Secure services with TLS

Estimated reading time: 5 minutes

After deploying a layer 7 routing solution, you have two options for securing your services with TLS:

Regardless of the option selected to secure swarm services, there are two steps required to route traffic with TLS:

  1. Create Docker secrets to manage from a central place the private key and certificate used for TLS.
  2. Add labels to your swarm service for UCP to reconfigure the proxy service.

Let the proxy handle TLS

The following example deploys a swarm service and lets the proxy service handle the TLS connection. All traffic between the proxy and the swarm service is not secured, so use this option only if you trust that no one can monitor traffic inside services running in your datacenter.

TLS Termination

Start by getting a private key and certificate for the TLS connection. Make sure the Common Name in the certificate matches the name where your service is going to be available.

You can generate a self-signed certificate for app.example.org by running:

openssl req \
  -new \
  -newkey rsa:4096 \
  -days 3650 \
  -nodes \
  -x509 \
  -subj "/C=US/ST=CA/L=SF/O=Docker-demo/CN=app.example.org" \
  -keyout app.example.org.key \
  -out app.example.org.cert

Then, create a docker-compose.yml file with the following content:

version: "3.2"

services:
  demo:
    image: ehazlett/docker-demo
    deploy:
      replicas: 1
      labels:
        com.docker.lb.hosts: app.example.org
        com.docker.lb.network: demo-network
        com.docker.lb.port: 8080
        com.docker.lb.ssl_cert: demo_app.example.org.cert
        com.docker.lb.ssl_key: demo_app.example.org.key
    environment:
      METADATA: proxy-handles-tls
    networks:
      - demo-network

networks:
  demo-network:
    driver: overlay
secrets:
  app.example.org.cert:
    file: ./app.example.org.cert
  app.example.org.key:
    file: ./app.example.org.key

Notice that the demo service has labels specifying that the proxy service should route app.example.org traffic to this service. All traffic between the service and proxy takes place using the demo-network network. The service also has labels specifying the Docker secrets to use on the proxy service for terminating the TLS connection.

Because the private key and certificate are stored as Docker secrets, you can easily scale the number of replicas used for running the proxy service. Docker distributes the secrets to the replicas.

Set up your CLI client with a UCP client bundle and deploy the service:

docker stack deploy --compose-file docker-compose.yml demo

The service is now running. To test that everything is working correctly, update your /etc/hosts file to map app.example.org to the IP address of a UCP node.

In a production deployment, you must create a DNS entry so that users can access the service using the domain name of your choice. After creating the DNS entry, you can access your service:

https://<hostname>:<https-port>

For this example:

  • hostname is the name you specified with the com.docker.lb.hosts label.
  • https-port is the port you configured in the UCP settings.

Browser screenshot

Because this example uses self-sign certificates, client tools like browsers display a warning that the connection is insecure.

You can also test from the CLI:

curl --insecure \
  --resolve <hostname>:<https-port>:<ucp-ip-address> \
  https://<hostname>:<https-port>/ping

If everything is properly configured, you should get a JSON payload:

{"instance":"f537436efb04","version":"0.1","request_id":"5a6a0488b20a73801aa89940b6f8c5d2"}

Because the proxy uses SNI to decide where to route traffic, make sure you are using a version of curl that includes the SNI header with insecure requests. Otherwise, curl displays an error saying that the SSL handshake was aborted.

Note

Currently there is no way to update expired certificates using this method. The proper way is to create a new secret then update the corresponding service.

Let your service handle TLS

The second option for securing with TLS involves encrypting traffic from end users to your swarm service.

End-to-end encryption

To do that, deploy your swarm service using the following docker-compose.yml file:

version: "3.2"

services:
  demo:
    image: ehazlett/docker-demo
    command: --tls-cert=/run/secrets/cert.pem --tls-key=/run/secrets/key.pem
    deploy:
      replicas: 1
      labels:
        com.docker.lb.hosts: app.example.org
        com.docker.lb.network: demo-network
        com.docker.lb.port: 8080
        com.docker.lb.ssl_passthrough: "true"
    environment:
      METADATA: end-to-end-TLS
    networks:
      - demo-network
    secrets:
      - source: app.example.org.cert
        target: /run/secrets/cert.pem
      - source: app.example.org.key
        target: /run/secrets/key.pem

networks:
  demo-network:
    driver: overlay
secrets:
  app.example.org.cert:
    file: ./app.example.org.cert
  app.example.org.key:
    file: ./app.example.org.key

The service is updated to start using the secrets with the private key and certificate. The service is also labeled with com.docker.lb.ssl_passthrough: true, signaling UCP to configure the proxy service such that TLS traffic for app.example.org is passed to the service.

Since the connection is fully encrypted from end-to-end, the proxy service cannot add metadata such as version information or request ID to the response headers.

routing, proxy, tls