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# Overview
This document explains how to enable VoIP relaying on your Home Server with
TURN.
The synapse Matrix Home Server supports integration with TURN server via the
[TURN server REST API](<http://tools.ietf.org/html/draft-uberti-behave-turn-rest-00>). This
allows the Home Server to generate credentials that are valid for use on the
TURN server through the use of a secret shared between the Home Server and the
TURN server.
The following sections describe how to install [coturn](<https://github.com/coturn/coturn>) (which implements the TURN REST API) and integrate it with synapse.
## Requirements
For TURN relaying with `coturn` to work, it must be hosted on a server/endpoint with a public IP.
Hosting TURN behind a NAT (even with appropriate port forwarding) is known to cause issues
and to often not work.
## `coturn` setup
### Initial installation
The TURN daemon `coturn` is available from a variety of sources such as native package managers, or installation from source.
#### Debian installation
Just install the debian package:
```sh
apt install coturn
```
This will install and start a systemd service called `coturn`.
#### Source installation
1. Download the [latest release](https://github.com/coturn/coturn/releases/latest) from github. Unpack it and `cd` into the directory.
1. Configure it:
./configure
> You may need to install `libevent2`: if so, you should do so in
> the way recommended by your operating system. You can ignore
> warnings about lack of database support: a database is unnecessary
> for this purpose.
1. Build and install it:
make
make install
### Configuration
1. Create or edit the config file in `/etc/turnserver.conf`. The relevant
lines, with example values, are:
use-auth-secret
static-auth-secret=[your secret key here]
realm=turn.myserver.org
See `turnserver.conf` for explanations of the options. One way to generate
the `static-auth-secret` is with `pwgen`:
pwgen -s 64 1
1. Consider your security settings. TURN lets users request a relay which will
connect to arbitrary IP addresses and ports. The following configuration is
suggested as a minimum starting point:
# VoIP traffic is all UDP. There is no reason to let users connect to arbitrary TCP endpoints via the relay.
no-tcp-relay
# don't let the relay ever try to connect to private IP address ranges within your network (if any)
# given the turn server is likely behind your firewall, remember to include any privileged public IPs too.
denied-peer-ip=10.0.0.0-10.255.255.255
denied-peer-ip=192.168.0.0-192.168.255.255
denied-peer-ip=172.16.0.0-172.31.255.255
# special case the turn server itself so that client->TURN->TURN->client flows work
allowed-peer-ip=10.0.0.1
# consider whether you want to limit the quota of relayed streams per user (or total) to avoid risk of DoS.
user-quota=12 # 4 streams per video call, so 12 streams = 3 simultaneous relayed calls per user.
total-quota=1200
1. Also consider supporting TLS/DTLS. To do this, add the following settings
to `turnserver.conf`:
# TLS certificates, including intermediate certs.
# For Let's Encrypt certificates, use `fullchain.pem` here.
cert=/path/to/fullchain.pem
# TLS private key file
pkey=/path/to/privkey.pem
1. Ensure your firewall allows traffic into the TURN server on the ports
you've configured it to listen on (By default: 3478 and 5349 for the TURN(s)
traffic (remember to allow both TCP and UDP traffic), and ports 49152-65535
for the UDP relay.)
1. (Re)start the turn server:
* If you used the Debian package (or have set up a systemd unit yourself):
```sh
systemctl restart coturn
```
* If you installed from source:
```sh
bin/turnserver -o
```
## Synapse setup
Your home server configuration file needs the following extra keys:
1. "`turn_uris`": This needs to be a yaml list of public-facing URIs
for your TURN server to be given out to your clients. Add separate
entries for each transport your TURN server supports.
2. "`turn_shared_secret`": This is the secret shared between your
Home server and your TURN server, so you should set it to the same
string you used in turnserver.conf.
3. "`turn_user_lifetime`": This is the amount of time credentials
generated by your Home Server are valid for (in milliseconds).
Shorter times offer less potential for abuse at the expense of
increased traffic between web clients and your home server to
refresh credentials. The TURN REST API specification recommends
one day (86400000).
4. "`turn_allow_guests`": Whether to allow guest users to use the
TURN server. This is enabled by default, as otherwise VoIP will
not work reliably for guests. However, it does introduce a
security risk as it lets guests connect to arbitrary endpoints
without having gone through a CAPTCHA or similar to register a
real account.
As an example, here is the relevant section of the config file for matrix.org:
turn_uris: [ "turn:turn.matrix.org:3478?transport=udp", "turn:turn.matrix.org:3478?transport=tcp" ]
turn_shared_secret: "n0t4ctuAllymatr1Xd0TorgSshar3d5ecret4obvIousreAsons"
turn_user_lifetime: 86400000
turn_allow_guests: True
After updating the homeserver configuration, you must restart synapse:
* If you use synctl:
```sh
cd /where/you/run/synapse
./synctl restart
```
* If you use systemd:
```
systemctl restart synapse.service
```
..and your Home Server now supports VoIP relaying!
|
