summaryrefslogtreecommitdiff
path: root/lib/pleroma/reverse_proxy.ex
blob: 466906f035dff1bd714fb360d507816dab4f061d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
# Pleroma: A lightweight social networking server
# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only

defmodule Pleroma.ReverseProxy do
  @range_headers ~w(range if-range)
  @keep_req_headers ~w(accept user-agent accept-encoding cache-control if-modified-since) ++
                      ~w(if-unmodified-since if-none-match) ++ @range_headers
  @resp_cache_headers ~w(etag date last-modified)
  @keep_resp_headers @resp_cache_headers ++
                       ~w(content-length content-type content-disposition content-encoding) ++
                       ~w(content-range accept-ranges vary)
  @default_cache_control_header "public, max-age=1209600"
  @valid_resp_codes [200, 206, 304]
  @max_read_duration :timer.seconds(30)
  @max_body_length :infinity
  @failed_request_ttl :timer.seconds(60)
  @methods ~w(GET HEAD)

  @cachex Pleroma.Config.get([:cachex, :provider], Cachex)

  def max_read_duration_default, do: @max_read_duration
  def default_cache_control_header, do: @default_cache_control_header

  @moduledoc """
  A reverse proxy.

      Pleroma.ReverseProxy.call(conn, url, options)

  It is not meant to be added into a plug pipeline, but to be called from another plug or controller.

  Supports `#{inspect(@methods)}` HTTP methods, and only allows `#{inspect(@valid_resp_codes)}` status codes.

  Responses are chunked to the client while downloading from the upstream.

  Some request / responses headers are preserved:

  * request: `#{inspect(@keep_req_headers)}`
  * response: `#{inspect(@keep_resp_headers)}`

  Options:

  * `redirect_on_failure` (default `false`). Redirects the client to the real remote URL if there's any HTTP
  errors. Any error during body processing will not be redirected as the response is chunked. This may expose
  remote URL, clients IPs, ….

  * `max_body_length` (default `#{inspect(@max_body_length)}`): limits the content length to be approximately the
  specified length. It is validated with the `content-length` header and also verified when proxying.

  * `max_read_duration` (default `#{inspect(@max_read_duration)}` ms): the total time the connection is allowed to
  read from the remote upstream.

  * `failed_request_ttl` (default `#{inspect(@failed_request_ttl)}` ms): the time the failed request is cached and cannot be retried.

  * `inline_content_types`:
    * `true` will not alter `content-disposition` (up to the upstream),
    * `false` will add `content-disposition: attachment` to any request,
    * a list of whitelisted content types

    * `keep_user_agent` will forward the client's user-agent to the upstream. This may be useful if the upstream is
    doing content transformation (encoding, …) depending on the request.

  * `req_headers`, `resp_headers` additional headers.

  * `http`: options for [hackney](https://github.com/benoitc/hackney) or [gun](https://github.com/ninenines/gun).

  """
  @default_options [pool: :media]

  @inline_content_types [
    "image/gif",
    "image/jpeg",
    "image/jpg",
    "image/png",
    "image/svg+xml",
    "audio/mpeg",
    "audio/mp3",
    "video/webm",
    "video/mp4",
    "video/quicktime"
  ]

  require Logger
  import Plug.Conn

  @type option() ::
          {:keep_user_agent, boolean}
          | {:max_read_duration, :timer.time() | :infinity}
          | {:max_body_length, non_neg_integer() | :infinity}
          | {:failed_request_ttl, :timer.time() | :infinity}
          | {:http, []}
          | {:req_headers, [{String.t(), String.t()}]}
          | {:resp_headers, [{String.t(), String.t()}]}
          | {:inline_content_types, boolean() | [String.t()]}
          | {:redirect_on_failure, boolean()}

  @spec call(Plug.Conn.t(), url :: String.t(), [option()]) :: Plug.Conn.t()
  def call(_conn, _url, _opts \\ [])

  def call(conn = %{method: method}, url, opts) when method in @methods do
    client_opts = Keyword.merge(@default_options, Keyword.get(opts, :http, []))

    req_headers = build_req_headers(conn.req_headers, opts)

    opts =
      if filename = Pleroma.Web.MediaProxy.filename(url) do
        Keyword.put_new(opts, :attachment_name, filename)
      else
        opts
      end

    with {:ok, nil} <- @cachex.get(:failed_proxy_url_cache, url),
         {:ok, code, headers, client} <- request(method, url, req_headers, client_opts),
         :ok <-
           header_length_constraint(
             headers,
             Keyword.get(opts, :max_body_length, @max_body_length)
           ) do
      response(conn, client, url, code, headers, opts)
    else
      {:ok, true} ->
        conn
        |> error_or_redirect(url, 500, "Request failed", opts)
        |> halt()

      {:ok, code, headers} ->
        head_response(conn, url, code, headers, opts)
        |> halt()

      {:error, {:invalid_http_response, code}} ->
        Logger.error("#{__MODULE__}: request to #{inspect(url)} failed with HTTP status #{code}")
        track_failed_url(url, code, opts)

        conn
        |> error_or_redirect(
          url,
          code,
          "Request failed: " <> Plug.Conn.Status.reason_phrase(code),
          opts
        )
        |> halt()

      {:error, error} ->
        Logger.error("#{__MODULE__}: request to #{inspect(url)} failed: #{inspect(error)}")
        track_failed_url(url, error, opts)

        conn
        |> error_or_redirect(url, 500, "Request failed", opts)
        |> halt()
    end
  end

  def call(conn, _, _) do
    conn
    |> send_resp(400, Plug.Conn.Status.reason_phrase(400))
    |> halt()
  end

  defp request(method, url, headers, opts) do
    Logger.debug("#{__MODULE__} #{method} #{url} #{inspect(headers)}")
    method = method |> String.downcase() |> String.to_existing_atom()

    case client().request(method, url, headers, "", opts) do
      {:ok, code, headers, client} when code in @valid_resp_codes ->
        {:ok, code, downcase_headers(headers), client}

      {:ok, code, headers} when code in @valid_resp_codes ->
        {:ok, code, downcase_headers(headers)}

      {:ok, code, _, _} ->
        {:error, {:invalid_http_response, code}}

      {:ok, code, _} ->
        {:error, {:invalid_http_response, code}}

      {:error, error} ->
        {:error, error}
    end
  end

  defp response(conn, client, url, status, headers, opts) do
    Logger.debug("#{__MODULE__} #{status} #{url} #{inspect(headers)}")

    result =
      conn
      |> put_resp_headers(build_resp_headers(headers, opts))
      |> send_chunked(status)
      |> chunk_reply(client, opts)

    case result do
      {:ok, conn} ->
        halt(conn)

      {:error, :closed, conn} ->
        client().close(client)
        halt(conn)

      {:error, error, conn} ->
        Logger.warn(
          "#{__MODULE__} request to #{url} failed while reading/chunking: #{inspect(error)}"
        )

        client().close(client)
        halt(conn)
    end
  end

  defp chunk_reply(conn, client, opts) do
    chunk_reply(conn, client, opts, 0, 0)
  end

  defp chunk_reply(conn, client, opts, sent_so_far, duration) do
    with {:ok, duration} <-
           check_read_duration(
             duration,
             Keyword.get(opts, :max_read_duration, @max_read_duration)
           ),
         {:ok, data, client} <- client().stream_body(client),
         {:ok, duration} <- increase_read_duration(duration),
         sent_so_far = sent_so_far + byte_size(data),
         :ok <-
           body_size_constraint(
             sent_so_far,
             Keyword.get(opts, :max_body_length, @max_body_length)
           ),
         {:ok, conn} <- chunk(conn, data) do
      chunk_reply(conn, client, opts, sent_so_far, duration)
    else
      :done -> {:ok, conn}
      {:error, error} -> {:error, error, conn}
    end
  end

  defp head_response(conn, url, code, headers, opts) do
    Logger.debug("#{__MODULE__} #{code} #{url} #{inspect(headers)}")

    conn
    |> put_resp_headers(build_resp_headers(headers, opts))
    |> send_resp(code, "")
  end

  defp error_or_redirect(conn, url, code, body, opts) do
    if Keyword.get(opts, :redirect_on_failure, false) do
      conn
      |> Phoenix.Controller.redirect(external: url)
      |> halt()
    else
      conn
      |> send_resp(code, body)
      |> halt
    end
  end

  defp downcase_headers(headers) do
    Enum.map(headers, fn {k, v} ->
      {String.downcase(k), v}
    end)
  end

  defp get_content_type(headers) do
    {_, content_type} =
      List.keyfind(headers, "content-type", 0, {"content-type", "application/octet-stream"})

    [content_type | _] = String.split(content_type, ";")
    content_type
  end

  defp put_resp_headers(conn, headers) do
    Enum.reduce(headers, conn, fn {k, v}, conn ->
      put_resp_header(conn, k, v)
    end)
  end

  defp build_req_headers(headers, opts) do
    headers
    |> downcase_headers()
    |> Enum.filter(fn {k, _} -> k in @keep_req_headers end)
    |> build_req_range_or_encoding_header(opts)
    |> build_req_user_agent_header(opts)
    |> Keyword.merge(Keyword.get(opts, :req_headers, []))
  end

  # Disable content-encoding if any @range_headers are requested (see #1823).
  defp build_req_range_or_encoding_header(headers, _opts) do
    range? = Enum.any?(headers, fn {header, _} -> Enum.member?(@range_headers, header) end)

    if range? && List.keymember?(headers, "accept-encoding", 0) do
      List.keydelete(headers, "accept-encoding", 0)
    else
      headers
    end
  end

  defp build_req_user_agent_header(headers, opts) do
    if Keyword.get(opts, :keep_user_agent, false) do
      List.keystore(
        headers,
        "user-agent",
        0,
        {"user-agent", Pleroma.Application.user_agent()}
      )
    else
      headers
    end
  end

  defp build_resp_headers(headers, opts) do
    headers
    |> Enum.filter(fn {k, _} -> k in @keep_resp_headers end)
    |> build_resp_cache_headers(opts)
    |> build_resp_content_disposition_header(opts)
    |> Keyword.merge(Keyword.get(opts, :resp_headers, []))
  end

  defp build_resp_cache_headers(headers, _opts) do
    has_cache? = Enum.any?(headers, fn {k, _} -> k in @resp_cache_headers end)

    cond do
      has_cache? ->
        # There's caching header present but no cache-control -- we need to set our own
        # as Plug defaults to "max-age=0, private, must-revalidate"
        List.keystore(
          headers,
          "cache-control",
          0,
          {"cache-control", @default_cache_control_header}
        )

      true ->
        List.keystore(
          headers,
          "cache-control",
          0,
          {"cache-control", @default_cache_control_header}
        )
    end
  end

  defp build_resp_content_disposition_header(headers, opts) do
    opt = Keyword.get(opts, :inline_content_types, @inline_content_types)

    content_type = get_content_type(headers)

    attachment? =
      cond do
        is_list(opt) && !Enum.member?(opt, content_type) -> true
        opt == false -> true
        true -> false
      end

    if attachment? do
      name =
        try do
          {{"content-disposition", content_disposition_string}, _} =
            List.keytake(headers, "content-disposition", 0)

          [name | _] =
            Regex.run(
              ~r/filename="((?:[^"\\]|\\.)*)"/u,
              content_disposition_string || "",
              capture: :all_but_first
            )

          name
        rescue
          MatchError -> Keyword.get(opts, :attachment_name, "attachment")
        end

      disposition = "attachment; filename=\"#{name}\""

      List.keystore(headers, "content-disposition", 0, {"content-disposition", disposition})
    else
      headers
    end
  end

  defp header_length_constraint(headers, limit) when is_integer(limit) and limit > 0 do
    with {_, size} <- List.keyfind(headers, "content-length", 0),
         {size, _} <- Integer.parse(size),
         true <- size <= limit do
      :ok
    else
      false ->
        {:error, :body_too_large}

      _ ->
        :ok
    end
  end

  defp header_length_constraint(_, _), do: :ok

  defp body_size_constraint(size, limit) when is_integer(limit) and limit > 0 and size >= limit do
    {:error, :body_too_large}
  end

  defp body_size_constraint(_, _), do: :ok

  defp check_read_duration(nil = _duration, max), do: check_read_duration(@max_read_duration, max)

  defp check_read_duration(duration, max)
       when is_integer(duration) and is_integer(max) and max > 0 do
    if duration > max do
      {:error, :read_duration_exceeded}
    else
      {:ok, {duration, :erlang.system_time(:millisecond)}}
    end
  end

  defp check_read_duration(_, _), do: {:ok, :no_duration_limit, :no_duration_limit}

  defp increase_read_duration({previous_duration, started})
       when is_integer(previous_duration) and is_integer(started) do
    duration = :erlang.system_time(:millisecond) - started
    {:ok, previous_duration + duration}
  end

  defp increase_read_duration(_) do
    {:ok, :no_duration_limit, :no_duration_limit}
  end

  defp client, do: Pleroma.ReverseProxy.Client

  defp track_failed_url(url, error, opts) do
    ttl =
      unless error in [:body_too_large, 400, 204] do
        Keyword.get(opts, :failed_request_ttl, @failed_request_ttl)
      else
        nil
      end

    @cachex.put(:failed_proxy_url_cache, url, true, ttl: ttl)
  end
end