# Specification: User Authentication System

**ID**: SPEC-200
**Version**: 2.1
**Date**: 2025-10-24
**Status**: Active
**Author**: Security Team
**Stakeholders**: Engineering, Product, Security

## Overview

This specification defines the authentication system for securing user access to the application. It covers user registration, login, session management, and password security.

## Background

The application requires a robust authentication system to protect user data and ensure only authorized users can access protected resources.

## Requirements

### User Registration

**REQ-001**: The system shall allow new users to register with an email address and password. [Related to SPEC-200/JOB-001]

**REQ-002**: WHEN a user registers, the system shall validate that the email address is in a valid format.

**REQ-003**: IF the email address is already registered, THEN the system shall reject the registration and display an error message.

**REQ-004**: The system shall require passwords to be at least 12 characters long.

### User Login

**REQ-005**: The system shall allow registered users to log in with their email and password. [Related to SPEC-200/JOB-001]

**REQ-006**: WHEN a user attempts to log in, the system shall verify the credentials against stored hashed passwords.

**REQ-007**: IF login credentials are invalid, THEN the system shall increment a failed login counter for the user account.

**REQ-008**: IF a user has 5 consecutive failed login attempts, THEN the system shall temporarily lock the account for 30 minutes.

### Session Management

**REQ-009**: The system shall create a secure session token upon successful login. [Related to SPEC-200/JOB-002]

**REQ-010**: The system shall expire session tokens after 24 hours of inactivity.

**REQ-011**: The system shall allow users to explicitly log out, invalidating their session token.

### Security

**NFR-001**: The system shall hash all passwords using bcrypt with a cost factor of at least 12.

**NFR-002**: The system shall use HTTPS for all authentication-related communications.

**NFR-003**: Session tokens shall be cryptographically secure random strings of at least 256 bits.

### Testing

**TEST-001**: The system shall provide test fixtures for creating authenticated test users.

## Security Considerations

All authentication operations must be logged for audit purposes. Password reset functionality is covered in SPEC-201.

## Related Specifications

- SPEC-201: Password Reset System
- SPEC-202: Two-Factor Authentication
- SPEC-203: API Authorization

## Revision History

- 2025-10-24: v2.1 - Added account lockout requirement
- 2025-09-15: v2.0 - Increased password length requirement
- 2025-08-01: v1.0 - Initial version
