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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 main
import (
"bytes"
"crypto"
"crypto/ecdsa"
"crypto/rsa"
"crypto/subtle"
"crypto/x509"
"encoding/asn1"
"errors"
"fmt"
"io"
"math/big"
"net"
"strconv"
)
type clientHandshakeState struct {
c *Conn
serverHello *serverHelloMsg
hello *clientHelloMsg
suite *cipherSuite
finishedHash finishedHash
masterSecret []byte
session *ClientSessionState
}
func (c *Conn) clientHandshake() error {
if c.config == nil {
c.config = defaultConfig()
}
if len(c.config.ServerName) == 0 && !c.config.InsecureSkipVerify {
return errors.New("tls: either ServerName or InsecureSkipVerify must be specified in the tls.Config")
}
c.sendHandshakeSeq = 0
c.recvHandshakeSeq = 0
hello := &clientHelloMsg{
isDTLS: c.isDTLS,
vers: c.config.maxVersion(),
compressionMethods: []uint8{compressionNone},
random: make([]byte, 32),
ocspStapling: true,
serverName: c.config.ServerName,
supportedCurves: c.config.curvePreferences(),
supportedPoints: []uint8{pointFormatUncompressed},
nextProtoNeg: len(c.config.NextProtos) > 0,
secureRenegotiation: true,
duplicateExtension: c.config.Bugs.DuplicateExtension,
}
if c.config.Bugs.SendClientVersion != 0 {
hello.vers = c.config.Bugs.SendClientVersion
}
possibleCipherSuites := c.config.cipherSuites()
hello.cipherSuites = make([]uint16, 0, len(possibleCipherSuites))
NextCipherSuite:
for _, suiteId := range possibleCipherSuites {
for _, suite := range cipherSuites {
if suite.id != suiteId {
continue
}
// Don't advertise TLS 1.2-only cipher suites unless
// we're attempting TLS 1.2.
if hello.vers < VersionTLS12 && suite.flags&suiteTLS12 != 0 {
continue
}
// Don't advertise non-DTLS cipher suites on DTLS.
if c.isDTLS && suite.flags&suiteNoDTLS != 0 {
continue
}
hello.cipherSuites = append(hello.cipherSuites, suiteId)
continue NextCipherSuite
}
}
if c.config.Bugs.SendFallbackSCSV {
hello.cipherSuites = append(hello.cipherSuites, fallbackSCSV)
}
_, err := io.ReadFull(c.config.rand(), hello.random)
if err != nil {
c.sendAlert(alertInternalError)
return errors.New("tls: short read from Rand: " + err.Error())
}
if hello.vers >= VersionTLS12 {
hello.signatureAndHashes = supportedSKXSignatureAlgorithms
}
var session *ClientSessionState
var cacheKey string
sessionCache := c.config.ClientSessionCache
if c.config.SessionTicketsDisabled {
sessionCache = nil
}
if sessionCache != nil {
hello.ticketSupported = true
// Try to resume a previously negotiated TLS session, if
// available.
cacheKey = clientSessionCacheKey(c.conn.RemoteAddr(), c.config)
candidateSession, ok := sessionCache.Get(cacheKey)
if ok {
// Check that the ciphersuite/version used for the
// previous session are still valid.
cipherSuiteOk := false
for _, id := range hello.cipherSuites {
if id == candidateSession.cipherSuite {
cipherSuiteOk = true
break
}
}
versOk := candidateSession.vers >= c.config.minVersion() &&
candidateSession.vers <= c.config.maxVersion()
if versOk && cipherSuiteOk {
session = candidateSession
}
}
}
if session != nil {
hello.sessionTicket = session.sessionTicket
// A random session ID is used to detect when the
// server accepted the ticket and is resuming a session
// (see RFC 5077).
hello.sessionId = make([]byte, 16)
if _, err := io.ReadFull(c.config.rand(), hello.sessionId); err != nil {
c.sendAlert(alertInternalError)
return errors.New("tls: short read from Rand: " + err.Error())
}
}
var helloBytes []byte
if c.config.Bugs.SendV2ClientHello {
v2Hello := &v2ClientHelloMsg{
vers: hello.vers,
cipherSuites: hello.cipherSuites,
// No session resumption for V2ClientHello.
sessionId: nil,
challenge: hello.random,
}
helloBytes = v2Hello.marshal()
c.writeV2Record(helloBytes)
} else {
helloBytes = hello.marshal()
c.writeRecord(recordTypeHandshake, helloBytes)
}
msg, err := c.readHandshake()
if err != nil {
return err
}
if c.isDTLS {
helloVerifyRequest, ok := msg.(*helloVerifyRequestMsg)
if ok {
hello.raw = nil
hello.cookie = helloVerifyRequest.cookie
helloBytes = hello.marshal()
c.writeRecord(recordTypeHandshake, helloBytes)
msg, err = c.readHandshake()
if err != nil {
return err
}
}
}
serverHello, ok := msg.(*serverHelloMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(serverHello, msg)
}
vers, ok := c.config.mutualVersion(serverHello.vers)
if !ok || vers < VersionTLS10 {
// TLS 1.0 is the minimum version supported as a client.
c.sendAlert(alertProtocolVersion)
return fmt.Errorf("tls: server selected unsupported protocol version %x", serverHello.vers)
}
c.vers = vers
c.haveVers = true
suite := mutualCipherSuite(c.config.cipherSuites(), serverHello.cipherSuite)
if suite == nil {
c.sendAlert(alertHandshakeFailure)
return fmt.Errorf("tls: server selected an unsupported cipher suite")
}
hs := &clientHandshakeState{
c: c,
serverHello: serverHello,
hello: hello,
suite: suite,
finishedHash: newFinishedHash(c.vers, suite),
session: session,
}
hs.writeHash(helloBytes, hs.c.sendHandshakeSeq-1)
hs.writeServerHash(hs.serverHello.marshal())
if c.config.Bugs.EarlyChangeCipherSpec > 0 {
hs.establishKeys()
c.writeRecord(recordTypeChangeCipherSpec, []byte{1})
}
isResume, err := hs.processServerHello()
if err != nil {
return err
}
if isResume {
if c.config.Bugs.EarlyChangeCipherSpec == 0 {
if err := hs.establishKeys(); err != nil {
return err
}
}
if err := hs.readSessionTicket(); err != nil {
return err
}
if err := hs.readFinished(); err != nil {
return err
}
if err := hs.sendFinished(); err != nil {
return err
}
} else {
if err := hs.doFullHandshake(); err != nil {
return err
}
if err := hs.establishKeys(); err != nil {
return err
}
if err := hs.sendFinished(); err != nil {
return err
}
if err := hs.readSessionTicket(); err != nil {
return err
}
if err := hs.readFinished(); err != nil {
return err
}
}
if sessionCache != nil && hs.session != nil && session != hs.session {
sessionCache.Put(cacheKey, hs.session)
}
c.didResume = isResume
c.handshakeComplete = true
c.cipherSuite = suite.id
return nil
}
func (hs *clientHandshakeState) doFullHandshake() error {
c := hs.c
msg, err := c.readHandshake()
if err != nil {
return err
}
certMsg, ok := msg.(*certificateMsg)
if !ok || len(certMsg.certificates) == 0 {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(certMsg, msg)
}
hs.writeServerHash(certMsg.marshal())
certs := make([]*x509.Certificate, len(certMsg.certificates))
for i, asn1Data := range certMsg.certificates {
cert, err := x509.ParseCertificate(asn1Data)
if err != nil {
c.sendAlert(alertBadCertificate)
return errors.New("tls: failed to parse certificate from server: " + err.Error())
}
certs[i] = cert
}
if !c.config.InsecureSkipVerify {
opts := x509.VerifyOptions{
Roots: c.config.RootCAs,
CurrentTime: c.config.time(),
DNSName: c.config.ServerName,
Intermediates: x509.NewCertPool(),
}
for i, cert := range certs {
if i == 0 {
continue
}
opts.Intermediates.AddCert(cert)
}
c.verifiedChains, err = certs[0].Verify(opts)
if err != nil {
c.sendAlert(alertBadCertificate)
return err
}
}
switch certs[0].PublicKey.(type) {
case *rsa.PublicKey, *ecdsa.PublicKey:
break
default:
c.sendAlert(alertUnsupportedCertificate)
return fmt.Errorf("tls: server's certificate contains an unsupported type of public key: %T", certs[0].PublicKey)
}
c.peerCertificates = certs
if hs.serverHello.ocspStapling {
msg, err = c.readHandshake()
if err != nil {
return err
}
cs, ok := msg.(*certificateStatusMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(cs, msg)
}
hs.writeServerHash(cs.marshal())
if cs.statusType == statusTypeOCSP {
c.ocspResponse = cs.response
}
}
msg, err = c.readHandshake()
if err != nil {
return err
}
keyAgreement := hs.suite.ka(c.vers)
skx, ok := msg.(*serverKeyExchangeMsg)
if ok {
hs.writeServerHash(skx.marshal())
err = keyAgreement.processServerKeyExchange(c.config, hs.hello, hs.serverHello, certs[0], skx)
if err != nil {
c.sendAlert(alertUnexpectedMessage)
return err
}
msg, err = c.readHandshake()
if err != nil {
return err
}
}
var chainToSend *Certificate
var certRequested bool
certReq, ok := msg.(*certificateRequestMsg)
if ok {
certRequested = true
// RFC 4346 on the certificateAuthorities field:
// A list of the distinguished names of acceptable certificate
// authorities. These distinguished names may specify a desired
// distinguished name for a root CA or for a subordinate CA;
// thus, this message can be used to describe both known roots
// and a desired authorization space. If the
// certificate_authorities list is empty then the client MAY
// send any certificate of the appropriate
// ClientCertificateType, unless there is some external
// arrangement to the contrary.
hs.writeServerHash(certReq.marshal())
var rsaAvail, ecdsaAvail bool
for _, certType := range certReq.certificateTypes {
switch certType {
case CertTypeRSASign:
rsaAvail = true
case CertTypeECDSASign:
ecdsaAvail = true
}
}
// We need to search our list of client certs for one
// where SignatureAlgorithm is RSA and the Issuer is in
// certReq.certificateAuthorities
findCert:
for i, chain := range c.config.Certificates {
if !rsaAvail && !ecdsaAvail {
continue
}
for j, cert := range chain.Certificate {
x509Cert := chain.Leaf
// parse the certificate if this isn't the leaf
// node, or if chain.Leaf was nil
if j != 0 || x509Cert == nil {
if x509Cert, err = x509.ParseCertificate(cert); err != nil {
c.sendAlert(alertInternalError)
return errors.New("tls: failed to parse client certificate #" + strconv.Itoa(i) + ": " + err.Error())
}
}
switch {
case rsaAvail && x509Cert.PublicKeyAlgorithm == x509.RSA:
case ecdsaAvail && x509Cert.PublicKeyAlgorithm == x509.ECDSA:
default:
continue findCert
}
if len(certReq.certificateAuthorities) == 0 {
// they gave us an empty list, so just take the
// first RSA cert from c.config.Certificates
chainToSend = &chain
break findCert
}
for _, ca := range certReq.certificateAuthorities {
if bytes.Equal(x509Cert.RawIssuer, ca) {
chainToSend = &chain
break findCert
}
}
}
}
msg, err = c.readHandshake()
if err != nil {
return err
}
}
shd, ok := msg.(*serverHelloDoneMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(shd, msg)
}
hs.writeServerHash(shd.marshal())
// If the server requested a certificate then we have to send a
// Certificate message, even if it's empty because we don't have a
// certificate to send.
if certRequested {
certMsg = new(certificateMsg)
if chainToSend != nil {
certMsg.certificates = chainToSend.Certificate
}
hs.writeClientHash(certMsg.marshal())
c.writeRecord(recordTypeHandshake, certMsg.marshal())
}
preMasterSecret, ckx, err := keyAgreement.generateClientKeyExchange(c.config, hs.hello, certs[0])
if err != nil {
c.sendAlert(alertInternalError)
return err
}
if ckx != nil {
if c.config.Bugs.EarlyChangeCipherSpec < 2 {
hs.writeClientHash(ckx.marshal())
}
c.writeRecord(recordTypeHandshake, ckx.marshal())
}
if chainToSend != nil {
var signed []byte
certVerify := &certificateVerifyMsg{
hasSignatureAndHash: c.vers >= VersionTLS12,
}
switch key := c.config.Certificates[0].PrivateKey.(type) {
case *ecdsa.PrivateKey:
certVerify.signatureAndHash, err = hs.finishedHash.selectClientCertSignatureAlgorithm(certReq.signatureAndHashes, signatureECDSA)
if err != nil {
break
}
var digest []byte
digest, _, err = hs.finishedHash.hashForClientCertificate(certVerify.signatureAndHash)
if err != nil {
break
}
var r, s *big.Int
r, s, err = ecdsa.Sign(c.config.rand(), key, digest)
if err == nil {
signed, err = asn1.Marshal(ecdsaSignature{r, s})
}
case *rsa.PrivateKey:
certVerify.signatureAndHash, err = hs.finishedHash.selectClientCertSignatureAlgorithm(certReq.signatureAndHashes, signatureRSA)
if err != nil {
break
}
var digest []byte
var hashFunc crypto.Hash
digest, hashFunc, err = hs.finishedHash.hashForClientCertificate(certVerify.signatureAndHash)
if err != nil {
break
}
signed, err = rsa.SignPKCS1v15(c.config.rand(), key, hashFunc, digest)
default:
err = errors.New("unknown private key type")
}
if err != nil {
c.sendAlert(alertInternalError)
return errors.New("tls: failed to sign handshake with client certificate: " + err.Error())
}
certVerify.signature = signed
hs.writeClientHash(certVerify.marshal())
c.writeRecord(recordTypeHandshake, certVerify.marshal())
}
hs.masterSecret = masterFromPreMasterSecret(c.vers, hs.suite, preMasterSecret, hs.hello.random, hs.serverHello.random)
return nil
}
func (hs *clientHandshakeState) establishKeys() error {
c := hs.c
clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV :=
keysFromMasterSecret(c.vers, hs.suite, hs.masterSecret, hs.hello.random, hs.serverHello.random, hs.suite.macLen, hs.suite.keyLen, hs.suite.ivLen)
var clientCipher, serverCipher interface{}
var clientHash, serverHash macFunction
if hs.suite.cipher != nil {
clientCipher = hs.suite.cipher(clientKey, clientIV, false /* not for reading */)
clientHash = hs.suite.mac(c.vers, clientMAC)
serverCipher = hs.suite.cipher(serverKey, serverIV, true /* for reading */)
serverHash = hs.suite.mac(c.vers, serverMAC)
} else {
clientCipher = hs.suite.aead(clientKey, clientIV)
serverCipher = hs.suite.aead(serverKey, serverIV)
}
c.in.prepareCipherSpec(c.vers, serverCipher, serverHash)
c.out.prepareCipherSpec(c.vers, clientCipher, clientHash)
return nil
}
func (hs *clientHandshakeState) serverResumedSession() bool {
// If the server responded with the same sessionId then it means the
// sessionTicket is being used to resume a TLS session.
return hs.session != nil && hs.hello.sessionId != nil &&
bytes.Equal(hs.serverHello.sessionId, hs.hello.sessionId)
}
func (hs *clientHandshakeState) processServerHello() (bool, error) {
c := hs.c
if hs.serverHello.compressionMethod != compressionNone {
c.sendAlert(alertUnexpectedMessage)
return false, errors.New("tls: server selected unsupported compression format")
}
if !hs.hello.nextProtoNeg && hs.serverHello.nextProtoNeg {
c.sendAlert(alertHandshakeFailure)
return false, errors.New("server advertised unrequested NPN extension")
}
if hs.serverResumedSession() {
// Restore masterSecret and peerCerts from previous state
hs.masterSecret = hs.session.masterSecret
c.peerCertificates = hs.session.serverCertificates
return true, nil
}
return false, nil
}
func (hs *clientHandshakeState) readFinished() error {
c := hs.c
c.readRecord(recordTypeChangeCipherSpec)
if err := c.in.error(); err != nil {
return err
}
msg, err := c.readHandshake()
if err != nil {
return err
}
serverFinished, ok := msg.(*finishedMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(serverFinished, msg)
}
if c.config.Bugs.EarlyChangeCipherSpec == 0 {
verify := hs.finishedHash.serverSum(hs.masterSecret)
if len(verify) != len(serverFinished.verifyData) ||
subtle.ConstantTimeCompare(verify, serverFinished.verifyData) != 1 {
c.sendAlert(alertHandshakeFailure)
return errors.New("tls: server's Finished message was incorrect")
}
}
hs.writeServerHash(serverFinished.marshal())
return nil
}
func (hs *clientHandshakeState) readSessionTicket() error {
if !hs.serverHello.ticketSupported {
return nil
}
c := hs.c
msg, err := c.readHandshake()
if err != nil {
return err
}
sessionTicketMsg, ok := msg.(*newSessionTicketMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(sessionTicketMsg, msg)
}
hs.writeServerHash(sessionTicketMsg.marshal())
hs.session = &ClientSessionState{
sessionTicket: sessionTicketMsg.ticket,
vers: c.vers,
cipherSuite: hs.suite.id,
masterSecret: hs.masterSecret,
serverCertificates: c.peerCertificates,
}
return nil
}
func (hs *clientHandshakeState) sendFinished() error {
c := hs.c
var postCCSBytes []byte
seqno := hs.c.sendHandshakeSeq
if hs.serverHello.nextProtoNeg {
nextProto := new(nextProtoMsg)
proto, fallback := mutualProtocol(c.config.NextProtos, hs.serverHello.nextProtos)
nextProto.proto = proto
c.clientProtocol = proto
c.clientProtocolFallback = fallback
nextProtoBytes := nextProto.marshal()
hs.writeHash(nextProtoBytes, seqno)
seqno++
postCCSBytes = append(postCCSBytes, nextProtoBytes...)
}
finished := new(finishedMsg)
if c.config.Bugs.EarlyChangeCipherSpec == 2 {
finished.verifyData = hs.finishedHash.clientSum(nil)
} else {
finished.verifyData = hs.finishedHash.clientSum(hs.masterSecret)
}
finishedBytes := finished.marshal()
hs.writeHash(finishedBytes, seqno)
postCCSBytes = append(postCCSBytes, finishedBytes...)
if c.config.Bugs.FragmentAcrossChangeCipherSpec {
c.writeRecord(recordTypeHandshake, postCCSBytes[:5])
postCCSBytes = postCCSBytes[5:]
}
if !c.config.Bugs.SkipChangeCipherSpec &&
c.config.Bugs.EarlyChangeCipherSpec == 0 {
c.writeRecord(recordTypeChangeCipherSpec, []byte{1})
}
c.writeRecord(recordTypeHandshake, postCCSBytes)
return nil
}
func (hs *clientHandshakeState) writeClientHash(msg []byte) {
// writeClientHash is called before writeRecord.
hs.writeHash(msg, hs.c.sendHandshakeSeq)
}
func (hs *clientHandshakeState) writeServerHash(msg []byte) {
// writeServerHash is called after readHandshake.
hs.writeHash(msg, hs.c.recvHandshakeSeq-1)
}
func (hs *clientHandshakeState) writeHash(msg []byte, seqno uint16) {
if hs.c.isDTLS {
// This is somewhat hacky. DTLS hashes a slightly different format.
// First, the TLS header.
hs.finishedHash.Write(msg[:4])
// Then the sequence number and reassembled fragment offset (always 0).
hs.finishedHash.Write([]byte{byte(seqno >> 8), byte(seqno), 0, 0, 0})
// Then the reassembled fragment (always equal to the message length).
hs.finishedHash.Write(msg[1:4])
// And then the message body.
hs.finishedHash.Write(msg[4:])
} else {
hs.finishedHash.Write(msg)
}
}
// clientSessionCacheKey returns a key used to cache sessionTickets that could
// be used to resume previously negotiated TLS sessions with a server.
func clientSessionCacheKey(serverAddr net.Addr, config *Config) string {
if len(config.ServerName) > 0 {
return config.ServerName
}
return serverAddr.String()
}
// mutualProtocol finds the mutual Next Protocol Negotiation protocol given the
// set of client and server supported protocols. The set of client supported
// protocols must not be empty. It returns the resulting protocol and flag
// indicating if the fallback case was reached.
func mutualProtocol(clientProtos, serverProtos []string) (string, bool) {
for _, s := range serverProtos {
for _, c := range clientProtos {
if s == c {
return s, false
}
}
}
return clientProtos[0], true
}