simple-object-server/SECURITY_REVIEW.md

Security Review - Simple Object Server

Date: 2025-01-10 Reviewed by: Security Audit Team

Executive Summary

This comprehensive security review analyzes the Simple Object Server C++23 application for potential vulnerabilities and security issues. The application provides a REST API for file storage with deduplication, metadata management, and token-based authentication. The review covered authentication, input validation, SQL injection risks, file upload security, rate limiting, CORS configuration, cryptographic implementations, error handling, and third-party dependencies.

Critical Issues (MUST FIX)

1. Hardcoded Authentication Tokens in Test Configuration [FIXED]

• Location: testing/sos_config.json:2-6 File removed
• Risk: CRITICAL RESOLVED - No longer exposed in repository
• Fix Implemented:
  • Removed hardcoded sos_config.json from repository
  • Added to .gitignore to prevent accidental commits
  • Created sos_config.json.example template
  • Test scripts now generate random tokens for each test run
  • Added generate_test_config.sh for dynamic token generation

2. No Token Hashing/Encryption [FIXED]

• Location: src/server.cpp:70-91
• Risk: CRITICAL RESOLVED - Tokens now use bcrypt hashing
• Fix Implemented:
  • Added bcrypt implementation in src/bcrypt.hpp
  • Server now verifies tokens against bcrypt hashes only
  • Created hash_token utility for generating secure hashes
  • Removed all plaintext token support for enhanced security
• Documentation: See README.md for token hashing instructions

3. **Weak Cryptographic Hash for Content [FIXED]

• Location: src/hash.cpp
• Risk: HIGH RESOLVED - Now using SHA-256 for content identification
• Fix Implemented:
  • Replaced XXHash with SHA-256 for all content hashing
  • Using OpenSSL's SHA-256 implementation for cryptographic security
  • All file hashes are now 256-bit SHA-256 hashes (64 hex characters)
  • Collision resistance: 2^128 operations needed for 50% probability
• Security Benefits:
  • Cryptographically secure against intentional collisions
  • Industry-standard hash function
  • Prevents malicious file substitution attacks

High-Risk Issues

4. Missing Security Headers [FIXED]

• Location: HTTP response handling throughout
• Risk: HIGH RESOLVED - Security headers now implemented
• Fix Implemented:
  • Added add_security_headers() method in server.cpp
  • Headers added to all HTTP responses across all endpoints
  • Implemented headers:
    • X-Frame-Options: DENY - Prevents clickjacking
    • X-Content-Type-Options: nosniff - Prevents MIME sniffing
    • X-XSS-Protection: 1; mode=block - Legacy XSS protection
    • Content-Security-Policy - Restrictive CSP preventing external resources
    • Referrer-Policy: strict-origin-when-cross-origin - Controls referrer info
    • Permissions-Policy - Disables unnecessary browser features
  • Note: HSTS header commented out by default (requires HTTPS configuration)

5. Insufficient Input Validation

• Location: Multiple endpoints (put_handler.cpp, update_handler.cpp)
• Risk: HIGH - Limited validation of input data
• Issues:
  • No maximum length validation for label:tag pairs
  • Limited JSON schema validation for metadata
  • No sanitization of special characters in labels/tags
  • File names from uploads used without proper sanitization
• Recommendation:
  • Implement comprehensive input validation schemas
  • Add length limits for all string inputs (e.g., max 255 chars for labels)
  • Validate against allowed character sets (alphanumeric + limited special chars)
  • Sanitize all user inputs before processing

Medium-Risk Issues

6. Information Disclosure in Error Messages

• Location: Error handling throughout (server.cpp:251, 263, 336-339)
• Risk: MEDIUM - Verbose error messages
• Issue: Error messages expose internal details:
  • File paths in error responses (server.cpp:263)
  • Database error details logged to console
  • Internal hash values in error messages
• Recommendation:
  • Implement generic error messages for production
  • Log detailed errors server-side only
  • Use error codes instead of descriptive messages
  • Implement structured logging with log levels

7. Weak Rate Limiting Configuration

• Location: src/server.cpp:123-126, testing/sos_config.json:8-9
• Risk: MEDIUM - Rate limiting only on authentication
• Issues:
  • Rate limiting only applies to failed auth attempts
  • No rate limiting on read operations
  • Test config has very weak limits (5 attempts in 2 seconds)
  • No distributed rate limiting for clustered deployments
• Recommendation:
  • Implement rate limiting for all endpoints
  • Use stronger default limits (e.g., 10 attempts per 300 seconds)
  • Consider per-IP and per-token rate limiting
  • Add configurable rate limits per endpoint type

8. CORS Wildcard Support

• Location: src/server.cpp:207-212
• Risk: MEDIUM - Potential for overly permissive CORS
• Issue: Support for wildcard (*) origins can lead to security misconfigurations
• Recommendation:
  • Require explicit origin listing in production
  • Validate origin format before accepting
  • Consider removing wildcard support entirely
  • Log CORS violations for monitoring

Low-Risk Issues

9. No Request Signing/HMAC

• Risk: LOW - No message integrity verification
• Issue: Requests are not signed, allowing potential tampering
• Recommendation: Consider implementing HMAC signing for write operations

10. Limited Monitoring/Alerting

• Risk: LOW - Insufficient security monitoring
• Issue: No built-in security event monitoring or alerting
• Recommendation:
  • Add metrics for failed auth attempts
  • Monitor for unusual access patterns
  • Implement alerting for security events

Good Security Practices Observed

Strengths

1. SQL Injection Protection: Excellent use of prepared statements with parameter binding throughout
2. Memory Safety: Modern C++23 with RAII patterns and smart pointers
3. File Upload Security:
   • Appropriate size limits (6GB max)
   • Content deduplication prevents storage exhaustion
   • Proper temporary file cleanup on errors
4. Path Traversal Protection: Files stored by hash, eliminating path traversal risks
5. Thread Safety: Proper use of mutexes for shared resources
6. Build Security: Static linking reduces dependency risks

Dependency Analysis

Third-Party Libraries

• Drogon Framework: Modern, actively maintained web framework
• nlohmann/json: Well-tested JSON library with good security track record
• SQLite3: Battle-tested database with good security history
• OpenSSL: Industry standard, though requires regular updates

Recommendations for Dependencies

1. Implement automated dependency scanning
2. Set up security alerts for known vulnerabilities
3. Regular dependency updates schedule
4. Consider using package pinning for reproducible builds

Security Architecture Recommendations

1. Defense in Depth

Implement multiple layers of security:

// Example: Layered validation
bool validateRequest(const Request& req) {
    if (!checkRateLimit(req)) return false;
    if (!authenticateToken(req)) return false;
    if (!validateInput(req)) return false;
    if (!authorizeAction(req)) return false;
    return true;
}

2. Secure Configuration Management

{
    "security": {
        "token_hash_algorithm": "argon2id",
        "token_min_length": 32,
        "enable_audit_log": true,
        "max_request_size": "100MB",
        "session_timeout": 3600
    }
}

3. Audit Logging Implementation

class AuditLogger {
    void logAuthAttempt(const std::string& ip, bool success);
    void logWriteOperation(const std::string& token, const std::string& operation);
    void logSecurityEvent(const std::string& event_type, const json& details);
};

Priority Action Items

1. CRITICAL - Immediate:

   • Remove hardcoded tokens from repository ✅ COMPLETED
   • Implement token hashing ✅ COMPLETED
   • Replace XXHash with SHA-256 for content identification

2. HIGH - Before Public Release:

   • Add security headers to all responses
   • Implement comprehensive input validation
   • Improve rate limiting coverage

3. MEDIUM - Within 30 Days:

   • Add security documentation (SECURITY.md)
   • Implement audit logging
   • Set up dependency scanning

4. LOW - Continuous Improvement:

   • Add request signing
   • Implement security monitoring
   • Regular security audits

Testing Recommendations

Security Testing Checklist

• Static analysis with clang-tidy and cppcheck
• Dynamic application security testing (DAST)
• Fuzzing for input validation
• Penetration testing for authentication bypass
• Load testing for DoS resilience
• Dependency vulnerability scanning

Example Security Test Cases

# Test authentication bypass
curl -X POST http://localhost:7703/upload -H "Authorization: Bearer invalid"

# Test SQL injection
curl "http://localhost:7703/metadata?key=test' OR '1'='1"

# Test path traversal
curl "http://localhost:7703/object/../../../etc/passwd"

# Test rate limiting
for i in {1..20}; do
    curl -X POST http://localhost:7703/upload -H "Authorization: Bearer wrong"
done

Compliance and Regulatory Considerations

1. Data Protection:

   • Implement data retention policies
   • Add secure deletion capabilities
   • Consider encryption at rest

2. Privacy:

   • Add privacy policy endpoint
   • Implement data subject rights (GDPR)
   • Metadata anonymization options

3. Audit Requirements:

   • Tamper-proof audit logs
   • Log retention policies
   • Security event correlation

Conclusion

The Simple Object Server demonstrates solid foundational security practices, particularly in SQL injection prevention and memory safety. However, critical vulnerabilities including hardcoded tokens, lack of token hashing, and use of non-cryptographic hashes for content identification must be addressed before public release.

The application would benefit from:

1. Immediate remediation of critical issues
2. Implementation of defense-in-depth strategies
3. Comprehensive security testing
4. Ongoing security monitoring and updates

With the recommended improvements, this application can achieve a robust security posture suitable for production deployment.

Resources

• OWASP Top 10
• CWE Top 25
• NIST Cybersecurity Framework
• ISO 27001 Standards