PoC Guide: nFactor for NetScaler Gateway Authentication with Native OTP

PoC Guide: nFactor for NetScaler Gateway Authentication with Native OTP

November 28, 2022

Author:  Matthew Brooks, Alyssa Ramella

Special thanks:  Himanshu Shukla Introduction

Implementing multifactor authentication is one of the best ways to verify identity, and improve security posture. Native (time-based) One Time Password (OTP) is a convenient way to implement another factor using readily available authenticator applications. It allows users to enter validation codes from their authenticator application, into a gateway form, to authenticate.

NetScaler Gateway supports Native OTP, and can provide authentication for various services including web services, VPN, and Citrix Virtual Apps and Desktops. In this POC Guide we demonstrate using it for authentication in a Citrix Virtual Apps and Desktops environment.

Conceptual Architecture

Overview

This guide demonstrates how to implement a Proof of Concept environment using two factor authentication with NetScaler Gateway. It uses LDAP to validate Active Directory credentials as the first factor, and Native OTP as the second factor.

It makes assumptions about the completed installation, and configuration of the following components:

• NetScaler Gateway installed, licensed, and configured with an externally reachable virtual server bound to a wildcard certificate
• NetScaler Gateway integrated with a Citrix Virtual Apps and Desktops environment which uses LDAP for authentication
• Endpoint with Citrix Workspace app installed
• A supported Authenticator app, that supports Time Based OTP, installed (including Microsoft Authenticator, Google Authenticator, or Citrix SSO)
• Active Directory (AD) is available in the environment

nFactor

LDAP Policies

First we create two LDAP policies which we reference later when we are building our nFactor flow.

Native OTP Registration

This LDAP registration policy is used to exchange, and store the key used to generate the time based OTP code.

1. Log in to the NetScaler ADC UI
2. Navigate to Security > AAA-Application Traffic > Policies > Authentication > Advanced Policies > Policy
3. Click Add
4. Enter polldap_notpmanage for the policy name, and change the Action Type to LDAP.
5. Click Add under Action
6. Populate the following fields:
   • Name - enter actldap_notpmanage
   • Server Name / IP address - select an FQDN or IP address for AD server/(s). We enter 192.0.2.50
   • Clear Authentication This setting along with the OTP Secret below indicate the policy will set, rather than get, object attributes
   • Base DN - enter the path to the AD user container. We enter DC=workspaces, DC=wwco, DC=net
   • Administrator Bind DN - enter the admin/service account to query AD to authenticate users. We enter workspacessrv@workspaces.wwco.net
   • Confirm / Administrator Password - enter / confirm the admin / service account password
   • Click Test Network Connectivity to ensure connection
   • Server Logon Name Attribute - in the second field below this field enter userPrincipalName
   • OTP Secret - Enter userParameters This is the User’s LDAP object that will get updated with the key that`s used with hash to generate the time based OTP code
7. Select Create

      8. Enter the expression true, and click OK

Native OTP Authentication

This LDAP authentication policy is used to do the first factor authentication.

1. Navigate to Security > AAA-Application Traffic > Policies > Authentication > Advanced Policies > Policy
2. Click Add
3. Enter polldap_notpauth for the policy name, and change the Action Type to LDAP.
4. Click Add under Action
5. Populate the following fields:
   • Name - enter actldap_notpauth
   • Server Name / IP address - select an FQDN or IP address for AD server/(s). We enter 192.0.2.50
   • Base DN - enter the path to the AD user container. We enter DC=workspaces, DC=wwco, DC=net
   • Administrator Bind DN - enter the admin/service account to query AD to authenticate users. We enter workspacessrv@workspaces.wwco.net
   • Confirm / Administrator Password - enter / confirm the admin / service account password
   • Click Test Network Connectivity to ensure connection
   • Server Logon Name Attribute - in the second field below this field enter userPrincipalName
6. Select Create

     7. Enter the expression true, and click OK

For more information see LDAP authentication policies

Login Schemas

Login Schemas are used when data needs to be gathered on behalf of a policy.

Native OTP lSchema - Single Authentication

This registration login schema corresponds to the LDAP registration policy.

1. Navigate to Security > AAA-Application Traffic > Login Schema
2. Select the Profile tab
3. Click Add under Profile, and name it prolschema_notpsingle
4. Click the pencil icon next to noschema
5. Click Login Schema, and scroll down to select SingleAuthManageOTP.xml, and select the blue Select in the right corner.
6. Click Create

Native OTP lSchema - Dual Authentication

This registration login schema corresponds to the dual factor authentication where the user enters both their password, and the OTP passcode.

1. Under the Profile tab click Add again
2. Enter the name pollschema_notpdual
3. Click Add under Profile, and also name it prolschema_notpdual
4. Click the pencil icon next to noschema
5. Click Login Schema, and scroll down to select DualAuth.xml, and select the blue Select in the right corner.
6. Click More
7. In the field Password Credential Index enter 1
8. Click Create

Native OTP AAA Virtual Server - Visualizer Flow

1. Next navigate to Security > AAA - Application Traffic > nFactor Visualizer > nFactor Flows
2. Click Add
3. Click the + sign to create the initial factor. This factor will not take action, rather handle directing incoming traffic to registration or authentication factor flows.
4. Enter factor0-notp, and click Create

Registration Flow

1. Select Add Policy
2. Select Add next to Select Policy
3. Enter name polfactor0-notpmanage
4. Set the Action Type to NO_AUTHN
5. Paste in HTTP.REQ.COOKIE.VALUE(“NSC_TASS”).EQ(“manageotp”) for the expression OR build it with Expression builder

You can optionally limit registration to endpoints on the internal network by adding a source IP address criteria such as http.req.cookie.value("NSC_TASS").eq("manageotp") && client.IP.SRC.IN_SUBNET(10.0.0.0/8)

1. Click Create, followed by Add

1. Select the green + to the right of the polfactor0-notpmanage policy you just created
2. Enter factor1-notpmanage, and click Create

1. In the new factor box, select Add Schema
2. Select prolschema_notpsingle, and click Ok
3. Select Add Policy
4. From the drop-down list under Select Policy select polldap_notpauth, and click Add
5. Select the green + to the right of the polldap_notpauth policy
6. Enter factor2-notpmanage, and click Create

1. In the new factor box, select Add Policy
2. From the drop-down list under Select Policy select polldap_notpmanage, and click Add

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Authentication Flow

1. Now in the initial factor box we created factor0-notp, select the blue +
2. Select Add next to Select Policy
3. Enter name polfactor0-notpauth
4. Set the Action Type to NO_AUTHN
5. Enter true for the expression
6. Click Create, followed by Add Notice that the policy priority has increased to 110 meaning it will be executed only if the above policy polfactor0-notpmanage at 100 is not a match.

1. Select the green + to the right of the polfactor0-notpauth policy you just created
2. Enter factor1-notpauth, and click Create
3. In the new factor box, select Add Schema
4. Select prolschema_notpdual, and click Ok
5. Select Add Policy
6. From the drop-down list under Select Policy select polldap_notpauth, and click Add
7. Select the green + to the right of the polldap_notpauth policy you just created
8. Enter OTPCheck, and click Create
9. Select Add Policy
10. From the drop-down list under Select Policy select polldap_notpmanage, and click Add
11. Select Done

Native OTP AAA Virtual Server

This AAA Virtual Server is where the policies and schema are bound with the appropriate priority.

1. Navigate to Traffic Management > SSL> Certificates > All Certificates to verify you have your domain certificate installed. In this POC example we used a wildcard certificate corresponding to our Active Directory domain. See NetScaler ADC SSL certificates for more information.
2. Next navigate to Security > AAA - Application Traffic > Virtual Servers, and select Add
3. Enter the following fields:
   • Name - a unique value. We enter nativeotp_authvserver
   • IP Address Type - Non Addressable
4. Click Ok
5. Select No Server Certificate, select the arrow under Select Server Certificate, select the domain certificate, click Select, Bind, and Continue
6. Under Advanced Authentication Policies, select No Nfactor Flow
7. Select the right arrow under Select nFactor Flow, select factor0_notp, click Select, click Bind

1. Click Continue, followed by Done

Traffic Policy

Now we create a traffic policy to relay the LDAP password to StoreFront, instead of the OTP passcode.

1. Navigate to NetScaler Gateway > Virtual Servers > Policies > Traffic
2. Select the Traffic Profiles Tab, and click Add
3. Enter the name notp_trafficprofile
4. Select HTTP
5. In the SSO Password Expression enter http.REQ.USER.ATTRIBUTE(1)

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1. Now click the Traffic Policies Tab
2. In the Request Profile field, select the notp_trafficprofile Traffic Profile you just created.
3. Enter the name nOTP_TrafficPolicy
4. In the Express box enter true
5. Click Create

Gateway Virtual Server

The Gateway Virtual Server is bound to the Native OTP AAA Virtual Server to provide authentication for Citrix Virtual Apps and Desktops.

1. Navigate to NetScaler Gateway > Virtual Servers
2. Select your current Gateway, and click Edit
3. Select Authentication Profile from the Advanced Settings panel on the right hand side
4. Select Add
5. Enter a profile name. We enter nativeotp_authprofile
6. Under Policy select the arrow, and select the Native OTP AAA Virtual Server nativeotp_authvserver
7. Click Create
8. Select Policies from the Advanced Settings panel on the right hand side
9. Select the + sign to Add
10. Under Choose Policy select Traffic, and under Choose Type select Request. The select Continue
11. Click the right arrow, select notp_trafficpolicy, and select OK
12. Click Done, and save the running configuration

​​​​​​​ User Endpoint

Now we test Native OTP by authenticating into our Citrix Virtual Apps and Desktops environment.

Registration with Citrix SSO app

First the user registers their device for Native OTP using the Citrix SSO app.

1. Open a browser, and navigate to the domain FQDN managed by the NetScaler Gateway with /manageotp appended to the end of the FQDN. We use https://gateway.workspaces.wwco.net/manageotp
2. After your browser is redirected to a login screen enter user UPN, and password

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1. On the next screen select Add Device, enter a name. We use iPhone7_nOTP

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1. Select Go, and a QR code appears

1. On your mobile device open your Citrix SSO app or other authenticator app such as Microsoft or Google’s (available for download from app stores)
2. Select Add New Token
3. Select Scan QR Code

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1. Select Aim your camera at the QR Code, and once it`s captured select Add

1. Select Save to store the token

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1. The Token is now active, and begins displaying OTP codes at 30 second intervals

1. Select Done and you see confirmation that the device was added successfully

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Citrix Virtual Apps and Desktops Authentication, Publication, and Launch

Then the user enters their UserPrincipalName, Password, and the OTP Passcode from the Citrix SSO app to access their virtual apps, and desktops.

1. Open a browser, and navigate to the domain FQDN managed by the NetScaler Gateway. We use https://gateway.workspaces.wwco.net
2. After your browser is redirected to a login screen enter user UserPrincipalName, and password
3. Open the Citrix SSO app enter the OTP code in the passcode field for the iPhone7_nOTP device entry

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1. Verify the users virtual apps, and desktops are enumerated, and launch once logged in

Troubleshooting

Here we look at a couple common troubleshooting areas for Native OTP.

NTP Errors

Upon login with your OTP code the page may post a message advising you to verify NTP synchronization. The NetScaler ADC’s time must be sync in order to generate the correct time based OTP. If you have not implemented NTP follow these steps:

• Set the time manually on your NetScaler ADC to the current time. This will speed up the synchronization that would otherwise take a longer period time
• Add NTP Server/s
• If you still get an NTP error upon submitting the OTP code see Time Display on NetScaler Does Not Sync Using NTP

• Cannot complete your request. - if this error message occurs after successful authentication it likely indicates an error passing user credentials to StoreFront. Verify the Dual Authentication schema and Traffic Policy settings.

• Try again or contact your help desk - this error message often indicates a LDAP login failure.

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• If you have verified the password is correct verify the Administrator bind password has been set. You may have had an existing LDAP authentication policy, and created the manage policy by selecting it, followed by selecting add. This step saves time by populating existing settings like the Base DN, and you may see the Administrator password field appears to be populated, but you MUST reenter the password.

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Summary

With Citrix Workspace, and NetScaler Gateway, Enterprises can improve their security posture by implementing multifactor authentication without making the user experience complex. Users can gain access to their Citrix Virtual Apps and Desktops, by entering their domain user name, and password, and then simply confirming their identity by entering a One Time Password from their registered authenticator app.

References

For more information refer to:

Native OTP Authentication – find more details regarding Native OTP implementation, and use cases.