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Security Enhancement: Context Preservation Protection

Overview

This document describes the comprehensive security enhancements implemented in the context preservation system to protect against regex denial-of-service (ReDoS) attacks and input validation vulnerabilities.

Security Vulnerabilities Addressed

1. Regex Denial-of-Service (ReDoS) Attacks

Original Risk: Unvalidated user input processed through regex operations could cause exponential backtracking, leading to application hang or crash.

Locations Fixed:

  • _parse_requirements(): Lines 84, 89, 97
  • _parse_constraints(): Lines 110, 118
  • _parse_success_criteria(): Line 133
  • _parse_target(): Lines 146, 152
  • get_latest_session_id(): Line 342

2. Input Size Attacks

Original Risk: Unlimited input size could cause memory exhaustion.

Protection Implemented:

  • Maximum input size: 50KB
  • Maximum line length: 1000 characters
  • Early validation before processing

3. Input Injection Attacks

Original Risk: Malicious content in user input could be stored and executed in various contexts.

Protection Implemented:

  • Unicode normalization (NFKC)
  • Character whitelist filtering
  • HTML escaping in output
  • Content sanitization

Security Architecture

SecurityConfig Class

Centralized security configuration with the following limits:

MAX_INPUT_SIZE = 50 * 1024      # 50KB maximum input
MAX_LINE_LENGTH = 1000          # Maximum line length
MAX_SENTENCES = 100             # Maximum sentences to process
MAX_BULLETS = 20                # Maximum bullet points
MAX_REQUIREMENTS = 10           # Maximum requirements
MAX_CONSTRAINTS = 5             # Maximum constraints
MAX_CRITERIA = 5                # Maximum success criteria
REGEX_TIMEOUT = 1.0             # 1 second regex timeout

SecurityValidator Class

Provides safe methods for all regex operations:

Input Validation

  • validate_input_size(): Enforces size limits
  • sanitize_input(): Applies whitelist filtering

Safe Regex Operations

  • safe_regex_finditer(): Timeout-protected finditer
  • safe_regex_search(): Timeout-protected search
  • safe_regex_findall(): Timeout-protected findall
  • safe_split(): Timeout-protected split

Protection Mechanisms

1. Timeout Protection

Implementation: SIGALRM signal-based timeouts (Unix/Linux/macOS) Fallback: Graceful degradation for Windows (no timeout) Duration: 1 second maximum for any regex operation

def timeout_handler(signum, frame):
    raise RegexTimeoutError(f"Regex operation timed out after {REGEX_TIMEOUT}s")

old_handler = signal.signal(signal.SIGALRM, timeout_handler)
signal.alarm(int(REGEX_TIMEOUT))
# ... regex operation ...
signal.alarm(0)
signal.signal(signal.SIGALRM, old_handler)

2. Input Sanitization

Character Whitelist: Only allows safe characters for text processing Unicode Normalization: Prevents encoding-based bypass attempts HTML Escaping: Protects against injection in output contexts

ALLOWED_CHARS = set(
    'abcdefghijklmnopqrstuvwxyz'
    'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
    '0123456789'
    ' \t\n\r'
    '.,!?;:'
    '()[]{}'
    '"\'\\-_'
    '*•-'
    '#@$%&+=<>/\\|`~'
)

3. Result Limiting

Max Results: All operations limit the number of results returned Memory Protection: Prevents memory exhaustion from large result sets Processing Limits: Bounds on sentences, lines, and operations processed

4. Error Handling

Fail-Safe Design: Operations fail securely with fallback responses Information Hiding: Security errors don't expose system internals Graceful Degradation: System continues operating when individual operations fail

except (RegexTimeoutError, Exception):
    # Secure fallback without exposing error details
    requirements.append("[Requirements extraction failed - manual review needed]")

Implementation Details

Modified Methods

  1. extract_original_request()
  2. Added input validation at entry point
  3. Secure error handling with sanitized responses

  4. Full input sanitization before processing

  5. _parse_requirements()

  6. Replaced unsafe re.finditer() with safe_regex_finditer()
  7. Replaced unsafe re.split() with safe_split()
  8. Replaced unsafe re.findall() with safe_regex_findall()

  9. Added length limits for extracted requirements

  10. _parse_constraints()

  11. Replaced unsafe re.search() with safe_regex_search()
  12. Replaced unsafe re.split() with safe_split()

  13. Added length and count limits

  14. _parse_success_criteria()

  15. Safe string operations with length limits

  16. Bounded line processing (max 100 lines)

  17. _parse_target()

  18. Replaced unsafe re.search() with safe_regex_search()
  19. Replaced unsafe re.split() with safe_split()

  20. Target length limits (max 200 characters)

  21. get_latest_session_id()

  22. Directory scanning limits (max 1000 directories)
  23. Safe regex matching with timeout protection

  24. Secure error handling

  25. _save_original_request()

  26. HTML escaping for all user content

  27. Prevention of injection in markdown output

  28. format_agent_context()

  29. HTML escaping for all displayed content
  30. Safe context injection

Testing

Comprehensive test suite covers:

Security Test Categories

  1. Input Validation Tests
  2. Oversized input rejection
  3. Long line detection

  4. Non-string input handling

  5. Sanitization Tests

  6. Malicious script removal
  7. Unicode normalization

  8. Character filtering

  9. Timeout Protection Tests

  10. Malicious regex patterns
  11. Operation time limits

  12. Graceful timeout handling

  13. Limit Enforcement Tests

  14. Result count limits
  15. Processing bounds

  16. Memory protection

  17. Edge Case Tests

  18. Empty input handling
  19. Whitespace-only input

  20. Unicode edge cases

  21. Performance Tests

  22. Large valid input processing
  23. DoS protection verification
  24. Deep nesting protection

Running Security Tests

cd /path/to/project
python -m pytest tests/test_context_preservation_security.py -v

Security Best Practices Applied

Defense in Depth

  • Multiple layers of protection
  • Input validation + sanitization + timeout + limits
  • Fail-safe error handling

Principle of Least Privilege

  • Minimal allowed character set
  • Restrictive processing limits
  • Limited result sets

Fail Secure

  • Default deny on validation failure
  • Secure error responses
  • No sensitive information leakage

Input Validation

  • Server-side validation (never trust client)
  • Whitelist approach over blacklist
  • Early validation before processing

Migration Guide

From Original to Secure Version

  1. Replace imports:
# Old
from context_preservation import ContextPreserver

# New
from context_preservation_secure import ContextPreserver
  1. Handle new exceptions:
try:
    result = preserver.extract_original_request(prompt)
except (InputValidationError, RegexTimeoutError) as e:
    # Handle security validation failures
    pass
  1. Update error handling:
  2. Check for security_error in response
  3. Handle sanitized error responses
  4. Monitor for timeout conditions

Backward Compatibility

  • All public APIs remain unchanged
  • Return value formats are preserved
  • New error conditions are additive

Monitoring and Alerting

Security Events to Monitor

  1. Input Validation Failures
  2. Oversized input attempts
  3. Character filtering events

  4. Encoding attack attempts

  5. Timeout Events

  6. Regex timeout occurrences
  7. Performance degradation

  8. Potential attack patterns

  9. Error Patterns

  10. Repeated validation failures
  11. Unusual input characteristics
  12. Processing anomalies
# Log security events
logger.warning(f"Input validation failed: {type(e).__name__}")
logger.info(f"Regex timeout occurred in {operation}")
logger.debug(f"Sanitized input: {original_length} -> {sanitized_length}")

Future Enhancements

Potential Improvements

  1. Advanced Rate Limiting
  2. Per-IP request limits
  3. Pattern-based throttling

  4. Adaptive thresholds

  5. Content Analysis

  6. Machine learning-based detection
  7. Pattern recognition

  8. Anomaly detection

  9. Enhanced Monitoring

  10. Real-time security metrics
  11. Attack pattern analysis

  12. Automated response

  13. Configuration Management

  14. Runtime security parameter tuning
  15. Environment-specific limits
  16. Dynamic threshold adjustment

Conclusion

The security enhancements provide comprehensive protection against regex DoS attacks and input validation vulnerabilities while maintaining full functionality and backward compatibility. The multi-layered approach ensures robust security without impacting legitimate use cases.

All security controls are tested, documented, and designed for long-term maintainability. The implementation follows security best practices and provides a foundation for future security enhancements.