AWSAccessKeyId not authorized - ruby-on-rails-4

Question

I am attempting to use a GET request to use the Amazon Mechanical Turk GetFileUploadURL function. However, I get this error code when attempting it.
AWS.NotAuthorized The identity contained in the request is not authorized to use this AWSAccessKeyId
This is the code I'm using to create the request.
now = DateTime.now
#For creating the signature hash
data = "AWSMechanicalTurkRequesterGetFileUploadURL" + now.to_s
sha256 = OpenSSL::Digest::SHA256.new
sig = OpenSSL::HMAC.digest(sha256, Rails.configuration.secret_key, data)
signature = Base64.encode64(sig)
puts "https://mechanicalturk.amazonaws.com", "/?Service=AWSMechanicalTurkRequester&AWSAccessKeyId=#{Rails.configuration.aws_key}&Version=2014-08-15&Operation=GetFileUploadURL&Signature=#{sig}&Timestamp=#{now}&AssignmentId=#{mturk_results[0][:AssignmentId]}&QuestionIdentifier=file1"
puts "\n\n"
uri = URI('https://mechanicalturk.amazonaws.com')
params = {:Service=>"AWSMechanicalTurkRequester", :AWSAccessKeyId=>Rails.configuration.aws_key, :Version=>"2014-08-15", :Operation=>"GetFileUPloadURL", :Signature=>sig, :Timestamp=>now, :AssignmentId=>mturk_results[0][:AssignmentId], :QuestionIdentifier=>"file1"}
uri.query = URI.encode_www_form(params)
res = 0
Net::HTTP.start(uri.host, uri.port,
:use_ssl => uri.scheme == 'https') do |http|
request = Net::HTTP::Get.new uri
res = http.request request # Net::HTTPResponse object
end
Any ideas as to what I'm doing wrong?

Answer 1

You'll need to format your TimeStamp correctly. The time stamp must be in UTC and in the following ISO 8601 format:
YYYYMMDD'T'HHMMSS'Z'. For example, 20150830T123600Z is a valid time stamp. Do not include milliseconds in the time stamp.
It needs to be of the form:
Timestamp=2016-04-23T08:00:05Z
While Ruby's DateTime.now method returns them of the form:
2016-08-05T10:43:27-07:00
You can read more about Timestamp and AWS signatures here:
http://docs.aws.amazon.com/general/latest/gr/sigv4-date-handling.html