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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
/**
* Parses a very small subset of HTML. This ensures that insecure HTML /
* javascript cannot be injected into WebUI.
* @param {string} s The string to parse.
* @param {!Array<string>=} opt_extraTags Optional extra allowed tags.
* @param {!Array<string>=} opt_extraAttrs
* Optional extra allowed attributes (all tags are run through these).
* @throws {Error} In case of non supported markup.
* @return {DocumentFragment} A document fragment containing the DOM tree.
*/
/* #export */ const parseHtmlSubset = (function() {
'use strict';
/** @typedef {function(!Node, string):boolean} */
let AllowFunction;
/** @type {!AllowFunction} */
const allowAttribute = (node, value) => true;
/**
* Allow-list of attributes in parseHtmlSubset.
* @type {!Map<string, !AllowFunction>}
* @const
*/
const allowedAttributes = new Map([
[
'href',
(node, value) => {
// Only allow a[href] starting with chrome:// and https://
return node.tagName === 'A' &&
(value.startsWith('chrome://') || value.startsWith('https://'));
}
],
[
'target',
(node, value) => {
// Only allow a[target='_blank'].
// TODO(dbeam): are there valid use cases for target !== '_blank'?
return node.tagName === 'A' && value === '_blank';
}
],
]);
/**
* Allow-list of optional attributes in parseHtmlSubset.
* @type {!Map<string, !AllowFunction>}
* @const
*/
const allowedOptionalAttributes = new Map([
['class', allowAttribute],
['id', allowAttribute],
['is', (node, value) => value === 'action-link' || value === ''],
['role', (node, value) => value === 'link'],
[
'src',
(node, value) => {
// Only allow img[src] starting with chrome://
return node.tagName === 'IMG' && value.startsWith('chrome://');
}
],
['tabindex', allowAttribute],
]);
/**
* Allow-list of tag names in parseHtmlSubset.
* @type {!Set<string>}
* @const
*/
const allowedTags =
new Set(['A', 'B', 'BR', 'DIV', 'P', 'PRE', 'SPAN', 'STRONG']);
/**
* Allow-list of optional tag names in parseHtmlSubset.
* @type {!Set<string>}
* @const
*/
const allowedOptionalTags = new Set(['IMG']);
/**
* This policy maps a given string to a `TrustedHTML` object
* without performing any validation. Callsites must ensure
* that the resulting object will only be used in inert
* documents. Initialized lazily.
* @type {!TrustedTypePolicy}
*/
let unsanitizedPolicy;
/**
* @param {!Array<string>} optTags an Array to merge.
* @return {!Set<string>} Set of allowed tags.
*/
function mergeTags(optTags) {
const clone = new Set(allowedTags);
optTags.forEach(str => {
const tag = str.toUpperCase();
if (allowedOptionalTags.has(tag)) {
clone.add(tag);
}
});
return clone;
}
/**
* @param {!Array<string>} optAttrs an Array to merge.
* @return {!Map<string, !AllowFunction>} Map of allowed
* attributes.
*/
function mergeAttrs(optAttrs) {
const clone = new Map([...allowedAttributes]);
optAttrs.forEach(key => {
if (allowedOptionalAttributes.has(key)) {
clone.set(key, allowedOptionalAttributes.get(key));
}
});
return clone;
}
function walk(n, f) {
f(n);
for (let i = 0; i < n.childNodes.length; i++) {
walk(n.childNodes[i], f);
}
}
function assertElement(tags, node) {
if (!tags.has(node.tagName)) {
throw Error(node.tagName + ' is not supported');
}
}
function assertAttribute(attrs, attrNode, node) {
const n = attrNode.nodeName;
const v = attrNode.nodeValue;
if (!attrs.has(n) || !attrs.get(n)(node, v)) {
throw Error(node.tagName + '[' + n + '="' + v + '"] is not supported');
}
}
return function(s, opt_extraTags, opt_extraAttrs) {
const tags = opt_extraTags ? mergeTags(opt_extraTags) : allowedTags;
const attrs =
opt_extraAttrs ? mergeAttrs(opt_extraAttrs) : allowedAttributes;
const doc = document.implementation.createHTMLDocument('');
const r = doc.createRange();
r.selectNode(doc.body);
if (window.trustedTypes) {
if (!unsanitizedPolicy) {
unsanitizedPolicy = trustedTypes.createPolicy(
'parse-html-subset', {createHTML: untrustedHTML => untrustedHTML});
}
s = unsanitizedPolicy.createHTML(s);
}
// This does not execute any scripts because the document has no view.
const df = r.createContextualFragment(s);
walk(df, function(node) {
switch (node.nodeType) {
case Node.ELEMENT_NODE:
assertElement(tags, node);
const nodeAttrs = node.attributes;
for (let i = 0; i < nodeAttrs.length; ++i) {
assertAttribute(attrs, nodeAttrs[i], node);
}
break;
case Node.COMMENT_NODE:
case Node.DOCUMENT_FRAGMENT_NODE:
case Node.TEXT_NODE:
break;
default:
throw Error('Node type ' + node.nodeType + ' is not supported');
}
});
return df;
};
})();
/* #ignore */ console.warn('crbug/1173575, non-JS module files deprecated.');
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