fix(auth): address Task 13 deployment review findings

tools/tht/internal/backup/restore_file_windows.go

@@ -0,0 +1,59 @@
+//go:build windows
+
+package backup
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+
+	"github.com/aritmolab/thothii/tools/tht/internal/safeio"
+	"golang.org/x/sys/windows"
+)
+
+func replaceRestoreFile(target string, contents []byte, mode os.FileMode) error {
+	if safeio.ValidateCanonicalPath(target) != nil || mode&os.ModeType != 0 || mode.Perm() == 0 {
+		return safeio.ErrUnsafeFile
+	}
+	parent := filepath.Dir(target)
+	resolved, err := filepath.EvalSymlinks(parent)
+	if err != nil || resolved != parent || !safeWindowsRestoreTarget(target) {
+		return safeio.ErrUnsafeFile
+	}
+	temporary, err := os.CreateTemp(parent, ".tht-restore-*.tmp")
+	if err != nil {
+		return safeio.ErrUnsafeFile
+	}
+	temporaryPath := temporary.Name()
+	defer os.Remove(temporaryPath)
+	if err := temporary.Chmod(mode.Perm()); err == nil {
+		_, err = temporary.Write(contents)
+	}
+	if err == nil {
+		err = temporary.Sync()
+	}
+	closeErr := temporary.Close()
+	if err == nil {
+		err = closeErr
+	}
+	if err != nil || !safeWindowsRestoreTarget(target) {
+		return safeio.ErrUnsafeFile
+	}
+	from, fromErr := windows.UTF16PtrFromString(temporaryPath)
+	to, toErr := windows.UTF16PtrFromString(target)
+	if fromErr != nil || toErr != nil {
+		return safeio.ErrUnsafeFile
+	}
+	if err := windows.MoveFileEx(from, to, windows.MOVEFILE_REPLACE_EXISTING|windows.MOVEFILE_WRITE_THROUGH); err != nil {
+		return safeio.ErrUnsafeFile
+	}
+	return nil
+}
+
+func safeWindowsRestoreTarget(target string) bool {
+	info, err := os.Lstat(target)
+	if errors.Is(err, os.ErrNotExist) {
+		return true
+	}
+	return err == nil && info.Mode().IsRegular() && info.Mode()&os.ModeSymlink == 0
+}