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# DANE

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- DNSSEC

DANE (DNS-based Authentication of Named Entities) is a protocol to allow X.509 certificates, commonly used for Transport Layer Security (TLS), to be bound to DNS names using Domain Name System Security Extensions (DNSSEC) instead of (or in complement of) a pre-defined list of Certificate Authorities (CA).

Warning This is not a trivial article. Make sure that you know what you are doing. Read Common mistakes before going any further.

## TLSA resource record

The TLSA resource record is an own type of DNS record. It consists of port number and protocol of the service secured by it. An example record for port 25 over tcp could look like `_25._tcp.example.com IN TLSA 3 0 1 $DATA`. The TLSA parameters `3 0 1` are explaining the data following it. The first number is the Certificate Usage Field, the second is the Selector Field and the third is named Matching Type Field.

Certificate Usage Field
Value | Name | Description
--- | --- | ---
0 | PKIX trust anchor | Hash contains a public CA from the x509 tree by which your cert has to be signed
1 | PKIX end entity | Hash contains your cert which also has to pass x509 validation
2 | DANE trust anchor | Hash contains a private CA (unknown to the x509 tree) by which your cert has to be signed
3 | DANE end entity | Hash contains your cert which is not matched against any other validation

Note Certificate Usage 0 and 1 are not allowed for use with email servers (port 25). See RFC 7672 3.1.3 for details.

Selector Field
Value | Name | Description
--- | --- | ---
0 | cert | DATA is based on the full cert
1 | SPKI | DATA is based on public key only

Matching Type Field
Value | Name | Description
--- | --- | ---
0 | Full | DATA is the full cert or SPKI
1 | sha256 | DATA is the sha256 hash of the cert or SPKI
2 | sha512 | DATA is the sha512 hash of the cert or SPKI

The RR can also easily be generated with ldns-dane(1) from ldns.

## SSHFP resource record

See OpenSSH#SSHFP record.

## DANE supporting software

- Postfix
- Exim > 4.85
- Prosody (via prosody-mod-s2s-auth-daneAUR)

## See also

- DANE Validator
- Firefox extension to check DNSSEC/DANE status of websites
- Common implementation mistakes
- Generate TLSA records online

Category:

- Domain Name System

DANE
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