S3 direct upload policy generator

generate-policy.rb

require 'base64'
require 'openssl'
require 'digest/sha1'

policy_document = '{"expiration": "2015-01-01T00:00:00Z",
  "conditions": [ 
    {"bucket": "BUCKET_NAME_HERE"}, 
    ["starts-with", "$key", "FOLDER_NAME_HERE/"],
    {"acl": "public-read"},
    ["starts-with", "$Content-Type", "image/"],
    ["content-length-range", 0, 2048576]
  ]
}'
aws_secret_key = 'SECRET_KEY_HERE'

policy = Base64.encode64(policy_document).gsub("\n","")

signature = Base64.encode64(
    OpenSSL::HMAC.digest(
        OpenSSL::Digest::Digest.new('sha1'), 
        aws_secret_key, policy)
    ).gsub("\n","")

puts ""
puts policy
puts ""
puts signature
puts ""