blob: 4535fd63c139767ba2cdd1d0f275f972c86a76f6 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
|
<?php
/**
* Piwik - Open source web analytics
*
* @link http://piwik.org
* @license http://www.gnu.org/licenses/gpl-3.0.html Gpl v3 or later
* @version $Id$
*
* @category Piwik
* @package Piwik
*/
/**
* Nonce class.
*
* A cryptographic nonce -- "number used only once" -- is often recommended as part of a robust defense against cross-site request forgery (CSRF/XSRF).
* Desrable characteristics: limited lifetime, uniqueness, unpredictability (pseudo-randomness).
*
* We use a session-dependent nonce with a configurable expiration that combines and hashes:
* - a private salt because it's non-public
* - time() because it's unique
* - a mix of PRNGs (pseudo-random number generators) to increase entropy and make it less predictable
*
* @package Piwik
*/
class Piwik_Nonce
{
/**
* Generate nonce
*
* @param string $id Unique id to avoid namespace conflicts, e.g., ModuleName.ActionName
* @param int $ttl Optional time-to-live in seconds; default is 5 minutes
* @return string Nonce
*/
static public function getNonce($id, $ttl = 300)
{
// save session-dependent nonce
$ns = new Zend_Session_Namespace($id);
$nonce = $ns->nonce;
// re-use an unexpired nonce (a small deviation from the "used only once" principle, so long as we do not reset the expiration)
// to handle browser pre-fetch or double fetch caused by some browser add-ons/extensions
if(empty($nonce))
{
// generate a new nonce
$nonce = md5(Piwik_Common::getSalt() . time() . Piwik_Common::generateUniqId());
$ns->nonce = $nonce;
$ns->setExpirationSeconds($ttl, 'nonce');
}
return $nonce;
}
/**
* Verify nonce and check referrer (if present, i.e., it may be suppressed by the browser or a proxy/network).
*
* @param string $id Unique id
* @param string $cnonce Nonce sent to client
* @return bool true if valid; false otherwise
*/
static public function verifyNonce($id, $cnonce)
{
$ns = new Zend_Session_Namespace($id);
$nonce = $ns->nonce;
// validate token
if(empty($cnonce) || $cnonce !== $nonce)
{
return false;
}
// validate referer
$referer = Piwik_Url::getReferer();
if(!empty($referer) && (Piwik_Url::getLocalReferer() === false))
{
return false;
}
// validate origin
$origin = Piwik_Url::getOrigin();
if(!empty($origin) &&
($origin == 'null'
|| !in_array($origin, Piwik_Url::getLocalOrigins())))
{
return false;
}
return true;
}
}
|
