AWS S3 CNAME Records are vulnerable

Using Console

Using CLI

To remediate the vulnerability of AWS S3 CNAME Records, you can follow the steps below using AWS CLI:Step 1: Identify the vulnerable CNAME record in AWS Route53:

Open the AWS Management Console and go to the Route53 service.
Select the hosted zone where the vulnerable CNAME record is located.
Identify the CNAME record that is pointing to an S3 bucket.

Step 2: Create an S3 Endpoint:

Open the AWS Management Console and go to the VPC service.
Select the VPC where your S3 bucket is located.
Click on “Endpoints” in the left sidebar.
Click on “Create Endpoint” and select com.amazonaws.<region>.s3 as the service name.
Choose the relevant route table and security groups.
Click on “Create Endpoint” to create the S3 endpoint.

Step 3: Update the CNAME record to use the S3 Endpoint:

Open the AWS CLI on your local machine.
Run the following command to update the CNAME record:

aws route53 change-resource-record-sets --hosted-zone-id <hosted-zone-id> --change-batch '{
  "Changes": [
    {
      "Action": "UPSERT",
      "ResourceRecordSet": {
        "Name": "<cname-record-name>",
        "Type": "CNAME",
        "TTL": 300,
        "ResourceRecords": [
          {
            "Value": "<s3-endpoint-domain>"
          }
        ]
      }
    }
  ]
}'

Replace <hosted-zone-id> with the ID of your hosted zone, <cname-record-name> with the name of the CNAME record, and <s3-endpoint-domain> with the domain name of the S3 endpoint you created in Step 2.Step 4: Verify the changes:

Wait for the changes to propagate, which may take a few minutes.
Use the following command to check the status of the change:

aws route53 get-change --id <change-id>

Replace <change-id> with the ID of the change returned in the previous step. 3. Once the change status is “INSYNC,” the CNAME record has been updated successfully.By following these steps, you can remediate the vulnerability of AWS S3 CNAME Records in AWS Route53 using AWS CLI.

Using Python

To remediate the vulnerability of AWS S3 CNAME Records in AWS Route53 using Python, follow these steps:

Install the required dependencies:
- boto3: AWS SDK for Python
- dnspython: DNS toolkit for Python
You can use the following command to install them:
```
pip install boto3 dnspython
```
Import the necessary modules in your Python script:
```
import boto3
import dns.resolver
```

Create a function to check for vulnerable CNAME records:

def check_vulnerable_cname(domain):
    try:
        resolver = dns.resolver.Resolver()
        cname_records = resolver.query(domain, 'CNAME')
        for record in cname_records:
            if record.target.to_text().endswith('.s3.amazonaws.com.'):
                print(f'{domain} has a vulnerable CNAME record pointing to {record.target.to_text()}')
    except dns.resolver.NXDOMAIN:
        print(f'{domain} does not exist')
    except dns.resolver.NoAnswer:
        print(f'{domain} does not have any CNAME records')

Create a function to fix the vulnerable CNAME records:

def fix_vulnerable_cname(domain):
    try:
        client = boto3.client('route53')
        hosted_zones = client.list_hosted_zones_by_name(DNSName=domain)
        for zone in hosted_zones['HostedZones']:
            zone_id = zone['Id']
            records = client.list_resource_record_sets(HostedZoneId=zone_id)
            for record in records['ResourceRecordSets']:
                if record['Type'] == 'CNAME' and record['ResourceRecords'][0]['Value'].endswith('.s3.amazonaws.com.'):
                    record['ResourceRecords'][0]['Value'] = '<new_value>'
                    client.change_resource_record_sets(
                        HostedZoneId=zone_id,
                        ChangeBatch={
                            'Changes': [
                                {
                                    'Action': 'UPSERT',
                                    'ResourceRecordSet': record
                                }
                            ]
                        }
                    )
                    print(f'Successfully fixed CNAME record in {zone["Name"]}')
    except Exception as e:
        print(f'Error: {str(e)}')

Note: Replace <new_value> with the desired value for the CNAME record.

Call the functions with the domain you want to check and fix:
```
domain = '<your_domain>'
check_vulnerable_cname(domain)
fix_vulnerable_cname(domain)
```
Note: Replace <your_domain> with the actual domain name.

By following these steps, you can check for vulnerable CNAME records and fix them in AWS Route53 using Python.

AWS Introduction

AWS Pricing

AWS Threats

AWS Misconfigurations

AWS S3 CNAME Records are vulnerable

More Info:

Risk Level

Address

Compliance Standards

Triage and Remediation

Remediation

AWS Introduction

AWS Pricing

AWS Threats

AWS Misconfigurations

​More Info:

​Risk Level

​Address

​Compliance Standards

​Triage and Remediation