How to Check SSL Certificate for an EC2 Instance in a Private Subnet Behind an ALB

Last Updated on December 17, 2023 by Vikash Ekka

Securing your website with SSL encryption is vital for protecting user data. When your EC2 instance is in a private subnet behind an Application Load Balancer (ALB), checking the SSL certificate is slightly different.

In this guide, we’ll walk you through the simple steps to do just that.

Step 1: Access Your EC2 Instance

1. Open a Terminal or Command Prompt:Begin by opening a terminal or command prompt on your computer.
2. Connect to Your EC2 Instance:Use the SSH command to connect to your EC2 instance. Replace your-key.pem with your private key file and your-ec2-private-ip with the private IP address of your instance:

ssh -i your-key.pem ec2-user@your-ec2-private-ip

Make sure to replace the placeholders with the actual file path and IP address.

Step 2: Verify the SSL Certificate

1. Run OpenSSL Command:Once connected to your EC2 instance, enter this command to get SSL certificate details:

openssl s_client -connect localhost:443 | openssl x509 -noout -text

This command connects to your instance on port 443 (HTTPS), retrieves the SSL certificate, and provides detailed information about it.

Step 3: Understanding the Certificate Information

The output provides various details about the SSL certificate:

• Version: Shows the certificate’s version.
• Serial Number: A unique ID for the certificate.
• Signature Algorithm: The method used for signing.
• Issuer Information: Details about the certificate issuer.
• Validity Period: Dates when the certificate is valid.
• Subject Information: Details about the certificate owner.
• Public Key Information: Info about the encryption key.
• Certificate Extensions: Additional features of the certificate.

Additional Tips

• Regularly Update Certificates: Keep SSL certificates up-to-date to maintain security.
• Use AWS Certificate Manager: For a seamless experience, consider AWS Certificate Manager for managing SSL certificates.
• Monitor Expiry Dates: Set reminders to renew certificates before they expire.

Conclusion

Verifying the SSL certificate of an EC2 instance in a private subnet behind an ALB is crucial for ensuring a secure website. By following these simple steps, you’re well on your way to providing a safe browsing experience for your users.

Remember, SSL certificates build trust with your audience. Regular maintenance and updates are key to a secure online environment. By taking these steps, you’re not only securing data but also building credibility for your website.