check option and packet length

libi2pd/Streaming.cpp

@@ -297,6 +297,11 @@ namespace stream
 	{
 		const uint8_t * optionData = packet->GetOptionData ();
 		size_t optionSize = packet->GetOptionSize ();
+		if (optionSize > packet->len)
+		{
+			LogPrint (eLogInfo, "Streaming: Invalid option size ", optionSize, " Discarded");
+			return false;
+		}	
 		if (flags & PACKET_FLAG_DELAY_REQUESTED)
 		{
 			if (!m_IsAckSendScheduled)

libi2pd/Streaming.h

@@ -78,7 +78,7 @@ namespace stream
 
 		Packet (): len (0), offset (0), sendTime (0), resent (false) {};
 		uint8_t * GetBuffer () { return buf + offset; };
-		size_t GetLength () const { return len - offset; };
+		size_t GetLength () const { return len > offset ? len - offset : 0; };
 
 		uint32_t GetSendStreamID () const { return bufbe32toh (buf); };
 		uint32_t GetReceiveStreamID () const { return bufbe32toh (buf + 4); };