fix(tar): enable unix paths in tar RootPath

src/ICSharpCode.SharpZipLib/Tar/TarArchive.cs

@@ -356,8 +356,7 @@ public string RootPath
 				{
 					throw new ObjectDisposedException("TarArchive");
 				}
-				// Convert to forward slashes for matching. Trim trailing / for correct final path
-				rootPath = value.Replace('\\', '/').TrimEnd('/');
+				rootPath = value.ToTarArchivePath().TrimEnd('/');
 			}
 		}
 
@@ -660,7 +659,9 @@ private void ExtractEntry(string destDir, TarEntry entry, bool allowParentTraver
 			string destFile = Path.Combine(destDir, name);
 			var destFileDir = Path.GetDirectoryName(Path.GetFullPath(destFile)) ?? "";
 
-			if (!allowParentTraversal && !destFileDir.StartsWith(destDir, StringComparison.InvariantCultureIgnoreCase))
+			var isRootDir = entry.IsDirectory && entry.Name == "";
+
+			if (!allowParentTraversal && !isRootDir && !destFileDir.StartsWith(destDir, StringComparison.InvariantCultureIgnoreCase))
 			{
 				throw new InvalidNameException("Parent traversal in paths is not allowed");
 			}

src/ICSharpCode.SharpZipLib/Tar/TarEntry.cs

@@ -372,15 +372,10 @@ public void GetFileTarHeader(TarHeader header, string file)
 						}
 			*/
 
-			name = name.Replace(Path.DirectorySeparatorChar, '/');
-
 			// No absolute pathnames
 			// Windows (and Posix?) paths can start with UNC style "\\NetworkDrive\",
 			// so we loop on starting /'s.
-			while (name.StartsWith("/", StringComparison.Ordinal))
-			{
-				name = name.Substring(1);
-			}
+			name = name.ToTarArchivePath();
 
 			header.LinkName = String.Empty;
 			header.Name = name;

src/ICSharpCode.SharpZipLib/Tar/TarStringExtension.cs

@@ -0,0 +1,13 @@
+using System.IO;
+using ICSharpCode.SharpZipLib.Core;
+
+namespace ICSharpCode.SharpZipLib.Tar
+{
+	internal static class TarStringExtension
+	{
+		public static string ToTarArchivePath(this string s)
+		{
+			return PathUtils.DropPathRoot(s).Replace(Path.DirectorySeparatorChar, '/');
+		}
+	}
+}

test/ICSharpCode.SharpZipLib.Tests/Tar/TarTests.cs

@@ -833,7 +833,7 @@ public void ParseHeaderWithEncoding(int length, string encodingName)
 			reparseHeader.ParseBuffer(headerbytes, enc);
 			Assert.AreEqual(name, reparseHeader.Name);
 			// top 100 bytes are name field in tar header
-			for (int i = 0;i < encodedName.Length;i++)
+			for (int i = 0; i < encodedName.Length; i++)
 			{
 				Assert.AreEqual(encodedName[i], headerbytes[i]);
 			}
@@ -852,9 +852,9 @@ public async Task StreamWithJapaneseNameAsync(int length, string encodingName)
 			var entryName = new string((char)0x3042, length);
 			var data = new byte[32];
 			var encoding = Encoding.GetEncoding(encodingName);
-			using(var memoryStream = new MemoryStream())
+			using (var memoryStream = new MemoryStream())
 			{
-				using(var tarOutput = new TarOutputStream(memoryStream, encoding))
+				using (var tarOutput = new TarOutputStream(memoryStream, encoding))
 				{
 					var entry = TarEntry.CreateTarEntry(entryName);
 					entry.Size = 32;
@@ -874,5 +874,47 @@ public async Task StreamWithJapaneseNameAsync(int length, string encodingName)
 				File.WriteAllBytes(Path.Combine(Path.GetTempPath(), $"jpnametest_{length}_{encodingName}.tar"), memoryStream.ToArray());
 			}
 		}
+		/// <summary>
+		/// This test could be considered integration test. it creates a tar archive with the root directory specified
+		/// Then extracts it and compares the two folders. This used to fail on unix due to issues with root folder handling
+		/// in the tar archive.
+		/// </summary>
+		[Test]
+		[Category("Tar")]
+		public void RootPathIsRespected()
+		{
+			using (var extractDirectory = new TempDir())
+			using (var tarFileName = new TempFile())
+			using (var tempDirectory = new TempDir())
+			{
+				tempDirectory.CreateDummyFile();
+
+				using (var tarFile = File.Open(tarFileName.FullName, FileMode.Create))
+				{
+					using (var tarOutputStream = TarArchive.CreateOutputTarArchive(tarFile))
+					{
+						tarOutputStream.RootPath = tempDirectory.FullName;
+						var entry = TarEntry.CreateEntryFromFile(tempDirectory.FullName);
+						tarOutputStream.WriteEntry(entry, true);
+					}
+				}
+
+				using (var file = File.OpenRead(tarFileName.FullName))
+				{
+					using (var archive = TarArchive.CreateInputTarArchive(file, Encoding.UTF8))
+					{
+						archive.ExtractContents(extractDirectory.FullName);
+					}
+				}
+
+				var expectationDirectory = new DirectoryInfo(tempDirectory.FullName);
+				foreach (var checkFile in expectationDirectory.GetFiles("", SearchOption.AllDirectories))
+				{
+					var relativePath = checkFile.FullName.Substring(expectationDirectory.FullName.Length + 1);
+					FileAssert.Exists(Path.Combine(extractDirectory.FullName, relativePath));
+					FileAssert.AreEqual(checkFile.FullName, Path.Combine(extractDirectory.FullName, relativePath));
+				}
+			}
+		}
 	}
 }