Commit 336e37d9 authored by vaartis's avatar vaartis

Make captcha (kocaptcha) stateless

Also rename seconds_retained to seconds_valid since that's how it is
now. Put it down from 180 to 20 seconds. The answer data is now
stored in an encrypted text transfered to the client and back, so no
ETS is needed
parent 61a88a67
......@@ -12,7 +12,7 @@ config :pleroma, Pleroma.Repo, types: Pleroma.PostgresTypes
config :pleroma, Pleroma.Captcha,
enabled: false,
seconds_retained: 180,
seconds_valid: 20,
method: Pleroma.Captcha.Kocaptcha
config :pleroma, Pleroma.Captcha.Kocaptcha, endpoint: "https://captcha.kotobank.ch"
......
......@@ -168,7 +168,7 @@ Web Push Notifications configuration. You can use the mix task `mix web_push.gen
## Pleroma.Captcha
* `enabled`: Whether the captcha should be shown on registration
* `method`: The method/service to use for captcha
* `seconds_retained`: The time in seconds for which the captcha is valid (stored in the cache)
* `seconds_valid`: The time in seconds for which the captcha is valid
### Pleroma.Captcha.Kocaptcha
Kocaptcha is a very simple captcha service with a single API endpoint,
......
defmodule Pleroma.Captcha do
use GenServer
@ets_options [:ordered_set, :private, :named_table, {:read_concurrency, true}]
@doc false
def start_link() do
GenServer.start_link(__MODULE__, [], name: __MODULE__)
......@@ -10,14 +8,6 @@ defmodule Pleroma.Captcha do
@doc false
def init(_) do
# Create a ETS table to store captchas
ets_name = Module.concat(method(), Ets)
^ets_name = :ets.new(Module.concat(method(), Ets), @ets_options)
# Clean up old captchas every few minutes
seconds_retained = Pleroma.Config.get!([__MODULE__, :seconds_retained])
Process.send_after(self(), :cleanup, 1000 * seconds_retained)
{:ok, nil}
end
......@@ -31,8 +21,8 @@ defmodule Pleroma.Captcha do
@doc """
Ask the configured captcha service to validate the captcha
"""
def validate(token, captcha) do
GenServer.call(__MODULE__, {:validate, token, captcha})
def validate(token, captcha, answer_data) do
GenServer.call(__MODULE__, {:validate, token, captcha, answer_data})
end
@doc false
......@@ -47,19 +37,8 @@ defmodule Pleroma.Captcha do
end
@doc false
def handle_call({:validate, token, captcha}, _from, state) do
{:reply, method().validate(token, captcha), state}
end
@doc false
def handle_info(:cleanup, state) do
:ok = method().cleanup()
seconds_retained = Pleroma.Config.get!([__MODULE__, :seconds_retained])
# Schedule the next clenup
Process.send_after(self(), :cleanup, 1000 * seconds_retained)
{:noreply, state}
def handle_call({:validate, token, captcha, answer_data}, _from, state) do
{:reply, method().validate(token, captcha, answer_data), state}
end
defp method, do: Pleroma.Config.get!([__MODULE__, :method])
......
......@@ -14,15 +14,15 @@ defmodule Pleroma.Captcha.Service do
Arguments:
* `token` the captcha is associated with
* `captcha` solution of the captcha to validate
* `answer_data` is the data needed to validate the answer (presumably encrypted)
Returns:
`true` if captcha is valid, `false` if not
"""
@callback validate(token :: String.t(), captcha :: String.t()) :: boolean
@doc """
This function is called periodically to clean up old captchas
"""
@callback cleanup() :: :ok
@callback validate(
token :: String.t(),
captcha :: String.t(),
answer_data :: String.t()
) :: :ok | {:error, String.t()}
end
defmodule Pleroma.Captcha.Kocaptcha do
alias Plug.Crypto.KeyGenerator
alias Plug.Crypto.MessageEncryptor
alias Calendar.DateTime
alias Pleroma.Captcha.Service
@behaviour Service
@ets __MODULE__.Ets
@impl Service
def new() do
endpoint = Pleroma.Config.get!([__MODULE__, :endpoint])
......@@ -18,50 +18,56 @@ defmodule Pleroma.Captcha.Kocaptcha do
json_resp = Poison.decode!(res.body)
token = json_resp["token"]
answer_md5 = json_resp["md5"]
true =
:ets.insert(
@ets,
{token, json_resp["md5"], DateTime.now_utc() |> DateTime.Format.unix()}
)
secret_key_base = Pleroma.Config.get!([Pleroma.Web.Endpoint, :secret_key_base])
%{type: :kocaptcha, token: token, url: endpoint <> json_resp["url"]}
end
end
@impl Service
def validate(token, captcha) 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)
# This make salt a little different for two keys
secret = KeyGenerator.generate(secret_key_base, token <> "_encrypt")
sign_secret = KeyGenerator.generate(secret_key_base, token <> "_sign")
# Basicallty 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_md5: answer_md5
}
|> :erlang.term_to_binary()
|> MessageEncryptor.encrypt(secret, sign_secret)
true
else
_ -> false
%{
type: :kocaptcha,
token: token,
url: endpoint <> json_resp["url"],
answer_data: encrypted_captcha_answer
}
end
end
@impl Service
def cleanup() do
seconds_retained = Pleroma.Config.get!([Pleroma.Captcha, :seconds_retained])
# If the time in ETS is less than current_time - seconds_retained, then the time has
# already passed
delete_after =
DateTime.subtract!(DateTime.now_utc(), seconds_retained) |> DateTime.Format.unix()
def validate(token, captcha, answer_data) 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")
:ets.select_delete(
@ets,
[
{
{:_, :_, :"$1"},
[{:<, :"$1", {:const, delete_after}}],
[true]
}
]
)
# 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
seconds_valid = Pleroma.Config.get!([Pleroma.Captcha, :seconds_valid])
valid_if_after = DateTime.subtract!(DateTime.now_utc(), seconds_valid)
:ok
with {:ok, data} <- MessageEncryptor.decrypt(answer_data, secret, sign_secret),
%{at: at, answer_md5: answer_md5} <- :erlang.binary_to_term(data) do
if DateTime.after?(at, valid_if_after) do
if not is_nil(captcha) and
:crypto.hash(:md5, captcha) |> Base.encode16() == String.upcase(answer_md5),
do: :ok,
else: {:error, "Invalid CAPTCHA"}
else
{:error, "CAPTCHA expired"}
end
else
_ -> {:error, "Invalid answer data"}
end
end
end
......@@ -136,22 +136,28 @@ defmodule Pleroma.Web.TwitterAPI.TwitterAPI do
password: params["password"],
password_confirmation: params["confirm"],
captcha_solution: params["captcha_solution"],
captcha_token: params["captcha_token"]
captcha_token: params["captcha_token"],
captcha_answer_data: params["captcha_answer_data"]
}
captcha_enabled = Pleroma.Config.get([Pleroma.Captcha, :enabled])
# true if captcha is disabled or enabled and valid, false otherwise
captcha_ok =
if !captcha_enabled do
true
:ok
else
Pleroma.Captcha.validate(params[:captcha_token], params[:captcha_solution])
Pleroma.Captcha.validate(
params[:captcha_token],
params[:captcha_solution],
params[:captcha_answer_data]
)
end
# Captcha invalid
if not captcha_ok do
if captcha_ok != :ok do
{:error, error} = captcha_ok
# I have no idea how this error handling works
{:error, %{error: Jason.encode!(%{captcha: ["Invalid CAPTCHA"]})}}
{:error, %{error: Jason.encode!(%{captcha: [error]})}}
else
registrations_open = Pleroma.Config.get([:instance, :registrations_open])
......
......@@ -25,16 +25,18 @@ defmodule Pleroma.CaptchaTest do
end
test "new and validate" do
assert Kocaptcha.new() == %{
type: :kocaptcha,
token: "afa1815e14e29355e6c8f6b143a39fa2",
url: "https://captcha.kotobank.ch/captchas/afa1815e14e29355e6c8f6b143a39fa2.png"
}
new = Kocaptcha.new()
assert new[:type] == :kocaptcha
assert new[:token] == "afa1815e14e29355e6c8f6b143a39fa2"
assert new[:url] ==
"https://captcha.kotobank.ch/captchas/afa1815e14e29355e6c8f6b143a39fa2.png"
assert Kocaptcha.validate(
"afa1815e14e29355e6c8f6b143a39fa2",
"7oEy8c"
)
new[:token],
"7oEy8c",
new[:answer_data]
) == :ok
end
end
end
......@@ -6,8 +6,5 @@ defmodule Pleroma.Captcha.Mock do
def new(), do: %{type: :mock}
@impl Service
def validate(_token, _captcha), do: true
@impl Service
def cleanup(), do: :ok
def validate(_token, _captcha, _data), do: :ok
end
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