Class: HTML::Pipeline::SanitizationFilter

Inherits:

Filter

• Object
• Filter
• HTML::Pipeline::SanitizationFilter

Defined in:

lib/html/pipeline_plus/sanitization_filter.rb

Overview

HTML filter with sanization routines and whitelists. This module defines what HTML is allowed in user provided content and fixes up issues with unbalanced tags and whatnot.

See the Sanitize docs for more information on the underlying library:

github.com/rgrove/sanitize/#readme

Context options:

:whitelist      - The sanitizer whitelist configuration to use. This
                  can be one of the options constants defined in this
                  class or a custom sanitize options hash.
:anchor_schemes - The URL schemes to allow in <a href> attributes. The
                  default set is provided in the ANCHOR_SCHEMES
                  constant in this class. If passed, this overrides any
                  schemes specified in the whitelist configuration.

This filter does not write additional information to the context.

Constant Summary

LISTS =

Set.new(%w[ul ol].freeze)

LIST_ITEM =

'li'.freeze

TABLE_ITEMS =

List of table child elements. These must be contained by a <table> element or they are not allowed through. Otherwise they can be used to break out of places we’re using tables to contain formatted user content (like pull request review comments).

Set.new(%w[tr td th].freeze)

TABLE =

'table'.freeze

TABLE_SECTIONS =

Set.new(%w[thead tbody tfoot].freeze)

ANCHOR_SCHEMES =

These schemes are the only ones allowed in <a href> attributes by default.

['http', 'https', 'mailto', 'xmpp', :relative, 'github-windows', 'github-mac', 'irc', 'ircs'].freeze

WHITELIST =

The main sanitization whitelist. Only these elements and attributes are allowed through by default.

{
  elements: %w[
    h1 h2 h3 h4 h5 h6 h7 h8 br b i strong em a pre code img tt
    div ins del sup sub p ol ul table thead tbody tfoot blockquote
    dl dt dd kbd q samp var hr ruby rt rp li tr td th s strike summary
    details caption figure figcaption
    abbr bdo cite dfn mark small span time wbr
  ].freeze,
  remove_contents: ['script'].freeze,
  attributes: {
    'a'          => ['href'].freeze,
    'img'        => %w[src longdesc].freeze,
    'div'        => %w[itemscope itemtype].freeze,
    'blockquote' => ['cite'].freeze,
    'del'        => ['cite'].freeze,
    'ins'        => ['cite'].freeze,
    'q'          => ['cite'].freeze,
    all: %w[abbr accept accept-charset
            accesskey action align alt
            aria-describedby aria-hidden aria-label aria-labelledby
            axis border cellpadding cellspacing char
            charoff charset checked
            clear cols colspan color
            compact coords datetime dir
            disabled enctype for frame
            headers height hreflang
            hspace ismap label lang
            maxlength media method
            multiple name nohref noshade
            nowrap open prompt readonly rel rev
            rows rowspan rules scope
            selected shape size span
            start summary tabindex target
            title type usemap valign value
            vspace width itemprop].freeze
  }.freeze,
  protocols: {
    'a'          => { 'href' => ANCHOR_SCHEMES }.freeze,
    'blockquote' => { 'cite' => ['http', 'https', :relative].freeze },
    'del'        => { 'cite' => ['http', 'https', :relative].freeze },
    'ins'        => { 'cite' => ['http', 'https', :relative].freeze },
    'q'          => { 'cite' => ['http', 'https', :relative].freeze },
    'img'        => {
      'src'      => ['http', 'https', :relative].freeze,
      'longdesc' => ['http', 'https', :relative].freeze
    }.freeze
  },
  transformers: [
    # Top-level <li> elements are removed because they can break out of
    # containing markup.
    lambda { |env|
      name = env[:node_name]
      node = env[:node]
      if name == LIST_ITEM && node.ancestors.none? { |n| LISTS.include?(n.name) }
        node.replace(node.children)
      end
    },

    # Table child elements that are not contained by a <table> are removed.
    lambda { |env|
      name = env[:node_name]
      node = env[:node]
      if (TABLE_SECTIONS.include?(name) || TABLE_ITEMS.include?(name)) && node.ancestors.none? { |n| n.name == TABLE }
        node.replace(node.children)
      end
    }
  ].freeze
}.freeze

LIMITED =

A more limited sanitization whitelist. This includes all attributes, protocols, and transformers from WHITELIST but with a more locked down set of allowed elements.

WHITELIST.merge(
  elements: %w[b i strong em a pre code img ins del sup sub mark abbr p ol ul li]
)

FULL =

Strip all HTML tags from the document.

{ elements: [] }.freeze

Instance Attribute Summary

Attributes inherited from Filter

#context, #result

Instance Method Summary

• #call ⇒ Object

  Sanitize markup using the Sanitize library.

• #whitelist ⇒ Object

  The whitelist to use when sanitizing.

Methods inherited from Filter

#base_url, call, #current_user, #doc, #has_ancestor?, #html, #initialize, #needs, #parse_html, #repository, to_document, to_html, #validate

Constructor Details

This class inherits a constructor from HTML::Pipeline::Filter

Instance Method Details

#call ⇒ Object

Sanitize markup using the Sanitize library.

# File 'lib/html/pipeline_plus/sanitization_filter.rb', line 120

def call
  Sanitize.clean_node!(doc, whitelist)
end

#whitelist ⇒ Object

The whitelist to use when sanitizing. This can be passed in the context hash to the filter but defaults to WHITELIST constant value above.

# File 'lib/html/pipeline_plus/sanitization_filter.rb', line 126

def whitelist
  whitelist = context[:whitelist] || WHITELIST
  anchor_schemes = context[:anchor_schemes]
  return whitelist unless anchor_schemes
  whitelist = whitelist.dup
  whitelist[:protocols] = (whitelist[:protocols] || {}).dup
  whitelist[:protocols]['a'] = (whitelist[:protocols]['a'] || {}).merge('href' => anchor_schemes)
  whitelist
end