Bucket policy to allow Cognito user in User Pool access to S3 bucket

Question

I am trying to add a bucket policy to my bucket because my bucket is in a root aws account, and I want to restricts other users, roles, etc. under the root account from accessing my bucket except for a specific Cognito user in my User Pool.

I do not want to also use an identity pool -- I would just like to refer to the Cognito user as the principal in my bucket policy. Is there any way to do this without using an identity pool? I can't find any example policies that do this.

Answer 1

You can set the Principle of your bucket policy as the auth role of your Cognito user. In my case, the Principle looks like

"Principal": {
    "AWS": "arn:aws:iam::123456789000:role/NAME_OF_MY-authRole"
},

Then, you can further control the access by changing the Resource. Here is the example from AWS docs .

"arn:aws:s3:::bucket-name/cognito/application-name/${cognito-identity.amazonaws.com:sub}",
                "arn:aws:s3:::bucket-name/cognito/application-name/${cognito-identity.amazonaws.com:sub}/*"