Trust Chain within the resolve response makes it evident that it is part of the same federation as the subject of the response. Thus, when the Trust Chains of both the issuer and the subject are available and the Federation Historical Keys endpoint is provided by the Trust Anchor, the resolve response becomes a long-lived attestation; it can be always verified, even when the Federation Keys change in the future. The response SHOULD contain the aud claim only if the requesting client is authenticated. These are the resolve response Claims: REQUIRED. String. Entity Identifier of the issuer of the resolve response. REQUIRED. String. Entity Identifier of the subject of the resolve response. REQUIRED. Number. Time when this resolution was issued. This is expressed as Seconds Since the Epoch, as defined in . REQUIRED. Number. Time when this resolution is no longer valid. This is expressed as Seconds Since the Epoch, as defined in . It MUST correspond to the exp value of the Trust Chain from which the resolve response was derived. REQUIRED. JSON object containing the resolved subject metadata, according to the requested type and expressed in the metadata format defined in . OPTIONAL. Array of objects, each representing a Trust Mark, as defined in . OPTIONAL. Array containing the sequence of Entity Statements that compose the Trust Chain, starting with the subject and ending with the selected Trust Anchor, sorted as shown in . 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. If the response is negative, the response is as defined in .

The following is a non-normative example of the JWT Claims Set for a resolve response: Resolve Response JWT Claims Set

The basic assumption of this specification is that an Entity should have direct trust in noone except the Trust Anchor and its own capabilities. However, Entities may establish a kind of transistive trust in other Entities. For example, the Trust Anchor states who its Subordinates are and Entities may choose to trust them. If a party uses the resolve service of another Entity to obtain federation data, it is trusting the resolver to perform validation of the cryptographically protected metadata correctly and to provide it with authentic results.

The listing endpoint is exposed by Federation Entities acting as a Trust Anchor, Intermediate, or Trust Mark issuer. The endpoint lists the Subordinates about which the Trust Anchor or Intermediate issues Entity Statements. As a Trust Mark issuer, the endpoint MAY list the Subordinates for which Trust Marks have been issued and are still valid, if the issuer exposing this endpoint supports Trust Mark filtering, as defined below. In both cases, the list contained in the result MAY be a very large list. The list endpoint location is published in the Entity's metadata for the federation_entity Entity Type in its federation_list_endpoint parameter.

The following example shows a tree of Entities belonging to the same federation including the Trust Anchor, Intermediate Entities, and Leaf Entities, discovered and collected through the Subordinate listing endpoints: Tree of Entities in a Federation Collected through Subordinate Listing Endpoints

The request MUST be an HTTP request using the GET method to a list endpoint with the following query parameters, encoded in application/x-www-form-urlencoded format. OPTIONAL. If the responder knows the Entity Type of all its Subordinates, the result MUST be filtered accordingly. If the responder does not support this feature it MUST use the HTTP status code 400 and the content type application/json, with the error code unsupported_parameter. OPTIONAL. Boolean. If the parameter trust_marked is present and set to true, the result contains only the Subordinates for which at least one Trust Mark have been issued and is still valid. If the responder does not support this feature it MUST use the HTTP status code 400 and set the content type to application/json, with the error code unsupported_parameter. OPTIONAL. If the responder has issued Trust Marks with the specified Trust Mark identifier, the list in the response MUST be filtered to only the Subordinates for which that Trust Mark identifier has been issued and is still valid. If the responder does not support this feature it MUST use the HTTP status code 400 and set the content type to application/json, with the error code unsupported_parameter. OPTIONAL. Boolean. If the parameter intermediate is present and set to true, then if the responder knows whether its Subordinates are Intermediates or not, the result MUST be filtered accordingly. If the responder does not support this feature it MUST use the HTTP status code 400 and the content type application/json, with the error code unsupported_parameter.

The following is a non-normative example of an HTTP GET request for a list of Subordinates: Subordinate Listing Request

A successful response MUST use the HTTP status code 200 with the content type application/json, containing a JSON array with the known Entity Identifiers. If the response is negative, the response is as defined in .

The following is a non-normative example of a response containing the Subordinate Entities: Subordinate Listing Response

This enables an Entity to check whether a Trust Mark is still active or not. The query MUST be sent to the Trust Mark issuer. The Trust Mark status endpoint location is published in the Entity's metadata for the federation_entity Entity Type in its federation_trust_mark_status_endpoint parameter.

The request MUST be an HTTP request using the POST method and the https scheme to a Trust Mark status endpoint with the following parameters, encoded in application/x-www-form-urlencoded format. OPTIONAL. The Entity Identifier of the Entity to which the Trust Mark was issued. OPTIONAL. Identifier of the Trust Mark. OPTIONAL. Number. Time when the Trust Mark was issued. If iat is not specified and the Trust Mark issuer has issued several Trust Marks with the identifier specified in the request to the Entity identified by sub, the most recent one is assumed. OPTIONAL. The whole Trust Mark. If trust_mark is used, then sub and trust_mark_id are not needed. If trust_mark is not used, then sub and trust_mark_id are REQUIRED.

The following is a non-normative example of a Trust Mark status request using sub and trust_mark_id: Trust Mark Status Request

A successful response MUST use the HTTP status code 200 with the content type application/json, to make it clear that the response contains a JSON object containing the data below: REQUIRED. Boolean. Whether the Trust Mark is active or not. If the response is negative, the response is as defined in .

The following is a non-normative example of a Trust Mark status response: Trust Mark Status Response

The Trust Marked Entities listing endpoint is exposed by Trust Mark issuers and lists all the Entities for which Trust Marks have been issued and are still valid. The Trust Marked Entities listing endpoint location is published in the Entity's metadata for the federation_entity Entity Type in its federation_trust_mark_list_endpoint parameter.

The request MUST be an HTTP request using the GET method to a list endpoint with the following query parameters, encoded in application/x-www-form-urlencoded format. REQUIRED. If the responder has issued Trust Marks with the specified Trust Mark identifier, the list obtained in the response MUST be filtered to only the Entities for which that Trust Mark identifier has been issued and is still valid. OPTIONAL. The Entity Identifier of the Entity to which the Trust Mark was issued. The list obtained in the response MUST be filtered to only the Entity matching this value.

The following is a non-normative example of an HTTP GET request for a list of Trust Marked Entities: Trust Marked Entities Listing Request

A successful response MUST use the HTTP status code 200 with the content type application/json, containing a JSON array with Entity Identifiers. If the response is negative, the response is as defined in .

The following is a non-normative example of a response, containing the Trust Marked Entities: Trust Marked Entities Listing Response

The Trust Mark endpoint is protected endpoint exposed by Trust Mark issuers to provide the Trust Marks to their owners. The Trust Mark endpoint is published in the federation_entity metadata using the federation_trust_mark_endpoint claim.

The HTTP request MUST use the POST method with the following query parameters, encoded in application/x-www-form-urlencoded format. REQUIRED. Trust Mark identifier. REQUIRED. Signed JWT using the private key of the subject's Federation Entity Key. The payload of the signed JWT MUST contain the following parameters: REQUIRED. The Entity Identifier of the subject. REQUIRED. This MUST the same as iss. REQUIRED. URL of the federation Trust Mark endpoint. 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 for details regarding date/times in general and UTC in particular. Expiration time on or after which the JWT 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. REQUIRED. It MUST be set to urn:ietf:params:oauth:client-assertion-type:jwt-bearer.

The following is a non-normative example of an HTTP request for a specific Trust Mark ID and a specific Entity: Trust Mark Request

A successful response MUST use the HTTP status code 200 with the content type application/trust-mark+jwt, containing the Trust Mark. If the specified Entity doesn't have the specified Trust Mark, the response is negative and MUST use the HTTP status code 404.

The following is a non-normative example of a response, containing the Trust Mark for the specified Entity (with line wraps within values for display purposes only): Trust Mark Response

Each Federation Entity MAY publish its previously used Federation Entity Keys at the historical keys endpoint defined in . The purpose of this endpoint is to provide the list of keys previously used by the Federation Entity to provide non-repudiation of statements signed by it after key rotation. This endpoint also discloses the reason for the retraction of the keys and whether they were expired or revoked, including the reason for the revocation. Note that an expired key can be later additionally marked as revoked, to indicate a key compromise event discovered after the expiration of the key. The publishing of the historical keys guarantees that Trust Chains will remain verifiable and usable as inputs to trust decisions after the key expiration, unless the key becomes revoked for a security reason.

The request MUST be an HTTP request using the GET method to the federation historical keys endpoint.

The following is a non-normative example of a historical keys request: Federation Historical Keys Request

A successful response MUST use the HTTP status code 200 with the content type application/jwk-set+jwt. The response is a signed JWT with the JWK Set as its payload. The JWT is explicitly typed by setting the typ header parameter to jwk-set+jwt. This is done to prevent cross-JWT confusion (see , section 3.11). The response JWT contains the following claims: REQUIRED. String. The Entity's Entity Identifier. REQUIRED. Number. Time when the signed JWT was issued, using the time format defined for the iat claim in . REQUIRED. Array of JSON objects containing the signing keys for the Entity in JWK format. Every JWK in the keys claim includes the following claims: REQUIRED. Parameter used to match a specific key. It is RECOMMENDED that the Key ID be the JWK Thumbprint of the key using the SHA-256 hash function. OPTIONAL. Time when the key was issued, using the time format defined for the iat claim in . REQUIRED. Expiration time, using the time format defined for the exp claim in , after which the key MUST NOT be considered to be valid. OPTIONAL. JSON object that contains the properties of the revocation, as defined below: REQUIRED. Time when the key was revoked or must be considered revoked, using the time format defined for the iat claim in . REQUIRED. Human-readable value that identifies the reason for the key revocation, as defined in Section 5.3.1 of . REQUIRED. Integer that identifies the reason for the key revocation, as defined in Section 5.3.1 of . Other members of the revoked object MAY be defined and used.

The following is a non-normative example of the JWT Claims Set for a historical keys response: Federation Historical Keys Response JWT Claims Set

The Federation Historical Keys endpoint solves the problem of verifying historical Trust Chains when the Federation Entity Keys have changed, either due to expiration or revocation. The Federation Historical Keys endpoint publishes the list of public keys used in the past by the Entity. These keys are needed to verify Trust Chains created in the past with Entity keys no longer published in the Entity's Entity Configuration. The Federation Historical Keys endpoint response contains a signed JWT that attests to all the expired and revoked Entity keys. On the basis of the attributes contained in the Entity Statements that form a Trust Chain, it MAY be also possible to verify the non-federation public keys used in the past by Leaf Entities for signature operations for OpenID Connect requests and responses. For example, an Entity Statement issued for a Leaf MAY also include the jwks claim for the Leaf's Entity Types, in its metadata or metadata_policy claims. A simple example: In the following Trust Chain, the Federation Intermediate attests to the Leaf's OpenID Connect RP jwks in the Subordinate Statement issued about the Leaf. The result is a Trust Chain that contains the Leaf's OpenID Connect RP JWK Set, needed to verify historical signature on Request Objects and any other signed JWT issued by the Leaf as an RP. This example Trust Chain contains: an Entity Configuration about the RP published by the RP, a Subordinate Statement about the RP published by Organization A, with the claim jwks contained in metadata or metadata_policy attesting the Leaf's OpenID Connect RP jwks, and a Subordinate Statement about Organization A published by Federation F.

If the request was malformed or an error occurred during the processing of the request, the response body SHOULD be a JSON object with the content type application/json. In compliance with , the following standardized error format SHOULD be used: REQUIRED. One of the following error codes SHOULD be used. The request is incomplete or does not comply with current specifications. The HTTP response status code SHOULD be 400 (Bad Request). The Client can not be authorized or is not a valid participant of the federation. The HTTP response status code SHOULD be 401 (Unauthorized). The requested Entity Identifier is "not found". The HTTP response status code SHOULD be 404 (Not Found). The server encountered an unexpected condition that prevented it from fulfilling the request. The HTTP response status code SHOULD be one in the 5xx range, like 500 (Internal Server Error). The server hosting the federation endpoint is currently unable to handle the request due to a temporary overloading or maintenance. The HTTP response status code SHOULD be 503 (Service Unavailable). The server does not support the requested parameter. Other error codes in the IANA "OAuth Extensions Error Registry" MAY also be used. REQUIRED. A human-readable short text describing the error.

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

An Entity (Party A) that wants to establish trust with another Entity (Party B) MUST have Party B's Entity Identifier and a list of Entity Identifiers of Trust Anchors and their public signing keys. Party A will first have to fetch sufficient Entity Statements to establish at least one chain of trust from Party B to one or more of the Trust Anchors. After that, Party A MUST validate the Trust Chains independently, and if there are multiple valid Trust Chains and if the application demands it, choose one to use.

Depending on the circumstances, Party A MAY be handed Party B'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 based on the Entity Identifier of Party B. 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 fetch endpoints, as defined in , are used to fetch Entity Statements about the Intermediates and Party B. Note: Federation participants SHOULD NOT attempt to fetch Entity Statements they already have obtained during this process to prevent loops. 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 Party B to at least one of the trusted Trust Anchors, then the list will be empty and there is no way of establishing trust in Party B's information. How Party A deals with this is out of scope for this specification.

The following sequence diagram represents the interactions between the RP, the OP, and the Trust Anchor during a trust evaluation made by the OP about the RP. Relating this to the the preceeding description, in this diagram, Party A is the OP and Party B is the RP. Resolving Trust Chain and Metadata from the Perspective of an OP | | | | | | | Evaluates authority_hints | | |-------------------------- | | | | | | |<------------------------- | | | | | | Entity Configuration Request | | |--------------------------------------->| | | | | | Entity Configuration Response | | |<---------------------------------------| | | | | | Obtains Fetch endpoint | | |----------------------- | | | | | | |<---------------------- | | | | | | Request Subordinate Statement about RP | | |--------------------------------------->| | | | | | Subordinate Statement about RP | | |<---------------------------------------| | | | | | Evaluates the Trust Chain | | |-------------------------- | | | | | | |<------------------------- | | | | | | Applies Metadata Policies | | |-------------------------- | | | | | | |<------------------------- | | | | | | Derives the RP's final Metadata | | |---------------------------------- | | | | | | |<--------------------------------- | ]]>

As described in , a Trust Chain consists of an ordered list of Entity Statements. So whichever way Party A 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. Let us refer to the Entity Statements in the Trust Chain as ES[j], where j = 0,...,i, with 0 being the index of the first Entity Statement and i being the zero-based index of the last. To validate the Trust Chain, the following MUST be done: For each Entity Statement ES[j], where j = 0,..,i: Verify that the statement contains all the required claims. Verify that iat has a value in the past. Verify that exp has a value that is in the future. For ES[0] (the Leaf's Entity Configuration), verify that iss == sub. For ES[0], verify that its signature validates with a public key in ES[0]["jwks"]. For each j = 0,...,i-1, verify that ES[j]["iss"] == ES[j+1]["sub"]. For each j = 0,...,i-1, verify the signature of ES[j] with a public key in ES[j+1]["jwks"]. For ES[i] (the Trust Anchor's Entity Configuration), verify that the issuer matches the Entity Identifier of the Trust Anchor. For ES[i], verify that its signature validates with a public key of the Trust Anchor. Verifying the signature is a much more expensive operation than verifying the correctness of the statement and the timestamps. An implementer MAY therefore choose not to verify the signatures until all the other checks have been done. Federation participants MAY cache Entity Statements and signature verification results until they expire, per .

If multiple valid Trust Chains are found, Party A will need to decide on which one to use. One simple rule would be to prefer a shorter chain over a longer one. Federation participants MAY follow other rules according to local policy.

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

If the federation topology is being updated, for example when a set of Leaf Entities is moved to a new Intermediate Entity, the Trust Chain validation may fail in a transient manner. Retrying after a period of time may resolve the situation.

This specification facilitates smoothly updating metadata and public keys. As described in , each Trust Chain has an expiration time. Federation participants MUST support refreshing a Trust Chain when it expires. How often a participant reevaluates the Trust Chain depends on how quickly it wants to find out that something has changed.

If a Leaf Entity publishes its public keys in its metadata using jwks, the expiration time of its Entity Configuration can be used to control how often the receiving Entity needs to fetch an updated set of public keys.

A Trust Anchor MUST publish an Entity Configuration about itself. The Trust Anchor SHOULD set an expiration time on its Entity Configuration, such that federation participants will re-fetch it at reasonable intervals. When a Trust Anchor rolls over its signing keys, it needs to: Add the new keys to the jwks representing the Trust Anchor's signing keys in its Entity Configuration. Keep signing the Entity Configuration and the Entity Statements using the old keys for a long enough time period to allow all Subordinates to have obtained the new keys. Switch to signing with the new keys. 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.

It is RECOMMENDED that Federation Operators provide a means of retrieving the public keys for the Trust Anchors it administers that is independent of those Trust Anchors' Entity Configurations. This is intended to provide redundancy in the eventuality of the compromise of the Web PKI infrastructure underlying retrieval of public keys from Entity Configurations. The keys retrieved via the independent mechanism specified by the Federation Operator SHOULD be compared to those retrieved via the Trust Anchor's Entity Configuration. 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.

Since the participants in federations are expected to check the Trust Chain on a regular frequent basis, this specification does not define a revocation process. Specific federations MAY make a different choice and will then have to define their own revocation process.

This section describes how the mechanisms defined in this specification are used to establish trust between an RP and an OP that have no explicit configuration or registration between them 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 use one or the other 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 uses the procedure described in .

Automatic Registration enables an RP to make Authentication Requests without a prior registration step with the OP. The OP resolves the RP's Entity Configuration from the Client ID in the Authentication Request, following the process defined in . Automatic Registration has the following characteristics: In all interactions with the OP, the RP employs its Entity Identifier as the Client ID. The OP retrieves the RP's Entity Configuration from the URL derived from the Entity Identifier, as described in . Since there is no registration step prior to the Authentication Request, the RP MUST NOT be supplied with a Client Secret. Instead, the Automatic Registration model requires the RP to use asymmetric cryptography to authenticate its requests. The OP MUST publish that it supports one or more request authentication methods using the openid_provider metadata parameter request_authentication_methods_supported. An OP that supports Automatic Registration MUST include the automatic keyword in its client_registration_types_supported metadata parameter.

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

When 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 parameters are used in the Request Object: REQUIRED. The Audience (aud) value MUST be or include the OP's Issuer Identifier URL. REQUIRED. The iss value MUST be the Client Identifier. MUST NOT be present. This, together with the value of aud, prevent reuse of the statement for private_key_jwt client authentication. REQUIRED. JWT ID. A unique identifier for the JWT, which can be used to prevent reuse of the Request Object. A Request Object MUST only be used once, unless conditions for reuse were negotiated between the parties; any such negotiation is beyond the scope of this specification. REQUIRED. Number. Expiration time after which the JWT MUST NOT be accepted for processing. OPTIONAL. Number. Time when the JWT was issued. OPTIONAL. Array containing the sequence of Entity Statements that comprise the Trust Chain between the RP making the request and the selected Trust Anchor, sorted as in . When the RP and the OP are part of the same federation, the RP MUST select a Trust Anchor that it has in common with the OP; otherwise, the RP is free to select the Trust Anchor to use.

When the trust_chain JWS header parameter is used in conjunction with the trust_chain request parameter, both contents MUST be identical. Otherwise the request MUST be rejected. When the trust_chain JWS header parameter or the trust_chain request parameter are used in the Authorization Request Object, the Relying Party informs the OP of the sequence of Entity Statements that proves the trust relationship between it and the selected Trust Anchor. Due to the large size of a Trust Chain, it may be necessary to use the HTTP POST method, request_uri, or a Pushed Authorization Request for the request.

The following is a non-normative example of the JWT Claims Set in a Request Object: Request Object JWT Claims Set

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

When the OP receives an incoming Authentication Request, the OP supports OpenID 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 resolve the Trust Chains related to the requestor. An RP MAY present a Trust Chain related to itself to the OP in the Request Object using the trust_chain request parameter defined in or the trust_chain JWS header parameter defined in . If the OP does not have a valid registration for the RP or its registration has expired, the OP MAY use the received Trust Chain as a hint for which path to take from the Leaf Entity to the Trust Anchor. The OP MAY evaluate the statements in the trust_chain to make its Federation Entity Discovery procedure more efficient, especially if the RP contains multiple authority hints in its Entity Configuration. If the OP already has a valid registration for the RP, it MAY use the received Trust Chain to update the RP's registration. Whenever the OP uses a Trust Chain submitted by an RP, the OP MUST fully verify it, including every Entity Statement contained in it. A Trust Chain may be relied upon by the OP because it has validated all of its statements. This is true whether these statements are retrieved from their URLs or whether they are provided via the trust_chain request parameter or the JWS header parameter in the Request Object. If the RP does not include the trust_chain request parameter or the JWS header parameter in the Request Object, or the OP does not support this feature, it then MUST validate the possible Trust Chains, starting with the RP's Entity Configuration, as described in , and resolve the RP metadata with Entity Type openid_relying_party. The OP SHOULD furthermore verify that the resolved metadata of the RP complies with the client metadata specification 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 Authentication Request by verifying the signature of the Request Object using the key material the client published in its metadata for the openid_relying_party Entity Type.

Pushed Authorization Requests provide an interoperable way to push a Request Object directly to the AS in exchange for a request_uri. There are four applicable authentication methods: JWT Client authentication, as described for private_key_jwt in Section 9 of OpenID Connect Core 1.0. mTLS using self-signed certificates, as described in Section 2.2 of . In this case, the self-signed certificate MUST be present as the value of an x5c claim for one key in the JWK Set describing the RP's keys. mTLS using public key infrastructure (PKI), as described in Section 2.1 of . A Request Object, as described in and . Note that if mTLS is used, TLS client authentication MUST be configured and, in the case of self-signed certificates, the server must omit the certificate chain validation.

Using the example above, a Pushed Authorization Request could look like this: Pushed Authorization Request

The requirements specified in also apply to Pushed Authorization Requests. Once the OP has the RP's metadata, it can verify the client using the keys published for the openid_relying_party Entity Type Identifier. This is where it diverges, depending on which client authentication method was used. If this method is used, then the OP verifies 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 valid. 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. If mTLS is used with a self-signed certificate, then the certificate MUST be present as the value of an x5c claim for a key in the JWK Set containing the RP's keys.

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 in understanding what is wrong. In addition to the error codes contained in the IANA "OAuth Extensions Error Registry" registry , this specification also defines the following error codes: No trusted Trust Anchor could be found. Trust chain validation failed.

The following is a non-normative example authentication error response: Authentication Error Response

Automatic Registration is designed to be able to be employed for use cases beyond OpenID Federation. For instance, ecosystems using OpenID Connect, OAuth 2.0, and FAPI can utilize Automatic Registration.

Using this method, the RP establishes its client registration with the OP by means of a dedicated registration request, similar to , but instead of its metadata, the RP submits its Entity Configuration or an entire Trust Chain. When the Explicit Registration is completed, the RP can proceed to make regular OpenID authentication requests to the OP. An OP that supports Explicit Registration MUST include the explicit keyword in its client_registration_types_supported metadata parameter and set the federation_registration_endpoint metadata parameter to the URL at which it receives Explicit Registration requests. Explicit Registration is suitable for implementation on top of the OpenID Connect Dynamic Client Registration 1.0 endpoint of an OP deployment. In contrast to Automatic Registration, it enables an OP to provision a Client ID, a client secret and metadata parameters. An example of an Explicit Registration is provided in .

The RP performs Explicit Client Registration as follows: Once the RP has determined a set of Trust Anchors it has in common with the OP, it chooses the subset it wants to proceed with. This may be a single Trust Anchor, or it can also be more than one. The RP MUST perform a Trust Chain and metadata resolution for the OP, as specified in . If the resolution is not successful the RP MUST abort the request. Using this subset of Trust Anchors, the RP chooses a set of authority_hints from the hints that are available to it. Each hint MUST, when used as a starting point for Trust Chain collection, lead to at least one of the Trust Anchors in the subset. If the RP has more than one Trust Anchor in common with the OP it MUST select a subset of Trust Anchors to proceed with. The subset may be as small as a single Trust Anchor, or include multiple ones. The RP will then construct its Entity Configuration, where the metadata statement chosen is influenced by the OP's metadata and where the authority_hints included are picked by the process described above. From its immediate Superior authorities, the RP MUST select one or more authority_hints so that every hint, when used as the starting point for a Trust Chain collection, leads to at least one of the Trust Anchors in the subset selected above. The RP MAY include its Entity Configuration in a Trust Chain regarding itself. In that case, the Registration Request will contain an array with the sequence of Entity Statements that compose the Trust Chain between the RP that is making the request and the selected Trust Anchor. The RP MUST include its metadata in its Entity Configuration and use the authority_hints selected above. The RP SHOULD select its metadata parameters to comply with the resolved OP metadata and thus ensure a successful registration with the OP. Note that if the submitted RP metadata is not compliant with the metadata of the OP, the OP may choose to modify it in order to make it compliant rather than reject the request with an error response. The Entity Configuration, or the entire Trust Chain, is sent, using HTTP POST, to the federation_registration_endpoint. The Entity Configuration or Trust Chain is the entire POST body. The RP MUST sign its Entity Configuration with a current Federation Entity Key in its possession. The content type of the Registration Request MUST be application/entity-statement+jwt when it contains only the Entity Configuration of the requestor. Otherwise, when it contains the Trust Chain, the content type of the Registration Request MUST be application/trust-chain+json. The RP MAY include its Entity Configuration in a Trust Chain that leads to the RP. In this case, the registration request will contain an array consisting of the sequence of statements that make up the Trust Chain between the RP and the Trust Anchor the RP selected. The following Entity Configuration claims are specified for use in Explicit Registration requests. Their full descriptions are in . REQUIRED. Its value MUST be the Entity Identifier of the RP. REQUIRED. Its value MUST be the Entity Identifier of the RP. REQUIRED. REQUIRED. REQUIRED. REQUIRED. Its value MUST be the Entity Identifier of the OP. REQUIRED. REQUIRED. It MUST contain the RP metadata under the openid_relying_party Entity Type Identifier. OPTIONAL. OPTIONAL. The request MUST be an HTTP request to the federation_registration_endpoint of the OP, using the POST method. When the RP submits an Entity Configuration the content type of the request MUST be application/entity-statement+jwt. When the RP submits a Trust Chain the content type MUST be application/trust-chain+json.

The OP processes the request as follows: Upon receiving a registration request, the OP MUST inspect the content type to determine whether it contains an Entity Configuration or an entire Trust Chain. If the request contains an Entity Configuration the OP MUST use it to complete the Federation Entity Discovery by collecting and evaluating the Trust Chains that start with the authority_hints in the Entity Configuration of the RP. After validating at least one Trust Chain, the OP MUST verify the signature of the received Entity Configuration. If the OP finds more than one acceptable Trust Chain, it MUST choose one Trust Anchor from those chains as the one to proceed with. If the request contains a Trust Chain, the OP MAY evaluate the statements in the Trust Chain to save the HTTP calls that are necessary to perform the Federation Entity Discovery, especially if the RP included more than one authority hint in its Entity Configuration. Otherwise the OP MUST extract the RP Entity Configuration from the Trust Chain and proceed according to Step 2, as if only an Entity Configuration was received. At this point, if the OP finds that it already has an existing client registration for the requesting RP, then that registration MUST be invalidated. The precise time of the invalidation is at the OP's discretion, as the OP may want to ensure the completion of concurrent OpenID authentication requests initiated by the RP while the registration request is being processed. The OP MAY retain client credentials and key material from the invalidated registration in order to verify past RP signatures and perform other cryptographic operations on past RP data. The OP will now use the RP metadata to create a client registration compliant with its own OP metadata and other applicable policies. The OP MAY provision the RP with a client_id other than the RP's Entity Identifier. This enables Explicit Registration to be implemented on top of the OpenID Connect Dynamic Client Registration 1.0 endpoint of an OP. If the RP is provisioned with a client_secret it MUST NOT expire before the expiration of the registration Entity Statement that will be returned to the RP. The OP SHOULD NOT provision the RP with a registration_access_token and a registration_client_uri because the expected way for the RP to update its registration is to make a new Explicit Registration request. If the RP is provisioned with a registration_access_token for some purpose, for example to let it independently check its registered metadata, the token MUST NOT allow modification of the registration. The OP MAY modify the received RP metadata, for example by substituting an invalid or unsupported parameter, in order to make it compliant with its own OP metadata and other policies. If the OP does not accept the RP metadata or is unwilling to modify it in order to make it compliant, it MUST return a client registration error response, with an appropriate error, such as invalid_client_metadata or invalid_redirect_uri, as specified in Section 3.3 of . The OP MUST assign an expiration time to the created registration. This time MUST NOT exceed the expiration time of the Trust Chain that the OP selected to process the request. If the OP created a client registration for the RP, it MUST then construct a success response in the form of an Entity Statement. The OP MUST set the trust_anchor_id claim of the Entity Statement to the Trust Anchor it selected to process the request. The authority_hints claim MUST be set to the OP's immediate Superior authority in the selected Trust Chain. The OP MUST set the exp claim to the expiration time of the created registration. The OP MAY choose to invalidate the registration before that, as explained in . The OP MUST express the client registration it created for the RP by means of the metadata claim, by placing the metadata parameters under the openid_relying_party Entity Type Identifier. The parameters MUST include the client_id that was provisioned for the RP. If the RP was provisioned with credentials, for example a client_secret, these MUST be included as well. The OP SHOULD include metadata parameters that have a default value, for example token_endpoint_auth_method which has a default value of client_secret_basic, in order to simplify the processing of the response by the RP. The OP MUST sign the registration Entity Statement with a current Federation Entity Key in its possession. The following Entity Statement claims are specified for use in Explicit Registration responses. REQUIRED. Its value MUST be the Entity Identifier of the OP. See for the full specification. REQUIRED. Its value MUST be the Entity Identifier of the RP. See for the full specification. REQUIRED. See for the full specification. REQUIRED. See for the full specification. REQUIRED. It MUST be a verbatim copy of the jwks of the received RP Entity Configuration. This MUST not be confused with the identically named RP metadata parameter. See for the full specification. REQUIRED. Its value MUST be the Entity Identifier of the RP. See for the full specification. This claim is specific to Explicit Registration responses and is not a general Entity Statement claim. REQUIRED. Its value MUST be the Entity Identifier of the Trust Anchor that the OP selected to process the Explicit Registration request. This claim is specific to Explicit Registration responses and is not a general Entity Statement claim. REQUIRED. It MUST be a single-element array, whose value references the immediate Superior authority of the OP in the Trust Chain that the OP selected to process the request. See for the full specification. REQUIRED. It MUST contain the registered RP metadata under the openid_relying_party Entity Type Identifier. See for the full specification. OPTIONAL. See for the full specification. A successful response MUST have an HTTP status code 200 and the content type application/entity-statement+jwt. For a client registration error, the response is as defined in and MAY use errors defined in Section 3.3 of and Section 3.2.2 of .

If the response indicates success, the RP MUST verify that its content is a valid Entity Statement and issued by the OP. The RP MUST ensure the signing Federation Entity Key used by the OP is present in the jwks claim of the Subordinate Statement issued by the OP's immediate Superior authority in a Trust Chain that the RP successfully resolved for the OP when it prepared the Explicit Registration request. The RP MUST verify that the trust_anchor_id represents one of its own Trust Anchors. The RP MUST verify that at least one of the authority_hints it specified in the Explicit Registration request leads to the Trust Anchor that the OP set in the trust_anchor_id claim. The RP MUST ensure that the metadata it was registered with at the OP complies with the Trust Chain openid_relying_party policies, which Trust Chain is resolved using the trust_anchor_id and authority_hints claims of the received registration Entity Statement. The RP SHOULD perform this check by applying the resolved policies to the metadata as specified in , or utilize another equivalent method. If the received registration Entity Statement does not pass the above checks, the RP MUST reject it. The RP MAY choose to retry the Explicit Registration request in order to work around a transient exception, for example due to a recent change of Entity metadata or metadata policy causing temporary misalignment of metadata.

An RP can utilize the exp claim of the registration Entity Statement to devise a suitable strategy for renewing its client registration. RP implementers should note that if the OP expiration of the client_id coincides with an OAuth 2.0 flow that was just initiated by the RP, this may cause OpenID Connect authentication requests, token requests, or UserInfo requests to suddenly fail. Renewing the RP registration prior to its expiration can prevent such errors from occurring and ensure the end-user experience is not disrupted. An OP MAY invalidate a client registration before the expiration that is indicated in the registration Entity Statement for the RP. An example reason could be the OP leaving the federation that was used to register the RP.

The validity of an Automatic or Explicit Registration at an OP MUST NOT exceed the lifetime of the Trust Chain the OP used to create the registration. An OP MAY choose to expire the registration at some earlier time, or choose to perform additional periodic reevaluations of the Trust Chain for the registered RP before the Trust Chain reaches its expiration time. Similarly, an RP that obtained an Automatic or Explicit Registration MUST NOT use it past the expiration of the Trust Chain the RP used to establish trust in the OP. For an RP using Automatic Registration, the trust in the OP MUST be successfully reevaluated before continuing to make requests to the OP. For an RP using Explicit Registration, the RP MUST successfully renew its registration. An RP MAY choose to perform additional periodic reevaluations of the Trust Chain for the OP before the Trust Chain reaches its expiration time.

The primary differences between Automatic Registration and Explicit Registration are: With Automatic Registration, there is no registration step prior to the Authentication Request, whereas with Explicit Registration, there is. (OpenID Connect Dynamic Client Registration 1.0 and OAuth 2.0 Dynamic Client Registration also employ a prior registration step.) With Automatic Registration, the Client ID value is the RP's Entity Identifier and is supplied to the OP by the RP, whereas with Explicit Registration, a Client ID is assigned by the OP and supplied to the RP. Instead of using a Client Secret to authenticate the client, with Automatic Registration, the client is authenticated by means of the RP proving that it controls a private key corresponding to one of its Entity Configuration's public keys.

Both Automatic and Explicit Client Registration support the submission of the Trust Chain embedded in the Request, calculated by the requestor and related to itself. This enables the following benefits in a federation: It solves the problem of OPs using RP metadata that has become stale. This stale data may occur when the OP uses cached RP metadata from a Trust Chain that has not reached its expiration time yet. The RP MAY notify the OP that a change has taken place by including the trust_chain header parameter or the trust_chain request parameter in the request, thus letting the OP update its Client Registration and preventing potential temporary faults due to stale metadata. It enables the RP to pass a verifiable hint for which trust path to take to build the Trust Chain. This can reduce the costs of RP Federation Entity Discovery for OPs in complex federations where the RP has multiple Trust Anchors or the Trust Chain resolution may result in dead-ends. It enables direct passing of the Entity Configuration, including any present Trust Marks, thus saving the OP from having to make an HTTP request to the RP /.well-known/openid-federation endpoint.

Human-readable claim values and claim values that reference human-readable values MAY be represented in multiple languages and scripts. This specification enables such representations in the same manner as defined in Section 5.2 of OpenID Connect Core 1.0. As described in OpenID Connect Core, to specify the languages and scripts, BCP47 language tags are added to member names, delimited by a # character. For example, family_name#ja-Kana-JP expresses the Family Name in Katakana in Japanese, which is commonly used to index and represent the phonetics of the Kanji representation of the same name represented as family_name#ja-Hani-JP. Language tags can be used in any data structures containing or referencing human-readable values, including metadata parameters and Trust Mark parameters. For instance, both organization_name and organization_name#de might occur together in metadata.

Some of the interfaces defined in this specification could be used for Denial-of-Service attacks (DoS), most notably, the resolve endpoint (), Explicit Client Registration (), and Automatic Client Registration () can be exploited as vectors of HTTP propagation attacks. If these endpoints are provided, some adequate defense methods are required, such as those described below and in . A Trust Mark can be statically validated using the public key of its issuer. The static validation of the Trust Marks represents a filter against propagation attacks. An attacker could exploit the Federation Entity Discovery mechanism and use an OpenID Federation to propagate many HTTP requests. For each authorization request crafted by an anonymous client, the OP would produce approximately three HTTP requests to third parties in the absence of Intermediates, and at least five HTTP requests with at least one Intermediate. If an OP does not find at least one valid Trust Mark in an Entity Configuration, it should reject the request and temporary ban the requestor. If client authentication is not demanded at the resolve endpoint then incoming requests should not result in the immediate collection (Federation Entity Discovery process) and evaluation of Trust Chains by default.

One of the fundamental design goals of this protocol is to protect messages end-to-end. This can not be accomplished by demanding TLS since TLS, in lots of cases, is not end-to-end but ends in a HTTPS to HTTP Reverse Proxy. Allowing unsigned error messages therefore opens up an attack vector for someone who wants to run a Denial of Service attack. This is not specific to OpenID Federation but equally valid for other protocols when HTTPS to HTTP reverse proxies are used.

This specification registers the following metadata entries in the IANA "OAuth Authorization Server Metadata" registry established by .

Metadata Name: client_registration_types_supported Metadata Description: Client Registration Types Supported Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification Metadata Name: federation_registration_endpoint Metadata Description: Federation Registration Endpoint Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification Metadata Name: request_authentication_methods_supported Metadata Description: Authentication request authentication methods supported Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification Metadata Name: request_authentication_signing_alg_values_supported Metadata Description: JSON array containing the JWS signing algorithms supported for the signature on the JWT used to authenticate the request Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification Metadata Name: signed_jwks_uri Metadata Description: URL referencing a signed JWT having this authorization server's JWK Set document as its payload Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification Metadata Name: jwks Metadata Description: JSON Web Key Set document, passed by value Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification Metadata Name: organization_name Metadata Description: Human-readable name representing the organization owning this authorization server Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification Metadata Name: contacts Metadata Description: Array of strings representing ways to contact people responsible for this authorization server, typically email addresses Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification Metadata Name: logo_uri Metadata Description: URL that references a logo for the organization owning this authorization server Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification Metadata Name: homepage_uri Metadata Description: URL of a Web page for the organization owning this authorization server Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification

This specification registers the following client metadata entries in the IANA "OAuth Dynamic Client Registration Metadata" registry established by .

Client Metadata Name: client_registration_types Client Metadata Description: An array of strings specifying the client registration types the RP wants to use Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification Client Metadata Name: signed_jwks_uri Client Metadata Description: URL referencing a signed JWT having the client's JWK Set document as its payload Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification Client Metadata Name: organization_name Client Metadata Description: Human-readable name representing the organization owning this client Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification Metadata Name: homepage_uri Metadata Description: URL of a Web page for the organization owning this client Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification

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

Name: missing_trust_anchor Usage Location: Authorization Request Protocol Extension: OpenID Federation Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Reference: of this specification Name: validation_failed Usage Location: Authorization Request Protocol Extension: OpenID Federation Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Reference: of this specification

This section registers the following media types in the "Media Types" registry in the manner described in .

Type name: application Subtype name: entity-statement+jwt Required parameters: n/a Optional parameters: n/a Encoding considerations: binary; An Entity Statement is a JWT; JWT values are encoded as a series of base64url-encoded values (some of which may be the empty string) separated by period ('.') characters. Security considerations: See of this specification Interoperability considerations: n/a Published specification: this specification Applications that use this media type: Applications that use this specification Fragment identifier considerations: n/a Additional information: Magic number(s): n/a File extension(s): n/a Macintosh file type code(s): n/a Person & email address to contact for further information: Michael B. Jones, michael_b_jones@hotmail.com Intended usage: COMMON Restrictions on usage: none Author: Michael B. Jones, michael_b_jones@hotmail.com Change controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Provisional registration? No Type name: application Subtype name: trust-mark+jwt Required parameters: n/a Optional parameters: n/a Encoding considerations: binary; A Trust Mark is a JWT; JWT values are encoded as a series of base64url-encoded values (some of which may be the empty string) separated by period ('.') characters. Security considerations: See of this specification Interoperability considerations: n/a Published specification: this specification Applications that use this media type: Applications that use this specification Fragment identifier considerations: n/a Additional information: Magic number(s): n/a File extension(s): n/a Macintosh file type code(s): n/a Person & email address to contact for further information: Michael B. Jones, michael_b_jones@hotmail.com Intended usage: COMMON Restrictions on usage: none Author: Michael B. Jones, michael_b_jones@hotmail.com Change controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Provisional registration? No Type name: application Subtype name: resolve-response+jwt Required parameters: n/a Optional parameters: n/a Encoding considerations: binary; An Entity Resolve Response is a signed JWT; JWT values are encoded as a series of base64url-encoded values (some of which may be the empty string) separated by period ('.') characters. Security considerations: See of this specification Interoperability considerations: n/a Published specification: this specification Applications that use this media type: Applications that use this specification Fragment identifier considerations: n/a Additional information: Magic number(s): n/a File extension(s): n/a Macintosh file type code(s): n/a Person & email address to contact for further information: Michael B. Jones, michael_b_jones@hotmail.com Intended usage: COMMON Restrictions on usage: none Author: Michael B. Jones, michael_b_jones@hotmail.com Change controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Provisional registration? No Type name: application Subtype name: trust-chain+json Required parameters: n/a Optional parameters: n/a Encoding considerations: binary; A Trust Chain is a JSON array of JWTs; JWT values are encoded as a series of base64url-encoded values (some of which may be the empty string) separated by period ('.') characters. Security considerations: See of this specification Interoperability considerations: n/a Published specification: this specification Applications that use this media type: Applications that use this specification Fragment identifier considerations: n/a Additional information: Magic number(s): n/a File extension(s): n/a Macintosh file type code(s): n/a Person & email address to contact for further information: Michael B. Jones, michael_b_jones@hotmail.com Intended usage: COMMON Restrictions on usage: none Author: Michael B. Jones, michael_b_jones@hotmail.com Change controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Provisional registration? No Type name: application Subtype name: trust-mark-delegation+jwt Required parameters: n/a Optional parameters: n/a Encoding considerations: binary; A Trust Mark delegation is a signed JWT; JWT values are encoded as a series of base64url-encoded values (some of which may be the empty string) separated by period ('.') characters. Security considerations: See of this specification Interoperability considerations: n/a Published specification: this specification Applications that use this media type: Applications that use this specification Fragment identifier considerations: n/a Additional information: Magic number(s): n/a File extension(s): n/a Macintosh file type code(s): n/a Person & email address to contact for further information: Roland Hedberg, roland@catalogix.se Intended usage: COMMON Restrictions on usage: none Author: Roland Hedberg, roland@catalogix.se Change controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Provisional registration? No

This specification registers the following parameter name in the IANA "OAuth Parameters" registry established by .

Parameter Name: trust_chain Parameter Usage Location: authorization request Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification

This specification registers the following JWS header parameter in the IANA "JSON Web Signature and Encryption Header Parameters" registry established by .

Header Parameter Name: trust_chain Header Parameter Description: OpenID Federation Trust Chain Header Parameter Usage Location: JWS Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification

This specification registers the following claim in the IANA "JSON Web Token Claims" registry established by .

Claim Name: keys Claim Description: Array of JWK values, as defined in RFC 7517 Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): Section of this specification Claim Name: id Claim Description: Identifier Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): Section of this specification Claim Name: ref Claim Description: Reference Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): Section of this specification Claim Name: delegation Claim Description: Delegation Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): Section of this specification

This specification registers the following parameters in the IANA "JSON Web Key Parameters" registry established by .

Parameter Name: iat Parameter Description: Issued At, as defined in RFC 7519 Used with "kty" Value(s): * Parameter Information Class: Public Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification Parameter Name: exp Parameter Description: Expiration Time, as defined in RFC 7519 Used with "kty" Value(s): * Parameter Information Class: Public Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification Parameter Name: revoked Parameter Description: Revoked Key Properties Used with "kty" Value(s): * Parameter Information Class: Public Change Controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification Document(s): of this specification

This specification registers the following well-known URI in the IANA "Well-Known URIs" registry established by .

URI suffix: openid-federation Change controller: OpenID Foundation Artifact Binding Working Group - openid-specs-ab@lists.openid.net Specification document: of this specification Related information: (none)

OpenID Connect Core 1.0 Nomura Research Institute, Ltd. Ping Identity Microsoft Google Salesforce OpenID Connect Discovery 1.0 Nomura Research Institute, Ltd. Ping Identity Microsoft Illumila OpenID Connect Dynamic Client Registration 1.0 Nomura Research Institute, Ltd. Ping Identity Microsoft Financial-grade API Security Profile 1.0 - Part 2: Advanced Nat Consulting Yubico Illumila OAuth Parameters IANA Media Types IANA JSON Object Signing and Encryption (JOSE) IANA JSON Web Token Claims IANA Well-Known URIs IANA

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

The following depicts a federation under the eduGAIN Trust Anchor: Participants Within the eduGAIN Federation 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 to 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.

These are the steps to set up a federation infrastructure: Generation of Trust Anchor signing keys. These MUST be public/private key pairs. Set up a signing service that can sign JWTs/Entity Statements using the Federation Entity Keys. Set up web services that can publish signed Entity Statements, one for the URL corresponding to the federation's Entity Identifier returning an Entity Configuration and the other one providing the fetch endpoint, as described in . Once these requirements have been satisfied, a Federation Operator can add Entities to the federation. Adding an Entity comes down to: Providing the Entity with the federation's Entity Identifier and the public part of the key pairs used by the federation operator for signing Entity Statements. Getting the Entity's Entity Identifier and the JWK Set that the Entity plans to publish in its Entity Configuration. Before the federation operator starts adding Entities, there must be policies 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 consider implementing other policies using the federation policy framework, as described in . With the federation in place, things can start happening.

Federation Entity Discovery is a sequence of steps that starts with the RP fetching the Entity Configuration of the OP Leaf Entity (in this case, https://op.umu.se) using the process defined in . What follows after that is this sequence of steps: Pick out the immediate Superior Entities using the authority hints. Fetch the Entity Configuration for each such Entity. This uses the process defined in . Use the fetch endpoint of each Superior to obtain Subordinate Statements about the Subordinate Entity, per . 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 Subordinate Statements issued by a Superior about its Subordinate are used together with the Entity Configuration issued by the Leaf. The Entity Configurations of Intermediates are not part of the Trust Chain.

The LIGO WIKI RP fetches the Entity Configuration from the OP (op.umu.se) using the process defined in .

The result is this Entity Configuration: Entity Configuration Issued by https://op.umu.se The authority_hints points to the Intermediate Entity https://umu.se. So that is the next step. This Entity Configuration is the first link in the Trust Chain.

The LIGO RP fetches the Entity Configuration from https://umu.se using the process defined in .

The request will look like this: Entity Configuration Issued by https://umu.se

And the GET will return: Entity Configuration JWT Claims Set The only piece of information that is used from this Entity Configuration in this process is the federation_fetch_endpoint, which is used in the next step.

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

The request will look like this: Request Subordinate Statement from https://umu.se about https://op.umu.se

And the result is this: Subordinate Statement Issued by https://umu.se about https://op.umu.se This Subordinate Statement is the second link in the Trust Chain.

The LIGO Wiki RP fetches the Entity Configuration from https://swamid.se using the process defined in .

The request will look like this: Request Entity Configuration from https://swamid.se

And the GET will return: Entity Configuration Issued by https://swamid.se The only piece of information that is used from this Entity Configuration in this process is the federation_fetch_endpoint, which is used in the next step.

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

The request will look like this: Request to https://swamid.se for Subordinate Statement about https://umu.se

And the result is this: Subordinate Statement Issued by https://swamid.se about https://umu.se This Subordinate Statement is the third link in the Trust Chain. If we assume that the issuer of this Subordinate Statement is not in the list of Trust Anchors the LIGO Wiki RP has access to, we have to go one step further.

The RP fetches the Entity Configuration from https://edugain.geant.org using the process defined in .

The request will look like this: Entity Configuration Requested from https://edugain.geant.org

And the GET will return: Entity Configuration issued by https://edugain.geant.org Within the Trust Anchor Entity Configuration, the Relying Party looks for the federation_fetch_endpoint and gets the updated Federation Entity Keys of the Trust Anchor. Each Entity within a Federation may change their Federation Entity Keys, or any other attributes, at any time. See for further details.

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

The request will look like this: Request to https://edugain.geant.org for Subordinate Statement about https://swamid.se

And the result is this: Subordinate Statement issued by https://edugain.geant.org about 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 Subordinate Statement would be the fourth link in the Trust Chain. The Trust Anchor's Entity Configuration MAY also be included in the Trust Chain; in this case, it would the fifth and final link. We now have retrieved all the members of the Trust Chain. Recapping, these Entity Statements were obtained: Entity Configuration for the Leaf Entity https://op.umu.se - the first link in the Trust Chain Entity Configuration for https://umu.se - not included in the Trust Chain Subordinate Statement issued by https://umu.se about https://op.umu.se - the second link in the Trust Chain Entity Configuration for https://swamid.se - not included in the Trust Chain Subordinate Statement issued by https://swamid.se about https://umu.se - the third link in the Trust Chain Entity Configuration for https://edugain.geant.org - optionally, the fifth and last link in the Trust Chain Subordinate Statement issued by https://edugain.geant.org about https://swamid.se - the fourth link in the Trust Chain Using the public keys of the Trust Anchor that the LIGO Wiki RP has been provided within some secure out-of-band way, it can now verify the Trust Chain as described in .

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

Combining the metadata policies from the three Subordinate 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: Final Metadata Derived from Trust Chain by Applying Metadata Policies We have now reached the end of the Provider Discovery process.

As described in , there are two ways that can be used to do client registration: 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. The RP will access the federation_registration_endpoint, which provides the RP's metadata. The OP MAY return a metadata policy that adds restrictions over and above what the Trust Chain already has defined.

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

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: https://edugain.geant.org https://swamid.se The OP starts to resolve metadata for the Client Identifier https://wiki.ligo.org by fetching the Entity Configuration using the process described in . The process is the same as described in and will result in a Trust Chain with the following Entity Statements: Entity Configuration for the Leaf Entity https://wiki.ligo.org Subordinate Statement issued by https://incommon.org about https://wiki.ligo.org Subordinate Statement issued by https://edugain.geant.org about https://incommon.org

Using the public keys of the Trust Anchor that the LIGO Wiki RP has been provided within some secure out-of-band way, it can now verify the Trust Chain as described in . We will not list the complete Entity Statements but only the metadata and metadata_policy parts. There are two metadata policies:

Metadata Policies Related to Multiple Metadata Types

Metadata Policy Related to the RP

Next, combine these and apply them to the metadata for wiki.ligo.org: Combined Metadata with Metadata Policy yet to be applied

The final result is: Final Metadata After Metadata Policy has been Applied Once the Trust Chain and the final Relying Party metadata have been obtained, the OpenID Provider has everything needed to validate the signature of the Request Object in the Authentication Request, using the public keys made available at the signed_jwks_uri endpoint.

Here the LIGO Wiki RP sends an Explicit Registration request to the federation_registration_endpoint of the OP (op.umu.se). The request contains the RP's Entity Configuration.

An example JWT Claims Set for the RP's Entity Configuration is: RP's Entity Configuration JWT Claims Set The OP receives the RP's Entity Configuration and proceeds with the sequence of steps laid out in . The OP successfully resolves the same RP metadata described in . It then registers the RP in compliance with its own OP metadata and returns the result in a registration Entity Statement. Assuming the OP does not support refresh tokens it will register the RP for the authorization_code grant type only. This is reflected in the metadata returned to the RP. The returned metadata also includes the client_id, the client_secret and other parameters that the OP provisioned for the RP.

Here is an example JWT Claims Set of the registration Entity Statement returned by the OP to the RP after successful explicit client registration: JWT Claims Set of Registration Entity Statement Returned by OP to RP after Explicit Client Registration

Copyright (c) 2023 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.

The authors wish to acknowledge the contributions of the following individuals and organizations to this specification: Pasquale Barbaro, Michele D'Amico, Andrii Deinega, Erick Domingues, Heather Flanagan, Joseph Heenan, Samuel Gulliksson, Takahiko Kawasaki, Torsten Lodderstedt, Francesco Marino, Roberto Polli, Jouke Roorda, Nat Sakimura, Mischa Sallé, Stefan Santesson, Marcos Sanz, Peter Brand, Michael Schwartz, Giada Sciarretta, Amir Sharif, Kristina Yasuda, and the JRA3T3 task force of GEANT4-2.

[[ To be removed from the final specification ]] -32 Tightened OpenID Connect Client Registration section. Tightened appendix examples. Fixed #2075: Trust Mark endpoint for the provisioning of the Trust Marks. Fixed #2085: Trust Marked Entities Listing, added sub urlquery parameter. Made fetch issuer unambiguous by making the iss parameter REQUIRED. Introduced the term "Subordinate Statement" and applied it throughout the specification. Also consistently use the term "registration Entity Statement" for Explicit Client Registration results. Clarified where Entity Statement claims can and cannot occur. Renamed policy_language_crit to metadata_policy_crit. Fixed #2093: Numbered the list defining the order policy operators are applied in. -31 Fixed #2068: Clarifications that authority_hints must only appear in Leaf and Intermediate Entity Configurations. Fixed #2062: Verified that metadata examples are consistent with the specification. Fixed #1724: Numbered figures by adding captions to them. Fixed #2033: Described the advantage of having the Trust Anchor host the resolve endpoint. Fixed #1659: Described use of the trust_chain header parameter in resolve responses. Addressed #2060: A concrete order must be specified for the application of all metadata policy operators. Addressed #2069: Metadata parameters with null value must be treated as error when applying metadata policies. Fixed #2034: Other use cases of Federation Automatic Registration, FAPI included. Moved the definitions of organization_name, contacts, logo_uri, policy_uri, and homepage_uri from the federation_entity Entity Type definition to the set of metadata parameters applicable to all Entity Types. Clarified the role of the Trust Anchor's Entity Configuration in Trust Chains. Fixed #1751: Provided guidance to prevent stuck clients. Fixed #2071: Removed most of the Claims Languages and Scripts text duplicating that in OpenID Connect Core. Tightened descriptions of constraints and Trust Marks. Tightened descriptions of Federation Endpoints. Fixed #2080: Defined federation_historical_keys_endpoint metadata parameter. Fixed #2081: Renamed trust_marks_owners to trust_mark_owners and renamed trust_marks_issuers to trust_mark_issuers. Fixed #2079: Renamed the id Trust Mark status request parameter to trust_mark_id to match the parameter names used in Subordinate listing requests and Trust Marked entities listing requests. -30 Clarifies that when the metadata policy combination process encounters an error, such as being unable to merge two operators, the policy combination MUST be considered invalid. Applications and protocols using Entity Statements MAY specify additional claims. Addressed #1655: The definitions of aud and trust_anchor_id are moved to the Explicit Client Registration section. Fixed #1957: Explicit Registration: Clarifies OP processing of Explicit Registration requests with a trust chain. Addressed #1655: Explicit Registration: Simplifies the expression of the registered RP metadata - the metadata policy mechanism is no longer used. Addressed #1655: Explicit Registration: An RP MUST always verify the metadata it was registered with. The standard Trust Chain resolution and application of metadata_policy is the SHOULD method, but RPs are free to utilize other methods yielding the same result, e.g. by calling a helper web endpoint provided by the Trust Anchor. Addressed #1655: Explicit Registration: Exact specification of the EC claims used in requests and the ES claims used in responses; normative language where necessary to remove ambiguities and guarantee interop. Explicit Registration: The exp (expiration) of the response ES must be the time when the OP is going to expire the client registration. Intended to inform the RP when its registration is going to expire so that it can re-register in advance and prevent stuck end-users if the registration expires in the middle of an OAuth flow. Explicit Registration: Replaces the hard requirement that OPs must periodically ensure that a valid Trust Chain for the RP can be established with non-normative text common to both Automatic and Explicit Registration. The Trust Chain expiration MUST be the primary method for OPs to control the validity of registrations. Resolving Trust Chain and Metadata: Adds a subsection describing the possibility of transient Trust Chain validation errors when the topology of a federation is updated and suggests a retry strategy. Updated contributor affiliations. Fixed #1947: Added source_endpoint as OPTIONAL in Entity Statement JWS. Historical keys response: iat is OPTIONAL. Added text on Trust Mark delegation. Fixed #2041: Added normative language mandating the https scheme and any optional port and path, for all the Entity Identifiers and the federation endpoints. Cite draft-ietf-oauth-resource-metadata. Fixed #2002: Added sequence diagrams and representations of the general architecture and the Trust Chain. Fixed #2061: Clarified that the constraints claim may only appear in statements issued by authorities. Fixed #2062: Require metadata statements for all Entity Type Identifiers that apply to an Entity. Replaced duplicative term "metadata type" with "Entity Type" and defined the term "Entity Type Identifier". Added section headings to the Metadata section to more cleanly separate Entity Type Identifiers from Metadata Extensions. Fixed #2064: Prohibited the use of null as a metadata value. Rewrote request_authentication_methods_supported description. Registered keys JWT claim and iat, exp, and revoked JWK parameters. Fixed #1727: Changed specification name from "OpenID Connect Federation" to "OpenID Federation". -29 Fixed #1921: brand new JWS Header parameter, trust_chain. Fixed #1879, #1881, #1883, #1885: introductionary text, metadata section, editorials. -28 Fixed #1823: Metadata policy clarification text on essential term and sub_set, one_of, superset_of. Listing endpoint - added the parameters trust_marked and trust_mark_id. Historical keys endpoint, references to rfc7517 and use of claim keys, correction in the normative text. Added the endpoint federation_trust_mark_list_endpoint for Trust Mark issuers. -27 Fixed #1756: Clarified that the authority_hints in the Entity Statement of an explicit registration response is single-valued. Added text about the usage of metadata besides metadata_policy. Fixed #1745 #1746: Non-normative example of Trust Mark status endpoint. Fixed #1747: Client Registration Response content-type set to application/entity-statement+jwt. Fixed #1740: Metadata policy example for OpenID Connect, removed scopes. Fixed #1755: clarification on the key to be used for Federation operations. The "essential" policy operator can be used in conjunction with one_of, subset_of, superset_of to make their presence optional. Fixed #1779: Entity Type as defined term. Added Sequence Diagram representing a Federation Entity Discovery and metadata evaluation. Fixed #1757: Federation Historical Keys endpoint support for revocation status. Endpoint enabled for all the Federation Entities. Fixed #1803: Subordinate is a defined term and other small editorial changes after Heather's revision. Added Cryptographic Trust Mechanism description. Fixed #1660: Clarified that Explicit Registration uses no parameters and added Explicit Registration example. Fixed #1782: Reference protected resource metadata draft. Fixed #1809: Replaced use of "trust issuers" terminology. Fixed #1661: Tightened descriptions of metadata standards used. Fixed #1801: Better described function of "essential" metadata operator. -26 Applied editorial improvements by Heather Flanagan. -25 Fixed #1684: disambiguation on the role federation_entity. Fixed #1703: Unsigned error response. Fixed #1693: Trust mark status endpoint HTTP method changed to POST. Fixed #1681: RS256 is not mandatory anymore for federation operations signatures. Fixed #1701: trust_chain parameter with PAR and redirect_uri. Fixed #1695: entity_type url paramenter for Listing endpoint. Fixed #1712: federation_entity claims: organization_name is recommended, logo_uri is added. Fixed #1702: removal of metadata type trust_mark_issuer, federation_status_endpoint moved in the federation_entity metadata and renamed to federation_trust_mark_status_endpoint. Fixed #1716: Clarified how to retrieve the RP's Entity Configuration when using Automatic Registration. Fixed #1656: Introductionary text review. -24 Fixed #1654: Text cleanup on how and who publishes the Entity Configuration. Relaxed JWK Set representations: jwks, signed_jwks_uri and jwks_uri can coexist in the same Metadata for interoperability purposes across different Federations. Fixed #1641: Federation Historical Keys endpoint. Fixed #1673: added resolve endpoint JWT claims. Fixed #1663: clarifications on the http status codes returning from /.well-known/openid-federation. Fixed #1667: serialization format for federation endpoint made explicit. Fixed #1662: ID Token section removed. Fixed #1680: removal of the claim operation in Generic Errors. Fixed #1669: error types in the section Generic Error Response. Added Vladimir Dzhuvinov as an editor. -23 Text on max_path_length Fixed #1634: Trust Chain explanatory text. Federation Entity Discovery as defined term. Fixed #1645: Federation Entity Keys as defined term. Fixed #1633: Explaination text about who signs the Trust Mark and how. Fixed #1650: typo in signed_jws_uri and jwks metadata claims. -22 Rewritten text about metadata processing when doing Explicit Client Registration. Fixed #1581: OP metadata claims enabled for AS. Fixed #1594: self-issued trust_chain in the Authorization Request. Fixed #1583: metadata policy one_of operator, explanatory text for multiple values. Fixed #1584: Stated that domain name constraints are as specified in Section 4.2.1.10 of . Added more text on considerations when using the resolve endpoint. Removal of aud parameter in the fetch endpoint request. General rewording with the terms Leaf Entity and Entity Configuration. Fixed #1588: Explicitly described the differences between Automatic and Explicit Registration. Fixed #1606: Described situation in which the requirement for signed requests with Automatic Registration could be relaxed. Fixed #1629: authz Request Object, audience explanatory text. Fixed #1630: Resolve endpoint response content type. Fixed #1608: submission of the Trust Chain in the Explicit Client Registration Request. -21 Fixed #1547: Metadata section restructured. Fixed #1548: request_authentication_signing_alg_values_supported clarification text about the usage of private_key_jwt and request_object. Added a new constraint, allowed_leaf_entity_types. Resolve endpoint: Removed iss paramenter in the request and specified the usage of the aud claim in the response. Fixed #1513: request_authentication_methods_supported according to IANA OAuth 2.0 AS metadata registered names. Fixed #1527: Defined the Trust Mark term and added non-normative examples. Added Security Considerations regarding the role of the Trust Marks. Editorial review, normative language, and typos. Fixed #1535: Removed the sub claim from the non-normative example of the Authorization Request Object. Fixed #1528: Added Claims Languages and Scripts section. Fixed #1456: Added language about space-delimited string parameters from RFC 6749. -20 Updated example for Resolve endpoint. Recommended that Key IDs be the JWK Thumbprint of the key. Fixed #1502 - Corrected usage of id_token_signed_response_alg. Fixed #1506 - Referenced RFC 9126 for Pushed Authorization Requests. Added Giuseppe De Marco as an editor and removed Samuel Gulliksson as an editor. Fixed #1508 - Editorial review. Fixed #1505 - Defined that signed_jwks_uri is preferred over jwks_uri and jwks. Fixed #1514 - Corrected RP metadata examples to use id_token_signed_response_alg. Fixed #1512 - Registered the error codes missing_trust_anchor and validation_failed. Also registered the OP Metadata parameters organization_name, request_authentication_methods_supported, request_authentication_signing_alg_values_supported, signed_jwks_uri, and jwks and the RP Metadata parameters client_registration_types (which was previously misregistered as client_registration_type), organization_name, and signed_jwks_uri. Defined the term Federation Operator and described redundant retrieval of Trust Anchor keys. Fixed #1519 - Corrected instances of client_registration_type to client_registration_types_supported. Fixed #1520 - Renamed federation_api_endpoint to federation_fetch_endpoint. Fixed #1521 - Changed swamid.sunet.se to swamid.se in examples. Fixed #1523 - Added request_parameter_supported to examples. Capitalized defined terms. -19 Fixed #1497 - Removed trust_mark claim from federation entity metadata. Fixed #1446 - Added trust_chain and removed is_leaf. Fixed #1479 - Added jwks claim in OP metadata. Fixed #1477 - Added request_authentication_methods_supported. Fixed #1474 - Added the request_authentication_signing_alg_values_supported OP metadata parameter. Rewrote trust_marks definition. -18 Added the jwks claim name for OP Metadata. Moved from a federation API to separate endpoints per operation. Added descriptions of the list, resolve and status federation endpoints. Registered the client_registration_types_supported and federation_registration_endpoint authorization server metadata parameters. Registered the client_registration_type dynamic client registration parameter. Registered and used the application/entity-statement+jwt media type. Registered the application/trust-mark+jwt media type. Trust marks: the claim mark has been renamed to logo_uri. New federation endpoint: Resolve Entity Statement. New federation endpoint: Trust Mark Status. Federation API, Fetch: iss parameter is optional. Trust Marks: added non-normative examples. Expanded Section 8.1: Included Entity configurations. Fixed #1373 - More clearly defined the term Entity Statement, both in the Terminology section and in the Entity Statement section. -17 Addressed many working group review comments. Changes included adding the Overall Architecture section, the trust_marks_issuers claim, and the Setting Up a Federation section. -16 Added Security Considerations section on Denial-of-Service attacks. -15 Added signed_jwks_uri, which had been lost somewhere along the road. -14 Rewrote the federation policy section. What previously was referred to as client authentication in connection with automatic client registration is now changed to be request authentication. Made a distinction between parameters and claims. Corrected the description of the intended behavior when essential is absent. -13 Added 'trust_marks' as a parameter in the Entity Statement. An RP's self-signed Entity Statement MUST have the OP's issuer identifier as the value of 'aud'. Added RS256 as default signing algorithm for Entity Statements. Specified that the value of 'aud' in the Entity Statement use in automatic client registration MUST have the ASs authorization endpoint URL as value. Also, the 'sub' claim MUST NOT be present. Separating the usage of merge and combine as proposed by Vladimir Dzhuvinov in Bitbucket issue #1157. An RP doing only explicit client registration are not required to publish and support a /.well-known/openid-federation. Every key in a JWK Set in an Entity Statement MUST have a kid. -12 Made JWK Set OPTIONAL in an Entity Statement returned by OP as response of an explicit client registration Renamed Entity type to client registration type. Added more text describing client_registration_auth_methods_supported. Made "Processing the Authentication Request" into two separate sections: one for Authentication Request and one for Pushed Authorization Request. Added example of URLs to some examples in the appendix. Changed the automatic client registration example in the appendix to use Request Object instead of a client_assertion. -11 Added section on Trust Marks. Clarified private_key_jwt usage in the authentication request. Fixed Bitbucket issues #1150 and #1155 by Vladimir Dzhuvinov. Fixed some examples to make them syntactically correct. -10 Incorporated additional review feedback from Marcos Sanz. The primary change was moving constraints to their own section of the Entity Statement. -09 Incorporated review feedback from Marcos Sanz. Major changes were as follows. Separated Entity configuration discovery from operations provided by the federation API. Defined new authentication error codes. Also incorporated review feedback from Michael B. Jones. -08 Incorporated review feedback from Michael B. Jones. Major changes were as follows. Deleted sub_is_leaf Entity Statement since it was redundant. Added client_registration_type RP registration metadata value and client_registration_types_supported OP metadata value. Deleted openid_discovery metadata type identifier since its purpose is already served by openid_provider. Entity identifier paths are now included when using the Federation API, enabling use in multi-tenant deployments sharing a common domain name. Renamed sub_is_leaf to is_leaf in the Entity Listings Request operation parameters. Added crit and policy_language_crit, enabling control over which Entity Statement and policy language extensions MUST be understood and processed. Renamed openid_client to openid_relying_party. Renamed oauth_service to oauth_authorization_server. Renamed implicit registration to automatic registration to avoid naming confusion with the implicit grant type. Renamed op to operation to avoid naming confusion with the use of "OP" as an acronym for "OpenID Provider". Renamed url to uri in several identifiers. Restored Open Issues appendix. Corrected document formatting issues. -07 Split metadata into metadata and metadata_policy Updated example -06 Some rewrites Added example of explicit client registration -05 A major rewrite. -04 Changed client metadata names scopes to rp_scopes and claims to rp_claims. Added Open Issues appendix. Added additional references. Editorial improvements. Added standard Notices section, which is present in all OpenID specifications.