== Architecture

image:../../images/authz-arch-overview.png[alt="Keycloak AuthZ Architecture Overview"]

From a design perspective, the {{book.project.module}} are based on a well defined set of authorization patterns providing a:

* **Policy Administration Point (PAP)**
+
Provides a set of UIs based on {{book.project.name}} Administration Console to manage resource servers, resources, scopes, permissions and policies.
Part of this also accomplished remotely through the use of the link:../service/protection-api.html[Protection API].
+

* **Policy Decision Point (PDP)**
+
Provides a distributable policy decision point to where authorization requests are sent and policies are evaluated accordingly with the permissions being requested. Part of this also accomplished remotely through the use of the
link:../service/authorization-api.html[Authorization] and link:../service/entitlement-api.html[Entitlement] APIs.
+

* **Policy Enforcement Point (PEP)**
+
Provides implementations for different environments to actually enforce authorization decisions at the resource server side.
Keycloak provides some built-in link:../enforcer/overview.html[Policy Enforcers].
+

* **Policy Information Point (PIP)**
+
Being based on {{book.project.name}} Authentication Server, you can obtain attributes from identities and runtime environment during the evaluation of authorization policies.

=== The Authorization Process

Two main process define the necessary steps to understand how to use KC to enable fine-grained authorization to your applications:

* *Resource Management*
* *Permission and Policy Management*

*Resource Management* involves all the necessary steps to define what is being protected.

image:../../images/resource-mgmt-process.png[alt="Resource Management Overview"]

First, you need to tell to {{book.project.name}} what are you looking to protect, which usually represents a web application or a set of one or more services. See link:../overview/terminology.html[Terminology] for more information about
Resource Servers.

Resource Servers are managed using the {{book.project.name}} Administration Console, where you can enable any registered client application as a resource server and start managing the resources and scopes you want to protect.

image:../../images/rs-r-scopes.png[alt="Resource Server Overview"]

A Resource can be a web page, a RESTFul resource, a file in your filesystem, an EJB, etc. They can represent a group of resources (just like a Class in Java) or they can represent a single and specific resource.

For instance, you may have a _Bank Account_ resource that represents all banking accounts define authorization policies that apply to all banking accounts. However
you may want to define specific policies for _Alice Account_, where only the owner is allowed to access some information or perform an operation.

Resources can be managed using {{book.project.name}} Administration Console or the link:../service/protection-api.html[Protection API]. In the latter case, resource servers are able to
manage their resources remotely.

Scopes usually represent the actions that can be performed on a resource, but they are not limited to that. You can also use scopes to represent a single or multiple attributes belonging to a resource.

Once you have your resource server and all the resources you want to protect configured, you can start working with the fun part: *Permission and Policy Management*.

*Permission and Policy Management* involves all the necessary steps to actually define the security and access requirements that govern your resources.

image:../../images/policy-mgmt-process.png[alt="Permission and Policy Management Overview"]

Policies define the conditions that must be satisfied to access or perform operations on something (resource or scope), but they are not tied with what they are protecting. They are generic and can be reused
to build permissions or even other more complex policies.

For instance, we may want to allow access to a group of resources only for users granted with a role "User Premium". In this case, we define a simple policy, based on Role-based Access Control (RBAC), that
tells exactly that.

{{book.project.name}} provides a few built-in policies covering the most common access control mechanisms. You can even create policies based on rules written using JavaScript or JBoss Drools.

Once you have your policies defined, you can start defining your permissions. Differently than policies, permissions are tied coupled with the resource they are protecting. Here you specify
what you want to protect (resource or scope) and the policies that must be satisfied in order to _GRANT_ or _DENY_ that permission to someone asking for it.


=== Authorization Services

Authorization Services consist of the following RESTFul APIs:

* *Protection API*
* *Authorization API*
* *Entitlement API*

Each of these services provide a specific API covering the different steps involved in the process of authorization.

==== Protection API

The *Protection API* is a https://docs.kantarainitiative.org/uma/rec-uma-core.html[UMA-compliant] endpoint providing a small set of operations
for resource servers in order help them managing their resources and scopes. Only resource servers are allowed to access this API, which also requires a
*uma_protection* scope.

The operations provided by the Protection API can be organized in two main groups:

* Resource Management
    ** Create Resource
    ** Delete Resource
    ** Find by Id
    ** Find All
    ** Find with filters (eg.: search by name, type or URI)
* Permission Management
    ** Issue Permission Tickets

[NOTE]
By default, Remote Resource Management is enabled. But you can also disable that from the administration console.

The issuance of Permission Tickets by the Protection API is an important part of the whole authorization process. As we'll see later, they represent the permissions
being requested by client and that are sent to the server in order to obtain a final token with all permissions granted during the evaluation of the permissions and policies
associated with the resources and scopes being requested.

For more information, see link:../service/protection-api.html[Protection API].

==== Authorization API

The *Authorization API* is also a https://docs.kantarainitiative.org/uma/rec-uma-core.html[UMA-compliant] endpoint providing a single operation that exchanges an ID Token and _Permission Ticket_
with a Requesting Party Token or RPT.

The RPT holds all permissions granted to a client and can be used to call a resource server in order to get access to its protected resources.

When asking a RPT you can also provide a previously issued RPT. In this case, the resulting RPT will consist of a union of the permissions from the previously RPT and the new ones
within a Permission Ticket.

image:../../images/authz-calls.png[alt="Authorization API Overview"]

For more information, see link:../service/authorization-api.html[Authorization API].

=== Entitlement API

The *Entitlement API* provides a 1-legged protocol to issue RPTs. Differently than the_Authorization API, the Entitlement API only expects an ID Token and the resulting RPT
consists of all permissions granted based on all resources belonging to a resource server.

image:../../images/entitlement-calls.png[alt="Entitlement API Overview"]

For more informationm, see link:../service/entitlement-api.html[Entitlement API].




