awskillswitch

AWS Kill Switch

AWS Kill Switch is a Lambda function (and proof of concept client) that an organization can implement in a dedicated "Security" account to give their security engineers the ability to quickly deploy restrictions during a security incident, including:

• Apply a service control policy (SCP) to freeze the state of a targeted account
• Detach all policies and delete inline policies from a targeted IAM role
• Revoke all sessions on a targeted IAM role or ALL customer managed IAM roles in a targeted account
• Delete a targeted IAM role (which also revokes all sessions)

Prerequisites

• Go

Tested on go1.21.3 on arm64.

Preparation

This tool requires you to have roles that you can assume from a dedicated "Security" account to your organization management account (apply_scp) or to any account in your organization (actions other than apply_scp). You can use AWS CloudFormation StackSets to automate the creation of these roles.

Required permissions

Prevent tampering

You should take steps to ensure that a threat actor cannot make modifications to the IAM role that you plan to assume during a security incident. Consider implementing a SCP like:

{    
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "DenyAccessToASpecificRole",
      "Effect": "Deny",
      "Action": [
        "iam:AttachRolePolicy",
        "iam:DeleteRole",
        "iam:DeleteRolePermissionsBoundary",
        "iam:DeleteRolePolicy",
        "iam:DetachRolePolicy",
        "iam:PutRolePermissionsBoundary",
        "iam:PutRolePolicy",
        "iam:UpdateAssumeRolePolicy",
        "iam:UpdateRole",
        "iam:UpdateRoleDescription"
      ],
      "Resource": [
        "arn:aws:iam::*:role/security-role"
      ]
    }
  ]
}

This example assumes that you created a service managed StackSet in your organization that automatically creates security-role in every account. With this SCP the threat actor will be unable to tamper with your role or attached policies, even if they have elevated permissions that would otherwise allow manipulation of roles and policies.

Installation

Clone the Repository

git clone https://github.com/secengjeff/awskillswitch.git

Installing

⚠ Before creating the awskillswitch Lambda function review awskillswitch.go and consider modifying switch.conf to meet your organization's unique requirements. By default the apply_scp action will restrict most IAM actions on the account. This may break your application.

Follow these steps to build the awskillswitch Lambda function and zip the binary:

cd awskillswitch

GOOS="linux" GOARCH="amd64" go build -o main awskillswitch.go

zip main.zip main switch.conf

Create an execution role (execution_role.json):

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Service": "lambda.amazonaws.com"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}

Create a permission policy (permission_policy.json):

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": "sts:AssumeRole",
            "Resource": "arn:aws:iam::*:role/*"
        },
        {
            "Effect": "Allow",
            "Action": [
                "logs:CreateLogGroup",
                "logs:CreateLogStream",
                "logs:PutLogEvents"
            ],
            "Resource": "arn:aws:logs:*:*:*"
        }
    ]
}

Deploy the execution role, permission policy, and create the Lambda function:

aws iam create-role --role-name executionRole --assume-role-policy-document file://execution_role.json

aws iam put-role-policy --role-name executionRole --policy-name permissionPolicy --policy-document file://permission_policy.json

aws lambda create-function --function-name awskillswitch --zip-file fileb://main.zip --handler main --runtime go1.x --role executionRoleArn --timeout 15 --memory-size 128

You can test the function using the included proof of concept client. You can use this as a standalone application or as an example of how to invoke the client from within your own tooling and automation:

cd awskillswitch/client

go build -o killswitchclient killswitchclient.go

Usage

⚠ The actions you take with this tool are one-way operations. Do not test/experiment in production. Any SCPs applied or IAM roles deleted will remain in this state until manual action is taken to remove the SCP or recreate deleted role and/or policies. Ensure that you have the the ability to reverse these changes and incorporate the appropriate steps in your incident response playbooks.

Environment

You can run this client locally by manually setting AWS CLI environment variables AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, and AWS_SESSION_TOKEN (if applicable) for any IAM user or assumed role with a policy that allows lambda:InvokeFunction for the ARN of the function that you created. It will not function if you're assuming a role using the AWS_PROFILE variable. You can also run this client from an EC2 instance with an instance policy that allows lambda:InvokeFunction for the ARN of the function that you created.

Flags

• action: Specifies the action to perform. Valid values are apply_scp, detach_policies, revoke_sessions or delete_role.
• lambda: The name or ARN of the AWS Lambda function to invoke.
• target_account: The AWS Account ID where the action will take place.
• role_to_assume: The IAM role that will be assumed by the Lambda function to perform the action.
• target_role: The name of the IAM role to delete (required only for the detach_policies and delete_role actions). You may specify ALL when used with the revoke_sessions action to apply the action to all customer managed IAM roles in the targeted account. This does not affect the assumed role, which is skipped in the function's loop.
• org_management_account: The AWS Organization's management account ID (required only for the apply_scp action).
• region: The AWS region where the Lambda function is deployed (defaults to us-east-1 if none provided)

If you prefer to call the Lambda function directly your application will need to invokeLambda with one of the following payloads:

To apply a restrictive SCP:

{
  "action": "apply_scp",
  "target_account_id": "123456789012",
  "role_to_assume": "RoleToAssume",
  "org_management_account": "998877665544"
}

This call will apply the SCP defined by scpPolicy in switch.conf to the AWS account 123456789012 by assuming RoleToAssume in AWS account 998877665544.

To detach policies from an IAM role:

{
  "action": "detach_policies",
  "target_account_id": "210987654321",
  "role_to_assume": "RoleToAssume",
  "target_role_name": "RoleToDetach"
}

This call will detach IAM policies and delete inline IAM policies from RoleToDetach in AWS account 210987654321 by assuming RoleToAssume in the same account. Currently active session tokens will remain valid with all relevant permissions until expired.

To revoke sessions:

{
  "action": "revoke_sessions",
  "target_account_id": "210987654321",
  "role_to_assume": "RoleToAssume",
  "target_role_name": "RoleToRevokeSessions"
}

This call will apply a new policy that invalidates session tokens issued prior to the current time for RoleToRevokeSessions in AWS account 210987654321 by assuming RoleToAssume in the same account.

{
  "action": "revoke_sessions",
  "target_account_id": "210987654321",
  "role_to_assume": "RoleToAssume",
  "target_role_name": "ALL"
}

This call will apply a new policy that invalidates session tokens issued prior to the current time for all customer managed IAM roles in AWS account 210987654321 by assuming RoleToAssume in the same account.

To delete an IAM role:

{
  "action": "delete_role",
  "target_account_id": "210987654321",
  "role_to_assume": "RoleToAssume",
  "target_role_name": "RoleToDelete"
}

This call will delete the IAM role RoleToDelete in AWS account 210987654321 by assuming RoleToAssume in the same account. Deleting a role will invalidate all session tokens for that role.

Example

Applying a restrictive SCP

./awskillswitch -action apply_scp -lambda "LambdaArn" -target_account "123456789012" -role_to_assume "RoleToAssume" -org_management_account "998877665544" -region "us-east-1"

This command will apply the SCP defined by scpPolicy in switch.conf to the AWS account 123456789012 by assuming RoleToAssume in AWS account 998877665544 using the LambdaArn function deployed to us-east-1.

Detaching policies from an IAM role:

./awskillswitch -action detach_policies -lambda "LambdaArn" -target_account "210987654321" -role_to_assume "RoleToAssume" -target_role "RoleToDelete" -region "us-east-1"

This command will detach IAM policies and delete inline policies from RoleToDetach in AWS account 210987654321 by assuming RoleToAssume in the same account using the LambdaArn Lambda function deployed to us-east-1. Currently active session tokens will remain valid with all relevant permissions until expired.

Deleting an IAM role:

./awskillswitch -action delete_role -lambda "LambdaArn" -target_account "210987654321" -role_to_assume "RoleToAssume" -target_role "RoleToDelete" -region "us-east-1"

This command will delete the IAM role RoleToDelete in AWS account 210987654321 by assuming RoleToAssume in the same account using the LambdaArn Lambda function deployed to us-east-1. Deleting a role will invalidate all session tokens for that role.

Revoking sessions:

./awskillswitch -action revoke_sessions -lambda "LambdaArn" -target_account "210987654321" -role_to_assume "RoleToAssume" -target_role "RoleToRevokeSessions" -region "us-east-1"

This command will apply a new policy that invalidates session tokens issued prior to the current time for RoleToRevokeSessions in AWS account 210987654321 by assuming RoleToAssume in the same account using the LambdaArn Lambda function deployed to us-east-1.

./awskillswitch -action revoke_sessions -lambda "LambdaArn" -target_account "210987654321" -role_to_assume "RoleToAssume" -target_role "ALL" -region "us-east-1"

This command will apply a new policy that invalidates session tokens issued prior to the current time for all customer managed IAM roles in AWS account 210987654321 by assuming RoleToAssume in the same account using the LambdaArn Lambda function deployed to us-east-1.

Built With

• aws-sdk-go - AWS SDK

• aws-lambda-go - AWS Lambda libraries

Authors

• Jeffrey Lyon - Initial release - @secengjeff

See also the list of contributors

License

This project is licensed under the Apache License - see the LICENSE file for details