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How to Find AWS CloudTrail S3 bucket is publicly accessible

Problem​

Allowing public access to CloudTrail log content may aid an adversary in identifying weaknesses in the affected accounts use or configuration.

info

This security check is part of the CIS Amazon Web Services Benchmarks and is rated severity critical.

Prerequisites​

This guide assumes that you have already installed and configured Resoto to collect your AWS cloud resources.

Directions​

  1. Execute the following search command in Resoto Shell or Resoto UI:

    > search is(aws_cloud_trail) and trail_status.is_logging==true --> is(aws_s3_bucket) and bucket_public_access_block_configuration.{block_public_acls!=true or ignore_public_acls!=true or block_public_policy!=true or restrict_public_buckets!=true} or bucket_acl.grants[*].{permission in [READ, READ_ACP] and grantee.uri=="http://acs.amazonaws.com/groups/global/AllUsers"}
    ​kind=aws_cloud_trail, ..., region=resoto-poweruser
    ​kind=aws_cloud_trail, ..., account=poweruser-team

  2. Pipe the search command into the dump command:

    > search is(aws_cloud_trail) and trail_status.is_logging==true --> is(aws_s3_bucket) and bucket_public_access_block_configuration.{block_public_acls!=true or ignore_public_acls!=true or block_public_policy!=true or restrict_public_buckets!=true} or bucket_acl.grants[*].{permission in [READ, READ_ACP] and grantee.uri=="http://acs.amazonaws.com/groups/global/AllUsers"} | dump
    ​reported:
    ​  id: /aws/cloudtrail/123
    ​  name: some-name
    ​  ctime: '2022-12-05T22:53:14Z'
    ​  kind: aws_cloud_trail
    ​  age: 2mo28d

    The command output will list the details of all non-compliant aws_cloud_trail resources.

  3. Fix detected issues by following the remediation steps:

    • Analyze Bucket policy to validate appropriate permissions.
    • Ensure the AllUsers principal is not granted privileges.
    • Ensure the AuthenticatedUsers principal is not granted privileges.
    note

    Please refer to the AWS CloudTrail documentation for details.

Further Reading​