belgie-oauth-server 0.19.2

OAuth 2.1 authorization server for Belgie

Belgie OAuth Server

[!WARNING] OAuthServer.adapter is required. Use a persistent adapter such as belgie.alchemy.oauth_server.OAuthServerAdapter so clients, authorization state, authorization codes, access tokens, refresh tokens, and consents survive process restarts.

Belgie OAuth Server is Belgie's OAuth 2.1 and OpenID Connect provider package, with a fixed /oauth2/* route layout and Pythonic naming.

Installation

uv add belgie-oauth-server

What It Provides

• Fixed /oauth2/* routes for authorize, token, register, introspect, revoke, userinfo, and end-session.
• OAuth and OIDC discovery metadata under /.well-known/oauth-authorization-server and /.well-known/openid-configuration.
• Client CRUD and consent CRUD RPC routes, including server-only /admin/oauth2/create-client and /admin/oauth2/update-client for restricted client fields.
• PKCE enforcement, pairwise subject identifiers, refresh-token rotation, prompt-aware login and consent flows, and dynamic client registration.
• Custom access-token claims, id-token claims, userinfo claims, and token response fields with reserved-field protections for standard OAuth/OIDC keys.

Provider-First Setup

The OAuth server no longer needs a baked-in static client. Configure the server first, then create clients through:

• authenticated client RPC routes such as /auth/oauth2/create-client
• server-only admin routes such as /auth/admin/oauth2/create-client
• POST /auth/oauth2/register when dynamic registration is enabled
• server-side calls to provider.register_client(...)

Quick Start

from collections.abc import AsyncGenerator
from typing import Annotated

from fastapi import Depends, FastAPI, Request
from fastapi.responses import HTMLResponse, RedirectResponse
from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine

from belgie import Belgie, BelgieClient, BelgieSettings
from belgie.alchemy import BelgieAdapter
from belgie.alchemy.oauth_server import OAuthServerAdapter
from belgie.oauth.server import OAuthLoginFlowClient, OAuthServer

app = FastAPI()

settings = BelgieSettings(
    secret="change-me",
    base_url="http://localhost:8000",
)

engine = create_async_engine("sqlite+aiosqlite:///./app.db")
session_maker = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    async with session_maker() as session:
        yield session


belgie = Belgie(
    settings=settings,
    adapter=BelgieAdapter(...),
    database=get_db,
)

oauth_plugin = belgie.add_plugin(
    OAuthServer(
        adapter=OAuthServerAdapter(...),
        base_url=settings.base_url,
        login_url="/login",
        consent_url="/consent",
        signup_url="/signup",
        valid_audiences=["http://localhost:8000/mcp"],
    ),
)

app.include_router(belgie.router)


@app.get("/login")
async def login(
    request: Request,
    oauth: Annotated[OAuthLoginFlowClient, Depends(oauth_plugin)],
) -> RedirectResponse:
    context = await oauth.try_resolve_login_context(request)
    if context is None:
        return RedirectResponse("/", status_code=302)
    return RedirectResponse(context.return_to, status_code=302)


@app.get("/consent")
async def consent(
    request: Request,
    oauth: Annotated[OAuthLoginFlowClient, Depends(oauth_plugin)],
) -> HTMLResponse:
    context = await oauth.resolve_login_context(request)
    return HTMLResponse(
        f"""
        <form method="post" action="/auth/oauth2/consent">
          <input type="hidden" name="state" value="{context.state}" />
          <input type="hidden" name="accept" value="true" />
          <button type="submit">Approve</button>
        </form>
        """
    )

After the server is running, create clients through /auth/oauth2/create-client or /auth/oauth2/register.

Important Behavior

• login_url and consent_url are required whenever the authorization_code grant is enabled.
• /auth/oauth2/create-client and /auth/oauth2/update-client only honor public client fields. Restricted fields such as skip_consent, enable_end_session, require_pkce, subject_type, metadata, and client_secret_expires_at belong on the server-only /auth/admin/oauth2/* routes.
• /auth/oauth2/authorize ignores resource. Send resource to /auth/oauth2/token when requesting a resource-bound access token.
• resource values sent to /auth/oauth2/token are validated against valid_audiences. Invalid resources return invalid_target.
• Public clients and offline_access requests always require PKCE.
• cached_trusted_clients and trusted_client_resolver can mark clients as trusted without allowing dynamic registration payloads to persist skip_consent.
• Consent is required for every non-trusted client until a matching consent record exists. Public PKCE clients are not implicitly trusted.
• /auth/oauth2/public-client requires an authenticated session. Use /auth/oauth2/public-client-prelogin only when allow_public_client_prelogin=True.
• Trusted clients are immutable through the RPC routes. Update them in config or directly in persistence instead.
• private_key_jwt, jwks, and jwks_uri are not part of the persisted client surface.

JWT And OIDC Behavior

• By default, access tokens are JWTs when a valid resource is requested at /auth/oauth2/token and opaque otherwise.
• disable_jwt_plugin=True switches to non-JWT access tokens:
  • access tokens are always opaque
  • confidential clients still receive an id_token
  • the id_token is signed in HS256 with the client's secret
  • public clients do not receive an id_token
  • JWKS is not exposed
• m2m_access_token_ttl_seconds lets machine-to-machine access tokens use a different default TTL than user tokens.

Protected Resource Metadata

Protected resources should publish their own /.well-known/oauth-protected-resource document. The OAuth server does not own that route.

Use build_protected_resource_metadata() to build the RFC 9728 document:

from fastapi import FastAPI
from fastapi.responses import JSONResponse

from belgie.oauth.server import OAuthServer, build_protected_resource_metadata

app = FastAPI()

oauth_settings = OAuthServer(...)


@app.get("/.well-known/oauth-protected-resource")
async def protected_resource_metadata() -> JSONResponse:
    metadata = build_protected_resource_metadata(
        "https://api.example.com/mcp",
        settings=oauth_settings,
        scopes_supported=["user"],
    )
    return JSONResponse(metadata.model_dump(mode="json", exclude_none=True))

Custom Claim Hooks

Belgie exposes these hook families with snake_case names:

• custom_access_token_claims
• custom_id_token_claims
• custom_userinfo_claims
• custom_token_response_fields

Reserved OAuth and OIDC fields are protected:

• custom_access_token_claims cannot overwrite standard JWT claims
• custom_id_token_claims cannot overwrite pinned OIDC claims
• custom_token_response_fields cannot overwrite standard token response fields

MCP Pairing

If you are protecting an MCP server, pair this package with belgie-mcp. The MCP plugin consumes the OAuth metadata, token verifier behavior, and protected resource metadata helper from this package.

Compatibility Notes

• OAuth server protocol routes are fixed to /oauth2/*.
• Restricted client fields are available through server-only /admin/oauth2/create-client and /admin/oauth2/update-client.
• In-config static OAuth client fields on OAuthServer were removed; create clients through DCR, RPC, admin, or your adapter/seed.
• The old auth-server-owned protected-resource metadata model is gone. Resource servers publish that metadata themselves.