feat: Add OIDC/SSO authentication support (#1008)

* feat: add OIDC/SSO database schema and models (Phase 1)

Add database foundation for OpenID Connect authentication:

Database Migrations:
- Create oidc_identities table (links users to OIDC accounts)
- Create oidc_state_nonces table (OAuth state/nonce for CSRF protection)
- Create auth_audit_log table (security event logging)
- Make password_digest nullable in users table (allow OIDC-only users)

Models:
- OIDCIdentity: Links users to external OIDC providers
- OIDCStateNonce: Temporary OAuth state management
- AuthAuditLog: Authentication event audit trail

Changes:
- Updated User model to allow null password_digest
- Added model associations in models/index.js
- All migrations tested and verified

Related to #977

* feat: add OIDC core services (Phase 2)

- Install openid-client@^6.2.0 for OIDC protocol support
- Implement providerConfig.js for loading providers from .env
  - Support single provider or numbered providers (OIDC_PROVIDER_1_*, etc.)
  - Auto-provision and admin email domain configuration
  - Provider caching for performance
- Implement stateManager.js for OAuth state/nonce management
  - CSRF protection with 10-minute TTL
  - One-time use state consumption
  - Automatic cleanup of expired states
- Implement auditService.js for authentication event logging
  - Track login success/failure, logout, OIDC linking/unlinking
  - Store IP address, user agent, and metadata
  - Support for event queries and retention cleanup
- Add comprehensive unit tests (60 tests, all passing)
  - providerConfig: 36 tests for env parsing and validation
  - stateManager: 12 tests for state lifecycle and security
  - auditService: 12 tests for event logging and queries

Phase 2 completes the backend core services needed for OIDC authentication.

* feat: implement OIDC authentication flow (Phase 3)

Core OIDC Flow (service.js):
- Provider discovery with issuer caching
- Authorization URL generation with state/nonce
- OAuth callback handling and token exchange
- ID token validation using openid-client
- Token refresh functionality

JIT User Provisioning (provisioningService.js):
- Auto-create users from OIDC claims
- Link existing email accounts to OIDC identities
- Admin role assignment based on email domain rules
- Automatic username generation from email
- Transaction-safe identity creation

Identity Management (oidcIdentityService.js):
- List user's linked OIDC identities
- Link additional providers to existing accounts
- Unlink identities with safety checks
- Prevent unlinking last auth method
- Update identity claims on login

HTTP Layer (controller.js + routes.js):
- GET /api/oidc/providers - List configured providers
- GET /api/oidc/auth/:slug - Initiate OIDC flow
- GET /api/oidc/callback/:slug - Handle OAuth callback
- POST /api/oidc/link/:slug - Link provider to current user
- DELETE /api/oidc/unlink/:id - Unlink identity
- GET /api/oidc/identities - Get user's identities

Integration:
- Register OIDC routes in Express app (public + authenticated)
- Update auth service to reject password login for OIDC-only users
- Audit logging for all OIDC operations
- Session creation on successful authentication

Security:
- State/nonce CSRF protection
- One-time use state consumption
- Transaction-safe user provisioning
- Foreign key constraints enforced

* feat: implement OIDC frontend login flow (Phase 4)

- Created OIDCProviderButtons component for SSO login options
- Created OIDCCallback component for OAuth callback handling
- Updated Login page to fetch and display OIDC providers
- Added /auth/callback/:provider route to App.tsx
- Added i18n translations for OIDC UI elements
- Downgraded openid-client to v5.7.0 (CommonJS compatibility)
- Fixed linting issues in backend OIDC modules

Phase 4 completes the frontend login flow for OIDC/SSO authentication.
Users can now see configured SSO providers on the login page.

* feat: implement OIDC account linking UI (Phase 5)

Add Connected Accounts section to Profile Security tab allowing users to:
- View linked OIDC provider accounts
- Link new SSO providers to their account
- Unlink OIDC identities with validation
- Prevent unlinking last authentication method

Backend changes:
- Add has_password virtual field to User model
- Include has_password in profile API response
- Track whether user has password set for validation

Frontend changes:
- Create oidcService for OIDC API operations
- Create ConnectedAccounts component with link/unlink flows
- Add confirmation dialog before unlinking accounts
- Validate that users cannot unlink their last auth method
- Show warning if user has no password set
- Integrate Connected Accounts into SecurityTab

User experience:
- View all linked SSO provider accounts with email and link date
- Link additional providers via "Link Provider" buttons
- Unlink with two-step confirmation to prevent accidents
- Clear error messages when unlinking would leave no auth method
- Warning message suggesting password setup for OIDC-only users

Fixes #977

* feat: complete OIDC documentation and UI improvements (Phase 6)

This commit completes Phase 6 of the OIDC/SSO implementation with comprehensive
documentation, bug fixes, and UI reorganization.

Documentation:
- Add comprehensive user guide at docs/10-oidc-sso.md with:
  - Setup guides for 6 major providers (Google, Okta, Keycloak, Authentik, PocketID, Azure AD)
  - Configuration examples for single and multiple providers
  - User features documentation (login, account linking, management)
  - Advanced topics (auto-provisioning, admin role assignment, hybrid auth)
  - Comprehensive troubleshooting section
  - Security considerations and best practices
- Update README.md with OIDC/SSO section and quick setup examples

Internationalization:
- Add i18n support to OIDCProviderButtons component
- Add translation keys for all OIDC UI text
- Update English translations with "sign_in_with" key

Bug Fixes:
- Fix oidcService.ts to correctly unwrap API responses
  - Backend returns {providers: [...]} and {identities: [...]}
  - Frontend was expecting plain arrays, causing "map is not a function" error
- Fix initiateOIDCLink to properly handle POST response

UI Improvements:
- Move OIDC/SSO to dedicated tab in profile settings
  - Create new OIDCTab component with green LinkIcon
  - Remove ConnectedAccounts from SecurityTab
  - Add OIDC tab between Security and API Keys tabs
  - Update ProfileSettings with new tab configuration
- Security tab now focuses solely on password management

Testing:
- All linting passes
- All tests pass (82 suites, 1223 tests)

Related to #977

* feat: add OIDC/SSO translations for all 24 languages

Add i18n support for OIDC/SSO features across all supported languages:
- "Sign in with {{provider}}" button text
- "OIDC/SSO" tab label in profile settings
- OIDC authentication flow messages

Translations added for: Arabic, Bulgarian, Danish, German, Greek, Spanish,
Finnish, French, Indonesian, Italian, Japanese, Korean, Dutch, Norwegian,
Polish, Portuguese, Romanian, Russian, Slovenian, Swedish, Turkish,
Ukrainian, Vietnamese, and Chinese.

* fix: resolve 13 CodeQL security alerts

This commit addresses critical security vulnerabilities identified by CodeQL scanning:

**Security Configuration (2 fixes)**
- Fix insecure Helmet configuration - enable CSP and HSTS in production
- Fix clear text cookie transmission - enable secure cookies in production

**Path Injection (3 fixes)**
- Add path validation in users/controller.js to prevent arbitrary file deletion
- Add path validation in users/service.js for avatar operations
- Add path sanitization in attachment-utils.js deleteFileFromDisk function

**Cross-Site Scripting (1 fix)**
- Fix XSS vulnerability in GeneralTab.tsx avatar URL handling
- Add URL sanitization to prevent javascript: protocol attacks

**URL Security (2 fixes)**
- Fix double escaping in url/service.js HTML entity decoding
- Fix incomplete URL sanitization for YouTube domain validation

**Denial of Service (1 fix)**
- Add loop bound protection in inboxProcessingService.js (10k char limit)

**Rate Limiting (3 fixes)**
- Add rate limiting to auth routes (register, verify-email)
- Add rate limiting to task attachment upload/delete endpoints
- Add rate limiting to user avatar upload/delete endpoints

**GitHub Actions Security (1 fix)**
- Add explicit read-only permissions to CI workflow

Note: CSRF middleware (#10) requires frontend changes and is tracked separately.

Relates to PR #1008

* fix: allow test files in path validation for tests

* fix: format long condition in attachment-utils for Prettier compliance

Break the path validation condition across multiple lines to meet Prettier formatting requirements and fix CI linting failure.

* fix: resolve CodeQL security alerts

- Add rate limiting to OIDC authentication routes using authLimiter and authenticatedApiLimiter
- Implement CSRF protection middleware using csrf-sync (skips for API tokens and test environment)
- Add CSRF token endpoint at /api/csrf-token
- Fix incomplete URL scheme validation in GeneralTab to block all dangerous schemes (javascript:, data:, vbscript:, file:)

This addresses 5 high-severity CodeQL security vulnerabilities:
- Missing rate limiting on OIDC auth routes
- Missing CSRF middleware protection
- Incomplete URL sanitization in avatar handling

All 1223 tests passing.

* fix: implement CSRF protection with lusca for CodeQL compliance

Add CSRF protection using lusca.csrf (CodeQL's recommended library) to
protect session-based authentication while supporting hybrid auth patterns.

Implementation:
- Pre-check middleware marks exempt requests (test env, Bearer tokens)
- Lusca CSRF middleware applied with exemption flag check
- Session-based requests require valid x-csrf-token header
- Bearer token requests exempt (don't use cookies)
- Test environment exempt for test execution

This addresses CodeQL security alert js/missing-token-validation while
maintaining support for both cookie-based and token-based authentication.

Related: #977 (OIDC/SSO authentication feature)

README.md

@@ -53,6 +53,12 @@ For the thinking behind tududi, read:
     - Receive daily digests of your tasks
     - Quick capture of ideas and todos on the go
 - **Open API & Access Tokens**: Versioned Swagger docs exposed at `/api/v1` plus personal API keys for integrating tududi with your own tooling or automations.
+- **OIDC/SSO Authentication**: Enterprise-ready Single Sign-On support with:
+    - Multiple OIDC providers (Google, Okta, Keycloak, Authentik, PocketID, Azure AD, and more)
+    - Just-In-Time (JIT) user provisioning
+    - Account linking for hybrid authentication
+    - Simple .env-based configuration perfect for self-hosters
+    - Automatic admin role assignment based on email domains
 
 ## 🗺️ Roadmap
 
@@ -97,6 +103,55 @@ docker run \
 | `loopback` | Trust loopback addresses (127.0.0.1/::1) |
 | `172.16.0.0/12` | Trust a specific subnet |
 
+### OIDC/SSO Authentication
+
+Tududi supports Single Sign-On via OpenID Connect (OIDC), allowing users to authenticate with external identity providers.
+
+**Quick Setup (Single Provider):**
+
+```bash
+docker run \
+  -e OIDC_ENABLED=true \
+  -e OIDC_PROVIDER_NAME=Google \
+  -e OIDC_PROVIDER_SLUG=google \
+  -e OIDC_ISSUER_URL=https://accounts.google.com \
+  -e OIDC_CLIENT_ID=your-client-id.apps.googleusercontent.com \
+  -e OIDC_CLIENT_SECRET=your-client-secret \
+  -e OIDC_SCOPE="openid profile email" \
+  -e OIDC_AUTO_PROVISION=true \
+  -e TUDUDI_BASE_URL=https://your-domain.com \
+  ...
+```
+
+**Multiple Providers:**
+
+```bash
+# Provider 1: Google
+-e OIDC_PROVIDER_1_NAME=Google \
+-e OIDC_PROVIDER_1_SLUG=google \
+-e OIDC_PROVIDER_1_ISSUER=https://accounts.google.com \
+-e OIDC_PROVIDER_1_CLIENT_ID=xxx \
+-e OIDC_PROVIDER_1_CLIENT_SECRET=xxx \
+
+# Provider 2: Company SSO
+-e OIDC_PROVIDER_2_NAME="Company SSO" \
+-e OIDC_PROVIDER_2_SLUG=okta \
+-e OIDC_PROVIDER_2_ISSUER=https://company.okta.com \
+-e OIDC_PROVIDER_2_CLIENT_ID=yyy \
+-e OIDC_PROVIDER_2_CLIENT_SECRET=yyy \
+-e OIDC_PROVIDER_2_ADMIN_EMAIL_DOMAINS=company.com \
+```
+
+**Supported Providers:** Google, Okta, Keycloak, Authentik, PocketID, Azure AD, and any OIDC-compliant provider
+
+**Key Features:**
+- Automatic user provisioning on first login
+- Account linking for existing users
+- Admin role assignment based on email domains
+- Hybrid authentication (email/password + SSO)
+
+**Documentation:** See [docs/10-oidc-sso.md](docs/10-oidc-sso.md) for detailed setup guides and provider-specific configuration.
+
 ### 📚 Documentation
 
 For detailed setup instructions, configuration options, and getting started guides, visit: