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magic-wormhole/docs/tor.md
Brian Warner c6ac04433f add docs/tor.md
2017-01-16 11:14:23 -05:00

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Tor Support in Magic-Wormhole

The wormhole command-line tool has built-in support for performing transfers over Tor. Just add --tor to use a running Tor instance:

wormhole send --tor myfile.jpg
 
wormhole receive --tor

You should use --tor rather than running wormhole under tsocks or torsocks because the magic-wormhole "Transit" protocol normally sends the IP addresses of each computer to its peer, to attempt a direct connection between the two (somewhat like the FTP protocol would do). External tor-ifying programs don't know about this, so they can't strip these addresses out. Using --tor puts magic-wormhole into a mode where it does not share any IP addresses.

--tor causes the program to look for a Tor control port in the three most common locations:

  • unix:/var/run/tor/control: Debian/Ubuntu Tor listen here
  • tcp:localhost:9051: the standard Tor control port
  • tcp:localhost:9151: control port for TorBrowser's embedded Tor

If wormhole is unable to establish a control-port connection to any of those locations, it will assume there is a SOCKS daemon listening on tcp:localhost:9050, and hope for the best (if no SOCKS daemon is available on that port, the initial Rendezvous connection will fail, and the program will exit with an error before doing anything else).

The default behavior will Just Work if:

  • you are on a Debian-like system, and the tor package is installed, or:
  • you have launched the tor daemon manually, or:
  • the TorBrowser application is running when you start wormhole

On Debian-like systems, if your account is a member of the debian-tor group, wormhole will use the control-port to ask for the right SOCKS port. If not, it should fall back to using the default SOCKS port on 9050. To add your account to the debian-tor group, use e.g. sudo adduser MYUSER debian-tor. Access to the control-port will be more significant in the future, whne wormhole can listen on "onion services": see below for details.

Other Ways To Reach Tor

If tor is installed, but you cannot use the control-port or SOCKS-port for some reason, then you can use --launch-tor to ask wormhole to start a new Tor daemon for the duration of the transfer (and then shut it down afterwards). This will add 30-40 seconds to program startup.

wormhole send --tor --launch-tor myfile.jpg

Alternatively, if you know of a pre-existing Tor daemon with a non-standard control-port, you can specify that control port with the --tor-control-port= argument:

wormhole send --tor --tor-control-port=tcp:127.0.0.1:9251 myfile.jpg

.onion servers

In the future, wormhole with --tor will listen on an ephemeral "onion service" when file transfers are requested. If both sides are Tor-capable, this will allow transfers to take place "directly" (via the Tor network) from sender to receiver, bypassing the Transit Relay server. This will require access to a Tor control-port (to ask Tor to create a new ephemeral onion service). SOCKS-port access will not be sufficient.

However the current version of wormhole does not use onion services. For now, if both sides use --tor, any file transfers must use the transit relay, since neither side will advertise any listening IP addresses.