How to Safely Retrieve Disk Volume Name Using Go\'s WinAPI GetVolumeInformation Function?

Calling the GetVolumeInformation WinAPI Function from Go To Retrieve Disk Volume Name

In this article, we'll address the issue faced while attempting to call the GetVolumeInformation function from Go. The goal is to obtain the volume name of a specified drive.

To begin, let's understand the problem. The code snippet is based on the specifications of the GetVolumeInformation function as defined in the Windows API. The intention was to retrieve the volume name through the lpVolumeNameBuffer parameter. However, the execution of this code resulted in an unexpected error, indicating a fault in accessing memory.

To resolve this issue, we need to analyze the problematic aspects of the code. One key point is the unsafe.Pointer type used when declaring the variables for the lpVolumeNameBuffer and other string-related parameters.

Unsafe Operations in Go

Go's unsafe package provides low-level access to the underlying system memory, bypassing type safety in order to perform arbitrary read and write operations. While powerful, this capability comes with the caveat of potential memory corruption if used carelessly.

In this case, using unsafe.Pointer to represent the string buffers violates type safety principles. To avoid such issues, we can utilize Go's own string handling capabilities.

Solution

The modified code below takes a safer approach:

<code class="go">package main

import (
    "fmt"
    "syscall"
)

func main() {
    var RootPathName = `C:\`
    var VolumeNameBuffer = make([]uint16, syscall.MAX_PATH+1)
    var nVolumeNameSize = uint32(len(VolumeNameBuffer))
    var VolumeSerialNumber uint32
    var MaximumComponentLength uint32
    var FileSystemFlags uint32
    var FileSystemNameBuffer = make([]uint16, 255)
    var nFileSystemNameSize uint32 = syscall.MAX_PATH + 1

    kernel32, _ := syscall.LoadLibrary("kernel32.dll")
    getVolume, _ := syscall.GetProcAddress(kernel32, "GetVolumeInformationW")

    var nargs uintptr = 8
    ret, _, callErr := syscall.Syscall9(uintptr(getVolume),
        nargs,
        uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(RootPathName))),
        uintptr(unsafe.Pointer(&VolumeNameBuffer[0])),
        uintptr(nVolumeNameSize),
        uintptr(unsafe.Pointer(&VolumeSerialNumber)),
        uintptr(unsafe.Pointer(&MaximumComponentLength)),
        uintptr(unsafe.Pointer(&FileSystemFlags)),
        uintptr(unsafe.Pointer(&FileSystemNameBuffer[0])),
        uintptr(nFileSystemNameSize),
        0)
    fmt.Println(ret, callErr, syscall.UTF16ToString(VolumeNameBuffer))
}</code>

In this version:

• VolumeNameBuffer and FileSystemNameBuffer are declared as slices of uint16 instead of unsafe pointers. This allows Go to handle the memory management and automatic conversion to and from UTF-16 strings.
• We use syscall.StringToUTF16Ptr to convert the RootPathName string to a UTF-16 pointer, ensuring proper string handling according to Windows conventions.

By adhering to type safety practices and utilizing Go's own string handling, we can effectively retrieve the volume name without encountering memory access issues.

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