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af7d1d3b67
# ignore-this-changeset Differential Revision: https://phabricator.services.mozilla.com/D36046 --HG-- extra : source : f3c632037a1064c41b1f8b02f477c854b2fb4362
184 lines
5.6 KiB
JavaScript
184 lines
5.6 KiB
JavaScript
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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"use strict";
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const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
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const { XPCOMUtils } = ChromeUtils.import(
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"resource://gre/modules/XPCOMUtils.jsm"
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);
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XPCOMUtils.defineLazyGlobalGetters(this, ["URL"]);
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// Debounce time in milliseconds - this should be long enough to account for
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// sync script tags that could appear between desired meta tags
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const TIMEOUT_DELAY = 1000;
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const ACCEPTED_PROTOCOLS = ["http:", "https:"];
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// Possible description tags, listed in order from least favourable to most favourable
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const DESCRIPTION_RULES = [
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"twitter:description",
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"description",
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"og:description",
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];
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// Possible image tags, listed in order from least favourable to most favourable
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const PREVIEW_IMAGE_RULES = [
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"thumbnail",
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"twitter:image",
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"og:image",
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"og:image:url",
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"og:image:secure_url",
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];
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/*
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* Checks if the incoming meta tag has a greater score than the current best
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* score by checking the index of the meta tag in the list of rules provided.
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*
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* @param {Array} aRules
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* The list of rules for a given type of meta tag
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* @param {String} aTag
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* The name or property of the incoming meta tag
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* @param {String} aEntry
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* The current best entry for the given meta tag
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*
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* @returns {Boolean} true if the incoming meta tag is better than the current
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* best meta tag of that same kind, false otherwise
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*/
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function shouldExtractMetadata(aRules, aTag, aEntry) {
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return aRules.indexOf(aTag) > aEntry.currMaxScore;
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}
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/*
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* Ensure that the preview image URL is safe and valid before storing
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*
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* @param {URL} aURL
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* A URL object that needs to be checked for valid principal and protocol
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*
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* @returns {Boolean} true if the preview URL is safe and can be stored, false otherwise
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*/
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function checkLoadURIStr(aURL) {
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if (!ACCEPTED_PROTOCOLS.includes(aURL.protocol)) {
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return false;
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}
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try {
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let ssm = Services.scriptSecurityManager;
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let principal = ssm.createNullPrincipal({});
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ssm.checkLoadURIStrWithPrincipal(
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principal,
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aURL.href,
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ssm.DISALLOW_INHERIT_PRINCIPAL
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);
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} catch (e) {
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return false;
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}
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return true;
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}
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var EXPORTED_SYMBOLS = ["ContentMetaHandler"];
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/*
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* This listens to DOMMetaAdded events and collects relevant metadata about the
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* meta tag received. Then, it sends the metadata gathered from the meta tags
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* and the url of the page as it's payload to be inserted into moz_places.
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*/
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var ContentMetaHandler = {
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init(chromeGlobal) {
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// Store a locally-scoped (for this chromeGlobal) mapping of the best
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// description and preview image collected so far for a given URL
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const metaTags = new Map();
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chromeGlobal.addEventListener("DOMMetaAdded", event => {
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const metaTag = event.originalTarget;
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const window = metaTag.ownerGlobal;
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// If there's no meta tag, or we're in a sub-frame, ignore this
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if (!metaTag || !metaTag.ownerDocument || window != window.top) {
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return;
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}
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this.handleMetaTag(metaTag, chromeGlobal, metaTags);
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});
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},
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handleMetaTag(metaTag, chromeGlobal, metaTags) {
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const url = metaTag.ownerDocument.documentURI;
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let name = metaTag.name;
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let prop = metaTag.getAttributeNS(null, "property");
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if (!name && !prop) {
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return;
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}
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let tag = name || prop;
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const entry = metaTags.get(url) || {
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description: { value: null, currMaxScore: -1 },
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image: { value: null, currMaxScore: -1 },
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timeout: null,
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};
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// Malformed meta tag - do not store it
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const content = metaTag.getAttributeNS(null, "content");
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if (!content) {
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return;
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}
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if (shouldExtractMetadata(DESCRIPTION_RULES, tag, entry.description)) {
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// Extract the description
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entry.description.value = content;
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entry.description.currMaxScore = DESCRIPTION_RULES.indexOf(tag);
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} else if (shouldExtractMetadata(PREVIEW_IMAGE_RULES, tag, entry.image)) {
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// Extract the preview image
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let value;
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try {
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value = new URL(content, url);
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} catch (e) {
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return;
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}
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if (value && checkLoadURIStr(value)) {
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entry.image.value = value.href;
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entry.image.currMaxScore = PREVIEW_IMAGE_RULES.indexOf(tag);
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}
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} else {
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// We don't care about other meta tags
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return;
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}
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if (!metaTags.has(url)) {
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metaTags.set(url, entry);
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}
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if (entry.timeout) {
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entry.timeout.delay = TIMEOUT_DELAY;
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} else {
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// We want to debounce incoming meta tags until we're certain we have the
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// best one for description and preview image, and only store that one
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entry.timeout = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
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entry.timeout.initWithCallback(
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() => {
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entry.timeout = null;
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// Save description and preview image to moz_places
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chromeGlobal.sendAsyncMessage("Meta:SetPageInfo", {
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url,
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description: entry.description.value,
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previewImageURL: entry.image.value,
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});
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// Telemetry for recording the size of page metadata
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let metadataSize = entry.description.value
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? entry.description.value.length
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: 0;
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metadataSize += entry.image.value ? entry.image.value.length : 0;
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Services.telemetry
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.getHistogramById("PAGE_METADATA_SIZE")
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.add(metadataSize);
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metaTags.delete(url);
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},
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TIMEOUT_DELAY,
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Ci.nsITimer.TYPE_ONE_SHOT
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);
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}
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},
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};
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