Granting your app access to S3

cors.xml

<?xml version="1.0" encoding="UTF-8"?>
<CORSConfiguration xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
    <CORSRule>
        <AllowedOrigin>*</AllowedOrigin>
        <AllowedMethod>GET</AllowedMethod>
        <MaxAgeSeconds>3000</MaxAgeSeconds>
        <AllowedHeader>*</AllowedHeader>
    </CORSRule>
</CORSConfiguration>

policy.json

{
	"Id": "GrantAppAccess",
	"Statement": [
		{
			"Sid": "AppObjects",
			"Effect": "Allow",
			"Principal": {
				"AWS": "[USER ARN]"
			},
			"Action": [
				"s3:GetObjectAcl",
				"s3:GetObject",
				"s3:PutObject",
				"s3:DeleteObject"
			],
			"Resource": "arn:aws:s3:::[BUCKET NAME]/*"
		},
		{
			"Sid": "AppBucket",
			"Effect": "Allow",
			"Principal": {
				"AWS": "[USER ARN]"
			},
			"Action": [
				"s3:ListBucket"
			],
			"Resource": "arn:aws:s3:::[BUCKET NAME]"
		},
		{
			"Sid": "AnonymousObjects",
			"Effect": "Allow",
			"Principal": "*",
			"Action": "s3:GetObject",
			"Resource": "arn:aws:s3:::[BUCKET NAME]/*"
		}
	]
}