10 Microsoft Certificate Authority Best Practices

Certificate Authorities (CAs) play a vital role in ensuring the security of digital communications. They are responsible for issuing and revoking digital certificates, which are used to authenticate and encrypt communications.

Microsoft Certificate Authorities (MSCAs) are a type of CA that is designed to work with the Microsoft Windows operating system. In this article, we will discuss 10 best practices for using MSCAs.

1. Use the Certificate Authority Web Enrollment (CAWEB)

The CAWEB is a web-based interface that allows users to request and manage certificates. It’s convenient because it can be used from anywhere, and it’s more secure than emailing certificate requests.

When using the CAWEB, make sure you’re using a strong password and two-factor authentication. You should also have a process in place for revoking and renewing certificates.

If you follow these best practices, you’ll be able to use the CAWEB securely and effectively.

2. Use a certificate template that is not configured to allow private key archival

If a certificate template is configured to allow private key archival, then the CA will export and archive the private keys of all certificates issued from that template. This means that if the CA’s database is ever compromised, an attacker could potentially extract the private keys for all of the certificates issued from that template.

To prevent this, make sure to use a certificate template that is not configured to allow private key archival. You can do this by opening the certificate template properties in the Certificate Templates console, selecting the Security tab, and then ensuring that the “Allow private key to be exported” option is disabled.

3. Configure the CA to use CSPs that are FIPS 140-2 compliant

The Federal Information Processing Standard (FIPS) 140-2 is a U.S. government standard that specifies the security requirements for cryptographic modules. A cryptographic module is a set of one or more algorithms used in conjunction with each other to perform encryption, decryption, digital signing, or hashing.

A CA that uses FIPS 140-2 compliant CSPs is more secure because the cryptographic algorithms used by the CA are more resistant to attack. This is especially important for CAs that issue digital certificates that are used for SSL/TLS connections, as these certificates are used to encrypt traffic between clients and servers.

Configuring a CA to use FIPS 140-2 compliant CSPs is not a difficult task, and there are many benefits to doing so. Therefore, it is recommended that all Microsoft Certificate Authorities be configured to use FIPS 140-2 compliant CSPs.

4. Do not install the root CA on an enterprise subordinate CA

The root CA is the most trusted certificate in the PKI hierarchy, and as such, it should be kept offline and highly secured. If the root CA were to be compromised, all of the certificates issued by that CA would be considered invalid.

By keeping the root CA offline and only installing it on enterprise subordinate CAs, you can help ensure that the root CA remains secure and that any certificates issued by that CA are still valid.

5. Do not configure the CA to publish certificates in Active Directory

When a CA is configured to publish certificates in Active Directory, any domain user can request and retrieve certificates from the CA. This presents a security risk because an attacker could request and retrieve a valid certificate for a malicious website, which would then be used to spoof the legitimate website and carry out phishing attacks.

To mitigate this risk, it’s recommended that you do not configure the CA to publish certificates in Active Directory. Instead, you should restrict access to the CA so that only authorized users can request and retrieve certificates.

6. Install only one CA role service per server

When you install multiple CA role services on the same server, they share the same configuration database. This can lead to problems, such as one service overwriting the other’s settings, or both services trying to use the same certificate template at the same time.

Installing only one CA role service per server avoids these problems and helps keep your PKI infrastructure running smoothly.

7. Disable auto enrollment for domain controllers

When auto enrollment is enabled, domain controllers will automatically enroll for and renew certificates from the CA. This means that the CA will issue a certificate to each domain controller in the environment without any administrator intervention.

The problem with this is that it can lead to domain controllers being issued certificates that they shouldn’t have. For example, if an attacker compromises a domain controller, they could use auto enrollment to get a valid certificate for that domain controller. They could then use that certificate to impersonate other domain controllers or services in the environment.

By disabling auto enrollment for domain controllers, you can ensure that only administrators can enroll domain controllers for certificates. This helps to prevent attackers from getting valid certificates for domain controllers that they shouldn’t have.

8. Restrict access to the CA database folder and log files

The CA database folder contains the certificate database and log files. These files contain sensitive information, such as the private keys for all issued certificates and pending certificate requests. If an attacker were to gain access to these files, they could use the private keys to impersonate any website or service that is using a certificate from your CA.

To protect your CA’s database and log files, you should restrict access to them to only those who absolutely need it. Ideally, only the administrator of the CA should have access to these files.

If you must allow others to access the CA database or log files, then you should consider using encryption to protect the data. For example, you could use Microsoft’s Encrypting File System (EFS) to encrypt the CA database files.

9. Back up your CA regularly

If your CA is ever compromised, the first thing you’ll want to do is restore it from a backup. This will ensure that any malicious changes made by the attacker are reverted and that you can continue issuing certificates as usual.

Backing up your CA also protects you from data loss in the event of a hardware or software failure. If your CA’s database becomes corrupted, you can restore it from a backup to avoid having to start from scratch.

To properly back up your CA, you should export its private key, certificate, and database onto a removable storage device such as a USB drive. These files should then be stored in a secure location such as a safe deposit box.

10. Monitor the health of your PKI infrastructure

Your PKI is the foundation of your digital security, and if it’s not healthy, your entire security posture is at risk. By monitoring the health of your PKI infrastructure, you can identify and fix problems before they cause serious security incidents.

There are many different aspects of PKI health that you need to monitor, including certificate expiration dates, CRL distribution points, and OCSP responders. You also need to monitor the performance of your PKI infrastructure to ensure that it can handle the load of your organization’s digital security needs.

The best way to monitor the health of your PKI infrastructure is to use a tool like Microsoft Certificate Services Management Pack. This management pack provides you with comprehensive visibility into the health of your PKI infrastructure and helps you quickly identify and fix problems.