140bbeec45
as per http://www.erisian.com.au/bitcoin-core-dev/log-2019-04-11.html#l-102. Description adapted from https://github.com/bitcoin/bitcoin/blob/master/src/init.cpp#L429. Also fixes a typo in doc/dependencies.md.
131 lines
6.6 KiB
Markdown
131 lines
6.6 KiB
Markdown
# TOR SUPPORT IN BITCOIN
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It is possible to run Bitcoin Core as a Tor hidden service, and connect to such services.
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The following directions assume you have a Tor proxy running on port 9050. Many distributions default to having a SOCKS proxy listening on port 9050, but others may not. In particular, the Tor Browser Bundle defaults to listening on port 9150. See [Tor Project FAQ:TBBSocksPort](https://www.torproject.org/docs/faq.html.en#TBBSocksPort) for how to properly
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configure Tor.
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## 1. Run Bitcoin Core behind a Tor proxy
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The first step is running Bitcoin Core behind a Tor proxy. This will already anonymize all
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outgoing connections, but more is possible.
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-proxy=ip:port Set the proxy server. If SOCKS5 is selected (default), this proxy
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server will be used to try to reach .onion addresses as well.
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-onion=ip:port Set the proxy server to use for Tor hidden services. You do not
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need to set this if it's the same as -proxy. You can use -noonion
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to explicitly disable access to hidden services.
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-listen When using -proxy, listening is disabled by default. If you want
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to run a hidden service (see next section), you'll need to enable
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it explicitly.
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-connect=X When behind a Tor proxy, you can specify .onion addresses instead
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-addnode=X of IP addresses or hostnames in these parameters. It requires
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-seednode=X SOCKS5. In Tor mode, such addresses can also be exchanged with
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other P2P nodes.
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-onlynet=onion Make outgoing connections only to .onion addresses. Incoming
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connections are not affected by this option. This option can be
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specified multiple times to allow multiple network types, e.g.
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ipv4, ipv6, or onion.
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In a typical situation, this suffices to run behind a Tor proxy:
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./bitcoind -proxy=127.0.0.1:9050
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## 2. Run a Bitcoin Core hidden server
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If you configure your Tor system accordingly, it is possible to make your node also
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reachable from the Tor network. Add these lines to your /etc/tor/torrc (or equivalent
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config file): *Needed for Tor version 0.2.7.0 and older versions of Tor only. For newer
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versions of Tor see [Section 3](#3-automatically-listen-on-tor).*
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HiddenServiceDir /var/lib/tor/bitcoin-service/
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HiddenServicePort 8333 127.0.0.1:8333
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HiddenServicePort 18333 127.0.0.1:18333
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The directory can be different of course, but (both) port numbers should be equal to
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your bitcoind's P2P listen port (8333 by default).
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-externalip=X You can tell bitcoin about its publicly reachable address using
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this option, and this can be a .onion address. Given the above
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configuration, you can find your .onion address in
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/var/lib/tor/bitcoin-service/hostname. For connections
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coming from unroutable addresses (such as 127.0.0.1, where the
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Tor proxy typically runs), .onion addresses are given
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preference for your node to advertise itself with.
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-listen You'll need to enable listening for incoming connections, as this
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is off by default behind a proxy.
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-discover When -externalip is specified, no attempt is made to discover local
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IPv4 or IPv6 addresses. If you want to run a dual stack, reachable
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from both Tor and IPv4 (or IPv6), you'll need to either pass your
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other addresses using -externalip, or explicitly enable -discover.
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Note that both addresses of a dual-stack system may be easily
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linkable using traffic analysis.
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In a typical situation, where you're only reachable via Tor, this should suffice:
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./bitcoind -proxy=127.0.0.1:9050 -externalip=57qr3yd1nyntf5k.onion -listen
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(obviously, replace the .onion address with your own). It should be noted that you still
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listen on all devices and another node could establish a clearnet connection, when knowing
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your address. To mitigate this, additionally bind the address of your Tor proxy:
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./bitcoind ... -bind=127.0.0.1
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If you don't care too much about hiding your node, and want to be reachable on IPv4
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as well, use `discover` instead:
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./bitcoind ... -discover
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and open port 8333 on your firewall (or use -upnp).
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If you only want to use Tor to reach .onion addresses, but not use it as a proxy
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for normal IPv4/IPv6 communication, use:
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./bitcoind -onion=127.0.0.1:9050 -externalip=57qr3yd1nyntf5k.onion -discover
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## 3. Automatically listen on Tor
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Starting with Tor version 0.2.7.1 it is possible, through Tor's control socket
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API, to create and destroy 'ephemeral' hidden services programmatically.
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Bitcoin Core has been updated to make use of this.
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This means that if Tor is running (and proper authentication has been configured),
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Bitcoin Core automatically creates a hidden service to listen on. This will positively
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affect the number of available .onion nodes.
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This new feature is enabled by default if Bitcoin Core is listening (`-listen`), and
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requires a Tor connection to work. It can be explicitly disabled with `-listenonion=0`
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and, if not disabled, configured using the `-torcontrol` and `-torpassword` settings.
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To show verbose debugging information, pass `-debug=tor`.
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Connecting to Tor's control socket API requires one of two authentication methods to be
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configured. It also requires the control socket to be enabled, e.g. put `ControlPort 9051`
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in `torrc` config file. For cookie authentication the user running bitcoind must have read
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access to the `CookieAuthFile` specified in Tor configuration. In some cases this is
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preconfigured and the creation of a hidden service is automatic. If permission problems
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are seen with `-debug=tor` they can be resolved by adding both the user running Tor and
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the user running bitcoind to the same group and setting permissions appropriately. On
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Debian-based systems the user running bitcoind can be added to the debian-tor group,
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which has the appropriate permissions.
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An alternative authentication method is the use
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of the `-torpassword=password` option. The `password` is the clear text form that
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was used when generating the hashed password for the `HashedControlPassword` option
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in the tor configuration file. The hashed password can be obtained with the command
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`tor --hash-password password` (read the tor manual for more details).
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## 4. Privacy recommendations
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- Do not add anything but Bitcoin Core ports to the hidden service created in section 2.
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If you run a web service too, create a new hidden service for that.
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Otherwise it is trivial to link them, which may reduce privacy. Hidden
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services created automatically (as in section 3) always have only one port
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open.
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