fastapi-authz

fastapi-authz is an authorization middleware for FastAPI, it's based on PyCasbin.

Installation

Clone this repo

git clone https://github.com/pycasbin/fastapi-authz.git
python setup.py install

Quickstart

This middleware is designed to work with another middleware which implement AuthenticationMiddleware interface.

import base64
import binascii

import casbin

from fastapi import FastAPI
from starlette.authentication import AuthenticationBackend, AuthenticationError, SimpleUser, AuthCredentials
from starlette.middleware.authentication import AuthenticationMiddleware

from fastapi_authz import CasbinMiddleware

app = FastAPI()


class BasicAuth(AuthenticationBackend):
    async def authenticate(self, request):
        if "Authorization" not in request.headers:
            return None

        auth = request.headers["Authorization"]
        try:
            scheme, credentials = auth.split()
            decoded = base64.b64decode(credentials).decode("ascii")
        except (ValueError, UnicodeDecodeError, binascii.Error):
            raise AuthenticationError("Invalid basic auth credentials")

        username, _, password = decoded.partition(":")
        return AuthCredentials(["authenticated"]), SimpleUser(username)


enforcer = casbin.Enforcer('../examples/rbac_model.conf', '../examples/rbac_policy.csv')

app.add_middleware(CasbinMiddleware, enforcer=enforcer)
app.add_middleware(AuthenticationMiddleware, backend=BasicAuth())


@app.get('/')
async def index():
    return "If you see this, you have been authenticated."


@app.get('/dataset1/protected')
async def auth_test():
    return "You must be alice to see this."

anonymous request

curl -i http://127.0.0.1:8000/dataset1/protected

HTTP/1.1 403 Forbidden
date: Mon, 01 Mar 2021 09:00:08 GMT
server: uvicorn
content-length: 11
content-type: application/json

"Forbidden"

authenticated request

curl -i -u alice:password http://127.0.0.1:8000/dataset1/protected

HTTP/1.1 200 OK
date: Mon, 01 Mar 2021 09:04:54 GMT
server: uvicorn
content-length: 32
content-type: application/json

"You must be alice to see this."

It used the casbin config from examples folder, and you can find this demo in demo folder.

You can also view the unit tests to understand this middleware.

Development

Run unit tests

Fork/Clone repository
Install flask-authz dependencies, and run pytest

pip install -r dev_requirements.txt
pip install -r requirements.txt
pytest

Update requirements with pip-tools

# update requirements.txt
pip-compile --no-annotate --no-header --rebuild requirements.in
# sync venv
pip-sync

Manually Bump Version

bumpversion major  # major release
or
bumpversion minor  # minor release
or
bumpversion patch  # hotfix release

Documentation

The authorization determines a request based on {subject, object, action}, which means what subject can perform what action on what object. In this plugin, the meanings are:

subject: the logged-in user name
object: the URL path for the web resource like dataset1/item1
action: HTTP method like GET, POST, PUT, DELETE, or the high-level actions you defined like “read-file”, " write-blog" (currently no official support in this middleware)

For how to write authorization policy and other details, please refer to the Casbin's documentation.

Getting Help

Casbin

License

This project is under Apache 2.0 License. See the LICENSE file for the full license text.