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   1 # Pleroma: A lightweight social networking server
   2 # Copyright © 2015-2020 Tymon Tobolski <https://github.com/teamon/tesla/blob/master/lib/tesla/middleware/follow_redirects.ex>
   3 # Copyright © 2020 Pleroma Authors <https://pleroma.social/>
   4 # SPDX-License-Identifier: AGPL-3.0-only
   5
   6 defmodule Pleroma.HTTP.Middleware.FollowRedirects do
   7   @moduledoc """
   8   Pool-aware version of https://github.com/teamon/tesla/blob/master/lib/tesla/middleware/follow_redirects.ex
   9
  10   Follow 3xx redirects
  11   ## Options
  12   - `:max_redirects` - limit number of redirects (default: `5`)
  13   """
  14
  15   alias Pleroma.Gun.ConnectionPool
  16
  17   @behaviour Tesla.Middleware
  18
  19   @max_redirects 5
  20   @redirect_statuses [301, 302, 303, 307, 308]
  21
  22   @impl Tesla.Middleware
  23   def call(env, next, opts \\ []) do
  24     max = Keyword.get(opts, :max_redirects, @max_redirects)
  25
  26     redirect(env, next, max)
  27   end
  28
  29   defp redirect(env, next, left) do
  30     opts = env.opts[:adapter]
  31
  32     case Tesla.run(env, next) do
  33       {:ok, %{status: status} = res} when status in @redirect_statuses and left > 0 ->
  34         release_conn(opts)
  35
  36         case Tesla.get_header(res, "location") do
  37           nil ->
  38             {:ok, res}
  39
  40           location ->
  41             location = parse_location(location, res)
  42
  43             case get_conn(location, opts) do
  44               {:ok, opts} ->
  45                 %{env | opts: Keyword.put(env.opts, :adapter, opts)}
  46                 |> new_request(res.status, location)
  47                 |> redirect(next, left - 1)
  48
  49               e ->
  50                 e
  51             end
  52         end
  53
  54       {:ok, %{status: status}} when status in @redirect_statuses ->
  55         release_conn(opts)
  56         {:error, {__MODULE__, :too_many_redirects}}
  57
  58       {:error, _} = e ->
  59         release_conn(opts)
  60         e
  61
  62       other ->
  63         unless opts[:body_as] == :chunks do
  64           release_conn(opts)
  65         end
  66
  67         other
  68     end
  69   end
  70
  71   defp get_conn(location, opts) do
  72     uri = URI.parse(location)
  73
  74     case ConnectionPool.get_conn(uri, opts) do
  75       {:ok, conn} ->
  76         {:ok, Keyword.merge(opts, conn: conn)}
  77
  78       e ->
  79         e
  80     end
  81   end
  82
  83   defp release_conn(opts) do
  84     ConnectionPool.release_conn(opts[:conn])
  85   end
  86
  87   # The 303 (See Other) redirect was added in HTTP/1.1 to indicate that the originally
  88   # requested resource is not available, however a related resource (or another redirect)
  89   # available via GET is available at the specified location.
  90   # https://tools.ietf.org/html/rfc7231#section-6.4.4
  91   defp new_request(env, 303, location), do: %{env | url: location, method: :get, query: []}
  92
  93   # The 307 (Temporary Redirect) status code indicates that the target
  94   # resource resides temporarily under a different URI and the user agent
  95   # MUST NOT change the request method (...)
  96   # https://tools.ietf.org/html/rfc7231#section-6.4.7
  97   defp new_request(env, 307, location), do: %{env | url: location}
  98
  99   defp new_request(env, _, location), do: %{env | url: location, query: []}
 100
 101   defp parse_location("https://" <> _rest = location, _env), do: location
 102   defp parse_location("http://" <> _rest = location, _env), do: location
 103
 104   defp parse_location(location, env) do
 105     env.url
 106     |> URI.parse()
 107     |> URI.merge(location)
 108     |> URI.to_string()
 109   end
 110 end