Cross-service confused deputy prevention

The confused deputy problem is a security issue where an entity that doesn't have permission to perform an action can coerce a more-privileged entity to perform the action. In AWS, cross-service impersonation can result in the confused deputy problem. Cross-service impersonation can occur when one service (the calling service) calls another service (the called service). The calling service can be manipulated to use its permissions to act on another customer's resources in a way it should not otherwise have permission to access. To prevent this, AWS provides tools that help you protect your data for all services with service principals that have been given access to resources in your account.

We recommend using the aws:SourceArn and aws:SourceAccount global condition context keys in resource policies to limit the permissions that Amazon Lookout for Metrics gives another service to the resource. If you use both global condition context keys, the aws:SourceAccount value and the account in the aws:SourceArn value must use the same account ID when used in the same policy statement.

The most effective way to protect against the confused deputy problem is to use the aws:SourceArn global condition context key with the full ARN of the resource. If you don't know the full ARN of the resource or if you are specifying multiple resources, use the aws:SourceArn global context condition key with wildcards (*) for the unknown portions of the ARN. For example, arn:aws:servicename::123456789012:*.

The following example shows how you can use the aws:SourceArn and aws:SourceAccount global condition context keys in Amazon SageMaker AI secret policies to prevent the confused deputy problem.

When you create a dataset in the console, or call the GetSampleData API operation directly, the trust policy can't refer to a specific resource. For existing detectors, you can specify the ARN of the detector.

Setting up a dataset

When you set up an Amazon S3 dataset, the console uses the service role that you provide to read sample data from the source bucket. For this operation, there isn't a specific resource to use for SourceArn. During setup, you can use a trust policy like the following, with a wildcard (*) for the SourceArn resource.

{
  "Version": "2012-10-17",
  "Statement": {
    "Effect": "Allow",
    "Principal": {
      "Service": "lookoutmetrics.amazonaws.com"
    },
    "Action": "sts:AssumeRole",
    "Condition": {
      "ArnLike": {
        "aws:SourceArn": "arn:aws:lookoutmetrics:us-east-2:123456789012:*"
      },
      "StringEquals": {
        "aws:SourceAccount": "123456789012"
      }
    }
  }
}

Replace the region name and account ID with yours. After you've created the detector, you can replace the ARN with that of the detector. If you call the GetSampleData API operation directly, consider creating a separate service role specifically for that task.

Updating the trust policy after setup

After setup, you can update the trust policy to refer to a specific detector ARN.

{
  "Version": "2012-10-17",
  "Statement": {
    "Effect": "Allow",
    "Principal": {
      "Service": "lookoutmetrics.amazonaws.com"
    },
    "Action": "sts:AssumeRole",
    "Condition": {
      "ArnLike": {
        "aws:SourceArn": "arn:aws:lookoutmetrics:us-east-2:123456789012:AnomalyDetector:my-detector"
      },
      "StringEquals": {
        "aws:SourceAccount": "123456789012"
      }
    }
  }
}