AuthHero

A simple authentication service.

Setup

Prerequisites

• Dependency management using poetry

  • If you'd rather not install poetry on your system, you can download the wheel from the Github Releases page and install the authhero package in a local virtual environment.

• PostgreSQL

  • The app will connect to a Postgres database running on localhost
  • If you'd rather not install Postgres, but still want to run the tests, you can skip the tests that need a database with: pytest -m "not functional"
  • Set up the local development and test databases with:

# Assumes username: postgres, without password (configurable)
./scripts/init_local_db.py

Installation

You can either setup a local virtual environment with poetry or install the authhero package with a wheel from the project's Releases page on Github.

Running

Run a local Flask dev server from the src directory with:

flask run

You should be able to see the Swagger API documentation with fully functioning UI to call the API on http://127.0.0.1:5000/.

User journey 🚀

• Register a new user with /auth/register
• Login with entered credentials at /auth/login
  • Save the api_key token provided in the response
  • In the Swagger Docs, enter the token in the Authorize menu on the top-right
• Interact with the User CRUD API at /users/*
  • Can view all active users
• Logging out will invalidate all of users active tokens, and the user will need to login again, and request a new token
• Deleting a user can only be done on the logged in user, and it is a soft-delete, where the user's API keys will no longer be able to be used for authentication.

Testing

There are two kinds of tests: "simple" unit tests and functional tests that, while not being true end-to-end tests, they test the full functionality, including the database.

• Inside a virtual env, run pytest from the repo root.
• Run only the unit tests with `pytest -m "not functional"

Due to time, only partial code coverage.

Design decisions

• Picked MVC to structure the code, since it should be a simple project
  • Would try the Repository pattern for more complex use cases
  • Added a layer for business logic, so as to not pollute models or views, in services.py files
• Flask as a simple web server, with the following libraries:
  • flask-restx - a handy library for building REST APIs in Flask, comes with integrated Swagger Docs.
  • SQLAlchemy - a database toolkit
  • bcrypt - for secure password hashing
• Configuration through Config objects
• Storing of hashed passwords using bcrypt (hashing and salt using default configuration)
• Minimal validation in User CRUD, done using flask_restx.reqparse
• No AUTOCOMMIT, prefer "Unit of Work" pattern
• PostgreSQL instead of SQLite
  • Slightly more complicated to set up, but since I had enough time to do so, I did :)
  • Much more likely to be used in a real product

Data Model:

• Two entities: User and ApiKey (one-to-many relationship)
• All models have the created_on and updated_on attributes for easy auditing and data analysis
• Implemented "soft" deletion of Users, with the is_active flag

Authentication

• Decided to implement only Token-authentication, due to time restrictions
• Currently can only authenticate from custom header: "X-API-KEY"
  • Authentication via querystring was not implemented due to time

Future improvements and ideas

• Use pydantic for configuration and secrets handling
  • Also add a ProductionConfig using this
• Document all possible responses and status codes
  • Did not cover all in docs due to time
• Handle all database errors since it's quite an important dependency
• Better test coverage - would've done more with more time
  • Also different tests:
    • end-to-end
    • smoke tests
    • load testing, for example with locust
• CI/CD system
• Docker container
• Kubernetes configuration
• User.id currently is currently an int that autoincrements from 1
  • In a distributed authentication system, would prefer uuid over int to avoid collision
  • If still int, would configure primary key generation differently
• Introduce role-based access and have a more sophisticated authorization system, with at least an "admin" role
• Have the authentication system be more abstract so that it's extendable to more ways of authenticating and/or providers, for example to be able to add JWT and OAuth

Addendum, after submitting the assignment...

Would also do the following improvements:

• Split off User attributes like first_name and last_name into a new table called Profile, so as to not affect the User model that is used for authentication.
• Do not return ints as status codes in views, but use classes provided by Flask
• As it is, I did not include any logging in the solution and instead relied on built in error-handling of the libraries used. For an actual solution, I would add way custom exceptions per level of abstraction, and then error-handling and logging.
• In an actual production-ready solution, I would also add integrations with a monitoring platform like Prometheus/Grafana, as well as Infrastructure-as-Code, like Terraform or Pulumi.