Upstream TLS

A HTTPProxy can proxy to an upstream TLS backend by annotating the upstream Kubernetes Service or by specifying the upstream protocol in the HTTPProxy services field. Applying the projectcontour.io/upstream-protocol.tls annotation to a Service object tells Contour that TLS should be enabled and which port should be used for the TLS connection. The same configuration can be specified by setting the protocol name in the spec.routes.services[].protocol field on the HTTPProxy object. If both the annotation and the protocol field are specified, the protocol field takes precedence. By default, the upstream TLS server certificate will not be validated, but validation can be requested by setting the spec.routes.services[].validation field. This field has mandatory caSecret, subjectName, and subjectNames fields, which specify the trusted root certificates with which to validate the server certificate and the expected server name(s).

Note: The subjectName field is deprecated in favor of subjectNames. When using subjectNames, the first entry must match the value for subjectName. The subjectName field also has a limit of 250 characters.

The caSecret can be a namespaced name of the form <namespace>/<secret-name>. If the CA secret’s namespace is not the same namespace as the HTTPProxy resource, TLS Certificate Delegation must be used to allow the owner of the CA certificate secret to delegate, for the purposes of referencing the CA certificate in a different namespace, permission to Contour to read the Secret object from another namespace.

Note: If spec.routes.services[].validation is present, spec.routes.services[].{name,port} must point to a Service with a matching projectcontour.io/upstream-protocol.tls Service annotation.

In the example below, the upstream service is named secure-backend and uses port 8443:

# httpproxy-example.yaml
apiVersion: projectcontour.io/v1
kind: HTTPProxy
metadata:
  name: example
spec:
  virtualhost:
    fqdn: www.example.com
  routes:
  - services:
    - name: secure-backend
      port: 8443
      validation:
        caSecret: my-certificate-authority
        subjectName: backend.example.com

# service-secure-backend.yaml
apiVersion: v1
kind: Service
metadata:
  name: secure-backend
  annotations:
    projectcontour.io/upstream-protocol.tls: "8443"
spec:
  ports:
  - name: https
    port: 8443
  selector:
    app: secure-backend

If the validation spec is defined on a service, but the secret which it references does not exist, Contour will reject the update and set the status of the HTTPProxy object accordingly. This helps prevent the case of proxying to an upstream where validation is requested, but not yet available.

Status:
  Current Status:  invalid
  Description:     route "/": service "tls-nginx": upstreamValidation requested but secret not found or misconfigured

Upstream Validation

When defining upstream services on a route, it’s possible to configure the connection from Envoy to the backend endpoint to communicate over TLS.

A CA certificate and a Subject Name must be provided, which are both used to verify the backend endpoint’s identity.

If specifying multiple Subject Names, SubjectNames and SubjectName must be configured such that SubjectNames[0] == SubjectName.

The CA certificate bundle for the backend service should be supplied in a Kubernetes Secret. The referenced Secret must be of type “Opaque” and have a data key named ca.crt. This data value must be a PEM-encoded certificate bundle.

In addition to the CA certificate and the subject name, the Kubernetes service must also be annotated with a Contour specific annotation: projectcontour.io/upstream-protocol.tls: <port> ( see annotations section).

Note: This annotation is applied to the Service not the Ingress or HTTPProxy object.

apiVersion: projectcontour.io/v1
kind: HTTPProxy
metadata:
  name: blog
  namespace: marketing
spec:
  routes:
    - services:
        - name: s2
          port: 80
          validation:
            caSecret: foo-ca-cert
            subjectName: foo.marketing
            subjectNames:
            - foo.marketing
            - bar.marketing

Envoy Client Certificate

Contour can be configured with a namespace/name in the Contour configuration file of a Kubernetes secret which Envoy uses as a client certificate when upstream TLS is configured for the backend. Envoy will send the certificate during TLS handshake when the backend applications request the client to present its certificate. Backend applications can validate the certificate to ensure that the connection is coming from Envoy.