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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at http://mozilla.org/MPL/2.0/. */
/**
* WebChannel is an abstraction that uses the Message Manager and Custom Events
* to create a two-way communication channel between chrome and content code.
*/
var EXPORTED_SYMBOLS = ["WebChannel", "WebChannelBroker"];
const ERRNO_UNKNOWN_ERROR = 999;
const ERROR_UNKNOWN = "UNKNOWN_ERROR";
const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
/**
* WebChannelBroker is a global object that helps manage WebChannel objects.
* This object handles channel registration, origin validation and message multiplexing.
*/
var WebChannelBroker = Object.create({
/**
* Register a new channel that callbacks messages
* based on proper origin and channel name
*
* @param channel {WebChannel}
*/
registerChannel(channel) {
if (!this._channelMap.has(channel)) {
this._channelMap.set(channel);
} else {
Cu.reportError("Failed to register the channel. Channel already exists.");
}
},
/**
* Unregister a channel
*
* @param channelToRemove {WebChannel}
* WebChannel to remove from the channel map
*
* Removes the specified channel from the channel map
*/
unregisterChannel(channelToRemove) {
if (!this._channelMap.delete(channelToRemove)) {
Cu.reportError("Failed to unregister the channel. Channel not found.");
}
},
/**
* Object to store pairs of message origins and callback functions
*/
_channelMap: new Map(),
/**
* Deliver a message to a registered channel.
*
* @returns bool whether we managed to find a registered channel.
*/
tryToDeliver(data, sendingContext) {
let validChannelFound = false;
data.message = data.message || {};
for (var channel of this._channelMap.keys()) {
if (
channel.id === data.id &&
channel._originCheckCallback(sendingContext.principal)
) {
validChannelFound = true;
channel.deliver(data, sendingContext);
}
}
return validChannelFound;
},
});
/**
* Creates a new WebChannel that listens and sends messages over some channel id
*
* @param id {String}
* WebChannel id
* @param originOrPermission {nsIURI/string}
* If an nsIURI, incoming events will be accepted from any origin matching
* that URI's origin.
* If a string, it names a permission, and incoming events will be accepted
* from any https:// origin that has been granted that permission by the
* permission manager.
* @constructor
*/
var WebChannel = function(id, originOrPermission) {
if (!id || !originOrPermission) {
throw new Error("WebChannel id and originOrPermission are required.");
}
this.id = id;
// originOrPermission can be either an nsIURI or a string representing a
// permission name.
if (typeof originOrPermission == "string") {
this._originCheckCallback = requestPrincipal => {
// Accept events from any secure origin having the named permission.
// The permission manager operates on domain names rather than true
// origins (bug 1066517). To mitigate that, we explicitly check that
// the scheme is https://.
let uri = Services.io.newURI(requestPrincipal.originNoSuffix);
if (uri.scheme != "https") {
return false;
}
// OK - we have https - now we can check the permission.
let perm = Services.perms.testExactPermissionFromPrincipal(
requestPrincipal,
originOrPermission
);
return perm == Ci.nsIPermissionManager.ALLOW_ACTION;
};
} else {
// Accept events from any origin matching the given URI.
// We deliberately use `originNoSuffix` here because we only want to
// restrict based on the site's origin, not on other origin attributes
// such as containers or private browsing.
this._originCheckCallback = requestPrincipal => {
return originOrPermission.prePath === requestPrincipal.originNoSuffix;
};
}
this._originOrPermission = originOrPermission;
};
WebChannel.prototype = {
/**
* WebChannel id
*/
id: null,
/**
* The originOrPermission value passed to the constructor, mainly for
* debugging and tests.
*/
_originOrPermission: null,
/**
* Callback that will be called with the principal of an incoming message
* to check if the request should be dispatched to the listeners.
*/
_originCheckCallback: null,
/**
* WebChannelBroker that manages WebChannels
*/
_broker: WebChannelBroker,
/**
* Callback that will be called with the contents of an incoming message
*/
_deliverCallback: null,
/**
* Registers the callback for messages on this channel
* Registers the channel itself with the WebChannelBroker
*
* @param callback {Function}
* Callback that will be called when there is a message
* @param {String} id
* The WebChannel id that was used for this message
* @param {Object} message
* The message itself
* @param sendingContext {Object}
* The sending context of the source of the message. Can be passed to
* `send` to respond to a message.
* @param sendingContext.browser {browser}
* The <browser> object that captured the
* WebChannelMessageToChrome.
* @param sendingContext.eventTarget {EventTarget}
* The <EventTarget> where the message was sent.
* @param sendingContext.principal {Principal}
* The <Principal> of the EventTarget where the
* message was sent.
*/
listen(callback) {
if (this._deliverCallback) {
throw new Error("Failed to listen. Listener already attached.");
} else if (!callback) {
throw new Error("Failed to listen. Callback argument missing.");
} else {
this._deliverCallback = callback;
this._broker.registerChannel(this);
}
},
/**
* Resets the callback for messages on this channel
* Removes the channel from the WebChannelBroker
*/
stopListening() {
this._broker.unregisterChannel(this);
this._deliverCallback = null;
},
/**
* Sends messages over the WebChannel id using the "WebChannelMessageToContent" event
*
* @param message {Object}
* The message object that will be sent
* @param target {Object}
* A <target> with the information of where to send the message.
* @param target.browsingContext {BrowsingContext}
* The browsingContext we should send the message to.
* @param target.principal {Principal}
* Principal of the target. Prevents messages from
* being dispatched to unexpected origins. The system principal
* can be specified to send to any target.
* @param [target.eventTarget] {EventTarget}
* Optional eventTarget within the browser, use to send to a
* specific element. Can be null; if not null, should be
* a ContentDOMReference.
*/
send(message, target) {
let { browsingContext, principal, eventTarget } = target;
if (message && browsingContext && principal) {
let { currentWindowGlobal } = browsingContext;
if (!currentWindowGlobal) {
Cu.reportError(
"Failed to send a WebChannel message. No currentWindowGlobal."
);
return;
}
currentWindowGlobal
.getActor("WebChannel")
.sendAsyncMessage("WebChannelMessageToContent", {
id: this.id,
message,
eventTarget,
principal,
});
} else if (!message) {
Cu.reportError("Failed to send a WebChannel message. Message not set.");
} else {
Cu.reportError("Failed to send a WebChannel message. Target invalid.");
}
},
/**
* Deliver WebChannel messages to the set "_channelCallback"
*
* @param data {Object}
* Message data
* @param sendingContext {Object}
* Message sending context.
* @param sendingContext.browsingContext {BrowsingContext}
* The browsingcontext from which the
* WebChannelMessageToChrome was sent.
* @param sendingContext.eventTarget {EventTarget}
* The <EventTarget> where the message was sent.
* Can be null; if not null, should be a ContentDOMReference.
* @param sendingContext.principal {Principal}
* The <Principal> of the EventTarget where the message was sent.
*
*/
deliver(data, sendingContext) {
if (this._deliverCallback) {
try {
this._deliverCallback(data.id, data.message, sendingContext);
} catch (ex) {
this.send(
{
errno: ERRNO_UNKNOWN_ERROR,
error: ex.message ? ex.message : ERROR_UNKNOWN,
},
sendingContext
);
Cu.reportError("Failed to execute WebChannel callback:");
Cu.reportError(ex);
}
} else {
Cu.reportError("No callback set for this channel.");
}
},
};