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   1 # Pleroma: A lightweight social networking server
   2 # Copyright © 2017-2018 Pleroma Authors <https://pleroma.social/>
   3 # SPDX-License-Identifier: AGPL-3.0-only
   4
   5 defmodule Pleroma.HTML do
   6   alias HtmlSanitizeEx.Scrubber
   7
   8   defp get_scrubbers(scrubber) when is_atom(scrubber), do: [scrubber]
   9   defp get_scrubbers(scrubbers) when is_list(scrubbers), do: scrubbers
  10   defp get_scrubbers(_), do: [Pleroma.HTML.Scrubber.Default]
  11
  12   def get_scrubbers() do
  13     Pleroma.Config.get([:markup, :scrub_policy])
  14     |> get_scrubbers
  15   end
  16
  17   def filter_tags(html, nil) do
  18     get_scrubbers()
  19     |> Enum.reduce(html, fn scrubber, html ->
  20       filter_tags(html, scrubber)
  21     end)
  22   end
  23
  24   def filter_tags(html, scrubber), do: Scrubber.scrub(html, scrubber)
  25   def filter_tags(html), do: filter_tags(html, nil)
  26   def strip_tags(html), do: Scrubber.scrub(html, Scrubber.StripTags)
  27 end
  28
  29 defmodule Pleroma.HTML.Scrubber.TwitterText do
  30   @moduledoc """
  31   An HTML scrubbing policy which limits to twitter-style text.  Only
  32   paragraphs, breaks and links are allowed through the filter.
  33   """
  34
  35   @markup Application.get_env(:pleroma, :markup)
  36   @uri_schemes Application.get_env(:pleroma, :uri_schemes, [])
  37   @valid_schemes Keyword.get(@uri_schemes, :valid_schemes, [])
  38
  39   require HtmlSanitizeEx.Scrubber.Meta
  40   alias HtmlSanitizeEx.Scrubber.Meta
  41
  42   def version do 0 end
  43   Meta.remove_cdata_sections_before_scrub()
  44   Meta.strip_comments()
  45
  46   # links
  47   Meta.allow_tag_with_uri_attributes("a", ["href", "data-user", "data-tag"], @valid_schemes)
  48   Meta.allow_tag_with_these_attributes("a", ["name", "title"])
  49
  50   # paragraphs and linebreaks
  51   Meta.allow_tag_with_these_attributes("br", [])
  52   Meta.allow_tag_with_these_attributes("p", [])
  53
  54   # microformats
  55   Meta.allow_tag_with_these_attributes("span", [])
  56
  57   # allow inline images for custom emoji
  58   @allow_inline_images Keyword.get(@markup, :allow_inline_images)
  59
  60   if @allow_inline_images do
  61     # restrict img tags to http/https only, because of MediaProxy.
  62     Meta.allow_tag_with_uri_attributes("img", ["src"], ["http", "https"])
  63
  64     Meta.allow_tag_with_these_attributes("img", [
  65       "width",
  66       "height",
  67       "title",
  68       "alt"
  69     ])
  70   end
  71
  72   Meta.strip_everything_not_covered()
  73 end
  74
  75 defmodule Pleroma.HTML.Scrubber.Default do
  76   @doc "The default HTML scrubbing policy: no "
  77
  78   require HtmlSanitizeEx.Scrubber.Meta
  79   alias HtmlSanitizeEx.Scrubber.Meta
  80   def version do 0 end
  81   @markup Application.get_env(:pleroma, :markup)
  82   @uri_schemes Application.get_env(:pleroma, :uri_schemes, [])
  83   @valid_schemes Keyword.get(@uri_schemes, :valid_schemes, [])
  84
  85   Meta.remove_cdata_sections_before_scrub()
  86   Meta.strip_comments()
  87
  88   Meta.allow_tag_with_uri_attributes("a", ["href", "data-user", "data-tag"], @valid_schemes)
  89   Meta.allow_tag_with_these_attributes("a", ["name", "title"])
  90
  91   Meta.allow_tag_with_these_attributes("abbr", ["title"])
  92
  93   Meta.allow_tag_with_these_attributes("b", [])
  94   Meta.allow_tag_with_these_attributes("blockquote", [])
  95   Meta.allow_tag_with_these_attributes("br", [])
  96   Meta.allow_tag_with_these_attributes("code", [])
  97   Meta.allow_tag_with_these_attributes("del", [])
  98   Meta.allow_tag_with_these_attributes("em", [])
  99   Meta.allow_tag_with_these_attributes("i", [])
 100   Meta.allow_tag_with_these_attributes("li", [])
 101   Meta.allow_tag_with_these_attributes("ol", [])
 102   Meta.allow_tag_with_these_attributes("p", [])
 103   Meta.allow_tag_with_these_attributes("pre", [])
 104   Meta.allow_tag_with_these_attributes("span", [])
 105   Meta.allow_tag_with_these_attributes("strong", [])
 106   Meta.allow_tag_with_these_attributes("u", [])
 107   Meta.allow_tag_with_these_attributes("ul", [])
 108
 109   @allow_inline_images Keyword.get(@markup, :allow_inline_images)
 110
 111   if @allow_inline_images do
 112     # restrict img tags to http/https only, because of MediaProxy.
 113     Meta.allow_tag_with_uri_attributes("img", ["src"], ["http", "https"])
 114
 115     Meta.allow_tag_with_these_attributes("img", [
 116       "width",
 117       "height",
 118       "title",
 119       "alt"
 120     ])
 121   end
 122
 123   @allow_tables Keyword.get(@markup, :allow_tables)
 124
 125   if @allow_tables do
 126     Meta.allow_tag_with_these_attributes("table", [])
 127     Meta.allow_tag_with_these_attributes("tbody", [])
 128     Meta.allow_tag_with_these_attributes("td", [])
 129     Meta.allow_tag_with_these_attributes("th", [])
 130     Meta.allow_tag_with_these_attributes("thead", [])
 131     Meta.allow_tag_with_these_attributes("tr", [])
 132   end
 133
 134   @allow_headings Keyword.get(@markup, :allow_headings)
 135
 136   if @allow_headings do
 137     Meta.allow_tag_with_these_attributes("h1", [])
 138     Meta.allow_tag_with_these_attributes("h2", [])
 139     Meta.allow_tag_with_these_attributes("h3", [])
 140     Meta.allow_tag_with_these_attributes("h4", [])
 141     Meta.allow_tag_with_these_attributes("h5", [])
 142   end
 143
 144   @allow_fonts Keyword.get(@markup, :allow_fonts)
 145
 146   if @allow_fonts do
 147     Meta.allow_tag_with_these_attributes("font", ["face"])
 148   end
 149
 150   Meta.strip_everything_not_covered()
 151 end
 152
 153 defmodule Pleroma.HTML.Transform.MediaProxy do
 154   @moduledoc "Transforms inline image URIs to use MediaProxy."
 155
 156   alias Pleroma.Web.MediaProxy
 157
 158   def version do 0 end
 159   def before_scrub(html), do: html
 160
 161   def scrub_attribute("img", {"src", "http" <> target}) do
 162     media_url =
 163       ("http" <> target)
 164       |> MediaProxy.url()
 165
 166     {"src", media_url}
 167   end
 168
 169   def scrub_attribute(_tag, attribute), do: attribute
 170
 171   def scrub({"img", attributes, children}) do
 172     attributes =
 173       attributes
 174       |> Enum.map(fn attr -> scrub_attribute("img", attr) end)
 175       |> Enum.reject(&is_nil(&1))
 176
 177     {"img", attributes, children}
 178   end
 179
 180   def scrub({:comment, _children}), do: ""
 181
 182   def scrub({tag, attributes, children}), do: {tag, attributes, children}
 183   def scrub({_tag, children}), do: children
 184   def scrub(text), do: text
 185 end