Ignore ACCESS_DENIED on volume scanning

To avoid need to escalate privilege when a machine has container volumes.
microsoft · Sep 11, 2023 · b2b9ebd · b2b9ebd
1 parent 9e96689
commit b2b9ebd
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Showing 3 changed files with 10 additions and 4 deletions.
diff --git a/Directory.Build.props b/Directory.Build.props
@@ -24,7 +24,7 @@
  <PropertyGroup>
 
  <!-- DOCSYNC: When changing version number update README.md -->
- <Version>0.3.6.0</Version>
+ <Version>0.3.7.0</Version>
  <AssemblyVersion>0.9.9999.0</AssemblyVersion>
 
  <Company>Microsoft</Company>

diff --git a/README.md b/README.md
@@ -43,6 +43,7 @@ File clones on Windows do not actually allocate space on-drive for the clone. Th
 
 [![NuGet version (CopyOnWrite)](https://img.shields.io/nuget/v/CopyOnWrite?style=plastic)](https://www.nuget.org/packages/CopyOnWrite)
 
+* 0.3.7 September 2023: Fix #30 - ignore ACCESS_DENIED on volume enumeration to avoid need to escalate privilege on Windows.
 * 0.3.6 July 2023: Set AssemblyVersion to 0.9.9999.0 to allow mixing different minor-version binaries from different packages in the same appdomain/process.
 * 0.3.5 July 2023: Set AssemblyVersion to 0.0.0.1 to allow mixing different minor-version binaries from different packages in the same appdomain/process.
 * 0.3.4 July 2023: Handle locked BitLocker volume during volume scan.

diff --git a/lib/Windows/VolumeInfoCache.cs b/lib/Windows/VolumeInfoCache.cs
@@ -103,6 +103,7 @@ public VolumeInfo GetVolumeForPath(string path)
  "If the drive was added recently you may need to recreate the filesystem cache.");
  }
 
+ private const int ERROR_ACCESS_DENIED = 5;
  private const int ERROR_NOT_READY = 21;
  private const int ERROR_INVALID_PARAMETER = 87;
  private const int ERROR_UNRECOGNIZED_VOLUME = 1005;
@@ -123,12 +124,16 @@ public VolumeInfo GetVolumeForPath(string path)
  {
  int lastErr = Marshal.GetLastWin32Error();
 
- // Some SD Card readers show a drive letter even when empty, and BitLocker can have a volume locked.
- // Instead of erroring out, let's just ignore those.
+ // Ignore:
+ // - Some SD Card readers show a drive letter even when empty.
+ // - BitLocker can have a volume locked.
+ // - Access denied can imply a volume needing escalated privilege to get its metadata,
+ // sometimes indicating a Windows container volume.
  if (lastErr == ERROR_UNRECOGNIZED_VOLUME ||
  lastErr == ERROR_NOT_READY ||
  lastErr == ERROR_INVALID_PARAMETER ||
- lastErr == FVE_E_LOCKED_VOLUME)
+ lastErr == FVE_E_LOCKED_VOLUME ||
+ lastErr == ERROR_ACCESS_DENIED)
  {
  return null;
  }