✨ Sanitize text to remove hidden unicode and control characters

DysonNetwork.Sphere/Chat/ChatController.cs

@@ -1,4 +1,6 @@
 using System.ComponentModel.DataAnnotations;
+using System.Globalization;
+using System.Text;
 using System.Text.RegularExpressions;
 using DysonNetwork.Sphere.Permission;
 using DysonNetwork.Sphere.Storage;
@@ -142,6 +144,8 @@ public partial class ChatController(AppDatabase db, ChatService cs, ChatRoomServ
     public async Task<ActionResult> SendMessage([FromBody] SendMessageRequest request, Guid roomId)
     {
         if (HttpContext.Items["CurrentUser"] is not Account.Account currentUser) return Unauthorized();
+
+        request.Content = TextSanitizer.Sanitize(request.Content);
         if (string.IsNullOrWhiteSpace(request.Content) &&
             (request.AttachmentsId == null || request.AttachmentsId.Count == 0))
             return BadRequest("You cannot send an empty message.");
@@ -218,6 +222,8 @@ public partial class ChatController(AppDatabase db, ChatService cs, ChatRoomServ
     {
         if (HttpContext.Items["CurrentUser"] is not Account.Account currentUser) return Unauthorized();
 
+        request.Content = TextSanitizer.Sanitize(request.Content);
+
         var message = await db.ChatMessages
             .Include(m => m.Sender)
             .Include(m => m.Sender.Account)
@@ -230,6 +236,10 @@ public partial class ChatController(AppDatabase db, ChatService cs, ChatRoomServ
         if (message.Sender.AccountId != currentUser.Id)
             return StatusCode(403, "You can only edit your own messages.");
 
+        if (string.IsNullOrWhiteSpace(request.Content) &&
+            (request.AttachmentsId == null || request.AttachmentsId.Count == 0))
+            return BadRequest("You cannot send an empty message.");
+
         if (request.RepliedMessageId.HasValue)
         {
             var repliedMessage = await db.ChatMessages

DysonNetwork.Sphere/Post/PostController.cs

@@ -3,6 +3,7 @@ using System.Text.Json;
 using DysonNetwork.Sphere.Account;
 using DysonNetwork.Sphere.Permission;
 using DysonNetwork.Sphere.Publisher;
+using DysonNetwork.Sphere.Storage;
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.EntityFrameworkCore;
@@ -149,6 +150,7 @@ public class PostController(
         [FromHeader(Name = "X-Pub")] string? publisherName
     )
     {
+        request.Content = TextSanitizer.Sanitize(request.Content);
         if (string.IsNullOrWhiteSpace(request.Content) && request.Attachments is { Count: 0 })
             return BadRequest("Content is required.");
         if (HttpContext.Items["CurrentUser"] is not Account.Account currentUser) return Unauthorized();
@@ -290,6 +292,7 @@ public class PostController(
     [HttpPatch("{id:guid}")]
     public async Task<ActionResult<Post>> UpdatePost(Guid id, [FromBody] PostRequest request)
     {
+        request.Content = TextSanitizer.Sanitize(request.Content);
         if (string.IsNullOrWhiteSpace(request.Content) && request.Attachments is { Count: 0 })
             return BadRequest("Content is required.");
         if (HttpContext.Items["CurrentUser"] is not Account.Account currentUser) return Unauthorized();

DysonNetwork.Sphere/Storage/TextSanitizer.cs

@@ -0,0 +1,24 @@
+using System.Globalization;
+using System.Text;
+
+namespace DysonNetwork.Sphere.Storage;
+
+public abstract class TextSanitizer
+{
+    public static string? Sanitize(string? text)
+    {
+        if (string.IsNullOrEmpty(text)) return text;
+
+        var filtered = new StringBuilder();
+        foreach (var ch in from ch in text
+                 let category = CharUnicodeInfo.GetUnicodeCategory(ch)
+                 where category is not (UnicodeCategory.Control or UnicodeCategory.Format
+                     or UnicodeCategory.NonSpacingMark)
+                 select ch)
+        {
+            filtered.Append(ch);
+        }
+        
+        return filtered.ToString(); 
+    }
+}