Native OTP support for authentication

NetScaler appliance supports one-time passwords (OTPs) without having to use a third-party server. One-time password is a highly secure option for authenticating to secure servers as the number or passcode generated is random. Previously, OTPs are offered by specialized firms, such as RSA with specific devices that generate random numbers. This system must be in constant communication with client to generate a number expected by the server.

In addition to reducing capital and operating expenses, this feature enhances the administrator’s control by keeping the entire configuration on the NetScaler appliance.

Note

Since third-party servers are no longer needed, the NetScaler administrator has to configure an interface to manage and validate user devices.

User must be registered with a NetScaler appliance virtual server to use the OTP solution. Registration is required only once per unique device, and can be restricted to certain environments. Configuring and validation of a registered user is similar to configuring an extra authentication policy.

Advantages of having Native OTP support

• Reduces operating cost by eliminating the need to have an extra infrastructure on an authenticating server in addition to the Active Directory.
• Consolidates configuration only to NetScaler appliance thus offering great control to administrators.
• Eliminates client’s dependence on an extra authentication server for generating a number expected by clients.

Native OTP workflow

The native OTP solution is a two-fold process and the workflow is classified as following:

• Device registration
• End user login

Important

You can skip the registration process if you are using third-party solutions or managing other devices apart from NetScaler appliance. The final string that you add must be in the NetScaler specified format.

The following figure depicts the device registration flow to register a new device to receive OTP.

Note

The device registration can be done using any number of factors. The single factor (as specified in the previous figure) is used as an example to explain the device registration process.

The following figure depicts the verification of OTP through the registered device.

Prerequisites

To use the native OTP feature, make sure the following prerequisites are met.

• NetScaler feature release version is 12.0 build 53.13 and later.
• Advanced or Premium edition license is installed on NetScaler Gateway.
• NetScaler appliance is configured with management IP and the management console is accessible both using a browser and command line.
• NetScaler is configured with authentication, authorization, and auditing virtual server to authenticate users.
• NetScaler appliance is configured with Unified Gateway and the authentication, authorization, and auditing profile is assigned to the Gateway virtual server.
• Native OTP solution is restricted to nFactor authentication flow. Advanced policies are required to configure the solution. For more details, see article CTX222713.

Also ensure the following for Active Directory:

• A minimum attribute length of 256 characters.
• Attribute type must be ‘DirectoryString’ such as UserParameters. These attributes can hold string values.
• Attribute string type must be Unicode, if device name is in non-English characters.
• NetScaler LDAP administrator must have write access to the selected AD attribute.
• NetScaler appliance and client machine must be synced to a common Network Time Server.

Configure Native OTP using the GUI

The native OTP registration is not just a single factor authentication. The following sections help you to configure the single and second factor authentication.

Create Login Schema for first factor

1. Navigate to Security AAA > Application Traffic > Login Schema.
2. Go to Profiles and click Add.
3. On the Create Authentication Login Schema page, enter lschema_first_factor under Name field and click Edit next to noschema.
4. Click the LoginSchema folder.
5. Scroll down to select SingleAuth.xml and click Select.
6. Click Create.
7. Click Policies and Click Add.

8. On the Create Authentication Login Schema Policy screen, enter the following values.

   Name: lschema_first_factor Profile: select lschema_first_factor from the list. Rule: HTTP.REQ.COOKIE.VALUE(“NSC_TASS”).EQ(“manageotp”)

Configure authentication, authorization, and auditing virtual server

1. Navigate to Security > AAA – Application Traffic > Authentication Virtual Servers. Click to edit the existing virtual server.
2. Click the + icon next to Login Schemas under Advanced Settings in the right pane.
3. Select No Login Schema.
4.  Click the arrow and select the lschema_first_factor Policy.
5.  Select the lschema_first_factor policy and Click Select.
6.  Click Bind.
7.  Scroll up and select 1 Authentication Policy under Advanced Authentication Policy.
8. Right-click the nFactor Policy and select Edit Binding.
9.  Click the + icon present under Select Next Factor, create a Next Factor, and click Bind.

10. On the Create Authentication PolicyLabel screen, enter the following, and click Continue:

    Name: OTP_manage_factor

    Login Schema: Lschema_Int

11. On the Authentication PolicyLabel screen, click the + icon to create a Policy.

12.  On the Create Authentication Policy screen, enter the following:

    Name. otp_manage_ldap

13. Select the Action type using the Action Type list.
14. In the Action field, click the + icon to create an Action.

15.  In the Create Authentication LDAP server page, select Server IP radio button, deselect the check box next to Authentication, enter the following values, and select Test Connection.

    Name: LDAP_no_auth

    IP Address: 192.168.10.11

    Base DN: DC=training, DC=lab

    Administrator: Administrator@training.lab

    Password: xxxxx

16. Scroll down to the Other Settings section. Use the drop-down menu to select the following options.

    Server Logon Name Attribute as New and type userprincipalname.

17. Use the drop-down menu to select SSO Name Attribute as New and type userprincipalname.
18. Enter “UserParameters” in the OTP Secret field and click More.

19. Enter the following Attributes.

    Attribute 1 = mail Attribute 2 = objectGUID Attribute 3 = immutableID

20. Click OK.
21. On the Create Authentication Policy page, set the Expression to true and click Create.
22. On the Create Authentication Policylabel page, click Bind, and click Done.
23. On the Policy Binding page, click Bind.
24. On the Authentication policy page, click Close and click Done.

Note

The authentication virtual server must be bound to RFWebUI portal theme. Bind a server certificate to the server. The server IP ‘1.2.3.5’ must have a corresponding FQDN that is, otpauth.server.com, for later use.

Create login schema for second factor OTP

1. Navigate to Security > AAA-Application Traffic > Virtual Servers. Select the virtual server to be edited.
2. Scroll down and select 1 Login Schema.
3. Click Add Binding.
4. Under Policy Binding section, click the + icon to add a policy.
5. On the Create Authentication Login Schema Policy page, enter Name as OTP, and click the + icon to create a profile.
6. On the Create Authentication Login Schema page, enter Name as OTP, and click the icon next to noschema.
7. Click the LoginSchema folder, select DualAuth.xml, and then click Select.
8. Click Create.
9. In the Rule section, enter True. Click Create.
10. Click Bind.
11. Notice the two factors of authentication. Click Close and click Done.

Configure content switching policy for manage OTP

The following configurations are required if you are using Unified Gateway.

1. Navigate to Traffic Management > Content Switching > Policies. Select the content switching policy, right click, and select Edit.

2. Edit the expression to evaluate the following OR statement and click OK:

Configure Native OTP using the CLI

You must have the following information to configure the OTP device management page:

• IP assigned to authentication virtual server
• FQDN corresponding to the assigned IP
• Server certificate for authentication virtual server

Note

Native OTP is a web-based solution only.

To configure the OTP device registration and management page

Create authentication virtual server

• add authentication vserver authvs SSL 1.2.3.5 443
• bind authentication vserver authvs -portaltheme RFWebUI
• bind ssl vserver authvs -certkeyname otpauthcert

Note

The authentication virtual server must be bound to RFWebUI portal theme. You must bind a server certificate to the server. The server IP ‘1.2.3.5’ must have a corresponding FQDN that is, otpauth.server.com, for later use.

To create LDAP logon action

add authentication ldapAction <LDAP ACTION NAME> -serverIP <SERVER IP> - serverPort <SERVER PORT> -ldapBase <BASE> -ldapBindDn <AD USER> -ldapBindDnPassword <PASSWO> -ldapLoginName <USER FORMAT>

Example:

add authentication ldapAction ldap_logon_action -serverIP 1.2.3.4 -serverPort 636 -ldapBase "OU=Users,DC=server,DC=com" -ldapBindDn administrator@ctxnsdev.com -ldapBindDnPassword PASSWORD -ldapLoginName userprincipalname

To add authentication policy for LDAP Logon

add authentication Policy auth_pol_ldap_logon -rule true -action ldap_logon_action

To present UI via LoginSchema

Show user name field and password field to users upon logon

add authentication loginSchema lschema_single_auth_manage_otp -authenticationSchema "/nsconfig/loginschema/LoginSchema/SingleAuthManageOTP.xml"

Display device registration and management page

Citrix recommends two ways of displaying the device registration and management screen: URL or host name.

• Using URL

  When the URL contains ‘/manageotp’

  • add authentication loginSchemaPolicy lpol_single_auth_manage_otp_by_url -rule "http.req.cookie.value("NSC_TASS").contains("manageotp")" -action lschema_single_auth_manage_otp
  • bind authentication vserver authvs -policy lpol_single_auth_manage_otp_by_url -priority 10 -gotoPriorityExpression END

• Using hostname

  When the host name is ‘alt.server.com’.

  • add authentication loginSchemaPolicy lpol_single_auth_manage_otp_by_host -rule "http.req.header("host").eq("alt.server.com")" -action lschema_single_auth_manage_otp
  • bind authentication vserver authvs -policy lpol_single_auth_manage_otp_by_host -priority 20 -gotoPriorityExpression END

To configure the user login page using the CLI

You must have the following information to configure the User Logon page:

• IP for a load balancing virtual server
• Corresponding FQDN for the load balancing virtual server
• Server certificate for the load balancing virtual server

Note

Reuse the existing authentication virtual server (authvs) for the two-factor authentication.

To create load balancing virtual server

• add lb vserver lbvs_https SSL 1.2.3.162 443 -persistenceType NONE -cltTimeout 180 - AuthenticationHost otpauth.server.com -Authentication ON -authnVsName authvs
• bind ssl vserver lbvs_https -certkeyname lbvs_server_cert

Back-end service in load balancing is represented as follows:

• add service iis_backendsso_server_com 1.2.3.210 HTTP 80
• bind lb vserver lbvs_https iis_backendsso_server_com

To create OTP passcode validation action

add authentication ldapAction <LDAP ACTION NAME> -serverIP <SERVER IP> -serverPort <SERVER PORT> -ldapBase <BASE> -ldapBindDn <AD USER> -ldapBindDnPassword <PASSWORD> -ldapLoginName <USER FORMAT> -authentication DISABLED -OTPSecret <LDAP ATTRIBUTE>

Example:

add authentication ldapAction ldap_otp_action -serverIP 1.2.3.4 -serverPort 636 -ldapBase "OU=Users,DC=server,DC=com" -ldapBindDn administrator@ctxnsdev. com -ldapBindDnPassword PASSWORD -ldapLoginName userprincipalname -authentication DISABLED -OTPSecret userParameters

Important

The difference between LDAP logon and OTP action is the need to disable the authentication and introduce a new parameter “OTPSecret.” The AD attribute value must not be used.

To add authentication policy for OTP passcode validation

add authentication Policy auth_pol_otp_validation -rule true -action ldap_otp_action

To present the two-factor authentication through LoginSchema

Add the UI for two factor authentication.

• add authentication loginSchema lscheme_dual_factor -authenticationSchema "/nsconfig/loginschema/LoginSchema/DualAuth.xml"
• add authentication loginSchemaPolicy lpol_dual_factor -rule true -action lscheme_dual_factor

To create passcode validation factor via policy label

Create a manage OTP flow policy label for next factor (first factor is LDAP logon)

• add authentication loginSchema lschema_noschema -authenticationSchema noschema
• add authentication policylabel manage_otp_flow_label -loginSchema lschema_noschema

To bind the OTP policy to the policy label

bind authentication policylabel manage_otp_flow_label -policyName auth_pol_otp_validation -priority 10 -gotoPriorityExpression NEXT

To bind the UI flow

Bind the LDAP logon followed by the OTP validation with authentication virtual server.

• bind authentication vserver authvs -policy auth_pol_ldap_logon -priority 10 -nextFactor manage_otp_flow_label -gotoPriorityExpression NEXT
• bind authentication vserver authvs -policy lpol_dual_factor -priority 30 -gotoPriorityExpression END

Register your device with NetScaler appliance

1. Navigate to your NetScaler FQDN (first public facing IP), with a /manageotp suffix. For example, https://otpauth.server.com/manageotp Login with user credentials.

2. Click the + icon to add a device.

   

3. Enter a device name and press Go. A barcode appears on screen.
4. Click Begin Setup and then click Scan Barcode.

5. Hover the device camera over the QR code. You can optionally enter the 16 digit code.

   

   Note

   The displayed QR code is valid for 3 minutes.

6. Upon successful scan, you are presented with a 6 digit time sensitive code that can be used to log in.

   

7. To test, click Done on the QR screen, then click the green check mark on the right.
8. Select your device from the drop-down menu and enter the code from Google Authenticator (must be blue, not red) and click Go.
9. Make sure to log out using the drop-down menu at the top right corner of the page.

Log in to NetScaler appliance using the OTP

1. Navigate to your first public facing URL and enter your OTP from Google Authenticator to log on.

2. Authenticate to the NetScaler splash page.

   

Securing OTP management

There are different ways of presenting OTP management page to end users. The most common way is to present the standalone OTP management page. However, care must be taken to ensure that OTP management page is served after meeting security requirements. A minimum of two factors must be validated before presenting user with OTP management page externally. This section describes best practices for presenting the OTP management page.

Marking active directory attributes as confidential

The OTP solution natively uses user’s active directory object to store certain information used in computation of OTP codes. Although the OTP solution is highly flexible and saves significant savings for the customers, the OTP attribute carries sensitive information that is critical for OTP. Customers must ensure that only users with explicit rights are able to view contents of this attribute.

• The Citrix ADC version 12.1 build 54.13 and later offers native OTP encryption of the data that is stored on the active directory and thus provides enhanced security.
• For customers who are on earlier versions of NetScaler, it is recommended to mark certain attributes as confidential to protect the OTP attribute on the active directory. When the attributes are marked as confidential, only users with explicit permissions can view those attributes.

For more information on marking attributes as confidential, see;

• https://support.microsoft.com/en-us/help/922836/how-to-mark-an-attribute-as-confidential-in-windows-server-2003-servic. Note: The ability to mark AD attributes as confidential was introduced in Windows Server 2003 but is available in all subsequent Windows Server versions.
• https://gallery.technet.microsoft.com/Hide-the-data-in-Active-d6f5d4d9

Single factor registration internally

Often times, customers do not use any third party vendor for two factor authentication. If such customers want to move to NetScaler’s OTP, users might have only AD credentials available. In these cases, an internal site can be hosted that uses just AD or Kerberos for registration of OTP devices. SingleAuthManangeOTP.xml login schema can be used to present this page based on the source.

Dual factor registration externally

When users access OTP management page externally, users must be prompted to present a second factor for even registering their devices. If customers have other OTP solutions (RSA token or others), they must be prompted to validate that before accessing self-service portal. If customers do not use any third party tokens, then the first device can be registered only from within the premises. Subsequent devices use one of the previously registered devices’ OTP. DualAuthManageOTP.xml can be used to show two password fields to end users.

Note

The “DualAuthManageOTP.xml” file is now available from NetScaler release 12.1 build 53.10, and is at /nsconfig/loginschema/LoginSchema directory.

Challenges with dual factor registration externally

The challenge that customers often face is to figure out when users are external. Users can alter parts of HTTP headers such as “Host” headers. Therefore, integral part of OTP management check is identifying the source. Usually, deployments have a NAT device facing internet along with firewall. All external accesses usually happen through that NAT device’s source IP (when seen from gateway). Internal accesses typically happen directly. Customers can apply this fact to identify the source.

OTP management flow

The following flow chart illustrates a typical OTP management flow for dual factor registration.

Configuration example

As mentioned above, the challenge with the flow diagram is identifying whether the user is external or not. Different organizations have different network configurations to identify that. In this example, assume that the user is coming from 10.x.x.x network, and therefore the user is considered internal. However, this needs to be corrected as per customer’s network.

Steps to configure dual factor registration externally:

• Configure log in form view

add expression is_external_user “CLIENT.IP.SRC.IN_SUBNET(10.0.0.0/8).NOT && http.req.cookie.value("NSC_TASS").eq("manageotp")”

add authentication loginSchema dualauth_registerotp -authenticationSchema DualAuthManageOTP.xml

add authentication loginSchemaPolicy dualauth_registerotp –rule “is_external_user && http.req.cookie.value("NSC_TASS").eq("manageotp")” –action dualauth_registerotp

add authentication loginSchema lschema_single_auth_manage_otp -authenticationSchema "LoginSchema/SingleAuthManageOTP.xml"

add authentication loginSchemaPolicy lschema_single_auth_manage_otp -rule "!is_external_user && http.req.cookie.value("NSC_TASS").eq("manageotp")" -action lschema_single_auth_manage_otp

add authentication vserver nfactor_gateway_auth SSL x.x.x.x 443

Bind appropriate certificates

bind authentication vserver nfactor_gateway_auth -policy lschema_single_auth_manage_otp -priority 85 -gotoPriorityExpression END

bind authentication vserver nfactor_gateway_auth -policy dualauth_registerotp -priority 80 -gotoPriorityExpression END

Note: Customers can also have other login schema policies at this point for actual login. These are omitted for brevity.

• Configure login factors

To configure login factors, add AD actions.

AD action for logon:

add authentication ldapAction ldap_action_login -serverIP <SERVER IP> -  serverPort <SERVER PORT> -ldapBase <BASE> -ldapBindDn <AD USER> -ldapBindDnPassword <PASSWO> -ldapLoginName <USER FORMAT>

AD action for OTP validation and registration:

add authentication ldapAction ldap_action_otp -serverIP <SERVER IP> -  serverPort <SERVER PORT> -ldapBase <BASE> -ldapBindDn <AD USER> -ldapBindDnPassword <PASSWO> -ldapLoginName <USER FORMAT> -authentication disabled –OTPSecret UserParameters

• Add policies

add authentication policy ldap_login_policy_internal –rule ‘!is_external_user’ –action ldap_action_login

add authentication policy ldap_login_otp_validation –rule ‘is_external_user -action ldap_action_otp

add authentication policy ldap_login_policy_external –rule ‘true’ –action ldap_action_login

add authentication policy ldap_login_otp_management –rule ‘true’ -action ldap_action_otp

• Add the OTP factor first

add authentication policylabel otp_management_factor

bind authentication policylabel otp_management_factor –policy ldap_login_otp_management –pri 100

• Add the AD validation factor for external users

add authentication policylabel ldap_login_external_factor

bind authentication policylabel ldap_login_external_factor –policy ldap_login_policy_external –pri 100 –nextFactor otp_management_factor

• Bind policies to virtual server

bind authentication vserver nfactor_gateway_auth –policy ldap_login_policy_internal –pri 100 –nextFactor otp_management_factor

bind authentication vserver nfactor_gateway_auth –policy ldap_login_otp_validation –pri 110 –nextFactor ldap_login_external_factor