From 8ab0234dda20c2e266c5dea98ca0f1b6795a3189 Mon Sep 17 00:00:00 2001
From: Hongfei Ding <lannka@users.noreply.github.com>
Date: Mon, 16 Jul 2018 16:13:32 -0700
Subject: [PATCH] Support referrerPolicy:no-referrer in amp-analytics (#16734)

* Support referrerPolicy:no-referrer in amp-analytics

* Add test

* Fix type checks.

* Add documentation
---
 builtins/amp-pixel.js                     | 55 +--------------
 examples/analytics.amp.html               | 18 +++++
 extensions/amp-analytics/0.1/transport.js | 23 ++++--
 extensions/amp-analytics/amp-analytics.md | 14 ++++
 src/pixel.js                              | 85 +++++++++++++++++++++++
 test/integration/test-amp-analytics.js    | 82 ++++++++++++++++++++++
 6 files changed, 217 insertions(+), 60 deletions(-)
 create mode 100644 src/pixel.js
 create mode 100644 test/integration/test-amp-analytics.js

diff --git a/builtins/amp-pixel.js b/builtins/amp-pixel.js
index d96b32383855..4f713b21d20b 100644
--- a/builtins/amp-pixel.js
+++ b/builtins/amp-pixel.js
@@ -16,11 +16,9 @@
 
 import {BaseElement} from '../src/base-element';
 import {Services} from '../src/services';
-import {createElementWithAttributes} from '../src/dom';
+import {createPixel} from '../src/pixel';
 import {dev, user} from '../src/log';
-import {dict} from '../src/utils/object';
 import {registerElement} from '../src/service/custom-element-registry';
-import {toWin} from '../src/types';
 
 const TAG = 'amp-pixel';
 
@@ -89,9 +87,7 @@ export class AmpPixel extends BaseElement {
       return Services.urlReplacementsForDoc(this.element)
           .expandUrlAsync(this.assertSource_(src))
           .then(src => {
-            const pixel = this.referrerPolicy_
-              ? createNoReferrerPixel(this.element, src)
-              : createImagePixel(this.win, src);
+            const pixel = createPixel(this.win, src, this.referrerPolicy_);
             dev().info(TAG, 'pixel triggered: ', src);
             return pixel;
           });
@@ -112,53 +108,6 @@ export class AmpPixel extends BaseElement {
   }
 }
 
-/**
- * @param {!Element} parentElement
- * @param {string} src
- * @return {!Element}
- */
-function createNoReferrerPixel(parentElement, src) {
-  if (isReferrerPolicySupported()) {
-    return createImagePixel(toWin(parentElement.ownerDocument.defaultView), src,
-        true);
-  } else {
-    // if "referrerPolicy" is not supported, use iframe wrapper
-    // to scrub the referrer.
-    const iframe = createElementWithAttributes(
-        /** @type {!Document} */ (parentElement.ownerDocument), 'iframe', dict({
-          'src': 'about:blank',
-        }));
-    parentElement.appendChild(iframe);
-    createImagePixel(iframe.contentWindow, src);
-    return iframe;
-  }
-}
-
-/**
- * @param {!Window} win
- * @param {string} src
- * @param {boolean=} noReferrer
- * @return {!Image}
- */
-function createImagePixel(win, src, noReferrer) {
-  const image = new win.Image();
-  if (noReferrer) {
-    image.referrerPolicy = 'no-referrer';
-  }
-  image.src = src;
-  return image;
-}
-
-/**
- * Check if element attribute "referrerPolicy" is supported by the browser.
- * At this moment (4/14/2017), Safari does not support it yet.
- *
- * @return {boolean}
- */
-export function isReferrerPolicySupported() {
-  return 'referrerPolicy' in Image.prototype;
-}
-
 /**
  * @param {!Window} win Destination window for the new element.
  */
diff --git a/examples/analytics.amp.html b/examples/analytics.amp.html
index 3a22e48e4389..a7775f8d29a4 100644
--- a/examples/analytics.amp.html
+++ b/examples/analytics.amp.html
@@ -29,6 +29,24 @@
 <div id="container">
 Container for analytics tags. Positioned far away from top to make sure that doesn't matter.
 
+<amp-analytics>
+  <script type="application/json">
+    {
+      "requests": {
+        "endpoint": "/analytics/no-referrer"
+      },
+      "triggers": {
+        "pageview": {
+          "on": "visible",
+          "request": "endpoint"
+        }
+      },
+      "transport": {
+        "referrerPolicy": "no-referrer"
+      }
+    }
+  </script>
+</amp-analytics>
 <amp-analytics id="analytics1">
 <script type="application/json">
 {
diff --git a/extensions/amp-analytics/0.1/transport.js b/extensions/amp-analytics/0.1/transport.js
index ca9edc1664fb..f2350e8a4068 100644
--- a/extensions/amp-analytics/0.1/transport.js
+++ b/extensions/amp-analytics/0.1/transport.js
@@ -20,6 +20,7 @@ import {
   checkCorsUrl,
   parseUrlDeprecated,
 } from '../../../src/url';
+import {createPixel} from '../../../src/pixel';
 import {dev, user} from '../../../src/log';
 import {loadPromise} from '../../../src/event-helper';
 import {removeElement} from '../../../src/dom';
@@ -31,11 +32,19 @@ const TAG_ = 'amp-analytics.Transport';
 /**
  * @param {!Window} win
  * @param {string} request
- * @param {!Object<string, string>} transportOptions
+ * @param {!Object<string, string|boolean>} transportOptions
  */
 export function sendRequest(win, request, transportOptions) {
   assertHttpsUrl(request, 'amp-analytics request');
   checkCorsUrl(request);
+
+  const referrerPolicy = transportOptions['referrerPolicy'];
+
+  if (referrerPolicy === 'no-referrer') {
+    transportOptions['beacon'] = false;
+    transportOptions['xhrpost'] = false;
+  }
+
   if (transportOptions['beacon'] &&
       Transport.sendRequestUsingBeacon(win, request)) {
     return;
@@ -48,7 +57,8 @@ export function sendRequest(win, request, transportOptions) {
   if (image) {
     const suppressWarnings = (typeof image == 'object' &&
         image['suppressWarnings']);
-    Transport.sendRequestUsingImage(request, suppressWarnings);
+    Transport.sendRequestUsingImage(
+        win, request, suppressWarnings, /** @type {string|undefined} */ (referrerPolicy));
     return;
   }
   user().warn(TAG_, 'Failed to send request', request, transportOptions);
@@ -60,14 +70,13 @@ export function sendRequest(win, request, transportOptions) {
 export class Transport {
 
   /**
+   * @param {!Window} win
    * @param {string} request
    * @param {boolean} suppressWarnings
+   * @param {string|undefined} referrerPolicy
    */
-  static sendRequestUsingImage(request, suppressWarnings) {
-    const image = new Image();
-    image.src = request;
-    image.width = 1;
-    image.height = 1;
+  static sendRequestUsingImage(win, request, suppressWarnings, referrerPolicy) {
+    const image = createPixel(win, request, referrerPolicy);
     loadPromise(image).then(() => {
       dev().fine(TAG_, 'Sent image request', request);
     }).catch(() => {
diff --git a/extensions/amp-analytics/amp-analytics.md b/extensions/amp-analytics/amp-analytics.md
index 789d67855e6f..a7f12f351b34 100644
--- a/extensions/amp-analytics/amp-analytics.md
+++ b/extensions/amp-analytics/amp-analytics.md
@@ -667,6 +667,20 @@ In the example below, an `iframe` URL is not specified, and `beacon` and `xhrpos
 
 To learn more, see [this example that implements iframe transport client API] (https://github.com/ampproject/amphtml/blob/master/examples/analytics-iframe-transport-remote-frame.html) and [this example page that incorporates that iframe](https://github.com/ampproject/amphtml/blob/master/examples/analytics-iframe-transport.amp.html). The example loads a [fake ad](https://github.com/ampproject/amphtml/blob/master/extensions/amp-ad-network-fake-impl/0.1/data/fake_amp_ad_with_iframe_transport.html), which contains the `amp-analytics` tag. Note that the fake ad content includes some extra configuration instructions that must be followed.
 
+##### Referrer Policy
+
+Referrer policy can be specified as `referrerPolicy` field in the `transport` config. Currently only `no-referrer` is supported.
+Referrer policy is only available for `image` transport. If `referrerPolicy: no-referrer` is specified, the `beacon` & `xhrpost` transports are overridden to `false`.
+
+```javascript
+"transport": {
+  "beacon": false,
+  "xhrpost": false,
+  "image": true,
+  "referrerPolicy": "no-referrer"
+}
+```
+
 ## Validation
 
 See [amp-analytics rules](https://github.com/ampproject/amphtml/blob/master/extensions/amp-analytics/validator-amp-analytics.protoascii) in the AMP validator specification.
diff --git a/src/pixel.js b/src/pixel.js
new file mode 100644
index 000000000000..f99d3745989a
--- /dev/null
+++ b/src/pixel.js
@@ -0,0 +1,85 @@
+/**
+ * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {createElementWithAttributes} from '../src/dom';
+import {dict} from '../src/utils/object';
+import {user} from '../src/log';
+
+/** @const {string} */
+const TAG = 'pixel';
+
+/**
+ * @param {!Window} win
+ * @param {string} src
+ * @param {?string=} referrerPolicy
+ * @return {!Element}
+ */
+export function createPixel(win, src, referrerPolicy) {
+  if (referrerPolicy && referrerPolicy !== 'no-referrer') {
+    user().error(TAG, 'Unsupported referrerPolicy: ' + referrerPolicy);
+  }
+
+  return referrerPolicy === 'no-referrer'
+    ? createNoReferrerPixel(win, src)
+    : createImagePixel(win, src);
+}
+
+/**
+ * @param {!Window} win
+ * @param {string} src
+ * @return {!Element}
+ */
+function createNoReferrerPixel(win, src) {
+  if (isReferrerPolicySupported()) {
+    return createImagePixel(win, src, true);
+  } else {
+    // if "referrerPolicy" is not supported, use iframe wrapper
+    // to scrub the referrer.
+    const iframe = createElementWithAttributes(
+        /** @type {!Document} */ (win.document), 'iframe', dict({
+          'src': 'about:blank',
+          'style': 'display:none',
+        }));
+    win.document.body.appendChild(iframe);
+    createImagePixel(iframe.contentWindow, src);
+    return iframe;
+  }
+}
+
+/**
+ * @param {!Window} win
+ * @param {string} src
+ * @param {boolean=} noReferrer
+ * @return {!Image}
+ */
+function createImagePixel(win, src, noReferrer = false) {
+  const image = new win.Image();
+  if (noReferrer) {
+    image.referrerPolicy = 'no-referrer';
+  }
+  image.src = src;
+  return image;
+}
+
+/**
+ * Check if element attribute "referrerPolicy" is supported by the browser.
+ * Safari 11.1 does not support it yet.
+ *
+ * @return {boolean}
+ */
+function isReferrerPolicySupported() {
+  return 'referrerPolicy' in Image.prototype;
+}
diff --git a/test/integration/test-amp-analytics.js b/test/integration/test-amp-analytics.js
new file mode 100644
index 000000000000..13729319dc40
--- /dev/null
+++ b/test/integration/test-amp-analytics.js
@@ -0,0 +1,82 @@
+/**
+ * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {
+  depositRequestUrl,
+  withdrawRequest,
+} from '../../testing/test-helper';
+
+describe.configure().run('amp-analytics', function() {
+  this.timeout(15000);
+
+  describes.integration('amp-analytics integration test', {
+    body:
+    `<amp-analytics>
+        <script type="application/json">
+        {
+          "requests": {
+            "endpoint": "${depositRequestUrl('analytics-has-referrer')}"
+          },
+          "triggers": {
+            "pageview": {
+              "on": "visible",
+              "request": "endpoint"
+            }
+          }
+        }
+        </script>
+    </amp-analytics>
+    `,
+    extensions: ['amp-analytics'],
+  }, env => {
+    it('should keep referrer if no referrerpolicy specified', () => {
+      return withdrawRequest(env.win,
+          'analytics-has-referrer').then(request => {
+        expect(request.headers.referer).to.be.ok;
+      });
+    });
+  });
+
+  describes.integration('amp-analytics integration test', {
+    body:
+    `<amp-analytics>
+        <script type="application/json">
+        {
+          "requests": {
+            "endpoint": "${depositRequestUrl('analytics-no-referrer')}"
+          },
+          "triggers": {
+            "pageview": {
+              "on": "visible",
+              "request": "endpoint"
+            }
+          },
+          "transport": {
+            "referrerPolicy": "no-referrer"
+          }
+        }
+        </script>
+    </amp-analytics>
+    `,
+    extensions: ['amp-analytics'],
+  }, env => {
+    it('should remove referrer if referrerpolicy=no-referrer', () => {
+      return withdrawRequest(env.win, 'analytics-no-referrer').then(request => {
+        expect(request.headers.referer).to.not.be.ok;
+      });
+    });
+  });
+});