From d0a4e1e3c2ff107327091d7ece191742f45e1429 Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Fri, 20 Sep 2019 15:00:27 +0900
Subject: [PATCH] Force a checksum check before skipping FileStore copy op

---
 osu.Game/IO/FileStore.cs | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/osu.Game/IO/FileStore.cs b/osu.Game/IO/FileStore.cs
index 370d6786f5..bf4e881ed0 100644
--- a/osu.Game/IO/FileStore.cs
+++ b/osu.Game/IO/FileStore.cs
@@ -50,7 +50,16 @@ namespace osu.Game.IO
                 string path = info.StoragePath;
 
                 // we may be re-adding a file to fix missing store entries.
-                if (!Storage.Exists(path))
+                bool requiresCopy = !Storage.Exists(path);
+
+                if (!requiresCopy)
+                {
+                    // even if the file already exists, check the existing checksum for safety.
+                    using (var stream = Storage.GetStream(path))
+                        requiresCopy |= stream.ComputeSHA2Hash() != hash;
+                }
+
+                if (requiresCopy)
                 {
                     data.Seek(0, SeekOrigin.Begin);