added code of mr#2067

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

@@ -16,7 +16,12 @@ defmodule Pleroma.Web.TwitterAPI.RemoteFollowController do
 
   @status_types ["Article", "Event", "Note", "Video", "Page", "Question"]
 
-  plug(OAuthScopesPlug, %{scopes: ["follow", "write:follows"]} when action in [:do_follow])
+  # Note: follower can submit the form (with password auth) not being signed in (having no token)
+  plug(
+    OAuthScopesPlug,
+    %{fallback: :proceed_unauthenticated, scopes: ["follow", "write:follows"]}
+    when action in [:do_follow]
+  )
 
   # GET /ostatus_subscribe
   #
@@ -61,6 +66,16 @@ defp is_status?(acct) do
 
   # POST  /ostatus_subscribe
   #
+  def do_follow(%{assigns: %{user: %User{} = user}} = conn, %{"user" => %{"id" => id}}) do
+    with {:fetch_user, %User{} = followee} <- {:fetch_user, User.get_cached_by_id(id)},
+         {:ok, _, _, _} <- CommonAPI.follow(user, followee) do
+      render(conn, "followed.html", %{error: false})
+    else
+      error ->
+        handle_follow_error(conn, error)
+    end
+  end
+
   def do_follow(conn, %{"authorization" => %{"name" => _, "password" => _, "id" => id}}) do
     with {:fetch_user, %User{} = followee} <- {:fetch_user, User.get_cached_by_id(id)},
          {_, {:ok, user}, _} <- {:auth, Authenticator.get_user(conn), followee},
@@ -72,14 +87,9 @@ def do_follow(conn, %{"authorization" => %{"name" => _, "password" => _, "id" =>
     end
   end
 
-  def do_follow(%{assigns: %{user: user}} = conn, %{"user" => %{"id" => id}}) do
-    with {:fetch_user, %User{} = followee} <- {:fetch_user, User.get_cached_by_id(id)},
-         {:ok, _, _, _} <- CommonAPI.follow(user, followee) do
-      render(conn, "followed.html", %{error: false})
-    else
-      error ->
-        handle_follow_error(conn, error)
-    end
+  def do_follow(%{assigns: %{user: nil}} = conn, _) do
+    Logger.debug("Insufficient permissions: follow | write:follows.")
+    render(conn, "followed.html", %{error: "Insufficient permissions: follow | write:follows."})
   end
 
   defp handle_follow_error(conn, {:auth, _, followee} = _) do

test/web/twitter_api/remote_follow_controller_test.exs

@@ -70,7 +70,24 @@ test "show follow page with error when user cannot fecth by `acct` link", %{conn
     end
   end
 
-  describe "POST /ostatus_subscribe - do_remote_follow/2 with assigned user " do
+  describe "POST /ostatus_subscribe - do_follow/2 with assigned user " do
+    test "required `follow | write:follows` scope", %{conn: conn} do
+      user = insert(:user)
+      user2 = insert(:user)
+      read_token = insert(:oauth_token, user: user, scopes: ["read"])
+
+      assert capture_log(fn ->
+               response =
+                 conn
+                 |> assign(:user, user)
+                 |> assign(:token, read_token)
+                 |> post(remote_follow_path(conn, :do_follow), %{"user" => %{"id" => user2.id}})
+                 |> response(200)
+
+               assert response =~ "Error following account"
+             end) =~ "Insufficient permissions: follow | write:follows."
+    end
+
     test "follows user", %{conn: conn} do
       user = insert(:user)
       user2 = insert(:user)
@@ -141,7 +158,7 @@ test "returns success result when user already in followers", %{conn: conn} do
     end
   end
 
-  describe "POST /ostatus_subscribe - do_remote_follow/2 without assigned user " do
+  describe "POST /ostatus_subscribe - follow/2 without assigned user " do
     test "follows", %{conn: conn} do
       user = insert(:user)
       user2 = insert(:user)