Docker how to use tls

According to the official docker docs docker security let's make tls connection to docker host:

go to the  docker host and generate CA key:

#  openssl genrsa -aes256 -out ca-key.pem 4096

then generate  CA certificate:

#  openssl req -new -x509 -days 365 -key ca-key.pem -sha256 -out ca.pem

Now create server private keey:

#  openssl genrsa -out server-key.pem 4096

And then certificate request:

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

Create extfile.cnf to be able connect to docker host via hostname or IP:

#  echo subjectAltName = DNS:$HOST,IP:10.10.10.20,IP:127.0.0.1 >> extfile.cnf
#  echo extendedKeyUsage = serverAuth >> extfile.cnf

Now, generate the signed certificate:

#  openssl x509 -req -days 365 -sha256 -in server.csr -CA ca.pem -CAkey ca-key.pem -CAcreateserial -out server-cert.pem -extfile extfile.cnf


Now we can generate clients' private key

#  openssl genrsa -out key.pem 4096
#  echo extendedKeyUsage = clientAuth > extfile-client.cnf

and request for certificate:

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

and create clinet's certificate:

#  openssl x509 -req -days 365 -sha256 -in client.csr -CA ca.pem -CAkey ca-key.pem -CAcreateserial -out cert.pem -extfile extfile-client.cnf


change permission :

#   chmod -v 0400 ca-key.pem key.pem server-key.pem
#   chmod -v 0444 ca.pem server-cert.pem cert.pem


Stop docker service and modify it:

#  systemctl stop docker

#  vi /usr/lib/systemd/system/docker.service

Modify ExecStart command:

ExecStart=/usr/bin/dockerd --tlsverify --tlscacert=/etc/docker/ca.pem --tlscert=/etc/docker/server-cert.pem --tlskey=/etc/docker/private/server-key.pem -H tcp://0.0.0.0:2376 -H unix:///var/run/docker.sock


and then reload daemon config and start docker service:

#  systemctl daemon-reload
#  systemct start docker

Add firewall rules:
#  firewall-cmd --permanent --zone=public --add-port=2376/tcp
#  firewall-cmd --reload




Now on the client host put the appropriate key, certificates: ca.pem, cert.pem, key.pem and set DOCKER_HOST variable :

#  export DOCKER_HOST=$HOST:2376

and try to connect to docker host :

#  docker --tlsverify --tlscacert=ca.pem --tlscert=cert.pem --tlskey=key.pem info