On Thursday, August 18, 2005 05:10:17 PM -0700 Nicholas Staff
<nick(_dot_)staff(_at_)comcast(_dot_)net> wrote:
>>
>>> yes , thats exactly what it does , they call it "Portal-Guided
>>> Entrance" on port :80 and 443.
>>
>> Does this work on port 443? I would assume the SSL security checks
>> wouldn't accept this.
>
> I believe the FQDN is not encrypted, though the part of the
url after the
> FQDN is (so one could redirect based on https:// and/or
specific FQDN's
> (whether http or https).
That's beside the point. According to RFC 2818 section 3.1,
where a hostname
is given in an https: URL, the client MUST check this
hostname against the
name in the server's certificate. This check will fail if the
connection is
redirected to a non-transparent proxy (assuming that the web
browser is
complying to RFC 2818, no CA in the browser's trusted CA list has been
compromised, and the crypto is not broken).
The redirection or hijacking happens way before the browser gets involved
(much lower layer). My guess (again just one possibility)is that the
portal is spoofing the address of the original destination and either
sending a reset or some kind of redirect.
Sure. But the result is that the thing the browser ends up with a
connection to is not the server the user intended to talk to. Since the
fake server doesn't have the real server's private key, it cannot
successfully complete an SSL negotiation with the client using the real
server's certificate. And unless some CA has been compromised, no other
certificate will have a server name which matches the one the user typed,
which will result in at least a warning, if not the browser aborting the
connection entirely. The result is that the user doesn't get to talk to
either the real site _or_ the redirected one.
The SSL protocol is designed specifically to protect against this attack.
-- Jeffrey T. Hutzelman (N3NHS) <jhutz+(_at_)cmu(_dot_)edu>
Sr. Research Systems Programmer
School of Computer Science - Research Computing Facility
Carnegie Mellon University - Pittsburgh, PA
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