This documentation guides you to use an Authenticator that adds LDAP users to confluence-users as they log in.

To use this Authenticator, change the line:

<authenticator class="com.atlassian.confluence.user.ConfluenceAuthenticator"/>

in <Confluence-Install directory>/confluence/WEB-INF/classes/seraph-config.xml to:

<authenticator class="com.atlassian.confluence.user.ConfluenceGroupJoiningAuthenticator"/>

If you are using Confluence 2.2 you need to download the ConfluenceGroupJoiningAuthenticator.class file and put it in WEB-INF/classes/com/atlassian/confluence/user. Confluence 2.3+ ships with this class. The class also ships with Confluence 2.6+, but resides within confluence-2.6.0.jar in WEB-INF/lib directory.