OAuth Integration Guide

How third-party apps integrate with the Brain OAuth 2.0 server: register a client, obtain user consent, exchange an authorization code for tokens, and call userinfo.

Try the in-app playground Open API reference Manage OAuth apps

Overview

This server implements the OAuth 2.0 authorization code grant (RFC 6749) for confidential and public clients (PKCE required for public). Access tokens are issued by Brain; this service handles authorization, token exchange, and userinfo proxying.

Authorization code flow

Create an app in the developer console and register redirect_uri values (HTTPS required except localhost).
Redirect the user to GET /oauth/authorize with client_id, redirect_uri, response_type=code; public clients must include PKCE parameters.
After sign-in and consent, the browser returns to redirect_uri with ?code=...&state=....
Your backend calls POST /oauth/token with the code to obtain access_token (and optional refresh_token).
Call GET /userinfo with Bearer access_token to load the user profile.

Endpoints

Method	Path	Role	Notes
GET	/oauth/authorize	Authorize (browser)	Consent UI; unauthenticated users are sent to login then returned here.
POST	/oauth/token	Token (server)	grant_type=authorization_code or refresh_token; client auth via Basic or form body.
GET	/userinfo	Userinfo (server)	Requires Authorization: Bearer; returns sub, email, name, and related claims.

Authorization request

Required: response_type=code, client_id, redirect_uri (must match a registered URI). Optional: scope, state; public clients require code_challenge and code_challenge_method=S256.

GET /oauth/authorize?response_type=code
  &client_id=YOUR_CLIENT_ID
  &redirect_uri=https%3A%2F%2Fapp.example%2Fcallback
  &scope=openid%20profile
  &state=RANDOM_STATE
  &code_challenge=CHALLENGE
  &code_challenge_method=S256

Token exchange

Exchange authorization code

POST /oauth/token
Content-Type: application/x-www-form-urlencoded

grant_type=authorization_code
&code=AUTH_CODE
&redirect_uri=https%3A%2F%2Fapp.example%2Fcallback
&client_id=YOUR_CLIENT_ID
&client_secret=YOUR_CLIENT_SECRET
&code_verifier=VERIFIER

Refresh token

POST /oauth/token
Content-Type: application/x-www-form-urlencoded

grant_type=refresh_token
&refresh_token=REFRESH_TOKEN
&client_id=YOUR_CLIENT_ID
&client_secret=YOUR_CLIENT_SECRET

// 200 OK { "access_token": "...", "token_type": "Bearer", "expires_in": 3600, "refresh_token": "...", "scope": "openid profile" }

PKCE (public clients)

Generate code_verifier before authorize, pass its S256 digest as code_challenge, then send code_verifier when exchanging the code. Confidential clients may omit PKCE.

Userinfo

Success returns JSON with sub (user id), email, name, and optional roles. Invalid or expired tokens yield 401 with error=invalid_token.

GET /userinfo
Authorization: Bearer ACCESS_TOKEN

Error responses

Authorization errors redirect with error and error_description query params; token and userinfo errors are JSON (e.g. invalid_request, invalid_grant, invalid_client, invalid_token).