Afaik that's the usual technique against session theft in php. Lot of php apps look the same.

Stephane Le 11 sept. 2013 23:13, "Rodrigo Castillo" rodrigo@corp.sonic.net a écrit :

I'm exploring the rcmail_session class to hunt down some intermittent issues with untimely session expiration, and to develop a better remember_me extension (or attempt to get it into core...).

I came across the following code

... /** * Setter for session lifetime */ public function set_lifetime($lifetime) { $this->lifetime = max(120, $lifetime);

    // valid time range is now - 1/2 lifetime to now + 1/2 lifetime
    $now = time();
    $this->now = $now - ($now % ($this->lifetime / 2));
}

... /**

 * Create session cookie from session data
 *
 * @param int Time slot to use
 */
function _mkcookie($timeslot)
{
    $auth_string = "$this->key,$this->secret,$**timeslot";
    return "S" . (function_exists('sha1') ? sha1($auth_string) :

md5($auth_string)); } ... /** * Check session authentication cookie * * @return boolean True if valid, False if not */ function check_auth() { ... if ($result && $this->_mkcookie($this->now) != $this->cookie) { ... }

It's quite deliberate, and it made me curious as to the reasoning behind the decision not to simply include a 'created_at' and 'expires_at' within the cookie, which would simplify the validation of the timespan. Is the reason for security, or perhaps a load-balancing? ______________________________**_________________ Roundcube Development discussion mailing list dev@lists.roundcube.net http://lists.roundcube.net/**mailman/listinfo/devhttp://lists.roundcube.net/mailman/listinfo/dev

Rodrigo Castillo wrote:

I'm exploring the rcmail_session class to hunt down some intermittent issues with untimely session expiration, and to develop a better remember_me extension (or attempt to get it into core...).

I came across the following code

... /** * Setter for session lifetime */ public function set_lifetime($lifetime) { $this->lifetime = max(120, $lifetime);

    // valid time range is now - 1/2 lifetime to now + 1/2 lifetime
    $now = time();
    $this->now = $now - ($now % ($this->lifetime / 2));
}

... /**

 * Create session cookie from session data
 *
 * @param int Time slot to use
 */
function _mkcookie($timeslot)
{
    $auth_string = "$this->key,$this->secret,$timeslot";
    return "S" . (function_exists('sha1') ? sha1($auth_string) :

md5($auth_string)); } ... /** * Check session authentication cookie * * @return boolean True if valid, False if not */ function check_auth() { ... if ($result && $this->_mkcookie($this->now) != $this->cookie) { ... }

It's quite deliberate, and it made me curious as to the reasoning behind the decision not to simply include a 'created_at' and 'expires_at' within the cookie, which would simplify the validation of the timespan. Is the reason for security, or perhaps a load-balancing?

The main reasons to encode a "timeslot" into the second cookie are:

• Have a cookie that changes its value during a session in order to reduce

the risk of session hijacking.

• Having the timeslot encoded in the cookie hash, it's kind of state-less

and we don't need to update the actual session data on every request just to extend the expiration date.

Regards, Thomas