Setting up TOR with c-lightning

To use any Tor features with c-lightning you must have Tor installed and running.

Note that we only support Tor v3: you can check your installed Tor version with tor --version or sudo tor --version

If Tor is not installed you can install it on Debian based Linux systems (Ubuntu, Debian, etc) with the following command:

sudo apt install tor

then /etc/init.d/tor start or sudo systemctl start tor depending on your system configuration.

Most default setting should be sufficient.

To keep a safe configuration for minimal harassment (See Tor FAQ) just check that this line is present in the Tor config file /etc/tor/torrc:

ExitPolicy reject *:* # no exits allowed

This does not affect c-lightning connect, listen, etc.. It will only prevent your node from becoming a Tor exit node. Only enable this if you are sure about the implications.

If you don’t want to create .onion addresses this should be enough.

There are several ways by which a c-lightning node can accept or make connections over Tor.

The node can be reached over Tor by connecting to its .onion address.

To provide the node with a .onion address you can:

  • create a non-persistent address with an auto service or
  • create a persistent address with a hidden service.

Quick Start On Linux

It is easy to create a single persistent Tor address and not announce a public IP. This is ideal for most setups where you have an ISP-provided router connecting your Internet to your local network and computer, as it does not require a stable public IP from your ISP (which might not give one to you for free), nor port forwarding (which can be hard to set up for random cheap router models). Tor provides NAT-traversal for free, so even if you or your ISP has a complex network between you and the Internet, as long as you can use Tor you can be connected to.

On most Linux distributions, making a standard installation of tor will automatically set it up to have a SOCKS5 proxy at port 9050. As well, you have to set up the Tor Control Port. On most Linux distributions there will be commented-out settings below in the /etc/tor/torrc:

ControlPort 9051
CookieAuthentication 1
CookieAuthFileGroupReadable 1

Uncomment those in, then restart tor (usually systemctl restart tor or sudo systemctl restart tor on most SystemD-based systems, including recent Debian and Ubuntu, or just restart the entire computer if you cannot figure it out).

On some systems (such as Arch Linux), you may also need to add the following setting:

DataDirectoryGroupReadable 1

You also need to make your user a member of the Tor group. “Your user” here is whatever user will run lightningd. On Debian-derived systems, the Tor group will most likely be debian-tor. You can try listing all groups with the below command, and check for a debian-tor or tor groupname.

getent group | cut -d: -f1 | sort

Alternately, you could check the group of the cookie file directly. Usually, on most Linux systems, that would be /run/tor/control.authcookie:

stat -c '%G' /run/tor/control.authcookie

Once you have determined the ${TORGROUP} and selected the ${LIGHTNINGUSER} that will run lightningd, run this as root:

usermod -a -G ${TORGROUP} ${LIGHTNINGUSER}

Then restart the computer (logging out and logging in again should also work). Confirm that ${LIGHTNINGUSER} is in ${TORGROUP} by running the groups command as ${LIGHTNINGUSER} and checking ${TORGROUP} is listed.

If the /run/tor/control.authcookie exists in your system, then log in as the user that will run lightningd and check this command:

cat /run/tor/control.authcookie > /dev/null

If the above prints nothing and returns, then C-Lightning “should” work with your Tor. If it prints an error, some configuration problem will likely prevent C-Lightning from working with your Tor.

Then make sure these are in your ${LIGHTNING_DIR}/config or other C-Lightning configuration (or prepend -- to each of them and add them to your lightningd invocation command line):

proxy=127.0.0.1:9050
bind-addr=127.0.0.1:9735
addr=statictor:127.0.0.1:9051
always-use-proxy=true
  1. proxy informs C-Lightning that you have a SOCKS5 proxy at port 9050. C-Lightning will assume that this is a Tor proxy, port 9050 is the default in most Linux distributions; you can double-check /etc/tor/torrc for a SocksPort entry to confirm the port number.
  2. bind-addr informs C-Lightning to bind itself to port 9735. This is needed for the subsequent statictor to work. 9735 is the normal Lightning Network port, so this setting may already be present. If you add a second bind-addr=... you may get errors, so choose this new one or keep the old one, but don’t keep both. This has to appear before any statictor: setting.
  3. addr=statictor: informs C-Lightning that you want to create a persistent hidden service that is based on your node private key. This informs C-Lightning as well that the Tor Control Port is 9051. You can also use bind-addr=statictor: instead to not announce the persistent hidden service, but if anyone wants to make a channel with you, you either have to connect to them, or you have to reveal your address to them explicitly (i.e. autopilots and the like will likely never connect to you).
  4. always-use-proxy informs C-Lightning to always use Tor even when connecting to nodes with public IPs. You can set this to false or remove it, if you are not privacy-conscious and find Tor is too slow for you.

Tor Browser and Orbot

It is possible to not install Tor on your computer, and rely on just Tor Browser. Tor Browser will run a built-in Tor instance, but with the proxy at port 9150 and the control port at 9151 (the normal Tor has, by default, the proxy at port 9050 and the control port at 9051). The mobile Orbot uses the same defaults as Tor Browser (9150 and 9151).

You can then use these settings for C-Lightning:

proxy=127.0.0.1:9150
bind-addr=127.0.0.1:9735
addr=statictor:127.0.0.1:9151
always-use-proxy=true

You will have to run C-Lightning after launching Tor Browser or Orbot, and keep Tor Browser or Orbot open as long as C-Lightning is running, but this is a setup which allows others to connect and fund channels to you, anywhere (no port forwarding! works wherever Tor works!), and you do not have to do anything more complicated than download and install Tor Browser. This may be useful for operating system distributions that do not have Tor in their repositories, assuming we can ever get C-Lightning running on those.

Detailed Discussion

Three Ways to Create .onion Addresses for C-lightning

You have have Tor create an onion address for you, and tell c-lightning to use that, or you can have c-lightning tell Tor to create the same onion address every time it starts up, or you can have c-lightning tell Tor to create a new onion address every time.

Tor-Created .onion Address

Having Tor create an onion address lets you run other services (e.g. a web server) at that same address, and you just tell that address to c-lightning and it doesn’t have to talk to the Tor server at all.

Put the following in your /etc/tor/torrc file:

HiddenServiceDir /var/lib/tor/lightningd-service_v3/
HiddenServiceVersion 3
HiddenServicePort 1234 127.0.0.1:9735

The hidden lightning service will be reachable at port 1234 (global port) of the .onion address, which will be created at the restart of the Tor service. Both types of addresses can coexist on the same node.

Save the file and restart the Tor service. In linux:

/etc/init.d/tor restart or sudo systemctl start tor depending on the configuration of your system.

You will find the newly created address (myaddress.onion) with:

sudo cat /var/lib/tor/lightningd-service_v3/hostname

Now you need to tell c-lightning to advertize that onion hostname and port, by placing announce-addr=myaddress.onion in your lightning config.

Letting C-lightning Control Tor

To have c-lightning control your Tor addresses, you have to tell Tor to accept control commands from c-lightning, either by using a cookie, or a password.

Service authenticated by password

This tells Tor to allow password access: you also need to tell lightningd what the password is.

Create a hash of your password with

tor --hash-password yourpassword

This returns a line like

16:533E3963988E038560A8C4EE6BBEE8DB106B38F9C8A7F81FE38D2A3B1F

Put these lines in the /etc/tor/torrc file:

ControlPort 9051
HashedControlPassword 16:533E3963988E038560A8C4EE6BBEE8DB106B38F9C8A7F81FE38D2A3B1F

Save the file and restart the Tor service.

Put tor-service-password=yourpassword (not the hash) in your lightning configuration file.

C-Lightning Creating Persistent Hidden Addresses

This is usually better than transient addresses, as nodes won’t have to wait for gossip propagation to find out your new address each time you restart.

Once you’ve configured access to Tor as described above, you need to add two lines in your lightningd config file:

  1. A local address which lightningd can tell Tor to connect to when connections come in, e.g. bind-addr=127.0.0.1:9735.
  2. After that, a addr=statictor:127.0.0.1:9051 to tell c-lightning to set up and announce a Tor onion address (and tell Tor to send connections to our real address, above).

You can use bind-addr if you want to set up the onion address and not announce it to the world for some reason.

You may add more addr lines if you want to advertize other addresses.

There is an older method, called “autotor” instead of “statictor” which creates a different Tor address on each restart, which is usually not very helpful; you need to use lightning-cli getinfo to see what address it is currently using, and other peers need to wait for fresh gossip messages if you announce it, before they can connect.

What do we support

| Case # | IP Number | Hidden service |Incoming / Outgoing Tor | | ——- | ————- | ————————- |————————- | 1 | Public | NO | Outgoing | | 2 | Public | FIXED BY TOR | Incoming [1] | | 3 | Public | FIXED BY C-LIGHTNING | Incoming [1] | | 4 | Not Announced | FIXED BY TOR | Incoming [1] | | 5 | Not Announced | FIXED BY C-LIGHTNING | Incoming [1] |

NOTE:

  1. In all the “Incoming” use case, the node can also make “Outgoing” Tor connections (connect to a .onion address) by adding the proxy=127.0.0.1:9050 option.

Case #1: Public IP address and no Tor address, but can connect to Tor addresses

Without a .onion address, the node won’t be reachable through Tor by other nodes but it will always be able to connect to a Tor enabled node (outbound connections), passing the connect request through the Tor service socks5 proxy. When the Tor service starts it creates a socks5 proxy which is by default at the address 127.0.0.1:9050.

If the node is started with the option proxy=127.0.0.1:9050 the node will be always able to connect to nodes with .onion address through the socks5 proxy.

You can always add this option, also in the other use cases, to add outgoing Tor capabilities.

If you want to connect to nodes ONLY via the Tor proxy, you have to add the always-use-proxy=true option (though if you only advertize Tor addresses, we also assume you want to always use the proxy).

You can announce your public IP address through the usual method: if your node is in an internal network:

bind-addr=internalIPAddress:port
announce-addr=externalIpAddress

or if it has a public IP address:

addr=externalIpAddress

TIP: If you are unsure which of the two is suitable for you, find your internal and external address and see if they match.

In linux:

Discover your external IP address with: curl ipinfo.io/ip

and your internal IP Address with: ip route get 1 | awk '{print $NF;exit}'

If they match you can use the --addr command line option.

Case #2: Public IP address, and a fixed Tor address in torrc

Other nodes can connect to you entirely over Tor, and the Tor address doesn’t change every time you restart.

You simply tell c-lightning to advertize both addresses (you can use sudo cat /var/lib/tor/lightningd-service_v3/hostname to get your Tor-assigned onion address).

If you have an internal IP address:

bind-addr=yourInternalIPAddress:port
announce-addr=yourexternalIPAddress:port
announce-addr=your.onionAddress:port

Or an external address:

addr=yourIPAddress:port
announce-addr=your.onionAddress:port

Case #3: Public IP address, and a fixed Tor address set by C-lightning

Other nodes can connect to you entirely over Tor, and the Tor address doesn’t change every time you restart.

See “Letting C-lightning Control Tor” for how to get c-lightning talking to Tor.

If you have an internal IP address:

bind-addr=yourInternalIPAddress:port
announce-addr=yourexternalIPAddress:port
addr=statictor:127.0.0.1:9051

Or an external address:

addr=yourIPAddress:port
addr=statictor:127.0.0.1:9051

Case #4: Unannounced IP address, and a fixed Tor address in torrc

Other nodes can only connect to you over Tor.

You simply tell c-lightning to advertize the Tor address (you can use sudo cat /var/lib/tor/lightningd-service_v3/hostname to get your Tor-assigned onion address).

announce-addr=your.onionAddress:port
proxy=127.0.0.1:9050
always-use-proxy=true

Case #4: Unannounced IP address, and a fixed Tor address set by C-lightning

Other nodes can only connect to you over Tor.

See “Letting C-lightning Control Tor” for how to get c-lightning talking to Tor.

addr=statictor:127.0.0.1:9051
proxy=127.0.0.1:9050
always-use-proxy=true

References

The lightningd-config manual page covers the various address cases in detail.

The Tor project