# Cross-service confused deputy prevention
<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) global condition context key in resource policies to limit the permissions that Amazon Q Business gives another service to the resource.

The value of `aws:SourceArn` must be `qbusiness::Application`.

The following example—which grants Amazon Q Business permission to perform a decryption action on an AWS KMS key within the scope of an Amazon Q Business application—shows how you can use the `aws:SourceArn` global condition context key in Amazon Q Business to prevent the confused deputy problem.

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#### [ JSON ]

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```
{
    "Version":"2012-10-17",		 	 	 
    "Statement": {
        "Sid": "ConfusedDeputyPreventionExamplePolicy",
        "Effect": "Allow",
        "Principal": {
            "Service": "qbusiness.amazonaws.com"
        },
        "Action": "kms:Decrypt",
        "Resource": [
            "arn:aws:qbusiness:us-east-1:111122223333:application/application-id/*"
        ],
        "Condition": {
            "ArnLike": {
                "aws:SourceArn": "arn:aws:qbusiness:us-east-1:111122223333:application/*"
            }
        }
    }
}
```

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