Setting up TOR with c-lightning

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

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.

Creation of an auto service for non-persistent .onion addresses

To provide the node a non-persistent .onion address it is necessary to access the Tor auto service. These types of addresses change each time the Tor service is restarted.

NOTE:If the node is required to be reachable only by persistent .onion addresses, this part can be skipped and it is necessary to set up a hidden service with the steps outlined in the next section.

To create and use the auto service follow these steps:

Edit the Tor config file /etc/tor/torrc

You can configure the service authenticated by cookie or by password:

Service authenticated by password

Alternatively, you can set the authentication to the service with a password by following these steps:

  1. Create a hash of your password with
tor --hash-password yourpassword

This returns a line like

16:533E3963988E038560A8C4EE6BBEE8DB106B38F9C8A7F81FE38D2A3B1F

  1. put these lines in the /etc/tor/torrc file:
ControlPort 9051
HashedControlPassword 16:533E3963988E038560A8C4EE6BBEE8DB106B38F9C8A7F81FE38D2A3B1F

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.

The auto service is used by adding --addr=autotor:127.0.0.1:9051 if you want the address to be public or --bind-addr=autotor:127.0.0.1:9051 if you don’t want to publish it.

In the case where the auto service is authenticated through a password, it will be necessary to add the option --tor-service-password=yourpassword (not the hash).

The created non-persistent .onion address wil be shown by the lightning-cli getinfocommand. The others nodes will be able to connect to this .onion address through the 9735 port.

Creation of a hidden service for a persistent .onion address

To have a persistent .onion address other nodes can connect to, it is necessary to set up a Tor Hidden Service.

NOTE: In the case where only non-persistent addresses are required,you don’t have to create the hidden service and you can skip this part.

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

HiddenServiceDir /var/lib/tor/lightningd-service_v2/
HiddenServicePort 1234 127.0.0.1:9735

If you want to create a version 3 address, you must also add HiddenServiceVersion 3 so the whole section will be:

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 with:

sudo cat /var/lib/tor/lightningd-service_v2/hostname 

or

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

in the case of a version 3 Tor address.

Now you are able to create:

  • Non-persistent version 2 .onion address via auto service (temp-v2)
  • Persistent version 2 and version 3 .onion addresseses (v2 and v3).

Let’s see how to use them.

What do we support

| Case # | IP Number | Tor address |Incoming / Outgoing Tor | | ——- | ————- | ————————- |————————- | 1 | Public | NO | Outgoing | | 2 | Public | v2 [1] | Incoming [4] | | 3 | Public | temp-v2 [2] | Incoming | | 4 | Not Announced | v2 | Incoming | | 5 | Not Announced | temp-v2 | Incoming | | 6 | Public | v3 [3] + temp-v2 | Incoming | | 7 | Not Announced | v3 + v2 + temp-v2 | Incoming | | 8 | Public | NO | Outcoing socks5 . |

NOTE:

  1. v2: The Version 2 onion address is persistent across Tor service restarts. It is created when you create the Tor Hidden Service.
  2. temp-v2: The Version 2 onion address changes at each restart of the Tor service. A non-persistent .onion address is generated by accessing an auto service.
  3. All the v3 addresses referes to .onion addresses version 3.
  4. 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 c-lightning has a public IP address and no Tor hidden service address, but can connect to an onion address via a Tor socks 5 proxy.

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.

You can announce your public IP address through the usual method:

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

if the node is into an internal network

--addr=externalIpAddress

if the node is not inside an internal network.

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 c-lightning has a public IP address and a fixed Tor hidden service address that is persistent, so that external users can connect to this node.

To have your external IP address and your .onion address announced, you use the

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

option.

If you are not inside an internal network you can use

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

your.onionAddress is the one created with the Tor hidden service (see above). The port is the one indicated as the hidden service port. If the hidden service creation line is HiddenServicePort 1234 127.0.0.1:9735 the .onion address will be reachable at the 1234 port (the global port).

It will be possible to connect to this node with:

lightning-cli connect nodeID .onionAddress globalPort 

through Tor where .onion address is in the form xxxxxxxxxxxxxxxxxxxxxxxxxx.onion, Or

lightning-cli connect nodeID yourexternalIPAddress Port

through Clearnet.

Case #3 c-lightning has a public IP address and a non-persisten Tor service address

In this case other nodes can connect to you via Clearnet or Tor.

To announce your IP address to the network, you add:

--bind-addr=internalAddress:port --announce-addr=yourExternalIPAddress

or --addr=yourExternalIPAddressif you are NOT on an internal network.

To get your non-persistent Tor address, add --addr=autotor:127.0.0.1:9051 if you want to announce it or --bind-addr=autotor:127.0.0.1:9051 if you don’t want to announce it.

If the auto service is protected by password (see above) it is necessary to specify it with the option --tor-service-password=yourpassword (not the hash).

You will obtain the generated non persisten .onion address by reading the results of the lightning-cli getinfo command. Other nodes will be able to connect to the .onion address through the 9735 port.

Case #4 c-lightning has no public IP address, but has a fixed Tor hidden service address that is persistent

Other nodes can connect to the announced .onion address created with the hidden service (see above).

In this case In the lightningd command line you will specify:

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

or --addr=your.onionAddress:port if you are NOT on an internal network.

Case #5 c-lightning has no public IP address, and has no fixed Tor hidden service address

In this case it is difficult to track the node. You specify just:

--bind-addr=yourInternalIPAddress:port --addr=autotor:127.0.0.1:9051

In the lightningd command line.

Other nodes will not be able to connect to you unless you communicate them how to reach you. You will find your .onion address with the command lightning-cli getinfo and the other nodes will be able to connect to it through the 9735 port.

Case #6 c-lightning has a public IP address and a fixed Tor V3 service address and a Tor V2 service address

You will be reachable via Clearnet, via Tor to the .onion V3 address and the .onion V2 address if this last is communicated to the node that wants to connect with our node.

to make your external IP address public you add:

--bind-addr=yourInternalAddress:port --announce-addr=yourexternalIPAddress:port`. 

If the node is not on an internal network the option will be: --addr=yourexternalIPAddress:port.

Once the .onion addresses have been created with the procedures oulined above, the node is already reachable at the .onion address.

To make your external .onion addresses public you add:

--announce-addr=.onionAddressV2:port --announce-addr=.onionAddressV3:port 

to the options to publish your IP number.

Case #7 c-lightning has no public IP address, a fixed Tor V3 service address, a fixed Tor V2 service address and also a 3rd non persisten V2 address

External users can connect to this node by Tor V2 and V3 and a random V2 until next tor release, then also (V3 randomly).

The Persistent addresses can be created with the steps outlined above.

To create your non-persistent Tor address, add --addr=autotor:127.0.0.1:9051 if you want to announce it or --bind-addr=autotor:127.0.0.1:9051 if you don’t want to announce it.

Also you must specify --tor-service-password=yourpassword (not the hash) to access the Tor service at 9051 If you have protected them with the password (no additional options if they are protected with a cookie file. See above).

To make your external .onion address (V2 and V3) public you add:

--bind-addr=yourInternalIPAddress:port --announce-addr=your.onionAddressV2:port --announce-addr=your.onionAddressV3:port

Case #8 c-lightning has a public IP address and no Tor addresses

The external address is communicated by the

--bind-addr=internalIPAddress:port --announce-addr=yourexternalIPAddress:port`

or --addr=yourexternalIPAddress:port if the node is not inside an internal network.

The node can connect to any V4/6 ip address via a IPV4/6 socks 5 proxy by specifing

--proxy=127.0.0.1:9050 --always-use-proxy=true

References

The Tor project