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Setting up SSL without a load balancer on Amazon ECS

July 18, 2020 - 3 min read

I was using ECS Fargate to serve a NodeJS API for a project, but Fargate essentially requires the use of a load balancer which costs $16 a month. I switched to using the EC2 version of ECS but was left with a problem of how to get SSL working to allow HTTPS traffic.

Overview

This process uses nginx to receive incoming traffic on the EC2 server and then forwards it to the Docker container. To utilize SSL, we use certbot, a free tool which generates SSL certificates and conveniently self-configures the nginx config.

This guide assumes you have a Docker container deployed to ECS EC2 with SSH access.

Install nginx

Before working on SSL, let's get a basic nginx server working on our EC2 instance. This will allow us to receive the incoming traffic and forward it to our Docker container (without HTTPS at this point).

To install nginx on EC2, which uses Amazon Linux 2, follow these commands:

sudo amazon-linux-extras enable nginx1

yum clean metadata
yum install nginx

sudo yum -y install nginx

Basic nginx config

Now that we have nginx installed, let's create a configuration file by first opening the default nginx config file:

sudo nano /etc/nginx/nginx.conf

Then paste the contents below, replacing server_name with your domain and port 5000 with the port your Docker container is listening on.

events { }

http {
  server {
    listen 80;
    listen [::]:80;

    server_name example.com;

    location / {
      proxy_pass http://localhost:5000/;
    }
  }
}

Next, check the syntax and reload nginx:

sudo nginx -t
sudo nginx -s reload

At this point you should be able to visit your domain in a web browser and be redirected to your Docker website/API using HTTP.

Install Certbot

To install certbot on Amazon Linux 2, follow these steps:

yum install python27-devel git

git clone https://github.com/letsencrypt/letsencrypt /opt/letsencrypt

/opt/letsencrypt/letsencrypt-auto --debug

We actually expect to get an error at this point because we are using Amazon's version of Linux. To fix this, follow these steps:

  • sudo nano /opt/letsencrypt/certbot-auto
  • Find this line in the file (likely around line 780): elif [ -f /etc/redhat-release ]; then
  • Replace the whole line with this:
elif [ -f /etc/redhat-release ] || grep 'cpe:.*:amazon_linux:2' /etc/os-release > /dev/null 2>&1; then

Run Certbot

Next, run the certbot command, which will configure things for you, replacing the domain with your own:

sudo /opt/letsencrypt/certbot-auto --nginx -d example.com --agree-tos

After prompting for your email address, certbot will send an automated challenge to your server and verify that you own it. When it passes, certbot will update your nginx config to include listening on port 443, referencing the SSL certificates, and redirecting HTTP requests to HTTPS.

For reference, cerbot saves three certificate files to /etc/letsencrypt/live/example.com/.

Validate certificates

To double-check our certificates are good-to-go, we can run these commands below. If valid, you should see an expire date three months from now returned.

# local option
sudo openssl x509 -noout -dates -in /etc/letsencrypt/live/example/cert.pem

# remote option
curl -sIv https://example.com |& grep expire

Setup auto renewal

Let's create a cronjob to automate renewal by opening your crontab with sudo nano /etc/crontab and pasting the code below. This will check daily at 3 am and will take care of the renewal process.

# Renew SSL Certs
0  3  *  *  *  ec2-user  /opt/letsencrypt/letsencrypt-auto --no-bootstrap renew --post-hook "systemctl reload nginx"

Further Reading

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