DNS-based Authentication of Named Entities (DANE) is an Internet security protocol to allow X.509 digital certificates, commonly used for Transport Layer Security (TLS), to be bound to domain names using Domain Name System Security Extensions (DNSSEC).
It is proposed in as a way to authenticate TLS client and server entities without a certificate authority (CA). It is updated with operational and deployment guidance in . Application specific usage of DANE is defined in for SMTP and for using DANE with Service (SRV) records.
Rationale
TLS/SSL encryption is currently based on certificates issued by certificate authorities (CAs). Within the last few years, a number of CA providers suffered serious security breaches, allowing the issuance of certificates for well-known domains to those who don't own those domains. Trusting a large number of CAs might be a problem because any breached CA could issue a certificate for any domain name. DANE enables the administrator of a domain name to certify the keys used in that domain's TLS clients or servers by storing them in the Domain Name System (DNS). DANE needs the DNS records to be signed with DNSSEC for its security model to work.
Additionally DANE allows a domain owner to specify which CA is allowed to issue certificates for a particular resource, which solves the problem of any CA being able to issue certificates for any domain.
DANE solves similar problems as:
Certificate Transparency Ensuring that rogue CAs cannot issue certificates without the permission of the domain holder without being detected DNS Certification Authority Authorization Limiting which CAs can issue certificates for a given domain
However, unlike DANE, those technologies have wide support from browsers.
Email encryption
Until recently, there has been no widely implemented standard for encrypted email transfer. Sending an email is security agnostic; there is no URI scheme to designate secure SMTP. Consequently, most email that is delivered over TLS uses only opportunistic encryption. Since DNSSEC provides authenticated denial of existence (allows a resolver to validate that a certain domain name does not exist), DANE enables an incremental transition to verified, encrypted SMTP without any other external mechanisms, as described by . A DANE record indicates that the sender must use TLS.
Additionally, exists for applying DANE to S/MIME, and standardises bindings for OpenPGP.
Support
Applications
Google Chrome does not support DANE, since Google Chrome wishes to eliminate the use of 1024-bit RSA within the browser (DNSSEC previously used a 1024-bit RSA signed root, and many zones are still signed with 1024-bit RSA, although the modern default is 256-bit ECDSA). According to Adam Langley the code was written and, although it is not in Chrome today, it remains available in add-on form. Mozilla Firefox does not support DANE, based on the reactions in tickets on the subjects DNSSEC and DANE are currently seen by Mozilla developers as outside of the scope of Firefox, addon support is available though. GNU Privacy Guard Allows fetching keys via OpenPGP DANE (--auto-key-locate). New option --export-options export-dane. (version 2.1.14)
Servers
Postfix
PowerMTA
Halon
Exim
Services
Posteo
Tutanota
Libraries
OpenSSL
GnuTLS
TLSA RR
The TLSA RR (Resource Record) for a service is located at a DNS name that specifies certificate constraints should be applied for the services at a certain TCP or UDP port. At least one of the TLSA RRs must provide a validation (path) for the certificate offered by the service at the specified address.
Not all protocols handle Common Name matching the same way. HTTP requires that the Common Name in the X.509 certificate provided by the service matches regardless of the TLSA asserting its validity. SMTP does not require the Common Name matches, if the certificate usage value is 3 (DANE-EE), but otherwise does require a Common Name match. It is important to verify if there are specific instructions for the protocol being used.
RR data fields
The RR itself has 4 fields of data, describing which level of validation the domain owner provides.
the certificate usage field
the selector field
the matching type field
the certificate association data
E.g.
Certificate usage
The first field after the TLSA text in the DNS RR, specifies how to verify the certificate.