Wildcard Certificates: My frivolous antics

by Shijaz Abdulla on 01.10.2007 at 09:31

A client wanted to publish two web services on SSL using ISA Server 2006: Outlook Web Access and Sharepoint Portal Server.

We know that ISA Server can only bind one SSL certificate per socket. This translates to one HTTPS URL/website per socket. What does this mean? Lets say I have my OWA at https://owa.shijaz.com/ and I have an SSL certificate issued to owa.shijaz.com. I also have my Sharepoint portal at https://portal.shijaz.com/ for which I have acquired a certificate with common name portal.shijaz.com.

While publishing, I can have only one web listener per socket and a web listener can accept at most ONE SSL certificate. If I apply the owa.shijaz.com certificate on my web listener, OWA will work fine, but users browsing to portal.shijaz.com will get a certificate warning/error. If I apply the portal.shijaz.com certificate, users browsing to owa.shijaz.com will get a certificate warning/error.

So what’s the solution? Wouldn’t it be great if we could order a certificate with common name *.shijaz.com and use the same certificate for both (or more) websites? Yes, you can! That’s called the WILDCARD Certificate!

Ordering a wildcard certificate is fairly simple, if you know how to order a normal SSL certificate. While generating an SSL request, simply enter *.yourdomain.com as the common name for the new certificate.


Wildcard certificates have a limitation that they are not available in 128-bit SGC and available only in standard encryption. The encryption level is decided by the user’s browser, rather than the certificate. So, if you’re securing a electronic payment website or a finance-related website, a wildcard certificate may not be what you should be looking at.

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