Let's Encrypt

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Resources

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

Tip
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

USE flags

certbot uses modules to enhance its features. To simplify the maintenance of this modular approach, the certbot ebuild uses expanded USE (USE_EXPAND) flags to denote which modules should be installed.

For example, to enable the rfc2136 module:

FILE /etc/portage/package.use/certbot

app-crypt/certbot CERTBOT_DNS: rfc2136

USE flags for app-crypt/certbot Let’s Encrypt client to automate deployment of X.509 certificates

`certbot-apache`	Enable Apache plugin.
`certbot-dns-dnsimple`	Enable DNSimple Authenticator plugin.
`certbot-dns-dnsmadeeasy`	Enable DNS Made Easy DNS Authenticator plugin.
`certbot-dns-gehirn`	Enable Gehirn Infrastructure Service DNS Authenticator plugin.
`certbot-dns-google`	Enable Google Cloud DNS Authenticator plugin.
`certbot-dns-linode`	Enable Linode DNS Authenticator plugin plugin.
`certbot-dns-luadns`	Enable LuaDNS Authenticator plugin.
`certbot-dns-nsone`	Enable NS1 DNS Authenticator plugin.
`certbot-dns-ovh`	Enable OVH DNS Authenticator plugin.
`certbot-dns-rfc2136`	Enable RFC 2136 DNS Authenticator plugin.
`certbot-dns-route53`	Enable Route53 DNS Authenticator plugin.
`certbot-dns-sakuracloud`	Enable Sakura Cloud DNS Authenticator plugin.
`certbot-nginx`	Enable Nginx plugin.
`doc`	Add extra documentation (API, Javadoc, etc). It is recommended to enable per package instead of globally
`selinux`	!!internal use only!! Security Enhanced Linux support, this must be set by the selinux profile or breakage will occur
`test`	Enable dependencies and/or preparations necessary to run tests (usually controlled by FEATURES=test but can be toggled independently)

Data provided by the Gentoo Package Database · Last update: 2025-03-11 22:13 More information about USE flags

Emerge

app-crypt/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

Certbot also supports numbers of DNS-plugins which automates the process of completing a dns-01 challenge (DNS01) by creating, and subsequently removing, TXT records. Starting from 3.2.0-r100, app-crypt/certbot package includes almost all supported DNS plugins.

Name	Packaged	Description	Documentation	Notes
certbot-dns-cloudflare	No	Plugin for Cloudflare API.	doc	Available in GURU repository.
certbot-dns-digitalocean	No	Plugin for Digital Ocean API.	doc
certbot-dns-dnsimple	Yes	Plugin for DNSimple API.	doc
certbot-dns-dnsmadeeasy	Yes	Plugin for DNS Made Easy API.	doc
certbot-dns-gehirn	Yes	Plugin for Gehirn Infrastructure Service DNS API.	doc
certbot-dns-google	Yes	Plugin for Google Cloud DNS API.	doc
certbot-dns-linode	Yes	Plugin for Linode API.	doc
certbot-dns-luadns	Yes	Plugin for LuaDNS API.	doc
certbot-dns-nsone	Yes	Plugin for NS1 API.	doc
certbot-dns-ovh	Yes	Plugin for OVH API.	doc
certbot-dns-rfc2136	Yes	Plugin using RFC 2136 Dynamic Updates.	doc
certbot-dns-route53	Yes	Plugin for Amazon Web Services Route 53 API.	doc
certbot-dns-sakuracloud	Yes	Plugin for Sakura Cloud DNS API.	doc

acme-tiny (optional)

Important
The package is masked by a missing keyword, to unmask it, follow the steps provided here.

app-crypt/acme-tiny is a short, auditable Python script which avoids a lot of the bloat included in the official certbot client:

root #emerge --ask app-crypt/acme-tiny

acme.sh (optional)

Another alternative available in Gentoo is the app-crypt/acme-sh client:

root #emerge --ask app-crypt/acme-sh

Configuration

certbot

Automatic configuration for existing web server

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

In order to use certbot with Apache web server, install the additional plugin:

root #emerge --ask app-crypt/certbot-apache

Automatic signing with temporary certbox webserver

In this configuration certbot will start a wizard and then initiate up a temporary web server instance in order to generate signed certificates. Choose the second option in the list (2), and follow the wizard. When running an existing web server, first disable the web server before running this mode, then restart the web server when finished (click [Expand] below to see wizard output).

root #

rc-service nginx stop

root #certbot certonly

Saving debug log to /var/log/letsencrypt/letsencrypt.log

How would you like to authenticate with the ACME CA?
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
1: Nginx Web Server plugin (nginx)
2: Spin up a temporary webserver (standalone)
3: Place files in webroot directory (webroot)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Select the appropriate number [1-3] then [enter] (press 'c' to cancel): 2
Plugins selected: Authenticator standalone, Installer None
Please enter in your domain name(s) (comma and/or space separated)  (Enter 'c'
to cancel): example.letsencrypt.org
Requesting a certificate for example.letsencrypt.org
Performing the following challenges:
http-01 challenge for example.letsencrypt.org
Waiting for verification...
Cleaning up challenges
 
IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/example.letsencrypt.org/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/example.letsencrypt.org/privkey.pem
   Your certificate will expire on 2021-07-17. To obtain a new or
   tweaked version of this certificate in the future, simply run
   certbot again. To non-interactively renew *all* of your
   certificates, run "certbot renew"
 - If you like Certbot, please consider supporting our work by:

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

root #rc-service nginx start

Manual certonly 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:

FILE /etc/nginx/vhost.d/example.vhostvhost configuration

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 acme-tiny 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:

FILE /etc/apache2/vhosts.d/00_default_vhost.confChallenge alias in Apache

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:

FILE /etc/apache2/vhosts.d/00_default_ssl_vhost.confSSL certificate settings for Apache

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 certificate file:

Important
acme-tiny may fail its own token availability check [1], even though the token is actually available. If the problem occurs, the check should be disabled using the --disable-check flag.

root #

/usr/bin/acme-tiny --account-key ./account.key --csr ./domain.csr --acme-dir  /var/www/localhost/acme-challenge/ > ./chained.pem

Reload configs for webserver:

root #service apache2 reload

or

root #service nginx reload

or

root #service lighttpd reload

Sample renewal script:

FILE /usr/bin/local/renew-le-certLetsEncrypt Cert renew 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/chained.pem.tmp || exit
mv /var/lib/letsencrypt/chained.pem.tmp /var/lib/letsencrypt/chained.pem
service apache2 reload

Add a monthly cron job:

FILE CRONJOB

# 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)

Renewal

Let's encrypt certificates only last 90 days before expiry, thankfully it is easy to renew certificates: run certbot renew to automatically renew all certbot certificates on the system. It is recommended to run this in a cron command, every 60 days.

To renew just a specific domain, run certbot certonly --force-renew -d example.com.

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.

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.

References

↑ https://letsencrypt.org/getting-started/

[1] ttps://letsencrypt.org/getting-started/

[1]

Let's Encrypt

Contents

Preliminary

Installation

certbot

USE flags

USE flags for app-crypt/certbot Let’s Encrypt client to automate deployment of X.509 certificates

Emerge

acme-tiny (optional)

acme.sh (optional)

Configuration

certbot

Automatic configuration for existing web server

Automatic signing with temporary certbox webserver

Manual certonly configuration

acme-tiny

Usage

certbot

Invocation

Renewal

acmetiny

See also

External resources

References