Contents

# frozen_string_literal: true

require 'logger'

begin
  require 'terrapin'
rescue LoadError
  puts "file_validators requires 'terrapin' gem as you are using" \
       ' file content type validations in strict mode'
end

module FileValidators
  module Utils
    class ContentTypeDetector
      EMPTY_CONTENT_TYPE = 'inode/x-empty'
      DEFAULT_CONTENT_TYPE = 'application/octet-stream'

      attr_accessor :file_path, :file_name

      def initialize(file_path, file_name)
        @file_path = file_path
        @file_name = file_name
      end

      # content type detection strategy:
      #
      # 1. invalid file_path: returns 'application/octet-stream'
      # 2. empty file: returns 'inode/x-empty'
      # 3. valid file: returns the content type using file command
      # 4. valid file but file commoand raises error: returns 'application/octet-stream'

      def detect
        if !File.exist?(file_path)
          DEFAULT_CONTENT_TYPE
        elsif File.zero?(file_path)
          EMPTY_CONTENT_TYPE
        else
          content_type_from_content
        end
      end

      private

      def content_type_from_content
        content_type = type_from_file_command

        if FileValidators::Utils::MediaTypeSpoofDetector.new(content_type, file_name).spoofed?
          logger.warn('A file with a spoofed media type has been detected by the file validators.')
        else
          content_type
        end
      end

      def type_from_file_command
        Terrapin::CommandLine.new('file', '-b --mime-type :file').run(file: @file_path).strip
      rescue Terrapin::CommandLineError => e
        logger.info(e.message)
        DEFAULT_CONTENT_TYPE
      end

      def logger
        Logger.new(STDOUT)
      end
    end
  end
end

Version data entries

1 entries across 1 versions & 1 rubygems

Version	Path
file_validators-3.0.0.beta1	lib/file_validators/utils/content_type_detector.rb