Addresses all critical and high-severity findings from Fable security review.
CRITICAL FIX#1: Server Certificate Validation Bypass
- File: CertificateRenewal.cs
- Issue: Agent accepted ANY server certificate when ServerCertThumbprint not configured
- Fix: Now validates against Windows trusted roots when pinning not configured
- Impact: Prevents MITM attacks during renewal requests
CRITICAL FIX#2: Certificate Revocation Check Incomplete
- Files: asset.py, client_cert.py, migration 0022
- Issue: Revocation check used hasattr() and silently skipped when columns missing
- Fix: Applied migration 0022, uncommented revocation columns, removed hasattr()
- Impact: Revoked certificates can no longer authenticate or renew
CRITICAL FIX#3: Expired Certificates Cannot Renew
- Files: routes.py (renewal endpoint), CertificateRenewal.cs
- Issue: Expired certs fail at TLS handshake before reaching renewal endpoint
- Fix: Added API key + hostname fallback for renewal when cert expired
- Agent now sends hostname in request body for API key authentication
- Impact: Agents can renew expired certificates, 30-day window becomes effective
HIGH FIX#4: Hostname Injection Vulnerability
- File: routes.py
- Issue: No validation before passing hostname to certificate generation
- Fix: Added regex validation - 1-64 chars, alphanumeric plus dot/hyphen/underscore
- Impact: Prevents injection attacks via malicious hostnames
HIGH FIX#5: Rate Limit Bypass via Clock Manipulation
- File: routes.py
- Issue: Naive UTC datetime arithmetic vulnerable to timezone changes
- Fix: Use timezone-aware datetime with explicit UTC conversion
- Impact: Rate limit cannot be bypassed via clock manipulation
HIGH FIX#6: Hard Process Termination Loses In-Flight Work
- File: Program.cs
- Issue: Environment.Exit(0) aborted in-flight work and could corrupt state
- Fix: Graceful return from RunHostAsync() instead of Environment.Exit()
- Impact: Service exits cleanly, no lost telemetry or corrupted local state
HIGH FIX#7: Missing Database Transaction Isolation
- File: routes.py
- Issue: Race condition in concurrent renewal requests
- Fix: Added with_for_update() row-level locking for both auth paths
- Impact: Prevents concurrent renewals from bypassing rate limit
MEDIUM FIX#8: Missing Audit Logging for Failures
- File: routes.py
- Issue: Failed renewal attempts not captured in audit trail
- Fix: Added AuditLog.log() for cert generation and database update failures
- Impact: Security monitoring can detect repeated renewal failures
SECURITY HARDENING:
- Server cert validation: Never accepts certificates blindly
- Revocation enforcement: Fail closed if columns missing
- Expired cert handling: Dual-auth allows renewal while maintaining security
- Input validation: Hostname must match safe character set
- Transaction safety: Row locks prevent race conditions
- Audit trail: All failures logged for security monitoring
OPERATIONAL IMPROVEMENTS:
- Agents can now renew expired certificates (no more manual intervention)
- Graceful shutdown prevents data loss during renewal
- Rate limiting immune to timezone issues
- Comprehensive audit trail for troubleshooting
ADR COMPLIANCE:
- Maintains ADR-001 (Asset as platform contract)
- Maintains ADR-006 (Collector contract - backward compatible)
- Database naming (snake_case columns)
- No unicode/emojis
- Security best practices: ALL CRITICAL/HIGH issues resolved
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
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