class Pipeline

# HTML filter with sanization routines and allowlists. 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:

#

# https://github.com/rgrove/sanitize/#readme

#

# Context options:

# :allowlist - The sanitizer allowlist 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 allowlist configuration.

#

# This filter does not write additional information to the context.

class SanitizationFilter < Filter

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

LIST_ITEM = 'li'.freeze

# 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).

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

TABLE = 'table'.freeze

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

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

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

# The main sanitization allowlist. Only these elements and attributes are

# allowed through by default.

ALLOWLIST = {

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 progress prompt readonly rel rev

role 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

# A more limited sanitization allowlist. This includes all attributes,

# protocols, and transformers from ALLOWLIST but with a more locked down

# set of allowed elements.

LIMITED = ALLOWLIST.merge(

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

)

# Strip all HTML tags from the document.

FULL = { elements: [] }.freeze

# Sanitize markup using the Sanitize library.

def call

Sanitize.clean_node!(doc, allowlist)

end

def whitelist

warn "[DEPRECATION] 'whitelist' is deprecated. Please use 'allowlist' instead."

allowlist

end

# The allowlist to use when sanitizing. This can be passed in the context

# hash to the filter but defaults to ALLOWLIST constant value above.

def allowlist

allowlist = context[:allowlist] || context[:whitelist] || ALLOWLIST

anchor_schemes = context[:anchor_schemes]

return allowlist unless anchor_schemes

allowlist = allowlist.dup

allowlist[:protocols] = (allowlist[:protocols] || {}).dup

allowlist[:protocols]['a'] = (allowlist[:protocols]['a'] || {}).merge('href' => anchor_schemes)

allowlist

end

end

end