Building a NetScaler Gateway from Scratch (SSL Labs A Grade)

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I was recently asked about building a NetScaler Gateway from scratch for ICA only connections.  I know this can be done using a wizard but if you want to know a little more about how it all hangs together or to name things how you want instead of the names given by the wizards then a manual build is the way to go.  The following article will walk you through building your NetScaler Gateway from the ground up and ending with a secure, working remote access solution.

This article assumes that you have LDAP Bind Credentials, All your SSL Certificates to hand and also have the appropriate firewall / NAT rules in place to access your gateway from the outside world.

The way I like to build a NetScaler Gateway is a similar approach to how I like to cook.  Get everything ready first then put it all together at the end.  I may seem that things are a little weird at first but not creating the gateway and building it out from there but trust me – it will all work in the end !

To have a working NetScaler thats secure you will need the following

• LDAP Methods (I know you should use 2Fa but in this case i am only binding LDAP)
• A Diffie Hellman Key
• Certificates
• A Custom Cipher Group
• Session Policies and Profiles for Web and Receiver access
• A Secure Transport Session Rewrite Policy
• Custom SSL Settings for SSL3
• TCP Profile for XenDesktop
• Secure Renegotiation only enabled for Secure Connections
• Secure Ticketing in place

So, lets get going.

LDAP

First log into your NetScaler and Navigate to the LDAP Policies shown below

Create a new policy and fill out the server and bind details.  Click on test connection to ensure that the connection is working correctly

Once connected fill out the Other Settings.  This is where you define what the user will log into the NetScaler Gateway with.  I have used SAMAccountName below but you could easily use UPN by defining it here.

Click on ok and you will see the LDAP Server Policy Created.

Next create an Authentication Policy with the value of ns_true and bind it to the LDAP server you have just defined

Thats it for LDAP – you “should” have a working LDAP server now.  To test this head over to the Authentication Dashboard

You should see your server shown there with a status of Up

Diffie Hellman

Navigate to the SSL section of the NetScaler shown below

On the right under Tools click on Create Diffie Hellman Key

Give the DH key a file name located on the NetScaler and set the parameter size to 2048

Click on Create to create the key

Certificates

Navigate to Server Certificates shown below

Click to Install a new certificate.  Provide your Cert and Key File and import it into the NetScaler

You should see your external certificate listed and valid

Next install the Root and Intemediary Certificates for your external certificate and your internal CA if applicable

In my case I have imported my Start SSL int and root as well as my internal root CA

If you look at my external certificate you can see that there is an intermediary certificate in-between the public cert and the root.

Navigate to the public certificate and right click to link it to the intermediary.

NOTE: Do not link the intermediary to the root as this will cause SSL Labs to see a anchor in the certificate chain

Custom Cipher Group

Next you will need to create a custom cipher group to apply to your gateway.  This will ensure that there are no insecure ciphers available externally from your gateway.

These ciphers were taken from Anton’s blog post about securing your SSL VIPS on NetScaler.  This can be found here.

Navigate to the Cipher Groups

Click to add a cipher group and assign the following ciphers for a VPX

• TLS1-ECDHE-RSA-AES256-SHA
  TLS1-ECDHE-RSA-AES128-SHA
  TLS1-DHE-RSA-AES-256-CBC-SHA
  TLS1-DHE-RSA-AES-128-CBC-SHA
  TLS1-AES-256-CBC-SHA
  TLS1-AES-128-CBC-SHA
  SSL3-DES-CBC3-SHA

Session Policies

Next you have to create the Session Policies that you will assign to the NetScaler Gateway.  A session policy are the settings that are applied to the client based on the method they are connecting to the gateway.  In this case I am going to provide settings for Native Citrix Receiver and the Web Client.

Navigate to Session Policies

First I will create 2 profiles – one for Native and one for Web

Click to create a Native Client Session Profile and follow the settings shown below

NOTE: On this section change the StoreFront service to match the StoreFront service you are providing internally

Click on create then add another Session Profile for the Web Client following the settings below

NOTE: On this section change the StoreFront service to match the StoreFront service you are providing internally, also note that you do not need the Account Services Address

Click Create and you will see 2 new session profiles created

Next you need to define the Session Policies and bind then to the profile.  The Session Policy is where you check the HTTP Header and determine what client the user is using and apply the relevant session profile

Create a Policy for Native using the following as the expression

REQ.HTTP.HEADER User-Agent CONTAINS CitrixReceiver

and bind this to your native profile

Next create a policy for web using the following as the expression

REQ.HTTP.HEADER User-Agent NOTCONTAINS CitrixReceiver && REQ.HTTP.HEADER Referer EXISTS

and bind this to your web profile

Secure Transport Session Header

You will now create the Secure Transport Session header to be put into your NetScaler Gateway sessions to abide by SSL Labs best practice

Navigate to Rewrite Actions and create a new action

Fill out the details as shown below

Then create a Rewrite Policy

and fill out as shown below binding it to your new Rewrite Action

So thats the basic elements done to make your NetScaler Gateway, lets put it all together

NetScaler Gateway

First navigate to NetScaler Gateway and add a new Virtual Server

Give it a name, IP Address in your DMZ and a Port you want to run the NetScaler Gateway on then click to expand More Settings

Select ICA Only from the settings displayed and click OK

Next you need to bind your Certificates you imported earlier

Click on the Server Certificate and bind your public SSL Cert and also on CA Certificates and bind the intermediarys and root CA’s for the public and internal CA’s

Next comes Authentication.  Click to add an authentication method to the NetScaler

Select LDAP and Primary

Bind your LDAP Policy you created earlier and click ok

Done

Nothing in this case for advanced authentication

Next click to edit the SSL Parameters as we need to enable Diffie Hellman and disable SSL 3

Enable Diffie Hellman and select the key file from the NetScaler you created earlier as well as setting the refresh time, also disable SSL 3

Next click to edit the Ciphers and remove the Default Group

Bind your new custom Cipher Group and click ok

NOTE: You can ignore this error from the GUI if you receive it

Next you will specify the TCP Profile to use ont he gateway, click to edit the profiles

Select the XA_XD profile from the list provided

Now you will bind the 2 session policies to the NetScaler Gateway

Click to add a policy

Select Session

Bind one of your profiles with a priority of 100

Then click to bind the other profile also as priority 100.  Once done you should see both profiles on the gateway

Next you will add the STS Rewrite policy to the Gateway.  Click to add another policy but select Rewrite from the drop down list

Select your SES Header Policy you created earlier

Click Bind

Next you need to specify a Secure Ticketing Authority for the Gateway

Click the + next to Published Applications on the right

Click on No STA Server to add your STA Server

Specify the HTTP or HTTPS path to the Secure Ticketing Authority

Click Bind

To check the STA is working click on the 1 STA Server link and it should show the STA as green

 

Finally navigate to Traffic Management and SSL and click on Advanced SSL Settings on the right

Change Deny SSL Renegotitation to NONSECURE

Don your NetScaler Gateway should show as UP and should be ready to test!

Lets Access the NetScaler Gateway!

Run a SSL Labs Test against the URL

Log into the Gateway – NOTE I am using SAMAccountName as this is what i specified in my LDAP policy

Display the StoreFront Apps

Launch a Desktop via the NetScaler Gateway

Thats it, all the details on how to build a basic NetScaler Gateway for ICA Connections.  Hope this helps some of you out especially the guy who asked me to write this article – you know who you are.

Have Fun Building!

b@m #NetScalerRocks