One or two years ago, I spent some time trying to understand how to connect Plone 2.0 to LDAP. I really had no luck as things were complicated. Reading out existing users from the directory might have been possible, but trying to create users was a thing never heard of.

I decided to check out the current state of Plone and LDAP again with amore modern version of Plone, in my case, Plone 2.5.2. After some heavy experimentation, I’ve come to the conclusion that the software involved has grown more mature, but it’s still hard to get it working.

Sources of Information

• http://plone.org/documentation/how-to/plone-2-5-and-openldap-integration-for-users-and-groups is the source of information in this matter. It’s rather long, but it’s worth reading.
• http://thread.gmane.org/gmane.comp.web.zope.plone.user/53770 is a very long thread on the plone-users mailing list, with many pieces of information.\
• http://article.gmane.org/gmane.comp.web.zope.plone.user/61148 is an article that makes some observations on what does work, and that doesn’t.\
• Do NOT read http://plone.org/documentation/how-to/ldap-authentication-with-plone
  • it’s only valid for Plone 2.1.

Software Requirements

• python-ldap. Make sure the python that is used to run Zope has this module available, or nothing at all will work.
• LDAPUserFolder. I used version 2.8beta. \
• LDAPMultiPlugins. I first tried version 1.4, but got some problems. Version 1.5, released yesterday(!), works much better.
• The LDAPMultiPlugins patch available at http://antiloop.plone.org/LDAPMultiPlugins-plone.org.patch. For me, it applied cleanly on top of LDAPMultiPlugins 1.5. It adds functionality that is available and needed by PlonePAS. Group memberships seems to work much better with this patch than without.
• Two patches, one on CMFPlone/RegistrationTool.py (download here), and one on PasswordResetTool/skins/PasswordReset/registered_notify_template.pt (download here). Without these, registration will fail. Please note that both patches are ugly hacks that are not long-term solutions to the problem.\
• This patch: http://www.zope.org/Collectors/PAS/53/plugin-registry-satisfaction.patch, or login after password reset will fail with a recursion depth error.

Installation

Drop LDAPUserFolder and LDAPMultiPlugins into your Products folder, apply patches listed above, and restart Zope.
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Configuration

Follow http://plone.org/documentation/how-to/plone-2-5-and-openldap-integration-for-users-and-groups. In short, you add a LDAP Multi Plugin to your PAS folder (acl_users in ZMI) by using the dropdown in the top right corner and then configure it.
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Theory of Operation\

Plone 2.5 uses PlonePAS, which is an adaption of Zope’s PAS (the Pluggable Authentication System) for its user/group handling. That is a good thing, as PAS is a very flexible system that can do just about anything.

To get LDAP users/groups/authentication, LDAPMultiPlugins need to be installed and configured. After configuration, LDAPMultiPlugins contain an LDAPUserFolder that is used to actually fetch information from LDAP. The different plugins in LDAPMultiPlugins then add functionality such as authentication, user and group enumeration et. al. to PlonePAS.

Configuration of which LDAP server(s) to use, which base to use etc are made by visiting acl_users -> <your LDAPMultiPlugin> -> Contents -> acl_users. A bit awkward to find, if you ask me.
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Notes

It’s very important to pay attention to the LDAP Schema tab under the LDAPUserFolder.

• The LDAP attribute used to keep the full name of the user must be mapped to fullname. In my case, this means that the LDAP attribute cn should be mapped to fullname. For other directory configurations the attribute may be named differently. Novell eDirectory for example, uses cn as username.

• The LDAP attributes used to keep the e-mail address of the user must be mapped to email. In most cases this means that the LDAP attribute mail should be mapped to email.
• Only attributes listed in the LDAP Schema tab are available in the dropdowns used to select which field to use as login name attribute, username etc in the configuration of LDAPUserFolder. \
• All attributes listed as MUST in the LDAP schemas used to create new users (and search for existing) must be listed under the LDAP Schema. If not, user registration will fail due to LDAP schema errors. \

It’s also very important to pay attention to the list of User Object Classes in the configure tab. This list is used both to construct the query used when searching for user objects, and to create new user objects at registration. At new user registration, an LDAP object is first created with all attributes (except the RDN attribute) set to [unset] in the LDAP database. As mentioned above, all attributes listed under the LDAP Schemas tab are filled with this value. Later on in the registration codepath, the attributes actually mapped to plone attributes are set (one attribute at a time, in separate LDAP requests).

The order of the PAS Plugins is very important. To get user registration to work, and for other things as well, the LDAP Multi Plugin should be at top of the list of plugins for each type of plugin.

For (much) better performance, add caching by visiting the Caches tab of both ZMI->acl_users and your LDAP Multi Plugin. Adding a cache to source_groups also seems like a good idea (there’s no cache tab, so you’ll have to find the URL to the cache management yourself - it’s something like http://uterus:8080/Plone/acl_users/source_groups/ZCacheable_manage. For me, it seems to work using the RAM Cache Manager that already exist in any Plone 2.5 installation.

That’s all the things I can remember as being important from yesterday’s late night session :-).
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