How to start a Citrix ADC / NetScaler WAF Project, Part 5: Field Formats


This is the fifth part of this blog. Part Part 1 2 3 4 5 Form-fields are a major gate to send malicious data to a web-server. It’s obvious, a website programmer does not want to do input validation twice, on the user and on the server-side. What could happen? If everything is tested on the client-side, data arriving on the server-side has to be good. Even worse: If an input field does not...

Citrix ADC / NetScaler and TLS 1.3


Last change: February 4th 2021. Thanks to Dirk Bautz! This is the 2nd part to my article “Which ciphers to use on a Citrix ADC /NetScaler?” This one had been about TLS versions up to 1.2 only. Moving from TLS 1.2 to TLS 1.3 on an existing Citrix ADC ( NetScaler) may be a big step with some obstacles to overcome. It needs some investigation. The problem? It seems to be easy: Just tick...

A simple way for a Citrix ADC (NetScaler) to respond with a 404 not found


I am a big fan of cheating if it comes to security. Giving wrong answers to questions may be misleading and will direct attackers into the wrong direction. This will cost time and, at the same time, rise the risk of being caught red-handed. If someone attacks a website, he has to be discrete and fast. Discrete to not get trapped, quick to be long gone in case the owner learns about the attack. So...

How to start a Citrix ADC / NetScaler WAF Project, Part 1: General


This is the forth part of this blog. Part Part 1 2 3 4 5 I am currently working on a Citrix ADC (NetScaler) WAF project. It’s a big international enterprise, security is of some concern to them. So everything hould be pretty much straight forward? Well, it never is. So, how to begin? Well, I almost forgot to mention: I have to introduce myself to the customer. “Hi, I’m Johannes...

AAA-default settings changed with Citrix ADC (NetScaler) 13 built 41.20


Yesterday I upgraded to NetScaler 13 built 41.20. Everything worked fine. No problems. But out of a sudden, my Exchange deployment failed to authenticate (I did it following Julian Mooren’s outstanding deployment guide). I did some further investigation and found all my other AAA servers don’t authenticate, even though the outcome of authentication requests was positive. I always saw...

Citrix ADC (NetScaler) 13: Pre-authenticating to TCP based services


photo by geralt (pixabay.com) last update: January 5th 2020 Recently I had to find a solution to block all connections to a TCP based service (SSH, TCP port 22), except of connections from IP addresses that pr-eauthenticated using a AAA vServer. This is something, most firewalls can do, but a Citrix ADC / NetScaler can’t. Ok, it can do, or would you think, I’ll write a blog about me failing...

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