Selected ASDM VPN Configuration Procedures for the Cisco ASA 5500 Series, Version 5.2
Configuring an LDAP AAA Server
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Configuring an LDAP AAA Server

Table Of Contents

Configuring an LDAP AAA Server

Overview of LDAP Transactions

Creating an LDAP Attribute Map

Configuring AAA Server Groups and Servers

Creating the LDAP AAA Server Groups

Configuring the LDAP AAA Servers

Configuring the Group Policy for LDAP Authorization

Configuring a Tunnel Group for LDAP Authentication


Configuring an LDAP AAA Server


This chapter presents an example configuration procedure for configuring security appliance user authentication and authorization using a Microsoft Active Directory Server (LDAP) that is on the same internal network as the security appliance. It includes the following sections.

Overview of LDAP Transactions

Creating an LDAP Attribute Map

Configuring AAA Server Groups and Servers

Configuring the Group Policy for LDAP Authorization

Configuring a Tunnel Group for LDAP Authentication

Overview of LDAP Transactions

Figure 6-1 shows the major transactions in security appliance user authentication and authorization using an LDAP directory server.

Figure 6-1 LDAP Authentication and Authorization Transaction Flow

Creating an LDAP Attribute Map

To configure the security appliance for LDAP authentication and authorization, you must first create an LDAP attribute map which maps customer-defined attribute names to Cisco LDAP attribute names. This prevents you from having to rename your existing attributes using the Cisco names that the security appliance understands.


Note To use the attribute mapping features correctly, you need to understand the Cisco LDAP attribute names and values as well as the user-defined attribute names and values. See the Cisco Security Appliance Command Line Configuration Guide appendix, "Configuring an External Server for Authorization and Authentication" for the list of Cisco LDAP attributes.


To create a new LDAP attribute map, perform the following steps:


Step 1 In the Cisco ASDM window, choose Configuration > Properties > AAA Setup > LDAP Attribute Map.

The LDAP Attribute Map area appears in the window on the right as shown in Figure 6-2.

Figure 6-2 LDAP Attribute Map Area

Step 2 In the LDAP Attribute Map area, click Add.

The Add LDAP Attribute Map dialog box appears as shown in Figure 6-3.

Figure 6-3 Add LDAP Attribute Map Dialog Box - Map Name Tab Selected

Step 3 In the Name field above the tabs, enter a name for the LDAP attribute map.

In this example, we name the attribute map ActiveDirectoryMapTable.

Step 4 If the Map Name tab is not selected, choose it now.

Step 5 In the Custom Name (user-defined attribute name) field on the Map Name tab, enter the name of an attribute that you want to map to a Cisco attribute name.

In this example, the custom name is department.

Step 6 Choose a Cisco name from the Cisco Name menu. The custom name maps to this Cisco name.

In this example, the Cisco name is cVPN3000-IETF-Radius-Class. As shown in Figure 6-1, the security appliance receives the user attributes from the authentication server upon validation of the user credentials. If a class attribute is among the user attributes returned, the security appliance interprets it as the group policy for that user, and it sends a request to the AAA server group configured for this group policy to obtain the group attributes.

Step 7 Click Add to include the name mapping in the attribute map.

Step 8 Click the Map Value tab and then click Add on the Map Value tab.

The Add LDAP Attributes Map Value dialog box appears as shown in Figure 6-4.

Figure 6-4 Add LDAP Attributes Map Value Dialog Box

Step 9 From the Custom Name menu, choose the custom attribute for which you want to map a value.

Step 10 Enter the custom (user-defined) value in the Custom Value field.

Step 11 Enter the Cisco value in the Cisco Value field.

Step 12 Click Add to include the value mapping in the attribute map.

Step 13 Repeat Step 4 through Step 12 for each attribute name and value to be mapped.

Step 14 After you have completed mapping all the names and values, click OK at the bottom of the Add LDAP Attribute Map window.

Step 15 Click Apply to complete the new LDAP attribute map and add it to the running security appliance configuration.


Configuring AAA Server Groups and Servers

Next, you configure AAA server groups and the AAA servers that go into them. You must configure two AAA server groups. You configure one server group as an authentication server group containing an authentication server that requests an LDAP search of the user records. You configure the other server group as an authorization server group containing an authorization server that requests an LDAP search of the group records. One notable difference between the two groups is that the AAA servers have different base DN fields to specify different Active Directory folders to search.

Creating the LDAP AAA Server Groups

To configure the two server groups, perform the following steps:


Step 1 In the Cisco ASDM window, choose Configuration > Properties > AAA Setup > AAA Servers.

The AAA Servers area appears in the right half of the window as shown in Figure 6-5.

Figure 6-5 The ASDM Window with AAA Servers Selected

The fields in the AAA Servers area are grouped into two areas: the Server Groups area and the Servers In The Selected Group area. The Server Groups area lets you configure AAA server groups and the protocols the security appliance uses to communicate with the servers listed in each group.

Step 2 In the Server Groups area, click Add.

The Add AAA Server Group dialog box appears as shown in Figure 6-6.

Figure 6-6 The Add AAA Server Group Dialog Box

Step 3 Enter the name of the server group in the Server Group field.

Use different names for the authentication server group and the authorization server group. In this example, we name the authentication server group ldap-authenticat (authenticate is truncated because of a sixteen character maximum) and the authorization server group ldap-authorize.

Step 4 Choose LDAP from the Protocol menu.

Step 5 For the Reactivation Mode, choose one of the following:

Depletion—Configures the security appliance to reactivate failed servers only after all of the servers in the group are inactive.

Timed—Configures the security appliance to reactive failed servers after 30 seconds of down time.

Step 6 In the Dead Time field, enter the number of minutes that elapse between the disabling of the last server in the group and the subsequent reenabling of all servers.

This field is not available if you selected Timed mode in Step 5.

Step 7 In the Max Failed Attempts field, enter the number of failed connection attempts (1 through 5) allowed before declaring a nonresponsive server inactive.

Step 8 Click OK to enter the newly configured server into the Server Groups table.

Step 9 Repeat Step 2 through Step 8 for the second AAA server group. When done, you should have an authentication server group and an authorization server group.


Configuring the LDAP AAA Servers

For each of the two AAA server groups, you next configure a AAA server. Again, one server is for authentication and one for authorization.

To add a new LDAP AAA server to each of the AAA server groups, perform the following steps:


Step 1 In the Cisco ASDM window, choose Configuration > Properties > AAA Setup > AAA Servers.

The AAA Servers area appears in the right half of the window.

Step 2 In the Server Group table, click the LDAP server group to which you want to add the LDAP server.

In this example, we configure the authentication server in the ldap-authenticat group and the authorization server in the ldap-authorize group.

Step 3 In the Servers in Selected Group area, click Add.

The Add AAA Server dialog box appears as shown in Figure 6-7.

Figure 6-7 The Add AAA Server Dialog Box

Step 4 From the Interface Name menu, choose either:

Inside if your LDAP server is on your internal network

-or-

Outside if your LDAP server is on an external network

In our example, the LDAP server is on the internal network.

Step 5 Enter the server name or IP address in the Server Name or IP Address field.

In our example, we use the IP address.

Step 6 In the Timeout field, enter the timeout interval in seconds.

This is the time after which the security appliance gives up on the request to the primary AAA server. If there is a standby server in the server group, the security appliance sends the request to the backup server.

Step 7 In the LDAP Parameters area, check Enable LDAP over SSL if you want all communications between the security appliance and the LDAP directory to be encrypted with SSL.


Warning If you do not check Enable LDAP over SSL, the security appliance and the LDAP directory exchange all data in the clear, including sensitive authentication and authorization data.


Step 8 Enter the server port to use in the Server Port field.

This is the TCP port number by which you access the server.

Step 9 From the Server Type menu, choose one of the following:

Sun Microsystems JAVA System Directory Server (formerly the Sun ONE Directory Server)

- or -

Microsoft Active Directory

- or -

Detect automatically

The security appliance supports authentication and password management features only on the Sun Microsystems JAVA System Directory Server (formerly named the Sun ONE Directory Server) and the Microsoft Active Directory. By selecting Detect automatically, you let the security appliance determine if the server is a Microsoft or a Sun server.


Note The DN configured on the security appliance to access a Sun directory server must be able to access the default password policy on that server. We recommend using the directory administrator, or a user with directory administrator privileges, as the DN. Alternatively, you can place an ACI on the default password policy.


Step 10 Enter one of the following into the Base DN field:

The base DN of the Active Directory folder holding the user attributes (typically a users folder) if you are configuring the authentication server

- or -

The base DN of the Active Directory folder holding the group attributes (typically a group folder) if you are configuring the authorization server

The base DN is the location in the LDAP hierarchy where the server should begin searching when it receives an authorization request. For example, OU=people, dc=cisco, dc=com.

Step 11 From the Scope menu, select one of the following:

One level beneath the Base DN

- or -

All levels beneath the Base DN

The scope specifies the extent of the search in the LDAP hierarchy that the server should make when it receives an authorization request. One Level Beneath the Base DN specifies a search only one level beneath the Base DN. This option is quicker. All Levels Beneath the Base DN specifies a search of the entire subtree hierarchy. This option takes more time.

Step 12 In the Naming Attribute(s) field, enter the Relative Distinguished Name attribute that uniquely identifies an entry on the LDAP server.

Common naming attributes are Common Name (cn) and User ID (uid).

Step 13 In the Login DN field, perform one of the following:

Enter the name of the directory object for security appliance authenticated binding. For example, cn=Administrator, cn=users, ou=people, dc=Example Corporation, dc=com.

- or -

Leave this field blank for anonymous access.

Some LDAP servers, including the Microsoft Active Directory server, require the security appliance to establish a handshake via authenticated binding before accepting requests for LDAP operations. The security appliance identifies itself for authenticated binding by including a Login DN field with the user authentication request. The Login DN field defines the security appliance authentication characteristics which should correspond to those of a user with administration privileges.

Step 14 Enter the password associated with the Login DN in the Login Password field.

The characters you type appear as asterisks.

Step 15 From the LDAP Attribute Map menu, choose the LDAP attribute map to apply to the LDAP server.

The LDAP attribute map translates user-defined LDAP attribute names and values into Cisco attribute names and values. To configure a new LDAP attribute map, see Creating an LDAP Attribute Map.

Step 16 Check SASL MD5 Authentication to use the MD5 mechanism of the Simple Authentication and Security Layer (SASL) to secure authentication communications between the security appliance and the LDAP server.

Step 17 Check SASL Kerberos Authentication to use the Kerberos mechanism of the Simple Authentication and Security Layer to secure authentication communications between the security appliance and the LDAP server.


Note If you configure more than one SASL method for a server, the security appliance uses the strongest method supported by both the server and the security appliance. For example, if both MD5 and Kerberos are supported by both the server and the security appliance, the security appliance selects Kerberos to secure communication with the server.


Step 18 If you checked SASL Kerberos authentication in Step 17, enter the Kerberos server group used for authentication in the Kerberos Server Group field.

Step 19 Repeat Step 3 through Step 18 to configure a AAA server in the other AAA server group.


Configuring the Group Policy for LDAP Authorization

After configuring the LDAP attribute map, the AAA server groups, and the LDAP servers within the groups, you next create an external group-policy that associates the group-name with the LDAP authorization server.


Note Comprehensive procedures for configuring group policies are provided elsewhere in this guide. The following steps are only those that apply to configuring AAA with LDAP.


To create a new group policy and assign the LDAP authorization server group to it, perform the following steps:


Step 1 In the Cisco ASDM window, select Configuration > VPN > General > Group Policy.

The Group Policy area appears in the right half of the window.

Step 2 Click Add and choose either Internal Group Policy or External Group Policy.

In this example, we choose External Group Policy because the LDAP server is external to the security appliance.

The Add Group Policy dialog box appears as shown in Figure 6-8.

Figure 6-8 Add Group Policy Dialog Box

Step 3 Enter the name of the new group policy in the name field.

The group policy name is web1 in our example.

Step 4 From the Server Group menu, choose the AAA authorization server group you created previously.

In our example, this is the server group named ldap-authorize.

Step 5 Click OK and then Apply to create the new group policy.


Configuring a Tunnel Group for LDAP Authentication

In the final major task, you create a tunnel group that specifies LDAP authentication by performing the following steps:


Step 1 In the Cisco ASDM window, select Configuration > VPN > General > Tunnel Group.

The Tunnel Group area appears on the right side of the ASDM window as shown in Figure 6-9.

Figure 6-9 Tunnel Group Area

Step 2 Click Add in the tunnel Group area and choose the type of tunnel group.

In our example, we choose IPSec for Remote Access.

The Add Tunnel Group dialog box appears.

Step 3 Choose the General tab, and then choose the AAA tab, as shown in Figure 6-10.

Figure 6-10 Add Tunnel Group Dialog Box with General and AAA Tabs Selected

Step 4 Enter the name of the tunnel group in the Name field.

In our example, the tunnel group name is ipsec-tunnelgroup.

Step 5 From the Authentication Server Group menu, chose the AAA server group you configured for authentication.

In our example, the authentication server group name is ldap-authenticat.

Step 6 Click OK at the bottom of the Add Tunnel Group dialog box.

Step 7 Click Apply at the bottom of the ASDM window to include the changes to the running configuration.

You have completed this example of the minimal steps required to configure the security appliance for LDAP authentication and authorization.