Add zone file generator

Signed-off-by: Knut Ahlers <knut@ahlers.me>

Dockerfile

@@ -1,6 +1,9 @@
 FROM golang:alpine
 
+ARG COREDNS_VERSION=v1.0.5
+
 ADD ./build.sh /usr/local/bin/build.sh
+ADD ./cron_generate.go /src/cron_generate.go
 RUN set -ex \
  && apk --no-cache add git bash \
  && bash /usr/local/bin/build.sh
@@ -11,6 +14,11 @@ LABEL maintainer Knut Ahlers <knut@ahlers.me>
 
 COPY --from=0 /go/bin/coredns /usr/local/bin/
 
+ADD ./requirements.txt /src/requirements.txt
+RUN set -ex \
+ && apk --no-cache add python3 \
+ && pip3 install -r /src/requirements.txt
+
 ADD . /src
 WORKDIR /src
 

build.sh

@@ -1,25 +1,17 @@
 #!/bin/bash
 set -euxo pipefail
 
-IFS=$'\n'
-
-GOPKGS=(
-  'github.com/coredns/coredns'
-  'github.com/Luzifer/alias'
-)
-
-for pkg in ${GOPKGS[@]}; do
-  go get -d -v "${pkg}"
-done
-
-PLUGINS=(
-  '/^file:file/ i alias:github.com/Luzifer/alias'
-)
+# Download sourcecode
+mkdir -p /go/src/github.com/coredns
+git clone https://github.com/coredns/coredns.git /go/src/github.com/coredns/coredns
 
+# Ensure version pinning
 cd /go/src/github.com/coredns/coredns
-for insert in ${PLUGINS[@]}; do
-  sed -i "${insert}" plugin.cfg
-done
+git reset --hard ${COREDNS_VERSION}
 
-go generate
+# Copy cron drop-in
+cp /src/cron_generate.go .
+
+# Get dependencies and build
+go get -d -v
 go install

cron_generate.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"context"
+	"os/exec"
+	"time"
+
+	"github.com/Sirupsen/logrus"
+	"github.com/robfig/cron"
+)
+
+func init() {
+	c := cron.New()
+	c.AddFunc("0 * * * * *", generateZonefiles)
+	c.Start()
+}
+
+func generateZonefiles() {
+	logger := logrus.WithFields(logrus.Fields{
+		"fkt": "generateZonefiles",
+	})
+
+	var (
+		iw = logger.WriterLevel(logrus.InfoLevel)
+		ew = logger.WriterLevel(logrus.ErrorLevel)
+	)
+
+	defer iw.Close()
+	defer ew.Close()
+
+	ctx, cancel := context.WithTimeout(context.Background(), 59*time.Second)
+	defer cancel()
+
+	cmd := exec.CommandContext(ctx, "/usr/bin/python", "generateZonefiles.py")
+	cmd.Stdout = iw
+	cmd.Stderr = ew
+	cmd.Dir = "/src"
+
+	if err := cmd.Run(); err != nil {
+		logger.WithError(err).Error("Command execution failed")
+	}
+}

generateZonefiles.py

@@ -0,0 +1,99 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+import os
+
+# Third-party imports
+import dns.resolver
+import dns.rdatatype
+import jinja2
+import yaml
+
+DEFAULT_TTL = 3600
+
+
+def default(d, key, default=None):
+    if key in d:
+        return d[key]
+    return default
+
+
+def resolve_alias(entry):
+    result = []
+
+    answers = []
+    answers.extend(dns.resolver.query(
+        entry['alias'], 'A', raise_on_no_answer=False))
+    answers.extend(dns.resolver.query(
+        entry['alias'], 'AAAA', raise_on_no_answer=False))
+
+    if len(answers) == 0:
+        raise Exception(
+            "Alias {} was not resolvable: No answers!".format(entry['alias']))
+
+    for rdata in answers:
+        new_entry = entry.copy()
+        del new_entry['alias']
+        new_entry['type'] = dns.rdatatype.to_text(rdata.rdtype)
+        new_entry['data'] = rdata.address
+        result.append(new_entry)
+
+    return result
+
+
+def sanitize(entry):
+    result = []
+
+    if entry['name'] == '':
+        entry['name'] = '@'
+
+    if 'alias' in entry:
+        return resolve_alias(entry)
+
+    for rr in entry['records']:
+        new_entry = entry.copy()
+        del new_entry['records']
+        new_entry['data'] = rr
+
+        if new_entry['type'] == 'TXT' and new_entry['data'][0] != '"':
+            new_entry['data'] = '"{}"'.format(new_entry['data'])
+
+        result.append(new_entry)
+
+    return result
+
+
+def write_zone(zone, ttl, soa, nameserver, mailserver, entries):
+    tpl = jinja2.Template(open("zone_template.j2").read())
+    zone_content = tpl.render({
+        "zone": zone,
+        "ttl": ttl,
+        "soa": soa,
+        "nameserver": nameserver,
+        "mailserver": mailserver,
+        "entries": entries,
+    })
+
+    with open("zones/tmp.{}".format(zone), 'w') as zf:
+        zf.write(zone_content)
+
+    # FIXME (kahlers): Check if contents changed
+    os.rename("zones/tmp.{}".format(zone), "zones/db.{}".format(zone))
+
+
+def main():
+    zone_data = yaml.load(open("zones.yml"))
+
+    for zone, config in zone_data['zones'].items():
+        ttl = default(config, "default_ttl", DEFAULT_TTL)
+
+        entries = []
+        for entry in config['entries']:
+            entries.extend(sanitize(entry))
+
+        write_zone(zone, ttl, zone_data['soa'],
+                   zone_data['nameserver'], default(config, 'mailserver', {}), entries)
+
+
+if __name__ == "__main__":
+    main()

requirements.txt

@@ -0,0 +1,3 @@
+jinja2
+PyYAML
+dnspython

zone_template.j2

@@ -0,0 +1,18 @@
+; Auto-generated using generateZonefiles.py
+
+$ORIGIN {{ zone }}.
+$TTL {{ ttl }}
+
+{{ zone }}. {{ ttl }} IN SOA {{ soa.auth_ns }} {{ soa.contact }} {{ soa.serial }} {{ soa.refresh }} {{ soa.retry }} {{ soa.expire }} {{ soa.ttl }}
+
+{% for ns in nameserver -%}
+{{ zone }}. {{ ttl }} IN NS {{ ns }}
+{% endfor %}
+{%- if mailserver | length > 0 %}
+{% for mailserver, weight in mailserver.items() -%}
+{{ zone }}. {{ ttl }} IN MX {{ weight }} {{ mailserver }}
+{% endfor -%}
+{%- endif %}
+{% for entry in entries -%}
+{{ entry.name }} {{ entry.ttl | default(ttl) }} {{ entry.class | default('IN') }} {{ entry.type }} {% if entry.weight %}{{ entry.weight }} {% endif %}{{ entry.data }}
+{% endfor -%}