hast-util-sanitize

hast utility to sanitize a tree.

Install

npm install hast-util-sanitize

Use

var h = require('hastscript')
var u = require('unist-builder')
var sanitize = require('hast-util-sanitize')
var toHtml = require('hast-util-to-html')

var tree = h('div', {onmouseover: 'alert("alpha")'}, [
  h(
    'a',
    {href: 'jAva script:alert("bravo")', onclick: 'alert("charlie")'},
    'delta'
  ),
  u('text', '\n'),
  h('script', 'alert("charlie")'),
  u('text', '\n'),
  h('img', {src: 'x', onerror: 'alert("delta")'}),
  u('text', '\n'),
  h('iframe', {src: 'javascript:alert("echo")'}),
  u('text', '\n'),
  h('math', h('mi', {'xlink:href': 'data:x,<script>alert("foxtrot")</script>'}))
])

var unsanitized = toHtml(tree)
var sanitized = toHtml(sanitize(tree))

console.log(unsanitized)
console.log(sanitized)

Unsanitized:

<div onmouseover="alert(&#x22;alpha&#x22;)"><a href="jAva script:alert(&#x22;bravo&#x22;)" onclick="alert(&#x22;charlie&#x22;)">delta</a>
<script>alert("charlie")</script>
<img src="x" onerror="alert(&#x22;delta&#x22;)">
<iframe src="javascript:alert(&#x22;echo&#x22;)"></iframe>
<math><mi xlink:href="data:x,<script>alert(&#x22;foxtrot&#x22;)</script>"></mi></math></div>

Sanitized:

<div><a>delta</a>

<img src="x">

</div>

API

`sanitize(tree[, schema])`

Sanitize a hast tree.

Parameters

tree (Node) — Tree to sanitize
schema (Schema, optional) — Schema defining how to sanitize

Returns

Node — A new, sanitized tree.

`Schema`

Configuration. If not given, defaults to GitHub style sanitation. If any top-level key isn’t given, it defaults to GitHub’s style too.

For a thorough sample, see github.json.

To extend the standard schema with a few changes, clone github.json like so:

var h = require('hastscript')
var merge = require('deepmerge')
var gh = require('hast-util-sanitize/lib/github')
var sanitize = require('hast-util-sanitize')

var schema = merge(gh, {attributes: {'*': ['className']}})

var tree = sanitize(h('div', {className: ['foo']}), schema)

// `tree` still has `className`.
console.log(tree)

`attributes`

Map of tag names to allowed property names (Object.<Array.<string>>).

The special '*' key defines property names allowed on all elements.

One special value, namely 'data*', can be used to allow all data properties.

"attributes": {
  "a": [
    "href"
  ],
  "img": [
    "src",
    "longDesc"
  ],
  // …
  "*": [
    "abbr",
    "accept",
    "acceptCharset",
    // …
    "vSpace",
    "width",
    "itemProp"
  ]
}

Instead of a single string (such as type), which allows any property value of that property name, it’s also possible to provide an array (such as ['type', 'checkbox']), where the first entry is the propery name, and the other entries are allowed property values.

This is how the default GitHub schema allows only disabled checkbox inputs:

"attributes": {
  // …
  "input": [
    ["type", "checkbox"],
    ["disabled", true]
  ],
  // …
}

`required`

Map of tag names to required property names and their default property value (Object.<Object.<*>>). If the defined keys do not exist in an element’s properties, they are added and set to the specified value.

Note that properties are first checked based on the schema at attributes, so properties could be removed by that step and then added again through required.

"required": {
  "input": {
    "type": "checkbox",
    "disabled": true
  }
}

`tagNames`

List of allowed tag names (Array.<string>).

"tagNames": [
  "h1",
  "h2",
  "h3",
  // …
  "strike",
  "summary",
  "details"
]

`protocols`

Map of protocols to allow in property values (Object.<Array.<string>>).

"protocols": {
  "href": [
    "http",
    "https",
    "mailto"
  ],
  // …
  "longDesc": [
    "http",
    "https"
  ]
}

`ancestors`

Map of tag names to their required ancestor elements (Object.<Array.<string>>).

"ancestors": {
  "li": [
    "ol",
    "ul"
  ],
  // …
  "tr": [
    "table"
  ]
}

`clobber`

List of allowed property names which can clobber (Array.<string>).

"clobber": [
  "name",
  "id"
]

`clobberPrefix`

Prefix to use before potentially clobbering property names (string).

"clobberPrefix": "user-content-"

`strip`

Names of elements to strip from the tree (Array.<string>).

By default, unsafe elements are replaced by their children. Some elements, should however be entirely stripped from the tree.

"strip": [
  "script"
]

`allowComments`

Whether to allow comments (boolean, default: false).

"allowComments": true

`allowDoctypes`

Whether to allow doctypes (boolean, default: false).

"allowDoctypes": true

Security

Improper use of hast-util-sanitize can open you up to a cross-site scripting (XSS) attack. The defaults are safe, but deviating from them is likely unsafe.

Use hast-util-sanitize after all other utilities, as other utilities are likely also unsafe.

rehype-sanitize — rehype plugin wrapper

Contribute

See contributing.md in syntax-tree/.github for ways to get started. See support.md for ways to get help.

This project has a code of conduct. By interacting with this repository, organization, or community you agree to abide by its terms.

viczam/hast-util-sanitize