Notify parent for DS update (RFC 9859)

api/desecapi/management/commands/notify-parent.py

@@ -0,0 +1,139 @@
+from django.core.management import BaseCommand, CommandError
+import dns.resolver
+
+from desecapi.models import Domain
+from desecapi.utils import gethostbyname_cached
+
+
+class Command(BaseCommand):
+    debug = False
+    help = "Notify parent to update the DS RRset."
+    report_agent = dns.name.from_text(  # Must be below one parent-side NS
+        # TODO Make a Domain property?
+        "notify-agent.ns.desec.cz."
+    )
+    resolver: dns.resolver.Resolver
+
+    def add_arguments(self, parser):
+        parser.add_argument(
+            "domain-name",
+            nargs="*",
+            help="Domain name to notify for. If omitted, notify for all domains known locally.",
+        )
+
+    def handle(self, *args, **options):
+        domains = Domain.objects.all()
+        self.debug = options.get("verbosity", 1) > 1
+
+        if options["domain-name"]:
+            domains = domains.filter(name__in=options["domain-name"])
+            domain_names = domains.values_list("name", flat=True)
+
+            for domain_name in options["domain-name"]:
+                if domain_name not in domain_names:
+                    raise CommandError("{} is not a known domain".format(domain_name))
+
+        self.resolver = dns.resolver.Resolver(configure=False)
+        self.resolver.nameservers = [gethostbyname_cached("resolver")]
+        self.resolver.flags = dns.flags.RD | dns.flags.AD
+
+        for domain in domains:
+            self.stdout.write("%s ... " % domain.name, ending="")
+            domain_name = dns.name.from_text(domain.name)
+            try:
+                answer = self._get_dsync(domain_name)
+            except dns.exception.ValidationFailure as e:
+                print(f"failed: {e}")
+                continue
+            except Exception as e:
+                print("failed")
+                msg = "Error while processing {}: {}".format(domain.name, e)
+                raise CommandError(msg)
+
+            if answer is None:
+                print("unsupported")
+            else:
+                notifies = 0
+                targets = 0
+                for dsync in answer:
+                    result = self._notify_domain(domain_name, dsync)
+                    try:
+                        result, response = result
+                    except TypeError:  # None: DSYNC was not for NOTIFY(SOA)
+                        continue
+                    targets += 1
+                    notifies += result
+                    if not result and self.debug:
+                        print(response)
+                print(
+                    f"notified, {notifies}/{targets} NOTIFY(SOA) targets confirmed (from {len(answer)} {answer.qname}/DSYNC total)"
+                )
+
+    def _resolve_securely(self, qname, rdtype):
+        if self.debug:
+            print(f"resolving {qname}/{rdtype} ...")
+        try:
+            answer = self.resolver.resolve(qname, rdtype)
+            response = answer.response
+        except dns.resolver.NoAnswer as e:
+            answer = None
+            response = e.response()
+        except dns.resolver.NXDOMAIN as e:
+            answer = None
+            response = e.response(qname)
+        finally:
+            if not (response.flags & dns.flags.AD):
+                raise dns.exception.ValidationFailure(
+                    f"unauthenticated response: {qname}/{rdtype}"
+                )
+            return answer, response
+
+    def _notify_domain(self, domain_name, dsync):
+        # Only process NOTIFY(CDS)
+        if dsync.scheme != 1 or dsync.rrtype != dns.rdatatype.CDS:
+            return
+
+        notify = dns.message.make_query(domain_name, dns.rdatatype.CDS)
+        notify.set_opcode(dns.opcode.NOTIFY)
+        notify.flags += dns.flags.AA - dns.flags.RD
+        opt = dns.edns.ReportChannelOption(self.report_agent)
+        notify.use_edns(edns=True, options=[opt])
+
+        response = dns.query.udp(
+            notify, gethostbyname_cached(dsync.target.to_text()), timeout=5
+        )
+
+        notify.flags += dns.flags.QR
+        # TODO why does this work despite of the EDNS0 option not being in the response?
+        return notify == response, response
+
+    def _get_dsync(self, domain_name):
+        # This implements the discovery algorithm from RFC 9859 Section 4.1
+
+        # Try child-specific (or wildcard), assuming parent one level up
+        qname = dns.name.Name((domain_name[0], "_dsync", *domain_name[1:]))
+        answer, response = self._resolve_securely(qname, dns.rdatatype.DSYNC)
+        if answer:
+            return answer
+
+        # Find parent
+        owner_names = [
+            rr.name
+            for rr in response.authority
+            if rr.rdtype == dns.rdatatype.SOA and rr.rdclass == dns.rdataclass.IN
+        ]
+        if len(owner_names) > 1:
+            ValueError("Negative response has several SOA records")
+        parent = owner_names[0]
+
+        # Try child-specific (or wildcard), with parent from previous negative response
+        infix = dns.name.from_text("_dsync").relativize(dns.name.root)
+        parent_qname = domain_name - parent + infix + parent
+        if parent_qname != qname:
+            answer, _ = self._resolve_securely(parent_qname, dns.rdatatype.DSYNC)
+            if answer:
+                return answer
+
+        # Try fall-back DSYNC record at _dsync.$parent
+        qname = infix + parent
+        return self._resolve_securely(qname, dns.rdatatype.DSYNC)[0]

api/desecapi/pdns.py

@@ -1,7 +1,5 @@
 import json
 import re
-import socket
-from functools import cache
 from hashlib import sha1
 
 import requests
@@ -10,6 +8,7 @@
 
 from desecapi import metrics
 from desecapi.exceptions import PDNSException, RequestEntityTooLarge
+from desecapi.utils import gethostbyname_cached
 
 SUPPORTED_RRSET_TYPES = {
     # https://doc.powerdns.com/authoritative/appendices/types.html
@@ -84,11 +83,6 @@
 }
 
 
-@cache
-def gethostbyname_cached(host):
-    return socket.gethostbyname(host)
-
-
 def _pdns_request(
     method, *, server, path, data=None, accept="application/json", **kwargs
 ):

api/desecapi/utils.py

@@ -0,0 +1,7 @@
+import socket
+from functools import cache
+
+
+@cache
+def gethostbyname_cached(host):
+    return socket.gethostbyname(host)

api/requirements.txt

@@ -9,7 +9,7 @@ django-celery-email~=3.0.0
 django-netfields~=1.3.2
 django-pgtrigger~=4.15.4
 django-prometheus~=2.4.1
-dnspython~=2.7.0
+dnspython~=2.8.0
 pyotp~=2.9.0
 psycopg[binary]~=3.2.10
 psl-dns~=1.1.1

docker-compose.yml

@@ -131,6 +131,7 @@ services:
     - nsmaster
     - celery-email
     - memcached
+    - resolver
     tmpfs:
     - /var/local/django_metrics:size=500m
     environment:
@@ -163,6 +164,7 @@ services:
       rearapi_dbapi:
       rearapi_ns:
         ipv4_address: ${DESECSTACK_IPV4_REAR_PREFIX16}.1.10
+      rearapi_resolver:
       rearwww:
       rearmonitoring_api:
     logging:
@@ -358,6 +360,23 @@ services:
         tag: "desec/prometheus"
     restart: unless-stopped
 
+  resolver:
+    build: resolver
+    image: desec/dedyn-resolver:latest
+    init: true
+    cap_add:
+    - NET_ADMIN
+    environment:
+    - DESECSTACK_IPV4_REAR_PREFIX16
+    networks:
+      rearapi_resolver:
+        ipv4_address: ${DESECSTACK_IPV4_REAR_PREFIX16}.9.2
+    logging:
+      driver: "syslog"
+      options:
+        tag: "desec/resolver"
+    restart: unless-stopped
+
 volumes:
   dbapi_postgres:
   dblord_mysql:
@@ -401,6 +420,13 @@ networks:
       config:
       - subnet: ${DESECSTACK_IPV4_REAR_PREFIX16}.1.0/24
         gateway: ${DESECSTACK_IPV4_REAR_PREFIX16}.1.1
+  rearapi_resolver:
+    driver: bridge
+    ipam:
+      driver: default
+      config:
+      - subnet: ${DESECSTACK_IPV4_REAR_PREFIX16}.9.0/24
+        gateway: ${DESECSTACK_IPV4_REAR_PREFIX16}.9.1
   rearwww:
     driver: bridge
     ipam:

resolver/Dockerfile

@@ -0,0 +1,11 @@
+FROM ubuntu:noble
+
+COPY ./entrypoint.sh /root/
+CMD ["/root/entrypoint.sh"]
+
+RUN apt-get update \
+    && apt-get install -y bind9-dnsutils gettext-base unbound \
+    && apt-get clean && rm -rf /var/lib/apt/lists/*
+
+RUN cp /usr/share/dns/root.key /var/lib/unbound/root.key
+COPY conf/ /etc/unbound/unbound.conf.d/

resolver/conf/resolver.conf.var

@@ -0,0 +1,19 @@
+server:
+  cache-max-ttl: 600
+  ede: yes
+  interface: 0.0.0.0@53
+  access-control: ${DESECSTACK_IPV4_REAR_PREFIX16}.0.0/16 allow
+
+  log-queries: no
+  log-replies: no
+  log-servfail: yes
+  verbosity: 1
+
+  do-daemonize: no
+
+  neg-cache-size: 4M
+  qname-minimisation: yes
+
+  deny-any: yes
+  logfile: /tmp/log
+  use-syslog: no

resolver/entrypoint.sh

@@ -0,0 +1,3 @@
+#!/bin/bash
+envsubst < /etc/unbound/unbound.conf.d/resolver.conf.var > /etc/unbound/unbound.conf.d/resolver.conf
+exec unbound