Safe session extension for merb

safe_session.rb

# Safe session extension for merb applications.  Generates a
# unique session salt for an application install automatically
# instead of requiring the user to do so themselves.
class SafeSession
  
  require "digest/sha1"
  attr_reader :salt
  
  # Attempts to load the session salt from the saltfile, if it does
  # not exist a new salt is generated 
  def initialize(filename = "config/salt")
    file_path = File.join(Merb.root, filename)
    if File.exists? file_path
      @salt = load_salt(file_path)
    else # saltfile doesn't exist, let's generate a salt
      @salt = generate_salt
      save_salt(file_path)
    end
  end
  
  private
  
  # Loads the salt from file
  def load_salt(filename)
    @salt = File.new(filename).read
  end
  
  # Saves a generated salt to file
  def save_salt(filename)
    File.new(filename, "w").write(@salt)
  end
  
  # Generates a new salt
  def generate_salt
    Digest.hexencode(Digest::SHA1.digest(
     "#{rand(2 ** 128) * ( Time.now.to_i * Process.pid )}"))
  end
  
end