138 lines
3.8 KiB
Elixir
138 lines
3.8 KiB
Elixir
# Pleroma: A lightweight social networking server
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# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
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# SPDX-License-Identifier: AGPL-3.0-only
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defmodule Mobilizon.Web.MediaProxy do
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@moduledoc """
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Module to proxify remote media
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"""
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alias Mobilizon.Config
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alias Mobilizon.Web
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@base64_opts [padding: false]
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@spec url(String.t() | nil) :: String.t() | nil
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def url(url) when is_nil(url) or url == "", do: nil
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def url("/" <> _ = url), do: url
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def url(url) do
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if enabled?() and url_proxiable?(url) do
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encode_url(url)
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else
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url
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end
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end
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@spec url_proxiable?(String.t()) :: boolean()
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def url_proxiable?(url) do
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not local?(url)
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end
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@spec enabled? :: boolean()
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def enabled?, do: Config.get([:media_proxy, :enabled], false)
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def local?(url), do: String.starts_with?(url, Web.Endpoint.url())
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@spec base64_sig64(String.t()) :: {String.t(), String.t()}
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defp base64_sig64(url) do
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base64 = Base.url_encode64(url, @base64_opts)
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sig64 =
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base64
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|> signed_url()
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|> Base.url_encode64(@base64_opts)
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{base64, sig64}
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end
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@spec encode_url(String.t()) :: String.t()
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def encode_url(url) do
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{base64, sig64} = base64_sig64(url)
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build_url(sig64, base64, filename(url))
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end
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@spec decode_url(String.t(), String.t()) :: {:ok, String.t()} | {:error, :invalid_signature}
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def decode_url(sig, url) do
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with {:ok, sig} <- Base.url_decode64(sig, @base64_opts),
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signature when signature == sig <- signed_url(url) do
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{:ok, Base.url_decode64!(url, @base64_opts)}
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else
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_ -> {:error, :invalid_signature}
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end
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end
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@spec signed_url(String.t()) :: String.t()
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defp signed_url(url) do
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sha_hmac(Config.get([Web.Endpoint, :secret_key_base]), url)
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end
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@spec sha_hmac(String.t(), String.t()) :: String.t()
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@compile {:no_warn_undefined, {:crypto, :mac, 4}}
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@compile {:no_warn_undefined, {:crypto, :hmac, 3}}
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defp sha_hmac(key, url) do
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# :crypto.hmac was removed in OTP24, but :crypto.mac was added in OTP 22.1
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# TODO: Remove me when we don't support OTP 21/22 anymore
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if function_exported?(:crypto, :mac, 4) do
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:crypto.mac(:hmac, :sha, key, url)
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else
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:crypto.hmac(:sha, key, url)
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end
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end
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@spec filename(String.t()) :: String.t() | nil
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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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@spec base_url :: String.t()
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def base_url do
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Web.Endpoint.url()
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end
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@spec proxy_url(String.t(), String.t(), String.t(), String.t() | nil) :: String.t()
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defp proxy_url(path, sig_base64, url_base64, filename) do
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[
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base_url(),
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path,
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sig_base64,
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url_base64,
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filename
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]
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|> Enum.filter(& &1)
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|> Path.join()
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end
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@spec build_url(String.t(), String.t(), String.t() | nil) :: String.t()
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def build_url(sig_base64, url_base64, filename \\ nil) do
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proxy_url("proxy", sig_base64, url_base64, filename)
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end
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@spec verify_request_path_and_url(Plug.Conn.t() | String.t(), String.t()) ::
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:ok | {:wrong_filename, String.t()}
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def verify_request_path_and_url(
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%Plug.Conn{params: %{"filename" => _}, request_path: request_path},
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url
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) do
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verify_request_path_and_url(request_path, url)
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end
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def verify_request_path_and_url(request_path, url) when is_binary(request_path) do
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filename = filename(url)
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if filename && not basename_matches?(request_path, filename) do
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{:wrong_filename, filename}
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else
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:ok
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end
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end
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def verify_request_path_and_url(_, _), do: :ok
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@spec basename_matches?(String.t(), String.t()) :: boolean()
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defp basename_matches?(path, filename) do
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basename = Path.basename(path)
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basename == filename or URI.decode(basename) == filename or URI.encode(basename) == filename
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end
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end
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