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feat(security): only warn when actually sanitizing HTML. (#10272) 

Previously, Angular would warn users when simply re-encoding text
outside of the ASCII range. While harmless, the log spam was annoying.

With this change, Angular specifically tracks whether anything was
stripped during sanitization, and only reports a warning if so.

Fixes #10206.
This commit is contained in:
Martin Probst 2016-07-26 11:39:09 -07:00 committed by GitHub
parent b449467940
commit 482c019199
2 changed files with 44 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

46
modules/@angular/platform-browser/src/security/html_sanitizer.ts
View File

@ -12,8 +12,6 @@ import {DomAdapter, getDOM} from '../dom/dom_adapter';
import {sanitizeSrcset, sanitizeUrl} from './url_sanitizer';
/** A <body> element that can be safely used to parse untrusted HTML. Lazily initialized below. */
let inertElement: HTMLElement = null;
/** Lazily initialized to make sure the DOM adapter gets set before use. */
@ -43,7 +41,7 @@ function getInertElement() {
function tagSet(tags: string): {[k: string]: boolean} {
let res: {[k: string]: boolean} = {};
for (let t of tags.split(',')) res[t.toLowerCase()] = true;
for (let t of tags.split(',')) res[t] = true;
return res;
}
@ -119,6 +117,9 @@ const VALID_ATTRS = merge(URI_ATTRS, SRCSET_ATTRS, HTML_ATTRS);
* attributes.
*/
class SanitizingHtmlSerializer {
// Explicitly track if something was stripped, to avoid accidentally warning of sanitization just
// because characters were re-encoded.
public sanitizedSomething = false;
private buf: string[] = [];
sanitizeChildren(el: Element): string {
@ -128,9 +129,12 @@ class SanitizingHtmlSerializer {
let current: Node = el.firstChild;
while (current) {
if (DOM.isElementNode(current)) {
this.startElement(current);
this.startElement(current as Element);
} else if (DOM.isTextNode(current)) {
this.chars(DOM.nodeValue(current));
} else {
// Strip non-element, non-text nodes.
this.sanitizedSomething = true;
}
if (DOM.firstChild(current)) {
current = DOM.firstChild(current);
@ -139,7 +143,7 @@ class SanitizingHtmlSerializer {
while (current) {
// Leaving the element. Walk up and to the right, closing tags as we go.
if (DOM.isElementNode(current)) {
this.endElement(DOM.nodeName(current).toLowerCase());
this.endElement(current as Element);
}
if (DOM.nextSibling(current)) {
current = DOM.nextSibling(current);
@ -151,15 +155,20 @@ class SanitizingHtmlSerializer {
return this.buf.join('');
}
private startElement(element: any) {
let tagName = DOM.nodeName(element).toLowerCase();
tagName = tagName.toLowerCase();
if (VALID_ELEMENTS.hasOwnProperty(tagName)) {
private startElement(element: Element) {
const tagName = DOM.nodeName(element).toLowerCase();
if (!VALID_ELEMENTS.hasOwnProperty(tagName)) {
this.sanitizedSomething = true;
return;
}
this.buf.push('<');
this.buf.push(tagName);
DOM.attributeMap(element).forEach((value: string, attrName: string) => {
let lower = attrName.toLowerCase();
if (!VALID_ATTRS.hasOwnProperty(lower)) return;
if (!VALID_ATTRS.hasOwnProperty(lower)) {
this.sanitizedSomething = true;
return;
}
// TODO(martinprobst): Special case image URIs for data:image/...
if (URI_ATTRS[lower]) value = sanitizeUrl(value);
if (SRCSET_ATTRS[lower]) value = sanitizeSrcset(value);
@ -171,10 +180,9 @@ class SanitizingHtmlSerializer {
});
this.buf.push('>');
}
}
private endElement(tagName: string) {
tagName = tagName.toLowerCase();
private endElement(current: Element) {
const tagName = DOM.nodeName(current).toLowerCase();
if (VALID_ELEMENTS.hasOwnProperty(tagName) && !VOID_ELEMENTS.hasOwnProperty(tagName)) {
this.buf.push('</');
this.buf.push(tagName);
@ -197,18 +205,18 @@ const NON_ALPHANUMERIC_REGEXP = /([^\#-~ |!])/g;
* @param value
* @returns {string} escaped text
*/
function encodeEntities(value: any /** TODO #9100 */) {
function encodeEntities(value: string) {
return value.replace(/&/g, '&amp;')
.replace(
SURROGATE_PAIR_REGEXP,
function(match: any /** TODO #9100 */) {
function(match: string) {
let hi = match.charCodeAt(0);
let low = match.charCodeAt(1);
return '&#' + (((hi - 0xD800) * 0x400) + (low - 0xDC00) + 0x10000) + ';';
})
.replace(
NON_ALPHANUMERIC_REGEXP,
function(match: any /** TODO #9100 */) { return '&#' + match.charCodeAt(0) + ';'; })
function(match: string) { return '&#' + match.charCodeAt(0) + ';'; })
.replace(/</g, '&lt;')
.replace(/>/g, '&gt;');
}
@ -220,14 +228,14 @@ function encodeEntities(value: any /** TODO #9100 */) {
* This is undesirable since we don't want to allow any of these custom attributes. This method
* strips them all.
*/
function stripCustomNsAttrs(el: any) {
function stripCustomNsAttrs(el: Element) {
DOM.attributeMap(el).forEach((_, attrName) => {
if (attrName === 'xmlns:ns1' || attrName.indexOf('ns1:') === 0) {
DOM.removeAttribute(el, attrName);
}
});
for (let n of DOM.childNodesAsList(el)) {
if (DOM.isElementNode(n)) stripCustomNsAttrs(n);
if (DOM.isElementNode(n)) stripCustomNsAttrs(n as Element);
}
}
@ -270,7 +278,7 @@ export function sanitizeHtml(unsafeHtmlInput: string): string {
DOM.removeChild(parent, child);
}
if (isDevMode() && safeHtml !== unsafeHtmlInput) {
if (isDevMode() && sanitizer.sanitizedSomething) {
DOM.log('WARNING: sanitizing HTML stripped some content (see http://g.co/ng/security#xss).');
}

4
modules/@angular/platform-browser/test/security/html_sanitizer_spec.ts
View File

@ -63,6 +63,10 @@ export function main() {
t.expect(sanitizeHtml('&#128640;')).toEqual('&#128640;');
t.expect(logMsgs).toEqual([]);
});
t.it('does not warn when just re-encoding text', () => {
t.expect(sanitizeHtml('<p>Hellö Wörld</p>')).toEqual('<p>Hell&#246; W&#246;rld</p>');
t.expect(logMsgs).toEqual([]);
});
t.it('escapes entities', () => {
t.expect(sanitizeHtml('<p>Hello &lt; World</p>')).toEqual('<p>Hello &lt; World</p>');
t.expect(sanitizeHtml('<p>Hello < World</p>')).toEqual('<p>Hello &lt; World</p>');