Examples to limit confused deputy problem

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. For more details, see Cross-service confused deputy prevention.

The following example logging/invocation policy allows any server (and workflow) in the account to assume the role.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "AllowAllServersWithWorkflowAttached",
            "Effect": "Allow",
            "Principal": {
                "Service": "transfer.amazonaws.com"
            },
            "Action": "sts:AssumeRole",
            "Condition": {
                "StringEquals": {
                    "aws:SourceAccount": "account-id"
                },
                "ArnLike": {
                   "aws:SourceArn": [
                     "arn:aws:transfer:region:account-id:server/*",
                     "arn:aws:transfer:region:account-id:workflow/*"
                   ]
                }
            }
        }
    ]
}

The following example logging/invocation policy allows a specific server (and workflow) to assume the role.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "AllowSpecificServerWithWorkflowAttached",
            "Effect": "Allow",
            "Principal": {
                "Service": "transfer.amazonaws.com"
            },
            "Action": "sts:AssumeRole",
            "Condition": {
                "StringEquals": {
                    "aws:SourceAccount": "account-id"
                },
                "ArnEquals": {
                   "aws:SourceArn": [
                       "arn:aws:transfer:region:account-id:server/server-id",
                       "arn:aws:transfer:region:account-id:workflow/workflow-id"
                   ]
                }
            }
        }
    ]
}