dokku-letsencrypt

dokku-letsencrypt is the official plugin for dokku that gives the ability to automatically retrieve and install TLS certificates from letsencrypt.org. During ACME validation, your app will stay available at any time.

By running this plugin, you agree to the Let’s Encrypt Subscriber Agreement automatically (because prompting you whether you agree might break running the plugin as part of a cronjob).

If you like Let’s Encrypt, please consider donating to Let’s Encrypt.

Installation

sudo dokku plugin:install https://github.com/dokku/dokku-letsencrypt.git

Upgrading from previous versions

sudo dokku plugin:update letsencrypt

Commands

$ dokku letsencrypt:help
    letsencrypt:active <app>                Verify if letsencrypt is active for an app
    letsencrypt:auto-renew                  Auto-renew all apps secured by letsencrypt if renewal is necessary
    letsencrypt:auto-renew <app>            Auto-renew app if renewal is necessary
    letsencrypt:cleanup <app>               Cleanup stale certificates and configurations
    letsencrypt:cron-job <--add|--remove>   Add or remove an auto-renewal cronjob
    letsencrypt:disable <app>               Disable letsencrypt for an app
    letsencrypt:enable <app>                Enable or renew letsencrypt for an app
    letsencrypt:list                        List letsencrypt-secured apps with certificate expiry
    letsencrypt:revoke <app>                Revoke letsencrypt certificate for app

Usage

If using this plugin with Cloudflare:

• The domain dns should be setup in “Proxied” mode
• SSL/TLS mode must be in “Full” mode
  • Using letsencrypt in “Flexible” mode will cause Cloudflare to detect your server as down
  • Using “Full” mode will require disabling SSL/TLS in cloudflare in order to renew the certificate.

If using “Flexible” SSL/TLS mode, avoid using this plugin.

See these two links for more details:

• https://community.cloudflare.com/t/lets-encrypt-ssl-cannot-renew-with-cloudflare/257666
• https://support.cloudflare.com/hc/en-us/articles/214820528-Validating-a-Let-s-Encrypt-Certificate-on-a-Site-Already-Active-on-Cloudflare

The app which is obtaining a letsencrypt certificate must already be deployed and accessible over the internet (i.e. in the browser) in order to add letsencrypt to your app. This plugin will fail to apply for an app that has otherwise only been created.

Obtain a Let’s encrypt TLS certificate for app myapp (you can also run this command to renew the certificate):

$ dokku letsencrypt:set myapp email your@email.tld
-----> Setting email to your@email.tld
$ dokku letsencrypt:enable myapp
=====> Let's Encrypt myapp...
-----> Updating letsencrypt docker image...
latest: Pulling from dokku/letsencrypt

Digest: sha256:20f2a619795c1a3252db6508f77d6d3648ad5b336e67caaf801126367dbdfa22
Status: Image is up to date for dokku/letsencrypt:latest
       done
-----> Enabling letsencrypt proxy for myapp...
-----> Getting letsencrypt certificate for myapp...
        - Domain 'myapp.mydomain.com'

[ removed various log messages for brevity ]

-----> Certificate retrieved successfully.
-----> Symlinking let's encrypt certificates
-----> Configuring SSL for myapp.mydomain.com...(using /var/lib/dokku/plugins/available/nginx-vhosts/templates/nginx.ssl.conf.template)
-----> Creating https nginx.conf
-----> Running nginx-pre-reload
       Reloading nginx
-----> Disabling letsencrypt proxy for myapp...
       done

Once the certificate is installed, you can use the certs:* built-in commands to edit and query your certificate.

You could also use the following command to set an email address for global. So you don’t need to type the email address for different application.

dokku letsencrypt:set --global email your@email.tld

Automatic certificate renewal

To enable the automatic renewal of certificates, a cronjob needs to be defined for the dokku user which will run daily and renew any certificates that are due to be renewed.

This can be done using the following command:

dokku letsencrypt:cron-job --add

Configuration

dokku-letsencrypt uses the Dokku environment variable manager for all configuration. The important environment variables are:

You can set a setting using dokku letsencrypt:set $APP $SETTING_NAME $SETTING_VALUE. When looking for a setting, the plugin will first look if it was defined for the current app and fall back to settings defined by --global.

Note: See “DNS-01 Challenge” for more information on configuration a dns-provider for DNS-01 based challenges and wildcard support.

Redirecting from HTTP to HTTPS

Dokku’s default nginx template will automatically redirect HTTP requests to HTTPS when a certificate is present.

You can customize the nginx template if you want different behaviour.

Design

dokku-letsencrypt gets around having to disable your web server using the following workflow:

1. Temporarily add a reverse proxy for the /.well-known/ path of your app to https://127.0.0.1:$ACMEPORT
2. Run the acme/lego Let’s Encrypt client in a Docker container binding to $ACMEPORT to complete the ACME challenge and retrieve the TLS certificates
3. Install the TLS certificates
4. Remove the reverse proxy and reload nginx

For a more in-depth explanation, see this blog post

Dockerfile and Image-based Deploys

When securing Dockerfile and Image-based deploys with dokku-letsencrypt, be aware of the proxy mechanism for dokku 0.6+.

For Dockerfile deploys - as well as those via git:from-image - Dokku will determine which ports a container exposes and proxies all those exposed ports in the Docker container by listening on the same port numbers on the host. This means that both the proxies for HTTP port 80 and HTTPS port 443 to the app’s container need to be manually configured using the dokku proxy:ports-* commands in order for certificate validation and browsing to the app via HTTPS to work.

A full workflow for creating a new Dockerfile/Image-based deployment (where the app is listening on port 5555) with dokku-letsencrypt would be:

1. Create a new app myapp in dokku and push to the dokku@myhost.com remote. This guide assumes that the Docker container will be listening for connections on port 5555 so replace container port numbers accordingly if necessary.
2. On the dokku host, use dokku ports:add myapp http:80:5555 to proxy HTTP port 80 to port 5555 on the Docker image
3. On the dokku host, use dokku letsencrypt:enable myapp to retrieve HTTPS certificates.
4. On the dokku host, use dokku ports:add myapp https:443:5555 to proxy HTTPS port 443 to port 5555 on the Docker image
5. (optional) On the dokku host, use dokku ports:remove myapp http:5555:5555 to remove a potential leftover proxy that was automatically configured on first deploy.

After these steps, the output of dokku ports:list myapp should look like this:

-----> Port mappings for myapp
-----> scheme             host port                 container port
https                     443                       5555

Replace the container port (5555 in the above example) with the port your app is listening on.

Note: Step 2 and step 4 cannot be joined together since a configured HTTPS proxy will include a ssl_certificate line in the app’s nginx config that will cause nginx config validation to fail because no valid HTTPS certificate is available until step 3 is completed.

Dealing with rate limit

Be aware that Let’s Encrypt is subject to rate limiting. The limit about the number of certificates you can add on a domain per week is a concern for dokku because of the default domain added to your new applications, named like <app>.<dokku-domain>: using dokku-letsencrypt on all your applications would create a certificate for each application subdomain on <dokku-domain>.

As a workaround, if you want to encrypt many applications, make sure to add a proper domain for each one and remove their default domain before running dokku-letsencrypt. For example, if your dokku domain is dokku.example.com and you want to encrypt your foo app:

dokku domains:add foo foo.com
dokku domains:remove foo foo.dokku.example.com
dokku letsencrypt:enable foo

While playing around with this plugin, you might want to switch to the let’s encrypt staging server by running dokku letsencrypt:set myapp server staging to enjoy much higher rate limits and switching back to the real server by running dokku letsencrypt:set myapp server once you are ready.

Generating a Cert for multiple domains

Your default dokku app is accessible under the root domain too. So if you have an application 00-default that is running under 00-default.mydomain.com it is accessible under mydomain.com too. Now if you enable letsencrypt for your 00-default application, it is not accessible anymore on mydomain.com. You can add the root domain to your dokku domains by typing:

dokku domains:add 00-default mydomain.com
dokku letsencrypt:enable 00-default

DNS-01 Challenge

Functionality sponsored by Orca Scan Ltd.

In order to provide a Letsencrypt certificate for a wildcard domain, a DNS-01 challenge must be used. To configure, the dns-provider property must be set to a supported Lego provider. Additionally, the environment variables used by the DNS provider must be set as letsencrypt properties with the prefix dns-provider-. Both global and app-specific properties are supported.

Warning: Before using a DNS-based challenge, ensure all DNS records - including wildcard records - are pointing at your server.

# set the provider to namecheap
dokku letsencrypt:set --global dns-provider namecheap

# set the properties necessary for namecheap usage
dokku letsencrypt:set --global dns-provider-NAMECHEAP_API_USER user
dokku letsencrypt:set --global dns-provider-NAMECHEAP_API_KEY key

Due to limitations in how certain DNS providers work, environment variables must not use the _FILE based method for referring to values in files.

Please see the Lego documentation for your DNS provider for more information on what configuration is necessary to utilize DNS-01 challenges.

Conditional enabling

dokku letsencrypt:enable <app> enables letsencrypt for an application or renews the certificate. This may lead to hitting rate limits with letsencrypt.

To avoid renewals, for example in a continuous deployment scenario, you could first check if letsencrypt has already been enabled for the app:

dokku letsencrypt:active <app> || dokku letsencrypt:enable <app>

License

This plugin is released under the MIT license. See the file LICENSE.