rM8EvyJn

1defmodule MyAppWeb.GraphQL.Types.EncId do
2  use Absinthe.Schema.Notation
3
4  defp secret_key(len \ 32) do
5    Application.get_env(:my_app, MyAppWeb.Endpoint)
6    |> Keyword.get(:secret_key_base, "")
7    |> String.slice(0, len)
8  end
9
10  defp pad_bytes(binary, block \ 16) do
11    padding_bits =
12      case rem(byte_size(binary), block) do
13        0 -> 0
14        r -> (block - r) * 8
15      end
16
17    <<0::size(padding_bits)>> <> binary
18  end
19
20  defp unpad_bytes(<<0, tail::bitstring>>), do: unpad_bytes(tail)
21  defp unpad_bytes(binary), do: binary
22
23  defp encrypt(raw_binary) do
24    padded_binary = pad_bytes(raw_binary)
25
26    :crypto.crypto_one_time(:aes_256_ecb, secret_key(), padded_binary, true)
27  end
28
29  defp decrypt(raw_enc) do
30    :crypto.crypto_one_time(:aes_256_ecb, secret_key(), raw_enc, false)
31    |> unpad_bytes()
32    |> :erlang.binary_to_term()
33  end
34
35  def serialize(id) do
36    id
37    |> :erlang.term_to_binary()
38    |> encrypt()
39    |> Base.url_encode64(padding: false)
40  end
41
42  def parse(%{value: enc_id}) do
43    try do
44      {:ok, raw_enc} = Base.url_decode64(enc_id, padding: false)
45      {:ok, decrypt(raw_enc)}
46    rescue
47      _ -> :error
48    end
49  end
50
51  scalar :enc_id, name: "EncId" do
52    serialize(&__MODULE__.serialize/1)
53
54    parse(&__MODULE__.parse/1)
55  end
56end