js/src/util/sanitizer.js

/**
 * --------------------------------------------------------------------------
 * Bootstrap (v5.2.1): util/sanitizer.js
 * Licensed under MIT (https://github.com/twbs/bootstrap/blob/main/LICENSE)
 * --------------------------------------------------------------------------
 */

const uriAttributes = new Set([
  'background',
  'cite',
  'href',
  'itemtype',
  'longdesc',
  'poster',
  'src',
  'xlink:href'
])

const ARIA_ATTRIBUTE_PATTERN = /^aria-[\w-]*$/i

/**
 * A pattern that recognizes a commonly useful subset of URLs that are safe.
 *
 * Shout-out to Angular https://github.com/angular/angular/blob/12.2.x/packages/core/src/sanitization/url_sanitizer.ts
 */
const SAFE_URL_PATTERN = /^(?:(?:https?|mailto|ftp|tel|file|sms):|[^#&/:?]*(?:[#/?]|$))/i

/**
 * A pattern that matches safe data URLs. Only matches image, video and audio types.
 *
 * Shout-out to Angular https://github.com/angular/angular/blob/12.2.x/packages/core/src/sanitization/url_sanitizer.ts
 */
const DATA_URL_PATTERN = /^data:(?:image\/(?:bmp|gif|jpeg|jpg|png|tiff|webp)|video\/(?:mpeg|mp4|ogg|webm)|audio\/(?:mp3|oga|ogg|opus));base64,[\d+/a-z]+=*$/i

const allowedAttribute = (attribute, allowedAttributeList) => {
  const attributeName = attribute.nodeName.toLowerCase()

  if (allowedAttributeList.includes(attributeName)) {
    if (uriAttributes.has(attributeName)) {
      return Boolean(SAFE_URL_PATTERN.test(attribute.nodeValue) || DATA_URL_PATTERN.test(attribute.nodeValue))
    }

    return true
  }

  // Check if a regular expression validates the attribute.
  return allowedAttributeList.filter(attributeRegex => attributeRegex instanceof RegExp)
    .some(regex => regex.test(attributeName))
}

export const DefaultAllowlist = {
  // Global attributes allowed on any supplied element below.
  '*': ['class', 'dir', 'id', 'lang', 'role', ARIA_ATTRIBUTE_PATTERN],
  a: ['target', 'href', 'title', 'rel'],
  area: [],
  b: [],
  br: [],
  col: [],
  code: [],
  div: [],
  em: [],
  hr: [],
  h1: [],
  h2: [],
  h3: [],
  h4: [],
  h5: [],
  h6: [],
  i: [],
  img: ['src', 'srcset', 'alt', 'title', 'width', 'height'],
  li: [],
  ol: [],
  p: [],
  pre: [],
  s: [],
  small: [],
  span: [],
  sub: [],
  sup: [],
  strong: [],
  u: [],
  ul: []
}

export function sanitizeHtml(unsafeHtml, allowList, sanitizeFunction) {
  if (!unsafeHtml.length) {
    return unsafeHtml
  }

  if (sanitizeFunction && typeof sanitizeFunction === 'function') {
    return sanitizeFunction(unsafeHtml)
  }

  const domParser = new window.DOMParser()
  const createdDocument = domParser.parseFromString(unsafeHtml, 'text/html')
  const elements = [].concat(...createdDocument.body.querySelectorAll('*'))

  for (const element of elements) {
    const elementName = element.nodeName.toLowerCase()

    if (!Object.keys(allowList).includes(elementName)) {
      element.remove()

      continue
    }

    const attributeList = [].concat(...element.attributes)
    const allowedAttributes = [].concat(allowList['*'] || [], allowList[elementName] || [])

    for (const attribute of attributeList) {
      if (!allowedAttribute(attribute, allowedAttributes)) {
        element.removeAttribute(attribute.nodeName)
      }
    }
  }

  return createdDocument.body.innerHTML
}