# Security Hardening Implementation Summary

## Overview

This document summarizes the security hardening improvements added to the authentication service. All changes are marked with clear comments in the code for easy identification.

## 1. OTP Logging Safety ✅

**Implementation:** `src/utils/otpLogger.js`

- **Safe OTP logging helper** that only logs in development mode
- Never logs OTPs to production or centralized logging systems
- Uses `logOtpForDebug()` function that:
  - Only logs when `NODE_ENV === 'development'`
  - Masks phone numbers (shows only last 4 digits)
  - Clearly marked as `[DEV-ONLY]`

**Updated Files:**
- `src/services/smsService.js` - Now uses safe logging instead of direct `console.log`

**Configuration:**
- No configuration needed - automatically detects environment

## 2. IP/Device Risk Controls ✅

**Implementation:** `src/services/riskScoring.js`

- **IP blocking**: Blocks logins from configured CIDR ranges (private IPs, test ranges)
- **Risk scoring**: Calculates risk score based on:
  - IP address changes
  - Device changes
  - User agent changes
- **Suspicious refresh detection**: Detects when refresh tokens are used from different environments

**Features:**
- Configurable blocked IP ranges via `BLOCKED_IP_RANGES` environment variable
- Optional OTP re-verification requirement for suspicious refreshes
- Risk scores logged to audit trail

**Updated Files:**
- `src/routes/authRoutes.js` - Integrated IP blocking and risk scoring

**Configuration:**
```bash
BLOCKED_IP_RANGES=10.0.0.0/8,172.16.0.0/12  # Comma-separated CIDR blocks
REQUIRE_OTP_ON_SUSPICIOUS_REFRESH=true      # Require OTP on suspicious refresh
```

## 3. Access Token Replay Mitigation ✅

**Implementation:** `src/middleware/stepUpAuth.js`

- **Step-up authentication middleware** for sensitive operations
- Requires either:
  - Recent OTP verification (within configurable window)
  - High assurance flag in token (set after OTP verification)
- Access tokens now include `high_assurance` claim after OTP verification

**Usage:**
```javascript
router.post('/users/me/change-phone', 
  authMiddleware, 
  requireRecentOtpOrReauth,
  async (req, res) => { ... }
);
```

**Updated Files:**
- `src/services/tokenService.js` - Added `highAssurance` option to `signAccessToken()`
- `src/middleware/authMiddleware.js` - Extracts `high_assurance` claim from token
- `src/routes/authRoutes.js` - Issues tokens with `highAssurance: true` after OTP verification

**Configuration:**
```bash
STEP_UP_OTP_WINDOW_MINUTES=5  # Time window for "recent" OTP (default: 5)
```

## 4. Refresh Token Theft Mitigation ✅

**Implementation:** Enhanced in `src/routes/authRoutes.js` and `src/services/riskScoring.js`

- **Environment fingerprinting**: Tracks IP, user-agent, device ID
- **Suspicious refresh detection**: Compares current refresh with previous environment
- **Optional OTP requirement**: Can require OTP re-verification for suspicious refreshes
- **Enhanced logging**: All suspicious refreshes logged with risk scores

**Features:**
- Detects IP changes, device changes, user-agent changes
- Calculates risk score (0-100)
- Logs suspicious events to audit trail
- Optionally blocks suspicious refreshes until OTP verification

**Configuration:**
```bash
REQUIRE_OTP_ON_SUSPICIOUS_REFRESH=true  # Require OTP on suspicious refresh
```

## 5. JWT Key Rotation & Secrets Management ✅

**Implementation:** `src/services/jwtKeys.js`

- **Multiple signing keys** with key IDs (kid) in JWT header
- **Active key for signing**: Configurable via `JWT_ACTIVE_KEY_ID`
- **Multiple verification keys**: Supports key rotation without breaking existing tokens
- **Strict claims validation**: Validates `iss`, `aud`, `exp`, `iat`, `nbf`

**Key Features:**
- Tokens include `kid` in header for key identification
- Supports multiple keys for graceful rotation
- Validates issuer and audience claims
- Backward compatible with legacy single-key setup

**Updated Files:**
- `src/services/tokenService.js` - Uses new key management system
- `src/middleware/authMiddleware.js` - Validates tokens with key rotation support

**Configuration:**
```bash
JWT_ACTIVE_KEY_ID=1  # Key ID for signing new tokens
JWT_KEYS_JSON='{"1":"secret1","2":"secret2"}'  # Multiple keys for rotation
JWT_ISSUER=farm-auth-service  # Issuer claim
JWT_AUDIENCE=mobile-app       # Audience claim
JWT_REFRESH_KEY_ID=1         # Key ID for refresh tokens (optional)
```

**TODO for Production:**
- Load keys from secrets manager (AWS Secrets Manager, HashiCorp Vault, etc.)
- See comments in `src/services/jwtKeys.js` for implementation example

## 6. Stricter JWT Claims Validation ✅

**Implementation:** `src/services/jwtKeys.js` - `validateTokenClaims()`

- **Issuer (iss) validation**: Ensures tokens are from correct service
- **Audience (aud) validation**: Ensures tokens are for correct application
- **Expiration (exp) validation**: Already handled, but now with clock skew tolerance
- **Issued at (iat) validation**: Prevents tokens issued in the future
- **Not before (nbf) validation**: Validates if present

**Features:**
- Configurable clock skew (default: 60 seconds)
- Centralized validation function
- Used in all token verification paths

**Configuration:**
- Claims values set via `JWT_ISSUER` and `JWT_AUDIENCE` environment variables

## 7. CORS Hardening ✅

**Implementation:** `src/index.js`

- **Strict origin whitelisting**: Only allows explicitly configured origins
- **No wildcard support**: Never uses `*` when credentials are involved
- **Clear warnings**: Logs when allowing all origins (development only)
- **Production requirement**: CORS origins must be configured in production

**Features:**
- Development mode: Allows all origins only if none configured (with warning)
- Production mode: Requires explicit origin whitelist
- Validates origin on every request
- Blocks unauthorized origins with 403

**Configuration:**
```bash
CORS_ALLOWED_ORIGINS=https://app.example.com,https://api.example.com
```

**WARNING:** Never use `*` as an allowed origin when credentials or tokens are involved.

## 8. CSRF Future-Proofing ✅

**Implementation:** `CSRF_NOTES.md`

- **Documentation**: Comprehensive notes on CSRF protection
- **Current status**: No CSRF protection needed (using Bearer tokens)
- **Future guidance**: Implementation strategy if moving to cookies

**Key Points:**
- Current implementation (Bearer tokens) is CSRF-safe
- If moving to HTTP-only cookies, CSRF protection becomes mandatory
- Recommended: SameSite cookies + CSRF token validation

## 9. Enhanced Audit Logging ✅

**Implementation:** `src/services/auditLogger.js`

- **Risk levels**: INFO, SUSPICIOUS, HIGH_RISK
- **Enhanced logging**: All events include risk level
- **Anomaly detection**: Helper functions for pattern detection
- **Suspicious event logging**: 
  - Multiple failed OTP attempts
  - Suspicious refresh events
  - Blocked IP logins

**Features:**
- Automatic `risk_level` column creation in `auth_audit` table
- Structured logging with metadata
- Easy integration with external alerting systems

**Updated Files:**
- `src/routes/authRoutes.js` - Uses enhanced audit logging throughout

**Logging Functions:**
- `logAuthEvent()` - General auth event logging
- `logSuspiciousOtpAttempt()` - Failed OTP attempts
- `logBlockedIpLogin()` - Blocked IP logins
- `logSuspiciousRefresh()` - Suspicious refresh events
- `checkAnomalies()` - Pattern detection (for future alerting)

**TODO for Production:**
- Integrate with external alerting (PagerDuty, Slack, email)
- See comments in `src/services/auditLogger.js` for implementation example

## 10. Input Validation ✅

**Implementation:** `src/middleware/validation.js`

- **Centralized validation**: Reusable middleware for all endpoints
- **Type checking**: Validates field types
- **Length limits**: Prevents DoS via large payloads
- **Format validation**: Validates phone numbers, OTP codes, etc.

**Validation Middleware:**
- `validateRequestOtpBody()` - OTP request validation
- `validateVerifyOtpBody()` - OTP verification validation
- `validateRefreshTokenBody()` - Refresh token validation
- `validateLogoutBody()` - Logout validation

**Features:**
- Validates required fields
- Validates field types
- Validates string lengths
- Validates formats (phone, OTP code)
- Prevents oversized payloads

**Updated Files:**
- `src/routes/authRoutes.js` - All endpoints use validation middleware

## Environment Variables Summary

### Required
```bash
DATABASE_URL=postgresql://...
JWT_ACCESS_SECRET=...  # Or use JWT_KEYS_JSON
JWT_REFRESH_SECRET=... # Or use JWT_KEYS_JSON
```

### Optional (with defaults)
```bash
# JWT Configuration
JWT_ACTIVE_KEY_ID=1
JWT_KEYS_JSON='{"1":"secret1","2":"secret2"}'
JWT_ISSUER=farm-auth-service
JWT_AUDIENCE=mobile-app
JWT_REFRESH_KEY_ID=1

# Security Hardening
BLOCKED_IP_RANGES=10.0.0.0/8,172.16.0.0/12
REQUIRE_OTP_ON_SUSPICIOUS_REFRESH=false
STEP_UP_OTP_WINDOW_MINUTES=5

# CORS
CORS_ALLOWED_ORIGINS=https://app.example.com

# Rate Limiting (from previous implementation)
OTP_REQ_PHONE_10MIN_LIMIT=3
OTP_REQ_PHONE_DAY_LIMIT=10
OTP_REQ_IP_10MIN_LIMIT=20
OTP_REQ_IP_DAY_LIMIT=100
OTP_VERIFY_MAX_ATTEMPTS=5
OTP_VERIFY_FAILED_PER_HOUR_LIMIT=10
OTP_TTL_SECONDS=120
```

## Code Markers

All security hardening code is marked with comments:
- `// === SECURITY HARDENING: OTP LOGGING ===`
- `// === SECURITY HARDENING: IP/DEVICE RISK ===`
- `// === SECURITY HARDENING: JWT KEY ROTATION ===`
- `// === SECURITY HARDENING: ACCESS TOKEN REPLAY MITIGATION ===`
- `// === SECURITY HARDENING: REFRESH TOKEN THEFT MITIGATION ===`
- `// === SECURITY HARDENING: AUDIT LOGS & ANOMALY FLAGS ===`
- `// === SECURITY HARDENING: INPUT VALIDATION ===`
- `// === SECURITY HARDENING: CORS ===`
- `// === SECURITY HARDENING: CSRF (FUTURE-PROOFING) ===`

## Testing Recommendations

1. **OTP Logging**: Verify OTPs are not logged in production
2. **IP Blocking**: Test with blocked IP ranges
3. **Risk Scoring**: Test with different IPs/devices
4. **JWT Key Rotation**: Test token verification with multiple keys
5. **CORS**: Test with allowed and blocked origins
6. **Input Validation**: Test with invalid payloads
7. **Audit Logging**: Verify risk levels are logged correctly

## Next Steps

1. **Secrets Management**: Integrate with AWS Secrets Manager or HashiCorp Vault
2. **Alerting**: Set up alerts for HIGH_RISK events
3. **Monitoring**: Monitor audit logs for suspicious patterns
4. **Key Rotation**: Implement automated key rotation process
5. **CSRF**: If moving to cookies, implement CSRF protection

## Files Created

- `src/utils/otpLogger.js` - Safe OTP logging
- `src/services/riskScoring.js` - IP/device risk scoring
- `src/services/jwtKeys.js` - JWT key management
- `src/middleware/validation.js` - Input validation
- `src/services/auditLogger.js` - Enhanced audit logging
- `src/middleware/stepUpAuth.js` - Step-up authentication
- `CSRF_NOTES.md` - CSRF protection documentation
- `SECURITY_HARDENING_SUMMARY.md` - This file

## Files Modified

- `src/services/smsService.js` - Safe OTP logging
- `src/services/tokenService.js` - JWT key rotation, claims validation
- `src/middleware/authMiddleware.js` - JWT key rotation support
- `src/routes/authRoutes.js` - All security features integrated
- `src/index.js` - CORS hardening
- `src/config.js` - New environment variables documented