292 lines
8.9 KiB
Go
292 lines
8.9 KiB
Go
package system // import "github.com/docker/docker/pkg/system"
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import (
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"os"
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"path/filepath"
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"regexp"
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"strconv"
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"strings"
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"sync"
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"syscall"
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"time"
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"unsafe"
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"golang.org/x/sys/windows"
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)
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const (
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// SddlAdministratorsLocalSystem is local administrators plus NT AUTHORITY\System
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SddlAdministratorsLocalSystem = "D:P(A;OICI;GA;;;BA)(A;OICI;GA;;;SY)"
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)
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// MkdirAllWithACL is a wrapper for MkdirAll that creates a directory
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// with an appropriate SDDL defined ACL.
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func MkdirAllWithACL(path string, perm os.FileMode, sddl string) error {
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return mkdirall(path, true, sddl)
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}
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// MkdirAll implementation that is volume path aware for Windows. It can be used
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// as a drop-in replacement for os.MkdirAll()
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func MkdirAll(path string, _ os.FileMode) error {
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return mkdirall(path, false, "")
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}
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// mkdirall is a custom version of os.MkdirAll modified for use on Windows
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// so that it is both volume path aware, and can create a directory with
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// a DACL.
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func mkdirall(path string, applyACL bool, sddl string) error {
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if re := regexp.MustCompile(`^\\\\\?\\Volume{[a-z0-9-]+}$`); re.MatchString(path) {
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return nil
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}
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// The rest of this method is largely copied from os.MkdirAll and should be kept
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// as-is to ensure compatibility.
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// Fast path: if we can tell whether path is a directory or file, stop with success or error.
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dir, err := os.Stat(path)
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if err == nil {
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if dir.IsDir() {
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return nil
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}
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return &os.PathError{
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Op: "mkdir",
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Path: path,
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Err: syscall.ENOTDIR,
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}
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}
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// Slow path: make sure parent exists and then call Mkdir for path.
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i := len(path)
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for i > 0 && os.IsPathSeparator(path[i-1]) { // Skip trailing path separator.
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i--
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}
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j := i
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for j > 0 && !os.IsPathSeparator(path[j-1]) { // Scan backward over element.
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j--
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}
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if j > 1 {
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// Create parent
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err = mkdirall(path[0:j-1], false, sddl)
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if err != nil {
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return err
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}
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}
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// Parent now exists; invoke os.Mkdir or mkdirWithACL and use its result.
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if applyACL {
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err = mkdirWithACL(path, sddl)
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} else {
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err = os.Mkdir(path, 0)
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}
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if err != nil {
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// Handle arguments like "foo/." by
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// double-checking that directory doesn't exist.
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dir, err1 := os.Lstat(path)
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if err1 == nil && dir.IsDir() {
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return nil
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}
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return err
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}
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return nil
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}
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// mkdirWithACL creates a new directory. If there is an error, it will be of
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// type *PathError. .
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//
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// This is a modified and combined version of os.Mkdir and windows.Mkdir
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// in golang to cater for creating a directory am ACL permitting full
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// access, with inheritance, to any subfolder/file for Built-in Administrators
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// and Local System.
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func mkdirWithACL(name string, sddl string) error {
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sa := windows.SecurityAttributes{Length: 0}
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sd, err := windows.SecurityDescriptorFromString(sddl)
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if err != nil {
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return &os.PathError{Op: "mkdir", Path: name, Err: err}
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}
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sa.Length = uint32(unsafe.Sizeof(sa))
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sa.InheritHandle = 1
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sa.SecurityDescriptor = sd
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namep, err := windows.UTF16PtrFromString(name)
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if err != nil {
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return &os.PathError{Op: "mkdir", Path: name, Err: err}
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}
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e := windows.CreateDirectory(namep, &sa)
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if e != nil {
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return &os.PathError{Op: "mkdir", Path: name, Err: e}
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}
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return nil
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}
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// IsAbs is a platform-specific wrapper for filepath.IsAbs. On Windows,
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// golang filepath.IsAbs does not consider a path \windows\system32 as absolute
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// as it doesn't start with a drive-letter/colon combination. However, in
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// docker we need to verify things such as WORKDIR /windows/system32 in
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// a Dockerfile (which gets translated to \windows\system32 when being processed
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// by the daemon. This SHOULD be treated as absolute from a docker processing
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// perspective.
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func IsAbs(path string) bool {
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if filepath.IsAbs(path) || strings.HasPrefix(path, string(os.PathSeparator)) {
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return true
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}
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return false
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}
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// The origin of the functions below here are the golang OS and windows packages,
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// slightly modified to only cope with files, not directories due to the
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// specific use case.
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//
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// The alteration is to allow a file on Windows to be opened with
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// FILE_FLAG_SEQUENTIAL_SCAN (particular for docker load), to avoid eating
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// the standby list, particularly when accessing large files such as layer.tar.
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// CreateSequential creates the named file with mode 0666 (before umask), truncating
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// it if it already exists. If successful, methods on the returned
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// File can be used for I/O; the associated file descriptor has mode
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// O_RDWR.
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// If there is an error, it will be of type *PathError.
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func CreateSequential(name string) (*os.File, error) {
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return OpenFileSequential(name, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0)
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}
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// OpenSequential opens the named file for reading. If successful, methods on
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// the returned file can be used for reading; the associated file
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// descriptor has mode O_RDONLY.
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// If there is an error, it will be of type *PathError.
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func OpenSequential(name string) (*os.File, error) {
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return OpenFileSequential(name, os.O_RDONLY, 0)
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}
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// OpenFileSequential is the generalized open call; most users will use Open
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// or Create instead.
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// If there is an error, it will be of type *PathError.
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func OpenFileSequential(name string, flag int, _ os.FileMode) (*os.File, error) {
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if name == "" {
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return nil, &os.PathError{Op: "open", Path: name, Err: syscall.ENOENT}
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}
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r, errf := windowsOpenFileSequential(name, flag, 0)
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if errf == nil {
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return r, nil
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}
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return nil, &os.PathError{Op: "open", Path: name, Err: errf}
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}
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func windowsOpenFileSequential(name string, flag int, _ os.FileMode) (file *os.File, err error) {
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r, e := windowsOpenSequential(name, flag|windows.O_CLOEXEC, 0)
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if e != nil {
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return nil, e
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}
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return os.NewFile(uintptr(r), name), nil
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}
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func makeInheritSa() *windows.SecurityAttributes {
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var sa windows.SecurityAttributes
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sa.Length = uint32(unsafe.Sizeof(sa))
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sa.InheritHandle = 1
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return &sa
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}
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func windowsOpenSequential(path string, mode int, _ uint32) (fd windows.Handle, err error) {
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if len(path) == 0 {
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return windows.InvalidHandle, windows.ERROR_FILE_NOT_FOUND
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}
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pathp, err := windows.UTF16PtrFromString(path)
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if err != nil {
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return windows.InvalidHandle, err
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}
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var access uint32
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switch mode & (windows.O_RDONLY | windows.O_WRONLY | windows.O_RDWR) {
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case windows.O_RDONLY:
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access = windows.GENERIC_READ
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case windows.O_WRONLY:
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access = windows.GENERIC_WRITE
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case windows.O_RDWR:
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access = windows.GENERIC_READ | windows.GENERIC_WRITE
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}
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if mode&windows.O_CREAT != 0 {
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access |= windows.GENERIC_WRITE
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}
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if mode&windows.O_APPEND != 0 {
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access &^= windows.GENERIC_WRITE
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access |= windows.FILE_APPEND_DATA
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}
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sharemode := uint32(windows.FILE_SHARE_READ | windows.FILE_SHARE_WRITE)
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var sa *windows.SecurityAttributes
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if mode&windows.O_CLOEXEC == 0 {
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sa = makeInheritSa()
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}
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var createmode uint32
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switch {
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case mode&(windows.O_CREAT|windows.O_EXCL) == (windows.O_CREAT | windows.O_EXCL):
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createmode = windows.CREATE_NEW
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case mode&(windows.O_CREAT|windows.O_TRUNC) == (windows.O_CREAT | windows.O_TRUNC):
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createmode = windows.CREATE_ALWAYS
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case mode&windows.O_CREAT == windows.O_CREAT:
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createmode = windows.OPEN_ALWAYS
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case mode&windows.O_TRUNC == windows.O_TRUNC:
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createmode = windows.TRUNCATE_EXISTING
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default:
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createmode = windows.OPEN_EXISTING
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}
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// Use FILE_FLAG_SEQUENTIAL_SCAN rather than FILE_ATTRIBUTE_NORMAL as implemented in golang.
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// https://msdn.microsoft.com/en-us/library/windows/desktop/aa363858(v=vs.85).aspx
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const fileFlagSequentialScan = 0x08000000 // FILE_FLAG_SEQUENTIAL_SCAN
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h, e := windows.CreateFile(pathp, access, sharemode, sa, createmode, fileFlagSequentialScan, 0)
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return h, e
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}
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// Helpers for TempFileSequential
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var rand uint32
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var randmu sync.Mutex
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func reseed() uint32 {
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return uint32(time.Now().UnixNano() + int64(os.Getpid()))
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}
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func nextSuffix() string {
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randmu.Lock()
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r := rand
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if r == 0 {
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r = reseed()
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}
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r = r*1664525 + 1013904223 // constants from Numerical Recipes
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rand = r
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randmu.Unlock()
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return strconv.Itoa(int(1e9 + r%1e9))[1:]
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}
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// TempFileSequential is a copy of ioutil.TempFile, modified to use sequential
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// file access. Below is the original comment from golang:
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// TempFile creates a new temporary file in the directory dir
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// with a name beginning with prefix, opens the file for reading
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// and writing, and returns the resulting *os.File.
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// If dir is the empty string, TempFile uses the default directory
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// for temporary files (see os.TempDir).
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// Multiple programs calling TempFile simultaneously
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// will not choose the same file. The caller can use f.Name()
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// to find the pathname of the file. It is the caller's responsibility
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// to remove the file when no longer needed.
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func TempFileSequential(dir, prefix string) (f *os.File, err error) {
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if dir == "" {
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dir = os.TempDir()
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}
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nconflict := 0
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for i := 0; i < 10000; i++ {
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name := filepath.Join(dir, prefix+nextSuffix())
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f, err = OpenFileSequential(name, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0600)
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if os.IsExist(err) {
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if nconflict++; nconflict > 10 {
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randmu.Lock()
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rand = reseed()
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randmu.Unlock()
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}
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continue
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}
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break
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}
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return
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}
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