Module: Rack::Pubcookie::DES

Included in:
Auth
Defined in:
lib/rack/pubcookie/des.rb

Instance Method Summary collapse

Instance Method Details

#des_decrypt(bytes, index1, index2) ⇒ Object 



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# File 'lib/rack/pubcookie/des.rb', line 5

def des_decrypt bytes, index1, index2
  # In the URL of #extract_username, the initial IVEC is defined around
  # line 63 and for some reason only the first byte is used in the xor'ing
  ivec = @key[index2, 8]
  ivec = ivec.map{ |i| i ^ 0x4c }

  key = @key[index1, 8]

  c  = OpenSSL::Cipher.new('des-cfb')
  c.decrypt
  c.key = key.pack('c*')
  c.iv  = ivec.pack('c*')

  # This should be offset by the size of the granting key? Not sure...
  signature = c.update(bytes[0..127].pack('c*'))
  decrypted = c.update(bytes[128..-1].pack('c*'))

  if @granting.public_key.verify(OpenSSL::Digest::MD5.new, signature, decrypted)
    decrypted
  else
    nil
  end
end