Creating an IAM role to allow Amazon Neptune to access Amazon S3 resources
Use the AmazonS3ReadOnlyAccess managed IAM policy to create a new
      IAM role that will allow Amazon Neptune access to Amazon S3 resources.
To create a new IAM role that allows Neptune access to Amazon S3
- Open the IAM console at https://console.amazonaws.cn/iam/ - . 
- In the navigation pane, choose Roles. 
- Choose Create role. 
- Under Amazon service, choose S3. 
- Choose Next: Permissions. 
- 
        Use the filter box to filter by the term S3 and check the box next to AmazonS3ReadOnlyAccess. NoteThis policy grants s3:Get*ands3:List*permissions to all buckets. Later steps restrict access to the role using the trust policy.The loader only requires s3:Get*ands3:List*permissions to the bucket you are loading from, so you can also restrict these permissions by the Amazon S3 resource.If your S3 bucket is encrypted, you need to add kms:Decryptpermissions
- Choose Next: Review. 
- Set Role Name to a name for your IAM role, for example: - NeptuneLoadFromS3. You can also add an optional Role Description value, such as "Allows Neptune to access Amazon S3 resources on your behalf."
- Choose Create Role. 
- In the navigation pane, choose Roles. 
- In the Search field, enter the name of the role you created, and choose the role when it appears in the list. 
- On the Trust Relationships tab, choose Edit trust relationship. 
- 
        In the text field, paste the following trust policy. 
- Choose Update trust policy. 
- Complete the steps in Adding the IAM Role to an Amazon Neptune Cluster.