You can set up secure HTTPS communication using a custom server certificate with your DC/OS cluster by setting up a proxy between the Admin Router and user agent requests coming from outside of the cluster. The HTTP Proxy must perform on-the-fly HTTP request and response header modification, because DC/OS is not aware of the custom hostname and port that is being used by user agents to address the HTTP proxy.

Configuring HAProxy in front of Admin Router

Use HAProxy to set up an HTTP proxy in front of the DC/OS Admin Router. This can be useful if you want to present a custom server certificate to user agents connecting to the cluster via HTTPS. DC/OS does not currently support adding your own certificates directly into Admin Router.

The following instructions provide a tested HAProxy configuration example that handles the named request/response rewriting. This example ensures that the communication between HAProxy and DC/OS Admin Router is TLS-encrypted.

Install HAProxy 1.6.9.
Create an HAProxy configuration for DC/OS. This example is for a DC/OS cluster on AWS. For more information on HAProxy configuration parameters, see the documentation.

NOTE: You can find your task IP by using the agent IP address DNS entry.

<taskname>.<framework_name>.agentip.dcos.thisdcos.directory

Where:

taskname: The name of the task.

framework_name: The name of the framework; if you are unsure, it is probably marathon.

global
  daemon
  log 127.0.0.1 local0
  log 127.0.0.1 local1 notice
  maxconn 20000
  pidfile /var/run/haproxy.pid
defaults
  log            global
  option         dontlog-normal
  mode		 http
  retries             3
  maxconn          20000
  timeout connect  5000
  timeout client  50000
  timeout server  50000

frontend http
  # Bind on port 9090. HAProxy will listen on port 9090 on each
  # available network for new HTTP connections.
  bind 0.0.0.0:9090
  # Specify your own server certificate chain and associated private key.
  # See https://cbonte.github.io/haproxy-dconv/configuration-1.6.html#5.1-crt
  # bind *:9091 ssl crt /path/to/browser-trusted.crt
  #
  # Name of backend configuration for DC/OS.
  default_backend dcos

  # Store request Host header temporarily in transaction scope
  # so that its value is accessible during response processing.
  # Note: RFC 7230 requires clients to send the Host header and
  # specifies it to contain both, host and port information.
  http-request set-var(txn.request_host_header) req.hdr(Host)

  # Overwrite Host header to 'dcoshost'. This makes the Location
  # header in DC/OS Admin Router upstream responses contain a
  # predictable hostname (NGINX uses this header value when
  # constructing absolute redirect URLs). That value is used
  # in the response Location header rewrite logic (see regular
  # expression-based rewrite in the backend section below).
  http-request set-header Host dcoshost

backend dcos
  # Option 1: use TLS-encrypted communication with DC/OS Admin Router and
  # perform server certificate verification (including hostname verification).
  # If you are using the community-supported version of DC/OS, you must
  # configure Admin Router with a custom TLS server certificate, see
  # /1.13/administering-clusters/. This step
  # is not required for DC/OS Enterprise.
  #
  # Explanation for the parameters in the following `server` definition line:
  #
  # 1.2.3.4:443
  #
  #   IP address and port that HAProxy uses to connect to DC/OS Admin
  #   Router. This needs to be adjusted to your setup.
  #
  #
  # ssl verify required
  #
  #   Instruct HAProxy to use TLS, and to error out if server certificate
  #   verification fails.
  #
  # ca-file dcos-ca.crt
  #
  #   The local file `dcos-ca.crt` is expected to contain the CA certificate
  #   that Admin Router's certificate will be verified against. It must be
  #   retrieved out-of-band (on Mesosphere DC/OS Enterprise this can be
  #   obtained via https://dcoshost/ca/dcos-ca.crt)
  #
  # verifyhost frontend-xxx.eu-central-1.elb.amazonaws.com
  #
  #   When verifying the TLS certificate presented by DC/OS Admin Router,
  #   perform hostname verification using the hostname specified here
  #   (expect the server certificate to contain a DNSName SAN that is
  #   equivalent to the hostname defined here). The hostname shown here is
  #   just an example and needs to be adjusted to your setup.

  server dcos-1 1.2.3.4:443 ssl verify required ca-file dcos-ca.crt verifyhost frontend-xxx.eu-central-1.elb.amazonaws.com

  # Option 2: use TLS-encrypted communication with DC/OS Admin Router, but do
  # not perform server certificate verification (warning: this is insecure, and
  # we hope that you know what you are doing).
  # server dcos-1 1.2.3.4:443 ssl verify none
  #
  # Rewrite response Location header if it contains an absolute URL
  # pointing to the 'dcoshost' host: replace 'dcoshost' with original
  # request Host header (containing hostname and port).
  http-response replace-header Location https?://dcoshost((/.*)?) "http://%[var(txn.request_host_header)]\1"

Start HAProxy with these settings.

HAProxy and Admin Router

Configuring HAProxy in front of an Admin Router

Configuring HAProxy in front of Admin Router