Module: Aikido::Zen::Sinks::File

Defined in:
lib/aikido/zen/sinks/file.rb

Defined Under Namespace

Modules: Helpers

Constant Summary collapse

SINK = 
Sinks.add("File", scanners: [Scanners::PathTraversalScanner])

Class Method Summary collapse

Class Method Details

.load_sinks! ⇒ Object 



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# File 'lib/aikido/zen/sinks/file.rb', line 17

def self.load_sinks!
  ::File.singleton_class.class_eval do
    extend Sinks::DSL

    # Create a copy of the original methods for internal use only to prevent
    # recursion in PathTraversalScanner.
    #
    # IMPORTANT: The aliases must be created before the method is overridden.
    alias_method :expand_path__internal_for_aikido_zen, :expand_path
    alias_method :join__internal_for_aikido_zen, :join

    sink_before :open do |path|
      Helpers.scan(path, "open")
    end

    sink_before :read do |path|
      Helpers.scan(path, "read")
    end

    sink_before :write do |path|
      Helpers.scan(path, "write")
    end

    sink_before :truncate do |file_name|
      Helpers.scan(file_name, "truncate")
    end

    sink_before :rename do |old_name, new_name|
      Helpers.scan(old_name, "rename")
      Helpers.scan(new_name, "rename")
    end

    sink_before :unlink do |*file_names|
      file_names.each do |file_name|
        Helpers.scan(file_name, "unlink")
      end
    end

    sink_before :delete do |*file_names|
      file_names.each do |file_name|
        Helpers.scan(file_name, "delete")
      end
    end

    sink_before :symlink do |old_name, new_name|
      Helpers.scan(old_name, "symlink")
      Helpers.scan(new_name, "symlink")
    end

    sink_before :chmod do |_mode_int, *file_names|
      file_names.each do |file_name|
        Helpers.scan(file_name, "chmod")
      end
    end

    sink_before :chown do |_owner_int, group_int, *file_names|
      file_names.each do |file_name|
        Helpers.scan(file_name, "chown")
      end
    end

    sink_before :utime do |_atime, _mtime, *file_names|
      file_names.each do |file_name|
        Helpers.scan(file_name, "utime")
      end
    end

    def join(*args, **kwargs, &blk)
      if Aikido::Zen.config.harden?
        # IMPORTANT: THE BEHAVIOR OF THIS METHOD IS CHANGED!
        #
        # File.join has undocumented behavior:
        #
        # File.join recursively joins nested string arrays.
        #
        # This prevents path traversal detection when an array originates
        # from user input that was assumed to be a string.
        #
        # This undocumented behavior has been restricted to support path
        # traversal detection.
        #
        # File.join no longer joins nested string arrays, but still accepts
        # a single string array argument.

        # File.join is often incorrectly called with a single array argument.
        #
        # i.e.
        #
        # File.join(["prefix", "filename"])
        #
        # This is considered acceptable.
        #
        # Calling File.join with a single string argument returns the string
        # argument itself, having no practical effect. Therefore, it can be
        # presumed that if File.join is called with a single array argument
        # then this was its intended usage, and the array did not originate
        # from user input that was assumed to be a string.
        strings = args
        strings = args.first if args.size == 1 && args.first.is_a?(Array)
        strings.each do |string|
          raise TypeError.new("Zen prevented implicit conversion of Array to String in hardened method. Visit https://github.com/AikidoSec/firewall-ruby for more information.") if string.is_a?(Array)
        end
      end

      result = join__internal_for_aikido_zen(*args, **kwargs, &blk)
      Sinks::DSL.safe do
        Helpers.scan(result, "join")
      end
      result
    end

    sink_before :expand_path do |file_name|
      Helpers.scan(file_name, "expand_path")
    end

    sink_before :realpath do |file_name|
      Helpers.scan(file_name, "realpath")
    end

    sink_before :realdirpath do |file_name|
      Helpers.scan(file_name, "realdirpath")
    end
  end

  ::File.class_eval do
    extend Sinks::DSL

    sink_before :initialize do |path|
      Helpers.scan(path, "new")
    end
  end
end