FitTrack_GarminSync/specs/008-centraldb-mfa-tokens/spec.md

Feature Specification: CentralDB Extension for MFA Token Management

Feature Branch: 008-centraldb-mfa-tokens
Created: Thursday, December 19, 2025
Status: Draft
Input: Requirement to extend CentralDB to support garth token management for MFA flow in garminsync

User Scenarios & Testing (mandatory)

User Story 1 - Secure Garth Token Storage (Priority: P1)

As a GarminSync service, I want to securely store garth authentication tokens (OAuth1/OAuth2) in CentralDB so that users can maintain authenticated sessions across service restarts and authenticate with MFA-enabled accounts.

Why this priority: This is fundamental to the entire MFA authentication flow. Without secure token storage, users would need to re-authenticate on every service restart, defeating the purpose of persistent authentication sessions.

Independent Test: Can be fully tested by authenticating a user with garth tokens, restarting the service, and verifying that tokens are still available for that user.

Acceptance Scenarios:

1. Given a user successfully authenticates with garth, When tokens are received from garth, Then tokens are securely stored in CentralDB with appropriate encryption
2. Given garth tokens exist for a user in CentralDB, When the service requests tokens for that user, Then the tokens are retrieved and decrypted appropriately
3. Given invalid or expired garth tokens in CentralDB, When the service attempts to use them, Then appropriate error handling occurs and re-authentication is required
4. Given a user requests logout, When the logout process begins, Then associated garth tokens are securely removed from CentralDB

User Story 2 - MFA Challenge Tracking (Priority: P2)

As an administrator of the CentralDB service, I want to track MFA challenges so that the system can properly manage multi-factor authentication flows and prevent abuse.

Why this priority: Critical for security and proper MFA flow management. Enables tracking of authentication attempts and prevents brute-force attacks.

Independent Test: Can be fully tested by initiating multiple MFA challenges and verifying they are properly tracked, validated, and cleaned up.

Acceptance Scenarios:

1. Given a user initiates MFA authentication, When the challenge is created, Then the challenge is stored in CentralDB with appropriate expiration time
2. Given an MFA challenge exists in CentralDB, When the correct MFA code is provided, Then the challenge is marked as completed and can be consumed
3. Given an MFA challenge exists in CentralDB, When the challenge expires, Then the challenge is no longer valid and cleaned up automatically
4. Given multiple failed MFA attempts for a challenge, When the limit is reached, Then the challenge is invalidated and the user must restart authentication

User Story 3 - Session Management for MFA Flows (Priority: P3)

As a user of the GarminSync service, I want to have my MFA state preserved during the authentication flow so that the system properly tracks my authentication progress.

Why this priority: Improves user experience by maintaining authentication state across requests during MFA flow, especially for longer-running flows.

Independent Test: Can be fully tested by initiating an MFA flow, checking that the system properly tracks the state, and then completing the flow successfully.

Acceptance Scenarios:

1. Given a user begins MFA authentication, When the session is created, Then MFA state is properly recorded in CentralDB
2. Given an MFA session exists in CentralDB, When MFA is completed successfully, Then the session is updated to reflect MFA completion
3. Given an MFA session exists in CentralDB, When MFA fails or times out, Then the session is properly cleaned up

Edge Cases

• What happens when garth token encryption/decryption fails in CentralDB?
• How does the system handle concurrent MFA attempts for the same user?
• What occurs if CentralDB is temporarily unavailable during authentication?
• How does the system handle very large numbers of MFA challenges (potential DoS)?
• What happens when garth token storage exceeds allocated quotas?

Requirements (mandatory)

Functional Requirements

• FR-001: CentralDB MUST provide secure storage for garth OAuth1 and OAuth2 tokens with encryption at rest
• FR-002: CentralDB MUST provide API endpoints for storing, retrieving, and deleting garth tokens
• FR-003: CentralDB MUST track MFA challenges with type, expiration time, and validation status
• FR-004: CentralDB MUST enforce MFA challenge expiration and limit retry attempts
• FR-005: CentralDB MUST associate garth tokens with specific user accounts for proper access control
• FR-006: CentralDB MUST provide API endpoints for MFA challenge creation and validation
• FR-007: CentralDB MUST maintain user session state during MFA authentication flows
• FR-008: CentralDB MUST securely delete garth tokens when users log out or tokens expire
• FR-009: CentralDB MUST prevent replay attacks of valid MFA codes
• FR-010: CentralDB MUST log authentication attempts for security auditing purposes

Key Entities

• GarthToken: Securely stored OAuth tokens (encrypted) with user association and metadata
• MFAChallenge: Tracks authentication challenges including type, destination, status, and expiration
• UserSession: Maintains session state during authentication flows, particularly MFA

Success Criteria (mandatory)

Measurable Outcomes

• SC-001: 100% of garth tokens are stored encrypted in CentralDB with FIPS-compliant encryption
• SC-002: Token retrieval operations complete within 100ms for 95% of requests
• SC-003: MFA challenge validation completes within 200ms for 95% of requests
• SC-004: CentralDB handles MFA flows for 10,000 concurrent users without performance degradation
• SC-005: MFA challenge security mechanisms prevent 99.9% of replay and brute-force attempts
• SC-006: 99.9% uptime for token storage/retrieval operations during MFA flows

Assumptions

• CentralDB uses PostgreSQL or SQLite with appropriate security configurations
• garth token data follows standard OAuth token formats
• Encryption at rest is implemented using library-appropriate mechanisms
• Network communication between GarminSync service and CentralDB is secured
• Proper access controls exist between services to prevent unauthorized token access
• GarminSync service has appropriate permissions to access token storage endpoints