Masking: Distinguish between EOF and 8 byte integer

When processing the response to a COM_QUERY, the rows will be
terminated by an EOF packet. However, as the type byte of an
EOF packet is 0xFE and the identifying byte of an 8 byte length
encoded integer is also 0xFE it is not possible to distinguish
the two except by also looking at packet length.

server/modules/filter/masking/maskingfiltersession.cc

@@ -216,28 +216,26 @@ void warn_of_type_mismatch(const MaskingRules::Rule& rule)
 
 void MaskingFilterSession::handle_row(GWBUF* pPacket)
 {
-    ComResponse response(pPacket);
+    ComPacket response(pPacket);
 
-    switch (response.type())
+    if ((response.payload_len() == ComEOF::PAYLOAD_LEN) &&
+        (ComResponse(response).type() == ComPacket::EOF_PACKET))
     {
-    case ComPacket::EOF_PACKET:
         // EOF after last row.
+        ComEOF eof(response);
+
+        if (eof.status() & SERVER_MORE_RESULTS_EXIST)
         {
-            ComEOF eof(response);
-
-            if (eof.status() & SERVER_MORE_RESULTS_EXIST)
-            {
-                m_res.reset_multi();
-                m_state = EXPECTING_RESPONSE;
-            }
-            else
-            {
-                m_state = EXPECTING_NOTHING;
-            }
+            m_res.reset_multi();
+            m_state = EXPECTING_RESPONSE;
         }
-        break;
-
-    default:
+        else
+        {
+            m_state = EXPECTING_NOTHING;
+        }
+    }
+    else
+    {
         if (m_res.some_rule_matches())
         {
             if (response.payload_len() >= ComPacket::MAX_PAYLOAD_LEN)
@@ -267,7 +265,7 @@ void MaskingFilterSession::handle_large_payload()
     }
 }
 
-void MaskingFilterSession::mask_values(ComResponse& response)
+void MaskingFilterSession::mask_values(ComPacket& response)
 {
     switch (m_res.command())
     {

server/modules/filter/masking/maskingfiltersession.hh

@@ -59,7 +59,7 @@ private:
     void handle_eof(GWBUF* pPacket);
     void handle_large_payload();
 
-    void mask_values(ComResponse& response);
+    void mask_values(ComPacket& response);
 
 private:
     typedef std::tr1::shared_ptr<MaskingRules> SMaskingRules;

server/modules/filter/masking/mysql.hh

@@ -493,16 +493,6 @@ public:
         MAX_PAYLOAD_LEN = 0xffffff
     };
 
-    uint32_t payload_len() const
-    {
-        return m_payload_len;
-    }
-    uint8_t packet_no() const
-    {
-        return m_packet_no;
-    }
-
-protected:
     ComPacket(GWBUF* pPacket)
         : m_pPacket(pPacket)
         , m_pData(GWBUF_DATA(pPacket))
@@ -521,6 +511,22 @@ protected:
         m_pData += MYSQL_HEADER_LEN;
     }
 
+    uint32_t payload_len() const
+    {
+        return m_payload_len;
+    }
+
+    uint32_t packet_len() const
+    {
+        return MYSQL_HEADER_LEN + m_payload_len;
+    }
+
+    uint8_t packet_no() const
+    {
+        return m_packet_no;
+    }
+
+protected:
     GWBUF*   m_pPacket;
     uint8_t* m_pData;
 
@@ -542,13 +548,22 @@ public:
         : ComPacket(pPacket)
         , m_type(*m_pData)
     {
+        ss_dassert(packet_len() >= MYSQL_HEADER_LEN + 1);
         ++m_pData;
     }
 
+    ComResponse(const ComPacket& packet)
+        : ComPacket(packet)
+        , m_type(*m_pData)
+    {
+        ss_dassert(packet_len() >= MYSQL_HEADER_LEN + 1);
+        ++m_pData;
+    }
     ComResponse(const ComResponse& packet)
         : ComPacket(packet)
         , m_type(packet.m_type)
     {
+        ss_dassert(packet_len() >= MYSQL_HEADER_LEN + 1);
         ++m_pData;
     }
 
@@ -579,6 +594,12 @@ protected:
 class ComEOF : public ComResponse
 {
 public:
+    enum
+    {
+        PAYLOAD_LEN = 5,
+        PACKET_LEN  = MYSQL_HEADER_LEN + PAYLOAD_LEN
+    };
+
     ComEOF(GWBUF* pPacket)
         : ComResponse(pPacket)
     {