Access Control Lists (ACLs) An access control list (ACL) is a mechanism that defines the permissions and restrictions associated with accessing a specific f...
Access Control Lists (ACLs)
An access control list (ACL) is a mechanism that defines the permissions and restrictions associated with accessing a specific file, directory, or resource. It is implemented by the operating system kernel and applies restrictions based on the identities and access rights of users, groups, and other entities.
Types of ACLs:
Directory ACLs: Control access to specific directories, including creating, reading, and writing files.
File ACLs: Define access permissions for individual files, such as read, write, or execute.
Security ACLs: Specify policies that apply to the entire system, such as restricting access for specific processes or users.
How ACLs Work:
An ACL is a list of rules that specify what operations can be performed on a resource by specific entities.
Each rule consists of a subject (the entity performing the operation) and a predicate (the specific action being restricted).
The operating system kernel reads the ACL and checks if the subject meets the required permissions to perform the specified action on the resource.
If the access control is met, the operation is allowed. Otherwise, it is denied.
Examples:
Consider a directory called "Documents" with an ACL that grants the "Admin" group read and write access. This means that only members of the "Admin" group can create, read, and modify files within the "Documents" directory.
An ACL for a file could restrict access for the "Everyone" group, preventing them from reading or writing to the file.
A security ACL could restrict all external access to the system, allowing only authorized users to connect and perform operations