The implicit grant is similar to the authorization code grant with two distinct differences.
It is intended to be used for user-agent-based clients (e.g. single page web apps) that can’t keep a client secret because all of the application code and storage is easily accessible.
Secondly instead of the authorization server returning an authorization code which is exchanged for an access token, the authorization server returns an access token.
The client will redirect the user to the authorization server with the following parameters in the query string:
response_type with the value token
client_id with the client identifier
redirect_uri with the client redirect URI. This parameter is optional, but if not sent the user will be redirected to a pre-registered redirect URI.
scope a space delimited list of scopes
state with a CSRF token. This parameter is optional but highly recommended. You should store the value of the CSRF token in the user’s session to be validated when they return.
All of these parameters will be validated by the authorization server.
The user will then be asked to login to the authorization server and approve the client.
If the user approves the client they will be redirected back to the authorization server with the following parameters in the query string:
token_type with the value Bearer
expires_in with an integer representing the TTL of the access token
access_token a JWT signed with the authorization server’s private key
state with the state parameter sent in the original request. You should compare this value with the value stored in the user’s session to ensure the authorization code obtained is in response to requests made by this client rather than another client application.
**Note** this grant does not return a refresh token.
Wherever you initialize your objects, initialize a new instance of the authorization server and bind the storage interfaces and authorization code grant:
Please note: These examples here demonstrate usage with the Slim Framework; Slim is not a requirement to use this library, you just need something that generates PSR7-compatible HTTP requests and responses.
The client will redirect the user to an authorization endpoint.