Let’s Encrypt has opened the floodgates of their public beta today, December 4th 2015. Today marks a milestone towards encrypting the web. In this post we’ll look at how to use this new tool to generate a free SSL certificate.

SSL activated

This article assumes you have a web server and Apache. You’re also going to want to have two SSH windows open, as the generator will have a few prompts and instructions to set up verification.

The workflow is broken into 3 segments:

  1. Choosing a domain to create a certificate for
  2. Verifying the domain
  3. Configuring Apache to serve your site over SSL

Installing the letsencrypt CLI tool

ssh into your server and clone the letsencrypt repository in your home directory and navigate into it.

git clone [email protected]:letsencrypt/letsencrypt.git
cd letsencrypt

Requesting a certificate

In the cloned repository exists a script letsencrypt-auto. This typically will automatically generate a certificate and configure your web server. I tend to lean towards manually doing things, especially in beta. That turned out to be a good thing since it indeed failed for me letsencrypt#1712

We’ll go ahead and start the manual flow

./letsencrypt certonly --manual

If this is the first time running the command, it will go ahead and download all the necessary packages. Let it run for a minute while it does that. You’ll next be prompted to type in your sudo password.

Upon allowing root access, you’ll enter a GUI flow of providing the domain(s) you’d like to generate certificates for

enter a domain

This will next let you know that your IP will be publicly logged. Agree, if you’re cool with that.

Verifying your domain

Upon providing your domain name and agreeing that your IP will be logged, you’ll now set up the verification. Here you’ll want to open a new ssh window. This message is a prompt waiting for you to hit ENTER to confirm that you’ve set things up, so we’ll leave this prompt as it is for now.

You should see output similar to

Make sure your web server displays the following content at
http://atticuswhite.com/.well-known/acme-challenge/THE_VERIFICATION_FILE before continuing:

THE_VERIFICATION_STRING

If you don't have HTTP server configured, you can run the following
command on the target server (as root):

mkdir -p /tmp/letsencrypt/public_html/.well-known/acme-challenge
cd /tmp/letsencrypt/public_html
printf "%s" THE_VERIFICATION_STRING > .well-known/acme-challenge/THE_VERIFICATION_FILE
# run only once per server:
$(command -v python2 || command -v python2.7 || command -v python2.6) -c \
"import BaseHTTPServer, SimpleHTTPServer; \
s = BaseHTTPServer.HTTPServer(('', 80), SimpleHTTPServer.SimpleHTTPRequestHandler); \
s.serve_forever()"
Press ENTER to continue

To summarize, you’re going to create a file in your served directory that will be used to verify that you indeed own the location that the domain serves. This article assumes you’re setting up an Apache server. If you have yet to set up a served directory, do that now. If you already have a directory that is serving your domain, navigate to that directory and create the following file path:

.well-known/acme-challenge/THE_VERIFICATION_FILE (ofcourse, THE_VERIFICATION_FILE should be what’s described in the message from letsencrypt-auto)

Next you’ll want put the verification string into the file.

cd /path/to/webserver/directory
mkdir -p .well-known/acme-challenge/THE_VERIFICATION_FILE
printf "%s" THE_VERIFICATION_STRING > .well-known/acme-challenge/THE_VERIFICATION_FILE

Verify that this file is properly being served before continuing. Navigate to http://your-domain.com/.well-known/acme-challenge/THE_VERIFICATION_FILE and make sure it’s outputting the verification string.

Once you have this confirmed, go back to your other ssh window and confirm the prompt by hitting ENTER.

If verification was successful, you should receive a confirmation message containing the location of your certificate, chain, and private key file:

IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at
   /etc/letsencrypt/live/your-domain.com/fullchain.pem. Your cert
   will expire on 2016-03-03. To obtain a new version of the
   certificate in the future, simply run Let's Encrypt again.
 - If like Let's Encrypt, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le

Awesome! Now let’s setup that cert.

Configuring the certificates

Head over to your Apache configuration directory. Depending on what version of Apache you’re running (Apache or Apache2) these next steps may vary. The overall configuration is the same in the end, however the directory structures are a bit different between the two.

cd /etc/apache2

We’re going to set up 3 things:

  1. The SSL mod
  2. A cache mod
  3. The SSL configuration

Inside mods-available will be ssl.conf, ssl.load, and socache_shmcb.load. If they do not exist in mods-enabled, you’re going to link them.

sudo ln -s mods-available/ssl.conf mods-enabled/ssl.conf
sudo ln -s mods-available/ssl.load mods-enabled/ssl.load
sudo ln -s mods-available/socache_shmcb.load mods-enabled/socache_shmcb.load

That takes care of 1 and 2. Now we’ll set up the SSL configuration.

Let’s assume you already have the non SSL configuration set up. If you don’t go ahead and set that up, we’ll make sure that it redirects to the SSL version below.

Open the configuration file for the non SSL virtual host and enter the following:

<VirtualHost *:443>
  ServerName your-server.com
  DocumentRoot /path/to/your-server
  SSLEngine on
  SSLCertificateFile /etc/letsencrypt/live/your-domain.com/cert.pem
  SSLCertificateKeyFile /etc/letsencrypt/live/your-domain.com/privkey.pem
  SSLCertificateChainFile /etc/letsencrypt/live/your-domain.com/chain.pem
</VirtualHost>

Go ahead and verify your configuration (service apache2 configtest) or restart your web server, typically service apache2 restart. You should now be able to access your site over SSL!

Redirecting non-SSL to your new SSL site

In order to do this, you’ll need to make sure you have the rewerite mod enabled. If you don’t see it in mods-enabled, go ahead and link it:

ln -s mods-available/rewrite.load mods-enabled/rewerite.load

In your site configuration, add the following lines:

RewriteEngine On
RewriteRule ^(.*)$ https://%{HTTP_HOST}$1 [R=301, L]

Voilla! You’re now secured. Give a big thanks to the team and community over at @LetsEncrypt and on GitHub!