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The main content of this article is to explain "what is the cause of the SELinux warning". Interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Now let the editor take you to learn "what is the cause of the SELinux warning?"

Reason 1: labeling error

The core concept of SELinux is tagging. Whether it is file system, directory, file, file startup descriptor, port, message interface, or network interface, everything requires a label and can only be executed in accordance with the permissions assigned by the tag. Even if the running Apache process is hacked and obtained uid=0 root privileges, it still cannot access files in a user's home directory. Because the content labeled userhome_t is not accessible by the Apache process labeled httpdt.

Therefore, if there is a problem with the annotation, SELinux will pop up a warning. How to deal with this type, you can refer to the previous article on this site on the use of semanage fcontext and restorecon commands. Of course, you can also follow the tips in the graphical SELinux debugging tool.

Reason 2: customized program running settings

After years of development, SELinux has accumulated a large number of policy files, which are recorded for the default run requests of most applications, and can be executed with appropriate minimum permissions. However, if you customize some running configurations or have special application requirements, you need to adjust some of the SELinux settings.

For most common custom requirements, SELinux is controlled by a Boolean value. You can refer to the use of the setsebool command in the previous article on this site. To know all the adjustable SELinux Boolean values, use the semanage boolean ­- l command. This can be solved through the graphical SELinux debugging tool or through the graphical system-config-selinux.

Reason 3: there is a problem with SELinux policy or application configuration

If you do not specifically modify the configuration but still receive SELinux warnings, the reason may be the SELinux policy or the application itself. At this point, it is recommended that you first submit an error report with the help of the SELinux debugging tool, and then deal with it as appropriate. If it has been reported, the solution is usually detailed in the comments on the error report.

At this point, if you want to ignore the SELinux warning and still run the application, there are several ways:

Set SELinux to allow mode to log warnings but not prevent running: setenforce 0.

Set a single annotation process to allow mode instead of the entire system, for example, you only want to run Apache: semange permissive-a httpd_t in allow mode

Follow the recommendations of the SELinux debugging tool to create and load a custom policy. The specific process varies according to the situation, and will be described in detail in the SELinux debugging tool.

Reason 4: the program has been compromised

SELinux is not an intrusion detection system, so currently SELinux debugging tools cannot actively identify intrusion attempts. However, when you find that the warning contains the following characteristics, it is very likely that the corresponding process has been breached by hackers:

Try turning off SELinux (/ etc/selinux) or setting a SELinux Boolean value.

Try to load the kernel module, write to the kernel directory, or boot image.

Try to read the file identified by shadow_t, which usually contains encrypted account information.

Attempt to overwrite the write log file.

Try to connect to an unwanted random port or mail port.

At this point, I believe you have a deeper understanding of "what caused the SELinux warning". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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