Tech pages/XEP-0368

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XEP-0368 can be used to provide encrypted XMPP service as well as HTTPS on the same port by utilizing ALPN TLS extension. Port 443 is commonly allowed by firewalls. To run multiple services on one port a proxy is needed to split the traffic between HTTP server and the XMPP server.

Note that this will not hide XMPP traffic from sufficiently intelligent firewalls as ALPN value is still sent unencrypted.

This page presents configuration hints for several popular proxies.

nginx

Nginx since version 1.13.10 has additional variable ($ssl_preread_alpn_protocols) available when using ngx_stream_ssl_preread module (this module must be included when compiling nginx).

The configuration below routes traffic with ALPN xmpp-client to server xmppserver and the rest (including HTTPS) to httpserver.

stream {
    upstream httpserver {
        server httpserver:8181;
    }

    upstream xmppserver {
        server xmppserver:5223;
    }

    upstream turnserver {
        server turnserver:3477;
    }

    map $ssl_preread_alpn_protocols $upstream {
        default httpserver;
        "xmpp-client" xmppserver;
        "stun.turn" turnserver;
        "stun.nat-discovery" turnserver;
    }

    server {
        listen 443;

        ssl_preread on;
        proxy_pass $upstream;
    }
}
 

Nginx will route only TLS traffic in this configuration so this configuration will work only with direct TLS (_xmpps-client SRV record). Connections that start unencrypted and then request encryption (STARTTLS, _xmpp-client record) will not work.

sslh

Here is a sample sslh.conf (Using at least sslh 1.18) to support XEP-0368 among other things:

verbose: false;
foreground: true;
inetd: false;
numeric: true;
transparent: false;
timeout: "2";
user: "nobody";
pidfile: "/run/sslh.pid";

# Note: I had to use IPs everywhere and not hostnames

# List of interfaces on which we should listen
listen:
(
    { host: "0.0.0.0"; port: "443"; },
);

# in this example:
# 5223 is a "direct-tls" xmpp port (prosody legacy_ssl_ports, ejabberd listen with tls: true)
# 442 is a https port (nginx, apache, etc)
# 22 is an ssh port (openssh)
# 5222 is a regular/plain/starttls xmpp port (prosody c2s_ports, ejabberd listen with starttls: true)
# 994 is "direct-tls" imap port, imaps (dovecot etc)
# 3477 is TURNS (TURN-over-TLS) port (coturn etc) NOTE: coturn by default (newer versions) rejects connections from localhost, you'd either need transparent mode, or to turn this off and open up all the risks it entails, for it to accept connections from sslh
 
protocols:
(
     { name: "tls";     host: "127.0.0.1"; port: "442";  alpn_protocols: [ "h2", "http/1.1" ]; },                  # https most common case
     { name: "tls";     host: "127.0.0.1"; port: "5223"; alpn_protocols: [ "xmpp-client" ]; },                     # check for XEP-0368 xmpp tls (this needs to be above SNI check below because XEP-0368 would send example.org in SNI)
     { name: "tls";     host: "127.0.0.1"; port: "442";  sni_hostnames:  [ "www.example.org", "example.org" ]; },  # specific hostnames go to https
     { name: "tls";     host: "127.0.0.1"; port: "3477"; alpn_protocols: [ "stun.turn", "stun.nat-discovery" ]; }, # turn should send ALPN, but if it doesn't...
     { name: "tls";     host: "127.0.0.1"; port: "3477"; sni_hostnames:  [ "turn.example.org" ]; },                # we can also match turn on SNI
     { name: "tls";     host: "127.0.0.1"; port: "994";  sni_hostnames:  [ "imap.example.org" ]; },                # other hostnames go to imaps
     { name: "tls";     host: "127.0.0.1"; port: "442"; },                                                         # anything else TLS assume for https
     { name: "ssh";     host: "127.0.0.1"; port: "22"; },                                                          # ssh goes to ssh
     { name: "xmpp";    host: "127.0.0.1"; port: "5222"; },                                                        # xmpp goes to regular xmpp port
     { name: "timeout"; host: "127.0.0.1"; port: "442"; }                                                          # send everything unknown to https
);

on-timeout: "timeout"; # if timeout elapses (2 seconds here) go to https
 

Another (incorrectly named) example can be found at the Debian Wiki

Transparent Proxying

If your XMPP server and protocol multiplexer are supporting the proxy protocol, you should consider enabling it. That way your XMPP server will see the real IPs of clients that connect to it.

Nginx

To enable the proxy protocol in nginx, modify your configuration as follows:

stream {
    ...

    server {
        listen 443;

        ssl_preread on;
        proxy_pass $upstream;
        proxy_protocol: on; <-- add this line
    }
}
 

ejabberd

In case of ejabberd, you want to add an additional handler that accepts the proxy protocol:

listen:
  ...
  -
    port: 5225
    use_proxy_protocol: true <-- Important!
    ip: "::"
    module: ejabberd_c2s
    max_stanza_size: 262144
    shaper: c2s_shaper
    access: c2s
    tls: true
    protocol_options: 'TLS_OPTIONS'
  ...
 

Note that you should only connect to this handler via the proxy protocol, as other connections will be refused.

Now ejabberd will display the real IPs of users that connect to your server via multiplexing over port 443.

DNS setup

You then need to setup your SRV Records so clients can find it, personally I have mine set up like so (for a JID like me@example.org):

_xmpps-client._tcp.example.org. 86400 IN SRV 5  0 443  xmpp.example.org.
_xmpp-client._tcp.example.org.  86400 IN SRV 10 0 443  xmpp.example.org.
_xmpp-client._tcp.example.org.  86400 IN SRV 15 0 5222 xmpp.example.org.

This prioritizes XEP-0368 TLS over port 443 first, then plain XMPP over 443 next, and lastly plain XMPP over 5222. A client that doesn't support XEP-0368 just skips the first record.

Please note the target can be anything, example.org, xmpp.example.org, or some.unrelated.domain.net, just as long as it's listening on those ports and has a valid certificate for example.org in this case.

If you have any questions feel free to ask the author of XEP-0368 via email, XMPP, or the nick moparisthebest in the XSF MUC