| 1 | //go:build windows |
| 2 | |
| 3 | package pathidentity |
| 4 | |
| 5 | import ( |
| 6 | "errors" |
| 7 | "fmt" |
| 8 | "path/filepath" |
| 9 | "strings" |
| 10 | "unsafe" |
| 11 | |
| 12 | "golang.org/x/sys/windows" |
| 13 | ) |
| 14 | |
| 15 | // The kernel reports exhausted reparse traversal as CANT_RESOLVE_FILENAME, |
| 16 | // rather than the synthetic syscall.ELOOP used by Go's userspace walker. |
| 17 | func platformLinkLoop(err error) bool { |
| 18 | return errors.Is(err, windows.ERROR_CANT_RESOLVE_FILENAME) |
| 19 | } |
| 20 | |
| 21 | // resolveExistingPath asks the kernel to follow all reparse points, including |
| 22 | // junctions. EvalSymlinks does not follow mount points reported as ModeIrregular: |
| 23 | // it can return the alias unchanged for a leaf and ENOTDIR for its descendants. |
| 24 | // This must be the primary resolver, not merely a fallback after an error. |
| 25 | func resolveExistingPath(path string) (string, error) { |
| 26 | handle, err := openPhysicalPath(path) |
| 27 | if err != nil { |
| 28 | return "", fmt.Errorf("open physical path: %w", err) |
| 29 | } |
| 30 | defer windows.CloseHandle(handle) |
| 31 | for size := uint32(256); size <= 65536; { |
| 32 | buf := make([]uint16, size) |
| 33 | n, err := windows.GetFinalPathNameByHandle(handle, &buf[0], size, 0) |
| 34 | if err != nil { |
| 35 | return "", fmt.Errorf("get final physical path: %w", err) |
| 36 | } |
| 37 | if n < size { |
| 38 | return stripExtendedPrefix(windows.UTF16ToString(buf[:n])), nil |
| 39 | } |
| 40 | if n >= 65536 { |
| 41 | break |
| 42 | } |
| 43 | size = n + 1 |
| 44 | } |
| 45 | return "", fmt.Errorf("final physical path exceeds 65536 UTF-16 units") |
| 46 | } |
| 47 | |
| 48 | // NtCreateFile avoids CreateFile's implicit SYNCHRONIZE requirement. Owners |
| 49 | // denied file attributes can still query security metadata via READ_CONTROL. |
| 50 | func openPhysicalPath(path string) (windows.Handle, error) { |
| 51 | name, err := windows.NewNTUnicodeString(ntPhysicalPath(path)) |
| 52 | if err != nil { |
| 53 | return 0, err |
| 54 | } |
| 55 | oa := windows.OBJECT_ATTRIBUTES{ObjectName: name, Attributes: windows.OBJ_CASE_INSENSITIVE} |
| 56 | oa.Length = uint32(unsafe.Sizeof(oa)) |
| 57 | var handle windows.Handle |
| 58 | var iosb windows.IO_STATUS_BLOCK |
| 59 | open := func(access uint32) error { |
| 60 | return windows.NtCreateFile(&handle, access, &oa, &iosb, nil, 0, |
| 61 | windows.FILE_SHARE_READ|windows.FILE_SHARE_WRITE|windows.FILE_SHARE_DELETE, |
| 62 | windows.FILE_OPEN, windows.FILE_OPEN_FOR_BACKUP_INTENT, 0, 0) |
| 63 | } |
| 64 | err = open(windows.FILE_READ_ATTRIBUTES) |
| 65 | if errors.Is(err, windows.STATUS_ACCESS_DENIED) { |
| 66 | err = open(windows.READ_CONTROL) |
| 67 | } |
| 68 | var status windows.NTStatus |
| 69 | if errors.As(err, &status) { |
| 70 | err = status.Errno() |
| 71 | } |
| 72 | return handle, err |
| 73 | } |
| 74 | |
| 75 | func ntPhysicalPath(path string) string { |
| 76 | extended := extendedWindowsPath(path) |
| 77 | return `\??\` + extended[4:] |
| 78 | } |
| 79 | |
| 80 | // Native Windows calls do not apply the long-path handling performed by os. |
| 81 | // Inputs here are already absolute and clean; preserve existing device paths. |
| 82 | func extendedWindowsPath(path string) string { |
| 83 | if strings.HasPrefix(path, `\\?\`) || strings.HasPrefix(path, `\\.\`) { |
| 84 | return path |
| 85 | } |
| 86 | if strings.HasPrefix(path, `\\`) { |
| 87 | return `\\?\UNC\` + path[2:] |
| 88 | } |
| 89 | if filepath.IsAbs(path) { |
| 90 | return `\\?\` + path |
| 91 | } |
| 92 | return path |
| 93 | } |
| 94 |