version chapril de mobilizon https://mobilizon.chapril.org/
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mobilizon.chapril.org-mobil.../lib/web/media_proxy.ex

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