Correctly report OpenSSL errors from cookie encryption

Without calling openssl_error_string() we pollute openssl global state
and some other library might report this as failure (eg. mysqlnd driver
when connecting to SSL enabled server).

Fixes #12293

Signed-off-by: Michal Čihař <michal@cihar.com>

ChangeLog

@@ -23,6 +23,7 @@ phpMyAdmin - ChangeLog
 - issue #11816 Fixed operation with lower_case_table_names=2
 - issue #12813 Fixed stored procedure execution
 - issue #12826 Honor user configured connection collation
+- issue #12293 Correctly report OpenSSL errors from cookie encryption
 
 4.6.5.2 (2016-12-05)
 - issue #12765 Fixed SQL export with newlines

libraries/plugins/auth/AuthenticationCookie.php

@@ -717,6 +717,18 @@ class AuthenticationCookie extends AuthenticationPlugin
         );
     }
 
+    /**
+     * Reports any SSL errors
+     *
+     * @return void
+     */
+    public function reportSSLErrors()
+    {
+        while (($ssl_err = openssl_error_string()) !== false) {
+            trigger_error('OpenSSL error: ' . $ssl_err, E_USER_ERROR);
+        }
+    }
+
     /**
      * Encryption using openssl's AES or phpseclib's AES
      * (phpseclib uses mcrypt when it is available)
@@ -739,6 +751,7 @@ class AuthenticationCookie extends AuthenticationPlugin
                 0,
                 $iv
             );
+            $this->reportSSLErrors();
         } else {
             $cipher = new Crypt\AES(Crypt\Base::MODE_CBC);
             $cipher->setIV($iv);
@@ -783,13 +796,15 @@ class AuthenticationCookie extends AuthenticationPlugin
         }
 
         if ($this->_use_openssl) {
-            return openssl_decrypt(
+            $result = openssl_decrypt(
                 $data['payload'],
                 'AES-128-CBC',
                 $secret,
                 0,
                 base64_decode($data['iv'])
             );
+            $this->reportSSLErrors();
+            return $result;
         } else {
             $cipher = new Crypt\AES(Crypt\Base::MODE_CBC);
             $cipher->setIV(base64_decode($data['iv']));