Use DeviceIoControl to enumerate shadow copies

shadow-copy-deviceiocontrol.ps1

<#
This does not work due to the unsupported CTL_CODE used in DeviceIoControl

DeviceIoControl() get buffer size failed - Incorrect function (Win32 ErrorCode 1 - 0x00000001)
At C:\temp\enumerate_snapshots.ps1:145 char:1
+ Get-ShadowCopy -Path "\\localhost\c$"
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Write-Error], WriteErrorException
    + FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException,Get-ShadowCopy
#>

Add-Type -TypeDefinition @'
using Microsoft.Win32.SafeHandles;
using System;
using System.IO;
using System.Runtime.InteropServices;
using System.Security.AccessControl;

namespace Win32
{
    public class NativeHelpers
    {
        // Usually define the structs for the output value. DeviceIoControl lpOutBuffer would typically
        // align to one of these structures but I couldn't find the docs for FSCTL_SRV_ENUMERATE_SNAPSHOTS
        [StructLayout(LayoutKind.Sequential)]
        public struct SNAPSHOT_STRUCT
        {
        }
    }

    public class NativeMethods
    {
        [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
        public static extern SafeFileHandle CreateFileW(
            string lpFileName,
            FileSystemRights dwDesiredAccess,
            FileShare dwShareMode,
            IntPtr lpSecurityAttributes,
            FileMode dwCreationDisposition,
            UInt32 dwFlagsAndAttributes,
            IntPtr hTemplateFile);
        
        [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
        public static extern bool DeviceIoControl(
            SafeFileHandle hDevice,
            UInt32 dwIoControlCode,
            IntPtr lpInBuffer,
            UInt32 nInBufferSize,
            IntPtr lpOutBuffer,
            UInt32 nOutBufferSize,
            out UInt32 lpBytesReturned,
            IntPtr lpOverlapped);
    }
}
'@

Function Get-LastWin32ExceptionMessage {
    param([int]$ErrorCode)
    $Exp = New-Object -TypeName System.ComponentModel.Win32Exception -ArgumentList $ErrorCode
    $ExpMsg = "{0} (Win32 ErrorCode {1} - 0x{1:X8})" -f $Exp.Message, $ErrorCode
    return $ExpMsg
}

Function Get-ShadowCopy {
    param (
        [Parameter(Mandatory = $true)]
        [System.String]
        $Path
    )
    # Not needed but I like to have human readable names instead of hex values when using them
    $FSCTL_SRV_ENUMERATE_SNAPSHOTS = 0x00144064
    $FILE_FLAG_BACKUP_SEMANTICS = 0x02000000

    # Create a SafeFileHandle of the path specified and make sure it is valid
    $Handle = [Win32.NativeMethods]::CreateFileW(
        $Path,
        [System.Security.AccessControl.FileSystemRights]"ListDirectory, ReadAttributes, Synchronize",
        [System.IO.FileShare]::ReadWrite,
        [System.IntPtr]::Zero,
        [System.IO.FileMode]::Open,
        $FILE_FLAG_BACKUP_SEMANTICS,
        [System.IntPtr]::Zero
    )
    if ($Handle.IsInvalid) {
        $LastError = [System.Runtime.InteropServices.Marshal]::GetLastWin32Error()
        $Msg = Get-LastWin32ExceptionMessage -ErrorCode $LastError
        Write-Error -Message "CreateFileW($Path) failed - $Msg"
        return
    }

    try {
        # Create an empty output buffer and get the size required
        $OutBuffer = [System.IntPtr]::Zero
        $OutBufferSize = 0
        $Result = [Win32.NativeMethods]::DeviceIoControl(
            $Handle,
            $FSCTL_SRV_ENUMERATE_SNAPSHOTS,
            [System.IntPtr]::Zero,
            0,
            $OutBuffer,
            $OutBufferSize,
            [Ref]$OutBufferSize,
            [System.IntPtr]::Zero
        )

        # If we didn't receive ERROR_INSUFFICIENT_BUFFER then fail, something else went wrong
        $LastError = [System.Runtime.InteropServices.Marshal]::GetLastWin32Error()
        if (-not $Result -and $LastError -ne 0x0000007A) {  # ERROR_INSUFFICIENT_BUFFER
            $Msg = Get-LastWin32ExceptionMessage -ErrorCode $LastError
            Write-Error -Message "DeviceIoControl() get buffer size failed - $Msg"
            return
        }

        ### ANYTHING BELOW HERE IS UNTESTED BECAUSE OF THE INVALID FUNCTION ERROR ###

        # Allocate the output buffer pointer with the size required
        $OutBuffer = [System.Runtime.InteropServices.Marshal]::AllocHGlobal($OutBufferSize)
        try {
            # Call DeviceIoControl once again but with out allocated output buffer
            $Result = [Win32.NativeMethods]::DeviceIoControl(
                $Handle,
                $FSCTL_SRV_ENUMERATE_SNAPSHOTS,
                [System.IntPtr]::Zero,
                0,
                $OutBuffer,
                $OutBufferSize,
                [Ref]$OutBufferSize,
                [System.IntPtr]::Zero
            )
            if (-not $Result) {
                $LastError = [System.Runtime.InteropServices.Marshal]::GetLastWin32Error()
                $Msg = Get-LastWin32ExceptionMessage -ErrorCode $LastError
                Write-Error -Message "DeviceIoControl() failed - $Msg"
                return
            }

            # Convert the pointer to the defined PInvoke structure. This could vary depending on the output buffer
            # defined by the CTL CODE
            $Snapshots = [System.Runtime.InteropServices.Marshal]::PtrToStructure($OutBuffer,
                [Type][Win32.NativeHelpers.SNAPSHOT_STRUCT])

            # Now do what must be done with the output structure
        } finally {
            # Ensure we free the unmanaged memory
            [System.Runtime.InteropServices.Marshal]::FreeHGlobal($OutBuffer)
        }
    } finally {
        # Technically not needed as a SafeFileHandle will auto dispose once the GC is called but it's good to be
        # explicit about these things
        $Handle.Dispose()
    }
}

Get-ShadowCopy -Path "\\localhost\c$"