Exposing the Dashboard

Instead of using linkerd dashboard every time you’d like to see what’s going on, you can expose the dashboard via an ingress. This will also expose Grafana.

• Nginx
• Traefik
• DNS Rebinding Protection

Nginx

Nginx with basic auth

A sample ingress definition is:

apiVersion: v1
kind: Secret
type: Opaque
metadata:
  name: web-ingress-auth
  namespace: linkerd
data:
  auth: YWRtaW46JGFwcjEkbjdDdTZnSGwkRTQ3b2dmN0NPOE5SWWpFakJPa1dNLgoK
---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: web-ingress
  namespace: linkerd
  annotations:
    kubernetes.io/ingress.class: 'nginx'
    nginx.ingress.kubernetes.io/upstream-vhost: $service_name.$namespace.svc.cluster.local:8084
    nginx.ingress.kubernetes.io/configuration-snippet: |
      proxy_set_header Origin "";
      proxy_hide_header l5d-remote-ip;
      proxy_hide_header l5d-server-id;
    nginx.ingress.kubernetes.io/auth-type: basic
    nginx.ingress.kubernetes.io/auth-secret: web-ingress-auth
    nginx.ingress.kubernetes.io/auth-realm: 'Authentication Required'
spec:
  rules:
    - host: dashboard.example.com
      http:
        paths:
          - backend:
              serviceName: linkerd-web
              servicePort: 8084

This exposes the dashboard at dashboard.example.com and protects it with basic auth using admin/admin. Take a look at the ingress-nginx documentation for details on how to change the username and password.

Nginx with oauth2-proxy

A more secure alternative to basic auth is using an authentication proxy, such as oauth2-proxy.

For reference on how to deploy and configure oauth2-proxy in kubernetes, see this blog post by Don Bowman.

tl;dr: If you deploy oauth2-proxy via the helm chart, the following values are required:

config:
  existingSecret: oauth2-proxy
  configFile: |-
    email_domains = [ "example.com" ]
    upstreams = [ "file:///dev/null" ]
ingress:
  enabled: true
  annotations:
    kubernetes.io/ingress.class: nginx
  path: /oauth2
ingress:
  hosts:
    - linkerd.example.com

Where the oauth2-proxy secret would contain the required oauth2 config such as, client-id client-secret and cookie-secret.

Once setup, a sample ingress would be:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: linkerd-web
  namespace: linkerd
  annotations:
    kubernetes.io/ingress.class: 'nginx'
    nginx.ingress.kubernetes.io/upstream-vhost: $service_name.$namespace.svc.cluster.local:8084
    nginx.ingress.kubernetes.io/configuration-snippet: |
      proxy_set_header Origin "";
      proxy_hide_header l5d-remote-ip;
      proxy_hide_header l5d-server-id;
    nginx.ingress.kubernetes.io/auth-signin: https://$host/oauth2/start?rd=$escaped_request_uri
    nginx.ingress.kubernetes.io/auth-url: https://$host/oauth2/auth
spec:
  rules:
    - host: linkerd.example.com
      http:
        paths:
          - backend:
              serviceName: linkerd-web
              servicePort: 8084

Traefik

A sample ingress definition is:

apiVersion: v1
kind: Secret
type: Opaque
metadata:
  name: web-ingress-auth
  namespace: linkerd
data:
  auth: YWRtaW46JGFwcjEkbjdDdTZnSGwkRTQ3b2dmN0NPOE5SWWpFakJPa1dNLgoK
---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: web-ingress
  namespace: linkerd
  annotations:
    kubernetes.io/ingress.class: 'traefik'
    ingress.kubernetes.io/custom-request-headers: l5d-dst-override:linkerd-web.linkerd.svc.cluster.local:8084
    traefik.ingress.kubernetes.io/auth-type: basic
    traefik.ingress.kubernetes.io/auth-secret: web-ingress-auth
spec:
  rules:
    - host: dashboard.example.com
      http:
        paths:
          - backend:
              serviceName: linkerd-web
              servicePort: 8084

This exposes the dashboard at dashboard.example.com and protects it with basic auth using admin/admin. Take a look at the Traefik documentation for details on how to change the username and password.

DNS Rebinding Protection

To prevent DNS-rebinding attacks, the dashboard rejects any request whose Host header is not localhost, 127.0.0.1 or the service name linkerd-web.linkerd.svc.

Note that this protection also covers the Grafana dashboard.

The ingress-nginx config above uses the nginx.ingress.kubernetes.io/upstream-vhost annotation to properly set the upstream Host header. Traefik on the other hand doesn’t offer that option, so you’ll have to manually set the required Host as explained below.

Tweaking Host Requirement

If your HTTP client (Ingress or otherwise) doesn’t allow to rewrite the Host header, you can change the validation regexp that the dashboard server uses, which is fed into the linkerd-web deployment via the enforced-host container argument.

If you’re managing Linkerd with Helm, then you can set the host using the enforcedHostRegexp value.

Another way of doing that is through Kustomize, as explained in Customizing Installation, using an overlay like this one:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: linkerd-web
spec:
  template:
    spec:
      containers:
        - name: web
          args:
            - -api-addr=linkerd-controller-api.linkerd.svc.cluster.local:8085
            - -grafana-addr=linkerd-grafana.linkerd.svc.cluster.local:3000
            - -controller-namespace=linkerd
            - -log-level=info
            - -enforced-host=^dashboard\.example\.com$

If you want to completely disable the Host header check, use an empty string for -enforced-host.