102 lines
3.2 KiB
Elixir
102 lines
3.2 KiB
Elixir
# Pleroma: A lightweight social networking server
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# Copyright © 2017-2020 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 Calendar.DateTime
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alias Plug.Crypto.KeyGenerator
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alias Plug.Crypto.MessageEncryptor
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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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if not enabled?() do
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%{type: :none}
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else
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new_captcha = method().new()
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# This make salt a little different for two keys
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{secret, sign_secret} = secret_pair(new_captcha[:token])
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# Basically 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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# Replace the answer with the encrypted answer
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%{new_captcha | answer_data: encrypted_captcha_answer}
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end
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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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with {:ok, %{at: at, answer_data: answer_md5}} <- validate_answer_data(token, answer_data),
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:ok <- validate_expiration(at),
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:ok <- validate_usage(token),
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:ok <- method().validate(token, captcha, answer_md5),
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{:ok, _} <- mark_captcha_as_used(token) do
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:ok
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end
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end
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def enabled?, do: Pleroma.Config.get([__MODULE__, :enabled], false)
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defp seconds_valid, do: Pleroma.Config.get!([__MODULE__, :seconds_valid])
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defp secret_pair(token) 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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{secret, sign_secret}
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end
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defp validate_answer_data(token, answer_data) do
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{secret, sign_secret} = secret_pair(token)
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with false <- is_nil(answer_data),
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{: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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{:ok, %{at: at, answer_data: answer_md5}}
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else
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_ -> {:error, :invalid_answer_data}
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end
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end
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defp validate_expiration(created_at) do
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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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valid_if_after = DateTime.subtract!(DateTime.now_utc(), seconds_valid())
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if DateTime.before?(created_at, valid_if_after) do
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{:error, :expired}
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else
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:ok
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end
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end
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defp validate_usage(token) do
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if is_nil(Cachex.get!(:used_captcha_cache, token)) do
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:ok
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else
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{:error, :already_used}
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end
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end
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defp mark_captcha_as_used(token) do
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ttl = seconds_valid() |> :timer.seconds()
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Cachex.put(:used_captcha_cache, token, true, ttl: ttl)
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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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