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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   Meta.remove_cdata_sections_before_scrub()
  43   Meta.strip_comments()
  44
  45   # links
  46   Meta.allow_tag_with_uri_attributes("a", ["href", "data-user", "data-tag"], @valid_schemes)
  47   Meta.allow_tag_with_these_attributes("a", ["name", "title"])
  48
  49   # paragraphs and linebreaks
  50   Meta.allow_tag_with_these_attributes("br", [])
  51   Meta.allow_tag_with_these_attributes("p", [])
  52
  53   # microformats
  54   Meta.allow_tag_with_these_attributes("span", [])
  55
  56   # allow inline images for custom emoji
  57   @allow_inline_images Keyword.get(@markup, :allow_inline_images)
  58
  59   if @allow_inline_images do
  60     # restrict img tags to http/https only, because of MediaProxy.
  61     Meta.allow_tag_with_uri_attributes("img", ["src"], ["http", "https"])
  62
  63     Meta.allow_tag_with_these_attributes("img", [
  64       "width",
  65       "height",
  66       "title",
  67       "alt"
  68     ])
  69   end
  70
  71   Meta.strip_everything_not_covered()
  72 end
  73
  74 defmodule Pleroma.HTML.Scrubber.Default do
  75   @doc "The default HTML scrubbing policy: no "
  76
  77   require HtmlSanitizeEx.Scrubber.Meta
  78   alias HtmlSanitizeEx.Scrubber.Meta
  79
  80   @markup Application.get_env(:pleroma, :markup)
  81   @uri_schemes Application.get_env(:pleroma, :uri_schemes, [])
  82   @valid_schemes Keyword.get(@uri_schemes, :valid_schemes, [])
  83
  84   Meta.remove_cdata_sections_before_scrub()
  85   Meta.strip_comments()
  86
  87   Meta.allow_tag_with_uri_attributes("a", ["href", "data-user", "data-tag"], @valid_schemes)
  88   Meta.allow_tag_with_these_attributes("a", ["name", "title"])
  89
  90   Meta.allow_tag_with_these_attributes("abbr", ["title"])
  91
  92   Meta.allow_tag_with_these_attributes("b", [])
  93   Meta.allow_tag_with_these_attributes("blockquote", [])
  94   Meta.allow_tag_with_these_attributes("br", [])
  95   Meta.allow_tag_with_these_attributes("code", [])
  96   Meta.allow_tag_with_these_attributes("del", [])
  97   Meta.allow_tag_with_these_attributes("em", [])
  98   Meta.allow_tag_with_these_attributes("i", [])
  99   Meta.allow_tag_with_these_attributes("li", [])
 100   Meta.allow_tag_with_these_attributes("ol", [])
 101   Meta.allow_tag_with_these_attributes("p", [])
 102   Meta.allow_tag_with_these_attributes("pre", [])
 103   Meta.allow_tag_with_these_attributes("span", [])
 104   Meta.allow_tag_with_these_attributes("strong", [])
 105   Meta.allow_tag_with_these_attributes("u", [])
 106   Meta.allow_tag_with_these_attributes("ul", [])
 107
 108   @allow_inline_images Keyword.get(@markup, :allow_inline_images)
 109
 110   if @allow_inline_images do
 111     # restrict img tags to http/https only, because of MediaProxy.
 112     Meta.allow_tag_with_uri_attributes("img", ["src"], ["http", "https"])
 113
 114     Meta.allow_tag_with_these_attributes("img", [
 115       "width",
 116       "height",
 117       "title",
 118       "alt"
 119     ])
 120   end
 121
 122   @allow_tables Keyword.get(@markup, :allow_tables)
 123
 124   if @allow_tables do
 125     Meta.allow_tag_with_these_attributes("table", [])
 126     Meta.allow_tag_with_these_attributes("tbody", [])
 127     Meta.allow_tag_with_these_attributes("td", [])
 128     Meta.allow_tag_with_these_attributes("th", [])
 129     Meta.allow_tag_with_these_attributes("thead", [])
 130     Meta.allow_tag_with_these_attributes("tr", [])
 131   end
 132
 133   @allow_headings Keyword.get(@markup, :allow_headings)
 134
 135   if @allow_headings do
 136     Meta.allow_tag_with_these_attributes("h1", [])
 137     Meta.allow_tag_with_these_attributes("h2", [])
 138     Meta.allow_tag_with_these_attributes("h3", [])
 139     Meta.allow_tag_with_these_attributes("h4", [])
 140     Meta.allow_tag_with_these_attributes("h5", [])
 141   end
 142
 143   @allow_fonts Keyword.get(@markup, :allow_fonts)
 144
 145   if @allow_fonts do
 146     Meta.allow_tag_with_these_attributes("font", ["face"])
 147   end
 148
 149   Meta.strip_everything_not_covered()
 150 end
 151
 152 defmodule Pleroma.HTML.Transform.MediaProxy do
 153   @moduledoc "Transforms inline image URIs to use MediaProxy."
 154
 155   alias Pleroma.Web.MediaProxy
 156
 157   def before_scrub(html), do: html
 158
 159   def scrub_attribute("img", {"src", "http" <> target}) do
 160     media_url =
 161       ("http" <> target)
 162       |> MediaProxy.url()
 163
 164     {"src", media_url}
 165   end
 166
 167   def scrub_attribute(_tag, attribute), do: attribute
 168
 169   def scrub({"img", attributes, children}) do
 170     attributes =
 171       attributes
 172       |> Enum.map(fn attr -> scrub_attribute("img", attr) end)
 173       |> Enum.reject(&is_nil(&1))
 174
 175     {"img", attributes, children}
 176   end
 177
 178   def scrub({:comment, _children}), do: ""
 179
 180   def scrub({tag, attributes, children}), do: {tag, attributes, children}
 181   def scrub({_tag, children}), do: children
 182   def scrub(text), do: text
 183 end