Bug: AWS ECS Cluster Grant_task_protection Permissions

Nov 25, 2025 by Alex Johnson 55 views

Bug: AWS ECS Cluster grant_task_protection Grants Incorrect Permissions

Introduction

This article addresses a critical bug found in the AWS Cloud Development Kit (CDK) concerning the aws_ecs.Cluster#grant_task_protection function within the aws-ecs library. Specifically, a regression introduced between versions 2.213.0 and 2.229.0 causes this function to grant incorrect permissions, potentially leading to security vulnerabilities and operational issues. We will delve into the details of the bug, its impact, the affected versions, and the steps to reproduce it. Understanding this issue is crucial for developers and system administrators utilizing AWS ECS and CDK for their containerized applications.

The core of the problem lies in how the grant_task_protection function constructs IAM (Identity and Access Management) resources. The function should generate a resource ARN (Amazon Resource Name) in the format arn:aws:ecs:{region}:{account_id}:task/{cluster_name}/*, which correctly targets tasks within the specified ECS cluster. However, the regression causes the function to generate an ARN in the format arn:aws:ecs:{region}:{account_id}:cluster/{cluster_name}/*, targeting the cluster itself rather than the individual tasks. This discrepancy in permissions can lead to unintended access controls and potential security risks.

This article aims to provide a comprehensive overview of the bug, its implications, and the steps to mitigate its impact. By understanding the root cause and the affected versions, developers can take proactive measures to ensure the security and stability of their AWS ECS deployments. The following sections will elaborate on the specifics of the bug, including the affected CDK versions, the expected and current behaviors, reproduction steps, and a possible solution.

Bug Description

The bug in aws_ecs.Cluster#grant_task_protection results in the function generating an incorrect IAM resource ARN. Instead of granting permissions to tasks within the ECS cluster, it grants permissions to the cluster itself. This regression was introduced between CDK versions 2.213.0 and 2.229.0, causing a significant change in how permissions are handled for task protection. The intended behavior is for the function to create an IAM statement that allows actions on tasks within the cluster, ensuring that tasks are protected from termination during scaling or deployment operations.

The resource ARN arn:aws:ecs:{region}:{account_id}:task/{cluster_name}/* is designed to target individual tasks within the cluster. This granular control is essential for maintaining security and ensuring that only authorized entities can perform actions on specific tasks. However, the current behavior generates the ARN arn:aws:ecs:{region}:{account_id}:cluster/{cluster_name}/*, which targets the cluster resource itself. This broad permission scope can lead to unintended consequences, such as allowing unauthorized entities to perform actions on the cluster, potentially disrupting the entire application.

The impact of this bug is significant, especially in production environments where task protection is crucial for maintaining application availability and stability. Incorrect permissions can lead to tasks being terminated prematurely, resulting in service disruptions and data loss. Therefore, it is essential for developers and system administrators to be aware of this issue and take appropriate measures to mitigate its impact. The following sections will provide detailed information on how to identify and reproduce the bug, as well as potential solutions to address the issue.

Regression Details

This issue is a regression, meaning it was introduced in a later version of the CDK after previously working correctly. The last known working version of the CDK library is 2.213.0. This means that if you are using version 2.213.0 or earlier, you are not affected by this bug. However, if you have upgraded to version 2.229.0 or later, you are likely experiencing this issue. Identifying regressions is crucial in software development as they can introduce unexpected behavior and compromise the stability of applications. In this case, the regression in aws_ecs.Cluster#grant_task_protection directly impacts the security and operational integrity of AWS ECS deployments.

The regression was likely introduced by a specific commit in the CDK repository. As mentioned in the bug report, the commit https://github.com/aws/aws-cdk/commit/21fd9593c1d451d68b0f3825c47286a41fa5ea37 appears to be the culprit. This commit changed the resource ARN generation from including the task resource-type to using the cluster ARN. By examining the changes in this commit, developers can gain a deeper understanding of the root cause of the regression and how it impacts the IAM policy generation.

The identified commit modifies the test snapshot packages/@aws-cdk-testing/framework-integ/test/aws-ecs/test/integ.cluster-grant-task-protection.js.snapshot/aws-ecs-integ.template.json. This snapshot change clearly demonstrates the shift from a task-specific ARN to a cluster-specific ARN. This level of detail is crucial for pinpointing the exact source of the bug and developing a targeted solution. The next sections will discuss the expected and current behaviors in more detail, providing a clear comparison of the correct and incorrect IAM policy generation.

Expected Behavior vs. Current Behavior

Expected Behavior

The expected behavior of aws_ecs.Cluster#grant_task_protection is to generate an IAM statement that grants permissions to perform actions on tasks within the specified ECS cluster. This means the resource ARN in the IAM policy should have the following structure:

arn:aws:ecs:{region}:{account_id}:task/{cluster_name}/*

This ARN targets individual tasks within the cluster, ensuring that the granted permissions are scoped to the tasks themselves. When task protection is enabled, ECS prevents tasks from being terminated during scale-in events or deployments. The grant_task_protection function should provide the necessary permissions for ECS to manage task protection effectively. The correct behavior ensures that only authorized entities can perform actions on tasks, maintaining the security and stability of the application.

The expected IAM policy should allow actions such as ecs:DescribeTasks, ecs:UpdateTaskProtection, and ecs:ListTasks on the specified tasks. These permissions are essential for ECS to manage task protection, monitor task status, and prevent accidental termination. By correctly scoping the permissions to the task level, the IAM policy adheres to the principle of least privilege, minimizing the risk of unintended access and security breaches.

Current Behavior

The current behavior, due to the regression, is that aws_ecs.Cluster#grant_task_protection generates an IAM statement with an incorrect resource ARN. Instead of targeting tasks, it targets the ECS cluster itself. The resource ARN in the generated IAM policy has the following structure:

arn:aws:ecs:{region}:{account_id}:cluster/{cluster_name}/*

This ARN targets the entire cluster, which is a much broader scope than intended. This means that the granted permissions apply to the cluster as a whole, rather than individual tasks. This can lead to unintended consequences and potential security vulnerabilities. For instance, an entity with permissions on the cluster could potentially perform actions that affect all tasks running within the cluster, not just the protected ones.

The incorrect IAM policy grants permissions at the cluster level, which is a significant deviation from the expected behavior. This broad permission scope violates the principle of least privilege and increases the risk of unauthorized access and actions. For example, an entity with cluster-level permissions might be able to modify cluster settings, scale the cluster, or even delete the cluster, which could have severe operational impacts. The next section will provide detailed steps on how to reproduce this bug and verify the incorrect IAM policy generation.

Reproduction Steps

To reproduce this bug, you need to use a CDK version between 2.229.0 and the latest version where the bug persists. The following steps outline how to reproduce the issue:

Set up a CDK project: If you don't already have a CDK project, create one using the CDK CLI:
```
cdk init app --language python
```
Install the necessary dependencies: Navigate to your project directory and install the required libraries:
```
pip install aws-cdk-lib
```

Write the CDK code: Modify your CDK stack to include an ECS cluster and call grant_task_protection on it. Here's an example using Python:

from aws_cdk import core
from aws_cdk import aws_ecs as ecs
from aws_cdk import aws_ec2 as ec2

class EcsTaskProtectionStack(core.Stack):
    def __init__(self, scope: core.Construct, id: str, **kwargs) -> None:
        super().__init__(scope, id, **kwargs)

        vpc = ec2.Vpc(self, "MyVpc", max_azs=2)

        cluster = ecs.Cluster(self, "MyCluster", vpc=vpc)

        cluster.grant_task_protection("your-principal") # Replace "your-principal" with an appropriate IAM principal

app = core.App()
EcsTaskProtectionStack(app, "EcsTaskProtectionStack")

app.synth()

Synthesize the CDK stack: Run the following command to synthesize the stack and generate the CloudFormation template:
```
cdk synth
```
Inspect the CloudFormation template: Open the generated cdk.out/EcsTaskProtectionStack.template.json file and look for the IAM policy statement created by grant_task_protection. You should find a resource ARN similar to the following:
```
{
  "Effect": "Allow",
  "Action": [
    "ecs:DescribeTasks",
    "ecs:UpdateTaskProtection",
    "ecs:ListTasks"
  ],
  "Resource": "arn:aws:ecs:{region}:{account_id}:cluster/{cluster_name}/*"  // Incorrect Resource ARN
}
```
Notice that the resource ARN targets the cluster instead of the tasks. This confirms the bug. By following these steps, you can reliably reproduce the bug and verify the incorrect IAM policy generation. The next section will discuss a possible solution to address this issue and restore the correct behavior of aws_ecs.Cluster#grant_task_protection.

Possible Solution

The identified root cause of the regression points to the commit that altered the resource ARN generation. The solution involves reverting the change that caused the resource ARN to target the cluster instead of the tasks. This can be achieved by modifying the CDK library code to construct the correct IAM resource ARN.

Specifically, the fix should ensure that the resource ARN is generated in the following format:

arn:aws:ecs:{region}:{account_id}:task/{cluster_name}/*

This requires updating the code within the aws_ecs.Cluster#grant_task_protection function to correctly build the ARN, including the task resource-type. The fix should also include updating the associated unit tests and integration tests to verify the correct behavior and prevent future regressions. Comprehensive testing is crucial to ensure that the fix does not introduce any new issues and that the function behaves as expected under various scenarios.

A possible implementation approach is to revert the specific lines of code in the problematic commit that changed the ARN generation logic. This can be done by creating a patch that undoes the changes introduced by the commit. The patch should then be applied to the CDK library code. After applying the patch, it is essential to run the tests to confirm that the fix works correctly and does not break any existing functionality.

Once the fix is implemented and tested, a new version of the CDK library should be released with the fix included. This will allow developers to upgrade their CDK versions and benefit from the corrected behavior. In the meantime, developers can also use workarounds, such as manually creating the IAM policy with the correct resource ARN, to mitigate the issue. The following section will discuss additional information and context related to this bug.

Conclusion

In conclusion, the regression in aws_ecs.Cluster#grant_task_protection represents a critical issue that can lead to incorrect IAM permissions and potential security vulnerabilities. The bug, introduced between CDK versions 2.213.0 and 2.229.0, causes the function to generate a cluster-level resource ARN instead of the task-level ARN, deviating from the expected behavior. This discrepancy can result in unintended access controls and operational disruptions. Understanding the bug's impact, reproduction steps, and potential solutions is crucial for developers and system administrators using AWS ECS and CDK.

By reverting the changes introduced in the identified commit and ensuring that the resource ARN is correctly generated, the CDK library can restore the intended behavior of aws_ecs.Cluster#grant_task_protection. Comprehensive testing and timely release of a fixed version are essential to address this issue effectively. In the interim, manual workarounds, such as creating the IAM policy with the correct resource ARN, can help mitigate the impact.

Staying informed about such issues and actively participating in the open-source community can help ensure the stability and security of your AWS deployments. We encourage developers to monitor the CDK issue tracker and release notes for updates on this bug and its resolution.

For further reading on AWS ECS and IAM, you can refer to the official AWS Documentation. This will provide you with a deeper understanding of the concepts and best practices for securing your cloud infrastructure.