Wednesday, July 18, 2012

Achieve Faster WebLogic Authentications with Faster Group Membership Lookups

In my last post  I wrote about the complicated and timely process of determining all of a user’s group memberships when an LDAP namespace includes nested and dynamic group memberships. I wrote about how you can simplify and speed up getting a user’s group memberships through the use of a dynamic “member of” attribute and specifically the orclMemberOf attribute in OID.

Today I’d like to extend this discussion to WebLogic server authentications.

A Review of LDAP Authenticators and Groups

As I’ve written about in the past, as part of the authentication process, LDAP authenticators do a search to determine what groups the user is a member of which in turn get used in determining the group memberships and roles for the JAAS subject and principals.

By default the WebLogic LDAP authenticators follow the long time consuming process I laid out in my last post for determining group memberships with nested groups. First, it searches all your groups to figure out which groups your user is directly a member of. Then for each of those groups, it searches all your groups again to see which of those groups your user is a member of.

It will continue to search your groups with the results of each subsequent search until you reach the configured maximum level of nested memberships that you want to pursue or all the searches come back empty.

Only it is actually quite a bit “worse” than that because for some reason when the authenticator finds a group within a group it doesn’t just use the DN of that group in the next search, it takes the name of that group based on the “group name attribute” setting in the authenticator and then does a search to find the group’s DN all over again. So, for every group found in a search of memberships for the user there will be 2 new LDAP searches performed. One to get the user’s DN again and one to get the groups that group is a member of.

In my post on tuning LDAP authenticators, I wrote about the importance of tuning the settings governing group membership searches in the authenticator and specifically about limiting the depth of the searches for nested group membership.

Speeding Things Up

Today, I’d like to cover how-to dramatically speed up this process by letting the directory do all the work for you. This is achieved by configuring the authenticator to take advantage of the dynamic ‘member of’ (orclMemberOf in the case of OID) attribute that I wrote about in my last post.

The setting that enables this behavior is in the Dynamic Groups section of the provider specific configuration for LDAP authenticators and is called User Dynamic Group DN Attribute. When configured the LDAP authenticator will skip all searches (for both direct and nested memberships) of dynamic groups. Instead it will add roles (group principals) to the user for every group returned by the LDAP directory (OID) in the value of the specified attribute.

Here is what you need to know about this setting:

1) When configured the authenticator will add roles (group principals) to the user for every group returned by the LDAP directory (OID) in the value of the specified attribute.
2) Despite the fact that the setting is part of the Dynamic Group section of the authenticator configuration, the authenticator will add roles for every group returned as part of the value of the attribute, regardless of whether that group is a static group or dynamic group.

3) That being said, the authenticator will still perform a search of memberships for all static groups even when the User Dynamic Group DN Attribute is defined. It will not however perform a membership search of dynamic groups; instead it assumes all dynamic group memberships are captured by the attribute value.

Note especially that the authenticator will still perform a full search of nested static groups even when User Dynamic Group DN Attribute is defined; even though the orclMemberOf attribute in OID includes static group memberships.
Putting It All Together
So, to dramatically improve your WebLogic authentication performance with nested groups I recommend that you configure your authenticators as follows:
1) Enter the appropriate LDAP attribute name for the value of User Dynamic Group DN Attribute based on the type of directory you are authenticating against.. Appropriate values include orclMemberOf for OID, memberof for DSEE, and ismemberof for AD.

2) Set the value of GroupMembershipSearching to limited. The default value is unlimited.

3) Set the value of Max Group Membership Search Level to 0. This will make the authenticator not perform searches for nested group memberships and limit it to performing a single search to find the users direct group memberships. Again, we will be relying on the value of the attribute specified in User Dynamic Group DN Attribute to give us the nested searches.

4) If you want to even eliminate the direct group membership search you can specify an empty Group Base DN. Note here that the Group Base DN must exist or you’ll get an error and a failed authentication. However, it can be empty. So, you can create cn=fakegroupbase as a sibling of cn=Groups,dc=example,dc=com.

5) If you recall in my previous post I mentioned that using the orclMemberOf attribute can result in duplicate listing when nested memberships are returned multiple times, once for each group that the user belongs to that is a member of another given group. Because of this, you’ll probably want to check the Ignore Duplicate Membership option in the authenticator.

Below is a screen shot of an OID authenticator configured with these options:

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