We are writing a code to do on-demand scan of a file from C# using Windows Defender APIs.
[DllImport(@"C:\Program Files\Windows Defender\MpClient.dll")]
public static extern int WDStatus(out bool pfEnabled);
[DllImport(@"C:\Program Files\Windows Defender\MpClient.dll")]
public static extern int MpManagerOpen(uint dwReserved, out IntPtr phMpHandle);
[DllImport(@"C:\Program Files\Windows Defender\MpClient.dll")]
public static extern int MpScanStart(IntPtr hMpHandle, uint ScanType, uint dwScanOptions, IntPtr pScanResources, IntPtr pCallbackInfo, out IntPtr phScanHandle);
[DllImport(@"C:\Program Files\Windows Defender\MpClient.dll")]
public static extern int MpHandleClose(IntPtr hMpHandle);
private void DoDefenderScan_Click(object sender, EventArgs e)
{
try
{
bool pfEnabled;
int result = WDStatus(out pfEnabled); //Returns the defender status - It's working properly.
ErrorHandler.ThrowOnFailure(result, VSConstants.S_OK);
IntPtr phMpHandle;
uint dwReserved = 0;
IntPtr phScanHandle;
MpManagerOpen(dwReserved, out phMpHandle); //Opens Defender and returns the handle in phMpHandle.
tagMPRESOURCE_INFO mpResourceInfo = new tagMPRESOURCE_INFO();
mpResourceInfo.Path = "eicar.com";
mpResourceInfo.Scheme = "file";
mpResourceInfo.Class = IntPtr.Zero;
tagMPRESOURCE_INFO[] pResourceList = new tagMPRESOURCE_INFO[1];
pResourceList.SetValue(mpResourceInfo, 0);
tagMPSCAN_RESOURCES scanResource = new tagMPSCAN_RESOURCES();
scanResource.dwResourceCount = 1;
scanResource.pResourceList = pResourceList;
IntPtr resourcePointer = StructToPtr(scanResource);
result = MpScanStart(phMpHandle, 3, 0, resourcePointer, IntPtr.Zero, out phScanHandle); **//Getting Access violation exception here**.
MpHandleClose(phMpHandle);
MpHandleClose(phScanHandle);
Marshal.FreeHGlobal(resourcePointer);
}
catch (Exception)
{ }
}
And the structure is defined here.
[StructLayout(LayoutKind.Sequential, Pack = 1)]
public struct tagMPSCAN_RESOURCES
{
public uint dwResourceCount;
[MarshalAs(UnmanagedType.ByValArray, ArraySubType = UnmanagedType.Struct, SizeConst = 1)]
public tagMPRESOURCE_INFO[] pResourceList;
}
[StructLayout(LayoutKind.Sequential, Pack = 1)]
public struct tagMPRESOURCE_INFO
{
[MarshalAs(UnmanagedType.LPWStr)]
public String Scheme;
[MarshalAs(UnmanagedType.LPWStr)]
public String Path;
public IntPtr Class;
}
public class MPRESOURCE_CLASS
{
public uint Value;
}
private static IntPtr StructToPtr(object obj)
{
var ptr = Marshal.AllocHGlobal(Marshal.SizeOf(obj));
Marshal.StructureToPtr(obj, ptr, false);
return ptr;
}
The code is written based on the documentation available at
https://msdn.microsoft.com/en-us/library/vs/alm/dn920144(v=vs.85).aspx
We are getting this exception
Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
at
result = MpScanStart(phMpHandle, 3, 0, resourcePointer, IntPtr.Zero, out phScanHandle); **//Getting Access violation exception here**.
What could be the problem? Is the format of struct is correct?
P.S - No information about MPRESOURCE_CLASS is available in msdn.
I'm not sure, whether this line of code is correct.
mpResourceInfo.Class = IntPtr.Zero;
Update:
Quick scan is working fine with this code:
result = MpScanStart(phMpHandle, 1, 0, IntPtr.Zero, IntPtr.Zero, out phScanHandle);
Defender logs in the event viewer [ Applications and Services Logs-Microsoft-Windows-Windows Defender/Operational ] as
Windows Defender scan has started.
Scan ID:{CDC2AC0D-7648-4313-851C-4D8B7B5EB5CD}
Scan Type:AntiSpyware
Scan Parameters:Quick Scan
I couldn't identify the problem here. So I ended up with Antimalware Scan Interface (AMSI) available starting from Windows 10.
I have written a sample C# code here.
One thing I found is AMSI requires Windows defender/any antivirus to be turned on to verify the file passed to API. But triggering a scan through MpClient.dll
will trigger a defender scan even if defender is turned off.
Also ensure your project targets x64
platform.
public enum AMSI_RESULT
{
AMSI_RESULT_CLEAN = 0,
AMSI_RESULT_NOT_DETECTED = 1,
AMSI_RESULT_DETECTED = 32768
}
[DllImport("Amsi.dll", EntryPoint = "AmsiInitialize", CallingConvention = CallingConvention.StdCall)]
public static extern int AmsiInitialize([MarshalAs(UnmanagedType.LPWStr)]string appName, out IntPtr amsiContext);
[DllImport("Amsi.dll", EntryPoint = "AmsiUninitialize", CallingConvention = CallingConvention.StdCall)]
public static extern void AmsiUninitialize(IntPtr amsiContext);
[DllImport("Amsi.dll", EntryPoint = "AmsiOpenSession", CallingConvention = CallingConvention.StdCall)]
public static extern int AmsiOpenSession(IntPtr amsiContext, out IntPtr session);
[DllImport("Amsi.dll", EntryPoint = "AmsiCloseSession", CallingConvention = CallingConvention.StdCall)]
public static extern void AmsiCloseSession(IntPtr amsiContext, IntPtr session);
[DllImport("Amsi.dll", EntryPoint = "AmsiScanString", CallingConvention = CallingConvention.StdCall)]
public static extern int AmsiScanString(IntPtr amsiContext, [InAttribute()] [MarshalAsAttribute(UnmanagedType.LPWStr)]string @string, [InAttribute()] [MarshalAsAttribute(UnmanagedType.LPWStr)]string contentName, IntPtr session, out AMSI_RESULT result);
[DllImport("Amsi.dll", EntryPoint = "AmsiScanBuffer", CallingConvention = CallingConvention.StdCall)]
public static extern int AmsiScanBuffer(IntPtr amsiContext, [In] [MarshalAs(UnmanagedType.LPArray)] byte[] buffer, uint length, [In()] [MarshalAs(UnmanagedType.LPWStr)] string contentName, IntPtr session, out AMSI_RESULT result);
//This method apparently exists on MSDN but not in AMSI.dll (version 4.9.10586.0)
[DllImport("Amsi.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.StdCall)]
public static extern bool AmsiResultIsMalware(AMSI_RESULT result);
private void CallAntimalwareScanInterface()
{
IntPtr amsiContext;
IntPtr session;
AMSI_RESULT result = 0;
int returnValue;
returnValue = AmsiInitialize("VirusScanAPI", out amsiContext); //appName is the name of the application consuming the Amsi.dll. Here my project name is VirusScanAPI.
returnValue = AmsiOpenSession(amsiContext, out session);
returnValue = AmsiScanString(amsiContext, @"X5O!P%@AP[4\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*", "EICAR", session, out result); //I've used EICAR test string.
AmsiCloseSession(amsiContext, session);
AmsiUninitialize(amsiContext);
}