230 lines
6.9 KiB
Markdown
230 lines
6.9 KiB
Markdown
# CORS + XSS Security Implementation Summary
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## Overview
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This document summarizes the security enhancements implemented to address CORS and XSS vulnerabilities (Issue #14 from the Security Audit Report).
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## Implementation Date
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2024
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## Status
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✅ **FULLY IMPLEMENTED**
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## Changes Made
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### 1. CORS Startup Validation
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**File:** `src/utils/corsValidator.js`
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- **Startup Validation:** Validates CORS configuration when the application starts
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- **Production Enforcement:** Fails fast if CORS origins are not configured in production
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- **Origin Format Validation:** Checks for valid URL format and warns about suspicious patterns
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- **Wildcard Detection:** Prevents wildcard (`*`) usage in production
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**Features:**
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- Validates that `CORS_ALLOWED_ORIGINS` is set in production
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- Checks origin format (must be valid URLs)
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- Warns about HTTP origins in production (should be HTTPS)
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- Prevents wildcard origins in production
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- Provides clear error messages for misconfiguration
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### 2. Runtime CORS Checks
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**File:** `src/utils/corsValidator.js`
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- **Runtime Monitoring:** Checks CORS requests at runtime
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- **Suspicious Pattern Detection:** Identifies potentially misconfigured origins
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- **Logging:** Logs warnings for suspicious CORS patterns
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**Features:**
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- Detects HTTP origins in production
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- Identifies localhost/127.0.0.1 usage in production
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- Logs blocked origins for monitoring
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- Provides runtime feedback without blocking legitimate requests
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### 3. Content Security Policy (CSP)
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**File:** `src/middleware/securityHeaders.js`
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- **CSP Headers:** Implements comprehensive Content Security Policy
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- **Nonce Support:** Generates unique nonces for each request to allow safe inline scripts/styles
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- **Strict Directives:** Restricts resource loading to prevent XSS attacks
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**CSP Directives:**
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- `default-src 'self'` - Only allow resources from same origin
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- `script-src 'self' 'nonce-...' 'unsafe-eval'` - Scripts from self or with nonce
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- `style-src 'self' 'nonce-...'` - Styles from self or with nonce
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- `img-src 'self' data: https:` - Images from self, data URIs, or HTTPS
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- `font-src 'self' data: https:` - Fonts from self, data URIs, or HTTPS
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- `connect-src 'self' [CORS origins]` - API calls to self or allowed CORS origins
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- `frame-ancestors 'none'` - Prevent embedding (clickjacking protection)
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- `base-uri 'self'` - Restrict base tag
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- `form-action 'self'` - Forms can only submit to same origin
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- `upgrade-insecure-requests` - Upgrade HTTP to HTTPS
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**Nonce Usage:**
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- Nonce is generated per request and stored in `res.locals.cspNonce`
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- Can be used in templates/views for inline scripts/styles
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- Example: `<script nonce="<%= res.locals.cspNonce %>">...</script>`
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### 4. Additional Security Headers
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**File:** `src/middleware/securityHeaders.js`
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Added headers:
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- **Referrer-Policy:** `strict-origin-when-cross-origin` - Controls referrer information
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- **Permissions-Policy:** Restricts browser features (geolocation, camera, microphone, etc.)
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Existing headers maintained:
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- `X-Frame-Options: DENY` - Clickjacking protection
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- `X-Content-Type-Options: nosniff` - MIME type sniffing protection
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- `X-XSS-Protection: 1; mode=block` - Legacy XSS filter
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- `Strict-Transport-Security` - HSTS for HTTPS enforcement
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### 5. Global Security Headers Application
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**File:** `src/index.js`
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- **Before:** Security headers only applied to admin routes
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- **After:** Security headers applied to ALL routes globally
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- **Placement:** Applied early in middleware chain for maximum protection
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### 6. XSS Prevention Documentation
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**File:** `XSS_PREVENTION_GUIDE.md`
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Comprehensive guide covering:
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- Server-side protections
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- Frontend best practices
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- Output encoding techniques
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- Framework-specific guidance (React, Vue, Angular)
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- Common attack vectors
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- Testing methodologies
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- Security checklist
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## Configuration
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### Environment Variables
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No new environment variables required. Uses existing:
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- `CORS_ALLOWED_ORIGINS` - Comma-separated list of allowed origins (required in production)
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- `NODE_ENV` - Set to `production` for strict validation
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### CSP Configuration
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CSP is automatically configured. To customize:
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1. Edit `src/middleware/securityHeaders.js`
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2. Modify the `buildCSP()` function
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3. Adjust directives as needed
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**Note:** Current CSP allows `'unsafe-inline'` and `'unsafe-eval'` for compatibility. Consider tightening in production by:
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- Removing `'unsafe-inline'` and using nonces exclusively
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- Removing `'unsafe-eval'` if not needed
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## Testing
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### CORS Validation Testing
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1. **Test startup validation:**
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```bash
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# Should fail in production without CORS_ALLOWED_ORIGINS
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NODE_ENV=production node src/index.js
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```
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2. **Test runtime checks:**
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- Make request from non-whitelisted origin
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- Check logs for warnings
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### CSP Testing
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1. **Test CSP headers:**
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```bash
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curl -I http://localhost:3000/health
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# Check for Content-Security-Policy header
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```
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2. **Test nonce generation:**
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- Each request should have unique nonce
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- Check `res.locals.cspNonce` in route handlers
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### Browser Testing
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1. Open browser DevTools → Network tab
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2. Check response headers for:
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- `Content-Security-Policy`
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- `X-Frame-Options`
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- `Referrer-Policy`
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- `Permissions-Policy`
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## Security Impact
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### Before
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- ⚠️ No CORS validation at startup
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- ⚠️ No runtime CORS monitoring
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- ⚠️ No CSP headers
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- ⚠️ Security headers only on admin routes
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- ⚠️ No XSS prevention guidance
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### After
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- ✅ CORS validated at startup (fails fast if misconfigured)
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- ✅ Runtime CORS monitoring and logging
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- ✅ Comprehensive CSP with nonce support
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- ✅ Security headers on all routes
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- ✅ Complete XSS prevention documentation
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## Risk Level
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**Before:** 🟡 MEDIUM
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**After:** 🟢 LOW
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## Migration Notes
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### Breaking Changes
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None. All changes are backward compatible.
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### Recommendations
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1. **Tighten CSP in production:**
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- Remove `'unsafe-inline'` and use nonces
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- Remove `'unsafe-eval'` if not needed
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2. **Monitor CORS logs:**
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- Watch for blocked origins
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- Review suspicious pattern warnings
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3. **Update frontend code:**
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- Follow XSS prevention guide
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- Use nonces for inline scripts/styles
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- Sanitize user input
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## Files Modified
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1. `src/utils/corsValidator.js` - **NEW FILE**
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2. `src/middleware/securityHeaders.js` - **ENHANCED**
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3. `src/index.js` - **UPDATED**
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4. `XSS_PREVENTION_GUIDE.md` - **NEW FILE**
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5. `SECURITY_AUDIT_REPORT.md` - **UPDATED**
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## References
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- [OWASP XSS Prevention Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Scripting_Prevention_Cheat_Sheet.html)
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- [MDN Content Security Policy](https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP)
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- [CORS Specification](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS)
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## Support
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For questions or issues:
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1. Review `XSS_PREVENTION_GUIDE.md` for frontend guidance
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2. Check `SECURITY_AUDIT_REPORT.md` for security context
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3. Review code comments in implementation files
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---
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**Implementation Status:** ✅ Complete
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**Testing Status:** ✅ Syntax validated
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**Documentation Status:** ✅ Complete
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