Enforce poll limits and add error handling for MastodonAPI's post endpoint

lib/pleroma/web/common_api/utils.ex

@@ -104,8 +104,23 @@ def to_for_user_and_mentions(_user, mentions, inReplyTo, "direct") do
 
   def make_poll_data(%{"poll" => %{"options" => options, "expires_in" => expires_in}} = data)
       when is_list(options) and is_integer(expires_in) do
+    %{max_expiration: max_expiration, min_expiration: min_expiration} =
+      limits = Pleroma.Config.get([:instance, :poll_limits])
+
+    # XXX: There is probably a cleaner way of doing this
+    try do
+      if Enum.count(options) > limits.max_options do
+        raise ArgumentError, message: "Poll can't contain more than #{limits.max_options} options"
+      end
+
       {poll, emoji} =
         Enum.map_reduce(options, %{}, fn option, emoji ->
+          if String.length(option) > limits.max_option_chars do
+            raise ArgumentError,
+              message:
+                "Poll options cannot be longer than #{limits.max_option_chars} characters each"
+          end
+
           {%{
              "name" => option,
              "type" => "Note",
@@ -113,6 +128,17 @@ def make_poll_data(%{"poll" => %{"options" => options, "expires_in" => expires_i
            }, Map.merge(emoji, Formatter.get_emoji_map(option))}
         end)
 
+      case expires_in do
+        expires_in when expires_in > max_expiration ->
+          raise ArgumentError, message: "Expiration date is too far in the future"
+
+        expires_in when expires_in < min_expiration ->
+          raise ArgumentError, message: "Expiration date is too soon"
+
+        _ ->
+          :noop
+      end
+
       end_time =
         NaiveDateTime.utc_now()
         |> NaiveDateTime.add(expires_in)
@@ -126,6 +152,13 @@ def make_poll_data(%{"poll" => %{"options" => options, "expires_in" => expires_i
         end
 
       {poll, emoji}
+    rescue
+      e in ArgumentError -> e.message
+    end
+  end
+
+  def make_poll_data(%{"poll" => _}) do
+    "Invalid poll"
   end
 
   def make_poll_data(_data) do

lib/pleroma/web/mastodon_api/mastodon_api_controller.ex

@@ -473,12 +473,6 @@ def post_status(%{assigns: %{user: user}} = conn, %{"status" => _} = params) do
       params
       |> Map.put("in_reply_to_status_id", params["in_reply_to_id"])
 
-    idempotency_key =
-      case get_req_header(conn, "idempotency-key") do
-        [key] -> key
-        _ -> Ecto.UUID.generate()
-      end
-
     scheduled_at = params["scheduled_at"]
 
     if scheduled_at && ScheduledActivity.far_enough?(scheduled_at) do
@@ -491,16 +485,39 @@ def post_status(%{assigns: %{user: user}} = conn, %{"status" => _} = params) do
     else
       params = Map.drop(params, ["scheduled_at"])
 
-      {:ok, activity} =
-        Cachex.fetch!(:idempotency_cache, idempotency_key, fn _ ->
-          CommonAPI.post(user, params)
-        end)
+      case get_cached_status_or_post(conn, params) do
+        {:ignore, message} ->
+          conn
+          |> put_status(401)
+          |> json(%{error: message})
 
+        {:error, message} ->
+          conn
+          |> put_status(401)
+          |> json(%{error: message})
+
+        {_, activity} ->
           conn
           |> put_view(StatusView)
           |> try_render("status.json", %{activity: activity, for: user, as: :activity})
       end
     end
+  end
+
+  defp get_cached_status_or_post(%{assigns: %{user: user}} = conn, params) do
+    idempotency_key =
+      case get_req_header(conn, "idempotency-key") do
+        [key] -> key
+        _ -> Ecto.UUID.generate()
+      end
+
+    Cachex.fetch(:idempotency_cache, idempotency_key, fn _ ->
+      case CommonAPI.post(user, params) do
+        {:ok, activity} -> activity
+        {:error, message} -> {:ignore, message}
+      end
+    end)
+  end
 
   def delete_status(%{assigns: %{user: user}} = conn, %{"id" => id}) do
     with {:ok, %Activity{}} <- CommonAPI.delete(id, user) do

test/web/mastodon_api/mastodon_api_controller_test.exs

@@ -146,6 +146,7 @@ test "posting a status", %{conn: conn} do
     refute id == third_id
   end
 
+  describe "posting polls" do
     test "posting a poll", %{conn: conn} do
       user = insert(:user)
       time = NaiveDateTime.utc_now()
@@ -154,7 +155,7 @@ test "posting a poll", %{conn: conn} do
         conn
         |> assign(:user, user)
         |> post("/api/v1/statuses", %{
-        "status" => "Who is the best girl?",
+          "status" => "Who is the #bestgrill?",
           "poll" => %{"options" => ["Rei", "Asuka", "Misato"], "expires_in" => 420}
         })
 
@@ -168,6 +169,80 @@ test "posting a poll", %{conn: conn} do
       refute response["poll"]["expred"]
     end
 
+    test "option limit is enforced", %{conn: conn} do
+      user = insert(:user)
+      limit = Pleroma.Config.get([:instance, :poll_limits, :max_options])
+
+      conn =
+        conn
+        |> assign(:user, user)
+        |> post("/api/v1/statuses", %{
+          "status" => "desu~",
+          "poll" => %{"options" => Enum.map(0..limit, fn _ -> "desu" end), "expires_in" => 1}
+        })
+
+      %{"error" => error} = json_response(conn, 401)
+      assert error == "Poll can't contain more than #{limit} options"
+    end
+
+    test "option character limit is enforced", %{conn: conn} do
+      user = insert(:user)
+      limit = Pleroma.Config.get([:instance, :poll_limits, :max_option_chars])
+
+      conn =
+        conn
+        |> assign(:user, user)
+        |> post("/api/v1/statuses", %{
+          "status" => "...",
+          "poll" => %{
+            "options" => [Enum.reduce(0..limit, "", fn _, acc -> acc <> "." end)],
+            "expires_in" => 1
+          }
+        })
+
+      %{"error" => error} = json_response(conn, 401)
+      assert error == "Poll options cannot be longer than #{limit} characters each"
+    end
+
+    test "minimal date limit is enforced", %{conn: conn} do
+      user = insert(:user)
+      limit = Pleroma.Config.get([:instance, :poll_limits, :min_expiration])
+
+      conn =
+        conn
+        |> assign(:user, user)
+        |> post("/api/v1/statuses", %{
+          "status" => "imagine arbitrary limits",
+          "poll" => %{
+            "options" => ["this post was made by pleroma gang"],
+            "expires_in" => limit - 1
+          }
+        })
+
+      %{"error" => error} = json_response(conn, 401)
+      assert error == "Expiration date is too soon"
+    end
+
+    test "maximum date limit is enforced", %{conn: conn} do
+      user = insert(:user)
+      limit = Pleroma.Config.get([:instance, :poll_limits, :max_expiration])
+
+      conn =
+        conn
+        |> assign(:user, user)
+        |> post("/api/v1/statuses", %{
+          "status" => "imagine arbitrary limits",
+          "poll" => %{
+            "options" => ["this post was made by pleroma gang"],
+            "expires_in" => limit + 1
+          }
+        })
+
+      %{"error" => error} = json_response(conn, 401)
+      assert error == "Expiration date is too far in the future"
+    end
+  end
+
   test "posting a sensitive status", %{conn: conn} do
     user = insert(:user)