feat: make Traefik trust forwarded headers from the host nginx

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-09-03 15:29:18 +09:00
parent 69d4502757
commit 2294c52095
1 changed files with 42 additions and 0 deletions
@@ -0,0 +1,42 @@
+# Make Traefik trust the X-Forwarded-* headers that the host nginx sets.
+#
+# Without this, Traefik rewrites every forwarded header from its own connection,
+# which is plain HTTP on port 80. The application then sees scheme=http even
+# though the browser connected over TLS. See docs/two-hop-proxy-header-contract.md.
+#
+# k3s installs Traefik through its bundled HelmChart, so values are overridden
+# with a HelmChartConfig rather than by editing the deployment. k3s reconciles
+# the chart and recreates the Traefik pod.
+#
+#   kubectl apply -f deploy/lab/k8s/traefik-forwarded-headers.yaml
+#   kubectl -n kube-system rollout status deploy/traefik --timeout=180s
+apiVersion: helm.cattle.io/v1
+kind: HelmChartConfig
+metadata:
+  name: traefik
+  namespace: kube-system
+spec:
+  valuesContent: |-
+    ports:
+      web:
+        forwardedHeaders:
+          # Requests arriving from these sources keep their existing
+          # X-Forwarded-* values instead of having them rewritten.
+          #
+          # 10.42.0.0/16 is the pod CIDR. It is required because the traefik
+          # Service uses externalTrafficPolicy: Cluster, so svclb SNATs the
+          # traffic and Traefik sees a pod-network address rather than the
+          # host nginx address.
+          #
+          # Trusting the whole pod CIDR means any pod in the cluster could
+          # forge these headers. That is acceptable in this lab and is the
+          # reason a production setup would narrow it — see the trade-off
+          # section in docs/two-hop-proxy-header-contract.md.
+          trustedIPs:
+            - 10.42.0.0/16
+            - 192.168.122.0/24
+      websecure:
+        forwardedHeaders:
+          trustedIPs:
+            - 10.42.0.0/16
+            - 192.168.122.0/24