OSF DCE Application Development Guide--Introduction and Style Guide

Security

• UUIDs to identify the objects must be created.

• The ACLs themselves on the relevant objects must be created.

• The ACLs must be stored, indexed by UUID, in the backing store database.

Setting up an ACL manager is a matter of making these eight things happen. The sample

application shows the easiest way of accomplishing this, namely by using the DCE ACL

library. See in particular the routine server_acl_mgr_setup() in sample_server.c.

Note, by the way, that discussing the details of setting up an ACL manager without ﬁrst

considering the representation and management of the objects themselves is a very

artiﬁcial thing to do. The excuse for doing it here is that ACL managers are the subject

of this section. However, keep in mind that ACLs are only an adjunct to the objects they

guard access to. In a real application one would never put the cart before the horse by

working out the details of ACL management before settling on the way object

management itself was to be done.

3.4.3.3 What is an Object?

Network operations are like grammatical sentences: they must have a subject (the client

performing some operation), a predicate (the operation itself), and an object (the

‘‘thing’’ on which the operation is performed). Although meaningful sentences can

sometimes omit some of its grammatical elements, a network operation must always

have all three of its elements.

In any application, distributed or not, an object is any externally accessible resource

which is under the application’s control. Objects can be anything: printers, ﬁles, other

machines, data—it all depends on the application. What these things have in common is

that they must be accessed through the application itself. Entities in a distributed

application request the use of these resources, via clients, from the application server;

and the server normally decides whether or not to grant use of a resource to an entity by

examining the object’s ACLs.

The object can have an existence quite independent of the application that manages it.

On the other hand, the state information associated with the object, which the application

must have access to in order to manage the object in a reasonable way, is maintained by

the application and is useful only to it. This information is stored in a backing store

database, where each separate record normally contains the state information for a single

object. An object’s ACLs qualify as state information for the purposes of this

discussion.

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