316 lines
8.9 KiB
Elixir
316 lines
8.9 KiB
Elixir
# Portions of this file are derived from Pleroma:
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# Pleroma: A lightweight social networking server
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# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
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# SPDX-License-Identifier: AGPL-3.0-only
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defmodule Mobilizon.Service.RichMedia.Parser do
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@moduledoc """
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Module to parse data in HTML pages
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"""
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@options [
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max_body: 2_000_000,
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timeout: 10_000,
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recv_timeout: 20_000,
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follow_redirect: true,
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# TODO: Remove me once Hackney/HTTPoison fixes their issue with TLS1.3 and OTP 23
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ssl: [{:versions, [:"tlsv1.2"]}]
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]
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alias Mobilizon.Config
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alias Mobilizon.Service.HTTP.RichMediaPreviewClient
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alias Mobilizon.Service.RichMedia.Favicon
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alias Plug.Conn.Utils
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require Logger
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defp parsers do
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Mobilizon.Config.get([:rich_media, :parsers])
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end
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def parse(nil), do: {:error, "No URL provided"}
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@spec parse(String.t()) :: {:ok, map()} | {:error, any()}
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def parse(url) do
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case Cachex.fetch(:rich_media_cache, url, fn _ ->
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case parse_url(url) do
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{:ok, data} -> {:commit, data}
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{:error, err} -> {:ignore, err}
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end
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end) do
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{status, value} when status in [:ok, :commit] ->
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{:ok, value}
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{_, err} ->
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{:error, err}
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end
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rescue
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e ->
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{:error, "Cachex error: #{inspect(e)}"}
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end
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@doc """
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Get a filename for the fetched data, using the response header or the last part of the URL
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"""
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@spec get_filename_from_response(Enum.t(), String.t()) :: String.t() | nil
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def get_filename_from_response(response_headers, url) do
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get_filename_from_headers(response_headers) || get_filename_from_url(url)
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end
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@spec parse_url(String.t(), Enum.t()) :: {:ok, map()} | {:error, any()}
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defp parse_url(url, options \\ []) do
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user_agent = Keyword.get(options, :user_agent, default_user_agent(url))
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headers = [{"User-Agent", user_agent}]
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Logger.debug("Fetching content at address #{inspect(url)}")
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try do
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with {:ok, _} <- prevent_local_address(url),
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{:ok, %{body: body, status: code, headers: response_headers}}
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when code in 200..299 <-
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RichMediaPreviewClient.get(
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url,
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headers: headers,
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opts: @options
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),
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{:is_html, _response_headers, true} <-
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{:is_html, response_headers, is_html(response_headers)} do
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body
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|> parse_html()
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|> maybe_parse()
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|> Map.put(:url, url)
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|> maybe_add_favicon()
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|> clean_parsed_data()
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|> check_parsed_data()
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|> check_remote_picture_path()
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else
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{:is_html, response_headers, false} ->
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data = get_data_for_media(response_headers, url)
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{:ok, data}
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{:error, err} ->
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Logger.debug("HTTP error: #{inspect(err)}")
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{:error, "HTTP error: #{inspect(err)}"}
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end
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rescue
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e ->
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{:error, "Parsing error: #{inspect(e)} #{inspect(__STACKTRACE__)}"}
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end
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end
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@spec get_data_for_media(Enum.t(), String.t()) :: map()
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defp get_data_for_media(response_headers, url) do
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data = %{title: get_filename_from_headers(response_headers) || get_filename_from_url(url)}
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if is_image(response_headers) do
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Map.put(data, :image_remote_url, url)
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else
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data
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end
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end
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@spec is_html(Enum.t()) :: boolean
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def is_html(headers) do
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headers
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|> get_header("Content-Type")
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|> content_type_header_matches(["text/html", "application/xhtml"])
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end
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@spec is_image(Enum.t()) :: boolean
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defp is_image(headers) do
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headers
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|> get_header("Content-Type")
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|> content_type_header_matches(["image/"])
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end
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@spec content_type_header_matches(String.t() | nil, Enum.t()) :: boolean
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defp content_type_header_matches(header, content_types)
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defp content_type_header_matches(nil, _content_types), do: false
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defp content_type_header_matches(header, content_types) when is_binary(header) do
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Enum.any?(content_types, fn content_type -> String.starts_with?(header, content_type) end)
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end
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@spec get_header(Enum.t(), String.t()) :: String.t() | nil
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defp get_header(headers, key) do
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key = String.downcase(key)
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case List.keyfind(headers, key, 0) do
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{^key, value} -> String.downcase(value)
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nil -> nil
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end
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end
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@spec get_filename_from_headers(Enum.t()) :: String.t() | nil
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defp get_filename_from_headers(headers) do
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case get_header(headers, "Content-Disposition") do
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nil -> nil
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content_disposition -> parse_content_disposition(content_disposition)
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end
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end
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@spec get_filename_from_url(String.t()) :: String.t()
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defp get_filename_from_url(url) do
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case URI.parse(url) do
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%URI{path: nil} ->
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nil
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%URI{path: path} ->
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path
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|> String.split("/", trim: true)
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|> Enum.at(-1)
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|> URI.decode()
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end
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end
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# The following is taken from https://github.com/elixir-plug/plug/blob/65986ad32f9aaae3be50dc80cbdd19b326578da7/lib/plug/parsers/multipart.ex#L207
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@spec parse_content_disposition(String.t()) :: String.t() | nil
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defp parse_content_disposition(disposition) do
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with [_, params] <- :binary.split(disposition, ";"),
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%{"name" => _name} = params <- Utils.params(params) do
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handle_disposition(params)
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else
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_ -> nil
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end
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end
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@spec handle_disposition(map()) :: String.t() | nil
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defp handle_disposition(params) do
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case params do
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%{"filename" => ""} ->
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nil
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%{"filename" => filename} ->
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filename
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%{"filename*" => ""} ->
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nil
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%{"filename*" => "utf-8''" <> filename} ->
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URI.decode(filename)
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_ ->
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nil
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end
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end
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defp parse_html(html), do: Floki.parse_document!(html)
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defp maybe_parse(html) do
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Enum.reduce_while(parsers(), %{}, fn parser, acc ->
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case parser.parse(html, acc) do
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{:ok, data} ->
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{:halt, data}
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{:error, _msg} ->
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{:cont, acc}
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end
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end)
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end
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defp check_parsed_data(%{title: title} = data)
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when is_binary(title) and byte_size(title) > 0 do
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data
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end
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defp check_parsed_data(data) do
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Logger.debug("Found metadata was invalid or incomplete: #{inspect(data)}")
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{:error, :invalid_parsed_data}
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end
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defp clean_parsed_data(data) do
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data
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|> Enum.reject(fn {key, val} ->
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case Jason.encode(%{key => val}) do
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{:ok, _} -> false
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_ -> true
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end
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end)
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|> Map.new()
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end
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defp prevent_local_address(url) do
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case URI.parse(url) do
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%URI{host: host} when not is_nil(host) ->
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host = String.downcase(host)
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if validate_hostname_not_localhost(host) && validate_hostname_only(host) &&
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validate_ip(host) do
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{:ok, url}
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else
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{:error, "Host violates local access rules"}
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end
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_ ->
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{:error, "Could not detect any host"}
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end
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end
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defp validate_hostname_not_localhost(hostname),
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do:
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hostname != "localhost" && !String.ends_with?(hostname, ".local") &&
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!String.ends_with?(hostname, ".localhost")
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defp validate_hostname_only(hostname),
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do: hostname |> String.graphemes() |> Enum.count(&(&1 == ".")) > 0
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defp validate_ip(hostname) do
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case hostname |> String.to_charlist() |> :inet.parse_address() do
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{:ok, address} ->
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!IpReserved.is_reserved?(address)
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# Not a valid IP
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{:error, _} ->
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true
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end
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end
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@spec maybe_add_favicon(map()) :: map()
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defp maybe_add_favicon(%{url: url} = data) do
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case Favicon.fetch(url) do
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{:ok, favicon_url} ->
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Logger.debug("Adding favicon #{favicon_url} to metadata")
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Map.put(data, :favicon_url, favicon_url)
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err ->
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Logger.debug("Failed to add favicon to metadata")
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Logger.debug(inspect(err))
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data
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end
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end
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@spec check_remote_picture_path(map()) :: map()
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defp check_remote_picture_path(%{image_remote_url: image_remote_url, url: url} = data) do
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Logger.debug("Checking image_remote_url #{image_remote_url}")
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image_uri = URI.parse(image_remote_url)
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uri = URI.parse(url)
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image_remote_url =
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cond do
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is_nil(image_uri.host) -> "#{uri.scheme}://#{uri.host}#{correct_path(image_remote_url)}"
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is_nil(image_uri.scheme) -> "#{uri.scheme}:#{image_remote_url}"
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true -> image_remote_url
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end
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data = Map.put(data, :image_remote_url, image_remote_url)
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{:ok, data}
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end
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defp check_remote_picture_path(data), do: {:ok, data}
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# Sometimes paths have "/" in front, sometimes not
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defp correct_path("/" <> _ = path), do: path
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defp correct_path(path), do: "/#{path}"
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# Twitter requires a well-know crawler user-agent to show server-rendered data
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defp default_user_agent("https://twitter.com/" <> _) do
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"Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)"
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end
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defp default_user_agent("https://mobile.twitter.com/" <> _) do
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"Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)"
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end
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defp default_user_agent(_url) do
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Config.instance_user_agent()
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end
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end
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