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extensions/chromium/contentscript.js

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+/*
+Copyright 2014 Mozilla Foundation
+
+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.
+*/
+
+"use strict";
+
+var VIEWER_URL = chrome.runtime.getURL("content/web/viewer.html");
+
+function getViewerURL(pdf_url) {
+  return VIEWER_URL + "?file=" + encodeURIComponent(pdf_url);
+}
+
+document.addEventListener("animationstart", onAnimationStart, true);
+if (document.contentType === "application/pdf") {
+  chrome.runtime.sendMessage({ action: "canRequestBody" }, maybeRenderPdfDoc);
+}
+
+function onAnimationStart(event) {
+  if (event.animationName === "pdfjs-detected-object-or-embed") {
+    watchObjectOrEmbed(event.target);
+  }
+}
+
+// Called for every <object> or <embed> element in the page.
+// This may change the type, src/data attributes and/or the child nodes of the
+// element. This function only affects elements for the first call. Subsequent
+// invocations have no effect.
+function watchObjectOrEmbed(elem) {
+  var mimeType = elem.type;
+  if (mimeType && mimeType.toLowerCase() !== "application/pdf") {
+    return;
+  }
+  // <embed src> <object data>
+  var srcAttribute = "src" in elem ? "src" : "data";
+  var path = elem[srcAttribute];
+  if (!mimeType && !/\.pdf($|[?#])/i.test(path)) {
+    return;
+  }
+
+  if (
+    elem.tagName === "EMBED" &&
+    elem.name === "plugin" &&
+    elem.parentNode === document.body &&
+    elem.parentNode.childElementCount === 1 &&
+    elem.src === location.href
+  ) {
+    // This page is most likely Chrome's default page that embeds a PDF file.
+    // The fact that the extension's background page did not intercept and
+    // redirect this PDF request means that this PDF cannot be opened by PDF.js,
+    // e.g. because it is a response to a POST request (as in #6174).
+    // A reduced test case to test PDF response to POST requests is available at
+    // https://robwu.nl/pdfjs/issue6174/.
+    // Until #4483 is fixed, POST requests should be ignored.
+    return;
+  }
+  if (elem.tagName === "EMBED" && elem.src === "about:blank") {
+    // Starting from Chrome 76, internal embeds do not have the original URL,
+    // but "about:blank" instead.
+    // See https://github.com/mozilla/pdf.js/issues/11137
+    return;
+  }
+
+  if (elem.__I_saw_this_element) {
+    return;
+  }
+  elem.__I_saw_this_element = true;
+
+  var tagName = elem.tagName.toUpperCase();
+  var updateEmbedOrObject;
+  if (tagName === "EMBED") {
+    updateEmbedOrObject = updateEmbedElement;
+  } else if (tagName === "OBJECT") {
+    updateEmbedOrObject = updateObjectElement;
+  } else {
+    return;
+  }
+
+  var lastSrc;
+  var isUpdating = false;
+
+  function updateViewerFrame() {
+    if (!isUpdating) {
+      isUpdating = true;
+      try {
+        if (lastSrc !== elem[srcAttribute]) {
+          updateEmbedOrObject(elem);
+          lastSrc = elem[srcAttribute];
+        }
+      } finally {
+        isUpdating = false;
+      }
+    }
+  }
+
+  updateViewerFrame();
+
+  // Watch for page-initiated changes of the src/data attribute.
+  var srcObserver = new MutationObserver(updateViewerFrame);
+  srcObserver.observe(elem, {
+    attributes: true,
+    childList: false,
+    characterData: false,
+    attributeFilter: [srcAttribute],
+  });
+}
+
+// Display the PDF Viewer in an <embed>.
+function updateEmbedElement(elem) {
+  if (elem.type === "text/html" && elem.src.lastIndexOf(VIEWER_URL, 0) === 0) {
+    // The viewer is already shown.
+    return;
+  }
+  // The <embed> tag needs to be removed and re-inserted before any src changes
+  // are effective.
+  var parentNode = elem.parentNode;
+  var nextSibling = elem.nextSibling;
+  if (parentNode) {
+    elem.remove();
+  }
+  elem.type = "text/html";
+  elem.src = getEmbeddedViewerURL(elem.src);
+
+  if (parentNode) {
+    // Suppress linter warning: insertBefore is preferable to
+    // nextSibling.before(elem) because nextSibling may be null.
+    // eslint-disable-next-line unicorn/prefer-modern-dom-apis
+    parentNode.insertBefore(elem, nextSibling);
+  }
+}
+
+// Display the PDF Viewer in an <object>.
+function updateObjectElement(elem) {
+  // <object> elements are terrible. Experiments (in49.0.2623.75) show that the
+  // following happens:
+  // - When fallback content is shown (e.g. because the built-in PDF Viewer is
+  //   disabled), updating the "data" attribute has no effect. Not surprising
+  //   considering that HTMLObjectElement::m_useFallbackContent is not reset
+  //   once it is set to true. Source:
+  //   WebKit/Source/core/html/HTMLObjectElement.cpp#378 (rev 749fe30d676b6c14).
+  // - When the built-in PDF Viewer plugin is enabled, updating the "data"
+  //   attribute reloads the content (provided that the type was correctly set).
+  // - When <object type=text/html data="chrome-extension://..."> is used
+  //   (tested with a data-URL, data:text/html,<object...>, the extension's
+  //   origin allowlist is not set up, so the viewer can't load the PDF file.
+  // - The content of the <object> tag may be affected by <param> tags.
+  //
+  // To make sure that our solution works for all cases, we will insert a frame
+  // as fallback content and force the <object> tag to render its fallback
+  // content.
+  var iframe = elem.firstElementChild;
+  if (!iframe || !iframe.__inserted_by_pdfjs) {
+    iframe = createFullSizeIframe();
+    elem.textContent = "";
+    elem.append(iframe);
+    iframe.__inserted_by_pdfjs = true;
+  }
+  iframe.src = getEmbeddedViewerURL(elem.data);
+
+  // Some bogus content type that is not handled by any plugin.
+  elem.type = "application/not-a-pee-dee-eff-type";
+  // Force the <object> to reload and render its fallback content.
+  elem.data += "";
+
+  // Usually the browser renders plugin content in this tag, which is completely
+  // oblivious of styles such as padding, but we insert and render child nodes,
+  // so force padding to be zero to avoid undesired dimension changes.
+  elem.style.padding = "0";
+
+  // <object> and <embed> elements have a "display:inline" style by default.
+  // Despite this property, when a plugin is loaded in the tag, the tag is
+  // treated like "display:inline-block". However, when the browser does not
+  // render plugin content, the <object> tag does not behave like that, and as
+  // a result the width and height is ignored.
+  // Force "display:inline-block" to make sure that the width/height as set by
+  // web pages is respected.
+  // (<embed> behaves as expected with the default display value, but setting it
+  // to display:inline-block doesn't hurt).
+  elem.style.display = "inline-block";
+}
+
+// Create an <iframe> element without borders that takes the full width and
+// height.
+function createFullSizeIframe() {
+  var iframe = document.createElement("iframe");
+  iframe.style.background = "none";
+  iframe.style.border = "none";
+  iframe.style.borderRadius = "none";
+  iframe.style.boxShadow = "none";
+  iframe.style.cssFloat = "none";
+  iframe.style.display = "block";
+  iframe.style.height = "100%";
+  iframe.style.margin = "0";
+  iframe.style.maxHeight = "none";
+  iframe.style.maxWidth = "none";
+  iframe.style.position = "static";
+  iframe.style.transform = "none";
+  iframe.style.visibility = "visible";
+  iframe.style.width = "100%";
+  return iframe;
+}
+
+// Get the viewer URL, provided that the path is a valid URL.
+function getEmbeddedViewerURL(path) {
+  var fragment = /^([^#]*)(#.*)?$/.exec(path);
+  path = fragment[1];
+  fragment = fragment[2] || "";
+
+  // Resolve relative path to document.
+  var a = document.createElement("a");
+  a.href = document.baseURI;
+  a.href = path;
+  path = a.href;
+  return getViewerURL(path) + fragment;
+}
+
+function maybeRenderPdfDoc(isNotPOST) {
+  if (!isNotPOST) {
+    // The document was loaded through a POST request, but we cannot access the
+    // original response body, nor safely send a new request to fetch the PDF.
+    // Until #4483 is fixed, POST requests should be ignored.
+    return;
+  }
+
+  // Detected PDF that was not redirected by the declarativeNetRequest rules.
+  // Maybe because this was served without Content-Type and sniffed as PDF.
+  // Or because this is Chrome 127-, which does not support responseHeaders
+  // condition in declarativeNetRequest (DNR), and PDF requests are therefore
+  // not redirected via DNR.
+
+  // In any case, load the viewer.
+  console.log(`Detected PDF via document, opening viewer for ${document.URL}`);
+
+  // Ideally we would use logic consistent with the DNR logic, like this:
+  // location.href = getEmbeddedViewerURL(document.URL);
+  // ... unfortunately, this causes Chrome to crash until version 129, fixed by
+  // https://chromium.googlesource.com/chromium/src/+/8c42358b2cc549553d939efe7d36515d80563da7%5E%21/
+  // Work around this by replacing the body with an iframe of the viewer.
+  // Interestingly, Chrome's built-in PDF viewer uses a similar technique.
+  const shadowRoot = document.body.attachShadow({ mode: "closed" });
+  const iframe = document.createElement("iframe");
+  iframe.style.position = "absolute";
+  iframe.style.top = "0";
+  iframe.style.left = "0";
+  iframe.style.width = "100%";
+  iframe.style.height = "100%";
+  iframe.style.border = "0 none";
+  iframe.src = getEmbeddedViewerURL(document.URL);
+  shadowRoot.append(iframe);
+}