fastapi-users/fastapi_users/router/oauth.py

from typing import Dict, List, Type, cast

import jwt
from fastapi import Depends, HTTPException, Query
from httpx_oauth.integrations.fastapi import OAuth2AuthorizeCallback
from httpx_oauth.oauth2 import BaseOAuth2
from starlette import status
from starlette.requests import Request
from starlette.responses import Response

from fastapi_users import models
from fastapi_users.authentication import Authenticator
from fastapi_users.db import BaseUserDatabase
from fastapi_users.password import generate_password, get_password_hash
from fastapi_users.router.common import ErrorCode, Event, EventHandlersRouter
from fastapi_users.utils import JWT_ALGORITHM, generate_jwt

STATE_TOKEN_AUDIENCE = "fastapi-users:oauth-state"


def generate_state_token(
    data: Dict[str, str], secret: str, lifetime_seconds: int = 3600
) -> str:
    data["aud"] = STATE_TOKEN_AUDIENCE
    return generate_jwt(data, lifetime_seconds, secret, JWT_ALGORITHM)


def decode_state_token(token: str, secret: str) -> Dict[str, str]:
    return jwt.decode(
        token, secret, audience=STATE_TOKEN_AUDIENCE, algorithms=[JWT_ALGORITHM],
    )


def get_oauth_router(
    oauth_client: BaseOAuth2,
    user_db: BaseUserDatabase[models.BaseUserDB],
    user_db_model: Type[models.BaseUserDB],
    authenticator: Authenticator,
    state_secret: str,
    redirect_url: str = None,
) -> EventHandlersRouter:
    """Generate a router with the OAuth routes."""
    router = EventHandlersRouter()
    callback_route_name = f"{oauth_client.name}-callback"

    if redirect_url is not None:
        oauth2_authorize_callback = OAuth2AuthorizeCallback(
            oauth_client, redirect_url=redirect_url,
        )
    else:
        oauth2_authorize_callback = OAuth2AuthorizeCallback(
            oauth_client, route_name=callback_route_name,
        )

    @router.get("/authorize")
    async def authorize(
        request: Request, authentication_backend: str, scopes: List[str] = Query(None),
    ):
        # Check that authentication_backend exists
        backend_exists = False
        for backend in authenticator.backends:
            if backend.name == authentication_backend:
                backend_exists = True
                break
        if not backend_exists:
            raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST)

        redirect_url = request.url_for(callback_route_name)
        state_data = {
            "authentication_backend": authentication_backend,
        }
        state = generate_state_token(state_data, state_secret)
        authorization_url = await oauth_client.get_authorization_url(
            redirect_url, state, scopes,
        )

        return {"authorization_url": authorization_url}

    @router.get("/callback", name=f"{oauth_client.name}-callback")
    async def callback(
        response: Response, access_token_state=Depends(oauth2_authorize_callback)
    ):
        token, state = access_token_state
        account_id, account_email = await oauth_client.get_id_email(
            token["access_token"]
        )

        try:
            state_data = decode_state_token(state, state_secret)
        except jwt.DecodeError:
            raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST)

        user = await user_db.get_by_oauth_account(oauth_client.name, account_id)

        new_oauth_account = models.BaseOAuthAccount(
            oauth_name=oauth_client.name,
            access_token=token["access_token"],
            expires_at=token["expires_at"],
            refresh_token=token.get("refresh_token"),
            account_id=account_id,
            account_email=account_email,
        )

        if not user:
            user = await user_db.get_by_email(account_email)
            if user:
                # Link account
                user.oauth_accounts.append(new_oauth_account)  # type: ignore
                await user_db.update(user)
            else:
                # Create account
                password = generate_password()
                user = user_db_model(
                    email=account_email,
                    hashed_password=get_password_hash(password),
                    oauth_accounts=[new_oauth_account],
                )
                await user_db.create(user)
                await router.run_handlers(Event.ON_AFTER_REGISTER, user)
        else:
            # Update oauth
            updated_oauth_accounts = []
            for oauth_account in user.oauth_accounts:  # type: ignore
                if oauth_account.account_id == account_id:
                    updated_oauth_accounts.append(new_oauth_account)
                else:
                    updated_oauth_accounts.append(oauth_account)
            user.oauth_accounts = updated_oauth_accounts  # type: ignore
            await user_db.update(user)

        if not user.is_active:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail=ErrorCode.LOGIN_BAD_CREDENTIALS,
            )

        # Authenticate
        for backend in authenticator.backends:
            if backend.name == state_data["authentication_backend"]:
                return await backend.get_login_response(
                    cast(models.BaseUserDB, user), response
                )

    return router