Rule: S3 Bucket Cross-Region Replication Enabled

This rule ensures S3 bucket cross-region replication is enabled for critical data redundancy and disaster recovery.

Rule	S3 bucket cross-region replication should be enabled
Framework	CISA-cyber-essentials
Severity	✔ Critical

Rule Description

S3 bucket cross-region replication should be enabled for CISA-cyber-essentials. This rule ensures that replication is set up between S3 buckets in different AWS regions for improved data availability, durability, and disaster recovery.

Troubleshooting Steps

1.
Verify IAM Permissions: Ensure that the user or role has the necessary IAM permissions for configuring cross-region replication. The user/role should have permissions like
```
s3:GetReplicationConfiguration
```
,
```
s3:PutReplicationConfiguration
```
, and
```
s3:ReplicateObject
```
to both source and destination buckets.

2.

Confirm Bucket Ownership: Verify that the user/role executing the configuration has ownership of both the source and destination buckets. Ownership is required to set up cross-region replication.

3.

Validate Bucket Names: Check if the correct bucket names are provided for both the source and destination buckets. The names should exactly match the existing S3 bucket names.

4.

Verify Bucket Versioning: Confirm that versioning is enabled on both the source and destination buckets. Cross-region replication requires versioning to track changes in replicated objects.

5.

Ensure Appropriate Regions: Cross-region replication should be set up between different AWS regions. Verify that the source and destination buckets are in different regions.

6.
Check Replication Status: Monitor the replication status after enabling it to ensure that replication is working as expected. You can view the replication metrics in the Amazon S3 console or use the AWS CLI command
```
aws s3api get-bucket-replication --bucket <bucket-name>
```
to retrieve the replication configuration.

Necessary Codes

No codes are mandatory for this rule. However, you can use the following AWS CLI commands for verification and replication status:

To check the replication configuration of a bucket:

aws s3api get-bucket-replication --bucket <bucket-name>

To enable cross-region replication on a bucket (example):

aws s3api put-bucket-replication --bucket <bucket-name> --replication-configuration "{
  \"Role\": \"arn:aws:iam::123456789012:role/replication-role\",
  \"Rules\": [
    {
      \"Status\": \"Enabled\",
      \"Destination\": {
        \"Bucket\": \"arn:aws:s3:::<destination-bucket>\",
        \"StorageClass\": \"STANDARD\"
      },
      \"ID\": \"r1\"
    }
  ]
}"

Step-by-Step Guide for Remediation

Follow these steps to enable S3 bucket cross-region replication for CISA-cyber-essentials:

1.

Identify the source and destination buckets: Determine the S3 bucket that will act as the source (existing bucket) and the destination (target bucket for replicated data).

2.

Verify IAM permissions: Ensure that the user or role intended to configure cross-region replication has the necessary permissions mentioned in the troubleshooting steps.

3.

Check ownership: Confirm that the user/role executing the configuration has ownership of both the source and destination buckets.

4.

Enable versioning: If not already enabled, enable versioning on both the source and destination buckets.

5.
Configure cross-region replication: Use the AWS CLI command mentioned in the necessary codes section to configure cross-region replication. Replace
```
<bucket-name>
```
with the actual bucket name and provide the appropriate ARN for the role specified in the command.

6.
Verify replication configuration: Validate the configuration by using the AWS CLI command
```
aws s3api get-bucket-replication --bucket <bucket-name>
```
. Ensure that the replication configuration shows the correct source bucket, destination bucket, and replication status as "Enabled".

7.

Monitor replication status: Keep an eye on the replication status. You can check the status using the same AWS CLI command mentioned in the troubleshooting steps.

By following these steps, you can enable S3 bucket cross-region replication for CISA-cyber-essentials.

Rule: S3 Bucket Cross-Region Replication Enabled

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