Study the three policy types of SELinux

SELinux is a security-enhanced Linux operating system security module. Its core is to improve system security through mandatory access control. In SELinux, policy types are an important part of defining security policies. According to different needs and scenarios, SELinux provides three different policy types, namely MLS (Multi-Level Security), TE (Type Enforcement), RBAC ( Role-Based Access Control). This article will explore these three different policy types and demonstrate their application through specific code examples.

MLS (Multi-Level Security)

MLS is one of the most basic and powerful security policy types of SELinux. It can implement different levels of security labels to control different levels of security in the system. Access rights between data and processes. In the MLS policy, different security labels are assigned to objects such as files and processes to ensure data confidentiality and system security.

The following is a simple example to demonstrate how to create an MLS policy and grant different levels of access permissions in SELinux:

# 设置文件安全标签
chcon system_u:object_r:top_secret_file:s0 secret_file.txt

# 创建一个进程并设置其安全标签
runcon -t top_secret_process_t my_program

In the above code example, we pass chcon and The runcon command assigns different security labels to files and processes respectively, so that the interaction and access permissions between them can be restricted based on these labels.

TE (Type Enforcement)

TE is another important policy type in SELinux. It limits operations and access permissions between processes, files and other objects by defining access control rules. TE policy types allow administrators to define detailed access rules to protect critical resources and sensitive data in the system.

The following is a simple example that shows how to use TE policy in SELinux to restrict a process's access to sensitive files:

# 创建一个TE策略模块文件
policy_module my_policy 1.0;

# 定义规则：允许进程只读访问secret_data文件
allow my_process_t secret_data_t:file {read};

# 编译并加载TE策略模块
checkmodule -M -m -o my_policy.mod my_policy.te
semodule_package -o my_policy.pp -m my_policy.mod
semodule -i my_policy.pp

In the above code example, we define TE by The policy module and access rules restrict the my_process_t process to only perform read-only operations on the secret_data_t file, thus ensuring the security of sensitive data in the system.

RBAC (Role-Based Access Control)

RBAC is the third policy type in SELinux, which manages the permissions of different users and processes in the system through role-based access control. RBAC policies allow administrators to assign different permissions to different roles, thereby achieving fine-grained permission management and control.

The following is a simple example that shows how to use RBAC policy in SELinux to assign different permissions to different roles:

# 创建一个RBAC角色
semanage login -a -s staff_r -r s0-s0:c0.c102 user1

# 为角色分配权限
semanage user -m -R 'staff_r' staff_t

# 将用户分配至角色
semanage login -a -s staff_r -r s0-s0:c0.c102 user2

In the above code example, we created it through the semanage command An RBAC role staff_r is created, and the staff_t permission is assigned to the role, and then users user1 and user2 are assigned to the staff_r role, thereby implementing role-based access control.

In summary, SELinux provides three different policy types: MLS, TE and RBAC, which are used to implement multi-level security, mandatory access control and role-based access control respectively. Through specific code examples, we can better understand how these policy types are applied and implemented, thereby improving the security and manageability of the system.

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