Add Basic HTTP Authentication to Index Route: Full example

[christianhpoe]

Hi,

thanks for this great package! Since I saw a few authentication questions and was struggling to implement it myself I thought i'd share my solution. Maybe you have feedback or find it helpful.

The trick is to overwrite the indexroute with a CustomAdmin Class and return a Response with a WWW-authenticate Header.

from starlette.authentication import (
    AuthCredentials, AuthenticationBackend, AuthenticationError, SimpleUser
)
from starlette.middleware import Middleware
from starlette.middleware.authentication import AuthenticationMiddleware
from starlette.responses import PlainTextResponse
from starlette.requests import Request
from starlette.responses import Response
import base64
import binascii


class BasicAuthBackend(AuthenticationBackend):
    async def authenticate(self, conn):
        if "Authorization" not in conn.headers:
            return 

        auth = conn.headers["Authorization"]
        try:
            scheme, credentials = auth.split()
            if scheme.lower() != 'basic':
                return
            decoded = base64.b64decode(credentials).decode("ascii")
        except (ValueError, UnicodeDecodeError, binascii.Error) as exc:
            raise AuthenticationError('Invalid basic auth credentials')

        username, _, password = decoded.partition(":")
        
        # TODO: You'd want to verify the username and password here.
        if not (secrets.compare_digest(username, "Yourusername") and secrets.compare_digest(password, "Yourpassword")):
            return
            
        return AuthCredentials(["authenticated"]), SimpleUser(username)


middlewares = [
    Middleware(AuthenticationMiddleware, backend=BasicAuthBackend())
]

### Add HTTP Basic Auth on Index route

class CustomAdmin(Admin):
    async def index(self, request: Request) -> Response:
        """Index route which can be overridden to create dashboards."""
        if not request.user.is_authenticated:
            return JSONResponse(content={"message": "Please authenticate!"}, status_code=401, headers={"WWW-Authenticate": "Basic"})
        return self.templates.TemplateResponse("index.html", {"request": request})

admin = CustomAdmin(app=app, engine=engine, middlewares=middlewares)

class AuthModelAdmin(ModelAdmin):
    def is_accessible(self, request: Request) -> bool:
        if not request.user.is_authenticated:
            return False
        return True
    def is_visible(self, request: Request) -> bool:
        if not request.user.is_authenticated:
            return False
        return True