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MediumGHSA-7852-w36x-6mf6 CWE-1240Published May 15, 2024

Laravel Encrypter Component Potential Decryption Failure Leading to Unintended Behavior

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Affected versions

0 → fixed in 5.5.405.6.0 → fixed in 5.6.15

Details

The Laravel Encrypter component is susceptible to a vulnerability that may result in decryption failure, leading to an unexpected return of `false`. Exploiting this issue requires the attacker to manipulate the encrypted payload before decryption. When combined with weak type comparisons in the application's code, such as the example below: ``` <?php $decyptedValue = decrypt($secret); if ($decryptedValue == '') { // Code is run even though decrypted value is false... } ```

The fix

check iv length

Taylor Otwell· Mar 30, 2018, 01:26 PM+2−328e53f23a7
src/Illuminate/Encryption/Encrypter.php+2 −3
@@ -206,9 +206,8 @@ protected function getJsonPayload($payload)
      */
     protected function validPayload($payload)
     {
-        return is_array($payload) && isset(
-            $payload['iv'], $payload['value'], $payload['mac']
-        );
+        return is_array($payload) && isset($payload['iv'], $payload['value'], $payload['mac']) &&
+               strlen(base64_decode($payload['iv'], true)) === openssl_cipher_iv_length($this->cipher);
     }
  
     /**

check iv length

Taylor Otwell· Mar 30, 2018, 01:24 PM+17−3886d261df0
src/Illuminate/Encryption/Encrypter.php+2 −3
@@ -206,9 +206,8 @@ protected function getJsonPayload($payload)
      */
     protected function validPayload($payload)
     {
-        return is_array($payload) && isset(
-            $payload['iv'], $payload['value'], $payload['mac']
-        );
+        return is_array($payload) && isset($payload['iv'], $payload['value'], $payload['mac']) &&
+               strlen(base64_decode($payload['iv'], true)) === openssl_cipher_iv_length($this->cipher);
     }
  
     /**
tests/Encryption/EncrypterTest.php+15 −0
@@ -102,4 +102,19 @@ public function testExceptionThrownWithDifferentKey()
         $b = new Encrypter(str_repeat('b', 16));
         $b->decrypt($a->encrypt('baz'));
     }
+ 
+    /**
+     * @expectedException \Illuminate\Contracts\Encryption\DecryptException
+     * @expectedExceptionMessage The payload is invalid.
+     */
+    public function testExceptionThrownWhenIvIsTooLong()
+    {
+        $e = new Encrypter(str_repeat('a', 16));
+        $payload = $e->encrypt('foo');
+        $data = json_decode(base64_decode($payload), true);
+        $data['iv'] .= $data['value'][0];
+        $data['value'] = substr($data['value'], 1);
+        $modified_payload = base64_encode(json_encode($data));
+        $e->decrypt($modified_payload);
+    }
 }

References