# KNEL-Football Security Model

## Overview

The KNEL-Football security model implements a defense-in-depth approach to create a highly secure, compliant Debian 13 operating system for tier0 infrastructure access.

**Copyright © 2026 Known Element Enterprises LLC**
**License: GNU Affero General Public License v3.0 only**

## Security Architecture

### Core Principles

1. **Least Privilege** - Users and processes have only necessary permissions
2. **Defense in Depth** - Multiple layers of security controls
3. **Zero Trust** - No implicit trust, all access must be authorized
4. **Immutability** - System configuration is not easily modifiable
5. **Minimal Attack Surface** - Only necessary services and packages included

### System Hardening Layers

#### 1. Boot Security Layer

- **UEFI-Only Boot** - No legacy BIOS support prevents boot attacks
- **Secure Boot** - Cryptographic verification of bootloader and kernel
- **Unified Kernel Image (UKI)** - Signed kernel+initramfs+cmdline bundle
- **Kernel Lockdown** - Kernel runs in confidentiality lockdown mode
- **Measured Boot** - Boot chain integrity measurement and attestation

##### Secure Boot Trust Chain

```
┌─────────────────────────────────────────────────────────────────────────────┐
│                        SECURE BOOT TRUST CHAIN                               │
├─────────────────────────────────────────────────────────────────────────────┤
│                                                                             │
│  ┌─────────────────────┐                                                    │
│  │   UEFI Firmware     │  ← Root of Trust (Hardware)                       │
│  └──────────┬──────────┘                                                    │
│             │ Verifies PK signature                                         │
│             ▼                                                               │
│  ┌─────────────────────┐                                                    │
│  │  PK (Platform Key)  │  ← RSA-4096, SHA-256, 3650 days                   │
│  │    Self-signed      │     Platform owner authorization                   │
│  └──────────┬──────────┘                                                    │
│             │ Signs KEK updates                                             │
│             ▼                                                               │
│  ┌─────────────────────┐                                                    │
│  │ KEK (Key Exchange)  │  ← RSA-4096, SHA-256, 3650 days                   │
│  │   Signed by PK      │     OS/key exchange authorization                  │
│  └──────────┬──────────┘                                                    │
│             │ Signs db updates                                              │
│             ▼                                                               │
│  ┌─────────────────────┐                                                    │
│  │ db (Signature DB)   │  ← RSA-4096, SHA-256, 3650 days                   │
│  │  Signed by KEK      │     Allowed EFI binaries                           │
│  └──────────┬──────────┘                                                    │
│             │ Verifies UKI signature                                        │
│             ▼                                                               │
│  ┌─────────────────────┐                                                    │
│  │   UKI (Unified      │  ← Signed EFI binary                              │
│  │   Kernel Image)     │     • linuxx64.efi.stub                           │
│  │                     │     • os-release                                  │
│  │                     │     • cmdline (lockdown=confidentiality)          │
│  │                     │     • linux (vmlinuz)                             │
│  │                     │     • initrd (initramfs)                          │
│  └──────────┬──────────┘                                                    │
│             │ Boots with lockdown                                           │
│             ▼                                                               │
│  ┌─────────────────────┐                                                    │
│  │   Linux Kernel      │  ← Kernel Lockdown Mode                           │
│  │   (Confidentiality) │     • module.sig_enforce=1                        │
│  │                     │     • No unsigned modules                         │
│  │                     │     • No /dev/mem access                          │
│  │                     │     • No kexec                                    │
│  └─────────────────────┘                                                    │
│                                                                             │
└─────────────────────────────────────────────────────────────────────────────┘
```

##### Secure Boot Keys

| Key | Purpose | Algorithm | Validity |
|-----|---------|-----------|----------|
| PK (Platform Key) | Authorizes KEK updates | RSA-4096, SHA-256 | 3650 days |
| KEK (Key Exchange Key) | Authorizes db updates | RSA-4096, SHA-256 | 3650 days |
| db (Signature Database) | Signs EFI binaries | RSA-4096, SHA-256 | 3650 days |

##### UKI Components

| Section | Content | Purpose |
|---------|---------|---------|
| .osrel | /etc/os-release | OS identification |
| .cmdline | Kernel parameters | lockdown=confidentiality, module.sig_enforce=1 |
| .linux | vmlinuz-{version} | Kernel image |
| .initrd | initrd.img-{version} | Initial ramdisk |

##### Kernel Lockdown Effects

When Secure Boot is active and kernel lockdown is enabled:
- **No unsigned kernel modules** - module.sig_enforce=1
- **No /dev/mem or /dev/kmem access** - Prevents direct memory manipulation
- **No kexec** - Cannot replace running kernel
- **No hibernation to untrusted storage** - Prevents data extraction
- **No iopl/ioperm** - Restricts I/O port access
- **No MSRs from userspace** - Restricts model-specific register access

##### Secure Boot Enforcement

- **Build Time**: Keys generated, UKI signed during ISO build
- **Install Time**: Keys enrolled in UEFI firmware (setup mode)
- **Boot Time**: UEFI verifies UKI signature before boot
- **Runtime**: Kernel enforces lockdown mode restrictions

#### 2. Network Security Layer

- **Network Isolation** - No general internet access
- **VPN-Only Access** - WireGuard tunnel required for all network traffic
- **Firewall Hardening** - Default deny policy with specific rules
- **Wireless Disabled** - WiFi and Bluetooth permanently disabled
- **Dynamic Configuration** - Firewall rules adapt to WireGuard endpoints

#### 3. System Security Layer

- **Kernel Module Blacklisting** - Prevents loading of dangerous modules
- **Service Hardening** - Unnecessary services disabled
- **Process Isolation** - Application sandboxing where applicable
- **Resource Limits** - Prevent resource exhaustion attacks
- **Audit Logging** - Comprehensive system activity monitoring

#### 4. Access Control Layer

- **Strong Authentication** - 14-character minimum password policy
- **No Auto-Login** - Manual authentication required
- **Privacy Mode** - Usernames hidden in display manager
- **Sudo Configuration** - Controlled administrative access
- **File Permissions** - Secure access controls on sensitive files

#### 5. Application Security Layer

- **Minimal Desktop** - IceWM provides minimal attack surface
- **Required Applications Only** - Only essential tools included
- **Secure Defaults** - Applications configured with secure settings
- **No Package Management** - System immutability through disabled package tools

## Threat Model

### Adversary Capabilities

| Capability | Mitigation | Effectiveness |
|-------------|-------------|---------------|
| Network-based attacks | Network isolation, firewall | High |
| Local privilege escalation | User permissions, audit | Medium |
| Physical access attacks | Encryption, secure boot | High |
| Social engineering | Training, documentation | Medium |
| Supply chain attacks | Source verification, testing | Medium |

### Attack Scenarios

#### Scenario 1: Network-based Attack
**Attack:** Attempt to compromise system via network connection
**Mitigation:** 
- No general network access available
- Only WireGuard tunnel traffic allowed
- Firewall default deny policy
- Dynamic endpoint-based rules

#### Scenario 2: USB-based Attack
**Attack:** Malicious USB device inserted
**Mitigation:**
- USB devices mounted with restrictive permissions
- No auto-execution from removable media
- Filesystem permissions restrict access
- Audit logging tracks USB activity

#### Scenario 3: Local Privilege Escalation
**Attack:** User attempts to gain root privileges
**Mitigation:**
- Strong password policies
- Sudo configuration with restrictions
- Audit logging tracks privilege usage
- System resource limits

#### Scenario 4: System Modification
**Attack:** Attempt to modify system configuration
**Mitigation:**
- Package management disabled
- Critical system files have immutable attributes
- Audit logging tracks configuration changes
- Regular compliance checks

## Security Controls

### Preventive Controls

1. **Network Controls**
   - Module blacklisting for WiFi/Bluetooth
   - Default deny firewall configuration
   - VPN-only network access
   - USB device restrictions

2. **System Controls**
   - Service hardening and disabling
   - Strong authentication policies
   - File permission hardening
   - System resource limits

3. **Boot Controls**
   - UEFI-only boot mode
   - Secure Boot verification
   - Measured boot attestation

### Detective Controls

1. **Logging and Monitoring**
   - Comprehensive audit daemon configuration
   - System event logging
   - Network traffic logging
   - User activity tracking

2. **Compliance Validation**
   - Automated compliance checks
   - Security configuration verification
   - Regular security assessments
   - Vulnerability scanning

### Corrective Controls

1. **Incident Response**
   - Automated alerting on security events
   - Isolation capabilities
   - System recovery procedures
   - Forensic preservation

## Risk Assessment

### High-Risk Areas

1. **USB Device Handling** - Medium Risk
   - **Mitigation:** Restrictive mounting, no auto-execution
   - **Residual Risk:** Low

2. **Physical Access** - Medium Risk
   - **Mitigation:** Full disk encryption, secure boot
   - **Residual Risk:** Low

3. **VPN Configuration** - Medium Risk
   - **Mitigation:** Encrypted configuration, authentication
   - **Residual Risk:** Low

### Low-Risk Areas

1. **Network-based Attacks** - Low Risk
   - **Mitigation:** Complete network isolation
   - **Residual Risk:** Minimal

2. **Remote Exploitation** - Low Risk
   - **Mitigation:** Minimal services, firewall
   - **Residual Risk:** Minimal

## Security Validation

### Testing Methodology

1. **Unit Testing** - Individual security function validation
2. **Integration Testing** - End-to-end security workflow testing
3. **Penetration Testing** - External security assessment
4. **Compliance Testing** - Automated validation against standards

### Validation Metrics

1. **Coverage Metrics** - 100% of security controls tested
2. **Compliance Metrics** - 100% compliance with frameworks
3. **Vulnerability Metrics** - Zero critical vulnerabilities
4. **Configuration Metrics** - 100% secure configuration validation

## Continuous Security

### Maintenance

1. **Security Updates** - Through controlled ISO rebuilds
2. **Configuration Changes** - Through verified, version-controlled updates
3. **Compliance Monitoring** - Continuous compliance validation
4. **Security Monitoring** - Real-time security event analysis

### Improvement

1. **Threat Intelligence** - Regular threat model updates
2. **Security Assessments** - Periodic security reviews
3. **Testing Enhancement** - Continuous test suite improvement
4. **Documentation Updates** - Regular security documentation revision

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**Copyright © 2026 Known Element Enterprises LLC**
**License: GNU Affero General Public License v3.0 only**

This security model is maintained as part of the KNEL-Football project and is updated when security requirements change or new threats emerge.