:title: Docker HTTPS Setup
:description: How to setup docker with https
:keywords: docker, example, https, daemon

.. _running_docker_https:

Running Docker with https
=========================

By default, Docker runs via a non-networked Unix socket. It can also optionally
communicate using a HTTP socket.

If you need Docker reachable via the network in a safe manner, you can enable
TLS by specifying the `tlsverify` flag and pointing Docker's `tlscacert` flag to a
trusted CA certificate.

In daemon mode, it will only allow connections from clients authenticated by a
certificate signed by that CA. In client mode, it will only connect to servers
with a certificate signed by that CA.

.. warning::

  Using TLS and managing a CA is an advanced topic. Please make you self familiar
  with openssl, x509 and tls before using it in production.

Create a CA, server and client keys with OpenSSL
------------------------------------------------

First, initialize the CA serial file and generate CA private and public keys:

.. code-block:: bash

    $ echo 01 > ca.srl
    $ openssl genrsa -des3 -out ca-key.pem
    $ openssl req -new -x509 -days 365 -key ca-key.pem -out ca.pem

Now that we have a CA, you can create a server key and certificate signing request.
Make sure that `"Common Name (e.g. server FQDN or YOUR name)"` matches the hostname you will use
to connect to Docker or just use '*' for a certificate valid for any hostname:

.. code-block:: bash

    $ openssl genrsa -des3 -out server-key.pem
    $ openssl req -new -key server-key.pem -out server.csr

Next we're going to sign the key with our CA:

.. code-block:: bash

    $ openssl x509 -req -days 365 -in server.csr -CA ca.pem -CAkey ca-key.pem \
      -out server-cert.pem

For client authentication, create a client key and certificate signing request:

.. code-block:: bash

    $ openssl genrsa -des3 -out client-key.pem
    $ openssl req -new -key client-key.pem -out client.csr


To make the key suitable for client authentication, create a extensions config file:

.. code-block:: bash

    $ echo extendedKeyUsage = clientAuth > extfile.cnf

Now sign the key:

.. code-block:: bash

    $ openssl x509 -req -days 365 -in client.csr -CA ca.pem -CAkey ca-key.pem \
      -out client-cert.pem -extfile extfile.cnf

Finally you need to remove the passphrase from the client and server key:

.. code-block:: bash

    $ openssl rsa -in server-key.pem -out server-key.pem
    $ openssl rsa -in client-key.pem -out client-key.pem
  
Now you can make the Docker daemon only accept connections from clients providing
a certificate trusted by our CA:

.. code-block:: bash

    $ sudo docker -d --tlsverify --tlscacert=ca.pem --tlscert=server-cert.pem --tlskey=server-key.pem \
      -H=0.0.0.0:4243

To be able to connect to Docker and validate its certificate, you now need to provide your client keys,
certificates and trusted CA:

.. code-block:: bash

   $ docker --tlsverify --tlscacert=ca.pem --tlscert=client-cert.pem --tlskey=client-key.pem \
     -H=dns-name-of-docker-host:4243

.. warning::

  As shown in the example above, you don't have to run the ``docker``
  client  with ``sudo`` or the ``docker`` group when you use
  certificate authentication. That means anyone with the keys can
  give any instructions to your Docker daemon, giving them root
  access to the machine hosting the daemon. Guard these keys as you
  would a root password!

Other modes
-----------
If you don't want to have complete two-way authentication, you can run Docker in
various other modes by mixing the flags.

Daemon modes
~~~~~~~~~~~~
- tlsverify, tlscacert, tlscert, tlskey set: Authenticate clients
- tls, tlscert, tlskey: Do not authenticate clients

Client modes
~~~~~~~~~~~~
- tls: Authenticate server based on public/default CA pool
- tlsverify, tlscacert: Authenticate server based on given CA
- tls, tlscert, tlskey: Authenticate with client certificate, do not authenticate
  server based on given CA
- tlsverify, tlscacert, tlscert, tlskey: Authenticate with client certificate,
  authenticate server based on given CA

The client will send its client certificate if found, so you just need to drop
your keys into `~/.docker/<ca, cert or key>.pem`
