From 09b4f120261a881c921c330f1fc8965553d699e4 Mon Sep 17 00:00:00 2001 From: Charles N Wyble Date: Fri, 20 Feb 2026 10:35:42 -0500 Subject: [PATCH] docs(audit): update FINDING-002 to informational (by design) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Firewall OUTPUT DROP policy confirmed as intentional for immutable system security model: - Zero traffic leakage (no DNS poisoning, NTP spoofing, C2 exfil) - Immutable system with no in-place updates - WireGuard endpoint loaded via USB disk - Time synchronized from host/hypervisor Updated risk summary: 1 HIGH (Secure Boot), 4 MEDIUM, 3 LOW, 2 INFO Remaining findings (001, 005, 006, 007, 008) to be addressed by software team per audit recommendations. 💘 Generated with Crush Assisted-by: GLM-4 via Crush --- docs/audit/2026-02-20/SUMMARY.md | 32 +++++++++++---------- docs/audit/2026-02-20/findings.md | 46 +++++++++++++++---------------- 2 files changed, 41 insertions(+), 37 deletions(-) diff --git a/docs/audit/2026-02-20/SUMMARY.md b/docs/audit/2026-02-20/SUMMARY.md index b29e763..2e7c0b8 100644 --- a/docs/audit/2026-02-20/SUMMARY.md +++ b/docs/audit/2026-02-20/SUMMARY.md @@ -30,10 +30,10 @@ KNEL-Football is a hardened Debian 13 Linux distribution designed as a **secure | Severity | Count | Key Areas | |----------|-------|-----------| | Critical | 0 | - | -| High | 2 | Secure Boot keys, Firewall output | +| High | 1 | Secure Boot keys | | Medium | 4 | Docker privileged, USB automount, KDF config, Supply chain | | Low | 3 | Test gaps, Documentation, Input validation | -| Info | 1 | Package management | +| Info | 2 | Firewall (by design), Package management | --- @@ -45,14 +45,19 @@ Keys generated at build time without HSM or secure storage. An attacker with bui **Impact**: Complete chain of trust compromise **Effort**: Medium (requires key management infrastructure) -### 2. Firewall Output Chain Blocks Essential Services (HIGH) -Default DROP policy on OUTPUT chain prevents DNS resolution, NTP synchronization, and system updates. - -**Impact**: System cannot function properly (DNS, time sync, updates) -**Effort**: Low (add explicit allow rules) - --- +## Design Decisions Confirmed + +### Firewall Output Policy (By Design) +The strict OUTPUT DROP policy was confirmed as **intentional** for an immutable system: +- Zero traffic leakage (no DNS poisoning, NTP spoofing, C2 exfiltration vectors) +- Immutable system with no in-place updates (CVEs handled by ISO regeneration) +- WireGuard endpoint loaded via USB disk (wg0.conf) +- Time synchronized from host/hypervisor + +**Assessment**: Defensible security posture for an air-gapped access terminal. + ## Positive Security Observations 1. **Strong SDLC Enforcement** - Pre-commit hooks enforce TDD, linting, and coverage @@ -67,9 +72,8 @@ Default DROP policy on OUTPUT chain prevents DNS resolution, NTP synchronization ## Recommendations Priority ### Must Fix Before Release -1. Fix firewall OUTPUT chain to allow DNS/NTP/updates -2. Disable USB automount (conflicts with security model) -3. Verify Argon2id KDF is actually used in LUKS +1. Disable USB automount (conflicts with security model) +2. Verify Argon2id KDF is actually used in LUKS ### Short-term (30 days) 1. Implement Secure Boot key management with HSM or air-gapped storage @@ -92,7 +96,7 @@ Default DROP policy on OUTPUT chain prevents DNS resolution, NTP synchronization | NIST SP 800-53 AC-19 | ⚠️ Issue | USB automount | | NIST SP 800-111 | ✅ Pass | LUKS2 encryption | | CIS Benchmark 6.x | ✅ Pass | Comprehensive audit logging | -| FedRAMP SC-7 | ⚠️ Issue | Firewall output policy | +| FedRAMP SC-7 | ✅ Pass | Strict output policy (by design) | --- @@ -105,9 +109,9 @@ Default DROP policy on OUTPUT chain prevents DNS resolution, NTP synchronization ## Conclusion -KNEL-Football demonstrates **mature security architecture** with strong foundations. The project is **suitable for production with remediation** of the two HIGH findings. The SDLC practices are exemplary and should be maintained. +KNEL-Football demonstrates **mature security architecture** with strong foundations. The project is **suitable for production with remediation** of the HIGH finding. The SDLC practices are exemplary and should be maintained. -**Recommendation**: Address firewall and Secure Boot key issues before release. The remaining findings can be addressed post-release with documented timelines. +**Recommendation**: Address Secure Boot key management before release. The firewall output policy is confirmed as intentional design for an immutable system. --- diff --git a/docs/audit/2026-02-20/findings.md b/docs/audit/2026-02-20/findings.md index efe24f6..25e18cd 100644 --- a/docs/audit/2026-02-20/findings.md +++ b/docs/audit/2026-02-20/findings.md @@ -33,9 +33,10 @@ ### Areas Requiring Attention 1. **Secure Boot Key Management**: Keys generated at build time without HSM or secure storage -2. **Firewall Output Policy**: Default DROP on output chain may break DNS/updates -3. **USB Automount**: Security risk for a secure workstation -4. **Supply Chain**: No SLSA/SBOM, unpinned Docker packages +2. **USB Automount**: Security risk for a secure workstation +3. **Supply Chain**: No SLSA/SBOM, unpinned Docker packages + +**Note**: The strict firewall OUTPUT policy (FINDING-002) was confirmed as **intentional design** for an immutable system with zero traffic leakage. --- @@ -83,11 +84,11 @@ openssl req -new -x509 -newkey rsa:4096 -sha256 -days 3650 \ --- -### FINDING-002: Firewall Output Chain Default DROP (HIGH) +### FINDING-002: Firewall Output Chain Default DROP (INFORMATIONAL - BY DESIGN) **Category**: Network Security -**Severity**: HIGH -**Status**: Open +**Severity**: INFORMATIONAL +**Status**: By Design - No Action Required **Description**: The nftables firewall configuration sets a default DROP policy on the OUTPUT chain, only allowing loopback, WireGuard traffic, and ICMP ping. @@ -106,27 +107,26 @@ chain output { } ``` -**Issues**: -1. No DNS (UDP/TCP 53) allowed - system cannot resolve hostnames -2. No NTP (UDP 123) allowed - time synchronization will fail -3. No HTTP/HTTPS allowed - system cannot fetch updates or time -4. WireGuard endpoint IP must be known at configuration time -5. No outbound rules for apt repositories +**Clarification from Project Team**: +This is an **intentional design choice** for an immutable system security model: -**Risk**: System may be unable to: -- Synchronize time (breaks Kerberos, certificate validation) -- Resolve DNS names -- Receive security updates -- Access WireGuard endpoint if IP changes +1. **Zero Traffic Leakage**: No DNS, no NTP, no HTTP/HTTPS - eliminates DNS poisoning, NTP spoofing, and C2 exfiltration vectors +2. **Immutable System**: Package management disabled, no in-place updates - CVEs handled by regenerating ISO and recreating VM +3. **WireGuard via USB**: Endpoint IP loaded from `wg0.conf` on USB disk at provisioning time +4. **Time from Host**: VM receives time from hypervisor/host system, no network time sync needed +5. **Known Endpoints**: WireGuard peer IP is static and pre-configured + +**Assessment**: +This is a **defensible security posture** for an air-gapped, immutable access terminal. The strict OUTPUT DROP policy prevents: +- Data exfiltration via DNS tunneling +- C2 beacon traffic +- Supply chain attacks via compromised update servers +- NTP-based attacks **Recommendation**: -1. Add explicit DNS rules (TCP/UDP 53 to known DNS servers) -2. Add NTP rules (UDP 123 to time servers) -3. Consider allowing HTTPS to specific update repositories -4. Document the firewall policy and required endpoints -5. Add validation that WireGuard endpoint is reachable +Document this design decision in the security model documentation for future auditors. -**Compliance Impact**: NIST SP 800-41, CIS Benchmark 3.x +**Compliance Impact**: NIST SP 800-41, CIS Benchmark 3.x - Compensating controls in place (immutable system, no package management) ---