# Prevent cross-service confused deputy problem
<a name="cross-service-confused-deputy-prevention"></a>

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 [https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_condition-keys.html#condition-keys-sourcearn](https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_condition-keys.html#condition-keys-sourcearn) and [https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_condition-keys.html#condition-keys-sourceaccount](https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_condition-keys.html#condition-keys-sourceaccount) global condition context keys in resource policies to limit the permissions that MSK Connect gives another service to the resource. If the `aws:SourceArn` value does not contain the account ID (for example, an Amazon S3 bucket ARN doesn't contain the account ID), you must use both global condition context keys to limit permissions. If you use both global condition context keys and the `aws:SourceArn` value contains the account ID, 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. Use `aws:SourceArn` if you want only one resource to be associated with the cross-service access. Use `aws:SourceAccount` if you want to allow any resource in that account to be associated with the cross-service use.

In the case of MSK Connect, the value of `aws:SourceArn` must be an MSK connector.

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:kafkaconnect:us-east-1:123456789012:connector/\$1* represents all connectors that belong to the account with ID 123456789012 in the US East (N. Virginia) Region.

The following example shows how you can use the `aws:SourceArn` and `aws:SourceAccount` global condition context keys in MSK Connect to prevent the confused deputy problem. Replace *123456789012* and arn:aws:kafkaconnect:*us-east-1*:*123456789012*:connector/*my-S3-Sink-Connector*/*abcd1234-5678-90ab-cdef-1234567890ab* with your AWS account and connector information.

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#### [ JSON ]

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```
{
  "Version":"2012-10-17",		 	 	 
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Service": " kafkaconnect.amazonaws.com"
      },
      "Action": "sts:AssumeRole",
      "Condition": {
        "StringEquals": {
          "aws:SourceAccount": "123456789012"
        },
        "ArnLike": {
        "aws:SourceArn": "arn:aws:kafkaconnect:us-east-1:123456789012:connector/my-S3-Sink-Connector/abcd1234-5678-90ab-cdef-1234567890ab"
        }
      }
    }   
  ]
}
```

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