Class: HTML::Pipeline::SanitizationFilter

Inherits:
Filter
  • Object
show all
Defined in:
lib/html/pipeline/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', :relative, 'github-windows', 'github-mac'].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
  ),
  :remove_contents => ['script'],
  :attributes => {
    'a'          => ['href'],
    'img'        => ['src', 'longdesc'],
    'div'        => ['itemscope', 'itemtype'],
    'blockquote' => ['cite'],
    'del'        => ['cite'],
    'ins'        => ['cite'],
    'q'          => ['cite'],
    :all         => ['abbr', 'accept', 'accept-charset',
                     'accesskey', 'action', 'align', 'alt', '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']
  },
  :protocols => {
    'a'          => {'href' => ANCHOR_SCHEMES},
    'blockquote' => {'cite' => ['http', 'https', :relative]},
    'del'        => {'cite' => ['http', 'https', :relative]},
    'ins'        => {'cite' => ['http', 'https', :relative]},
    'q'          => {'cite' => ['http', 'https', :relative]},
    'img'        => {
      'src'      => ['http', 'https', :relative],
      'longdesc' => ['http', 'https', :relative]
    }
  },
  :transformers => [
    # Top-level <li> elements are removed because they can break out of
    # containing markup.
    lambda { |env|
      name, node = env[:node_name], env[:node]
      if name == LIST_ITEM && !node.ancestors.any?{ |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, node = env[:node_name], env[:node]
      if (TABLE_SECTIONS.include?(name) || TABLE_ITEMS.include?(name)) && !node.ancestors.any? { |n| n.name == TABLE }
        node.replace(node.children)
      end
    }
  ]
}
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 p ol ul li))
FULL =

Strip all HTML tags from the document.

{ :elements => [] }

Instance Attribute Summary

Attributes inherited from Filter

#context, #result

Instance Method Summary collapse

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

#callObject

Sanitize markup using the Sanitize library.



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# File 'lib/html/pipeline/sanitization_filter.rb', line 118

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

#whitelistObject

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



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# File 'lib/html/pipeline/sanitization_filter.rb', line 124

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