Add base CAPTCHA support (currently only kocaptcha)

config/config.exs

@@ -10,6 +10,13 @@ config :pleroma, ecto_repos: [Pleroma.Repo]
 
 config :pleroma, Pleroma.Repo, types: Pleroma.PostgresTypes
 
+config :pleroma, Pleroma.Captcha,
+  method: Pleroma.Captcha.Kocaptcha
+
+# Kocaptcha is a very simple captcha service, the source code is here: https://github.com/koto-bank/kocaptcha
+config :pleroma, Pleroma.Captcha.Kocaptcha,
+  endpoint: "http://localhost:9093"
+
 # Upload configuration
 config :pleroma, Pleroma.Upload,
   uploader: Pleroma.Uploaders.Local,

lib/pleroma/application.ex

@@ -24,6 +24,7 @@ defmodule Pleroma.Application do
         # Start the Ecto repository
         supervisor(Pleroma.Repo, []),
         worker(Pleroma.Emoji, []),
+        worker(Pleroma.Captcha, []),
         worker(
           Cachex,
           [

lib/pleroma/captcha.ex

@@ -0,0 +1,68 @@
+defmodule Pleroma.Captcha do
+  use GenServer
+
+  @ets __MODULE__.Ets
+  @ets_options [:ordered_set, :private, :named_table, {:read_concurrency, true}]
+
+
+  @doc false
+  def start_link() do
+    GenServer.start_link(__MODULE__, [], name: __MODULE__)
+  end
+
+
+  @doc false
+  def init(_) do
+    @ets = :ets.new(@ets, @ets_options)
+
+    {:ok, nil}
+  end
+
+  def new() do
+    GenServer.call(__MODULE__, :new)
+  end
+
+  def validate(token, captcha) do
+    GenServer.call(__MODULE__, {:validate, token, captcha})
+  end
+
+  @doc false
+  def handle_call(:new, _from, state) do
+    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
+  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}
+    else
+      e -> IO.inspect(e); {:reply, false, state}
+    end
+  end
+end

lib/pleroma/web/router.ex

@@ -99,6 +99,7 @@ defmodule Pleroma.Web.Router do
     get("/password_reset/:token", UtilController, :show_password_reset)
     post("/password_reset", UtilController, :password_reset)
     get("/emoji", UtilController, :emoji)
+    get("/captcha", UtilController, :captcha)
   end
 
   scope "/api/pleroma/admin", Pleroma.Web.AdminAPI do

lib/pleroma/web/twitter_api/controllers/util_controller.ex

@@ -284,4 +284,8 @@ defmodule Pleroma.Web.TwitterAPI.UtilController do
         json(conn, %{error: msg})
     end
   end
+
+  def captcha(conn, _params) do
+    json(conn, Pleroma.Captcha.new())
+  end
 end

lib/pleroma/web/twitter_api/twitter_api.ex

@@ -132,9 +132,16 @@ defmodule Pleroma.Web.TwitterAPI.TwitterAPI do
       bio: User.parse_bio(params["bio"]),
       email: params["email"],
       password: params["password"],
-      password_confirmation: params["confirm"]
+      password_confirmation: params["confirm"],
+      captcha_solution: params["captcha_solution"],
+      captcha_token: params["captcha_token"]
     }
 
+    # Captcha invalid
+    if not Pleroma.Captcha.validate(params[:captcha_token], params[:captcha_solution]) do
+      # I have no idea how this error handling works
+      {:error, %{error: Jason.encode!(%{captcha: ["Invalid CAPTCHA"]})}}
+    else
       registrations_open = Pleroma.Config.get([:instance, :registrations_open])
 
       # no need to query DB if registration is open
@@ -159,6 +166,7 @@ defmodule Pleroma.Web.TwitterAPI.TwitterAPI do
             {:error, %{error: errors}}
           end
 
+
         !registrations_open && is_nil(token) ->
             {:error, "Invalid token"}
 
@@ -166,6 +174,7 @@ defmodule Pleroma.Web.TwitterAPI.TwitterAPI do
             {:error, "Expired token"}
       end
     end
+  end
 
   def password_reset(nickname_or_email) do
     with true <- is_binary(nickname_or_email),