Manual Chapter :
NTLM Authentication for Microsoft Exchange Clients
Applies To:
Show VersionsBIG-IP APM
- 16.0.1, 16.0.0
NTLM Authentication for Microsoft Exchange Clients
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.
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).
Configure a
machine account
You configure a machine account so that Access
Policy Manager (APM) can establish a secure channel to a domain controller.
- On the Main tab, click.A new Machine Account screen opens.
- In the Configuration area, in theMachine Account Namefield, type a name.
- In theDomain FQDNfield, type the fully qualified domain name (FQDN) for the domain that you want the machine account to join.
- In theDomain Controller FQDNfield, type the FQDN for a domain controller.
- In theAdmin Userfield, type the name of a user who has administrator privilege.
- In theAdmin Passwordfield, 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.
- ClickJoin.
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. If the
NetBIOS Domain Name
field on the machine account is empty, delete the configuration and recreate it. The
field populates.Create an NTLM Auth configuration
Create an NTLM Auth configuration to specify the domain controllers that a machine
account can use to log in.
- On the Main tab, click.A new NTLM Auth Configuration screen opens.
- In theNamefield, type a name.
- From theMachine Account Namelist, select the machine account configuration to which this NTLM Auth configuration applies.You can assign the same machine account to multiple NTLM authentication configurations.
- For each domain controller, type a fully qualified domain name (FQDN) and clickAdd.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.You should add only domain controllers that belong to one domain.
- ClickFinished.
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.
For every server realm, you must create a delegation account in that realm.
- Open the Active Directory Users and Computers administrative tool and create a new user account.The user account should be dedicated for delegation, and thePassword never expiressetting enabled.
- 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 assetspnandktpass, refer to Microsoft documentation.If you use thektpasscommand, it sets the SPN on the Windows server and creates a keytab file. APM Kerberos SSO does not need or use a keytab file.
- 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-Lapm4Registered ServicePrincipalNames for CN=apm4,OU=users,DC=yosemite,DC=lab,DC=dnet,DC=com: HTTP/apm4.yosemite.lab.dnet.comwhereapm4is the name of the user account that you created.
- Return to the Active Directory Users and Computers screen to open your account again.A Delegation tab should appear.
- Click the Delegation tab.
- SelectTrust this user for delegation to specified services only.
- SelectUse any authentication protocol, and add all your services to the list underServices 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.
- ClickOK.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.
To complete this task,
you need to know the service principal name (SPN) for the delegation
account.
- On the Main tab, click.The Kerberos screen opens.
- ClickCreate.The New SSO Configuration screen opens.
- In theNamefield, type a name for the SSO configuration.The maximum length of a single sign-on configuration is 225 characters, including the partition name.
- From theLog Settinglist, select one of the following options:
- Select an existing APM log setting.
- ClickCreateto create a new log setting.
- In the Credentials Source area, specify the credentials that you want cached for Single Sign-On.
- In theKerberos Realmfield, type the name of the realm in uppercase.For example,MY.HOST.LAB.MYNET.COM
- In theAccount Namefield, type the name of the Active Directory account configured for delegation.Type the account name in SPN format.In this exampleHTTP/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.
- In theAccount PasswordandConfirm Account Passwordfields, type the delegation account password.
- ClickFinished.
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
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.
- On the Main tab, click.A list of Exchange profiles displays.
- ClickCreate.A Create New Exchange Profile popup screen displays general settings.
- In theExchange Namefield, type a name for the Exchange profile.
- From theParent Profilelist, select a profile.The Exchange profile inherits settings from the parent profile that you select.APM supplies a default Exchange profile named exchange.
- Repeat these steps for one or more Microsoft Exchange services:
- From Service Settings on the left, select an Exchange service.Settings for the service are displayed in the right pane.
- In theURLfield, 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.
- From theFront End Authenticationlist, select the type of authentication to use:Basic,Basic-NTLM, orNTLM.Only the applicable authentication types for the particular the Exchange service are included on the list.If you selectNTLMorBasic-NTLM, you must also select a configuration fromNTLM Configurationlist on the General Settings screen.
- From theSSO Configurationlist, select an SSO configuration, if needed, for use after initial login.ForBasic-NTLMandNTLMauthentication types, only Kerberos SSO is supported.
You configured settings for one or more Microsoft Exchange services. - ClickOK.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.
- On the Main tab, click.The Access Profiles (Per-Session Policies) screen opens.
- ClickCreate.The New Profile screen opens.
- In theNamefield, type a unique name for the access profile.
- In the Configurations area from theExchangelist, 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 theSSO Configurationlist in this access profile.
- In the Language Settings area, add and remove accepted languages, and set the default language.If no browser language matches one in the accepted languages list, the browser uses the default language.
- ClickFinished.
- 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.
- Click the name of the access profile.The Properties screen opens.
- On the menu bar, clickLogs.The General Properties screen opens.
- In the Log Settings area, move log settings from theAvailablelist to theSelectedlist.
- ClickUpdate.
You can configure log settings in thearea of the product.
The access
profile displays in the Access Profiles List. Default-log-setting is assigned to the
access profile.
Verify 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.
Log settings are configured in the
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.The Access Profiles (Per-Session Policies) screen opens.
- Click the name of the access profile that you want to edit.The properties screen opens.
- On the menu bar, clickLogs.The access profile log settings display.
- Move log settings between theAvailableandSelectedlists.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.Logging is disabled when theSelectedlist is empty.
- ClickUpdate.
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.
NTLM authentication occurs before an access policy runs. If NTLM
authentication fails, an error displays and the access policy does
not run.
- On the Main tab, click.The Access Profiles (Per-Session Policies) screen opens.
- In the Per-Session Policy column, click theEditlink 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 item.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 Endpoint Security (Server-Side) tab, selectClient for MS Exchangeand clickAdd Itemto 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.
- ClickSave.The properties screen closes and the policy displays.
- Check whether the Outlook Anywhere client authenticated using NTLM.
- Click the[+]sign on the successful branch after the Client for MS Exchange action.An Add Item window opens.
- On theAuthenticationtab, selectNTLM Auth Result.
- ClickAdd Item.A popup screen opens.
- ClickSave.The properties screen closes and the policy displays.
- Configure a branch in the access policy for an Outlook Anywhere client that has authenticated using NTLM.
- Click the[+]sign on the successful branch after the NTLM Auth Result action.An Add Item window opens.
- On the Assignment tab, selectSSO Credential Mappingand clickAdd Item.The SSO Credential Mapping screen opens.
- ClickSave.The properties screen closes and the policy displays.
- On the fallback branch after the SSO Credential Mapping action, click theDenyending.A popup screen opens.
- SelectAllowand clickSave.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.
- Configure a branch in the access policy for an Outlook Anywhere client that uses HTTP Basic authentication.
- Click the[+]sign on the fallback branch after the NTLM Auth Result action.An Add Item window opens.
- On the Logon tab, selectLogon Pageand click theAdd Itembutton.The Logon Page Agent properties screen opens.
- Make any changes that you require to logon page properties and clickSave.The properties screen closes and the policy displays.
- On the Successful branch after the Logon Page action, add an authentication action.
- On the Successful branch after the authentication action, add an SSO Credential Mapping action.
- 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. - 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.
- Click theApply Access Policylink 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.
To
apply this access policy to network traffic, add the access profile to a virtual
server.
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
You associate the access profile with the virtual
server so that the system can apply the profile to incoming traffic.
- On the Main tab, click.The Virtual Server List screen opens.
- Click the name of the virtual server you want to modify.
- In the Access Policy area, from theAccess Profilelist, select the access profile that you configured earlier.
- ClickUpdateto save the changes.
Maintain 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.
- On the Main tab, click.The Machine Account screen opens.
- 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.
- Click theRenew Machine Passwordbutton.The screen refreshes and displays the updated date and 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.
Logging at the default level,
Notice
,
is recommended. - On the Main tab, click.A log settings table screen opens.
- Select the check box for the log setting that you want to update and clickEdit.A popup screen opens.
- To configure settings for access system logging, selectAccess System Logsfrom the left pane.Access System Logs settings display in the right panel.
- For theECAsetting, select a log level.Setting the log level toDebugcan adversely impact system performance.
- ClickOK.The popup screen closes.