audit2allow

The audit2allow command is a part of the policycoreutils package in SELinux, designed to help administrators create custom policy modules based on the audit logs. It reads SELinux denial messages from audit logs and generates policy rules that, if applied, would allow the previously denied actions. This tool is useful for troubleshooting and fine-tuning SELinux policies to permit necessary actions while maintaining security.

Purpose of audit2allow

The main purposes of audit2allow are to:

• Generate SELinux policy modules that allow actions previously denied by the SELinux policy.

• Facilitate the process of customizing and extending SELinux policies based on actual usage patterns.

• Help administrators quickly create and apply policy changes to address legitimate access issues.

Key Features and Functionality

1. Policy Module Generation: Generates SELinux policy modules from audit logs to allow denied actions.

2. Custom Policy Creation: Helps create custom SELinux policies tailored to the specific needs and configurations of a system.

3. Integration with Audit Logs: Works with SELinux audit logs to identify and address denied actions.

4. Automated Rule Creation: Automates the process of writing SELinux policy rules, reducing the complexity and effort required.

Usage

To use audit2allow, you typically need SELinux audit messages as input. These messages can be obtained from audit logs using tools like ausearch. Here’s how you can use audit2allow effectively:

1. Get Denial Messages with ausearch: Use ausearch to search for SELinux denial messages in the audit logs.

2. Pipe Output to audit2allow: Pipe the output of ausearch to audit2allow to generate policy rules.

Example Commands

Example 1: Basic Usage

ausearch -m avc -ts recent | audit2allow -M mypol

This command searches for recent SELinux denials (-m avc -ts recent), pipes the results to audit2allow, and generates a policy module named mypol.

Example 2: Generating Policy Module from a Specific Log File

cat /var/log/audit/audit.log | audit2allow -M mypol

This command reads the audit log file and pipes its contents to audit2allow to generate a policy module named mypol.

Example 3: Generating Policy Rules

ausearch -m avc -ts recent | audit2allow

This command prints the policy rules that would allow the denied actions without generating a policy module file.

Example Output

Running audit2allow might produce output similar to the following:

module mypol 1.0;

require {
    type httpd_t;
    type httpd_config_t;
    class file read;
}

#============= httpd_t ==============
allow httpd_t httpd_config_t:file read;

Steps to Apply the Policy Module

1. Generate the Module: Use audit2allow to create a policy module file, e.g., mypol.pp.

2. Install the Module: Install the generated policy module using semodule.

semodule -i mypol.pp

Benefits

• Ease of Policy Adjustment: Simplifies the process of adjusting SELinux policies to accommodate necessary access.

• Automated Rule Creation: Automates the creation of SELinux policy rules, reducing manual effort and potential errors.

• Tailored Security: Helps create custom SELinux policies tailored to specific applications and environments.

Security Considerations

• Review Generated Policies: Always review the policy rules generated by audit2allow to ensure they do not inadvertently weaken the security of the system.

• Least Privilege Principle: Apply the principle of least privilege when modifying SELinux policies, allowing only the necessary permissions.

• Test Changes: Test the new policy modules in a controlled environment before deploying them to production systems.

Conclusion

The audit2allow command is a powerful tool for administrators working with SELinux. It helps generate custom policy modules based on audit logs, making it easier to permit legitimate access while maintaining security. By using audit2allow, administrators can efficiently troubleshoot and refine SELinux policies to fit their specific needs.