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coredns.io/content/plugins/tls.md
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Miek Gieben 9d3c78f16f Sync notes from coredns
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Signed-off-by: Miek Gieben <miek@miek.nl>
2019-03-03 14:12:07 +00:00

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+++
title = "tls"
description = "*tls* allows you to configure the server certificates for the TLS and gRPC servers."
weight = 34
tags = [ "plugin", "tls" ]
categories = [ "plugin" ]
date = "2019-03-03T14:11:50.605544"
+++
## Description
CoreDNS supports queries that are encrypted using TLS (DNS over Transport Layer Security, RFC 7858)
or are using gRPC (https://grpc.io/, not an IETF standard). Normally DNS traffic isn't encrypted at
all (DNSSEC only signs resource records).
The *proxy* plugin also support gRPC (`protocol gRPC`), meaning you can chain CoreDNS servers
using this protocol.
The *tls* "plugin" allows you to configure the cryptographic keys that are needed for both
DNS-over-TLS and DNS-over-gRPC. If the `tls` directive is omitted, then no encryption takes place.
The gRPC protobuffer is defined in `pb/dns.proto`. It defines the proto as a simple wrapper for the
wire data of a DNS message.
## Syntax
~~~ txt
tls CERT KEY [CA]
~~~
Parameter CA is optional. If not set, system CAs can be used to verify the client certificate
## Examples
Start a DNS-over-TLS server that picks up incoming DNS-over-TLS queries on port 5553 and uses the
nameservers defined in `/etc/resolv.conf` to resolve the query. This proxy path uses plain old DNS.
~~~
tls://.:5553 {
tls cert.pem key.pem ca.pem
proxy . /etc/resolv.conf
}
~~~
Start a DNS-over-gRPC server that is similar to the previous example, but using DNS-over-gRPC for
incoming queries.
~~~
grpc://. {
tls cert.pem key.pem ca.pem
proxy . /etc/resolv.conf
}
~~~
Only Knot DNS' `kdig` supports DNS-over-TLS queries, no command line client supports gRPC making
debugging these transports harder than it should be.
## Also See
RFC 7858 and https://grpc.io.