[tor-dev] Different trust levels using single client instance

bancfc at openmailbox.org bancfc at openmailbox.org
Sat Nov 5 15:30:26 UTC 2016

On 2016-11-05 01:36, teor wrote:
>> On 5 Nov. 2016, at 11:26, Patrick Schleizer 
>> <patrick-mailinglists at whonix.org> wrote:
>> Thank you for your answers!
>> teor:
>>> * Caching of DNS, HS descriptors, preemptive circuits, etc.
>> Can you please elaborate on 'etc.'?
>> I am asking because stream isolation for DNS already has a ticket:
>> https://trac.torproject.org/projects/tor/ticket/20555
>> HS cache isolation also has a ticket:
>> https://trac.torproject.org/projects/tor/ticket/15938
>> Looks like preemptive circuits isolation does not have a ticket yet.
> Preemptive circuits aren't a caching mechanism, and can't really be
> isolated in the way you think - circuits are isolated by existing
> mechanisms, but this is likely not enough to defend against hostile
> clients sharing an instance.
> Isolation is a defence against the remote end, not the client end.
>> If you could please elaborate on 'etc.' we might be able to complete 
>> the
>> stack of missing tickets.
> Circuit cannibalisation (yet another thing that can't be isolated)
> SSL state
> Guard state
> Consensus availability and content
> Descriptor availability and content
> Connectivity (or lack thereof)
> Uptime
> ControlPort config information
> ControlPort config changes
> And many more.
> The supported way to isolate many of these things is to run a separate
> Tor instance, preferably on a separate machine on a separate network.
> We don't even recommend running a SOCKS client and a hidden service
> on the same instance.
> T
> --

Thanks. This is very useful info to keep in mind since it affects usage 
advice. A

There is one more related scenario of single Gateway - Workstation pair 
where the Workstation VM is rolled back to a clean state between 
different sessions however only a NEWNYM is triggered on the Gateway 
without restarts. My guess is that many of the risks you detailed still 
hold so I want to find out what is the best opsec to handle this:

Do these risks persist across reboot of the Tor VM?

Is restarting of the Tor process enough?

Or should we recommend instead that users make an initial clean snapshot 
of the Tor VM and roll back to this instead?

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