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Let's Encrypt
certbot, previously known as Let's Encrypt client, is a free, automated, and open certificate authority client.
From the official website: "Anyone who has gone through the trouble of setting up a secure website knows what a hassle getting and maintaining a certificate can be. Let’s Encrypt automates away the pain and lets site operators turn on and manage HTTPS with simple commands."[1]
Preliminary
Point an external IP at HTTP (port 80/TCP) and HTTPS (port 443/TCP) at a web server and setup DNS for it. This is important. You have to prove you own the IP/domain. You could use dynamic DNS if necessary.
Installation
It is helpful to read the official documentation and official installation instructions (select Gentoo from the Operating System dropdown) before proceeding with this article.
certbot
app-crypt/certbot Certbot is an easy-to-use automatic client that fetches and deploys SSL/TLS certificates for your web server. Certbot can automatically configure your web server to start serving over HTTPS immediately.
root #
emerge --ask app-crypt/certbot
acme-tiny (optional)
app-crypt/acme-tiny is a short, auditable Python script which avoids a lot of the bloat included in the official client.
root #
emerge --ask app-crypt/acme-tiny
Configuration
certbot
Automatic configuration
Run certbot with the corresponding web-server plugin and domain. Certbot automatically changes the vhost configuration. For example. for nginx
root #
certbot --nginx -d example.com
Manual configuration
Run certbot with the corresponding web-server plugin and domain, with the certonly option:
root #
certbot --nginx certonly -d example.com
Configure your virtual host. For example, for nginx:
server { listen 80; server_name example.org; return 301 https://$host$request_uri; } server { listen 443 default_server ssl; server_name example.org; root /var/www/example/htdocs; ssl_certificate /etc/letsencrypt/live/example.org/fullchain.pem; ssl_certificate_key /etc/letsencrypt/live/example.org/privkey.pem; location / { # set nginx configuration } }
acme-tiny
The documentation on [1] is the best place to look for the most up to date information, but has been summarized below:
Make a directory for challenges to be created in:
root #
mkdir /var/www/localhost/acme-challenge/
Add this to the Apache http vhost; IE port 80 vhost:
Alias /.well-known/acme-challenge/ /var/www/localhost/acme-challenge/ <Directory /var/www/localhost/acme-challenge/> AllowOverride None Require all granted </Directory>
Set these in the Apache https vhost; IE port 443 vhost:
SSLCertificateFile /var/lib/letsencrypt/chained.pem SSLCertificateKeyFile /var/lib/letsencrypt/domain.key
Make a directory to hold the various files related to LE:
root #
mkdir /var/lib/letsencrypt
root #
cd /var/lib/letsencrypt
Create an account key, domain key and a CSR (replace www.example.co.uk with your host name):
root #
openssl genrsa 4096 > account.key
root #
openssl genrsa 4096 > domain.key
root #
openssl req -new -sha256 -key domain.key -subj "/CN=www.example.co.uk" > domain.csr
Register and create the various certificate files: Check let's encrypt currently used intermediate certificate
root #
/usr/bin/acme-tiny --account-key ./account.key --csr ./domain.csr --acme-dir /var/www/localhost/acme-challenge/ > ./signed.crt
root #
wget -O - https://letsencrypt.org/certs/lets-encrypt-x3-cross-signed.pem > intermediate.pem
root #
cat signed.crt intermediate.pem > chained.pem
Reload configs for webserver:
root #
service apache2 reload
or
root #
service nginx reload
or
root #
service lighttpd reload
Sample renewal script:
#!/bin/sh /usr/bin/acme-tiny --account-key /var/lib/letsencrypt/account.key --csr /var/lib/letsencrypt/domain.csr --acme-dir /var/www/localhost/acme-challenge/ > /var/lib/letsencrypt/signed.crt || exit wget -O - https://letsencrypt.org/certs/lets-encrypt-x3-cross-signed.pem > intermediate.pem cat /var/lib/letsencrypt/signed.crt intermediate.pem > /var/lib/letsencrypt/chained.pem service apache2 reload
Add a monthly cron job:
# Renew Lets Encrypt certificate 0 0 1 * * /usr/local/bin/renew-le-cert.sh 2>> /var/log/acme_tiny.log
Usage
certbot
Invocation
user $
certbot --help
letsencrypt [SUBCOMMAND] [options] [-d domain] [-d domain] ... The Let's Encrypt agent can obtain and install HTTPS/TLS/SSL certificates. By default, it will attempt to use a webserver both for obtaining and installing the cert. Major SUBCOMMANDS are: (default) run Obtain & install a cert in your current webserver certonly Obtain cert, but do not install it (aka "auth") install Install a previously obtained cert in a server revoke Revoke a previously obtained certificate rollback Rollback server configuration changes made during install config_changes Show changes made to server config during installation plugins Display information about installed plugins Choice of server plugins for obtaining and installing cert: (the apache plugin is not installed) --standalone Run a standalone webserver for authentication (nginx support is experimental, buggy, and not installed by default) --webroot Place files in a server's webroot folder for authentication OR use different plugins to obtain (authenticate) the cert and then install it: --authenticator standalone --installer apache More detailed help: -h, --help [topic] print this message, or detailed help on a topic; the available topics are: all, automation, paths, security, testing, or any of the subcommands or plugins (certonly, install, nginx, apache, standalone, webroot, etc)
acmetiny
For those that are not interested in using scripts or want to configure things manually the first time, the author of acme-tiny has provided a webpage that gives step by step instructions along with javascript to help walk you through setting up your certificates. The guide may be found on Get HTTPS for Free website.
See also
- Apache - The most popular HTTP server used the Internet.
- Nginx - A small, robust, and high-performance HTTP server and reverse proxy.
- Lighttpd - a very lightweight HTTP server.
External resources
- Manual installation - In the event manual installation is preferred. Note: Portage will not track the installation if the Let's Encrypt is manually installed; this is not recommended by Gentoo developers.