debian-mirror-gitlab/app/assets/javascripts/lib/dompurify.js

import { sanitize as dompurifySanitize, addHook } from 'dompurify';
import { getNormalizedURL, getBaseURL, relativePathToAbsolute } from '~/lib/utils/url_utility';

const defaultConfig = {
  // Safely allow SVG <use> tags
  ADD_TAGS: ['use', 'gl-emoji', 'copy-code'],
  // Prevent possible XSS attacks with data-* attributes used by @rails/ujs
  // See https://gitlab.com/gitlab-org/gitlab-ui/-/issues/1421
  FORBID_ATTR: ['data-remote', 'data-url', 'data-type', 'data-method'],
  FORBID_TAGS: ['style', 'mstyle'],
};

// Only icons urls from `gon` are allowed
const getAllowedIconUrls = (gon = window.gon) =>
  [gon.sprite_file_icons, gon.sprite_icons]
    .filter(Boolean)
    .map((path) => relativePathToAbsolute(path, getBaseURL()));

const isUrlAllowed = (url) =>
  getAllowedIconUrls().some((allowedUrl) => getNormalizedURL(url).startsWith(allowedUrl));

const isHrefSafe = (url) => url.match(/^#/) || isUrlAllowed(url);

const removeUnsafeHref = (node, attr) => {
  if (!node.hasAttribute(attr)) {
    return;
  }

  if (!isHrefSafe(node.getAttribute(attr))) {
    node.removeAttribute(attr);
  }
};

/**
 * Sanitize icons' <use> tag attributes, to safely include
 * svgs such as in:
 *
 * <svg viewBox="0 0 100 100">
 *   <use href="/assets/icons-xxx.svg#icon_name"></use>
 * </svg>
 *
 * It validates both href & xlink:href attributes.
 * Note that `xlink:href` is deprecated, but still in use
 * https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/xlink:href
 *
 * @param {Object} node - Node to sanitize
 */
const sanitizeSvgIcon = (node) => {
  removeUnsafeHref(node, 'href');
  removeUnsafeHref(node, 'xlink:href');
};

addHook('afterSanitizeAttributes', (node) => {
  if (node.tagName.toLowerCase() === 'use') {
    sanitizeSvgIcon(node);
  }
});

export const sanitize = (val, config) => dompurifySanitize(val, { ...defaultConfig, ...config });