// Copyright 2013 The Closure Library 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.
/**
* @fileoverview The TrustedResourceUrl type and its builders.
*
* TODO(xtof): Link to document stating type contract.
*/
goog.provide('goog.html.TrustedResourceUrl');
goog.require('goog.asserts');
goog.require('goog.i18n.bidi.Dir');
goog.require('goog.i18n.bidi.DirectionalString');
goog.require('goog.string.Const');
goog.require('goog.string.TypedString');
/**
* A URL which is under application control and from which script, CSS, and
* other resources that represent executable code, can be fetched.
*
* Given that the URL can only be constructed from strings under application
* control and is used to load resources, bugs resulting in a malformed URL
* should not have a security impact and are likely to be easily detectable
* during testing. Given the wide number of non-RFC compliant URLs in use,
* stricter validation could prevent some applications from being able to use
* this type.
*
* Instances of this type must be created via the factory method,
* ({@code goog.html.TrustedResourceUrl.fromConstant}), and not by invoking its
* constructor. The constructor intentionally takes no parameters and the type
* is immutable; hence only a default instance corresponding to the empty
* string can be obtained via constructor invocation.
*
* @see goog.html.TrustedResourceUrl#fromConstant
* @constructor
* @final
* @struct
* @implements {goog.i18n.bidi.DirectionalString}
* @implements {goog.string.TypedString}
*/
goog.html.TrustedResourceUrl = function() {
/**
* The contained value of this TrustedResourceUrl. The field has a purposely
* ugly name to make (non-compiled) code that attempts to directly access this
* field stand out.
* @private {string}
*/
this.privateDoNotAccessOrElseTrustedResourceUrlWrappedValue_ = '';
/**
* A type marker used to implement additional run-time type checking.
* @see goog.html.TrustedResourceUrl#unwrap
* @const
* @private
*/
this.TRUSTED_RESOURCE_URL_TYPE_MARKER_GOOG_HTML_SECURITY_PRIVATE_ =
goog.html.TrustedResourceUrl.TYPE_MARKER_GOOG_HTML_SECURITY_PRIVATE_;
};
/**
* @override
* @const
*/
goog.html.TrustedResourceUrl.prototype.implementsGoogStringTypedString = true;
/**
* Returns this TrustedResourceUrl's value as a string.
*
* IMPORTANT: In code where it is security relevant that an object's type is
* indeed {@code TrustedResourceUrl}, use
* {@code goog.html.TrustedResourceUrl.unwrap} instead of this method. If in
* doubt, assume that it's security relevant. In particular, note that
* goog.html functions which return a goog.html type do not guarantee that
* the returned instance is of the right type. For example:
*
* <pre>
* var fakeSafeHtml = new String('fake');
* fakeSafeHtml.__proto__ = goog.html.SafeHtml.prototype;
* var newSafeHtml = goog.html.SafeHtml.htmlEscape(fakeSafeHtml);
* // newSafeHtml is just an alias for fakeSafeHtml, it's passed through by
* // goog.html.SafeHtml.htmlEscape() as fakeSafeHtml instanceof
* // goog.html.SafeHtml.
* </pre>
*
* @see goog.html.TrustedResourceUrl#unwrap
* @override
*/
goog.html.TrustedResourceUrl.prototype.getTypedStringValue = function() {
return this.privateDoNotAccessOrElseTrustedResourceUrlWrappedValue_;
};
/**
* @override
* @const
*/
goog.html.TrustedResourceUrl.prototype.implementsGoogI18nBidiDirectionalString =
true;
/**
* Returns this URLs directionality, which is always {@code LTR}.
* @override
*/
goog.html.TrustedResourceUrl.prototype.getDirection = function() {
return goog.i18n.bidi.Dir.LTR;
};
if (goog.DEBUG) {
/**
* Returns a debug string-representation of this value.
*
* To obtain the actual string value wrapped in a TrustedResourceUrl, use
* {@code goog.html.TrustedResourceUrl.unwrap}.
*
* @see goog.html.TrustedResourceUrl#unwrap
* @override
*/
goog.html.TrustedResourceUrl.prototype.toString = function() {
return 'TrustedResourceUrl{' +
this.privateDoNotAccessOrElseTrustedResourceUrlWrappedValue_ + '}';
};
}
/**
* Performs a runtime check that the provided object is indeed a
* TrustedResourceUrl object, and returns its value.
*
* @param {!goog.html.TrustedResourceUrl} trustedResourceUrl The object to
* extract from.
* @return {string} The trustedResourceUrl object's contained string, unless
* the run-time type check fails. In that case, {@code unwrap} returns an
* innocuous string, or, if assertions are enabled, throws
* {@code goog.asserts.AssertionError}.
*/
goog.html.TrustedResourceUrl.unwrap = function(trustedResourceUrl) {
// Perform additional Run-time type-checking to ensure that
// trustedResourceUrl is indeed an instance of the expected type. This
// provides some additional protection against security bugs due to
// application code that disables type checks.
// Specifically, the following checks are performed:
// 1. The object is an instance of the expected type.
// 2. The object is not an instance of a subclass.
// 3. The object carries a type marker for the expected type. "Faking" an
// object requires a reference to the type marker, which has names intended
// to stand out in code reviews.
if (trustedResourceUrl instanceof goog.html.TrustedResourceUrl &&
trustedResourceUrl.constructor === goog.html.TrustedResourceUrl &&
trustedResourceUrl
.TRUSTED_RESOURCE_URL_TYPE_MARKER_GOOG_HTML_SECURITY_PRIVATE_ ===
goog.html.TrustedResourceUrl
.TYPE_MARKER_GOOG_HTML_SECURITY_PRIVATE_) {
return trustedResourceUrl
.privateDoNotAccessOrElseTrustedResourceUrlWrappedValue_;
} else {
goog.asserts.fail('expected object of type TrustedResourceUrl, got \'' +
trustedResourceUrl + '\'');
return 'type_error:TrustedResourceUrl';
}
};
/**
* Creates a TrustedResourceUrl object from a compile-time constant string.
*
* Compile-time constant strings are inherently program-controlled and hence
* trusted.
*
* @param {!goog.string.Const} url A compile-time-constant string from which to
* create a TrustedResourceUrl.
* @return {!goog.html.TrustedResourceUrl} A TrustedResourceUrl object
* initialized to {@code url}.
*/
goog.html.TrustedResourceUrl.fromConstant = function(url) {
return goog.html.TrustedResourceUrl
.createTrustedResourceUrlSecurityPrivateDoNotAccessOrElse(
goog.string.Const.unwrap(url));
};
/**
* Type marker for the TrustedResourceUrl type, used to implement additional
* run-time type checking.
* @const
* @private
*/
goog.html.TrustedResourceUrl.TYPE_MARKER_GOOG_HTML_SECURITY_PRIVATE_ = {};
/**
* Package-internal utility method to create TrustedResourceUrl instances.
*
* @param {string} url The string to initialize the TrustedResourceUrl object
* with.
* @return {!goog.html.TrustedResourceUrl} The initialized TrustedResourceUrl
* object.
* @package
*/
goog.html.TrustedResourceUrl.
createTrustedResourceUrlSecurityPrivateDoNotAccessOrElse = function(url) {
var trustedResourceUrl = new goog.html.TrustedResourceUrl();
trustedResourceUrl.privateDoNotAccessOrElseTrustedResourceUrlWrappedValue_ =
url;
return trustedResourceUrl;
};
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