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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package tls
import (
"fmt"
"hash"
"io"
)
// writerEnableApplicationData is a message which instructs recordWriter to
// start reading and transmitting data from the application data channel.
type writerEnableApplicationData struct{}
// writerChangeCipherSpec updates the encryption and MAC functions and resets
// the sequence count.
type writerChangeCipherSpec struct {
encryptor encryptor
mac hash.Hash
}
// writerSetVersion sets the version number bytes that we included in the
// record header for future records.
type writerSetVersion struct {
major, minor uint8
}
// A recordWriter accepts messages from the handshake processor and
// application data. It writes them to the outgoing connection and blocks on
// writing. It doesn't read from the application data channel until the
// handshake processor has signaled that the handshake is complete.
type recordWriter struct {
writer io.Writer
encryptor encryptor
mac hash.Hash
seqNum uint64
major, minor uint8
shutdown bool
appChan <-chan []byte
controlChan <-chan interface{}
header [13]byte
}
func (w *recordWriter) loop(writer io.Writer, appChan <-chan []byte, controlChan <-chan interface{}) {
w.writer = writer
w.encryptor = nop{}
w.mac = nop{}
w.appChan = appChan
w.controlChan = controlChan
for !w.shutdown {
msg := <-controlChan
if _, ok := msg.(writerEnableApplicationData); ok {
break
}
w.processControlMessage(msg)
}
for !w.shutdown {
// Always process control messages first.
if controlMsg, ok := <-controlChan; ok {
w.processControlMessage(controlMsg)
continue
}
select {
case controlMsg := <-controlChan:
w.processControlMessage(controlMsg)
case appMsg := <-appChan:
w.processAppMessage(appMsg)
}
}
if !closed(appChan) {
go func() {
for _ = range appChan {
}
}()
}
if !closed(controlChan) {
go func() {
for _ = range controlChan {
}
}()
}
}
// fillMACHeader generates a MAC header. See RFC 4346, section 6.2.3.1.
func fillMACHeader(header *[13]byte, seqNum uint64, length int, r *record) {
header[0] = uint8(seqNum >> 56)
header[1] = uint8(seqNum >> 48)
header[2] = uint8(seqNum >> 40)
header[3] = uint8(seqNum >> 32)
header[4] = uint8(seqNum >> 24)
header[5] = uint8(seqNum >> 16)
header[6] = uint8(seqNum >> 8)
header[7] = uint8(seqNum)
header[8] = uint8(r.contentType)
header[9] = r.major
header[10] = r.minor
header[11] = uint8(length >> 8)
header[12] = uint8(length)
}
func (w *recordWriter) writeRecord(r *record) {
w.mac.Reset()
fillMACHeader(&w.header, w.seqNum, len(r.payload), r)
w.mac.Write(w.header[0:13])
w.mac.Write(r.payload)
macBytes := w.mac.Sum()
w.encryptor.XORKeyStream(r.payload)
w.encryptor.XORKeyStream(macBytes)
length := len(r.payload) + len(macBytes)
w.header[11] = uint8(length >> 8)
w.header[12] = uint8(length)
w.writer.Write(w.header[8:13])
w.writer.Write(r.payload)
w.writer.Write(macBytes)
w.seqNum++
}
func (w *recordWriter) processControlMessage(controlMsg interface{}) {
if controlMsg == nil {
w.shutdown = true
return
}
switch msg := controlMsg.(type) {
case writerChangeCipherSpec:
w.writeRecord(&record{recordTypeChangeCipherSpec, w.major, w.minor, []byte{0x01}})
w.encryptor = msg.encryptor
w.mac = msg.mac
w.seqNum = 0
case writerSetVersion:
w.major = msg.major
w.minor = msg.minor
case alert:
w.writeRecord(&record{recordTypeAlert, w.major, w.minor, []byte{byte(msg.level), byte(msg.error)}})
case handshakeMessage:
// TODO(agl): marshal may return a slice too large for a single record.
w.writeRecord(&record{recordTypeHandshake, w.major, w.minor, msg.marshal()})
default:
fmt.Printf("processControlMessage: unknown %#v\n", msg)
}
}
func (w *recordWriter) processAppMessage(appMsg []byte) {
if closed(w.appChan) {
w.writeRecord(&record{recordTypeApplicationData, w.major, w.minor, []byte{byte(alertCloseNotify)}})
w.shutdown = true
return
}
var done int
for done < len(appMsg) {
todo := len(appMsg)
if todo > maxTLSPlaintext {
todo = maxTLSPlaintext
}
w.writeRecord(&record{recordTypeApplicationData, w.major, w.minor, appMsg[done : done+todo]})
done += todo
}
}
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