[tor-talk] Tor TransparentProxy with iptables breaks connections ?

Sun Aug 24 17:56:13 UTC 2014

Hi elrippo thanks for the inputs.
Your implementation is good (in our opinion) because you block 
everything (INPUT DROP) and then allow only the strict necessary.
We'll take your path, it will require some testing on a test server 
because you know what happens when you cut yourself out of the server 
with iptables .. :)
or block the entire service because of a mistyped rule :)

Wish you a nice sunday,
RuggedInbox team

On 2014-08-23 18:43, elrippo wrote:
> Take a look at example f.) ->
> https://elrippoisland.net/public/how_to/anonymity.html
> 
>> Hello again :)
>> 
>> At https://ruggedinbox.com we are running a 'standard' email server,
>> using postfix, dovecot, and so on ..
>> 
>> The server is also able to receive and send emails to the onionland,
>> thanks to Tor providing DNS resolution for onion addresses and 
>> 'unbound'
>> for the clearnet.
>> 
>> As you may know, the full setup needs some iptables magic, as 
>> documented
>> in:
>> https://trac.torproject.org/projects/tor/wiki/doc/TransparentProxy
>> https://lists.torproject.org/pipermail/tor-talk/2014-March/032503.html
>> https://lists.torproject.org/pipermail/tor-talk/2014-March/032507.html
>> 
>> so we run the following rules:
>> 1. iptables -t nat -A OUTPUT -p tcp -d 10.192.0.0/10 -j REDIRECT
>> --to-ports 9040
>> 2. iptables -A OUTPUT -m conntrack --ctstate INVALID -j DROP
>> 3. iptables -A OUTPUT ! -o lo ! -d 127.0.0.1 ! -s 127.0.0.1 -p tcp -m
>> tcp --tcp-flags ACK,FIN ACK,FIN -j DROP
>> 4. iptables -A OUTPUT ! -o lo ! -d 127.0.0.1 ! -s 127.0.0.1 -p tcp -m
>> tcp --tcp-flags ACK,RST ACK,RST -j DROP
>> 
>> but it looks like the third rule breaks connections: the mail client
>> timeouts while checking POP mailboxes, randomly but very often.
>> 
>> 
>> Do you think that is safe to discard the third and forth rules ?
>> And if not, do you have other suggestions to be safe and prevent leaks 
>> ?
>> 
>> 
>> Thank you very much for supporting,
>> we look forward to publish all ruggedinbox's configuration as soon as
>> everything works ok
>> (and perhaps a 'ruggedinbox distro')
>> in order to have a starting base on which discuss and request for
>> comments,
>> which will help people to build their private email server, secure,
>> spam-resistant and Tor-aware :)
> 
> --
> We don't bubble you, we don't spoof you ;)
> Keep your data encrypted!
> Log you soon,
> your Admin
> elrippo at elrippoisland.net
> 
> Encrypted messages are welcome.
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