Self Signed Certificate (https) in Raspberry PI with Apache

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HyperText Transfer Protocol Secure (https) is a communication protocol adding a security layer to classic http. It uses TLS and certificates communication between two computers, reducing man-in-the-middle attack risks. Beside common configuration, you can set a self signed configuration on Raspberry Pi running Apache web services

Https (which uses port 443 instead of default http port 80) became a common standard as cyber security risks increased over the time. Today it can be a requirement for some services to run correctly (like, for example, IdeaSpaceVR project or Grocy project). In this tutorial I’m going to show how to setup a self signed certificate in your Raspberry PI running Apache web server.

How TLS Handshake Works

TLS (Transport Layer Security) grants security in https connections. It defines the way two computers (a client and a server) has to establish their communication respecting this security protocol.

Before starting communication, web server needs to get “verified” by an external Certification Authority (CA). This external part checks that that server, at that URL, is really who claims to be. When this step is successfully performed, the CA emits a certificate (with encrypted keys) which includes Certification Authority references. This certificate is usually limited to a specific time: server owners need to renew its certificate before this goes expired.

When a client connects to that server (with an https url), it receives the certificate and verify with CA that the certificate is correct (keys haven’t been modified by unwanted malicious intruder). Client can then share with server all required keys to encrypt communication.

This “three parties verification” assures better security on communication and reduce interference risks.

In some circumstances, web server can’t be reached from certification authority to be verified. In these case, a self signed certificate can be a valid workaround as it allow establishing TLS handshake. What changes is that the same server is working also as CA and is issuing its own certificate. This result on common browsers accepting this connection, but warning you that certificate can’t be verified from an indipendent third party.

Self signed certificates is useful in a number of cases. For example, you could prefer not conecting your apache server to internet, leaving it closed ino a local network (home). Or you could need to test your application in a development environment, not connected to internet. In these cases, your security is assured because your service is restriced to a secure network.

For this guide I’m going to use a Raspberry PI Zero W, but this procedure applies to all Raspberry PI computer boards.

What We Need

As usual, I suggest adding from now to your favourite ecommerce shopping chart all needed hardware, so that at the end you will be able to evaluate overall costs and decide if continuing with the project or removing them from shopping chart. So, hardware will be only:

Check hardware prices with following links:

Amazon raspberry pi boards box
Amazon raspberry pi Zero W box
Amazon Micro SD box
Amazon Raspberry PI Power Supply box

Step-by-Step Procedure

Prepare OS

Start installing your operating system. You can install Raspberry PI OS Lite (for a fast, headless environment) or install Raspberry PI OS Desktop (in this case, working from its internal terminal).

Make your OS up to date. From terminal:

sudo apt update && sudo apt upgrade

We need to install our application server: Apache. This is deeply covered in my tutorial to install LAMP server in Raspberry PI. For this project, we need to install only Apache, so use following terminal command:

sudo apt install apache2 -y

Verify that apache service is running with systemctl:

pi@raspberrypi:~ $ sudo systemctl status apache2.service
 apache2.service - The Apache HTTP Server
    Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
    Active: active (running) since Sat 2021-02-06 13:27:40 GMT; 1min 49s ago
 Main PID: 8741 (apache2)
     Tasks: 55 (limit: 881)
    CGroup: /system.slice/apache2.service
            ├─8741 /usr/sbin/apache2 -k start
            ├─8742 /usr/sbin/apache2 -k start
            └─8743 /usr/sbin/apache2 -k start
Feb 06 13:27:39 raspberrypi systemd[1]: Starting The Apache HTTP Server…
Feb 06 13:27:40 raspberrypi apachectl[8730]: AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using ....
Feb 06 13:27:40 raspberrypi systemd[1]: Started The Apache HTTP Server.

If everything is ok, you can go with your favourite browser and use http (without “S”) to reach your Raspberry PI’s IP address (mine one for this tutorial is for Apache default page:

raspberry pi zero w apache default page

Please note that if you try, at this point, to use https you will get an error (ERR_CONNECTION_REFUSED).

Generate Private Key and Certificate

We’ll use OpenSSL package (already available in Raspberry PI OS) to generate the self signed certificate. We’ll also include following options:

  • req: This subcommand enables certificate request and certificate generating utility
  • -x509: this option outputs a self signed certificate instead of an external certificate request
  • -nodes: this option requires a not encrypted private key
  • -days 356: this option sets expiration days to 365. default value is 30 days
  • -newkey rsa:2048: this option creates a new certificate request and a new private key. The argument rsa:nbits, where nbits is the number of bits, generates an RSA key nbits in size.
  • -keyout: This options set private key name (optional, using a full path you can also put key in desired folder)
  • -out: This option set certificate name (optional, using a full path you can also put certificate in desired folder)

You can use whatever certificate/key file name you want. It is important that you then refer correctly files in following configuration. From terminal:

sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout private.key -out certificate.crt

After generating the private key, OpenSSL will ask you for some info requests. Answer according to your preferences. The most important line is “Common Name”, which will require domain name or IP address (this being my case):

Country Name (2 letter code) [AU]:
State or Province Name (full name) [Some-State]:
Locality Name (eg, city) []:
Organization Name (eg, company) [Internet Widgits Pty Ltd]:
Organizational Unit Name (eg, section) []:
Common Name (e.g. server FQDN or YOUR name) []:
Email Address []:

You will have now 2 files in your folder. With “cat” terminal command you can verify that certificate has first and last row indicating begin and end of certificate, with encrypted data inside these limiters:

pi@raspberrypi:~ $ cat certificate.crt
..... (omitted incomprensible chars) .....

Same for private key, which will require sudo permissions for catting text:

pi@raspberrypi:~ $ sudo cat private.key
..... (omitted incompresible chars) .....

Move certificate and private key in ssl folder:

sudo mv private.key /etc/ssl/private/
sudo mv certificate.crt /etc/ssl/certs/

Configure Apache to use Self Signed Certificate and Key

Edit Apache 000-default.conf, the default Apache Virtual Host file. Remember default ports (https=443, http=80). From terminal:

sudo nano /etc/apache2/sites-available/000-default.conf

You will find a pre-configured generic VirtualHost answering to port 80 (*:80). Append following code to add a new VirtualHost which will answer to all requests received on port 443 (https):

<VirtualHost *:443>
        ServerAdmin webmaster@localhost
        DocumentRoot /var/www/html
        ErrorLog ${APACHE_LOG_DIR}/error.log
        CustomLog ${APACHE_LOG_DIR}/access.log combined
        SSLEngine on
        SSLProtocol all -SSLv2
        SSLCipherSuite HIGH:MEDIUM:!aNULL:!MD5
        SSLCertificateFile "/etc/ssl/certs/certificate.crt"
        SSLCertificateKeyFile "/etc/ssl/private/private.key"

Close and save. From terminal, enable ssl, check configuration (if you used IP address, you can skip “Could not reliably determine the server’s fully qualified domain name” warnings) and restart apache:

sudo a2enmod ssl
sudo apache2ctl configtest
sudo systemctl restart apache2.service

Back to browser, change http to https (with same URL using Raspberry PI’s IP address). You will get a warning (whose page appearence can change with different browsers):

raspberry pi zero w https self signed warning

Depending on browser, you will find a different way to continue: for example, in FIrefox Advanced button + “Accept the risk and continue”, in Chrome “Advanced” + “Proceed to x.x.x.x (not secure)”. Go on, as this is your Raspberry PI and you are sure of that. You will get apache default https page with a different padlock icon:

raspberry pi zero w apache default page https

Redirecting Http to Https

One more addictional feature, you could need routing all http connections to https pages. This trick can be achieved by adding a Redirect in your Apache default configuration. From terminal

sudo nano /etc/apache2/sites-available/000-default.conf

Change first virtual block (answering to port 80) by adding following row:

<VirtualHost *:80>
        . . .
        Redirect "/" "https://your_domain_or_IP/"
        . . .

Close and save. Restart apache service:

sudo systemctl restart apache2.service

From now your http connections will be automatically redirected to their https pages.


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