1 files changed, 129 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch/middleware/static.rb b/actionpack/lib/action_dispatch/middleware/static.rb
new file mode 100644
index 0000000000..1f2f7757a3
--- /dev/null
+++ b/actionpack/lib/action_dispatch/middleware/static.rb
@@ -0,0 +1,129 @@
+# frozen_string_literal: true
+
+require "rack/utils"
+require "active_support/core_ext/uri"
+
+module ActionDispatch
+  # This middleware returns a file's contents from disk in the body response.
+  # When initialized, it can accept optional HTTP headers, which will be set
+  # when a response containing a file's contents is delivered.
+  #
+  # This middleware will render the file specified in <tt>env["PATH_INFO"]</tt>
+  # where the base path is in the +root+ directory. For example, if the +root+
+  # is set to +public/+, then a request with <tt>env["PATH_INFO"]</tt> of
+  # +assets/application.js+ will return a response with the contents of a file
+  # located at +public/assets/application.js+ if the file exists. If the file
+  # does not exist, a 404 "File not Found" response will be returned.
+  class FileHandler
+    def initialize(root, index: "index", headers: {})
+      @root          = root.chomp("/").b
+      @file_server   = ::Rack::File.new(@root, headers)
+      @index         = index
+    end
+
+    # Takes a path to a file. If the file is found, has valid encoding, and has
+    # correct read permissions, the return value is a URI-escaped string
+    # representing the filename. Otherwise, false is returned.
+    #
+    # Used by the +Static+ class to check the existence of a valid file
+    # in the server's +public/+ directory (see Static#call).
+    def match?(path)
+      path = ::Rack::Utils.unescape_path path
+      return false unless ::Rack::Utils.valid_path? path
+      path = ::Rack::Utils.clean_path_info path
+
+      paths = [path, "#{path}#{ext}", "#{path}/#{@index}#{ext}"]
+
+      if match = paths.detect { |p|
+        path = File.join(@root, p.b)
+        begin
+          File.file?(path) && File.readable?(path)
+        rescue SystemCallError
+          false
+        end
+      }
+        return ::Rack::Utils.escape_path(match).b
+      end
+    end
+
+    def call(env)
+      serve(Rack::Request.new(env))
+    end
+
+    def serve(request)
+      path      = request.path_info
+      gzip_path = gzip_file_path(path)
+
+      if gzip_path && gzip_encoding_accepted?(request)
+        request.path_info           = gzip_path
+        status, headers, body       = @file_server.call(request.env)
+        if status == 304
+          return [status, headers, body]
+        end
+        headers["Content-Encoding"] = "gzip"
+        headers["Content-Type"]     = content_type(path)
+      else
+        status, headers, body = @file_server.call(request.env)
+      end
+
+      headers["Vary"] = "Accept-Encoding" if gzip_path
+
+      [status, headers, body]
+    ensure
+      request.path_info = path
+    end
+
+    private
+      def ext
+        ::ActionController::Base.default_static_extension
+      end
+
+      def content_type(path)
+        ::Rack::Mime.mime_type(::File.extname(path), "text/plain")
+      end
+
+      def gzip_encoding_accepted?(request)
+        request.accept_encoding.any? { |enc, quality| enc =~ /\bgzip\b/i }
+      end
+
+      def gzip_file_path(path)
+        can_gzip_mime = content_type(path) =~ /\A(?:text\/|application\/javascript)/
+        gzip_path     = "#{path}.gz"
+        if can_gzip_mime && File.exist?(File.join(@root, ::Rack::Utils.unescape_path(gzip_path)))
+          gzip_path
+        else
+          false
+        end
+      end
+  end
+
+  # This middleware will attempt to return the contents of a file's body from
+  # disk in the response. If a file is not found on disk, the request will be
+  # delegated to the application stack. This middleware is commonly initialized
+  # to serve assets from a server's +public/+ directory.
+  #
+  # This middleware verifies the path to ensure that only files
+  # living in the root directory can be rendered. A request cannot
+  # produce a directory traversal using this middleware. Only 'GET' and 'HEAD'
+  # requests will result in a file being returned.
+  class Static
+    def initialize(app, path, index: "index", headers: {})
+      @app = app
+      @file_handler = FileHandler.new(path, index: index, headers: headers)
+    end
+
+    def call(env)
+      req = Rack::Request.new env
+
+      if req.get? || req.head?
+        path = req.path_info.chomp("/")
+        if match = @file_handler.match?(path)
+          req.path_info = match
+          return @file_handler.serve(req)
+        end
+      end
+
+      @app.call(req.env)
+    end
+  end
+end