CVE-2021-32840 (published 2022-01-26T21:15Z)

SharpZipLib (or #ziplib) is a Zip, GZip, Tar and BZip2 library. Prior to version 1.3.3, a TAR file entry `../evil.txt` may be extracted in the parent directory of `destFolder`. This leads to arbitrary file write that may lead to code execution. The vulnerability was patched in version 1.3.3.

Severity: HIGH
CVSS v2 base score: 7.5 (AV:N/AC:L/Au:N/C:P/I:P/A:P)
CVSS v3 base score: 9.8, CRITICAL (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)

Weakness information:
cwe_id: CWE-22
cwe_name: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
description: The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
extended_description: 
            Many file operations are intended to take place within a restricted directory. By using special elements such as ".." and "/" separators, attackers can escape outside of the restricted location to access files or directories that are elsewhere on the system. One of the most common special elements is the "../" sequence, which in most modern operating systems is interpreted as the parent directory of the current location. This is referred to as relative path traversal. Path traversal also covers the use of absolute pathnames such as "/usr/local/bin" to access unexpected files. This is referred to as absolute path traversal.
         
         

Fix information:
repo_url: https://github.com/icsharpcode/SharpZipLib
commit_details: repo_url: https://github.com/icsharpcode/SharpZipLib
author: nils måsén
author_date: 2021-09-18 11:46:25+02:00
msg: test: add tests for tar path traversal
repository: repo_url: https://github.com/icsharpcode/SharpZipLib
repo_name: icsharpcode/SharpZipLib
description: #ziplib is a Zip, GZip, Tar and BZip2 library written entirely in C# for the .NET platform.
repo_language: C#
owner: icsharpcode
file_changes: filename: ICSharpCode.SharpZipLib.Tests.csproj
change_type: ModificationType.MODIFY
diff: @@ -5,6 +5,7 @@
 		<TargetFrameworks>netcoreapp3.1;net46</TargetFrameworks>
     <ApplicationIcon />
     <StartupObject />
+		<LangVersion>8</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>

programming_language: PowerShell
filename: TarArchiveTests.cs
change_type: ModificationType.ADD
diff: @@ -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));
+		}
+	}
+}

programming_language: C#