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Identity providers

Open Payments requires any authorization server that issues interactive grants to be integrated with an IdP.

An interactive grant is a grant that requires explicit user interaction/consent from the resource owner before an access token can be issued. In Open Payments, an interactive grant must be issued before an outgoing payment resource can be created.

After the interactive grant request is initiated and the authorization server sets the session, the server provides the client with the IdP URI in which to redirect the user.

The following diagram illustrates the flow of an interactive grant.

sequenceDiagram autonumber
    Client ->>Authorization server (AS): Sends interactive grant request
    Authorization server (AS)-->>Client: 200 returns interact redirect uri and continue uri
    Client ->>Authorization server (AS): Navigates to interact redirect uri
    Authorization server (AS)->>Authorization server (AS): Starts interaction and sets session
    Authorization server (AS)-->>Client: 302 temporary redirect to identity provider 
uri with grant info in query string
    Client ->>Identity provider (IdP): Redirects to identity provider
    Identity provider (IdP)->>Identity provider (IdP): Resource owner (e.g. client user) 
accepts interaction
    Identity provider (IdP)->>Authorization server (AS): Sends interaction choice
    Authorization server (AS) -->>Identity provider (IdP): 202 choice accepted
    Identity provider (IdP)->>Authorization server (AS): Requests to finish interaction
    Authorization server (AS)->>Authorization server (AS): Ends session
    Authorization server (AS)-->>Identity provider (IdP): 302 temporary redirect to finish url 
(defined in initial grant request) 
secured with unique hash and 
interact_ref in query string
    Identity provider (IdP)->>Client instance: Follows redirect
    Client->>Client: Verifies hash
    Client->>Authorization server (AS): Sends grant continuation request with 
interact_ref in body to continue uri
    Authorization server (AS)->>Client: 200 returns grant access token