add DoH support

* add instructions on how to use the resolvers
* additionally, configure better caching on CoreDNS
* tweak the main domain used
* reorganise the README a bit

README.md

@@ -1,17 +1,54 @@
 # [`coredns`](https://git.dotya.ml/dotya.ml/coredns)
 
-this repo contains configuration files for [CoreDNS](https://coredns.io/) set
-up as a simple [DNS over TLS (DoT)](https://en.wikipedia.org/wiki/DNS_over_TLS)
-forwarding resolver, that is relying on a locally running
-[`dnscrypt-proxy`](https://github.com/DNSCrypt/dnscrypt-proxy) instance for any
-and all queries.
+this repo contains the configuration files for [CoreDNS](https://coredns.io/)
+set up as a [DNS over TLS (DoT)](https://en.wikipedia.org/wiki/DNS_over_TLS)
+and [DNS over HTTPS (DoH)](https://en.wikipedia.org/wiki/DNS_over_HTTPS)
+forwarding resolver that relies on a locally running
+[`dnscrypt-proxy`](https://github.com/DNSCrypt/dnscrypt-proxy) instance for
+resolution of any and all queries.
 
-since the `systemd` service runs under an unprivileged user (here coredns,
-which doesn't by default have access to `/etc/letsencrypt`), certs need to be
-supplied to `coredns` another way: `copycerts_coredns.{path,service,timer}`.
+CoreDNS is configured to run under an unprivileged user (see
+`coredns.service`), which doesn't by default have access to `/etc/letsencrypt`.
+the TLS certs therefore need to be supplied to CoreDNS using another way - see
+the `copycerts_coredns.{path,service,timer}` units.
 
-### TO DO
+## how to use this - tl;dr
+
+### DoT
+```
+dns.dotya.ml
+```
+### DoH
+```
+https://dns.dotya.ml/dns-query
+```
+### DoH alt port
+```
+https://dns.dotya.ml:4053/dns-query
+```
+
+## how to use this - the long version
+
+the base domain here is `dns.dotya.ml`.
+
+for DoT, simply configure the domain directly as the standard port (`:853/tcp`)
+is used.
+
+for DoH, append `/dns-query` to the base domain and optionally prefix it with
+`https://`, i.e. configure `dns.dotya.ml/dns-query` or
+`https://dns.dotya.ml/dns-query` as the DoH server (in e.g.
+[Firefox](https://mzl.la/3PeuP0z)).
+
+it is worth noting that the DoH server natively listens on `:4053`, but is
+additionally proxied by `nginx` so that it can be found on a standard HTTPS
+port and blends in better.  
+that means that both configurations can be used, whereas one uses a
+non-standard port but does not depend on `nginx` running (which it does
+anyway), and the other uses a standard DoH port but could become unavailable in
+the event of `nginx` crashing for some reason.
+
+## TO DO
 - [ ] automated deployment (preferably using `ansible` + `drone`)
 
-### LICENSE
+## LICENSE
 WTFPLv2, see [LICENSE](LICENSE) for details

etc/coredns/Corefile

@@ -1,6 +1,5 @@
 tls://.:853 {
 	reload
-	errors
 
 	# certs need to be either copied or mounted here.
 	tls /var/lib/coredns/certs/fullchain.pem /var/lib/coredns/certs/privkey.pem {
@@ -15,9 +14,43 @@ tls://.:853 {
 	}
 
 	cache {
-		success	2048
+		success	4096
 		denial	2048
+		prefetch 512
+		keepttl
 	}
+
+	whoami
+	health
+	errors
+	# log
+}
+
+https://.:4053 {
+	reload
+
+	tls /var/lib/coredns/certs/fullchain.pem /var/lib/coredns/certs/privkey.pem {
+		client_auth verify_if_given
+	}
+
+	loadbalance
+	forward . 127.0.0.50:53 ::1 {
+		health_check 7s
+		expire 600s
+		policy sequential
+	}
+
+	cache {
+		success	4096
+		denial	2048
+		prefetch 512
+		keepttl
+	}
+
+	whoami
+	health
+	errors
+	# log
 }
 
 # vim: noexpandtab

etc/systemd/system/copy_coredns.path

@@ -1,9 +1,9 @@
 [Unit]
-Description=Watching for changes to dotya.ml certs and triggering copy service
-ConditionPathExists=/etc/letsencrypt/live/dotya.ml
+Description=Watching for changes to TLS certs and triggering the copy service
+ConditionPathExists=/etc/letsencrypt/live/dns.dotya.ml
 
 [Path]
-PathChanged=/etc/letsencrypt/live/dotya.ml
+PathChanged=/etc/letsencrypt/live/dns.dotya.ml
 TriggerLimitIntervalSec=30s
 TriggerLimitBurst=30
 

etc/systemd/system/copy_coredns.service

@@ -1,13 +1,13 @@
 [Unit]
-Description=Copy dotya.ml certs for coredns.service
+Description=Copy TLS certs for coredns.service
 # technically, the below should have no impact
 After=network.target
 PartOf=coredns.service
-ConditionPathExists=/etc/letsencrypt/live/dotya.ml
+ConditionPathExists=/etc/letsencrypt/live/dns.dotya.ml
 
 [Service]
 Type=oneshot
-Environment=DOMAIN=dotya.ml
+Environment=DOMAIN=dns.dotya.ml
 ExecStartPre=bash -c "mkdir -pv /var/lib/coredns/certs"
 ExecStart=bash -c "cp -f -v --dereference /etc/letsencrypt/live/${DOMAIN}/* /var/lib/coredns/certs/"
 ExecStopPost=bash -c "chown -Rv coredns:root /var/lib/coredns"

etc/systemd/system/copy_coredns.timer

@@ -1,5 +1,5 @@
 [Unit]
-Description=Weekly copy of dotya.ml certs for coredns
+Description=Weekly copy of TLS certs for coredns.service
 
 [Timer]
 OnCalendar=weekly

etc/systemd/system/coredns.service

@@ -2,6 +2,8 @@
 Description=CoreDNS server
 Documentation=https://coredns.io
 After=network.target
+Wants=dnscrypt-proxy.service
+Upholds=dnscrypt-proxy.service
 
 [Service]
 PermissionsStartOnly=true