🛡️ AWS VPC Route Table for VPC Peering does not follow the least privilege principle🟢⚪
- Contextual name: 🛡️ Route Table for VPC Peering does not follow the least privilege principle🟢⚪
- ID:
/ce/ca/aws/vpc/route-table-for-vpc-peering-least-privilege - Tags:
- Policy Type:
COMPLIANCE_POLICY - Policy Categories:
SECURITY
Description
Description
Once a VPC peering connection is established, routing tables must be updated to establish any connections between the peered VPCs. These routes can be as specific as desired - even peering a VPC to only a single host on the other side of the connection.
Rationale
Being highly selective in peering routing tables is a very effective way of minimizing the impact of breach as resources outside of these routes are inaccessible to the peered VPC.
Audit
Review routing tables of peered VPCs for whether they route all subnets of each VPC and whether that is necessary to accomplish the intended purposes for peering the VPCs.
From Command Line
- List all the route tables from a VPC and check if
GatewayIdis pointing to a<peering_connection_id>(e.g. pcx-1a2b3c4d) and ifDestinationCidrBlockis as specific as desired:aws ec2 describe-route-tables --filter "Name=vpc-id,Values=<vpc_id>" --query "RouteTables[*].{RouteTableId:RouteTableId, VpcId:VpcId, Routes:Routes, AssociatedSubnets:Associations[*].SubnetId}"
... [see more](description.md)
Remediation
Remediation
Remove and add route table entries to ensure that the least number of subnets or hosts as is required to accomplish the purpose for peering are routable.
From Command Line
- For each
<route_table_id>containing routes non compliant with your routing policy (which grants more than desiredleast access), delete the non compliant route:aws ec2 delete-route --route-table-id <route_table_id> --destination-cidr-block <non_compliant_destination_CIDR>
- Create a new compliant route:
aws ec2 create-route --route-table-id <route_table_id> --destination-cidr-block <compliant_destination_CIDR> --vpc-peering-connection-id <peering_connection_id>