Global Privilege in Authorization Systems

A global privilege is an authorization that grants access across a very broad or entire set of resources within a system, rather than being restricted to specific individual resources. For example, a user account with a 'system administrator' global privilege might inherently have read, write, and execute permissions on all system files and configurations, unless specifically overridden or restricted by more granular rules. It simplifies permission management for highly trusted entities, as a single grant bestows wide-ranging power.

Centralized Authorization

Global privileges generally work well in a centralized authorization system. In such a system, a single authority, like a dedicated authorization server or a central directory service, manages all access decisions and privilege assignments. When a global privilege is granted, it is recorded and enforced by this single point of control. This setup makes it easier to maintain consistency and ensure that the global privilege is interpreted and applied uniformly across all resources governed by that central authority. Management overhead for such privileges is minimal because there is only one place to define and revoke them.

Distributed Authorization

Global privileges present more challenges in a distributed authorization system. In a distributed model, authorization decisions are made across multiple, often independent, nodes or components. Granting a global privilege requires each participating node to correctly interpret and enforce that privilege within its local context. This can lead to issues such as:

• Inconsistency: Different nodes might have varying implementations or interpretations of what a 'global' privilege entails, leading to inconsistent access control.
• Propagation Challenges: Ensuring that changes to a global privilege are propagated promptly and consistently to all distributed authorization points can be complex and introduce latency.
• Lack of Granularity: While seemingly efficient, a global privilege can contradict the need for fine-grained control often sought in distributed environments where different parts of the system may belong to different administrative domains.

While possible to implement, managing global privileges effectively in a distributed system necessitates robust synchronization mechanisms and clear, consistent policies across all nodes to avoid security vulnerabilities or operational complexities. For example, models like the one proposed by Kahan for the WWW (see J. Kahan, "A distributed authorization model for WWW," May 1995) would need careful consideration for how global privileges are propagated and enforced across disparate web servers.