fix(tar): permit slashed output dir

fixes an issue where TarArchive.ExtractContents would cause
an InvalidNameException when the destination dir ended with /

adds additional tests for combinations of tar file names
and extraction destination paths

Author: piksel

src/ICSharpCode.SharpZipLib/Tar/TarArchive.cs

@@ -613,7 +613,7 @@ public void ExtractContents(string destinationDirectory, bool allowParentTravers
 				throw new ObjectDisposedException("TarArchive");
 			}
 
-			var fullDistDir = Path.GetFullPath(destinationDirectory);
+			var fullDistDir = Path.GetFullPath(destinationDirectory).TrimEnd('/', '\\');
 
 			while (true)
 			{

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

@@ -13,9 +13,12 @@ public class TarArchiveTests
 		[Test]
 		[Category("Tar")]
 		[Category("CreatesTempFile")]
-		public void ExtractingContentsWithNonTraversalPathSucceeds()
+		[TestCase("output")]
+		[TestCase("output/")]
+		[TestCase(@"output\")]
+		public void ExtractingContentsWithNonTraversalPathSucceeds(string outputDir)
 		{
-			Assert.DoesNotThrow(() => ExtractTarOK("output", "test-good", allowTraverse: false));
+			Assert.DoesNotThrow(() => ExtractTarOK(outputDir, "test-good", allowTraverse: false));
 		}
 
 		[Test]
@@ -30,12 +33,26 @@ public void ExtractingContentsWithExplicitlyAllowedTraversalPathSucceeds()
 		[Category("Tar")]
 		[Category("CreatesTempFile")]
 		[TestCase("output", "../file")]
+		[TestCase("output/", "../file")]
 		[TestCase("output", "../output.txt")]
 		public void ExtractingContentsWithDisallowedPathsFails(string outputDir, string fileName)
 		{
 			Assert.Throws<InvalidNameException>(() => ExtractTarOK(outputDir, fileName, allowTraverse: false));
 		}
 
+		[Test]
+		[Category("Tar")]
+		[Category("CreatesTempFile")]
+		[Platform(Include = "Win", Reason = "Backslashes are only treated as path separators on windows")]
+		[TestCase(@"output\", @"..\file")]
+		[TestCase(@"output/", @"..\file")]
+		[TestCase("output", @"..\output.txt")]
+		[TestCase(@"output\", @"..\output.txt")]
+		public void ExtractingContentsOnWindowsWithDisallowedPathsFails(string outputDir, string fileName)
+		{
+			Assert.Throws<InvalidNameException>(() => ExtractTarOK(outputDir, fileName, allowTraverse: false));
+		}
+		
 		public void ExtractTarOK(string outputDir, string fileName, bool allowTraverse)
 		{
 			var fileContent = Encoding.UTF8.GetBytes("file content");