NetScaler Cipher Lists - 2017 Edition with ChaCha20 Support

Citrix did release a new NetScaler Release/Firmware in December 2017 with Support for a subset of the ChaCha20 Ciphers, so that means I had to update my Cipher Lists. The NetScaler Firmware starting to support ChaCha20 is 12.0-56.20 and this time the ChaCha20 Ciphers are only supported on VPX Appliances. Let's hope that Citrix will add MPX Support and the Rest of the ChaCha20 Ciphers in a subsequent NetScaler Release.

So here are the updated Cipher Groups:

  • Modern Compatibility:
  • Intermediate Compatibility:

Currently the Intermediate Cipher Group is still vulnerable to the ROBOT Attack because of the Ciphers starting with TLS_RSA. I suggest using the Modern Compatibility Cipher Group to remediate against the ROBOT Attack.

Perfect Forward Secrecy and NetScaler MPX Revisited

My last Blogpost regarding Perfect Forward Secrecy on NetScaler got a lot of Comments and in the meantime Citrix released a new NetScaler Firmware Versions ( which now enables us to use ECDHE Ciphers even on "low end" NetScaler MPX Models like the MPX 5500.

With the new Firmware it's now possible to enable PFS for all modern Clients/Browser and receive an A+ in the SSLLabs Test.

Okay, let's start:

First step is to create a new Cipher Group where we will bind all the new Ciphers we want and need.

Unfortunately changing the Order via the NetScaler GUI is not very user-friendly (Hey Citrix, please enable us to easily change the Cipher Order) so I resorted to the Command Line. Below are the commands to create a new Cipher Group called "THEN-High" and bind the Ciphers in a preferred Order (I'm open for Discussions on the Order and Ciphers if you disagree or got a better Order):

Important: Make sure to order the Ciphers in the preferred order (thanks again to David Chivers for pointing this out) or you may not get Forward Secrecy to work on some Clients/Browser.

Cipher List for MPX/SDX and VPX (starting with Build 11.0-65.31) Appliances:

Legacy Cipher List for MPX/SDX and VPX (starting with Build 11.0-65.31) Appliances (includes Support for WinXP, Java and Android 2.x):

Cipher List for VPX starting with Build 10.5-57.7 up to 11.0-64.34:

Legacy Cipher List for VPX Builds starting with Build 10.5-57.7 up to 11.0-64.34 (includes Support for WinXP, Java and Android 2.x):

Since NetScaler 11 Citrix now seems to enforce compatible Ciphers on the VPX Platform.

All SHA2 and GCM Cipher Suites are not (yet?) supported on the VPX. Since NetScaler Build 11.0-65.31 the VPX now supports all AES-GCM/SHA2 Ciphers. Hooray!

And thats what it looks like in the GUI:

Don't forget to create a Diffie Hellmann Key (2048bit Keysize recommended) and configure it under the SSL Parameters on the vServer (or use the new SSL Profiles Feature). You can find a detailed How-To in my old Blogpost here.

The next Step is to bind the newly created Cipher Group to the vServer. When I did this via the GUI my Cipher Order wasn't honored (Bug? Anyone else?) so again I needed to use the Command Line:

bind ssl vserver <vServerName> -cipherName THEN-High

(Update: With the 10.5-57.7 NetScaler Build this Bug has been fixed by Citrix! You can now use the GUI to bind the Cipher Group.)

Don't forget to bind ECC Curves on the vServer or you won't be able to use the newer ECDHE Ciphers. I recommend binding the Curves P_256, P_384 and P_521.

bind ssl vserver <vServerName> -eccCurveName P_256 P_384 P_521

Let's take a look in the GUI (note the correct Cipher Order):

After configuring everything correctly you should check it using the SSLLabs Test. Here is my Result with the latest Firmware and the described Settings:

(Update: With the 10.5-57.7 NetScaler Build you can now get the A+ Rating in the SSLLabs Test because Citrix added TLS_FALLBACK_SCSV Support)

As always feel free to leave a Comment.


#1 - 19.05.2015 - Cipher Reordering Bug has been fixed by Citrix with the 10.5-57.7 NetScaler Build
#2 - 19.05.2015 - Note regarding TLS_FALLBACK_SCSV Support in the 10.5-57.7 NetScaler Build
#3 - 22.05.2015 - Added specific Cipher List for NetScaler VPX with the 10.5-57.7 NetScaler Build
#4 - 21.06.2015 - Added Note regarding binding ECC Curves.
#5 - 30.06.2015 - Updated MPX/SDX Cipher List with some new Ciphers for broader Client Support.
#6 - 01.07.2015 - Changed VPX Cipher Suite for NetScaler 11 regarding the support of SHA2 and GCM Cipher Suites
#7 - 10.09.2015 - Added MPX/SDX Cipher List without DHE Ciphers (Logjam)
#8 - 02.03.2016 - Added 2 new Ciphers for the VPX Platform Cipher Group
#9 - 04.03.2016 - moved Code to GitHub Gists for Versioning and Change Tracking
#10 - 22.03.2016 - Since NetScaler 11.0-65.31 the VPX now supports all AES-GCM/SHA2 Ciphers. Hooray!

Enable Forward Secrecy and Secure Ciphers on a NetScaler MPX

See my new Blogpost for an updated Configuration with full ECDHE Cipher Support

I recently "hardened" our public facing NetScaler vServers (mainly our Access Gateway) and thought I'd share the Steps I took to accomplish that.

I wanted to enable/use Perfect Forward Secrecy (PFS) on our Access Gateway vServer and only use strong and secure Ciphers (no more RC4 with TLS 1.x).

  • Create a new Cipher Group with secure Ciphers

So let's create a new Cipher Group on the NetScaler. You can do this unter the "Traffic Management" -> "SSL" -> "Cipher Group" Node in the GUI.

 Name your new Cipher Group and add the following Cipher Suites:

  • TLS1-DHE-RSA-AES-128-CBC-SHA (provides Forward Secrecy (PFS) for some Browsers)
  • TLS1-DHE-RSA-AES-256-CBC-SHA (provides Forward Secrecy (PFS) for some Browsers)
  • TLS1-AES-128-CBC-SHA
  • TLS1-AES-256-CBC-SHA
  • SSL3-RC4-SHA (remove if you don't need SSL3 Compatibility for WinXP and only want to use TLS)
  • SSL3-DES-CBC3-SHA (use this Cipher to enable IE8 on WinXP to access your vServer)

Your newly created Cipher Group should look like this:

  • Create a Diffie Hellman Key (DH) for PFS

The first step is to create a Diffie Hellman Key under the Traffic Management -> SSL Node.

I created a 1024-bit DH Key because a larger DH Key will decrease the SSL Performance of the NetScaler and I'm not sure if the SSL Accelerator Card in the MPX 5500 supports DH Keys larger than 1024 (maybe a Citrite can enlighten us in the Comments). It's currently a compromise between Security and Performance.

Update: Since NetScaler Firmware 10.5 DH Keys with 2048 Bits are supported to be offloaded to the SSL Accelerator Cards in MPX Appliances. So use a 2048 bit DH Key instead of a 1024 bit Key if possible.

  • Enable the new Cipher Suite and DH Key on your vServers

The last step is to enable the new Cipher Suite and the DH Key on the vServers you want to provide PFS. Let's open up a vServer (your Access Gateway vServer for example) and configure it:

First let's go into the Ciphers Menu. Clear out everything under "Configured Cipher Groups" and "Configured Ciphers" and only add your newly created Cipher Group (called THEN-Default in my example). It should look like this:

Now let's pop into the SSL Parameters Menu from your vServer. Make sure to tick the "Enable DH Param" Box and select the newly created DH Key File. Also make sure to use a fairly high number under the "Refresh Count", I choose a value of 1000. When finished it should look something like this:

Now save your running config and go ahead and test your public vServer with the SSL Labs Test Suite. When configured correctly you should see the following results from the SSL Labs Test:

The green FS next to a Browser/OS Combination means PFS can and will be used when connecting to your vServer, just the way we like it.