# dnssec

*dnssec* enables on-the-fly DNSSEC signing of served data.

## Syntax

~~~
dnssec [ZONES...]
~~~

* **ZONES** zones that should be signed. If empty, the zones from the configuration block
    are used.

If keys are not specified (see below), a key is generated and used for all signing operations. The
DNSSEC signing will treat this key a CSK (common signing key), forgoing the ZSK/KSK split. All
signing operations are done online. Authenticated denial of existence is implemented with NSEC black
lies. Using ECDSA as an algorithm is preferred as this leads to smaller signatures (compared to
RSA). NSEC3 is *not* supported.

A single signing key can be specified by using the `key` directive.

NOTE: Key generation has not been implemented yet.

~~~
dnssec [ZONES... ] {
    key file KEY...
    cache_capacity CAPACITY
}
~~~

* `key file` indicates that key file(s) should be read from disk. When multiple keys are specified, RRsets
  will be signed with all keys. Generating a key can be done with `dnssec-keygen`: `dnssec-keygen -a
  ECDSAP256SHA256 <zonename>`. A key created for zone *A* can be safely used for zone *B*.

* `cache_capacity` indicates the capacity of the cache. The dnssec middleware uses a cache to store
  RRSIGs. The default capacity is 10000.

## Metrics

If monitoring is enabled (via the *prometheus* directive) then the following metrics are exported:

* coredns_dnssec_cache_size{type} - total elements in the cache, type is "signature".
* coredns_dnssec_cache_capacity{type} - total capacity of the cache, type is "signature".
* coredns_dnssec_cache_hits_total - Counter of cache hits.
* coredns_dnssec_cache_misses_total - Counter of cache misses.

## Examples

Sign responses for `example.org` with the key "Kexample.org.+013+45330.key".

~~~
example.org:53 {
    dnssec {
        key file /etc/coredns/Kexample.org.+013+45330.key
    }
    whoami
}
~~~

## Bugs

Multiple *dnssec* middlewares inside one server stanza will silently overwrite earlier ones, here
`example.local` will overwrite the one for `cluster.local`.

~~~
.:53 {
    kubernetes cluster.local
    dnssec cluster.local {
      key file /etc/coredns/cluster.local
    }
    dnssec example.local {
      key file /etc/coredns/example.local
    }
    whoami
}
~~~