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1327 lines (1165 loc) · 40.4 KB
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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-Go file.
package reality
import (
"bytes"
"context"
"crypto"
"crypto/ecdsa"
"crypto/ed25519"
"crypto/mlkem"
"crypto/rsa"
"crypto/subtle"
"crypto/x509"
"encoding/binary"
"errors"
"fmt"
"hash"
"io"
"net"
"slices"
"strings"
"time"
"github.com/xtls/reality/fips140tls"
"github.com/xtls/reality/hpke"
"github.com/xtls/reality/tls13"
)
type clientHandshakeState struct {
c *Conn
ctx context.Context
serverHello *serverHelloMsg
hello *clientHelloMsg
suite *cipherSuite
finishedHash finishedHash
masterSecret []byte
session *SessionState // the session being resumed
ticket []byte // a fresh ticket received during this handshake
}
var testingOnlyForceClientHelloSignatureAlgorithms []SignatureScheme
func (c *Conn) makeClientHello() (*clientHelloMsg, *keySharePrivateKeys, *echClientContext, error) {
config := c.config
if len(config.ServerName) == 0 && !config.InsecureSkipVerify {
return nil, nil, nil, errors.New("tls: either ServerName or InsecureSkipVerify must be specified in the tls.Config")
}
nextProtosLength := 0
for _, proto := range config.NextProtos {
if l := len(proto); l == 0 || l > 255 {
return nil, nil, nil, errors.New("tls: invalid NextProtos value")
} else {
nextProtosLength += 1 + l
}
}
if nextProtosLength > 0xffff {
return nil, nil, nil, errors.New("tls: NextProtos values too large")
}
supportedVersions := config.supportedVersions(roleClient)
if len(supportedVersions) == 0 {
return nil, nil, nil, errors.New("tls: no supported versions satisfy MinVersion and MaxVersion")
}
// Since supportedVersions is sorted in descending order, the first element
// is the maximum version and the last element is the minimum version.
maxVersion := supportedVersions[0]
minVersion := supportedVersions[len(supportedVersions)-1]
hello := &clientHelloMsg{
vers: maxVersion,
compressionMethods: []uint8{compressionNone},
random: make([]byte, 32),
extendedMasterSecret: true,
ocspStapling: true,
scts: true,
serverName: hostnameInSNI(config.ServerName),
supportedCurves: config.curvePreferences(maxVersion),
supportedPoints: []uint8{pointFormatUncompressed},
secureRenegotiationSupported: true,
alpnProtocols: config.NextProtos,
supportedVersions: supportedVersions,
}
// The version at the beginning of the ClientHello was capped at TLS 1.2
// for compatibility reasons. The supported_versions extension is used
// to negotiate versions now. See RFC 8446, Section 4.2.1.
if hello.vers > VersionTLS12 {
hello.vers = VersionTLS12
}
if c.handshakes > 0 {
hello.secureRenegotiation = c.clientFinished[:]
}
hello.cipherSuites = config.cipherSuites(hasAESGCMHardwareSupport)
// Don't advertise TLS 1.2-only cipher suites unless we're attempting TLS 1.2.
if maxVersion < VersionTLS12 {
hello.cipherSuites = slices.DeleteFunc(hello.cipherSuites, func(id uint16) bool {
return cipherSuiteByID(id).flags&suiteTLS12 != 0
})
}
_, err := io.ReadFull(config.rand(), hello.random)
if err != nil {
return nil, nil, nil, errors.New("tls: short read from Rand: " + err.Error())
}
// A random session ID is used to detect when the server accepted a ticket
// and is resuming a session (see RFC 5077). In TLS 1.3, it's always set as
// a compatibility measure (see RFC 8446, Section 4.1.2).
//
// The session ID is not set for QUIC connections (see RFC 9001, Section 8.4).
if c.quic == nil {
hello.sessionId = make([]byte, 32)
if _, err := io.ReadFull(config.rand(), hello.sessionId); err != nil {
return nil, nil, nil, errors.New("tls: short read from Rand: " + err.Error())
}
}
if maxVersion >= VersionTLS12 {
hello.supportedSignatureAlgorithms = supportedSignatureAlgorithms(minVersion)
hello.supportedSignatureAlgorithmsCert = supportedSignatureAlgorithmsCert()
}
if testingOnlyForceClientHelloSignatureAlgorithms != nil {
hello.supportedSignatureAlgorithms = testingOnlyForceClientHelloSignatureAlgorithms
}
var keyShareKeys *keySharePrivateKeys
if maxVersion >= VersionTLS13 {
// Reset the list of ciphers when the client only supports TLS 1.3.
if minVersion >= VersionTLS13 {
hello.cipherSuites = nil
}
if fips140tls.Required() {
hello.cipherSuites = append(hello.cipherSuites, allowedCipherSuitesTLS13FIPS...)
} else if hasAESGCMHardwareSupport {
hello.cipherSuites = append(hello.cipherSuites, defaultCipherSuitesTLS13...)
} else {
hello.cipherSuites = append(hello.cipherSuites, defaultCipherSuitesTLS13NoAES...)
}
if len(hello.supportedCurves) == 0 {
return nil, nil, nil, errors.New("tls: no supported elliptic curves for ECDHE")
}
curveID := hello.supportedCurves[0]
keyShareKeys = &keySharePrivateKeys{curveID: curveID}
// Note that if X25519MLKEM768 is supported, it will be first because
// the preference order is fixed.
if curveID == X25519MLKEM768 {
keyShareKeys.ecdhe, err = generateECDHEKey(config.rand(), X25519)
if err != nil {
return nil, nil, nil, err
}
seed := make([]byte, mlkem.SeedSize)
if _, err := io.ReadFull(config.rand(), seed); err != nil {
return nil, nil, nil, err
}
keyShareKeys.mlkem, err = mlkem.NewDecapsulationKey768(seed)
if err != nil {
return nil, nil, nil, err
}
mlkemEncapsulationKey := keyShareKeys.mlkem.EncapsulationKey().Bytes()
x25519EphemeralKey := keyShareKeys.ecdhe.PublicKey().Bytes()
hello.keyShares = []keyShare{
{group: X25519MLKEM768, data: append(mlkemEncapsulationKey, x25519EphemeralKey...)},
}
// If both X25519MLKEM768 and X25519 are supported, we send both key
// shares (as a fallback) and we reuse the same X25519 ephemeral
// key, as allowed by draft-ietf-tls-hybrid-design-09, Section 3.2.
if slices.Contains(hello.supportedCurves, X25519) {
hello.keyShares = append(hello.keyShares, keyShare{group: X25519, data: x25519EphemeralKey})
}
} else {
if _, ok := curveForCurveID(curveID); !ok {
return nil, nil, nil, errors.New("tls: CurvePreferences includes unsupported curve")
}
keyShareKeys.ecdhe, err = generateECDHEKey(config.rand(), curveID)
if err != nil {
return nil, nil, nil, err
}
hello.keyShares = []keyShare{{group: curveID, data: keyShareKeys.ecdhe.PublicKey().Bytes()}}
}
}
if c.quic != nil {
p, err := c.quicGetTransportParameters()
if err != nil {
return nil, nil, nil, err
}
if p == nil {
p = []byte{}
}
hello.quicTransportParameters = p
}
var ech *echClientContext
if c.config.EncryptedClientHelloConfigList != nil {
if c.config.MinVersion != 0 && c.config.MinVersion < VersionTLS13 {
return nil, nil, nil, errors.New("tls: MinVersion must be >= VersionTLS13 if EncryptedClientHelloConfigList is populated")
}
if c.config.MaxVersion != 0 && c.config.MaxVersion <= VersionTLS12 {
return nil, nil, nil, errors.New("tls: MaxVersion must be >= VersionTLS13 if EncryptedClientHelloConfigList is populated")
}
echConfigs, err := parseECHConfigList(c.config.EncryptedClientHelloConfigList)
if err != nil {
return nil, nil, nil, err
}
echConfig := pickECHConfig(echConfigs)
if echConfig == nil {
return nil, nil, nil, errors.New("tls: EncryptedClientHelloConfigList contains no valid configs")
}
ech = &echClientContext{config: echConfig}
hello.encryptedClientHello = []byte{1} // indicate inner hello
// We need to explicitly set these 1.2 fields to nil, as we do not
// marshal them when encoding the inner hello, otherwise transcripts
// will later mismatch.
hello.supportedPoints = nil
hello.ticketSupported = false
hello.secureRenegotiationSupported = false
hello.extendedMasterSecret = false
echPK, err := hpke.ParseHPKEPublicKey(ech.config.KemID, ech.config.PublicKey)
if err != nil {
return nil, nil, nil, err
}
suite, err := pickECHCipherSuite(ech.config.SymmetricCipherSuite)
if err != nil {
return nil, nil, nil, err
}
ech.kdfID, ech.aeadID = suite.KDFID, suite.AEADID
info := append([]byte("tls ech\x00"), ech.config.raw...)
ech.encapsulatedKey, ech.hpkeContext, err = hpke.SetupSender(ech.config.KemID, suite.KDFID, suite.AEADID, echPK, info)
if err != nil {
return nil, nil, nil, err
}
}
return hello, keyShareKeys, ech, nil
}
type echClientContext struct {
config *EchConfig
hpkeContext *hpke.Sender
encapsulatedKey []byte
innerHello *clientHelloMsg
innerTranscript hash.Hash
kdfID uint16
aeadID uint16
echRejected bool
retryConfigs []byte
}
func (c *Conn) clientHandshake(ctx context.Context) (err error) {
if c.config == nil {
c.config = defaultConfig()
}
// This may be a renegotiation handshake, in which case some fields
// need to be reset.
c.didResume = false
c.curveID = 0
hello, keyShareKeys, ech, err := c.makeClientHello()
if err != nil {
return err
}
c.serverName = hello.serverName
session, earlySecret, binderKey, err := c.loadSession(hello)
if err != nil {
return err
}
if session != nil {
defer func() {
// If we got a handshake failure when resuming a session, throw away
// the session ticket. See RFC 5077, Section 3.2.
//
// RFC 8446 makes no mention of dropping tickets on failure, but it
// does require servers to abort on invalid binders, so we need to
// delete tickets to recover from a corrupted PSK.
if err != nil {
if cacheKey := c.clientSessionCacheKey(); cacheKey != "" {
c.config.ClientSessionCache.Put(cacheKey, nil)
}
}
}()
}
if ech != nil {
// Split hello into inner and outer
ech.innerHello = hello.clone()
// Overwrite the server name in the outer hello with the public facing
// name.
hello.serverName = string(ech.config.PublicName)
// Generate a new random for the outer hello.
hello.random = make([]byte, 32)
_, err = io.ReadFull(c.config.rand(), hello.random)
if err != nil {
return errors.New("tls: short read from Rand: " + err.Error())
}
// NOTE: we don't do PSK GREASE, in line with boringssl, it's meant to
// work around _possibly_ broken middleboxes, but there is little-to-no
// evidence that this is actually a problem.
if err := computeAndUpdateOuterECHExtension(hello, ech.innerHello, ech, true); err != nil {
return err
}
}
c.serverName = hello.serverName
if _, err := c.writeHandshakeRecord(hello, nil); err != nil {
return err
}
if hello.earlyData {
suite := cipherSuiteTLS13ByID(session.cipherSuite)
transcript := suite.hash.New()
if err := transcriptMsg(hello, transcript); err != nil {
return err
}
earlyTrafficSecret := earlySecret.ClientEarlyTrafficSecret(transcript)
c.quicSetWriteSecret(QUICEncryptionLevelEarly, suite.id, earlyTrafficSecret)
}
// serverHelloMsg is not included in the transcript
msg, err := c.readHandshake(nil)
if err != nil {
return err
}
serverHello, ok := msg.(*serverHelloMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(serverHello, msg)
}
if err := c.pickTLSVersion(serverHello); err != nil {
return err
}
// If we are negotiating a protocol version that's lower than what we
// support, check for the server downgrade canaries.
// See RFC 8446, Section 4.1.3.
maxVers := c.config.maxSupportedVersion(roleClient)
tls12Downgrade := string(serverHello.random[24:]) == downgradeCanaryTLS12
tls11Downgrade := string(serverHello.random[24:]) == downgradeCanaryTLS11
if maxVers == VersionTLS13 && c.vers <= VersionTLS12 && (tls12Downgrade || tls11Downgrade) ||
maxVers == VersionTLS12 && c.vers <= VersionTLS11 && tls11Downgrade {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: downgrade attempt detected, possibly due to a MitM attack or a broken middlebox")
}
if c.vers == VersionTLS13 {
hs := &clientHandshakeStateTLS13{
c: c,
ctx: ctx,
serverHello: serverHello,
hello: hello,
keyShareKeys: keyShareKeys,
session: session,
earlySecret: earlySecret,
binderKey: binderKey,
echContext: ech,
}
return hs.handshake()
}
hs := &clientHandshakeState{
c: c,
ctx: ctx,
serverHello: serverHello,
hello: hello,
session: session,
}
return hs.handshake()
}
func (c *Conn) loadSession(hello *clientHelloMsg) (
session *SessionState, earlySecret *tls13.EarlySecret, binderKey []byte, err error) {
if c.config.SessionTicketsDisabled || c.config.ClientSessionCache == nil {
return nil, nil, nil, nil
}
echInner := bytes.Equal(hello.encryptedClientHello, []byte{1})
// ticketSupported is a TLS 1.2 extension (as TLS 1.3 replaced tickets with PSK
// identities) and ECH requires and forces TLS 1.3.
hello.ticketSupported = true && !echInner
if hello.supportedVersions[0] == VersionTLS13 {
// Require DHE on resumption as it guarantees forward secrecy against
// compromise of the session ticket key. See RFC 8446, Section 4.2.9.
hello.pskModes = []uint8{pskModeDHE}
}
// Session resumption is not allowed if renegotiating because
// renegotiation is primarily used to allow a client to send a client
// certificate, which would be skipped if session resumption occurred.
if c.handshakes != 0 {
return nil, nil, nil, nil
}
// Try to resume a previously negotiated TLS session, if available.
cacheKey := c.clientSessionCacheKey()
if cacheKey == "" {
return nil, nil, nil, nil
}
cs, ok := c.config.ClientSessionCache.Get(cacheKey)
if !ok || cs == nil {
return nil, nil, nil, nil
}
session = cs.session
// Check that version used for the previous session is still valid.
versOk := false
for _, v := range hello.supportedVersions {
if v == session.version {
versOk = true
break
}
}
if !versOk {
return nil, nil, nil, nil
}
// Check that the cached server certificate is not expired, and that it's
// valid for the ServerName. This should be ensured by the cache key, but
// protect the application from a faulty ClientSessionCache implementation.
if c.config.time().After(session.peerCertificates[0].NotAfter) {
// Expired certificate, delete the entry.
c.config.ClientSessionCache.Put(cacheKey, nil)
return nil, nil, nil, nil
}
if !c.config.InsecureSkipVerify {
if len(session.verifiedChains) == 0 {
// The original connection had InsecureSkipVerify, while this doesn't.
return nil, nil, nil, nil
}
if err := session.peerCertificates[0].VerifyHostname(c.config.ServerName); err != nil {
return nil, nil, nil, nil
}
}
if session.version != VersionTLS13 {
// In TLS 1.2 the cipher suite must match the resumed session. Ensure we
// are still offering it.
if mutualCipherSuite(hello.cipherSuites, session.cipherSuite) == nil {
return nil, nil, nil, nil
}
// FIPS 140-3 requires the use of Extended Master Secret.
if !session.extMasterSecret && fips140tls.Required() {
return nil, nil, nil, nil
}
hello.sessionTicket = session.ticket
return
}
// Check that the session ticket is not expired.
if c.config.time().After(time.Unix(int64(session.useBy), 0)) {
c.config.ClientSessionCache.Put(cacheKey, nil)
return nil, nil, nil, nil
}
// In TLS 1.3 the KDF hash must match the resumed session. Ensure we
// offer at least one cipher suite with that hash.
cipherSuite := cipherSuiteTLS13ByID(session.cipherSuite)
if cipherSuite == nil {
return nil, nil, nil, nil
}
cipherSuiteOk := false
for _, offeredID := range hello.cipherSuites {
offeredSuite := cipherSuiteTLS13ByID(offeredID)
if offeredSuite != nil && offeredSuite.hash == cipherSuite.hash {
cipherSuiteOk = true
break
}
}
if !cipherSuiteOk {
return nil, nil, nil, nil
}
if c.quic != nil {
if c.quic.enableSessionEvents {
c.quicResumeSession(session)
}
// For 0-RTT, the cipher suite has to match exactly, and we need to be
// offering the same ALPN.
if session.EarlyData && mutualCipherSuiteTLS13(hello.cipherSuites, session.cipherSuite) != nil {
for _, alpn := range hello.alpnProtocols {
if alpn == session.alpnProtocol {
hello.earlyData = true
break
}
}
}
}
// Set the pre_shared_key extension. See RFC 8446, Section 4.2.11.1.
ticketAge := c.config.time().Sub(time.Unix(int64(session.createdAt), 0))
identity := pskIdentity{
label: session.ticket,
obfuscatedTicketAge: uint32(ticketAge/time.Millisecond) + session.ageAdd,
}
hello.pskIdentities = []pskIdentity{identity}
hello.pskBinders = [][]byte{make([]byte, cipherSuite.hash.Size())}
// Compute the PSK binders. See RFC 8446, Section 4.2.11.2.
earlySecret = tls13.NewEarlySecret(cipherSuite.hash.New, session.secret)
binderKey = earlySecret.ResumptionBinderKey()
transcript := cipherSuite.hash.New()
if err := computeAndUpdatePSK(hello, binderKey, transcript, cipherSuite.finishedHash); err != nil {
return nil, nil, nil, err
}
return
}
func (c *Conn) pickTLSVersion(serverHello *serverHelloMsg) error {
peerVersion := serverHello.vers
if serverHello.supportedVersion != 0 {
peerVersion = serverHello.supportedVersion
}
vers, ok := c.config.mutualVersion(roleClient, []uint16{peerVersion})
if !ok {
c.sendAlert(alertProtocolVersion)
return fmt.Errorf("tls: server selected unsupported protocol version %x", peerVersion)
}
c.vers = vers
c.haveVers = true
c.in.version = vers
c.out.version = vers
return nil
}
// Does the handshake, either a full one or resumes old session. Requires hs.c,
// hs.hello, hs.serverHello, and, optionally, hs.session to be set.
func (hs *clientHandshakeState) handshake() error {
c := hs.c
// If we did not load a session (hs.session == nil), but we did set a
// session ID in the transmitted client hello (hs.hello.sessionId != nil),
// it means we tried to negotiate TLS 1.3 and sent a random session ID as a
// compatibility measure (see RFC 8446, Section 4.1.2).
//
// Since we're now handshaking for TLS 1.2, if the server echoed the
// transmitted ID back to us, we know mischief is afoot: the session ID
// was random and can't possibly be recognized by the server.
if hs.session == nil && hs.hello.sessionId != nil && bytes.Equal(hs.hello.sessionId, hs.serverHello.sessionId) {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: server echoed TLS 1.3 compatibility session ID in TLS 1.2")
}
isResume, err := hs.processServerHello()
if err != nil {
return err
}
hs.finishedHash = newFinishedHash(c.vers, hs.suite)
// No signatures of the handshake are needed in a resumption.
// Otherwise, in a full handshake, if we don't have any certificates
// configured then we will never send a CertificateVerify message and
// thus no signatures are needed in that case either.
if isResume || (len(c.config.Certificates) == 0 && c.config.GetClientCertificate == nil) {
hs.finishedHash.discardHandshakeBuffer()
}
if err := transcriptMsg(hs.hello, &hs.finishedHash); err != nil {
return err
}
if err := transcriptMsg(hs.serverHello, &hs.finishedHash); err != nil {
return err
}
c.buffering = true
c.didResume = isResume
if isResume {
if err := hs.establishKeys(); err != nil {
return err
}
if err := hs.readSessionTicket(); err != nil {
return err
}
if err := hs.readFinished(c.serverFinished[:]); err != nil {
return err
}
c.clientFinishedIsFirst = false
// Make sure the connection is still being verified whether or not this
// is a resumption. Resumptions currently don't reverify certificates so
// they don't call verifyServerCertificate. See Issue 31641.
if c.config.VerifyConnection != nil {
if err := c.config.VerifyConnection(c.connectionStateLocked()); err != nil {
c.sendAlert(alertBadCertificate)
return err
}
}
if err := hs.sendFinished(c.clientFinished[:]); err != nil {
return err
}
if _, err := c.flush(); 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(c.clientFinished[:]); err != nil {
return err
}
if _, err := c.flush(); err != nil {
return err
}
c.clientFinishedIsFirst = true
if err := hs.readSessionTicket(); err != nil {
return err
}
if err := hs.readFinished(c.serverFinished[:]); err != nil {
return err
}
}
if err := hs.saveSessionTicket(); err != nil {
return err
}
c.ekm = ekmFromMasterSecret(c.vers, hs.suite, hs.masterSecret, hs.hello.random, hs.serverHello.random)
c.isHandshakeComplete.Store(true)
return nil
}
func (hs *clientHandshakeState) pickCipherSuite() error {
if hs.suite = mutualCipherSuite(hs.hello.cipherSuites, hs.serverHello.cipherSuite); hs.suite == nil {
hs.c.sendAlert(alertHandshakeFailure)
return errors.New("tls: server chose an unconfigured cipher suite")
}
hs.c.cipherSuite = hs.suite.id
return nil
}
func (hs *clientHandshakeState) doFullHandshake() error {
c := hs.c
msg, err := c.readHandshake(&hs.finishedHash)
if err != nil {
return err
}
certMsg, ok := msg.(*certificateMsg)
if !ok || len(certMsg.certificates) == 0 {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(certMsg, msg)
}
msg, err = c.readHandshake(&hs.finishedHash)
if err != nil {
return err
}
cs, ok := msg.(*certificateStatusMsg)
if ok {
// RFC4366 on Certificate Status Request:
// The server MAY return a "certificate_status" message.
if !hs.serverHello.ocspStapling {
// If a server returns a "CertificateStatus" message, then the
// server MUST have included an extension of type "status_request"
// with empty "extension_data" in the extended server hello.
c.sendAlert(alertUnexpectedMessage)
return errors.New("tls: received unexpected CertificateStatus message")
}
c.ocspResponse = cs.response
msg, err = c.readHandshake(&hs.finishedHash)
if err != nil {
return err
}
}
if c.handshakes == 0 {
// If this is the first handshake on a connection, process and
// (optionally) verify the server's certificates.
if err := c.verifyServerCertificate(certMsg.certificates); err != nil {
return err
}
} else {
// This is a renegotiation handshake. We require that the
// server's identity (i.e. leaf certificate) is unchanged and
// thus any previous trust decision is still valid.
//
// See https://mitls.org/pages/attacks/3SHAKE for the
// motivation behind this requirement.
if !bytes.Equal(c.peerCertificates[0].Raw, certMsg.certificates[0]) {
c.sendAlert(alertBadCertificate)
return errors.New("tls: server's identity changed during renegotiation")
}
}
keyAgreement := hs.suite.ka(c.vers)
skx, ok := msg.(*serverKeyExchangeMsg)
if ok {
err = keyAgreement.processServerKeyExchange(c.config, hs.hello, hs.serverHello, c.peerCertificates[0], skx)
if err != nil {
c.sendAlert(alertIllegalParameter)
return err
}
if len(skx.key) >= 3 && skx.key[0] == 3 /* named curve */ {
c.curveID = CurveID(binary.BigEndian.Uint16(skx.key[1:]))
}
msg, err = c.readHandshake(&hs.finishedHash)
if err != nil {
return err
}
}
var chainToSend *Certificate
var certRequested bool
certReq, ok := msg.(*certificateRequestMsg)
if ok {
certRequested = true
cri := certificateRequestInfoFromMsg(hs.ctx, c.vers, certReq)
if chainToSend, err = c.getClientCertificate(cri); err != nil {
c.sendAlert(alertInternalError)
return err
}
msg, err = c.readHandshake(&hs.finishedHash)
if err != nil {
return err
}
}
shd, ok := msg.(*serverHelloDoneMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(shd, msg)
}
// 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)
certMsg.certificates = chainToSend.Certificate
if _, err := hs.c.writeHandshakeRecord(certMsg, &hs.finishedHash); err != nil {
return err
}
}
preMasterSecret, ckx, err := keyAgreement.generateClientKeyExchange(c.config, hs.hello, c.peerCertificates[0])
if err != nil {
c.sendAlert(alertInternalError)
return err
}
if ckx != nil {
if _, err := hs.c.writeHandshakeRecord(ckx, &hs.finishedHash); err != nil {
return err
}
}
if hs.serverHello.extendedMasterSecret {
c.extMasterSecret = true
hs.masterSecret = extMasterFromPreMasterSecret(c.vers, hs.suite, preMasterSecret,
hs.finishedHash.Sum())
} else {
if fips140tls.Required() {
c.sendAlert(alertHandshakeFailure)
return errors.New("tls: FIPS 140-3 requires the use of Extended Master Secret")
}
hs.masterSecret = masterFromPreMasterSecret(c.vers, hs.suite, preMasterSecret,
hs.hello.random, hs.serverHello.random)
}
if err := c.config.writeKeyLog(keyLogLabelTLS12, hs.hello.random, hs.masterSecret); err != nil {
c.sendAlert(alertInternalError)
return errors.New("tls: failed to write to key log: " + err.Error())
}
if chainToSend != nil && len(chainToSend.Certificate) > 0 {
certVerify := &certificateVerifyMsg{}
key, ok := chainToSend.PrivateKey.(crypto.Signer)
if !ok {
c.sendAlert(alertInternalError)
return fmt.Errorf("tls: client certificate private key of type %T does not implement crypto.Signer", chainToSend.PrivateKey)
}
var sigType uint8
var sigHash crypto.Hash
if c.vers >= VersionTLS12 {
signatureAlgorithm, err := selectSignatureScheme(c.vers, chainToSend, certReq.supportedSignatureAlgorithms)
if err != nil {
c.sendAlert(alertIllegalParameter)
return err
}
sigType, sigHash, err = typeAndHashFromSignatureScheme(signatureAlgorithm)
if err != nil {
return c.sendAlert(alertInternalError)
}
certVerify.hasSignatureAlgorithm = true
certVerify.signatureAlgorithm = signatureAlgorithm
} else {
sigType, sigHash, err = legacyTypeAndHashFromPublicKey(key.Public())
if err != nil {
c.sendAlert(alertIllegalParameter)
return err
}
}
signed := hs.finishedHash.hashForClientCertificate(sigType, sigHash)
signOpts := crypto.SignerOpts(sigHash)
if sigType == signatureRSAPSS {
signOpts = &rsa.PSSOptions{SaltLength: rsa.PSSSaltLengthEqualsHash, Hash: sigHash}
}
certVerify.signature, err = key.Sign(c.config.rand(), signed, signOpts)
if err != nil {
c.sendAlert(alertInternalError)
return err
}
if _, err := hs.c.writeHandshakeRecord(certVerify, &hs.finishedHash); err != nil {
return err
}
}
hs.finishedHash.discardHandshakeBuffer()
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 any
var clientHash, serverHash hash.Hash
if hs.suite.cipher != nil {
clientCipher = hs.suite.cipher(clientKey, clientIV, false /* not for reading */)
clientHash = hs.suite.mac(clientMAC)
serverCipher = hs.suite.cipher(serverKey, serverIV, true /* for reading */)
serverHash = hs.suite.mac(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 err := hs.pickCipherSuite(); err != nil {
return false, err
}
if hs.serverHello.compressionMethod != compressionNone {
c.sendAlert(alertIllegalParameter)
return false, errors.New("tls: server selected unsupported compression format")
}
supportsPointFormat := false
offeredNonCompressedFormat := false
for _, format := range hs.serverHello.supportedPoints {
if format == pointFormatUncompressed {
supportsPointFormat = true
} else {
offeredNonCompressedFormat = true
}
}
if !supportsPointFormat && offeredNonCompressedFormat {
return false, errors.New("tls: server offered only incompatible point formats")
}
if c.handshakes == 0 && hs.serverHello.secureRenegotiationSupported {
c.secureRenegotiation = true
if len(hs.serverHello.secureRenegotiation) != 0 {
c.sendAlert(alertHandshakeFailure)
return false, errors.New("tls: initial handshake had non-empty renegotiation extension")
}
}
if c.handshakes > 0 && c.secureRenegotiation {
var expectedSecureRenegotiation [24]byte
copy(expectedSecureRenegotiation[:], c.clientFinished[:])
copy(expectedSecureRenegotiation[12:], c.serverFinished[:])
if !bytes.Equal(hs.serverHello.secureRenegotiation, expectedSecureRenegotiation[:]) {
c.sendAlert(alertHandshakeFailure)
return false, errors.New("tls: incorrect renegotiation extension contents")
}
}
if err := checkALPN(hs.hello.alpnProtocols, hs.serverHello.alpnProtocol, false); err != nil {
c.sendAlert(alertUnsupportedExtension)
return false, err
}
c.clientProtocol = hs.serverHello.alpnProtocol
c.scts = hs.serverHello.scts
if !hs.serverResumedSession() {
return false, nil
}
if hs.session.version != c.vers {
c.sendAlert(alertHandshakeFailure)
return false, errors.New("tls: server resumed a session with a different version")
}
if hs.session.cipherSuite != hs.suite.id {
c.sendAlert(alertHandshakeFailure)
return false, errors.New("tls: server resumed a session with a different cipher suite")
}
// RFC 7627, Section 5.3
if hs.session.extMasterSecret != hs.serverHello.extendedMasterSecret {
c.sendAlert(alertHandshakeFailure)
return false, errors.New("tls: server resumed a session with a different EMS extension")
}
// Restore master secret and certificates from previous state
hs.masterSecret = hs.session.secret
c.extMasterSecret = hs.session.extMasterSecret
c.peerCertificates = hs.session.peerCertificates
c.verifiedChains = hs.session.verifiedChains
c.ocspResponse = hs.session.ocspResponse
// Let the ServerHello SCTs override the session SCTs from the original
// connection, if any are provided.
if len(c.scts) == 0 && len(hs.session.scts) != 0 {
c.scts = hs.session.scts
}
c.curveID = hs.session.curveID
return true, nil
}
// checkALPN ensure that the server's choice of ALPN protocol is compatible with
// the protocols that we advertised in the ClientHello.
func checkALPN(clientProtos []string, serverProto string, quic bool) error {
if serverProto == "" {
if quic && len(clientProtos) > 0 {
// RFC 9001, Section 8.1
return errors.New("tls: server did not select an ALPN protocol")
}
return nil
}
if len(clientProtos) == 0 {
return errors.New("tls: server advertised unrequested ALPN extension")
}
for _, proto := range clientProtos {
if proto == serverProto {
return nil
}
}
return errors.New("tls: server selected unadvertised ALPN protocol")
}
func (hs *clientHandshakeState) readFinished(out []byte) error {
c := hs.c
if err := c.readChangeCipherSpec(); err != nil {
return err
}
// finishedMsg is included in the transcript, but not until after we
// check the client version, since the state before this message was
// sent is used during verification.
msg, err := c.readHandshake(nil)
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