Add initial middleware package.

appengine/middleware/appengine.go

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package middleware
+
+import (
+        "fmt"
+        "net/http"
+
+        "github.com/julienschmidt/httprouter"
+        "github.com/luci/gae/service/info"
+        "github.com/luci/luci-go/common/logging"
+        "golang.org/x/net/context"
+)
+
+var devAppserverBypassFn = func(c context.Context) bool {
+        return info.Get(c).IsDevAppServer()
+}
+
+// RequireCron ensures that this handler was run from the appengine 'cron'
+// service. Otherwise it aborts the request with a StatusForbidden.
+//
+// This middleware has no effect when using 'BaseTest' or when running under
+// dev_appserver.py
+func RequireCron(h Handler) Handler {
+        return func(c context.Context, rw http.ResponseWriter, r *http.Request, p httprouter.Params) {
+                if !devAppserverBypassFn(c) {
+                        if r.Header.Get("X-Appengine-Cron") != "true" {
+                                rw.WriteHeader(http.StatusForbidden)
+                                logging.Errorf(c, "request not made from cron")
+                                fmt.Fprint(rw, "error: must be run from cron")
+                                return
+                        }
+                }
+                h(c, rw, r, p)
+        }
+}
+
+// RequireTaskQueue ensures that this handler was run from the specified
+// appengine 'taskqueue' queue. Otherwise it aborts the request with
+// a StatusForbidden.
+//
+// if `queue` is the empty string, than this simply checks that this handler was
+// run from ANY appengine taskqueue.
+//
+// This middleware has no effect when using 'BaseTest' or when running under
+// dev_appserver.py
+func RequireTaskQueue(queue string, h Handler) Handler {
+        return func(c context.Context, rw http.ResponseWriter, r *http.Request, p httprouter.Params) {
+                if !devAppserverBypassFn(c) {
+                        qName := r.Header.Get("X-AppEngine-QueueName")
+                        if qName == "" || (queue != "" && queue != qName) {
+                                rw.WriteHeader(http.StatusForbidden)
+                                logging.Errorf(c, "request made from wrong taskqueue: %q v %q", qName, queue)
+                                fmt.Fprintf(rw, "error: must be run from the correct taskqueue")
+                                return
+                        }
+                }
+                h(c, rw, r, p)
+        }
+}