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// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package safefilepath
import (
"internal/bytealg"
"syscall"
)
func localize(path string) (string, error) {
for i := 0; i < len(path); i++ {
switch path[i] {
case ':', '\\', 0:
return "", errInvalidPath
}
}
containsSlash := false
for p := path; p != ""; {
// Find the next path element.
var element string
i := bytealg.IndexByteString(p, '/')
if i < 0 {
element = p
p = ""
} else {
containsSlash = true
element = p[:i]
p = p[i+1:]
}
if IsReservedName(element) {
return "", errInvalidPath
}
}
if containsSlash {
// We can't depend on strings, so substitute \ for / manually.
buf := []byte(path)
for i, b := range buf {
if b == '/' {
buf[i] = '\\'
}
}
path = string(buf)
}
return path, nil
}
// IsReservedName reports if name is a Windows reserved device name.
// It does not detect names with an extension, which are also reserved on some Windows versions.
//
// For details, search for PRN in
// https://docs.microsoft.com/en-us/windows/desktop/fileio/naming-a-file.
func IsReservedName(name string) bool {
// Device names can have arbitrary trailing characters following a dot or colon.
base := name
for i := 0; i < len(base); i++ {
switch base[i] {
case ':', '.':
base = base[:i]
}
}
// Trailing spaces in the last path element are ignored.
for len(base) > 0 && base[len(base)-1] == ' ' {
base = base[:len(base)-1]
}
if !isReservedBaseName(base) {
return false
}
if len(base) == len(name) {
return true
}
// The path element is a reserved name with an extension.
// Some Windows versions consider this a reserved name,
// while others do not. Use FullPath to see if the name is
// reserved.
if p, _ := syscall.FullPath(name); len(p) >= 4 && p[:4] == `\\.\` {
return true
}
return false
}
func isReservedBaseName(name string) bool {
if len(name) == 3 {
switch string([]byte{toUpper(name[0]), toUpper(name[1]), toUpper(name[2])}) {
case "CON", "PRN", "AUX", "NUL":
return true
}
}
if len(name) >= 4 {
switch string([]byte{toUpper(name[0]), toUpper(name[1]), toUpper(name[2])}) {
case "COM", "LPT":
if len(name) == 4 && '1' <= name[3] && name[3] <= '9' {
return true
}
// Superscript ¹, ², and ³ are considered numbers as well.
switch name[3:] {
case "\u00b2", "\u00b3", "\u00b9":
return true
}
return false
}
}
// Passing CONIN$ or CONOUT$ to CreateFile opens a console handle.
// https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea#consoles
//
// While CONIN$ and CONOUT$ aren't documented as being files,
// they behave the same as CON. For example, ./CONIN$ also opens the console input.
if len(name) == 6 && name[5] == '$' && equalFold(name, "CONIN$") {
return true
}
if len(name) == 7 && name[6] == '$' && equalFold(name, "CONOUT$") {
return true
}
return false
}
func equalFold(a, b string) bool {
if len(a) != len(b) {
return false
}
for i := 0; i < len(a); i++ {
if toUpper(a[i]) != toUpper(b[i]) {
return false
}
}
return true
}
func toUpper(c byte) byte {
if 'a' <= c && c <= 'z' {
return c - ('a' - 'A')
}
return c
}
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