Tar entries should be able to handle paths that begin with "./", including the root path itself

[carlossanlop]

Description

Bug found while investigating this issue: #70509

TarReader.GetNextEntry is unable to retrieve entries that have the path set to ./.

Reproduction Steps

Download https://dotnetcli.azureedge.net/dotnet/Runtime/6.0.5-servicing.22213.9/dotnet-runtime-6.0.5-osx-x64.tar.gz

string targetPath = "D:/some/destination";
using FileStream compressedStream = File.OpenRead(@"D:/path/to/dotnet-runtime-6.0.5-osx-x64.tar.gz");
using GZipStream decompressor = new(compressedStream, CompressionMode.Decompress);
TarFile.ExtractToDirectory(source: decompressor, destinationDirectoryName: targetPath, overwriteFiles: true);

Expected behavior

The archive is extracted.

Actual behavior

    System.IO.IOException : Extracting the Tar entry './' would have resulted in a file outside the specified destination directory: 'C:\Users\carlos\AppData\Local\Temp\zm5gtquh.qu5\'

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

[ghost]

Tagging subscribers to this area: @dotnet/area-system-io
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

Bug found while investigating this issue: #70509

TarReader.GetNextEntry is unable to retrieve entries that have the path set to .\.

Reproduction Steps

Download https://dotnetcli.azureedge.net/dotnet/Runtime/6.0.5-servicing.22213.9/dotnet-runtime-6.0.5-osx-x64.tar.gz

string targetPath = "D:/some/destination";
using FileStream compressedStream = File.OpenRead(@"D:/path/to/dotnet-runtime-6.0.5-osx-x64.tar.gz");
using GZipStream decompressor = new(compressedStream, CompressionMode.Decompress);
TarFile.ExtractToDirectory(source: decompressor, destinationDirectoryName: targetPath, overwriteFiles: true);

Expected behavior

The archive is extracted.

Actual behavior

    System.IO.IOException : Extracting the Tar entry './' would have resulted in a file outside the specified destination directory: 'C:\Users\carlos\AppData\Local\Temp\zm5gtquh.qu5\'

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

Author:	carlossanlop
Assignees:	carlossanlop
Labels:	area-System.IO
Milestone:	7.0.0

[carlossanlop]

The prefix ./ gets added to files when the tar command is executed with explicit addition of the ./ prefix on the individual entries to be archived:

tar -cvf target.tar ./file.txt ./directory/

This usually happens when the file is added by tabbing for autocomplete.

The prefix is not added if you use * to include all files in a location:

tar -cvf target.tar *

So to add the ./ entry to the archive (the cause of this bug), you'd have to execute the command using:

tar -cvf target.tar ./

Which would add all the files in the current directory (excluding the tar archive you're creating), will prepend the ./ prefix to all the entries, and will also include the single entry ./ at the beginning of the archive.

When you open such archive with 7-zip, it shows at the root a single directory entry named . and all the rest of the entries are under that directory.