[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

Re: "Practical onion hacking: finding the real address of Tor clients"

On 10/24/06, George Shaffer <George.Shaffer@xxxxxxxxxxx> wrote:
It's not that I don't trust my firewall, I just don't want to invite
random attacks, because a broad probe of many port 80s, happens to find
an open one on my machine.

as you mentioned further down, the presence of your node in the directory will do more to "invite attacks" than an open port 80 i suspect.

you can configure other ports, but 80/443 are recommended precisely
because most firewalls let web traffic pass (and thus these clients
behind restrictive firewalls can still use Tor).

Either way though, packets are now sent from the Tor node system that
can be fingerprinted to determine the OS, version, and some other facts
about the OS running the Tor node and possibly firewall.

your OS is usually displayed in the directory as well. for example: http://serifos.eecs.harvard.edu/cgi-bin/desc.pl?q=peertechdata [Linux i686]

Does Tor have any [<unknown vulnerabilities>]? ...

like any network software there are a number of things you can do to address security concerns. Tor has a good security record, but certainly isn't perfect. you might check http://wiki.noreply.org/noreply/OperationalSecurity for details but you appear to be familiar with the usual tricks.

I could put Tor on an individual client rather than the firewall. Then I
have to set up Tor on each client I might want to use.

i like this approach, with the client serving VPN connections (PPTP, OpenVPN) that force a default route through it and Tor for any users on the same internal network. it does not make much sense to run a server and lots of clients behind the same IP if you can just share use of the server.

when a user wants to be anonymous, they activate the privacy vpn, and
no IP leakage (even javascript, flash, etc) occurs.  when they are
finished, just disconnect.

see http://wiki.noreply.org/noreply/TheOnionRouter/TransparentProxy
for more info.

you could even use a virtual machine for the tor server.  there is
some rough detail to do this with janusvm in the "Alternative
Solutions" mentioned here:

TOR as a server runs on hundreds, rather than tens of thousands to
millions of computers, so it is not likely to have (yet) attracted much
malicious scrutiny. Once a single malicious attacker decides to focus on
Tor, he can get the source code to help him, but the Tor community does
not have the resources to find a quick solution, the way the large open
source communities do.

this feels like a straw man. there are valid security bones to pick with Tor but capable and motivated developers are behind it. would more support / community be helpful? absolutely. but size alone is less useful a metric than you think...

one last comment:
an additional reason to run a server which i haven't seen listed in
this thread is hidden services.  while not a compelling feature, they
are useful for some purposes.

best regards,