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// Copyright 2018 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 (
"bytes"
"crypto"
"crypto/hmac"
"crypto/rsa"
"errors"
"fmt"
"hash"
"sync/atomic"
"time"
)
type clientHandshakeStateTLS13 struct {
c *Conn
serverHello *serverHelloMsg
hello *clientHelloMsg
ecdheParams ecdheParameters
session *ClientSessionState
earlySecret []byte
binderKey []byte
certReq *certificateRequestMsgTLS13
usingPSK bool
sentDummyCCS bool
suite *cipherSuiteTLS13
transcript hash.Hash
masterSecret []byte
trafficSecret []byte // client_application_traffic_secret_0
uconn *UConn // [UTLS]
}
// handshake requires hs.c, hs.hello, hs.serverHello, hs.ecdheParams, and,
// optionally, hs.session, hs.earlySecret and hs.binderKey to be set.
func (hs *clientHandshakeStateTLS13) handshake() error {
c := hs.c
// The server must not select TLS 1.3 in a renegotiation. See RFC 8446,
// sections 4.1.2 and 4.1.3.
if c.handshakes > 0 {
c.sendAlert(alertProtocolVersion)
return errors.New("tls: server selected TLS 1.3 in a renegotiation")
}
// Consistency check on the presence of a keyShare and its parameters.
if hs.ecdheParams == nil || len(hs.hello.keyShares) < 1 { // [uTLS]
// keyshares "< 1" instead of "!= 1", as uTLS may send multiple
return c.sendAlert(alertInternalError)
}
if err := hs.checkServerHelloOrHRR(); err != nil {
return err
}
hs.transcript = hs.suite.hash.New()
hs.transcript.Write(hs.hello.marshal())
if bytes.Equal(hs.serverHello.random, helloRetryRequestRandom) {
if err := hs.sendDummyChangeCipherSpec(); err != nil {
return err
}
if err := hs.processHelloRetryRequest(); err != nil {
return err
}
}
hs.transcript.Write(hs.serverHello.marshal())
c.buffering = true
if err := hs.processServerHello(); err != nil {
return err
}
if err := hs.sendDummyChangeCipherSpec(); err != nil {
return err
}
if err := hs.establishHandshakeKeys(); err != nil {
return err
}
if err := hs.readServerParameters(); err != nil {
return err
}
if err := hs.readServerCertificate(); err != nil {
return err
}
if err := hs.readServerFinished(); err != nil {
return err
}
if err := hs.sendClientCertificate(); err != nil {
return err
}
if err := hs.sendClientFinished(); err != nil {
return err
}
if _, err := c.flush(); err != nil {
return err
}
atomic.StoreUint32(&c.handshakeStatus, 1)
return nil
}
// checkServerHelloOrHRR does validity checks that apply to both ServerHello and
// HelloRetryRequest messages. It sets hs.suite.
func (hs *clientHandshakeStateTLS13) checkServerHelloOrHRR() error {
c := hs.c
if hs.serverHello.supportedVersion == 0 {
c.sendAlert(alertMissingExtension)
return errors.New("tls: server selected TLS 1.3 using the legacy version field")
}
if hs.serverHello.supportedVersion != VersionTLS13 {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: server selected an invalid version after a HelloRetryRequest")
}
if hs.serverHello.vers != VersionTLS12 {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: server sent an incorrect legacy version")
}
if hs.serverHello.nextProtoNeg ||
len(hs.serverHello.nextProtos) != 0 ||
hs.serverHello.ocspStapling ||
hs.serverHello.ticketSupported ||
hs.serverHello.secureRenegotiationSupported ||
len(hs.serverHello.secureRenegotiation) != 0 ||
len(hs.serverHello.alpnProtocol) != 0 ||
len(hs.serverHello.scts) != 0 {
c.sendAlert(alertUnsupportedExtension)
return errors.New("tls: server sent a ServerHello extension forbidden in TLS 1.3")
}
if !bytes.Equal(hs.hello.sessionId, hs.serverHello.sessionId) {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: server did not echo the legacy session ID")
}
if hs.serverHello.compressionMethod != compressionNone {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: server selected unsupported compression format")
}
selectedSuite := mutualCipherSuiteTLS13(hs.hello.cipherSuites, hs.serverHello.cipherSuite)
if hs.suite != nil && selectedSuite != hs.suite {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: server changed cipher suite after a HelloRetryRequest")
}
if selectedSuite == nil {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: server chose an unconfigured cipher suite")
}
hs.suite = selectedSuite
c.cipherSuite = hs.suite.id
return nil
}
// sendDummyChangeCipherSpec sends a ChangeCipherSpec record for compatibility
// with middleboxes that didn't implement TLS correctly. See RFC 8446, Appendix D.4.
func (hs *clientHandshakeStateTLS13) sendDummyChangeCipherSpec() error {
if hs.sentDummyCCS {
return nil
}
hs.sentDummyCCS = true
_, err := hs.c.writeRecord(recordTypeChangeCipherSpec, []byte{1})
return err
}
// processHelloRetryRequest handles the HRR in hs.serverHello, modifies and
// resends hs.hello, and reads the new ServerHello into hs.serverHello.
func (hs *clientHandshakeStateTLS13) processHelloRetryRequest() error {
c := hs.c
// The first ClientHello gets double-hashed into the transcript upon a
// HelloRetryRequest. See RFC 8446, Section 4.4.1.
chHash := hs.transcript.Sum(nil)
hs.transcript.Reset()
hs.transcript.Write([]byte{typeMessageHash, 0, 0, uint8(len(chHash))})
hs.transcript.Write(chHash)
hs.transcript.Write(hs.serverHello.marshal())
if hs.serverHello.serverShare.group != 0 {
c.sendAlert(alertDecodeError)
return errors.New("tls: received malformed key_share extension")
}
curveID := hs.serverHello.selectedGroup
if curveID == 0 {
c.sendAlert(alertMissingExtension)
return errors.New("tls: received HelloRetryRequest without selected group")
}
curveOK := false
for _, id := range hs.hello.supportedCurves {
if id == curveID {
curveOK = true
break
}
}
if !curveOK {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: server selected unsupported group")
}
if hs.ecdheParams.CurveID() == curveID {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: server sent an unnecessary HelloRetryRequest message")
}
if _, ok := curveForCurveID(curveID); curveID != X25519 && !ok {
c.sendAlert(alertInternalError)
return errors.New("tls: CurvePreferences includes unsupported curve")
}
params, err := generateECDHEParameters(c.config.rand(), curveID)
if err != nil {
c.sendAlert(alertInternalError)
return err
}
hs.ecdheParams = params
hs.hello.keyShares = []keyShare{{group: curveID, data: params.PublicKey()}}
hs.hello.cookie = hs.serverHello.cookie
hs.hello.raw = nil
if len(hs.hello.pskIdentities) > 0 {
pskSuite := cipherSuiteTLS13ByID(hs.session.cipherSuite)
if pskSuite == nil {
return c.sendAlert(alertInternalError)
}
if pskSuite.hash == hs.suite.hash {
// Update binders and obfuscated_ticket_age.
ticketAge := uint32(c.config.time().Sub(hs.session.receivedAt) / time.Millisecond)
hs.hello.pskIdentities[0].obfuscatedTicketAge = ticketAge + hs.session.ageAdd
transcript := hs.suite.hash.New()
transcript.Write([]byte{typeMessageHash, 0, 0, uint8(len(chHash))})
transcript.Write(chHash)
transcript.Write(hs.serverHello.marshal())
transcript.Write(hs.hello.marshalWithoutBinders())
pskBinders := [][]byte{hs.suite.finishedHash(hs.binderKey, transcript)}
hs.hello.updateBinders(pskBinders)
} else {
// Server selected a cipher suite incompatible with the PSK.
hs.hello.pskIdentities = nil
hs.hello.pskBinders = nil
}
}
// [UTLS SECTION BEGINS]
// crypto/tls code above this point had changed crypto/tls structures in accordance with HRR, and is about
// to call default marshaller.
// Instead, we fill uTLS-specific structs and call uTLS marshaller.
// Only extensionCookie, extensionPreSharedKey, extensionKeyShare, extensionEarlyData, extensionSupportedVersions,
// and utlsExtensionPadding are supposed to change
if hs.uconn != nil {
if hs.uconn.ClientHelloID != HelloGolang {
if len(hs.hello.pskIdentities) > 0 {
// TODO: wait for someone who cares about PSK to implement
return errors.New("uTLS does not support reprocessing of PSK key triggered by HelloRetryRequest")
}
keyShareExtFound := false
for _, ext := range hs.uconn.Extensions {
// new ks seems to be generated either way
if ks, ok := ext.(*KeyShareExtension); ok {
ks.KeyShares = keyShares(hs.hello.keyShares).ToPublic()
keyShareExtFound = true
}
}
if !keyShareExtFound {
return errors.New("uTLS: received HelloRetryRequest, but keyshare not found among client's " +
"uconn.Extensions")
}
if len(hs.serverHello.cookie) > 0 {
// serverHello specified a cookie, let's echo it
cookieFound := false
for _, ext := range hs.uconn.Extensions {
if ks, ok := ext.(*CookieExtension); ok {
ks.Cookie = hs.serverHello.cookie
cookieFound = true
}
}
if !cookieFound {
// pick a random index where to add cookieExtension
// -2 instead of -1 is a lazy way to ensure that PSK is still a last extension
p, err := newPRNG()
if err != nil {
return err
}
cookieIndex := p.Intn(len(hs.uconn.Extensions) - 2)
if cookieIndex >= len(hs.uconn.Extensions) {
// this check is for empty hs.uconn.Extensions
return fmt.Errorf("cookieIndex >= len(hs.uconn.Extensions): %v >= %v",
cookieIndex, len(hs.uconn.Extensions))
}
hs.uconn.Extensions = append(hs.uconn.Extensions[:cookieIndex],
append([]TLSExtension{&CookieExtension{Cookie: hs.serverHello.cookie}},
hs.uconn.Extensions[cookieIndex:]...)...)
}
}
if err = hs.uconn.MarshalClientHello(); err != nil {
return err
}
hs.hello.raw = hs.uconn.HandshakeState.Hello.Raw
}
}
// [UTLS SECTION ENDS]
hs.transcript.Write(hs.hello.marshal())
if _, err := c.writeRecord(recordTypeHandshake, hs.hello.marshal()); err != nil {
return err
}
msg, err := c.readHandshake()
if err != nil {
return err
}
serverHello, ok := msg.(*serverHelloMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(serverHello, msg)
}
hs.serverHello = serverHello
if err := hs.checkServerHelloOrHRR(); err != nil {
return err
}
return nil
}
func (hs *clientHandshakeStateTLS13) processServerHello() error {
c := hs.c
if bytes.Equal(hs.serverHello.random, helloRetryRequestRandom) {
c.sendAlert(alertUnexpectedMessage)
return errors.New("tls: server sent two HelloRetryRequest messages")
}
if len(hs.serverHello.cookie) != 0 {
c.sendAlert(alertUnsupportedExtension)
return errors.New("tls: server sent a cookie in a normal ServerHello")
}
if hs.serverHello.selectedGroup != 0 {
c.sendAlert(alertDecodeError)
return errors.New("tls: malformed key_share extension")
}
if hs.serverHello.serverShare.group == 0 {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: server did not send a key share")
}
if hs.serverHello.serverShare.group != hs.ecdheParams.CurveID() {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: server selected unsupported group")
}
if !hs.serverHello.selectedIdentityPresent {
return nil
}
if int(hs.serverHello.selectedIdentity) >= len(hs.hello.pskIdentities) {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: server selected an invalid PSK")
}
if len(hs.hello.pskIdentities) != 1 || hs.session == nil {
return c.sendAlert(alertInternalError)
}
pskSuite := cipherSuiteTLS13ByID(hs.session.cipherSuite)
if pskSuite == nil {
return c.sendAlert(alertInternalError)
}
if pskSuite.hash != hs.suite.hash {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: server selected an invalid PSK and cipher suite pair")
}
hs.usingPSK = true
c.didResume = true
c.peerCertificates = hs.session.serverCertificates
c.verifiedChains = hs.session.verifiedChains
return nil
}
func (hs *clientHandshakeStateTLS13) establishHandshakeKeys() error {
c := hs.c
sharedKey := hs.ecdheParams.SharedKey(hs.serverHello.serverShare.data)
if sharedKey == nil {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: invalid server key share")
}
earlySecret := hs.earlySecret
if !hs.usingPSK {
earlySecret = hs.suite.extract(nil, nil)
}
handshakeSecret := hs.suite.extract(sharedKey,
hs.suite.deriveSecret(earlySecret, "derived", nil))
clientSecret := hs.suite.deriveSecret(handshakeSecret,
clientHandshakeTrafficLabel, hs.transcript)
c.out.setTrafficSecret(hs.suite, clientSecret)
serverSecret := hs.suite.deriveSecret(handshakeSecret,
serverHandshakeTrafficLabel, hs.transcript)
c.in.setTrafficSecret(hs.suite, serverSecret)
err := c.config.writeKeyLog(keyLogLabelClientHandshake, hs.hello.random, clientSecret)
if err != nil {
c.sendAlert(alertInternalError)
return err
}
err = c.config.writeKeyLog(keyLogLabelServerHandshake, hs.hello.random, serverSecret)
if err != nil {
c.sendAlert(alertInternalError)
return err
}
hs.masterSecret = hs.suite.extract(nil,
hs.suite.deriveSecret(handshakeSecret, "derived", nil))
return nil
}
func (hs *clientHandshakeStateTLS13) readServerParameters() error {
c := hs.c
msg, err := c.readHandshake()
if err != nil {
return err
}
encryptedExtensions, ok := msg.(*encryptedExtensionsMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(encryptedExtensions, msg)
}
hs.transcript.Write(encryptedExtensions.marshal())
if len(encryptedExtensions.alpnProtocol) != 0 && len(hs.hello.alpnProtocols) == 0 {
c.sendAlert(alertUnsupportedExtension)
return errors.New("tls: server advertised unrequested ALPN extension")
}
c.clientProtocol = encryptedExtensions.alpnProtocol
return nil
}
func (hs *clientHandshakeStateTLS13) readServerCertificate() error {
c := hs.c
// Either a PSK or a certificate is always used, but not both.
// See RFC 8446, Section 4.1.1.
if hs.usingPSK {
return nil
}
msg, err := c.readHandshake()
if err != nil {
return err
}
certReq, ok := msg.(*certificateRequestMsgTLS13)
if ok {
hs.transcript.Write(certReq.marshal())
hs.certReq = certReq
msg, err = c.readHandshake()
if err != nil {
return err
}
}
certMsg, ok := msg.(*certificateMsgTLS13)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(certMsg, msg)
}
if len(certMsg.certificate.Certificate) == 0 {
c.sendAlert(alertDecodeError)
return errors.New("tls: received empty certificates message")
}
hs.transcript.Write(certMsg.marshal())
c.scts = certMsg.certificate.SignedCertificateTimestamps
c.ocspResponse = certMsg.certificate.OCSPStaple
if err := c.verifyServerCertificate(certMsg.certificate.Certificate); err != nil {
return err
}
msg, err = c.readHandshake()
if err != nil {
return err
}
certVerify, ok := msg.(*certificateVerifyMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(certVerify, msg)
}
// See RFC 8446, Section 4.4.3.
if !isSupportedSignatureAlgorithm(certVerify.signatureAlgorithm, supportedSignatureAlgorithms) {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: invalid certificate signature algorithm")
}
sigType := signatureFromSignatureScheme(certVerify.signatureAlgorithm)
sigHash, err := hashFromSignatureScheme(certVerify.signatureAlgorithm)
if sigType == 0 || err != nil {
c.sendAlert(alertInternalError)
return err
}
if sigType == signaturePKCS1v15 || sigHash == crypto.SHA1 {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: invalid certificate signature algorithm")
}
h := sigHash.New()
writeSignedMessage(h, serverSignatureContext, hs.transcript)
if err := verifyHandshakeSignature(sigType, c.peerCertificates[0].PublicKey,
sigHash, h.Sum(nil), certVerify.signature); err != nil {
c.sendAlert(alertDecryptError)
return errors.New("tls: invalid certificate signature")
}
hs.transcript.Write(certVerify.marshal())
return nil
}
func (hs *clientHandshakeStateTLS13) readServerFinished() error {
c := hs.c
msg, err := c.readHandshake()
if err != nil {
return err
}
finished, ok := msg.(*finishedMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(finished, msg)
}
expectedMAC := hs.suite.finishedHash(c.in.trafficSecret, hs.transcript)
if !hmac.Equal(expectedMAC, finished.verifyData) {
c.sendAlert(alertDecryptError)
return errors.New("tls: invalid server finished hash")
}
hs.transcript.Write(finished.marshal())
// Derive secrets that take context through the server Finished.
hs.trafficSecret = hs.suite.deriveSecret(hs.masterSecret,
clientApplicationTrafficLabel, hs.transcript)
serverSecret := hs.suite.deriveSecret(hs.masterSecret,
serverApplicationTrafficLabel, hs.transcript)
c.in.setTrafficSecret(hs.suite, serverSecret)
err = c.config.writeKeyLog(keyLogLabelClientTraffic, hs.hello.random, hs.trafficSecret)
if err != nil {
c.sendAlert(alertInternalError)
return err
}
err = c.config.writeKeyLog(keyLogLabelServerTraffic, hs.hello.random, serverSecret)
if err != nil {
c.sendAlert(alertInternalError)
return err
}
c.ekm = hs.suite.exportKeyingMaterial(hs.masterSecret, hs.transcript)
return nil
}
func (hs *clientHandshakeStateTLS13) sendClientCertificate() error {
c := hs.c
if hs.certReq == nil {
return nil
}
cert, err := c.getClientCertificate(&CertificateRequestInfo{
AcceptableCAs: hs.certReq.certificateAuthorities,
SignatureSchemes: hs.certReq.supportedSignatureAlgorithms,
})
if err != nil {
return err
}
certMsg := new(certificateMsgTLS13)
certMsg.certificate = *cert
certMsg.scts = hs.certReq.scts && len(cert.SignedCertificateTimestamps) > 0
certMsg.ocspStapling = hs.certReq.ocspStapling && len(cert.OCSPStaple) > 0
hs.transcript.Write(certMsg.marshal())
if _, err := c.writeRecord(recordTypeHandshake, certMsg.marshal()); err != nil {
return err
}
// If the client is sending an empty certificate message, skip the CertificateVerify.
if len(cert.Certificate) == 0 {
return nil
}
certVerifyMsg := new(certificateVerifyMsg)
certVerifyMsg.hasSignatureAlgorithm = true
supportedAlgs := signatureSchemesForCertificate(cert)
if supportedAlgs == nil {
c.sendAlert(alertInternalError)
return fmt.Errorf("tls: unsupported certificate key (%T)", cert.PrivateKey)
}
// Pick signature scheme in server preference order, as the client
// preference order is not configurable.
for _, preferredAlg := range hs.certReq.supportedSignatureAlgorithms {
if isSupportedSignatureAlgorithm(preferredAlg, supportedAlgs) {
certVerifyMsg.signatureAlgorithm = preferredAlg
break
}
}
sigType := signatureFromSignatureScheme(certVerifyMsg.signatureAlgorithm)
sigHash, err := hashFromSignatureScheme(certVerifyMsg.signatureAlgorithm)
if sigType == 0 || err != nil {
// getClientCertificate returned a certificate incompatible with the
// CertificateRequestInfo supported signature algorithms.
c.sendAlert(alertInternalError)
return err
}
h := sigHash.New()
writeSignedMessage(h, clientSignatureContext, hs.transcript)
signOpts := crypto.SignerOpts(sigHash)
if sigType == signatureRSAPSS {
signOpts = &rsa.PSSOptions{SaltLength: rsa.PSSSaltLengthEqualsHash, Hash: sigHash}
}
sig, err := cert.PrivateKey.(crypto.Signer).Sign(c.config.rand(), h.Sum(nil), signOpts)
if err != nil {
c.sendAlert(alertInternalError)
return errors.New("tls: failed to sign handshake: " + err.Error())
}
certVerifyMsg.signature = sig
hs.transcript.Write(certVerifyMsg.marshal())
if _, err := c.writeRecord(recordTypeHandshake, certVerifyMsg.marshal()); err != nil {
return err
}
return nil
}
func (hs *clientHandshakeStateTLS13) sendClientFinished() error {
c := hs.c
finished := &finishedMsg{
verifyData: hs.suite.finishedHash(c.out.trafficSecret, hs.transcript),
}
hs.transcript.Write(finished.marshal())
if _, err := c.writeRecord(recordTypeHandshake, finished.marshal()); err != nil {
return err
}
c.out.setTrafficSecret(hs.suite, hs.trafficSecret)
if !c.config.SessionTicketsDisabled && c.config.ClientSessionCache != nil {
c.resumptionSecret = hs.suite.deriveSecret(hs.masterSecret,
resumptionLabel, hs.transcript)
}
return nil
}
func (c *Conn) handleNewSessionTicket(msg *newSessionTicketMsgTLS13) error {
if !c.isClient {
c.sendAlert(alertUnexpectedMessage)
return errors.New("tls: received new session ticket from a client")
}
if c.config.SessionTicketsDisabled || c.config.ClientSessionCache == nil {
return nil
}
// See RFC 8446, Section 4.6.1.
if msg.lifetime == 0 {
return nil
}
lifetime := time.Duration(msg.lifetime) * time.Second
if lifetime > maxSessionTicketLifetime {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: received a session ticket with invalid lifetime")
}
cipherSuite := cipherSuiteTLS13ByID(c.cipherSuite)
if cipherSuite == nil || c.resumptionSecret == nil {
return c.sendAlert(alertInternalError)
}
// Save the resumption_master_secret and nonce instead of deriving the PSK
// to do the least amount of work on NewSessionTicket messages before we
// know if the ticket will be used. Forward secrecy of resumed connections
// is guaranteed by the requirement for pskModeDHE.
session := &ClientSessionState{
sessionTicket: msg.label,
vers: c.vers,
cipherSuite: c.cipherSuite,
masterSecret: c.resumptionSecret,
serverCertificates: c.peerCertificates,
verifiedChains: c.verifiedChains,
receivedAt: c.config.time(),
nonce: msg.nonce,
useBy: c.config.time().Add(lifetime),
ageAdd: msg.ageAdd,
}
cacheKey := clientSessionCacheKey(c.conn.RemoteAddr(), c.config)
c.config.ClientSessionCache.Put(cacheKey, session)
return nil
}
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