Class: Rack::Facebook::MethodFix

Inherits:
Object
  • Object
show all
Defined in:
lib/rack/facebook/method-fix.rb

Instance Method Summary collapse

Constructor Details

#initialize(app, settings = {}) ⇒ MethodFix

Returns a new instance of MethodFix.



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# File 'lib/rack/facebook/method-fix.rb', line 5

def initialize(app, settings={})
  @app = app
  @settings = settings
end

Instance Method Details

#call(env) ⇒ Object 



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# File 'lib/rack/facebook/method-fix.rb', line 10

def call(env)
  unless env_excluded?(env)
    if env["REQUEST_METHOD"] == "POST"
      request = Request.new(env)
      if @settings[:secret_id] && request.params["signed_request"]
        env["REQUEST_METHOD"] = "GET" if signed_request_valid?(@settings[:secret_id], request)
      else
        env["REQUEST_METHOD"] = "GET" if request.params["signed_request"]
      end
    end
  end
  @app.call(env)
end

#signed_request_valid?(secret_id, request) ⇒ Boolean

Code adapted from github.com/nsanta/fbgraph

Returns:

  • (Boolean) 


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# File 'lib/rack/facebook/method-fix.rb', line 25

def signed_request_valid?(secret_id, request)
  encoded_signature, payload = request.params["signed_request"].split(".", 2)
  signature = ""
  valid = true

  url_decode_64(encoded_signature).each_byte do |byte|
    signature << "%02x" % byte
  end

  data = JSON.parse(url_decode_64(payload))
  if data["algorithm"].to_s.upcase != "HMAC-SHA256"
    valid = false
  end

  expected_signature = OpenSSL::HMAC.hexdigest("sha256", secret_id, payload)
  if expected_signature != signature
    valid = false
  end

  valid
end

#url_decode_64(string) ⇒ Object 



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# File 'lib/rack/facebook/method-fix.rb', line 47

def url_decode_64(string)
  encoded_string = string.gsub("-", "+").gsub("_", "/")
  encoded_string += "=" while !(encoded_string.size % 4).zero?
  Base64.decode64(encoded_string)
end