FIX AWS SDK PHP DynamoDb StandardSessionConnection binary safety

fixes silverstripe#32

.travis.yml

@@ -9,12 +9,12 @@ env:
 matrix:
   fast_finish: true
   include:
-    - php: 5.6
-      env: DB=MYSQL PHPUNIT_TEST=1 PHPCS_TEST=1
-    - php: 7.0
-      env: DB=MYSQL PHPUNIT_TEST=1
     - php: 7.1
       env: DB=MYSQL PHPUNIT_TEST=1
+    - php: 7.2
+      env: DB=MYSQL PHPUNIT_TEST=1 PHPCS_TEST=1
+    - php: 7.3
+      env: DB=MYSQL PHPUNIT_TEST=1
 
 before_script:
   - composer self-update || true

code/DynamoDbClient.php

@@ -0,0 +1,81 @@
+<?php
+
+namespace SilverStripe\DynamoDb;
+
+/**
+ * DynamoDbClient extension that handles sessions as binary strings rather than textual content.
+ *
+ * Current AWS SDK PHP (<= 3.102.1) implementation passes session data as 'S'.
+ * This class overloads DynamoDbClient::updateItem method, intercepts the session table updates
+ * and substitutes the data type from 'S' to 'B' (from string to binary).
+ * PHP string is the php binary data type, so this should work seamlessly.
+ *
+ * @see https://github.com/silverstripe/silverstripe-dynamodb/issues/32
+ */
+class DynamoDbClient extends \Aws\DynamoDb\DynamoDbClient
+{
+    /**
+     * The name of the DynamoDB table where
+     * sessions are stored
+     *
+     * @var string
+     */
+    private $sessionTable;
+
+    /**
+     * The name of the data attribute of the session table
+     * where sessions are stored
+     *
+     * @var string
+     */
+    private $dataAttribute;
+
+    /**
+     * Initialize the client with the session table
+     *
+     * @param string $sessionTable The session table name
+     *
+     * {@inheritdoc}
+     */
+    public function __construct($sessionTable, ...$args)
+    {
+        $this->sessionTable = $sessionTable;
+        parent::__construct(...$args);
+    }
+
+    /**
+     * Initialize the client with the session data attribute (within the session table)
+     * This method must be used to finish the client initialization, otherwise session updates will not be
+     * intercepted and amended
+     *
+     * @param string $dataAttribute attribute of the session table where session data is persisted
+     */
+    public function setSessionTableDataAttribute($dataAttribute)
+    {
+        $this->dataAttribute = $dataAttribute;
+    }
+
+    public function updateItem($attributes, ...$extra)
+    {
+        $this->patchSessionUpdate($attributes);
+        return parent::updateItem($attributes, ...$extra);
+    }
+
+    /**
+     * Update the session data type from 'S' to 'B' (from string to binary)
+     *
+     * @param mixed &$data Data to be updated in-place
+     */
+    private function patchSessionUpdate(&$data) {
+        if (!isset($data['TableName']) || $data['TableName'] !== $this->sessionTable) {
+            return;
+        }
+
+        if (!isset($data['AttributeUpdates'][$this->dataAttribute]['Value']['S'])) {
+            return;
+        }
+
+        $data['AttributeUpdates'][$this->dataAttribute]['Value']['B'] = $data['AttributeUpdates'][$this->dataAttribute]['Value']['S'];
+        unset($data['AttributeUpdates'][$this->dataAttribute]['Value']['S']);
+    }
+}

code/Model/DynamoDbSession.php

@@ -2,8 +2,8 @@
 
 namespace SilverStripe\DynamoDb\Model;
 
-use Aws\DynamoDb\DynamoDbClient;
-use Aws\DynamoDb\SessionHandler;
+use SilverStripe\DynamoDb\DynamoDbClient;
+use SilverStripe\DynamoDb\SessionHandler;
 use Aws\DoctrineCacheAdapter;
 use Doctrine\Common\Cache\ApcuCache;
 use SilverStripe\Core\Config\Config;
@@ -78,7 +78,8 @@ public static function get()
 
     public function __construct($options, $table)
     {
-        $this->client = new DynamoDbClient(array_merge(['version' => '2012-08-10'], $options));
+        $this->client = new DynamoDbClient($table, array_merge(['version' => '2012-08-10'], $options));
+
         $this->table = $table;
         $this->handler = SessionHandler::fromClient(
             $this->client,

code/SessionHandler.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace SilverStripe\DynamoDb;
+
+use Aws\DynamoDb\SessionConnectionInterface;
+
+/**
+ * The only purpose of this class is to finish our custom
+ * \SilverStripe\DynamoDb\DynamoDbClient initialization.
+ * To do so it simply needs to pass session data attribute
+ * from SessionConnection to DynamoDbClient::setSessionTableDataAttribute
+ * so the latter may intercept session table updates intelligently.
+ *
+ * @see \SilverStripe\DynamoDb\DynamoDbClient
+ */
+class SessionHandler extends \Aws\DynamoDb\SessionHandler
+{
+    /**
+     * @var SessionConnectionInterface
+     */
+    private $connection;
+
+    public static function fromClient(\Aws\DynamoDb\DynamoDbClient $client, array $config = [])
+    {
+        $handler = parent::fromClient($client, $config);
+        $client->setSessionTableDataAttribute($handler->connection->getDataAttribute());
+
+        return $handler;
+    }
+
+    public function __construct(SessionConnectionInterface $connection)
+    {
+        $this->connection = $connection;
+        parent::__construct($connection);
+    }
+}

composer.json

@@ -21,7 +21,8 @@
 		"silverstripe/framework": "^4@dev"
 	},
 	"require-dev": {
-		"phpunit/PHPUnit": "^5.7"
+		"phpunit/PHPUnit": "^5.7",
+		"squizlabs/php_codesniffer": "^3.0",
 	},
 	"autoload": {
     "psr-4": {