# Authentication Specification

## Purpose

Manage user authentication via Authentik OAuth with secure session handling.
## Requirements
### Requirement: OAuth2/OIDC Flow
The system SHALL support OAuth2/OIDC authentication via Authentik with fully configurable endpoints and SHALL validate Authentik-issued tokens via JWKS before creating local sessions.

#### Scenario: User login
- GIVEN a user clicks the login button
- WHEN the frontend redirects to Authentik authorization endpoint
- THEN the redirect URI SHALL be constructed from environment-configured domains
- AND the Authentik authorize URL SHALL be read from environment variables

#### Scenario: Token exchange and validation
- GIVEN Authentik has redirected with authorization code
- WHEN the callback endpoint receives the code
- THEN it exchanges the code for provider tokens at the configured token URL
- AND verifies token signature using the configured JWKS URL
- AND validates the issuer and audience from environment configuration
- AND upserts the local user account
- AND mints internal access and refresh tokens

### Requirement: Session Security
The system SHALL protect sessions using httpOnly cookies and SHALL apply secure cookie defaults by environment.

#### Scenario: Cookie attributes in production
- GIVEN successful authentication in production
- WHEN cookies are set
- THEN access_token cookie SHALL be httpOnly
- AND access_token cookie SHALL have Secure flag
- AND access_token cookie SHALL have SameSite=strict
- AND refresh_token cookie SHALL have the same attributes

#### Scenario: Cookie attributes in localhost development
- GIVEN successful authentication in localhost development
- WHEN cookies are set
- THEN access_token cookie SHALL be httpOnly
- AND access_token cookie SHALL have Secure=false
- AND access_token cookie SHALL have SameSite=lax
- AND refresh_token cookie SHALL have the same attributes

### Requirement: Token Refresh
The system SHALL support automatic token refresh with server-side refresh token storage, rotation, and revocation.

#### Scenario: Access token expiration
- GIVEN a user has an expired access token
- WHEN the user makes an authenticated request that can refresh
- THEN the system validates the refresh token against non-expired, non-revoked DB state
- AND rotates the refresh token
- AND issues a new internal access token

#### Scenario: Refresh token reuse detection
- GIVEN a refresh token has already been rotated or revoked
- WHEN it is presented again to the refresh endpoint
- THEN the system rejects the request with unauthorized status
- AND invalidates the token chain for the session

### Requirement: Session Termination
The system SHALL support explicit logout with refresh token invalidation.

#### Scenario: User logout
- GIVEN an authenticated user
- WHEN the user clicks logout
- THEN all auth cookies are cleared
- AND the refresh token is invalidated in server-side storage

## Dependencies

- Authentik OIDC provider configured
- Database models: User

## Quality Gates

- `pytest` must pass
- `mypy .` must pass
- `ruff check .` must pass