Wildcard SSL Certificate for Second-Level Subdomain – Is It Possible?

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Wildcard SSL Certificate for Second-Level Subdomain

Guide on How to Use Wildcard SSL Certificate for Second-Level Subdomain

Securing subdomains is not always an easy task. Typically, the Wildcard SSL certificate is marketed as being able to secure ‘unlimited subdomains.’ However, it is not entirely true. It makes people think that all subdomains at all different levels can be secured with a single certificate, which is not the case, creating a lot of confusion and misunderstandings.

So is there a solution? Let’s find out. But before we do that, let us understand what a wildcard SSL certificate is.

What is a Wildcard SSL Certificate Second-Level Subdomain?

A wildcard SSL certificate is a digital SSL certificate that secures several subdomains that are part of a primary domain. With it, any subdomains a  website has can be secured. For example, if your domain name is www.yourwebsite.com, the certificate can be used to secure any subdomains like blog.yourwebsite.com, store.yourwebsite.com, etc.

The asterisk (*) character is referred to as the ‘wildcard’ character in the certificate’s Common Name (CN) field. Due to this, a subdomain of the primary domain, regardless of its name, can use the certificate.

Key Features of Wildcard SSL Certificate

Coverage for Multiple Subdomains

With a certificate, you can secure all subdomains under a main domain with just one SSL. For example: a certificate for *.yoursitename.com can secure blog.yoursitename.com, shop.yoursitename.com, and any other subdomain that you create.

Web Browser Compatibility

The certificates are compatible with all major web browsers, including Internet Explorer, Firefox, Chrome, and Safari.

Easy Installation

The certificates can be installed on the server in the same way as other SSL certificates. Once installed, the certificate will automatically apply to all subdomains.

When you create a CSR for a Wildcard SSL certificate, you use an asterisk (*) to encrypt the first-level subdomain you need to add encryption. Having said that, if you have another subdomain at the second level, you cannot use that certificate for security. This can pose a complicated issue for companies that employ multi-level subdomains in their web architecture, especially when there are misunderstandings about Wildcard SSL certs functionality.

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What is a Multi-Level Subdomain?

In simple terms, it refers to a subdomain that is two levels deep, like sub2.sub1.yourwebsite.com. A multi-level wildcard SSL can secure any number of subdomains at the same level (e.g., *.yourwebsite.com covers sub1.yourwebsite.com, sub2.yourwebsite.com, etc.). But, securing a second-level subdomain requires a certificate with a specific set of features.

This type of SSL certificate should include the top-level domain (yourwebsite.com) and the specific second-level subdomain (sub1.yourwebsite.com, sub2.yourwebsite.com, etc.) in the SAN (subject alternative name) field.

The answer is a Multi-Domain Wildcard SSL certificate!

What is a Multi-Domain Wildcard Certificate?

Multi-Domain Wildcard SSL certificate is the top-end SSL certificate which allows to protect multi level subdomains such as sub1.sub2.yourwebsite.com, sub2.sub3.yourwebsite.com, etc. MDC wildcard SSL is also known as a multi-level wildcard certificate in the industry. It is specially built and designed for large-scale online businesses where primary domains hold multi level subdomains on the multiple servers.

It can secure many levels of subdomains under a fully qualified domain name, in contrast to a regular wildcard certificate that can only secure a single level of subdomains. This indicates that it can secure both subdomains that are immediately beneath the main domain and others that are nested in a hierarchy of levels.

For instance, if your website has the domain ‘yourwebsite.com’ and several subdomains like;

  • Mail.yourwebsite.com
  • Store.yourwebsite.com
  • Blog.store.yourwebsite.com
  • Products.store.yourwebsite.com

A multi-level wildcard SSL certificate with the common name ‘*.store.yourwebsite.com’ can secure all of these subdomains.

Key Features of Multi-Domain Wildcard Certificate

Multiple Validation Levels

Multi-Level Wildcard SSL certificates can be issued with various validation levels, including Domain Validation (DV) and Organization Validation (OV) depending on the level of trust and security you require.

Web Browser Compatibility

The certificates are compatible with all major web browsers, mobile devices, control panel, and email servers, which means that visitors to your website will not receive any security warnings or errors.

Unlimited Server Licenses

The certificate includes unlimited server licensing which allows website owners to install the same certificate on multiple servers without paying any extra changes.

Add Up to 250 Websites or Subdomains

MDC wildcard has capacity to allow the certificate owners to add up to 250 websites, subdomains, and other SAN options. You can edit, update, or remove any SAN at any time on multiple servers.

How to Secure Second Level Subdomain Using Wildcard SSL?

A multi-level wildcard SSL since it’s designed to help organizations with complex website structures that use multi-level subdomains. For instance, you can use it to secure multiple websites and their first-level subdomains, as well as several sets of second-level ones, with a single certificate. Let us show an your website for better understanding.

Consider the following Certificate Signing Request (CSR):

  • FQDN: yourwebsite.com
  • Wildcard SAN: *.yourwebsite.com
  • Wildcard SAN: *.mail.yourwebsite.com
  • Wildcard SAN: *.members.yourwebsite.com
  • Wildcard SAN: *.dev.yourwebsite.com
  • Wildcard SAN: *.yourwebsite2.com
  • Wildcard SAN: *.ftp.yourwebsite2.com
  • Wildcard SAN: *.shop.yourwebsite2.com

With this CSR, you can secure two websites, all their first-level subdomains, and five sets of second-level subdomains using a single Multi-Domain Wildcard SSL certificate.

Note: The certificate will not provide coverage for two subdomain levels of mail.yourwebsite.com. To cover two levels, a separate Wildcard SSL certificate would be required. However, this Wildcard SSL certificate would cover any new directories added under mail.yourwebsite.com.

A Certificate Authority issues a multi-domain certificate based on the domain names listed in the SAN field of the certificate. The placeholder, represented by an asterisk, can only replace one field in the domain name submitted to the Certificate Authority (CA). Including too many variables in the certificate would decrease its security and reliability.

Moreover, it can put a risk to your internal security. For instance, if someone with access to the private key and certificate sets up a subdomain website that is covered by the SSL, it could compromise the internal security of the organization.

Ending Words

A Multi-Domain Wildcard SSL certificate is a versatile solution for those who need to secure multiple domains and subdomains at multiple levels within a single domain. With this ability to secure an unlimited number of subdomains, both at the first and subsequent levels, Multi-Domain Wildcard SSL certificates provide strong encryption and trust for website visitors while simplifying SSL management for website owners. It is a perfect balance of security, flexibility, and convenience for organizations with multiple domains.

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Janki Mehta

Janki Mehta

Janki Mehta is a Cyber-Security Enthusiast who constantly updates herself with new advancements in the Web/Cyber Security niche. Along with theoretical knowledge, she also implements her practical expertise in day-to-day tasks and helps others to protect themselves from threats.

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