Rule: Application Load Balancers with Desync Mitigation Mode
This rule emphasizes configuring Application Load Balancers with defensive or strictest desync mitigation mode.
| Rule | Application Load Balancers should be configured with defensive or strictest desync mitigation mode |
| Framework | AWS Foundational Security Best Practices |
| Severity | ✔ Medium |
Rule Description:
AWS Foundational Security Best Practices recommends configuring Application Load Balancers with defensive or strictest desync mitigation mode. This setting helps to protect against potential desynchronization attacks and ensures the security and reliability of the load balancer.
Troubleshooting Steps:
If you encounter any issues or errors related to the desync mitigation mode configuration on an Application Load Balancer, you can follow the troubleshooting steps below:
- 1.
Check Load Balancer Logs: Review the logs for the Application Load Balancer to identify any potential errors or warnings related to the desync mitigation mode settings.
- 2.
Verify Configuration: Double-check the configuration settings for the Application Load Balancer. Ensure that the correct desync mitigation mode is selected and applied.
- 3.
Review Security Group Rules: Ensure that the security group associated with the Application Load Balancer allows the necessary traffic and ports to pass through. Adjust the rules if needed.
- 4.
Review Network Access Control Lists (ACLs): Check the network ACLs associated with the subnets where the load balancer resides. Ensure that they do not block any necessary traffic.
- 5.
Load Balancer Health Checks: Review the health check settings for the load balancer's target groups. Ensure that they are correctly configured and the associated resources are healthy.
- 6.
Rotate Access Credentials: If all the above steps do not resolve the issue, consider rotating the access credentials for the load balancer. Generate new AWS access keys and update them in your configurations.
Code:
In most cases, troubleshooting Desync mitigation mode issues on an Application Load Balancer can be resolved through configuration checks. However, if specific CLI commands are required, follow the steps below:
- 1.To describe the configuration of an Application Load Balancer:
aws elbv2 describe-load-balancers --load-balancer-arns <load_balancer_arn>
- 1.To update the desync mitigation mode of an Application Load Balancer:
aws elbv2 modify-load-balancer-attributes --load-balancer-arn <load_balancer_arn> --attributes Key=desync-mitigation-mode.enabled,Value=true/false
Ensure to replace
<load_balancer_arn>Remediation Steps:
To configure an Application Load Balancer with the defensive or strictest desync mitigation mode, follow the step-by-step guide below:
- 1.
Open the AWS Management Console and navigate to the EC2 service.
- 2.
In the EC2 Dashboard, click on "Load Balancers" in the left navigation menu.
- 3.
Select the Application Load Balancer that needs to be configured with the desync mitigation mode.
- 4.
Click on the "Listeners" tab and locate the listener for which you want to enable desync mitigation mode.
- 5.
Click on the "Edit" button next to the listener.
- 6.
In the "Edit Listener" dialog box, scroll down to the "Desync Mitigation Mode" section.
- 7.
Choose either "Defensive" or "Strictest" from the dropdown menu, depending on your desired level of mitigation.
- 8.
Click on the "Save" button to apply the changes.
Once saved, the Application Load Balancer will be configured with the chosen desync mitigation mode, providing better protection against potential desynchronization attacks.
Note: Always ensure to thoroughly test the load balancer's functionality after making any configuration changes to guarantee optimal performance.