The certbot-dns-clounds plugin automates the process of completing a dns-01 challenge (acme.challenges.DNS01) by creating, and subsequently removing, TXT records using the ClouDNS API.

Named Arguments

--dns-cloudns-credentials	ClouDNS credentials INI file. (Required)
--dns-cloudns-propagation-seconds	The number of seconds to wait for DNS to propagate before asking the ACME server to verify the DNS record. (Default: 60)
--dns-cloudns-nameserver	Nameserver used to resolve CNAME aliases. (See the Challenge Delegation section below.) (Default: System default)

Credentials

Use of this plugin requires a configuration file containing the ClouDNS API credentials.

# Target user ID (see https://www.cloudns.net/api-settings/)
dns_cloudns_auth_id=1234
# Alternatively, one of the following two options can be set:
# dns_cloudns_sub_auth_id=1234
# dns_cloudns_sub_auth_user=foobar

# API password
dns_cloudns_auth_password=password1

The path to this file can be provided interactively or using the --dns-cloudns-credentials command-line argument. Certbot records the path to this file for use during renewal, but does not store the file's contents.

Caution

You should protect your credentials, as they can be used to potentially add, update, or delete any record in the target DNS server. Users who can read this file can use these credentials to issue arbitrary API calls on your behalf. Users who can cause Certbot to run using these credentials can complete a dns-01 challenge to acquire new certificates or revoke existing certificates for associated domains, even if those domains aren't being managed by this server.

Certbot will emit a warning if it detects that the credentials file can be accessed by other users on your system. The warning reads "Unsafe permissions on credentials configuration file", followed by the path to the credentials file. This warning will be emitted each time Certbot uses the credentials file, including for renewal, and cannot be silenced except by addressing the issue (e.g., by using a command like chmod 600 to restrict access to the file).

Challenge Delegation

The dns-cloudns plugin supports delegation of dns-01 challenges to other DNS zones through the use of CNAME records.

As stated in the Let's Encrypt documentation:

Since Let’s Encrypt follows the DNS standards when looking up TXT records for DNS-01 validation, you can use CNAME records or NS records to delegate answering the challenge to other DNS zones. This can be used to delegate the _acme-challenge subdomain to a validation-specific server or zone. It can also be used if your DNS provider is slow to update, and you want to delegate to a quicker-updating server.

This allows the credentials provided to certbot to be limited to either a sub-zone of the verified domain, or even a completely separate throw-away domain. This idea is further discussed in this article <https://www.eff.org/deeplinks/2018/02/ technical-deep-dive-securing-automation-acme-dns-challenge-validation> by the Electronic Frontier Foundation.

To resolve CNAME aliases properly, Certbot needs to be able to access a public DNS server. In some setups, especially corporate networks, the challenged domain might be resolved by a local server instead, hiding configured CNAME and TXT records from Certbot. In these cases setting the --dns-cloudns-nameserver option to any public nameserver (e.g. 1.1.1.1) should resolve the issue.

Installation

Install the plugin using pip:

pip install certbot-dns-cloudns

Examples

certbot certonly \
  --authenticator dns-cloudns \
  --dns-cloudns-credentials ~/.secrets/certbot/cloudns.ini \
  -d example.com

certbot certonly \
  --authenticator dns-cloudns \
  --dns-cloudns-credentials ~/.secrets/certbot/cloudns.ini \
  -d example.com \
  -d www.example.com

certbot certonly \
  --authenticator dns-cloudns \
  --dns-cloudns-credentials ~/.secrets/certbot/cloudns.ini \
  --dns-cloudns-propagation-seconds 30 \
  -d example.com

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