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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   def filter_tags(html, scrubbers) when is_list(scrubbers) do
   9     Enum.reduce(scrubbers, html, fn scrubber, html ->
  10       filter_tags(html, scrubber)
  11     end)
  12   end
  13
  14   def filter_tags(html, scrubber), do: Scrubber.scrub(html, scrubber)
  15   def filter_tags(html), do: filter_tags(html, nil)
  16   def strip_tags(html), do: Scrubber.scrub(html, Scrubber.StripTags)
  17 end
  18
  19 defmodule Pleroma.HTML.Scrubber.TwitterText do
  20   @moduledoc """
  21   An HTML scrubbing policy which limits to twitter-style text.  Only
  22   paragraphs, breaks and links are allowed through the filter.
  23   """
  24
  25   @markup Application.get_env(:pleroma, :markup)
  26   @uri_schemes Application.get_env(:pleroma, :uri_schemes, [])
  27   @valid_schemes Keyword.get(@uri_schemes, :valid_schemes, [])
  28
  29   require HtmlSanitizeEx.Scrubber.Meta
  30   alias HtmlSanitizeEx.Scrubber.Meta
  31
  32   def version do
  33     0
  34   end
  35
  36   Meta.remove_cdata_sections_before_scrub()
  37   Meta.strip_comments()
  38
  39   # links
  40   Meta.allow_tag_with_uri_attributes("a", ["href", "data-user", "data-tag"], @valid_schemes)
  41   Meta.allow_tag_with_these_attributes("a", ["name", "title"])
  42
  43   # paragraphs and linebreaks
  44   Meta.allow_tag_with_these_attributes("br", [])
  45   Meta.allow_tag_with_these_attributes("p", [])
  46
  47   # microformats
  48   Meta.allow_tag_with_these_attributes("span", [])
  49
  50   # allow inline images for custom emoji
  51   @allow_inline_images Keyword.get(@markup, :allow_inline_images)
  52
  53   if @allow_inline_images do
  54     # restrict img tags to http/https only, because of MediaProxy.
  55     Meta.allow_tag_with_uri_attributes("img", ["src"], ["http", "https"])
  56
  57     Meta.allow_tag_with_these_attributes("img", [
  58       "width",
  59       "height",
  60       "title",
  61       "alt"
  62     ])
  63   end
  64
  65   Meta.strip_everything_not_covered()
  66 end
  67
  68 defmodule Pleroma.HTML.Scrubber.Default do
  69   @doc "The default HTML scrubbing policy: no "
  70
  71   require HtmlSanitizeEx.Scrubber.Meta
  72   alias HtmlSanitizeEx.Scrubber.Meta
  73
  74   def version do
  75     0
  76   end
  77
  78   @markup Application.get_env(:pleroma, :markup)
  79   @uri_schemes Application.get_env(:pleroma, :uri_schemes, [])
  80   @valid_schemes Keyword.get(@uri_schemes, :valid_schemes, [])
  81
  82   Meta.remove_cdata_sections_before_scrub()
  83   Meta.strip_comments()
  84
  85   Meta.allow_tag_with_uri_attributes("a", ["href", "data-user", "data-tag"], @valid_schemes)
  86   Meta.allow_tag_with_these_attributes("a", ["name", "title"])
  87
  88   Meta.allow_tag_with_these_attributes("abbr", ["title"])
  89
  90   Meta.allow_tag_with_these_attributes("b", [])
  91   Meta.allow_tag_with_these_attributes("blockquote", [])
  92   Meta.allow_tag_with_these_attributes("br", [])
  93   Meta.allow_tag_with_these_attributes("code", [])
  94   Meta.allow_tag_with_these_attributes("del", [])
  95   Meta.allow_tag_with_these_attributes("em", [])
  96   Meta.allow_tag_with_these_attributes("i", [])
  97   Meta.allow_tag_with_these_attributes("li", [])
  98   Meta.allow_tag_with_these_attributes("ol", [])
  99   Meta.allow_tag_with_these_attributes("p", [])
 100   Meta.allow_tag_with_these_attributes("pre", [])
 101   Meta.allow_tag_with_these_attributes("span", [])
 102   Meta.allow_tag_with_these_attributes("strong", [])
 103   Meta.allow_tag_with_these_attributes("u", [])
 104   Meta.allow_tag_with_these_attributes("ul", [])
 105
 106   @allow_inline_images Keyword.get(@markup, :allow_inline_images)
 107
 108   if @allow_inline_images do
 109     # restrict img tags to http/https only, because of MediaProxy.
 110     Meta.allow_tag_with_uri_attributes("img", ["src"], ["http", "https"])
 111
 112     Meta.allow_tag_with_these_attributes("img", [
 113       "width",
 114       "height",
 115       "title",
 116       "alt"
 117     ])
 118   end
 119
 120   @allow_tables Keyword.get(@markup, :allow_tables)
 121
 122   if @allow_tables do
 123     Meta.allow_tag_with_these_attributes("table", [])
 124     Meta.allow_tag_with_these_attributes("tbody", [])
 125     Meta.allow_tag_with_these_attributes("td", [])
 126     Meta.allow_tag_with_these_attributes("th", [])
 127     Meta.allow_tag_with_these_attributes("thead", [])
 128     Meta.allow_tag_with_these_attributes("tr", [])
 129   end
 130
 131   @allow_headings Keyword.get(@markup, :allow_headings)
 132
 133   if @allow_headings do
 134     Meta.allow_tag_with_these_attributes("h1", [])
 135     Meta.allow_tag_with_these_attributes("h2", [])
 136     Meta.allow_tag_with_these_attributes("h3", [])
 137     Meta.allow_tag_with_these_attributes("h4", [])
 138     Meta.allow_tag_with_these_attributes("h5", [])
 139   end
 140
 141   @allow_fonts Keyword.get(@markup, :allow_fonts)
 142
 143   if @allow_fonts do
 144     Meta.allow_tag_with_these_attributes("font", ["face"])
 145   end
 146
 147   Meta.strip_everything_not_covered()
 148 end
 149
 150 defmodule Pleroma.HTML.Transform.MediaProxy do
 151   @moduledoc "Transforms inline image URIs to use MediaProxy."
 152
 153   def version do
 154     0
 155   end
 156
 157   alias Pleroma.Web.MediaProxy
 158
 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