111 lines
3.5 KiB
Elixir
111 lines
3.5 KiB
Elixir
# Pleroma: A lightweight social networking server
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# Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
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# SPDX-License-Identifier: AGPL-3.0-only
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defmodule Pleroma.Captcha do
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alias Plug.Crypto.KeyGenerator
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alias Plug.Crypto.MessageEncryptor
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alias Calendar.DateTime
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use GenServer
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@doc false
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def start_link() do
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GenServer.start_link(__MODULE__, [], name: __MODULE__)
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end
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@doc false
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def init(_) do
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{:ok, nil}
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end
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@doc """
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Ask the configured captcha service for a new captcha
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"""
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def new() do
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GenServer.call(__MODULE__, :new)
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end
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@doc """
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Ask the configured captcha service to validate the captcha
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"""
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def validate(token, captcha, answer_data) do
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GenServer.call(__MODULE__, {:validate, token, captcha, answer_data})
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end
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@doc false
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def handle_call(:new, _from, state) do
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enabled = Pleroma.Config.get([__MODULE__, :enabled])
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if !enabled do
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{:reply, %{type: :none}, state}
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else
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new_captcha = method().new()
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secret_key_base = Pleroma.Config.get!([Pleroma.Web.Endpoint, :secret_key_base])
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# This make salt a little different for two keys
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token = new_captcha[:token]
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secret = KeyGenerator.generate(secret_key_base, token <> "_encrypt")
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sign_secret = KeyGenerator.generate(secret_key_base, token <> "_sign")
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# Basicallty copy what Phoenix.Token does here, add the time to
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# the actual data and make it a binary to then encrypt it
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encrypted_captcha_answer =
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%{
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at: DateTime.now_utc(),
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answer_data: new_captcha[:answer_data]
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}
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|> :erlang.term_to_binary()
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|> MessageEncryptor.encrypt(secret, sign_secret)
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{
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:reply,
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# Repalce the answer with the encrypted answer
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%{new_captcha | answer_data: encrypted_captcha_answer},
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state
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}
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end
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end
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@doc false
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def handle_call({:validate, token, captcha, answer_data}, _from, state) do
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secret_key_base = Pleroma.Config.get!([Pleroma.Web.Endpoint, :secret_key_base])
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secret = KeyGenerator.generate(secret_key_base, token <> "_encrypt")
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sign_secret = KeyGenerator.generate(secret_key_base, token <> "_sign")
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# If the time found is less than (current_time - seconds_valid), then the time has already passed.
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# Later we check that the time found is more than the presumed invalidatation time, that means
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# that the data is still valid and the captcha can be checked
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seconds_valid = Pleroma.Config.get!([Pleroma.Captcha, :seconds_valid])
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valid_if_after = DateTime.subtract!(DateTime.now_utc(), seconds_valid)
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result =
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with {:ok, data} <- MessageEncryptor.decrypt(answer_data, secret, sign_secret),
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%{at: at, answer_data: answer_md5} <- :erlang.binary_to_term(data) do
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try do
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if DateTime.before?(at, valid_if_after), do: throw({:error, "CAPTCHA expired"})
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if not is_nil(Cachex.get!(:used_captcha_cache, token)),
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do: throw({:error, "CAPTCHA already used"})
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res = method().validate(token, captcha, answer_md5)
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# Throw if an error occurs
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if res != :ok, do: throw(res)
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# Mark this captcha as used
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{:ok, _} =
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Cachex.put(:used_captcha_cache, token, true, ttl: :timer.seconds(seconds_valid))
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:ok
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catch
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:throw, e -> e
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end
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else
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_ -> {:error, "Invalid answer data"}
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end
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{:reply, result, state}
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end
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defp method, do: Pleroma.Config.get!([__MODULE__, :method])
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end
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