• 👉 Overview
• 👀 What ?
• 🧐 Why ?
• ⛏️ How ?
• ⏳ When ?
• ⚙️ Technical Explanations
• 🖇️ References

👉 Overview

👀 What ?

Windows Constrained Delegation (CD) is a security feature in Microsoft Windows Active Directory (AD) that allows a service to impersonate a user to other services, while limiting the services that the user can be impersonated to. This feature is designed to allow services to perform actions on behalf of users, without giving the service unrestricted access to the user's permissions.

🧐 Why ?

Understanding Windows CD is crucial for both system administrators and cybersecurity professionals. For administrators, CD is a powerful tool for managing service permissions in an AD environment. For cybersecurity professionals, CD is a potential attack vector if not correctly configured. Misconfigured CD can lead to privilege escalation, where an attacker gains unauthorized access to resources.

⛏️ How ?

To implement CD, you first must configure a service to use Kerberos authentication. Then, in the AD, you specify the services to which the user can be impersonated. This is done in the Delegation tab of the service's Properties dialog. It is important to limit the services to the minimum necessary to reduce potential attack surface. Regular audits of CD configurations can help identify and rectify any misconfigurations.

⏳ When ?

Windows CD has been a feature in Windows Server since the 2000 version. However, its security implications have become more widely recognized in recent years as attackers have become more sophisticated in exploiting misconfigurations.

⚙️ Technical Explanations

At a technical level, CD works by modifying the Service Principal Name (SPN) attribute in the user's AD object. The SPN is a unique identifier for each service. When a service tries to impersonate a user, the Kerberos Key Distribution Center (KDC) checks the user's SPN against the list of services allowed in the CD configuration. If the service is in the list, the KDC issues a ticket granting the service the user's permissions. If not, the impersonation request is denied. This process ensures that only authorized services can impersonate a user, and only to the specified services.

🖇️ References