You must set up LDAP in Alfresco Content Services.
Detailed instructions are available in http://docs.alfresco.com/5.2/concepts/auth-ldap-intro.html
For a working example of an LDAP subsystem, check the LDAP demo provided in the activiti-share-connector.zip. The demo amp file contains sample LDAP configuration files for getting Alfresco Content Services setup up with an LDAP (it contains no Share Connector files) configuration.
- Unzip the activiti.alfresco.repo-demo-ldap-X.X.X.amp file by renaming it from .amp to .zip. You'll see some files marked with ACTIVITI SHARE CONNECTOR DEMO in the ldap-authentication.properties file.
- Configure the ldap-authentication.properties file to match your LDAP settings, and then zip the files again and rename it back to .amp before dropping into the amps folder.