git.squeep.com Git - akkoma/blob - lib/pleroma/captcha/captcha.ex

   1 defmodule Pleroma.Captcha do
   2   alias Plug.Crypto.KeyGenerator
   3   alias Plug.Crypto.MessageEncryptor
   4   alias Calendar.DateTime
   5
   6   use GenServer
   7
   8   @doc false
   9   def start_link() do
  10     GenServer.start_link(__MODULE__, [], name: __MODULE__)
  11   end
  12
  13   @doc false
  14   def init(_) do
  15     {:ok, nil}
  16   end
  17
  18   @doc """
  19   Ask the configured captcha service for a new captcha
  20   """
  21   def new() do
  22     GenServer.call(__MODULE__, :new)
  23   end
  24
  25   @doc """
  26   Ask the configured captcha service to validate the captcha
  27   """
  28   def validate(token, captcha, answer_data) do
  29     GenServer.call(__MODULE__, {:validate, token, captcha, answer_data})
  30   end
  31
  32   @doc false
  33   def handle_call(:new, _from, state) do
  34     enabled = Pleroma.Config.get([__MODULE__, :enabled])
  35
  36     if !enabled do
  37       {:reply, %{type: :none}, state}
  38     else
  39       new_captcha = method().new()
  40
  41       secret_key_base = Pleroma.Config.get!([Pleroma.Web.Endpoint, :secret_key_base])
  42
  43       # This make salt a little different for two keys
  44       token = new_captcha[:token]
  45       secret = KeyGenerator.generate(secret_key_base, token <> "_encrypt")
  46       sign_secret = KeyGenerator.generate(secret_key_base, token <> "_sign")
  47       # Basicallty copy what Phoenix.Token does here, add the time to
  48       # the actual data and make it a binary to then encrypt it
  49       encrypted_captcha_answer =
  50         %{
  51           at: DateTime.now_utc(),
  52           answer_data: new_captcha[:answer_data]
  53         }
  54         |> :erlang.term_to_binary()
  55         |> MessageEncryptor.encrypt(secret, sign_secret)
  56
  57       {
  58         :reply,
  59         # Repalce the answer with the encrypted answer
  60         %{new_captcha | answer_data: encrypted_captcha_answer},
  61         state
  62       }
  63     end
  64   end
  65
  66   @doc false
  67   def handle_call({:validate, token, captcha, answer_data}, _from, state) do
  68     secret_key_base = Pleroma.Config.get!([Pleroma.Web.Endpoint, :secret_key_base])
  69     secret = KeyGenerator.generate(secret_key_base, token <> "_encrypt")
  70     sign_secret = KeyGenerator.generate(secret_key_base, token <> "_sign")
  71
  72     # If the time found is less than (current_time - seconds_valid), then the time has already passed.
  73     # Later we check that the time found is more than the presumed invalidatation time, that means
  74     # that the data is still valid and the captcha can be checked
  75     seconds_valid = Pleroma.Config.get!([Pleroma.Captcha, :seconds_valid])
  76     valid_if_after = DateTime.subtract!(DateTime.now_utc(), seconds_valid)
  77
  78     result =
  79       with {:ok, data} <- MessageEncryptor.decrypt(answer_data, secret, sign_secret),
  80            %{at: at, answer_data: answer_md5} <- :erlang.binary_to_term(data) do
  81         try do
  82           if DateTime.before?(at, valid_if_after), do: throw({:error, "CAPTCHA expired"})
  83
  84           if not is_nil(Cachex.get!(:used_captcha_cache, token)),
  85             do: throw({:error, "CAPTCHA already used"})
  86
  87           res = method().validate(token, captcha, answer_md5)
  88           # Throw if an error occurs
  89           if res != :ok, do: throw(res)
  90
  91           # Mark this captcha as used
  92           {:ok, _} =
  93             Cachex.put(:used_captcha_cache, token, true, ttl: :timer.seconds(seconds_valid))
  94
  95           :ok
  96         catch
  97           :throw, e -> e
  98         end
  99       else
 100         _ -> {:error, "Invalid answer data"}
 101       end
 102
 103     {:reply, result, state}
 104   end
 105
 106   defp method, do: Pleroma.Config.get!([__MODULE__, :method])
 107 end