PHP shmop.c module permits write of arbitrary memory.
From: Stefano Di Paola (stefano.dipaola_at_wisec.it)
To: Bugtraq <email@example.com> Date: Sun, 19 Dec 2004 19:40:54 +0100
Title: Php shmop write of arbitrary memory - Safe Mode Bypass
Affected: Php <= 5.0.2 & 4.3.9 if shmop module is loaded.
Vulnerability Type: Input Validation - write of arbitrary memory
Shared Memory PHP Module has a memory leak when shmop_write function
checks for offset bounds.
This flaw could lead to bypass Safe Mode and other bad things.
shmop.c in PHP_FUNCTION(shmop_write)
function does not check if the 'offset' value is negative,
so it is possible to overwrite arbitrary memory with:
memcpy(shmop->addr + offset, data, writesize);
this, in particular can be used to set safe_mode to off.
Attached there's a Proof of concept for this vuln.
It needs some gdb debugging or print the address of core_globals.safe_mode
and some try to get the right distance to set in '$offset'.
Of course shmop.so needs to be loaded as module or embedded in php bins.:)
Update php to 5.0.3 or 4.3.10
Stefano Di Paola
-- ......---oOOo--------oOOo---...... Stefano Di Paola Software Engineer Email: stefano.dipaola_at_wisec.it Email: stefano.dipaola1_at_tin.it Web: www.wisec.it ..................................
- application/x-php attachment: safe_mode_bypass.php