helm-charts/freesailarr/templates/freesailarr.networkpolicy.yaml

{{- /*
NetworkPolicy for freesailarr (Gitea #5).

TEN CONTAINERS IN ONE POD, BEHIND A VPN, AND THE POLICY IS SIMPLER THAN THAT
SOUNDS - for one reason worth stating first: the containers talk to each other
over LOCALHOST. They share a network namespace, so none of that traffic ever
reaches a network interface and NO NetworkPolicy has anything to say about it.
Prowlarr reaching Radarr, Recyclarr reaching Sonarr, every one of those hops is
invisible here. What this policy governs is only what enters or leaves the pod.

INBOUND is the eight published web interfaces plus gluetun's health server, and
almost all of them are probe ports - the kubelet opens an HTTP connection to
each container's own interface - so they are one rule on the probe path. The
newznab port of mediathekarr is the exception: nothing probes it, and its only
consumer is Prowlarr in this same pod over localhost, so it is restricted by
source and that costs nothing.

OUTBOUND IS WHERE THIS CHART IS UNLIKE EVERY OTHER ONE HERE, because the pod's
network namespace belongs to gluetun. Every connection the *arr containers make
goes into the WireGuard tunnel and leaves the pod as UDP to the VPN endpoint -
so a NetworkPolicy sees the OUTER packets and almost nothing else. Three rules
cover it: DNS, UDP 51820 for the tunnel itself, and 443 for gluetun's own
server-list API. Indexer and tracker traffic needs no rule of its own; it is
already inside the tunnel.

AND THE TUNNEL RULE IS THE ONE THAT CAN BREAK THIS CHART, which is also why it
is well covered: gluetun's health server returns 200 only while the tunnel is
up, and all three of its probes address it. A blocked UDP 51820 therefore means
a pod that never becomes Ready - visibly, in the install-test, which brings up
a real tunnel. 51820 is WireGuard's standard port and Mullvad's; Mullvad also
offers 53, 123, 500 and 4500 for obfuscation, and a release using one of those
needs networkPolicy.egress.extraPorts. Note that extraPorts is TCP only, so an
alternative UDP port needs the rule here widened instead - said plainly,
because it is a limit of the shared values shape and not an oversight.

WHAT THIS OBJECT IS: a ceiling on reachability, not an authentication layer.
Only the ports declared below are reachable at all - whatever else the process
binds, now or after the next app update, is blocked without anyone having to
notice it exists.

WHAT IT IS NOT:
  - EGRESS IS COARSE. A NetworkPolicy matches CIDRs and selectors and NEVER
    hostnames, so "only to the database host" cannot be expressed at all. This
    cluster's CNI is Canal (Flannel plus Calico for policy) and has no FQDN
    rule; Calico's GlobalNetworkSet could express one but would bind this chart
    to Calico, the same argument that kept implementation-specific objects out
    of the Gateway-API sweep (#114). Each egress rule therefore permits its
    PORT to any destination.
  - NOT A BOUNDARY WHERE THE CNI DOES NOT ENFORCE ONE. An unenforced policy is
    accepted by the API server and filters nothing, so everything reads as
    configured while nothing is filtered.
  - THE REASONING IS IN TEMPLATE COMMENTS, not in "#" comments: those are part
    of the rendered object, travel into the cluster and appear in every release
    diff. ci/run-networkpolicy-test.sh fails on a rendered "#".

THE PORT NUMBERS BELOW ARE POD PORTS, NEVER NODEPORTS. A NetworkPolicy is
evaluated at the pod's network interface, after kube-proxy has already
translated a NodePort to the targetPort, so a NodePort number here would match
nothing while looking strict - and, being the only rule for that port, would
block every inbound connection instead. ci/run-networkpolicy-test.sh asserts
every port here against the containerPorts of the pod spec this policy
selects.
*/ -}}
{{- if .Values.networkPolicy.enabled }}
{{- $np := .Values.networkPolicy }}
{{- $ns := .Release.Namespace }}
{{- $probeSources := $np.probeSources | default list }}
{{- $allowedNs := $np.allowedNamespaces | default list }}
{{- $ic := $np.ingressController | default dict }}
{{- $routed := or .Values.ingress.enabled .Values.httpRoute.enabled }}
{{- /* networkPolicy.ingress - the policy's INBOUND side, and not the same thing
       as networkPolicy.ingressController (the SOURCE SELECTOR for the ingress
       controller's pods, a SIBLING of it and no part of it) nor as the
       top-level .Values.ingress (the Ingress object). All three match a search
       for "ingress"; one round of this work already mistook the second for an
       inbound escape hatch on the strength of the substring. */}}
{{- $npIngress := $np.ingress | default dict }}
{{- $ambientMesh := $npIngress.ambientMesh }}
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: {{ .Release.Name }}-{{ .Chart.Name }}-networkpolicy
  labels:
    app: {{ .Release.Name }}-{{ .Chart.Name }}-networkpolicy
spec:
  {{- /*
  Selects the StatefulSet's pods. ci/run-networkpolicy-test.sh fails if
  this matches no pod spec of the same render - which is the mistake that
  would otherwise leave a policy in the namespace filtering nothing, and
  its usual cause is a label renamed in the workload template.
  */}}
  podSelector:
    matchLabels:
      app: {{ .Release.Name }}-{{ .Chart.Name }}-sfs
  policyTypes:
    - Ingress
    {{- /*
    Egress is listed, and for this chart it is unusually meaningful: because the
    pod's network namespace belongs to gluetun, the only things that leave it are
    the tunnel, DNS and gluetun's control-plane calls. Everything the applications
    do is encapsulated. So three narrow rules really do describe the pod's whole
    outbound surface - which is rare here.
    */}}
    - Egress
  ingress:
    {{- /*
    THE PROBE PATH, nine ports of it. gluetun's health server (9999) plus the eight
    web interfaces the kubelet probes directly: qBittorrent (8080), Prowlarr
    (9696), FlareSolverr (8191), Radarr (7878), Sonarr (8989), Seerr (5055), Bazarr
    (6767) and Mediathekarr (5007). Every one of them is addressed by at least one
    httpGet probe, so none of them can be restricted by source without the worker
    node's IP.

    Recyclarr is absent from this list on purpose: it declares no port and its
    probes are exec probes, so there is nothing to allow.
    */}}
    - ports:
        - protocol: TCP
          port: 9999
        - protocol: TCP
          port: 8080
        - protocol: TCP
          port: 9696
        - protocol: TCP
          port: 8191
        - protocol: TCP
          port: 7878
        - protocol: TCP
          port: 8989
        - protocol: TCP
          port: 5055
        - protocol: TCP
          port: 6767
        - protocol: TCP
          port: 5007
        {{- if $ambientMesh }}
        {{- /* FIRST HALF OF networkPolicy.ingress.ambientMesh (Gitea #143). 15008/TCP
               is ztunnel's HBONE tunnel, the port every inbound connection arrives on
               once the namespace carries istio.io/dataplane-mode - ambient "does not
               and will never bypass Kubernetes NetworkPolicy enforcement", so without
               it a pod in the mesh is simply unreachable.

               It is the one port here that is NOT a containerPort of the selected pod
               spec: ztunnel terminates it, not the application. ci/run-networkpolicy-
               test.sh therefore holds a NAMED exception for exactly this number, gated
               on exactly this value - and assertion 7 of that script proves, on a
               second render, that 15008 stays the ONLY such port and that it is absent
               while the value is false.

               NOT MEASURED: that 15008 alone suffices comes from Istio's
               documentation. Measured on this cluster is only which listeners ztunnel
               opens. Provable at the first namespace to join the mesh; none has. */}}
        - protocol: TCP
          port: 15008
        {{- end }}
      {{- if $probeSources }}
      {{- /*
      RESTRICTED, because the operator supplied probeSources. The kubelet's probes
      come from the IP of the WORKER NODE running the pod, so that address has to be
      in the list or the pod never becomes Ready - and a pod that is never Ready
      reads as a broken application rather than as a policy.

      The ingress controller is added to the same rule - this chart renders TWO
      Ingresses, the main one and qBittorrent's, and both go dark the moment this
      list is filled without it.
      */}}
      from:
        - namespaceSelector:
            matchLabels:
              {{- /*
              Set by Kubernetes itself on every namespace (>= 1.21), so this needs no
              labelling work on a namespace this chart does not own.
              */}}
              kubernetes.io/metadata.name: {{ $ns }}
        {{- if and $routed $ic.namespace }}
        {{- /*
        ONE from-entry with TWO selectors, which is an AND: pods carrying these labels
        IN that namespace. Written as two list entries it would be an OR, and would
        open the port to every pod in kube-system.
        */}}
        - namespaceSelector:
            matchLabels:
              kubernetes.io/metadata.name: {{ $ic.namespace | quote }}
          {{- with $ic.podLabels }}
          podSelector:
            matchLabels:
              {{- toYaml . | nindent 14 }}
          {{- end }}
        {{- end }}
        {{- range $allowedNs }}
        - namespaceSelector:
            matchLabels:
              kubernetes.io/metadata.name: {{ . | quote }}
        {{- end }}
        {{- range $probeSources }}
        - ipBlock:
            cidr: {{ . | quote }}
        {{- end }}
        {{- if $ambientMesh }}
        {{- /* SECOND HALF OF networkPolicy.ingress.ambientMesh, and the reason it is
               one value and not two. Inside the mesh the kubelet's probes are
               redirected and no longer arrive from the worker node's address: they
               arrive from 169.254.7.127.

               An operator who only opens 15008 by hand writes a policy that passes
               review - and the moment probeSources is non-empty every probe is
               dropped, the pod never becomes Ready, and the symptom reads as a broken
               application rather than as a policy. That is assertion 4 of
               ci/run-networkpolicy-test.sh one value further along. A switch whose
               halves can only be had together cannot be set halfway.

               Only in this branch, because this is the only branch with a "from" list:
               with no sources restricted the rule is open and needs no peer. The IPv6
               counterpart is deliberately absent - this cluster is SingleStack IPv4,
               and an ipBlock of the wrong family is accepted and matches nothing.

               UNPROVEN IN OPERATION: probeSources is empty in every chart here, so no
               release reaches this branch. CI proves its render, through the overlays
               in ci/networkpolicy. */}}
        - ipBlock:
            cidr: 169.254.7.127/32
        {{- end }}
      {{- else }}
      {{- /*
      NO "from" SELECTOR, WHICH MEANS OPEN - deliberately, and only inside the
      cluster, because this port carries no NodePort. The alternative was to guess
      the worker node CIDRs, and a wrong guess blocks every kubelet probe: the pod
      stays un-Ready, the rollout times out, and the cause looks like the
      application. An empty "from: []" would be worse than either - it allows
      everything too, but while reading as a restriction. Narrow it with
      networkPolicy.probeSources.
      */}}
      {{- end }}
    {{- /*
    MEDIATHEKARR'S NEWZNAB PORT, and the one inbound port here that can be
    restricted: no probe addresses it. Its only consumer is Prowlarr, which runs in
    THIS pod and reaches it over localhost - traffic no NetworkPolicy sees at all -
    so restricting this rule to the release's own namespace plus allowedNamespaces
    costs nothing and removes a port from the cluster's reach.
    */}}
    - ports:
        - protocol: TCP
          port: 5008
      from:
        - namespaceSelector:
            matchLabels:
              {{- /*
              Set by Kubernetes itself on every namespace (>= 1.21), so this needs no
              labelling work on a namespace this chart does not own.
              */}}
              kubernetes.io/metadata.name: {{ $ns }}
        {{- range $allowedNs }}
        - namespaceSelector:
            matchLabels:
              kubernetes.io/metadata.name: {{ . | quote }}
        {{- end }}
  egress:
    {{- /*
    DNS, unconditionally. There is no value to switch this off, and that is
    deliberate: a knob whose only other setting breaks every name lookup in
    the pod is a trap and not a feature.
    */}}
    - ports:
        - protocol: UDP
          port: 53
        - protocol: TCP
          port: 53
    {{- /*
    THE WIREGUARD TUNNEL, and the rule this chart cannot live without. Everything
    the *arr containers do leaves the pod inside this tunnel, so blocking it
    blocks all of them at once - and gluetun's health server, which all three of
    its probes address, returns 200 only while the tunnel is up. The pod would
    never become Ready.

    51820 is WireGuard's standard port and Mullvad's. Mullvad also offers 53, 123,
    500 and 4500 for obfuscation; a release using one of those must widen THIS rule,
    because networkPolicy.egress.extraPorts is TCP only.
    */}}
    - ports:
        - protocol: UDP
          port: 51820
    {{- /*
    Outbound HTTPS, for gluetun's own control-plane traffic: it fetches and caches
    the provider's server list over the API before the tunnel exists, so this
    cannot go through the tunnel. Indexer and tracker traffic does NOT need a rule
    here - it is already inside the tunnel by the time it leaves the pod.
    */}}
    - ports:
        - protocol: TCP
          port: 443
    {{- with $np.egress }}
    {{- with .extraPorts }}
    {{- /*
    Ports only, to any destination - see the header. This is the operator's
    escape hatch from the egress cap, and the only alternative to switching
    the whole policy off.
    */}}
    - ports:
        {{- range . }}
        - protocol: TCP
          port: {{ int . }}
        {{- end }}
    {{- end }}
    {{- end }}
{{- end }}