Selecting a CRL Distribution Point
Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2
Because CRLs are valid only for a limited time, PKI clients need to retrieve a new CRL periodically. Windows Server 2003 PKI applications look in the CRL distribution point extension for a URL that points to a network location from which the CRL object can be retrieved. Because CRLs for enterprise CAs are stored in Active Directory, they can be accessed by means of LDAP. In comparison, because CRLs for stand-alone CAs are stored in a directory on the server, they can be accessed by means of HTTP, FTP, and so on as long as the CA is online. Therefore, you should set the CRL distribution point after the CA has been installed.
The system account writes the CRL to its distribution point, whether the CRL is published manually or is published according to an established schedule. Therefore you must ensure that the system accounts for CAs have permission to write to the CRL distribution point.
Because the CRL path is also included in every certificate, you must define the CRL location and its access path before deploying certificates. If an application performs revocation checking and a valid CRL is not available on the local computer, it rejects the certificate.
You can modify the CRL distribution point by using the Certification Authority MMC snap-in. In this way, you can change the location where the CRL is published to meet the needs of users in your organization. You must move the CRL distribution point from the CA configuration folder to a Web server to change the location of the CRL, and you must move each new CRL to the new distribution point, or else the chain will break when the previous CRL expires.
- On root CAs, you must also modify the CRL distribution point in the CAPolicy.inf file so that the root CA certificate references the correct CDP and AIA paths, if specified.
If you are using certificates on the Internet, you must have at least one HTTPs-accessible location for all certificates that are not limited to internal use.