nextcloud/lib/private/Security/CSRF/CsrfToken.php

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<?php
/**
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* @copyright Copyright (c) 2016, ownCloud, Inc.
*
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* @author Lukas Reschke <lukas@statuscode.ch>
*
* @license AGPL-3.0
*
* This code is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License, version 3,
* along with this program. If not, see <http://www.gnu.org/licenses/>
*
*/
namespace OC\Security\CSRF;
/**
* Class CsrfToken represents the stored or provided CSRF token. To mitigate
* BREACH alike vulnerabilities the token is returned in an encrypted value as
* well in an unencrypted value. For display measures to the user always the
* unencrypted one should be chosen.
*
* @package OC\Security\CSRF
*/
class CsrfToken {
/** @var string */
private $value;
Add support for CSP nonces CSP nonces are a feature available with CSP v2. Basically instead of saying "JS resources from the same domain are ok to be served" we now say "Ressources from everywhere are allowed as long as they add a `nonce` attribute to the script tag with the right nonce. At the moment the nonce is basically just a `<?php p(base64_encode($_['requesttoken'])) ?>`, we have to decode the requesttoken since `:` is not an allowed value in the nonce. So if somebody does on their own include JS files (instead of using the `addScript` public API, they now must also include that attribute.) IE does currently not implement CSP v2, thus there is a whitelist included that delivers the new CSP v2 policy to newer browsers. Check http://caniuse.com/#feat=contentsecuritypolicy2 for the current browser support list. An alternative approach would be to just add `'unsafe-inline'` as well as `'unsafe-inline'` is ignored by CSPv2 when a nonce is set. But this would make this security feature unusable at all in IE. Not worth it at the moment IMO. Implementing this offers the following advantages: 1. **Security:** As we host resources from the same domain by design we don't have to worry about 'self' anymore being in the whitelist 2. **Performance:** We can move oc.js again to inline JS. This makes the loading way quicker as we don't have to load on every load of a new web page a blocking dynamically non-cached JavaScript file. If you want to toy with CSP see also https://csp-evaluator.withgoogle.com/ Signed-off-by: Lukas Reschke <lukas@statuscode.ch>
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/** @var string */
private $encryptedValue = '';
/**
* @param string $value Value of the token. Can be encrypted or not encrypted.
*/
public function __construct($value) {
$this->value = $value;
}
/**
* Encrypted value of the token. This is used to mitigate BREACH alike
* vulnerabilities. For display measures do use this functionality.
*
* @return string
*/
public function getEncryptedValue() {
Add support for CSP nonces CSP nonces are a feature available with CSP v2. Basically instead of saying "JS resources from the same domain are ok to be served" we now say "Ressources from everywhere are allowed as long as they add a `nonce` attribute to the script tag with the right nonce. At the moment the nonce is basically just a `<?php p(base64_encode($_['requesttoken'])) ?>`, we have to decode the requesttoken since `:` is not an allowed value in the nonce. So if somebody does on their own include JS files (instead of using the `addScript` public API, they now must also include that attribute.) IE does currently not implement CSP v2, thus there is a whitelist included that delivers the new CSP v2 policy to newer browsers. Check http://caniuse.com/#feat=contentsecuritypolicy2 for the current browser support list. An alternative approach would be to just add `'unsafe-inline'` as well as `'unsafe-inline'` is ignored by CSPv2 when a nonce is set. But this would make this security feature unusable at all in IE. Not worth it at the moment IMO. Implementing this offers the following advantages: 1. **Security:** As we host resources from the same domain by design we don't have to worry about 'self' anymore being in the whitelist 2. **Performance:** We can move oc.js again to inline JS. This makes the loading way quicker as we don't have to load on every load of a new web page a blocking dynamically non-cached JavaScript file. If you want to toy with CSP see also https://csp-evaluator.withgoogle.com/ Signed-off-by: Lukas Reschke <lukas@statuscode.ch>
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if($this->encryptedValue === '') {
$sharedSecret = random_bytes(strlen($this->value));
$this->encryptedValue = base64_encode($this->value ^ $sharedSecret) . ':' . base64_encode($sharedSecret);
Add support for CSP nonces CSP nonces are a feature available with CSP v2. Basically instead of saying "JS resources from the same domain are ok to be served" we now say "Ressources from everywhere are allowed as long as they add a `nonce` attribute to the script tag with the right nonce. At the moment the nonce is basically just a `<?php p(base64_encode($_['requesttoken'])) ?>`, we have to decode the requesttoken since `:` is not an allowed value in the nonce. So if somebody does on their own include JS files (instead of using the `addScript` public API, they now must also include that attribute.) IE does currently not implement CSP v2, thus there is a whitelist included that delivers the new CSP v2 policy to newer browsers. Check http://caniuse.com/#feat=contentsecuritypolicy2 for the current browser support list. An alternative approach would be to just add `'unsafe-inline'` as well as `'unsafe-inline'` is ignored by CSPv2 when a nonce is set. But this would make this security feature unusable at all in IE. Not worth it at the moment IMO. Implementing this offers the following advantages: 1. **Security:** As we host resources from the same domain by design we don't have to worry about 'self' anymore being in the whitelist 2. **Performance:** We can move oc.js again to inline JS. This makes the loading way quicker as we don't have to load on every load of a new web page a blocking dynamically non-cached JavaScript file. If you want to toy with CSP see also https://csp-evaluator.withgoogle.com/ Signed-off-by: Lukas Reschke <lukas@statuscode.ch>
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}
return $this->encryptedValue;
}
/**
* The unencrypted value of the token. Used for decrypting an already
* encrypted token.
*
* @return string
*/
public function getDecryptedValue() {
$token = explode(':', $this->value);
if (count($token) !== 2) {
return '';
}
$obfuscatedToken = $token[0];
$secret = $token[1];
return base64_decode($obfuscatedToken) ^ base64_decode($secret);
}
}