system: You are an expert security code reviewer. You will be shown a source code file along with a multiple-choice question listing several function or class names from that file. Your task is to identify which one contains the specified CWE vulnerability.

OUTPUT FORMAT: Respond with the single letter of the correct option, wrapped in \boxed{...}. Example: `\boxed{B}`. Output the boxed letter ONLY -- no explanation, no other text.

user: ```python
import argparse
import logging
import socket
import json

import paramiko
from paramiko import AuthenticationException
from paramiko.ssh_exception import NoValidConnectionsError


class Provision:
    def __init__(self, current_private_key, key_json, host_json, digitalocean=False, vultr=False):
        self.ssh_client = paramiko.SSHClient()
        self.ssh_client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
        self.ssh_client.load_system_host_keys()
        self.log = logging
        self.log.basicConfig(format='%(levelname)s: %(message)s', level=logging.DEBUG)

        try:
            self.keys = json.load(open(key_json))
        except IOError:
            self.log.warning(
                "Can't seem to find the file: {}. Please provide a valid json key file location.".format(key_json))

            self.hosts = {}

        try:
            self.hosts.update(self.__fetch_from_cloud__(digitalocean, 'digitalocean')) if digitalocean else None
        except KeyError:
            self.log.error("The DigitalOcean token you provided is invalid!")

        try:
            self.hosts.update(self.__fetch_from_cloud__(vultr, 'vultr')) if vultr else None
        except KeyError:
            self.log.error("The Vultr token you provided is invalid!")

        try:
            json.load(open(host_json)) if host_json else None
        except IOError:
            self.log.warning(
                "Can't seem to find the file: {}. Please provide a valid json hosts file location.".format(host_json))

        try:
            self.current_private_key = current_private_key
        except IOError:
            self.log.warning(
                "Can't seem to find the file: {}. Please provide the machine private key location.".format(
                    current_private_key))

    @staticmethod
    def __fetch_from_cloud__(token, platform, default_user='root'):
        response = {}

        if 'digitalocean' in platform.lower():
            import digitalocean
            try:
                [response.update({droplet.name: {"user": default_user, "host": droplet.ip_address}}) for droplet in
                 digitalocean.Manager(token=token).get_all_droplets()]
            except digitalocean.baseapi.DataReadError:
                raise KeyError

        elif 'vultr' in platform.lower():
            import vultr
            try:
                [response.update({vc2['label']: {"user:": default_user, "host": vc2['main_ip']}}) for vc2 in
                 vultr.Vultr(token).server.list().values()]
            except vultr.utils.VultrError:
                raise KeyError
        return response

    def connect(self):
        def cmd_for_keys():
            users_keys = ''
            for user, public_key in self.keys.iteritems():
                users_keys += '#{user}\n{key}\n\n'.format(user=user, key=public_key)
            return {'cmd': 'echo "# Authorized_keys\n\n{keys}\n\n"> ~/.ssh/authorized_keys'.format(keys=users_keys)}

        try:
            cmd_dict = cmd_for_keys()

            for name, instance in self.hosts.iteritems():
                try:
                    self.ssh_client.connect(instance['host'], username=instance['user'],
                                            key_filename=self.current_private_key)
                    self.ssh_client.exec_command(cmd_dict['cmd'])
                    self.ssh_client.close()
                    self.log.info('Manage to provision keys to host {}'.format(name))

                except (AuthenticationException, NoValidConnectionsError) as e:
                    self.log.error('Failed to connect to host:{} Error:{}'.format(name, e))

                except socket.error as e:
                    self.log.error('Connection timeout to host:{} Error:{}'.format(name, e))

                except paramiko.ssh_exception.BadHostKeyException as e:
                    self.log.error('Failed to connect to host, invalid host key! Error:{}'.format(e))
        except AttributeError:
            self.log.error('Please check you provided all the required attributes (SEE --help)')


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description='Provision ssh keys from a JSON to bulk of instances.')

    parser.add_argument('-i', '--identity_file', metavar='identity file',
                        help='Location of the machine identity file(private key)', required=True)

    parser.add_argument('-k', '--keys_file', metavar='Keys file location',
                        help='Set the location for the key json file(default in the same folder)', required=False)

    parser.add_argument('-H', '--hosts_file', metavar='Hosts file location',
                        help='Set the location for the hosts json file(default in the same folder)', required=False)

    parser.add_argument('-d', '--digitalocean', metavar='DigitalOcean token',
                        help='Add DigitalOcean token for provision ssh-keys to all DigitalOcean account droplets',
                        required=False)

    parser.add_argument('-V', '--vultr', metavar='Vultr token',
                        help='Add Vultr token for provision ssh-keys to all Vultr account vc2 instances',
                        required=False)

    parser.add_argument('-v', '--version', action='version', version='SSH Key provisioner 0.3')

    args = vars(parser.parse_args())

    Provision(current_private_key=args.get('identity_file'),
              key_json=args.get('keys_file') if args.get('keys_file') else 'keys.json',
              host_json=args.get('hosts_file') if args.get('hosts_file') else 'hosts.json',
              digitalocean=args.get('digitalocean'),
              vultr=args.get('vultr')).connect()

```

Which of the following functions or classes contains a `CWE-295: Improper Certificate Validation` vulnerability?

  A) __init__
  B) cmd_for_keys
  C) Provision
  D) connect
Answer: A