Getting Let’s Encrypt SSL Certificates on Linux and FreeBSD

First install certbot. This is basically the Python script that will read the web server configuration and make the request to the Let’s Encrypt API.

On Debian or Ubuntu:

sudo apt install certbot
sudo apt install python3-certbot-nginx
sudo apt install python3-certbot-apache

On FreeBSD:

sudo pkg install py37-certbot
sudo pkg install py37-certbot-nginx
sudo pkg install py37-certbot-apache
sudo pkg install py37-acme

Note that certbot can only match virtual hosts that listen on port 80.

Run this command for Nginx:

sudo certbot certonly --nginx

Or for Apache:

sudo certbot certonly --apache

Certificates will get saved in /etc/letsencrypt/live on Linux, or /usr/local/etc/letsencrypt/live on FreeBSD

In each sub-directory, there will be 4 files created:

  • privkey.pem = The private key
  • cert.pem = The SSL certificate
  • fullchain.pem = SSL cert + Intermediate Cert chain. This format is required by NGINX and some other web servers
  • chain.pem = Just the intermediate cert

Here’s a Python script that will create a list of all directories with Let’s Encrypt certs:

#!/usr/bin/env python3

import sys, os

if "linux" in sys.platform:
    src_dir = "/etc/letsencrypt/live"
if "freebsd" in sys.platform:
    src_dir = "/usr/local/etc/letsencrypt/live"

sites = [ for f in os.scandir(src_dir) if f.is_dir() ]
for site in sites:
    if os.path.exists(src_dir + "/" + site + "/cert.pem"):
        print("Letsencrypt certificate exists for site:", site)

Migrating from CGI to WSGI for Python Web Scripts on Apache

I began finally migrating some old scripts from PHP to Python late last year, and while I was happy to finally have my PHP days behind me, I noticed the script execution was disappointing. On average, a Python CGI script would run 20-80% slower than an equivalent PHP script. At first I chalked it up to slower libraries, but even basic ones that didn’t rely on database or anything fancy still seemed to be incurring a performance hit.

Yesterday I happened to come across mention of WSGI, which is essentially a Python-specific replacement for CGI. I realized the overhead of CGI probably explained why my Python scripts were slower than PHP. So I wanted to give WSGI a spin and see if it could help.

Like PHP, WSGI is an Apache module that is not included in many pre-packaged versions. So first step is to install it.

On Debian/Ubuntu:

sudo apt-get install libapache2-mod-wsgi-py3

The install process should auto-activate the module.

cd /etc/apache2/mods-enabled/

ls -la wsgi*
lrwxrwxrwx 1 root root 27 Mar 23 22:13 wsgi.conf -> ../mods-available/wsgi.conf
lrwxrwxrwx 1 root root 27 Mar 23 22:13 wsgi.load -> ../mods-available/wsgi.load

On FreeBSD, the module does not get auto-activated and must be loaded via a config file:

sudo pkg install ap24-py37-mod_wsgi

# Create /usr/local/etc/apache24/Includes/wsgi.conf
# or similar, and add this line:
LoadModule wsgi_module libexec/apache24/

Like CGI, the directory with the WSGI script will need special permissions. As a security best practice, it’s a good idea to have scripts located outside of any DocumentRoot, so the scripts can’t accidentally get served as plain files.

<Directory "/var/www/scripts">
  Require all granted

As for the WSGI script itself, it’s similar to AWS Lambda, using a pre-defined function. However, it returns an array or bytes rather than a dictionary. Here’s a simple one that will just spit out the host, path, and query string as JSON:

def application(environ, start_response):

    import json, traceback

        request = {
            'host': environ.get('HTTP_HOST', 'localhost'),
            'path': environ.get('REQUEST_URI', '/'),
            'query_string': {}
        if '?' in request['path']:
            request['path'], query_string = environ.get('REQUEST_URI', '/').split('?')
            for _ in query_string.split('&'):
                [key, value] = _.split('=')
                request['query_string'][key] = value

        output = json.dumps(request, sort_keys=True, indent=2)
        response_headers = [
            ('Content-type', 'application/json'),
            ('Content-Length', str(len(output))),
            ('X-Backend-Server', 'Apache + mod_wsgi')
        start_response('200 OK', response_headers)
        return [ output.encode('utf-8') ]
        response_headers = [ ('Content-type', 'text/plain') ]
        start_response('500 Internal Server Error', response_headers)
        error = traceback.format_exc()
        return [ str(error).encode('utf-8') ]

The last step is route certain paths to WSGI script. This is done in the Apache VirtualHost configuration:

WSGIPythonPath /var/www/scripts

<VirtualHost *:80>
  DocumentRoot /home/www/html
  Header set Access-Control-Allow-Origin: "*"
  Header set Access-Control-Allow-Methods: "*"
  Header set Access-Control-Allow-Headers: "Origin, X-Requested-With, Content-Type, Accept, Authorization"
  WSGIScriptAlias /myapp /var/www/scripts/myapp.wsgi

Upon migrating a test URL from CGI to WSGI, the page load time dropped significantly:

The improvement is thanks to a 50-90% reduction in “wait” and “receive” times, via ThousandEyes:

I’d next want to look at more advanced Python Web Frameworks like Flask, Bottle, WheezyWeb and Tornado. Django is of course a popular option too, but I know from experience it won’t be the fastest. Flask isn’t the fastest either, but it is the framework for Google SAE which I plan to learn after mastering AWS Lambda.

Enabling SSL (HTTPS) on Apache 2.4 Ubuntu, with a good rating from SSL Labs as a bonus

Start by installing Apache 2.4.  This will run on port 80 out of the box:

sudo su
apt install apache2
apt install apache2-doc

To use SSL/TLS/HTTPS aka port 443 as well, follow these additional steps:

Activate the SSL, socache_shmcb, and rewrite modules:

cd /etc/apache2/mods-enabled/
ln -s ../mods-available/ssl.load .
ln -s ../mods-available/socache_shmcb.load .

Optionally, activate the headers, rewrite and proxy modules, as they are often useful:

ln -s ../mods-available/headers.load .
ln -s ../mods-available/rewrite.load .
ln -s ../mods-available/cgi.load .

Copy the default ssl.conf file over and edit it:

cp /etc/apache2/mods-available/ssl.conf /etc/apache2/conf-enabled/
nano /etc/apache2/conf-enabled/ssl.conf

Near the bottom, modify these lines so that the AES-GCM protocols are preferred and only TLS 1.2 is supported

   #SSLCipherSuite HIGH:!aNULL   
   SSLHonorCipherOrder on
   SSLProtocol TLSv1.2

Then edit /etc/apache2/sites-enabled/000-default.conf so it has default virtual hosts on both port 80 and port 443:

<VirtualHost _default_:80>
   ServerName localhost
   ServerAdmin webmaster@localhost
   DocumentRoot /var/www/html
   ErrorLog ${APACHE_LOG_DIR}/error.log
   CustomLog ${APACHE_LOG_DIR}/access.log combined
<VirtualHost _default_:443>
   ServerName localhost
   ServerAdmin webmaster@localhost
   DocumentRoot /var/www/html
   ErrorLog ${APACHE_LOG_DIR}/error.log
   CustomLog ${APACHE_LOG_DIR}/access.log combined
   SSLEngine On
   SSLCertificateKeyFile /etc/ssl/private/ssl-cert-snakeoil.key
   SSLCertificateFile /etc/ssl/certs/ssl-cert-snakeoil.pem

Restart Apache and you should now have service for both HTTP (port 80) and HTTPS (port 443)

apachectl configtest
Syntax OK
apachectl restart

Run the site through SSL labs and the rating should be high, other than the self-signed certificate.