note 45124 added to function.session-regenerate-id
| From: | timo at frenay dot net | Date: | Thu, 26 Aug 2004 18:32:08 +0000 |
| Subject: | note 45124 added to function.session-regenerate-id | ||
| Groups: | php.notes | ||
| Request: | Send a blank email to php-notes+get-75350@lists.php.net to get a copy of this message | ||
This function is vital in preventing session fixation attacks, but is unfortunately missing in PHP
versions prior to 4.3.2. This creates a serious security problem if you can't update your PHP
version, like me. Therefore I attempted to port this function to PHP itself:
<?php
if (!function_exists('session_regenerate_id')) {
function php_combined_lcg() {
$tv = gettimeofday();
$lcg['s1'] = $tv['sec'] ^ (~$tv['usec']);
$lcg['s2'] = posix_getpid();
$q = (int) ($lcg['s1'] / 53668);
$lcg['s1'] = (int) (40014 * ($lcg['s1'] - 53668 * $q) - 12211 * $q);
if ($lcg['s1'] < 0)
$lcg['s1'] += 2147483563;
$q = (int) ($lcg['s2'] / 52774);
$lcg['s2'] = (int) (40692 * ($lcg['s2'] - 52774 * $q) - 3791 * $q);
if ($lcg['s2'] < 0)
$lcg['s2'] += 2147483399;
$z = (int) ($lcg['s1'] - $lcg['s2']);
if ($z < 1) {
$z += 2147483562;
}
return $z * 4.656613e-10;
}
function session_regenerate_id() {
$tv = gettimeofday();
$buf = sprintf("%.15s%ld%ld%0.8f", $_SERVER['REMOTE_ADDR'],
$tv['sec'], $tv['usec'], php_combined_lcg() * 10);
session_id(md5($buf));
if (ini_get('session.use_cookies'))
setcookie('PHPSESSID', session_id(), NULL, '/');
return TRUE;
}
}
?>
To test this:
<?php
session_start();
$sid = session_id();
session_regenerate_id();
echo "Old session ID: ", $sid, "\nNew session ID: ", session_id(),
"\n";
?>
- will output something similar to:
Old session ID: 6e3521f44be4fc452b368e703f044ca1
New session ID: 1c6dac9a3e794f164d4115872b902471
----
Manual Page -- http://www.php.net/manual/en/function.session-regenerate-id.php
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