packets: discard connection on zero sequence ID

AUTHORS

@@ -74,6 +74,7 @@ Maciej Zimnoch <maciej.zimnoch at codilime.com>
 Michael Woolnough <michael.woolnough at gmail.com>
 Nathanial Murphy <nathanial.murphy at gmail.com>
 Nicola Peduzzi <thenikso at gmail.com>
+Oliver Bone <owbone at github.com>
 Olivier Mengué <dolmen at cpan.org>
 oscarzhao <oscarzhaosl at gmail.com>
 Paul Bonser <misterpib at gmail.com>

packets.go

@@ -43,10 +43,20 @@ func (mc *mysqlConn) readPacket() ([]byte, error) {
  pktLen := int(uint32(data[0]) | uint32(data[1])<<8 | uint32(data[2])<<16)
 
  // check packet sync [8 bit]
- if data[3] != mc.sequence {
- if data[3] > mc.sequence {
+ if sequenceID := data[3]; sequenceID != mc.sequence {
+ if sequenceID > mc.sequence {
  return nil, ErrPktSyncMul
  }
+
+ if sequenceID == 0 {
+ // If the sequence ID is zero then this is not a response to any
+ // packet that the client has sent. It's likely an error packet
+ // that the server sent simultaneously.
+ errLog.Print("received packet with zero sequence ID")
+ mc.Close()
+ return nil, ErrInvalidConn
+ }
+
  return nil, ErrPktSync
  }
  mc.sequence++

packets_test.go

@@ -134,9 +134,9 @@ func TestReadPacketWrongSequenceID(t *testing.T) {
  }
 
  // too low sequence id
- conn.data = []byte{0x01, 0x00, 0x00, 0x00, 0xff}
+ conn.data = []byte{0x01, 0x00, 0x00, 0x01, 0xff}
  conn.maxReads = 1
- mc.sequence = 1
+ mc.sequence = 2
  _, err := mc.readPacket()
  if err != ErrPktSync {
  t.Errorf("expected ErrPktSync, got %v", err)
@@ -155,6 +155,27 @@ func TestReadPacketWrongSequenceID(t *testing.T) {
  }
 }
 
+func TestReadPacketZeroSequenceID(t *testing.T) {
+ conn := new(mockConn)
+ mc := &mysqlConn{
+ buf: newBuffer(conn),
+ closech: make(chan struct{}),
+ }
+
+ conn.data = []byte{0x01, 0x00, 0x00, 0x00, 0xff}
+ conn.maxReads = 1
+ mc.sequence = 1
+ _, err := mc.readPacket()
+ if err != ErrInvalidConn {
+ t.Errorf("expected ErrInvalidConn, got %v", err)
+ }
+
+ // The connection should not be returned to the pool.
+ if mc.IsValid() {
+ t.Errorf("expected connection to no longer be valid")
+ }
+}
+
 func TestReadPacketSplit(t *testing.T) {
  conn := new(mockConn)
  mc := &mysqlConn{