philomena/lib/philomena_web/plugs/scraper_plug.ex

61 lines
1.6 KiB
Elixir

defmodule PhilomenaWeb.ScraperPlug do
@filename_regex ~r/filename="([^"]+)"/
@spec init(keyword()) :: keyword()
def init(opts) do
opts
end
@spec call(Plug.Conn.t(), keyword()) :: Plug.Conn.t()
def call(conn, opts) do
params_name = Keyword.get(opts, :params_name, "image")
params_key = Keyword.get(opts, :params_key, "image")
case conn.params do
%{^params_name => %{^params_key => %Plug.Upload{}}} ->
conn
%{"scraper_cache" => url} when not is_nil(url) and url != "" ->
url
|> PhilomenaProxy.Http.get()
|> maybe_fixup_params(url, opts, conn)
_ ->
conn
end
end
# Writing the tempfile doesn't allow traversal
# sobelow_skip ["Traversal.FileModule"]
defp maybe_fixup_params({:ok, %{status: 200} = resp}, url, opts, conn) do
params_name = Keyword.get(opts, :params_name, "image")
params_key = Keyword.get(opts, :params_key, "image")
name = extract_filename(url, resp.headers)
file = Plug.Upload.random_file!(UUID.uuid1())
File.write!(file, resp.body)
fake_upload = %Plug.Upload{
path: file,
content_type: "application/octet-stream",
filename: name
}
put_in(conn.params[params_name][params_key], fake_upload)
end
defp maybe_fixup_params(_response, _url, _opts, conn), do: conn
defp extract_filename(url, headers) do
name =
with [value | _] <- headers["content-disposition"],
[name] <- Regex.run(@filename_regex, value, capture: :all_but_first) do
name
else
_ ->
Path.basename(url)
end
String.slice(name, 0, 127)
end
end