SSHScan/sshscan.py at master · evict/SSHScan · GitHub

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#!/usr/bin/env python3

import sys

import socket

import struct

from yaml import safe_load

from typing import List, Tuple

from secrets import token_bytes

from binascii import hexlify

from optparse import OptionParser, OptionGroup

def banner():

banner = """

_____ _____ _ _ _____

/ ___/ ___| | | / ___|

\ `--.\ `--.| |_| \ `--. ___ __ _ _ __

`--. \`--. | _ |`--. \/ __/ _` | '_ \\

/\__/ /\__/ | | | /\__/ | (_| (_| | | | |

\____/\____/\_| |_\____/ \___\__,_|_| |_|

evict

"""

return banner

def print_columns(cipherlist):

# adjust the amount of columns to display

cols = 2

while len(cipherlist) % cols != 0:

cipherlist.append("")

else:

split = [

cipherlist[i : i + int(len(cipherlist) / cols)]

for i in range(0, len(cipherlist), int(len(cipherlist) / cols))

]

for row in zip(*split):

print(" " + "".join(str.ljust(c, 37) for c in row))

print("\n")

def return_diff_list(detected, strong):

results = []

for item in detected:

if item not in strong:

results.append(item)

return results

def parse_results(version, kex, salg, enc, mac, cmpv):

version = version.decode("utf-8").rstrip()

kex = kex.decode("utf-8").split(",")

salg = salg.decode("utf-8").split(",")

enc = enc.decode("utf-8").split(",")

mac = mac.decode("utf-8").split(",")

cmpv = cmpv.decode("utf-8").split(",")

with open("config.yml") as fd:

config = safe_load(fd)

weak_ciphers = return_diff_list(enc, config["ciphers"])

weak_macs = return_diff_list(mac, config["macs"])

weak_kex = return_diff_list(kex, config["kex"])

weak_hka = return_diff_list(salg, config["hka"])

compression = True if "zlib@openssh.com" in cmpv else False

print(" [+] Detected the following ciphers: ")

print_columns(enc)

print(" [+] Detected the following KEX algorithms: ")

print_columns(kex)

print(" [+] Detected the following MACs: ")

print_columns(mac)

print(" [+] Detected the following HostKey algorithms: ")

print_columns(salg)

print(" [+] Target SSH version is: %s" % version)

print(" [+] Retrieving ciphers...")

if weak_ciphers:

print(" [+] Detected the following weak ciphers: ")

print_columns(weak_ciphers)

else:

print(" [+] No weak ciphers detected!")

if weak_kex:

print(" [+] Detected the following weak KEX algorithms: ")

print_columns(weak_kex)

else:

print(" [+] No weak KEX detected!")

if weak_macs:

print(" [+] Detected the following weak MACs: ")

print_columns(weak_macs)

else:

print(" [+] No weak MACs detected!")

if weak_hka:

print(" [+] Detected the following weak HostKey algorithms: ")

print_columns(weak_hka)

else:

print(" [+] No weak HostKey algorithms detected!")

if compression:

print(" [+] Compression has been enabled!")

def unpack_ssh_name_list(kex, n):

"""

Unpack the name-list from the packet

The comma separated list is preceded by an unsigned

integer which specifies the size of the list.

"""

size = struct.unpack("!I", kex[n : n + 4])[0] + 1

# jump to the name-list

n += 3

payload = struct.unpack(f"!{size}p", kex[n : n + size])[0]

# to the next integer

n += size

return payload, n

def unpack_msg_kex_init(kex):

# the MSG for KEXINIT looks as follows

# byte SSH_MSG_KEXINIT

# byte[16] cookie (random bytes)

# name-list kex_algorithms

# name-list server_host_key_algorithms

# name-list encryption_algorithms_client_to_server

# name-list encryption_algorithms_server_to_client

# name-list mac_algorithms_client_to_server

# name-list mac_algorithms_server_to_client

# name-list compression_algorithms_client_to_server

# name-list compression_algorithms_server_to_client

# name-list languages_client_to_server

# name-list languages_server_to_client

# boolean first_kex_packet_follows

# uint32 0 (reserved for future extension)

packet_size = struct.unpack("!I", kex[0:4])[0]

print(f"[*] KEX size: {packet_size}")

message = kex[5] # 20 == SSH_MSG_KEXINIT

if message != 20:

raise ValueError("did not receive SSH_MSG_KEXINIT")

cookie = struct.unpack("!16p", kex[6:22])[0]

print(f"[*] server cookie: {hexlify(cookie).decode('utf-8')}")

kex_size = struct.unpack("!I", kex[22:26])[0]

kex_size += 1

kex_algos = struct.unpack(f"!{kex_size}p", kex[25 : 25 + kex_size])[0]

n = 25 + kex_size

server_host_key_algo, n = unpack_ssh_name_list(kex, n)

enc_client_to_server, n = unpack_ssh_name_list(kex, n)

enc_server_to_client, n = unpack_ssh_name_list(kex, n)

mac_client_to_server, n = unpack_ssh_name_list(kex, n)

mac_server_to_client, n = unpack_ssh_name_list(kex, n)

cmp_client_to_server, n = unpack_ssh_name_list(kex, n)

cmp_server_to_client, n = unpack_ssh_name_list(kex, n)

return (

kex_algos,

server_host_key_algo,

enc_server_to_client,

mac_server_to_client,

cmp_server_to_client,

)

def pack_msg_kexinit_for_server(kex, salg, enc, mac, cmpv):

kex_fmt = f"!I{len(kex)}s"

sal_fmt = f"!I{len(salg)}s"

enc_fmt = f"!I{len(enc)}s"

mac_fmt = f"!I{len(mac)}s"

cmp_fmt = f"!I{len(cmpv)}s"

kex = struct.pack(kex_fmt, len(kex), kex)

sal = struct.pack(sal_fmt, len(salg), salg)

enc = struct.pack(enc_fmt, len(enc), enc)

mac = struct.pack(mac_fmt, len(mac), mac)

cmpv = struct.pack(cmp_fmt, len(cmpv), cmpv)

# languages are not used, therefore null

# 4 bytes are reserved

remain = b"\x00\x00\x00\x00"

packet = b"\x20"

packet += token_bytes(16)

packet += kex

packet += sal

# we are lazy and have the ctos and stoc options same.

# this should not be the case

packet += enc

packet += mac

packet += cmpv

packet += b"\x00"

packet += remain

packet += b"\x00" * 8

# + unsigned int + header

size = len(packet) + 4 + 2

# properly calculate the padding with length % 8

padding_len = size % 8

if padding_len < 4:

padding_len = 4

return _pack_packet(packet)

def retrieve_initial_kexinit(host: str, port: int) -> Tuple[List, List]:

s = return_socket_for_host(host, port)

version = s.recv(2048)

s.send(version)

kex_init = s.recv(4096)

s.close()

return kex_init, version

def return_socket_for_host(host, port):

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

s.connect((host, port))

return s

def _pack_packet(packet):

block_size = 8

# https://github.com/paramiko/paramiko/blob/master/paramiko/packet.py#L631

padding_len = 3 + block_size - ((len(packet) + 8) % block_size) + 1

if padding_len < block_size:

padding_len = block_size

header = struct.pack(">IB", len(packet) + padding_len, padding_len)

padding = b"\x00" * padding_len

packet = header + packet + padding

return packet

def main():

print(banner())

parser = OptionParser(usage="usage %prog [options]", version="%prog 2.0")

parameters = OptionGroup(parser, "Options")

parameters.add_option(

"-t",

"--target",

type="string",

help="Specify target as 'target' or 'target:port' (port 22 is default)",

dest="target",

)

parameters.add_option(

"-l",

"--target-list",

type="string",

help="File with targets: 'target' or 'target:port' seperated by a newline (port 22 is default)",

dest="targetlist",

)

parser.add_option_group(parameters)

options, arguments = parser.parse_args()

targets = []

target = options.target

targetlist = options.targetlist

if target:

targets.append(target)

else:

if targetlist:

with open(targetlist) as fd:

for item in fd.readlines():

targets.append(item.rstrip())

else:

print("[-] No target specified!")

sys.exit(0)

# we send first packets to make sure we match keys

for target in targets:

if ":" not in target:

target += ":22"

host, port = target.split(":")

port = int(port)

try:

kex_init, version = retrieve_initial_kexinit(host, port)

except socket.timeout:

print(" [-] Timeout while connecting to %s on port %i\n" % (host, port))

except socket.error as e:

if e.errno == 61:

print(" [-] %s\n" % (e.strerror))

else:

print(

" [-] Error while connecting to %s on port %i\n" % (host, port)

)

# parse the server KEXINIT message

kex, salg, enc, mac, cmpv = unpack_msg_kex_init(kex_init)

parse_results(version, kex, salg, enc, mac, cmpv)

if __name__ == "__main__":

main()

SSHScan/sshscan.py at master · evict/SSHScan · GitHub

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