Source file src/crypto/tls/handshake_client.go

     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/internal/hpke"
    14  	"crypto/internal/mlkem768"
    15  	"crypto/rsa"
    16  	"crypto/subtle"
    17  	"crypto/x509"
    18  	"errors"
    19  	"fmt"
    20  	"hash"
    21  	"internal/byteorder"
    22  	"internal/godebug"
    23  	"io"
    24  	"net"
    25  	"strconv"
    26  	"strings"
    27  	"time"
    28  )
    29  
    30  type clientHandshakeState struct {
    31  	c            *Conn
    32  	ctx          context.Context
    33  	serverHello  *serverHelloMsg
    34  	hello        *clientHelloMsg
    35  	suite        *cipherSuite
    36  	finishedHash finishedHash
    37  	masterSecret []byte
    38  	session      *SessionState // the session being resumed
    39  	ticket       []byte        // a fresh ticket received during this handshake
    40  }
    41  
    42  var testingOnlyForceClientHelloSignatureAlgorithms []SignatureScheme
    43  
    44  func (c *Conn) makeClientHello() (*clientHelloMsg, *keySharePrivateKeys, *echContext, error) {
    45  	config := c.config
    46  	if len(config.ServerName) == 0 && !config.InsecureSkipVerify {
    47  		return nil, nil, nil, errors.New("tls: either ServerName or InsecureSkipVerify must be specified in the tls.Config")
    48  	}
    49  
    50  	nextProtosLength := 0
    51  	for _, proto := range config.NextProtos {
    52  		if l := len(proto); l == 0 || l > 255 {
    53  			return nil, nil, nil, errors.New("tls: invalid NextProtos value")
    54  		} else {
    55  			nextProtosLength += 1 + l
    56  		}
    57  	}
    58  	if nextProtosLength > 0xffff {
    59  		return nil, nil, nil, errors.New("tls: NextProtos values too large")
    60  	}
    61  
    62  	supportedVersions := config.supportedVersions(roleClient)
    63  	if len(supportedVersions) == 0 {
    64  		return nil, nil, nil, errors.New("tls: no supported versions satisfy MinVersion and MaxVersion")
    65  	}
    66  	maxVersion := config.maxSupportedVersion(roleClient)
    67  
    68  	hello := &clientHelloMsg{
    69  		vers:                         maxVersion,
    70  		compressionMethods:           []uint8{compressionNone},
    71  		random:                       make([]byte, 32),
    72  		extendedMasterSecret:         true,
    73  		ocspStapling:                 true,
    74  		scts:                         true,
    75  		serverName:                   hostnameInSNI(config.ServerName),
    76  		supportedCurves:              config.curvePreferences(maxVersion),
    77  		supportedPoints:              []uint8{pointFormatUncompressed},
    78  		secureRenegotiationSupported: true,
    79  		alpnProtocols:                config.NextProtos,
    80  		supportedVersions:            supportedVersions,
    81  	}
    82  
    83  	// The version at the beginning of the ClientHello was capped at TLS 1.2
    84  	// for compatibility reasons. The supported_versions extension is used
    85  	// to negotiate versions now. See RFC 8446, Section 4.2.1.
    86  	if hello.vers > VersionTLS12 {
    87  		hello.vers = VersionTLS12
    88  	}
    89  
    90  	if c.handshakes > 0 {
    91  		hello.secureRenegotiation = c.clientFinished[:]
    92  	}
    93  
    94  	preferenceOrder := cipherSuitesPreferenceOrder
    95  	if !hasAESGCMHardwareSupport {
    96  		preferenceOrder = cipherSuitesPreferenceOrderNoAES
    97  	}
    98  	configCipherSuites := config.cipherSuites()
    99  	hello.cipherSuites = make([]uint16, 0, len(configCipherSuites))
   100  
   101  	for _, suiteId := range preferenceOrder {
   102  		suite := mutualCipherSuite(configCipherSuites, suiteId)
   103  		if suite == nil {
   104  			continue
   105  		}
   106  		// Don't advertise TLS 1.2-only cipher suites unless
   107  		// we're attempting TLS 1.2.
   108  		if maxVersion < VersionTLS12 && suite.flags&suiteTLS12 != 0 {
   109  			continue
   110  		}
   111  		hello.cipherSuites = append(hello.cipherSuites, suiteId)
   112  	}
   113  
   114  	_, err := io.ReadFull(config.rand(), hello.random)
   115  	if err != nil {
   116  		return nil, nil, nil, errors.New("tls: short read from Rand: " + err.Error())
   117  	}
   118  
   119  	// A random session ID is used to detect when the server accepted a ticket
   120  	// and is resuming a session (see RFC 5077). In TLS 1.3, it's always set as
   121  	// a compatibility measure (see RFC 8446, Section 4.1.2).
   122  	//
   123  	// The session ID is not set for QUIC connections (see RFC 9001, Section 8.4).
   124  	if c.quic == nil {
   125  		hello.sessionId = make([]byte, 32)
   126  		if _, err := io.ReadFull(config.rand(), hello.sessionId); err != nil {
   127  			return nil, nil, nil, errors.New("tls: short read from Rand: " + err.Error())
   128  		}
   129  	}
   130  
   131  	if maxVersion >= VersionTLS12 {
   132  		hello.supportedSignatureAlgorithms = supportedSignatureAlgorithms()
   133  	}
   134  	if testingOnlyForceClientHelloSignatureAlgorithms != nil {
   135  		hello.supportedSignatureAlgorithms = testingOnlyForceClientHelloSignatureAlgorithms
   136  	}
   137  
   138  	var keyShareKeys *keySharePrivateKeys
   139  	if hello.supportedVersions[0] == VersionTLS13 {
   140  		// Reset the list of ciphers when the client only supports TLS 1.3.
   141  		if len(hello.supportedVersions) == 1 {
   142  			hello.cipherSuites = nil
   143  		}
   144  		if needFIPS() {
   145  			hello.cipherSuites = append(hello.cipherSuites, defaultCipherSuitesTLS13FIPS...)
   146  		} else if hasAESGCMHardwareSupport {
   147  			hello.cipherSuites = append(hello.cipherSuites, defaultCipherSuitesTLS13...)
   148  		} else {
   149  			hello.cipherSuites = append(hello.cipherSuites, defaultCipherSuitesTLS13NoAES...)
   150  		}
   151  
   152  		if len(hello.supportedCurves) == 0 {
   153  			return nil, nil, nil, errors.New("tls: no supported elliptic curves for ECDHE")
   154  		}
   155  		curveID := hello.supportedCurves[0]
   156  		keyShareKeys = &keySharePrivateKeys{curveID: curveID}
   157  		if curveID == x25519Kyber768Draft00 {
   158  			keyShareKeys.ecdhe, err = generateECDHEKey(config.rand(), X25519)
   159  			if err != nil {
   160  				return nil, nil, nil, err
   161  			}
   162  			seed := make([]byte, mlkem768.SeedSize)
   163  			if _, err := io.ReadFull(config.rand(), seed); err != nil {
   164  				return nil, nil, nil, err
   165  			}
   166  			keyShareKeys.kyber, err = mlkem768.NewKeyFromSeed(seed)
   167  			if err != nil {
   168  				return nil, nil, nil, err
   169  			}
   170  			// For draft-tls-westerbaan-xyber768d00-03, we send both a hybrid
   171  			// and a standard X25519 key share, since most servers will only
   172  			// support the latter. We reuse the same X25519 ephemeral key for
   173  			// both, as allowed by draft-ietf-tls-hybrid-design-09, Section 3.2.
   174  			hello.keyShares = []keyShare{
   175  				{group: x25519Kyber768Draft00, data: append(keyShareKeys.ecdhe.PublicKey().Bytes(),
   176  					keyShareKeys.kyber.EncapsulationKey()...)},
   177  				{group: X25519, data: keyShareKeys.ecdhe.PublicKey().Bytes()},
   178  			}
   179  		} else {
   180  			if _, ok := curveForCurveID(curveID); !ok {
   181  				return nil, nil, nil, errors.New("tls: CurvePreferences includes unsupported curve")
   182  			}
   183  			keyShareKeys.ecdhe, err = generateECDHEKey(config.rand(), curveID)
   184  			if err != nil {
   185  				return nil, nil, nil, err
   186  			}
   187  			hello.keyShares = []keyShare{{group: curveID, data: keyShareKeys.ecdhe.PublicKey().Bytes()}}
   188  		}
   189  	}
   190  
   191  	if c.quic != nil {
   192  		p, err := c.quicGetTransportParameters()
   193  		if err != nil {
   194  			return nil, nil, nil, err
   195  		}
   196  		if p == nil {
   197  			p = []byte{}
   198  		}
   199  		hello.quicTransportParameters = p
   200  	}
   201  
   202  	var ech *echContext
   203  	if c.config.EncryptedClientHelloConfigList != nil {
   204  		if c.config.MinVersion != 0 && c.config.MinVersion < VersionTLS13 {
   205  			return nil, nil, nil, errors.New("tls: MinVersion must be >= VersionTLS13 if EncryptedClientHelloConfigList is populated")
   206  		}
   207  		if c.config.MaxVersion != 0 && c.config.MaxVersion <= VersionTLS12 {
   208  			return nil, nil, nil, errors.New("tls: MaxVersion must be >= VersionTLS13 if EncryptedClientHelloConfigList is populated")
   209  		}
   210  		echConfigs, err := parseECHConfigList(c.config.EncryptedClientHelloConfigList)
   211  		if err != nil {
   212  			return nil, nil, nil, err
   213  		}
   214  		echConfig := pickECHConfig(echConfigs)
   215  		if echConfig == nil {
   216  			return nil, nil, nil, errors.New("tls: EncryptedClientHelloConfigList contains no valid configs")
   217  		}
   218  		ech = &echContext{config: echConfig}
   219  		hello.encryptedClientHello = []byte{1} // indicate inner hello
   220  		// We need to explicitly set these 1.2 fields to nil, as we do not
   221  		// marshal them when encoding the inner hello, otherwise transcripts
   222  		// will later mismatch.
   223  		hello.supportedPoints = nil
   224  		hello.ticketSupported = false
   225  		hello.secureRenegotiationSupported = false
   226  		hello.extendedMasterSecret = false
   227  
   228  		echPK, err := hpke.ParseHPKEPublicKey(ech.config.KemID, ech.config.PublicKey)
   229  		if err != nil {
   230  			return nil, nil, nil, err
   231  		}
   232  		suite, err := pickECHCipherSuite(ech.config.SymmetricCipherSuite)
   233  		if err != nil {
   234  			return nil, nil, nil, err
   235  		}
   236  		ech.kdfID, ech.aeadID = suite.KDFID, suite.AEADID
   237  		info := append([]byte("tls ech\x00"), ech.config.raw...)
   238  		ech.encapsulatedKey, ech.hpkeContext, err = hpke.SetupSender(ech.config.KemID, suite.KDFID, suite.AEADID, echPK, info)
   239  		if err != nil {
   240  			return nil, nil, nil, err
   241  		}
   242  	}
   243  
   244  	return hello, keyShareKeys, ech, nil
   245  }
   246  
   247  type echContext struct {
   248  	config          *echConfig
   249  	hpkeContext     *hpke.Sender
   250  	encapsulatedKey []byte
   251  	innerHello      *clientHelloMsg
   252  	innerTranscript hash.Hash
   253  	kdfID           uint16
   254  	aeadID          uint16
   255  	echRejected     bool
   256  }
   257  
   258  func (c *Conn) clientHandshake(ctx context.Context) (err error) {
   259  	if c.config == nil {
   260  		c.config = defaultConfig()
   261  	}
   262  
   263  	// This may be a renegotiation handshake, in which case some fields
   264  	// need to be reset.
   265  	c.didResume = false
   266  
   267  	hello, keyShareKeys, ech, err := c.makeClientHello()
   268  	if err != nil {
   269  		return err
   270  	}
   271  
   272  	session, earlySecret, binderKey, err := c.loadSession(hello)
   273  	if err != nil {
   274  		return err
   275  	}
   276  	if session != nil {
   277  		defer func() {
   278  			// If we got a handshake failure when resuming a session, throw away
   279  			// the session ticket. See RFC 5077, Section 3.2.
   280  			//
   281  			// RFC 8446 makes no mention of dropping tickets on failure, but it
   282  			// does require servers to abort on invalid binders, so we need to
   283  			// delete tickets to recover from a corrupted PSK.
   284  			if err != nil {
   285  				if cacheKey := c.clientSessionCacheKey(); cacheKey != "" {
   286  					c.config.ClientSessionCache.Put(cacheKey, nil)
   287  				}
   288  			}
   289  		}()
   290  	}
   291  
   292  	if ech != nil {
   293  		// Split hello into inner and outer
   294  		ech.innerHello = hello.clone()
   295  
   296  		// Overwrite the server name in the outer hello with the public facing
   297  		// name.
   298  		hello.serverName = string(ech.config.PublicName)
   299  		// Generate a new random for the outer hello.
   300  		hello.random = make([]byte, 32)
   301  		_, err = io.ReadFull(c.config.rand(), hello.random)
   302  		if err != nil {
   303  			return errors.New("tls: short read from Rand: " + err.Error())
   304  		}
   305  
   306  		// NOTE: we don't do PSK GREASE, in line with boringssl, it's meant to
   307  		// work around _possibly_ broken middleboxes, but there is little-to-no
   308  		// evidence that this is actually a problem.
   309  
   310  		if err := computeAndUpdateOuterECHExtension(hello, ech.innerHello, ech, true); err != nil {
   311  			return err
   312  		}
   313  	}
   314  
   315  	c.serverName = hello.serverName
   316  
   317  	if _, err := c.writeHandshakeRecord(hello, nil); err != nil {
   318  		return err
   319  	}
   320  
   321  	if hello.earlyData {
   322  		suite := cipherSuiteTLS13ByID(session.cipherSuite)
   323  		transcript := suite.hash.New()
   324  		if err := transcriptMsg(hello, transcript); err != nil {
   325  			return err
   326  		}
   327  		earlyTrafficSecret := suite.deriveSecret(earlySecret, clientEarlyTrafficLabel, transcript)
   328  		c.quicSetWriteSecret(QUICEncryptionLevelEarly, suite.id, earlyTrafficSecret)
   329  	}
   330  
   331  	// serverHelloMsg is not included in the transcript
   332  	msg, err := c.readHandshake(nil)
   333  	if err != nil {
   334  		return err
   335  	}
   336  
   337  	serverHello, ok := msg.(*serverHelloMsg)
   338  	if !ok {
   339  		c.sendAlert(alertUnexpectedMessage)
   340  		return unexpectedMessageError(serverHello, msg)
   341  	}
   342  
   343  	if err := c.pickTLSVersion(serverHello); err != nil {
   344  		return err
   345  	}
   346  
   347  	// If we are negotiating a protocol version that's lower than what we
   348  	// support, check for the server downgrade canaries.
   349  	// See RFC 8446, Section 4.1.3.
   350  	maxVers := c.config.maxSupportedVersion(roleClient)
   351  	tls12Downgrade := string(serverHello.random[24:]) == downgradeCanaryTLS12
   352  	tls11Downgrade := string(serverHello.random[24:]) == downgradeCanaryTLS11
   353  	if maxVers == VersionTLS13 && c.vers <= VersionTLS12 && (tls12Downgrade || tls11Downgrade) ||
   354  		maxVers == VersionTLS12 && c.vers <= VersionTLS11 && tls11Downgrade {
   355  		c.sendAlert(alertIllegalParameter)
   356  		return errors.New("tls: downgrade attempt detected, possibly due to a MitM attack or a broken middlebox")
   357  	}
   358  
   359  	if c.vers == VersionTLS13 {
   360  		hs := &clientHandshakeStateTLS13{
   361  			c:            c,
   362  			ctx:          ctx,
   363  			serverHello:  serverHello,
   364  			hello:        hello,
   365  			keyShareKeys: keyShareKeys,
   366  			session:      session,
   367  			earlySecret:  earlySecret,
   368  			binderKey:    binderKey,
   369  			echContext:   ech,
   370  		}
   371  		return hs.handshake()
   372  	}
   373  
   374  	hs := &clientHandshakeState{
   375  		c:           c,
   376  		ctx:         ctx,
   377  		serverHello: serverHello,
   378  		hello:       hello,
   379  		session:     session,
   380  	}
   381  	return hs.handshake()
   382  }
   383  
   384  func (c *Conn) loadSession(hello *clientHelloMsg) (
   385  	session *SessionState, earlySecret, binderKey []byte, err error) {
   386  	if c.config.SessionTicketsDisabled || c.config.ClientSessionCache == nil {
   387  		return nil, nil, nil, nil
   388  	}
   389  
   390  	echInner := bytes.Equal(hello.encryptedClientHello, []byte{1})
   391  
   392  	// ticketSupported is a TLS 1.2 extension (as TLS 1.3 replaced tickets with PSK
   393  	// identities) and ECH requires and forces TLS 1.3.
   394  	hello.ticketSupported = true && !echInner
   395  
   396  	if hello.supportedVersions[0] == VersionTLS13 {
   397  		// Require DHE on resumption as it guarantees forward secrecy against
   398  		// compromise of the session ticket key. See RFC 8446, Section 4.2.9.
   399  		hello.pskModes = []uint8{pskModeDHE}
   400  	}
   401  
   402  	// Session resumption is not allowed if renegotiating because
   403  	// renegotiation is primarily used to allow a client to send a client
   404  	// certificate, which would be skipped if session resumption occurred.
   405  	if c.handshakes != 0 {
   406  		return nil, nil, nil, nil
   407  	}
   408  
   409  	// Try to resume a previously negotiated TLS session, if available.
   410  	cacheKey := c.clientSessionCacheKey()
   411  	if cacheKey == "" {
   412  		return nil, nil, nil, nil
   413  	}
   414  	cs, ok := c.config.ClientSessionCache.Get(cacheKey)
   415  	if !ok || cs == nil {
   416  		return nil, nil, nil, nil
   417  	}
   418  	session = cs.session
   419  
   420  	// Check that version used for the previous session is still valid.
   421  	versOk := false
   422  	for _, v := range hello.supportedVersions {
   423  		if v == session.version {
   424  			versOk = true
   425  			break
   426  		}
   427  	}
   428  	if !versOk {
   429  		return nil, nil, nil, nil
   430  	}
   431  
   432  	// Check that the cached server certificate is not expired, and that it's
   433  	// valid for the ServerName. This should be ensured by the cache key, but
   434  	// protect the application from a faulty ClientSessionCache implementation.
   435  	if c.config.time().After(session.peerCertificates[0].NotAfter) {
   436  		// Expired certificate, delete the entry.
   437  		c.config.ClientSessionCache.Put(cacheKey, nil)
   438  		return nil, nil, nil, nil
   439  	}
   440  	if !c.config.InsecureSkipVerify {
   441  		if len(session.verifiedChains) == 0 {
   442  			// The original connection had InsecureSkipVerify, while this doesn't.
   443  			return nil, nil, nil, nil
   444  		}
   445  		if err := session.peerCertificates[0].VerifyHostname(c.config.ServerName); err != nil {
   446  			return nil, nil, nil, nil
   447  		}
   448  	}
   449  
   450  	if session.version != VersionTLS13 {
   451  		// In TLS 1.2 the cipher suite must match the resumed session. Ensure we
   452  		// are still offering it.
   453  		if mutualCipherSuite(hello.cipherSuites, session.cipherSuite) == nil {
   454  			return nil, nil, nil, nil
   455  		}
   456  
   457  		hello.sessionTicket = session.ticket
   458  		return
   459  	}
   460  
   461  	// Check that the session ticket is not expired.
   462  	if c.config.time().After(time.Unix(int64(session.useBy), 0)) {
   463  		c.config.ClientSessionCache.Put(cacheKey, nil)
   464  		return nil, nil, nil, nil
   465  	}
   466  
   467  	// In TLS 1.3 the KDF hash must match the resumed session. Ensure we
   468  	// offer at least one cipher suite with that hash.
   469  	cipherSuite := cipherSuiteTLS13ByID(session.cipherSuite)
   470  	if cipherSuite == nil {
   471  		return nil, nil, nil, nil
   472  	}
   473  	cipherSuiteOk := false
   474  	for _, offeredID := range hello.cipherSuites {
   475  		offeredSuite := cipherSuiteTLS13ByID(offeredID)
   476  		if offeredSuite != nil && offeredSuite.hash == cipherSuite.hash {
   477  			cipherSuiteOk = true
   478  			break
   479  		}
   480  	}
   481  	if !cipherSuiteOk {
   482  		return nil, nil, nil, nil
   483  	}
   484  
   485  	if c.quic != nil {
   486  		if c.quic.enableSessionEvents {
   487  			c.quicResumeSession(session)
   488  		}
   489  
   490  		// For 0-RTT, the cipher suite has to match exactly, and we need to be
   491  		// offering the same ALPN.
   492  		if session.EarlyData && mutualCipherSuiteTLS13(hello.cipherSuites, session.cipherSuite) != nil {
   493  			for _, alpn := range hello.alpnProtocols {
   494  				if alpn == session.alpnProtocol {
   495  					hello.earlyData = true
   496  					break
   497  				}
   498  			}
   499  		}
   500  	}
   501  
   502  	// Set the pre_shared_key extension. See RFC 8446, Section 4.2.11.1.
   503  	ticketAge := c.config.time().Sub(time.Unix(int64(session.createdAt), 0))
   504  	identity := pskIdentity{
   505  		label:               session.ticket,
   506  		obfuscatedTicketAge: uint32(ticketAge/time.Millisecond) + session.ageAdd,
   507  	}
   508  	hello.pskIdentities = []pskIdentity{identity}
   509  	hello.pskBinders = [][]byte{make([]byte, cipherSuite.hash.Size())}
   510  
   511  	// Compute the PSK binders. See RFC 8446, Section 4.2.11.2.
   512  	earlySecret = cipherSuite.extract(session.secret, nil)
   513  	binderKey = cipherSuite.deriveSecret(earlySecret, resumptionBinderLabel, nil)
   514  	transcript := cipherSuite.hash.New()
   515  	if err := computeAndUpdatePSK(hello, binderKey, transcript, cipherSuite.finishedHash); err != nil {
   516  		return nil, nil, nil, err
   517  	}
   518  
   519  	return
   520  }
   521  
   522  func (c *Conn) pickTLSVersion(serverHello *serverHelloMsg) error {
   523  	peerVersion := serverHello.vers
   524  	if serverHello.supportedVersion != 0 {
   525  		peerVersion = serverHello.supportedVersion
   526  	}
   527  
   528  	vers, ok := c.config.mutualVersion(roleClient, []uint16{peerVersion})
   529  	if !ok {
   530  		c.sendAlert(alertProtocolVersion)
   531  		return fmt.Errorf("tls: server selected unsupported protocol version %x", peerVersion)
   532  	}
   533  
   534  	c.vers = vers
   535  	c.haveVers = true
   536  	c.in.version = vers
   537  	c.out.version = vers
   538  
   539  	return nil
   540  }
   541  
   542  // Does the handshake, either a full one or resumes old session. Requires hs.c,
   543  // hs.hello, hs.serverHello, and, optionally, hs.session to be set.
   544  func (hs *clientHandshakeState) handshake() error {
   545  	c := hs.c
   546  
   547  	isResume, err := hs.processServerHello()
   548  	if err != nil {
   549  		return err
   550  	}
   551  
   552  	hs.finishedHash = newFinishedHash(c.vers, hs.suite)
   553  
   554  	// No signatures of the handshake are needed in a resumption.
   555  	// Otherwise, in a full handshake, if we don't have any certificates
   556  	// configured then we will never send a CertificateVerify message and
   557  	// thus no signatures are needed in that case either.
   558  	if isResume || (len(c.config.Certificates) == 0 && c.config.GetClientCertificate == nil) {
   559  		hs.finishedHash.discardHandshakeBuffer()
   560  	}
   561  
   562  	if err := transcriptMsg(hs.hello, &hs.finishedHash); err != nil {
   563  		return err
   564  	}
   565  	if err := transcriptMsg(hs.serverHello, &hs.finishedHash); err != nil {
   566  		return err
   567  	}
   568  
   569  	c.buffering = true
   570  	c.didResume = isResume
   571  	if isResume {
   572  		if err := hs.establishKeys(); err != nil {
   573  			return err
   574  		}
   575  		if err := hs.readSessionTicket(); err != nil {
   576  			return err
   577  		}
   578  		if err := hs.readFinished(c.serverFinished[:]); err != nil {
   579  			return err
   580  		}
   581  		c.clientFinishedIsFirst = false
   582  		// Make sure the connection is still being verified whether or not this
   583  		// is a resumption. Resumptions currently don't reverify certificates so
   584  		// they don't call verifyServerCertificate. See Issue 31641.
   585  		if c.config.VerifyConnection != nil {
   586  			if err := c.config.VerifyConnection(c.connectionStateLocked()); err != nil {
   587  				c.sendAlert(alertBadCertificate)
   588  				return err
   589  			}
   590  		}
   591  		if err := hs.sendFinished(c.clientFinished[:]); err != nil {
   592  			return err
   593  		}
   594  		if _, err := c.flush(); err != nil {
   595  			return err
   596  		}
   597  	} else {
   598  		if err := hs.doFullHandshake(); err != nil {
   599  			return err
   600  		}
   601  		if err := hs.establishKeys(); err != nil {
   602  			return err
   603  		}
   604  		if err := hs.sendFinished(c.clientFinished[:]); err != nil {
   605  			return err
   606  		}
   607  		if _, err := c.flush(); err != nil {
   608  			return err
   609  		}
   610  		c.clientFinishedIsFirst = true
   611  		if err := hs.readSessionTicket(); err != nil {
   612  			return err
   613  		}
   614  		if err := hs.readFinished(c.serverFinished[:]); err != nil {
   615  			return err
   616  		}
   617  	}
   618  	if err := hs.saveSessionTicket(); err != nil {
   619  		return err
   620  	}
   621  
   622  	c.ekm = ekmFromMasterSecret(c.vers, hs.suite, hs.masterSecret, hs.hello.random, hs.serverHello.random)
   623  	c.isHandshakeComplete.Store(true)
   624  
   625  	return nil
   626  }
   627  
   628  func (hs *clientHandshakeState) pickCipherSuite() error {
   629  	if hs.suite = mutualCipherSuite(hs.hello.cipherSuites, hs.serverHello.cipherSuite); hs.suite == nil {
   630  		hs.c.sendAlert(alertHandshakeFailure)
   631  		return errors.New("tls: server chose an unconfigured cipher suite")
   632  	}
   633  
   634  	if hs.c.config.CipherSuites == nil && !needFIPS() && rsaKexCiphers[hs.suite.id] {
   635  		tlsrsakex.Value() // ensure godebug is initialized
   636  		tlsrsakex.IncNonDefault()
   637  	}
   638  	if hs.c.config.CipherSuites == nil && !needFIPS() && tdesCiphers[hs.suite.id] {
   639  		tls3des.Value() // ensure godebug is initialized
   640  		tls3des.IncNonDefault()
   641  	}
   642  
   643  	hs.c.cipherSuite = hs.suite.id
   644  	return nil
   645  }
   646  
   647  func (hs *clientHandshakeState) doFullHandshake() error {
   648  	c := hs.c
   649  
   650  	msg, err := c.readHandshake(&hs.finishedHash)
   651  	if err != nil {
   652  		return err
   653  	}
   654  	certMsg, ok := msg.(*certificateMsg)
   655  	if !ok || len(certMsg.certificates) == 0 {
   656  		c.sendAlert(alertUnexpectedMessage)
   657  		return unexpectedMessageError(certMsg, msg)
   658  	}
   659  
   660  	msg, err = c.readHandshake(&hs.finishedHash)
   661  	if err != nil {
   662  		return err
   663  	}
   664  
   665  	cs, ok := msg.(*certificateStatusMsg)
   666  	if ok {
   667  		// RFC4366 on Certificate Status Request:
   668  		// The server MAY return a "certificate_status" message.
   669  
   670  		if !hs.serverHello.ocspStapling {
   671  			// If a server returns a "CertificateStatus" message, then the
   672  			// server MUST have included an extension of type "status_request"
   673  			// with empty "extension_data" in the extended server hello.
   674  
   675  			c.sendAlert(alertUnexpectedMessage)
   676  			return errors.New("tls: received unexpected CertificateStatus message")
   677  		}
   678  
   679  		c.ocspResponse = cs.response
   680  
   681  		msg, err = c.readHandshake(&hs.finishedHash)
   682  		if err != nil {
   683  			return err
   684  		}
   685  	}
   686  
   687  	if c.handshakes == 0 {
   688  		// If this is the first handshake on a connection, process and
   689  		// (optionally) verify the server's certificates.
   690  		if err := c.verifyServerCertificate(certMsg.certificates); err != nil {
   691  			return err
   692  		}
   693  	} else {
   694  		// This is a renegotiation handshake. We require that the
   695  		// server's identity (i.e. leaf certificate) is unchanged and
   696  		// thus any previous trust decision is still valid.
   697  		//
   698  		// See https://mitls.org/pages/attacks/3SHAKE for the
   699  		// motivation behind this requirement.
   700  		if !bytes.Equal(c.peerCertificates[0].Raw, certMsg.certificates[0]) {
   701  			c.sendAlert(alertBadCertificate)
   702  			return errors.New("tls: server's identity changed during renegotiation")
   703  		}
   704  	}
   705  
   706  	keyAgreement := hs.suite.ka(c.vers)
   707  
   708  	skx, ok := msg.(*serverKeyExchangeMsg)
   709  	if ok {
   710  		err = keyAgreement.processServerKeyExchange(c.config, hs.hello, hs.serverHello, c.peerCertificates[0], skx)
   711  		if err != nil {
   712  			c.sendAlert(alertUnexpectedMessage)
   713  			return err
   714  		}
   715  		if len(skx.key) >= 3 && skx.key[0] == 3 /* named curve */ {
   716  			c.curveID = CurveID(byteorder.BeUint16(skx.key[1:]))
   717  		}
   718  
   719  		msg, err = c.readHandshake(&hs.finishedHash)
   720  		if err != nil {
   721  			return err
   722  		}
   723  	}
   724  
   725  	var chainToSend *Certificate
   726  	var certRequested bool
   727  	certReq, ok := msg.(*certificateRequestMsg)
   728  	if ok {
   729  		certRequested = true
   730  
   731  		cri := certificateRequestInfoFromMsg(hs.ctx, c.vers, certReq)
   732  		if chainToSend, err = c.getClientCertificate(cri); err != nil {
   733  			c.sendAlert(alertInternalError)
   734  			return err
   735  		}
   736  
   737  		msg, err = c.readHandshake(&hs.finishedHash)
   738  		if err != nil {
   739  			return err
   740  		}
   741  	}
   742  
   743  	shd, ok := msg.(*serverHelloDoneMsg)
   744  	if !ok {
   745  		c.sendAlert(alertUnexpectedMessage)
   746  		return unexpectedMessageError(shd, msg)
   747  	}
   748  
   749  	// If the server requested a certificate then we have to send a
   750  	// Certificate message, even if it's empty because we don't have a
   751  	// certificate to send.
   752  	if certRequested {
   753  		certMsg = new(certificateMsg)
   754  		certMsg.certificates = chainToSend.Certificate
   755  		if _, err := hs.c.writeHandshakeRecord(certMsg, &hs.finishedHash); err != nil {
   756  			return err
   757  		}
   758  	}
   759  
   760  	preMasterSecret, ckx, err := keyAgreement.generateClientKeyExchange(c.config, hs.hello, c.peerCertificates[0])
   761  	if err != nil {
   762  		c.sendAlert(alertInternalError)
   763  		return err
   764  	}
   765  	if ckx != nil {
   766  		if _, err := hs.c.writeHandshakeRecord(ckx, &hs.finishedHash); err != nil {
   767  			return err
   768  		}
   769  	}
   770  
   771  	if hs.serverHello.extendedMasterSecret {
   772  		c.extMasterSecret = true
   773  		hs.masterSecret = extMasterFromPreMasterSecret(c.vers, hs.suite, preMasterSecret,
   774  			hs.finishedHash.Sum())
   775  	} else {
   776  		hs.masterSecret = masterFromPreMasterSecret(c.vers, hs.suite, preMasterSecret,
   777  			hs.hello.random, hs.serverHello.random)
   778  	}
   779  	if err := c.config.writeKeyLog(keyLogLabelTLS12, hs.hello.random, hs.masterSecret); err != nil {
   780  		c.sendAlert(alertInternalError)
   781  		return errors.New("tls: failed to write to key log: " + err.Error())
   782  	}
   783  
   784  	if chainToSend != nil && len(chainToSend.Certificate) > 0 {
   785  		certVerify := &certificateVerifyMsg{}
   786  
   787  		key, ok := chainToSend.PrivateKey.(crypto.Signer)
   788  		if !ok {
   789  			c.sendAlert(alertInternalError)
   790  			return fmt.Errorf("tls: client certificate private key of type %T does not implement crypto.Signer", chainToSend.PrivateKey)
   791  		}
   792  
   793  		var sigType uint8
   794  		var sigHash crypto.Hash
   795  		if c.vers >= VersionTLS12 {
   796  			signatureAlgorithm, err := selectSignatureScheme(c.vers, chainToSend, certReq.supportedSignatureAlgorithms)
   797  			if err != nil {
   798  				c.sendAlert(alertIllegalParameter)
   799  				return err
   800  			}
   801  			sigType, sigHash, err = typeAndHashFromSignatureScheme(signatureAlgorithm)
   802  			if err != nil {
   803  				return c.sendAlert(alertInternalError)
   804  			}
   805  			certVerify.hasSignatureAlgorithm = true
   806  			certVerify.signatureAlgorithm = signatureAlgorithm
   807  		} else {
   808  			sigType, sigHash, err = legacyTypeAndHashFromPublicKey(key.Public())
   809  			if err != nil {
   810  				c.sendAlert(alertIllegalParameter)
   811  				return err
   812  			}
   813  		}
   814  
   815  		signed := hs.finishedHash.hashForClientCertificate(sigType, sigHash)
   816  		signOpts := crypto.SignerOpts(sigHash)
   817  		if sigType == signatureRSAPSS {
   818  			signOpts = &rsa.PSSOptions{SaltLength: rsa.PSSSaltLengthEqualsHash, Hash: sigHash}
   819  		}
   820  		certVerify.signature, err = key.Sign(c.config.rand(), signed, signOpts)
   821  		if err != nil {
   822  			c.sendAlert(alertInternalError)
   823  			return err
   824  		}
   825  
   826  		if _, err := hs.c.writeHandshakeRecord(certVerify, &hs.finishedHash); err != nil {
   827  			return err
   828  		}
   829  	}
   830  
   831  	hs.finishedHash.discardHandshakeBuffer()
   832  
   833  	return nil
   834  }
   835  
   836  func (hs *clientHandshakeState) establishKeys() error {
   837  	c := hs.c
   838  
   839  	clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV :=
   840  		keysFromMasterSecret(c.vers, hs.suite, hs.masterSecret, hs.hello.random, hs.serverHello.random, hs.suite.macLen, hs.suite.keyLen, hs.suite.ivLen)
   841  	var clientCipher, serverCipher any
   842  	var clientHash, serverHash hash.Hash
   843  	if hs.suite.cipher != nil {
   844  		clientCipher = hs.suite.cipher(clientKey, clientIV, false /* not for reading */)
   845  		clientHash = hs.suite.mac(clientMAC)
   846  		serverCipher = hs.suite.cipher(serverKey, serverIV, true /* for reading */)
   847  		serverHash = hs.suite.mac(serverMAC)
   848  	} else {
   849  		clientCipher = hs.suite.aead(clientKey, clientIV)
   850  		serverCipher = hs.suite.aead(serverKey, serverIV)
   851  	}
   852  
   853  	c.in.prepareCipherSpec(c.vers, serverCipher, serverHash)
   854  	c.out.prepareCipherSpec(c.vers, clientCipher, clientHash)
   855  	return nil
   856  }
   857  
   858  func (hs *clientHandshakeState) serverResumedSession() bool {
   859  	// If the server responded with the same sessionId then it means the
   860  	// sessionTicket is being used to resume a TLS session.
   861  	return hs.session != nil && hs.hello.sessionId != nil &&
   862  		bytes.Equal(hs.serverHello.sessionId, hs.hello.sessionId)
   863  }
   864  
   865  func (hs *clientHandshakeState) processServerHello() (bool, error) {
   866  	c := hs.c
   867  
   868  	if err := hs.pickCipherSuite(); err != nil {
   869  		return false, err
   870  	}
   871  
   872  	if hs.serverHello.compressionMethod != compressionNone {
   873  		c.sendAlert(alertUnexpectedMessage)
   874  		return false, errors.New("tls: server selected unsupported compression format")
   875  	}
   876  
   877  	if c.handshakes == 0 && hs.serverHello.secureRenegotiationSupported {
   878  		c.secureRenegotiation = true
   879  		if len(hs.serverHello.secureRenegotiation) != 0 {
   880  			c.sendAlert(alertHandshakeFailure)
   881  			return false, errors.New("tls: initial handshake had non-empty renegotiation extension")
   882  		}
   883  	}
   884  
   885  	if c.handshakes > 0 && c.secureRenegotiation {
   886  		var expectedSecureRenegotiation [24]byte
   887  		copy(expectedSecureRenegotiation[:], c.clientFinished[:])
   888  		copy(expectedSecureRenegotiation[12:], c.serverFinished[:])
   889  		if !bytes.Equal(hs.serverHello.secureRenegotiation, expectedSecureRenegotiation[:]) {
   890  			c.sendAlert(alertHandshakeFailure)
   891  			return false, errors.New("tls: incorrect renegotiation extension contents")
   892  		}
   893  	}
   894  
   895  	if err := checkALPN(hs.hello.alpnProtocols, hs.serverHello.alpnProtocol, false); err != nil {
   896  		c.sendAlert(alertUnsupportedExtension)
   897  		return false, err
   898  	}
   899  	c.clientProtocol = hs.serverHello.alpnProtocol
   900  
   901  	c.scts = hs.serverHello.scts
   902  
   903  	if !hs.serverResumedSession() {
   904  		return false, nil
   905  	}
   906  
   907  	if hs.session.version != c.vers {
   908  		c.sendAlert(alertHandshakeFailure)
   909  		return false, errors.New("tls: server resumed a session with a different version")
   910  	}
   911  
   912  	if hs.session.cipherSuite != hs.suite.id {
   913  		c.sendAlert(alertHandshakeFailure)
   914  		return false, errors.New("tls: server resumed a session with a different cipher suite")
   915  	}
   916  
   917  	// RFC 7627, Section 5.3
   918  	if hs.session.extMasterSecret != hs.serverHello.extendedMasterSecret {
   919  		c.sendAlert(alertHandshakeFailure)
   920  		return false, errors.New("tls: server resumed a session with a different EMS extension")
   921  	}
   922  
   923  	// Restore master secret and certificates from previous state
   924  	hs.masterSecret = hs.session.secret
   925  	c.extMasterSecret = hs.session.extMasterSecret
   926  	c.peerCertificates = hs.session.peerCertificates
   927  	c.activeCertHandles = hs.c.activeCertHandles
   928  	c.verifiedChains = hs.session.verifiedChains
   929  	c.ocspResponse = hs.session.ocspResponse
   930  	// Let the ServerHello SCTs override the session SCTs from the original
   931  	// connection, if any are provided
   932  	if len(c.scts) == 0 && len(hs.session.scts) != 0 {
   933  		c.scts = hs.session.scts
   934  	}
   935  
   936  	return true, nil
   937  }
   938  
   939  // checkALPN ensure that the server's choice of ALPN protocol is compatible with
   940  // the protocols that we advertised in the Client Hello.
   941  func checkALPN(clientProtos []string, serverProto string, quic bool) error {
   942  	if serverProto == "" {
   943  		if quic && len(clientProtos) > 0 {
   944  			// RFC 9001, Section 8.1
   945  			return errors.New("tls: server did not select an ALPN protocol")
   946  		}
   947  		return nil
   948  	}
   949  	if len(clientProtos) == 0 {
   950  		return errors.New("tls: server advertised unrequested ALPN extension")
   951  	}
   952  	for _, proto := range clientProtos {
   953  		if proto == serverProto {
   954  			return nil
   955  		}
   956  	}
   957  	return errors.New("tls: server selected unadvertised ALPN protocol")
   958  }
   959  
   960  func (hs *clientHandshakeState) readFinished(out []byte) error {
   961  	c := hs.c
   962  
   963  	if err := c.readChangeCipherSpec(); err != nil {
   964  		return err
   965  	}
   966  
   967  	// finishedMsg is included in the transcript, but not until after we
   968  	// check the client version, since the state before this message was
   969  	// sent is used during verification.
   970  	msg, err := c.readHandshake(nil)
   971  	if err != nil {
   972  		return err
   973  	}
   974  	serverFinished, ok := msg.(*finishedMsg)
   975  	if !ok {
   976  		c.sendAlert(alertUnexpectedMessage)
   977  		return unexpectedMessageError(serverFinished, msg)
   978  	}
   979  
   980  	verify := hs.finishedHash.serverSum(hs.masterSecret)
   981  	if len(verify) != len(serverFinished.verifyData) ||
   982  		subtle.ConstantTimeCompare(verify, serverFinished.verifyData) != 1 {
   983  		c.sendAlert(alertHandshakeFailure)
   984  		return errors.New("tls: server's Finished message was incorrect")
   985  	}
   986  
   987  	if err := transcriptMsg(serverFinished, &hs.finishedHash); err != nil {
   988  		return err
   989  	}
   990  
   991  	copy(out, verify)
   992  	return nil
   993  }
   994  
   995  func (hs *clientHandshakeState) readSessionTicket() error {
   996  	if !hs.serverHello.ticketSupported {
   997  		return nil
   998  	}
   999  	c := hs.c
  1000  
  1001  	if !hs.hello.ticketSupported {
  1002  		c.sendAlert(alertIllegalParameter)
  1003  		return errors.New("tls: server sent unrequested session ticket")
  1004  	}
  1005  
  1006  	msg, err := c.readHandshake(&hs.finishedHash)
  1007  	if err != nil {
  1008  		return err
  1009  	}
  1010  	sessionTicketMsg, ok := msg.(*newSessionTicketMsg)
  1011  	if !ok {
  1012  		c.sendAlert(alertUnexpectedMessage)
  1013  		return unexpectedMessageError(sessionTicketMsg, msg)
  1014  	}
  1015  
  1016  	hs.ticket = sessionTicketMsg.ticket
  1017  	return nil
  1018  }
  1019  
  1020  func (hs *clientHandshakeState) saveSessionTicket() error {
  1021  	if hs.ticket == nil {
  1022  		return nil
  1023  	}
  1024  	c := hs.c
  1025  
  1026  	cacheKey := c.clientSessionCacheKey()
  1027  	if cacheKey == "" {
  1028  		return nil
  1029  	}
  1030  
  1031  	session := c.sessionState()
  1032  	session.secret = hs.masterSecret
  1033  	session.ticket = hs.ticket
  1034  
  1035  	cs := &ClientSessionState{session: session}
  1036  	c.config.ClientSessionCache.Put(cacheKey, cs)
  1037  	return nil
  1038  }
  1039  
  1040  func (hs *clientHandshakeState) sendFinished(out []byte) error {
  1041  	c := hs.c
  1042  
  1043  	if err := c.writeChangeCipherRecord(); err != nil {
  1044  		return err
  1045  	}
  1046  
  1047  	finished := new(finishedMsg)
  1048  	finished.verifyData = hs.finishedHash.clientSum(hs.masterSecret)
  1049  	if _, err := hs.c.writeHandshakeRecord(finished, &hs.finishedHash); err != nil {
  1050  		return err
  1051  	}
  1052  	copy(out, finished.verifyData)
  1053  	return nil
  1054  }
  1055  
  1056  // defaultMaxRSAKeySize is the maximum RSA key size in bits that we are willing
  1057  // to verify the signatures of during a TLS handshake.
  1058  const defaultMaxRSAKeySize = 8192
  1059  
  1060  var tlsmaxrsasize = godebug.New("tlsmaxrsasize")
  1061  
  1062  func checkKeySize(n int) (max int, ok bool) {
  1063  	if v := tlsmaxrsasize.Value(); v != "" {
  1064  		if max, err := strconv.Atoi(v); err == nil {
  1065  			if (n <= max) != (n <= defaultMaxRSAKeySize) {
  1066  				tlsmaxrsasize.IncNonDefault()
  1067  			}
  1068  			return max, n <= max
  1069  		}
  1070  	}
  1071  	return defaultMaxRSAKeySize, n <= defaultMaxRSAKeySize
  1072  }
  1073  
  1074  // verifyServerCertificate parses and verifies the provided chain, setting
  1075  // c.verifiedChains and c.peerCertificates or sending the appropriate alert.
  1076  func (c *Conn) verifyServerCertificate(certificates [][]byte) error {
  1077  	activeHandles := make([]*activeCert, len(certificates))
  1078  	certs := make([]*x509.Certificate, len(certificates))
  1079  	for i, asn1Data := range certificates {
  1080  		cert, err := globalCertCache.newCert(asn1Data)
  1081  		if err != nil {
  1082  			c.sendAlert(alertBadCertificate)
  1083  			return errors.New("tls: failed to parse certificate from server: " + err.Error())
  1084  		}
  1085  		if cert.cert.PublicKeyAlgorithm == x509.RSA {
  1086  			n := cert.cert.PublicKey.(*rsa.PublicKey).N.BitLen()
  1087  			if max, ok := checkKeySize(n); !ok {
  1088  				c.sendAlert(alertBadCertificate)
  1089  				return fmt.Errorf("tls: server sent certificate containing RSA key larger than %d bits", max)
  1090  			}
  1091  		}
  1092  		activeHandles[i] = cert
  1093  		certs[i] = cert.cert
  1094  	}
  1095  
  1096  	echRejected := c.config.EncryptedClientHelloConfigList != nil && !c.echAccepted
  1097  	if echRejected {
  1098  		if c.config.EncryptedClientHelloRejectionVerify != nil {
  1099  			if err := c.config.EncryptedClientHelloRejectionVerify(c.connectionStateLocked()); err != nil {
  1100  				c.sendAlert(alertBadCertificate)
  1101  				return err
  1102  			}
  1103  		} else {
  1104  			opts := x509.VerifyOptions{
  1105  				Roots:         c.config.RootCAs,
  1106  				CurrentTime:   c.config.time(),
  1107  				DNSName:       c.serverName,
  1108  				Intermediates: x509.NewCertPool(),
  1109  			}
  1110  
  1111  			for _, cert := range certs[1:] {
  1112  				opts.Intermediates.AddCert(cert)
  1113  			}
  1114  			var err error
  1115  			c.verifiedChains, err = certs[0].Verify(opts)
  1116  			if err != nil {
  1117  				c.sendAlert(alertBadCertificate)
  1118  				return &CertificateVerificationError{UnverifiedCertificates: certs, Err: err}
  1119  			}
  1120  		}
  1121  	} else if !c.config.InsecureSkipVerify {
  1122  		opts := x509.VerifyOptions{
  1123  			Roots:         c.config.RootCAs,
  1124  			CurrentTime:   c.config.time(),
  1125  			DNSName:       c.config.ServerName,
  1126  			Intermediates: x509.NewCertPool(),
  1127  		}
  1128  
  1129  		for _, cert := range certs[1:] {
  1130  			opts.Intermediates.AddCert(cert)
  1131  		}
  1132  		var err error
  1133  		c.verifiedChains, err = certs[0].Verify(opts)
  1134  		if err != nil {
  1135  			c.sendAlert(alertBadCertificate)
  1136  			return &CertificateVerificationError{UnverifiedCertificates: certs, Err: err}
  1137  		}
  1138  	}
  1139  
  1140  	switch certs[0].PublicKey.(type) {
  1141  	case *rsa.PublicKey, *ecdsa.PublicKey, ed25519.PublicKey:
  1142  		break
  1143  	default:
  1144  		c.sendAlert(alertUnsupportedCertificate)
  1145  		return fmt.Errorf("tls: server's certificate contains an unsupported type of public key: %T", certs[0].PublicKey)
  1146  	}
  1147  
  1148  	c.activeCertHandles = activeHandles
  1149  	c.peerCertificates = certs
  1150  
  1151  	if c.config.VerifyPeerCertificate != nil && !echRejected {
  1152  		if err := c.config.VerifyPeerCertificate(certificates, c.verifiedChains); err != nil {
  1153  			c.sendAlert(alertBadCertificate)
  1154  			return err
  1155  		}
  1156  	}
  1157  
  1158  	if c.config.VerifyConnection != nil && !echRejected {
  1159  		if err := c.config.VerifyConnection(c.connectionStateLocked()); err != nil {
  1160  			c.sendAlert(alertBadCertificate)
  1161  			return err
  1162  		}
  1163  	}
  1164  
  1165  	return nil
  1166  }
  1167  
  1168  // certificateRequestInfoFromMsg generates a CertificateRequestInfo from a TLS
  1169  // <= 1.2 CertificateRequest, making an effort to fill in missing information.
  1170  func certificateRequestInfoFromMsg(ctx context.Context, vers uint16, certReq *certificateRequestMsg) *CertificateRequestInfo {
  1171  	cri := &CertificateRequestInfo{
  1172  		AcceptableCAs: certReq.certificateAuthorities,
  1173  		Version:       vers,
  1174  		ctx:           ctx,
  1175  	}
  1176  
  1177  	var rsaAvail, ecAvail bool
  1178  	for _, certType := range certReq.certificateTypes {
  1179  		switch certType {
  1180  		case certTypeRSASign:
  1181  			rsaAvail = true
  1182  		case certTypeECDSASign:
  1183  			ecAvail = true
  1184  		}
  1185  	}
  1186  
  1187  	if !certReq.hasSignatureAlgorithm {
  1188  		// Prior to TLS 1.2, signature schemes did not exist. In this case we
  1189  		// make up a list based on the acceptable certificate types, to help
  1190  		// GetClientCertificate and SupportsCertificate select the right certificate.
  1191  		// The hash part of the SignatureScheme is a lie here, because
  1192  		// TLS 1.0 and 1.1 always use MD5+SHA1 for RSA and SHA1 for ECDSA.
  1193  		switch {
  1194  		case rsaAvail && ecAvail:
  1195  			cri.SignatureSchemes = []SignatureScheme{
  1196  				ECDSAWithP256AndSHA256, ECDSAWithP384AndSHA384, ECDSAWithP521AndSHA512,
  1197  				PKCS1WithSHA256, PKCS1WithSHA384, PKCS1WithSHA512, PKCS1WithSHA1,
  1198  			}
  1199  		case rsaAvail:
  1200  			cri.SignatureSchemes = []SignatureScheme{
  1201  				PKCS1WithSHA256, PKCS1WithSHA384, PKCS1WithSHA512, PKCS1WithSHA1,
  1202  			}
  1203  		case ecAvail:
  1204  			cri.SignatureSchemes = []SignatureScheme{
  1205  				ECDSAWithP256AndSHA256, ECDSAWithP384AndSHA384, ECDSAWithP521AndSHA512,
  1206  			}
  1207  		}
  1208  		return cri
  1209  	}
  1210  
  1211  	// Filter the signature schemes based on the certificate types.
  1212  	// See RFC 5246, Section 7.4.4 (where it calls this "somewhat complicated").
  1213  	cri.SignatureSchemes = make([]SignatureScheme, 0, len(certReq.supportedSignatureAlgorithms))
  1214  	for _, sigScheme := range certReq.supportedSignatureAlgorithms {
  1215  		sigType, _, err := typeAndHashFromSignatureScheme(sigScheme)
  1216  		if err != nil {
  1217  			continue
  1218  		}
  1219  		switch sigType {
  1220  		case signatureECDSA, signatureEd25519:
  1221  			if ecAvail {
  1222  				cri.SignatureSchemes = append(cri.SignatureSchemes, sigScheme)
  1223  			}
  1224  		case signatureRSAPSS, signaturePKCS1v15:
  1225  			if rsaAvail {
  1226  				cri.SignatureSchemes = append(cri.SignatureSchemes, sigScheme)
  1227  			}
  1228  		}
  1229  	}
  1230  
  1231  	return cri
  1232  }
  1233  
  1234  func (c *Conn) getClientCertificate(cri *CertificateRequestInfo) (*Certificate, error) {
  1235  	if c.config.GetClientCertificate != nil {
  1236  		return c.config.GetClientCertificate(cri)
  1237  	}
  1238  
  1239  	for _, chain := range c.config.Certificates {
  1240  		if err := cri.SupportsCertificate(&chain); err != nil {
  1241  			continue
  1242  		}
  1243  		return &chain, nil
  1244  	}
  1245  
  1246  	// No acceptable certificate found. Don't send a certificate.
  1247  	return new(Certificate), nil
  1248  }
  1249  
  1250  // clientSessionCacheKey returns a key used to cache sessionTickets that could
  1251  // be used to resume previously negotiated TLS sessions with a server.
  1252  func (c *Conn) clientSessionCacheKey() string {
  1253  	if len(c.config.ServerName) > 0 {
  1254  		return c.config.ServerName
  1255  	}
  1256  	if c.conn != nil {
  1257  		return c.conn.RemoteAddr().String()
  1258  	}
  1259  	return ""
  1260  }
  1261  
  1262  // hostnameInSNI converts name into an appropriate hostname for SNI.
  1263  // Literal IP addresses and absolute FQDNs are not permitted as SNI values.
  1264  // See RFC 6066, Section 3.
  1265  func hostnameInSNI(name string) string {
  1266  	host := name
  1267  	if len(host) > 0 && host[0] == '[' && host[len(host)-1] == ']' {
  1268  		host = host[1 : len(host)-1]
  1269  	}
  1270  	if i := strings.LastIndex(host, "%"); i > 0 {
  1271  		host = host[:i]
  1272  	}
  1273  	if net.ParseIP(host) != nil {
  1274  		return ""
  1275  	}
  1276  	for len(name) > 0 && name[len(name)-1] == '.' {
  1277  		name = name[:len(name)-1]
  1278  	}
  1279  	return name
  1280  }
  1281  
  1282  func computeAndUpdatePSK(m *clientHelloMsg, binderKey []byte, transcript hash.Hash, finishedHash func([]byte, hash.Hash) []byte) error {
  1283  	helloBytes, err := m.marshalWithoutBinders()
  1284  	if err != nil {
  1285  		return err
  1286  	}
  1287  	transcript.Write(helloBytes)
  1288  	pskBinders := [][]byte{finishedHash(binderKey, transcript)}
  1289  	return m.updateBinders(pskBinders)
  1290  }
  1291  

View as plain text