Information
Amazon S3 provides Block public access (bucket settings) and Block public access (account settings) to help you manage public access to Amazon S3 resources. By default, S3 buckets and objects are created with public access disabled. However, an IAM principle with sufficient S3 permissions can enable public access at the bucket and/or object level. While enabled, Block public access (bucket settings) prevents an individual bucket, and its contained objects, from becoming publicly accessible. Similarly, Block public access (account settings) prevents all buckets, and contained objects, from becoming publicly accessible across the entire account.
Rationale:
Amazon S3 Block public access (bucket settings) prevents the accidental or malicious public exposure of data contained within the respective bucket(s).
Amazon S3 Block public access (account settings) prevents the accidental or malicious public exposure of data contained within all buckets of the respective AWS account.
Whether blocking public access to all or some buckets is an organizational decision that should be based on data sensitivity, least privilege, and use case.
Impact:
When you apply Block Public Access settings to an account, the settings apply to all AWS Regions globally. The settings might not take effect in all Regions immediately or simultaneously, but they eventually propagate to all Regions.
NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.
Solution
If utilizing Block Public Access (bucket settings)
From Console:
Login to AWS Management Console and open the Amazon S3 console using https://console.aws.amazon.com/s3/
Select the Check box next to the Bucket.
Click on 'Edit public access settings'.
Click 'Block all public access'
Repeat for all the buckets in your AWS account that contain sensitive data.
From Command Line:
List all of the S3 Buckets
aws s3 ls
Set the public access to true on that bucket
aws s3api put-public-access-block --bucket <name-of-bucket> --public-access-block-configuration 'BlockPublicAcls=true,IgnorePublicAcls=true,BlockPublicPolicy=true,RestrictPublicBuckets=true'
If utilizing Block Public Access (account settings)
From Console:
If the output reads true for the separate configuration settings then it is set on the account.
Login to AWS Management Console and open the Amazon S3 console using https://console.aws.amazon.com/s3/
Choose Block public access (account settings)
Choose Edit to change the block public access settings for all the buckets in your AWS account
Choose the settings you want to change, and then choose Save. For details about each setting, pause on the i icons.
When you're asked for confirmation, enter confirm. Then Click Confirm to save your changes.
From Command Line:
To set Public access settings for this account, run the following command:
aws s3control put-public-access-block
--public-access-block-configuration BlockPublicAcls=true, IgnorePublicAcls=true, BlockPublicPolicy=true, RestrictPublicBuckets=true
--account-id <value>