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Table of Contents
Overview
lnd currently has complete support for using Lightning over
Tor. Usage of Lightning over Tor is valuable as
routing nodes no longer need to potentially expose their location via their
advertised IP address. Additionally, leaf nodes can also protect their location
by using Tor for anonymous networking to establish connections.
With widespread usage of Onion Services within the network, concerns about the difficulty of proper NAT traversal are alleviated, as usage of Onion Services allows nodes to accept inbound connections even if they're behind a NAT.
At the time of writing this documentation, lnd supports both types of onion
services: v2 and v3. However, only v2 onion services can automatically be
created and set up by lnd until Tor Control support for v3 onion services is
implemented in the stable release of the Tor daemon. v3 onion services can be
used as long as they are set up manually. We'll cover the steps on how to do
these things below.
Before following the remainder of this documentation, you should ensure that you already have Tor installed locally. Official instructions to install the latest release of Tor can be found here.
NOTE: This documentation covers how to ensure that lnd's Lightning
protocol traffic is tunneled over Tor. Users must ensure that when also running
a Bitcoin full-node, that it is also proxying all traffic over Tor. If using the
neutrino backend for lnd, then it will automatically also default to Tor
usage if active within lnd.
Getting Started
First, you'll want to run tor locally before starting up lnd. Depending on
how you installed Tor, you'll find the configuration file at
/usr/local/etc/tor/torrc. Here's an example configuration file that we'll be
using for the remainder of the tutorial:
SOCKSPort 9050
Log notice stdout
ControlPort 9051
CookieAuthentication 1
With the configuration file created, you'll then want to start the Tor daemon:
⛰ tor
Feb 05 17:02:06.501 [notice] Tor 0.3.1.8 (git-ad5027f7dc790624) running on Darwin with Libevent 2.1.8-stable, OpenSSL 1.0.2l, Zlib 1.2.8, Liblzma N/A, and Libzstd N/A.
Feb 05 17:02:06.502 [notice] Tor can't help you if you use it wrong! Learn how to be safe at https://www.torproject.org/download/download#warning
Feb 05 17:02:06.502 [notice] Read configuration file "/usr/local/etc/tor/torrc".
Feb 05 17:02:06.506 [notice] Opening Socks listener on 127.0.0.1:9050
Feb 05 17:02:06.506 [notice] Opening Control listener on 127.0.0.1:9051
Once the tor daemon has started and it has finished bootstrapping, you'll see this in the logs:
Feb 05 17:02:06.000 [notice] Bootstrapped 0%: Starting
Feb 05 17:02:07.000 [notice] Starting with guard context "default"
Feb 05 17:02:07.000 [notice] Bootstrapped 80%: Connecting to the Tor network
Feb 05 17:02:07.000 [notice] Bootstrapped 85%: Finishing handshake with first hop
Feb 05 17:02:08.000 [notice] Bootstrapped 90%: Establishing a Tor circuit
Feb 05 17:02:11.000 [notice] Tor has successfully opened a circuit. Looks like client functionality is working.
Feb 05 17:02:11.000 [notice] Bootstrapped 100%: Done
This indicates the daemon is fully bootstrapped and ready to proxy connections.
At this point, we can now start lnd with the relevant arguments:
⛰ ./lnd -h
<snip>
Tor:
--tor.active Allow outbound and inbound connections to be routed through Tor
--tor.socks= The port that Tor's exposed SOCKS5 proxy is listening on -- NOTE port must be between 1024 and 65535 (default: 9050)
--tor.dns= The DNS server as IP:PORT that Tor will use for SRV queries - NOTE must have TCP resolution enabled (default: soa.nodes.lightning.directory:53)
--tor.streamisolation Enable Tor stream isolation by randomizing user credentials for each connection.
--tor.controlport= The port that Tor is listening on for Tor control connections -- NOTE port must be between 1024 and 65535 (default: 9051)
--tor.v2 Automatically set up a v2 onion service to listen for inbound connections
--tor.v3 Use a v3 onion service to listen for inbound connections
--tor.privatekeypath= The path to the private key of the onion service being created (default: /Users/user/Library/Application Support/Lnd/onion_private_key)
There are a couple things here, so let's dissect them. The --tor.active flag
allows lnd to route all outbound and inbound connections through Tor.
Outbound connections are possible with the use of the --tor.socks and
--tor.dns arguments. The --tor.socks argument should point to the interface
that the Tor daemon is listening on to proxy connections. The --tor.dns flag
is required in order to be able to properly automatically bootstrap a set of
peer connections. The tor daemon doesn't currently support proxying SRV
queries over Tor. So instead, we need to connect directly to the authoritative
DNS server over TCP, in order query for SRV records that we can use to
bootstrap our connections.
Inbound connections are possible due to lnd automatically creating a v2 onion
service. A path to save the onion service's private key can be specified with
the --tor.privatekeypath flag. A v3 onion service can also be used, but it
must be created manually. We'll expand on how this works in Listening for
Inbound Connections.
Most of these arguments have defaults, so as long as they apply to you, routing all outbound and inbound connections through Tor can simply be done with:
⛰ ./lnd --tor.active --tor.v2
Outbound support only can also be used with:
⛰ ./lnd --tor.active
This will allow you to make all outgoing connections over Tor, but still allow regular (clearnet) incoming connections.
Tor Stream Isolation
Our support for Tor also has an additional privacy enhancing modified: stream isolation. Usage of this mode means that Tor will always use new circuit for each connection. This added features means that it's harder to correlate connections. As otherwise, several applications using Tor might share the same circuit.
Activating stream isolation is very straightforward, we only require the specification of an additional argument:
⛰ ./lnd --tor.active --tor.streamisolation
Listening for Inbound Connections
In order to listen for inbound connections through Tor, an onion service must be created. There are two types of onion services: v2 and v3.
v2 Onion Services
v2 onion services can be created automatically by lnd and are currently the
default. To do so, run lnd with the following arguments:
⛰ ./lnd --tor.active --tor.v2
This will automatically create a hidden service for your node to use to listen
for inbound connections and advertise itself to the network. The onion service's
private key is saved to a file named onion_private_key in lnd's base
directory. This will allow lnd to recreate the same hidden service upon
restart. If you wish to generate a new onion service, you can simply delete this
file. The path to this private key file can also be modified with the
--tor.privatekeypath argument.
v3 Onion Services
v3 onion services are the latest generation of onion services and they provide a number of advantages over the legacy v2 onion services. To learn more about these benefits, see Intro to Next Gen Onion Services.
Unfortunately, at the time of writing this, v3 onion service support is still
at an alpha level in the Tor daemon, so we're unable to automatically set them
up within lnd unlike with v2 onion services. However, they can still be run
manually! To do so, append the following lines to the torrc sample from above:
HiddenServiceDir PATH_TO_HIDDEN_SERVICE
HiddenServiceVersion 3
HiddenServicePort PORT_ONION_SERVICE_LISTENS_ON ADDRESS_LND_LISTENS_ON
If needed, instructions on how to set up a v3 onion service manually can be found here.
Once the v3 onion service is set up, lnd is able to use it to listen for
inbound connections. You'll also need the onion service's hostname in order to
advertise your node to the network. To do so, run lnd with the following
arguments:
⛰ ./lnd --tor.active --tor.v3 --externalip=ONION_SERVICE_HOSTNAME
Once v3 onion service support is stable, lnd will be updated to also
automatically set up v3 onion services.