certbot

Renewing Let's Encrypt SSL Certificate with Docker

Let’s Encrypt CA issues short-lived certificates (90 days). Automated renewal process is preferred, recommended, and encouraged. But in a few situations, automated process is not available, here is how to do it manually when SSL certificate was installed with Docker:

First, update the container to the latest version. The latest version can be found from the release page in GitHub.

The latest is v0.9.1:

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$ docker pull quay.io/letsencrypt/letsencrypt:v0.9.1

Turn off application (if running as a Docker container) to free up the HTTPS port 443:

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$ docker stop app

Renew the certificate by issuing renew command:

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$ docker run -it --rm -p 443:443 --name certbot \
-v /etc/letsencrypt:/etc/letsencrypt \
-v /var/log/letsencrypt:/var/log/letsencrypt \
quay.io/letsencrypt/letsencrypt:v0.9.1 renew
Saving debug log to /var/log/letsencrypt/letsencrypt.log
-------------------------------------------------------------------------------
Processing /etc/letsencrypt/renewal/example.com.conf
-------------------------------------------------------------------------------
Cert is due for renewal, auto-renewing...
Starting new HTTPS connection (1): acme-v01.api.letsencrypt.org
Renewing an existing certificate
Performing the following challenges:
tls-sni-01 challenge for example.com
Waiting for verification...
Cleaning up challenges
Generating key (2048 bits): /etc/letsencrypt/keys/0001_key-certbot.pem
Creating CSR: /etc/letsencrypt/csr/0001_csr-certbot.pem
-------------------------------------------------------------------------------
new certificate deployed without reload, fullchain is
/etc/letsencrypt/live/example.com/fullchain.pem
-------------------------------------------------------------------------------
Congratulations, all renewals succeeded. The following certs have been renewed:
/etc/letsencrypt/live/example.com/fullchain.pem (success)

Restart app (it’s start not restart):

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$ docker start app

Check the expiration date:

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$ echo | openssl s_client -connect example.com:443 2> /dev/null | \
openssl x509 -noout -dates
notBefore=Oct 9 12:00:00 2016 GMT
notAfter=Jan 7 12:00:00 2017 GMT

For more information on renewing, see the Renewing Certificates section from the Certbot documentation.

Settings:

  • Certbot v0.9.1
  • Docker v1.12.1

Getting Let's Encrypt SSL Certificate with Docker

Let’s Encrypt is a free, open, and automated certificate authority (CA). And its Certbot is a fully-featured, extensible client for Let’s Encrypt CA that can automate the tasks of getting, renewing and even installing SSL certificates.

First, you need to get Certbot. There are a few ways to install Certbot. But with Docker, you don’t need to install, you just need to download the Docker image and run the container. However, the caveat is that this method does not install the certificate automatically respecting to your web server. But if you’re like me, running your server in another Docker container, this might be the way to go.

Let’s start.

First, download the image. You can download the latest version (tag):

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$ docker pull quay.io/letsencrypt/letsencrypt:latest

But the latest usually is not a stable release:

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$ docker run -it --rm quay.io/letsencrypt/letsencrypt:latest --version
certbot 0.10.0.dev0

Therefore, it’s better to use a specific release, which can be found in Certbot’s GitHub page: https://github.com/certbot/certbot/releases.

The latest one now is v0.9.1. We can pull that from Quay.io:

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$ docker pull quay.io/letsencrypt/letsencrypt:v0.9.1

Confirm the release version:

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$ docker run -it --rm quay.io/letsencrypt/letsencrypt:v0.9.1 --version
certbot 0.9.1

Let’s take a look at the Docker image:

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$ docker inspect quay.io/letsencrypt/letsencrypt:v0.9.1

Dropping things don’t care, the output is:

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[
{
"RepoTags": [
"quay.io/letsencrypt/letsencrypt:v0.9.1"
],
"ContainerConfig": {
"ExposedPorts": {
"443/tcp": {}
},
"Cmd": [
"/bin/sh",
"-c",
"#(nop) ENTRYPOINT \u0026{[\"certbot\"]}"
],
"Volumes": {
"/etc/letsencrypt": {},
"/var/lib/letsencrypt": {}
},
"Entrypoint": [
"certbot"
]
}
}
]

The ENTRYPOINT is certbot binary:

An ENTRYPOINT allows you to configure a container that will run as an executable.[^1]

And the command line arguments to docker run becomes the arguments to certbot command. As we saw earlier to obtain the release version by using --version.

You can override the ENTRYPOINT instruction using the docker run --entrypoint flag.[^1]

For example, to override and run the container without executing the certbot command:

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$ docker run -it --rm --name certbot --entrypoint /bin/bash \
quay.io/letsencrypt/letsencrypt:v0.9.1

But we are more concerning about others, such as exposed port and mapped volumes. The exposed port is 443, HTTPS port. The most important volume (directory) is /etc/letsencrypt. All generated keys and issued certificates can be found in there. Directory /var/lib/letsencrypt is the default working directory, some backup stuff are stored. I have yet to find it useful. However, the logs directory /var/log/letsencrypt is not being used. This could be useful if things went haywire.

Installing Let's Encrypt SSL Certificate on Google App Engine Using Certbot

Let’s Encrypt is a free, open, and automated certificate authority. And its Certbot is a fully-featured, extensible client for Let’s Encrypt CA that can automate the tasks of getting, renewing and even installing SSL certificates.

Sounds great! However, not yet to be simple and automated, especially working cloud providers such as Google Cloud Platform and its Google App Engine or GAE.

But it’s free. Yes, it’s free. Free software works better. Free certificate authority works better than others.

GAE is a managed service. The place to stored SSL certificate is in separate machines (load balancers). The current automated domain validation by Certbot mostly work with a single machine. Therefore, when the machine issues certificate request is not the same machine to be validated, we need find another way, hopefully an automated method to perform domain validation across machines.

Before creating an automated method, let’s see if we can do it manually. Certbot supports a number of different plugins that can be used to obtain and/or install certificates. A plugin is like an extension that supports a particular web server. Let’s see if we can find a plugin that supports GAE.

Here are some supported by Certbot:

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$ certbot --help plugins
plugins:
Certbot client supports an extensible plugins architecture. See 'certbot
plugins' for a list of all installed plugins and their names. You can
force a particular plugin by setting options provided below. Running
--help will list flags specific to that plugin.
--apache Obtain and install certs using Apache (default: False)
--nginx Obtain and install certs using Nginx (default: False)
--standalone Obtain certs using a "standalone" webserver. (default:
False)
--manual Provide laborious manual instructions for obtaining a
cert (default: False)
--webroot Obtain certs by placing files in a webroot directory.
(default: False)

And there are also a number of third-party plugins, see the User Guide in Certbot Documentation. But there is none for GAE. It looks like there are only three possible options to try: standalone, webroot and manual.

Let’s start with the standalone method, and issue that from the local machine:

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$ sudo certbot certonly --standalone -d example.com

If you’re the first time running the command, you will be prompted for email and agreement screens. Both email and agreement can be automated via --email and --agree-tos options. That’s the automated part.

After freeing up the ports 80 and 443, run into some issues:

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Failed authorization procedure. example.com (tls-sni-01): urn:acme:error:connection
:: The server could not connect to the client to verify the domain :: Failed to
connect to 0.0.0.0:443 for TLS-SNI-01 challenge, example.com (tls-sni-01):
urn:acme:error:connection :: The server could not connect to the client to verify the
domain :: Failed to connect to 0.0.0.0:443 for TLS-SNI-01 challenge
IMPORTANT NOTES:
- The following errors were reported by the server:
Domain: example.com
Type: connection
Detail: Failed to connect to 0.0.0.0:443 for TLS-SNI-01
challenge
To fix these errors, please make sure that your domain name was
entered correctly and the DNS A record(s) for that domain
contain(s) the right IP address. Additionally, please check that
your computer has a publicly routable IP address and that no
firewalls are preventing the server from communicating with the
client. If you're using the webroot plugin, you should also verify
that you are serving files from the webroot path you provided.

The standalone plugin runs its own simple web server to prove that you control the domain. Ownership or domain validation is the key here. It needs the current computer that just issued the certbot command to have a publicly routable IP address. That’s not going to be happening in my local computer behind NAT. And webroot plugin needs a running web server. It can’t be run from the local machine as well. Domain validation are done automatically with both standalone and webroot plugins. Furthermore, domain validation requests are coming from Let’s Encrypt servers, therefore, you can’t have the machine issuing the certificate request behind a NAT or load balancing methods without properly routing the requests.

Since automated methods mostly require the requester and domain owner to be residing on the same machine, we can try to move the request to the Google cloud. Otherwise, there is one more plugin to try, the manual plugin. The manual method (plugin) helps you obtain a cert by giving you instructions to perform domain validation yourself.

Installing Let's Encrypt Certbot 0.8.x on Debian Jessie

Let’s Encrypt is a free, open, and automated certificate authority. And its Certbot is “a fully-featured, extensible client for the Let’s Encrypt CA (or any other CA that speaks the ACME protocol) that can automate the tasks of obtaining certificates and configuring webservers to use them.”[^1]

There are a number of ways to obtain and install SSL certificates issued by Let’s Encrypt CA. This is about installing Certbot 0.8.0 release on Debian Jessie. But before continuing, a few things to think about:

The Let’s Encrypt Client (Certbot) presently only runs on Unix-ish OSes that include Python 2.6 or 2.7; Python 3.x support will hopefully be added in the future. … currently it supports modern OSes based on Debian, Fedora, SUSE, Gentoo and Darwin.[^1]

That’s why using Docker container installation method might be a better choice, because it does not mess up your existing libraries and it can use supported operating systems which might not be the one you are using.

Anyhow, the current installation settings are:

  • Debian 8.5 Jessie
  • Python 2.7.9
  • Certbot 0.8.0

Certbot is available for Debian Jessie via backports.

Backports are recompiled packages from testing (mostly) and unstable (in a few cases only, e.g. security updates) in a stable environment so that they will run without new libraries (whenever it is possible) on a Debian stable distribution.

Backports cannot be tested as extensively as Debian stable, and backports are provided on an as-is basis, with risk of incompatibilities with other components in Debian stable. Use with care!

It is therefore recommended to select single backported packages that fit your needs, and not use all available backports.

Again, there’s why it might be a better idea to use a container. But, let’s proceed.

Add a new file named backports.list to /etc/apt/sources.list.d/ directory:

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$ sudo bash -c 'echo "deb http://ftp.debian.org/debian jessie-backports main" > \
/etc/apt/sources.list.d/backports.list'

Update:

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$ sudo apt-get update

All backports are deactivated by default, therefore, to install Certbot package from backports, run:

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$ sudo apt-get install certbot -t jessie-backports
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
dialog python-acme python-certbot python-cffi-backend python-configargparse python-configobj python-cryptography
python-dialog python-enum34 python-funcsigs python-idna python-ipaddress python-mock python-ndg-httpsclient python-openssl
python-parsedatetime python-pbr python-psutil python-pyasn1 python-pyicu python-requests python-rfc3339 python-six
python-tz python-urllib3 python-zope.component python-zope.event python-zope.interface
Suggested packages:
python-certbot-apache python-certbot-doc python-acme-doc python-configobj-doc python-cryptography-doc
python-cryptography-vectors python-enum34-doc python-funcsigs-doc python-mock-doc python-openssl-doc python-openssl-dbg
python-psutil-doc doc-base python-ntlm
Recommended packages:
letsencrypt
The following NEW packages will be installed:
certbot dialog python-acme python-certbot python-cffi-backend python-configargparse python-configobj python-cryptography
python-dialog python-enum34 python-funcsigs python-idna python-ipaddress python-mock python-ndg-httpsclient python-openssl
python-parsedatetime python-pbr python-psutil python-pyasn1 python-pyicu python-requests python-rfc3339 python-tz
python-urllib3 python-zope.component python-zope.event python-zope.interface
The following packages will be upgraded:
python-six
1 upgraded, 28 newly installed, 0 to remove and 163 not upgraded.
Need to get 1,881 kB of archives.
After this operation, 10.5 MB of additional disk space will be used.
Do you want to continue? [Y/n]

APT option -t lets you have simple control over which distribution packages will be retrieved from. In this case, the distribution jessie-backports is used.

Interesting to know that there is letsencrypt package, could this be the old client? Let’s query the APT’s package cache:

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$ apt-cache show letsencrypt
Package: letsencrypt
Source: python-certbot
Version: 0.8.0-1~bpo8+2
Installed-Size: 29
Maintainer: Debian Let's Encrypt
Architecture: all
Depends: certbot
Description-en: transitional dummy package
This is a transitional dummy package for the rename of letsencrypt to certbot.
It can safely be removed.

Yes, it’s a dummy package. It has been renamed. And from the documentation:

Until May 2016, Certbot was named simply letsencrypt or letsencrypt-auto, depending on install method.[^1]

Let’s poke around on the installed package:

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$ certbot --version
certbot 0.8.0

It’s not yet 1.0.

Obtaining the quick help:

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$ certbot --help
certbot [SUBCOMMAND] [options] [-d domain] [-d domain] ...
Certbot 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
renew Renew previously obtained certs that are near expiry
revoke Revoke a previously obtained certificate
register Perform tasks related to registering with the CA
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, register, nginx, apache, standalone, webroot,
etc.)

Now it’s time to obtain the certificate.

[^1]: Certbot Documentation