How to Config Security-Enhanced Linux (SELinux) Policies

Last modified on October 27, 2020 1 min read

HIRE US 🖐
We're available to do freelance project. Take a look at our services!

Security-Enhanced Linux (SELinux) is a Linux kernel security module that provides a mechanism for supporting access control security policies, including mandatory access controls (MAC). SELinux is a set of kernel modifications and user-space tools that have been added to various Linux distributions. It was originally developed by NASA.

Table of Contents

  1. Install Packages
  2. Context Types
  3. Create Policies
  4. Apply Policies
  5. Semanage vs Chcon

Install Packages

At first, we need to ensure that we’ve installed semanage. The semanage command is used to change the SELinux context of a file or directory persistently. The policycoreutils-python package contains semanage.

# CentOS 7
sudo yum install -y policycoreutils-python

# CentOS 8
sudo dnf install -y policycoreutils-python-utils

# Ubuntu
sudo apt install -y policycoreutils-python-utils

For troubleshooting SELinux issues, we’re going to install another package. It’s optional to install:

 # CentOS
sudo yum install -y setroubleshoot

# Ubuntu
sudo apt install -y setroubleshoot

Context Types

Run this command to see all context types for Apache:

man httpd_selinux

See existing policies:

semanage fcontext -l

These 4 are common types:

httpd_sys_content_t Read-only directories and files
httpd_sys_rw_content_t Readable & writable directories and files
httpd_log_t Assign to logs directory
httpd_cache_t Assign to caches directory

Create Policies

May applications like WordPress require to assign policies. To assign httpd_sys_content_t context to the /var/www/domain.com directory, child directories and files:

semanage fcontext -a -t httpd_sys_content_t '/var/www/domain.com(/.*)?'

To assign httpd_sys_rw_content_t context to the /var/www/domain.com directory, child directories and files:

semanage fcontext -a -t httpd_sys_rw_content_t '/var/www/domain.com(/.*)?'

Assign httpd_log_t to logs directories:

semanage fcontext -a -t httpd_log_t '/var/www/domain.com/logs(/.*)?'

Assign httpd_cache_t to logs directories:

semanage fcontext -a -t httpd_cache_t '/var/www/domain.com/caches(/.*)?'

Apply Policies

We’ve created our policies. Now we need to  apply the context changes by running this command:

sudo restorecon -R -v /var/www/domain.com

After changing any context, we need to re-apply the context changes. We can verify our context types:

ls -lZ /var/www/domain.com

Semanage vs Chcon

Like semanage, we can change the SElinux context for files using chcon. Chcon temporarily changes the context of files where semanage changes persistently. Here are some examples:

sudo chcon -t httpd_sys_rw_content_t -R /var/www/domain.com
sudo chcon -t httpd_log_t -R /var/www/domain.com/logs
sudo chcon -t httpd_cache_t -R /var/www/domain.com/caches

# Apply on single file
sudo chcon -t httpd_sys_rw_content_t /var/www/domain.com/i.php
That’s it. Thanks for reading. 🙂

Author

Hey, I'm Md Obydullah. I build open-source projects and write on Laravel, Linux server, modern JavaScript and more on web development.

Follow

Leave a Reply

Your email address will not be published. Required fields are marked *