Duo for Citrix Gateway - Basic Secondary Authentication Instructions

1. Ensure that Perl and a compiler toolchain are installed. On most recent RPM-based distributions — like Fedora, RedHat Enterprise, and CentOS — you can install these by running (as root):

   $ yum install gcc make libffi-devel perl zlib-devel diffutils

   On Debian-derived systems, install these dependencies by running (as root):

   $ apt-get install build-essential libffi-dev perl zlib1g-dev

2. Download the most recent Authentication Proxy for Unix from https://dl.duosecurity.com/duoauthproxy-latest-src.tgz. Depending on your download method, the actual filename may reflect the version e.g. duoauthproxy-5.4.0-src.tgz. View checksums for Duo downloads here.

3. Extract the Authentication Proxy files and build it as follows:

   $ tar xzf duoauthproxy-latest-src.tgz
   $ cd duoauthproxy-version-src
   $ make

4. Install the authentication proxy (as root):

   $ cd duoauthproxy-build
   $ ./install

   Follow the prompts to complete the installation. The installer creates a user to run the proxy service and a group to own the log directory and files. You can accept the default user and group names or enter your own.

If you ever need to uninstall the proxy, run /opt/duoauthproxy/uninstall.

Open a root shell and run:

# /opt/duoauthproxy/bin/authproxyctl start

To ensure the proxy started successfully, run:

# /opt/duoauthproxy/bin/authproxyctl status

Authentication Proxy service output is written to the authproxy.log file, which can be found in the log subdirectory.

To stop and restart the Authentication Proxy, open a root shell and run:

# /opt/duoauthproxy/bin/authproxyctl restart

1. Log in to the Citrix NetScaler administrative interface.
2. Navigate to NetScaler Gateway → Virtual Servers in the left panel of the administrative interface.
3. Select your existing NetScaler Gateway Virtual Server, and then click Edit.
4. On the "VPN Virtual Server" page, click the plus sign (+) next to Authentication to add a new authentication policy.

5. On the "Choose Type" page, select the RADIUS policy and Secondary type from the drop-down menus and click Continue.

   

6. On the next "Choose Type" screen, click the plus sign (+) next to the "Policy Binding" → "Select Policy" box.

7. On the "Create Authentication RADIUS Policy" page, enter a name for the policy (like CitrixWebPortal), and then click the plus sign (+) next to the "Server" box to create a new RADIUS server for Duo authentication for web browser clients.

8. On the "Create Authentication RADIUS Server" page, enter the information for your Duo Authentication Proxy server:

   Name	CitrixWebPortal (or another descriptive name)
   Server Name or IP Address	The hostname or IP address of your Duo Authentication Proxy server.
   Port	The port configured for radius_server_iframe on the Duo Authentication Proxy (1812 in the example)
   Time-out (seconds)	60
   Secret Key	The RADIUS secret shared with your Duo Authentication Proxy
   Confirm Secret Key	The RADIUS secret shared with your Duo Authentication Proxy

   Citrix Gateway

   

9. Click Create to add the Duo CitrixWebPortal RADIUS server and return to the "Create Authentication RADIUS Policy" page.

10. Click the Expression Editor link on the "Create Authentication RADIUS Policy" page to add an expression with the following details:

    Expression Type	General
    Flow Type	REQ
    Protocol	HTTP
    Qualifier	HEADER
    Operator	NOTCONTAINS
    Value*	CitrixReceiver
    Header Name*	User-Agent

    

11. When the Server and Expression information is correct click Create to save the new CitrixWebPortal policy and return to the "Choose Type" page.

    

12. On the "Choose Type" page, make sure the new RADIUS authentication policy you just created is selected. Set the Priority under "Binding Details" to 100 and click Bind.

    

13. Binding the new authentication policy returns you to the "VPN Virtual Server" page. Click the plus sign (+) next to Authentication again to add a second new authentication policy.

14. On the "Choose Type" page, select the RADIUS policy and Secondary type from the drop-down menus and click Continue.

    

15. On the next "Choose Type" screen, click the Add Binding button.

16. Click the plus sign (+) next to the "Policy Binding" → "Select Policy" box.

17. On the "Create Authentication RADIUS Policy" page, enter a name for the policy (like CitrixReceiver), and then click the plus sign (+) next to the "Server" box to create a new RADIUS server for Duo authentication for Citrix Receiver or Workspace clients.

18. On the "Create Authentication RADIUS Server" page, enter the information for your Duo Authentication Proxy server:

    Name	Duo CitrixReceiver (or some descriptive name)
    Server Name or IP Address	The hostname or IP address of your Duo Authentication Proxy server.
    Port	The port configured for radius_server_duo_only on the Duo Authentication Proxy (18120 in the example)
    Time-out (seconds)	60
    Secret Key	The RADIUS secret shared with your Duo Authentication Proxy
    Confirm Secret Key	The RADIUS secret shared with your Duo Authentication Proxy
    Send Calling Station ID	Check this box in order to send the IP address of Citrix Receiver or Workspace clients to Duo

    

19. Click Create to add the Duo CitrixReceiver RADIUS server and return to the "Create Authentication RADIUS Policy" page.

20. Click the Expression Editor link on the "Create Authentication RADIUS Policy" page to add an expression with the following details:

    Expression Type	General
    Flow Type	REQ
    Protocol	HTTP
    Qualifier	HEADER
    Operator	CONTAINS
    Value*	CitrixReceiver
    Header Name*	User-Agent

    

21. When the Server and Expression information is correct click Create to save the new CitrixReceiver policy and return to the "Choose Type" page.

    

22. On the "Choose Type" page, make sure the new RADIUS authentication policy you just created is selected. Set the Priority under "Binding Details" to 110 and click Bind.

    

23. Verify that your new policies for Receiver or Workspace and browser clients are both listed and are bound in the correct order. Click Close to save the new policy configuration.

    

24. Verify that you have two RADIUS policies for Secondary Authentication and click Done.

25. Save all of the changes made to the running config.

1. Log in to the Citrix NetScaler administrative interface.
2. Navigate to NetScaler Gateway → Virtual Servers in the left panel of the administrative interface.
3. Select your existing NetScaler Gateway Virtual Server, and then click Edit.
4. On the "VPN Virtual Server" page, click the plus sign (+) next to Basic Authentication to add a new authentication policy.

5. On the "Choose Type" page, select the RADIUS policy and Secondary type from the drop-down menus and click Continue.

   

6. On the next "Choose Type" screen, click the plus sign (+) next to the "Policy Binding" → "Select Policy" box.

7. On the "Create Authentication RADIUS Policy" page, enter a name for the policy (like CitrixWebPortal), and then click the plus sign (+) next to the "Server" box to create a new RADIUS server for Duo authentication for web browser clients.

8. On the "Create Authentication RADIUS Server" page, enter the information for your Duo Authentication Proxy server:

   Name	CitrixWebPortal (or another descriptive name)
   Server Name or IP Address	The hostname or IP address of your Duo Authentication Proxy server.
   Port	The port configured for radius_server_iframe on the Duo Authentication Proxy (1812 in the example)
   Time-out (seconds)	60
   Secret Key	The RADIUS secret shared with your Duo Authentication Proxy
   Confirm Secret Key	The RADIUS secret shared with your Duo Authentication Proxy

   

9. Click Create to add the CitrixWebPortal RADIUS server and return to the "Create Authentication RADIUS Policy" page.

10. Click the Expression Editor link on the "Create Authentication RADIUS Policy" page to add an expression with the following details:

    Expression Type	General
    Flow Type	REQ
    Protocol	HTTP
    Qualifier	HEADER
    Operator	NOTCONTAINS
    Value*	CitrixReceiver
    Header Name*	User-Agent

    

11. When the Server and Expression information is correct click Create to save the new CitrixWebPortal policy and return to the "Choose Type" page.

    

12. On the "Choose Type" page, make sure the new RADIUS authentication policy you just created is selected. Set the Priority under "Binding Details" to 100 and click Bind.

    

13. Binding the new authentication policy returns you to the "VPN Virtual Server" page. Click the plus sign (+) next to Authentication again to add a second new authentication policy.

14. On the "Choose Type" page, select the RADIUS policy and Secondary type from the drop-down menus and click Continue.

    

15. On the next "Choose Type" screen, click the Add Binding button.

16. Click the plus sign (+) next to the "Policy Binding" → "Select Policy" box.

17. On the "Create Authentication RADIUS Policy" page, enter a name for the policy (like CitrixReceiver), and then click the plus sign (+) next to the "Server" box to create a new RADIUS server for Duo authentication for Citrix Receiver or Workspace clients.

18. On the "Create Authentication RADIUS Server" page, enter the information for your Duo Authentication Proxy server:

    Name	CitrixReceiver (or another descriptive name)
    Server Name or IP Address	The hostname or IP address of your Duo Authentication Proxy server.
    Port	The port configured for radius_server_duo_only on the Duo Authentication Proxy (18120 in the example)
    Time-out (seconds)	60
    Secret Key	The RADIUS secret shared with your Duo Authentication Proxy
    Confirm Secret Key	The RADIUS secret shared with your Duo Authentication Proxy
    Send Calling Station ID	Check this box in order to send the IP address of Citrix Receiver or Workspace clients to Duo

    

19. Click Create to add the CitrixReceiver RADIUS server and return to the "Create Authentication RADIUS Policy" page.

20. Click the Expression Editor link on the "Create Authentication RADIUS Policy" page to add an expression with the following details:

    Expression Type	General
    Flow Type	REQ
    Protocol	HTTP
    Qualifier	HEADER
    Operator	CONTAINS
    Value*	CitrixReceiver
    Header Name*	User-Agent

    

21. When the Server and Expression information is correct click Create to save the new CitrixReceiver policy and return to the "Choose Type" page.

    

22. On the "Choose Type" page, make sure the new RADIUS authentication policy you just created is selected. Set the Priority under "Binding Details" to 110 and click Bind.

    

23. Verify that your new policies for Receiver or Workspace and browser clients are both listed and are bound in the correct order. Click Close to save the new policy configuration.

    

24. Verify that you have two RADIUS policies for Secondary Authentication and click Done.

25. Save all of the changes made to the running config.

1. Create the custom theme directory as described in the Citrix document Creating a Custom Theme for the Logon Page. To gain shell access, SSH in to your Citrix NetScaler then type shell, then enter the commands.

   Example:

   $ mkdir /var/ns_gui_custom; cd /netscaler; tar -cvzf /var/ns_gui_custom/customtheme.tar.gz ns_gui/*
   

2. In the Citrix NetScaler administrative interface, navigate to NetScaler Gateway → Global Settings in the left panel of the administrative interface. Click Change global settings.

3. Click the Client Experience tab and change the UI Theme dropdown option to Custom. Click OK to apply the change.

4. Edit /var/ns_gui_custom/ns_gui/vpn/index.html to add two Duo modifications to the beginning of the file as shown here (changes are between the "DUO modification" and "end DUO modification" comments):

   <!-- DUO modification -->
   <!DOCTYPE html>
   <!-- end DUO modification -->
   <HTML><HEAD><TITLE>NetScaler Gateway</TITLE>
   <link rel="SHORTCUT ICON" href="/vpn/images/AccessGateway.ico" type="image/vnd.microsoft.icon">
   <META http-equiv="Content-Type" content="text/html; charset=UTF-8">
   <!-- DUO modification -->
   <META http-equiv="X-UA-Compatible" content="IE=edge">
   <!-- end DUO modification -->
   <META content=noindex,nofollow,noarchive name=robots>
   <LINK href="/vpn/images/caxtonstyle.css" type=text/css rel=STYLESHEET>
   <script type="text/javascript" src="/vpn/resources.js"></script>
   <script type="text/javascript" language="javascript">

5. Edit /var/ns_gui_custom/ns_gui/vpn/login.js to make the following modifications to the ns_showpwd_default() and function ns_showpwd_greenbubble() functions within the js file:

   • Add var DUO_ENABLED = true; on a new line before the var pwc = ns_getcookie("pwcount"); line.

   • Append the string && !DUO_ENABLED to both instances of pwc == 2.

   The edited ns_showpwd() and functions should look match the below example. Changes are in RED between the "// DUO modification" and "// end DUO modification" comments. Do not alter any of the text shown in white. If your editor shows you ^M control characters at line endings you should preserve them.

   function ns_showpwd_default()
   {
       // DUO modification
       var DUO_ENABLED = true;
       // end DUO modification
       var pwc = ns_getcookie("pwcount");
       document.write('<TR><TD align=right style="padding-right:10px;white-space:nowrap;"><SPAN class=CTXMSAM_LogonFont>' + _("Password"));
       // DUO modification
       if ( pwc == 2 && !DUO_ENABLED ) { document.write('&nbsp;1'); }
       // end DUO modification
       document.write(':</SPAN></TD>');
       document.write('<TD colspan=2 style="padding-right:8px;"><input class=CTXMSAM_ContentFont type="Password" title="' + _("Enter password") + '" name="passwd" size="30" maxlength="127" style="width:100%;"></TD></TR>');
       // DUO modification
       if ( pwc == 2 && !DUO_ENABLED ) {
       // end DUO modification
       document.write('<TR><TD align=right style="padding-right:10px;white-space:nowrap;"><SPAN class=CTXMSAM_LogonFont>' + _("Password2") + '</SPAN></TD> <TD colspan=2 style="padding-right:8px;"><input class=CTXMSAM_ContentFont type="Password" title="' + _("Enter password") + '" name="passwd1" size="30" maxlength="127" style="width:100%;"></TD></TR>');
       }
       UnsetCookie("pwcount");
   }
   
   function ns_showpwd_greenbubble()
   {
       // DUO modification
       var DUO_ENABLED = true;
       // end DUO modification
       var pwc = ns_getcookie("pwcount");
       document.write('<div class="field CredentialTypepassword"><div class="left"><label class="label plain"><SPAN>' + _("Password"));
       // DUO modification
       if ( pwc == 2 && !DUO_ENABLED ) { document.write('&nbsp;1'); }
       // end DUO modification
       document.write(':</SPAN></label></div>');
       document.write('<div class="right"><input class="prePopulatedCredential"  autocomplete="off" spellcheck="false" type="Password" title="' + _("Enter password") + '" name="passwd" size="30" maxlength="127"></div></div>');
       // DUO modification
       if ( pwc == 2 && !DUO_ENABLED ) {
       // end DUO modification
       document.write('<div class="field CredentialTypepassword"><div class="left"><label class="label plain"><SPAN>' + _("Password2") + '</SPAN></label></div><div class="right"><input class="prePopulatedCredential"  autocomplete="off" spellcheck="false" type="Password" title="' + _("Enter password") + '" name="passwd1" size="30" maxlength="127"></div></div>');
       }
       UnsetCookie("pwcount");
   }

1. Create the custom theme directory as described in the Citrix document Creating a Custom Theme for the Logon Page. To gain shell access, SSH in to your Citrix NetScaler then type shell, then enter the commands.

   Example:

   $ mkdir /var/ns_gui_custom; cd /netscaler; tar -cvzf /var/ns_gui_custom/customtheme.tar.gz ns_gui/*
   

2. Copy the CSS theme for your chosen base design (Green Bubbles or Default) to a "Custom" folder as shown on the Citrix page Customizing the User Portal: Manually creating a custom portal configuration page.

   Default Theme Example:

   $ cp -r /var/netscaler/logon/themes/Default /var/netscaler/logon/themes/Custom
   

   Green Bubbles Theme Example:

   $ cp -r /var/netscaler/logon/themes/Greenbubble /var/netscaler/logon/themes/Custom
   

3. In the Citrix NetScaler administrative interface, navigate to NetScaler Gateway → Global Settings in the left panel of the administrative interface. Click Change global settings.

4. Click the Client Experience tab and change the UI Theme dropdown option to Custom. Click OK to apply the change.

5. Make a backup copy of /var/ns_gui_custom/ns_gui/vpn/js/gateway_login_form_view.js and edit to add the following modifications to the rdx.gateway_login_form_view.prototype.make_view = function() function within the js file:

   • Add var DUO_ENABLED = true; on a new line before the if (pwc ==2) line.

   • Append the string && !DUO_ENABLED to the instance of pwc == 2.

   The edited portion of /var/ns_gui_custom/ns_gui/vpn/js/gateway_login_form_view.js should match the below example. Changes are in RED between the "// DUO modification" and "// end DUO modification" comments. Do not alter any of the text shown in white. If your editor shows you ^M control characters at line endings you should preserve them.

   password2.appendTo(left_pass2);
   enter_passwd2.appendTo(right_pass2);
   var pwc = ns_getcookie("pwcount");
   
   // DUO modification
   var DUO_ENABLED = true;
   // end DUO modification
   // DUO modification
   if (pwc ==2 && !DUO_ENABLED)
   // end DUO modification
   {
           form.append(field_pass2);
   }

With a Rewrite Policy

Rewrite policies can be bound to individual NetScaler Gateway virtual servers instead of globally to all virtual servers. Ensure that the Rewrite feature is enabled on your NetScaler by going to System → Settings → Configure Basic Features and verifying that the "Rewrite" feature is checked in the NetScaler administrative interface.

1. SSH in to your Citrix NetScaler.

2. Enter the following commands to create rewrite actions that will hide the second password field:

   add rewrite action rw_act_insert_var_DUO_ENABLED insert_before_all "HTTP.RES.BODY(120000).SET_TEXT_MODE(IGNORECASE)" "\"var DUO_ENABLED = true;\"" -pattern "if (pwc ==2"
   
   add rewrite action rw_act_insert_DUO_ENABLED insert_after_all "HTTP.RES.BODY(120000).SET_TEXT_MODE(IGNORECASE)" "\" && !DUO_ENABLED\"" -pattern "if (pwc ==2"

3. Next, enter the following commands to create rewrite policies that apply the actions created in step #2 to the gateway_login_form_view.js file:

   add rewrite policy rw_pol_insert_var_DUO_ENABLED "HTTP.REQ.URL.CONTAINS(\"gateway_login_form_view.js\")" rw_act_insert_var_DUO_ENABLED
   
   add rewrite policy rw_pol_insert_DUO_ENABLED "HTTP.REQ.URL.CONTAINS(\"gateway_login_form_view.js\")" rw_act_insert_DUO_ENABLED

4. In the Citrix NetScaler administrative interface, navigate to NetScaler Gateway → Virtual Servers. Click on the virtual server where you added Duo secondary authentication to access its properties page.

5. Scroll down to the Policies section and click the plus sign (+) to add the Duo rewrite policies.

6. On the "Choose Type" page, select Rewrite from the "Choose Policy" drop-down and Response from the "Choose Type" dropdown. Click Continue.

   

7. On the next "Choose Type" page, click on the "Select Policy" Click to select field in the "Policy Binding" section of the page. This shows you the list of rewrite policies you created from the shell earlier. Select the rw_pol_insert_var_DUO_ENABLED policy and click the Select button to return to the "Choose Type" page.

8. When back on the "Choose Type" page, change the "Goto Expression" to NEXT. You usually do not need to change the "Priority" from the default value assigned. Click the Bind button to bind the first rewrite policy to your virtual server.

   

9. Click the plus sign (+) in the "Policies" section again to bind the second Duo rewrite policy. Once again, select Rewrite from the "Choose Policy" drop-down and Response from the "Choose Type" dropdown and then click Continue.

   

10. On the "Policy Binding page, click the Add Binding button. Click on the "Select Policy" Click to select field to bring up the list of policies. Select the rw_pol_insert_DUO_ENABLED policy and click the Select button to return to the "Policy Binding" page.

11. When back on the "Policy Binding" page, leave the "Goto Expression" set to END. You usually do not need to change the "Priority" from the default value assigned, just make sure that it has a greater number than the priority vaule assigned to the first bound policy (e.g. if the first one was priority 100 the second policy priority should be 110). Click the Bind button to bind the second rewrite policy to your virtual server.

    

12. Now you should see both "DUO_ENABLED" rewrite policies listed in the correct order (rw_pol_insert_var_DUO_ENABLED before rw_pol_insert_DUO_ENABLED). Click Close to finish.

    

13. Verify that you have two additional Rewrite policies listed under "Response Policies" and click Done.

14. Save all of the changes made to the running config.

15. Reboot the device.

With JS File Editing

This method requires applying a custom theme at the global level, so it applies the Duo customizations to all your NetScaler Gateway virtual servers.

1. Create the custom theme directory as described in the Citrix document Customizing the User Portal - A Note on Older Portal Customizations. To gain shell access, SSH in to your Citrix NetScaler then type shell, then enter the commands.

   Example:

   $ mkdir /var/ns_gui_custom; cd /netscaler; tar -cvzf /var/ns_gui_custom/customtheme.tar.gz ns_gui/*
   

2. Copy the CSS theme for your chosen base design (X1, Green Bubbles, or Default) to a "Custom" folder.

   Default Theme Example:

   $ cp -r /var/netscaler/logon/themes/Default /var/netscaler/logon/themes/Custom
   

   Green Bubbles Theme Example:

   $ cp -r /var/netscaler/logon/themes/Greenbubble /var/netscaler/logon/themes/Custom
   

   X1 Theme Example:

   $ cp -r /var/netscaler/logon/themes/X1 /var/netscaler/logon/themes/Custom
   

3. In the Citrix NetScaler administrative interface, navigate to NetScaler Gateway → Global Settings in the left panel of the administrative interface. Click Change Global Settings.

4. Click the Client Experience tab and change the UI Theme dropdown option to Custom. Click OK to apply the change.

5. Make a backup copy of /var/ns_gui_custom/ns_gui/vpn/js/gateway_login_form_view.js and edit to add the following modifications to the form.append(title,field_username,field_pass); section within the js file:

   • Add var DUO_ENABLED = true; on a new line before the if (pwc ==2) line.

   • Append the string && !DUO_ENABLED to the instance of pwc == 2.

   The edited portion of /var/ns_gui_custom/ns_gui/vpn/js/gateway_login_form_view.js should match the below example. Changes are in RED between the "// DUO modification" and "// end DUO modification" comments. Do not alter any of the text shown in white. If your editor shows you ^M control characters at line endings you should preserve them.

   field_pass.append(left_pass,right_pass);
   password1.appendTo(left_pass);
   enter_passwd_dummy.appendTo(right_pass);
   enter_passwd.appendTo(right_pass);
   field_pass2.append(left_pass2,right_pass2);
   password2.appendTo(left_pass2);
   enter_passwd2_dummy.appendTo(right_pass2);
   enter_passwd2.appendTo(right_pass2);
   // DUO modification
   var DUO_ENABLED = true;
   // end DUO modification
   // DUO modification
   if (pwc ==2 && !DUO_ENABLED)
   // end DUO modification
   {
       form.append(field_pass2);
   }