test: add tests for tar path traversal

test/ICSharpCode.SharpZipLib.Tests/ICSharpCode.SharpZipLib.Tests.csproj

@@ -5,6 +5,7 @@
 		<TargetFrameworks>netcoreapp3.1;net46</TargetFrameworks>
     <ApplicationIcon />
     <StartupObject />
+		<LangVersion>8</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>

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

@@ -0,0 +1,73 @@
+using System.IO;
+using System.Text;
+using ICSharpCode.SharpZipLib.Core;
+using ICSharpCode.SharpZipLib.Tar;
+using static ICSharpCode.SharpZipLib.Tests.TestSupport.Utils;
+using NUnit.Framework;
+
+namespace ICSharpCode.SharpZipLib.Tests.Tar
+{
+	[TestFixture]
+	public class TarArchiveTests
+	{
+		[Test]
+		[Category("Tar")]
+		[Category("CreatesTempFile")]
+		public void ExtractingContentsWithNonTraversalPathSucceeds()
+		{
+			Assert.DoesNotThrow(() => ExtractTarOK("output", "test-good", allowTraverse: false));
+		}
+
+		[Test]
+		[Category("Tar")]
+		[Category("CreatesTempFile")]
+		public void ExtractingContentsWithExplicitlyAllowedTraversalPathSucceeds()
+		{
+			Assert.DoesNotThrow(() => ExtractTarOK("output", "../file", allowTraverse: true));
+		}
+
+		[Test]
+		[Category("Tar")]
+		[Category("CreatesTempFile")]
+		[TestCase("output", "../file")]
+		[TestCase("output", "../output.txt")]
+		public void ExtractingContentsWithDisallowedPathsFails(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");
+			using var tempDir = new TempDir();
+
+			var tempPath = tempDir.Fullpath;
+			var extractPath = Path.Combine(tempPath, outputDir);
+			var expectedOutputFile = Path.Combine(extractPath, fileName);
+
+			using var archiveStream = new MemoryStream();
+
+			Directory.CreateDirectory(extractPath);
+
+			using (var tos = new TarOutputStream(archiveStream, Encoding.UTF8){IsStreamOwner = false})
+			{
+				var entry = TarEntry.CreateTarEntry(fileName);
+				entry.Size = fileContent.Length;
+				tos.PutNextEntry(entry);
+				tos.Write(fileContent, 0, fileContent.Length);
+				tos.CloseEntry();
+			}
+
+			archiveStream.Position = 0;
+
+			using (var ta = TarArchive.CreateInputTarArchive(archiveStream, Encoding.UTF8))
+			{
+				ta.ProgressMessageEvent += (archive, entry, message) 
+					=> TestContext.WriteLine($"{entry.Name} {entry.Size} {message}");
+				ta.ExtractContents(extractPath, allowTraverse);
+			}
+
+			Assert.That(File.Exists(expectedOutputFile));
+		}
+	}
+}