Attribute-based access control

Attribute-based access control (ABAC), also known as policy-based access control for IAM, defines an access control paradigm whereby a subject's authorization to perform a set of operations is determined by evaluating attributes associated with the subject, object, requested operations, and, in some cases, environment attributes.

ABAC policy rules are generated as Boolean functions of the subject's attributes, the object's attributes, and the environment attributes.

Unlike role-based access control (RBAC), which defines roles that carry a specific set of privileges associated with them and to which subjects are assigned, ABAC can express complex rule sets that can evaluate many different attributes. Through defining consistent subject and object attributes into security policies, ABAC eliminates the need for explicit authorizations to individuals’ subjects needed in a non-ABAC access method, reducing the complexity of managing access lists and groups.

Attribute values can be set-valued or atomic-valued. Set-valued attributes contain more than one atomic value. Examples are ''role'' and ''project''. Atomic-valued attributes contain only one atomic value. Examples are ''clearance'' and ''sensitivity''. Attributes can be compared to static values or to one another, thus enabling relation-based access control.

Although the concept itself existed for many years, ABAC is considered a "next generation" authorization model because it provides dynamic, context-aware and risk-intelligent access control to resources allowing access control policies that include specific attributes from many different information systems to be defined to resolve an authorization and achieve an efficient regulatory compliance, allowing enterprises flexibility in their implementations based on their existing infrastructures.

Attribute-based access control is sometimes referred to as policy-based access control (PBAC) or claims-based access control (CBAC), which is a Microsoft-specific term. The key standards that implement ABAC are XACML and ALFA (XACML).

Dimensions of attribute-based access control

ABAC can be seen as:
* Externalized authorization management
* Dynamic authorization management
* Policy-based access control
* Fine-grained authorization

Components

Architecture

ABAC comes with a recommended architecture which is as follows:

# The PEP or Policy Enforcement Point: it is responsible for protecting the apps & data you want to apply ABAC to. The PEP inspects the request and generates an authorization request from which it sends to the PDP.
# The PDP or Policy Decision Point is the brain of the architecture. This is the piece which evaluates incoming requests against policies it has been configured with. The PDP returns a Permit/ Deny decision. The PDP may also use PIPs to retrieve missing