Add detection of Windows reserved filenames #891
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Add `IsReservedName` method to detect Windows reserved filenames by checking if Path.GetFullPath returns a path that starts with "\\.\\" or "\\?\\".
This handles the differences between older and newer Windows versions where:
- Older Windows: Path.GetFullPath("COM3.txt") gives "\\.\COM3.txt"
- Newer Windows: Path.GetFullPath("COM3.txt") gives "COM3.txt"
pviano-ria
approved these changes
Apr 2, 2025
airceluearth
approved these changes
Apr 2, 2025
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Description
This PR adds functionality to detect Windows reserved filenames (like COM1, LPT1, etc.) in the WindowsNameTransform class. The implementation adds a new
IsReservedNamemethod that detects reserved names despite differences between different Windows versions.Background
I encountered an issue on a Windows 10 based system today where an InvalidNameException was thrown:
The only problem was that this was completely unrelated to parent traversal but was actually because the filename was
C:\example\folder\con.xhtml, which in Windows 10 is considered a reserved word. The incorrect exception message about the parent directory traversal led us down the wrong path when diagnosing the file's issue, so I wanted to update SharpZipLib to handle this scenario better.Additional Information
To make this slightly more complicated, Windows has changed how it handles reserved names across different OS versions:
More information on this can be found on the dotnet/runtime issue and Microsoft's own Naming Conventions Guide.
Solution
The new
IsReservedNamemethod usesPath.GetFullPath()and checks if the result starts with\\.\or\\?\, which identifies Windows reserved names. When detected, the code throws anInvalidNameExceptionwith an appropriate message pointing to Microsoft's documentation.Changes
IsReservedNamemethod with detailed documentationMakeValidNameto check for reserved namesWindowsNameTransformHandling.csto check theInvalidNameExceptionis being thrown as expectedI certify that I own, and have sufficient rights to contribute, all source code and related material intended to be compiled or integrated with the source code for the SharpZipLib open source product (the "Contribution"). My Contribution is licensed under the MIT License.