Steps to enable TLS in Docker for secure configuration

$ openssl genrsa -aes256 -out ca-key.pem 4096
Generating RSA private key, 4096 bit long modulus
............................................................................................................................................................................................................++
........++
e is 65537 (0x10001)
Enter pass phrase for ca-key.pem:
Verifying - Enter pass phrase for ca-key.pem:

$ openssl req -new -x509 -days 365 -key ca-key.pem -sha256 -out ca.pem
Enter pass phrase for ca-key.pem:
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:
State or Province Name (full name) [Some-State]:Queensland
Locality Name (eg, city) []:Brisbane
Organization Name (eg, company) [Internet Widgits Pty Ltd]:Docker Inc
Organizational Unit Name (eg, section) []:Sales
Common Name (eg server FQDN or YOUR name) []:$HOST
Email Address []:[email protected]

$ openssl genrsa -out server-key.pem 4096
Generating RSA private key, 4096 bit long modulus
.....................................................................................++
.................................................................................................................++
e is 65537 (0x10001)

$ openssl req -subj "/CN=$HOST" -sha256 -new -key server-key.pem -out server.csr

$ echo subjectAltName = DNS:$HOST,IP:$HOST:127.0.0.1 >> extfile.cnf

 $ echo extendedKeyUsage = serverAuth >> extfile.cnf

$ openssl x509 -req -days 365 -sha256 -in server.csr -CA ca.pem -CAkey ca-key.pem \
 -CAcreateserial -out server-cert.pem -extfile extfile.cnf
Signature ok
subject=/CN=your.host.com
Getting CA Private Key
Enter pass phrase for ca-key.pem:

$ openssl genrsa -out key.pem 4096
Generating RSA private key, 4096 bit long modulus
.........................................................++
................++
e is 65537 (0x10001)

$ openssl req -subj '/CN=client' -new -key key.pem -out client.csr

echo extendedKeyUsage = clientAuth > extfile-client.cnf

$ openssl x509 -req -days 365 -sha256 -in client.csr -CA ca.pem -CAkey ca-key.pem \
 -CAcreateserial -out cert.pem -extfile extfile-client.cnf
Signature ok
subject=/CN=client
Getting CA Private Key
Enter pass phrase for ca-key.pem:

[Unit]
Description=Docker Application Container Engine
Documentation=http://docs.docker.io

[Service]
Environment="PATH=/opt/kube/bin:/bin:/sbin:/usr/bin:/usr/sbin"
ExecStart=/opt/kube/bin/dockerd --tlsverify --tlscacert=/root/docker/ca.pem --tlscert=/root/docker/server-cert.pem --tlskey=/root/docker/server-key.pem -H unix:///var/run/docker.sock -H tcp://0.0.0.0:2375
ExecStartPost=/sbin/iptables -I FORWARD -s 0.0.0.0/0 -j ACCEPT
ExecReload=/bin/kill -s HUP $MAINPID
Restart=on-failure
RestartSec=5
LimitNOFILE=infinity
LimitNPROC=infinity
LimitCORE=infinity
Delegate=yes
KillMode=process

[Install]
WantedBy=multi-user.target

systemctl daemon-reload
systemctl restart docker.service

systemctl status docker.service
● docker.service - Docker Application Container Engine
  Loaded: loaded (/etc/systemd/system/docker.service; enabled; vendor preset: enabled)
  Active: active (running) since Thu 2019-08-08 19:22:26 CST; 1 min ago

docker --tlsverify --tlscacert=ca.pem --tlscert=cert.pem --tlskey=key.pem -H=$HOST:2375 version can be connected

DefaultDockerClientConfig.Builder builder =
        DefaultDockerClientConfig.createDefaultConfigBuilder()
          .withDockerHost("tcp://" + server + ":2375")
          .withApiVersion("1.30");
      if (containerConfiguration.getDockerTlsVerify()) {
        builder = builder.withDockerTlsVerify(true)
          .withDockerCertPath("E:\\docker\\");
      }
  return DockerClientBuilder.getInstance(builder.build()).build()