Let’s Encrypt all the things

Let’s Encrypt all the things

This site is being served as https and yours can be too! Keep reading and find out how to get free valid browser trusted https certificates. Slides of my talk at the SagLacIO inside!

What’s Let’s Encrypt?

Let’s Encrypt is a new Certificate Authority: It’s free, automated, and open.

Have a look at Let’s Encrypt website and their FAQ if you didn’t do it yet!

Getting started

I’ll jump straight to what’s interesting; What are the steps to have a fully working and valid free https certificate on a website behind nginx and how to get a nice score on ssltest.

Most of the things needed to get started are described on Let’s Encrypt getting started page along with most up to date informations.

Have a look to Get HTTPS for free! on github which shows you what happens in the background when using the client. Everything is client side!

Install letsencrypt

Grab letsencrypt official client on your server this way:

git clone https://github.com/letsencrypt/letsencrypt
cd letsencrypt
./letsencrypt-auto --help

nginx configuration

Thanks to @jipiboily, he shared me the awesome letsecure.me website. Here’s how my updated nginx configuration looks like: /etc/nginx/site-available/gableroux.conf

# gableroux.com configuration generated from salt

## https redirect
server {
  listen 80;
  listen [::]:80;
  server_name gableroux.com;

  location ~ '/.well-known/acme-challenge' {
    default_type "text/plain";
    root /var/www;

  location / {
    return 301 https://$server_name$request_uri;

## www removal
server {
  listen 80;
  listen [::]:80;
  server_name www.gableroux.com;

  location ~ '/.well-known/acme-challenge' {
    default_type "text/plain";
    root /var/www;

  location / {
    return 301 https://gableroux.com$request_uri;

## Main server config
server {
  listen 443 ssl http2;
  server_name gableroux.com;
  root /var/www/gableroux.com/_side;

  index  index.html;

  ### SSL Config (using letsencrypt)
  ssl_certificate /etc/letsencrypt/live/gableroux.com/fullchain.pem;
  ssl_certificate_key /etc/letsencrypt/live/gableroux.com/privkey.pem;

  # Generate ssl_dhparam using `openssl dhparam -out dhparams.pem 4096`
  ssl_dhparam /etc/nginx/dhparams.pem;

  # Secure headers
  add_header Strict-Transport-Security "max-age=31557600; includeSubDomains";
  add_header X-Frame-Options "SAMEORIGIN";
  add_header X-Content-Type-Options "nosniff";
  add_header X-Xss-Protection "1";
  ## allows google fonts from stylesheets and google analytics for scripts
  ## Using 'unsafe-inline' due to some pages still doing this (angular app somewhere)
  ## Commented as this was to restrictive. Most of the things here are static anyway
  #add_header Content-Security-Policy "default-src 'self' *.googleapis.com *.google-analytics.com *.facebook.net *.facebook.com *.feedly.com; style-src 'self' 'unsafe-inline'; script-src 'self' 'unsafe-inline'; img-src 'self'";

  ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
  ssl_prefer_server_ciphers on;

  ssl_session_timeout 5m;
  ssl_session_cache shared:SSL:128m;
  ssl_stapling on;
  ssl_stapling_verify on;

  # Your favorite resolver may be used instead of the Google one below

  ### Logs
  access_log  /var/log/nginx/gableroux.com.access.log;
  error_log   /var/log/nginx/gableroux.com.error.log;

  ### Serve root
  location / {
    root  /var/www/gableroux.com/_site;

    #### Todo: better 404

It should get you on tracks.

_site is the public folder of my static website, but really, this is up to you. Grab what fits your needs in the config ;)

Request a cert + renew command

First, create a config file:


rsa-key-size = 4096
email = lebreton.gabriel@gmail.com
domains = gableroux.com, www.gableroux.com
webroot-path = /var/www/

Then run the following:

letsencrypt-auto certonly -a webroot --renew-by-default \
--config /usr/local/etc/le-renew-webroot.ini

Yay https! Now run the above command in a daily cron job at a random hour to auto renew! Let’s Encrypt certificates expires after 3 months and you don’t want to do this by hand ;). That’s it, no more human intervention ever.

Try running ssltest on gableroux.com. Spoiler, it looks like this:
A+ ssltest gableroux.com result

Edit: OpenSSL Padding Oracle vulnerability (CVE-2016-2107)

So there is a new problem in the wild! My ssltest went from an A+ to an F in no time! Here’s an handy tool to verify vulnerability: FiloSottile/CVE-2016-2107

Solution: upgrade to openssl 1.0.2h (64bit)

On trusty Ubuntu 14.04 LTS

openssl version -v

OpenSSL 1.0.1f 6 Jan 2014

These will take a few minutes to run:

wget https://www.openssl.org/source/openssl-1.0.2h.tar.gz
tar -xzvf openssl-1.0.2h.tar.gz
cd openssl-1.0.2h
sudo ./config
sudo make
sudo make install
sudo ln -sf /usr/local/ssl/bin/openssl $(which openssl)
openssl version -v

OpenSSL 1.0.2h 3 May 2016

Inspired by Miguel’s solution

I was still getting the error, and I found this blog post: How to fix high severity OpenSSL bugs (Memory corruption, Padding oracle) in Ubuntu, CentOS, RedHat, OpenSuse and other Linux servers

apt-get install --only-upgrade libssl1.0.0

Now verify it did apply the patch by reading the changelog:

zgrep -ie "CVE-2016-2107" /usr/share/doc/libssl1.0.0/changelog.Debian.gz
  • debian/patches/CVE-2016-2107.patch: check that there are enough
  • CVE-2016-2107

Great! But still an F

From nginx announcement, upgrade nginx to 1.11.1-1.

sudo apt-get install --upgrade nginx

Now let’s verify again localy

CVE-2016-2107 gableroux.com
2016/06/10 13:32:17 Vulnerable: false

Awesome, scoring A+ again, solved! :)

The slides

Btw, there are a few interesting links at the end of the slides.

See full page presentation website