The Railsgoat application stores user's Social Security Numbers in plain-text within the database and because of this, it fails to adequately protect these numbers from theft. Additionally, the user's full SSN is sent back to the user within an HTTP response from the application.

The WorkInfo model (app/models/work_info.rb) is missing code to encrypt this data prior to storage. Additionally, while code exists to render only the last 4 numbers of an SSN (shown below), at no time is it used.

          # We should probably use this
          def last_four
            "***-**-" << self.decrypt_ssn[-4,4]
          end
        

SSN Storage - SOLUTION

There is a lot of guidance on adequately protecting sensitive data at rest and using a layered defensive approach. Make no mistake, this should not be your sole means of securing sensitive data. That being said, there are at least four precautions that should be taken.

The sensitive data is encrypted everywhere, including backups

Only authorized users can access decrypted copies of the data

Use a strong algorithm

Strong key is generated, protected from unauthorized access, and key change is planned for.

In the following code, we demonstrate switching from the storage of full SSN(s) in clear-text to storing them in the AES-256 encrypted format. The first thing to do is build the encrypt and decrypt functions. These can be found within app/models/work_info.rb.

          def encrypt_ssn
             aes = OpenSSL::Cipher::Cipher.new(cipher_type)
             aes.encrypt
             aes.key = key
             aes.iv = iv if iv != nil
             self.encrypted_ssn = aes.update(self.SSN) + aes.final
             self.SSN = nil
          end

          def decrypt_ssn
             aes = OpenSSL::Cipher::Cipher.new(cipher_type)
             aes.decrypt
             aes.key = key
             aes.iv = iv if iv != nil
             aes.update(self.encrypted_ssn) + aes.final
          end

          def key
            raise "Key Missing" if !(KEY)
            KEY
          end

          def iv
            raise "No IV for this User" if !(self.key_management.iv)
            self.key_management.iv
          end

          def cipher_type
            'aes-256-cbc'
          end
        

Also within the WorkInfo model, we add the following line of code...

           before_save :encrypt_ssn
        

The remaining pieces are:

We "seed" the database with per-user initialization vectors (IV) and store them within the key_management table

Separate production and development encryption keys. Production keys should be stored in an HSM, environment variable, etc. but never within the source code. Development keys are irrelevant if not being used for real data

Change the view where SSNs are called and rendered to the user so that the "last_four" method is called instead

For new user's who are registering, we create an initialization specific to their account

         # SEED DATA
         work_info.each do |wi|
          list = [:user_id, :SSN]
          info = WorkInfo.new(wi.reject {|k| list.include?(k)})
          info.user_id = wi[:user_id]
          info.build_key_management({:user_id => wi[:user_id], :iv => SecureRandom.hex(32) })
          info.SSN = wi[:SSN]
          info.save
        end
        

        # SEPARATE PROD AND DEV KEYS (config/initializers/key.rb)
        if Rails.env.production?
          # Specify env variable/location/etc. to retrieve key from
        elsif Rails.env.development?
          KEY = "123456789101112123456789101112123456789101112"
        end
        

        # CHANGE VIEW TO CALL LAST FOUR METHOD (app/views/work_info/index.html.erb)
        <%= CGI.unescapeHTML("<td class="ssn"><%= @user.work_info.last_four %></td>") %>
        

      def build_benefits_data
         build_retirement(POPULATE_RETIREMENTS.shuffle.first)
         build_paid_time_off(POPULATE_PAID_TIME_OFF.shuffle.first).schedule.build(POPULATE_SCHEDULE.shuffle.first)
         build_work_info(POPULATE_WORK_INFO.shuffle.first)
         # Uncomment below line to use encrypted SSN(s)
         work_info.build_key_management(:iv => SecureRandom.hex(32))
         performance.build(POPULATE_PERFORMANCE.shuffle.first)
      end
       

My SSN seems pretty important, hope it's kept safe!