Move frame wrapper

wrappers/mtproto_frame.go

@@ -0,0 +1,151 @@
+package wrappers
+
+import (
+	"bytes"
+	"crypto/aes"
+	"encoding/binary"
+	"hash/crc32"
+	"io"
+	"io/ioutil"
+	"net"
+
+	"github.com/juju/errors"
+)
+
+const (
+	mtprotoFrameMinMessageLength = 12
+	mtprotoFrameMaxMessageLength = 16777216
+)
+
+var mtprotoFramePadding = []byte{0x04, 0x00, 0x00, 0x00}
+
+type MTProtoFrame struct {
+	conn       WrapStreamReadWriteCloser
+	readSeqNo  int32
+	writeSeqNo int32
+}
+
+func (m *MTProtoFrame) Read() ([]byte, error) {
+	buf := &bytes.Buffer{}
+	sum := crc32.NewIEEE()
+	writer := io.MultiWriter(buf, sum)
+
+	for {
+		buf.Reset()
+		sum.Reset()
+		if _, err := io.CopyN(writer, m.conn, 4); err != nil {
+			return nil, errors.Annotate(err, "Cannot read frame padding")
+		}
+		if !bytes.Equal(buf.Bytes(), mtprotoFramePadding) {
+			break
+		}
+	}
+
+	messageLength := binary.LittleEndian.Uint32(buf.Bytes())
+	m.LogDebug("Read MTProto frame",
+		"messageLength", messageLength,
+		"sequence_number", m.readSeqNo,
+	)
+	if messageLength%4 != 0 || messageLength < mtprotoFrameMinMessageLength || messageLength > mtprotoFrameMaxMessageLength {
+		return nil, errors.Errorf("Incorrect frame message length %d", messageLength)
+	}
+
+	buf.Reset()
+	buf.Grow(int(messageLength) - 4 - 4)
+	if _, err := io.CopyN(writer, m.conn, int64(messageLength)-4-4); err != nil {
+		return nil, errors.Annotate(err, "Cannot read the message frame")
+	}
+
+	var seqNo int32
+	binary.Read(buf, binary.LittleEndian, &seqNo)
+	if seqNo != m.readSeqNo {
+		return nil, errors.Errorf("Unexpected sequence number %d (wait for %d)", seqNo, m.readSeqNo)
+	}
+
+	data, _ := ioutil.ReadAll(buf)
+	buf.Reset()
+	// write to buf, not to writer. This is because we are going to fetch
+	// crc32 checksum.
+	if _, err := io.CopyN(buf, m.conn, 4); err != nil {
+		return nil, errors.Annotate(err, "Cannot read checksum")
+	}
+
+	checksum := binary.LittleEndian.Uint32(buf.Bytes())
+	if checksum != sum.Sum32() {
+		return nil, errors.Errorf("CRC32 checksum mismatch. Wait for %d, got %d", sum.Sum32(), checksum)
+	}
+
+	m.LogDebug("Read MTProto frame",
+		"messageLength", messageLength,
+		"sequence_number", m.readSeqNo,
+		"dataLength", len(data),
+		"checksum", checksum,
+	)
+	m.readSeqNo++
+
+	return data, nil
+}
+
+func (m *MTProtoFrame) Write(p []byte) (int, error) {
+	messageLength := 4 + 4 + len(p) + 4
+	paddingLength := (aes.BlockSize - messageLength%aes.BlockSize) % aes.BlockSize
+
+	buf := &bytes.Buffer{}
+	buf.Grow(messageLength + paddingLength)
+
+	binary.Write(buf, binary.LittleEndian, uint32(messageLength))
+	binary.Write(buf, binary.LittleEndian, m.writeSeqNo)
+	buf.Write(p)
+
+	checksum := crc32.ChecksumIEEE(buf.Bytes())
+	binary.Write(buf, binary.LittleEndian, checksum)
+	buf.Write(bytes.Repeat(mtprotoFramePadding, paddingLength/4))
+
+	m.LogDebug("Write MTProto frame",
+		"length", len(p),
+		"sequence_number", m.writeSeqNo,
+		"crc32", checksum,
+		"frame_length", buf.Len(),
+	)
+	m.writeSeqNo++
+
+	_, err := m.conn.Write(buf.Bytes())
+
+	return len(p), err
+}
+
+func (m *MTProtoFrame) LogDebug(msg string, data ...interface{}) {
+	m.conn.LogDebug(msg, data...)
+}
+
+func (m *MTProtoFrame) LogInfo(msg string, data ...interface{}) {
+	m.conn.LogInfo(msg, data...)
+}
+
+func (m *MTProtoFrame) LogWarn(msg string, data ...interface{}) {
+	m.conn.LogWarn(msg, data...)
+}
+
+func (m *MTProtoFrame) LogError(msg string, data ...interface{}) {
+	m.conn.LogError(msg, data...)
+}
+
+func (m *MTProtoFrame) LocalAddr() *net.TCPAddr {
+	return m.conn.LocalAddr()
+}
+
+func (m *MTProtoFrame) RemoteAddr() *net.TCPAddr {
+	return m.conn.RemoteAddr()
+}
+
+func (m *MTProtoFrame) Close() error {
+	return m.conn.Close()
+}
+
+func NewMTProtoFrame(conn WrapStreamReadWriteCloser, seqNo int32) WrapPacketReadWriteCloser {
+	return &MTProtoFrame{
+		conn:       conn,
+		readSeqNo:  seqNo,
+		writeSeqNo: seqNo,
+	}
+}