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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 (
"crypto/hmac";
"crypto/rc4";
"crypto/rsa";
"crypto/sha1";
"crypto/subtle";
"crypto/x509";
"io";
)
// A serverHandshake performs the server side of the TLS 1.1 handshake protocol.
type clientHandshake struct {
writeChan chan<- interface{};
controlChan chan<- interface{};
msgChan <-chan interface{};
config *Config;
}
func (h *clientHandshake) loop(writeChan chan<- interface{}, controlChan chan<- interface{}, msgChan <-chan interface{}, config *Config) {
h.writeChan = writeChan;
h.controlChan = controlChan;
h.msgChan = msgChan;
h.config = config;
defer close(writeChan);
defer close(controlChan);
finishedHash := newFinishedHash();
hello := &clientHelloMsg{
major: defaultMajor,
minor: defaultMinor,
cipherSuites: []uint16{TLS_RSA_WITH_RC4_128_SHA},
compressionMethods: []uint8{compressionNone},
random: make([]byte, 32),
};
currentTime := uint32(config.Time());
hello.random[0] = byte(currentTime >> 24);
hello.random[1] = byte(currentTime >> 16);
hello.random[2] = byte(currentTime >> 8);
hello.random[3] = byte(currentTime);
_, err := io.ReadFull(config.Rand, hello.random[4:]);
if err != nil {
h.error(alertInternalError);
return;
}
finishedHash.Write(hello.marshal());
writeChan <- writerSetVersion{defaultMajor, defaultMinor};
writeChan <- hello;
serverHello, ok := h.readHandshakeMsg().(*serverHelloMsg);
if !ok {
h.error(alertUnexpectedMessage);
return;
}
finishedHash.Write(serverHello.marshal());
major, minor, ok := mutualVersion(serverHello.major, serverHello.minor);
if !ok {
h.error(alertProtocolVersion);
return;
}
writeChan <- writerSetVersion{major, minor};
if serverHello.cipherSuite != TLS_RSA_WITH_RC4_128_SHA ||
serverHello.compressionMethod != compressionNone {
h.error(alertUnexpectedMessage);
return;
}
certMsg, ok := h.readHandshakeMsg().(*certificateMsg);
if !ok || len(certMsg.certificates) == 0 {
h.error(alertUnexpectedMessage);
return;
}
finishedHash.Write(certMsg.marshal());
certs := make([]*x509.Certificate, len(certMsg.certificates));
for i, asn1Data := range certMsg.certificates {
cert, err := x509.ParseCertificate(asn1Data);
if err != nil {
h.error(alertBadCertificate);
return;
}
certs[i] = cert;
}
// TODO(agl): do better validation of certs: max path length, name restrictions etc.
for i := 1; i < len(certs); i++ {
if certs[i-1].CheckSignatureFrom(certs[i]) != nil {
h.error(alertBadCertificate);
return;
}
}
if config.RootCAs != nil {
root := config.RootCAs.FindParent(certs[len(certs)-1]);
if root == nil {
h.error(alertBadCertificate);
return;
}
if certs[len(certs)-1].CheckSignatureFrom(root) != nil {
h.error(alertBadCertificate);
return;
}
}
pub, ok := certs[0].PublicKey.(*rsa.PublicKey);
if !ok {
h.error(alertUnsupportedCertificate);
return;
}
shd, ok := h.readHandshakeMsg().(*serverHelloDoneMsg);
if !ok {
h.error(alertUnexpectedMessage);
return;
}
finishedHash.Write(shd.marshal());
ckx := new(clientKeyExchangeMsg);
preMasterSecret := make([]byte, 48);
// Note that the version number in the preMasterSecret must be the
// version offered in the ClientHello.
preMasterSecret[0] = defaultMajor;
preMasterSecret[1] = defaultMinor;
_, err = io.ReadFull(config.Rand, preMasterSecret[2:]);
if err != nil {
h.error(alertInternalError);
return;
}
ckx.ciphertext, err = rsa.EncryptPKCS1v15(config.Rand, pub, preMasterSecret);
if err != nil {
h.error(alertInternalError);
return;
}
finishedHash.Write(ckx.marshal());
writeChan <- ckx;
suite := cipherSuites[0];
masterSecret, clientMAC, serverMAC, clientKey, serverKey :=
keysFromPreMasterSecret11(preMasterSecret, hello.random, serverHello.random, suite.hashLength, suite.cipherKeyLength);
cipher, _ := rc4.NewCipher(clientKey);
writeChan <- writerChangeCipherSpec{cipher, hmac.New(sha1.New(), clientMAC)};
finished := new(finishedMsg);
finished.verifyData = finishedHash.clientSum(masterSecret);
finishedHash.Write(finished.marshal());
writeChan <- finished;
// TODO(agl): this is cut-through mode which should probably be an option.
writeChan <- writerEnableApplicationData{};
_, ok = h.readHandshakeMsg().(changeCipherSpec);
if !ok {
h.error(alertUnexpectedMessage);
return;
}
cipher2, _ := rc4.NewCipher(serverKey);
controlChan <- &newCipherSpec{cipher2, hmac.New(sha1.New(), serverMAC)};
serverFinished, ok := h.readHandshakeMsg().(*finishedMsg);
if !ok {
h.error(alertUnexpectedMessage);
return;
}
verify := finishedHash.serverSum(masterSecret);
if len(verify) != len(serverFinished.verifyData) ||
subtle.ConstantTimeCompare(verify, serverFinished.verifyData) != 1 {
h.error(alertHandshakeFailure);
return;
}
controlChan <- ConnectionState{true, "TLS_RSA_WITH_RC4_128_SHA", 0};
// This should just block forever.
_ = h.readHandshakeMsg();
h.error(alertUnexpectedMessage);
return;
}
func (h *clientHandshake) readHandshakeMsg() interface{} {
v := <-h.msgChan;
if closed(h.msgChan) {
// If the channel closed then the processor received an error
// from the peer and we don't want to echo it back to them.
h.msgChan = nil;
return 0;
}
if _, ok := v.(alert); ok {
// We got an alert from the processor. We forward to the writer
// and shutdown.
h.writeChan <- v;
h.msgChan = nil;
return 0;
}
return v;
}
func (h *clientHandshake) error(e alertType) {
if h.msgChan != nil {
// If we didn't get an error from the processor, then we need
// to tell it about the error.
go func() {
for _ = range h.msgChan {
}
}();
h.controlChan <- ConnectionState{false, "", e};
close(h.controlChan);
h.writeChan <- alert{alertLevelError, e};
}
}
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