Date: Sun, 17 Sep 2006 13:38:32 +0200
From: Paul Sebastian Ziegler <psz@...erved.de>
To: full-disclosure <full-disclosure@...ts.grok.org.uk>
Subject: Re: AFS - The Ultimate Sulution? -- What is the
 point?

Those are good ideas to push the concept even further.
But this was a mindgame anyway. In answer to what Maguro said:
Yes, it would still be possible to root the system, but how would that
help to get another user?
Even if the system is rooted you would only have access to your own
files and could not even crack other user's pws since they aren't in
your password-file.

As you said this requires that the AFS-Server is being kept up to date.
But the Images wouldn't have to be. Apart from this AFS hasn't had a
major security-issue in the past several years.

Of course somebody could be hardlogging on a workstation, but it
wouldn't be possible to sniff pws from the kerberos-session due to
encryption. So also a rooted workstation with eth0 put into promiscuous
mode would be of no use.

Paul

Dude VanWinkle wrote:
> why not just use a dumb terminal if you are going to go to all that trouble?
> 
> -JP
> 
> On 9/15/06, Dean Pierce <piercede@....edu> wrote:
>> There is the convenience issue of the speed that the image transfers
>> across the network.
>>
>> There is also the issue that infected workstations may be collecting
>> passwords.
>>
>> My suggestion would be to use the harddrives in the workstation to store
>> the boot images, and have the minimal operating system on some sort of
>> USB device or something that the employees can take home with them, and
>> carry around etc.
>>
>> The employee can then..
>>
>>  1. plug in the USB device
>>  2. boot the machine
>>  3. enter device password (to decrypt the rest of the device)
>>  4. the USB device should then be removed
>>  5. enter the network username and password (remote authentication)
>>  6. select which operating system to boot to
>>     - now the system checks the hash of the selected image,
>>       and submits it to a central server for approval
>>     - if image is approved, the system is booted
>>     - network mounts are mounted based on user policy etc
>>
>> Workstations would then need to be locked down, allowed only to ever
>> boot to the USB device or whatever, and might employ some bios tricks to
>> only boot devices that have been signed etc. A decent chassis alarm
>> system would also need to be in place to avoid tampering.  Network
>> topology should also be static, and trigger alarms if anything is changed.
>>
>> It would then be up to the sysadmins to keep the images up to date (not
>> just security-wise, but also with the latest software).
>>
>> If the employee is working with sensitive information (that the
>> sysadmins should not have access to), the data should all be stored in
>> an encrypted state on the remote filesystems, and decrypted on the fly
>> on the workstation when needed.
>>
>> problems that may still exist:
>>
>> 1. weak sysadmin security policies
>> 2. weak add/remove/refresh user policies
>> 3. weakness in the encryption protocols
>> 4. USB devices can be cloned
>>
>> 1 and 2 can be mitigated with strict rules and a positive work
>> environment, and proactive education (preventing bribes/social
>> engineering etc).  3 is the fault of the cryptanalysts, and 4 can be
>> dealt with by using devices with non-readable sections and on-board
>> crypto (like a smartcard etc).
>>
>> Different things can be enforced more or less based on paranoia levels,
>> but I would say this system is reasonably simple, and prevents most
>> nastiness, and could even remain pretty stable if the images were not
>> updated frequently.  With using old images, there is the chance of worms
>>  infecting the workstation in the morning, but a decent IPS should
>> prevent that, and it would be much easier to clean up later.
>>
>> Also employees might use recent attacks against eachother to gain
>> information on other employees that they do not have access to.  IPS
>> should see this though, and if you are really worried, you can make it
>> so all writable directories that a user has are mounted without execute
>> permissions or something.
>>
>> The user experience is not much more complicated than most current
>> setups, and I believe this does go pretty far to protect the
>> workstations from pretty much any sort of malicious tampering, which was
>> the goal I think.
>>
>>    - DEAN
>>
>>
>> マグロ原子 wrote:
>>> In-Reply-To: <4509C2FE.8020104@...erved.de>
>>>
>>> I don't really see the point... Possible vulnerabilities (if I didn't
>>> horribly misunderstand something):
>>>
>>> *The AFS server would still need to be updated to keep it secure.
>>> *If the imaged OS is rootable:
>>> **The AFS clients that load the images could be replaced by phishnets.
>>> **The attacker could pose as the user having access to Kerberos
>>> credentials. (So rm -r / would delete the users "securely kept files")
>>>
>>> Or do users only have read-only access to their files?? That doesn't
>>> seem useful.
>>>
>>> Nyoro~n
>>>
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>>
>>
>> _______________________________________________
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>>
> 
> _______________________________________________
> Full-Disclosure - We believe in it.
> Charter: http://lists.grok.org.uk/full-disclosure-charter.html
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