This is the Ruby code I use to test/validate S3 access policies.

simplest-s3-upload.rb

require 'fog'

connection = Fog::Storage.new({
  :provider                 => 'AWS',
  :aws_access_key_id        => 'access_key_id',
  :aws_secret_access_key    => 'secret_acces_key'
})

directory = connection.directories.get('bucket_name')

puts directory.to_s

file = directory.files.create ({:body => "test", :key => "test"})
puts file.to_s