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How to log requests that would be dropped by "Drop invalid HTTP Requests"

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For security reasons, I would like to activate "Drop invalid HTTP requests" in the nshttp_default_profile.

Because there are already several content switches and loadbalancing vservers configured on our appliance, I would like to log the affected requests.

Best option would be to log potentially dropped requests before activating the setting.


I tried a rewrite policy as well as a responder policy with "http.req.is_valid.not", bound them globally and then sent invalid requests. I know the requests are invalid, because when setting "drop invalid http requests", they are actually dropped.

But the hit counter of both policies does not count up.


Did I do something wrong? Is this the wrong approach? Any other ideas?



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it's a request generated with Burp Suite which is able to trigger a HTTP Request Smuggling attack.

Setting "Drop invalid HTTP Requests" prevents this attack, but my policies with "http.req.is_valid.not" are not triggered.

I think the main reason why the request is dropped is because of the content-length set in the header does noch match the real content length (what makes the attack possible)

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  • 1 month later...

Hi Nils

The profile is dropping invalid requests before they are processed by the responder engine. 
If you do the VIP (or CS) statistics you will find the counter of invalid requests dropped and the rate. 
For this reason the policy has no hits. 


Regarding Http smuggling, you can mediate this by applying the ns_http_default_strict_validation profile.
There is a citrix guide here:


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Thinking about it
I don't know at what level of the flow the policies on SYSTEM GLOBAL intervene. But you can give it a try
You can try to configure a syslog policy with external server including the "Debug" level (I suggest putting "ALL") and binding the policy to SYSTEM GLOBAL


Then see in the logs that arrive if there are the details you are interested in

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