Warnings running through Tor #725

I'm getting warning in Vidalia running bitcoin through Tor:

Your application (using socks4 to port 8333) is giving Tor only an IP address. Applications that do DNS resolves themselves may leak information. Consider using Socks4A (e.g. via privoxy or socat) instead. For more information, please see http://wiki.noreply.org/noreply/TheOnionRouter/TorFAQ#SOCKSAndDNS.

From a brief chat in #Tor on irc.oftc.net:

You can modify your socks code to connect to a hostname (you can use an IP address as hostname without any trouble, if you're using socks5) or you can use socks4a and stuff will also just work

I don't know nuthin about SOCKS, but I'm hoping somebody else does and can fix this...

The bitcoin protocol only exchanges peer addresses as IPs, isn't it?

Does it ever connect to a hostname instead of an IP? (only for seeding maybe?) If so, it indeed should do this directly through SOCKS, and not by first looking up the name using DNS, as this exposes the host name to anyone listening for DNS requests.

Edit: DNS lookups should be only used when -dns is passed (which sets fAllowDNS). In practice, it always does DNS lookups for showmyip.com etc when determining the external IP address, and when lookup up the IRC server (!) irc.lfnet.org.

This is half real half bogus, — the warning is generated because of the assumption that if the socks port is seeing IP addresses the client did its own DNS requests which have leaked out. (e.g. lots of apps can be configured to use a proxy but still end up using the libc resolver and then deanonymizing data leaks out via DNS, tor can't see the leak but it can see connections to IPs instead of names) For the most part we don't use DNS— the exceptions being the stuff mentioned above and DNSSeed which can't be usefully done using tor's integrated dns (see the other issue I opened on dnsseed+tor). We should make sure to use dns via tor for the things where we do dns and disable showmyip when using tor (dnsseed is now disabled already) Unfortunately that warning will remain, but after those things are fixed the warning will be completely bogus and I don't think there is anything we can do about that. :(