This is a text-only version of the following page on https://raymii.org:

This is a text-only version of the following page on https://raymii.org:
---
Title : nginx 1.15.2, ssl_preread_protocol, multiplex HTTPS and SSH on the same port
Author : Remy van Elst
Date : 06-08-2018
Last update : 12-01-2020
URL : https://raymii.org/s/tutorials/nginx_1.15.2_ssl_preread_protocol_multiplex_https_and_ssh_on_the_same_port.html
Format : Markdown/HTML
---

The NGINX blog recently had a [nice article on a new feature of NGINX 1.15.2,
$ssl _preread_ protocol][1]. This allows you to multiplex HTTPS and other SSL
protocols on the same port, or as their blog states, 'to distinguish between
SSL/TLS and other protocols when forwarding traffic using a TCP (stream) proxy'.
This can be used to run SSH and HTTPS on the same port (or any other SSL
protocol next to HTTPS). By running SSH and HTTPS on the same port, one can
circumvent certain firewall restrictions. If the session looks like HTTPS, nginx
will handle it, if it looks like something else, it will forward it to the
configured other program. I used to use [SSLH][2] to get this functionality, but
now it's built into the nginx webserver.

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This small guide will cover the installation of the latest version of nginx on
Ubuntu and configuring this multiplex feature.

You must use NGINX in proxy mode. This means that nginx will act as a load
balancer or proxy in front of your application (like Django, Rails, etc).

- Update 12-01-2020: added apt-key add. Added example of ssh and https on the
same server.

### Install the latest version of NGINX

nginx provides [a repository][4] for both CentOS, Debian/Ubuntu and SUSE. In
this example we will use Ubuntu.

Download the signing key:

wget http://nginx.org/keys/nginx_signing.key

Trust the signing key:

apt-key add nginx_signing.key

Add the repository:

echo "deb http://nginx.org/packages/mainline/ubuntu/ bionic nginx" > /etc/apt/sources.list.d/nginx.list
echo "deb-src http://nginx.org/packages/mainline/ubuntu/ bionic nginx" >> /etc/apt/sources.list.d/nginx.list

Replace `bionic` with your version of Ubuntu (use `lsb_release -a` to find out).

Install nginx from the newly added repository:

apt-get update;
apt-get install nginx

### Configure nginx for ssl _preread_ protocol

Quoted from the [nginx blog][1]:

The following configuration snippet uses the `$ssl_preread_protocol` variable in
a map block to set the `$upstream variable` to the name of the upstream group
appropriate for the protocol being used on the connection. The `proxy_pass`
directive then forwards the request to the selected upstream group. Note that
the `ssl_preread` on directive must be included in the server block for the
`$ssl_preread_protocol` variable to work.

This piece of configuration must go in the root of your nginx config, not inside
a `server` block.

stream {
upstream ssh {
server 192.0.2.10:22;
}

upstream https {
server 192.0.2.20:443;
}

map $ssl_preread_protocol $upstream {
default ssh;
"TLSv1.2" https;
"TLSv1.3" https;
"TLSv1.1" https;
"TLSv1.0" https;
}

# SSH and SSL on the same port
server {
listen 443;

proxy_pass $upstream;
ssl_preread on;
}
}

In this case, if the protocol detected is `TLSv1.2`, HTTPS is assumed and the
traffix is forwarded to the HTTPS server (`192.0.2.20`). Otherwise the traffic is
forwarded to the SSH host (`192.0.2.10`).

#### SSH and HTTPS on the same server

If you want to split `ssh` and `https` on the same server, the configuration is
a little bit different. You first must make sure that there is no other website
listening on port `:443`, because that is what nginx will use for its proxy.

Not even another site withing nginx is allowed to use port 443. Change your `listen`
blocks to use port `8443`, for example:

listen [::]:8443 http2;
listen 8443 http2;

The configuration for ssh/ssl must not go in a `server` directive, but in the
root of your nginx config:

stream {
upstream ssh {
server 127.0.0.1:22;
}

upstream https {
server 127.0.0.1:8443;
}

map $ssl_preread_protocol $upstream {
default ssh;
"TLSv1.2" https;
"TLSv1.3" https;
"TLSv1.1" https;
"TLSv1.0" https;
}
#
# SSH and SSL on the same port
server {
listen 443;
proxy_pass $upstream;
ssl_preread on;
}
}

### More fun with ssl_preread

The `ssl_preread` module can detect more than the protocol. The SNI server name is also supported, which allows for proxy forwarding to different backend servers based on the requested SSL hostname. [Quoting the documentation][5]:

map $ssl_preread_server_name $name {
backend.example.com backend;
default backend2;
}

upstream backend {
server 192.168.0.1:12345;
server 192.168.0.2:12345;
}

upstream backend2 {
server 192.168.0.3:12345;
server 192.168.0.4:12345;
}

server {
listen 12346;
proxy_pass $name;
ssl_preread on;
}

Do note that this also requires a newer version of nginx than by default in the
Ubuntu 16.04 or 18.04 release.

[1]: http://web.archive.org/web/20180806131633/https://www.nginx.com/blog/running-non-ssl-protocols-over-ssl-port-nginx-1-15-2/
[2]: https://github.com/yrutschle/sslh
[3]: https://www.digitalocean.com/?refcode=7435ae6b8212
[4]: http://nginx.org/en/linux_packages.html#mainline
[5]: http://web.archive.org/web/20180806133249/https://nginx.org/en/docs/stream/ngx_stream_ssl_preread_module.html

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