Run containers with SSL on development environmets

Secure Sockets Layer (SSL) is a standard security technology for establishing an encrypted link between a server and a client. In the context of Docker, SSL can be used to secure the communication between Docker containers and clients that connect to them.

ssl

Table of Contents

Setting up SSL on Docker Containers

To set up SSL on Docker containers, you typically need to create a self-signed SSL certificate and configure your Docker container to use it. Here’s a basic step-by-step guide.

Install mkcert

MacOs 

brew install mkcert

Linux (Ubuntu/Debian based) 

curl -JLO "https://dl.filippo.io/mkcert/latest?for=linux/amd64"
chmod +x mkcert-v*-linux-amd64
sudo cp mkcert-v*-linux-amd64 /usr/local/bin/mkcert

Windows 

choco install mkcert

Install CA on your machine 

mkcert -install

Generate certificate 

mkcert localhost 127.0.0.1 ::1

Created a new certificate valid for the following names 📜
 - "localhost"
 - "127.0.0.1"
 - "::1"

The certificate is at "./localhost+2.pem" and the key at "./localhost+2-key.pem" ✅

It will expire on 22 April 2026 🗓

Prepare nginx

Create the following directories on your docker-compose file location:

mkdir -p proxy/certs
mkdir -p proxy/conf

Place the certificates under proxy/certs.

Add your nginx configuration to proxy/conf/nginx.conf:

worker_processes 1;

events {
    worker_connections 1024;
}

http {
    server {
        listen 443 ssl;
        server_name localhost;

        ssl_certificate /etc/nginx/certs/localhost+2.pem;
        ssl_certificate_key /etc/nginx/certs/localhost+2-key.pem;

        location / {
            proxy_pass http://my-service:8080;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
        }
    }
}

Break down nginx configuration

  • worker_processes 1;: This sets the number of worker processes. In this case, it’s set to 1.

  • events { worker_connections 1024; }: This block configures the events module. The worker_connections directive sets the maximum number of simultaneous connections that can be opened by a worker process.

  • http { ... }: This block is where the main configuration for handling HTTP and HTTPS requests is done.

  • server { ... }: This block defines a server that listens on the SSL port (443) and responds to requests for the specified server_name (localhost in this case).

  • listen 443 ssl;: This tells Nginx to listen on port 443 with SSL.

  • ssl_certificate /etc/nginx/certs/localhost+2.pem;: This specifies the location of the SSL certificate file.

  • ssl_certificate_key /etc/nginx/certs/localhost+2-key.pem;: This specifies the location of the SSL certificate key file.

  • location / { ... }: This block defines how to respond to requests for the root URL (“/”). In this case, it’s set up to proxy these requests to another service.

  • proxy_pass http://my-service:8080;: This line tells Nginx to forward the incoming requests to the service running at http://my-service:8080.

  • The proxy_set_header directives are used to add HTTP headers to the request that is forwarded to the proxied service. This is useful for letting the proxied service know about the original request’s details.

Make sure you update listen 443 ssl; to use the port you want to communicate with your service.

Make sure you update proxy_pass http://my-service:8080; with the name of your service present on the docker-compose file.

Add nginx to compose file

Add nginx to docker-compose:

version: '3'

services:
  proxy:
    image: nginx:latest
    ports:
      - 443:443
    volumes:
      - ./proxy/conf/nginx.conf:/etc/nginx/nginx.conf
      - ./proxy/certs:/etc/nginx/certs 
  my-service:
    image: my-service:latest
    ports:
      - 80:80