23s2s

✏️ Editing: cloudlinux_bun_migration_cleanup.py

#!/opt/cloudlinux/venv/bin/python3 -bb
# coding:utf-8

"""Remove one account-owned Bun migration scratch transaction safely."""

import errno
import os
import re
import stat
import sys

TRANSACTION = re.compile(r'^\.cl-bun-migration-[0-9a-f]{32}$')
OPEN_DIRECTORY = os.O_RDONLY | os.O_DIRECTORY | os.O_NOFOLLOW

def _remove_tree(directory_fd):
    """Delete entries by descriptor, refusing to traverse symlinked dirs.

One single post-order pass. Re-deriving each directory's path from the
    transaction root cost one `open` per component, twice per directory --
    quadratic in a depth the account chooses. Only the directory being
    emptied holds a descriptor; a popped frame reaches its parent through
    `..` and proves it is the inode it descended from.
    """
    def open_directory(dir_fd, name):
        child_fd = os.open(name, OPEN_DIRECTORY, dir_fd=dir_fd)
        try:
            return child_fd, os.fstat(child_fd)
        except BaseException:
            os.close(child_fd)
            raise

current_fd = os.dup(directory_fd)
    root_stat = os.fstat(current_fd)
    frames = [{'name': None, 'names': None, 'index': 0,
               'dev': root_stat.st_dev, 'ino': root_stat.st_ino}]
    try:
        while frames:
            frame = frames[-1]
            if frame['names'] is None:
                frame['names'] = os.listdir(current_fd)
            if frame['index'] >= len(frame['names']):
                if frame['name'] is None:
                    frames.pop()
                    continue
                parent_fd, parent_stat = open_directory(current_fd, '..')
                above = frames[-2]
                try:
                    if (parent_stat.st_dev != above['dev']
                            or parent_stat.st_ino != above['ino']):
                        raise OSError(errno.ENOTDIR,
                                      'transaction changed while cleaning')
                    os.rmdir(frame['name'], dir_fd=parent_fd)
                except BaseException:
                    os.close(parent_fd)
                    raise
                os.close(current_fd)
                current_fd = parent_fd
                frames.pop()
                continue
            name = frame['names'][frame['index']]
            frame['index'] += 1
            entry_stat = os.stat(name, dir_fd=current_fd, follow_symlinks=False)
            if stat.S_ISDIR(entry_stat.st_mode):
                child_fd, child_stat = open_directory(current_fd, name)
                os.close(current_fd)
                current_fd = child_fd
                frames.append({'name': name, 'names': None, 'index': 0,
                               'dev': child_stat.st_dev,
                               'ino': child_stat.st_ino})
            else:
                # A symlink is an entry in the transaction, never a path
                # to traverse. unlinkat removes the link itself.
                os.unlink(name, dir_fd=current_fd)
    finally:
        os.close(current_fd)

def clean(home, transaction):
    if not TRANSACTION.match(transaction):
        raise ValueError('invalid migration transaction')
    home_fd = os.open(home, OPEN_DIRECTORY)
    try:
        try:
            scratch_fd = os.open('.cl-bun-migration', OPEN_DIRECTORY, dir_fd=home_fd)
        except OSError as exc:
            if exc.errno == errno.ENOENT:
                return
            raise
        try:
            try:
                transaction_fd = os.open(transaction, OPEN_DIRECTORY, dir_fd=scratch_fd)
            except OSError as exc:
                if exc.errno == errno.ENOENT:
                    return
                raise
            try:
                _remove_tree(transaction_fd)
            finally:
                os.close(transaction_fd)
            os.rmdir(transaction, dir_fd=scratch_fd)
        finally:
            os.close(scratch_fd)
        try:
            os.rmdir('.cl-bun-migration', dir_fd=home_fd)
        except OSError as exc:
            if exc.errno not in (errno.ENOENT, errno.ENOTEMPTY):
                raise
    finally:
        os.close(home_fd)

def main(argv=None):
    argv = sys.argv[1:] if argv is None else argv
    if len(argv) != 2:
        sys.stderr.write('usage: cloudlinux_bun_migration_cleanup HOME TRANSACTION\n')
        return 2
    try:
        clean(argv[0], argv[1])
    except (OSError, ValueError) as exc:
        sys.stderr.write('migration scratch cleanup refused: %s\n' % exc)
        return 1
    return 0

if __name__ == '__main__':
    sys.exit(main())

Sid Gifari From Gifari Industries - BD Cyber Security Team