KBS `resource-path`: Docs & Testing Mismatch In Resource Policy

Dec 4, 2025 by Alex Johnson 64 views

Addressing the Discrepancy in KBS `resource-path` Documentation and Testing

Introduction

This article delves into a critical issue concerning the Kubernetes Secret Store (KBS) resource policy, specifically the discrepancy between the documentation and the actual implementation of resource-path. This mismatch primarily affects the evaluation of KBS resource policies and necessitates immediate attention to ensure consistency and accuracy across the system. The core of the issue lies in how the resource-path is handled within the KBS plugin model, leading to a divergence between the documented path structure and the one encountered by API server users. This article will explore the technical details of the bug, its implications, and the suggested fixes to align the documentation, testing, and implementation.

The Core of the Issue: Mismatch in `resource-path` Handling

The heart of the problem resides in the way resource-path is processed within the KBS plugin model. The transition to this new model introduced a change in how the resource-path is constructed and evaluated. In the current implementation, the resource-path passed to the evaluate() function takes a specific format, which is crucial for policy evaluation. Let's examine the code snippet to understand this better:

let endpoint = format!("{base_path}{additional_path}");

This code illustrates that the endpoint, which is the resource-path used for policy evaluation, is constructed by combining the base_path and additional_path. The implication of this construction is significant when we consider how the path is parsed for policy evaluation. Specifically, when the path is split using path := split(data["resource-path"], "/"), the resulting structure deviates from the expected format.

In this scenario, path[0] resolves to resource, which is a crucial detail. The documented “three-segment path format: <TOP>/<MIDDLE>/<TAIL>” effectively starts from path[1] onwards. This means that any policy written expecting the traditional path structure—where <TOP> would be path[0]—will not function correctly under the new plugin model. This is where the mismatch becomes apparent: policies designed based on the old path structure will likely lead to unexpected behavior, such as PolicyDeny outcomes, due to the incorrect parsing of the resource-path.

The discrepancy extends beyond just the code implementation; it also impacts the tests and documentation. While numerous tests exist that run the evaluate() function with resource-path set, they predominantly adhere to the old path structure. This means that the existing test suite may not accurately reflect the reality faced by API server users under the new plugin model. The tests, therefore, do not catch the issues arising from the changed endpoint structure.

To summarize, the core issue is a misalignment between the documented and actual structure of resource-path in the KBS plugin model. This misalignment affects policy evaluation, making existing policies potentially ineffective and leading to unexpected outcomes. Furthermore, the current test suite does not adequately address this issue, as it largely relies on the old path structure. Correcting this discrepancy is essential to ensure the KBS functions as expected and that policies are evaluated accurately.

The Bug's Impact: Reproducing the Issue

Understanding how to reproduce a bug is crucial for verifying its existence and ensuring that any proposed fixes effectively address the problem. In the case of the KBS resource-path discrepancy, the reproduction steps are straightforward: any policy that relies on the assumption that path[0] corresponds to the <TOP> segment of the resource path will demonstrate the issue.

Consider a scenario where a policy is designed to deny access based on the top-level resource category. For instance, a policy might be written to deny access to resources where path[0] equals a specific value, say, secrets. In the pre-plugin model world, this would have functioned as expected, with path[0] indeed representing the top-level resource category.

However, with the introduction of the plugin model and the change in how resource-path is constructed, this same policy will likely fail. As we established earlier, the endpoint format now prepends the resource segment to the path, making path[0] equal to resource rather than the intended <TOP> segment. Consequently, the policy, expecting path[0] to be, for example, secrets, will not trigger under the intended conditions. Instead, it will either deny access inappropriately or, more likely, not trigger at all, as the condition path[0] == secrets will never be met.

To reproduce this issue, one can select any policy that tests path[0] == <TOP> and run it within the new plugin model environment. The expected outcome is PolicyDeny (or a lack of the intended policy enforcement), confirming that the policy is not functioning as designed due to the path structure mismatch. This straightforward reproduction method underscores the significance of the bug, as it affects any policy built on the assumption of the old path structure.

This scenario highlights the importance of aligning documentation, testing, and implementation. Policies written based on outdated documentation or assumptions will not function correctly, leading to potential security vulnerabilities or operational disruptions. Similarly, tests that do not reflect the current resource-path structure will fail to catch these issues, resulting in a false sense of security. Therefore, a comprehensive approach involving updating documentation, revising tests, and adjusting policy logic is necessary to resolve this bug effectively.

Suggested Fixes: A Comprehensive Approach

Addressing the discrepancy in KBS resource-path handling requires a multi-faceted approach that encompasses documentation updates, enhanced testing, and codebase adjustments. The suggested fixes aim to align the documentation with the current implementation, ensure that testing accurately reflects real-world usage, and update the code to maintain consistency.

1. Documentation Overhaul

The first and perhaps most critical step is to update all documentation to reflect the resource/<TOP>/<MIDDLE>/<TAIL> model. This ensures that users and developers have an accurate understanding of the resource-path structure when writing and deploying policies. The documentation should clearly explain how the path is constructed and parsed within the plugin model, emphasizing that path[0] now resolves to resource.

This update should not be limited to a single document or section; rather, it should be a comprehensive review and revision of all relevant documentation. This includes user guides, developer documentation, API references, and any other materials that discuss resource-path or policy evaluation. The goal is to create a consistent and accurate picture of how resource-path works in the current KBS environment.

2. Enhanced End-to-End (E2E) Testing

To ensure the integrity of the resource-path structure, it is essential to introduce end-to-end (E2E) tests that specifically target this aspect. These tests should simulate real-world scenarios where policies are evaluated based on the resource/<TOP>/<MIDDLE>/<TAIL> structure. By creating E2E tests, we can verify that the entire system, from policy definition to evaluation, functions correctly with the new path structure.

E2E tests are particularly valuable because they assess the system as a whole, rather than focusing on individual components. This means that they can catch issues that might be missed by unit tests or integration tests. In the context of resource-path, E2E tests can confirm that policies are correctly evaluated when deployed in a production-like environment.

These tests should cover a variety of scenarios, including policies that target different segments of the path and policies that use complex conditions. By thoroughly testing the resource-path structure, we can build confidence in the system's ability to enforce policies accurately.

3. Unit Test Updates

In addition to E2E tests, it is crucial to update the existing unit tests to align with the new endpoint structure. While E2E tests provide a comprehensive view of the system, unit tests offer a more granular level of testing. By updating unit tests, we can ensure that individual components of the policy evaluation process are functioning correctly with the resource/<TOP>/<MIDDLE>/<TAIL> model.

This involves reviewing all unit tests that utilize resource-path and modifying them to reflect the new structure. Tests that previously assumed path[0] was the <TOP> segment should be adjusted to account for the resource prefix. This may require changes to the test setup, assertions, and expected outcomes.

Updating unit tests not only improves the accuracy of the test suite but also provides a valuable opportunity to review and refactor the codebase. By examining the code through the lens of the new resource-path structure, we can identify potential areas for improvement and ensure that the system is robust and maintainable.

Summary of Fixes

In summary, the suggested fixes encompass a comprehensive strategy to address the resource-path discrepancy. By updating documentation, adding E2E tests, and revising unit tests, we can ensure that the KBS functions correctly and that policies are evaluated accurately. This multi-faceted approach is essential for maintaining the integrity and reliability of the system.

Conclusion

The discrepancy in KBS resource-path documentation and testing presents a significant challenge that requires a thorough and coordinated response. By addressing the issue through comprehensive documentation updates, enhanced testing methodologies, and necessary code adjustments, we can ensure the KBS functions as intended, providing a robust and reliable policy evaluation mechanism. The suggested fixes, encompassing documentation overhaul, E2E testing, and unit test updates, form a holistic strategy to realign the system with its intended functionality.

This effort to resolve the resource-path discrepancy underscores the importance of maintaining consistency across documentation, testing, and implementation. A robust system is not only built on sound code but also on clear documentation that accurately reflects the system's behavior and a comprehensive testing framework that validates its functionality. By prioritizing these aspects, we can enhance the reliability and usability of the KBS, ensuring it meets the needs of its users and stakeholders.

In conclusion, resolving the resource-path issue is a crucial step towards ensuring the long-term health and reliability of the KBS. By taking a comprehensive approach to documentation, testing, and code updates, we can restore confidence in the system and ensure it continues to serve its intended purpose effectively. For further reading on Kubernetes security best practices, consider exploring resources available on the Kubernetes website.