Secure services with TLS
Estimated reading time: 5 minutesAfter deploying a layer 7 routing solution, you have two options for securing your services with TLS:
- Let the proxy terminate the TLS connection. All traffic between end-users and the proxy is encrypted, but the traffic going between the proxy and your swarm service is not secured.
- Let your swarm service terminate the TLS connection. The end-to-end traffic is encrypted and the proxy service allows TLS traffic to passthrough unchanged.
Regardless of the option selected to secure swarm services, there are two steps required to route traffic with TLS:
- Create Docker secrets to manage from a central place the private key and certificate used for TLS.
- 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.
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 thecom.docker.lb.hosts
label.https-port
is the port you configured in the UCP settings.
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.
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.