Source file src/crypto/tls/handshake_client.go

Documentation: crypto/tls

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package tls
     6  
     7  import (
     8  	"bytes"
     9  	"context"
    10  	"crypto"
    11  	"crypto/ecdsa"
    12  	"crypto/ed25519"
    13  	"crypto/rsa"
    14  	"crypto/subtle"
    15  	"crypto/x509"
    16  	"errors"
    17  	"fmt"
    18  	"hash"
    19  	"io"
    20  	"net"
    21  	"strings"
    22  	"sync/atomic"
    23  	"time"
    24  )
    25  
    26  type clientHandshakeState struct {
    27  	c            *Conn
    28  	ctx          context.Context
    29  	serverHello  *serverHelloMsg
    30  	hello        *clientHelloMsg
    31  	suite        *cipherSuite
    32  	finishedHash finishedHash
    33  	masterSecret []byte
    34  	session      *ClientSessionState
    35  }
    36  
    37  func (c *Conn) makeClientHello() (*clientHelloMsg, ecdheParameters, error) {
    38  	config := c.config
    39  	if len(config.ServerName) == 0 && !config.InsecureSkipVerify {
    40  		return nil, nil, errors.New("tls: either ServerName or InsecureSkipVerify must be specified in the tls.Config")
    41  	}
    42  
    43  	nextProtosLength := 0
    44  	for _, proto := range config.NextProtos {
    45  		if l := len(proto); l == 0 || l > 255 {
    46  			return nil, nil, errors.New("tls: invalid NextProtos value")
    47  		} else {
    48  			nextProtosLength += 1 + l
    49  		}
    50  	}
    51  	if nextProtosLength > 0xffff {
    52  		return nil, nil, errors.New("tls: NextProtos values too large")
    53  	}
    54  
    55  	supportedVersions := config.supportedVersions()
    56  	if len(supportedVersions) == 0 {
    57  		return nil, nil, errors.New("tls: no supported versions satisfy MinVersion and MaxVersion")
    58  	}
    59  
    60  	clientHelloVersion := config.maxSupportedVersion()
    61  	// The version at the beginning of the ClientHello was capped at TLS 1.2
    62  	// for compatibility reasons. The supported_versions extension is used
    63  	// to negotiate versions now. See RFC 8446, Section 4.2.1.
    64  	if clientHelloVersion > VersionTLS12 {
    65  		clientHelloVersion = VersionTLS12
    66  	}
    67  
    68  	hello := &clientHelloMsg{
    69  		vers:                         clientHelloVersion,
    70  		compressionMethods:           []uint8{compressionNone},
    71  		random:                       make([]byte, 32),
    72  		sessionId:                    make([]byte, 32),
    73  		ocspStapling:                 true,
    74  		scts:                         true,
    75  		serverName:                   hostnameInSNI(config.ServerName),
    76  		supportedCurves:              config.curvePreferences(),
    77  		supportedPoints:              []uint8{pointFormatUncompressed},
    78  		secureRenegotiationSupported: true,
    79  		alpnProtocols:                config.NextProtos,
    80  		supportedVersions:            supportedVersions,
    81  	}
    82  
    83  	if c.handshakes > 0 {
    84  		hello.secureRenegotiation = c.clientFinished[:]
    85  	}
    86  
    87  	preferenceOrder := cipherSuitesPreferenceOrder
    88  	if !hasAESGCMHardwareSupport {
    89  		preferenceOrder = cipherSuitesPreferenceOrderNoAES
    90  	}
    91  	configCipherSuites := config.cipherSuites()
    92  	hello.cipherSuites = make([]uint16, 0, len(configCipherSuites))
    93  
    94  	for _, suiteId := range preferenceOrder {
    95  		suite := mutualCipherSuite(configCipherSuites, suiteId)
    96  		if suite == nil {
    97  			continue
    98  		}
    99  		// Don't advertise TLS 1.2-only cipher suites unless
   100  		// we're attempting TLS 1.2.
   101  		if hello.vers < VersionTLS12 && suite.flags&suiteTLS12 != 0 {
   102  			continue
   103  		}
   104  		hello.cipherSuites = append(hello.cipherSuites, suiteId)
   105  	}
   106  
   107  	_, err := io.ReadFull(config.rand(), hello.random)
   108  	if err != nil {
   109  		return nil, nil, errors.New("tls: short read from Rand: " + err.Error())
   110  	}
   111  
   112  	// A random session ID is used to detect when the server accepted a ticket
   113  	// and is resuming a session (see RFC 5077). In TLS 1.3, it's always set as
   114  	// a compatibility measure (see RFC 8446, Section 4.1.2).
   115  	if _, err := io.ReadFull(config.rand(), hello.sessionId); err != nil {
   116  		return nil, nil, errors.New("tls: short read from Rand: " + err.Error())
   117  	}
   118  
   119  	if hello.vers >= VersionTLS12 {
   120  		hello.supportedSignatureAlgorithms = supportedSignatureAlgorithms
   121  	}
   122  
   123  	var params ecdheParameters
   124  	if hello.supportedVersions[0] == VersionTLS13 {
   125  		if hasAESGCMHardwareSupport {
   126  			hello.cipherSuites = append(hello.cipherSuites, defaultCipherSuitesTLS13...)
   127  		} else {
   128  			hello.cipherSuites = append(hello.cipherSuites, defaultCipherSuitesTLS13NoAES...)
   129  		}
   130  
   131  		curveID := config.curvePreferences()[0]
   132  		if _, ok := curveForCurveID(curveID); curveID != X25519 && !ok {
   133  			return nil, nil, errors.New("tls: CurvePreferences includes unsupported curve")
   134  		}
   135  		params, err = generateECDHEParameters(config.rand(), curveID)
   136  		if err != nil {
   137  			return nil, nil, err
   138  		}
   139  		hello.keyShares = []keyShare{{group: curveID, data: params.PublicKey()}}
   140  	}
   141  
   142  	return hello, params, nil
   143  }
   144  
   145  func (c *Conn) clientHandshake(ctx context.Context) (err error) {
   146  	if c.config == nil {
   147  		c.config = defaultConfig()
   148  	}
   149  
   150  	// This may be a renegotiation handshake, in which case some fields
   151  	// need to be reset.
   152  	c.didResume = false
   153  
   154  	hello, ecdheParams, err := c.makeClientHello()
   155  	if err != nil {
   156  		return err
   157  	}
   158  	c.serverName = hello.serverName
   159  
   160  	cacheKey, session, earlySecret, binderKey := c.loadSession(hello)
   161  	if cacheKey != "" && session != nil {
   162  		defer func() {
   163  			// If we got a handshake failure when resuming a session, throw away
   164  			// the session ticket. See RFC 5077, Section 3.2.
   165  			//
   166  			// RFC 8446 makes no mention of dropping tickets on failure, but it
   167  			// does require servers to abort on invalid binders, so we need to
   168  			// delete tickets to recover from a corrupted PSK.
   169  			if err != nil {
   170  				c.config.ClientSessionCache.Put(cacheKey, nil)
   171  			}
   172  		}()
   173  	}
   174  
   175  	if _, err := c.writeRecord(recordTypeHandshake, hello.marshal()); err != nil {
   176  		return err
   177  	}
   178  
   179  	msg, err := c.readHandshake()
   180  	if err != nil {
   181  		return err
   182  	}
   183  
   184  	serverHello, ok := msg.(*serverHelloMsg)
   185  	if !ok {
   186  		c.sendAlert(alertUnexpectedMessage)
   187  		return unexpectedMessageError(serverHello, msg)
   188  	}
   189  
   190  	if err := c.pickTLSVersion(serverHello); err != nil {
   191  		return err
   192  	}
   193  
   194  	// If we are negotiating a protocol version that's lower than what we
   195  	// support, check for the server downgrade canaries.
   196  	// See RFC 8446, Section 4.1.3.
   197  	maxVers := c.config.maxSupportedVersion()
   198  	tls12Downgrade := string(serverHello.random[24:]) == downgradeCanaryTLS12
   199  	tls11Downgrade := string(serverHello.random[24:]) == downgradeCanaryTLS11
   200  	if maxVers == VersionTLS13 && c.vers <= VersionTLS12 && (tls12Downgrade || tls11Downgrade) ||
   201  		maxVers == VersionTLS12 && c.vers <= VersionTLS11 && tls11Downgrade {
   202  		c.sendAlert(alertIllegalParameter)
   203  		return errors.New("tls: downgrade attempt detected, possibly due to a MitM attack or a broken middlebox")
   204  	}
   205  
   206  	if c.vers == VersionTLS13 {
   207  		hs := &clientHandshakeStateTLS13{
   208  			c:           c,
   209  			ctx:         ctx,
   210  			serverHello: serverHello,
   211  			hello:       hello,
   212  			ecdheParams: ecdheParams,
   213  			session:     session,
   214  			earlySecret: earlySecret,
   215  			binderKey:   binderKey,
   216  		}
   217  
   218  		// In TLS 1.3, session tickets are delivered after the handshake.
   219  		return hs.handshake()
   220  	}
   221  
   222  	hs := &clientHandshakeState{
   223  		c:           c,
   224  		ctx:         ctx,
   225  		serverHello: serverHello,
   226  		hello:       hello,
   227  		session:     session,
   228  	}
   229  
   230  	if err := hs.handshake(); err != nil {
   231  		return err
   232  	}
   233  
   234  	// If we had a successful handshake and hs.session is different from
   235  	// the one already cached - cache a new one.
   236  	if cacheKey != "" && hs.session != nil && session != hs.session {
   237  		c.config.ClientSessionCache.Put(cacheKey, hs.session)
   238  	}
   239  
   240  	return nil
   241  }
   242  
   243  func (c *Conn) loadSession(hello *clientHelloMsg) (cacheKey string,
   244  	session *ClientSessionState, earlySecret, binderKey []byte) {
   245  	if c.config.SessionTicketsDisabled || c.config.ClientSessionCache == nil {
   246  		return "", nil, nil, nil
   247  	}
   248  
   249  	hello.ticketSupported = true
   250  
   251  	if hello.supportedVersions[0] == VersionTLS13 {
   252  		// Require DHE on resumption as it guarantees forward secrecy against
   253  		// compromise of the session ticket key. See RFC 8446, Section 4.2.9.
   254  		hello.pskModes = []uint8{pskModeDHE}
   255  	}
   256  
   257  	// Session resumption is not allowed if renegotiating because
   258  	// renegotiation is primarily used to allow a client to send a client
   259  	// certificate, which would be skipped if session resumption occurred.
   260  	if c.handshakes != 0 {
   261  		return "", nil, nil, nil
   262  	}
   263  
   264  	// Try to resume a previously negotiated TLS session, if available.
   265  	cacheKey = clientSessionCacheKey(c.conn.RemoteAddr(), c.config)
   266  	session, ok := c.config.ClientSessionCache.Get(cacheKey)
   267  	if !ok || session == nil {
   268  		return cacheKey, nil, nil, nil
   269  	}
   270  
   271  	// Check that version used for the previous session is still valid.
   272  	versOk := false
   273  	for _, v := range hello.supportedVersions {
   274  		if v == session.vers {
   275  			versOk = true
   276  			break
   277  		}
   278  	}
   279  	if !versOk {
   280  		return cacheKey, nil, nil, nil
   281  	}
   282  
   283  	// Check that the cached server certificate is not expired, and that it's
   284  	// valid for the ServerName. This should be ensured by the cache key, but
   285  	// protect the application from a faulty ClientSessionCache implementation.
   286  	if !c.config.InsecureSkipVerify {
   287  		if len(session.verifiedChains) == 0 {
   288  			// The original connection had InsecureSkipVerify, while this doesn't.
   289  			return cacheKey, nil, nil, nil
   290  		}
   291  		serverCert := session.serverCertificates[0]
   292  		if c.config.time().After(serverCert.NotAfter) {
   293  			// Expired certificate, delete the entry.
   294  			c.config.ClientSessionCache.Put(cacheKey, nil)
   295  			return cacheKey, nil, nil, nil
   296  		}
   297  		if err := serverCert.VerifyHostname(c.config.ServerName); err != nil {
   298  			return cacheKey, nil, nil, nil
   299  		}
   300  	}
   301  
   302  	if session.vers != VersionTLS13 {
   303  		// In TLS 1.2 the cipher suite must match the resumed session. Ensure we
   304  		// are still offering it.
   305  		if mutualCipherSuite(hello.cipherSuites, session.cipherSuite) == nil {
   306  			return cacheKey, nil, nil, nil
   307  		}
   308  
   309  		hello.sessionTicket = session.sessionTicket
   310  		return
   311  	}
   312  
   313  	// Check that the session ticket is not expired.
   314  	if c.config.time().After(session.useBy) {
   315  		c.config.ClientSessionCache.Put(cacheKey, nil)
   316  		return cacheKey, nil, nil, nil
   317  	}
   318  
   319  	// In TLS 1.3 the KDF hash must match the resumed session. Ensure we
   320  	// offer at least one cipher suite with that hash.
   321  	cipherSuite := cipherSuiteTLS13ByID(session.cipherSuite)
   322  	if cipherSuite == nil {
   323  		return cacheKey, nil, nil, nil
   324  	}
   325  	cipherSuiteOk := false
   326  	for _, offeredID := range hello.cipherSuites {
   327  		offeredSuite := cipherSuiteTLS13ByID(offeredID)
   328  		if offeredSuite != nil && offeredSuite.hash == cipherSuite.hash {
   329  			cipherSuiteOk = true
   330  			break
   331  		}
   332  	}
   333  	if !cipherSuiteOk {
   334  		return cacheKey, nil, nil, nil
   335  	}
   336  
   337  	// Set the pre_shared_key extension. See RFC 8446, Section 4.2.11.1.
   338  	ticketAge := uint32(c.config.time().Sub(session.receivedAt) / time.Millisecond)
   339  	identity := pskIdentity{
   340  		label:               session.sessionTicket,
   341  		obfuscatedTicketAge: ticketAge + session.ageAdd,
   342  	}
   343  	hello.pskIdentities = []pskIdentity{identity}
   344  	hello.pskBinders = [][]byte{make([]byte, cipherSuite.hash.Size())}
   345  
   346  	// Compute the PSK binders. See RFC 8446, Section 4.2.11.2.
   347  	psk := cipherSuite.expandLabel(session.masterSecret, "resumption",
   348  		session.nonce, cipherSuite.hash.Size())
   349  	earlySecret = cipherSuite.extract(psk, nil)
   350  	binderKey = cipherSuite.deriveSecret(earlySecret, resumptionBinderLabel, nil)
   351  	transcript := cipherSuite.hash.New()
   352  	transcript.Write(hello.marshalWithoutBinders())
   353  	pskBinders := [][]byte{cipherSuite.finishedHash(binderKey, transcript)}
   354  	hello.updateBinders(pskBinders)
   355  
   356  	return
   357  }
   358  
   359  func (c *Conn) pickTLSVersion(serverHello *serverHelloMsg) error {
   360  	peerVersion := serverHello.vers
   361  	if serverHello.supportedVersion != 0 {
   362  		peerVersion = serverHello.supportedVersion
   363  	}
   364  
   365  	vers, ok := c.config.mutualVersion([]uint16{peerVersion})
   366  	if !ok {
   367  		c.sendAlert(alertProtocolVersion)
   368  		return fmt.Errorf("tls: server selected unsupported protocol version %x", peerVersion)
   369  	}
   370  
   371  	c.vers = vers
   372  	c.haveVers = true
   373  	c.in.version = vers
   374  	c.out.version = vers
   375  
   376  	return nil
   377  }
   378  
   379  // Does the handshake, either a full one or resumes old session. Requires hs.c,
   380  // hs.hello, hs.serverHello, and, optionally, hs.session to be set.
   381  func (hs *clientHandshakeState) handshake() error {
   382  	c := hs.c
   383  
   384  	isResume, err := hs.processServerHello()
   385  	if err != nil {
   386  		return err
   387  	}
   388  
   389  	hs.finishedHash = newFinishedHash(c.vers, hs.suite)
   390  
   391  	// No signatures of the handshake are needed in a resumption.
   392  	// Otherwise, in a full handshake, if we don't have any certificates
   393  	// configured then we will never send a CertificateVerify message and
   394  	// thus no signatures are needed in that case either.
   395  	if isResume || (len(c.config.Certificates) == 0 && c.config.GetClientCertificate == nil) {
   396  		hs.finishedHash.discardHandshakeBuffer()
   397  	}
   398  
   399  	hs.finishedHash.Write(hs.hello.marshal())
   400  	hs.finishedHash.Write(hs.serverHello.marshal())
   401  
   402  	c.buffering = true
   403  	c.didResume = isResume
   404  	if isResume {
   405  		if err := hs.establishKeys(); err != nil {
   406  			return err
   407  		}
   408  		if err := hs.readSessionTicket(); err != nil {
   409  			return err
   410  		}
   411  		if err := hs.readFinished(c.serverFinished[:]); err != nil {
   412  			return err
   413  		}
   414  		c.clientFinishedIsFirst = false
   415  		// Make sure the connection is still being verified whether or not this
   416  		// is a resumption. Resumptions currently don't reverify certificates so
   417  		// they don't call verifyServerCertificate. See Issue 31641.
   418  		if c.config.VerifyConnection != nil {
   419  			if err := c.config.VerifyConnection(c.connectionStateLocked()); err != nil {
   420  				c.sendAlert(alertBadCertificate)
   421  				return err
   422  			}
   423  		}
   424  		if err := hs.sendFinished(c.clientFinished[:]); err != nil {
   425  			return err
   426  		}
   427  		if _, err := c.flush(); err != nil {
   428  			return err
   429  		}
   430  	} else {
   431  		if err := hs.doFullHandshake(); err != nil {
   432  			return err
   433  		}
   434  		if err := hs.establishKeys(); err != nil {
   435  			return err
   436  		}
   437  		if err := hs.sendFinished(c.clientFinished[:]); err != nil {
   438  			return err
   439  		}
   440  		if _, err := c.flush(); err != nil {
   441  			return err
   442  		}
   443  		c.clientFinishedIsFirst = true
   444  		if err := hs.readSessionTicket(); err != nil {
   445  			return err
   446  		}
   447  		if err := hs.readFinished(c.serverFinished[:]); err != nil {
   448  			return err
   449  		}
   450  	}
   451  
   452  	c.ekm = ekmFromMasterSecret(c.vers, hs.suite, hs.masterSecret, hs.hello.random, hs.serverHello.random)
   453  	atomic.StoreUint32(&c.handshakeStatus, 1)
   454  
   455  	return nil
   456  }
   457  
   458  func (hs *clientHandshakeState) pickCipherSuite() error {
   459  	if hs.suite = mutualCipherSuite(hs.hello.cipherSuites, hs.serverHello.cipherSuite); hs.suite == nil {
   460  		hs.c.sendAlert(alertHandshakeFailure)
   461  		return errors.New("tls: server chose an unconfigured cipher suite")
   462  	}
   463  
   464  	hs.c.cipherSuite = hs.suite.id
   465  	return nil
   466  }
   467  
   468  func (hs *clientHandshakeState) doFullHandshake() error {
   469  	c := hs.c
   470  
   471  	msg, err := c.readHandshake()
   472  	if err != nil {
   473  		return err
   474  	}
   475  	certMsg, ok := msg.(*certificateMsg)
   476  	if !ok || len(certMsg.certificates) == 0 {
   477  		c.sendAlert(alertUnexpectedMessage)
   478  		return unexpectedMessageError(certMsg, msg)
   479  	}
   480  	hs.finishedHash.Write(certMsg.marshal())
   481  
   482  	msg, err = c.readHandshake()
   483  	if err != nil {
   484  		return err
   485  	}
   486  
   487  	cs, ok := msg.(*certificateStatusMsg)
   488  	if ok {
   489  		// RFC4366 on Certificate Status Request:
   490  		// The server MAY return a "certificate_status" message.
   491  
   492  		if !hs.serverHello.ocspStapling {
   493  			// If a server returns a "CertificateStatus" message, then the
   494  			// server MUST have included an extension of type "status_request"
   495  			// with empty "extension_data" in the extended server hello.
   496  
   497  			c.sendAlert(alertUnexpectedMessage)
   498  			return errors.New("tls: received unexpected CertificateStatus message")
   499  		}
   500  		hs.finishedHash.Write(cs.marshal())
   501  
   502  		c.ocspResponse = cs.response
   503  
   504  		msg, err = c.readHandshake()
   505  		if err != nil {
   506  			return err
   507  		}
   508  	}
   509  
   510  	if c.handshakes == 0 {
   511  		// If this is the first handshake on a connection, process and
   512  		// (optionally) verify the server's certificates.
   513  		if err := c.verifyServerCertificate(certMsg.certificates); err != nil {
   514  			return err
   515  		}
   516  	} else {
   517  		// This is a renegotiation handshake. We require that the
   518  		// server's identity (i.e. leaf certificate) is unchanged and
   519  		// thus any previous trust decision is still valid.
   520  		//
   521  		// See https://mitls.org/pages/attacks/3SHAKE for the
   522  		// motivation behind this requirement.
   523  		if !bytes.Equal(c.peerCertificates[0].Raw, certMsg.certificates[0]) {
   524  			c.sendAlert(alertBadCertificate)
   525  			return errors.New("tls: server's identity changed during renegotiation")
   526  		}
   527  	}
   528  
   529  	keyAgreement := hs.suite.ka(c.vers)
   530  
   531  	skx, ok := msg.(*serverKeyExchangeMsg)
   532  	if ok {
   533  		hs.finishedHash.Write(skx.marshal())
   534  		err = keyAgreement.processServerKeyExchange(c.config, hs.hello, hs.serverHello, c.peerCertificates[0], skx)
   535  		if err != nil {
   536  			c.sendAlert(alertUnexpectedMessage)
   537  			return err
   538  		}
   539  
   540  		msg, err = c.readHandshake()
   541  		if err != nil {
   542  			return err
   543  		}
   544  	}
   545  
   546  	var chainToSend *Certificate
   547  	var certRequested bool
   548  	certReq, ok := msg.(*certificateRequestMsg)
   549  	if ok {
   550  		certRequested = true
   551  		hs.finishedHash.Write(certReq.marshal())
   552  
   553  		cri := certificateRequestInfoFromMsg(hs.ctx, c.vers, certReq)
   554  		if chainToSend, err = c.getClientCertificate(cri); err != nil {
   555  			c.sendAlert(alertInternalError)
   556  			return err
   557  		}
   558  
   559  		msg, err = c.readHandshake()
   560  		if err != nil {
   561  			return err
   562  		}
   563  	}
   564  
   565  	shd, ok := msg.(*serverHelloDoneMsg)
   566  	if !ok {
   567  		c.sendAlert(alertUnexpectedMessage)
   568  		return unexpectedMessageError(shd, msg)
   569  	}
   570  	hs.finishedHash.Write(shd.marshal())
   571  
   572  	// If the server requested a certificate then we have to send a
   573  	// Certificate message, even if it's empty because we don't have a
   574  	// certificate to send.
   575  	if certRequested {
   576  		certMsg = new(certificateMsg)
   577  		certMsg.certificates = chainToSend.Certificate
   578  		hs.finishedHash.Write(certMsg.marshal())
   579  		if _, err := c.writeRecord(recordTypeHandshake, certMsg.marshal()); err != nil {
   580  			return err
   581  		}
   582  	}
   583  
   584  	preMasterSecret, ckx, err := keyAgreement.generateClientKeyExchange(c.config, hs.hello, c.peerCertificates[0])
   585  	if err != nil {
   586  		c.sendAlert(alertInternalError)
   587  		return err
   588  	}
   589  	if ckx != nil {
   590  		hs.finishedHash.Write(ckx.marshal())
   591  		if _, err := c.writeRecord(recordTypeHandshake, ckx.marshal()); err != nil {
   592  			return err
   593  		}
   594  	}
   595  
   596  	if chainToSend != nil && len(chainToSend.Certificate) > 0 {
   597  		certVerify := &certificateVerifyMsg{}
   598  
   599  		key, ok := chainToSend.PrivateKey.(crypto.Signer)
   600  		if !ok {
   601  			c.sendAlert(alertInternalError)
   602  			return fmt.Errorf("tls: client certificate private key of type %T does not implement crypto.Signer", chainToSend.PrivateKey)
   603  		}
   604  
   605  		var sigType uint8
   606  		var sigHash crypto.Hash
   607  		if c.vers >= VersionTLS12 {
   608  			signatureAlgorithm, err := selectSignatureScheme(c.vers, chainToSend, certReq.supportedSignatureAlgorithms)
   609  			if err != nil {
   610  				c.sendAlert(alertIllegalParameter)
   611  				return err
   612  			}
   613  			sigType, sigHash, err = typeAndHashFromSignatureScheme(signatureAlgorithm)
   614  			if err != nil {
   615  				return c.sendAlert(alertInternalError)
   616  			}
   617  			certVerify.hasSignatureAlgorithm = true
   618  			certVerify.signatureAlgorithm = signatureAlgorithm
   619  		} else {
   620  			sigType, sigHash, err = legacyTypeAndHashFromPublicKey(key.Public())
   621  			if err != nil {
   622  				c.sendAlert(alertIllegalParameter)
   623  				return err
   624  			}
   625  		}
   626  
   627  		signed := hs.finishedHash.hashForClientCertificate(sigType, sigHash, hs.masterSecret)
   628  		signOpts := crypto.SignerOpts(sigHash)
   629  		if sigType == signatureRSAPSS {
   630  			signOpts = &rsa.PSSOptions{SaltLength: rsa.PSSSaltLengthEqualsHash, Hash: sigHash}
   631  		}
   632  		certVerify.signature, err = key.Sign(c.config.rand(), signed, signOpts)
   633  		if err != nil {
   634  			c.sendAlert(alertInternalError)
   635  			return err
   636  		}
   637  
   638  		hs.finishedHash.Write(certVerify.marshal())
   639  		if _, err := c.writeRecord(recordTypeHandshake, certVerify.marshal()); err != nil {
   640  			return err
   641  		}
   642  	}
   643  
   644  	hs.masterSecret = masterFromPreMasterSecret(c.vers, hs.suite, preMasterSecret, hs.hello.random, hs.serverHello.random)
   645  	if err := c.config.writeKeyLog(keyLogLabelTLS12, hs.hello.random, hs.masterSecret); err != nil {
   646  		c.sendAlert(alertInternalError)
   647  		return errors.New("tls: failed to write to key log: " + err.Error())
   648  	}
   649  
   650  	hs.finishedHash.discardHandshakeBuffer()
   651  
   652  	return nil
   653  }
   654  
   655  func (hs *clientHandshakeState) establishKeys() error {
   656  	c := hs.c
   657  
   658  	clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV :=
   659  		keysFromMasterSecret(c.vers, hs.suite, hs.masterSecret, hs.hello.random, hs.serverHello.random, hs.suite.macLen, hs.suite.keyLen, hs.suite.ivLen)
   660  	var clientCipher, serverCipher interface{}
   661  	var clientHash, serverHash hash.Hash
   662  	if hs.suite.cipher != nil {
   663  		clientCipher = hs.suite.cipher(clientKey, clientIV, false /* not for reading */)
   664  		clientHash = hs.suite.mac(clientMAC)
   665  		serverCipher = hs.suite.cipher(serverKey, serverIV, true /* for reading */)
   666  		serverHash = hs.suite.mac(serverMAC)
   667  	} else {
   668  		clientCipher = hs.suite.aead(clientKey, clientIV)
   669  		serverCipher = hs.suite.aead(serverKey, serverIV)
   670  	}
   671  
   672  	c.in.prepareCipherSpec(c.vers, serverCipher, serverHash)
   673  	c.out.prepareCipherSpec(c.vers, clientCipher, clientHash)
   674  	return nil
   675  }
   676  
   677  func (hs *clientHandshakeState) serverResumedSession() bool {
   678  	// If the server responded with the same sessionId then it means the
   679  	// sessionTicket is being used to resume a TLS session.
   680  	return hs.session != nil && hs.hello.sessionId != nil &&
   681  		bytes.Equal(hs.serverHello.sessionId, hs.hello.sessionId)
   682  }
   683  
   684  func (hs *clientHandshakeState) processServerHello() (bool, error) {
   685  	c := hs.c
   686  
   687  	if err := hs.pickCipherSuite(); err != nil {
   688  		return false, err
   689  	}
   690  
   691  	if hs.serverHello.compressionMethod != compressionNone {
   692  		c.sendAlert(alertUnexpectedMessage)
   693  		return false, errors.New("tls: server selected unsupported compression format")
   694  	}
   695  
   696  	if c.handshakes == 0 && hs.serverHello.secureRenegotiationSupported {
   697  		c.secureRenegotiation = true
   698  		if len(hs.serverHello.secureRenegotiation) != 0 {
   699  			c.sendAlert(alertHandshakeFailure)
   700  			return false, errors.New("tls: initial handshake had non-empty renegotiation extension")
   701  		}
   702  	}
   703  
   704  	if c.handshakes > 0 && c.secureRenegotiation {
   705  		var expectedSecureRenegotiation [24]byte
   706  		copy(expectedSecureRenegotiation[:], c.clientFinished[:])
   707  		copy(expectedSecureRenegotiation[12:], c.serverFinished[:])
   708  		if !bytes.Equal(hs.serverHello.secureRenegotiation, expectedSecureRenegotiation[:]) {
   709  			c.sendAlert(alertHandshakeFailure)
   710  			return false, errors.New("tls: incorrect renegotiation extension contents")
   711  		}
   712  	}
   713  
   714  	if err := checkALPN(hs.hello.alpnProtocols, hs.serverHello.alpnProtocol); err != nil {
   715  		c.sendAlert(alertUnsupportedExtension)
   716  		return false, err
   717  	}
   718  	c.clientProtocol = hs.serverHello.alpnProtocol
   719  
   720  	c.scts = hs.serverHello.scts
   721  
   722  	if !hs.serverResumedSession() {
   723  		return false, nil
   724  	}
   725  
   726  	if hs.session.vers != c.vers {
   727  		c.sendAlert(alertHandshakeFailure)
   728  		return false, errors.New("tls: server resumed a session with a different version")
   729  	}
   730  
   731  	if hs.session.cipherSuite != hs.suite.id {
   732  		c.sendAlert(alertHandshakeFailure)
   733  		return false, errors.New("tls: server resumed a session with a different cipher suite")
   734  	}
   735  
   736  	// Restore masterSecret, peerCerts, and ocspResponse from previous state
   737  	hs.masterSecret = hs.session.masterSecret
   738  	c.peerCertificates = hs.session.serverCertificates
   739  	c.verifiedChains = hs.session.verifiedChains
   740  	c.ocspResponse = hs.session.ocspResponse
   741  	// Let the ServerHello SCTs override the session SCTs from the original
   742  	// connection, if any are provided
   743  	if len(c.scts) == 0 && len(hs.session.scts) != 0 {
   744  		c.scts = hs.session.scts
   745  	}
   746  
   747  	return true, nil
   748  }
   749  
   750  // checkALPN ensure that the server's choice of ALPN protocol is compatible with
   751  // the protocols that we advertised in the Client Hello.
   752  func checkALPN(clientProtos []string, serverProto string) error {
   753  	if serverProto == "" {
   754  		return nil
   755  	}
   756  	if len(clientProtos) == 0 {
   757  		return errors.New("tls: server advertised unrequested ALPN extension")
   758  	}
   759  	for _, proto := range clientProtos {
   760  		if proto == serverProto {
   761  			return nil
   762  		}
   763  	}
   764  	return errors.New("tls: server selected unadvertised ALPN protocol")
   765  }
   766  
   767  func (hs *clientHandshakeState) readFinished(out []byte) error {
   768  	c := hs.c
   769  
   770  	if err := c.readChangeCipherSpec(); err != nil {
   771  		return err
   772  	}
   773  
   774  	msg, err := c.readHandshake()
   775  	if err != nil {
   776  		return err
   777  	}
   778  	serverFinished, ok := msg.(*finishedMsg)
   779  	if !ok {
   780  		c.sendAlert(alertUnexpectedMessage)
   781  		return unexpectedMessageError(serverFinished, msg)
   782  	}
   783  
   784  	verify := hs.finishedHash.serverSum(hs.masterSecret)
   785  	if len(verify) != len(serverFinished.verifyData) ||
   786  		subtle.ConstantTimeCompare(verify, serverFinished.verifyData) != 1 {
   787  		c.sendAlert(alertHandshakeFailure)
   788  		return errors.New("tls: server's Finished message was incorrect")
   789  	}
   790  	hs.finishedHash.Write(serverFinished.marshal())
   791  	copy(out, verify)
   792  	return nil
   793  }
   794  
   795  func (hs *clientHandshakeState) readSessionTicket() error {
   796  	if !hs.serverHello.ticketSupported {
   797  		return nil
   798  	}
   799  
   800  	c := hs.c
   801  	msg, err := c.readHandshake()
   802  	if err != nil {
   803  		return err
   804  	}
   805  	sessionTicketMsg, ok := msg.(*newSessionTicketMsg)
   806  	if !ok {
   807  		c.sendAlert(alertUnexpectedMessage)
   808  		return unexpectedMessageError(sessionTicketMsg, msg)
   809  	}
   810  	hs.finishedHash.Write(sessionTicketMsg.marshal())
   811  
   812  	hs.session = &ClientSessionState{
   813  		sessionTicket:      sessionTicketMsg.ticket,
   814  		vers:               c.vers,
   815  		cipherSuite:        hs.suite.id,
   816  		masterSecret:       hs.masterSecret,
   817  		serverCertificates: c.peerCertificates,
   818  		verifiedChains:     c.verifiedChains,
   819  		receivedAt:         c.config.time(),
   820  		ocspResponse:       c.ocspResponse,
   821  		scts:               c.scts,
   822  	}
   823  
   824  	return nil
   825  }
   826  
   827  func (hs *clientHandshakeState) sendFinished(out []byte) error {
   828  	c := hs.c
   829  
   830  	if _, err := c.writeRecord(recordTypeChangeCipherSpec, []byte{1}); err != nil {
   831  		return err
   832  	}
   833  
   834  	finished := new(finishedMsg)
   835  	finished.verifyData = hs.finishedHash.clientSum(hs.masterSecret)
   836  	hs.finishedHash.Write(finished.marshal())
   837  	if _, err := c.writeRecord(recordTypeHandshake, finished.marshal()); err != nil {
   838  		return err
   839  	}
   840  	copy(out, finished.verifyData)
   841  	return nil
   842  }
   843  
   844  // verifyServerCertificate parses and verifies the provided chain, setting
   845  // c.verifiedChains and c.peerCertificates or sending the appropriate alert.
   846  func (c *Conn) verifyServerCertificate(certificates [][]byte) error {
   847  	certs := make([]*x509.Certificate, len(certificates))
   848  	for i, asn1Data := range certificates {
   849  		cert, err := x509.ParseCertificate(asn1Data)
   850  		if err != nil {
   851  			c.sendAlert(alertBadCertificate)
   852  			return errors.New("tls: failed to parse certificate from server: " + err.Error())
   853  		}
   854  		certs[i] = cert
   855  	}
   856  
   857  	if !c.config.InsecureSkipVerify {
   858  		opts := x509.VerifyOptions{
   859  			Roots:         c.config.RootCAs,
   860  			CurrentTime:   c.config.time(),
   861  			DNSName:       c.config.ServerName,
   862  			Intermediates: x509.NewCertPool(),
   863  		}
   864  		for _, cert := range certs[1:] {
   865  			opts.Intermediates.AddCert(cert)
   866  		}
   867  		var err error
   868  		c.verifiedChains, err = certs[0].Verify(opts)
   869  		if err != nil {
   870  			c.sendAlert(alertBadCertificate)
   871  			return err
   872  		}
   873  	}
   874  
   875  	switch certs[0].PublicKey.(type) {
   876  	case *rsa.PublicKey, *ecdsa.PublicKey, ed25519.PublicKey:
   877  		break
   878  	default:
   879  		c.sendAlert(alertUnsupportedCertificate)
   880  		return fmt.Errorf("tls: server's certificate contains an unsupported type of public key: %T", certs[0].PublicKey)
   881  	}
   882  
   883  	c.peerCertificates = certs
   884  
   885  	if c.config.VerifyPeerCertificate != nil {
   886  		if err := c.config.VerifyPeerCertificate(certificates, c.verifiedChains); err != nil {
   887  			c.sendAlert(alertBadCertificate)
   888  			return err
   889  		}
   890  	}
   891  
   892  	if c.config.VerifyConnection != nil {
   893  		if err := c.config.VerifyConnection(c.connectionStateLocked()); err != nil {
   894  			c.sendAlert(alertBadCertificate)
   895  			return err
   896  		}
   897  	}
   898  
   899  	return nil
   900  }
   901  
   902  // certificateRequestInfoFromMsg generates a CertificateRequestInfo from a TLS
   903  // <= 1.2 CertificateRequest, making an effort to fill in missing information.
   904  func certificateRequestInfoFromMsg(ctx context.Context, vers uint16, certReq *certificateRequestMsg) *CertificateRequestInfo {
   905  	cri := &CertificateRequestInfo{
   906  		AcceptableCAs: certReq.certificateAuthorities,
   907  		Version:       vers,
   908  		ctx:           ctx,
   909  	}
   910  
   911  	var rsaAvail, ecAvail bool
   912  	for _, certType := range certReq.certificateTypes {
   913  		switch certType {
   914  		case certTypeRSASign:
   915  			rsaAvail = true
   916  		case certTypeECDSASign:
   917  			ecAvail = true
   918  		}
   919  	}
   920  
   921  	if !certReq.hasSignatureAlgorithm {
   922  		// Prior to TLS 1.2, signature schemes did not exist. In this case we
   923  		// make up a list based on the acceptable certificate types, to help
   924  		// GetClientCertificate and SupportsCertificate select the right certificate.
   925  		// The hash part of the SignatureScheme is a lie here, because
   926  		// TLS 1.0 and 1.1 always use MD5+SHA1 for RSA and SHA1 for ECDSA.
   927  		switch {
   928  		case rsaAvail && ecAvail:
   929  			cri.SignatureSchemes = []SignatureScheme{
   930  				ECDSAWithP256AndSHA256, ECDSAWithP384AndSHA384, ECDSAWithP521AndSHA512,
   931  				PKCS1WithSHA256, PKCS1WithSHA384, PKCS1WithSHA512, PKCS1WithSHA1,
   932  			}
   933  		case rsaAvail:
   934  			cri.SignatureSchemes = []SignatureScheme{
   935  				PKCS1WithSHA256, PKCS1WithSHA384, PKCS1WithSHA512, PKCS1WithSHA1,
   936  			}
   937  		case ecAvail:
   938  			cri.SignatureSchemes = []SignatureScheme{
   939  				ECDSAWithP256AndSHA256, ECDSAWithP384AndSHA384, ECDSAWithP521AndSHA512,
   940  			}
   941  		}
   942  		return cri
   943  	}
   944  
   945  	// Filter the signature schemes based on the certificate types.
   946  	// See RFC 5246, Section 7.4.4 (where it calls this "somewhat complicated").
   947  	cri.SignatureSchemes = make([]SignatureScheme, 0, len(certReq.supportedSignatureAlgorithms))
   948  	for _, sigScheme := range certReq.supportedSignatureAlgorithms {
   949  		sigType, _, err := typeAndHashFromSignatureScheme(sigScheme)
   950  		if err != nil {
   951  			continue
   952  		}
   953  		switch sigType {
   954  		case signatureECDSA, signatureEd25519:
   955  			if ecAvail {
   956  				cri.SignatureSchemes = append(cri.SignatureSchemes, sigScheme)
   957  			}
   958  		case signatureRSAPSS, signaturePKCS1v15:
   959  			if rsaAvail {
   960  				cri.SignatureSchemes = append(cri.SignatureSchemes, sigScheme)
   961  			}
   962  		}
   963  	}
   964  
   965  	return cri
   966  }
   967  
   968  func (c *Conn) getClientCertificate(cri *CertificateRequestInfo) (*Certificate, error) {
   969  	if c.config.GetClientCertificate != nil {
   970  		return c.config.GetClientCertificate(cri)
   971  	}
   972  
   973  	for _, chain := range c.config.Certificates {
   974  		if err := cri.SupportsCertificate(&chain); err != nil {
   975  			continue
   976  		}
   977  		return &chain, nil
   978  	}
   979  
   980  	// No acceptable certificate found. Don't send a certificate.
   981  	return new(Certificate), nil
   982  }
   983  
   984  // clientSessionCacheKey returns a key used to cache sessionTickets that could
   985  // be used to resume previously negotiated TLS sessions with a server.
   986  func clientSessionCacheKey(serverAddr net.Addr, config *Config) string {
   987  	if len(config.ServerName) > 0 {
   988  		return config.ServerName
   989  	}
   990  	return serverAddr.String()
   991  }
   992  
   993  // hostnameInSNI converts name into an appropriate hostname for SNI.
   994  // Literal IP addresses and absolute FQDNs are not permitted as SNI values.
   995  // See RFC 6066, Section 3.
   996  func hostnameInSNI(name string) string {
   997  	host := name
   998  	if len(host) > 0 && host[0] == '[' && host[len(host)-1] == ']' {
   999  		host = host[1 : len(host)-1]
  1000  	}
  1001  	if i := strings.LastIndex(host, "%"); i > 0 {
  1002  		host = host[:i]
  1003  	}
  1004  	if net.ParseIP(host) != nil {
  1005  		return ""
  1006  	}
  1007  	for len(name) > 0 && name[len(name)-1] == '.' {
  1008  		name = name[:len(name)-1]
  1009  	}
  1010  	return name
  1011  }
  1012  

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