Objective: To enforce strict security policies at the kernel level, preventing unauthorized resource access by compromised services.

1. The Vulnerability: Excessive Privilege & Service Exploitation

Traditional Linux permissions (Discretionary Access Control) are often insufficient if a root-level service is compromised. Without Mandatory Access Control, a compromised web server could potentially access sensitive user home directories or system configuration files.

2. Technical Execution: SELinux Policy Enforcement

I deployed Security-Enhanced Linux (SELinux) to enforce granular security policies on the host system. By managing SELinux modes and rules, I ensured that even “root” users or services were restricted to the minimum resources required for their specific function.

ComponentValuePurpose
SELinux ModeEnforcingActively blocks and logs all policy violations.
Policy TypeTargetedRestricts specific network services while allowing normal user activity.
Diagnostic Toolaudit2allowAnalyzes logs to resolve policy-based service issues.

3. Execution Workflow

  1. Mode Verification: Evaluated current system posture using getenforce and transitioned the system to Enforcing mode.
  2. Policy Configuration: Applied specific rules to allow web services (e.g., Apache/Nginx) to access only designated web root folders.
  3. Violation Analysis: Monitored system logs to identify blocked actions that indicated either an attack or a misconfigured policy.
  4. Remediation: Utilized diagnostic tools to generate and apply custom policy modules to allow legitimate service operations.

4. Key Commands

# Example: Checking the current SELinux enforcement status
sestatus

# Example: Troubleshooting a blocked service by searching the audit log
grep "denied" /var/log/audit/audit.log | audit2allow -M my_service_fix

5. Evidence of Work

RESOURCES_NODE_01
Discovery
Caption: Discovery phase showing the mandatory access control architecture and mode descriptions.

RESOURCES_NODE_01
Results
Caption: Results/Impact phase demonstrating the analysis of logs and the resolution of policy violations for critical services.

6. Professional Impact

Implementing SELinux provides a vital layer of defense for System Integrity. By enforcing a “Least Privilege” model at the kernel level, I ensured that even if a service is exploited, the damage is contained within its predefined policy. This significantly reduces the organization’s attack surface and protects sensitive OS resources from unauthorized access.