authorization-code-grant-with-pkce.md

Authorization Code Grant with Proof Key for Code Exchange (PKCE)

The authorization code protocol is part of OAuth 2.0 (defined in OAuth 2.0 RFC 7636). It involves the exchange of an authorization code for a token. This is the recommended authorization code flow in the OAuth 2.1 draft.

Principle of function

---
title: Authorization Code Grant with Proof Key for Code Exchange (PKCE)
---
sequenceDiagram
  actor User
  User->>App: Click sign-in link (1)

  activate App
  Note right of App: Generate code_verifier and<br/>code_challenge
  App->>Identity Provider: Authorization code request & code_challenge (2)
  deactivate App

  Identity Provider-->>User: Redirect to login/authorization prompt (3)
  User-->>Identity Provider: Authenticate (3)
  Identity Provider->>App: Authorization code (3)

  activate App
  App->>Identity Provider: Authorization code & code verifier (4)
  Note right of Identity Provider: Validate authorization code &<br/>code_verifier
  Identity Provider->>App: Access token and ID token (4)
  deactivate App

  App->>Your API: Request protected data with access token (5)

Loading

1. The user clicks sign-in within the application.
2. signinRedirect() or signinPopup() must be used to start the flow.
3. The identity provider authenticates the user and stores the code_challenge and redirects the user back to the application with an authorization code.
4. signinCallback() handles this callback by sending this authorization code and code_verifier to the identity provider and receiving in return the access token and ID token.
5. The access token is now accessible via getUser()?.access_token and inserted into the requests to your protected API.