2017-08-31 22:05:18 +01:00
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/**
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* @license
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* Copyright Google Inc. All Rights Reserved.
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*
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* Use of this source code is governed by an MIT-style license that can be
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* found in the LICENSE file at https://angular.io/license
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*/
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/**
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* This helper class is used to get hold of an inert tree of DOM elements containing dirty HTML
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* that needs sanitizing.
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* Depending upon browser support we must use one of three strategies for doing this.
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* Support: Safari 10.x -> XHR strategy
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* Support: Firefox -> DomParser strategy
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* Default: InertDocument strategy
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*/
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export class InertBodyHelper {
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private inertBodyElement: HTMLElement;
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private inertDocument: Document;
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2017-08-31 22:05:18 +01:00
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2018-03-01 13:16:13 -08:00
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constructor(private defaultDoc: Document) {
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this.inertDocument = this.defaultDoc.implementation.createHTMLDocument('sanitization-inert');
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this.inertBodyElement = this.inertDocument.body;
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2017-08-31 22:05:18 +01:00
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if (this.inertBodyElement == null) {
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// usually there should be only one body element in the document, but IE doesn't have any, so
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// we need to create one.
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const inertHtml = this.inertDocument.createElement('html');
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this.inertDocument.appendChild(inertHtml);
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this.inertBodyElement = this.inertDocument.createElement('body');
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inertHtml.appendChild(this.inertBodyElement);
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2017-08-31 22:05:18 +01:00
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}
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2018-03-01 13:16:13 -08:00
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this.inertBodyElement.innerHTML = '<svg><g onload="this.parentNode.remove()"></g></svg>';
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if (this.inertBodyElement.querySelector && !this.inertBodyElement.querySelector('svg')) {
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// We just hit the Safari 10.1 bug - which allows JS to run inside the SVG G element
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// so use the XHR strategy.
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this.getInertBodyElement = this.getInertBodyElement_XHR;
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return;
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}
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2018-03-01 13:16:13 -08:00
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this.inertBodyElement.innerHTML =
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'<svg><p><style><img src="</style><img src=x onerror=alert(1)//">';
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if (this.inertBodyElement.querySelector && this.inertBodyElement.querySelector('svg img')) {
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// We just hit the Firefox bug - which prevents the inner img JS from being sanitized
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// so use the DOMParser strategy, if it is available.
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// If the DOMParser is not available then we are not in Firefox (Server/WebWorker?) so we
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// fall through to the default strategy below.
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if (isDOMParserAvailable()) {
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this.getInertBodyElement = this.getInertBodyElement_DOMParser;
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return;
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}
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}
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// None of the bugs were hit so it is safe for us to use the default InertDocument strategy
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this.getInertBodyElement = this.getInertBodyElement_InertDocument;
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}
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/**
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* Get an inert DOM element containing DOM created from the dirty HTML string provided.
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* The implementation of this is determined in the constructor, when the class is instantiated.
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*/
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getInertBodyElement: (html: string) => HTMLElement | null;
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/**
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* Use XHR to create and fill an inert body element (on Safari 10.1)
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* See
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* https://github.com/cure53/DOMPurify/blob/a992d3a75031cb8bb032e5ea8399ba972bdf9a65/src/purify.js#L439-L449
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*/
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private getInertBodyElement_XHR(html: string) {
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// We add these extra elements to ensure that the rest of the content is parsed as expected
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// e.g. leading whitespace is maintained and tags like `<meta>` do not get hoisted to the
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// `<head>` tag.
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html = '<body><remove></remove>' + html + '</body>';
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try {
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html = encodeURI(html);
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} catch (e) {
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return null;
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}
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const xhr = new XMLHttpRequest();
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xhr.responseType = 'document';
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xhr.open('GET', 'data:text/html;charset=utf-8,' + html, false);
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xhr.send(null);
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const body: HTMLBodyElement = xhr.response.body;
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body.removeChild(body.firstChild !);
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return body;
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}
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/**
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* Use DOMParser to create and fill an inert body element (on Firefox)
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* See https://github.com/cure53/DOMPurify/releases/tag/0.6.7
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*
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*/
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private getInertBodyElement_DOMParser(html: string) {
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// We add these extra elements to ensure that the rest of the content is parsed as expected
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// e.g. leading whitespace is maintained and tags like `<meta>` do not get hoisted to the
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// `<head>` tag.
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html = '<body><remove></remove>' + html + '</body>';
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try {
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const body = new (window as any)
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.DOMParser()
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.parseFromString(html, 'text/html')
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.body as HTMLBodyElement;
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body.removeChild(body.firstChild !);
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return body;
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} catch (e) {
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return null;
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}
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}
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/**
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* Use an HTML5 `template` element, if supported, or an inert body element created via
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* `createHtmlDocument` to create and fill an inert DOM element.
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* This is the default sane strategy to use if the browser does not require one of the specialised
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* strategies above.
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*/
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private getInertBodyElement_InertDocument(html: string) {
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// Prefer using <template> element if supported.
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const templateEl = this.inertDocument.createElement('template');
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if ('content' in templateEl) {
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templateEl.innerHTML = html;
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return templateEl;
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}
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2018-03-01 13:16:13 -08:00
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this.inertBodyElement.innerHTML = html;
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// Support: IE 9-11 only
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// strip custom-namespaced attributes on IE<=11
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if ((this.defaultDoc as any).documentMode) {
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2017-08-31 22:05:18 +01:00
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this.stripCustomNsAttrs(this.inertBodyElement);
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}
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return this.inertBodyElement;
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}
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/**
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* When IE9-11 comes across an unknown namespaced attribute e.g. 'xlink:foo' it adds 'xmlns:ns1'
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* attribute to declare ns1 namespace and prefixes the attribute with 'ns1' (e.g.
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* 'ns1:xlink:foo').
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*
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* This is undesirable since we don't want to allow any of these custom attributes. This method
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* strips them all.
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*/
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private stripCustomNsAttrs(el: Element) {
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const elAttrs = el.attributes;
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// loop backwards so that we can support removals.
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for (let i = elAttrs.length - 1; 0 < i; i--) {
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const attrib = elAttrs.item(i);
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const attrName = attrib.name;
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if (attrName === 'xmlns:ns1' || attrName.indexOf('ns1:') === 0) {
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el.removeAttribute(attrName);
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}
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}
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let childNode = el.firstChild;
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while (childNode) {
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if (childNode.nodeType === Node.ELEMENT_NODE) this.stripCustomNsAttrs(childNode as Element);
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childNode = childNode.nextSibling;
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}
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}
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}
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/**
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* We need to determine whether the DOMParser exists in the global context.
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* The try-catch is because, on some browsers, trying to access this property
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* on window can actually throw an error.
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*
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* @suppress {uselessCode}
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*/
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function isDOMParserAvailable() {
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try {
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return !!(window as any).DOMParser;
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} catch (e) {
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return false;
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}
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}
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