mirror of
https://github.com/rocky-linux/peridot.git
synced 2024-11-30 16:46:27 +00:00
84 lines
3.0 KiB
Go
84 lines
3.0 KiB
Go
//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 (
|
|
"fmt"
|
|
"os"
|
|
|
|
"golang.org/x/sys/unix"
|
|
)
|
|
|
|
// OpenatInRoot is equivalent to OpenInRoot, except that the root is provided
|
|
// using an *os.File handle, to ensure that the correct root directory is used.
|
|
func OpenatInRoot(root *os.File, unsafePath string) (*os.File, error) {
|
|
handle, remainingPath, err := partialLookupInRoot(root, unsafePath)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
if remainingPath != "" {
|
|
_ = handle.Close()
|
|
return nil, &os.PathError{Op: "securejoin.OpenInRoot", Path: unsafePath, Err: unix.ENOENT}
|
|
}
|
|
return handle, nil
|
|
}
|
|
|
|
// OpenInRoot safely opens the provided unsafePath within the root.
|
|
// Effectively, OpenInRoot(root, unsafePath) is equivalent to
|
|
//
|
|
// path, _ := securejoin.SecureJoin(root, unsafePath)
|
|
// handle, err := os.OpenFile(path, unix.O_PATH|unix.O_CLOEXEC)
|
|
//
|
|
// But is much safer. The above implementation is unsafe because if an attacker
|
|
// can modify the filesystem tree between SecureJoin and OpenFile, it is
|
|
// possible for the returned file to be outside of the root.
|
|
//
|
|
// Note that the returned handle is an O_PATH handle, meaning that only a very
|
|
// limited set of operations will work on the handle. This is done to avoid
|
|
// accidentally opening an untrusted file that could cause issues (such as a
|
|
// disconnected TTY that could cause a DoS, or some other issue). In order to
|
|
// use the returned handle, you can "upgrade" it to a proper handle using
|
|
// Reopen.
|
|
func OpenInRoot(root, unsafePath string) (*os.File, error) {
|
|
rootDir, err := os.OpenFile(root, unix.O_PATH|unix.O_DIRECTORY|unix.O_CLOEXEC, 0)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
defer rootDir.Close()
|
|
return OpenatInRoot(rootDir, unsafePath)
|
|
}
|
|
|
|
// Reopen takes an *os.File handle and re-opens it through /proc/self/fd.
|
|
// Reopen(file, flags) is effectively equivalent to
|
|
//
|
|
// fdPath := fmt.Sprintf("/proc/self/fd/%d", file.Fd())
|
|
// os.OpenFile(fdPath, flags|unix.O_CLOEXEC)
|
|
//
|
|
// But with some extra hardenings to ensure that we are not tricked by a
|
|
// maliciously-configured /proc mount. While this attack scenario is not
|
|
// common, in container runtimes it is possible for higher-level runtimes to be
|
|
// tricked into configuring an unsafe /proc that can be used to attack file
|
|
// operations. See CVE-2019-19921 for more details.
|
|
func Reopen(handle *os.File, flags int) (*os.File, error) {
|
|
procRoot, err := getProcRoot()
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
flags |= unix.O_CLOEXEC
|
|
fdPath := fmt.Sprintf("fd/%d", handle.Fd())
|
|
return doProcSelfMagiclink(procRoot, fdPath, func(procDirHandle *os.File, base string) (*os.File, error) {
|
|
// Rather than just wrapping openatFile, open-code it so we can copy
|
|
// handle.Name().
|
|
reopenFd, err := unix.Openat(int(procDirHandle.Fd()), base, flags, 0)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("reopen fd %d: %w", handle.Fd(), err)
|
|
}
|
|
return os.NewFile(uintptr(reopenFd), handle.Name()), nil
|
|
})
|
|
}
|