Users are unable to upgrade Apple iOS via iTunes. They can download the upgrade package but upgrade fails and iTunes has an error message.
This issue still occurs even if you bypass authentication for the iTunes/11.1 user agent.
The iTunes application does a POST request after downloading the upgrade package to http://gs.apple.com and the user-agent is set as "InetURL/1.0", which does not match the authentication bypass rule set for User-Agent: iTunes/11.1
To resolve the issue, bypass authentication for User-Agent: InetURL/1.0.
In the Visual Policy Manager, create a Request Header Object in the Web Authentication Layer as shown below: