What is the security policy of SELinux in Android?

SELinux is a security-enhanced operating system for Linux that protects against malicious software and attacks through Mandatory Access Control (MAC) mechanisms. Its security policy is based on SELinux policy sources (SEPolicy), which are written by policy developers and configured according to system requirements.

The main components of SELinux security policies include the following:

1. Tags in SELinux assign a security label to each file, process, and device, containing information about the object’s security context such as user identity, role, type, and access permissions. Through these tags, SELinux performs precise access control on system resources.
2. Policy rules: SELinux defines permissions for a process to access or deny operations on an object through policy rules. These rules are matched based on the security labels of objects, helping to protect the security of system resources. Policy rules include type enforcement rules, access control rules, and constraint rules.
3. SELinux uses a Mandatory Access Control (MAC) model, which requires explicit authorization for access to system resources. Even if a user has sufficient permissions, access to system resources is denied without authorization from SELinux. This model helps prevent unauthorized access and malicious operations.
4. Security Context: SELinux uses security context to identify and control the access permissions of objects. A security context is a string that contains tags describing the security attributes of the object. By using security context, SELinux can enforce access control based on policy rules, ensuring that objects can only be accessed by processes with the appropriate permissions.

Overall, SELinux’s security policies protect system resources by using mechanisms such as labels, policy rules, mandatory access control models, and security contexts to prevent unauthorized access and malicious operations.