Securing access to openHAB

openHAB has mainly two ways to be accessed:

  1. Through the command line console, which is done through SSH and thus always authenticated and encrypted. You will find all details about this in the Console documentation.
  2. Through HTTP(S), which we will look at in the following.

Encrypted Communication

Webserver Ports

openHAB has a built-in webserver, which listens on port 8080 for HTTP and 8443 for HTTPS requests. In general, it is advised to use HTTPS communication over HTTP.

The default ports 8080 and 8443 can be changed by setting the environment variables OPENHAB_HTTP_PORT resp. OPENHAB_HTTPS_PORT. In an apt installation, you would best do this in the file /etc/default/openhab2.

SSL Certificates

On the very first start, openHAB generates a personal (self-signed, 256-bit ECC) SSL certificate and stores it in the Jetty keystore (in ${USER_DATA}etc/keystore). This process makes sure that every installation has an individual certificate, so that nobody else can falsely mimic your server. Note that on slow hardware, this certificate generation can take up to several minutes, so be patient on a first start - it is all for your own security.

Authentication and Access Control

openHAB does not (yet) support restricting access through HTTP(S) for certain users - there is no authentication in place, nor is there a limitation of functionality or information that different users can access.

Security Warning: It is vitally important that you MUST NOT directly expose your openHAB instance to the Internet (e.g. by opening a port in your firewall)!

If you want to limit access to only certain network interfaces, you can do so in the file $OPENHAB_USERDATA/etc/org.ops4j.pax.web.cfg by editing the org.ops4j.pax.web.listening.addresses parameter. Setting it to

org.ops4j.pax.web.listening.addresses = 127.0.0.1

will e.g. only allow requests through the local loopback interface.

Options for Secure Remote Access

Clearly, having remote access to your openHAB instance is something most users would not want to miss. There are different options to do so.

VPN Connection

The most secure option is probably to create a VPN connection to your home network. Doing so will allow you to access your openHAB instance in the same way as if you were at home. There are many different solutions for VPN, so we cannot give any specific advice here, what to use and how to set in up.

myopenHAB Cloud Service

You can use an openHAB Cloud instance to which openHAB creates a tunnel connection and which forwards all requests through this tunnel. openHAB will see these incoming requests as originating from the local loopback interface.

The simplest way to get hold of such an openHAB Cloud is to register an account at myopenHAB.org, which is operated by the openHAB Foundation.

Running openHAB Behind a Reverse Proxy

A reverse proxy simply directs client requests to the appropriate server. This means you can proxy connections to http://mydomain_or_myip to your openHAB runtime. You just have to replace mydomain_or_myip with either an internal or external IP (e.g. xx.xx.xx.xx) or a domain if you own one that links to the external IP of openHAB (e.g. openhab.mydomain.tld).

Running openHAB behind a reverse proxy allows you to access your openHAB runtime via port 80 (HTTP) and 443 (HTTPS). It also provides you a simple way of protecting your server with authentication and secure certificates.

The good news is that openHABian already offers the possibility to activate a preconfigured NGINX reverse proxy, which includes setting up authentication and a valid Let’s Encrypt certificate.

Table of Content:

Setting up NGINX

These are the steps required to use NGINX, a lightweight HTTP server, although you can use Apache HTTP server or any other HTTP server which supports reverse proxying.

Installation

NGINX runs as a service in most Linux distributions, installation should be as simple as:

sudo apt-get update && sudo apt-get install nginx

Once installed, you can test to see if the service is running correctly by going to http://mydomain_or_myip, you should see the default “Welcome to nginx” page. If you don’t, you may need to check your firewall or ports and check if port 80 (and 443 for HTTPS later) is not blocked and that services can use it.

Basic Configuration

NGINX configures the server when it starts up based on configuration files. The location of the default setup is /etc/nginx/sites-enabled/default. To allow NGINX to proxy openHAB, you need to change this file (make a backup of it in a different folder first).

The recommended configuration below assumes that you run the reverse proxy on the same machine as your openHAB runtime. If this doesn’t fit for you, you just have to replace proxy_pass http://localhost:8080/ by your openHAB runtime hostname (such as http://youropenhabhostname:8080/).

server {
    listen                                    80;
    server_name                               mydomain_or_myip;

    location / {
        proxy_pass                            http://localhost:8080/;
        proxy_set_header Host                 $http_host;
        proxy_set_header X-Real-IP            $remote_addr;
        proxy_set_header X-Forwarded-For      $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto    $scheme;
    }
}

It is also recommended to name the file to something relevant to what it’s doing, if you already have a default file in place, then you can rename it via:

sudo mv /etc/nginx/sites-enabled/default /etc/nginx/sites-enabled/openhab

Otherwise, create a new file. Every file in the sites-enabled folder gets processed by NGINX, so make sure you only have one per site.

After saving over the file but before you commit the changes to our server, you should test to see if our changes contain any errors; this is done with the command:

sudo nginx -t

If you see that the test is successful, you can restart the NGINX service with…

sudo service nginx restart

…and then go to http://mydomain_or_myip to see your openHAB server.

Authentication with NGINX

For further security, you may wish to ask for a username and password before users have access to openHAB. This is fairly simple in NGINX once you have the reverse proxy setup, you just need to provide the server with a basic authentication user file.

Note: There is currently an issue with Proxy Authentication and HABmin when using some browsers. If you require HABmin, consider connecting locally or using Safari for now.

Creating the First User

You will be using htpasswd to generate a username/password file, this utility can be found in the apache2-utils package:

sudo apt-get install apache2-utils

To generate a file that NGINX can use you use the following command, don’t forget to change username to something meaningful!

sudo htpasswd -c /etc/nginx/.htpasswd username

You will receive a prompt to create a password for this username, once finished the file will be created. You’re then free to reference the file to NGINX.

Referencing the File in the NGINX Configuration

Now the configuration file (/etc/nginx/sites-enabled/openhab) needs to be edited to use this password. Open the configuration file and add the following lines underneath the proxy_* settings:

        auth_basic                            "Username and Password Required";
        auth_basic_user_file                  /etc/nginx/.htpasswd;

Once done, test and restart your NGINX service and authentication should now be enabled on your server!

Adding or Removing users

To add new users to your site, you must use following command, do not use the -c modifier again as this will remove all previously created users:

sudo htpasswd /etc/nginx/.htpasswd username

and to delete an existing user:

sudo htpasswd -D /etc/nginx/.htpasswd username

Once again, any changes you make to these files must be followed with restarting the NGINX service otherwise no changes will be made.

Making Exceptions for Specific IP addresses

It is often desirable to allow specific IPs (e.g. the local network) to access openHAB without needing to prompt for a password or to block everyone else entirely. In these cases NGINX can use the satisfy any directive followed by allow and deny lines to make these exceptions. These lines are placed in the location{} block. For example, by adding the lines:

        satisfy  any;
        allow    192.168.0.1/24;
        allow    127.0.0.1;
        deny     all;

NGINX will allow anyone within the 192.168.0.1/24 range and the localhost to connect without a password. If you have setup a password following the previous section, then the rest will be prompted for a password for access.

Setting up a Domain

To generate a trusted certificate, you need to own a domain. To acquire your own domain, you can use one of the following methods:

Method Example Links Note
Purchasing a domain name GoDaddy, Namecheap, Enom, Register You should have an IP adress that doesn’t change (i.e. fixed), or changes rarely, and then update the DNS A record so that your domain/subdomain to point towards your IP.
Obtaining a free domain FreeNom Setup is the same as above.
Using a “Dynamic DNS” sevice No-IP, Dyn Uses a client to automatically update your IP to a domain of you choice, some Dynamic DNS services offer a free domain too.

Enabling HTTPS

Encrypting the communication between client and the server is important because it protects against eavesdropping and possible forgery. The following options are available depending if you have a valid domain:

If you have a valid domain and can change the DNS to point towards your IP, follow the instructions for Let’s Encrypt If you need to use an internal or external IP to connect to openHAB, follow the instructions for OpenSSL

Using OpenSSL to Generate Self-Signed Certificates

OpenSSL is also packaged for most Linux distributions, installing it should be as simple as:

sudo apt-get install openssl

Once complete, you need to create a directory where our certificates can be placed:

sudo mkdir -p /etc/ssl/certs

Now OpenSSL can be told to generate a 2048 bit long RSA key and a certificate that is valid for a year:

sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout /etc/ssl/openhab.key -out /etc/ssl/openhab.crt

You will be prompted for some information which you will need to fill out for the certificate, when it asks for a Common Name, you may enter your IP Address: Common Name (e.g. server FQDN or YOUR name) []: xx.xx.xx.xx

Adding the Certificates to Your Proxy Server

The certificate and key should have been placed in /etc/ssl/. NGINX needs to be told where these files are and then enable the reverse proxy to direct HTTPS traffic. In the NGINX configuration, place the following underneath your server_name variable:

  ssl_certificate                 /etc/ssl/openhab.crt;
  ssl_certificate_key             /etc/ssl/openhab.key;

Using Let’s Encrypt to Generate Trusted Certificates

Skip this step if you have no domain name or have already followed the instructions for OpenSSL

Let’s Encrypt is a service that allows anyone with a valid domain to automatically generate a trusted certificate, these certificates are usually accepted by a browser without any warnings.

Setting up the NGINX Proxy Server to Handle the Certificate Generation Procedure

Let’s Encrypt needs to validate that the server has control of the domain. The simplest way of doing this is using a webroot plugin to place a file on the server, and then access it using a specific url: /.well-known/acme-challenge. Since the proxy only forwards traffic to the openHAB server, the server needs to be told to handle requests at this address differently.

First, create a directory that Certbot can be given access to:

sudo mkdir -p /var/www/mydomain

Next add the new location parameter to your NGINX config, this should be placed above the last brace in the server setting:

  location /.well-known/acme-challenge/ {
    root                            /var/www/mydomain;
  }
Using Certbot

Certbot is a tool which simplifies the process of obtaining secure certificates. The tool may not be packaged for some Linux distributions so installation instructions may vary, check out their website and follow the instructions using the webroot mode. Don’t forget to change the example domain to your own! An example of a valid certbot command (in this case for Debian Jessie) would be:

sudo certbot certonly --webroot -w /var/www/mydomain -d mydomain
Adding the Certificates to Your Proxy Server

The certificate and key should have been placed in /etc/letsencrypt/live/mydomain_or_myip. NGINX needs to be told where these files are and then enable the reverse proxy to direct HTTPS traffic, using Strict Transport Security to prevent man-in-the-middle attacks. In the NGINX configuration, place the following underneath your server_name variable:

    ssl_certificate                 /etc/letsencrypt/live/mydomain_or_myip/fullchain.pem;
    ssl_certificate_key             /etc/letsencrypt/live/mydomain_or_myip/privkey.pem;
    add_header                      Strict-Transport-Security "max-age=31536000";

Setting Your NGINX Server to Listen to the HTTPS Port

Regardless of the option you choose, make sure you change the port to listen in on HTTPS traffic.

    listen                          443 ssl;

After restarting NGINX service, you will be using a valid HTTPS certificate. You can check by going to https://mydomain_or_myip and confirming with your browser that you have a valid certificate. These certificates expire within a few months so it is important to run the updater in a cron expression (and also restart NGINX) as explained in the Certbot setup instructions. If you want to keep hold of a HTTP server for some reason, just add listen 80; and remove the Strict-Transport-Security line.

Redirecting HTTP Traffic to HTTPS

You may want to redirect all HTTP traffic to HTTPS, you can do this by adding the following to the NGINX configuration. This will essentially replace the HTTP url with the HTTPS version!

server {
    listen                          80;
    server_name                     mydomain_or_myip;
    return 301                      https://$server_name$request_uri;
}

Putting it All Together

After following all the steps on this page, you should have a NGINX server configuration (/etc/nginx/sites-enabled/openhab) that looks like this:

server {
    listen                          80;
    server_name                     mydomain_or_myip;
    return 301                      https://$server_name$request_uri;
}
server {
    listen                          443 ssl;
    server_name                     mydomain_or_myip;

    ssl_certificate                 /etc/letsencrypt/live/mydomain/fullchain.pem; # or /etc/ssl/openhab.crt
    ssl_certificate_key             /etc/letsencrypt/live/mydomain/privkey.pem;   # or /etc/ssl/openhab.key
    add_header                      Strict-Transport-Security "max-age=31536000"; # Remove if using self-signed and are having trouble.

    location / {
        proxy_pass                              http://localhost:8080/;
        proxy_set_header Host                   $http_host;
        proxy_set_header X-Real-IP              $remote_addr;
        proxy_set_header X-Forwarded-For        $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto      $scheme;
        satisfy                                 any;
        allow                                   192.168.0.1/24;
        allow                                   127.0.0.1;
        deny                                    all;
        auth_basic                              "Username and Password Required";
        auth_basic_user_file                    /etc/nginx/.htpasswd;
    }

    #### When using Let's Encrypt Only ####
    location /.well-known/acme-challenge/ {
        root                                    /var/www/mydomain;
    }
}

Additional HTTPS Security

To test your security settings SSL Labs provides a tool for testing your domain against ideal settings (Make sure you check “Do not show the results on the boards” if you dont want your domain seen).

This optional section is for those who would like to strengthen the HTTPS security on openHAB, it can be applied regardless of which HTTPS method you used above, but you need to follow at least one of them first.

First, we need to generate a stronger key exchange, to do this we can generate an additional key with OpenSSL Note: this will take a few minutes to complete:

mkdir -p /etc/nginx/ssl
openssl dhparam -out /etc/nginx/ssl/dhparam.pem 4096

Now we can configure NGINX to use this key, as well as telling the client to use specific cyphers and SSL settings, just add the following under your ssl_certificate ** settings but above location *. All of these settings are customisable, but make sure you read up on what these do first before changing them:

    ssl_protocols                   TLSv1 TLSv1.1 TLSv1.2;
    ssl_prefer_server_ciphers       on;
    ssl_dhparam                     /etc/nginx/ssl/dhparam.pem;
    ssl_ciphers                     ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA:HIGH:!aNULL:!eNULL:!LOW:!3DES:!MD5:!EXP:!CBC:!EDH:!kEDH:!PSK:!SRP:!kECDH;
    ssl_session_timeout             1d;
    ssl_session_cache               shared:SSL:10m;
    keepalive_timeout               70;

Feel free to test the new configuration again on SSL Labs. If you’re achieving A or A+ here, then your client-openHAB communication is very secure.

Further Reading

The setup above is a suggestion for high compatibility with an A+ rating at the time of writing, however flaws in these settings (particularly the cyphers) may become known overtime. The following articles may be useful when understanding and changing these settings.