full-disclosure - OSX Safari "PAC" url DoS

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Date: Wed Jun 22 01:06:15 2005
From: mac at msg.net (mac@....net)
Subject: OSX Safari "PAC" url DoS

Tiger's System Preferences set to fetch a PAC File URL from a web server
acts as a denial of service attack against the server where PAC is hosted.

Flawed PAC retrieval code in Safari 2.0 (412) generates HTTP requests
to the PAC URL many times for each page browsed, drowning your PAC server
with "GET" requests. Finally the web server may crash due to load, after
which the browser is unable to browse anywhere.

Refusing requests showing a UserAgent of "CFNetwork/1.1" can help
protect your PAC web server against this denial of service, as will
manually resetting all Tiger workstations back to manual proxy.

Thanks to I. Claymore and S. Karel for assistance in confirming this flaw.

mac@....net