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authorreivilibre <reivilibre@users.noreply.github.com>2022-07-26 11:13:04 +0000
committerreivilibre <reivilibre@users.noreply.github.com>2022-07-26 11:13:04 +0000
commit55354482cd7fdda060fe77597c3f8dbf86d82bda (patch)
tree88f00837b60bbb0f43658d4c4e9af33f9bd7d4a9 /v1.64/turn-howto.html
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downloadsynapse-55354482cd7fdda060fe77597c3f8dbf86d82bda.tar.xz
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+<!DOCTYPE HTML>
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+
+                        <h1 id="overview"><a class="header" href="#overview">Overview</a></h1>
+<p>This document explains how to enable VoIP relaying on your homeserver with
+TURN.</p>
+<p>The synapse Matrix homeserver supports integration with TURN server via the
+<a href="https://tools.ietf.org/html/draft-uberti-behave-turn-rest-00">TURN server REST API</a>. This
+allows the homeserver to generate credentials that are valid for use on the
+TURN server through the use of a secret shared between the homeserver and the
+TURN server.</p>
+<p>The following sections describe how to install <a href="https://github.com/coturn/coturn">coturn</a> (which implements the TURN REST API) and integrate it with synapse.</p>
+<h2 id="requirements"><a class="header" href="#requirements">Requirements</a></h2>
+<p>For TURN relaying with <code>coturn</code> to work, it must be hosted on a server/endpoint with a public IP.</p>
+<p>Hosting TURN behind NAT requires port forwaring and for the NAT gateway to have a public IP.
+However, even with appropriate configuration, NAT is known to cause issues and to often not work.</p>
+<h2 id="coturn-setup"><a class="header" href="#coturn-setup"><code>coturn</code> setup</a></h2>
+<h3 id="initial-installation"><a class="header" href="#initial-installation">Initial installation</a></h3>
+<p>The TURN daemon <code>coturn</code> is available from a variety of sources such as native package managers, or installation from source.</p>
+<h4 id="debian-installation"><a class="header" href="#debian-installation">Debian installation</a></h4>
+<p>Just install the debian package:</p>
+<pre><code class="language-sh">apt install coturn
+</code></pre>
+<p>This will install and start a systemd service called <code>coturn</code>.</p>
+<h4 id="source-installation"><a class="header" href="#source-installation">Source installation</a></h4>
+<ol>
+<li>
+<p>Download the <a href="https://github.com/coturn/coturn/releases/latest">latest release</a> from github.  Unpack it and <code>cd</code> into the directory.</p>
+</li>
+<li>
+<p>Configure it:</p>
+<pre><code class="language-sh">./configure
+</code></pre>
+<p>You may need to install <code>libevent2</code>: 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.</p>
+</li>
+<li>
+<p>Build and install it:</p>
+<pre><code class="language-sh">make
+make install
+</code></pre>
+</li>
+</ol>
+<h3 id="configuration"><a class="header" href="#configuration">Configuration</a></h3>
+<ol>
+<li>
+<p>Create or edit the config file in <code>/etc/turnserver.conf</code>. The relevant
+lines, with example values, are:</p>
+<pre><code>use-auth-secret
+static-auth-secret=[your secret key here]
+realm=turn.myserver.org
+</code></pre>
+<p>See <code>turnserver.conf</code> for explanations of the options. One way to generate
+the <code>static-auth-secret</code> is with <code>pwgen</code>:</p>
+<pre><code class="language-sh">pwgen -s 64 1
+</code></pre>
+<p>A <code>realm</code> must be specified, but its value is somewhat arbitrary. (It is
+sent to clients as part of the authentication flow.) It is conventional to
+set it to be your server name.</p>
+</li>
+<li>
+<p>You will most likely want to configure coturn to write logs somewhere. The
+easiest way is normally to send them to the syslog:</p>
+<pre><code class="language-sh">syslog
+</code></pre>
+<p>(in which case, the logs will be available via <code>journalctl -u coturn</code> on a
+systemd system). Alternatively, coturn can be configured to write to a
+logfile - check the example config file supplied with coturn.</p>
+</li>
+<li>
+<p>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:</p>
+<pre><code># 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
+
+# recommended additional local peers to block, to mitigate external access to internal services.
+# https://www.rtcsec.com/article/slack-webrtc-turn-compromise-and-bug-bounty/#how-to-fix-an-open-turn-relay-to-address-this-vulnerability
+no-multicast-peers
+denied-peer-ip=0.0.0.0-0.255.255.255
+denied-peer-ip=100.64.0.0-100.127.255.255
+denied-peer-ip=127.0.0.0-127.255.255.255
+denied-peer-ip=169.254.0.0-169.254.255.255
+denied-peer-ip=192.0.0.0-192.0.0.255
+denied-peer-ip=192.0.2.0-192.0.2.255
+denied-peer-ip=192.88.99.0-192.88.99.255
+denied-peer-ip=198.18.0.0-198.19.255.255
+denied-peer-ip=198.51.100.0-198.51.100.255
+denied-peer-ip=203.0.113.0-203.0.113.255
+denied-peer-ip=240.0.0.0-255.255.255.255
+
+# special case the turn server itself so that client-&gt;TURN-&gt;TURN-&gt;client flows work
+# this should be one of the turn server's listening IPs
+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
+</code></pre>
+</li>
+<li>
+<p>Also consider supporting TLS/DTLS. To do this, add the following settings
+to <code>turnserver.conf</code>:</p>
+<pre><code># 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
+
+# Ensure the configuration lines that disable TLS/DTLS are commented-out or removed
+#no-tls
+#no-dtls
+</code></pre>
+<p>In this case, replace the <code>turn:</code> schemes in the <code>turn_uris</code> settings below
+with <code>turns:</code>.</p>
+<p>We recommend that you only try to set up TLS/DTLS once you have set up a
+basic installation and got it working.</p>
+<p>NB: If your TLS certificate was provided by Let's Encrypt, TLS/DTLS will
+not work with any Matrix client that uses Chromium's WebRTC library. This
+currently includes Element Android &amp; iOS; for more details, see their
+<a href="https://github.com/vector-im/element-android/issues/1533">respective</a>
+<a href="https://github.com/vector-im/element-ios/issues/2712">issues</a> as well as the underlying
+<a href="https://bugs.chromium.org/p/webrtc/issues/detail?id=11710">WebRTC issue</a>.
+Consider using a ZeroSSL certificate for your TURN server as a working alternative.</p>
+</li>
+<li>
+<p>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 TURN
+traffic (remember to allow both TCP and UDP traffic), and ports 49152-65535
+for the UDP relay.)</p>
+</li>
+<li>
+<p>If your TURN server is behind NAT, the NAT gateway must have an external,
+publicly-reachable IP address. You must configure coturn to advertise that
+address to connecting clients:</p>
+<pre><code>external-ip=EXTERNAL_NAT_IPv4_ADDRESS
+</code></pre>
+<p>You may optionally limit the TURN server to listen only on the local
+address that is mapped by NAT to the external address:</p>
+<pre><code>listening-ip=INTERNAL_TURNSERVER_IPv4_ADDRESS
+</code></pre>
+<p>If your NAT gateway is reachable over both IPv4 and IPv6, you may
+configure coturn to advertise each available address:</p>
+<pre><code>external-ip=EXTERNAL_NAT_IPv4_ADDRESS
+external-ip=EXTERNAL_NAT_IPv6_ADDRESS
+</code></pre>
+<p>When advertising an external IPv6 address, ensure that the firewall and
+network settings of the system running your TURN server are configured to
+accept IPv6 traffic, and that the TURN server is listening on the local
+IPv6 address that is mapped by NAT to the external IPv6 address.</p>
+</li>
+<li>
+<p>(Re)start the turn server:</p>
+<ul>
+<li>
+<p>If you used the Debian package (or have set up a systemd unit yourself):</p>
+<pre><code class="language-sh">systemctl restart coturn
+</code></pre>
+</li>
+<li>
+<p>If you installed from source:</p>
+<pre><code class="language-sh">bin/turnserver -o
+</code></pre>
+</li>
+</ul>
+</li>
+</ol>
+<h2 id="synapse-setup"><a class="header" href="#synapse-setup">Synapse setup</a></h2>
+<p>Your homeserver configuration file needs the following extra keys:</p>
+<ol>
+<li>&quot;<code>turn_uris</code>&quot;: 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.</li>
+<li>&quot;<code>turn_shared_secret</code>&quot;: This is the secret shared between your
+homeserver and your TURN server, so you should set it to the same
+string you used in turnserver.conf.</li>
+<li>&quot;<code>turn_user_lifetime</code>&quot;: This is the amount of time credentials
+generated by your homeserver are valid for (in milliseconds).
+Shorter times offer less potential for abuse at the expense of
+increased traffic between web clients and your homeserver to
+refresh credentials. The TURN REST API specification recommends
+one day (86400000).</li>
+<li>&quot;<code>turn_allow_guests</code>&quot;: 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.</li>
+</ol>
+<p>As an example, here is the relevant section of the config file for <code>matrix.org</code>. The
+<code>turn_uris</code> are appropriate for TURN servers listening on the default ports, with no TLS.</p>
+<pre><code>turn_uris: [ &quot;turn:turn.matrix.org?transport=udp&quot;, &quot;turn:turn.matrix.org?transport=tcp&quot; ]
+turn_shared_secret: &quot;n0t4ctuAllymatr1Xd0TorgSshar3d5ecret4obvIousreAsons&quot;
+turn_user_lifetime: 86400000
+turn_allow_guests: True
+</code></pre>
+<p>After updating the homeserver configuration, you must restart synapse:</p>
+<ul>
+<li>If you use synctl:
+<pre><code class="language-sh"># Depending on how Synapse is installed, synctl may already be on
+# your PATH. If not, you may need to activate a virtual environment.
+synctl restart
+</code></pre>
+</li>
+<li>If you use systemd:
+<pre><code class="language-sh">systemctl restart matrix-synapse.service
+</code></pre>
+</li>
+</ul>
+<p>... and then reload any clients (or wait an hour for them to refresh their
+settings).</p>
+<h2 id="troubleshooting"><a class="header" href="#troubleshooting">Troubleshooting</a></h2>
+<p>The normal symptoms of a misconfigured TURN server are that calls between
+devices on different networks ring, but get stuck at &quot;call
+connecting&quot;. Unfortunately, troubleshooting this can be tricky.</p>
+<p>Here are a few things to try:</p>
+<ul>
+<li>
+<p>Check that you have opened your firewall to allow TCP and UDP traffic to the
+TURN ports (normally 3478 and 5349).</p>
+</li>
+<li>
+<p>Check that you have opened your firewall to allow UDP traffic to the UDP
+relay ports (49152-65535 by default).</p>
+</li>
+<li>
+<p>Try disabling <code>coturn</code>'s TLS/DTLS listeners and enable only its (unencrypted)
+TCP/UDP listeners. (This will only leave signaling traffic unencrypted;
+voice &amp; video WebRTC traffic is always encrypted.)</p>
+</li>
+<li>
+<p>Some WebRTC implementations (notably, that of Google Chrome) appear to get
+confused by TURN servers which are reachable over IPv6 (this appears to be
+an unexpected side-effect of its handling of multiple IP addresses as
+defined by
+<a href="https://tools.ietf.org/html/draft-ietf-rtcweb-ip-handling-12"><code>draft-ietf-rtcweb-ip-handling</code></a>).</p>
+<p>Try removing any AAAA records for your TURN server, so that it is only
+reachable over IPv4.</p>
+</li>
+<li>
+<p>If your TURN server is behind NAT:</p>
+<ul>
+<li>
+<p>double-check that your NAT gateway is correctly forwarding all TURN
+ports (normally 3478 &amp; 5349 for TCP &amp; UDP TURN traffic, and 49152-65535 for the UDP
+relay) to the NAT-internal address of your TURN server. If advertising
+both IPv4 and IPv6 external addresses via the <code>external-ip</code> option, ensure
+that the NAT is forwarding both IPv4 and IPv6 traffic to the IPv4 and IPv6
+internal addresses of your TURN server. When in doubt, remove AAAA records
+for your TURN server and specify only an IPv4 address as your <code>external-ip</code>.</p>
+</li>
+<li>
+<p>ensure that your TURN server uses the NAT gateway as its default route.</p>
+</li>
+</ul>
+</li>
+<li>
+<p>Enable more verbose logging in coturn via the <code>verbose</code> setting:</p>
+<pre><code>verbose
+</code></pre>
+<p>... and then see if there are any clues in its logs.</p>
+</li>
+<li>
+<p>If you are using a browser-based client under Chrome, check
+<code>chrome://webrtc-internals/</code> for insights into the internals of the
+negotiation. On Firefox, check the &quot;Connection Log&quot; on <code>about:webrtc</code>.</p>
+<p>(Understanding the output is beyond the scope of this document!)</p>
+</li>
+<li>
+<p>You can test your Matrix homeserver TURN setup with <a href="https://test.voip.librepush.net/">https://test.voip.librepush.net/</a>.
+Note that this test is not fully reliable yet, so don't be discouraged if
+the test fails.
+<a href="https://github.com/matrix-org/voip-tester">Here</a> is the github repo of the
+source of the tester, where you can file bug reports.</p>
+</li>
+<li>
+<p>There is a WebRTC test tool at
+<a href="https://webrtc.github.io/samples/src/content/peerconnection/trickle-ice/">https://webrtc.github.io/samples/src/content/peerconnection/trickle-ice/</a>. To
+use it, you will need a username/password for your TURN server. You can
+either:</p>
+<ul>
+<li>
+<p>look for the <code>GET /_matrix/client/r0/voip/turnServer</code> request made by a
+matrix client to your homeserver in your browser's network inspector. In
+the response you should see <code>username</code> and <code>password</code>. Or:</p>
+</li>
+<li>
+<p>Use the following shell commands:</p>
+<pre><code class="language-sh">secret=staticAuthSecretHere
+
+u=$((`date +%s` + 3600)):test
+p=$(echo -n $u | openssl dgst -hmac $secret -sha1 -binary | base64)
+echo -e &quot;username: $u\npassword: $p&quot;
+</code></pre>
+<p>Or:</p>
+</li>
+<li>
+<p>Temporarily configure coturn to accept a static username/password. To do
+this, comment out <code>use-auth-secret</code> and <code>static-auth-secret</code> and add the
+following:</p>
+<pre><code>lt-cred-mech
+user=username:password
+</code></pre>
+<p><strong>Note</strong>: these settings will not take effect unless <code>use-auth-secret</code>
+and <code>static-auth-secret</code> are disabled.</p>
+<p>Restart coturn after changing the configuration file.</p>
+<p>Remember to restore the original settings to go back to testing with
+Matrix clients!</p>
+</li>
+</ul>
+<p>If the TURN server is working correctly, you should see at least one <code>relay</code>
+entry in the results.</p>
+</li>
+</ul>
+
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