akkoma/lib/pleroma/web/media_proxy/media_proxy.ex

144 lines
3.7 KiB
Elixir

# Pleroma: A lightweight social networking server
# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only
defmodule Pleroma.Web.MediaProxy do
alias Pleroma.Config
alias Pleroma.Upload
alias Pleroma.Web
@base64_opts [padding: false]
def url(url) when is_nil(url) or url == "", do: nil
def url("/" <> _ = url), do: url
def url(url) do
if not enabled?() or local?(url) or whitelisted?(url) do
url
else
encode_url(url)
end
end
# Note: routing all URLs to preview handler (even local and whitelisted).
# Preview handler will call url/1 on decoded URLs, and applicable ones will detour media proxy.
def preview_url(url) do
if preview_enabled?() do
encode_preview_url(url)
else
url
end
end
def enabled?, do: Config.get([:media_proxy, :enabled], false)
# Note: media proxy must be enabled for media preview proxy in order to load all
# non-local non-whitelisted URLs through it and be sure that body size constraint is preserved.
def preview_enabled?, do: enabled?() and Config.get([:media_preview_proxy, :enabled], false)
def local?(url), do: String.starts_with?(url, Pleroma.Web.base_url())
def whitelisted?(url) do
%{host: domain} = URI.parse(url)
mediaproxy_whitelist = Config.get([:media_proxy, :whitelist])
upload_base_url_domain =
if !is_nil(Config.get([Upload, :base_url])) do
[URI.parse(Config.get([Upload, :base_url])).host]
else
[]
end
whitelist = mediaproxy_whitelist ++ upload_base_url_domain
Enum.any?(whitelist, fn pattern ->
String.equivalent?(domain, pattern)
end)
end
defp base64_sig64(url) do
base64 = Base.url_encode64(url, @base64_opts)
sig64 =
base64
|> signed_url()
|> Base.url_encode64(@base64_opts)
{base64, sig64}
end
def encode_url(url) do
{base64, sig64} = base64_sig64(url)
build_url(sig64, base64, filename(url))
end
def encode_preview_url(url) do
{base64, sig64} = base64_sig64(url)
build_preview_url(sig64, base64, filename(url))
end
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
defp signed_url(url) do
:crypto.hmac(:sha, Config.get([Web.Endpoint, :secret_key_base]), url)
end
def filename(url_or_path) do
if path = URI.parse(url_or_path).path, do: Path.basename(path)
end
defp proxy_url(path, sig_base64, url_base64, filename) do
[
Pleroma.Config.get([:media_proxy, :base_url], Web.base_url()),
path,
sig_base64,
url_base64,
filename
]
|> Enum.filter(& &1)
|> Path.join()
end
def build_url(sig_base64, url_base64, filename \\ nil) do
proxy_url("proxy", sig_base64, url_base64, filename)
end
def build_preview_url(sig_base64, url_base64, filename \\ nil) do
proxy_url("proxy/preview", sig_base64, url_base64, filename)
end
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
defp basename_matches?(path, filename) do
basename = Path.basename(path)
basename == filename or URI.decode(basename) == filename or URI.encode(basename) == filename
end
end