// +build windows
package system
import (
"os"
"path/filepath"
"regexp"
"strconv"
"strings"
"sync"
"syscall"
"time"
"unsafe"
winio "github.com/Microsoft/go-winio"
"golang.org/x/sys/windows"
)
const (
// SddlAdministratorsLocalSystem is local administrators plus NT AUTHORITY\System
SddlAdministratorsLocalSystem = "D:P(A;OICI;GA;;;BA)(A;OICI;GA;;;SY)"
// SddlNtvmAdministratorsLocalSystem is NT VIRTUAL MACHINE\Virtual Machines plus local administrators plus NT AUTHORITY\System
SddlNtvmAdministratorsLocalSystem = "D:P(A;OICI;GA;;;S-1-5-83-0)(A;OICI;GA;;;BA)(A;OICI;GA;;;SY)"
)
// MkdirAllWithACL is a wrapper for MkdirAll that creates a directory
// with an appropriate SDDL defined ACL.
func MkdirAllWithACL(path string, perm os.FileMode, sddl string) error {
return mkdirall(path, true, sddl)
}
// MkdirAll implementation that is volume path aware for Windows.
func MkdirAll(path string, _ os.FileMode, sddl string) error {
return mkdirall(path, false, sddl)
}
// mkdirall is a custom version of os.MkdirAll modified for use on Windows
// so that it is both volume path aware, and can create a directory with
// a DACL.
func mkdirall(path string, applyACL bool, sddl string) error {
if re := regexp.MustCompile(`^\\\\\?\\Volume{[a-z0-9-]+}$`); re.MatchString(path) {
return nil
}
// The rest of this method is largely copied from os.MkdirAll and should be kept
// as-is to ensure compatibility.
// 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 && os.IsPathSeparator(path[i-1]) { // Skip trailing path separator.
i--
}
j := i
for j > 0 && !os.IsPathSeparator(path[j-1]) { // Scan backward over element.
j--
}
if j > 1 {
// Create parent
err = mkdirall(path[0:j-1], false, sddl)
if err != nil {
return err
}
}
// Parent now exists; invoke os.Mkdir or mkdirWithACL and use its result.
if applyACL {
err = mkdirWithACL(path, sddl)
} else {
err = os.Mkdir(path, 0)
}
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
}
// mkdirWithACL creates a new directory. If there is an error, it will be of
// type *PathError. .
//
// This is a modified and combined version of os.Mkdir and windows.Mkdir
// in golang to cater for creating a directory am ACL permitting full
// access, with inheritance, to any subfolder/file for Built-in Administrators
// and Local System.
func mkdirWithACL(name string, sddl string) error {
sa := windows.SecurityAttributes{Length: 0}
sd, err := winio.SddlToSecurityDescriptor(sddl)
if err != nil {
return &os.PathError{Op: "mkdir", Path: name, Err: err}
}
sa.Length = uint32(unsafe.Sizeof(sa))
sa.InheritHandle = 1
sa.SecurityDescriptor = uintptr(unsafe.Pointer(&sd[0]))
namep, err := windows.UTF16PtrFromString(name)
if err != nil {
return &os.PathError{Op: "mkdir", Path: name, Err: err}
}
e := windows.CreateDirectory(namep, &sa)
if e != nil {
return &os.PathError{Op: "mkdir", Path: name, Err: e}
}
return nil
}
// IsAbs is a platform-specific wrapper for filepath.IsAbs. On Windows,
// golang filepath.IsAbs does not consider a path \windows\system32 as absolute
// as it doesn't start with a drive-letter/colon combination. However, in
// docker we need to verify things such as WORKDIR /windows/system32 in
// a Dockerfile (which gets translated to \windows\system32 when being processed
// by the daemon. This SHOULD be treated as absolute from a docker processing
// perspective.
func IsAbs(path string) bool {
if !filepath.IsAbs(path) {
if !strings.HasPrefix(path, string(os.PathSeparator)) {
return false
}
}
return true
}
// The origin of the functions below here are the golang OS and windows packages,
// slightly modified to only cope with files, not directories due to the
// specific use case.
//
// The alteration is to allow a file on Windows to be opened with
// FILE_FLAG_SEQUENTIAL_SCAN (particular for docker load), to avoid eating
// the standby list, particularly when accessing large files such as layer.tar.
// CreateSequential creates the named file with mode 0666 (before umask), truncating
// it if it already exists. If successful, methods on the returned
// File can be used for I/O; the associated file descriptor has mode
// O_RDWR.
// If there is an error, it will be of type *PathError.
func CreateSequential(name string) (*os.File, error) {
return OpenFileSequential(name, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0)
}
// OpenSequential opens the named file for reading. If successful, methods on
// the returned file can be used for reading; the associated file
// descriptor has mode O_RDONLY.
// If there is an error, it will be of type *PathError.
func OpenSequential(name string) (*os.File, error) {
return OpenFileSequential(name, os.O_RDONLY, 0)
}
// OpenFileSequential is the generalized open call; most users will use Open
// or Create instead.
// If there is an error, it will be of type *PathError.
func OpenFileSequential(name string, flag int, _ os.FileMode) (*os.File, error) {
if name == "" {
return nil, &os.PathError{Op: "open", Path: name, Err: syscall.ENOENT}
}
r, errf := windowsOpenFileSequential(name, flag, 0)
if errf == nil {
return r, nil
}
return nil, &os.PathError{Op: "open", Path: name, Err: errf}
}
func windowsOpenFileSequential(name string, flag int, _ os.FileMode) (file *os.File, err error) {
r, e := windowsOpenSequential(name, flag|windows.O_CLOEXEC, 0)
if e != nil {
return nil, e
}
return os.NewFile(uintptr(r), name), nil
}
func makeInheritSa() *windows.SecurityAttributes {
var sa windows.SecurityAttributes
sa.Length = uint32(unsafe.Sizeof(sa))
sa.InheritHandle = 1
return &sa
}
func windowsOpenSequential(path string, mode int, _ uint32) (fd windows.Handle, err error) {
if len(path) == 0 {
return windows.InvalidHandle, windows.ERROR_FILE_NOT_FOUND
}
pathp, err := windows.UTF16PtrFromString(path)
if err != nil {
return windows.InvalidHandle, err
}
var access uint32
switch mode & (windows.O_RDONLY | windows.O_WRONLY | windows.O_RDWR) {
case windows.O_RDONLY:
access = windows.GENERIC_READ
case windows.O_WRONLY:
access = windows.GENERIC_WRITE
case windows.O_RDWR:
access = windows.GENERIC_READ | windows.GENERIC_WRITE
}
if mode&windows.O_CREAT != 0 {
access |= windows.GENERIC_WRITE
}
if mode&windows.O_APPEND != 0 {
access &^= windows.GENERIC_WRITE
access |= windows.FILE_APPEND_DATA
}
sharemode := uint32(windows.FILE_SHARE_READ | windows.FILE_SHARE_WRITE)
var sa *windows.SecurityAttributes
if mode&windows.O_CLOEXEC == 0 {
sa = makeInheritSa()
}
var createmode uint32
switch {
case mode&(windows.O_CREAT|windows.O_EXCL) == (windows.O_CREAT | windows.O_EXCL):
createmode = windows.CREATE_NEW
case mode&(windows.O_CREAT|windows.O_TRUNC) == (windows.O_CREAT | windows.O_TRUNC):
createmode = windows.CREATE_ALWAYS
case mode&windows.O_CREAT == windows.O_CREAT:
createmode = windows.OPEN_ALWAYS
case mode&windows.O_TRUNC == windows.O_TRUNC:
createmode = windows.TRUNCATE_EXISTING
default:
createmode = windows.OPEN_EXISTING
}
// Use FILE_FLAG_SEQUENTIAL_SCAN rather than FILE_ATTRIBUTE_NORMAL as implemented in golang.
//https://msdn.microsoft.com/en-us/library/windows/desktop/aa363858(v=vs.85).aspx
const fileFlagSequentialScan = 0x08000000 // FILE_FLAG_SEQUENTIAL_SCAN
h, e := windows.CreateFile(pathp, access, sharemode, sa, createmode, fileFlagSequentialScan, 0)
return h, e
}
// Helpers for TempFileSequential
var rand uint32
var randmu sync.Mutex
func reseed() uint32 {
return uint32(time.Now().UnixNano() + int64(os.Getpid()))
}
func nextSuffix() string {
randmu.Lock()
r := rand
if r == 0 {
r = reseed()
}
r = r*1664525 + 1013904223 // constants from Numerical Recipes
rand = r
randmu.Unlock()
return strconv.Itoa(int(1e9 + r%1e9))[1:]
}
// TempFileSequential is a copy of ioutil.TempFile, modified to use sequential
// file access. Below is the original comment from golang:
// TempFile creates a new temporary file in the directory dir
// with a name beginning with prefix, opens the file for reading
// and writing, and returns the resulting *os.File.
// If dir is the empty string, TempFile uses the default directory
// for temporary files (see os.TempDir).
// Multiple programs calling TempFile simultaneously
// will not choose the same file. The caller can use f.Name()
// to find the pathname of the file. It is the caller's responsibility
// to remove the file when no longer needed.
func TempFileSequential(dir, prefix string) (f *os.File, err error) {
if dir == "" {
dir = os.TempDir()
}
nconflict := 0
for i := 0; i < 10000; i++ {
name := filepath.Join(dir, prefix+nextSuffix())
f, err = OpenFileSequential(name, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0600)
if os.IsExist(err) {
if nconflict++; nconflict > 10 {
randmu.Lock()
rand = reseed()
randmu.Unlock()
}
continue
}
break
}
return
}