A new feature in digital certificates is the Subject Alternative Name property. This allows you to have a certificate for more than one URI (i.e. www.c7solutions.com and www.c7solutions.co.uk) in the same certificate. It also means that in web servers such as IIS you can bind this certificate to the site and use up only one IP address.
A number of commercial companies now sell certificates with the Subject Alternative Name field set, but this article describes how to use the Exchange Server 2007 command line to create certificate requests for other web sites that can be uploaded to Microsoft Certificate Server (which does not support this property in its own web pages) to create certificates for web servers such as IIS (which also do not support this property in the requests that they make).
The command that you need to run is via PowerShell, and specifically via the Microsoft Exchange Server 2007 extensions to PowerShell. So start up the Microsoft Management Shell and enter the following (replacing your domain names as indicated:
New-ExchangeCertificate -GenerateRequest:$true -Path c:\newCert.req -DomainName www.domain.com,sales.domain.com,support.domain.com -PrivateKeyExportable:$true -FriendlyName “My New Certificate” -IncludeAcceptedDomains:$false -Force:$true
The DomainName property is set to each URL that you want the certificate to be valid for, with the first value in the string being the value for the Subject field and all the values each being used in the Subject Alternative Name field.
Once you have executed the command above you will have a file with the name set in the Path property. This file can be opened in Notepad and used in Microsoft Certificate Services:
- Browse to your Microsoft Certificate Services URL and click Request a certificate
- Click advanced certificate request
- Click submit a certificate…
- Copy and paste the entire text of the certificate request from notepad into the Saved Request field on this page and select Web Server as the Certificate Template. Click Submit.
- With a default installation the Web Server template value will not be present and that needs to be enabled by your Certificate Services administrator for your user account
- With the default installation of Certificate Services, the certificate will now be ready to download. Click Download certificate (or Download Certificate Chain if the end server does not trust your issuer) to save your certificate to the computer.
- Install the certificate on to the same computer that you issued the request from (this is a very important step), and then you can export the certificate and import it on your web server or firewalls.
To install the certificate, run the Import-ExchangeCertificate powershell command on the same computer as the request was issued from (this is a very important, it must be on the same computer). This is a simpler command to run that the creation of the request above.
The syntax of this command is (where the filename is the name of the file downloaded above):
To export the certificate to your web server or firewall you need to open the local computer certificate store in the Microsoft Management Console – run mmc, add a snap-in and choose Certificates, Computer account. You will find your certificates under the Personal store. You can right-click these certificates and export them (with the private key) to a .pfx file. This file can then be imported using the MMC tool on the web server or firewall ready for importing using an mmc with the certificates/computer account snap-in load into it.