A Rack middleware app to spoof the Server header.

lie_server.rb

module Rack
  #
  # The LieServer is a simple Rack middleware app which allows one to spoof
  # the +Server+ header in responses for every request, requests to certain
  # sub-directories or paths which match a regular expression.
  #
  # Be deceitful to would be attackers, tell them your running IIS 3.0.
  #
  # MIT License - Hal Brodigan (postmodern.mod3 at gmail.com)
  #
  class LieServer

    #
    # Initializes the lie server.
    #
    # @param [#call] app
    #   The Rack app to lie for.
    #
    # @param [Hash{Regexp,String => String}] options
    #   Additional lie options.
    #
    # @example
    #   use Rack::LieServer, '/' => 'IIS 3.0'
    #
    # @example
    #   use Rack::LieServer, /\.asp$/ => 'Apache',
    #                        '/' => 'Nginx'
    #
    def initialize(app,options={})
      @app = app

      patterns = []
      paths = {}

      options.each do |pattern,lie|
        if pattern.kind_of?(Regexp)
          patterns << [pattern, lie]
        else
          paths[pattern] = lie
        end
      end

      @routes = patterns + paths.sort.reverse
    end

    def call(env)
      code, headers, body = @app.call(env)
      path = env['PATH_INFO']

      pattern, lie = @routes.find do |pattern,lie|
        if pattern.kind_of?(Regexp)
          path =~ pattern
        else
          path[0,pattern.length] == pattern
        end
      end

      headers['Server'] = lie if lie

      [code, headers, body]
    end

  end
end