rate limiter: disable based on if remote ip was found, not on if the plug was enabled

The current rate limiter disable logic won't trigger when the remote ip
is not forwarded, only when the remoteip plug is not enabled, which is
not the case on most instances since it's enabled by default. This
changes the behavior to warn and disable  when the remote ip was not forwarded,
even if the RemoteIP plug is enabled.

Also closes #1620

config/test.exs

@@ -92,6 +92,8 @@
 
 config :pleroma, Pleroma.Emails.NewUsersDigestEmail, enabled: true
 
+config :pleroma, Pleroma.Plugs.RemoteIp, enabled: false
+
 if File.exists?("./config/test.secret.exs") do
   import_config "test.secret.exs"
 else

lib/pleroma/plugs/rate_limiter/rate_limiter.ex

@@ -78,7 +78,7 @@ def init(plug_opts) do
   end
 
   def call(conn, plug_opts) do
-    if disabled?() do
+    if disabled?(conn) do
       handle_disabled(conn)
     else
       action_settings = action_settings(plug_opts)
@@ -87,9 +87,9 @@ def call(conn, plug_opts) do
   end
 
   defp handle_disabled(conn) do
-    if Config.get(:env) == :prod do
-      Logger.warn("Rate limiter is disabled for localhost/socket")
-    end
+    Logger.warn(
+      "Rate limiter disabled due to forwarded IP not being found. Please ensure your reverse proxy is providing the X-Forwarded-For header or disable the RemoteIP plug/rate limiter."
+    )
 
     conn
   end
@@ -109,16 +109,21 @@ defp handle(conn, action_settings) do
     end
   end
 
-  def disabled? do
+  def disabled?(conn) do
     localhost_or_socket =
-      Config.get([Pleroma.Web.Endpoint, :http, :ip])
-      |> Tuple.to_list()
-      |> Enum.join(".")
-      |> String.match?(~r/^local|^127.0.0.1/)
+      case Config.get([Pleroma.Web.Endpoint, :http, :ip]) do
+        {127, 0, 0, 1} -> true
+        {0, 0, 0, 0, 0, 0, 0, 1} -> true
+        {:local, _} -> true
+        _ -> false
+      end
 
-    remote_ip_disabled = not Config.get([Pleroma.Plugs.RemoteIp, :enabled])
+    remote_ip_not_found =
+      if Map.has_key?(conn.assigns, :remote_ip_found),
+        do: !conn.assigns.remote_ip_found,
+        else: false
 
-    localhost_or_socket and remote_ip_disabled
+    localhost_or_socket and remote_ip_not_found
   end
 
   @inspect_bucket_not_found {:error, :not_found}

lib/pleroma/plugs/remote_ip.ex

@@ -7,6 +7,8 @@ defmodule Pleroma.Plugs.RemoteIp do
   This is a shim to call [`RemoteIp`](https://git.pleroma.social/pleroma/remote_ip) but with runtime configuration.
   """
 
+  import Plug.Conn
+
   @behaviour Plug
 
   @headers ~w[
@@ -26,11 +28,12 @@ defmodule Pleroma.Plugs.RemoteIp do
 
   def init(_), do: nil
 
-  def call(conn, _) do
+  def call(%{remote_ip: original_remote_ip} = conn, _) do
     config = Pleroma.Config.get(__MODULE__, [])
 
     if Keyword.get(config, :enabled, false) do
-      RemoteIp.call(conn, remote_ip_opts(config))
+      %{remote_ip: new_remote_ip} = conn = RemoteIp.call(conn, remote_ip_opts(config))
+      assign(conn, :remote_ip_found, original_remote_ip != new_remote_ip)
     else
       conn
     end

test/plugs/rate_limiter_test.exs

@@ -3,8 +3,7 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.Plugs.RateLimiterTest do
-  use ExUnit.Case, async: true
-  use Plug.Test
+  use Pleroma.Web.ConnCase
 
   alias Pleroma.Config
   alias Pleroma.Plugs.RateLimiter
@@ -36,63 +35,44 @@ test "config is required for plug to work" do
                |> RateLimiter.init()
                |> RateLimiter.action_settings()
     end
+  end
 
-    test "it is disabled for localhost" do
-      Config.put([:rate_limit, @limiter_name], {1, 1})
-      Config.put([Pleroma.Web.Endpoint, :http, :ip], {127, 0, 0, 1})
-      Config.put([Pleroma.Plugs.RemoteIp, :enabled], false)
+  test "it is disabled if it remote ip plug is enabled but no remote ip is found" do
+    Config.put([Pleroma.Web.Endpoint, :http, :ip], {127, 0, 0, 1})
+    assert RateLimiter.disabled?(Plug.Conn.assign(build_conn(), :remote_ip_found, false))
+  end
 
-      assert RateLimiter.disabled?() == true
-    end
+  test "it restricts based on config values" do
+    limiter_name = :test_plug_opts
+    scale = 80
+    limit = 5
 
-    test "it is disabled for socket" do
-      Config.put([:rate_limit, @limiter_name], {1, 1})
-      Config.put([Pleroma.Web.Endpoint, :http, :ip], {:local, "/path/to/pleroma.sock"})
-      Config.put([Pleroma.Plugs.RemoteIp, :enabled], false)
+    Config.put([Pleroma.Web.Endpoint, :http, :ip], {8, 8, 8, 8})
+    Config.put([:rate_limit, limiter_name], {scale, limit})
 
-      assert RateLimiter.disabled?() == true
-    end
-
-    test "it is enabled for socket when remote ip is enabled" do
-      Config.put([:rate_limit, @limiter_name], {1, 1})
-      Config.put([Pleroma.Web.Endpoint, :http, :ip], {:local, "/path/to/pleroma.sock"})
-      Config.put([Pleroma.Plugs.RemoteIp, :enabled], true)
-
-      assert RateLimiter.disabled?() == false
-    end
-
-    test "it restricts based on config values" do
-      limiter_name = :test_plug_opts
-      scale = 80
-      limit = 5
-
-      Config.put([Pleroma.Web.Endpoint, :http, :ip], {8, 8, 8, 8})
-      Config.put([:rate_limit, limiter_name], {scale, limit})
-
-      plug_opts = RateLimiter.init(name: limiter_name)
-      conn = conn(:get, "/")
-
-      for i <- 1..5 do
-        conn = RateLimiter.call(conn, plug_opts)
-        assert {^i, _} = RateLimiter.inspect_bucket(conn, limiter_name, plug_opts)
-        Process.sleep(10)
-      end
+    plug_opts = RateLimiter.init(name: limiter_name)
+    conn = conn(:get, "/")
 
+    for i <- 1..5 do
       conn = RateLimiter.call(conn, plug_opts)
-      assert %{"error" => "Throttled"} = Phoenix.ConnTest.json_response(conn, :too_many_requests)
-      assert conn.halted
-
-      Process.sleep(50)
-
-      conn = conn(:get, "/")
-
-      conn = RateLimiter.call(conn, plug_opts)
-      assert {1, 4} = RateLimiter.inspect_bucket(conn, limiter_name, plug_opts)
-
-      refute conn.status == Plug.Conn.Status.code(:too_many_requests)
-      refute conn.resp_body
-      refute conn.halted
+      assert {^i, _} = RateLimiter.inspect_bucket(conn, limiter_name, plug_opts)
+      Process.sleep(10)
     end
+
+    conn = RateLimiter.call(conn, plug_opts)
+    assert %{"error" => "Throttled"} = Phoenix.ConnTest.json_response(conn, :too_many_requests)
+    assert conn.halted
+
+    Process.sleep(50)
+
+    conn = conn(:get, "/")
+
+    conn = RateLimiter.call(conn, plug_opts)
+    assert {1, 4} = RateLimiter.inspect_bucket(conn, limiter_name, plug_opts)
+
+    refute conn.status == Plug.Conn.Status.code(:too_many_requests)
+    refute conn.resp_body
+    refute conn.halted
   end
 
   describe "options" do

test/web/mastodon_api/controllers/account_controller_test.exs

@@ -756,10 +756,6 @@ test "returns forbidden if token is invalid", %{conn: conn, valid_params: valid_
   end
 
   describe "create account by app / rate limit" do
-    clear_config([Pleroma.Plugs.RemoteIp, :enabled]) do
-      Pleroma.Config.put([Pleroma.Plugs.RemoteIp, :enabled], true)
-    end
-
     clear_config([:rate_limit, :app_account_creation]) do
       Pleroma.Config.put([:rate_limit, :app_account_creation], {10_000, 2})
     end