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

# 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