PEAR LiveUser File Access Vulnerabilities

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# GulfTech Security Research            February 21, 2006
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# Vendor : Markus Wolff
# URL : http://pear.php.net/package/LiveUser/
# Version : PEAR LiveUser <= 0.16.8
# Risk : Arbitrary File Access
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Description:
LiveUser is a user authentication and permission management
framework that is part of php's PEAR Library. LiveUser has
many different features, including the ability to remember
a user via cookies. Unfortunately there is an issue with
how extracted cookie data is handled by the LiveUser library
within the remember feature which makes it possible for an
attacker to gain access to, and even delete potentially
sensitive files on the webserver. An updated version of the
LiveUser framework has been released, and users are advised
to upgrade to LiveUser 0.16.9



Arbitrary File Access:
There is an arbitrary file access vulnerability in PEAR LiveUser
that allows an attacker to access arbitrary files on the server

$cookieData = $_COOKIE[$this->_options['cookie']['name']];
if (strlen($cookieData) < 65
    // kill all old style remember me cookies
    || (strpos($cookieData, ':') && strpos($cookieData, ':') < 64)
) {
    // Delete cookie if it's not valid, keeping it messes up the
    // authentication process
    $this->deleteRememberCookie();
    $this->_stack->push(LIVEUSER_ERROR_COOKIE, 'error', array(),
        'Wrong data in cookie store in LiveUser::readRememberMeCookie()');
    return false;
}

$store_id = substr($cookieData, 0, 32);
$passwd_id = substr($cookieData, 32, 32);
$handle = substr($cookieData, 64);

$dir = $this->_options['cookie']['savedir'];

$fh = @fopen($dir . '/' . $store_id . '.lu', 'rb');
if (!$fh) {
    $this->deleteRememberCookie();
    $this->_stack->push(LIVEUSER_ERROR_CONFIG, 'exception', array(),
        'Cannot open file for reading');
    return false;
}

$fields = fread($fh, 4096);
fclose($fh);
if (!$fields) {
    $this->deleteRememberCookie();
    $this->_stack->push(LIVEUSER_ERROR_CONFIG, 'exception', array(),
        'Cannot read file');
    return false;
}

The above code is taken from LiveUser.php @ lines 1269-1303 and
clearly shows the $store_id variable being assigned unsanitized
data, which is passed to an fopen called shortly thereafter. The
good news is that as far as I can tell this issues can not be
abused in a real world scenario much further than enumerating
file existence on the local filesystem.



Arbitrary File Deletion:
Similar to the previously mentioned issue, this vulnerability may
allow a malicious user to delete arbitrary files on the local
server by supplying malicious cookie data.

$cookieData = $_COOKIE[$this->_options['cookie']['name']];
if (strlen($cookieData) < 65) {
    $this->_stack->push(LIVEUSER_ERROR_COOKIE, 'error', array(),
        'Wrong data in cookie store in LiveUser::deleteRememberCookie()');
    return false;
}

$store_id = substr($cookieData, 0, 32);
@unlink($this->_options['cookie']['savedir'] . '/'.$store_id.'.lu');

The above code is also taken from LiveUser.php and resides @ lines
1343-1351. Here we see user supplied data being used in an unlink
call which could allow an attacker to delete arbitrary files on the
local server by traversing out of the cwd and terminating the fopen
call with a null byte.



Solution:
An updated version of the LiveUser framework has been released to
address these issues. The current release is LiveUser 0.16.9 and
users should update their LiveUser libraries as soon as possible.
Special thanks to Lukas Smith for a very prompt resolution!



Credits:
James Bercegay of the GulfTech Security Research Team



Related Info:
The original advisory can be found at the following location
http://www.gulftech.org/?node=research&article_id=00103-02212006