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Microsoft CA certificate validity period

Using a Microsoft CA is very common in network to issue self-signed certificates. Last week I had to configure a Windows IIS server with client certificate authorization. Remote people (non Active Directory users) need a client certificate to browse to a specific website. The communication between the remote user and the website is secure by a default SSL web certificate.

The website is configured to require SSL and client certificate authentication. Within IIS I configured Client Certificate Mappings to authenticate the remote users. To create Client Certificate Mappings I had to generate client certificates. Client certificates can be generated by installing a Microsoft Certificate Authority. You can also use OpenSSL to generate client certificate, but this customers has a complete Microsoft Windows environment, so I decided to install a Microsoft CA.

You can install two kinds of CA’s:

  • Stand-alone CA
  • Enterprise CA

A standalone CA does not issue certificates independent of administrator intervention. The reasoning for this is based upon the fact that a standalone CA doesn’t tap into a local or domain user account. Instead, it relies upon human intervention as a ‘last check’ method prior to issuing a certificate. Standalone CA certificates are also not distributed automatically, but further require a delivery method, such as group policy (for local domain users), or via further human intervention. For Web and Internet access, this is the type of CA to use.

The enterprise CA adds a new level of flexibility and ability to the certificate picture, but also added complexity. The Enterprise CA is integrated with Active Directory, and only provides certificates to members within that Active Directory. This pretty much kills the idea of having both an extranet or secure Internet communications along with secure local domain communications. Enterprise Certificates can, however, be used in a manner that falls within the ‘not often, but still really nifty’ category. Enterprise Certificates can be used to bypass repeated and redundant domain authentication, and when properly configured, can be used to further enhance the standard Kerberos authentication methods. Enterprise Certificates are automatically issued for every user account when it is created. The certificate itself, since it is a file, can be stored on any storage location and can still be valid. In keeping along this train of thought, it is possible to place a certificate on a card or plug-in device that can be used to authenticate a user during the normal Kerberos authentication process. These specialized devices are called Smart Cards, and while Smart Card implementation is somewhat expensive, several large corporations have implemented this technology as an added safety factor. […] Source

I decided to install a Standalone CA server, so client certificates can be generated with credentials from the remote users. When using an Enterprise CA, the client certificate contains the credentials from the Windows users who generates the request. The Enterprise CA requires Windows Integrated Authentication to perform a request.

Everything is working perfectly, the only caveat was the validity period of the client certificates. By default, the lifetime of a certificate that is issued by a Stand-alone Certificate Authority CA is one year. The validity period that is defined in the registry affects all certificates that are issued by Stand-alone and Enterprise CAs. For Enterprise CAs, the default registry setting is two years. I used the following procedure to change the default validity period from one year to two years.

  1. Click Start, and then click Run
  2. In the Open box, type regedit, and then click OK
  3. Locate, and then click the following registry key:
    • HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\CertSvc\Configuration\<CAName>
  4. In the right pane, double-click ValidityPeriod
  5. In the Value data box, type one of the following, and click OK
    • Days
    • Weeks
    • Months
    • Years
  6. In the right pane, double-click ValidityPeriodUnits
  7. In the Value data box, type the numeric value that you want, and then click OK. In my situation I used the value 2
  8. Stop and then restart the Certificate Services service. To do so
    • Click Start, and then click Run
    • In the Open box, type cmd, and then click OK
    • At the command prompt, type the following lines.
    • net stop certsvc
    • net start certsvc
  9. Type exit to quit Command prompt.

I found this procedure in the Microsoft Knowledge Base and used it on Microsoft Windows 2003 and Microsoft Windows 2008.