Date: Thu, 1 Sep 2005 13:19:15 -0600
From: "Mark Senior" <Mark.Senior@....ab.ca>
To: <liudieyu@...rella.name>
Cc: <bugtraq@...urityfocus.com>
Subject: RE:  Re: secure client-side platform


Your attack tree below is of the form:
 A and ( B or C or D) and E

I submit a simpler one of the form:
 A or (B and C)

A - there is an exploitable vulnerability (in the remote-code-execution
sense) in the DNS response handling code on your livecd.  You send out a
query, a malicious response reaches you before the real one & gets
through the firewall, and you're done.

OR
	B - There is an exploitable vulnerability in the public key
verification process in the browser on your livecd.  This vulnerability
could be a remote-code-execution vulnerability, or it could be limited
to causing the browser to present a certificate as legitimate when it
isn't. AND

	C - The attacker is able to redirect you to a malicous https
server by e.g. DNS, ARP, or routing protocol attacks somewhere upstream.

C should be pretty much taken as a given, otherwise why bother with SSL
at all?

Regards
Mark


> -----Original Message-----
> From: liudieyu umbrella.name [mailto:liudieyu umbrella.name] 
> Sent: August 31, 2005 21:25
> To: bugtraq@...urityfocus.com
> Subject: Re: secure client-side platform
> 
> 
> 
> #1, we are talking about how to do critical secret 
> communication in a secure way, right? so forget about those 
> putting win9x 24/7 on DSL ... let them continue contributing 
> to the spam and zombie business ;-)
> 
> imagine i'm going to access an e-gold acocunt of $1M ... 
>     first i unplug the network cable and remove harddrive;
>     then boot with a clean livecd;
>     later start firewall and then plug the network cable;
>     run "mozilla-firefox about:blank";
>     directly go to HTTPS-secured website;
>     once done, reboot.
> i cannot figure out what could go wrong in the above process ...
> 
> clean read-only OS is a solution against "once owned, stay 
> owned" (trojan stays in system until next format)
> 
> it does not solve the problem of the vulnerabilities in 
> client software like mozilla (as joxean and keith suggested)
> 
> if we only have encryption-secured connection to trusted 
> server, assuming enemy do not have control over the trusted 
> server itself, our computer can only be compromised if:
>      * enemy have total control over the communication channel
>        between us and the trusted server
>      * AND 
>        - there is a vulnerability in the certificate/publickey 
>          verification process of client software like mozilla
>        - OR the mathematic foundation of publickey-privatekey 
>          sign/encrypt trick got a problem.
>        - OR we clicked YES in the 
>          certificate-is-invalid-continue-or-not dialog
>      * AND 
>       enemy got vulnerability to exploit after going thru the 
>       certificate verification process taken in our side.
> 
> chances are rare, hum? the very last sentence of my trooseid 
> article is:
> Never touch any not-encryption-secured connection during a 
> secret-communication op.
> you read it, right?
> 
> Q: can you really trust Google?
> A: it's really up to you which server you choose to store and 
> transfer encrypted secrets. in my view, the Gmail service of 
> google is just a good example here ... you got service better 
> than google's gmail, of course go ahead ... )
> 
> honestly, i have not used the tools mentioned in the "why not 
> ... " part below. it gonna take some time to evaluate those 
> solutions by myself.
> 
> ####################
> 
> "you got a problem"
> *** 1 ***
>          Joxean Koret <joxeankoret@...oo.es>  [+] I think 
> this is a bad idea. What about client software vulnerabilities?
> You can have a system that were secure but 
> 
> currently it's not. 
>  [+] Various applications, such as web browsers, mail 
> clients, etc... needs to be constantly updated to fix the newest 
> 
> vulnerabilities.
> *** 2 ***
>          "Keith Oxenrider" <web10198@...-biotech.com>  [+] I 
> am sure you will be hearing this from many others, but 
> basically it is impossible to secure client side computing if 
> 
> the client every goes outside of your control (one presumes 
> that if it remains inside your control you have effective 
> 
> controls).  Clearly, server side computing is entirely within 
> the control of whomsoever owns (or 0wns) the server, so there 
> 
> is implicit trust when you connect (can you really trust 
> Google to protect your content?).
>  [+] While your recommendations, if used, will obviously 
> increase the baseline security of the average person, you can't 
> 
> guarentee anything.  Smart card developers run into many of 
> these issues and they don't have to deal with buggy commodity OSs 
> 
> and browsers.  Since the vast majority of users don't even 
> bother to keep their machines patched (people STILL use Win9x 
> 
> connected 24/7 to DSL, btw), offering suggestions on how to 
> make their computer even more difficult to use is unlikely to win 
> 
> any converts.
>  [+] Those of us who are already paranoid and have done their 
> homework know there is no way to ensure on-line security 
> 
> besides never doing anything on-line.
>  [+] Something to keep in mind, a read-only OS is only as 
> good as its patch level when it was written and will decay with 
> 
> time eventually (soon) reaching an insecure state that can 
> easily be penatrated.
> 
> 
> "why not ..."
> *** 1 ***
>          Joxean Koret <joxeankoret yahoo.es> Why not use a 
> system like LTSP (Linux Terminal Server Project) or any other 
> "Think Client" based system?
> *** 2 ***
>          "Beauford, Jason" <jbeauford EightInOnePet.com> 
> Tinfoil Hat linux ..silly.  http://tinfoilhat.shmoo.com/
> *** 3 ***
>          "Gustavo Paredes" <gustavo.paredes internet-solutions.com.co>
> Do you know secuware? www.secuware.com
> 
> ####################
> 
> how to have a secure client-side platform for secret communication?
>     ... transferring and storing secret messages, online banking, etc
> 
> i got some fresh ideas in mind, and would like to share it here:
> 0. watch network with sniffer, so be sure no byte is sent to 
> weird destinations 1. read-only operating system(knoppix, 
> etc), so every boot is a fresh start 2. get every secret 
> processed in memory and stored as encrypted in remote server
> 
> any suggesion or fresh idea on this topic is welcome
> 
> this document for ordinary people on the street:
> http://umbrella.name/upid/trooseid
> 
> bugtraq guys can directly go to the conclusion part:
> http://umbrella.name/computer/trooseid/trooseid_online/#conclusion
> 
> 

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