Analyze the working mode of SELinux

Title: SELinux working mode analysis and code examples

In modern computer systems, security has always been a crucial aspect. In order to protect servers and applications from malicious attacks, many operating systems provide a security mechanism called SELinux (Security-Enhanced Linux). SELinux is a mandatory access control (MAC) system that can implement fine-grained access control to system resources. This article will analyze the working mode of SELinux and provide specific code examples to help readers better understand.

Basic principles of SELinux

In traditional UNIX systems, access control mainly uses user-based access control (DAC), that is, access is determined by the user's permissions on files and processes. permissions. SELinux introduces the concept of mandatory access control (MAC), extending access control to more fine-grained objects, such as processes, files, and ports. Access control is implemented by assigning a security context to each object and subject.

The working mode of SELinux mainly includes three basic components: policy file (Policy), context (Context) and decision engine (Decision Engine). The policy file defines the operations and access rules allowed by the system, the context is used to identify the security attributes of objects and subjects, and the decision engine makes access control decisions based on the policy file and context.

SELinux working mode analysis

The working modes of SELinux can be divided into three types: Enforcing, Permissive and Disabled. Below we'll break down each mode in detail and provide corresponding code examples.

Enforcing mode

In Enforcing mode, SELinux will strictly enforce the access rules defined in the policy file and deny any access requests that violate the rules. This is the most commonly used mode of SELinux and one of the most secure modes.

Enforcing mode sample code:

# 查看当前SELinux模式 getenforce # 设置SELinux为Enforcing模式 setenforce 1 # 运行一个需要进行文件访问的程序 ./my_program

Permissive mode

In Permissive mode, SELinux will record violations of access requests but will not prevent their execution. This mode is mainly used for debugging and troubleshooting problems, and can help developers locate problems and optimize policy files.

Permissive mode sample code:

# 设置SELinux为Permissive模式 setenforce 0 # 运行一个需要进行文件访问的程序 ./my_program

Disabled mode

In Disabled mode, SELinux will be completely turned off, and the system will return to the traditional DAC access control mode. This mode is generally not recommended because it reduces system security.

Disabled mode sample code:

# 查看当前SELinux模式 getenforce # 关闭SELinux setenforce 0 # 运行一个需要进行文件访问的程序 ./my_program

Conclusion

Through the above analysis of SELinux working mode and introduction of code examples, I believe that readers have an understanding of the working principle and usage of SELinux. gain a deeper understanding. In practical applications, selecting the appropriate working mode according to specific needs can effectively improve the security and stability of the system. I hope this article can help readers better master the application and configuration skills of SELinux.

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