OpenDJ directory server has one default administrator that can manage all aspects of the server.

In an earlier post, I’ve described how to create multiple administrative accounts in OpenDJ, and in another one, I’ve talked about the Privilege system and how it can be used to tailor the administrative roles of each account.

In most enterprises, administrators are usually employees and therefore have their own entries and password. For auditing purpose, security processes require that a change or an administrative task on the directory be done as the true person and not the administrative account. But often there are multiple administrators, and they can change role frequently. So what is the best practice for granting employees some administrative privileges ?

An efficient and manageable way  is to create an Administrators’ group and grant the privileges to all members of that group. When an employee, is no longer administrator, simply remove him from the group and he will loose all privileges associated. Likewise, adding a new administrator is just adding a member in the group.

With OpenDJ, this can be done with 2 simple entries : a group and a privilege collective attribute subentry.

The Group :

dn: cn=Administrators,ou=Groups,dc=example,dc=com
objectClass: groupOfNames
objectClass: top
description: LDAP Administrators Group
cn: Administrators
member: uid=ludo,ou=People,dc=example,dc=com
member: uid=Matt,ou=people,dc=example,dc=com

The Collective Attribute Subentry :

dn: cn=Administrators Privilege,dc=example,dc=com
objectClass: extensibleObject
objectClass: collectiveAttributeSubentry
objectClass: top
objectClass: subentry
cn: Administrators Privilege
ds-privilege-name;collective: config-read
ds-privilege-name;collective: config-write
ds-privilege-name;collective: ldif-export
ds-privilege-name;collective: modify-acl
ds-privilege-name;collective: password-reset
ds-privilege-name;collective: proxied-auth
subtreeSpecification: {base "ou=people", specificationFilter
  "(isMemberOf=cn=Administrators,ou=groups,dc=example,dc=com)" }

How does it work ?

Collective Attributes is a standard based LDAP functionality that allows to define attributes and value that are defined once and appear in all entries that match the subtreeSpecification. Collective Attributes are defined in RFC 3671. For those who are familiar with Sun Directory Server’s Class Of Service, Collective Attributes provide a similar function, but based on industry approved standard.

OpenDJ collective attributes feature supports a few extensions to facilitate their use.

First, the standard way to define a collective attribute is to define it in the schema with a “c–” prefix. With OpenDJ, any existing attribute can be defined as collective with the ;collective attribute option.

Second, the scope of a Collective Attribute subentry as defined by the standard is a subtree, but the only filter possible is to specify the object class it applies to. We’ve extended the specificationFilter to accept an arbitrary LDAP filter, allowing a finer grained control of which entries are targeted.

In the example above, the filter is used to restrict the Privilege Collective Attribute subentry to apply only to entries that have the isMemberOf attribute with the value “cn=Administrators,ou=Groups,dc=example,dc=com”.

IsMemberOf is an operational read-only attribute (virtual) that is a back-link to the groups a user belongs to. OpenDJ does support the isMemberOf attribute for static groups, nested static groups and dynamic groups.

The subtreeSpecification also contains a base “ou=people” to restrict the targeted entries to the ou=people subtree. There are additional field allowed in the subtreeSpecification to indicate a depth in the tree for example.

As a result, collective attribute subentries, combined with groups, provide a flexible way to “inject” attributes and values to a specified set of entries, either to grant them specific privileges like in our example, or to decorate entries based on some common properties.

This said, remember that privileges are set in addition to the Access Controls. So giving a user the password-reset privilege for example, will be useless if there is no ACI allowing him or her to modify the userPassword attribute of other users. Granting access through an ACI to a group is as simple as using groupdn=”ldap:///cn=Administrators,dc=example,dc=com”;  to designate the authorized identities.