Merge pull request #7531 from thaJeztah/sys_windows

sys: optimize and refactor MkdirAllWithACL()

sys/filesys_windows.go

@@ -25,28 +25,36 @@ import (
 	"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)"
-)
-
-// MkdirAllWithACL is a wrapper for MkdirAll that creates a directory
-// ACL'd for Builtin Administrators and Local System.
-func MkdirAllWithACL(path string, perm os.FileMode) error {
-	return mkdirall(path, true)
+// SddlAdministratorsLocalSystem is local administrators plus NT AUTHORITY\System.
+const SddlAdministratorsLocalSystem = "D:P(A;OICI;GA;;;BA)(A;OICI;GA;;;SY)"
+
+// volumePath is a regular expression to check if a path is a Windows
+// volume path (e.g., "\\?\Volume{4c1b02c1-d990-11dc-99ae-806e6f6e6963}"
+// or "\\?\Volume{4c1b02c1-d990-11dc-99ae-806e6f6e6963}\").
+var volumePath = regexp.MustCompile(`^\\\\\?\\Volume{[a-z0-9-]+}\\?$`)
+
+// MkdirAllWithACL is a custom version of os.MkdirAll modified for use on Windows
+// so that it is both volume path aware, and to create a directory
+// an appropriate SDDL defined ACL for Builtin Administrators and Local System.
+func MkdirAllWithACL(path string, _ os.FileMode) error {
+	sa, err := makeSecurityAttributes(SddlAdministratorsLocalSystem)
+	if err != nil {
+		return &os.PathError{Op: "mkdirall", Path: path, Err: err}
+	}
+	return mkdirall(path, sa)
 }
 
-// MkdirAll implementation that is volume path aware for Windows. It can be used
-// as a drop-in replacement for os.MkdirAll()
+// MkdirAll is a custom version of os.MkdirAll that is volume path aware for
+// Windows. It can be used as a drop-in replacement for os.MkdirAll.
 func MkdirAll(path string, _ os.FileMode) error {
-	return mkdirall(path, false)
+	return mkdirall(path, nil)
 }
 
 // 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, adminAndLocalSystem bool) error {
-	if re := regexp.MustCompile(`^\\\\\?\\Volume{[a-z0-9-]+}$`); re.MatchString(path) {
+func mkdirall(path string, perm *windows.SecurityAttributes) error {
+	if volumePath.MatchString(path) {
 		return nil
 	}
 
@@ -59,11 +67,7 @@ func mkdirall(path string, adminAndLocalSystem bool) error {
 		if dir.IsDir() {
 			return nil
 		}
-		return &os.PathError{
-			Op:   "mkdir",
-			Path: path,
-			Err:  syscall.ENOTDIR,
-		}
+		return &os.PathError{Op: "mkdir", Path: path, Err: syscall.ENOTDIR}
 	}
 
 	// Slow path: make sure parent exists and then call Mkdir for path.
@@ -78,20 +82,15 @@ func mkdirall(path string, adminAndLocalSystem bool) error {
 	}
 
 	if j > 1 {
-		// Create parent
-		err = mkdirall(path[0:j-1], adminAndLocalSystem)
+		// Create parent.
+		err = mkdirall(fixRootDirectory(path[:j-1]), perm)
 		if err != nil {
 			return err
 		}
 	}
 
-	// Parent now exists; invoke os.Mkdir or mkdirWithACL and use its result.
-	if adminAndLocalSystem {
-		err = mkdirWithACL(path)
-	} else {
-		err = os.Mkdir(path, 0)
-	}
-
+	// Parent now exists; invoke Mkdir and use its result.
+	err = mkdirWithACL(path, perm)
 	if err != nil {
 		// Handle arguments like "foo/." by
 		// double-checking that directory doesn't exist.
@@ -111,24 +110,42 @@ func mkdirall(path string, adminAndLocalSystem bool) error {
 // 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) error {
-	sa := windows.SecurityAttributes{Length: 0}
-	sd, err := windows.SecurityDescriptorFromString(SddlAdministratorsLocalSystem)
-	if err != nil {
-		return &os.PathError{Op: "mkdir", Path: name, Err: err}
+func mkdirWithACL(name string, sa *windows.SecurityAttributes) error {
+	if sa == nil {
+		return os.Mkdir(name, 0)
 	}
-	sa.Length = uint32(unsafe.Sizeof(sa))
-	sa.InheritHandle = 1
-	sa.SecurityDescriptor = sd
 
 	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}
+	err = windows.CreateDirectory(namep, sa)
+	if err != nil {
+		return &os.PathError{Op: "mkdir", Path: name, Err: err}
 	}
 	return nil
 }
+
+// fixRootDirectory fixes a reference to a drive's root directory to
+// have the required trailing slash.
+func fixRootDirectory(p string) string {
+	if len(p) == len(`\\?\c:`) {
+		if os.IsPathSeparator(p[0]) && os.IsPathSeparator(p[1]) && p[2] == '?' && os.IsPathSeparator(p[3]) && p[5] == ':' {
+			return p + `\`
+		}
+	}
+	return p
+}
+
+func makeSecurityAttributes(sddl string) (*windows.SecurityAttributes, error) {
+	var sa windows.SecurityAttributes
+	sa.Length = uint32(unsafe.Sizeof(sa))
+	sa.InheritHandle = 1
+	var err error
+	sa.SecurityDescriptor, err = windows.SecurityDescriptorFromString(sddl)
+	if err != nil {
+		return nil, err
+	}
+	return &sa, nil
+}