394 lines
12 KiB
Elixir
394 lines
12 KiB
Elixir
# Portions of this file are derived from Pleroma:
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# Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
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# SPDX-License-Identifier: AGPL-3.0-only
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# Upstream: https://git.pleroma.social/pleroma/pleroma/blob/develop/lib/pleroma/reverse_proxy.ex
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defmodule Mobilizon.Web.ReverseProxy do
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@keep_req_headers ~w(accept user-agent accept-encoding cache-control
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if-modified-since if-unmodified-since if-none-match if-range range)
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@resp_cache_headers ~w(etag date last-modified cache-control)
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@keep_resp_headers @resp_cache_headers ++ ~w(content-type content-disposition
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content-encoding content-range accept-ranges vary)
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@default_cache_control_header "public, max-age=1209600"
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@valid_resp_codes [200, 206, 304]
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@max_read_duration :timer.seconds(30)
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@max_body_length :infinity
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@methods ~w(GET HEAD)
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@moduledoc """
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A reverse proxy.
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Mobilizon.Web.ReverseProxy.call(conn, url, options)
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It is not meant to be added into a plug pipeline, but to be called from another
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plug or controller.
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Supports `#{inspect(@methods)}` HTTP methods, and only allows
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`#{inspect(@valid_resp_codes)}` status codes.
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Responses are chunked to the client while downloading from the upstream.
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Some request / responses headers are preserved:
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* request: `#{inspect(@keep_req_headers)}`
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* response: `#{inspect(@keep_resp_headers)}`
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If no caching headers (`#{inspect(@resp_cache_headers)}`) are returned by
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upstream, `cache-control` will be set to `#{inspect(@default_cache_control_header)}`.
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Options:
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* `redirect_on_failure` (default `false`). Redirects the client to the real
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remote URL if there's any HTTP errors. Any error during body processing will
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not be redirected as the response is chunked. This may expose remote URL,
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clients IPs, ….
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* `max_body_length` (default `#{inspect(@max_body_length)}`): limits the
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content length to be approximately the specified length. It is validated with
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the `content-length` header and also verified when proxying.
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* `max_read_duration` (default `#{inspect(@max_read_duration)}` ms): the total
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time the connection is allowed to read from the remote upstream.
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* `inline_content_types`:
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* `true` will not alter `content-disposition` (up to the upstream),
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* `false` will add `content-disposition: attachment` to any request,
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* a list of allowlisted content types
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* `keep_user_agent` will forward the client's user-agent to the upstream.
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This may be useful if the upstream is doing content transformation
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(encoding, …) depending on the request.
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* `req_headers`, `resp_headers` additional headers.
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* `http`: options for [hackney](https://github.com/benoitc/hackney).
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"""
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import Plug.Conn
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alias Plug.Conn
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require Logger
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@type option ::
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{:keep_user_agent, boolean}
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| {:max_read_duration, :timer.time() | :infinity}
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| {:max_body_length, non_neg_integer | :infinity}
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| {:http, []}
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| {:req_headers, [{String.t(), String.t()}]}
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| {:resp_headers, [{String.t(), String.t()}]}
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| {:inline_content_types, boolean | [String.t()]}
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| {:redirect_on_failure, boolean}
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@hackney Application.get_env(:mobilizon, :hackney, :hackney)
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@default_hackney_options []
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@inline_content_types [
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"image/gif",
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"image/jpeg",
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"image/jpg",
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"image/png",
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"image/svg+xml",
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"audio/mpeg",
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"audio/mp3",
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"video/webm",
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"video/mp4",
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"video/quicktime"
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]
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@spec call(Plug.Conn.t(), url :: String.t(), [option]) :: Plug.Conn.t()
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def call(_conn, _url, _opts \\ [])
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def call(conn = %{method: method}, url, opts) when method in @methods do
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hackney_opts =
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@default_hackney_options
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|> Keyword.merge(Keyword.get(opts, :http, []))
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req_headers = build_req_headers(conn.req_headers, opts)
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opts =
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if filename = filename(url) do
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Keyword.put_new(opts, :attachment_name, filename)
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else
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opts
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end
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with {:ok, code, headers, client} <- request(method, url, req_headers, hackney_opts),
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:ok <- header_length_constraint(headers, Keyword.get(opts, :max_body_length)) do
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response(conn, client, url, code, headers, opts)
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else
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{:ok, code, headers} ->
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conn
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|> head_response(url, code, headers, opts)
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|> halt()
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{:error, {:invalid_http_response, code}} ->
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Logger.error("#{__MODULE__}: request to #{inspect(url)} failed with HTTP status #{code}")
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conn
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|> error_or_redirect(
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url,
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code,
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"Request failed: " <> Conn.Status.reason_phrase(code),
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opts
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)
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|> halt()
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{:error, error} ->
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Logger.error("#{__MODULE__}: request to #{inspect(url)} failed: #{inspect(error)}")
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conn
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|> error_or_redirect(url, 500, "Request failed", opts)
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|> halt()
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end
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end
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def call(conn, _, _) do
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conn
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|> send_resp(400, Conn.Status.reason_phrase(400))
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|> halt()
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end
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defp request(method, url, headers, hackney_opts) do
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Logger.debug("#{__MODULE__} #{method} #{url} #{inspect(headers)}")
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method = method |> String.downcase() |> String.to_existing_atom()
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case @hackney.request(method, url, headers, "", hackney_opts) do
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{:ok, code, headers, client} when code in @valid_resp_codes ->
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{:ok, code, downcase_headers(headers), client}
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{:ok, code, headers} when code in @valid_resp_codes ->
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{:ok, code, downcase_headers(headers)}
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{:ok, code, _, _} ->
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{:error, {:invalid_http_response, code}}
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{:error, error} ->
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{:error, error}
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end
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end
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defp response(conn, client, url, status, headers, opts) do
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result =
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conn
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|> put_resp_headers(build_resp_headers(headers, opts))
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|> send_chunked(status)
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|> chunk_reply(client, opts)
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case result do
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{:ok, conn} ->
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halt(conn)
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{:error, :closed, conn} ->
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:hackney.close(client)
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halt(conn)
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{:error, error, conn} ->
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Logger.warn(
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"#{__MODULE__} request to #{url} failed while reading/chunking: #{inspect(error)}"
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)
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:hackney.close(client)
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halt(conn)
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end
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end
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defp chunk_reply(conn, client, opts) do
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chunk_reply(conn, client, opts, 0, 0)
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end
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defp chunk_reply(conn, client, opts, sent_so_far, duration) do
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with {:ok, duration} <-
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check_read_duration(
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duration,
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Keyword.get(opts, :max_read_duration, @max_read_duration)
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),
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{:ok, data} <- @hackney.stream_body(client),
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{:ok, duration} <- increase_read_duration(duration),
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sent_so_far = sent_so_far + byte_size(data),
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:ok <- body_size_constraint(sent_so_far, Keyword.get(opts, :max_body_size)),
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{:ok, conn} <- chunk(conn, data) do
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chunk_reply(conn, client, opts, sent_so_far, duration)
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else
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:done -> {:ok, conn}
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{:error, error} -> {:error, error, conn}
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end
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end
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defp head_response(conn, _url, code, headers, opts) do
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conn
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|> put_resp_headers(build_resp_headers(headers, opts))
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|> send_resp(code, "")
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end
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defp error_or_redirect(conn, url, code, body, opts) do
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if Keyword.get(opts, :redirect_on_failure, false) do
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conn
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|> Phoenix.Controller.redirect(external: url)
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|> halt()
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else
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conn
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|> send_resp(code, body)
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|> halt
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end
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end
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defp downcase_headers(headers) do
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Enum.map(headers, fn {k, v} ->
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{String.downcase(k), v}
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end)
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end
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defp get_content_type(headers) do
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{_, content_type} =
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List.keyfind(headers, "content-type", 0, {"content-type", "application/octet-stream"})
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[content_type | _] = String.split(content_type, ";")
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content_type
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end
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defp put_resp_headers(conn, headers) do
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Enum.reduce(headers, conn, fn {k, v}, conn ->
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put_resp_header(conn, k, v)
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end)
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end
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defp build_req_headers(headers, opts) do
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headers
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|> downcase_headers()
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|> Enum.filter(fn {k, _} -> k in @keep_req_headers end)
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|> (fn headers ->
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headers = headers ++ Keyword.get(opts, :req_headers, [])
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if Keyword.get(opts, :keep_user_agent, false) do
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List.keystore(
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headers,
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"user-agent",
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0,
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{"user-agent", Mobilizon.user_agent()}
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)
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else
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headers
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end
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end).()
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end
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defp build_resp_headers(headers, opts) do
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headers
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|> Enum.filter(fn {k, _} -> k in @keep_resp_headers end)
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|> build_resp_cache_headers(opts)
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|> build_resp_content_disposition_header(opts)
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|> (fn headers -> headers ++ Keyword.get(opts, :resp_headers, []) end).()
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end
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defp build_resp_cache_headers(headers, _opts) do
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has_cache? = Enum.any?(headers, fn {k, _} -> k in @resp_cache_headers end)
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has_cache_control? = List.keymember?(headers, "cache-control", 0)
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cond do
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has_cache? && has_cache_control? ->
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headers
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has_cache? ->
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# There's caching header present but no cache-control -- we need to explicitely override it
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# to public as Plug defaults to "max-age=0, private, must-revalidate"
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List.keystore(headers, "cache-control", 0, {"cache-control", "public"})
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true ->
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List.keystore(
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headers,
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"cache-control",
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0,
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{"cache-control", @default_cache_control_header}
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)
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end
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end
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defp build_resp_content_disposition_header(headers, opts) do
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opt = Keyword.get(opts, :inline_content_types, @inline_content_types)
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content_type = get_content_type(headers)
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attachment? =
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cond do
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is_list(opt) && !Enum.member?(opt, content_type) -> true
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opt == false -> true
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true -> false
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end
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if attachment? do
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name =
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try do
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{{"content-disposition", content_disposition_string}, _} =
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List.keytake(headers, "content-disposition", 0)
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[name | _] =
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Regex.run(
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~r/filename="((?:[^"\\]|\\.)*)"/u,
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content_disposition_string || "",
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capture: :all_but_first
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)
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name
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rescue
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MatchError -> Keyword.get(opts, :attachment_name, "attachment")
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end
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disposition = "attachment; filename=\"#{name}\""
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List.keystore(headers, "content-disposition", 0, {"content-disposition", disposition})
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else
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headers
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end
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end
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defp header_length_constraint(headers, limit) when is_integer(limit) and limit > 0 do
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with {_, size} <- List.keyfind(headers, "content-length", 0),
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{size, _} <- Integer.parse(size),
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true <- size <= limit do
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:ok
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else
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false ->
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{:error, :body_too_large}
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_ ->
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:ok
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end
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end
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defp header_length_constraint(_, _), do: :ok
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defp body_size_constraint(size, limit) when is_integer(limit) and limit > 0 and size >= limit do
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{:error, :body_too_large}
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end
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defp body_size_constraint(_, _), do: :ok
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defp check_read_duration(duration, max)
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when is_integer(duration) and is_integer(max) and max > 0 do
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if duration > max do
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{:error, :read_duration_exceeded}
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else
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{:ok, {duration, :erlang.system_time(:millisecond)}}
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end
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end
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defp check_read_duration(_, _), do: {:ok, :no_duration_limit, :no_duration_limit}
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defp increase_read_duration({previous_duration, started})
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when is_integer(previous_duration) and is_integer(started) do
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duration = :erlang.system_time(:millisecond) - started
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{:ok, previous_duration + duration}
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end
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defp increase_read_duration(_) do
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{:ok, :no_duration_limit, :no_duration_limit}
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end
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def filename(url_or_path) do
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if path = URI.parse(url_or_path).path, do: Path.basename(path)
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end
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end
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