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)


51
52
53
54
55
# 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_keyObject



139
140
141
# File 'lib/aws_product_sign.rb', line 139

def access_key
  return @access_key
end

#access_key=(a) ⇒ Object



142
143
144
# 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.



65
66
67
68
# 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.



73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
# 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.



107
108
109
110
111
112
# 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.



128
129
130
131
132
133
134
# 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



57
58
59
# File 'lib/aws_product_sign.rb', line 57

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

#secret_keyObject



136
137
138
# File 'lib/aws_product_sign.rb', line 136

def secret_key
  return @secret_key
end

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



114
115
116
117
118
119
120
121
122
123
124
# 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.



99
100
101
102
103
# 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