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Manual Chapter: NTLM Authentication for Microsoft Exchange Clients
Manual Chapter
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Overview: Configuring APM for Exchange clients that use NTLM authentication

Access Policy Manager® (APM®) supports Microsoft Exchange clients that are configured to use NTLM, by checking NTLM outside of the APM session as needed. APM requires a machine account and an NTLM Auth configuration to perform these checks. APM requires an Exchange profile to support Microsoft Exchange clients, regardless of the authentication they are configured to use.

Task summary

About using NTLM authentication

Microsoft software systems use NTLM as an integrated single sign-on (SSO) mechanism. However, in an Active Directory-based SSO scheme, Kerberos replaces NTLM as the default authentication protocol. NTLM is still used when a domain controller is not available or is unreachable, such as when the client is not Kerberos-capable, the server is not joined to a domain, or the user authenticates remotely over the web.

About configuration requirements for NTLM authentication

In Access Policy Manager®, you need to configure these elements:

  • Machine account
  • NTLM authentication configuration
  • Kerberos SSO configuration
  • Exchange profile that specifies the NTLM authentication configuration and specifies Kerberos SSO configurations for the specific Microsoft Exchange services supported
  • Access profile that specifies the Exchange profile
  • Access policy
  • Pool of servers for the Exchange service to support Outlook Anywhere, supply a pool of Outlook Anywhere servers
  • Virtual server that specifies the access profile and the pool

You also need to configure a special account in Active Directory for Kerberos constrained delegation (KDC).

About reusing a machine account for different BIG-IP systems

You can use the same machine account for two BIG-IP® systems when they are in an active-standby configuration. Otherwise, F5® recommends that you create a new NTLM machine account using the Access Policy Manager® user interface on each BIG-IP system.

Creating a new NTLM machine account on each BIG-IP system is helpful, for example, when two systems independently update their configurations without propagating them, or when you replicate the configuration into different BIG-IP systems using any configuration replication method. If you export a configuration and import it on another system, the machine account is included; however, after the import completes, you still need a new machine account and an NTLM authentication configuration that uses the new machine account on the target system.

About Outlook Anywhere and NTLM authentication

Access Policy Manager® (APM®)supports Outlook Anywhere clients that are configured to use NTLM and HTTP Basic protocols independently. Typically, mobile devices use HTTP Basic authentication, while Outlook Anywhere clients can use both NTLM and HTTP Basic authentication. APM determines whether a client uses NTLM or HTTP Basic authentication and enforces the use of one or the other. After a client authenticates with NTLM or HTTP Basic, APM supports single sign-on with the back-end application or server using Kerberos constrained delegation (KCD).

Configuring a machine account

You configure a machine account so that Access Policy Manager® (APM®) can establish a secure channel to a domain controller.
  1. On the Main tab, click Access > Authentication > NTLM > Machine Account .
    A new Machine Account screen opens.
  2. In the Configuration area, in the Machine Account Name field, type a name.
  3. In the Domain FQDN field, type the fully qualified domain name (FQDN) for the domain that you want the machine account to join.
  4. Optional: In the Domain Controller FQDN field, type the FQDN for a domain controller.
  5. In the Admin User field, type the name of a user who has administrator privilege.
  6. In the Admin Password field, type the password for the admin user.
    APM uses these credentials to create the machine account on the domain controller. However, APM does not store the credentials and you do not need them to update an existing machine account configuration later.
  7. Click Join.
This creates a machine account and joins it to the specified domain. This also creates a non-editable NetBIOS Domain Name field that is automatically populated.
Note: If the NetBIOS Domain Name field on the machine account is empty, delete the configuration and recreate it. The field populates.

Creating an NTLM Auth configuration

Create an NTLM Auth configuration to specify the domain controllers that a machine account can use to log in.
  1. On the Main tab, click Access > Authentication > NTLM > NTLM Auth Configuration .
    A new NTLM Auth Configuration screen opens.
  2. In the Name field, type a name.
  3. From the Machine Account Name list, select the machine account configuration to which this NTLM Auth configuration applies.
    You can assign the same machine account to multiple NTLM authentication configurations.
  4. For each domain controller, type a fully qualified domain name (FQDN) and click Add.
    Note: You should add only domain controllers that belong to one domain.
    By specifying more than one domain controller, you enable high availability. If the first domain controller on the list is not available, Access Policy Manager® tries the next domain controller on the list, successively.
  5. Click Finished.
This specifies the domain controllers that a machine account can use to log in.

Setting up a delegation account to support Kerberos SSO

Before you can configure Kerberos SSO in Access Policy Manager®, you must create a delegation account in Active Directory.
Note: For every server realm, you must create a delegation account in that realm.
  1. Open the Active Directory Users and Computers administrative tool and create a new user account.
    The user account should be dedicated for delegation, and the Password never expires setting enabled.
  2. Set the service principal name (SPN) on the Windows server for the user account.
    For the support tools that you can use, and for the commands, such as setspn and ktpass, refer to Microsoft documentation.
    Note: If you use the ktpass command, it sets the SPN on the Windows server and creates a keytab file. APM Kerberos SSO does not need or use a keytab file.
  3. Verify the result of setting the SPN.
    This example is purely for illustration. Refer to Microsoft documentation for up-to-date commands and correct usage.

    C:\Users\Administrator> setspn -L apm4

    Registered ServicePrincipalNames for CN=apm4,OU=users,DC=yosemite,DC=lab,DC=dnet,DC=com: HTTP/apm4.yosemite.lab.dnet.com where apm4 is the name of the user account that you created.
  4. Return to the Active Directory Users and Computers screen to open your account again.
    A Delegation tab should appear.
  5. Click the Delegation tab.
  6. Select Trust this user for delegation to specified services only.
  7. Select Use any authentication protocol, and add all your services to the list under Services to which this account can present delegated credentials.
    Every service should have Service Type HTTP (or http) and host name of the pool member or web application resource host that you will use in your configuration.
  8. Click OK.
    This creates the new delegation account.

Creating a Kerberos SSO configuration in APM

Before you start, you must have configured a delegation account in Active Directory.
To support Kerberos single sign-on authentication from Access Policy Manager® (APM®), you must create a Kerberos SSO configuration.
Note: To complete this task, you need to know the service principal name (SPN) for the delegation account.
  1. On the Main tab, click Access > Single Sign-On > Kerberos .
    The Kerberos screen opens.
  2. Click Create.
    The New SSO Configuration screen opens.
  3. In the Name field, type a name for the SSO configuration.
  4. From the Log Setting list, select one of the following options:
    • Select an existing APM log setting.
    • Click Create to create a new log setting.
  5. In the Credentials Source area, specify the credentials that you want cached for Single Sign-On.
  6. In the Kerberos Realm field, type the name of the realm in uppercase.
    For example, MY.HOST.LAB.MYNET.COM
  7. In the Account Name field, type the name of the Active Directory account configured for delegation.
    Type the account name in SPN format.
    In this example HTTP/apm4.my.host.lab.mynet.com@MY.HOST.LAB.MYNET.COM, apm4 is the delegation account, apm4.my.host.lab.mynet.com is its fully qualified domain name, and MY.HOST.LAB.MYNET.COM is the realm.
  8. In the Account Password and Confirm Account Password fields, type the delegation account password.
  9. Click Finished.

Configuring an Exchange profile

If any of the Microsoft Exchange clients you support authenticate using NTLM, you must first create these objects:
  • A machine account

  • An NTLM Auth configuration

  • At least one Kerberos SSO configuration

Note: For Access Policy Manager® (APM®) to support Kerberos SSO, a delegation account is required on Active Directory.
You create an Exchange profile to specify how to handle traffic from Microsoft Exchange clients.
  1. On the Main tab, click Access > Connectivity / VPN > Microsoft Exchange .
    A list of Exchange profiles displays.
  2. Click Create.
    A Create New Exchange Profile popup screen displays general settings.
  3. In the Exchange Name field, type a name for the Exchange profile.
  4. From the Parent Profile list, select a profile.
    The Exchange profile inherits settings from the parent profile that you select.
    Note: APM supplies a default Exchange profile named exchange.
  5. Repeat these steps for one or more Microsoft Exchange services:
    1. From Service Settings on the left, select an Exchange service.
      Settings for the service are displayed in the right pane.
    2. In the URL field, retain any default settings that are displayed or type a path to use to match the Exchange client.
      Default settings for this field are supplied in the default exchange profile.
    3. From the Front End Authentication list, select the type of authentication to use: Basic, Basic-NTLM, or NTLM.
      Only the applicable authentication types for the particular the Exchange service are included on the list.
      Note: If you select NTLM or Basic-NTLM, you must also select a configuration from NTLM Configuration list on the General Settings screen.
    4. From the SSO Configuration list, select an SSO configuration, if needed, for use after initial login.
      For Basic-NTLMand NTLM authentication types, only Kerberos SSO is supported.
    You configured settings for one or more Microsoft Exchange services.
  6. Click OK.
    The screen closes.
The Exchange profile is displayed on the list.
Apply this Exchange profile by adding it to an access profile.

Creating an access profile for Exchange clients

You create an access profile to provide the access policy configuration for a virtual server that establishes a secured session. You add an Exchange profile to the access profile to specify how to handle traffic from Microsoft Exchange clients.
  1. On the Main tab, click Access > Profiles / Policies .
    The Access Profiles (Per-Session Policies) screen opens.
  2. Click Create.
    The New Profile screen opens.
  3. 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.
  4. Optional: In the Configurations area from the Exchange list, select an Exchange profile.
    Exchange profiles specify any SSO configurations for Microsoft Exchange services, such as Autodiscover, Outlook Anywhere, and so on. The configuration in the Exchange profile is used for Microsoft Exchange clients regardless of any SSO configuration you select from the SSO Configuration list in this access profile.
  5. 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.
  6. Click Finished.
  7. To change from using the default-log-settings that APM automatically adds to the access profile, you can do this.:
    Logging occurs for a session only when a log setting is specified for the access profile.
    1. Click the name of the access profile.
      The Properties screen opens.
    2. On the menu bar, click Logs.
      The General Properties screen opens.
    3. In the Log Settings area, move log settings from the Available list to the Selected list.
    4. Click Update.
    You can configure log settings in the Access > Overview > Event Log > Settings area of the product.
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 > Overview > Event Log > Settings 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.
  1. On the Main tab, click Access > Profiles / Policies .
    The Access Profiles (Per-Session Policies) screen opens.
  2. Click the name of the access profile that you want to edit.
    The properties screen opens.
  3. On the menu bar, click Logs.
    The access profile log settings display.
  4. 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.
  5. Click Update.
An access profile is in effect when it is assigned to a virtual server.

Configuring an access policy for NTLM authentication

You configure an access policy for NTLM authentication to support Outlook Anywhere clients that log in using NTLM to also gain SSO access to a backend server that is protected by Kerberos KCD.
Note: NTLM authentication occurs before an access policy runs. If NTLM authentication fails, an error displays and the access policy does not run.
  1. On the Main tab, click Access > Profiles / Policies .
    The Access Profiles (Per-Session Policies) screen opens.
  2. In the Per-Session 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.
  3. Click the (+) icon anywhere in the access policy to add a new 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.
  4. On the Endpoint Security (Server-Side) tab, select Client for MS Exchange and click Add Item to add the action to the access policy.
    A Client for MS Exchange action determines whether the client is using Microsoft Exchange or ActiveSync protocols. You must add this action before an NTLM Auth Result action.
    The Client for MS Exchange action popup screen opens.
  5. Click Save.
    The properties screen closes and the policy displays.
  6. Check whether the Outlook Anywhere client authenticated using NTLM.
    1. Click the [+] sign on the successful branch after the Client for MS Exchange action.
      An Add Item window opens.
    2. On the Authentication tab, select NTLM Auth Result.
    3. Click Add Item.
      A popup screen opens.
    4. Click Save.
      The properties screen closes and the policy displays.
  7. Configure a branch in the access policy for an Outlook Anywhere client that has authenticated using NTLM.
    1. Click the [+] sign on the successful branch after the NTLM Auth Result action.
      An Add Item window opens.
    2. On the Assignment tab, select SSO Credential Mapping and click Add Item.
      The SSO Credential Mapping screen opens.
    3. Click Save.
      The properties screen closes and the policy displays.
    4. On the fallback branch after the SSO Credential Mapping action, click the Deny ending.
      A popup screen opens.
    5. Select Allow and click Save.
      You have completed a branch in the access policy for an Outlook Anywhere client that, having previously authenticated with NTLM, has SSO (Kerberos KCD) access on the back end.
  8. Configure a branch in the access policy for an Outlook Anywhere client that uses HTTP Basic authentication.
    1. Click the [+] sign on the fallback branch after the NTLM Auth Result action.
      An Add Item window opens.
    2. On the Logon tab, select Logon Page and click the Add Item button.
      The Logon Page Agent properties screen opens.
    3. Make any changes that you require to logon page properties and click Save.
      The properties screen closes and the policy displays.
    4. On the Successful branch after the Logon Page action, add an authentication action.
    5. On the Successful branch after the authentication action, add an SSO Credential Mapping action.
    6. On the fallback branch after SSO Credential Mapping, change the ending from Deny to Allow.
    You have completed a branch in the access policy to authenticate an Outlook Anywhere client that uses HTTP Basic authentication and provides SSO (Kerberos KCD) access for the client on the back end.
  9. Optional: On the fallback branch after the MS Exchange Client action, configure a branch for a client that is not an Outlook Anywhere client.
    You could add Logon Page, authentication, and SSO Credential Mapping actions or other actions here.
  10. Click the Apply Access Policy link to apply and activate the changes to the policy.
You have created an access policy that checks whether the client is an Outlook Anywhere client and whether such a client has authenticated using NTLM. If so, the policy provides SSO (Kerberos KCD) access on the backend server.
When NTLM authentication has passed, perform SSO Credential Mapping;                     otherwise, present a Logon Page and perform authentication.

Example access policy with actions based on whether NTLM authentication occurred

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.

Adding the access profile to the virtual server

  1. On the Main tab, click Local Traffic > Virtual Servers .
    The Virtual Server List screen opens.
  2. Click the name of the virtual server you want to modify.
  3. In the Access Policy area, from the Access Profile list, select the access profile that you configured earlier.
  4. Click Update to save the changes.
Your access policy is now associated with the virtual server.

Maintaining a machine account

In some networks, administrators run scripts to find and delete outdated machine accounts on the domain controllers. To keep the machine account up-to-date, you can renew the password periodically.
  1. On the Main tab, click Access > Authentication > NTLM > Machine Account .
    The Machine Account screen opens.
  2. Click the name of a machine account.
    The properties screen opens and displays the date and time of the last update to the machine account password.
  3. Click the Renew Machine Password button.
    The screen refreshes and displays the updated date and time.
This changes the machine account last modified time.

Updating the log level for NTLM for Exchange clients

Before you follow these steps, you must have an access profile that you configured to use for NTLM authentication of Microsoft Exchange clients. You must know the name of the log setting that is assigned to that access profile. (The default-log-setting is assigned by default, but your access profile configuration might be different.)
You can change the level of logging for NTLM authentication for Microsoft Exchange clients.
Note: Logging at the default level, Notice, is recommended.
  1. On the Main tab, click Access > Overview > Event Logs > Settings .
    A log settings table screen opens.
  2. Select the check box for the log setting that you want to update and click Edit.
    A popup screen opens.
  3. To configure settings for access system logging, select Access System Logs from the left pane.
    Access System Logs settings display in the right panel.
  4. For the ECA setting, select a log level.
    Note: Setting the log level to Debug can adversely impact system performance.
  5. Click OK.
    The popup screen closes.
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