External Service Routing

HTTPProxy supports routing traffic to ExternalName service types, but this is disabled by default, as it can lead to inadvertent exposure of the Envoy Admin UI, allowing remote shutdown and restart of Envoy. Please see this security advisory for all the details. It can also be used to expose services in namespaces a user does not have access to, using an ExternalName of service.namespace.svc.cluster.local. Please see this Kubernetes security advisory for more details.

We do not recommend enabling ExternalName Services without a strong use case, and understanding of the security implications.

However, To enable ExternalName processing, you must set the enableExternalNameService configuration file setting to true. This will allow the following configuration to be valid.

ExternalName Support

Contour looks at the spec.externalName field of the service and configures the route to use that DNS name instead of utilizing EDS.

Note that hostnames of localhost or some other synonyms will be rejected (because of the aforementioned security issues).

There’s nothing specific in the HTTPProxy object that needs to be configured other than referencing a service of type ExternalName. HTTPProxy supports the requestHeadersPolicy field to rewrite the Host header after first handling a request and before proxying to an upstream service. This field can be used to ensure that the forwarded HTTP request contains the hostname that the external resource is expecting.

Note: The ports are required to be specified.

# httpproxy-externalname.yaml
apiVersion: v1
kind: Service
metadata:
  labels:
    run: externaldns
  name: externaldns
  namespace: default
spec:
  externalName: foo-basic.bar.com
  ports:
  - name: http
    port: 80
    protocol: TCP
    targetPort: 80
  type: ExternalName

To proxy to another resource outside the cluster (e.g. A hosted object store bucket for example), configure that external resource in a service type externalName. Then define a requestHeadersPolicy which replaces the Host header with the value of the external name service defined previously. Finally, if the upstream service is served over TLS, set the protocol field on the service to tls or annotate the external name service with: projectcontour.io/upstream-protocol.tls: 443,https, assuming your service had a port 443 and name https.