Use case insensitive check

Author: Hinton

src/Core/Platform/Mailer/HandlebarMailRenderer.cs

@@ -98,8 +98,8 @@ private async Task<string> ReadSourceAsync(Assembly assembly, string template)
             var baseDirectory = Path.GetFullPath(_globalSettings.MailTemplateDirectory);
 
             // Ensure the resolved path is within the configured directory
-            if (!diskPath.StartsWith(baseDirectory + Path.DirectorySeparatorChar) &&
-                diskPath != baseDirectory)
+            if (!diskPath.StartsWith(baseDirectory + Path.DirectorySeparatorChar, StringComparison.OrdinalIgnoreCase) &&
+                !diskPath.Equals(baseDirectory, StringComparison.OrdinalIgnoreCase))
             {
                 _logger.LogWarning("Template path traversal attempt detected: {Template}", template);
                 return null;

test/Core.Test/Platform/Mailer/HandlebarMailRendererTests.cs

@@ -62,4 +62,111 @@ public async Task RenderAsync_LoadsFromDisk_WhenSelfHostedAndFileExists()
             }
         }
     }
+
+    [Theory]
+    [InlineData("../../../etc/passwd")]
+    [InlineData("../../../../malicious.txt")]
+    [InlineData("../../malicious.txt")]
+    [InlineData("../malicious.txt")]
+    public async Task ReadSourceFromDiskAsync_PrevenetsPathTraversal_WhenMaliciousPathProvided(string maliciousPath)
+    {
+        var logger = Substitute.For<ILogger<HandlebarMailRenderer>>();
+        var tempDir = Path.Combine(Path.GetTempPath(), Guid.NewGuid().ToString());
+        Directory.CreateDirectory(tempDir);
+
+        try
+        {
+            var globalSettings = new GlobalSettings
+            {
+                SelfHosted = true,
+                MailTemplateDirectory = tempDir
+            };
+
+            // Create a malicious file outside the template directory
+            var maliciousFile = Path.Combine(Path.GetTempPath(), "malicious.txt");
+            await File.WriteAllTextAsync(maliciousFile, "Malicious Content");
+
+            var renderer = new HandlebarMailRenderer(logger, globalSettings);
+
+            // Use reflection to call the private ReadSourceFromDiskAsync method
+            var method = typeof(HandlebarMailRenderer).GetMethod("ReadSourceFromDiskAsync",
+                System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
+            var task = (Task<string?>)method!.Invoke(renderer, new object[] { maliciousPath })!;
+            var result = await task;
+
+            // Should return null and not load the malicious file
+            Assert.Null(result);
+
+            // Verify that a warning was logged for the path traversal attempt
+            logger.Received(1).Log(
+                LogLevel.Warning,
+                Arg.Any<EventId>(),
+                Arg.Any<object>(),
+                Arg.Any<Exception>(),
+                Arg.Any<Func<object, Exception, string>>());
+
+            // Cleanup malicious file
+            if (File.Exists(maliciousFile))
+            {
+                File.Delete(maliciousFile);
+            }
+        }
+        finally
+        {
+            // Cleanup
+            if (Directory.Exists(tempDir))
+            {
+                Directory.Delete(tempDir, true);
+            }
+        }
+    }
+
+    [Fact]
+    public async Task ReadSourceFromDiskAsync_AllowsValidFileWithDifferentCase_WhenCaseInsensitiveFileSystem()
+    {
+        var logger = Substitute.For<ILogger<HandlebarMailRenderer>>();
+        var tempDir = Path.Combine(Path.GetTempPath(), Guid.NewGuid().ToString());
+        Directory.CreateDirectory(tempDir);
+
+        try
+        {
+            var globalSettings = new GlobalSettings
+            {
+                SelfHosted = true,
+                MailTemplateDirectory = tempDir
+            };
+
+            // Create a test template file
+            var templateFileName = "TestTemplate.hbs";
+            var templatePath = Path.Combine(tempDir, templateFileName);
+            await File.WriteAllTextAsync(templatePath, "Test Content");
+
+            var renderer = new HandlebarMailRenderer(logger, globalSettings);
+
+            // Try to read with different case (should work on case-insensitive file systems like Windows/macOS)
+            var method = typeof(HandlebarMailRenderer).GetMethod("ReadSourceFromDiskAsync",
+                System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
+            var task = (Task<string?>)method!.Invoke(renderer, new object[] { templateFileName })!;
+            var result = await task;
+
+            // Should successfully read the file
+            Assert.Equal("Test Content", result);
+
+            // Verify no warning was logged
+            logger.DidNotReceive().Log(
+                LogLevel.Warning,
+                Arg.Any<EventId>(),
+                Arg.Any<object>(),
+                Arg.Any<Exception>(),
+                Arg.Any<Func<object, Exception, string>>());
+        }
+        finally
+        {
+            // Cleanup
+            if (Directory.Exists(tempDir))
+            {
+                Directory.Delete(tempDir, true);
+            }
+        }
+    }
 }