src/crypto/tls/handshake_server.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         "context"
   9         "crypto"
  10         "crypto/ecdsa"
  11         "crypto/ed25519"
  12         "crypto/rsa"
  13         "crypto/subtle"
  14         "crypto/x509"
  15         "errors"
  16         "fmt"
  17         "hash"
  18         "io"
  19         "sync/atomic"
  20         "time"
  21 )
  22
  23 // serverHandshakeState contains details of a server handshake in progress.
  24 // It's discarded once the handshake has completed.
  25 type serverHandshakeState struct {
  26         c            *Conn
  27         ctx          context.Context
  28         clientHello  *clientHelloMsg
  29         hello        *serverHelloMsg
  30         suite        *cipherSuite
  31         ecdheOk      bool
  32         ecSignOk     bool
  33         rsaDecryptOk bool
  34         rsaSignOk    bool
  35         sessionState *sessionState
  36         finishedHash finishedHash
  37         masterSecret []byte
  38         cert         *Certificate
  39 }
  40
  41 // serverHandshake performs a TLS handshake as a server.
  42 func (c *Conn) serverHandshake(ctx context.Context) error {
  43         clientHello, err := c.readClientHello(ctx)
  44         if err != nil {
  45                 return err
  46         }
  47
  48         if c.vers == VersionTLS13 {
  49                 hs := serverHandshakeStateTLS13{
  50                         c:           c,
  51                         ctx:         ctx,
  52                         clientHello: clientHello,
  53                 }
  54                 return hs.handshake()
  55         }
  56
  57         hs := serverHandshakeState{
  58                 c:           c,
  59                 ctx:         ctx,
  60                 clientHello: clientHello,
  61         }
  62         return hs.handshake()
  63 }
  64
  65 func (hs *serverHandshakeState) handshake() error {
  66         c := hs.c
  67
  68         if err := hs.processClientHello(); err != nil {
  69                 return err
  70         }
  71
  72         // For an overview of TLS handshaking, see RFC 5246, Section 7.3.
  73         c.buffering = true
  74         if hs.checkForResumption() {
  75                 // The client has included a session ticket and so we do an abbreviated handshake.
  76                 c.didResume = true
  77                 if err := hs.doResumeHandshake(); err != nil {
  78                         return err
  79                 }
  80                 if err := hs.establishKeys(); err != nil {
  81                         return err
  82                 }
  83                 if err := hs.sendSessionTicket(); err != nil {
  84                         return err
  85                 }
  86                 if err := hs.sendFinished(c.serverFinished[:]); err != nil {
  87                         return err
  88                 }
  89                 if _, err := c.flush(); err != nil {
  90                         return err
  91                 }
  92                 c.clientFinishedIsFirst = false
  93                 if err := hs.readFinished(nil); err != nil {
  94                         return err
  95                 }
  96         } else {
  97                 // The client didn't include a session ticket, or it wasn't
  98                 // valid so we do a full handshake.
  99                 if err := hs.pickCipherSuite(); err != nil {
 100                         return err
 101                 }
 102                 if err := hs.doFullHandshake(); err != nil {
 103                         return err
 104                 }
 105                 if err := hs.establishKeys(); err != nil {
 106                         return err
 107                 }
 108                 if err := hs.readFinished(c.clientFinished[:]); err != nil {
 109                         return err
 110                 }
 111                 c.clientFinishedIsFirst = true
 112                 c.buffering = true
 113                 if err := hs.sendSessionTicket(); err != nil {
 114                         return err
 115                 }
 116                 if err := hs.sendFinished(nil); err != nil {
 117                         return err
 118                 }
 119                 if _, err := c.flush(); err != nil {
 120                         return err
 121                 }
 122         }
 123
 124         c.ekm = ekmFromMasterSecret(c.vers, hs.suite, hs.masterSecret, hs.clientHello.random, hs.hello.random)
 125         atomic.StoreUint32(&c.handshakeStatus, 1)
 126
 127         return nil
 128 }
 129
 130 // readClientHello reads a ClientHello message and selects the protocol version.
 131 func (c *Conn) readClientHello(ctx context.Context) (*clientHelloMsg, error) {
 132         msg, err := c.readHandshake()
 133         if err != nil {
 134                 return nil, err
 135         }
 136         clientHello, ok := msg.(*clientHelloMsg)
 137         if !ok {
 138                 c.sendAlert(alertUnexpectedMessage)
 139                 return nil, unexpectedMessageError(clientHello, msg)
 140         }
 141
 142         var configForClient *Config
 143         originalConfig := c.config
 144         if c.config.GetConfigForClient != nil {
 145                 chi := clientHelloInfo(ctx, c, clientHello)
 146                 if configForClient, err = c.config.GetConfigForClient(chi); err != nil {
 147                         c.sendAlert(alertInternalError)
 148                         return nil, err
 149                 } else if configForClient != nil {
 150                         c.config = configForClient
 151                 }
 152         }
 153         c.ticketKeys = originalConfig.ticketKeys(configForClient)
 154
 155         clientVersions := clientHello.supportedVersions
 156         if len(clientHello.supportedVersions) == 0 {
 157                 clientVersions = supportedVersionsFromMax(clientHello.vers)
 158         }
 159         c.vers, ok = c.config.mutualVersion(clientVersions)
 160         if !ok {
 161                 c.sendAlert(alertProtocolVersion)
 162                 return nil, fmt.Errorf("tls: client offered only unsupported versions: %x", clientVersions)
 163         }
 164         c.haveVers = true
 165         c.in.version = c.vers
 166         c.out.version = c.vers
 167
 168         return clientHello, nil
 169 }
 170
 171 func (hs *serverHandshakeState) processClientHello() error {
 172         c := hs.c
 173
 174         hs.hello = new(serverHelloMsg)
 175         hs.hello.vers = c.vers
 176
 177         foundCompression := false
 178         // We only support null compression, so check that the client offered it.
 179         for _, compression := range hs.clientHello.compressionMethods {
 180                 if compression == compressionNone {
 181                         foundCompression = true
 182                         break
 183                 }
 184         }
 185
 186         if !foundCompression {
 187                 c.sendAlert(alertHandshakeFailure)
 188                 return errors.New("tls: client does not support uncompressed connections")
 189         }
 190
 191         hs.hello.random = make([]byte, 32)
 192         serverRandom := hs.hello.random
 193         // Downgrade protection canaries. See RFC 8446, Section 4.1.3.
 194         maxVers := c.config.maxSupportedVersion()
 195         if maxVers >= VersionTLS12 && c.vers < maxVers || testingOnlyForceDowngradeCanary {
 196                 if c.vers == VersionTLS12 {
 197                         copy(serverRandom[24:], downgradeCanaryTLS12)
 198                 } else {
 199                         copy(serverRandom[24:], downgradeCanaryTLS11)
 200                 }
 201                 serverRandom = serverRandom[:24]
 202         }
 203         _, err := io.ReadFull(c.config.rand(), serverRandom)
 204         if err != nil {
 205                 c.sendAlert(alertInternalError)
 206                 return err
 207         }
 208
 209         if len(hs.clientHello.secureRenegotiation) != 0 {
 210                 c.sendAlert(alertHandshakeFailure)
 211                 return errors.New("tls: initial handshake had non-empty renegotiation extension")
 212         }
 213
 214         hs.hello.secureRenegotiationSupported = hs.clientHello.secureRenegotiationSupported
 215         hs.hello.compressionMethod = compressionNone
 216         if len(hs.clientHello.serverName) > 0 {
 217                 c.serverName = hs.clientHello.serverName
 218         }
 219
 220         if len(c.config.NextProtos) > 0 && len(hs.clientHello.alpnProtocols) > 0 {
 221                 selectedProto := mutualProtocol(hs.clientHello.alpnProtocols, c.config.NextProtos)
 222                 if selectedProto == "" {
 223                         c.sendAlert(alertNoApplicationProtocol)
 224                         return fmt.Errorf("tls: client requested unsupported application protocols (%s)", hs.clientHello.alpnProtocols)
 225                 }
 226                 hs.hello.alpnProtocol = selectedProto
 227                 c.clientProtocol = selectedProto
 228         }
 229
 230         hs.cert, err = c.config.getCertificate(clientHelloInfo(hs.ctx, c, hs.clientHello))
 231         if err != nil {
 232                 if err == errNoCertificates {
 233                         c.sendAlert(alertUnrecognizedName)
 234                 } else {
 235                         c.sendAlert(alertInternalError)
 236                 }
 237                 return err
 238         }
 239         if hs.clientHello.scts {
 240                 hs.hello.scts = hs.cert.SignedCertificateTimestamps
 241         }
 242
 243         hs.ecdheOk = supportsECDHE(c.config, hs.clientHello.supportedCurves, hs.clientHello.supportedPoints)
 244
 245         if hs.ecdheOk {
 246                 // Although omitting the ec_point_formats extension is permitted, some
 247                 // old OpenSSL version will refuse to handshake if not present.
 248                 //
 249                 // Per RFC 4492, section 5.1.2, implementations MUST support the
 250                 // uncompressed point format. See golang.org/issue/31943.
 251                 hs.hello.supportedPoints = []uint8{pointFormatUncompressed}
 252         }
 253
 254         if priv, ok := hs.cert.PrivateKey.(crypto.Signer); ok {
 255                 switch priv.Public().(type) {
 256                 case *ecdsa.PublicKey:
 257                         hs.ecSignOk = true
 258                 case ed25519.PublicKey:
 259                         hs.ecSignOk = true
 260                 case *rsa.PublicKey:
 261                         hs.rsaSignOk = true
 262                 default:
 263                         c.sendAlert(alertInternalError)
 264                         return fmt.Errorf("tls: unsupported signing key type (%T)", priv.Public())
 265                 }
 266         }
 267         if priv, ok := hs.cert.PrivateKey.(crypto.Decrypter); ok {
 268                 switch priv.Public().(type) {
 269                 case *rsa.PublicKey:
 270                         hs.rsaDecryptOk = true
 271                 default:
 272                         c.sendAlert(alertInternalError)
 273                         return fmt.Errorf("tls: unsupported decryption key type (%T)", priv.Public())
 274                 }
 275         }
 276
 277         return nil
 278 }
 279
 280 // supportsECDHE returns whether ECDHE key exchanges can be used with this
 281 // pre-TLS 1.3 client.
 282 func supportsECDHE(c *Config, supportedCurves []CurveID, supportedPoints []uint8) bool {
 283         supportsCurve := false
 284         for _, curve := range supportedCurves {
 285                 if c.supportsCurve(curve) {
 286                         supportsCurve = true
 287                         break
 288                 }
 289         }
 290
 291         supportsPointFormat := false
 292         for _, pointFormat := range supportedPoints {
 293                 if pointFormat == pointFormatUncompressed {
 294                         supportsPointFormat = true
 295                         break
 296                 }
 297         }
 298
 299         return supportsCurve && supportsPointFormat
 300 }
 301
 302 func (hs *serverHandshakeState) pickCipherSuite() error {
 303         c := hs.c
 304
 305         preferenceOrder := cipherSuitesPreferenceOrder
 306         if !hasAESGCMHardwareSupport || !aesgcmPreferred(hs.clientHello.cipherSuites) {
 307                 preferenceOrder = cipherSuitesPreferenceOrderNoAES
 308         }
 309
 310         configCipherSuites := c.config.cipherSuites()
 311         preferenceList := make([]uint16, 0, len(configCipherSuites))
 312         for _, suiteID := range preferenceOrder {
 313                 for _, id := range configCipherSuites {
 314                         if id == suiteID {
 315                                 preferenceList = append(preferenceList, id)
 316                                 break
 317                         }
 318                 }
 319         }
 320
 321         hs.suite = selectCipherSuite(preferenceList, hs.clientHello.cipherSuites, hs.cipherSuiteOk)
 322         if hs.suite == nil {
 323                 c.sendAlert(alertHandshakeFailure)
 324                 return errors.New("tls: no cipher suite supported by both client and server")
 325         }
 326         c.cipherSuite = hs.suite.id
 327
 328         for _, id := range hs.clientHello.cipherSuites {
 329                 if id == TLS_FALLBACK_SCSV {
 330                         // The client is doing a fallback connection. See RFC 7507.
 331                         if hs.clientHello.vers < c.config.maxSupportedVersion() {
 332                                 c.sendAlert(alertInappropriateFallback)
 333                                 return errors.New("tls: client using inappropriate protocol fallback")
 334                         }
 335                         break
 336                 }
 337         }
 338
 339         return nil
 340 }
 341
 342 func (hs *serverHandshakeState) cipherSuiteOk(c *cipherSuite) bool {
 343         if c.flags&suiteECDHE != 0 {
 344                 if !hs.ecdheOk {
 345                         return false
 346                 }
 347                 if c.flags&suiteECSign != 0 {
 348                         if !hs.ecSignOk {
 349                                 return false
 350                         }
 351                 } else if !hs.rsaSignOk {
 352                         return false
 353                 }
 354         } else if !hs.rsaDecryptOk {
 355                 return false
 356         }
 357         if hs.c.vers < VersionTLS12 && c.flags&suiteTLS12 != 0 {
 358                 return false
 359         }
 360         return true
 361 }
 362
 363 // checkForResumption reports whether we should perform resumption on this connection.
 364 func (hs *serverHandshakeState) checkForResumption() bool {
 365         c := hs.c
 366
 367         if c.config.SessionTicketsDisabled {
 368                 return false
 369         }
 370
 371         plaintext, usedOldKey := c.decryptTicket(hs.clientHello.sessionTicket)
 372         if plaintext == nil {
 373                 return false
 374         }
 375         hs.sessionState = &sessionState{usedOldKey: usedOldKey}
 376         ok := hs.sessionState.unmarshal(plaintext)
 377         if !ok {
 378                 return false
 379         }
 380
 381         createdAt := time.Unix(int64(hs.sessionState.createdAt), 0)
 382         if c.config.time().Sub(createdAt) > maxSessionTicketLifetime {
 383                 return false
 384         }
 385
 386         // Never resume a session for a different TLS version.
 387         if c.vers != hs.sessionState.vers {
 388                 return false
 389         }
 390
 391         cipherSuiteOk := false
 392         // Check that the client is still offering the ciphersuite in the session.
 393         for _, id := range hs.clientHello.cipherSuites {
 394                 if id == hs.sessionState.cipherSuite {
 395                         cipherSuiteOk = true
 396                         break
 397                 }
 398         }
 399         if !cipherSuiteOk {
 400                 return false
 401         }
 402
 403         // Check that we also support the ciphersuite from the session.
 404         hs.suite = selectCipherSuite([]uint16{hs.sessionState.cipherSuite},
 405                 c.config.cipherSuites(), hs.cipherSuiteOk)
 406         if hs.suite == nil {
 407                 return false
 408         }
 409
 410         sessionHasClientCerts := len(hs.sessionState.certificates) != 0
 411         needClientCerts := requiresClientCert(c.config.ClientAuth)
 412         if needClientCerts && !sessionHasClientCerts {
 413                 return false
 414         }
 415         if sessionHasClientCerts && c.config.ClientAuth == NoClientCert {
 416                 return false
 417         }
 418
 419         return true
 420 }
 421
 422 func (hs *serverHandshakeState) doResumeHandshake() error {
 423         c := hs.c
 424
 425         hs.hello.cipherSuite = hs.suite.id
 426         c.cipherSuite = hs.suite.id
 427         // We echo the client's session ID in the ServerHello to let it know
 428         // that we're doing a resumption.
 429         hs.hello.sessionId = hs.clientHello.sessionId
 430         hs.hello.ticketSupported = hs.sessionState.usedOldKey
 431         hs.finishedHash = newFinishedHash(c.vers, hs.suite)
 432         hs.finishedHash.discardHandshakeBuffer()
 433         hs.finishedHash.Write(hs.clientHello.marshal())
 434         hs.finishedHash.Write(hs.hello.marshal())
 435         if _, err := c.writeRecord(recordTypeHandshake, hs.hello.marshal()); err != nil {
 436                 return err
 437         }
 438
 439         if err := c.processCertsFromClient(Certificate{
 440                 Certificate: hs.sessionState.certificates,
 441         }); err != nil {
 442                 return err
 443         }
 444
 445         if c.config.VerifyConnection != nil {
 446                 if err := c.config.VerifyConnection(c.connectionStateLocked()); err != nil {
 447                         c.sendAlert(alertBadCertificate)
 448                         return err
 449                 }
 450         }
 451
 452         hs.masterSecret = hs.sessionState.masterSecret
 453
 454         return nil
 455 }
 456
 457 func (hs *serverHandshakeState) doFullHandshake() error {
 458         c := hs.c
 459
 460         if hs.clientHello.ocspStapling && len(hs.cert.OCSPStaple) > 0 {
 461                 hs.hello.ocspStapling = true
 462         }
 463
 464         hs.hello.ticketSupported = hs.clientHello.ticketSupported && !c.config.SessionTicketsDisabled
 465         hs.hello.cipherSuite = hs.suite.id
 466
 467         hs.finishedHash = newFinishedHash(hs.c.vers, hs.suite)
 468         if c.config.ClientAuth == NoClientCert {
 469                 // No need to keep a full record of the handshake if client
 470                 // certificates won't be used.
 471                 hs.finishedHash.discardHandshakeBuffer()
 472         }
 473         hs.finishedHash.Write(hs.clientHello.marshal())
 474         hs.finishedHash.Write(hs.hello.marshal())
 475         if _, err := c.writeRecord(recordTypeHandshake, hs.hello.marshal()); err != nil {
 476                 return err
 477         }
 478
 479         certMsg := new(certificateMsg)
 480         certMsg.certificates = hs.cert.Certificate
 481         hs.finishedHash.Write(certMsg.marshal())
 482         if _, err := c.writeRecord(recordTypeHandshake, certMsg.marshal()); err != nil {
 483                 return err
 484         }
 485
 486         if hs.hello.ocspStapling {
 487                 certStatus := new(certificateStatusMsg)
 488                 certStatus.response = hs.cert.OCSPStaple
 489                 hs.finishedHash.Write(certStatus.marshal())
 490                 if _, err := c.writeRecord(recordTypeHandshake, certStatus.marshal()); err != nil {
 491                         return err
 492                 }
 493         }
 494
 495         keyAgreement := hs.suite.ka(c.vers)
 496         skx, err := keyAgreement.generateServerKeyExchange(c.config, hs.cert, hs.clientHello, hs.hello)
 497         if err != nil {
 498                 c.sendAlert(alertHandshakeFailure)
 499                 return err
 500         }
 501         if skx != nil {
 502                 hs.finishedHash.Write(skx.marshal())
 503                 if _, err := c.writeRecord(recordTypeHandshake, skx.marshal()); err != nil {
 504                         return err
 505                 }
 506         }
 507
 508         var certReq *certificateRequestMsg
 509         if c.config.ClientAuth >= RequestClientCert {
 510                 // Request a client certificate
 511                 certReq = new(certificateRequestMsg)
 512                 certReq.certificateTypes = []byte{
 513                         byte(certTypeRSASign),
 514                         byte(certTypeECDSASign),
 515                 }
 516                 if c.vers >= VersionTLS12 {
 517                         certReq.hasSignatureAlgorithm = true
 518                         certReq.supportedSignatureAlgorithms = supportedSignatureAlgorithms()
 519                 }
 520
 521                 // An empty list of certificateAuthorities signals to
 522                 // the client that it may send any certificate in response
 523                 // to our request. When we know the CAs we trust, then
 524                 // we can send them down, so that the client can choose
 525                 // an appropriate certificate to give to us.
 526                 if c.config.ClientCAs != nil {
 527                         certReq.certificateAuthorities = c.config.ClientCAs.Subjects()
 528                 }
 529                 hs.finishedHash.Write(certReq.marshal())
 530                 if _, err := c.writeRecord(recordTypeHandshake, certReq.marshal()); err != nil {
 531                         return err
 532                 }
 533         }
 534
 535         helloDone := new(serverHelloDoneMsg)
 536         hs.finishedHash.Write(helloDone.marshal())
 537         if _, err := c.writeRecord(recordTypeHandshake, helloDone.marshal()); err != nil {
 538                 return err
 539         }
 540
 541         if _, err := c.flush(); err != nil {
 542                 return err
 543         }
 544
 545         var pub crypto.PublicKey // public key for client auth, if any
 546
 547         msg, err := c.readHandshake()
 548         if err != nil {
 549                 return err
 550         }
 551
 552         // If we requested a client certificate, then the client must send a
 553         // certificate message, even if it's empty.
 554         if c.config.ClientAuth >= RequestClientCert {
 555                 certMsg, ok := msg.(*certificateMsg)
 556                 if !ok {
 557                         c.sendAlert(alertUnexpectedMessage)
 558                         return unexpectedMessageError(certMsg, msg)
 559                 }
 560                 hs.finishedHash.Write(certMsg.marshal())
 561
 562                 if err := c.processCertsFromClient(Certificate{
 563                         Certificate: certMsg.certificates,
 564                 }); err != nil {
 565                         return err
 566                 }
 567                 if len(certMsg.certificates) != 0 {
 568                         pub = c.peerCertificates[0].PublicKey
 569                 }
 570
 571                 msg, err = c.readHandshake()
 572                 if err != nil {
 573                         return err
 574                 }
 575         }
 576         if c.config.VerifyConnection != nil {
 577                 if err := c.config.VerifyConnection(c.connectionStateLocked()); err != nil {
 578                         c.sendAlert(alertBadCertificate)
 579                         return err
 580                 }
 581         }
 582
 583         // Get client key exchange
 584         ckx, ok := msg.(*clientKeyExchangeMsg)
 585         if !ok {
 586                 c.sendAlert(alertUnexpectedMessage)
 587                 return unexpectedMessageError(ckx, msg)
 588         }
 589         hs.finishedHash.Write(ckx.marshal())
 590
 591         preMasterSecret, err := keyAgreement.processClientKeyExchange(c.config, hs.cert, ckx, c.vers)
 592         if err != nil {
 593                 c.sendAlert(alertHandshakeFailure)
 594                 return err
 595         }
 596         hs.masterSecret = masterFromPreMasterSecret(c.vers, hs.suite, preMasterSecret, hs.clientHello.random, hs.hello.random)
 597         if err := c.config.writeKeyLog(keyLogLabelTLS12, hs.clientHello.random, hs.masterSecret); err != nil {
 598                 c.sendAlert(alertInternalError)
 599                 return err
 600         }
 601
 602         // If we received a client cert in response to our certificate request message,
 603         // the client will send us a certificateVerifyMsg immediately after the
 604         // clientKeyExchangeMsg. This message is a digest of all preceding
 605         // handshake-layer messages that is signed using the private key corresponding
 606         // to the client's certificate. This allows us to verify that the client is in
 607         // possession of the private key of the certificate.
 608         if len(c.peerCertificates) > 0 {
 609                 msg, err = c.readHandshake()
 610                 if err != nil {
 611                         return err
 612                 }
 613                 certVerify, ok := msg.(*certificateVerifyMsg)
 614                 if !ok {
 615                         c.sendAlert(alertUnexpectedMessage)
 616                         return unexpectedMessageError(certVerify, msg)
 617                 }
 618
 619                 var sigType uint8
 620                 var sigHash crypto.Hash
 621                 if c.vers >= VersionTLS12 {
 622                         if !isSupportedSignatureAlgorithm(certVerify.signatureAlgorithm, certReq.supportedSignatureAlgorithms) {
 623                                 c.sendAlert(alertIllegalParameter)
 624                                 return errors.New("tls: client certificate used with invalid signature algorithm")
 625                         }
 626                         sigType, sigHash, err = typeAndHashFromSignatureScheme(certVerify.signatureAlgorithm)
 627                         if err != nil {
 628                                 return c.sendAlert(alertInternalError)
 629                         }
 630                 } else {
 631                         sigType, sigHash, err = legacyTypeAndHashFromPublicKey(pub)
 632                         if err != nil {
 633                                 c.sendAlert(alertIllegalParameter)
 634                                 return err
 635                         }
 636                 }
 637
 638                 signed := hs.finishedHash.hashForClientCertificate(sigType, sigHash, hs.masterSecret)
 639                 if err := verifyHandshakeSignature(sigType, pub, sigHash, signed, certVerify.signature); err != nil {
 640                         c.sendAlert(alertDecryptError)
 641                         return errors.New("tls: invalid signature by the client certificate: " + err.Error())
 642                 }
 643
 644                 hs.finishedHash.Write(certVerify.marshal())
 645         }
 646
 647         hs.finishedHash.discardHandshakeBuffer()
 648
 649         return nil
 650 }
 651
 652 func (hs *serverHandshakeState) establishKeys() error {
 653         c := hs.c
 654
 655         clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV :=
 656                 keysFromMasterSecret(c.vers, hs.suite, hs.masterSecret, hs.clientHello.random, hs.hello.random, hs.suite.macLen, hs.suite.keyLen, hs.suite.ivLen)
 657
 658         var clientCipher, serverCipher interface{}
 659         var clientHash, serverHash hash.Hash
 660
 661         if hs.suite.aead == nil {
 662                 clientCipher = hs.suite.cipher(clientKey, clientIV, true /* for reading */)
 663                 clientHash = hs.suite.mac(clientMAC)
 664                 serverCipher = hs.suite.cipher(serverKey, serverIV, false /* not for reading */)
 665                 serverHash = hs.suite.mac(serverMAC)
 666         } else {
 667                 clientCipher = hs.suite.aead(clientKey, clientIV)
 668                 serverCipher = hs.suite.aead(serverKey, serverIV)
 669         }
 670
 671         c.in.prepareCipherSpec(c.vers, clientCipher, clientHash)
 672         c.out.prepareCipherSpec(c.vers, serverCipher, serverHash)
 673
 674         return nil
 675 }
 676
 677 func (hs *serverHandshakeState) readFinished(out []byte) error {
 678         c := hs.c
 679
 680         if err := c.readChangeCipherSpec(); err != nil {
 681                 return err
 682         }
 683
 684         msg, err := c.readHandshake()
 685         if err != nil {
 686                 return err
 687         }
 688         clientFinished, ok := msg.(*finishedMsg)
 689         if !ok {
 690                 c.sendAlert(alertUnexpectedMessage)
 691                 return unexpectedMessageError(clientFinished, msg)
 692         }
 693
 694         verify := hs.finishedHash.clientSum(hs.masterSecret)
 695         if len(verify) != len(clientFinished.verifyData) ||
 696                 subtle.ConstantTimeCompare(verify, clientFinished.verifyData) != 1 {
 697                 c.sendAlert(alertHandshakeFailure)
 698                 return errors.New("tls: client's Finished message is incorrect")
 699         }
 700
 701         hs.finishedHash.Write(clientFinished.marshal())
 702         copy(out, verify)
 703         return nil
 704 }
 705
 706 func (hs *serverHandshakeState) sendSessionTicket() error {
 707         // ticketSupported is set in a resumption handshake if the
 708         // ticket from the client was encrypted with an old session
 709         // ticket key and thus a refreshed ticket should be sent.
 710         if !hs.hello.ticketSupported {
 711                 return nil
 712         }
 713
 714         c := hs.c
 715         m := new(newSessionTicketMsg)
 716
 717         createdAt := uint64(c.config.time().Unix())
 718         if hs.sessionState != nil {
 719                 // If this is re-wrapping an old key, then keep
 720                 // the original time it was created.
 721                 createdAt = hs.sessionState.createdAt
 722         }
 723
 724         var certsFromClient [][]byte
 725         for _, cert := range c.peerCertificates {
 726                 certsFromClient = append(certsFromClient, cert.Raw)
 727         }
 728         state := sessionState{
 729                 vers:         c.vers,
 730                 cipherSuite:  hs.suite.id,
 731                 createdAt:    createdAt,
 732                 masterSecret: hs.masterSecret,
 733                 certificates: certsFromClient,
 734         }
 735         var err error
 736         m.ticket, err = c.encryptTicket(state.marshal())
 737         if err != nil {
 738                 return err
 739         }
 740
 741         hs.finishedHash.Write(m.marshal())
 742         if _, err := c.writeRecord(recordTypeHandshake, m.marshal()); err != nil {
 743                 return err
 744         }
 745
 746         return nil
 747 }
 748
 749 func (hs *serverHandshakeState) sendFinished(out []byte) error {
 750         c := hs.c
 751
 752         if _, err := c.writeRecord(recordTypeChangeCipherSpec, []byte{1}); err != nil {
 753                 return err
 754         }
 755
 756         finished := new(finishedMsg)
 757         finished.verifyData = hs.finishedHash.serverSum(hs.masterSecret)
 758         hs.finishedHash.Write(finished.marshal())
 759         if _, err := c.writeRecord(recordTypeHandshake, finished.marshal()); err != nil {
 760                 return err
 761         }
 762
 763         copy(out, finished.verifyData)
 764
 765         return nil
 766 }
 767
 768 // processCertsFromClient takes a chain of client certificates either from a
 769 // Certificates message or from a sessionState and verifies them. It returns
 770 // the public key of the leaf certificate.
 771 func (c *Conn) processCertsFromClient(certificate Certificate) error {
 772         certificates := certificate.Certificate
 773         certs := make([]*x509.Certificate, len(certificates))
 774         var err error
 775         for i, asn1Data := range certificates {
 776                 if certs[i], err = x509.ParseCertificate(asn1Data); err != nil {
 777                         c.sendAlert(alertBadCertificate)
 778                         return errors.New("tls: failed to parse client certificate: " + err.Error())
 779                 }
 780         }
 781
 782         if len(certs) == 0 && requiresClientCert(c.config.ClientAuth) {
 783                 c.sendAlert(alertBadCertificate)
 784                 return errors.New("tls: client didn't provide a certificate")
 785         }
 786
 787         if c.config.ClientAuth >= VerifyClientCertIfGiven && len(certs) > 0 {
 788                 opts := x509.VerifyOptions{
 789                         IsBoring: isBoringCertificate,
 790
 791                         Roots:         c.config.ClientCAs,
 792                         CurrentTime:   c.config.time(),
 793                         Intermediates: x509.NewCertPool(),
 794                         KeyUsages:     []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth},
 795                 }
 796
 797                 for _, cert := range certs[1:] {
 798                         opts.Intermediates.AddCert(cert)
 799                 }
 800
 801                 chains, err := certs[0].Verify(opts)
 802                 if err != nil {
 803                         c.sendAlert(alertBadCertificate)
 804                         return errors.New("tls: failed to verify client certificate: " + err.Error())
 805                 }
 806
 807                 c.verifiedChains = chains
 808         }
 809
 810         c.peerCertificates = certs
 811         c.ocspResponse = certificate.OCSPStaple
 812         c.scts = certificate.SignedCertificateTimestamps
 813
 814         if len(certs) > 0 {
 815                 switch certs[0].PublicKey.(type) {
 816                 case *ecdsa.PublicKey, *rsa.PublicKey, ed25519.PublicKey:
 817                 default:
 818                         c.sendAlert(alertUnsupportedCertificate)
 819                         return fmt.Errorf("tls: client certificate contains an unsupported public key of type %T", certs[0].PublicKey)
 820                 }
 821         }
 822
 823         if c.config.VerifyPeerCertificate != nil {
 824                 if err := c.config.VerifyPeerCertificate(certificates, c.verifiedChains); err != nil {
 825                         c.sendAlert(alertBadCertificate)
 826                         return err
 827                 }
 828         }
 829
 830         return nil
 831 }
 832
 833 func clientHelloInfo(ctx context.Context, c *Conn, clientHello *clientHelloMsg) *ClientHelloInfo {
 834         supportedVersions := clientHello.supportedVersions
 835         if len(clientHello.supportedVersions) == 0 {
 836                 supportedVersions = supportedVersionsFromMax(clientHello.vers)
 837         }
 838
 839         return &ClientHelloInfo{
 840                 CipherSuites:      clientHello.cipherSuites,
 841                 ServerName:        clientHello.serverName,
 842                 SupportedCurves:   clientHello.supportedCurves,
 843                 SupportedPoints:   clientHello.supportedPoints,
 844                 SignatureSchemes:  clientHello.supportedSignatureAlgorithms,
 845                 SupportedProtos:   clientHello.alpnProtocols,
 846                 SupportedVersions: supportedVersions,
 847                 Conn:              c.conn,
 848                 config:            c.config,
 849                 ctx:               ctx,
 850         }
 851 }