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Chapter: Configure an External AAA Server for VPN
Chapter Contents
- About External AAA Servers
- Guidelines For Using External AAA Servers
- Configure Multiple Certificate Authentication
- Configure LDAP Authorization for VPN
- Active Directory/LDAP VPN Remote Access Authorization Examples
About External AAA Servers
This ASA can be configured to use an external LDAP, RADIUS, or TACACS+ server to support Authentication, Authorization, and Accounting (AAA) for the ASA. The external AAA server enforces configured permissions and attributes. Before you configure the ASA to use an external server, you must configure the external AAA server with the correct ASA authorization attributes and, from a subset of these attributes, assign specific permissions to individual users.
Understanding Policy Enforcement of Authorization Attributes
The ASA supports several methods of applying user authorization attributes (also called user entitlements or permissions) to VPN connections. You can configure the ASA to obtain user attributes from any combination of:
- a Dynamic Access Policy (DAP) on the ASA
- an external RADIUS or LDAP authentication and/or authorization server
- a group policy on the ASA
If the ASA receives attributes from all sources, the attributes are evaluated, merged, and applied to the user policy. If there are conflicts between attributes, the DAP attributes take precedence.
The ASA applies attributes in the following order:
- DAP attributes on the ASA—Introduced in Version 8.0(2), these attributes take precedence over all others. If you set a bookmark or URL list in DAP, it overrides a bookmark or URL list set in the group policy.
- User attributes on the AAA server—The server returns these attributes after successful user authentication and/or authorization. Do not confuse these with attributes that are set for individual users in the local AAA database on the ASA (User Accounts in ASDM).
- Group policy configured on the ASA—If a RADIUS server returns the value of the RADIUS CLASS attribute IETF-Class-25 (OU=group-policy) for the user, the ASA places the user in the group policy of the same name and enforces any attributes in the group policy that are not returned by the server.For LDAP servers, any attribute name can be used to set the group policy for the session. The LDAP attribute map that you configure on the ASA maps the LDAP attribute to the Cisco attribute IETF-Radius-Class.
- Group policy assigned by the Connection Profile (called tunnel-group in the CLI)—The Connection Profile has the preliminary settings for the connection, and includes a default group policy applied to the user before authentication. All users connecting to the ASA initially belong to this group, which provides any attributes that are missing from the DAP, user attributes returned by the server, or the group policy assigned to the user.
- Default group policy assigned by the ASA (DfltGrpPolicy)—System default attributes provide any values that are missing from the DAP, user attributes, group policy, or connection profile.
Guidelines For Using External AAA Servers
The ASA enforces the LDAP attributes based on attribute name, not numeric ID. RADIUS attributes, are enforced by numeric ID, not by name.
For ASDM Version 7.0, LDAP attributes include the cVPN3000 prefix. For ASDM Versions 7.1 and later, this prefix was removed.
LDAP attributes are a subset of the Radius attributes, which are listed in the Radius chapter.
Configure Multiple Certificate Authentication
You can now validate multiple certificates per session with AnyConnect SSL and IKEv2 client protocols. For example, you can make sure that the issuer name of the machine certificate matches a particular CA and therefore that the device is a corporate-issued device.
The multiple certificates option allows certificate authentication of both the machine and user via certificates. Without this option, you could only do certificate authentication of one or the other, but not both.
The pre-fill username field allows a field from the second (user) certificate to be parsed and used for subsequent AAA authentication in a AAA and certificate authenticated connection. The username for both primary and secondary prefill is always retrieved from the second (user) certificate received from the client.
With multiple certificate authentication, two certificates are authenticated: the second (user) certificate received from the client is the one that the pre-fill and username-from-certificate primary and secondary usernames are parsed from.The existing authentication webvpn attributes is modified to include an option for multiple-certificate authentication:
tunnel-group <name> webvpn-attributes
authentication {[aaa] [certificate | multiple-certificate] | saml}With multiple-certificate authentication, you can make policy decisions based on the fields of a certificate used to authenticate that connection attempt. The user and machine certificate received from the client during multiple-certificate authentication is loaded into DAP to allow policies to be configured based on the field of the certificate. To add multiple certificate authentication using Dynamic Access Policies (DAP) so that you can set up rules to allow or disallow connection attempts, refer to Add Multiple Certificate Authentication to DAP in the appropriate release of the ASA VPN ASDM Configuration Guide.
Configure LDAP Authorization for VPN
After LDAP authentication for VPN access has succeeded, the ASA queries the LDAP server, which returns LDAP attributes. These attributes generally include authorization data that applies to the VPN session.
You may require authorization from an LDAP directory server that is separate and distinct from the authentication mechanism. For example, if you use an SDI or certificate server for authentication, no authorization information is passed back. For user authorizations in this case, you can query an LDAP directory after successful authentication, accomplishing authentication and authorization in two steps.
To set up VPN user authorization using LDAP, perform the following steps.
Procedure
| Step 1 | Create a AAA server group.aaa-server server_group protocol {kerberos | ldap | nt | radius | sdi | tacacs+}Example: hostname(config)# aaa-server servergroup1 protocol ldap hostname(config-aaa-server-group) |
| Step 2 | Create an IPsec remote access tunnel group named remotegrp.tunnel-group groupnameExample: hostname(config)# tunnel-group remotegrp |
| Step 3 | Associate the server group and the tunnel group.tunnel-group groupname general-attributesExample: hostname(config)# tunnel-group remotegrp general-attributes |
| Step 4 | Assigns a new tunnel group to a previously created AAA server group for authorization.authorization-server-group group-tagExample: hostname(config-general)# authorization-server-group ldap_dir_1 |
Example
The following example shows commands for enabling user authorization with LDAP. The example then creates an IPsec remote access tunnel group named RAVPN and assigns that new tunnel group to the previously created LDAP AAA server group for authorization:
hostname(config)# tunnel-group RAVPN type remote-access
hostname(config)# tunnel-group RAVPN general-attributes
hostname(config-general)# authorization-server-group (inside) LDAP
hostname(config-general)#
After you complete this configuration work, you can then configure additional LDAP authorization parameters such as a directory password, a starting point for searching a directory, and the scope of a directory search by entering the following commands:
hostname(config)# aaa-server LDAP protocol ldap
hostname(config-aaa-server-group)# aaa-server LDAP (inside) host 10.0.2.128
hostname(config-aaa-server-host)# ldap-base-dn DC=AD,DC=LAB,DC=COM
hostname(config-aaa-server-host)# ldap-group-base-dn DC=AD,DC=LAB,DC=COM
hostname(config-aaa-server-host)# ldap-scope subtree
hostname(config-aaa-server-host)# ldap-login-dn AD\cisco
hostname(config-aaa-server-host)# ldap-login-password cisco123
hostname(config-aaa-server-host)# ldap-over-ssl enable
hostname(config-aaa-server-host)# server-type microsoft
Active Directory/LDAP VPN Remote Access Authorization Examples
This section presents example procedures for configuring authentication and authorization on the ASA using the Microsoft Active Directory server. It includes the following topics:
- Policy Enforcement of User-Based Attributes
- Place LDAP Users in a Specific Group Policy
- Enforce Static IP Address Assignment for AnyConnect Tunnels
- Enforce Dial-in Allow or Deny Access
- Enforce Logon Hours and Time-of-Day Rules
Other configuration examples available on Cisco.com include the following TechNotes.
- ASA/PIX: Mapping VPN Clients to VPN Group Policies Through LDAP Configuration Example
- PIX/ASA 8.0: Use LDAP Authentication to Assign a Group Policy at Login
- Policy Enforcement of User-Based Attributes
- Place LDAP Users in a Specific Group Policy
- Enforce Static IP Address Assignment for AnyConnect Tunnels
- Enforce Dial-in Allow or Deny Access
- Enforce Logon Hours and Time-of-Day Rules
Policy Enforcement of User-Based Attributes
This example displays a simple banner to the user, showing how you can map any standard LDAP attribute to a well-known Vendor-Specific Attribute (VSA), and you can map one or more LDAP attribute(s) to one or more Cisco LDAP attributes. It applies to any connection type, including the IPsec VPN client, AnyConnect SSL VPN client, or clientless SSL VPN.
To enforce a simple banner for a user who is configured on an AD LDAP server use the Office field in the General tab to enter the banner text. This field uses the attribute named physicalDeliveryOfficeName. On the ASA, create an attribute map that maps physicalDeliveryOfficeName to the Cisco attribute Banner1.
During authentication, the ASA retrieves the value of physicalDeliveryOfficeName from the server, maps the value to the Cisco attribute Banner1, and displays the banner to the user.
Procedure
Place LDAP Users in a Specific Group Policy
This example applies to any connection type, including the IPsec VPN client, AnyConnect SSL VPN client, or clientless SSL VPN. In this example, User1 is connecting through a clientless SSL VPN connection.
To place an LDAP user into a specific group policy use the Department field of the Organization tab to enter the name of the group policy. Then create an attribute map, and map Department to the Cisco attribute IETF-Radius-Class.
During authentication, the ASA retrieves the value of Department from the server, maps the value to the IETF-Radius-Class, and places User1 in the group policy.
Procedure
Enforce Static IP Address Assignment for AnyConnect Tunnels
This example applies to full-tunnel clients, such as the IPsec client and the SSL VPN clients.
To enforce static AnyConnect static IP assignments configure the AnyConnect client user Web1 to receive a static IP address, enter the address in the Assign Static IP Address field of the Dialin tab on the AD LDAP server (this field uses the msRADIUSFramedIPAddress attribute), and create an attribute map that maps this attribute to the Cisco attribute IETF-Radius-Framed-IP-Address.
During authentication, the ASA retrieves the value of msRADIUSFramedIPAddress from the server, maps the value to the Cisco attribute IETF-Radius-Framed-IP-Address, and provides the static address to User1.
Procedure
Enforce Dial-in Allow or Deny Access
This example creates an LDAP attribute map that specifies the tunneling protocols allowed by the user. You map the allow access and deny access settings on the Dialin tab to the Cisco attribute Tunneling-Protocol, which supports the following bitmap values:
| Value | Tunneling Protocol |
|---|---|
| 1 | PPTP |
| 2 | L2TP |
| 4 | IPsec (IKEv1) |
| 8 | L2TP/IPsec |
| 16 | Clientless SSL |
| 32 | SSL client—AnyConnect or SSL VPN client |
| 64 | IPsec (IKEv2) |
1 (1) IPsec and L2TP over IPsec are not supported simultaneously. Therefore, the values 4 and 8 are mutually exclusive.2 (2) See note 1.
Use this attribute to create an Allow Access (TRUE) or a Deny Access (FALSE) condition for the protocols, and enforce the method for which the user is allowed access.
See Tech Note ASA/PIX: Mapping VPN Clients to VPN Group Policies Through LDAP Configuration Example for another example of enforcing dial-in allow access or deny access.
Procedure
Enforce Logon Hours and Time-of-Day Rules
The following example shows how to configure and enforce the hours that a clientless SSL user (such as a business partner) is allowed to access the network.
On the AD server, use the Office field to enter the name of the partner, which uses the physicalDeliveryOfficeName attribute. Then we create an attribute map on the ASA to map that attribute to the Cisco attribute Access-Hours. During authentication, the ASA retrieves the value of physicalDeliveryOfficeName and maps it to Access-Hours.
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