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# Element Call

Element Call enables users to have audio and videocalls with groups, while
maintaining full E2E encryption.

It requires several bits of software and entries in .well-known/matrix/client

This bit is for later, but here's a nice bit of documentation to start:

https://sspaeth.de/2024/11/sfu/


# Install prerequisites

Define an entry in DNS for Livekit and Call, e.g. `livekit.matrixdev.example.com`
and `call.matrixdev.example.com`. Get certificates for them.

Expand `.well-known/matrix/client` to contain the pointer to the SFU:

```
"org.matrix.msc4143.rtc_foci": [
      {
        "type": "livekit",
        "livekit_service_url": "https://livekit.matrixdev.example.com"
      }
  ]
```

Create `.well-known/element/element.json`, which is opened by Element-web and
ElementX to find the Element Call widget. It should contain something like
this:

```
{
    "call": {
        "widget_url": "https://call.matrixdev.example.com"
    }
}
```

Make sure it is served as `application/json`, just like the other .well-known
files.


lk-jwt-service is a small Go program that handles authorization tokens. You'll need a
Go compiler, so install that:

```
apt install golang
```


# lk-jwt-service {#livekit}

Get the latest source code and comile it (preferably *NOT* as root):

```
git clone https://github.com/element-hq/lk-jwt-service.git
cd lk-jwt-service
go build -o lk-jwt-service
```

You'll then notice that you need a newer compiler, so we'll download that and add it to
our PATH (again not as root):

```
wget https://go.dev/dl/go1.23.3.linux-amd64.tar.gz
tar xvfz go1.23.3.linux-amd64.tar.gz
cd go/bin
export PATH=`pwd`:$PATH
cd
```

Now, compile:

```
cd lk-jwt-service
go build -o lk-jwt-service
```

Copy and chown the binary to `/usr/local/sbin` (yes: as root):

```
cp ~user/lk-jwt-service/lk-jwt-service /usr/local/sbin
chown root:root /usr/local/sbin/lk-jwt-service
```

Create a service file for systemd, something like this:

```
# This thing does authorization for Element Call

[Unit]
Description=LiveKit JWT Service
After=network.target

[Service]
Restart=always
User=www-data
Group=www-data
#WorkingDirectory=/opt/lk-jwt-service
EnvironmentFile=/etc/lk-jwt-service/config
ExecStart=/usr/local/sbin/lk-jwt-service

[Install]
WantedBy=multi-user.target
```

Not sure about the `WorkingDirectory`, so it's commented out until it turns
out to be necessary. We read the options from `/etc/lk-jwt-service/config`,
which we make read-only for group `www-data` and non-accessible by anyone
else.

```
mkdir /etc/lk-jwt-service
vi /etc/lk-jwt-service/config
chgrp -R www-data /etc/lk-jwt-service
chmod -R o-rwx /etc/lk-jwt-service
```

The contents of `/etc/lk-jwt-service/config` are not fully known yet (see
further, installation of the actual LiveKit, the SFU), but for now it's enough
to fill it with this:

```
LIVEKIT_URL=wss://livekit.matrixdev.example.com
LIVEKIT_SECRET=xxx
LIVEKIT_KEY=xxx
LK_JWT_PORT=8080
```

Now enable and start this thing:

```
systemctl enable --now lk-jwt-service
```