NetScaler Gateway 12 – LDAP Authentication

Last Modified: Oct 2, 2017 @ 7:03 am

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LDAP Load Balancing

Before you create an LDAP authentication policy, load balance the Domain Controllers. If you don’t load balance your Domain Controllers, then when users enter an incorrect password, the user account will be prematurely locked out.

If you have multiple domains, create different Load Balancing Virtual Servers for each domain. These multiple Load Balancing Virtual Servers can share the same VIP if their port numbers are different. Or you can use a different VIP for each domain.

Verify LDAPS

Use the tool ldp.exe to verify that the Domain Controllers have valid certificates installed, and the LDAP service account is able to bind to the LDAP tree.

  1. ldp.exe is included with the Remote Server Administration Tools (AD DS Snap-Ins and Command-Line Tools). On Windows Servers, install it from Server Manager > Add Roles and Features > Features > Remote Server Administration Tools > Role Administration Tools > AD DS and AD LDS Tools > AD DS Tools.
  2. Run ldp.exe.
  3. Open the Connection menu, and click Connect.
  4. In the Connect box:
    1. Enter the FQDN of a Domain Controller.
    2. Check the box next to SSL.
    3. Change the port to 636.
  5. Click OK.
  6. If it connected successfully, you can then attempt a bind. If the connection was unsuccessful, then there’s probably an issue with the certificate installed on the Domain Controller.
  7. Open the Connection menu, and click Bind.
  8. In the Bind box:
    1. Change the Bind type to Simple bind.
    2. Enter the service account credentials. You can enter DOMAIN\Username, or you can enter Username@Domain.com.
  9. Click OK.
  10. Look in the right pane to verify a successful bind. If not, fix the credentials and try again.
  11. Once you have successfully binded, you can view the directory tree by opening the View menu, and click Tree.
  12. Click the drop-down to view the directory partitions.
  13. Repeat these steps to verify each Domain Controller, and any load balanced LDAPS.

LDAP Authentication Server

You can configure StoreFrontAuth as an alternative to LDAP. StoreFrontAuth delegates authentication to StoreFront servers, instead of performing authentication on NetScaler.

To create the LDAP Authentication Server, do the following:

  1. On the left, expand Authentication, and click Dashboard.
  2. On the right, click Add.
  3. Change the Choose Server Type drop-down to LDAP.
  4. In the Name field, enter LDAP-Corp or similar as the name. If you have multiple domains, you’ll need a separate LDAP Server per domain. so make sure you include the domain name.
  5. Change the selection to Server IP. Enter the VIP of the load balancing vServer for LDAP.
  6. Change the Security Type drop-down to SSL.
  7. Enter 636 as the Port. Scroll down.

  8. In the Connection Settings section, in the Base DN field, enter your Active Directory DNS domain name in LDAP format.
  9. In the Administrator Bind DN field, enter the credentials of the LDAP bind account in userPrincipalName format. Domain\Username also works.
  10. Enter the Administrator Password.
  11. Click Test Connection. NetScaler will attempt to login to the LDAP IP. Scroll down.
  12. In the Other Settings section, use the drop-down next to Server Logon Name Attribute, Group Attribute, and Sub Attribute Name to select the default fields for Active Directory.
  13. On the right side of the Other Settings section, check the box next to Allow Password Change.

  14. If you want to restrict NetScaler Gateway access to only members of a specific AD group, in the Search Filter field, enter memberOf=<GroupDN>. See the example below:
    memberOf=CN=CitrixRemote,OU=Citrix,DC=corp,DC=local
    You can add :1.2.840.113556.1.4.1941: to the Search Filter so it searches through nested groups. Without this, users will need to be direct members of the filtered group.
    memberOf:1.2.840.113556.1.4.1941:=CN=CitrixRemote,OU=Citrix,DC=corp,DC=local

    1. An easy way to get the full distinguished name of the group is through Active Directory Users and Computers.
    2. Open the View menu, and enable Advanced Features. The Attribute Editor is only present if this feature is enabled.
    3. Browse to the group object, right-click it, and click Properties. Note: you cannot use Find. Instead, you must navigate through the tree to find the object.
    4. Switch to the Extensions page. On the right, switch to the Attribute Editor tab. This tab is only visible if Advanced Features are enabled, and you didn’t use the Find feature.
    5. Scroll down to distinguishedName, double-click it, and then copy it to the clipboard.
    6. Back on the NetScaler, in the Search Filter field, type in memberOf= and then paste the Distinguished Name right after the equals sign. Don’t worry about spaces.
  15. For another LDAP Search Filter expression, see¬†CTX226808¬†Expression to exclude multiple domains by using search filter in LDAP on NetScaler¬† ūüí°
    !(|(userprincipalname=*@aa.lab.com)(userprincipalname=*@ns.lab.com)
  16. Scroll down, and click More.
  17. For Nested Group Extraction, if desired, change the selection to Enabled. Configuring Nested Group Extraction allows the Nested Groups to be used for AAA Groups.
    1. Set Group Name Identifier to samAccountName.
    2. Set Group Search Attribute to memberOf. Select << New >> first.
    3. Set Group Search Sub-Attribute to CN. Select << New >> first.
    4. For the Group Search Filter field, see CTX123795 Example of LDAP Nested Group Search Filter Syntax.
  18. Scroll down, and click Create.

    add authentication ldapAction Corp-Gateway -serverIP 10.2.2.11 -serverPort 636 -ldapBase "dc=corp,dc=local" -ldapBindDn "corp\\ctxsvc" -ldapBindDnPassword Passw0rd -ldapLoginName samaccountname -searchFilter "memberOf:1.2.840.113556.1.4.1941:=CN=Citrix Remote,CN=Users,DC=corp,DC=local" -groupAttrName memberOf -subAttributeName CN -secType SSL -passwdChange ENABLED
  19. The status of the LDAP Server should be Up.

LDAP Policy Expression

The Authentication Dashboard doesn’t allow you to create the LDAP Policy, so you must create it elsewhere.

You can create the LDAP policy now. Or you can wait and create it later when you bind the LDAP Server to the NetScaler Gateway vServer.

To create it now:

  1. You can use the menu Search box to find one of the nodes that lets you create Basic Authentication Policies.

    1. Or, navigate to NetScaler Gateway > Policies > Authentication > LDAP.
  2. On the right, in the Policies tab, click Add.
  3. Change the Server drop-down to the LDAP Server you created earlier.
  4. Give the LDAP Policy a name (one for each domain).
  5. In the Expression box, enter ns_true.
    • NetScaler Gateway 12 does not support Advanced Authentication policies directly on the Gateway vServer. If you prefer Advanced Authentication Policies, then you’ll instead need to configure nFactor.
  6. Click Create.

     add authentication ldapPolicy LDAP-Corp ns_true LDAP-Corp
  7. If you see a message about deprecation, click OK and ignore it.

Gateway Authentication Feedback

  1. On the left, under NetScaler Gateway, click Global Settings.
  2. On the right, in the right column, click Change authentication AAA settings.
  3. If desired, check the box for Enable Enhanced Authentication Feedback. This feature provides a message to users if authentication fails. The message users receive include password errors, account disabled or locked, or the user is not found, to name a few. This setting might not be advisable in a secure environment.
  4. Click OK.

    set aaa parameter -enableEnhancedAuthFeedback YES

Next Step

Multiple Domains – UPN Method

Cascade – To support multiple Active Directory domains on a NetScaler Gateway, you create multiple LDAP authentication policies, one for each Active Directory domain, and bind all of the LDAP policies to the NetScaler Gateway Virtual Server. When the user logs into NetScaler Gateway, only the username and password are entered. The NetScaler will then loop through each of the LDAP policies in priority order until it finds one that contains the entered username/password.

Same user/password in multiple domains РWhat if the same username is present in multiple domains? As NetScaler loops through the LDAP policies, as soon as it finds one with the specified username, it will try to authenticate with that particular LDAP policy. If the password doesn’t match the user account for the attempted domain, then a failed logon attempt will be logged in that domain, and NetScaler will try the next domain.

Unfortunately, the only way to enter a realm/domain name during user authentication is to require users to login using userPrincipalNames. To use userPrincipalName, set the LDAP Policy/Server with the Server Logon Name Attribute set to userPrincipalName.

You can even do a combination of policies: some with samAccountName, and some with userPrincipalName. The samAccountName policies would be searched in priority order, and the userPrincipalName policies can be used to override the search order. Bind the userPrincipalName policies higher (lower priority number) than the samAccountName policies.

NetScaler supports adding a domain name drop-down list to the logon page. Then use Cookie expressions in the auth policies and session policies. However, this probably doesn’t work for Receivers. See¬†CTX203873¬†How to Add Drop-Down Menu with Domain Names on Logon Page for NetScaler Gateway 11.0 64.x and later releases for details.
User-added image

Another option for a domain drop-down is nFactor Authentication for Gateway. This also doesn’t fully work with Receiver Self-service.

After authentication is complete, a Session Policy will be applied that has the StoreFront URL. The NetScaler Gateway will attempt to log into StoreFront using Single Sign-on so the user doesn’t have to login again. When logging into NetScaler Gateway, only two fields are required: username and password. However, when logging in to StoreFront, a third field is required: domain name. So how does NetScaler specify the domain name while logging in to StoreFront?

There are two methods of specifying the domain:

  • AAA Group – Configure multiple session policies with unique¬†Single Sign-on Domains. ¬†Inside the Session Policy is a field called Single Sign-on Domain for specifying the domain name. If there is only one Active Directory domain, then you can use the same Session Policy for all users. However, if there are multiple domains, then you would need multiple Session Policies, one for each Active Directory domain. But as the NetScaler loops through the LDAP policies during authentication, once a successful LDAP policy is found,¬†you need a method¬†of linking an LDAP policy with a Session Policy that has the corresponding SSO Domain. This is typically done using AAA groups. To use this method, see Multiple Domains – AAA Group Method.
  • userPrincipalName – Alternatively, configure the LDAP policy/server to extract the user‚Äôs UPN, and then authenticate to StoreFront using UPN. This is the easiest method, but some domains don‚Äôt have userPrincipalNames configured correctly.

The userPrincipalName method is detailed below:

  1. In each of your NetScaler LDAP policies/servers, in the Other Settings section, in the SSO Name Attribute field, enter userPrincipalName¬†(select –<< New >>– first). Make sure there are no spaces after this attribute name. NetScaler will pull this attribute from AD, and use it to Single Sign-on¬†the user to¬†StoreFront.
  2. In StoreFront Console, in the middle, right-click your Store, and click Manage Authentication Methods.
  3. On the right, click the gear icon, and then click Configure Trusted Domains.
  4. In the Trusted domains box, select Any domain.
  5. Or add your UPN domain suffixes in DNS format. The advantage of entering domain names is that you can select a default domain. The DNS format is required for UPN logins (e.g. SSO from NetScaler Gateway).
  6. On the NetScaler Gateway Virtual Server, bind LDAP authentication polices in priority order. It will search them in order until it finds a match.
  7. In your Session Policies/Profiles, in the Published Applications tab, make sure Single Sign-on Domain is not configured. Since NetScaler is using the userPrincipalName, there’s no need to specify a domain. If the Single Sign-on Domain field is configured, then Single Sign-on authentication will fail.

Multiple Domains – AAA Groups Method

Another method of specifying the domain name when performing Single Sign-on to StoreFront is to use a unique session policy/profile for each domain. Use AAA Groups to distinguish one domain from another.

  1. Go to NetScaler Gateway > Policies > Authentication > LDAP.
  2. On the right, switch to the Servers tab.
  3. Make sure all domains are in the list. Edit one of the domains.
  4. Scroll down to the Other Settings section,
  5. In the Default Authentication Group field, enter a new, unique group name. Each domain must a different group name. This group is only locally significant and does not need to be added to AD. Click OK.
  6. Edit another domain, and specify a new unique group name. Each domain has a different group name.
  7. Go to NetScaler Gateway > User Administration > AAA Groups.
  8. On the right, click Add.
  9. Name the group so it exactly matches the group name you specified in the LDAP server. Click OK.
  10. On the right, in the Advanced Settings section, add the Policies section.
  11. On the left, in the Policies section, click the Plus icon.

    1. Select Session, and click Continue.
    2. Click the plus icon to create a new policy.
    3. Give the Policy a name that indicates the domain. You will have a separate policy for each domain.
    4. Click the plus icon to create a new profile.
    5. Give the Profile a name that indicates the domain. You will have a separate profile for each domain.
    6. Switch to the Published Applications tab.
    7. Check the Override Global box next to Single Sign-on Domain. Enter the domain name that StoreFront is expecting. Click Create.
    8. Give the policy a ns_true expression, and click Create.
    9. In the Priority field, give it a number that is lower than any other Session Policy that has Single Sign-on Domain configured. Click OK.
    10. Click Done.
  12. Create another AAA Group.
  13. Give it a name that matches the Default Authorization Group configured for the next domain.
  14. Create another Session Policy for the next domain.
  15. Create another profile for the next domain. On the Published Applications tab, specify the domain name of the next domain.
  16. Bind the new policy with a low Priority number.
  17. When a user logs in, NetScaler loops through LDAP policies until one of them works. NetScaler adds the user to the Default Authentication Group specified in the LDAP Server. NetScaler finds a matching AAA Group and applies the Session Policy that has SSON Domain configured. Since the policy is bound with a low priority number, it overrides any other policy that also has SSON Domain configured.

2 thoughts on “NetScaler Gateway 12 – LDAP Authentication”

  1. Hey Carl, great documentation as always! I noticed in Step 12 under “LDAP Authentication Server” your screenshot shows the “cn” value in the “SSO Name Attribute” drop-down although you mention to select the “Sub Attribute Name”. Just thought I’d share.

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