DNS Certification Authority Authorization (CAA) uses the Internet's Domain Name System to specify which certificate authorities may be regarded as authoritative for a domain. This is intended to support additional cross-checking at the client end of TLS connections[dubious – discuss] to attempt to prevent certificates issued by CAs other than the specified CAs from being used to spoof the identity of websites or perform man-in-the-middle attacks on them.
DNS Certification Authority Authorization is specified by RFC 6844. It defines a new "CAA" DNS Resource Record type for name-value pairs that can carry a wide range of information to be used as part of the CA authorization process. Use of CAA, where available, to validate certificates is recommended, but not mandatory. Furthermore the certificate evaluator should consider, that the CAA records may have changed in the time between the certificate was issued and the certificate is observed by the evaluator.[1]
Structure of CAA resource record
Each CAA resource recored contains a flags byte and tag-value pair, hereafter referred to as property.[clarification needed]
Currently one flag is defined: Issuer Critical represented by the byte value '1'. If set, the "corresponding property tag must be understood if the semantics of the CAA record to be correctly interpreted by an issuer."[2]
Beside the flag, three property tags are defined:
issue: This property authorizes the holder of the domain to issue certificates for the domain in which the property is published.
issuewild: This property acts like issue but allows wildcard certificates.
iodef: This property specifies a URL for reporting certificate issues. This is not mandatory for the client.
Supported Server
As of 2016[update], CAA records are supported in the BIND DNS server,[3] the NSD authoritative DNS server (as of version 4.0.1),[4] the Knot DNS server (since version 2.2.0).[5] and PowerDNS (since version 4.0.0).[6]
References
- ^ P. Hallam-Baker and R. Stradling (January 2013). "RFC 6844: DNS Certification Authority Authorization (CAA) Resource Record". Internet Engineering Task Force.
- ^ P. Hallam-Baker and R. Stradling (January 2013). "RFC 6844: DNS Certification Authority Authorization (CAA) Resource Record". Internet Engineering Task Force.
- ^ Vicky Risk (August 29, 2014). "Certificate Authority Authorization Records". Internet Systems Consortium.
- ^ NLNet Labs (January 27, 2014). "NSD: Name Server Daemon Releases". NLNet Labs.
- ^ Včelak, Jan. "[knot-dns-users] Knot DNS 2.2.0 release". Retrieved 2016-04-26.
- ^ "Supported Record Types". PowerDNS.com.
See also