SELinux, the Linux security mechanism, has certain important concepts that a user should be aware of. Only after understanding these concepts will we be able to work well with this security mechanism. One of these key concepts is SELinux context. A context in SELinux is defined as additional information about a process or file that this security mechanism can use to make access control decisions.
This additional information contains the following four objects:
- SELinux User: Identifies the identity of the user who accesses, owns, modifies, or deletes a process or file on Linux-based operating systems. If a user has access to a particular file or process on Linux, then their identity is explicitly mentioned in the SELinux security policy. This means that a Linux user is always addressed by his or her identity.
- Role: Based on this entity, the user is allowed or denied access to a specific object in SELinux. The concept of a role derives from one of the very well-known access control models, that is, role-based access control (RBAC). This model is especially useful when many users have the same access rights. Instead of associating each individual user with specific access rights, access rights are associated with a specific role. Access rights associated with a specific user role are automatically assigned to that user.
- Type: This object is used to define file types and process domains in SELinux. Using this entity, access is granted if and only if there is a rule for that particular type in the SELinux access control policy, as well as a rule for granting access, and not vice versa.
- Level: This object represents Multi-Level Security (MLS) and Multi-Category Security (MCS). Security levels are defined in terms such as high, low, etc.
In short, SELinux context is a combination of these four attributes. SELinux grants or denies the user access to files or processes using these four attributes.
This article shows methods to list all SELinux contexts on CentOS 8.
Methods for enumerating SELinux contexts on CentOS 8
To list all SELinux contexts on CentOS 8, you can choose any of the four methods below:
Method # 1: Using the semanage command
To list SELinux contexts for all files and processes on your CentOS 8 system, run the following command in your CentOS 8 terminal:
$ sudo semanage fcontext –l | grep httpd_log_t
This command cannot work without root user rights. Make sure to use the “sudo” keyword in this command; otherwise, an error message is displayed. Therefore, it is better to use this command in the same way as above to save your precious time.
As soon as this command completes its execution, all SELinux contexts will be displayed in your terminal. You can scroll up, down, left, or right for a complete view of all SELinux contexts on CentOS 8.
Method # 2: Using the “ls” Command
To get all the SELinux file contexts on CentOS 8, you can also run the following command in your CentOS 8 terminal:
$ sudo ls –lZ /root
SELinux file contexts are stored in the “root” directory. You must have root privileges to access this directory. In other words, you must run this command along with the sudo keyword, just like we do.
After executing this command, you can view all SELinux file contexts in your CentOS 8 terminal.
Method # 3: Using the “ps” Command
We have listed all the SELinux file contexts in the method shown above. Sometimes you may only need to list all the SELinux process contexts on CentOS 8. You can get these contexts only by running the following command in a terminal:
$ sudo ps axZ
You must have root user privileges to run the above command. In other words, you must run this command along with the sudo keyword, just like we do.
After running this command, you can view all the contexts of the SELinux process in the terminal.
Method # 4: Using the “id” command
In other cases, you may only want to get the current SELinux user contexts on CentOS 8. You can list all the current SELinux user contexts by running the following command in your CentOS 8 terminal:
$ id –Z
After executing this command, you can view all current user SELinux contexts in the terminal as shown in the image below. This is all information related to your current user on a CentOS 8 system.
In this article, first, we have shared with you a method to list all SELinux contexts at once. We then shared with you methods for listing all SELinux files, processes, and user contexts individually. This gives you a very good opportunity to play with SELinux contexts. If you want to see all the process and SELinux file contexts at once, use Method 1. However, if this is not the case, you can choose Method 2, Method 3, or Method 4 as per your requirements. …