Ensure that your AWS S3 buckets are not granting FULL_CONTROL access to authenticated users (i.e. signed AWS accounts or AWS IAM users) in order to prevent unauthorized access. An S3 bucket that allows full control access to authenticated users will give any AWS account or IAM user the ability to LIST (READ) objects, UPLOAD/DELETE (WRITE) objects, VIEW (READ_ACP) objects permissions and EDIT (WRITE_ACP) permissions for the objects within the bucket. Cloud Conformity strongly recommends against setting all these permissions for the 'Any Authenticated AWS User' ACL predefined group in production.
This rule can help you with the following compliance standards:
For further details on compliance standards supported by Conformity, see here.
This rule can help you work with the AWS Well-Architected Framework.
This rule resolution is part of the Conformity Security & Compliance tool for AWS.
Granting authenticated "FULL_CONTROL" access to AWS S3 buckets can allow other AWS accounts or IAM users to view, upload, modify and delete S3 objects without any restrictions. Exposing your S3 buckets to AWS signed accounts or users can lead to data leaks, data loss and unexpected charges for the S3 service.
To determine if your S3 buckets allow full access to AWS authenticated users, perform the following:
Remediation / Resolution
To deny authenticated FULL_CONTROL access to your Amazon S3 buckets, perform the following operations:Note: An S3 bucket can be deemed compliant if implements either "AccessControl": "Private" or sets the "PublicAccessBlockConfiguration" feature options to true. The following CloudFormation template uses both for added security.
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S3 Bucket Authenticated Users 'FULL_CONTROL' Access
Risk level: Very High