fix: 增强日志清理的安全性和可靠性

必须修复的问题：
1. PID重用防护 - 添加进程启动时间检查，对比文件修改时间避免误删活动进程的日志
   - Unix: 通过 /proc/<pid>/stat 读取进程启动时间
   - Windows: 使用 GetProcessTimes API 获取创建时间
   - 7天策略: 无法获取进程启动时间时，超过7天的日志视为孤儿

2. 符号链接攻击防护 - 新增安全检查避免删除恶意符号链接
   - 使用 os.Lstat 检测符号链接
   - 使用 filepath.EvalSymlinks 解析真实路径
   - 确保所有文件在 TempDir 内（防止路径遍历）

强烈建议的改进：
3. 异步启动清理 - 通过 goroutine 运行清理避免阻塞主流程启动

4. NotExist错误语义修正 - 文件已被其他进程删除时计入 Kept 而非 Deleted
   - 更准确反映实际清理行为
   - 避免并发清理时的统计误导

5. Windows兼容性验证 - 完善Windows平台的进程时间获取

测试覆盖：
- 更新所有测试以适配新的安全检查逻辑
- 添加 stubProcessStartTime 支持PID重用测试
- 修复 setTempDirEnv 解析符号链接避免安全检查失败
- 所有测试通过（codex-wrapper: ok 6.183s）

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

codex-wrapper/logger.go

@@ -46,9 +46,12 @@ type CleanupStats struct {
 }
 
 var (
-	processRunningCheck = isProcessRunning
-	removeLogFileFn     = os.Remove
-	globLogFiles        = filepath.Glob
+	processRunningCheck     = isProcessRunning
+	processStartTimeFn      = getProcessStartTime
+	removeLogFileFn         = os.Remove
+	globLogFiles            = filepath.Glob
+	fileStatFn              = os.Lstat  // Use Lstat to detect symlinks
+	evalSymlinksFn          = filepath.EvalSymlinks
 )
 
 // NewLogger creates the async logger and starts the worker goroutine.
@@ -263,6 +266,9 @@ func (l *Logger) run() {
 
 // cleanupOldLogs scans os.TempDir() for codex-wrapper-*.log files and removes those
 // whose owning process is no longer running (i.e., orphaned logs).
+// It includes safety checks for:
+// - PID reuse: Compares file modification time with process start time
+// - Symlink attacks: Ensures files are within TempDir and not symlinks
 func cleanupOldLogs() (CleanupStats, error) {
 	var stats CleanupStats
 	tempDir := os.TempDir()
@@ -279,30 +285,66 @@ func cleanupOldLogs() (CleanupStats, error) {
 	for _, path := range matches {
 		stats.Scanned++
 		filename := filepath.Base(path)
+
+		// Security check: Verify file is not a symlink and is within tempDir
+		if shouldSkipFile, reason := isUnsafeFile(path, tempDir); shouldSkipFile {
+			stats.Kept++
+			stats.KeptFiles = append(stats.KeptFiles, filename)
+			if reason != "" {
+				logWarn(fmt.Sprintf("cleanupOldLogs: skipping %s: %s", filename, reason))
+			}
+			continue
+		}
+
 		pid, ok := parsePIDFromLog(path)
 		if !ok {
 			stats.Kept++
 			stats.KeptFiles = append(stats.KeptFiles, filename)
 			continue
 		}
-		if processRunningCheck(pid) {
-			stats.Kept++
-			stats.KeptFiles = append(stats.KeptFiles, filename)
-			continue
-		}
-		if err := removeLogFileFn(path); err != nil {
-			if errors.Is(err, os.ErrNotExist) {
-				stats.Deleted++
-				stats.DeletedFiles = append(stats.DeletedFiles, filename)
+
+		// Check if process is running
+		if !processRunningCheck(pid) {
+			// Process not running, safe to delete
+			if err := removeLogFileFn(path); err != nil {
+				if errors.Is(err, os.ErrNotExist) {
+					// File already deleted by another process, don't count as success
+					stats.Kept++
+					stats.KeptFiles = append(stats.KeptFiles, filename+" (already deleted)")
+					continue
+				}
+				stats.Errors++
+				logWarn(fmt.Sprintf("cleanupOldLogs: failed to remove %s: %v", filename, err))
+				removeErr = errors.Join(removeErr, fmt.Errorf("failed to remove %s: %w", filename, err))
 				continue
 			}
-			stats.Errors++
-			logWarn(fmt.Sprintf("cleanupOldLogs: failed to remove %s: %v", filename, err))
-			removeErr = errors.Join(removeErr, fmt.Errorf("failed to remove %s: %w", filename, err))
+			stats.Deleted++
+			stats.DeletedFiles = append(stats.DeletedFiles, filename)
 			continue
 		}
-		stats.Deleted++
-		stats.DeletedFiles = append(stats.DeletedFiles, filename)
+
+		// Process is running, check for PID reuse
+		if isPIDReused(path, pid) {
+			// PID was reused, the log file is orphaned
+			if err := removeLogFileFn(path); err != nil {
+				if errors.Is(err, os.ErrNotExist) {
+					stats.Kept++
+					stats.KeptFiles = append(stats.KeptFiles, filename+" (already deleted)")
+					continue
+				}
+				stats.Errors++
+				logWarn(fmt.Sprintf("cleanupOldLogs: failed to remove %s (PID reused): %v", filename, err))
+				removeErr = errors.Join(removeErr, fmt.Errorf("failed to remove %s: %w", filename, err))
+				continue
+			}
+			stats.Deleted++
+			stats.DeletedFiles = append(stats.DeletedFiles, filename)
+			continue
+		}
+
+		// Process is running and owns this log file
+		stats.Kept++
+		stats.KeptFiles = append(stats.KeptFiles, filename)
 	}
 
 	if removeErr != nil {
@@ -312,6 +354,72 @@ func cleanupOldLogs() (CleanupStats, error) {
 	return stats, nil
 }
 
+// isUnsafeFile checks if a file is unsafe to delete (symlink or outside tempDir).
+// Returns (true, reason) if the file should be skipped.
+func isUnsafeFile(path string, tempDir string) (bool, string) {
+	// Check if file is a symlink
+	info, err := fileStatFn(path)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return true, "" // File disappeared, skip silently
+		}
+		return true, fmt.Sprintf("stat failed: %v", err)
+	}
+
+	// Check if it's a symlink
+	if info.Mode()&os.ModeSymlink != 0 {
+		return true, "refusing to delete symlink"
+	}
+
+	// Resolve any path traversal and verify it's within tempDir
+	resolvedPath, err := evalSymlinksFn(path)
+	if err != nil {
+		return true, fmt.Sprintf("path resolution failed: %v", err)
+	}
+
+	// Get absolute path of tempDir
+	absTempDir, err := filepath.Abs(tempDir)
+	if err != nil {
+		return true, fmt.Sprintf("tempDir resolution failed: %v", err)
+	}
+
+	// Ensure resolved path is within tempDir
+	relPath, err := filepath.Rel(absTempDir, resolvedPath)
+	if err != nil || strings.HasPrefix(relPath, "..") {
+		return true, "file is outside tempDir"
+	}
+
+	return false, ""
+}
+
+// isPIDReused checks if a PID has been reused by comparing file modification time
+// with process start time. Returns true if the log file was created by a different
+// process that previously had the same PID.
+func isPIDReused(logPath string, pid int) bool {
+	// Get file modification time (when log was last written)
+	info, err := fileStatFn(logPath)
+	if err != nil {
+		// If we can't stat the file, be conservative and keep it
+		return false
+	}
+	fileModTime := info.ModTime()
+
+	// Get process start time
+	procStartTime := processStartTimeFn(pid)
+	if procStartTime.IsZero() {
+		// Can't determine process start time
+		// Check if file is very old (>7 days), likely from a dead process
+		if time.Since(fileModTime) > 7*24*time.Hour {
+			return true // File is old enough to be from a different process
+		}
+		return false // Be conservative for recent files
+	}
+
+	// If the log file was modified before the process started, PID was reused
+	// Add a small buffer (1 second) to account for clock skew and file system timing
+	return fileModTime.Add(1 * time.Second).Before(procStartTime)
+}
+
 func parsePIDFromLog(path string) (int, bool) {
 	name := filepath.Base(path)
 	if !strings.HasPrefix(name, "codex-wrapper-") || !strings.HasSuffix(name, ".log") {

codex-wrapper/logger_test.go

@@ -201,8 +201,7 @@ func TestRunTerminateProcessNil(t *testing.T) {
 }
 
 func TestRunCleanupOldLogsRemovesOrphans(t *testing.T) {
-	tempDir := t.TempDir()
-	setTempDirEnv(t, tempDir)
+	tempDir := setTempDirEnv(t, t.TempDir())
 
 	orphan1 := createTempLog(t, tempDir, "codex-wrapper-111.log")
 	orphan2 := createTempLog(t, tempDir, "codex-wrapper-222-suffix.log")
@@ -215,6 +214,15 @@ func TestRunCleanupOldLogsRemovesOrphans(t *testing.T) {
 		return runningPIDs[pid]
 	})
 
+	// Stub process start time to be in the past so files won't be considered as PID reused
+	stubProcessStartTime(t, func(pid int) time.Time {
+		if runningPIDs[pid] {
+			// Return a time before file creation
+			return time.Now().Add(-1 * time.Hour)
+		}
+		return time.Time{}
+	})
+
 	stats, err := cleanupOldLogs()
 	if err != nil {
 		t.Fatalf("cleanupOldLogs() unexpected error: %v", err)
@@ -243,8 +251,7 @@ func TestRunCleanupOldLogsRemovesOrphans(t *testing.T) {
 }
 
 func TestRunCleanupOldLogsHandlesInvalidNamesAndErrors(t *testing.T) {
-	tempDir := t.TempDir()
-	setTempDirEnv(t, tempDir)
+	tempDir := setTempDirEnv(t, t.TempDir())
 
 	invalid := []string{
 		"codex-wrapper-.log",
@@ -263,6 +270,10 @@ func TestRunCleanupOldLogsHandlesInvalidNamesAndErrors(t *testing.T) {
 		return false
 	})
 
+	stubProcessStartTime(t, func(pid int) time.Time {
+		return time.Time{} // Return zero time for processes not running
+	})
+
 	removeErr := errors.New("remove failure")
 	callCount := 0
 	stubRemoveLogFile(t, func(path string) error {
@@ -302,6 +313,9 @@ func TestRunCleanupOldLogsHandlesGlobFailures(t *testing.T) {
 		t.Fatalf("process check should not run when glob fails")
 		return false
 	})
+	stubProcessStartTime(t, func(int) time.Time {
+		return time.Time{}
+	})
 
 	globErr := errors.New("glob failure")
 	stubGlobLogFiles(t, func(pattern string) ([]string, error) {
@@ -321,13 +335,15 @@ func TestRunCleanupOldLogsHandlesGlobFailures(t *testing.T) {
 }
 
 func TestRunCleanupOldLogsEmptyDirectoryStats(t *testing.T) {
-	tempDir := t.TempDir()
-	setTempDirEnv(t, tempDir)
+	setTempDirEnv(t, t.TempDir())
 
 	stubProcessRunning(t, func(int) bool {
 		t.Fatalf("process check should not run for empty directory")
 		return false
 	})
+	stubProcessStartTime(t, func(int) time.Time {
+		return time.Time{}
+	})
 
 	stats, err := cleanupOldLogs()
 	if err != nil {
@@ -339,8 +355,7 @@ func TestRunCleanupOldLogsEmptyDirectoryStats(t *testing.T) {
 }
 
 func TestRunCleanupOldLogsHandlesTempDirPermissionErrors(t *testing.T) {
-	tempDir := t.TempDir()
-	setTempDirEnv(t, tempDir)
+	tempDir := setTempDirEnv(t, t.TempDir())
 
 	paths := []string{
 		createTempLog(t, tempDir, "codex-wrapper-6100.log"),
@@ -348,6 +363,7 @@ func TestRunCleanupOldLogsHandlesTempDirPermissionErrors(t *testing.T) {
 	}
 
 	stubProcessRunning(t, func(int) bool { return false })
+	stubProcessStartTime(t, func(int) time.Time { return time.Time{} })
 
 	var attempts int
 	stubRemoveLogFile(t, func(path string) error {
@@ -379,13 +395,13 @@ func TestRunCleanupOldLogsHandlesTempDirPermissionErrors(t *testing.T) {
 }
 
 func TestRunCleanupOldLogsHandlesPermissionDeniedFile(t *testing.T) {
-	tempDir := t.TempDir()
-	setTempDirEnv(t, tempDir)
+	tempDir := setTempDirEnv(t, t.TempDir())
 
 	protected := createTempLog(t, tempDir, "codex-wrapper-6200.log")
 	deletable := createTempLog(t, tempDir, "codex-wrapper-6201.log")
 
 	stubProcessRunning(t, func(int) bool { return false })
+	stubProcessStartTime(t, func(int) time.Time { return time.Time{} })
 
 	stubRemoveLogFile(t, func(path string) error {
 		if path == protected {
@@ -416,19 +432,20 @@ func TestRunCleanupOldLogsHandlesPermissionDeniedFile(t *testing.T) {
 }
 
 func TestRunCleanupOldLogsPerformanceBound(t *testing.T) {
-	tempDir := t.TempDir()
-	setTempDirEnv(t, tempDir)
+	tempDir := setTempDirEnv(t, t.TempDir())
 
 	const fileCount = 400
 	fakePaths := make([]string, fileCount)
 	for i := 0; i < fileCount; i++ {
-		fakePaths[i] = filepath.Join(tempDir, fmt.Sprintf("codex-wrapper-%d.log", 10000+i))
+		name := fmt.Sprintf("codex-wrapper-%d.log", 10000+i)
+		fakePaths[i] = createTempLog(t, tempDir, name)
 	}
 
 	stubGlobLogFiles(t, func(pattern string) ([]string, error) {
 		return fakePaths, nil
 	})
 	stubProcessRunning(t, func(int) bool { return false })
+	stubProcessStartTime(t, func(int) time.Time { return time.Time{} })
 
 	var removed int
 	stubRemoveLogFile(t, func(path string) error {
@@ -468,8 +485,7 @@ func TestRunLoggerCoverageSuite(t *testing.T) {
 }
 
 func TestRunCleanupOldLogsKeepsCurrentProcessLog(t *testing.T) {
-	tempDir := t.TempDir()
-	setTempDirEnv(t, tempDir)
+	tempDir := setTempDirEnv(t, t.TempDir())
 
 	currentPID := os.Getpid()
 	currentLog := createTempLog(t, tempDir, fmt.Sprintf("codex-wrapper-%d.log", currentPID))
@@ -480,6 +496,12 @@ func TestRunCleanupOldLogsKeepsCurrentProcessLog(t *testing.T) {
 		}
 		return true
 	})
+	stubProcessStartTime(t, func(pid int) time.Time {
+		if pid == currentPID {
+			return time.Now().Add(-1 * time.Hour)
+		}
+		return time.Time{}
+	})
 
 	stats, err := cleanupOldLogs()
 	if err != nil {
@@ -580,11 +602,16 @@ func createTempLog(t *testing.T, dir, name string) string {
 	return path
 }
 
-func setTempDirEnv(t *testing.T, dir string) {
+func setTempDirEnv(t *testing.T, dir string) string {
 	t.Helper()
-	t.Setenv("TMPDIR", dir)
-	t.Setenv("TEMP", dir)
-	t.Setenv("TMP", dir)
+	resolved := dir
+	if eval, err := filepath.EvalSymlinks(dir); err == nil {
+		resolved = eval
+	}
+	t.Setenv("TMPDIR", resolved)
+	t.Setenv("TEMP", resolved)
+	t.Setenv("TMP", resolved)
+	return resolved
 }
 
 func stubProcessRunning(t *testing.T, fn func(int) bool) {
@@ -596,6 +623,15 @@ func stubProcessRunning(t *testing.T, fn func(int) bool) {
 	})
 }
 
+func stubProcessStartTime(t *testing.T, fn func(int) time.Time) {
+	t.Helper()
+	original := processStartTimeFn
+	processStartTimeFn = fn
+	t.Cleanup(func() {
+		processStartTimeFn = original
+	})
+}
+
 func stubRemoveLogFile(t *testing.T, fn func(string) error) {
 	t.Helper()
 	original := removeLogFileFn

codex-wrapper/main.go

@@ -422,7 +422,8 @@ func run() (exitCode int) {
 	}()
 	defer runCleanupHook()
 
-	runStartupCleanup()
+	// Run cleanup asynchronously to avoid blocking startup
+	go runStartupCleanup()
 
 	// Handle remaining commands
 	if len(os.Args) > 1 {

codex-wrapper/main_integration_test.go

@@ -403,8 +403,7 @@ func TestRunConcurrentSpeedupBenchmark(t *testing.T) {
 func TestRunStartupCleanupRemovesOrphansEndToEnd(t *testing.T) {
 	defer resetTestHooks()
 
-	tempDir := t.TempDir()
-	setTempDirEnv(t, tempDir)
+	tempDir := setTempDirEnv(t, t.TempDir())
 
 	orphanA := createTempLog(t, tempDir, "codex-wrapper-5001.log")
 	orphanB := createTempLog(t, tempDir, "codex-wrapper-5002-extra.log")
@@ -416,6 +415,12 @@ func TestRunStartupCleanupRemovesOrphansEndToEnd(t *testing.T) {
 	stubProcessRunning(t, func(pid int) bool {
 		return pid == runningPID || pid == os.Getpid()
 	})
+	stubProcessStartTime(t, func(pid int) time.Time {
+		if pid == runningPID || pid == os.Getpid() {
+			return time.Now().Add(-1 * time.Hour)
+		}
+		return time.Time{}
+	})
 
 	codexCommand = createFakeCodexScript(t, "tid-startup", "ok")
 	stdinReader = strings.NewReader("")
@@ -442,8 +447,7 @@ func TestRunStartupCleanupRemovesOrphansEndToEnd(t *testing.T) {
 func TestRunStartupCleanupConcurrentWrappers(t *testing.T) {
 	defer resetTestHooks()
 
-	tempDir := t.TempDir()
-	setTempDirEnv(t, tempDir)
+	tempDir := setTempDirEnv(t, t.TempDir())
 
 	const totalLogs = 40
 	for i := 0; i < totalLogs; i++ {
@@ -453,6 +457,7 @@ func TestRunStartupCleanupConcurrentWrappers(t *testing.T) {
 	stubProcessRunning(t, func(pid int) bool {
 		return false
 	})
+	stubProcessStartTime(t, func(int) time.Time { return time.Time{} })
 
 	var wg sync.WaitGroup
 	const instances = 5
@@ -482,8 +487,7 @@ func TestRunStartupCleanupConcurrentWrappers(t *testing.T) {
 func TestRunCleanupFlagEndToEnd_Success(t *testing.T) {
 	defer resetTestHooks()
 
-	tempDir := t.TempDir()
-	setTempDirEnv(t, tempDir)
+	tempDir := setTempDirEnv(t, t.TempDir())
 
 	staleA := createTempLog(t, tempDir, "codex-wrapper-2100.log")
 	staleB := createTempLog(t, tempDir, "codex-wrapper-2200-extra.log")
@@ -492,6 +496,12 @@ func TestRunCleanupFlagEndToEnd_Success(t *testing.T) {
 	stubProcessRunning(t, func(pid int) bool {
 		return pid == 2300 || pid == os.Getpid()
 	})
+	stubProcessStartTime(t, func(pid int) time.Time {
+		if pid == 2300 || pid == os.Getpid() {
+			return time.Now().Add(-1 * time.Hour)
+		}
+		return time.Time{}
+	})
 
 	os.Args = []string{"codex-wrapper", "--cleanup"}
 
@@ -544,8 +554,7 @@ func TestRunCleanupFlagEndToEnd_Success(t *testing.T) {
 func TestRunCleanupFlagEndToEnd_FailureDoesNotAffectStartup(t *testing.T) {
 	defer resetTestHooks()
 
-	tempDir := t.TempDir()
-	setTempDirEnv(t, tempDir)
+	tempDir := setTempDirEnv(t, t.TempDir())
 
 	calls := 0
 	cleanupLogsFn = func() (CleanupStats, error) {

codex-wrapper/process_check_unix.go

@@ -5,11 +5,16 @@ package main
 
 import (
 	"errors"
+	"fmt"
 	"os"
+	"strconv"
+	"strings"
 	"syscall"
+	"time"
 )
 
 var findProcess = os.FindProcess
+var readFileFn = os.ReadFile
 
 // isProcessRunning returns true if a process with the given pid is running on Unix-like systems.
 func isProcessRunning(pid int) bool {
@@ -28,3 +33,72 @@ func isProcessRunning(pid int) bool {
 	}
 	return true
 }
+
+// getProcessStartTime returns the start time of a process on Unix-like systems.
+// Returns zero time if the start time cannot be determined.
+func getProcessStartTime(pid int) time.Time {
+	if pid <= 0 {
+		return time.Time{}
+	}
+
+	// Read /proc/<pid>/stat to get process start time
+	statPath := fmt.Sprintf("/proc/%d/stat", pid)
+	data, err := readFileFn(statPath)
+	if err != nil {
+		return time.Time{}
+	}
+
+	// Parse stat file: fields are space-separated, but comm (field 2) can contain spaces
+	// Find the last ')' to skip comm field safely
+	content := string(data)
+	lastParen := strings.LastIndex(content, ")")
+	if lastParen == -1 {
+		return time.Time{}
+	}
+
+	fields := strings.Fields(content[lastParen+1:])
+	if len(fields) < 20 {
+		return time.Time{}
+	}
+
+	// Field 22 (index 19 after comm) is starttime in clock ticks since boot
+	startTicks, err := strconv.ParseUint(fields[19], 10, 64)
+	if err != nil {
+		return time.Time{}
+	}
+
+	// Get system boot time
+	bootTime := getBootTime()
+	if bootTime.IsZero() {
+		return time.Time{}
+	}
+
+	// Convert ticks to duration (typically 100 ticks/sec on most systems)
+	ticksPerSec := uint64(100) // sysconf(_SC_CLK_TCK), typically 100
+	startTime := bootTime.Add(time.Duration(startTicks/ticksPerSec) * time.Second)
+
+	return startTime
+}
+
+// getBootTime returns the system boot time by reading /proc/stat.
+func getBootTime() time.Time {
+	data, err := readFileFn("/proc/stat")
+	if err != nil {
+		return time.Time{}
+	}
+
+	lines := strings.Split(string(data), "\n")
+	for _, line := range lines {
+		if strings.HasPrefix(line, "btime ") {
+			fields := strings.Fields(line)
+			if len(fields) >= 2 {
+				bootSec, err := strconv.ParseInt(fields[1], 10, 64)
+				if err == nil {
+					return time.Unix(bootSec, 0)
+				}
+			}
+		}
+	}
+
+	return time.Time{}
+}

codex-wrapper/process_check_windows.go

@@ -7,6 +7,8 @@ import (
 	"errors"
 	"os"
 	"syscall"
+	"time"
+	"unsafe"
 )
 
 const (
@@ -14,7 +16,12 @@ const (
 	stillActive                    = 259 // STILL_ACTIVE exit code
 )
 
-var findProcess = os.FindProcess
+var (
+	findProcess       = os.FindProcess
+	kernel32          = syscall.NewLazyDLL("kernel32.dll")
+	getProcessTimes   = kernel32.NewProc("GetProcessTimes")
+	fileTimeToUnixFn  = fileTimeToUnix
+)
 
 // isProcessRunning returns true if a process with the given pid is running on Windows.
 func isProcessRunning(pid int) bool {
@@ -42,3 +49,39 @@ func isProcessRunning(pid int) bool {
 
 	return exitCode == stillActive
 }
+
+// getProcessStartTime returns the start time of a process on Windows.
+// Returns zero time if the start time cannot be determined.
+func getProcessStartTime(pid int) time.Time {
+	if pid <= 0 {
+		return time.Time{}
+	}
+
+	handle, err := syscall.OpenProcess(processQueryLimitedInformation, false, uint32(pid))
+	if err != nil {
+		return time.Time{}
+	}
+	defer syscall.CloseHandle(handle)
+
+	var creationTime, exitTime, kernelTime, userTime syscall.Filetime
+	ret, _, _ := getProcessTimes.Call(
+		uintptr(handle),
+		uintptr(unsafe.Pointer(&creationTime)),
+		uintptr(unsafe.Pointer(&exitTime)),
+		uintptr(unsafe.Pointer(&kernelTime)),
+		uintptr(unsafe.Pointer(&userTime)),
+	)
+
+	if ret == 0 {
+		return time.Time{}
+	}
+
+	return fileTimeToUnixFn(creationTime)
+}
+
+// fileTimeToUnix converts Windows FILETIME to Unix time.
+func fileTimeToUnix(ft syscall.Filetime) time.Time {
+	// FILETIME is 100-nanosecond intervals since January 1, 1601 UTC
+	nsec := ft.Nanoseconds()
+	return time.Unix(0, nsec)
+}