# Security Policy for Feature Flags Module

## Overview

The Feature Flags module controls feature availability and gradual rollouts. Security is critical as this module directly influences application behavior and can be targeted for unauthorized access control manipulation.

## Security Considerations

### Flag Configuration Security

1. **Configuration Source Validation**: Validate all flag configuration sources (files, environment variables, remote services) before applying.
2. **Type Safety**: Enforce strict typing for flag values to prevent injection attacks.
3. **Default Deny**: When flag configuration is unavailable, default to the most restrictive behavior.
4. **Audit Logging**: Log all flag state changes with timestamps and source information.

### Access Control

1. **Flag Override Protection**: Restrict who can override flag values at runtime.
2. **Environment Isolation**: Ensure production flag configurations cannot be modified from development environments.
3. **API Authentication**: Require authentication for any remote flag management APIs.
4. **Rate Limiting**: Implement rate limiting on flag evaluation endpoints to prevent enumeration attacks.

### Data Protection

1. **Sensitive Flags**: Mark flags that control security-sensitive features for enhanced protection.
2. **No Secrets in Flags**: Never store secrets, credentials, or sensitive data as flag values.
3. **Flag Value Masking**: Mask or redact sensitive flag values in logs and debug output.

## Threat Model

| Threat | Impact | Mitigation |
|--------|--------|------------|
| Flag configuration tampering | Unauthorized feature access | Configuration integrity checks, signed configs |
| Flag enumeration | Information disclosure | Rate limiting, authentication |
| Flag injection | Feature bypass | Input validation, type checking |
| Replay attacks | Stale configuration | Timestamp validation, configuration versioning |

## Secure Implementation Patterns

```python
# Example: Secure flag evaluation with validation
def get_feature_flag(flag_name: str, default: bool = False) -> bool:
    """Securely evaluate a feature flag."""
    # Validate flag name (prevent injection)
    if not is_valid_flag_name(flag_name):
        logger.warning(f"Invalid flag name attempted: {flag_name}")
        return default

    # Check authorization for flag access
    if not current_user_can_access_flag(flag_name):
        return default

    # Get and validate flag value
    value = _get_flag_value(flag_name)
    if value is None:
        return default

    # Log access for audit
    audit_log.record_flag_access(flag_name, value)

    return value
```

## Compliance

- Configuration changes must be traceable
- Flag states must be auditable
- Access to flag management must be role-based

## Vulnerability Reporting

Report security vulnerabilities via the main project's security reporting process. Include:
- Flag name(s) affected
- Expected vs actual behavior
- Steps to reproduce
