Security of WHM backups to an AWS S3 bucket

When you give your Web Hosting Manager (WHM) the ability to send a copy of your backup to Amazon’s AWS S3 service, you have to hand it a Key and Secret that give it that permission.

The worst option is to hand over a Secret and Key related to your own log in.

The best is to:

1. Create a policy which
   • Only gives access to a single bucket
   • Only allows the least access required for the task
   • Only allows connections from trusted IP addresses
2. Create a Group to connect the policy to
3. Create a user (for the WHM) to connect to the group

For validation of connection to S3 WHM currently requires the ability to write objects, list all objects in a bucket, delete objects. Now for some this is frustratingly more than you want to hand over. In theory WHM could make do with just the ability to write to the bucket, but at the moment we have to make all those abilities available.

Luckily, the fact we’re also limiting by IP and then Secret and Key—which WHM encrypts when you submit them—should make it highly unlikely anybody else will be able to abuse the ability to delete objects.

Here is the example policy that I have in place. Feel free to copy, personalise and use:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "WHMBackupAccess",
            "Effect": "Allow",
            "Action": [
                "s3:PutObject",
                "s3:GetObject",
                "s3:ListBucket",
                "s3:DeleteObject"
            ],
            "Resource": [
                "arn:aws:s3:::YOUR_BUCKET_NAME",
                "arn:aws:s3:::YOUR_BUCKET_NAME/*"
            ],
            "Condition": {
                "IpAddress": {
                    "aws:SourceIp": "YOUR_SERVER_IP/32"
                }
            }
        }    
    ]
}

If you’re in need of help putting this all together, let me know and I might expand this post to include how to do the setup inside WHM and the AWS console.