# 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:

```bash
sudo apt install tor
```
then `/etc/init.d/tor start` or `sudo systemctl enable --now 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.

Note: c-lightning also support IPv4/6 address discovery behind NAT routers.
For this to work you need to forward the TCP port 9735 to your node.
In this case you don't need TOR to punch through your firewall.
This usually has the benefit of quicker and more stable connections but does not
offer additional privacy.

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 restart 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 cookie

This tells Tor to create a cookie file each time: lightningd will have
to be in the same group as tor (e.g. debian-tor): you can look at
`/run/tor/control.authcookie` to check the group name.

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

```
ControlPort 9051
CookieAuthentication 1
CookieAuthFileGroupReadable 1
```

Save the file and restart the Tor service.

##### 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](https://www.torproject.org/)

[tor FAQ]: https://www.torproject.org/docs/faq.html.en#WhatIsTor

[Tor Hidden Service]: https://www.torproject.org/docs/onion-services.html.en

[.onion addresses version 3]: https://blog.torproject.org/we-want-you-test-next-gen-onion-services