4.3 Configuring an LDAP Server with YaST

Use YaST to set up an LDAP server. Typical use cases for LDAP servers include the management of user account data and the configuration of mail, DNS, and DHCP servers.

Figure 4-2 YaST LDAP Server Configuration

Figure 4-3 YaST LDAP Server—New Database

To set up an LDAP server for user account data, make sure the yast2-ldap-server and openldap2 packages and packages they depend on are installed. Then proceed as follows:

  1. Log in as root.

  2. Start YaST and select Network Services > LDAP Server to invoke the configuration wizard.

  3. Configure the Global Settings of your LDAP server (you can change these settings later)—see Figure 4-2:

    1. Set LDAP to be started.

    2. If the LDAP server should announce its services via SLP, check Register at an SLP Daemon.

    3. Configure Firewall Settings.

    4. Click Next.

  4. Consider to Enable TLS. TLS is an encryption technology. For more information, see Step 4.

  5. Confirm Basic Database Settings with entering an LDAP Administrator Password and then clicking Next—see Figure 4-2.

  6. Check the LDAP Server Configuration Summary and click Finish to exit the configuration wizard.

Figure 4-4 YaST LDAP Server Configuration

For changes or additional configuration start the LDAP server module again and in the left pane expand Global Settings to make subentries visible—see Figure 4-4:

  1. With Log Level Settings, configure the degree of logging activity (verbosity) of the LDAP server. From the predefined list, select or deselect the logging options according to your needs. The more options are enabled, the larger your log files grow.

  2. From Allow/Disallow Features determine the connection types the LDAP server should allow. Choose from:

    LDAPv2 Bind Requests

    This option enables connection requests (bind requests) from clients using the previous version of the protocol (LDAPv2).

    Anonymous Bind When Credentials Not Empty

    Normally the LDAP server denies any authentication attempts with empty credentials (DN or password). Enabling this option, however, makes it possible to connect with a password and no DN to establish an anonymous connection.

    Unauthenticated Bind When DN Not Empty

    Enabling this option makes it possible to connect without authentication (anonymously) using a DN but no password.

    Unauthenticated Update Options to Process

    Enabling this option allows non-authenticated (anonymous) update operations. Access is restricted according to ACLs and other rules .

  3. Then from Allow/Disallow Features determine which flags the LDAP server should disallow. Choose from:

    Disable Acceptance of Anonymous Bind Requests

    Disable Simple Bind Authentication

    Disable Forcing Session to Anonymous Status upon StartTLS Operation Receipt

    Disallow the StartTLS Operation if Authenticated

  4. To configure secure communication between client and server, proceed with TLS Settings:

    1. Activate Enable TLS to enable TLS and SSL encryption of the client/server communication.

    2. Either Import Certificate by specifying the exact path to its location or enable the Use Common Server Certificate. If the Use Common Server Certificate is not available because it has not been created during installation, go for Launch CA Management Module first— for more information, see Section 16.2, YaST Modules for CA Management.

Add Schema files to be included in the server's configuration by selecting Schema Files in the left part of the dialog. The default selection of schema files applies to the server providing a source of YaST user account data.

YaST allows to add traditional Schema files (usually with a name ending in .schema) or LDIF files containing Schema definitions in OpenLDAP's LDIF Schema format.

Figure 4-5 YaST LDAP Server Database Configuration

To configure the databases managed by your LDAP server, proceed as follows:

  1. Select the Databases item in the left part of the dialog.

  2. Click Add Database to add the new database.

  3. Enter the requested data:

    Base DN

    Enter the base DN of your LDAP server.

    Administrator DN

    Enter the DN of the administrator in charge of the server. If you check Append Base DN, only provide the cn of the administrator and the system fills in the rest automatically.

    LDAP Administrator Password

    Enter the password for the database administrator.

    Use This Database as the Default for OpenLDAP Clients

    For convenience, check this option if wanted.

  4. In the next dialog, enable enforcement of password policies to provide extra security to your LDAP server:

    1. Check Enable Password Policies to be able to specify a password policy.

    2. Activate Hash Clear Text Passwords to have clear text passwords be hashed before they are written to the database whenever they are added or modified.

    3. Disclose "Account Locked" Status provides a meaningful error message to bind requests to locked accounts.

      WARNING: Locked Accounts in Security Sensitive Environments

      Do not use the Disclose "Account Locked" Status option if your environment is sensitive to security issues, because the Locked Account error message provides security sensitive information that can be exploited by a potential attacker.

    4. Enter the DN of the default policy object. To use a DN other than the one suggested by YaST, enter your choice. Otherwise accept the default settings.

  5. Complete the database configuration by clicking Finish.

If you have not opted for password policies, your server is ready to run at this point. If you chose to enable password policies, proceed with the configuration of the password policy in detail. If you chose a password policy object that does not yet exist, YaST creates one:

  1. Enter the LDAP server password. In the navigation tree below Databases expand your database object and activate the Password Policy Configuration item.

  2. Make sure Enable Password Policies is activated. Then click Edit Policy.

  3. Configure the password change policies:

    1. Determine the number of passwords stored in the password history. Saved passwords may not be reused by the user.

    2. Determine whether users can change their password and whether they need to change their password after a reset by the administrator. Optionally require the old password for password changes.

    3. Determine whether and to what extent passwords should be subject to quality checking. Set a minimum password length that must be met before a password is valid. If you select Accept Uncheckable Passwords, users are allowed to use encrypted passwords although the quality checks cannot be performed. If you opt for Only Accept Checked Passwords only those passwords that pass the quality tests are accepted as valid.

  4. Configure the password aging policies:

    1. Determine the minimum password age (the time that needs to pass between two valid password changes) and the maximum password age.

    2. Determine the time between a password expiration warning and the actual password expiration.

    3. Set the number of postponement uses of an expired password before the password expires entirely.

  5. Configure the lockout policies:

    1. Enable password locking.

    2. Determine the number of bind failures that trigger a password lock.

    3. Determine the duration of the password lock.

    4. Determine for how long password failures are kept in the cache before they are purged.

  6. Apply your password policy settings with OK.

To edit a previously created database, select its base DN in the tree to the left. In the right part of the window, YaST displays a dialog similar to the one used for the creation of a new database—with the main difference that the base DN entry is grayed out and cannot be changed.

After leaving the LDAP server configuration by selecting Finish, you are ready to go with a basic working configuration for your LDAP server. To fine-tune this setup, make use of OpenLDAP's dynamic configuration backend.

The OpenLDAP's dynamic configuration backend stores the configuration in an LDAP database itself. That database consists of a set of .ldif files in /etc/openldap/slapd.d. There is no need to access these files directly. To access the settings you can either use the YaST LDAP server module (the yast2-ldap-server package) or an LDAP client such as ldapmodify or ldapsearch. For more information on the dymanic configuration of OpenLDAP, see the OpenLDAP Administration Guide.