Manual Chapter : Active Directory Authentication

Applies To:

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BIG-IP APM

12.1.6

Active Directory Authentication

About Active Directory authentication

You can authenticate using Active Directory authentication with Access Policy Manager^®. We support using Kerberos-based authentication through Active Directory.

About Active Directory password management

Access Policy Manager^® (APM^®) supports password management for Active Directory authentication.

How APM supports password reset

The process works in this sequence:

Access Policy Manager uses the client's user name and password to authenticate against the Active Directory server on behalf of the client.
If the user password on the Active Directory server has expired, Access Policy Manager returns a new logon screen back to the user, requesting that the user change the password.
After the user submits the new password, Access Policy Manager attempts to change the password on the Active Directory server. If this is successful, the user's authentication is validated.

If the password change fails, it is likely that the Active Directory server rejected it because the password did not meet the minimum requirements such as password length.

Number of attempts APM provides for password reset

In the AD Auth action, APM provides a Max Password Reset Attempts Allowed property.

Change password option

In the Logon page action, APM provides a Checkbox property in the visual policy editor. You can add the option on the APM logon screen to change the log on password.

About AAA high availability

Using AAA high availability with Access Policy Manager^® (APM^®), you can configure multiple authentication servers to process requests, so that if one authentication server goes down or loses connectivity, the others can resume authentication requests, and new sessions can be established, as usual.

Note: Although new authentications fail if the BIG-IP^® system loses connectivity to the server, existing sessions are unaffected provided that they do not attempt to re-authenticate.

APM supports the following AAA servers for high availability: RADIUS, Active Directory, LDAP, CRLDP, and TACACS+. APM supports high availability by providing the option to create a pool of server connections when you configure the supported type of AAA server.

Note: If you use AAA with pools, such as RADIUS pools or Active Directory pools, APM assigns each pool member with a different number for the pool member's priority group value. Since APM does not support AAA load balancing, APM must define each pool member with a different priority group. The priority group number increases automatically with each created pool member.

About how APM handles binary values in Active Directory attributes

For Active Directory, Access Policy Manager^® (APM^®) converts an attribute value to hex only if the value contains unprintable characters. If the session variable contains several values, and one or more of those values is unprintable, then APM converts only those particular values to hex.

An attribute with a single unprintable value

7ecc84a2.session.ad.last.attr.objectSid 58 /
 0x01050000000000051500000013fe8e97c03cd5b5ad04e2e255040000

Attributes with multiple values, both printable and unprintable (binary)

7ecc84a2.session.ad.last.attr.memberOf 460 | 
CN=printable group,OU=groups,OU=someco,DC=sherwood,DC=labt,DC=fp,DC=somelabnet,DC=com | 
0x434e3d756e7072696e7461626c6520c2bdc2a12067726f75702c4f553d67726f7570732c4f553d66352 | /
c44433d73686572776f6f642c44433d6c6162742c44433d66702c44433d66356e65742c44433d636f6d | /
CN=Domain Users,CN=Users,DC=smith,DC=labt,DC=fp,DC=somlabnet,DC=com | /
CN=CERTSVC_DCOM_ACCESS,CN=Users,DC=smith,DC=labt,DC=fp,DC=somelabnet,DC=com | /
CN=Users,CN=Builtin,DC=smith,DC=labt,DC=fp,DC=somelabnet,DC=com |

Task summary for Active Directory authentication

This task list includes all steps required to set up this configuration. If you are adding Active Directory authentication to an existing access policy, you do not need to create another access profile, and the access policy might already include a logon page.

Task list

Configuring an Active Directory AAA server

You configure an Active Directory AAA server in Access Policy Manager (APM) to specify domain controllers for APM to use for authenticating users.

On the Main tab, click Access > Authentication > Active Directory.
The Active Directory Servers list screen opens.
Click Create.
The New Server properties screen opens.
In the Name field, type a unique name for the authentication server.
In the Domain Name field, type the name of the Windows domain.
For the Server Connection setting, select one of these options:
Note: When configuring an Active Directory AAA server that is located in a nondefault route domain, you must select Use Pool and specify the pool containing the Active Directory server.
- Select Use Pool to set up high availability for the AAA server.
  Note: The Timeout value does not apply if you select Use Pool.
- Select Direct to set up the AAA server for standalone functionality.
If you selected Direct, type a name in the Domain Controller field.
If you selected Use Pool, configure the pool:
1. Type a name in the Domain Controller Pool Name field.
2. Specify the Domain Controllers in the pool by typing the IP address and host name for each, and clicking the Add button.
3. To monitor the health of the AAA server, you have the option of selecting a health monitor: only the gateway_icmp monitor is appropriate in this case; you can select it from the Server Pool Monitor list.
In the Admin Name field, type a case-sensitive name for an administrator who has Active Directory administrative permissions.
An administrator name and password are required for an AD Query access policy item to succeed when it includes particular options. Credentials are required when a query includes an option to fetch a primary group (or nested groups), prompt a user to change a password, or perform a complexity check for a password reset.
In the Admin Password field, type the administrator password associated with the Domain Name.
In the Verify Admin Password field, retype the administrator password associated with the Domain Name setting.
In the Group Cache Lifetime field, type the number of days.
The default lifetime is 30 days.
In the Password Security Object Cache Lifetime field, type the number of days.
The default lifetime is 30 days.
To clear cache, click the Clear Cache button. It is useful in cases where stale tickets exist on the system.
From the Kerberos Preauthentication Encryption Type list, select an encryption type.
The default is None. If you specify an encryption type, the BIG-IP system includes Kerberos pre-authentication data within the first authentication service request (AS-REQ) packet.
Specify whether to enable Kerberos KDC Validation. The Kerberos Key Distribution Center (KDC) is a network service that supplies session tickets and temporary session keys to users and computers within an Active Directory domain. The KDC runs on each domain controller and is responsible for authenticating users. The KDC validation allows you to prevent a KDC spoofing attack.
You configure a KDC validation by importing a keytab file that you exported from the Kerberos KDC. When you enable the KDC validation, after obtaining the ticket-granting ticket (TGT) and validating the user, the BIG-IP system requests a service ticket on behalf of the user. It validates the returned service ticket against the secret key for the KDC, which is stored in a keytab file. When the validation with the keytab file fails, the KDC server is considered untrusted, and the user is not authenticated.
In the Service Name field, specify the Kerberos service name. This Service Name field displays after you enable KDC Validation.
Note: The service name should be given as service-class/service-hostname. For example, HTTP/app1, HOST/hostbigip. The BIG-IP system appends the domain name based on the user’s domain in the authentication request.
In the Keytab File area, locate and upload the keytab file containing Kerberos encrypted keys. It contains the service keys that the server uses to authenticate the client. This option displays after you enable KDC Validation.
To use a stored file, click Use Stored File. To upload and use a new file, click Upload New File. Click Choose File to browse and select the keytab file.
In the Timeout field, accept the default value or type a number of seconds.
Note: The Timeout value does not apply if you selected Use Pool.

The timeout specifies the number of seconds to reach the AAA Active Directory server initially. After the connection is made, the timeout for subsequent operations against the AAA Active Directory server is 180 seconds and is not configurable.
Click Finished.
The new server displays on the list.

The new Active Directory server is added to the Active Directory Servers list.

Create a new keytab file with the ktpass command

To create a new keytab file for host SPN on the Windows DC, perform the following procedure.

Log in to the Windows DC as an administrator.
Open Active Directory Users and Computers and create a new user account for each HTTP service account.
Note: For security purposes, F5 recommends selecting the This account supports Kerberos AES 256 bit encryption check box on the Account tab in the user Properties after the account is created.

Open a command prompt and create a new keytab file using the following syntax:

ktpass -princ <userPrincipalName> -mapuser <service account distinguishedName> crypto <encryption type> -ptype KRB5_NT_PRINCIPAL -pass <password> -out <keytab filename>

For example:

ktpass -princ HTTP/app1.example.com@EXAMPLE.COM -mapuser http_app1 crypto AES256-SHA1 -ptype KRB5_NT_PRINCIPAL -pass pass1234 -out app1example.keytab

Repeat steps 2 and 3 to generate a keytab file for each child domain if the given domain has child domains.

Merge all individual keytab files before uploading to the BIG-IP system.

Merge the keytab files with the ktutil utility

You can use the ktutil utility, available on the BIG-IP APM, to merge multiple keytab files into a single keytab file with individual entries for each service.

Using a utility like SCP or WinSCP, upload all your keytab files you created in the Creating a new keytab file with the ktpass command procedure to the BIG-IP APM system for merging. For example, you can upload them to the /var/tmp directory.
Log in to the BIG-IP command line.
Start the ktutil utility by entering the following command:
```
ktutil
```
To read each keytab file you uploaded in step 1, use the following command syntax in ktutil:
```
read_kt <keytab filename>
```
For example, if you uploaded your keytab files to the /var/tmp directories, enter the following commands:
```
read_kt /var/tmp/app1example.keytab
```
```
read_kt /var/tmp/app2example.keytab
```
```
read_kt /var/tmp/app3example.keytab
```
To merge and write the multiple keytab files, use the following command syntax in ktutil:
```
write_kt <merged keytab filename>
```
For example, enter the following command to write and save the merged keytab file:
```
write_kt /var/tmp/appservice.keytab
```
To quit the ktutil utility, enter the following command:
```
quit
```

Creating an access profile

You create an access profile to provide the access policy configuration for a virtual server that establishes a secured session.

On the Main tab, click Access Policy > Access Profiles .
The Access Profiles List screen opens.
Click Create.
The New Profile screen opens.
In the Name field, type a name for the access profile.
Note: An access profile name must be unique among all access profile and any per-request policy names.
From the Profile Type list, select one these options:
- LTM-APM: Select for a web access management configuration.
- SSL-VPN: Select to configure network access, portal access, or application access. (Most access policy items are available for this type.)
- ALL: Select to support LTM-APM and SSL-VPN access types.
- SSO: Select to configure matching virtual servers for Single Sign-On (SSO).
  Note: No access policy is associated with this type of access profile
- RDG-RAP: Select to validate connections to hosts behind APM when APM acts as a gateway for RDP clients.
- SWG - Explicit: Select to configure access using Secure Web Gateway explicit forward proxy.
- SWG - Transparent: Select to configure access using Secure Web Gateway transparent forward proxy.
- System Authentication: Select to configure administrator access to the BIG-IP^® system (when using APM as a pluggable authentication module).
- Identity Service: Used internally to provide identity service for a supported integration. Only APM creates this type of profile.
  Note: You can edit Identity Service profile properties.
Note: Depending on licensing, you might not see all of these profile types.

Additional settings display.
In the Language Settings area, add and remove accepted languages, and set the default language.
A browser uses the highest priority accepted language. If no browser language matches the accepted languages list, the browser uses the default language.
Click Finished.

The access profile displays in the Access Profiles List. Default-log-setting is assigned to the access profile.

Verifying log settings for the access profile

Confirm that the correct log settings are selected for the access profile to ensure that events are logged as you intend.

Note: Log settings are configured in the Access Policy Event Logs area of the product. They enable and disable logging for access system and URL request filtering events. Log settings also specify log publishers that send log messages to specified destinations.

On the Main tab, click Access Policy > Access Profiles .
The Access Profiles List screen opens.
Click the name of the access profile that you want to edit.
The properties screen opens.
On the menu bar, click Logs.
The access profile log settings display.
Move log settings between the Available and Selected lists.
You can assign up to three log settings that enable access system logging to an access profile. You can assign additional log settings to an access profile provided that they enable logging for URl request logging only.
Note: Logging is disabled when the Selected list is empty.
Click Update.

An access profile is in effect when it is assigned to a virtual server.

Configuring Active Directory authentication

Before you configure an access policy to use Active Directory authentication, you must have at least one Active Directory AAA server configured.

You create an access policy like this one to obtain user credentials and use them to authenticate the user against an external Active Directory server before granting access.

On the Main tab, click Access Policy > Access Profiles .
The Access Profiles List screen opens.
In the Access Policy column, click the Edit link for the access profile you want to configure.
The visual policy editor opens the access policy in a separate screen.
Click the (+) icon anywhere in the access policy to add a new action item.
Note: Only an applicable subset of access policy items is available for selection in the visual policy editor for any access profile type.

A popup screen opens, listing predefined actions on tabs such as General Purpose, Authentication, and so on.
On the Logon tab, select Logon Page and click the Add Item button.
The Logon Page Agent properties screen opens.
Make any changes that you require to the logon page properties and click Save.
The properties screen closes and the visual policy editor displays.
Click the (+) icon anywhere in the access policy to add a new action item.
Note: Only an applicable subset of access policy items is available for selection in the visual policy editor for any access profile type.

A popup screen opens, listing predefined actions on tabs such as General Purpose, Authentication, and so on.
On the Authentication tab, select AD Auth and click Add Item.
A Properties popup screen opens.
From the Server list, select the AAA Active Directory server to use for authentication, and click Save.

You can also set these options.

Option	Description
Cross Domain Support	Specifies whether AD cross domain authentication support is enabled for AD Auth agent.
Complexity check for Password Reset	Specifies whether Access Policy Manager^® performs a password policy check. Note: Enabling this option increases overall authentication traffic significantly because Access Policy Manager must retrieve additional information. Because this option might require administrative privileges, if you enable it you should specify the administrator name and password on the AAA Active Directory server configuration page.
Show Extended Error	When enabled, displays the comprehensive error messages generated by the authentication server to show on the user's Logon page. This setting is intended for use in testing only in a production or debugging environment. If you enable this setting in a live environment, your system might be vulnerable to malicious attacks
Max Logon Attempts Allowed	Specifies the number of user authentication logon attempts to allow. Note: To use this access policy for Citrix Receiver client access, set the value to 1.
Max Password Reset Attempts Allowed	Specifies the number of times that Access Policy Manager^® allows the user to try to change password.

Click Apply Access Policy to save your configuration.

This adds a logon page and Active Directory authentication to the access policy.

To apply this access policy to network traffic, add the access profile to a virtual server.

Note: To ensure that logging is configured to meet your requirements, verify the log settings for the access profile.

Creating a virtual server

When creating a virtual server for an access policy, specify an IP address for a single host as the destination address.

On the Main tab, click Local Traffic > Virtual Servers .
The Virtual Server List screen opens.
Click the Create button.
The New Virtual Server screen opens.
In the Name field, type a unique name for the virtual server.
In the Destination Address field, type the IP address for a host virtual server.
This field accepts an address in CIDR format (IP address/prefix). However, when you type the complete IP address for a host, you do not need to type a prefix after the address.
In the Service Port field, type a port number or select a service name from the Service Port list.
From the HTTP Profile list, select http.
If you use server SSL for this connection, from the SSL Profile (Server) list, select a server SSL profile.
If you use client SSL for this profile, from the SSL Profile (Client) list, select a client SSL profile.
In the Access Policy area, from the Access Profile list, select the access profile that you configured earlier.
From the Connectivity Profile list, select a connectivity profile.
You can select the default connectivity profile, connectivity if you have not defined a specific profile for the traffic that is directed to this virtual server.
Click Finished.

You have configured a host virtual server and associated an access profile with it.

Testing AAA high availability for supported authentication servers

To effectively test that high availability works for your authentication servers, you should have two servers that are accessible, where you can remove one of them from the network.

Note: High availability is supported for these authentication server types only: RADIUS, Active Directory, LDAP, CRLDP, and TACACS+.

If you configured a supported authentication server type to use a pool of connection servers, you can test the configuration using these steps.

Begin a tcpdump on the Access Policy Manager^®, using a protocol analyzer, and scanning for packets destined for the specific port for your authentication server.
Log in to the virtual server with both servers active.
Using the tcpdump records, verify that the requests are being sent to the higher priority server.
Log out of the virtual server.
Disable the higher-priority server.
Log in to the virtual server again.
Verify that the request is being sent to the other server.
Log out again, re-enabling the server, and try one more time to verify that the new requests are being sent to the high priority server.

Example access policy using Active Directory authentication and query

This is an example of an access policy with all the associated elements that are needed to authenticate and authorize your users with Active Directory authentication and Active Directory query.

Example of an access policy for AD auth query

Example of an access policy for AD auth and query

Importing Active Directory user groups

Import user groups from an Active Directory server to make them available for assigning resources to an Active Directory group. When you configure the AD Group Resource Assign access policy item, you can type group names to exactly match those on the Active Directory server, or you can select them from the imported list of groups.

Select Access Policy > AAA Servers > Active Directory .
The Active Directory Servers screen displays.
Click the name of the server that you want to update.
The Properties screen displays.
From the menu bar, click Groups.
From the Groups area of the screen, click Update.
The screen displays the number of groups, the date last updated, and the list of groups.

Assigning resources to an AD group

You can select groups from a list that you upload from an Active Directory server; alternately, or in addition. you can type group names to exactly match Active Directory groups. If you plan to select groups and have not updated the list recently, update it from the Groups screen for the AAA Active Directory server before you start.

Use an AD Group Resource Assign action to assign resources to one or more groups that are configured on the Active Directory server. For every group to which a user belongs, the corresponding resources will be assigned to the session.

On an access policy branch, click the (+) icon to add an item to the access policy.
A popup screen displays actions on tabs, such as General Purpose and Authentication, and provides a search field.
On the Assignment tab, select the AD Group Resource Assign agent, and click Add Item.
The AD Group Resource Assign screen opens, displaying a blank entry in the Groups area.
To make a list of groups available, select a server from the Server list.
A brief pause occurs while the agent retrieves any groups that were previously uploaded from the Active Directory server to the BIG-IP^® system.
To add an entry, click Add entry.
An entry must include at least one group and the resources to be assigned to it. You can add multiple entries.

A numbered entry displays in the Groups area.
In the Groups area, click the edit link for the entry that you want to update.
A popup screen opens to the Groups tab.
If you need to add a group, in the New Group field, type the name of a group that exists on the server and click Add group manually.
When the access policy runs, this action queries the group names using the memberOf attribute in the directory.

The group displays in the list on the Groups tab.
Select at least one group.
Repeat these substeps for each type of resource that you require.
The screen displays one tab for each resource type.
1. Click a tab.
2. Select the resources that you want to assign to the selected groups.
Typical resource assignment rules apply. For example, you can assign multiple webtop links to a group, but you can assign only one webtop.
Click the Update button.
The LDAP Group Resource Assign screen opens, and displays the groups and resources in the entry in the Groups table.
Create any additional entries that you require.
Click Save.
The properties screen closes and the visual policy editor displays.

This configures an AD group resource assign action and adds it to the access policy.

Active Directory authentication session variables

When the AD Auth access policy item runs, it populates session variables which are then available for use in access policy rules. The tables list the session variables for the Active Directory access policy items and for a logon access policy item.

Session variables for Active Directory authentication

Session Variable	Description
session.ad.last.actualdomain	AD Auth agent sets this variable to the actual user domain used for successful Active Directory authentication, whether cross-domain support is enabled or disabled.
session.ad.last.authresult	Provides the result of the Active Directory authentication. The available values are: 0: Failed 1: Passed
session.ad.last.errmsg	Displays the error message for the last login. If session.ad.last.authresultis set to 0, then session.ad.last.errmsg might be useful for troubleshooting purposes.

Common session variables

Session Variable	Description
session.logon.last.username	Provides user credentials. The username string is stored after encrypting, using the system's client key.
session.logon.last.password	Provides user credentials. The password string is stored after encrypting, using the system's client key.

Active Directory cross-domain support rules

Rules	Explanation
Cross-domain support and split domain from username are both enabled.	If you enable cross domain support, and enable split domain username at the login page, and then the user enters his user name, such as user@domain.com, Access Policy Manager^® uses the user@domain.com as the user principal name to authenticate the user against USERNAME.COM domain.
Cross-domain support is enabled but split domain from username is disabled	Access Policy Manager handles the user's input as a simple user name and escape "@" and "\" chars. In other words, Access Policy Manager uses user\@userdomain.com@DEFAULTREALM.COM to authenticate the user, where DEFAULTREALM.COM is the domain name that was configured on the AAA AD Server configuration page.
If user does not specify a user's domain	Regardless of whether split domain from username option is enabled or disabled, Access Policy Manager uses user@defaultrealm.com to authenticate the user.

Active Directory authentication and query troubleshooting tips

You might run into problems with Active Directory authentication and query processes in some instances. Follow these tips to try to resolve any issues you might encounter.

Active Directory auth authentication and query troubleshooting

Possible error messages	Possible explanations and corrective actions
`Domain controller reply did not match expectations.(-1765328237)`	This error occurs when the principal/domain name does not match the domain controller server's database. For example, if the actual domain is SALES.MYCOMPANY.COM, and the administrator specifies STRESS as the domain, then the krb5.conf file displays the following: `default_realm = SALES SALES = { domain controller = (domain controller server) admin = (admin server)` So, when the administrator tries to authenticate with useraccount@SALES, the krb5 library notices that the principal name SALES differs from the actual one in the server database.

Possible error messages

Possible explanations and corrective actions

Domain controller reply did not match expectations.(-1765328237)

This error occurs when the principal/domain name does not match the domain controller server's database. For example, if the actual domain is SALES.MYCOMPANY.COM, and the administrator specifies STRESS as the domain, then the krb5.conf file displays the following: default_realm = SALES SALES = { domain controller = (domain controller server) admin = (admin server) So, when the administrator tries to authenticate with useraccount@SALES, the krb5 library notices that the principal name SALES differs from the actual one in the server database.

Additional troubleshooting tips for Active Directory authentication

You should	Steps to take
Check that your access policy is attempting to perform authentication	Refer to the message boxes in your access policy to display information on what the access policy is attempting to do. Refer to /var/log/apm to view authentication attempts by the access policy. Note: Make sure that your log level is set to the appropriate level. The default log level is notice.
Confirm network connectivity	Access the Access Policy Manager^® through the command line interface and check your connectivity by pinging the Active Directory server using the host entry in the AAA Server box. Confirm that the Active Directory port (88 or 389) is not blocked between the Access Policy Manager, and the Active Directory server.
Check the Active Directory server configuration	Confirm that the Active Directory server name can be resolved to the correct IP address, and that the reverse name resolution (IP address to name) is also possible. Confirm that the Active Directory server and the Access Policy Manager have the correct time setting configured. Note: Since Active Directory is sensitive to time settings, use NTP to set the correct time on the Access Policy Manager.
Capture a TCP dump	Take a TCP dump from the Access Policy Manager when authentication attempts are made. For example, `%tcpdump-i 1.1 -s /tmp/dump`. You must first determine what interface the self IP address is on. These TCP dumps indicate activities between the Access Policy Manager and the authentication server. Run the authentication test. After authentication fails, stop the TCP dump, and download the TCP dump to a client system, and use an analyzer to troubleshoot. Important: If you decide to escalate the issue to customer support, you must provide a capture of the TCP dump when you encounter authentication issues that you cannot otherwise resolve on your own.

Overview: Using Active Directory Trusted Domains

Active Directory Trusted Domains option in BIG-IP^® Access Policy Manager^® (APM^®) manages Active Directory AAA trusted domains. For enterprises that are service providers, their customers might have their own enterprise network infrastructure. Using APM, the service provider provides access to their customers' networks. To avoid network traffic collisions between two customer networks, the service provider separates each customer using route domains. A route domain is a configuration object that isolates network traffic for a particular application on the network. The service provider uses Active Directory to authenticate their customer users. However, each customer's Active Directory service can contain multiple trusted domains or forests. The service provider can use the Active Directory Trusted Domains option to authenticate users across all trusted domains or forests for a customer.

Configuring an Active Directory Trusted Domain

You must create at least one Active Directory AAA server before you can configure an Active Directory Trusted Domain.

Configure an Active Directory Trusted Domain in Access Policy Manager ^®(APM^®) to authenticate users in route domains with at least one trusted domain.

On the Main tab, click Access Policy > AAA Servers > Active Directory Trusted Domains .
The Active Directory Trusted Domains list screen opens.
Click Create.
The Create New Active Directory Trusted Domains screen opens.
In the Name field, type a name for the Active Directory Trusted Domain.
In the Description field, type a description for the Active Directory Trusted Domain.
For the XXX setting, in the Available list, select the Active Directory AAA server that you want to add to the Trusted Domain, and click << to move the Active Directory AAA server into the Selected list.
From the Root list, select a root domain.
You use the root domain for an initial authentication request, such as an entry point to an Active Directory forest.
Click OK.

You have now added an Active Directory Trusted Domain to the Active Directory Trusted Domain list.

You can now add the Active Directory Trusted Domain option to either the AD Auth agent or the AD Query agent in the visual policy editor.

Note: You can select a trusted domain only if you enable the Cross Domain support option.

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