How to Verify the Integrity of an SSL/TLS Certificate and Private Key Pair?

Introduction

It is good practice to protect the SSL/TLS certificate and the associated private key as bad actors could cause significant harm if they were to gain unauthorized access to either of them. This process is done by ensuring that the certificate used within your application corresponds with the private key present and is in proper working condition.

As you’ll learn here, this check is an important step in ensuring you protect your messages while communicating online.

Why Verify Certificate and Key Pair Integrity?

Verifying the integrity of your SSL/TLS certificate and private key pair is essential because:

• It makes sure that your encrypted communication is safe from the prying eyes of other people.
• It eliminates possible mistakes you can make while installing or renewing certificates at your organization.
• It assists in finding disparities that may cause disruptions in the provision of services.

Steps to Check the Integrity of an SSL Certificate

To verify the integrity of your SSL/TLS certificate, follow these steps:

Check the Certificate Details:

Open your terminal and use the following OpenSSL command:

openssl x509 -in your_certificate.crt -text -noout

Replace your_certificate.crt with your actual certificate file name.

This command displays detailed information about your certificate, including the issuer, validity period, and subject.

Verify the Certificate Chain:

Use this command to ensure your certificate is properly chained:

openssl verify/ -verbose -CAfile intermediate_certificate crt your_certificate.crt

Replace intermediate_certificate.crt with your CA’s intermediate certificate and your_certificate.crt with your SSL certificate.

Check Certificate Expiration:

Verify your certificate’s validity period:

openssl x509 -noout -dates -in your_certificate.crt

This will show the ‘notBefore’ and ‘notAfter’ of your certificate.

Also Read: How to Fix the Expired Intermediate SSL Certificate Error?

Verify Files Integrity

To ensure the integrity of both your certificate and private key files:

Extract Certificate Modulus:

openssl x509 -noout -modulus -in your_certificate.crt | openssl md5

Extract Private Key Modulus: 

openssl rsa -noout -modulus -in your_private_key.key | openssl md5

Compare Results:

If the outputs are identical, you’ve got a valid certificate and a private key pair here.

Check File Permissions:

ls -l your_private_key.key

Ensure your private key has restricted permissions. The permissions of the files should be set to 600 or even less than that.

Verify Private Key Integrity:

openssl rsa -check -in your_private_key.key 

It checks if the private key is valid and not corrupted.

Best Practices for Certificate and Key Management

• The private key should be safeguarded properly and access to it should be restricted to only those personnel that are allowed.
• Ensure that you conduct periodic checkups on your certificates and keys in order to confirm that they have not been breached.
• Subscribing to alerts on certificates or use Automated Certificate Management Tool that will ensure that one can be warned on when the certificate is expiring, thus not leading to disruptions of services.
• Make sure to utilize powerful encryption on your certificates and select appropriate key lengths.

Also Read: PKI Certificate Management: Avoid Common Pitfalls & Embrace Best Practices

Winding Up

It is critical to routinely check the SSL/TLS certificate and the related private key pair for compromises that can lead to the exposure of a website. Following these steps will allow you to check whether your encryption is correctly implemented, and your users’ data is secure.

It is also important to run these checks after the certificates have been renewed or after any server modifications.

Certera is a best source of an abundant choice of SSL and excellent advice to suit your needs. In this article, we propose several SSL certificates and utilities to ensure the security of your site.