Files
helm-charts/rss-bridge/values.yaml
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jklein 7e6b3beed5 rss-bridge: pin the unprivileged-port sysctl, quote env values
Follow-up to the template-chart hardening fixes in #133, which landed
while this branch was open.

The env block now quotes names, values and keyRef fields. Without it a
value like "5" renders as a YAML number and the API server rejects the
whole manifest. RSS-Bridge takes numeric settings that way
(RSSBRIDGE_http_timeout), so this was reachable with the first env entry
anyone adds.

The port-80 question is settled by measurement rather than by the
"it works in k3d" reasoning #133 warns about. Same pod spec in k3d
(k3s v1.35.5), only ip_unprivileged_port_start changed:

  1024, capabilities.drop [ALL]      nginx: bind() to 0.0.0.0:80 failed
                                     (13: Permission denied)
  1024, plus NET_BIND_SERVICE        identical failure - for a non-root
                                     process the capability lands in the
                                     permitted but not the effective
                                     set, so it buys nothing
  0                                  binds, HTTP 200

So the chart cannot buy safety with a capability the way samba does, and
port 80 is not negotiable either: nginx is configured for it inside the
image and the entrypoint's only lever is a sed against a read-only
/etc/nginx. What it can do is stop depending on the node default - the
pod securityContext now pins the sysctl to 0, so the bind no longer
relies on cluster configuration. Verified: the chart-installed pod
reports 0 and answers 200 through the Service.

Worth recording how that failure looks without probes: the entrypoint
backgrounds nginx and then execs php-fpm, so a failed bind leaves a
container reporting Running with no web server at all. Both test pods
above were Running. The probes on /?action=health are what turn it into
a pod that never becomes Ready.

trivy config still reports 0 to act on; the KSV-0117 statement is
updated to the measured reasoning.
2026-08-23 23:39:49 +02:00

224 lines
10 KiB
YAML

# Scale the whole chart down without uninstalling it: scaleDown: true renders
# every Deployment/StatefulSet with replicas: 0 (and suspends CronJobs) and
# takes precedence over any per-workload replicas value. PVCs, Secrets and
# Services stay in place; scaleDown: false brings the workloads back up.
scaleDown: false
# The bridges RSS-Bridge offers, rendered into the ConfigMap as whitelist.txt
# and mounted at /app/whitelist.txt.
#
# A list rather than a blob of file content: the file format is one bridge name
# per line, and the application trims and filters every line before use
# (lib/Configuration.php), so nothing is lost by modelling it as YAML - while a
# hardcoded file body in the template could not be changed without editing the
# chart.
#
# The single entry "*" is RSS-Bridge's own wildcard and enables every bridge.
# It is the default here because it is exactly what the image does when no
# whitelist.txt exists at all, so a default install behaves like stock
# RSS-Bridge instead of silently serving nothing. Installations that want a
# narrower set list the bridge names explicitly:
#
# whitelist:
# - Youtube
# - Heise
#
# Changing this value rolls the pod - the deployment carries a checksum over
# the rendered ConfigMap (see rss-bridge.deployment.yaml). Without that the
# change would not reach the running container at all: the whitelist is a
# subPath mount, which the kubelet never refreshes.
whitelist:
- "*"
rssBridge:
# Replica count for this workload; 0 is allowed and scales it down.
# The chart-global scaleDown flag takes precedence.
replicas: 1
# Verified against the image, not assumed (issue #128).
#
# The image ships no USER and runs everything as root by default. It does,
# however, run fully hardened once its writable paths are provided: nginx and
# php-fpm both start, the front page renders and real bridges fetch feeds.
#
# uid/gid 33 is www-data, and it is not interchangeable: /app and every file
# in it is owned by www-data in the image, nginx.conf declares "user
# www-data" and the php-fpm pool declares "user = www-data". Both emit a
# harmless notice that those directives are ignored when the master process
# is not root, and then serve normally as uid 33.
securityContext:
pod:
runAsNonRoot: true
runAsUser: 33
runAsGroup: 33
fsGroup: 33
fsGroupChangePolicy: Always
seccompProfile:
type: RuntimeDefault
# Why this chart listens on the privileged port 80, and why that is safe.
#
# nginx is configured for port 80 inside the image. The only lever the
# entrypoint offers is HTTP_PORT, which runs a sed against
# /etc/nginx/sites-enabled/default - impossible with a read-only root
# filesystem. So the choice is port 80 or readOnlyRootFilesystem, and
# port 80 is the cheaper of the two. (The Service selects the port by
# NAME, so the number is invisible to it either way.)
#
# Kubernetes sets net.ipv4.ip_unprivileged_port_start=0 in the pod
# network namespace, so binding 80 needs no capability at all. But that
# is a runtime default, not a guarantee, and relying on it silently is
# exactly the trap the template-chart warns about - so the chart pins the
# value instead of inheriting it.
#
# Measured in k3d (k3s v1.35.5), same pod spec, only this value changed:
# sysctl 1024, capabilities.drop [ALL] -> nginx: bind() to
# 0.0.0.0:80 failed (13: Permission denied)
# sysctl 1024, plus NET_BIND_SERVICE added -> identical failure.
# Adding the capability does NOT help: for a non-root process it
# lands in the permitted set but not the effective/ambient one, so
# it buys nothing here. That is why this chart does not add it.
# sysctl 0 (this default) -> binds, HTTP 200.
#
# Note how that failure looks without probes: the entrypoint starts nginx
# in the background and then execs php-fpm, so a failed bind leaves a
# container that reports Running with no web server at all. The probes on
# /?action=health turn that silent failure into a pod that never becomes
# Ready.
sysctls:
- name: net.ipv4.ip_unprivileged_port_start
value: "0"
container:
allowPrivilegeEscalation: false
readOnlyRootFilesystem: true
runAsNonRoot: true
capabilities:
drop:
- ALL
# All three probes hit RSS-Bridge's own health action, which renders a fixed
# 49-byte JSON document without touching the file cache or any remote site.
# That keeps liveness free of external dependencies (guideline 3): a scraped
# website going down, or a cache directory that is not writable, must not
# restart the pod.
#
# Deliberately not "/": the front page enumerates every enabled bridge and
# answers with roughly 1.5 MB, which is a wasteful thing to fetch every ten
# seconds forever.
livenessProbe:
httpGet:
path: /?action=health
port: rss-bridge-port
periodSeconds: 10
timeoutSeconds: 5
failureThreshold: 3
readinessProbe:
httpGet:
path: /?action=health
port: rss-bridge-port
periodSeconds: 10
timeoutSeconds: 5
failureThreshold: 3
# The startup probe gates liveness/readiness, so those need no
# initialDelaySeconds. Startup budget = 5s * 30 = 150s, which is generous:
# the container is ready in about two seconds (nginx plus php-fpm, no
# migrations, no warm-up).
startupProbe:
httpGet:
path: /?action=health
port: rss-bridge-port
periodSeconds: 5
timeoutSeconds: 5
failureThreshold: 30
# Extra environment variables. Values are rendered through tpl; the value,
# secretKeyRef and configMapKeyRef forms are supported.
#
# RSS-Bridge maps RSSBRIDGE_<section>_<key> onto its config, so for example
# "RSSBRIDGE_system_timezone: Europe/Berlin" works here.
env: []
resources:
# Limits are optional: memory and ephemeral-storage limits default to
# limitFactor x the request, an explicitly set limit always wins, and a
# CPU limit is only set when configured explicitly under "limits".
limitFactor: 3
requests:
cpu: 0.1
# Measured with the shipped image: about 59 MiB resident while idle and
# roughly 89 MiB after serving feeds, so the previous 20Mi request was
# a third of what the workload actually occupies around the clock.
memory: 128Mi
# The previous manifest requested 2Gi of ephemeral storage - identical to
# its limit - and thereby reserved two gigabytes of node scheduling
# capacity for a workload that does not come close to using it.
#
# Everything RSS-Bridge writes was enumerated by running the image with a
# writable root filesystem, exercising every whitelisted bridge and then
# reading the container's diff layer. The only path that grows is the
# feed cache under /app/cache: 17 entries and 2.2 MB after fetching all
# five bridges, largest single entry 196 KB, and the application purges
# it on its own (FileCache enable_purge). /run and /var/lib/nginx add
# under 100 KB together.
#
# 64Mi is therefore roughly thirty times the measured footprint while
# freeing 97% of the old reservation. The limit below stays large, so
# the decoupling costs no safety margin (same shape as gotenberg, #106).
ephemeralStorage: 64Mi
limits:
# Set explicitly rather than left to limitFactor x request.
#
# memory: the manifest this chart replaces capped the container at
# 100Mi, but five concurrent feed fetches were measured peaking at
# 119 MiB - the old limit was already below the real peak, and php-fpm
# is configured for up to five workers with a 128M PHP memory_limit
# each. 512Mi covers the measured peak with room to spare and still
# bounds a runaway bridge.
memory: 512Mi
# Unchanged from the previous manifest on purpose: a large cap costs
# nothing (it reserves no capacity) and guarantees this change cannot
# make eviction more likely than it is today.
ephemeralStorage: 2Gi
# No CPU limit by default (repo standard): CPU is compressible, so a limit
# only throttles. The previous manifest capped CPU at 0.5.
ingress:
# Gates the whole Ingress template. Checked in both directions per guideline
# 1: nothing outside this template reads an ingress value - the container
# takes no domain in its environment and nginx serves as default_server
# without a server_name - so switching the Ingress off frees every value
# below, and none of them needs a separate required().
enabled: true
clusterIssuer: null
className: nginx
# Extra annotations for the Ingress; merged with the cert-manager
# cluster-issuer annotation the chart always sets.
annotations: {}
# The hosts this Ingress serves. Required - the chart ships no default,
# because hostnames are installation data and have no business in a chart.
#
# Each entry is a host plus an OPTIONAL tlsSecretName:
#
# hosts:
# - host: rss-bridge.example.com
# - host: feeds.example.com
# tlsSecretName: tls-legacy-feeds-ingress
#
# Entries sharing a tlsSecretName are grouped into one tls entry, so they
# share a single certificate with several SANs. Entries with distinct names
# get one certificate each. Omitting tlsSecretName falls back to the repo
# convention, tls-<release>-<chart>-ingress.
#
# DOCUMENTED DEVIATION - why the secret name is configurable at all:
#
# The repo convention (guideline 4) is exactly one TLS secret per Ingress,
# named tls-<release>-<chart>-ingress. The installation this chart takes over
# has grown three separate secrets, one per host, from three years of
# kubectl apply. Renaming them would not be a cosmetic cleanup: cert-manager
# keys certificates by secret name, so three new names mean three fresh
# issuances, and the service is unreachable on each host until its
# certificate is issued. That is a self-inflicted outage plus three
# avoidable Let's Encrypt issuances, for a deployment that has been running
# untouched for over a year.
#
# Making host and secret name per-entry values keeps the existing names in
# place today and turns the eventual consolidation onto one certificate - or
# the retirement of the legacy hostnames - into a values change instead of a
# template change (the explicit ask from cluster-config#33).
hosts: null