-defmodule Pleroma.Captcha do
- use GenServer
-
- @ets __MODULE__.Ets
- @ets_options [:ordered_set, :private, :named_table, {:read_concurrency, true}]
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+defmodule Pleroma.Captcha do
+ alias Calendar.DateTime
+ alias Plug.Crypto.KeyGenerator
+ alias Plug.Crypto.MessageEncryptor
+
+ @cachex Pleroma.Config.get([:cachex, :provider], Cachex)
+
+ @doc """
+ Ask the configured captcha service for a new captcha
+ """
+ def new do
+ if not enabled?() do
+ %{type: :none}
+ else
+ new_captcha = method().new()
+
+ # This make salt a little different for two keys
+ {secret, sign_secret} = secret_pair(new_captcha[:token])
+
+ # Basically copy what Phoenix.Token does here, add the time to
+ # the actual data and make it a binary to then encrypt it
+ encrypted_captcha_answer =
+ %{
+ at: DateTime.now_utc(),
+ answer_data: new_captcha[:answer_data]
+ }
+ |> :erlang.term_to_binary()
+ |> MessageEncryptor.encrypt(secret, sign_secret)
+
+ # Replace the answer with the encrypted answer
+ %{new_captcha | answer_data: encrypted_captcha_answer}
+ end
+ end
- @doc false
- def start_link() do
- GenServer.start_link(__MODULE__, [], name: __MODULE__)
+ @doc """
+ Ask the configured captcha service to validate the captcha
+ """
+ def validate(token, captcha, answer_data) do
+ with {:ok, %{at: at, answer_data: answer_md5}} <- validate_answer_data(token, answer_data),
+ :ok <- validate_expiration(at),
+ :ok <- validate_usage(token),
+ :ok <- method().validate(token, captcha, answer_md5),
+ {:ok, _} <- mark_captcha_as_used(token) do
+ :ok
+ end
end
+ def enabled?, do: Pleroma.Config.get([__MODULE__, :enabled], false)
- @doc false
- def init(_) do
- @ets = :ets.new(@ets, @ets_options)
+ defp seconds_valid, do: Pleroma.Config.get!([__MODULE__, :seconds_valid])
- {:ok, nil}
- end
+ defp secret_pair(token) do
+ secret_key_base = Pleroma.Config.get!([Pleroma.Web.Endpoint, :secret_key_base])
+ secret = KeyGenerator.generate(secret_key_base, token <> "_encrypt")
+ sign_secret = KeyGenerator.generate(secret_key_base, token <> "_sign")
- def new() do
- GenServer.call(__MODULE__, :new)
+ {secret, sign_secret}
end
- def validate(token, captcha) do
- GenServer.call(__MODULE__, {:validate, token, captcha})
+ defp validate_answer_data(token, answer_data) do
+ {secret, sign_secret} = secret_pair(token)
+
+ with false <- is_nil(answer_data),
+ {:ok, data} <- MessageEncryptor.decrypt(answer_data, secret, sign_secret),
+ %{at: at, answer_data: answer_md5} <- :erlang.binary_to_term(data) do
+ {:ok, %{at: at, answer_data: answer_md5}}
+ else
+ _ -> {:error, :invalid_answer_data}
+ end
end
- @doc false
- def handle_call(:new, _from, state) do
- enabled = Pleroma.Config.get([__MODULE__, :enabled])
+ defp validate_expiration(created_at) do
+ # If the time found is less than (current_time-seconds_valid) then the time has already passed
+ # Later we check that the time found is more than the presumed invalidatation time, that means
+ # that the data is still valid and the captcha can be checked
+
+ valid_if_after = DateTime.subtract!(DateTime.now_utc(), seconds_valid())
- if !enabled do
- {
- :reply,
- %{type: :none},
- state
- }
+ if DateTime.before?(created_at, valid_if_after) do
+ {:error, :expired}
else
- method = Pleroma.Config.get!([__MODULE__, :method])
-
- case method do
- __MODULE__.Kocaptcha ->
- endpoint = Pleroma.Config.get!([method, :endpoint])
- case HTTPoison.get(endpoint <> "/new") do
- {:error, _} ->
- %{error: "Kocaptcha service unavailable"}
- {:ok, res} ->
- json_resp = Poison.decode!(res.body)
-
- token = json_resp["token"]
-
- true = :ets.insert(@ets, {token, json_resp["md5"]})
-
- {
- :reply,
- %{type: :kocaptcha, token: token, url: endpoint <> json_resp["url"]},
- state
- }
- end
- end
+ :ok
end
end
- @doc false
- def handle_call({:validate, token, captcha}, _from, state) do
- with false <- is_nil(captcha),
- [{^token, saved_md5}] <- :ets.lookup(@ets, token),
- true <- (:crypto.hash(:md5, captcha) |> Base.encode16) == String.upcase(saved_md5) do
- # Clear the saved value
- :ets.delete(@ets, token)
-
- {:reply, true, state}
+ defp validate_usage(token) do
+ if is_nil(@cachex.get!(:used_captcha_cache, token)) do
+ :ok
else
- e -> IO.inspect(e); {:reply, false, state}
+ {:error, :already_used}
end
end
+
+ defp mark_captcha_as_used(token) do
+ ttl = seconds_valid() |> :timer.seconds()
+ @cachex.put(:used_captcha_cache, token, true, ttl: ttl)
+ end
+
+ defp method, do: Pleroma.Config.get!([__MODULE__, :method])
end