FAuth

An ergonomic, plug-and-play authentication library for FastAPI.

fauth eliminates boilerplate around JWT, password hashing, user fetching, and Role-Based Access Control (RBAC) by leveraging FastAPI's Dependency Injection (Depends), Pydantic models, and Python Protocols.

Features

• Protocol-Based User Fetching — Complete inversion of control. You implement a simple UserLoader protocol to define how to fetch a user from a token payload.
• Plug-and-Play Configuration — Centralized settings via Pydantic (AuthConfig). Configure once, inject everywhere.
• Pluggable Transports — Extensible Transport protocol with a built-in BearerTransport for Authorization header tokens.
• Automatic OpenAPI/Swagger UI Support — Integrated security schemes that automatically show the "Authorize" button and security lock icons in Swagger UI.
• Built-in Password Hashing & Crypto — Modern Argon2 via pwdlib and utilities for creating/decoding JWT access and refresh tokens.
• RBAC — Flexible require_roles and require_permissions dependencies with customizable user model field names.
• Secure Router — SecureAPIRouter applies authentication as a router-level dependency, securing all its routes automatically.
• Structured Logging — Built-in structlog-based logging for authentication events, token operations, and security failures.
• Type Safety — Fully annotated for MyPy and IDE integration.

Installation

pip install fauth

Or with uv:

uv add fauth