syncthing/lib/fs/basicfs_windows.go
Jakob Borg dd92b2b8f4
all: Tweak error creation (#6391)
- In the few places where we wrap errors, use the new Go 1.13 "%w"
  construction instead of %s or %v.

- Where we create errors with constant strings, consistently use
  errors.New and not fmt.Errorf.

- Remove capitalization from errors in the few places where we had that.
2020-03-03 22:40:00 +01:00

326 lines
8.7 KiB
Go

// Copyright (C) 2014 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
// +build windows
package fs
import (
"bytes"
"errors"
"os"
"path/filepath"
"strings"
"syscall"
"unsafe"
)
var errNotSupported = errors.New("symlinks not supported")
func (BasicFilesystem) SymlinksSupported() bool {
return false
}
func (BasicFilesystem) ReadSymlink(path string) (string, error) {
return "", errNotSupported
}
func (BasicFilesystem) CreateSymlink(target, name string) error {
return errNotSupported
}
// Required due to https://github.com/golang/go/issues/10900
func (f *BasicFilesystem) mkdirAll(path string, perm os.FileMode) error {
// Fast path: if we can tell whether path is a directory or file, stop with success or error.
dir, err := os.Stat(path)
if err == nil {
if dir.IsDir() {
return nil
}
return &os.PathError{
Op: "mkdir",
Path: path,
Err: syscall.ENOTDIR,
}
}
// Slow path: make sure parent exists and then call Mkdir for path.
i := len(path)
for i > 0 && IsPathSeparator(path[i-1]) { // Skip trailing path separator.
i--
}
j := i
for j > 0 && !IsPathSeparator(path[j-1]) { // Scan backward over element.
j--
}
if j > 1 {
// Create parent
parent := path[0 : j-1]
if parent != filepath.VolumeName(parent) {
err = f.mkdirAll(parent, perm)
if err != nil {
return err
}
}
}
// Parent now exists; invoke Mkdir and use its result.
err = os.Mkdir(path, perm)
if err != nil {
// Handle arguments like "foo/." by
// double-checking that directory doesn't exist.
dir, err1 := os.Lstat(path)
if err1 == nil && dir.IsDir() {
return nil
}
return err
}
return nil
}
func (f *BasicFilesystem) Unhide(name string) error {
name, err := f.rooted(name)
if err != nil {
return err
}
p, err := syscall.UTF16PtrFromString(name)
if err != nil {
return err
}
attrs, err := syscall.GetFileAttributes(p)
if err != nil {
return err
}
attrs &^= syscall.FILE_ATTRIBUTE_HIDDEN
return syscall.SetFileAttributes(p, attrs)
}
func (f *BasicFilesystem) Hide(name string) error {
name, err := f.rooted(name)
if err != nil {
return err
}
p, err := syscall.UTF16PtrFromString(name)
if err != nil {
return err
}
attrs, err := syscall.GetFileAttributes(p)
if err != nil {
return err
}
attrs |= syscall.FILE_ATTRIBUTE_HIDDEN
return syscall.SetFileAttributes(p, attrs)
}
func (f *BasicFilesystem) Roots() ([]string, error) {
kernel32, err := syscall.LoadDLL("kernel32.dll")
if err != nil {
return nil, err
}
getLogicalDriveStringsHandle, err := kernel32.FindProc("GetLogicalDriveStringsA")
if err != nil {
return nil, err
}
buffer := [1024]byte{}
bufferSize := uint32(len(buffer))
hr, _, _ := getLogicalDriveStringsHandle.Call(uintptr(unsafe.Pointer(&bufferSize)), uintptr(unsafe.Pointer(&buffer)))
if hr == 0 {
return nil, errors.New("syscall failed")
}
var drives []string
parts := bytes.Split(buffer[:], []byte{0})
for _, part := range parts {
if len(part) == 0 {
break
}
drives = append(drives, string(part))
}
return drives, nil
}
// unrootedChecked returns the path relative to the folder root (same as
// unrooted) or an error if the given path is not a subpath and handles the
// special case when the given path is the folder root without a trailing
// pathseparator.
func (f *BasicFilesystem) unrootedChecked(absPath string, roots []string) (string, error) {
absPath = f.resolveWin83(absPath)
lowerAbsPath := UnicodeLowercase(absPath)
for _, root := range roots {
lowerRoot := UnicodeLowercase(root)
if lowerAbsPath+string(PathSeparator) == lowerRoot {
return ".", nil
}
if strings.HasPrefix(lowerAbsPath, lowerRoot) {
return rel(absPath, root), nil
}
}
return "", f.newErrWatchEventOutsideRoot(lowerAbsPath, roots)
}
func rel(path, prefix string) string {
lowerRel := strings.TrimPrefix(strings.TrimPrefix(UnicodeLowercase(path), UnicodeLowercase(prefix)), string(PathSeparator))
return path[len(path)-len(lowerRel):]
}
func (f *BasicFilesystem) resolveWin83(absPath string) string {
if !isMaybeWin83(absPath) {
return absPath
}
if in, err := syscall.UTF16FromString(absPath); err == nil {
out := make([]uint16, 4*len(absPath)) // *2 for UTF16 and *2 to double path length
if n, err := syscall.GetLongPathName(&in[0], &out[0], uint32(len(out))); err == nil {
if n <= uint32(len(out)) {
return syscall.UTF16ToString(out[:n])
}
out = make([]uint16, n)
if _, err = syscall.GetLongPathName(&in[0], &out[0], n); err == nil {
return syscall.UTF16ToString(out)
}
}
}
// Failed getting the long path. Return the part of the path which is
// already a long path.
lowerRoot := UnicodeLowercase(f.root)
for absPath = filepath.Dir(absPath); strings.HasPrefix(UnicodeLowercase(absPath), lowerRoot); absPath = filepath.Dir(absPath) {
if !isMaybeWin83(absPath) {
return absPath
}
}
return f.root
}
func isMaybeWin83(absPath string) bool {
if !strings.Contains(absPath, "~") {
return false
}
if strings.Contains(filepath.Dir(absPath), "~") {
return true
}
return strings.Contains(strings.TrimPrefix(filepath.Base(absPath), WindowsTempPrefix), "~")
}
func getFinalPathName(in string) (string, error) {
// Return the normalized path
// Wrap the call to GetFinalPathNameByHandleW
// The string returned by this function uses the \?\ syntax
// Implies GetFullPathName + GetLongPathName
kernel32, err := syscall.LoadDLL("kernel32.dll")
if err != nil {
return "", err
}
GetFinalPathNameByHandleW, err := kernel32.FindProc("GetFinalPathNameByHandleW")
// https://github.com/golang/go/blob/ff048033e4304898245d843e79ed1a0897006c6d/src/internal/syscall/windows/syscall_windows.go#L303
if err != nil {
return "", err
}
inPath, err := syscall.UTF16PtrFromString(in)
if err != nil {
return "", err
}
// Get a file handler
h, err := syscall.CreateFile(inPath,
syscall.GENERIC_READ,
syscall.FILE_SHARE_READ,
nil,
syscall.OPEN_EXISTING,
uint32(syscall.FILE_FLAG_BACKUP_SEMANTICS),
0)
if err != nil {
return "", err
}
defer syscall.CloseHandle(h)
// Call GetFinalPathNameByHandleW
var VOLUME_NAME_DOS uint32 = 0x0 // not yet defined in syscall
var bufSize uint32 = syscall.MAX_PATH // 260
for i := 0; i < 2; i++ {
buf := make([]uint16, bufSize)
var ret uintptr
ret, _, err = GetFinalPathNameByHandleW.Call(
uintptr(h), // HANDLE hFile
uintptr(unsafe.Pointer(&buf[0])), // LPWSTR lpszFilePath
uintptr(bufSize), // DWORD cchFilePath
uintptr(VOLUME_NAME_DOS), // DWORD dwFlags
)
// The returned value is the actual length of the norm path
// After Win 10 build 1607, MAX_PATH limitations have been removed
// so it is necessary to check newBufSize
newBufSize := uint32(ret) + 1
if ret == 0 || newBufSize > bufSize*100 {
break
}
if newBufSize <= bufSize {
return syscall.UTF16ToString(buf), nil
}
bufSize = newBufSize
}
return "", err
}
func evalSymlinks(in string) (string, error) {
out, err := filepath.EvalSymlinks(in)
if err != nil && strings.HasPrefix(in, `\\?\`) {
// Try again without the `\\?\` prefix
out, err = filepath.EvalSymlinks(in[4:])
}
if err != nil {
// Try to get a normalized path from Win-API
var err1 error
out, err1 = getFinalPathName(in)
if err1 != nil {
return "", err // return the prior error
}
// Trim UNC prefix, equivalent to
// https://github.com/golang/go/blob/2396101e0590cb7d77556924249c26af0ccd9eff/src/os/file_windows.go#L470
if strings.HasPrefix(out, `\\?\UNC\`) {
out = `\` + out[7:] // path like \\server\share\...
} else {
out = strings.TrimPrefix(out, `\\?\`)
}
}
return longFilenameSupport(out), nil
}
// watchPaths adjust the folder root for use with the notify backend and the
// corresponding absolute path to be passed to notify to watch name.
func (f *BasicFilesystem) watchPaths(name string) (string, []string, error) {
root, err := evalSymlinks(f.root)
if err != nil {
return "", nil, err
}
// Remove `\\?\` prefix if the path is just a drive letter as a dirty
// fix for https://github.com/syncthing/syncthing/issues/5578
if filepath.Clean(name) == "." && len(root) <= 7 && len(root) > 4 && root[:4] == `\\?\` {
root = root[4:]
}
absName, err := rooted(name, root)
if err != nil {
return "", nil, err
}
roots := []string{f.resolveWin83(root)}
absName = f.resolveWin83(absName)
// Events returned from fs watching are all over the place, so allow
// both the user's input and the result of "canonicalizing" the path.
if roots[0] != f.root {
roots = append(roots, f.root)
}
return filepath.Join(absName, "..."), roots, nil
}