Eliminate dangling elastic IPs by performing analysis on your resources within all your AWS accounts.
Project description
Table of Contents
dnsdefender
Eliminate dangling elastic IPs by performing analysis on your resources within all your AWS accounts.
dnsdefender obtains all the DNS records present in all of your AWS accounts (Route53), and can optionally take in records via CSV input, or via Cloudflare.
After these records are collected, dnsdefender iterates through all of your AWS Elastic IPs and Network Interface Public IPs and collects this data.
By having a complete picture of the DNS records (from route53, file input or cloudflare) and having a complete picture of the AWS IPs owned by your organization, this tool can detect subdomains that are pointing to dangling elastic IPs (IPs you no longer own).
The problem
When you are deploying infrastructure to AWS, you may spin up EC2 instances which have an IP associated with them. When you create DNS records pointing to these IPs, but forget to remove the DNS records after the EC2 instance has been given a new IP or destroyed, you are susceptible to subdomain takeover attacks.
There has been a great amount of research done on elastic IP takeovers, where it is possible for attackers to continually claim elastic IPs until they obtain an IP associated with a subdomain of the company they are targeting.
While AWS frequently bans accounts that are attempting to perform this attack pattern, no long term fix has been released by AWS.
The impact of dangling elastic IP subdomain takeover attacks are more serious than a typical subdomain takeover where you can only control the content being served. With dangling elastic IP takeovers, it is possible for an attacker to do the following:
Claim SSL certificates for the subdomain
Listen for traffic on all ports (potentially discovering sensitive information still being sent to the subdomain)
Run server-side scripts with the ability to steal HTTPOnly cookies, typically leading to a one-click account takeover attack when cookies are scoped to *.domain.com
Project Features
Dynamically iterates through each AWS profile configured in .aws/config
Pulls A records from AWS Route53
Pulls A records from Cloudflare (optional)
Pulls A records from CSV input (optional)
Iterate through all regions, a single region, or a comma delimitted list of regions
Obtains all Elastic IPs associated with all of your AWS accounts
Obtains all Public IPs associated with all of your AWS accounts
Cross checks the DNS records, with IPs owned by your organization to detect potential takeovers
Slack Webhook support to send notifications of takeovers
Important:
In order for this tool to be effective, it must have a complete picture of your AWS environment. If it does not have a complete picture, it will lead to false positive findings.
Installing dnsdefender
Installing dnsdefender is as simple as running: pip install dnsdefender. The CLI tool will then be accessible via the dnsdefender command.
This requires a Python 3.x environment.
Using dnsdefender
❯ dnsdefender scan aws --help Usage: dnsdefender scan aws [OPTIONS] Scan for dangling elastic IPs inside your AWS accounts. Options: --profile TEXT Specify a specific AWS profile to run dnsdefender on. --skipascii Skip printing the ASCII art when starting up dnsdefender. --json Only return a JSON object. --slackwebhook TEXT Specify a Slack webhook URL to send notifications about potential takeovers. --records PATH Manually specify DNS records to check against. dnsdefender will check these IPs after checking retrieved DNS records. See records.csv for an example. --whitelist PATH Specify filepath having list of IPs to whitelist -- zones TEXT Comma delimited list of zones to run on. -- olddnsentries PATH Specify filepath having list of old DNS entries to check against. --cloudflaretoken TEXT Pull DNS records from Cloudflare, provide a CF API token. --allregions Run on all regions. --exclude TEXT Comma delimited list of profile names to exclude. --regions TEXT Comma delimited list of regions to run on. --help Show this message and exit.
Example Commands
Run dnsdefender with access to Cloudflare DNS records, send notifications to a Slack webhook, iterate through every AWS profile configured in .aws/config or .aws/credentials for all AWS regions
❯ dnsdefender scan aws --cloudflaretoken APIKEY --slackwebhook https://hooks.slack.com/services/KEY --allregions
Run dnsdefender with a manually input list of subdomain A records (see records.csv in this repo for example file):
❯ dnsdefender scan aws --records records.csv
You can specify specific regions using --regions set to a comma delimited list of regions i.e. us-east-1,us-west-1.
Example Output
❯ dnsdefender scan aws --cloudflaretoken whougonnacall Obtaining all zone names from Cloudflare. Obtaining DNS A records for all zones from Cloudflare. Obtained 33 DNS A records so far. Obtaining Route53 hosted zones for AWS profile: default. Obtaining Route53 hosted zones for AWS profile: account-five. Obtaining Route53 hosted zones for AWS profile: account-four. Obtaining Route53 hosted zones for AWS profile: account-four-deploy. Obtaining Route53 hosted zones for AWS profile: account-two-deploy. Obtaining Route53 hosted zones for AWS profile: account-one-deploy. Obtaining Route53 hosted zones for AWS profile: account-three-deploy. Obtaining Route53 hosted zones for AWS profile: account-six. Obtaining Route53 hosted zones for AWS profile: account-seven. Obtaining Route53 hosted zones for AWS profile: account-one. Obtained 124 DNS A records so far. Obtaining EIPs for region: us-east-1, profile: default Obtaining IPs for network interfaces for region: us-east-1, profile: default Obtaining EIPs for region: us-east-1, profile: account-five Obtaining IPs for network interfaces for region: us-east-1, profile: account-five Obtaining EIPs for region: us-east-1, profile: account-four Obtaining IPs for network interfaces for region: us-east-1, profile: account-four Obtaining EIPs for region: us-east-1, profile: account-four-deploy Obtaining IPs for network interfaces for region: us-east-1, profile: account-four-deploy Obtaining EIPs for region: us-east-1, profile: account-two-deploy Obtaining IPs for network interfaces for region: us-east-1, profile: account-two-deploy Obtaining EIPs for region: us-east-1, profile: account-one-deploy Obtaining IPs for network interfaces for region: us-east-1, profile: account-one-deploy Obtaining EIPs for region: us-east-1, profile: account-three-deploy Obtaining IPs for network interfaces for region: us-east-1, profile: account-three-deploy Obtaining EIPs for region: us-east-1, profile: account-six Obtaining IPs for network interfaces for region: us-east-1, profile: account-six Obtaining EIPs for region: us-east-1, profile: account-seven Obtaining IPs for network interfaces for region: us-east-1, profile: account-seven Obtaining EIPs for region: us-east-1, profile: account-one Obtaining IPs for network interfaces for region: us-east-1, profile: account-one Obtained 415 unique elastic IPs from AWS. Takeover possible: {'name': 'takeover.assetnotecloud.com', 'records': ['52.54.24.193']}
Setting up your AWS accounts
The first step is creating keys or roles in your AWS accounts that grant the privileges necessary to read Route53 records and describe elastic addresses and EC2 network interfaces.
To create a new IAM user in AWS, visit the following URL: https://console.aws.amazon.com/iam/home#/users$new?step=details
Choose Access key - Programmatic access only, and click Next: Permissions.
Click Attach existing policies directly and then click Create policy.
Click JSON and then paste in the following policy:
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "dnsdefenderPolicy",
"Effect": "Allow",
"Action": [
"ec2:DescribeAddresses",
"ec2:DescribeNetworkInterfaces",
"route53:ListResourceRecordSets",
"route53:ListHostedZonesByName",
"route53:GetTrafficPolicyInstance",
"route53:GetTrafficPolicy"
],
"Resource": "*"
}
]
}
Click Next: Tags and then Next: Review.
Set the name of the policy to be dnsdefenderPolicy.
Click Create Policy.
Go to https://console.aws.amazon.com/iam/home#/users$new?step=permissions&accessKey&userNames=dnsdefender&permissionType=policies
Select dnsdefenderPolicy.
Click Next: Tags and then Next: Review.
Click on Create user and setup the AWS credentials in your .aws/credentials file.
Repeat the above steps for each AWS account you own.
This tool will work with however you’ve setup your AWS configuration (multiple keys, or cross-account assume role profiles). This is managed by boto3, the library used to interface with AWS.
An example configuration looks like this:
.aws/credentials:
[default] aws_access_key_id = AKIAIII... aws_secret_access_key = faAaAaA...
.aws/config:
[default] output = table region = us-east-1 [profile account-one] role_arn = arn:aws:iam::911111111113:role/Ec2Route53Access source_profile = default region = us-east-1 [profile account-two] role_arn = arn:aws:iam::911111111112:role/Ec2Route53Access source_profile = default region = us-east-1 [profile account-three] region = us-east-1 role_arn = arn:aws:iam::911111111111:role/Ec2Route53Access source_profile = default
Alternatively, instead of having roles which are assumed, you can also configure the .aws/credentials file to have a list of profiles and assocaited keys with scoped access.
Once your AWS configuration has been set with all the accounts in your AWS environment, you can then run the tool using the following command:
Setting up your AWS permissions for –roles
dnsdefender can use roles instead of profiles which removes the need of having so many credentials at one place. However, roles approach will require creating additional IAM policies within you organisation.
Roles can be used via --roles roles.csv or --autoroles flags. To setup --roles to work, one needs to create dnsdefenderTargetAccountRole role named exactly like that in every account that is being scanned:
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "dnsdefenderTargetAccountRole",
"Effect": "Allow",
"Action": [
"ec2:DescribeAddresses",
"ec2:DescribeNetworkInterfaces",
"route53:ListResourceRecordSets",
"route53:ListHostedZonesByName",
"route53:GetTrafficPolicyInstance",
"route53:GetTrafficPolicy"
],
"Resource": "*"
}
]
}
The dnsdefender will be running in lambda/ec2/whatever with dnsdefender role - let’s call it dnsdefender master role. The master role must be able to assume TargetAccountRoles.
resource "aws_iam_policy" "dnsdefender_target_account_roles" {
name = "dnsdefender_target_account_roles"
path = "/"
description = "Allow inspecting DNS and elastic IP data."
policy = jsonencode({
"Version" : "2012-10-17",
"Statement" : [
{
"Effect" : "Allow",
"Action" : "sts:AssumeRole",
"Resource" : ["arn:aws:iam::*:role/dnsdefenderTargetAccountRole"]
}]
})
tags = {
Project = "dnsdefender"
}
}
Setting up your AWS permissions for –autoroles
Automatic account discovery requires additional permission compared to –roles. After setting up –roles to work, consider adding following IAM policy in an account that has organisation overview:
{
sid = "BaseAccess"
actions = [
"organizations:DescribeAccount",
"organizations:ListAccounts"
]
resources = ["*"]
effect = "Allow"
}
}
Then, in the account that is running dnsdefender, attach following policy to dnsdefender master role so it can assume the organisation lookup role:
{
"Version" : "2012-10-17",
"Statement" : [
{
"Effect" : "Allow",
"Action" : "sts:AssumeRole",
"Resource" : ["arn:aws:iam::ORG_LOOKUP_ACCOUNT_ID:role/ta-application-security-prd-dnsdefender-org-role"]
}]
}
Don’t forget to replace ORG_LOOKUP_ACCOUNT_ID with actual account ID.
Setting up Cloudflare (Optional)
If you want dnsdefender to pull in all the A records that you have set in Cloudflare, you will have to setup an API token that can read zones.
https://dash.cloudflare.com/profile/api-tokens
Setup a Cloudflare API token like shown in the screenshot below:
Once you have obtained this API token, make a note of it somewhere (password manager). In order to use it with dnsdefender, pass it in via the cloudflaretoken argument.
Testing dnsdefenders
Clone this repo.
Install virtualenv using pip3 install virtualenv
Create a virtual environment using virtualenv venv
Activate virtual environment using . venv/bin/activate
Install dnsdefender by going to root of repo. pip3 install --editable .
Make your changes and run the dnsdefender command.
Project details
Release history Release notifications | RSS feed
Download files
Download the file for your platform. If you're not sure which to choose, learn more about installing packages.
Source Distribution
Built Distribution
Hashes for dnsdefender-1.0.3-py3-none-any.whl
Algorithm | Hash digest | |
---|---|---|
SHA256 | a60392ad6bf3a52e86a5f1c92c2d44aa6794196d44d7c058fbdd5f7bfbf7fe15 |
|
MD5 | 71593c8f5183265868c9223916fd39b8 |
|
BLAKE2b-256 | 27c0f8c944eab031cb2a8e22a1596a885903817be049a46a07097d2688dc472c |