Refactor rich media parsers to restrict the allowed properties

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/service/rich_media/parsers/meta_tags_parser.ex

@@ -7,12 +7,21 @@ defmodule Mobilizon.Service.RichMedia.Parsers.MetaTagsParser do
   @moduledoc """
   Module to parse meta tags data in HTML pages
   """
-  def parse(html, data, prefix, error_message, key_name, value_name \\ "content") do
+
+  def parse(
+        html,
+        data,
+        prefix,
+        error_message,
+        key_name,
+        value_name \\ :content,
+        allowed_attributes \\ []
+      ) do
     meta_data =
       html
       |> get_elements(key_name, prefix)
       |> Enum.reduce(data, fn el, acc ->
-        attributes = normalize_attributes(el, prefix, key_name, value_name)
+        attributes = normalize_attributes(el, prefix, key_name, value_name, allowed_attributes)
 
         Map.merge(acc, attributes)
       end)
@@ -27,18 +36,23 @@ defmodule Mobilizon.Service.RichMedia.Parsers.MetaTagsParser do
   end
 
   defp get_elements(html, key_name, prefix) do
-    html |> Floki.find("meta[#{key_name}^='#{prefix}:']")
+    html |> Floki.find("meta[#{to_string(key_name)}^='#{prefix}:']")
   end
 
-  defp normalize_attributes(html_node, prefix, key_name, value_name) do
+  defp normalize_attributes(html_node, prefix, key_name, value_name, allowed_attributes) do
     {_tag, attributes, _children} = html_node
 
     data =
-      Enum.into(attributes, %{}, fn {name, value} ->
+      attributes
+      |> Enum.into(%{}, fn {name, value} ->
         {name, String.trim_leading(value, "#{prefix}:")}
       end)
 
-    %{String.to_atom(data[key_name]) => data[value_name]}
+    if data[to_string(key_name)] in Enum.map(allowed_attributes, &to_string/1) do
+      %{String.to_existing_atom(data[to_string(key_name)]) => data[to_string(value_name)]}
+    else
+      %{}
+    end
   end
 
   defp maybe_put_title(%{title: _} = meta, _), do: meta

lib/service/rich_media/parsers/oembed_parser.ex

@@ -41,10 +41,31 @@ defmodule Mobilizon.Service.RichMedia.Parsers.OEmbed do
     {:ok, Enum.into(attributes, %{})["href"]}
   end
 
+  @oembed_allowed_attributes [
+    :type,
+    :version,
+    :html,
+    :width,
+    :height,
+    :title,
+    :author_name,
+    :author_url,
+    :provider_name,
+    :provider_url,
+    :cache_age,
+    :thumbnail_url,
+    :thumbnail_width,
+    :thumbnail_height,
+    :url
+  ]
+
   defp get_oembed_data(url) do
     with {:ok, %{body: json}} <- Tesla.get(url, opts: @http_options),
          {:ok, data} <- Jason.decode(json),
-         data <- data |> Map.new(fn {k, v} -> {String.to_atom(k), v} end) do
+         data <-
+           data
+           |> Map.new(fn {k, v} -> {String.to_existing_atom(k), v} end)
+           |> Map.take(@oembed_allowed_attributes) do
       {:ok, data}
     end
   end

lib/service/rich_media/parsers/ogp.ex

@@ -10,6 +10,26 @@ defmodule Mobilizon.Service.RichMedia.Parsers.OGP do
   require Logger
   alias Mobilizon.Service.RichMedia.Parsers.MetaTagsParser
 
+  @opengraph_properties [
+    :title,
+    :type,
+    :image,
+    :url,
+    :audio,
+    :description,
+    :determiner,
+    :locale,
+    :"locale:alternate",
+    :site_name,
+    :video,
+    :"image:url",
+    :"image.secure_url",
+    :"image:type",
+    :"image:width",
+    :"image:height",
+    :"image:alt"
+  ]
+
   def parse(html, data) do
     Logger.debug("Using OpenGraph card parser")
 
@@ -19,7 +39,9 @@ defmodule Mobilizon.Service.RichMedia.Parsers.OGP do
              data,
              "og",
              "No OGP metadata found",
-             "property"
+             :property,
+             :content,
+             @opengraph_properties
            ) do
       data = transform_tags(data)
       Logger.debug("Data found with OpenGraph card parser")
@@ -29,9 +51,11 @@ defmodule Mobilizon.Service.RichMedia.Parsers.OGP do
 
   defp transform_tags(data) do
     data
-    |> Map.put(:image_remote_url, Map.get(data, :image))
-    |> Map.put(:width, get_integer_value(data, :"image:width"))
-    |> Map.put(:height, get_integer_value(data, :"image:height"))
+    |> Enum.reject(fn {_, v} -> is_nil(v) end)
+    |> Map.new()
+    |> Map.update(:image_remote_url, Map.get(data, :image), & &1)
+    |> Map.update(:width, get_integer_value(data, :"image:width"), & &1)
+    |> Map.update(:height, get_integer_value(data, :"image:height"), & &1)
   end
 
   @spec get_integer_value(map(), atom()) :: integer() | nil

lib/service/rich_media/parsers/twitter_card.ex

@@ -10,25 +10,49 @@ defmodule Mobilizon.Service.RichMedia.Parsers.TwitterCard do
   alias Mobilizon.Service.RichMedia.Parsers.MetaTagsParser
   require Logger
 
+  @twitter_card_properties [
+    :card,
+    :site,
+    :creator,
+    :title,
+    :description,
+    :image,
+    :"image:alt"
+  ]
+
   @spec parse(String.t(), map()) :: {:ok, map()} | {:error, String.t()}
   def parse(html, data) do
     Logger.debug("Using Twitter card parser")
 
-    res =
-      data
-      |> parse_name_attrs(html)
-      |> parse_property_attrs(html)
-
+    with {:ok, data} <- parse_name_attrs(data, html),
+         {:ok, data} <- parse_property_attrs(data, html),
+         data <- transform_tags(data) do
       Logger.debug("Data found with Twitter card parser")
-    Logger.debug(inspect(res))
-    res
+      Logger.debug(inspect(data))
+      data
+    end
   end
 
   defp parse_name_attrs(data, html) do
-    MetaTagsParser.parse(html, data, "twitter", %{}, "name")
+    MetaTagsParser.parse(html, data, "twitter", %{}, :name, :content, [:"twitter:card"])
   end
 
   defp parse_property_attrs({_, data}, html) do
-    MetaTagsParser.parse(html, data, "twitter", "No twitter card metadata found", "property")
+    MetaTagsParser.parse(
+      html,
+      data,
+      "twitter",
+      "No twitter card metadata found",
+      :property,
+      :content,
+      @twitter_card_properties
+    )
+  end
+
+  defp transform_tags(data) do
+    data
+    |> Enum.reject(fn {_, v} -> is_nil(v) end)
+    |> Map.new()
+    |> Map.update(:image_remote_url, Map.get(data, :image), & &1)
   end
 end