About signed URL's in Amazon S3

So I have been reading about signed URL's and some of its benefits. Especially the part about hot linking. Our app doesn't allow users to embed media (photo, video, audio) from our site. So signed URL's looks like the right direction. Mostly to prevent hotlinking.

So now that I know my requirements. I have a few questions.

1. Does this mean I have to add a policy to my bucket, denying read-write access to any of the files or folders in the bucket?
2. Do I have to create signed URL's for each page visit? So let's say 100 users visit the same page where the song can be played. Does this mean I have to create 100 signed URL's?
3. Creating S3 signed URL's are free?

Touching on point #2. Is it normal practice for Amazon S3 to create several signed 开发者_StackOverflow中文版URL's? I mean what happens if 1,000 users end up coming to the same song page..

Your thoughts?

REFERENCE:

For anyone interested on how I was able to generate signed url's. Based on https://github.com/appoxy/aws gem and the docs at http://rubydoc.info/gems/aws/2.4.5/frames :

s3 = Aws::S3.new(APP_CONFIG['amazon_access_key_id'], APP_CONFIG['amazon_secret_access_key'])
bucket_gen = Aws::S3Generator::Bucket.create(s3, 'bucket_name')
signed_url = bucket_gen.get(URI.unescape(URI.parse(URI.escape('http://bucket_name.s3.amazonaws.com/uploads/foobar.mp3')).path[1..-1]), 1.hour)

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1. By default, your bucket will be set to private. When you upload files to S3, you can set the ACL (permissions) - in your case, you'll want to make sure the files are private.

2. The simplest solution is to create new signed urls for each visitor. You could do something like generate new urls everyday, store them somewhere, and then use those but that adds complexity for little benefit. The one place where you might need this though is too enable client side caching. Everytime you create a new url, the browser sees it as a different file and will download a fresh copy. If this isn't the behaviour you want, you need to generate urls that expire far in the future and reuse those - but that will reduce the effectiveness of preventing hotlinking.

3. Yes, generating urls are free. They are generated on the client and don't touch S3. I suppose there is a time/processing cost, but I have created pages with hundreds of urls that are generated on each visit and have not noticed any performance issues.