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CAA Records

What are CAA records


Certification Authority Authorization (CAA) records allow a DNS domain name holder to specify one or more Certification Authorities (CAs) authorized to issue certificates for that domain.  (RFC 6844)

  • CAA records are intended to prevent CAs from improperly issuing certificates.
  • CAA records can set policy for the entire domain, or for specific hostnames.
  • CAA records are also inherited by subdomains, therefore a CAA record set on example.com will also apply to any subdomain, such as subdomain.example.com (unless overridden).
  • CAA records can control the issuance single-name certificates, wildcard certificates, or both.

Configuration

Flag

There is currently only one flag defined, “issuer critical” at a value of 1. If a CA does not understand the flag value for an issuer critical record, then the CA will return with “no issue” for the certification.

All records will have the default issuer critical value of 0, which means they are “not critical”.

Type (Tag)

Type allows you to choose how you want certificates to be issued by the CA. Each CAA record can contain only one tag-value pair.

Options:

  • issue: Explicitly authorizes a single certificate authority to issue a certificate (any type) for the hostname.
  • issuewild: Authorization to issue certificates that specify a wildcard domain. Please note: issuewild properties take precedence over issue properties when specified.
  • iodef: (Incident Description Exchange Format) Specifies a means of reporting certificate issue requests or cases of certificate issue for the corresponding domain that violate the security policy of the issuer or the domain name holder.

Provider (Value)

Specify the domain name of the CA provider to which the CAA record applies. The Value field will automatically populate with the FQDN of the CA provider. If your CA is not in this list, select Other and enter the domain name in the Value box.

The <character-string> encoding of the value field is specified in [RFC1035], Section 5.1.

Canonical Format


When you are configuring CAA records you will need to present the record values in the following format:

<flags> <tag> <value>

example.com. CAA 0 issuessl.com

 

Use Cases


Let’s create a CAA record for a domain which authorizes certificates to be issued by Comodo and SSL.

example.com. CAA 0 issue “comodo.com”

example.com CAA 0 issue “ssl.com”

What if we want only Comodo to issue certificates? We would change the flag value to 1.

example.com. CAA 1 issue “comodo.com”

example.com CAA 0 issue “ssl.com”

If Comodo does not understand the record information, it will not return a certification. Instead, SSL will respond.

Now, what if we wanted to issue a wild card for SSL? We would change the type value to issuewild.

example.com. CAA 0 issue “comodo.com”

example.com CAA 0 issuewild “ssl.com”

Since wild cards take precedence, Comodo will not be able to issue a wild card certificate.

If you want to receive policy violations from CAs, you can change the type to iodef and replace the provider value with your contact email preceded by mailto: 

example.com. CAA 0 iodef “mailto:admin@example.com”

 

How to Configure CAA Records

1.Select Managed DNS and click on Domains
AXFR1

2. Select the Domain Name you want to add an A record to.
select a domain

3. Under the CAA Records section, click the plus_icon to add a record.
caa record 1

4. In this screen, you will add the record information. Follow the steps below:

A) Name: This will be the identifier for your record. It is important to note, the domain name is automatically appended to the “Name” field of the record.
B) TTL: Edit the TTL. Time to Live is measured in seconds and is the amount of time the record will cache in resolving name servers and web browsers.
C) Providers: In the drop down menu choose your CA (certificate authority) provider. The hostname of your provider will automatically populate the Value box. If your provider is not listed, then choose other, and enter the hostname of the provider in the Value box.
D) Tag: Tags allow you to choose how you want certificates to be issued by the CA. Each CAA record can contain only one tag-value pair. Refer to the Configuration section for more details on the kinds of tags.
E) Note: Add a helpful note with keywords so you can search for your records later.
F) Save and Close: Save your changes. Don’t forget to commit your changes.add caa record 2

 Information on the NX Domain feature can be found in the Disabling a Record tutorial.