From 0bba2fb986ff6a439d43a8b3f795a219800b2269 Mon Sep 17 00:00:00 2001
From: Carl Johnsen <carl-johannes@di.ku.dk>
Date: Fri, 6 Feb 2026 12:16:23 +0100
Subject: [PATCH] Mountpoint is not supported for disk image backup

---
 .../Library/Main/Operation/BackupHandler.cs    | 18 ++++++++++++------
 proprietary/DiskImage/SourceProvider.cs        |  8 ++++----
 2 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/Duplicati/Library/Main/Operation/BackupHandler.cs b/Duplicati/Library/Main/Operation/BackupHandler.cs
index 8d2806c50..fcdf22c6c 100644
--- a/Duplicati/Library/Main/Operation/BackupHandler.cs
+++ b/Duplicati/Library/Main/Operation/BackupHandler.cs
@@ -156,22 +156,27 @@ namespace Duplicati.Library.Main.Operation
                         foreach (var url in entry)
                         {
                             var sanitizedUrl = Library.Utility.Utility.GetUrlWithoutCredentials(url);
-                            var m = Regex.Match(url, @"^@(?<mountpoint>[^|]+)\|(?<url>.+)$", RegexOptions.IgnoreCase);
+                            var m = Regex.Match(url, @"^@(?<mountpoint>[^|]+\|)*(?<url>.+)$", RegexOptions.IgnoreCase);
                             if (m.Success)
                             {
                                 var mountpoint = m.Groups["mountpoint"].Value;
 
-                                if (mountpoint.Any(x => Path.GetInvalidPathChars().Contains(x)))
-                                    throw new UserInformationException(string.Format("The mountpoint \"{0}\" contains invalid characters", mountpoint), "InvalidMountpoint");
-                                if (!Path.IsPathRooted(mountpoint))
-                                    throw new UserInformationException(string.Format("The mountpoint \"{0}\" is not a valid rooted mountpoint", mountpoint), "InvalidMountpoint");
+                                if (!string.IsNullOrEmpty(mountpoint))
+                                {
+                                    if (mountpoint.Any(x => Path.GetInvalidPathChars().Contains(x)))
+                                        throw new UserInformationException(string.Format("The mountpoint \"{0}\" contains invalid characters", mountpoint), "InvalidMountpoint");
+                                    if (!Path.IsPathRooted(mountpoint))
+                                        throw new UserInformationException(string.Format("The mountpoint \"{0}\" is not a valid rooted mountpoint", mountpoint), "InvalidMountpoint");
+                                    mountpoint = Path.GetFullPath(mountpoint);
+                                }
 
                                 var backendurl = m.Groups["url"].Value;
 
                                 ISourceProvider provider;
                                 try
                                 {
-                                    provider = await SourceProviderLoader.GetSourceProvider(backendurl, Path.GetFullPath(mountpoint), options.RawOptions, cancellationToken).ConfigureAwait(false);
+                                    // TODO double check that all providers that require a mountpoint throws correctly when mountpoint is not set.
+                                    provider = await SourceProviderLoader.GetSourceProvider(backendurl, mountpoint, options.RawOptions, cancellationToken).ConfigureAwait(false);
                                 }
                                 catch (Exception ex)
                                 {
@@ -181,6 +186,7 @@ namespace Duplicati.Library.Main.Operation
                                         continue;
                                     }
 
+                                    Console.WriteLine(ex.StackTrace);
                                     throw new UserInformationException($"Failed to load source provider for \"{sanitizedUrl}\": {ex.Message}", "SourceProviderFailed", ex);
                                 }
 
diff --git a/proprietary/DiskImage/SourceProvider.cs b/proprietary/DiskImage/SourceProvider.cs
index 1b19a840c..1723b01be 100644
--- a/proprietary/DiskImage/SourceProvider.cs
+++ b/proprietary/DiskImage/SourceProvider.cs
@@ -16,7 +16,6 @@ namespace Duplicati.Proprietary.DiskImage;
 public sealed class SourceProvider : ISourceProviderModule, IDisposable
 {
     private readonly string _devicePath;
-    private readonly string _mountPoint;
     private IRawDisk? _disk;
     private bool _disposed;
 
@@ -25,17 +24,18 @@ public sealed class SourceProvider : ISourceProviderModule, IDisposable
     public SourceProvider()
     {
         _devicePath = null!;
-        _mountPoint = null!;
     }
 
     public SourceProvider(string url, string mountPoint, Dictionary<string, string?> options)
     {
-        _mountPoint = mountPoint;
+        if (!string.IsNullOrEmpty(mountPoint))
+            throw new UserInformationException("Mount point option is not supported for DiskImage provider. The entire disk will be mounted/treated as root.", "MountPointNotSupported");
+
         var uri = new Library.Utility.Uri(url);
         _devicePath = uri.HostAndPath;
     }
 
-    public string MountedPath => _mountPoint;
+    public string MountedPath => $"root{System.IO.Path.DirectorySeparatorChar}";
 
     public string DisplayName => Strings.ProviderDisplayName;