core-lightning/doc/TOR.md

Setting up TOR with c-lightning

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

Note that Tor v2 onion services are deprecated since mid-2020 and that C-lightning deprecated their support since mid-2021.

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

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 cookie

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

ControlPort 9051
CookieAuthentication 1
CookieAuthFileGroupReadable 1

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

2. 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 will be shown by the lightning-cli getinfo command. The other 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.

Automatic persistent .onion address

It is possible to generate persistent .onion addresses automatically.

Add the following lines in the /etc/tor/torrc file (you might already have done this if for example you connected Bitcoin over Tor):

ControlPort 9051
CookieAuthentication 1
CookieAuthFileGroupReadable 1

Then you can use --addr=statictor:127.0.0.1:9051 instead of --announce-addr=.onionAddressV3. By default V3 onion addresses are generated.

Note that you have to specify a --bind-addr first before using --addr=statictor:. Generally --bind-addr=127.0.0.1:9735 should work fine.

You can also have multiple persistent .onion addresses by adding /torblob=BLOB, where BLOB is 32 to 64 random bytes of text. Note that this blob will be used to derive the secret key behind the .onion address and you should keep the blob secret otherwise anyone who steals it can spoof your .onion address and block incoming data to your node via this .onion address. You can then specify multiple statictor: options with different BLOBs.

However, even if you have multiple persistent addresses, you can only announce up to one onion service (v3). This is a limitation of the BOLT spec. It is still possible for other nodes to contact you by those other hidden services.

Finally, the default external port number for the autogenerated persistent .onion address will be 9735, but you can change this by adding /torport=9999 to change the external port for the .onion address.

Explicit Control

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_v3/hostname

Now you are able to create:

• Persistent version 3 hidden services.

Let's see how to use them.

What do we support

Case #	IP Number	Hidden service	Incoming / Outgoing Tor
1	Public	NO	Outgoing
6	Public	v3	Incoming [1]
7	Not Announced	v3	Incoming
8	Public	NO	Outcoing socks5 .

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 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`

or

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

options.

If you are not inside an internal network you can use

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

or

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

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).

For statictor the 127.0.0.1 is your computer, and 9051 is the Tor Control Port you set up in the /etc/tor/torrc file.

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 hidden service

You will be reachable via Clearnet, via Tor to the .onion if it 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 hidden service public you add:

--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

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 service public you add:

--bind-addr=yourInternalIPAddress: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