system: You are an expert security code reviewer. You will be shown a source code file. Your task is to name the single function or class that contains the specified CWE vulnerability.

OUTPUT FORMAT: Respond with the exact function or class name (no parentheses, no qualifiers, no module prefixes), wrapped in \boxed{...}. Example: `\boxed{salted_hmac}`. Output the boxed name ONLY -- no explanation, no other text.

user: ```python
#! /usr/bin/env python3

import struct
import tarfile
import os.path as path
from os import urandom, remove
from Crypto.Cipher import AES
from hashlib import sha256


__version__ = '21.6.15'


DEFAULT_CHUNCK_SIZE = 256 * 1024
EXTENTION = '.pcrypt'
DEFAULT_ENCRYPTED_FILENAME = 'b1gs3cr3t' + EXTENTION
COLORS = {
    'red':    '\033[1;31m',
    'white':  '\033[1;37m',
    'gray':   '\033[1;30m',
    'yellow': '\033[1;33m',
    'reset':  '\033[0m'
}


class PrintError(Exception):
    pass


def print_colorized(text, parameters=[]):
    print(text.format(*parameters, **COLORS))


def _open_file(filename, mode):
    try:
        fd = open(filename, mode)
    except Exception as open_reason:
        raise PrintError('Could not open file {!r}: {}'.format(filename, open_reason))
    return fd


def _maybe_remove_file(filename):
    # It may take a while for large files
    while True:
        try:
            path.exists(filename) and remove(filename) and print_colorized('{gray}Removed file {}{reset}', [filename])
        except KeyboardInterrupt:
            print_colorized('{red}DO NOT TRY TO EXIT THE PROGRAM while it\'s removing its files{reset}')
            continue
        break


def encrypt_file(key, input_filename, output_filename, chunk_size=None):
    if chunk_size is None:
        chunk_size = DEFAULT_CHUNCK_SIZE

    # This code is highly inspired by:
    # https://eli.thegreenplace.net/2010/06/25/aes-encryption-of-files-in-python-with-pycrypto
    iv = urandom(16)
    encryptor = AES.new(key, AES.MODE_CBC, iv)

    input_fd = _open_file(input_filename, 'rb')
    input_file_size = path.getsize(input_filename)

    output_fd = _open_file(output_filename, 'wb')
    output_fd.write(struct.pack('<Q', input_file_size))
    output_fd.write(iv)

    encrypted_size = 0
    dots_in_line_count = 0
    print_colorized('{white}Attempt to encrypt data{reset} {gray}to {!r}{reset}', [output_filename])
    print_colorized('{gray}Printing a dot after encrypting each 10MB of data{reset}')
    while True:
        chunk = input_fd.read(chunk_size)
        chunk_length = len(chunk)
        if chunk_length == 0:
            break
        if chunk_length % 16 != 0:
            chunk += b' ' * (16 - chunk_length % 16)
        try:
            output_fd.write(encryptor.encrypt(chunk))
        except Exception as write_reason:
            # Probably 'no space left' exception
            _maybe_remove_file(output_filename)
            raise PrintError('Could not write to output file {!r}: {}'.format(output_filename, write_reason))
        encrypted_size += chunk_length
        # 0xA00000: 10MB
        if encrypted_size > 0xA00000:
            encrypted_size = 0
            print('.', end='', flush=True)
            dots_in_line_count += 1
            if dots_in_line_count >= 80:
                dots_in_line_count = 0
                print()
    print()
    input_fd.close()
    output_fd.close()
    print_colorized('{white}Encrypted{reset}')


def decrypt_file(key, input_filename, output_filename, chunk_size=None):
    if not input_filename.endswith(EXTENTION):
        raise PrintError('The file {!r} is not encrypted by pcrypt'.format(input_filename))
    if chunk_size is None:
        chunk_size = DEFAULT_CHUNCK_SIZE
    if path.exists(output_filename):
        raise PrintError('Output file {!r} already exists'.format(output_filename))
    if not path.exists(input_filename):
        raise PrintError('Could not found input file {!r}'.format(input_filename))

    # This code is highly inspired by:
    # https://eli.thegreenplace.net/2010/06/25/aes-encryption-of-files-in-python-with-pycrypto
    input_fd = _open_file(input_filename, 'rb')
    output_file_size = struct.unpack('<Q', input_fd.read(struct.calcsize('Q')))[0]
    iv = input_fd.read(16)
    decrypter = AES.new(key, AES.MODE_CBC, iv)

    output_fd = _open_file(output_filename, 'wb')

    decrypted_size = 0
    dots_in_line_count = 0
    print_colorized('{white}Attempt to decrypt data{reset} {gray}to {!r}{reset}', [output_filename])
    print_colorized('{gray}Printing a dot after decrypting each 10MB of data{reset}')
    while True:
        chunk = input_fd.read(chunk_size)
        chunk_length = len(chunk)
        if chunk_length == 0:
            break
        try:
            output_fd.write(decrypter.decrypt(chunk))
        except Exception as write_reason:
            # Probably 'no space left' exception
            _maybe_remove_file(output_filename)
            raise PrintError('Could not write to output file {!r}: {}'.format(output_filename, write_reason))

        decrypted_size += chunk_length
        # 0xA00000: 10MB
        if decrypted_size > 0xA00000:
            decrypted_size = 0
            print('.', end='', flush=True)
            dots_in_line_count += 1
            if dots_in_line_count >= 80:
                dots_in_line_count = 0
                print()
    print()
    input_fd.close()
    output_fd.truncate(output_file_size)
    output_fd.close()
    print_colorized('{white}Decrypted{reset}')


def make_tar_archive(filenames, output_filename, path_prefix):
    if path.exists(output_filename):
        raise PrintError('Output file {!r} already exists'.format(output_filename))

    try:
        tar = tarfile.open(output_filename, "w:gz")
    except Exception as open_reason:
        raise PrintError('Could not open tar archive {!r}: {}'.format(output_filename, open_reason))
    print_colorized('{gray}Attempt to make a tar archive{reset}')
    for filename in filenames:
        print_colorized('{gray}Attempt to add {!r} to archive{reset}', [filename])
        try:
            tar.add(filename, arcname=path.relpath(filename, path_prefix))
        except Exception as add_reason:
            raise PrintError('Could not add file {!r} to tar archive: {}'.format(filename, add_reason))
    tar.close()


def extract_archive(input_filename):
    try:
        tar = tarfile.open(input_filename)
    except Exception as open_reason:
        print_colorized('{gray}Could not open decrypted tar archive {!r}: {}{reset}', [input_filename, open_reason])
        raise PrintError('Maybe the password is wrong!')

    def log_and_yield_members(members):
        for member in members:
            print_colorized('{gray}Attempt to extract {!r} from tar archive{reset}', [member.name])
            yield member

    print_colorized('{gray}Attempt to extract files from tar archive{reset}')
    try:
        tar.extractall(members=log_and_yield_members(tar))
    except Exception as extract_reason:
        raise PrintError('Could not extract archive {!r}: {}'.format(input_filename, extract_reason))


if __name__ == '__main__':
    import argparse
    from os import getcwd
    from time import time
    from getpass import getpass
    from glob import glob


    def read_password(show_password_in_prompt):
        text = '{yellow}Enter password: {reset}'.format(**COLORS)
        password = input(text) if show_password_in_prompt else getpass(prompt=text)
        print()
        # make it 32 bytes
        return sha256(password.encode()).digest()


    def should_we_stop():
        return input(
            '{white}Continue? [{yellow}y{reset}{white}/{reset}{yellow}N{reset}{white}]: {reset}'.format(**COLORS)
        ).lower() != 'y'


    def main(args, tmp_tar_filename):
        if args.decrypt:
            input_file = DEFAULT_ENCRYPTED_FILENAME if args.file is None else args.file
            input_file = path.join(args.directory, input_file)
            print_colorized('{white}Going to decrypt {!r}{reset}', [input_file])
            if should_we_stop():
                return
            decrypt_file(read_password(args.show_password_in_prompt), input_file, tmp_tar_filename)
            extract_archive(tmp_tar_filename)
        else:  # args.encrypt (which is default)
            if args.file is None:
                output_file = path.dirname(args.directory) + EXTENTION
                if path.exists(output_file):
                    raise PrintError('Encrypted file {!r} already exists'.format(output_file))
                input_files = [x for x in glob(path.join(args.directory, '**'), recursive=True)]
                if input_files is []:
                    raise PrintError('Could not found any file to encrypt')
                sorted(input_files)
                print_colorized('{white}Going to encrypt following files:{reset}')
                for input_file in input_files:
                    print_colorized('{gray}{}{reset}', [input_file])
            else:
                input_file = path.join(args.directory, args.file)
                if not path.exists(input_file):
                    raise PrintError('Input file {!r} does not exist'.format(input_file))
                output_file = input_file + EXTENTION
                if path.exists(output_file):
                    raise PrintError('Encrypted file {!r} already exists'.format(output_file))
                input_files = [input_file]
                print_colorized('{white}Going to encrypt {gray}{!r}{reset}{reset}', [input_file])
            if should_we_stop():
                return
            password = read_password(args.show_password_in_prompt)
            make_tar_archive(input_files, tmp_tar_filename, '')
            encrypt_file(password, tmp_tar_filename, output_file)

    parser = argparse.ArgumentParser(description='Simple encryption utility for files/directories')
    parser.add_argument(
        '-d',
        default=getcwd(),
        dest='directory',
        help='In decryption mode it should be directory name that contains the encrypted file and in encryption mode it'
             ' should be the directory that you want to encrypt all or one of its files. Note that in encryption mode i'
             'f -f is not set, it encrypts all internal directories too. Its default value is current working directory'
             ' or %(default)s.'
    )
    parser.add_argument(
        '-f',
        default=None,
        dest='file',
        help='The filename to (en|de)crypt.'
    )
    parser.add_argument(
        '-D',
        action='store_true',
        default=False,
        dest='decrypt',
        help='Switches to decryption mode. If -f is not set, It tries to decrypt its default encrypted file name which '
             'is {!r}'.format(DEFAULT_ENCRYPTED_FILENAME)
    )
    parser.add_argument(
        '-E',
        action='store_true',
        default=False,
        dest='encrypt',
        help='Switches to encryption mode (which is the default behaviour). The default encrypted file name for directo'
             'ries (when -f is not set) is {!r}'.format(DEFAULT_ENCRYPTED_FILENAME)
    )
    parser.add_argument(
        '--show-password',
        action='store_true',
        default=False,
        dest='show_password_in_prompt',
        help='Shows your password when you type/paste it.'
    )
    parser.add_argument(
        '--no-color',
        action='store_true',
        default=False,
        dest='no_color',
        help='Makes it print plain text instead of colorized text.'
    )
    parser.add_argument(
        '-v',
        action='store_true',
        default=False,
        dest='print_version_and_exit',
        help='Prints version number ({}) and exits.'.format(__version__)
    )
    args = parser.parse_args()
    status_code = 0
    if args.print_version_and_exit:
        print(__version__)
        exit(status_code)
    if args.encrypt and args.decrypt:
        parser.error('Using -E and -D with each other is not allowed')
    if args.no_color:
        COLORS = {x[0]: '' for x in COLORS.items()}

    tmp_tar_filename = str(int(time())) + '.tar.gz'
    try:
        main(args, tmp_tar_filename)
        print_colorized('{white}Done{reset}')
    except KeyboardInterrupt:
        print()
        status_code = 1
    except PrintError as reason:
        print_colorized('{red}{}{reset}', [reason])
        status_code = 1
    except Exception:
        _maybe_remove_file(tmp_tar_filename)
        raise
    _maybe_remove_file(tmp_tar_filename)
    exit(status_code)

```

Name the function or class in this code that contains a `CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')` vulnerability.
Answer: extract_archive