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Safari exhibited what we regard as a severe and unacceptable bug with regard to CAS login. The LoginTicket gymnastics and special treatment of Safari are is in response to that bug.
The bug
For any sufficiently old enough version of Safari, there can be no redirects at all. Back when we first discovered this bug, we tried out HTTP 30x redirects, <META HTTP-EQUIV="refresh" ...>, and Javascript window.location="...", and found that Safari did not behave in any of those cases. The exact behavior was:
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I don't know exactly which version of Safari fixed this bug, but you won't see this behavior in new versions of Safari.
The special treatment
CAS 2.0.12 does not redirect from CAS to the Service with a ticket. It instead paints a screen on which users must manually click a link to head along to the service with the ticket.
To be safe, you should do exactly what the current CAS distribution does – if it's Safari, display the "Click here to continue" screen. Take a look at our goService.jsp.