1 files changed, 78 insertions, 0 deletions
diff --git a/tests/Jellyfin.Controller.Tests/IO/FileSystemHelperTests.cs b/tests/Jellyfin.Controller.Tests/IO/FileSystemHelperTests.cs
new file mode 100644
index 0000000000..b4ec2f1903
--- /dev/null
+++ b/tests/Jellyfin.Controller.Tests/IO/FileSystemHelperTests.cs
@@ -0,0 +1,78 @@
+using System;
+using System.IO;
+using MediaBrowser.Controller.IO;
+using Xunit;
+
+namespace Jellyfin.Controller.Tests.IO;
+
+public class FileSystemHelperTests
+{
+    private static readonly string _parentPath = Path.Combine(Path.GetTempPath(), "jellyfin-test", "root", "default");
+
+    [Theory]
+    [InlineData("Movies")]
+    [InlineData("My Movies")]
+    [InlineData("..2")]
+    [InlineData("a.b")]
+    public void GetChildPath_ValidName_ReturnsPathInsideParent(string name)
+    {
+        var path = FileSystemHelper.GetChildPath(_parentPath, name);
+
+        Assert.Equal(Path.Combine(_parentPath, name), path);
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("   ")]
+    [InlineData(".")]
+    [InlineData("..")]
+    [InlineData("../..")]
+    [InlineData("../../etc")]
+    [InlineData("Movies/../..")]
+    [InlineData("/var/lib/jellyfin/data")]
+    [InlineData("sub/folder")]
+    [InlineData("with\0null")]
+    public void GetChildPath_EscapingName_ReturnsNull(string name)
+    {
+        Assert.Null(FileSystemHelper.GetChildPath(_parentPath, name));
+    }
+
+    [Theory]
+    [InlineData("..\\..")]
+    [InlineData("sub\\folder")]
+    [InlineData("C:\\Windows")]
+    public void GetChildPath_WindowsSeparator_DoesNotEscapeParent(string name)
+    {
+        var path = FileSystemHelper.GetChildPath(_parentPath, name);
+
+        // On Windows these are rejected outright, on other platforms a backslash is a legal file name character.
+        Assert.True(path is null || string.Equals(Path.GetDirectoryName(path), _parentPath, StringComparison.Ordinal));
+    }
+
+    [Theory]
+    [InlineData("...")]
+    [InlineData("Movies.")]
+    [InlineData("Movies ")]
+    public void GetChildPath_TrailingDotOrSpace_RejectedOnWindows(string name)
+    {
+        var path = FileSystemHelper.GetChildPath(_parentPath, name);
+
+        if (OperatingSystem.IsWindows())
+        {
+            // Windows trims trailing dots and spaces, so the name would resolve to the parent or to a different child.
+            Assert.Null(path);
+        }
+        else
+        {
+            Assert.Equal(Path.Combine(_parentPath, name), path);
+        }
+    }
+
+    [Fact]
+    public void GetChildPath_ParentWithTrailingSeparator_ReturnsPathInsideParent()
+    {
+        var path = FileSystemHelper.GetChildPath(_parentPath + Path.DirectorySeparatorChar, "Movies");
+
+        Assert.Equal(Path.Combine(_parentPath, "Movies"), path);
+    }
+}