Creating tar file from a directory owned by an unknown group throws an exception on Linux

[chylex]

Description

Calling TarFile.CreateFromDirectory on a directory that is owned by a group that does not exist in /etc/group, and is only identified by its GID, fails with an exception.

Creating an archive using the tar executable itself works as expected.

Reproduction Steps

I made an example Dockerfile, so that everything is isolated from the actual system, and it's similar to the scenario in which I found the issue (archiving a mounted folder owned by a group and user that exists on the host, but not in the container itself).

It creates a folder /app/example with a file, both of which are owned by a user and group that don't exist in the container. Then installs dotnet-script, and creates and runs a C# script file with the following line:

System.Formats.Tar.TarFile.CreateFromDirectory(Args[0], "out/test.tar", false);

FROM mcr.microsoft.com/dotnet/sdk:7.0

RUN mkdir -p /app/example          && \
    touch /app/example/example.txt && \
    chown -R 1234:1234 /app/example

RUN dotnet tool install --tool-path /app dotnet-script
RUN echo 'System.Formats.Tar.TarFile.CreateFromDirectory(Args[0], "out/test.tar", false);' > /app/Test.csx

# Uncomment to work around the issue:
# RUN groupadd test --gid 1234

WORKDIR /app

ENTRYPOINT ["/app/dotnet-script", "Test.csx", "--", "/app/example/"]

Put the Dockerfile in a directory, then create a directory named out, and run:

docker run --rm --mount type=bind,source="$(pwd)/out",target=/app/out -it "$(docker build -q .)"

This will build and launch the image. The out folder will contain the tar archive.

Expected behavior

Create a tar archive from the folder.

Actual behavior

The application crashes and leaves you with an empty tar archive.

System.IO.IOException: No such file or directory
   at Interop.Sys.GetGroupName(UInt32 gid)
   at System.Formats.Tar.TarWriter.ConstructEntryForWriting(String fullPath, String entryName, FileOptions fileOptions)
   at System.Formats.Tar.TarFile.CreateFromDirectoryInternal(String sourceDirectoryName, Stream destination, Boolean includeBaseDirectory, Boolean leaveOpen)
   at System.Formats.Tar.TarFile.CreateFromDirectory(String sourceDirectoryName, String destinationFileName, Boolean includeBaseDirectory)
   at Submission#0.<<Initialize>>d__0.MoveNext() in /app/Test.csx:line 1

Regression?

No response

Known Workarounds

• Create the missing groups. It seems that there is no need to create the missing users, only the groups.
• Use Process to call the tar program manually, since tar does not have the same issue.

Configuration

Same environment as the mcr.microsoft.com/dotnet/sdk:7.0 Docker image. The issue is specific to Linux (or perhaps more broadly Unix, but I have not verified that).

Other information

No response

[am11]

This was fixed in #81070 for .NET 8 and backport is in progress: #81139. You can test it with the preview build of .NET 8 (which dotnet-script doesn't support unfortunately):

FROM mcr.microsoft.com/dotnet/nightly/sdk:8.0-preview

RUN mkdir -p /app/example          && \
    touch /app/example/example.txt && \
    chown -R 1234:1234 /app/example

RUN dotnet new console -o /app
RUN echo 'System.Formats.Tar.TarFile.CreateFromDirectory(args[0], "out/test.tar", false);' > /app/Program.cs
RUN dotnet build /app

# Uncomment to work around the issue:
# RUN groupadd test --gid 1234

WORKDIR /app

RUN mkdir out

ENTRYPOINT ["dotnet", "run", "--", "/app/example/"]

$ docker build . -t gh-81658
$ docker run gh-81658
$ echo $?
0 # no error

Change the first line to FROM mcr.microsoft.com/dotnet/sdk:7.0 and it will currently throw the same exception (exit code 134), until the backport is completed and new release is out.

[smasher164]

Duplicate of #81047.