Unconstrained Delegation is a feature within Active Directory environments that allows designated services to act on behalf of users, requesting access to other network resources without requiring additional authentication. This delegation model grants specified services a broad authority, making them trusted to impersonate any user to any service.
Unconstrained delegation is the insecure legacy version of Kerberos Delegation which was later followed by constrained delegation and eventually resource-constrained delegation. This capability is intended to streamline service interactions, particularly in complex, multi-tiered network architectures where services must communicate across boundaries securely and efficiently.
At its core, Unconstrained Delegation operates by leveraging Kerberos tickets. When a user authenticates to a service enabled for Unconstrained Delegation, the Key Distribution Center (KDC) issues a Ticket-Granting Ticket (TGT) along with the usual service ticket. This TGT, which effectively proves the user’s identity, can then be presented by the service to the KDC to request tickets to other services on behalf of the user. This process allows for seamless access across services without repeated user authentication prompts.
However, Unconstrained Delegation contrasts sharply with its more restrictive counterpart, Constrained Delegation. While Unconstrained Delegation places no limitations on the services to which the delegated service can request access on behalf of the user, Constrained Delegation tightly controls this by specifying exactly which services are accessible.
This distinction is crucial for security planning, as the broader permissions associated with Unconstrained Delegation pose a greater risk if misconfigured or exploited by malicious actors.
The use of Unconstrained Delegation is typically reserved for scenarios where services require extensive cross-domain interactions that cannot be efficiently managed through Constrained Delegation. Examples include highly integrated application environments and situations where services need to perform wide-ranging actions across various network segments on behalf of users.
Despite its utility, the security implications of granting such wide-reaching delegation rights necessitate careful consideration and management to prevent abuse.
The utility of Unconstrained Delegation, particularly in complex IT environments, is undeniable. Broad permissions model introduces substantial security risks, making it a target for exploitation in cyber attacks. The primary concern with Unconstrained Delegation revolves around its potential misuse for lateral movement and privilege escalation within a network.
One of the most significant risks is that if an attacker compromises a service account enabled for Unconstrained Delegation, they gain the ability to request access tokens for any other service on behalf of any user.
It is possible to use this capability to access sensitive information or to take unauthorized actions across the network, effectively turning a single compromised account into a gateway for widespread network penetration. It is especially concerning in environments where service accounts with Unconstrained Delegation privileges have not been properly secured or monitored.
The exploitation of Unconstrained Delegation can also facilitate the execution of sophisticated cyber attacks, including Kerberoasting. Kerberoasting takes advantage of the Kerberos protocol’s use of weak encryption for certain aspects of ticket exchange.
Attackers can request service tickets on behalf of any user for services enabled for Unconstrained Delegation, then attempt to crack the tickets offline to discover service account passwords. This attack vector underscores the importance of strong, complex passwords for service accounts and highlights the risks associated with Unconstrained Delegation.
The inherent complexity and administrative overhead associated with managing Unconstrained Delegation settings introduces another layer of risk. Misconfigurations can result in unauthorized access to services, and IT environments are dynamic, so what is secure today may not be secure tomorrow. To mitigate these risks, continuous vigilance, regular audits, and a thorough understanding of delegation settings are essential.
There have been a number of real-world incidents that illustrate the dangers of improperly managed Unconstrained Delegation. Attackers have taken advantage of this vulnerability to move laterally within networks, escalate their privileges, and cause significant damage to an organization’s IT infrastructure. These incidents serve as powerful reminders of the potential consequences of overlooking the security implications of Unconstrained Delegation.
Securing Unconstrained Delegation necessitates a proactive multi-layered approach, focused on minimizing its inherent risks while leveraging its functionality. Achieving a balance between operational requirements and robust security measures requires the adoption of best practices.
Here are strategic practices to enhance the security of Unconstrained Delegation:
Transitioning to Constrained Delegation provides a tighter security model by explicitly limiting the services to which a delegated account can present delegated credentials. This limitation significantly reduces the risk of unauthorized access through delegation, making it a preferred alternative to Unconstrained Delegation whenever feasible.
Continuous monitoring and periodic audits of delegation settings are crucial. Organizations should implement solutions that provide visibility into how delegated permissions are being used and by whom. Regular reviews help identify misconfigurations or unnecessary delegation permissions that could expose the network to risks.
Minimize the number of accounts with Unconstrained Delegation permissions and ensure that these accounts possess only the necessary privileges for their intended functions. This practice limits the potential damage an attacker can inflict if they compromise a delegated account.
Enhancing the authentication requirements for accounts with delegation permissions adds an additional layer of security. Implementing Multi-Factor Authentication (MFA) and strong password policies for these accounts can help protect against credential theft and misuse.
Network segmentation can limit the scope of lateral movement in case of an account compromise. By dividing the network into segments with controlled access, organizations can reduce the reach of accounts with Unconstrained Delegation and contain potential breaches more effectively.
Utilizing advanced security solutions that can detect and respond to anomalous activities associated with Unconstrained Delegation can significantly enhance protection. Solutions that offer Identity Threat Detection and Response (ITDR) capabilities can identify suspicious patterns of behavior related to delegation, such as abnormal access requests, and provide real-time mitigation.
It is essential that IT and security teams are aware of the risks associated with Unconstrained Delegation and understand best practices for its secure use. By scheduling regular training sessions, it is possible to maintain a high level of attention and ensure that security considerations are incorporated into the management of delegation settings.
Incorporating these best practices into security strategies can help organizations mitigate the risks associated with Unconstrained Delegation, ensuring that the convenience and functionality it offers do not compromise network security.
Finding where Unconstrained Delegation has been enabled in your Active Directory (AD) environment is crucial for understanding potential security risks and ensuring your network’s integrity. Here’s a systematic approach to identify these configurations:
PowerShell is a powerful tool for managing and querying Active Directory environments. You can use it to find accounts with Unconstrained Delegation enabled by executing a simple script.
For those who prefer a graphical user interface (GUI), the Active Directory Users and Computers (ADUC) tool can be used:
