Fix TarWriter.TarEntry exception when adding file whose Unix group owner does not exist in the system

src/libraries/Common/src/Interop/Unix/System.Native/Interop.GetGroupName.cs

@@ -7,19 +7,26 @@
 using System;
 using System.Collections.Generic;
 using System.Reflection;
+using System.IO;
+using System.Diagnostics.CodeAnalysis;
 
 internal static partial class Interop
 {
  internal static partial class Sys
  {
  /// <summary>
- /// Gets the group name associated to the specified group ID.
+ /// Tries to get the group name associated to the specified group ID.
  /// </summary>
  /// <param name="gid">The group ID.</param>
- /// <returns>On success, return a string with the group name. On failure, throws an IOException.</returns>
- internal static string GetGroupName(uint gid) => GetGroupNameInternal(gid) ?? throw GetIOException(GetLastErrorInfo());
+ /// <param name="groupName">When this method returns true, gets the value of the group name associated with the specified id. On failure, it is null.</param>
+ /// <returns>On success, returns true. On failure, returns false.</returns>
+ internal static bool TryGetGroupName(uint gid, [NotNullWhen(returnValue: true)] out string? groupName)
+ {
+ groupName = GetGroupName(gid);
+ return groupName != null;
+ }
 
  [LibraryImport(Libraries.SystemNative, EntryPoint = "SystemNative_GetGroupName", StringMarshalling = StringMarshalling.Utf8, SetLastError = true)]
- private static unsafe partial string? GetGroupNameInternal(uint uid);
+ private static unsafe partial string? GetGroupName(uint uid);
  }
 }

src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarWriter.Unix.cs

@@ -82,8 +82,10 @@ private TarEntry ConstructEntryForWriting(string fullPath, string entryName, Fil
  entry._header._gid = (int)status.Gid;
  if (!_groupIdentifiers.TryGetValue(status.Gid, out string? gName))
  {
- gName = Interop.Sys.GetGroupName(status.Gid);
- _groupIdentifiers.Add(status.Gid, gName);
+ if (Interop.Sys.TryGetGroupName(status.Gid, out gName))
+ {
+ _groupIdentifiers.Add(status.Gid, gName);
+ }
  }
  entry._header._gName = gName;
 

src/libraries/System.Formats.Tar/tests/TarWriter/TarWriter.File.Base.Unix.cs

@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Diagnostics;
 using System.IO;
 using Xunit;
 
@@ -20,7 +21,7 @@ protected void VerifyPlatformSpecificMetadata(string filePath, TarEntry entry)
 
  if (entry is PosixTarEntry posix)
  {
-string gname = Interop.Sys.GetGroupName(status.Gid);
+Assert.True(Interop.Sys.TryGetGroupName(status.Gid, out string gname));
  string uname = Interop.Sys.GetUserNameFromPasswd(status.Uid);
 
  Assert.Equal(gname, posix.GroupName);
@@ -51,5 +52,49 @@ protected void VerifyPlatformSpecificMetadata(string filePath, TarEntry entry)
  }
  }
  }
+
+ protected int CreateGroup(string groupName)
+ {
+ Execute("groupadd", groupName);
+ return GetGroupId(groupName);
+ }
+
+ protected int GetGroupId(string groupName)
+ {
+ string standardOutput = Execute("getent", $"group {groupName}");
+ string[] values = standardOutput.Split(':', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
+ return int.Parse(values[^1]);
+ }
+
+ protected void SetGroupAsOwnerOfFile(string groupName, string filePath) =>
+ Execute("chgrp", $"{groupName} {filePath}");
+
+
+ protected void DeleteGroup(string groupName) =>
+ Execute("groupdel", groupName);
+
+ private string Execute(string command, string arguments)
+ {
+ using Process p = new Process();
+
+ p.StartInfo.UseShellExecute = false;
+ p.StartInfo.FileName = command;
+ p.StartInfo.Arguments = arguments;
+ p.StartInfo.RedirectStandardOutput = true;
+ p.StartInfo.RedirectStandardError = true;
+
+ p.Start();
+ p.WaitForExit();
+
+ string standardOutput = p.StandardOutput.ReadToEnd();
+ string standardError = p.StandardError.ReadToEnd();
+
+ if (p.ExitCode != 0)
+ {
+ throw new IOException($"Error '{p.ExitCode}' when executing '{command} {arguments}'. Message: {standardError}");
+ }
+
+ return standardOutput;
+ }
  }
 }

src/libraries/System.Formats.Tar/tests/TarWriter/TarWriter.WriteEntry.File.Tests.Unix.cs

@@ -139,5 +139,49 @@ public void Add_CharacterDevice(TarEntryFormat format)
 
  }, format.ToString(), new RemoteInvokeOptions { RunAsSudo = true }).Dispose();
  }
+
+ [ConditionalTheory(nameof(IsRemoteExecutorSupportedAndPrivilegedProcess))]
+ [InlineData(TarEntryFormat.Ustar)]
+ [InlineData(TarEntryFormat.Pax)]
+ [InlineData(TarEntryFormat.Gnu)]
+ public void CreateEntryFromFileOwnedByNonExistentGroup(TarEntryFormat f)
+ {
+ RemoteExecutor.Invoke((string strFormat) =>
+ {
+ using TempDirectory root = new TempDirectory();
+
+ string fileName = "file.txt";
+ string filePath = Path.Join(root.Path, fileName);
+ File.Create(filePath).Dispose();
+
+ string groupName = Path.GetRandomFileName()[0..6];
+ int groupId = CreateGroup(groupName);
+
+ try
+ {
+ SetGroupAsOwnerOfFile(groupName, filePath);
+ }
+ finally
+ {
+ DeleteGroup(groupName);
+ }
+
+ using MemoryStream archive = new MemoryStream();
+ using (TarWriter writer = new TarWriter(archive, Enum.Parse<TarEntryFormat>(strFormat), leaveOpen: true))
+ {
+ writer.WriteEntry(filePath, fileName); // Should not throw
+ }
+ archive.Seek(0, SeekOrigin.Begin);
+
+ using (TarReader reader = new TarReader(archive, leaveOpen: false))
+ {
+ PosixTarEntry entry = reader.GetNextEntry() as PosixTarEntry;
+ Assert.NotNull(entry);
+ Assert.Equal(entry.GroupName, string.Empty);
+ Assert.Equal(groupId, entry.Gid);
+ Assert.Null(reader.GetNextEntry());
+ }
+ }, f.ToString(), new RemoteInvokeOptions { RunAsSudo = true }).Dispose();
+ }
  }
 }

src/libraries/System.Formats.Tar/tests/TarWriter/TarWriter.WriteEntryAsync.File.Tests.Unix.cs

@@ -149,5 +149,49 @@ public void Add_CharacterDevice_Async(TarEntryFormat format)
  }
  }, format.ToString(), new RemoteInvokeOptions { RunAsSudo = true }).Dispose();
  }
+
+ [ConditionalTheory(nameof(IsRemoteExecutorSupportedAndPrivilegedProcess))]
+ [InlineData(TarEntryFormat.Ustar)]
+ [InlineData(TarEntryFormat.Pax)]
+ [InlineData(TarEntryFormat.Gnu)]
+ public void CreateEntryFromFileOwnedByNonExistentGroup_Async(TarEntryFormat f)
+ {
+ RemoteExecutor.Invoke(async (string strFormat) =>
+ {
+ using TempDirectory root = new TempDirectory();
+
+ string fileName = "file.txt";
+ string filePath = Path.Join(root.Path, fileName);
+ File.Create(filePath).Dispose();
+
+ string groupName = Path.GetRandomFileName()[0..6];
+ int groupId = CreateGroup(groupName);
+
+ try
+ {
+ SetGroupAsOwnerOfFile(groupName, filePath);
+ }
+ finally
+ {
+ DeleteGroup(groupName);
+ }
+
+ await using MemoryStream archive = new MemoryStream();
+ await using (TarWriter writer = new TarWriter(archive, Enum.Parse<TarEntryFormat>(strFormat), leaveOpen: true))
+ {
+ await writer.WriteEntryAsync(filePath, fileName); // Should not throw
+ }
+ archive.Seek(0, SeekOrigin.Begin);
+
+ await using (TarReader reader = new TarReader(archive, leaveOpen: false))
+ {
+ PosixTarEntry entry = await reader.GetNextEntryAsync() as PosixTarEntry;
+ Assert.NotNull(entry);
+ Assert.Equal(entry.GroupName, string.Empty);
+ Assert.Equal(groupId, entry.Gid);
+ Assert.Null(await reader.GetNextEntryAsync());
+ }
+ }, f.ToString(), new RemoteInvokeOptions { RunAsSudo = true }).Dispose();
+ }
  }
 }