Enforce IMDSv2 on EC2 Instances

ID: ec2-imdsv2

Severity: medium

Author: princechaddha

Tags: cloud,devops,aws,amazon,ec2,aws-cloud-config

Description

Ensure all EC2 instances use Instance Metadata Service Version 2 (IMDSv2) for enhanced security when requesting instance metadata, protecting against certain types of attacks that target the older version, IMDSv1.

YAML Source

id: ec2-imdsv2
info:
  name: Enforce IMDSv2 on EC2 Instances
  author: princechaddha
  severity: medium
  description: |
    Ensure all EC2 instances use Instance Metadata Service Version 2 (IMDSv2) for enhanced security when requesting instance metadata, protecting against certain types of attacks that target the older version, IMDSv1.
  impact: |
    Using IMDSv1 can expose EC2 instances to server-side request forgery (SSRF) attacks, potentially allowing attackers to access sensitive instance metadata.
  remediation: |
    Modify the EC2 instance metadata options to set `HttpTokens` to `required`, enforcing the use of IMDSv2. This can be done via the AWS Management Console, CLI, or EC2 API.
  reference:
    - https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/configuring-instance-metadata-service.html
  metadata:
    max-request: 2
  tags: cloud,devops,aws,amazon,ec2,aws-cloud-config
variables:
  region: "us-east-1"

flow: |
  code(1)
  for(let InstancesName of iterate(template.instances)){
    set("ec2instance", InstancesName)
    code(2)
  }

self-contained: true
code:
  - engine:
      - sh
      - bash
    source: |
      aws ec2 describe-instances --region $region --output table --query 'Reservations[*].Instances[*].InstanceId' --output json

    extractors:
      - type: json
        name: instances
        internal: true
        json:
          - '.[]'

  - engine:
      - sh
      - bash
    source: |
         aws ec2 describe-instances --region $region --instance-ids $ec2instance --query 'Reservations[*].Instances[*].MetadataOptions.HttpTokens[]'
    matchers:
      - type: word
        words:
          - "optional"

    extractors:
      - type: dsl
        dsl:
          - 'ami + " is publically shared"'
# digest: 4b0a00483046022100ed32122c0c343a1bb2a451e86a01a7bed4de98d4b7912c4b127fb6d4d13c447e022100e0016e38a2488e93c0900e056f3fb2528a51ba8663e130710729c396f4784bdb:922c64590222798bb761d5b6d8e72950

Guide to check the vulnerabilities

This template is used to detect vulnerabilities in web applications. It can be used with the Nuclei tool to scan for specific patterns or behaviors.

$ nuclei -u "URL" -t "cloud/aws/ec2/ec2-imdsv2.yaml"

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