From: Adam Back <aba@dcs.ex.ac.uk>
Date: Fri, 9 Oct 1998 04:36:48 +0800
To: fod@brd.ie
Subject: HTTPS:// hyperlink spoofing (Re: propose: `cypherpunks license')
In-Reply-To: <361CE49F.C858A2CE@brd.ie>
Message-ID: <199810081956.UAA14156@server.eternity.org>
MIME-Version: 1.0
Content-Type: text/plain




Frank O'Dwyer writes:
> In fact, it's funny that you tout a "secure web server" as "strong
> crypto" since in that context SSL is usually vulnerable to being
> end-run by web spoofing. Oops. Oh well, it uses strong crypto, so it
> must be good.

As to your web spoofing comments, (which I just read, see:

	http://www.brd.ie/papers/sslpaper/sslpaper.html

) this is a specific instance of the mapping problem, ie. how do you
know that the web page you ended up at belongs to the company you
heard about, or found by a web search or hypertext link on someones
page.  The hierarchical CA model says that you believe it is so
because the CA tells you it is so.

(Franks comment on the (in)security of following an unsecured
hypertext link was that the unsecured hypertext reference could be
modified in an active attack to point to their own (secured) page, and
then accept your payment instead of the company you intended to buy
from).

Netscape 4 behaves in the following way, depending on the situation.

1) the site is using a cert signed by a CA the browser does not
recognise

In this case it shows you through a nice series of dialog box (in
microsofts wizard style), which is quite useful in explaining the
issues.

2) the site is using a cert signed by a CA the browser does recognise

In this case the browser does one of two things depending on whether
you are currently viewing a secure page, or not:

a) from insecure page shows dialog box telling you you are visiting a
secured page, and to click security for more info (clicking security
will show you the cert content, company name, CA details).

b) from secure page shows _nothing_, just goes right into the page
without further comment!  (default setup, freshly installed netscape
4.04 / linux).

(I tried this going from c2net, then typing in cypherpunks.to (Lucky's
site)), if you do click on security button you then get the cert info
again.

  www.cypherpunks.to
  Cypherpunks Jihad
  Cypherpunks Tonga
  Cyberspace, none, TO

Part b) I view as a problem because it doesn't even by default show
you anything.  They could at least present the click through.  They
seem to be treating the secure / insecure as a binary state.

Could someone verify this in later revisions of netscape?

The basic problem though is that even if you do the `nagging dialog
box' click throughs with option to disable, chances are most people
will disable them, because they will get annoyed.

The simplest way to reduce this risk would be for a company to secure
all of it's web pages.  But this isn't going to do that much, because
people often don't know the web page URL.  (Frank notes all this).

Also spoofed company names which look similar to companies in real
life also are possible, for example there was a case of a BT Telekom
or something trying to spoof customers into parting with their money.
This is a problem with gullible consumers.

But if people started from print media advertisement, and typed in the
URL and the URL was signed by a CA then they are at least as secure as
the non-net situation.

In general though, I think there is a solution to this problem:
encrypt all the pages.

The other hard problem is now that you know you are visiting the web
page of FooBar Inc, as attested by Thawte (or whoever), how do you
know that FooBar won't take your money and run.  This is a general
reputation question, with the normal solutions.  If it's an expensive
item, you perhaps check them out, ask around for others experiences,
check with any reputation ratings services (trade groups, etc).

Adam
-- 
print pack"C*",split/\D+/,`echo "16iII*o\U@{$/=$z;[(pop,pop,unpack"H*",<>
)]}\EsMsKsN0[lN*1lK[d2%Sa2/d0<X+d*lMLa^*lN%0]dsXx++lMlN/dsM0<J]dsJxp"|dc`