This is a resource for new users, it explains in very broad terms what SELinux does, how to get it and so on.
What does SELinux do?
SELinux controls access between applications and resources. By using a mandatory security policy SELinux enforces the security goals of the system regardless of whether applications misbehave or users act carelessly. SELinux is capable of enforcing a wide range of security goals, from simply sandboxing applications to locking down network facing daemons and restricting users to only the resources they need to work.
How do I know if SELinux is on?
If you use Red Hat Enterprise Linux or Fedora it is enabled by default. To see whether it is actively enforcing the policy you can run getenforce:
[root@localhost ~]# getenforce Enforcing
If it says Enforcing (as above) your system is being protected by SELinux. If it says permissive SELinux is enabled but is only logging failed accesses, not denying them. If it says Disabled then SELinux is not enabled on your system.
How do I get it?
SELinux isn't a distribution by itself but a security enhancement to Linux that can be enabled by your distribution or vendor (or yourself if you are very motivated).
|Distribution||How to get it|
|Red Hat Enterprise Linux (4+)||Default|
Why do I have it?
Your distribution or vendor may have chosen to enable SELinux by default. They are doing this because they want added security protections on the versions of Linux they ship. A huge amount of effort has gone in to creating security policies that protect your system from intrusions while at the same time allowing users to behave the way they normally do. Leaving SELinux enabled on these systems is a good idea because it can protect you from zero-day and known vulnerabilities while balancing your need to use your system the way you need to.
Where can I find help?
There are several mailing lists and IRC channels depending on what distribution you are running and what you need help with. See the Mailing lists and IRC channels page for a full list.
This site has additional documentation that can help you use SELinux. You can start with the administrators and users page.
The SELinux Notebook
Some of the sections from Volume 1 - The SELinux Notebook - The Foundations are available on this site.
The Notebook sections describe the SELinux services built into Fedora 12 and should give a high level description of the major components that provide Mandatory Access Control services for GNU / Linux.
Hopefully it will show how all the SELinux components link together and how SELinux-aware applications and their object managers have been implemented (such as X-Windows, SE-PostgreSQL and virtual machines).
The major sections are:
- SELinux Overview
- Mandatory Access Control (MAC)
- Type Enforcement (TE)
- Role-Based Access Control (RBAC)
- Security Context
- Multi-Level Security and Multi-Category Security
- Types of SELinux Policy
- SELinux Permissive and Enforcing Modes
- Audit Logs
- PAM Login Process
- Linux Security Module and SELinux
- SELinux Networking Support
- SELinux Virtual Machine Support
- SELinux X-Windows Support
- SELinux PostgreSQL Support (ver 8.4)
- SELinux PostgreSQL Support (ver 9.0)
- Apache SELinux Support
- Reference Policy Support
Relevant F-12 Packages
The following are the rpm packages installed on the test machine used for all code listings, testing and research:
checkpolicy-2.0.19-3.fc12.i686 checkpolicy-2.0.19-3.fc12.src coreutils-7.6-8.f12.src ipsec-tools-0.7.3-4.fc12.i686 kernel-18.104.22.168-127.fc12.i686 kernel-22.214.171.124-127.fc12.src libselinux-2.0.90-5.fc12.i686 libselinux-devel-2.0.90-5.fc12.i686 libselinux-python-2.0.90-5.fc12.i686 libselinux-utils-2.0.90-5.fc12.i686 libsemanage-2.0.45-1.fc12.i686 libsemanage-devel-2.0.45-1.fc12.i686 libsemanage-python-2.0.45-1.fc12.i686 libsepol-2.0.41-3.fc12.i686 libsepol-devel-2.0.41-3.fc12.i686 libsepol-static-2.0.41-3.fc12.i686 libsepol-2.0.41-3.fc12.src libvirt-0.7.1-15.f12.src mcstrans-0.3.1-3.fc12.i686 mod_selinux-2.2.2015-3.fc12.src netlabel_tools-0.19-3.fc12.i686 policycoreutils-2.0.79-1.fc12.i686 policycoreutils-gui-2.0.79-1.fc12.i686 policycoreutils-sandbox-2.0.79-1.fc12.i686 policycoreutils-python-2.0.79-1.fc12.i686 policycoreutils-newrole-2.0.79-1.fc12.i686 postgresql-libs-8.4.3-1.fc12.i686 postgresql-8.4.3-1.fc12.i686 postgresql-server-8.4.3-1.fc12.i686 qemu-0.12.3-2.fc12.src selinux-policy-3.6.32-103.fc12.src selinux-policy-3.6.32-103.fc12.noarch selinux-policy-doc-3.6.32-103.fc12.noarch selinux-policy-minimum-3.6.32-103.fc12.noarch selinux-policy-mls-3.6.32-103.fc12.noarch selinux-policy-targeted-3.6.32-103.fc12.noarch sepostgresql-8.4.2-2583.fc12.i686 setools-3.3.6-4.fc12.i686 setools-console-3.3.6-4.fc12.i686 setools-gui-3.3.6-4.fc12.i686 setools-libs-3.3.6-4.fc12.i686 setools-libs-java-3.3.6-4.fc12.i686 setools-libs-tcl-3.3.6-4.fc12.i686 xen-3.4.2-1.fc12.src
The gcc tools will be required to compile and link the test “C” applications used in some of the scenarios (gcc-4.4.2-20.i686 and libgcc-4.4.2-20.i686 rpms are installed on the test machine that is using the kernel-126.96.36.199-127.fc12.i686 rpm).