HP UX Red Hat Direry Server Software manual ACI Placement, ACI Evaluation, ACI Limitations

Chapter 6. Managing Access Control

1.2. ACI Placement

If an entry containing an ACI does not have any child entries, the ACI applies to that entry only. If the entry has child entries, the ACI applies to the entry itself and all entries below it. As a direct consequence, when the server evaluates access permissions to any given entry, it verifies the ACIs for every entry between the one requested and the directory suffix, as well as the ACIs on the entry itself.

The aci attribute is multi-valued, which means that you can define several ACIs for the same entry or subtree.

An ACI created on an entry can be set so it does not apply directly to that entry but to some or all of the entries in the subtree below it. The advantage of this is that general ACIs can be placed at a high level in the directory tree that effectively apply to entries more likely to be located lower in the tree. For example, an ACI that targets entries that include the inetorgperson object class can be created at the level of an organizationalUnit entry or a locality entry.

Minimize the number of ACIs in the directory tree by placing general rules at high level branch points. To limit the scope of more specific rules, place them as close as possible to leaf entries.

NOTE

ACIs placed in the root DSE entry apply only to that entry.

1.3. ACI Evaluation

To evaluate the access rights to a particular entry, the server compiles a list of the ACIs present on the entry itself and on the parent entries back up to the top level entry stored on the Directory Server. ACIs are evaluated across all of the databases for a particular Directory Server but not across all Directory Server instances.

The evaluation of this list of ACIs is done based on the semantics of the ACIs, not on their placement in the directory tree. This means that ACIs that are close to the root of the directory tree do not take precedence over ACIs that are closer to the leaves of the directory tree.

For Directory Server ACIs, the precedence rule is that ACIs that deny access take precedence over ACIs that allow access. Between ACIs that allow access, union semantics apply, so there is no precedence.

For example, if you deny write permission at the directory's root level, then none of the users can write to the directory, regardless of the specific permissions you grant them. To grant a specific user write permissions to the directory, you have to restrict the scope of the original denial for write permission so that it does not include the user.

1.4. ACI Limitations

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