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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     filter_tags(html, get_scrubbers())
  19   end
  20
  21   def filter_tags(html, scrubbers) when is_list(scrubbers) do
  22     Enum.reduce(scrubbers, html, fn scrubber, html ->
  23       filter_tags(html, scrubber)
  24     end)
  25   end
  26
  27   def filter_tags(html, scrubber), do: Scrubber.scrub(html, scrubber)
  28   def filter_tags(html), do: filter_tags(html, nil)
  29   def strip_tags(html), do: Scrubber.scrub(html, Scrubber.StripTags)
  30 end
  31
  32 defmodule Pleroma.HTML.Scrubber.TwitterText do
  33   @moduledoc """
  34   An HTML scrubbing policy which limits to twitter-style text.  Only
  35   paragraphs, breaks and links are allowed through the filter.
  36   """
  37
  38   @markup Application.get_env(:pleroma, :markup)
  39   @uri_schemes Application.get_env(:pleroma, :uri_schemes, [])
  40   @valid_schemes Keyword.get(@uri_schemes, :valid_schemes, [])
  41
  42   require HtmlSanitizeEx.Scrubber.Meta
  43   alias HtmlSanitizeEx.Scrubber.Meta
  44
  45   def version do
  46     0
  47   end
  48
  49   Meta.remove_cdata_sections_before_scrub()
  50   Meta.strip_comments()
  51
  52   # links
  53   Meta.allow_tag_with_uri_attributes("a", ["href", "data-user", "data-tag"], @valid_schemes)
  54   Meta.allow_tag_with_these_attributes("a", ["name", "title"])
  55
  56   # paragraphs and linebreaks
  57   Meta.allow_tag_with_these_attributes("br", [])
  58   Meta.allow_tag_with_these_attributes("p", [])
  59
  60   # microformats
  61   Meta.allow_tag_with_these_attributes("span", [])
  62
  63   # allow inline images for custom emoji
  64   @allow_inline_images Keyword.get(@markup, :allow_inline_images)
  65
  66   if @allow_inline_images do
  67     # restrict img tags to http/https only, because of MediaProxy.
  68     Meta.allow_tag_with_uri_attributes("img", ["src"], ["http", "https"])
  69
  70     Meta.allow_tag_with_these_attributes("img", [
  71       "width",
  72       "height",
  73       "title",
  74       "alt"
  75     ])
  76   end
  77
  78   Meta.strip_everything_not_covered()
  79 end
  80
  81 defmodule Pleroma.HTML.Scrubber.Default do
  82   @doc "The default HTML scrubbing policy: no "
  83
  84   require HtmlSanitizeEx.Scrubber.Meta
  85   alias HtmlSanitizeEx.Scrubber.Meta
  86
  87   def version do
  88     0
  89   end
  90
  91   @markup Application.get_env(:pleroma, :markup)
  92   @uri_schemes Application.get_env(:pleroma, :uri_schemes, [])
  93   @valid_schemes Keyword.get(@uri_schemes, :valid_schemes, [])
  94
  95   Meta.remove_cdata_sections_before_scrub()
  96   Meta.strip_comments()
  97
  98   Meta.allow_tag_with_uri_attributes("a", ["href", "data-user", "data-tag"], @valid_schemes)
  99   Meta.allow_tag_with_these_attributes("a", ["name", "title"])
 100
 101   Meta.allow_tag_with_these_attributes("abbr", ["title"])
 102
 103   Meta.allow_tag_with_these_attributes("b", [])
 104   Meta.allow_tag_with_these_attributes("blockquote", [])
 105   Meta.allow_tag_with_these_attributes("br", [])
 106   Meta.allow_tag_with_these_attributes("code", [])
 107   Meta.allow_tag_with_these_attributes("del", [])
 108   Meta.allow_tag_with_these_attributes("em", [])
 109   Meta.allow_tag_with_these_attributes("i", [])
 110   Meta.allow_tag_with_these_attributes("li", [])
 111   Meta.allow_tag_with_these_attributes("ol", [])
 112   Meta.allow_tag_with_these_attributes("p", [])
 113   Meta.allow_tag_with_these_attributes("pre", [])
 114   Meta.allow_tag_with_these_attributes("span", [])
 115   Meta.allow_tag_with_these_attributes("strong", [])
 116   Meta.allow_tag_with_these_attributes("u", [])
 117   Meta.allow_tag_with_these_attributes("ul", [])
 118
 119   @allow_inline_images Keyword.get(@markup, :allow_inline_images)
 120
 121   if @allow_inline_images do
 122     # restrict img tags to http/https only, because of MediaProxy.
 123     Meta.allow_tag_with_uri_attributes("img", ["src"], ["http", "https"])
 124
 125     Meta.allow_tag_with_these_attributes("img", [
 126       "width",
 127       "height",
 128       "title",
 129       "alt"
 130     ])
 131   end
 132
 133   @allow_tables Keyword.get(@markup, :allow_tables)
 134
 135   if @allow_tables do
 136     Meta.allow_tag_with_these_attributes("table", [])
 137     Meta.allow_tag_with_these_attributes("tbody", [])
 138     Meta.allow_tag_with_these_attributes("td", [])
 139     Meta.allow_tag_with_these_attributes("th", [])
 140     Meta.allow_tag_with_these_attributes("thead", [])
 141     Meta.allow_tag_with_these_attributes("tr", [])
 142   end
 143
 144   @allow_headings Keyword.get(@markup, :allow_headings)
 145
 146   if @allow_headings do
 147     Meta.allow_tag_with_these_attributes("h1", [])
 148     Meta.allow_tag_with_these_attributes("h2", [])
 149     Meta.allow_tag_with_these_attributes("h3", [])
 150     Meta.allow_tag_with_these_attributes("h4", [])
 151     Meta.allow_tag_with_these_attributes("h5", [])
 152   end
 153
 154   @allow_fonts Keyword.get(@markup, :allow_fonts)
 155
 156   if @allow_fonts do
 157     Meta.allow_tag_with_these_attributes("font", ["face"])
 158   end
 159
 160   Meta.strip_everything_not_covered()
 161 end
 162
 163 defmodule Pleroma.HTML.Transform.MediaProxy do
 164   @moduledoc "Transforms inline image URIs to use MediaProxy."
 165
 166   alias Pleroma.Web.MediaProxy
 167
 168   def version do
 169     0
 170   end
 171
 172   def before_scrub(html), do: html
 173
 174   def scrub_attribute("img", {"src", "http" <> target}) do
 175     media_url =
 176       ("http" <> target)
 177       |> MediaProxy.url()
 178
 179     {"src", media_url}
 180   end
 181
 182   def scrub_attribute(_tag, attribute), do: attribute
 183
 184   def scrub({"img", attributes, children}) do
 185     attributes =
 186       attributes
 187       |> Enum.map(fn attr -> scrub_attribute("img", attr) end)
 188       |> Enum.reject(&is_nil(&1))
 189
 190     {"img", attributes, children}
 191   end
 192
 193   def scrub({:comment, _children}), do: ""
 194
 195   def scrub({tag, attributes, children}), do: {tag, attributes, children}
 196   def scrub({_tag, children}), do: children
 197   def scrub(text), do: text
 198 end