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//go:build linux
// Copyright (C) 2024 SUSE LLC. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package securejoin
import (
"os"
"path/filepath"
"golang.org/x/sys/unix"
)
func dupFile(f *os.File) (*os.File, error) {
fd, err := unix.FcntlInt(f.Fd(), unix.F_DUPFD_CLOEXEC, 0)
if err != nil {
return nil, os.NewSyscallError("fcntl(F_DUPFD_CLOEXEC)", err)
}
return os.NewFile(uintptr(fd), f.Name()), nil
}
func openatFile(dir *os.File, path string, flags int, mode int) (*os.File, error) {
// Make sure we always set O_CLOEXEC.
flags |= unix.O_CLOEXEC
fd, err := unix.Openat(int(dir.Fd()), path, flags, uint32(mode))
if err != nil {
return nil, &os.PathError{Op: "openat", Path: dir.Name() + "/" + path, Err: err}
}
// All of the paths we use with openatFile(2) are guaranteed to be
// lexically safe, so we can use path.Join here.
fullPath := filepath.Join(dir.Name(), path)
return os.NewFile(uintptr(fd), fullPath), nil
}
func fstatatFile(dir *os.File, path string, flags int) (unix.Stat_t, error) {
var stat unix.Stat_t
if err := unix.Fstatat(int(dir.Fd()), path, &stat, flags); err != nil {
return stat, &os.PathError{Op: "fstatat", Path: dir.Name() + "/" + path, Err: err}
}
return stat, nil
}
func readlinkatFile(dir *os.File, path string) (string, error) {
size := 4096
for {
linkBuf := make([]byte, size)
n, err := unix.Readlinkat(int(dir.Fd()), path, linkBuf)
if err != nil {
return "", &os.PathError{Op: "readlinkat", Path: dir.Name() + "/" + path, Err: err}
}
if n != size {
return string(linkBuf[:n]), nil
}
// Possible truncation, resize the buffer.
size *= 2
}
}
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