Add ResolvePath tests (#276)

Add required computestorage APIs to allow for running tests of
`ResolvePath`.

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

internal/computestorage/computestorage.go

@@ -0,0 +1,48 @@
+//go:build windows
+
+package computestorage
+
+import (
+	"fmt"
+
+	"golang.org/x/sys/windows"
+
+	"github.com/Microsoft/go-winio/internal/interop"
+)
+
+//go:generate go run github.com/Microsoft/go-winio/tools/mkwinsyscall -output zsyscall_windows.go computestorage.go
+
+// https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcsformatwritablelayervhd
+//
+//sys hcsFormatWritableLayerVhd(handle windows.Handle) (hr error) = computestorage.HcsFormatWritableLayerVhd?
+
+// FormatWritableLayerVHD formats a virtual disk for use as a writable container layer.
+//
+// If the VHD is not mounted it will be temporarily mounted.
+//
+// NOTE: This API had a breaking change in the operating system after Windows Server 2019.
+// On ws2019 the API expects to get passed a file handle from CreateFile for the vhd that
+// the caller wants to format. On > ws2019, its expected that the caller passes a vhd handle
+// that can be obtained from the virtdisk APIs.
+func FormatWritableLayerVHD(vhdHandle windows.Handle) (err error) {
+	err = hcsFormatWritableLayerVhd(vhdHandle)
+	if err != nil {
+		return fmt.Errorf("failed to format writable layer vhd: %w", err)
+	}
+	return nil
+}
+
+// https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcsgetlayervhdmountpath
+//
+//sys hcsGetLayerVhdMountPath(vhdHandle windows.Handle, mountPath **uint16) (hr error) = computestorage.HcsGetLayerVhdMountPath?
+
+// GetLayerVHDMountPath returns the volume path for a virtual disk of a writable container layer.
+func GetLayerVHDMountPath(vhdHandle windows.Handle) (path string, err error) {
+	var mountPath *uint16
+	err = hcsGetLayerVhdMountPath(vhdHandle, &mountPath)
+	if err != nil {
+		return "", fmt.Errorf("failed to get vhd mount path: %w", err)
+	}
+	path = interop.ConvertAndFreeCoTaskMemString(mountPath)
+	return path, nil
+}

internal/computestorage/doc.go

@@ -0,0 +1 @@
+package computestorage

internal/computestorage/zsyscall_windows.go

@@ -0,0 +1,77 @@
+//go:build windows
+
+// Code generated by 'go generate' using "github.com/Microsoft/go-winio/tools/mkwinsyscall"; DO NOT EDIT.
+
+package computestorage
+
+import (
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+var _ unsafe.Pointer
+
+// Do the interface allocations only once for common
+// Errno values.
+const (
+	errnoERROR_IO_PENDING = 997
+)
+
+var (
+	errERROR_IO_PENDING error = syscall.Errno(errnoERROR_IO_PENDING)
+	errERROR_EINVAL     error = syscall.EINVAL
+)
+
+// errnoErr returns common boxed Errno values, to prevent
+// allocations at runtime.
+func errnoErr(e syscall.Errno) error {
+	switch e {
+	case 0:
+		return errERROR_EINVAL
+	case errnoERROR_IO_PENDING:
+		return errERROR_IO_PENDING
+	}
+	// TODO: add more here, after collecting data on the common
+	// error values see on Windows. (perhaps when running
+	// all.bat?)
+	return e
+}
+
+var (
+	modcomputestorage = windows.NewLazySystemDLL("computestorage.dll")
+
+	procHcsFormatWritableLayerVhd = modcomputestorage.NewProc("HcsFormatWritableLayerVhd")
+	procHcsGetLayerVhdMountPath   = modcomputestorage.NewProc("HcsGetLayerVhdMountPath")
+)
+
+func hcsFormatWritableLayerVhd(handle windows.Handle) (hr error) {
+	hr = procHcsFormatWritableLayerVhd.Find()
+	if hr != nil {
+		return
+	}
+	r0, _, _ := syscall.Syscall(procHcsFormatWritableLayerVhd.Addr(), 1, uintptr(handle), 0, 0)
+	if int32(r0) < 0 {
+		if r0&0x1fff0000 == 0x00070000 {
+			r0 &= 0xffff
+		}
+		hr = syscall.Errno(r0)
+	}
+	return
+}
+
+func hcsGetLayerVhdMountPath(vhdHandle windows.Handle, mountPath **uint16) (hr error) {
+	hr = procHcsGetLayerVhdMountPath.Find()
+	if hr != nil {
+		return
+	}
+	r0, _, _ := syscall.Syscall(procHcsGetLayerVhdMountPath.Addr(), 2, uintptr(vhdHandle), uintptr(unsafe.Pointer(mountPath)), 0)
+	if int32(r0) < 0 {
+		if r0&0x1fff0000 == 0x00070000 {
+			r0 &= 0xffff
+		}
+		hr = syscall.Errno(r0)
+	}
+	return
+}

internal/interop/doc.go

@@ -0,0 +1 @@
+package interop

internal/interop/interop.go

@@ -0,0 +1,25 @@
+//go:build windows
+
+package interop
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+//go:generate go run github.com/Microsoft/go-winio/tools/mkwinsyscall -output zsyscall_windows.go interop.go
+
+//sys coTaskMemFree(buffer unsafe.Pointer) = api_ms_win_core_com_l1_1_0.CoTaskMemFree
+
+func ConvertAndFreeCoTaskMemString(buffer *uint16) string {
+	str := syscall.UTF16ToString((*[1 << 29]uint16)(unsafe.Pointer(buffer))[:])
+	coTaskMemFree(unsafe.Pointer(buffer))
+	return str
+}
+
+func Win32FromHresult(hr uintptr) syscall.Errno {
+	if hr&0x1fff0000 == 0x00070000 {
+		return syscall.Errno(hr & 0xffff)
+	}
+	return syscall.Errno(hr)
+}

internal/interop/zsyscall_windows.go

@@ -0,0 +1,51 @@
+//go:build windows
+
+// Code generated by 'go generate' using "github.com/Microsoft/go-winio/tools/mkwinsyscall"; DO NOT EDIT.
+
+package interop
+
+import (
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+var _ unsafe.Pointer
+
+// Do the interface allocations only once for common
+// Errno values.
+const (
+	errnoERROR_IO_PENDING = 997
+)
+
+var (
+	errERROR_IO_PENDING error = syscall.Errno(errnoERROR_IO_PENDING)
+	errERROR_EINVAL     error = syscall.EINVAL
+)
+
+// errnoErr returns common boxed Errno values, to prevent
+// allocations at runtime.
+func errnoErr(e syscall.Errno) error {
+	switch e {
+	case 0:
+		return errERROR_EINVAL
+	case errnoERROR_IO_PENDING:
+		return errERROR_IO_PENDING
+	}
+	// TODO: add more here, after collecting data on the common
+	// error values see on Windows. (perhaps when running
+	// all.bat?)
+	return e
+}
+
+var (
+	modapi_ms_win_core_com_l1_1_0 = windows.NewLazySystemDLL("api-ms-win-core-com-l1-1-0.dll")
+
+	procCoTaskMemFree = modapi_ms_win_core_com_l1_1_0.NewProc("CoTaskMemFree")
+)
+
+func coTaskMemFree(buffer unsafe.Pointer) {
+	syscall.Syscall(procCoTaskMemFree.Addr(), 1, uintptr(buffer), 0, 0)
+	return
+}

pkg/fs/resolve.go

@@ -20,28 +20,9 @@ import (
 // It is intended to address short-comings of [filepath.EvalSymlinks], which does not work
 // well on Windows.
 func ResolvePath(path string) (string, error) {
-	// We are not able to use builtin Go functionality for opening a directory path:
-	//   - os.Open on a directory returns a os.File where Fd() is a search handle from FindFirstFile.
-	//   - syscall.Open does not provide a way to specify FILE_FLAG_BACKUP_SEMANTICS, which is needed to
-	//     open a directory.
-	//
-	// We could use os.Open if the path is a file, but it's easier to just use the same code for both.
-	// Therefore, we call windows.CreateFile directly.
-	h, err := fs.CreateFile(
-		path,
-		fs.FILE_ANY_ACCESS, // access
-		fs.FILE_SHARE_READ|fs.FILE_SHARE_WRITE|fs.FILE_SHARE_DELETE,
-		nil, // security attributes
-		fs.OPEN_EXISTING,
-		fs.FILE_FLAG_BACKUP_SEMANTICS, // Needed to open a directory handle.
-		fs.NullHandle,                 // template file
-	)
+	h, err := openMetadata(path)
 	if err != nil {
-		return "", &os.PathError{
-			Op:   "CreateFile",
-			Path: path,
-			Err:  err,
-		}
+		return "", err
 	}
 	defer windows.CloseHandle(h) //nolint:errcheck
 
@@ -126,3 +107,33 @@ func ResolvePath(path string) (string, error) {
 	}
 	return rPath, err
 }
+
+// openMetadata takes a path, opens it with only meta-data access, and returns the resulting handle.
+// It works for both file and directory paths.
+func openMetadata(path string) (windows.Handle, error) {
+	// We are not able to use builtin Go functionality for opening a directory path:
+	//   - os.Open on a directory returns a os.File where Fd() is a search handle from FindFirstFile.
+	//   - syscall.Open does not provide a way to specify FILE_FLAG_BACKUP_SEMANTICS, which is needed to
+	//     open a directory.
+	//
+	// We could use os.Open if the path is a file, but it's easier to just use the same code for both.
+	// Therefore, we call windows.CreateFile directly.
+	h, err := fs.CreateFile(
+		path,
+		fs.FILE_ANY_ACCESS,
+		fs.FILE_SHARE_READ|fs.FILE_SHARE_WRITE|fs.FILE_SHARE_DELETE,
+		nil, // security attributes
+		fs.OPEN_EXISTING,
+		fs.FILE_FLAG_BACKUP_SEMANTICS, // Needed to open a directory handle.
+		fs.NullHandle,
+	)
+
+	if err != nil {
+		return 0, &os.PathError{
+			Op:   "CreateFile",
+			Path: path,
+			Err:  err,
+		}
+	}
+	return h, nil
+}

pkg/fs/resolve_test.go

@@ -0,0 +1,222 @@
+//go:build windows
+
+package fs
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"syscall"
+	"testing"
+
+	"golang.org/x/sys/windows"
+
+	"github.com/Microsoft/go-winio/internal/computestorage"
+	"github.com/Microsoft/go-winio/internal/fs"
+	"github.com/Microsoft/go-winio/vhd"
+)
+
+func getWindowsBuildNumber() uint32 {
+	// RtlGetVersion ignores manifest requirements
+	vex := windows.RtlGetVersion()
+	return vex.BuildNumber
+}
+
+func makeSymlink(t *testing.T, oldName string, newName string) {
+	if err := os.Symlink(oldName, newName); err != nil {
+		t.Fatalf("creating symlink: %s", err)
+	}
+}
+
+func getVolumeGUIDPath(t *testing.T, path string) string {
+	h, err := openMetadata(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer windows.CloseHandle(h) //nolint:errcheck
+	final, err := fs.GetFinalPathNameByHandle(h, fs.FILE_NAME_OPENED|fs.VOLUME_NAME_GUID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return final
+}
+
+func openDisk(path string) (windows.Handle, error) {
+	h, err := fs.CreateFile(
+		path,
+		windows.GENERIC_READ|windows.GENERIC_WRITE,
+		fs.FILE_SHARE_READ|fs.FILE_SHARE_WRITE,
+		nil, // security attributes
+		fs.OPEN_EXISTING,
+		windows.FILE_ATTRIBUTE_NORMAL|fs.FILE_FLAG_NO_BUFFERING,
+		fs.NullHandle)
+	if err != nil {
+		return 0, &os.PathError{
+			Op:   "CreateFile",
+			Path: path,
+			Err:  err,
+		}
+	}
+	return h, nil
+}
+
+func formatVHD(vhdHandle windows.Handle) error {
+	h := vhdHandle
+	// Pre-19H1 HcsFormatWritableLayerVhd expects a disk handle.
+	// On newer builds it expects a VHD handle instead.
+	// Open a handle to the VHD's disk object if needed.
+
+	// Windows Server 1903, aka 19H1
+	if getWindowsBuildNumber() < 18362 {
+		diskPath, err := vhd.GetVirtualDiskPhysicalPath(syscall.Handle(h))
+		if err != nil {
+			return err
+		}
+		diskHandle, err := openDisk(diskPath)
+		if err != nil {
+			return err
+		}
+		defer windows.CloseHandle(diskHandle) //nolint:errcheck // cleanup code
+		h = diskHandle
+	}
+	// Formatting a disk directly in Windows is a pain, so we use FormatWritableLayerVhd to do it.
+	// It has a side effect of creating a sandbox directory on the formatted volume, but it's safe
+	// to just ignore that for our purposes here.
+	return computestorage.FormatWritableLayerVHD(h)
+}
+
+// Creates a VHD with a NTFS volume. Returns the volume path.
+func setupVHDVolume(t *testing.T, vhdPath string) string {
+	vhdHandle, err := vhd.CreateVirtualDisk(vhdPath,
+		vhd.VirtualDiskAccessNone, vhd.CreateVirtualDiskFlagNone,
+		&vhd.CreateVirtualDiskParameters{
+			Version: 2,
+			Version2: vhd.CreateVersion2{
+				MaximumSize:      5 * 1024 * 1024 * 1024, // 5GB, thin provisioned
+				BlockSizeInBytes: 1 * 1024 * 1024,        // 1MB
+			},
+		})
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() {
+		_ = windows.CloseHandle(windows.Handle(vhdHandle))
+	})
+	if err := vhd.AttachVirtualDisk(vhdHandle, vhd.AttachVirtualDiskFlagNone, &vhd.AttachVirtualDiskParameters{Version: 1}); err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() {
+		if err := vhd.DetachVirtualDisk(vhdHandle); err != nil {
+			t.Fatal(err)
+		}
+	})
+	if err := formatVHD(windows.Handle(vhdHandle)); err != nil {
+		t.Fatalf("failed to format VHD: %s", err)
+	}
+	// Get the path for the volume that was just created on the disk.
+	volumePath, err := computestorage.GetLayerVHDMountPath(windows.Handle(vhdHandle))
+	if err != nil {
+		t.Fatal(err)
+	}
+	return volumePath
+}
+
+func writeFile(t *testing.T, path string, content []byte) {
+	if err := os.WriteFile(path, content, 0644); err != nil { //nolint:gosec // test file, can have permissive mode
+		t.Fatal(err)
+	}
+}
+
+func mountVolume(t *testing.T, volumePath string, mountPoint string) {
+	// Create the mount point directory.
+	if err := os.Mkdir(mountPoint, 0644); err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() {
+		if err := os.Remove(mountPoint); err != nil {
+			t.Fatal(err)
+		}
+	})
+	// Volume path must end in a slash.
+	if !strings.HasSuffix(volumePath, `\`) {
+		volumePath += `\`
+	}
+	volumePathU16, err := windows.UTF16PtrFromString(volumePath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Mount point must end in a slash.
+	if !strings.HasSuffix(mountPoint, `\`) {
+		mountPoint += `\`
+	}
+	mountPointU16, err := windows.UTF16PtrFromString(mountPoint)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := windows.SetVolumeMountPoint(mountPointU16, volumePathU16); err != nil {
+		t.Fatalf("failed to mount %s onto %s: %s", volumePath, mountPoint, err)
+	}
+	t.Cleanup(func() {
+		if err := windows.DeleteVolumeMountPoint(mountPointU16); err != nil {
+			t.Fatalf("failed to delete mount on %s: %s", mountPoint, err)
+		}
+	})
+}
+
+func TestResolvePath(t *testing.T) {
+	if !windows.GetCurrentProcessToken().IsElevated() {
+		t.Fatal("test requires elevated privileges")
+	}
+
+	// Set up some data to be used by the test cases.
+	volumePathC := getVolumeGUIDPath(t, `C:\`)
+	dir := t.TempDir()
+
+	makeSymlink(t, `C:\windows`, filepath.Join(dir, "lnk1"))
+	makeSymlink(t, `\\localhost\c$\windows`, filepath.Join(dir, "lnk2"))
+
+	volumePathVHD1 := setupVHDVolume(t, filepath.Join(dir, "foo.vhdx"))
+	writeFile(t, filepath.Join(volumePathVHD1, "data.txt"), []byte("test content 1"))
+	makeSymlink(t, filepath.Join(volumePathVHD1, "data.txt"), filepath.Join(dir, "lnk3"))
+
+	volumePathVHD2 := setupVHDVolume(t, filepath.Join(dir, "bar.vhdx"))
+	writeFile(t, filepath.Join(volumePathVHD2, "data.txt"), []byte("test content 2"))
+	makeSymlink(t, filepath.Join(volumePathVHD2, "data.txt"), filepath.Join(dir, "lnk4"))
+	mountVolume(t, volumePathVHD2, filepath.Join(dir, "mnt"))
+
+	for _, tc := range []struct {
+		input       string
+		expected    string
+		description string
+	}{
+		{`C:\windows`, volumePathC + `Windows`, "local path"},
+		{filepath.Join(dir, "lnk1"), volumePathC + `Windows`, "symlink to local path"},
+		{`\\localhost\c$\windows`, `\\localhost\c$\Windows`, "UNC path"},
+		{filepath.Join(dir, "lnk2"), `\\localhost\c$\Windows`, "symlink to UNC path"},
+		{filepath.Join(volumePathVHD1, "data.txt"), filepath.Join(volumePathVHD1, "data.txt"), "volume with no mount point"},
+		{filepath.Join(dir, "lnk3"), filepath.Join(volumePathVHD1, "data.txt"), "symlink to volume with no mount point"},
+		{filepath.Join(dir, "mnt", "data.txt"), filepath.Join(volumePathVHD2, "data.txt"), "volume with mount point"},
+		{filepath.Join(dir, "lnk4"), filepath.Join(volumePathVHD2, "data.txt"), "symlink to volume with mount point"},
+	} {
+		t.Run(tc.description, func(t *testing.T) {
+			actual, err := ResolvePath(tc.input)
+			if err != nil {
+				t.Fatalf("resolvePath should return no error, but %v", err)
+			}
+			if actual != tc.expected {
+				t.Fatalf("expected %v but got %v", tc.expected, actual)
+			}
+			// Make sure EvalSymlinks works with the resolved path, as an extra safety measure.
+			p, err := filepath.EvalSymlinks(actual)
+			if err != nil {
+				t.Fatalf("EvalSymlinks should return no error, but %v", err)
+			}
+			// As an extra-extra safety, check that resolvePath(x) == EvalSymlinks(resolvePath(x)).
+			// EvalSymlinks normalizes UNC path casing, but resolvePath may not, so compare with
+			// case-insensitivity here.
+			if !strings.EqualFold(actual, p) {
+				t.Fatalf("EvalSymlinks should resolve to the same path. Expected %v but got %v", actual, p)
+			}
+		})
+	}
+}