Ensure Routing Tables for VPC Peering Are "Least Access" Rule
This rule ensures that routing tables for VPC peering are configured to provide the least access possible.
| Rule | Ensure routing tables for VPC peering are "least access" |
| Framework | cis_v140 |
| Severity | ✔ High |
CIS v1.4.0 Rule: VPC Peering Least Access
Description of the Rule
"AWS VPC (Virtual Private Cloud) peering allows private connectivity between two VPCs, enabling you to route traffic via private IP addresses. The 'least access' principle in the context of VPC peering is about ensuring that only necessary routes are enabled in the routing tables to prevent any unwanted access or data exposure between peered VPCs. This principle is aligned with the CIS (Center for Internet Security) AWS Foundations Benchmark recommendations, which focus on security best practices."
Troubleshooting Steps
Troubleshooting issues related to routing tables in VPC peering typically involve the following:
- 1.Verify the existence of VPC peering connections.
- 2.Ensure that the routes in the VPC routing tables are minimal and only allow traffic to and from required networks.
- 3.Check that security groups and network ACLs (access control lists) are appropriately configured to enforce least access principles.
If there is a breakdown in connectivity or an over-permissive route:
- Review the routes in each VPC's routing table for any overly permissive CIDR blocks.
- Verify that network ACLs and security group rules align with the least access principle.
- Confirm that there are no overlapping CIDR ranges causing route conflicts.
Necessary Codes and CLI Commands
CLI Command to Describe VPC Peering Connections
aws ec2 describe-vpc-peering-connections --region <your-region>
Replace
<your-region>CLI Command to Describe Route Tables
aws ec2 describe-route-tables --region <your-region>
Replace
<your-region>CLI Command to Modify the Route Table (If Necessary)
aws ec2 replace-route --route-table-id <route-table-id> --destination-cidr-block <destination-cidr> --vpc-peering-connection-id <peering-connection-id> --region <your-region>
Replace
<route-table-id><destination-cidr><peering-connection-id><your-region>Step-by-Step Guide for Remediation
Step 1: Evaluate Current Routes
Review current routing tables' routes to ensure they comply with least access practices. This can be done either through the AWS Management Console or using the AWS CLI.
Step 2: Amend Overly Permissive Routes
If any routes are too permissive, they must be replaced with more restrictive routes that only allow necessary traffic.
Step 3: Update Security Groups and ACLs
Review and update security groups and network ACLs to ensure they are as restrictive as necessary, complying with the least access principle.
Step 4: Continuous Monitoring
Set up regular reviews and automated monitoring to ensure compliance is maintained over time, and any changes are reviewed and authorized.
By adhering to this guide and regularly reviewing and maintaining least access routes, an AWS environment can be aligned with CIS recommendations granting you not only strong security posture but also optimizing your VPC for search engines as it demonstrates a well-maintained and compliance-focused infrastructure.