Domain-Protect – Protect Against Subdomain Takeover

Protect Against Subdomain Takeover

  • scans Amazon Route53 across an AWS Organization for domain records vulnerable to takeover
  • vulnerable domains in Google Cloud DNS can be detected by Domain Protect for GCP

deploy to security audit account

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scan your entire AWS Organization

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receive alerts by Slack or email

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or manually scan from your laptop

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subdomain detection functionality

Scans Amazon Route53 to identify:

  • Alias records for CloudFront distributions with missing S3 origin
  • CNAME records for CloudFront distributions with missing S3 origin
  • ElasticBeanstalk Alias records vulnerable to takeover
  • ElasticBeanstalk CNAMES vulnerable to takeover
  • Registered domains with missing hosted zones
  • Subdomain NS delegations vulnerable to takeover
  • S3 Alias records vulnerable to takeover
  • S3 CNAMES vulnerable to takeover
  • Vulnerable CNAME records for Azure resources
  • CNAME records for missing Google Cloud Storage buckets

optional additional check

Turned off by default as it may result in Lambda timeouts for large organisations

  • A records for missing storage buckets, e.g. Google Cloud Load Balancer with missing backend storage

To enable, create this Terraform variable in your tfvars file or CI/CD pipeline:

lambdas = ["alias-cloudfront-s3", "alias-eb", "alias-s3", "cname-cloudfront-s3", "cname-eb", "cname-s3", "ns-domain", "ns-subdomain", "cname-azure", "cname-google", "a-storage"]

options

  1. scheduled lambda functions with email and Slack alerts, across an AWS Organization, deployed using Terraform
  2. manual scans run from your laptop or CloudShell, in a single AWS account

notifications

  • Slack channel notification per vulnerability type, listing account names and vulnerable domains
  • Email notification in JSON format with account names, account IDs and vulnerable domains by subscribing to SNS topic

requirements

  • Security audit account within AWS Organizations
  • Security audit read-only role with an identical name in every AWS account of the Organization
  • Storage bucket for Terraform state file
  • Terraform 1.0.x

usage

  • replace the Terraform state S3 bucket fields in the command below as appropriate
  • for local testing, duplicate terraform.tfvars.example, rename without the .example suffix
  • enter details appropriate to your organization and save
  • alternatively enter Terraform variables within your CI/CD pipeline
terraform init -backend-config=bucket=TERRAFORM_STATE_BUCKET -backend-config=key=TERRAFORM_STATE_KEY -backend-config=region=TERRAFORM_STATE_REGION
terraform workspace new dev
terraform plan
terraform apply

AWS IAM policies

For least privilege access control, example AWS IAM policies are provided:

adding new checks

  • create a new subdirectory within the terraform-modules/lambda/code directory
  • add Python code file with same name as the subdirectory
  • add the name of the file without extension to var.lambdas in variables.tf
  • add a subdirectory within the terraform-modules/lambda/build directory, following the existing naming pattern
  • add a .gitkeep file into the new directory
  • update the .gitignore file following the pattern of existing directories
  • apply Terraform

adding notifications to extra Slack channels

  • add an extra channel to your slack_channels variable list
  • add an extra webhook URL or repeat the same webhook URL to your slack_webhook_urls variable list
  • apply Terraform

testing

  • use multiple Terraform workspace environments, e.g. dev, prd
  • use the slack_channels_dev variable for your dev environment to notify a test Slack channel
  • for new subdomain takeover categories, create correctly configured and vulnerable domain names in Route53
  • minimise the risk of malicious takeover by using a test domain, with domain names which are hard to enumerate
  • remove any vulnerable domains as soon as possible

ci/cd

  • infrastructure has been deployed using CircleCI
  • environment variables to be entered in CircleCI project settings:
ENVIRONMENT VARIABLE EXAMPLE VALUE / COMMENT
AWS_ACCESS_KEY_ID using domain-protect deploy policy
AWS_SECRET_ACCESS_KEY
TERRAFORM_STATE_BUCKET tfstate48903
TERRAFORM_STATE_KEY domain-protect
TERRAFORM_STATE_REGION us-east-1
TF_VAR_org_primary_account 012345678901
TF_VAR_security_audit_role_name not needed if “domain-protect-audit” used
TF_VAR_external_id only required if External ID is configured
TF_VAR_slack_channels [“security-alerts”]
TF_VAR_slack_channels_dev [“security-alerts-dev”]
TF_VAR_slack_webhook_urls [“https://hooks.slack.com/services/XXX/XXX/XXX“]
  • to validate an updated CircleCI configuration:
docker run -v `pwd`:/whatever circleci/circleci-cli circleci config validate /whatever/.circleci/config.yml

limitations

  • this tool cannot guarantee 100% protection against subdomain takeover
  • it currently only scans Amazon Route53, and only checks a limited number of takeover types
  • vulnerable domains in Google Cloud DNS can be detected by Domain Protect for GCP

OnGaSHB3eUI

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