Enforce IMDSv2 for AWS EC2 Instances

Enforcing IMDSv2 for AWS EC2 instances enhances security by requiring session-based authentication to access instance metadata, mitigating the risk of unauthorized metadata exposure through vulnerabilities like SSRF (Server-Side Request Forgery). This helps ensure that only authorized applications and users can retrieve sensitive instance data.

This policy pack can help you configure the following settings for EC2 instances:

Enforce IMDSv2, which requires session-based authentication
Set the PUT response hop limit to restrict IMDS access

Review policy settings →

Getting Started

Requirements

Terraform
Guardrails mods:
- @turbot/aws-ec2

Credentials

To create a policy pack through Terraform:

Ensure you have Turbot/Admin permissions (or higher) in Guardrails
Create access keys in Guardrails

And then set your credentials:

export TURBOT_WORKSPACE=myworkspace.acme.com
export TURBOT_ACCESS_KEY=acce6ac5-access-key-here
export TURBOT_SECRET_KEY=a8af61ec-secret-key-here

Please see Turbot Guardrails Provider authentication for additional authentication methods.

Usage

Install Policy Pack

Note
By default, installed policy packs are not attached to any resources.

Policy packs must be attached to resources in order for their policy settings to take effect.

Clone:

git clone https://github.com/turbot/guardrails-samples.git
cd guardrails-samples/policy_packs/aws/ec2/enforce_imdsv2_for_instances

Run the Terraform to create the policy pack in your workspace:

terraform init
terraform plan

Then apply the changes:

terraform apply

Apply Policy Pack

Log into your Guardrails workspace and attach the policy pack to a resource.

If this policy pack is attached to a Guardrails folder, its policies will be applied to all accounts and resources in that folder. The policy pack can also be attached to multiple resources.

For more information, please see Policy Packs.

Enable Enforcement

Tip
You can also update the policy settings in this policy pack directly in the Guardrails console.

Please note your Terraform state file will then become out of sync and the policy settings should then only be managed in the console.

By default, the policies are set to Check in the pack's policy settings. To enable automated enforcements, you can switch these policies settings by adding a comment to the Check setting and removing the comment from one of the listed enforcement options:

resource "turbot_policy_setting" "aws_ec2_instance_metadata_service" {
  resource = turbot_policy_pack.main.id
  type     = "tmod:@turbot/aws-ec2#/policy/types/instanceMetadataService"
  # value    = "Check: Enabled for V2 only"
  value    =  "Enforce: Enabled for V2 only"
}

Then re-apply the changes:

terraform plan
terraform apply