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francois
418
eme_interception.js
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418
eme_interception.js
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/**
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* Hooks EME calls and forwards them for analysis and decryption.
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*
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* Most of the code here was borrowed from https://github.com/google/eme_logger/blob/master/eme_listeners.js
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*/
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var lastReceivedLicenseRequest = null;
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var lastReceivedLicenseResponse = null;
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/** Set up the EME listeners. */
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function startEMEInterception()
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{
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var listener = new EmeInterception();
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listener.setUpListeners();
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}
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/**
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* Gets called whenever an EME method is getting called or an EME event fires
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*/
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EmeInterception.onOperation = function(operationType, args)
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{
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if (operationType == "GenerateRequestCall")
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{
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// got initData
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// console.log(args);
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}
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else if (operationType == "MessageEvent")
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{
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var licenseRequest = args.message;
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lastReceivedLicenseRequest = licenseRequest;
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}
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else if (operationType == "UpdateCall")
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{
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var licenseResponse = args[0];
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lastReceivedLicenseResponse = licenseResponse;
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// OK, let's try to decrypt it, assuming the response correlates to the request
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WidevineCrypto.decryptContentKey(lastReceivedLicenseRequest, lastReceivedLicenseResponse);
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}
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};
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/**
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* Manager for EME event and method listeners.
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* @constructor
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*/
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function EmeInterception()
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{
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this.unprefixedEmeEnabled = Navigator.prototype.requestMediaKeySystemAccess ? true : false;
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this.prefixedEmeEnabled = HTMLMediaElement.prototype.webkitGenerateKeyRequest ? true : false;
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}
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/**
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* The number of types of HTML Media Elements to track.
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* @const {number}
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*/
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EmeInterception.NUM_MEDIA_ELEMENT_TYPES = 3;
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/**
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* Sets up EME listeners for whichever type of EME is enabled.
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*/
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EmeInterception.prototype.setUpListeners = function()
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{
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if (!this.unprefixedEmeEnabled && !this.prefixedEmeEnabled) {
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// EME is not enabled, just ignore
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return;
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}
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if (this.unprefixedEmeEnabled) {
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this.addListenersToNavigator_();
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}
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if (this.prefixedEmeEnabled) {
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// Prefixed EME is enabled
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}
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this.addListenersToAllEmeElements_();
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};
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/**
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* Adds listeners to the EME methods on the Navigator object.
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* @private
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*/
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EmeInterception.prototype.addListenersToNavigator_ = function()
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{
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if (navigator.listenersAdded_)
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return;
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var originalRequestMediaKeySystemAccessFn = EmeInterception.extendEmeMethod(
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navigator,
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navigator.requestMediaKeySystemAccess,
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"RequestMediaKeySystemAccessCall");
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navigator.requestMediaKeySystemAccess = function()
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{
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var options = arguments[1];
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// slice "It is recommended that a robustness level be specified" warning
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var modifiedArguments = arguments;
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var modifiedOptions = EmeInterception.addRobustnessLevelIfNeeded(options);
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modifiedArguments[1] = modifiedOptions;
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var result = originalRequestMediaKeySystemAccessFn.apply(null, modifiedArguments);
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// Attach listeners to returned MediaKeySystemAccess object
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return result.then(function(mediaKeySystemAccess)
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{
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this.addListenersToMediaKeySystemAccess_(mediaKeySystemAccess);
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return Promise.resolve(mediaKeySystemAccess);
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}.bind(this));
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}.bind(this);
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navigator.listenersAdded_ = true;
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};
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/**
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* Adds listeners to the EME methods on a MediaKeySystemAccess object.
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* @param {MediaKeySystemAccess} mediaKeySystemAccess A MediaKeySystemAccess
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* object to add listeners to.
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* @private
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*/
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EmeInterception.prototype.addListenersToMediaKeySystemAccess_ = function(mediaKeySystemAccess)
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{
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if (mediaKeySystemAccess.listenersAdded_) {
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return;
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}
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mediaKeySystemAccess.originalGetConfiguration = mediaKeySystemAccess.getConfiguration;
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mediaKeySystemAccess.getConfiguration = EmeInterception.extendEmeMethod(
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mediaKeySystemAccess,
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mediaKeySystemAccess.getConfiguration,
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"GetConfigurationCall");
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var originalCreateMediaKeysFn = EmeInterception.extendEmeMethod(
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mediaKeySystemAccess,
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mediaKeySystemAccess.createMediaKeys,
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"CreateMediaKeysCall");
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mediaKeySystemAccess.createMediaKeys = function()
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{
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var result = originalCreateMediaKeysFn.apply(null, arguments);
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// Attach listeners to returned MediaKeys object
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return result.then(function(mediaKeys) {
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mediaKeys.keySystem_ = mediaKeySystemAccess.keySystem;
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this.addListenersToMediaKeys_(mediaKeys);
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return Promise.resolve(mediaKeys);
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}.bind(this));
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}.bind(this);
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mediaKeySystemAccess.listenersAdded_ = true;
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};
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/**
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* Adds listeners to the EME methods on a MediaKeys object.
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* @param {MediaKeys} mediaKeys A MediaKeys object to add listeners to.
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* @private
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*/
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EmeInterception.prototype.addListenersToMediaKeys_ = function(mediaKeys)
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{
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if (mediaKeys.listenersAdded_) {
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return;
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}
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var originalCreateSessionFn = EmeInterception.extendEmeMethod(mediaKeys, mediaKeys.createSession, "CreateSessionCall");
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mediaKeys.createSession = function()
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{
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var result = originalCreateSessionFn.apply(null, arguments);
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result.keySystem_ = mediaKeys.keySystem_;
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// Attach listeners to returned MediaKeySession object
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this.addListenersToMediaKeySession_(result);
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return result;
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}.bind(this);
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mediaKeys.setServerCertificate = EmeInterception.extendEmeMethod(mediaKeys, mediaKeys.setServerCertificate, "SetServerCertificateCall");
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mediaKeys.listenersAdded_ = true;
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};
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/** Adds listeners to the EME methods and events on a MediaKeySession object.
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* @param {MediaKeySession} session A MediaKeySession object to add
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* listeners to.
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* @private
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*/
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EmeInterception.prototype.addListenersToMediaKeySession_ = function(session)
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{
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if (session.listenersAdded_) {
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return;
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}
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session.generateRequest = EmeInterception.extendEmeMethod(session,session.generateRequest, "GenerateRequestCall");
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session.load = EmeInterception.extendEmeMethod(session, session.load, "LoadCall");
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session.update = EmeInterception.extendEmeMethod(session,session.update, "UpdateCall");
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session.close = EmeInterception.extendEmeMethod(session, session.close, "CloseCall");
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session.remove = EmeInterception.extendEmeMethod(session, session.remove, "RemoveCall");
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session.addEventListener('message', function(e)
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{
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e.keySystem = session.keySystem_;
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EmeInterception.interceptEvent("MessageEvent", e);
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});
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session.addEventListener('keystatuseschange', EmeInterception.interceptEvent.bind(null, "KeyStatusesChangeEvent"));
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session.listenersAdded_ = true;
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};
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/**
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* Adds listeners to all currently created media elements (audio, video) and sets up a
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* mutation-summary observer to add listeners to any newly created media
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* elements.
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* @private
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*/
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EmeInterception.prototype.addListenersToAllEmeElements_ = function()
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{
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this.addEmeInterceptionToInitialMediaElements_();
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// TODO: Use MutationObserver directry
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// var observer = new MutationSummary({
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// callback: function(summaries) {
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// applyListeners(summaries);
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// },
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// queries: [{element: 'video'}, {element: 'audio'}, {element: 'media'}]
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// });
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// var applyListeners = function(summaries) {
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// for (var i = 0; i < EmeInterception.NUM_MEDIA_ELEMENT_TYPES; i++) {
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// var elements = summaries[i];
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// elements.added.forEach(function(element) {
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// this.addListenersToEmeElement_(element, true);
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// }.bind(this));
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// }
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// }.bind(this);
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};
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/**
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* Adds listeners to the EME elements currently in the document.
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* @private
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*/
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EmeInterception.prototype.addEmeInterceptionToInitialMediaElements_ = function()
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{
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var audioElements = document.getElementsByTagName('audio');
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for (var i = 0; i < audioElements.length; ++i) {
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this.addListenersToEmeElement_(audioElements[i], false);
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}
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var videoElements = document.getElementsByTagName('video');
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for (var i = 0; i < videoElements.length; ++i) {
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this.addListenersToEmeElement_(videoElements[i], false);
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}
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var mediaElements = document.getElementsByTagName('media');
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for (var i = 0; i < mediaElements.length; ++i) {
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this.addListenersToEmeElement_(mediaElements[i], false);
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}
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};
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/**
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* Adds method and event listeners to media element.
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* @param {HTMLMediaElement} element A HTMLMedia element to add listeners to.
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* @private
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*/
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EmeInterception.prototype.addListenersToEmeElement_ = function(element)
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{
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this.addEmeEventListeners_(element);
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this.addEmeMethodListeners_(element);
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console.info('EME listeners successfully added to:', element);
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};
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/**
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* Adds event listeners to a media element.
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* @param {HTMLMediaElement} element A HTMLMedia element to add listeners to.
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* @private
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*/
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EmeInterception.prototype.addEmeEventListeners_ = function(element)
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{
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if (element.eventListenersAdded_) {
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return;
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}
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if (this.prefixedEmeEnabled)
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{
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element.addEventListener('webkitneedkey', EmeInterception.interceptEvent.bind(null, "NeedKeyEvent"));
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element.addEventListener('webkitkeymessage', EmeInterception.interceptEvent.bind(null, "KeyMessageEvent"));
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element.addEventListener('webkitkeyadded', EmeInterception.interceptEvent.bind(null, "KeyAddedEvent"));
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element.addEventListener('webkitkeyerror', EmeInterception.interceptEvent.bind(null, "KeyErrorEvent"));
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}
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element.addEventListener('encrypted', EmeInterception.interceptEvent.bind(null, "EncryptedEvent"));
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element.addEventListener('play', EmeInterception.interceptEvent.bind(null, "PlayEvent"));
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element.addEventListener('error', function(e) {
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console.error('Error Event');
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EmeInterception.interceptEvent("ErrorEvent", e);
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});
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element.eventListenersAdded_ = true;
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};
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/**
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* Adds method listeners to a media element.
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* @param {HTMLMediaElement} element A HTMLMedia element to add listeners to.
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* @private
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*/
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EmeInterception.prototype.addEmeMethodListeners_ = function(element)
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{
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if (element.methodListenersAdded_) {
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return;
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}
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element.play = EmeInterception.extendEmeMethod(element, element.play, "PlayCall");
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if (this.prefixedEmeEnabled) {
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element.canPlayType = EmeInterception.extendEmeMethod(element, element.canPlayType, "CanPlayTypeCall");
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element.webkitGenerateKeyRequest = EmeInterception.extendEmeMethod(element, element.webkitGenerateKeyRequest, "GenerateKeyRequestCall");
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element.webkitAddKey = EmeInterception.extendEmeMethod(element, element.webkitAddKey, "AddKeyCall");
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element.webkitCancelKeyRequest = EmeInterception.extendEmeMethod(element, element.webkitCancelKeyRequest, "CancelKeyRequestCall");
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}
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if (this.unprefixedEmeEnabled) {
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element.setMediaKeys = EmeInterception.extendEmeMethod(element, element.setMediaKeys, "SetMediaKeysCall");
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}
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element.methodListenersAdded_ = true;
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};
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/**
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* Creates a wrapper function that logs calls to the given method.
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* @param {!Object} element An element or object whose function
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* call will be logged.
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* @param {!Function} originalFn The function to log.
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* @param {!Function} type The constructor for a logger class that will
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* be instantiated to log the originalFn call.
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* @return {!Function} The new version, with logging, of orginalFn.
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*/
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EmeInterception.extendEmeMethod = function(element, originalFn, type)
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{
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return function()
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{
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try
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{
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var result = originalFn.apply(element, arguments);
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var args = [].slice.call(arguments);
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EmeInterception.interceptCall(type, args, result, element);
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}
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catch (e)
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{
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console.error(e);
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}
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return result;
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};
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};
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/**
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* Intercepts a method call to the console and a separate frame.
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* @param {!Function} constructor The constructor for a logger class that will
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* be instantiated to log this call.
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* @param {Array} args The arguments this call was made with.
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* @param {Object} result The result of this method call.
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* @param {!Object} target The element this method was called on.
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* @return {!eme.EmeMethodCall} The data that has been logged.
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*/
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EmeInterception.interceptCall = function(type, args, result, target)
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{
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EmeInterception.onOperation(type, args);
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return args;
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};
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/**
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* Intercepts an event to the console and a separate frame.
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* @param {!Function} constructor The constructor for a logger class that will
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* be instantiated to log this event.
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* @param {!Event} event An EME event.
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* @return {!eme.EmeEvent} The data that has been logged.
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*/
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EmeInterception.interceptEvent = function(type, event)
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{
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EmeInterception.onOperation(type, event);
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return event;
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};
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EmeInterception.addRobustnessLevelIfNeeded = function(options)
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{
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for (var i = 0; i < options.length; i++)
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{
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var option = options[i];
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var videoCapabilities = option["videoCapabilities"];
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var audioCapabilties = option["audioCapabilities"];
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if (videoCapabilities != null)
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{
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for (var j = 0; j < videoCapabilities.length; j++)
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if (videoCapabilities[j]["robustness"] == undefined) videoCapabilities[j]["robustness"] = "SW_SECURE_CRYPTO";
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}
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if (audioCapabilties != null)
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{
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for (var j = 0; j < audioCapabilties.length; j++)
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if (audioCapabilties[j]["robustness"] == undefined) audioCapabilties[j]["robustness"] = "SW_SECURE_CRYPTO";
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}
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option["videoCapabilities"] = videoCapabilities;
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option["audioCapabilities"] = audioCapabilties;
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options[i] = option;
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}
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return options;
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}
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startEMEInterception();
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Reference in New Issue
Block a user