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halfconn.go
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halfconn.go
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package krach
import (
"fmt"
"sync"
"github.com/sirupsen/logrus"
)
type halfConn struct {
cs *cipherState
conn *Conn
lock *sync.Mutex
debug bool
}
func newHalfConn(conn *Conn, cs *cipherState) *halfConn {
return &halfConn{
conn: conn,
cs: cs,
lock: &sync.Mutex{},
debug: conn.config.Debug,
}
}
func (h *halfConn) write(inBuf []byte) (n int, err error) {
h.lock.Lock()
defer h.lock.Unlock()
if len(inBuf) == 0 {
return 0, nil
}
if len(inBuf) > maxMsgLen-macSize-15 /*max amount of padding*/ -1 /*padding prefix */ {
return 0, fmt.Errorf("%d bytes exceeds the maximum allowed message lnegth of %d bytes", len(inBuf), maxMsgLen)
}
origLen := len(inBuf)
packetBuf := bufPool.Get().(*buf)
packetBuf.index = 1
// TODO check max length
packetBuf.resize(len(inBuf))
packetBuf.copyInto(inBuf)
packetBuf.pad()
packetBuf.ensureCapacity(len(packetBuf.data) + macSize)
if h.debug {
logrus.WithFields(logrus.Fields{
"n": h.cs.n,
"k": h.cs.k,
}).Debug("Encrypting message")
}
packetBuf.data = h.cs.Encrypt(packetBuf.data[:0], nil, packetBuf.data)
packetBuf.index = 0
length := packetBuf.size()
lenBuf := make([]byte, 2)
endianess.PutUint16(lenBuf, length)
if h.debug {
logrus.WithFields(logrus.Fields{
"length": length,
"lenBuf": lenBuf,
"component": "halfconn.write",
}).Debug("Sending length prefix")
}
_, err = h.conn.netConn.Write(lenBuf)
if err != nil {
return 0, err
}
for n < int(length) {
n1, err := h.conn.netConn.Write(packetBuf.data[n+packetBuf.index:])
if err != nil {
return 0, err
}
if h.debug {
logrus.WithFields(logrus.Fields{
"packetData": packetBuf.data[n+packetBuf.index:],
"packetLength": len(packetBuf.data[n+packetBuf.index:]),
"totalPacketLength": len(packetBuf.data[n+packetBuf.index:]) + len(lenBuf),
"component": "halfconn.write",
}).Debug("Writing encrypted packet")
}
n = n + n1
}
packetBuf.reset()
bufPool.Put(packetBuf)
return origLen, nil
}
func (h *halfConn) read(inBuf []byte) (n int, err error) {
h.lock.Lock()
defer h.lock.Unlock()
packetBuf := bufPool.Get().(*buf)
packetBuf.index = 0
packetBuf.ensureLength(2)
_, err = h.conn.netConn.Read(packetBuf.data[packetBuf.index : packetBuf.index+2])
if err != nil {
return 0, err
}
expectedLength := endianess.Uint16(packetBuf.data[packetBuf.index : packetBuf.index+2])
if h.debug {
logrus.WithFields(logrus.Fields{
"expectedLength": expectedLength,
"lengthPrefix": packetBuf.data[packetBuf.index : packetBuf.index+2],
"component": "halfconn.read",
}).Debug("Received length prefix")
}
minPayloadLength := int(expectedLength) - macSize - 15 /*max padding bytes */ - 1 /*pad length field*/
if len(inBuf) < minPayloadLength {
return 0, fmt.Errorf("buffer too small. Can't read %d expected bytes into a buffer of %d bytes", minPayloadLength, len(inBuf))
}
packetBuf.reset()
packetBuf.index = 0
packetBuf.ensureLength(int(expectedLength))
n = 0
for n < int(expectedLength) {
n1, err := h.conn.netConn.Read(packetBuf.data[n:])
if err != nil {
return 0, err
}
n = n + n1
}
if h.debug {
logrus.WithFields(logrus.Fields{
"packetData": packetBuf.data[:n],
"dataLength": len(packetBuf.data[:n]),
"component": "halfconn.read",
}).Debug("Received encrypted data")
}
if h.debug {
logrus.WithFields(logrus.Fields{
"n": h.cs.n,
"k": h.cs.k,
}).Debug("Decrypting message")
}
_, err = h.cs.Decrypt(packetBuf.data[:0], nil, packetBuf.data[:n])
if err != nil {
return 0, err
}
packetBuf.data = packetBuf.data[0 : n-macSize] /* Remove MAC data */
packetBuf.index = 1
packetBuf.copyOutUnpadded(inBuf)
payloadLength := packetBuf.sizeUnpadded()
if h.debug {
logrus.WithFields(logrus.Fields{
"payloadLength": payloadLength,
"payload": inBuf[:payloadLength],
"component": "halfconn.read",
}).Debug("Got unencrypted payload")
}
packetBuf.reset()
bufPool.Put(packetBuf)
return int(payloadLength), nil
}