Release v1.0.0

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ env:
 jobs:
   build:
 
-    # We need to run on Windows as we're supporting .NET Framework
+    # We need to run on Windows as we're supporting .NET Framework and using MIcrosoft AMSI
     runs-on: windows-latest
 
     permissions:

ByteGuard.FileValidator.Scanners.Amsi.slnx

@@ -5,7 +5,10 @@
     <File Path="Directory.Version.props" />
     <File Path="LICENSE" />
     <File Path="README.md" />
+    <File Path=".github/workflows/ci.yml" />
   </Folder>
-  <Folder Name="/tests/" />
-  <Project Path="src/ByteGuard.FileValidator.Scanners.Amsi/ByteGuard.FileValidator.Scanners.Amsi.csproj" />
+  <Folder Name="/tests/">
+    <Project Path="tests/ByteGuard.FileValidator.Scanner.Amsi.Tests.Unit/ByteGuard.FileValidator.Scanner.Amsi.Tests.Unit.csproj" />
+  </Folder>
+  <Project Path="src/ByteGuard.FileValidator.Scanner.Amsi/ByteGuard.FileValidator.Scanner.Amsi.csproj" />
 </Solution>

Directory.Version.props

@@ -1,5 +1,5 @@
 <Project>
   <PropertyGroup>
-    <VersionPrefix>0.1.0</VersionPrefix>
+    <VersionPrefix>1.0.0</VersionPrefix>
   </PropertyGroup>
 </Project>

README.md

@@ -1,2 +1,111 @@
 
-# ByteGuard.FileValidator.Scanners.Amsi ![NuGet Version](https://img.shields.io/nuget/v/ByteGuard.FileValidator.Scanners.Amsi)
+# ByteGuard.FileValidator.Scanners.Amsi ![NuGet Version](https://img.shields.io/nuget/v/ByteGuard.FileValidator.Scanners.Amsi)
+
+`ByteGuard.FileValidator.Scanners.Amsi` is a Microsoft Antimalware Scan Interface (AMSI) specific antimalware scanner implementation for [`ByteGuard.FileValidator`](https://www.nuget.org/packages/ByteGuard.FileValidator).
+
+ AMSI is a Windows API that allows applications to submit content for scanning and receive a verdict from the installed antimalware provider. It lets you route files through the OS antimalware engine (_for example Microsoft Defender or any other AMSI-integrated AV_) before they’re accepted by your application.
+
+> ⚠️ **Important:** This package is one layer in a defense-in-depth strategy.  
+> It does **not** replace endpoint protection, sandboxing, input validation, or other security controls.
+
+> ⚠️ **Important:** This package uses the Microsoft Antimalware Scan Interface (AMSI) and will submit content to the installed antimalware engine on the host (_e.g., Microsoft Defender_). Malicious samples or test files (_such as the EICAR test file_) may trigger alerts and incidents in your security monitoring. Make sure your security/operations team is aware of this integration before running tests in shared or production environments.
+
+## Features
+
+- **AMSI-based** implementation of `IAntimalwareScanner` for `ByteGuard.FileValidator`
+- Works with **any AMSI-compatible antivirus** installed on the host machine
+
+## Prerequisites
+
+- **Operating system**
+  - Windows 10+ or Windows Server 2016+ (_AMSI is available and supported on these versions_).
+- **Antimalware**
+  - An AMSI-integrated antimalware engine installed and enabled (_e.g. Microsoft Defender Antivirus_).
+- **Core packages**
+  - [`ByteGuard.FileValidator`](https://www.nuget.org/packages/ByteGuard.FileValidator)
+
+## Getting Started
+
+### Installation
+This package is published and installed via [NuGet](https://www.nuget.org/packages/ByteGuard.FileValidator.Scanners.Amsi).
+
+Reference the package in your project:
+```bash
+dotnet add package ByteGuard.FileValidator.Scanners.Amsi
+```
+
+## Usage
+
+```csharp
+using ByteGuard.FileValidator;
+using ByteGuard.FileValidator.Scanners.Amsi;
+
+var amsiConfig = new AmsiScannerConfiguration()
+{
+    ApplicationName = "MyApplication"
+};
+
+var amsiScanner = new AmsiAntimalwareScanner(amsiConfig);
+
+var configuration = //...;
+var fileValidator = new FileValidator(configuration, amsiScanner);
+
+var isValid = fileValidator.IsValidFile(fileStream, fileName);
+```
+
+The `FileValidator` will automatically scan the file once provided as argument, and whenever using either `IsValidFile` or `IsMalwareClean` functions.
+
+## Configuration
+`AmsiScannerConfiguration` supports the following settings:
+
+| Settings | Required | Description |
+| -- | -- | -- |
+| `ApplicationName` | Yes | The logical name used when registering the AMSI session (_helps AV engines with context_). | 
+
+### Example
+```csharp
+[HttpPost("upload")]
+public async Task<IActionResult> Upload(IFormFile file)
+{
+    using var stream = file.OpenReadStream();
+
+    var amsiConfig = new AmsiScannerConfiguration()
+    {
+        ApplicationName = "MyApplication"
+    };
+
+    var amsiScanner = new AmsiAntimalwareScanner(amsiConfig);
+
+    var configuration = //...
+    var validator = new FileValidator(configuration, amsiScanner);
+
+    if (!validator.IsValidFile(file.FileName, stream))
+    {
+        return BadRequest("Invalid or unsupported file.");
+    }
+
+    // Proceed with processing/saving...
+
+    return Ok();
+}
+```
+
+### Testing the AMSI integration
+
+If you verify the integration using known test signatures (for example, the EICAR test file), be aware that:
+
+- The installed AV engine may quarantine or block the file.
+- Alerts may be raised and forwarded to your SIEM / security team.
+- In tightly monitored environments, you should coordinate with your security team before running such tests.
+
+
+## Security notes & limitations
+
+- AMSI relies on the underlying antimalware provider for detection. If the provider is disabled, misconfigured, or missing signatures, detection quality will be affected. 
+- Attackers constantly attempt to evade or disable AMSI; **treat AMSI as a signal, not as a guarantee**.
+- **Always** combine this package with:
+  - Principle of least privilege for storage and processing
+  - Endpoint protection and monitoring
+
+## License
+_ByteGuard.FileValidator.Scanners.Amsi is Copyright © ByteGuard Contributors - Provided under the MIT license._

src/ByteGuard.FileValidator.Scanner.Amsi/AmsiAntimalwareScanner.cs

@@ -0,0 +1,66 @@
+using System.ComponentModel;
+#if NET5_0_OR_GREATER
+using System.Runtime.Versioning;
+#endif
+using ByteGuard.FileValidator.Scanner.Amsi.Integration;
+using ByteGuard.FileValidator.Scanners;
+
+namespace ByteGuard.FileValidator.Scanner.Amsi;
+
+/// <summary>
+/// Microsoft Antimalware Scan Interface (AMSI) antimalware scanner implementation.
+/// </summary>
+#if NET5_0_OR_GREATER
+[SupportedOSPlatform("windows")]
+#endif
+public class AmsiAntimalwareScanner : IAntimalwareScanner<AmsiScannerConfiguration>
+{
+    private readonly AmsiScannerConfiguration _configuration;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="AmsiAntimalwareScanner"/> class.
+    /// </summary>
+    /// <param name="configuration">Scanner configuration.</param>
+    /// <exception cref="ArgumentNullException">Thrown if the <paramref name="configuration"/> is <c>null</c>.</exception>
+    /// <exception cref="ArgumentException">Thrown if the <paramref name="configuration.ApplicationName"/> is <c>null></c> or whitespace.</exception>
+    public AmsiAntimalwareScanner(AmsiScannerConfiguration configuration)
+    {
+        if (configuration == null)
+        {
+            throw new ArgumentNullException(nameof(configuration));
+        }
+
+        if (string.IsNullOrWhiteSpace(configuration.ApplicationName))
+        {
+            throw new ArgumentException("ApplicationName must be provided in the configuration.", nameof(configuration));
+        }
+
+        _configuration = configuration;
+    }
+
+    /// <summary>
+    /// Scans the provided content stream for malware using Windows Antimalware Scan Interface (AMSI).
+    /// </summary>
+    /// <param name="contentStream">Content stream.</param>
+    /// <param name="fileName">Filename.</param>
+    /// <returns><c>true</c> if no malware was detected in the file, <c>false</c> otherwise.</returns>
+    /// <exception cref="Win32Exception">Thrown if the AMSI API call fails.</exception>
+    public bool IsClean(Stream contentStream, string fileName)
+    {
+        var content = ReadStreamToByteArray(contentStream);
+
+        using var context = AmsiContext.Create(_configuration.ApplicationName);
+        using var session = context.CreateSession();
+
+        var isMalware = session.IsMalware(content, fileName);
+        return !isMalware;
+    }
+
+    private byte[] ReadStreamToByteArray(Stream stream)
+    {
+        using var ms = new MemoryStream();
+        stream.CopyTo(ms);
+
+        return ms.ToArray();
+    }
+}

src/ByteGuard.FileValidator.Scanner.Amsi/ByteGuard.FileValidator.Scanner.Amsi.csproj

@@ -0,0 +1,28 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFrameworks>netstandard2.0;net481;net8.0;net9.0;net10.0</TargetFrameworks>
+    <Authors>ByteGuard Contributors</Authors>
+    <Description>ByteGuard File Validator Microsoft Antimalware Scan Interface (AMSI) antimalware scanner.</Description>
+    <PackageProjectUrl>https://github.com/ByteGuard-HQ/byteguard-file-validator-scanner-amsi</PackageProjectUrl>
+    <RepositoryUrl>https://github.com/ByteGuard-HQ/byteguard-file-validator-scanner-amsi</RepositoryUrl>
+    <RepositoryType>git</RepositoryType>
+    <PackageTags>byteguard file-validator scanner amsi</PackageTags>
+    <PackageReadmeFile>README.md</PackageReadmeFile>
+    <PackageIcon>icon.png</PackageIcon>
+    <Copyright>Copyright © ByteGuard Contributors</Copyright>
+    <PackageLicenseExpression>MIT</PackageLicenseExpression>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <None Include="..\..\README.md" Pack="true" PackagePath="\" />
+    <None Include="..\..\assets\icon.png" Pack="true" PackagePath="\" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="ByteGuard.FileValidator" Version="1.1.0" />
+  </ItemGroup>
+
+
+
+</Project>

src/ByteGuard.FileValidator.Scanner.Amsi/Configuration/AmsiScannerConfiguration.cs

@@ -0,0 +1,15 @@
+namespace ByteGuard.FileValidator.Scanner.Amsi;
+
+/// <summary>
+/// Configuration for the Microsoft Antimalware Scan Interface (AMSI) scanner.
+/// </summary>
+public class AmsiScannerConfiguration
+{
+    /// <summary>
+    /// Name of the application integrating with Microsoft Antimalware Scan Interface (AMSI).
+    /// </summary>
+    /// <remarks>
+    /// The name, version, or GUID string of the app calling the AMSI API.
+    /// </remarks>
+    public string ApplicationName { get; set; } = default!;
+}

src/ByteGuard.FileValidator.Scanner.Amsi/Integration/Amsi.cs

@@ -0,0 +1,88 @@
+using System.Runtime.InteropServices;
+#if NET5_0_OR_GREATER
+using System.Runtime.Versioning;
+#endif
+
+namespace ByteGuard.FileValidator.Scanner.Amsi.Integration;
+
+/// <summary>
+/// Dynamically loaded Antimalware Scan Interface from System32. Will only work on Windows clients and servers.
+/// </summary>
+#if NET5_0_OR_GREATER
+[SupportedOSPlatform("windows")]
+#endif
+internal static class Amsi
+{
+    /// <summary>
+    /// Initialize the AMSI API.
+    /// </summary>
+    /// <param name="appName">The name, version, or GUID string of the app calling the AMSI API.</param>
+    /// <param name="amsiContext">Out generated AMSI context that must be passed to all subsequent calls to the AMSI API.</param>
+    [DefaultDllImportSearchPaths(DllImportSearchPath.System32)]
+    [DllImport("Amsi.dll", EntryPoint = "AmsiInitialize", CallingConvention = CallingConvention.StdCall)]
+    internal static extern int AmsiInitialize([MarshalAs(UnmanagedType.LPWStr)] string appName, out AmsiContextSafeHandle amsiContext);
+
+    /// <summary>
+    /// Remove the instance of the AMSI API that was originally opened by <see cref="AmsiInitialize"/>.
+    /// </summary>
+    /// <param name="amsiContext">The context handle that was initially received from <see cref="AmsiInitialize"/>.</param>
+    [DefaultDllImportSearchPaths(DllImportSearchPath.System32)]
+    [DllImport("Amsi.dll", EntryPoint = "AmsiUninitialize", CallingConvention = CallingConvention.StdCall)]
+    internal static extern void AmsiUninitialize(IntPtr amsiContext);
+
+    /// <summary>
+    /// Opens a session within which multiple scan requests can be correlated.
+    /// </summary>
+    /// <param name="amsiContext">The context handle that was initially received from <see cref="AmsiInitialize"/>.</param>
+    /// <param name="session">Out generated AMSI session that must be passed to all subsequent calls to the AMSI API within the session.</param>
+    [DefaultDllImportSearchPaths(DllImportSearchPath.System32)]
+    [DllImport("Amsi.dll", EntryPoint = "AmsiOpenSession", CallingConvention = CallingConvention.StdCall)]
+    internal static extern int AmsiOpenSession(AmsiContextSafeHandle amsiContext, out AmsiSessionSafeHandle session);
+
+    /// <summary>
+    /// Close a session that was opened by <see cref="AmsiOpenSession"/>.
+    /// </summary>
+    /// <param name="amsiContext">The context handle that was initially received from <see cref="AmsiInitialize"/>.</param>
+    /// <param name="session">The session handle that was initially received from <see cref="AmsiOpenSession"/>.</param>
+    [DefaultDllImportSearchPaths(DllImportSearchPath.System32)]
+    [DllImport("Amsi.dll", EntryPoint = "AmsiCloseSession", CallingConvention = CallingConvention.StdCall)]
+    internal static extern void AmsiCloseSession(AmsiContextSafeHandle amsiContext, IntPtr session);
+
+    /// <summary>
+    /// Scans a string for malware.
+    /// </summary>
+    /// <remarks>
+    /// It's recommended to use <see cref="AmsiResultIsMalware"/> to interpret the returning result.
+    /// </remarks>
+    /// <param name="amsiContext">The context handle that was initially received from <see cref="AmsiInitialize"/>.</param>
+    /// <param name="payload">The string to be scanned.</param>
+    /// <param name="contentName">The filename, URL, unique script ID, or similar of the content being scanned.</param>
+    /// <param name="session">If multiple scan requests are to be correlated within a session, set session to the session handle that was initially received from <see cref="AmsiOpenSession"/>. Otherwise, set session to <c>null</c>.</param>
+    /// <param name="result">Out result of the scan (see <see cref="AmsiResult"/>).</param>
+    [DefaultDllImportSearchPaths(DllImportSearchPath.System32)]
+    [DllImport("Amsi.dll", EntryPoint = "AmsiScanString", CallingConvention = CallingConvention.StdCall)]
+    internal static extern int AmsiScanString(AmsiContextSafeHandle amsiContext, [In, MarshalAs(UnmanagedType.LPWStr)] string payload, [In, MarshalAs(UnmanagedType.LPWStr)] string contentName, AmsiSessionSafeHandle session, out AmsiResult result);
+
+    /// <summary>
+    /// Scans a buffer-full of content for malware.
+    /// </summary>
+    /// <remarks>
+    /// It's recommended to use <see cref="AmsiResultIsMalware"/> to interpret the returning result.
+    /// </remarks>
+    /// <param name="amsiContext">The context handle that was initially received from <see cref="AmsiInitialize"/>.</param>
+    /// <param name="buffer">The buffer from which to read the data to be scanned.</param>
+    /// <param name="length">The length, in bytes, of the data to be read from buffer.</param>
+    /// <param name="contentName">The filename, URL, unique script ID, or similar of the content being scanned.</param>
+    /// <param name="session">If multiple scan requests are to be correlated within a session, set session to the session handle that was initially received from <see cref="AmsiOpenSession"/>. Otherwise, set session to <c>null</c>.</param>
+    /// <param name="result">Out result of the scan (see <see cref="AmsiResult"/>).</param>
+    [DefaultDllImportSearchPaths(DllImportSearchPath.System32)]
+    [DllImport("Amsi.dll", EntryPoint = "AmsiScanBuffer", CallingConvention = CallingConvention.StdCall)]
+    internal static extern int AmsiScanBuffer(AmsiContextSafeHandle amsiContext, byte[] buffer, uint length, [In, MarshalAs(UnmanagedType.LPWStr)] string contentName, AmsiSessionSafeHandle session, out AmsiResult result);
+
+    /// <summary>
+    /// Determines if the result of a scan indicates that the content should be blocked.
+    /// </summary>
+    /// <param name="result">Result of a scan from either <see cref="AmsiScanString"/> or <see cref="AmsiScanBuffer"/>.</param>
+    /// <returns><c>true</c> if the result is considered a malware detection, <c>false</c> otherwise.</returns>
+    internal static bool AmsiResultIsMalware(AmsiResult result) => result >= AmsiResult.AMSI_RESULT_DETECTED;
+}