Add authenticated TLS support for API

Docker-DCO-1.1-Signed-off-by: Johannes 'fish' Ziemke <github@freigeist.org> (github: discordianfish)

docs/sources/examples/https.rst

@@ -0,0 +1,126 @@
+: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`