Exception thrown (rarely) in TarHeader with empty array

I have a unit test that goes though some SharpZipLib methods. Every once in a while it fails in a VM which the following error:

ModTime cannot be before Jan 1st 1970 (Parameter 'value')
at ICSharpCode.SharpZipLib.Tar.TarHeader.set_ModTime(DateTime value)
at ICSharpCode.SharpZipLib.Tar.TarHeader.ParseBuffer(Byte[] header, Encoding nameEncoding)
at ICSharpCode.SharpZipLib.Tar.TarInputStream.GetNextEntryAsync(CancellationToken ct, Boolean isAsync)
at ICSharpCode.SharpZipLib.Tar.TarInputStream.GetNextEntry()

The code that is throwing that exception is the below one and is ALWAYS called with input Array.Empty<byte>():

public static byte[] Dummy(this byte[] data) {
    using var inStream = new MemoryStream(data);
    using var outStream = new MemoryStream();
    using var gzipStream = new GZipInputStream(inStream);
    using var tarInputStream = new TarInputStream(gzipStream, Encoding.UTF8);
    while (tarInputStream.GetNextEntry() is { } tarEntry) {
    }

    return outStream.ToArray();
}

The “fun” part is that this NEVER happens in my local machine. Only in the CICD pipeline, once in a while. The CICD pipeline is a newly booted ubuntu-20.04 container on Azure Devops.

Steps to reproduce

1. Boot a ubuntu-20.04 container (freshly booted?)
2. Run the function
3. Repeat until it happens

Expected behavior

A dummy empty tar.gz archive should be enumerated

Actual behavior

An exception is (rarely) thrown.

Version of SharpZipLib

1.4.0

Obtained from (only keep the relevant lines)

• Package installed using NuGet

[piksel]

It’s definitively caused by the re-use of a shared array pool array. The array is not zeroed, so when reading from an empty source it will treat the “garbage” data in the array as input.

[DiogoRoloOS]

That makes sense. Thank you for the explanation.