Access Control with Muradora

Muradora utilizes the XACML PDP engine (melcoe-pdp) and XACML-PEP (melcoe-pep, ie. the authorization layer which sits in-front of Fedora) to give end users the ability to control accesses to their digital objects. Importantly, this feature is provided via a GUI that hides the complexity of XACML from the end users, while still allowing them a high degree of flexibility in specifying the criteria on which access restrictions are made.

Specifying Access Control

Brief XACML Introduction

Generic Actions

It should be noted that while there are multiple actions that are available to the user, many of these actions ultimately boil down to a small set of generic actions. An example is the "search" and "browse" functions which can be equated to performing a "read" on a particular resource.

An important motivation behind the use of XACML is that policies should be expressed in these generic actions so that they can be reuse and inter-operate across a set of heterogeneous applications. For that reason, we have abstract all the operations to a generic set consisting of: "create, read, update, delete, publish, admin". This action vocabulary can be extended should the need arises. The use of a generic set of actions also helps us in our design of a simple access control GUI.

In terms of Fedora, these actions are then mapped to the respective Fedora-specific operations to ensure a consistent access control irrespective of how the users access Fedora; either via Muradora or directly via one of its interfaces such as the API-A, API-M, or REST interfaces.

The meaning of these actions when applied to a particular resource (such as collection, object, or datastream) are explained in the table below. Hopefully, their meanings are quite intuitive. Not all actions will be available to all resources since those combinations do not make sense.

Action/Resource	Collection	Object	Datastream
Create	Add new objects to this collection	Add new datastream to this object	N/A
Read	View, search, browse all objects (including sub-collections) in this collection	View, search and browse this object	View, search, browse this datastream
Update	Same as "create" but also includes renaming this collection and deleting objects from this collection	Same as "create" but includes deleting datastreams and modifying the object's properties	Modify the current datastream
Delete	Delete the collection including its children	Delete the current object	Delete the current datastream
Publish	N/A	Make the current object search-able and browse-able	N/A
Admin	Set access policy for this collection	Set access policy for this object |	Set access policy for this datastream

Access Control Policy Precedence

Advanced Policies

Administrator Permissions

Any user with the role "administrator" will be allowed complete access to Fedora and Muradora functionality. This is defined in a default XACML bootstrap policy that is loaded into Melcoe PDP.

Public/Anonymous Permissions

By default, non-authenticated users will be given the role "public". The default bootstrap policy that is loaded into Melcoe PDP allows these users to perform "read" operations (eg. Search and Browse) on the repository. To alter these permissions, an administrator can log in and change it via the Administrator Panel\Global Access Control (see "Restricting Muradora Functionality" below).

Restricting Muradora Functionality