From df3e56f4223262aa9ca2a20607a973aa0013227a Mon Sep 17 00:00:00 2001
From: Laura Hausmann <laura@hausmann.dev>
Date: Wed, 19 Feb 2025 16:37:11 +0100
Subject: [PATCH] [backend/core] Prevent creation of pure renote replies

---
 .../Controllers/Mastodon/StatusController.cs     | 11 +++++++++++
 Iceshrimp.Backend/Core/Services/NoteService.cs   | 16 ++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/Iceshrimp.Backend/Controllers/Mastodon/StatusController.cs b/Iceshrimp.Backend/Controllers/Mastodon/StatusController.cs
index b00373e3..5411fb86 100644
--- a/Iceshrimp.Backend/Controllers/Mastodon/StatusController.cs
+++ b/Iceshrimp.Backend/Controllers/Mastodon/StatusController.cs
@@ -437,6 +437,17 @@ public class StatusController(
 			};
 
 			newText = quoteUri != null ? parsed.SkipLast(1).Serialize() : parsed.Serialize();
+
+			if (
+				newText.AsSpan().Trim().Length == 0
+				&& request.Cw?.AsSpan().Trim().Length is null or 0
+				&& request.Poll is null or { Options.Count: 0 }
+				&& attachments?.Count is null or 0
+			)
+			{
+				quoteUri = null;
+				newText  = null;
+			}
 		}
 
 		if (request is { Sensitive: true, MediaIds.Count: > 0 })
diff --git a/Iceshrimp.Backend/Core/Services/NoteService.cs b/Iceshrimp.Backend/Core/Services/NoteService.cs
index 6f4f63fa..842d0df6 100644
--- a/Iceshrimp.Backend/Core/Services/NoteService.cs
+++ b/Iceshrimp.Backend/Core/Services/NoteService.cs
@@ -241,6 +241,18 @@ public class NoteService(
 		var combinedAltText = data.Attachments?.Select(p => p.Comment).Where(c => c != null);
 		policySvc.CallRewriteHooks(data, IRewritePolicy.HookLocationEnum.PostLogic);
 
+		if (
+			(data.Renote != null || data.RenoteUri != null)
+			&& (data.Reply != null || data.ReplyUri != null)
+			&& data.ParsedText is not { Length: > 0 }
+			&& data.Cw == null
+			&& data.Poll == null
+			&& data.Attachments is not { Count: > 0 }
+		)
+		{
+			throw GracefulException.UnprocessableEntity("Refusing to create a pure renote reply");
+		}
+
 		var noteId   = IdHelpers.GenerateSnowflakeId(data.CreatedAt);
 		var threadId = data.Reply?.ThreadId ?? noteId;
 
@@ -754,6 +766,10 @@ public class NoteService(
 			note.RepliesCollection = data.ASNote.Replies?.Id;
 
 		policySvc.CallRewriteHooks(data, IRewritePolicy.HookLocationEnum.PostLogic);
+
+		if (note.IsPureRenote && (note.ReplyId != null || note.ReplyUri != null))
+			throw GracefulException.UnprocessableEntity("Refusing to update note to a pure renote reply");
+
 		await db.SaveChangesAsync();
 		eventSvc.RaiseNoteUpdated(this, note);