Added additional checking if response length is beyond a reasonable limit (10mb)

src/Connector/Exception/FailedToSendCommand.php

@@ -65,6 +65,30 @@ public static function fromEmptyResponseSize(Command $attemptedCommand, Connecti
         ));
     }
 
+    public static function fromFailedResponseUnpack(Command $attemptedCommand, ConnectionAddress $connectionAddress) : self
+    {
+        return new self(sprintf(
+            'Response length could not be unpacked for %s (maybe invalid format?). Address was: %s',
+            get_class($attemptedCommand),
+            $connectionAddress->toString()
+        ));
+    }
+
+    public static function fromTooLargeResponseLength(
+        int $responseLengthReturned,
+        int $responseLengthLimit,
+        Command $attemptedCommand,
+        ConnectionAddress $connectionAddress
+    ) : self {
+        return new self(sprintf(
+            'Response length returned (%d) exceeded our limit for reading (%d) for %s. Address was: %s',
+            $responseLengthReturned,
+            $responseLengthLimit,
+            get_class($attemptedCommand),
+            $connectionAddress->toString()
+        ));
+    }
+
     /** @param resource $socketResource */
     public static function readingResponseContentFromSocket(Command $attemptedCommand, $socketResource, ConnectionAddress $connectionAddress) : self
     {

src/Connector/SocketConnector.php

@@ -14,6 +14,8 @@
 use const E_STRICT;
 use const E_WARNING;
 use const SOCK_STREAM;
+use function array_key_exists;
+use function is_array;
 use function json_encode;
 use function pack;
 use function register_shutdown_function;
@@ -32,6 +34,8 @@
 /** @internal */
 final class SocketConnector implements Connector
 {
+    private const MAXIMUM_RESPONSE_LENGTH_TO_READ = 10000000;
+
     /** @var resource */
     private $socket;
 
@@ -139,17 +143,34 @@ public function sendCommand(Command $message) : string
         }
 
         // Read the response back and drop it. Needed for socket liveness
-        $responseLength = @socket_read($this->socket, 4);
+        $responseLengthPacked = @socket_read($this->socket, 4);
 
-        if ($responseLength === false) {
+        if ($responseLengthPacked === false) {
             throw Exception\FailedToSendCommand::readingResponseSizeFromSocket($message, $this->socket, $this->connectionAddress);
         }
 
-        if ($responseLength === '') {
+        if ($responseLengthPacked === '') {
             throw Exception\FailedToSendCommand::fromEmptyResponseSize($message, $this->connectionAddress);
         }
 
-        $dataRead = @socket_read($this->socket, unpack('N', $responseLength)[1]);
+        $responseLengthUnpacked = unpack('Nlen', $responseLengthPacked);
+
+        if (! is_array($responseLengthUnpacked) || ! array_key_exists('len', $responseLengthUnpacked)) {
+            throw Exception\FailedToSendCommand::fromFailedResponseUnpack($message, $this->connectionAddress);
+        }
+
+        $responseLength = (int) $responseLengthUnpacked['len'];
+
+        if ($responseLength > self::MAXIMUM_RESPONSE_LENGTH_TO_READ) {
+            throw Exception\FailedToSendCommand::fromTooLargeResponseLength(
+                $responseLength,
+                self::MAXIMUM_RESPONSE_LENGTH_TO_READ,
+                $message,
+                $this->connectionAddress
+            );
+        }
+
+        $dataRead = @socket_read($this->socket, $responseLength);
 
         if ($dataRead === false) {
             throw Exception\FailedToSendCommand::readingResponseContentFromSocket($message, $this->socket, $this->connectionAddress);