@recaptime-dev's working patches + fork for Phorge, a community fork of Phabricator. (Upstream dev and stable branches are at upstream/main and upstream/stable respectively.)
hq.recaptime.dev/wiki/Phorge
phorge
phabricator
Proof of concept mitigation of BREACH
Summary: Ref T3684 for discussion. This could be cleaned up a bit (it would be nice to draw entropy once per request, for instance, and maybe respect CSRF_TOKEN_LENGTH more closely) but should effectively mitigate BREACH.
Test Plan: Submitted forms; submitted forms after mucking with CSRF and observed CSRF error. Verified that source now has "B@..." tokens.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T3684
Differential Revision: https://secure.phabricator.com/D6686
+58
-7
+51
-5
src/applications/people/storage/PhabricatorUser.php
+51
-5
src/applications/people/storage/PhabricatorUser.php
···
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}
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const CSRF_CYCLE_FREQUENCY = 3600;
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+
const CSRF_SALT_LENGTH = 8;
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const CSRF_TOKEN_LENGTH = 16;
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const CSRF_BREACH_PREFIX = 'B@';
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const EMAIL_CYCLE_FREQUENCY = 86400;
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const EMAIL_TOKEN_LENGTH = 24;
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-
public function getCSRFToken($offset = 0) {
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private function getRawCSRFToken($offset = 0) {
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return $this->generateToken(
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time() + (self::CSRF_CYCLE_FREQUENCY * $offset),
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self::CSRF_CYCLE_FREQUENCY,
···
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self::CSRF_TOKEN_LENGTH);
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}
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-
public function validateCSRFToken($token) {
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/**
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* @phutil-external-symbol class PhabricatorStartup
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+
*/
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public function getCSRFToken() {
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$salt = PhabricatorStartup::getGlobal('csrf.salt');
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if (!$salt) {
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+
$salt = Filesystem::readRandomCharacters(self::CSRF_SALT_LENGTH);
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PhabricatorStartup::setGlobal('csrf.salt', $salt);
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}
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// Generate a token hash to mitigate BREACH attacks against SSL. See
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// discussion in T3684.
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$token = $this->getRawCSRFToken();
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+
$hash = PhabricatorHash::digest($token, $salt);
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return 'B@'.$salt.substr($hash, 0, self::CSRF_TOKEN_LENGTH);
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}
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+
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public function validateCSRFToken($token) {
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if (!$this->getPHID()) {
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return true;
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}
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$salt = null;
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+
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$version = 'plain';
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+
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// This is a BREACH-mitigating token. See T3684.
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$breach_prefix = self::CSRF_BREACH_PREFIX;
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$breach_prelen = strlen($breach_prefix);
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+
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if (!strncmp($token, $breach_prefix, $breach_prelen)) {
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$version = 'breach';
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$salt = substr($token, $breach_prelen, self::CSRF_SALT_LENGTH);
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$token = substr($token, $breach_prelen + self::CSRF_SALT_LENGTH);
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}
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+
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// When the user posts a form, we check that it contains a valid CSRF token.
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// Tokens cycle each hour (every CSRF_CYLCE_FREQUENCY seconds) and we accept
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// either the current token, the next token (users can submit a "future"
···
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$csrf_window = 6;
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for ($ii = -$csrf_window; $ii <= 1; $ii++) {
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-
$valid = $this->getCSRFToken($ii);
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-
if ($token == $valid) {
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-
return true;
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+
$valid = $this->getRawCSRFToken($ii);
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switch ($version) {
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// TODO: We can remove this after the BREACH version has been in the
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// wild for a while.
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case 'plain':
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if ($token == $valid) {
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return true;
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}
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break;
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case 'breach':
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$digest = PhabricatorHash::digest($valid, $salt);
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if (substr($digest, 0, self::CSRF_TOKEN_LENGTH) == $token) {
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return true;
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}
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break;
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default:
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throw new Exception("Unknown CSRF token format!");
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}
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}
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+5
-2
src/infrastructure/util/PhabricatorHash.php
+5
-2
src/infrastructure/util/PhabricatorHash.php
···
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* @param string Input string.
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* @return string 32-byte hexidecimal SHA1+HMAC hash.
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*/
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-
public static function digest($string) {
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-
$key = PhabricatorEnv::getEnvConfig('security.hmac-key');
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+
public static function digest($string, $key = null) {
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+
if ($key === null) {
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$key = PhabricatorEnv::getEnvConfig('security.hmac-key');
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+
}
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+
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if (!$key) {
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throw new Exception(
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"Set a 'security.hmac-key' in your Phabricator configuration!");
+2
support/PhabricatorStartup.php
+2
support/PhabricatorStartup.php
···
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if (!array_key_exists($key, self::$globals)) {
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return $default;
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}
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+
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return self::$globals[$key];
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}
64
65
···
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private static function validateGlobal($key) {
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static $globals = array(
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'log.access' => true,
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'csrf.salt' => true,
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);
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if (empty($globals[$key])) {