fastauth

A modular, Pydantic-native, async-only authentication library for FastAPI.

pip install fastauth-py

from fastapi import FastAPI
from pydantic import SecretStr

from fastauth import FastAuth, FastAuthOptions
from fastauth.database import memory
from fastauth.providers import email_password

app_secret = "replace-me-with-a-secret-from-your-application-config"

auth = FastAuth(
    FastAuthOptions(
        secret_key=SecretStr(app_secret),
        database=memory(),
    ),
    plugins=[email_password()],
)

app = FastAPI(lifespan=auth.lifespan)
auth.mount(app)

That's it. You now have /auth/sign-up/email, /auth/sign-in/email, /auth/sign-out, /auth/get-session, /auth/verify-email, /auth/forgot-password, /auth/reset-password, /auth/change-password, /auth/set-password, /auth/verify-password, /auth/user, /auth/delete-account, /auth/delete-account/request, /auth/delete-account/confirm, /auth/change-email/{request,confirm}, /auth/sessions (list / revoke / revoke-others), /auth/refresh, and /auth/health wired into your FastAPI application. Rate-limiting, account-lockout, and refresh tokens are part of the router. CSRF and security headers are ASGI middleware installed by auth.mount(app). If you use auth.as_asgi() instead, fastauth returns a standalone app with the same routes and middleware already installed.

Why fastauth

Built deliberately for the modern Python web stack — FastAPI + Pydantic v2 + async-only + MongoDB or Postgres persistence:

• Pydantic v2 everywhere. Every public domain model, request body, and response is a BaseModel. Runtime wiring may use ordinary Python types internally, but the API boundary stays Pydantic-native.
• Async-only. No sync wrappers, no thread-pool shims. Your event loop doesn't get hijacked.
• Strict-typed. pyright --strict passes with 0 errors, 0 warnings. py.typed marker ships with the wheel — your IDE and your CI get full type information.
• Source-agnostic options. FastAuthOptions is a plain BaseModel. The framework never reads process-level configuration. You build config from your application settings object, vault client, parameter store, or test fixture and pass it in explicitly.
• Plugins as first-class extension points. Seven built-in providers (email_password(), api_key(), jwt(), email_otp(), audit_logs(), openapi(), test_utils()) — each contributes endpoints, event handlers, lifecycle hooks, and rate-limit policies through a tight Plugin ABC. Write your own for OAuth providers, webhooks, custom MFA — whatever your app needs.
• Capability-based storage protocols. DatabaseAdapter covers the core auth flows. Optional surfaces (ApiKeyStore, JwksKeyStore, AuditLogStore, RateLimitStore) are only required when you enable the matching plugin or database-backed feature.
• Pure events. A single typed EventBus carries 19 concrete AuthEvent subclasses (UserSignedUp, UserEmailVerified, PasswordChanged, AccountLockedOut, …). Subscribe and react — send emails, ping Slack, write audit rows, whatever.

What's in the box

Auth flows

• Sign-up / sign-in / sign-out by email or username
• Email verification with anti-enumeration
• Password reset with anti-enumeration and session-wide revoke
• Authenticated change-password (keeps current session, revokes others)
• Authenticated profile update, set-password, verify-password, and account deletion with password or email-token verification
• Authenticated change-email with re-verification
• Refresh tokens with one-time-use rotation and family-revocation on reuse (OAuth 2.1-style theft detection)
• Multi-session management: list, revoke one, revoke-all-except-current

Sessions

• Database-backed sessions (revocable, IP/UA bound) or JWT sessions (stateless, JWKS-signed). One config flag flips between them.
• JWKS with auto-generated keys, AES-GCM at-rest encryption with master-key rotation support, and an opt-in set-auth-jwt response header that attaches a JWT to every authenticated response.
• Local key signing or plug in your own KmsSigner (HSM, AWS KMS, GCP KMS, …) via a tiny Protocol.
• JWT/JWKS crypto has not been independently audited. For high-stakes production deployments, use an external KMS/HSM signer and run your own security review before relying on local private-key storage.

Security

• Argon2id password hashing (configurable cost).
• Account lockout — HTTP 423 + Retry-After after 5 failed sign-ins in 15 min.
• CSRF middleware — Origin/Referer validation on state-changing methods, bearer-only requests are exempt.
• Rate limiting with /64 IPv6-subnet bucketing, per-(IP, path) windowing, pluggable storage (memory, MongoDB, Postgres).
• Security headers — HSTS, X-Frame-Options, X-Content-Type-Options, Referrer-Policy on by default; opt-in Permissions-Policy and CSP.

Plugins (each optional)

• email_password() — sign-up, sign-in, password reset, email verification, account management, refresh tokens, and session management.
• api_key() — create/verify/list/update/delete API keys with optional refilling quotas and per-key rate limits.
• jwt() — /auth/token to mint a JWT from a session, /auth/jwks for the public key set.
• email_otp() — passwordless sign-in, email verification, password reset, and (optional) email change via 6-digit OTPs delivered to email. Hashed storage, per-OTP attempt cap, lockout-coupled.
• audit_logs() — auto-captures every AuthEvent into a paginated audit-log collection.
• openapi() — Scalar UI at /auth/reference, OpenAPI 3.1 schema at /auth/openapi.json.
• test_utils() — factories, login helpers, OTP capture for tests.

Developer experience

• CurrentUser / CurrentSession FastAPI dependencies with optional variants, both Depends(...) and Annotated[...] calling styles documented.
• Explicit storage wiring — choose memory(), mongo(database), postgres(url), or custom(adapter, backend=...). Fastauth never reads storage settings from the process environment.
• auth.mount(app) — install routes, CSRF, and security headers on your FastAPI app in one call. FastAuth.as_asgi() still returns a standalone app when you want fastauth mounted separately.
• Typer CLI — fastauth init --backend memory|mongo|postgres, fastauth migrate, fastauth generate-secret.
• mkdocs-material docs + quickstart example app with its own test suite.

Installation

# Core (in-memory adapter only — useful for tests and local dev)
pip install fastauth-py

# MongoDB-backed production
pip install fastauth-py[beanie,jwt]

# Postgres-backed production
pip install fastauth-py[postgres,jwt]

# All implemented optional extras
pip install fastauth-py[beanie,postgres,jwt,cli,docs]

Extras: beanie (MongoDB), postgres (SQLAlchemy async + asyncpg), jwt (JOSE signing + crypto for at-rest JWK encryption), cli (Typer CLI), docs (mkdocs-material toolchain).

Python 3.11+ required. FastAPI 0.115+, Pydantic 2.8+.

Protecting routes

from fastapi import Depends
from fastauth import UserView

@app.get("/me")
async def me(user: UserView = Depends(auth.require_user)) -> UserView:
    return user

Or with the Annotated style (FastAPI's idiom):

from typing import Annotated
from fastapi import Depends
from fastauth import UserView

CurrentUser = Annotated[UserView, Depends(auth.require_user)]

@app.get("/me")
async def me(user: CurrentUser) -> UserView:
    return user

Cookie auth and Authorization: Bearer … both work — fastauth handles either transparently. Use auth.optional_user if anonymous requests are allowed.

Configuration

FastAuthOptions is a plain pydantic.BaseModel. Every field has a sensible default; pass only what you want to override:

from pydantic import SecretStr
from datetime import timedelta

from fastauth import FastAuth, FastAuthOptions
from fastauth.database import memory
from fastauth.options import (
    AppOptions, CookieOptions, CsrfOptions,
    LockoutOptions, RefreshTokenOptions, SecurityHeadersOptions,
)
from fastauth.providers import email_password

options = FastAuthOptions(
    secret_key=SecretStr("…"),
    database=memory(),
    app=AppOptions(name="My App", base_url="https://myapp.com"),
    cookie=CookieOptions(secure=True, same_site="strict"),
    csrf=CsrfOptions(trusted_origins=("https://myapp.com",)),
    lockout=LockoutOptions(max_failures=10, window=timedelta(minutes=5)),
    refresh_token=RefreshTokenOptions(max_age=timedelta(days=14)),
    security_headers=SecurityHeadersOptions(
        content_security_policy="default-src 'self'",
    ),
)

auth = FastAuth(options, plugins=[email_password()])

16 sub-configs cover app, session, cookie, password, email, email_verification, password_reset, email_change, delete_account, rate_limit, csrf, lockout, refresh_token, security_headers, advanced, plus the top-level database backend. Plugins are behavior objects passed to FastAuth(..., plugins=[...]).

See docs/concepts/config.md for the full reference.

Documentation

Full docs site: mkdocs serve from a checkout.

• Quickstart
• Config · Sessions · Plugins · Adapters · CSRF · Events · Hooks
• Email verification guide · Password reset guide · User management guide · KMS signing guide

Project layout

fastauth/
├── options.py / exceptions.py         # top-level
├── domain/        # pure data: enums, models, events
├── security/      # auth primitives: passwords, tokens, sessions, jwt,
│                  #                  refresh_tokens, lockout, rate_limit
├── storage/       # Core/optional adapter protocols + InMemory/Beanie/Postgres backends
├── messaging/     # email + Jinja2 templates
├── flows/         # sign-up, sign-in, verification, refresh, …
├── plugins/       # email_password, email_otp, api_key, jwt, audit_logs, openapi, test_utils
├── runtime/       # FastAuth, AuthContext, AuthApi, EventBus, hooks
├── web/           # FastAPI integration + CSRF + security headers
└── cli/           # Typer CLI

Status

v0.7.0 — current release. Coverage spans unit tests, adapter-contract tests, integration flows, CLI behavior, and the quickstart example. pyright --strict is clean. See CHANGELOG.md for the detailed feature list.

Roadmap:

• OAuth providers (Google → GitHub → Apple → Microsoft)
• 2FA / TOTP
• Webhooks
• HIBP password breach check
• Audit-log enrichment (geo-IP, UA parsing)

Contributing

See CONTRIBUTING.md for the project-wide rules (no leading-underscore names, async-only, Pydantic-everywhere, …). Quick development loop:

uv sync --all-extras
uv run ruff check
uv run pyright
uv run pytest
uv run mkdocs serve

License

MIT — see LICENSE.