Admission controllers

Admission controllers offer an essential layer for enforcing policies and ensuring that only authorized and secure configurations are allowed into your clusters.

In the context of network security and zero trust, admission controllers help enforce strict access controls and prevent malicious activity by validating, mutating, and rejecting requests before they reach the Kubernetes API server. Some admission controllers, like Wiz, primarily serve as validating admission controllers (except for Wiz Image Trust, which also mutates the image spec). 

Admission controllers play a pivotal role in maintaining a zero-trust security posture, which assumes no trust for any user or system, whether internal or external. They ensure that all requests for changes to the Kubernetes environment are validated against security policies, reducing the attack surface and ensuring that only secure, compliant configurations are deployed. 

Key Roles of Admission Controllers in Network Security & Zero Trust: 

1. Enforcing Security Policies: Admission controllers can validate requests based on predefined security policies, such as ensuring containers only run with the least privilege, requiring certain labels or annotations, or blocking insecure configurations. This helps prevent misconfigurations and malicious code from being deployed, reinforcing a zero-trust approach. 

2. Mutating Requests for Security Compliance: Some admission controllers can modify requests to meet security requirements automatically. For example, they can inject security-sidecar containers into pods, ensuring that the security context for containers meets predefined standards before they’re allowed to run. 

3. Preventing Malicious Changes: Admission controllers allow you to define rules that detect and block unauthorized or malicious actions, such as privileged escalations or the deployment of unapproved container images. This proactive defense ensures that only trusted resources can access or modify critical components of your Kubernetes environment. 

4. Integrating with Network Security Policies: Admission controllers can be configured to enforce network policies, ensuring that containers and pods communicate only in authorized, secure ways. By enforcing access control rules, these controllers help reduce lateral movement and limit the attack surface, aligning with the principles of zero trust. 

By leveraging admission controllers, security teams can strengthen their Kubernetes security framework, enhance network security, and uphold the zero-trust model across their clusters. This module will explore how to configure and use admission controllers effectively to support a zero-trust security model, ensuring that only safe and secure actions are allowed within your Kubernetes environment.