Class: AwsProductSign

Inherits:
Object
  • Object
show all
Defined in:
lib/aws_product_sign.rb

Overview

Then you can go on to use those new params in rails url_for or the URI

builder of your choice. Values are not URI-escaped yet. Or mutate the
params passsed in with #add_signature! instead. 

Returning a new params hash, leaving your input untouched:

query_string_component = aws_signer.add_signature( params )

Or mutate your input:
aws_signer.add_signature!(params)

At the moment this class can’t handle a query string where you need the same key twice. I don’t think the AWS service ever uses that though?

This class also assumes a GET request.

Instance Method Summary collapse

Constructor Details

#initialize(options = {}) ⇒ AwsProductSign

Returns a new instance of AwsProductSign.

Raises:

  • (Exception) 


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# File 'lib/aws_product_sign.rb', line 51

def initialize(options = {})
  @secret_key = options[:secret_key]
  raise Exception.new("You must supply a :secret_key") unless @secret_key
  @access_key = options[:access_key]
end

Instance Method Details

#access_key ⇒ Object 



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# File 'lib/aws_product_sign.rb', line 139

def access_key
  return @access_key
end

#access_key=(a) ⇒ Object 



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# File 'lib/aws_product_sign.rb', line 142

def access_key=(a)
  @access_key = a
end

#add_signature(params) ⇒ Object

Pass in a hash representing params for a query string.

param keys should be strings, not symbols please. Will return a param with the “Signature” key/value added, without modifying original.



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# File 'lib/aws_product_sign.rb', line 65

def add_signature(params)
  # Make a copy to not modify original  
  add_signature!( Hash[params]  )
end

#add_signature!(params) ⇒ Object

Like #add_signature, but will mutate the hash passed in, adding a “Signature” key/value to hash passed in, and return hash too.



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# File 'lib/aws_product_sign.rb', line 73

def add_signature!(params)
  
  # supply timestamp and access key if not already provided
  params["Timestamp"] ||= Time.now.iso8601
  params["AWSAccessKeyId"] ||= access_key
  # Existing "Signature"? That's gotta go before we generate a new
  # signature and add it. 
  params.delete("Signature")

  query_string = canonical_querystring(params)

  string_to_sign = string_to_sign(query_string)
  
  # chomp is important!  the base64 encoded version will have a newline at the end
  # which amazon does not want. 
  digest  = OpenSSL::Digest.new('sha256')
  signature = Base64.encode64(OpenSSL::HMAC.digest(digest, secret_key, string_to_sign)).chomp
  
  params["Signature"] = signature

  #order doesn't matter for the actual request, we return the hash
  #and let client turn it into a url.
  return params
end

#canonical_querystring(params) ⇒ Object

param keys should be strings, not symbols please. return a string joined by & in canonical order.



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# File 'lib/aws_product_sign.rb', line 107

def canonical_querystring(params)
  # I hope this built-in sort sorts by byte order, that's what's required. 
  values = params.keys.sort.collect {|key|  [url_encode(key), url_encode(params[key].to_s)].join("=") }
  
  return values.join("&")
end

#hash_to_query(hash) ⇒ Object

Turns a hash into a query string, returns the query string. url-encodes everything to Amazon’s specifications.



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# File 'lib/aws_product_sign.rb', line 128

def hash_to_query(hash)
  hash.collect do |key, value|
    
    url_encode(key) + "=" + url_encode(value)
  
  end.join("&")
end

#query_with_signature(hash) ⇒ Object 



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# File 'lib/aws_product_sign.rb', line 57

def query_with_signature(hash)
  return hash_to_query( add_signature(hash)  )
end

#secret_key ⇒ Object 



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# File 'lib/aws_product_sign.rb', line 136

def secret_key
  return @secret_key
end

#string_to_sign(query_string, options = {}) ⇒ Object 



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# File 'lib/aws_product_sign.rb', line 114

def string_to_sign(query_string, options = {})
  options[:verb] = "GET"
  options[:request_uri] = "/onca/xml"
  options[:host] = "webservices.amazon.com"

  
  return options[:verb] + "\n" + 
      options[:host].downcase + "\n" +
      options[:request_uri] + "\n" +
      query_string
end

#url_encode(string) ⇒ Object

Insist on specific method of URL encoding, RFC3986.



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# File 'lib/aws_product_sign.rb', line 99

def url_encode(string)
  # It's kinda like CGI.escape, except CGI.escape is encoding a tilde when
  # it ought not to be, so we turn it back. Also space NEEDS to be %20 not +.
  return CGI.escape(string).gsub("%7E", "~").gsub("+", "%20")
end