Revision: 3134
Author: olavmrk
Date: Wed Aug 1 23:25:23 2012
Log: SAML2_Utils: Fix for attack against PKCS#1 v1.5 described in a
new paper.
See:
http://www.nds.rub.de/research/publications/breaking-xml-encryption-pkcs15/
This fix avoids the problems described in that paper by taking two
measures:
- Require that decrypted contents is at least 4 bytes, since that is the
shortest length of an XML element.
- Generate a (invalid) symmetric key that is deterministic for a given
encrypted key and private key.
Merged into 1.9-branch from r3132.
http://code.google.com/p/simplesamlphp/source/detail?r=3134
Modified:
/branches/simplesamlphp-1.9/lib/SAML2/Utils.php
=======================================
--- /branches/simplesamlphp-1.9/lib/SAML2/Utils.php Fri Mar 30 04:12:48 2012
+++ /branches/simplesamlphp-1.9/lib/SAML2/Utils.php Wed Aug 1 23:25:23 2012
@@ -398,9 +398,13 @@
SimpleSAML_Logger::error('Failed to decrypt symmetric key: ' .
$e->getMessage());
/* Create a replacement key, so that it looks like we fail in the same
way as if the key was correctly padded. */
- /* We base the symmetric key on the encrypted key, so that we always
behave the same way for a given input key. */
+ /* We base the symmetric key on the encrypted key and private key, so
that we always behave the
+ * same way for a given input key.
+ */
$encryptedKey = $encKey->getCipherValue();
- $key = md5($encryptedKey, TRUE);
+ $pkey =
openssl_pkey_get_details($symmetricKeyInfo->key);
+ $pkey = sha1(serialize($pkey), TRUE);
+ $key = sha1($encryptedKey . $pkey, TRUE);
/* Make sure that the key has the correct
length. */
if (strlen($key) > $keySize) {
@@ -431,7 +435,7 @@
*/
$xml = '<root xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";>'.$decrypted.'</root>';
$newDoc = new DOMDocument();
- if (!$newDoc->loadXML($xml)) {
+ if (!@$newDoc->loadXML($xml)) {
throw new Exception('Failed to parse decrypted XML. Maybe the wrong
sharedkey was used?');
}
$decryptedElement = $newDoc->firstChild->firstChild;
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