I\'m following Hartl\'s railstutorial.org and have arrived at 11.4.4: Image upload in production. What I\'ve done:
The root of the problem indeed turned out to be the permissions. It was necessary to write a custom policy and set the CORS configuration on the bucket. For any future users that want to implement this chapter of the rails tutorial, see Writing an IAM policy and CORS configuration for Amazon S3 for the necessary code.