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Behaviour: Authorization Servers

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Keys

Authorization Server Public Keys

Authorization Servers MUST provide all public keys used for signing tokens at a non-protected endpoint, the location of which will correspond with the value of the “jwks_uri” property at the server metadata endpoint, for example /jwks.

The format of the keys MUST be the JSON Web Key (JWK) format described in Section 4 of RFC 8414 and MUST form a JSON Web Key Set (JWKS) described in Section 5 of RFC 8414. Authorization Servers MAY present more than one key within a JSON Web Key Set, with each key being an entry in the “keys” array.

Where multiple Authorization Servers exist in a single deployment they SHOULD each host a copy of each other’s public keys in order to prevent Resource Servers having to make requests to every instance.

Changing Keys

When transitioning to a new public/private key pair used for signing tokens an Authorization Server SHOULD provide both the old and new public key at the public key endpoint until all tokens that may be verified by the old public key would have expired. However, if a private key is known to be compromised, the Authorization Server MUST remove it from the public key endpoint immediately.

Authorization Servers SHOULD provide new public keys at the public key endpoint for at least 2 hours before issuing tokens signed by the corresponding private key to allow time for clients to cache the new public key.

Client Registration

Authorization Servers MUST NOT grant tokens to unregistered clients.

Authorization Servers SHOULD support a manual mechanism for registering clients (e.g an HTML web form) allowing the client type and redirect URIs to be provided.

Clients and Authorization Servers MUST provide for the OAuth 2.0 Dynamic Client Registration Protocol RFC 7591 to allow dynamic registration of clients to the Authorization Server to allow for zero-configuration setup.

Authorization Servers MAY additionally support the OAuth 2.0 Dynamic Client Registration Management Protocol RFC 7592 to allow clients to check and modify existing registrations.

Authorization Servers MUST support authentication of dynamic client registrations via one or more of the mechanisms below, which are listed in order of preference:

Where dynamic client registrations request the client_credentials grant type they MUST be subject to one of the explicit authentication steps listed above. Authorization Servers MAY be configured to grant implicit authentication where only the authorization_code grant type is requested.

After successful registration, an Authorization Server MUST generate a Client ID and, in the case of a confidential client, a client secret. The Client ID MUST be at least 20 characters long, to help prevent brute-force attacks, and MUST be unique to each client. Public clients MUST NOT be issued with a client secret, and Authorization Servers MUST NOT accept client credentials as valid authentication for a public client, however the Authorization Server MAY issue a client secret or other credentials for a specific installation of a native application client on a specific device, in line with Section 10.1 of RFC 6749.

Client credentials MUST be returned to the client in the response of a successful dynamic client registration. The method by which client credentials are passed to a client during manual registration is beyond the scope of this specification.

AMWA NMOS Specifications MAY specify additional registration parameters where they require them. Where clients and Authorization Servers that support OAuth 2.0 are used with these specifications they SHALL use these parameters in all OAuth 2.0 registration mechanisms they support.

Client Authentication

Authorization Servers MUST provide support client authentication at the token and revocation endpoints using the following methods. Additional methods MAY also be supported.

The security considerations outlined in Section 10.1 of RFC 6749 SHOULD be abided by with regards to client authentication.

Client Deregistration

Authorization Servers SHOULD support deregistration of clients in the case of a compromised client. The means by which this client deregistration occurs is beyond the scope of this specification.

Responding to Token Requests

Refer to Token Requests for information on supported OAuth 2.0 grants, requesting Access Tokens and refreshing and revoking tokens.

Audit Requirements

Authorization Servers MUST securely provide a log of each authorization and client registration which is performed, including initial token generation and token refreshes. Logs MUST include an accurate timestamp and an identifier for the user who authorized the action. Logs MUST NOT contain sensitive information such as secrets.

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