When passing HTML traffic through Sentry to a web server, the web server may respond with an error or issue a redirect upon receiving the request from Sentry. Often this is caused by the web server failing validation of the User Agent HTTP Request Header.
The default behavior in Sentry is to overwrite the client's User Agent header, replacing the value with "Forum Systems". With web services traffic (SOAP, XML, etc..) this is typically not a problem. However, with HTML traffic the web servers often validate the incoming User Agent header to determine what type of browser is accessing the site.
An example of a User Agent HTTP Header set by a browser (in this case Chrome):
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/33.0.1750.154 Safari/537.36
The User Agent header on the request passed through Sentry with default settings:
User-Agent: Forum Systems
To resolve the problem, configure Sentry to proxy the client's User Agent header by enabling the "Proxy Client's User Agent" option.
This change can be System-wide or Policy specific
- Global change
As seen in the following image this change is applied on the System>>Settings>>System screen of the WebAdmin interface. Please note that this option affects all policies on the system:
2. Policy change
This change takes place on the Remote Network Policy of the content policy in question as shown in the following image: