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Some security against XSRF-attacks

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Tobias Hößl 2012-03-12 20:17:37 +00:00
parent 9574f7df03
commit 59766b944c
13 changed files with 131 additions and 38 deletions
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46
include/security.php
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@ -288,3 +288,49 @@ function item_permissions_sql($owner_id,$remote_verified = false,$groups = null)
}
/*
* Functions used to protect against Cross-Site Request Forgery
* The security token has to base on at least one value that an attacker can't know - here it's the session ID and the private key.
* In this implementation, a security token is reusable (if the user submits a form, goes back and resubmits the form, maybe with small changes;
* or if the security token is used for ajax-calls that happen several times), but only valid for a certain amout of time (3hours).
* The "typename" seperates the security tokens of different types of forms. This could be relevant in the following case:
* A security token is used to protekt a link from CSRF (e.g. the "delete this profile"-link).
* If the new page contains by any chance external elements, then the used security token is exposed by the referrer.
* Actually, important actions should not be triggered by Links / GET-Requests at all, but somethimes they still are,
* so this mechanism brings in some damage control (the attacker would be able to forge a request to a form of this type, but not to forms of other types).
*/
function get_form_security_token($typename = "") {
$a = get_app();
$timestamp = time();
$sec_hash = hash('whirlpool', $a->user["guid"] . $a->user["prvkey"] . session_id() . $timestamp . $typename);
return $timestamp . "." . $sec_hash;
}
function check_form_security_token($typename = "", $formname = 'form_security_token') {
if (!x($_REQUEST, $formname)) return false;
$hash = $_REQUEST[$formname];
$max_livetime = 10800; // 3 hours
$a = get_app();
$x = explode(".", $hash);
if (time() > (IntVal($x[0]) + $max_livetime)) return false;
$sec_hash = hash('whirlpool', $a->user["guid"] . $a->user["prvkey"] . session_id() . $x[0] . $typename);
return ($sec_hash == $x[1]);
}
function check_form_security_std_err_msg() {
return t('The form security token was not correct. This probably happened because the form has been opened for too long (>3 hours) before subitting it.') . EOL;
}
function check_form_security_token_redirectOnErr($err_redirect, $typename = "", $formname = 'form_security_token') {
if (!check_form_security_token($typename, $formname)) {
$a = get_app();
notice( check_form_security_std_err_msg() );
goaway($a->get_baseurl() . $err_redirect );
}
}