A role is an alternate grouping mechanism that is designed to be more efficient and easier for applications to use. While roles are defined and administered like groups, a generated role attribute in each member entry automatically indicates the roles of an entry. For example, an application can read the roles of an entry, rather than having to select a group and browse the members list.
By default, the scope of a role is limited to the subtree where the scope is defined. However, you can extend scoping of the nested role. You can allow the scope to nest roles located in other subtrees and to have members anywhere in the directory. For details see To Extend the Scope of a Role and Example of a Nested Role Definition.
This section explains how to use roles securely, and how to manage roles from the command line.
To use roles securely, you must set access control instructions (ACIs) to protect appropriate attributes. For example, user A possesses the managed role, MR. Managed roles are equivalent to static groups, and explicitly assign a role to each member entry by adding the nsRoleDN attribute to the entry. The MR role has been locked using account inactivation through the command line. This means that user A cannot bind to the server because the nsAccountLock attribute is computed as “true” for that user. However, suppose the user was already bound and noticed that he is now locked through the MR role. If no ACI exists to prevent the user from having write access to the nsRoleDN attribute, the user can remove the nsRoleDN attribute from his own entry and unlock himself.
To prevent users from removing the nsRoleDN attribute, you must apply ACIs. With filtered roles, you must protect the part of the filter that would prevent the user from being able to relinquish the filtered role by modifying an attribute. Users should not be allowed to add, delete, or modify the attribute used by the filtered role. In the same way, if the value of the filter attribute is computed, all the attributes that can modify the value of the filter attribute need to be protected. As nested roles can contain filtered and managed roles, the preceding points should be considered for each of the roles that are contained in the nested role.
For detailed instructions on setting ACIs for security, see Chapter 6, Directory Server Access Control.
Roles are defined in entries that the Directory Administrator can access through command-line utilities. After you create a role, you assign members to the role as follows:
Members of a managed role have the nsRoleDN attribute in their entry.
Members of a filtered role are entries that match the filter specified in the nsRoleFilter attribute.
Members of a nested role are members of the roles that are specified in the nsRoleDN attributes of the nested role definition entry.
$ ldapmodify -a -h host1 -p 1389 -D cn=admin,cn=Administrators,cn=config -w - dn: cn=Marketing,ou=marketing,ou=People,dc=example,dc=com objectclass: top objectclass: LDAPsubentry objectclass: nsRoleDefinition objectclass: nsSimpleRoleDefinition objectclass: nsManagedRoleDefinition cn: Marketing description: managed role for marketing staff
Assign the role to a marketing staff member who is named Bob by updating his entry as follows:
$ ldapmodify -h host1 -p 1389 -D cn=admin,cn=Administrators,cn=config -w - dn: cn=Bob Arnold,ou=marketing,ou=People,dc=example,dc=com changetype: modify add: nsRoleDN nsRoleDN: cn=Marketing,ou=marketing,ou=People,dc=example,dc=com
The nsRoleDN attribute indicates that the entry is a member of a managed role. The managed role is identified by the DN of its role definition. To allow users to modify their own nsRoleDN attribute, but to prevent users from adding or removing the nsManagedDisabledRole, add the following ACI:
aci: (targetattr="nsRoleDN")(targattrfilters="add=nsRoleDN: (!(nsRoleDN=cn=AdministratorRole,dc=example,dc=com)), del=nsRoleDN:(!(nsRoleDN=cn=nsManagedDisabledRole,dc=example, dc=com)") (version3.0;aci "allow mod of nsRoleDN by self except for critical values"; allow(write) userdn="ldap:///self";)
$ ldapmodify -a -h host1 -p 1389 -D cn=admin,cn=Administrators,cn=config -w - dn: cn=ManagerFilter,ou=sales,ou=People,dc=example,dc=com objectclass: top objectclass: LDAPsubentry objectclass: nsRoleDefinition objectclass: nsComplexRoleDefinition objectclass: nsFilteredRoleDefinition cn: ManagerFilter nsRoleFilter: (isManager=True) Description: filtered role for sales managers
Notice that the nsFilteredRoleDefinition object class inherits from the LDAPsubentry, nsRoleDefinition, and nsComplexRoleDefinition object classes. The nsRoleFilter attribute specifies a filter that finds all employees in the ou=sales organization that have subordinates, for example:
$ ldapsearch -h host1 -p 1389 -D cn=admin,cn=Administrators,cn=config -w - \ -b "ou=People,dc=example,dc=com" -s sub "(cn=*Fuentes)" dn: cn=Carla Fuentes,ou=sales,ou=People,dc=example,dc=comcn: Carla Fuentes isManager: TRUE... nsRole: cn=ManagerFilter,ou=sales,ou=People, dc=example,dc=com
The filter string of a filtered role can be based on any attribute, except computed attributes that are generated by the CoS mechanism.
When filtered role members are user entries, you can choose to restrict their ability to add or remove themselves from the role. Protect the filtered attributes with ACIs.
The roles that are nested within the nested role are specified by using the nsRoleDN attribute. Use the following command to create a role that contains both the marketing staff and sales manager members of the roles created in the previous examples:
$ ldapmodify -a -h host1 -p 1389 -D cn=admin,cn=Administrators,cn=config -w - dn: cn=MarketingSales,ou=marketing,ou=People,dc=example,dc=com objectclass: top objectclass: LDAPsubentry objectclass: nsRoleDefinition objectclass: nsComplexRoleDefinition objectclass: nsNestedRoleDefinition cn: MarketingSales nsRoleDN: cn=ManagerFilter,ou=sales,ou=People,dc=example,dc=com nsRoleDN: cn=Marketing,ou=marketing,ou=People,dc=example,dc=com nsRoleScopeDN: ou=sales,ou=People,dc=example,dc=com
Notice that the nsNestedRoleDefinition object class inherits from the LDAPsubentry, nsRoleDefinition, and nsComplexRoleDefinition object classes. The nsRoleDN attributes contain the DN of the marketing managed role and the sales managers filtered role. Both of the users in the previous examples, Bob and Carla, would be members of this new nested role.
The scope of this filter includes the default scope, which is the subtree where the filter is located, and the subtree below any values of the nsRoleScopeDN attribute. In this case, the ManagerFilter is in the ou=sales,ou=People,dc=example,dc=com subtree. This subtree must be added to the scope.
Directory Server provides an attribute that allows the scope of a role to be extended beyond the subtree of the role definition entry. This single-valued attribute, nsRoleScopeDN, contains the DN of the scope to be added to an existing role. The nsRoleScopeDN attribute can only be added to a nested role. See Example of a Nested Role Definition.
You cannot use DSCC to perform this task. Use the command line, as described in this procedure.
The nsRoleScopeDN attribute enables you to extend the scope of a role in one subtree to include an entry in another subtree. For example, imagine two main subtrees in the example.com directory tree: o=eng,dc=example,dc=com ( the engineering subtree) and o=sales,dc=example,dc=com (the sales subtree.) A user in the engineering subtree requires access to a sales application governed by a role in the sales subtree (SalesAppManagedRole). To extend the scope of the role, do the following:
Create a role for the user in the engineering subtree.
For example, create the role EngineerManagedRole. This example uses a managed role, but it could just as well have been a filtered or nested role.
Create a nested role, for example, SalesAppPlusEngNestedRole , in the sales subtree to house the newly created EngineerManagedRole and the initial SalesAppManagedRole .
Add the nsRoleScopeDN attribute to the SalesAppPlusEngNestedRole, with the DN of the engineering subtree scope that you want to add, in this case, o=eng,dc=example,dc=com.
The necessary permissions must be granted to the engineering user so that he can access the SalesAppPlusEngNestedRole role and, in turn, the sales application. In addition, the entire scope of the role must be replicated.
The restriction of extended scope to nested roles means that an administrator who previously managed roles in one domain only has rights to use the roles that already exist in the other domain. The administrator is not able to create an arbitrary role in the other domain.