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In [1] information security, computer science, and other fields, the principle of least privilege (PoLP), also known as the principle of minimal privilege (PoMP) or the principle of least authority (PoLA), requires that in a particular abstraction layer of a computing environment, every module (such as a process, a user, or a program, depending on the subject) must be able to access only the ...
Separation of privilege: Where feasible, a protection mechanism that requires two keys to unlock it is more robust and flexible than one that allows access to the presenter of only a single key. Least privilege: Every program and every user of the system should operate using the least set of privileges necessary to complete the job.
In computer programming and computer security, privilege separation (privsep) is one software-based technique for implementing the principle of least privilege. [1] [2] With privilege separation, a program is divided into parts which are limited to the specific privileges they require in order to perform a specific task.
Tasks are tagged with a privilege level. Resources (segments, pages, ports, etc.) and the privileged instructions are tagged with a demanded privilege level. When a task tries to use a resource, or execute a privileged instruction, the processor determines whether it has the permission (if not, a "protection fault" interrupt is generated).
There are 4 privilege levels ranging from 0 which is the most privileged, to 3 which is least privileged. Most modern operating systems use level 0 for the kernel/executive, and use level 3 for application programs. Any resource available to level n is also available to levels 0 to n, so the privilege levels are rings.
Normally, applications use system.privilege.admin, but another may be used, such as a lower right for security, or a higher right if higher access is needed. If the right the application has is not suitable for a task, the application may need to authenticate again to increase the privilege level.
Consider this quote: "Least privilege has also—and arguably incorrectly—been interpreted in the context of distribution of discretionary access control permissions, even to the point of asserting that, e.g., giving user U read/write access to file F violates least privilege if U can complete his authorized tasks with only read permission."
Capability-based security refers to the principle of designing user programs such that they directly share capabilities with each other according to the principle of least privilege, and to the operating system infrastructure necessary to make such transactions efficient and secure.