Rule: S3 buckets should prohibit public write access
This rule ensures S3 buckets do not allow public write access, maintaining data security.
| Rule | S3 buckets should prohibit public write access |
| Framework | NIST 800-53 Revision 5 |
| Severity | ✔ High |
Rule Description:
This rule ensures that all S3 buckets in an AWS account are configured to prohibit public write access. This is done to comply with the security requirements specified in the NIST 800-53 Revision 5 guidelines. By disallowing public write access, the risk of unauthorized modification or deletion of data from S3 buckets is mitigated.
Troubleshooting Steps:
If any S3 bucket in your account allows public write access, you may encounter data security issues. Here are the troubleshooting steps to identify and remediate this issue:
- 1.
Log in to the AWS Management Console.
- 2.
Navigate to the S3 service.
- 3.
Review the list of buckets in your account.
- 4.
For each bucket, check the bucket's permissions and access control settings.
- 5.
Look for any bucket policies, access control lists (ACLs), or grants that allow the "s3:PutObject" action for the "public" or "all users" group.
- 6.
If you find a bucket with such permissions, take note of its name for remediation.
- 7.
Ensure that the bucket should indeed prohibit public write access. If it's intentionally configured to allow public write access, it may not require remediation.
Remediation:
To remediate an S3 bucket allowing public write access, follow these step-by-step instructions:
- 1.
Log in to the AWS Management Console.
- 2.
Navigate to the S3 service.
- 3.
Find and click on the name of the bucket that allows public write access.
- 4.
In the bucket details, click on the "Permissions" tab.
- 5.
Review the bucket policy, ACLs, and grants to identify the specific configuration allowing public write access.
- 6.
Depending on the specific settings discovered, choose one of the following options to remediate:
a. Option 1: Remove "s3:PutObject" permissions for the "public" or "all users" group, if explicitly granted.
b. Option 2: Modify the bucket policy to disallow public write access by removing or updating the relevant policy statements.
c. Option 3: Replace the existing bucket policy with a new policy that denies public write access by default and explicitly grants access only to authorized entities.
- 7.
If required, consult the AWS IAM documentation for guidance on creating or modifying bucket policies.
- 8.
After making the necessary changes, save the updated permissions configuration.
- 9.
Test the bucket's access controls to verify that public write access has been effectively prohibited.
- 10.
Repeat the above steps for any additional S3 buckets that allow public write access.
Additional Information:
It is important to regularly review the permissions and access controls of your S3 buckets to ensure compliance with security best practices. Implementing strict access controls helps protect sensitive data stored in S3 and reduces the risk of unauthorized access or modification. Regular auditing and monitoring of your S3 bucket permissions is also recommended to maintain security over time.
Relevant Code:
In the context of this rule, there are no specific code snippets provided as the remediation steps involve using the AWS Management Console to configure S3 bucket permissions. However, if you prefer to use the AWS Command Line Interface (CLI) for remediation, you can utilize the following command:
aws s3api put-bucket-acl --bucket BUCKET_NAME --acl private
Replace
BUCKET_NAMENote: Using the CLI requires appropriate IAM permissions to perform the necessary actions.