Chapter 2
Policy Language, Modeling, and Lifecycle
How expressive can your security controls be, and how easily can they evolve with your cloud-native infrastructure? This chapter dives deep into the sophisticated policy language at the heart of KubeArmor-decoding its syntax, semantics, and administration lifecycle. You'll discover how precision modeling, dynamic adaptation, and advanced scoping keep your defenses sharp, resilient, and always aligned with both developer intent and operational realities.
2.1 The Structure of KubeArmor Policies
KubeArmor policies define the security posture of containerized workloads by specifying constraints on file operations, process executions, and network communications. These policies are composed of declarative rules expressed in a structured schema, which KubeArmor's enforcement engine interprets to realize fine-grained control over system behavior. The architecture of a KubeArmor policy centers on a hierarchical organization of metadata, selectors, and permission rules that mediate between the Kubernetes environment and security primitives.
At the highest level, a KubeArmor policy is represented as a YAML manifest that integrates seamlessly within Kubernetes' declarative configuration paradigm. The top-level fields provide metadata and specification references, essential for identifying the policy's target scope and enforcement context. Notably, the selector field plays a vital role by filtering the set of pods or containers to which the policy applies based on label matching, ensuring precision in policy application.
The core semantic elements of a KubeArmor policy reside within three principal rule types: file, process, and network rules. Each rule type encapsulates conditions unique to its domain and articulates associated policy actions such as Allow or Block. Below, the formal syntactic constructs and semantic interpretations for these rules are examined in detail.
Selectors and Match Conditions
Selectors in KubeArmor policies determine the policy's applicability within the cluster environment. They employ label-based matching on Kubernetes objects, most commonly pods and namespaces, to specify the workloads governed by the policy. For example:
selector: matchLabels: app: frontend environment: production Semantically, the selector accepts a pod if its labels include all specified key-value pairs. This form of conjunctive matching is essential for isolating security boundaries at various granularities.
The rules themselves may specify match conditions for files, processes, or network packets. These match conditions predicate the enforcement logic by evaluating attributes such as file paths, process names, syscalls, network protocols, and destination ports. Conditions may specify exact matches or prefix-based matches, broadening expressiveness while maintaining performance efficiency.
File Rules
File rules focus on governing read, write, or execution operations on file system objects by containerized workloads. Their syntax includes fields such as path, operation, and optionally action. For example:
file: matchPaths: - path: /etc/passwd operation: [read, write] action: Block - path: /app/config/ operation: [read] action: Allow Here, matchPaths defines an array of path-condition mappings. Each entry specifies the target file or directory path and the file operations whose access is regulated. The operation list may contain values such as read, write, append, and execute. The action determines whether matched operations are permitted or denied.
KubeArmor enforces these rules by intercepting system calls (e.g., open, read, write) and comparing the invoked operation against policy conditions. If a match occurs and the action is Block, the system call is denied, effectively isolating workloads from unauthorized file interactions.
Process Rules
Process rules constrain the execution of processes within containers. They specify criteria such as the executable path, command-line arguments, or the user identity under which the process runs. A typical process rule structure is:
process: matchPaths: - path: /usr/bin/curl action: Allow - path: /bin/bash action: Block Here, path references the absolute path of the executable file. By defining a whitelist or blacklist of binaries, operators can enforce strict...
