src/crypto/tls/handshake_server_tls13.go

   1 // Copyright 2018 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/hmac"
  12         "crypto/rsa"
  13         "errors"
  14         "hash"
  15         "io"
  16         "sync/atomic"
  17         "time"
  18 )
  19
  20 // maxClientPSKIdentities is the number of client PSK identities the server will
  21 // attempt to validate. It will ignore the rest not to let cheap ClientHello
  22 // messages cause too much work in session ticket decryption attempts.
  23 const maxClientPSKIdentities = 5
  24
  25 type serverHandshakeStateTLS13 struct {
  26         c               *Conn
  27         ctx             context.Context
  28         clientHello     *clientHelloMsg
  29         hello           *serverHelloMsg
  30         sentDummyCCS    bool
  31         usingPSK        bool
  32         suite           *cipherSuiteTLS13
  33         cert            *Certificate
  34         sigAlg          SignatureScheme
  35         earlySecret     []byte
  36         sharedKey       []byte
  37         handshakeSecret []byte
  38         masterSecret    []byte
  39         trafficSecret   []byte // client_application_traffic_secret_0
  40         transcript      hash.Hash
  41         clientFinished  []byte
  42 }
  43
  44 func (hs *serverHandshakeStateTLS13) handshake() error {
  45         c := hs.c
  46
  47         if needFIPS() {
  48                 return errors.New("tls: internal error: TLS 1.3 reached in FIPS mode")
  49         }
  50
  51         // For an overview of the TLS 1.3 handshake, see RFC 8446, Section 2.
  52         if err := hs.processClientHello(); err != nil {
  53                 return err
  54         }
  55         if err := hs.checkForResumption(); err != nil {
  56                 return err
  57         }
  58         if err := hs.pickCertificate(); err != nil {
  59                 return err
  60         }
  61         c.buffering = true
  62         if err := hs.sendServerParameters(); err != nil {
  63                 return err
  64         }
  65         if err := hs.sendServerCertificate(); err != nil {
  66                 return err
  67         }
  68         if err := hs.sendServerFinished(); err != nil {
  69                 return err
  70         }
  71         // Note that at this point we could start sending application data without
  72         // waiting for the client's second flight, but the application might not
  73         // expect the lack of replay protection of the ClientHello parameters.
  74         if _, err := c.flush(); err != nil {
  75                 return err
  76         }
  77         if err := hs.readClientCertificate(); err != nil {
  78                 return err
  79         }
  80         if err := hs.readClientFinished(); err != nil {
  81                 return err
  82         }
  83
  84         atomic.StoreUint32(&c.handshakeStatus, 1)
  85
  86         return nil
  87 }
  88
  89 func (hs *serverHandshakeStateTLS13) processClientHello() error {
  90         c := hs.c
  91
  92         hs.hello = new(serverHelloMsg)
  93
  94         // TLS 1.3 froze the ServerHello.legacy_version field, and uses
  95         // supported_versions instead. See RFC 8446, sections 4.1.3 and 4.2.1.
  96         hs.hello.vers = VersionTLS12
  97         hs.hello.supportedVersion = c.vers
  98
  99         if len(hs.clientHello.supportedVersions) == 0 {
 100                 c.sendAlert(alertIllegalParameter)
 101                 return errors.New("tls: client used the legacy version field to negotiate TLS 1.3")
 102         }
 103
 104         // Abort if the client is doing a fallback and landing lower than what we
 105         // support. See RFC 7507, which however does not specify the interaction
 106         // with supported_versions. The only difference is that with
 107         // supported_versions a client has a chance to attempt a [TLS 1.2, TLS 1.4]
 108         // handshake in case TLS 1.3 is broken but 1.2 is not. Alas, in that case,
 109         // it will have to drop the TLS_FALLBACK_SCSV protection if it falls back to
 110         // TLS 1.2, because a TLS 1.3 server would abort here. The situation before
 111         // supported_versions was not better because there was just no way to do a
 112         // TLS 1.4 handshake without risking the server selecting TLS 1.3.
 113         for _, id := range hs.clientHello.cipherSuites {
 114                 if id == TLS_FALLBACK_SCSV {
 115                         // Use c.vers instead of max(supported_versions) because an attacker
 116                         // could defeat this by adding an arbitrary high version otherwise.
 117                         if c.vers < c.config.maxSupportedVersion() {
 118                                 c.sendAlert(alertInappropriateFallback)
 119                                 return errors.New("tls: client using inappropriate protocol fallback")
 120                         }
 121                         break
 122                 }
 123         }
 124
 125         if len(hs.clientHello.compressionMethods) != 1 ||
 126                 hs.clientHello.compressionMethods[0] != compressionNone {
 127                 c.sendAlert(alertIllegalParameter)
 128                 return errors.New("tls: TLS 1.3 client supports illegal compression methods")
 129         }
 130
 131         hs.hello.random = make([]byte, 32)
 132         if _, err := io.ReadFull(c.config.rand(), hs.hello.random); err != nil {
 133                 c.sendAlert(alertInternalError)
 134                 return err
 135         }
 136
 137         if len(hs.clientHello.secureRenegotiation) != 0 {
 138                 c.sendAlert(alertHandshakeFailure)
 139                 return errors.New("tls: initial handshake had non-empty renegotiation extension")
 140         }
 141
 142         if hs.clientHello.earlyData {
 143                 // See RFC 8446, Section 4.2.10 for the complicated behavior required
 144                 // here. The scenario is that a different server at our address offered
 145                 // to accept early data in the past, which we can't handle. For now, all
 146                 // 0-RTT enabled session tickets need to expire before a Go server can
 147                 // replace a server or join a pool. That's the same requirement that
 148                 // applies to mixing or replacing with any TLS 1.2 server.
 149                 c.sendAlert(alertUnsupportedExtension)
 150                 return errors.New("tls: client sent unexpected early data")
 151         }
 152
 153         hs.hello.sessionId = hs.clientHello.sessionId
 154         hs.hello.compressionMethod = compressionNone
 155
 156         preferenceList := defaultCipherSuitesTLS13
 157         if !hasAESGCMHardwareSupport || !aesgcmPreferred(hs.clientHello.cipherSuites) {
 158                 preferenceList = defaultCipherSuitesTLS13NoAES
 159         }
 160         for _, suiteID := range preferenceList {
 161                 hs.suite = mutualCipherSuiteTLS13(hs.clientHello.cipherSuites, suiteID)
 162                 if hs.suite != nil {
 163                         break
 164                 }
 165         }
 166         if hs.suite == nil {
 167                 c.sendAlert(alertHandshakeFailure)
 168                 return errors.New("tls: no cipher suite supported by both client and server")
 169         }
 170         c.cipherSuite = hs.suite.id
 171         hs.hello.cipherSuite = hs.suite.id
 172         hs.transcript = hs.suite.hash.New()
 173
 174         // Pick the ECDHE group in server preference order, but give priority to
 175         // groups with a key share, to avoid a HelloRetryRequest round-trip.
 176         var selectedGroup CurveID
 177         var clientKeyShare *keyShare
 178 GroupSelection:
 179         for _, preferredGroup := range c.config.curvePreferences() {
 180                 for _, ks := range hs.clientHello.keyShares {
 181                         if ks.group == preferredGroup {
 182                                 selectedGroup = ks.group
 183                                 clientKeyShare = &ks
 184                                 break GroupSelection
 185                         }
 186                 }
 187                 if selectedGroup != 0 {
 188                         continue
 189                 }
 190                 for _, group := range hs.clientHello.supportedCurves {
 191                         if group == preferredGroup {
 192                                 selectedGroup = group
 193                                 break
 194                         }
 195                 }
 196         }
 197         if selectedGroup == 0 {
 198                 c.sendAlert(alertHandshakeFailure)
 199                 return errors.New("tls: no ECDHE curve supported by both client and server")
 200         }
 201         if clientKeyShare == nil {
 202                 if err := hs.doHelloRetryRequest(selectedGroup); err != nil {
 203                         return err
 204                 }
 205                 clientKeyShare = &hs.clientHello.keyShares[0]
 206         }
 207
 208         if _, ok := curveForCurveID(selectedGroup); selectedGroup != X25519 && !ok {
 209                 c.sendAlert(alertInternalError)
 210                 return errors.New("tls: CurvePreferences includes unsupported curve")
 211         }
 212         params, err := generateECDHEParameters(c.config.rand(), selectedGroup)
 213         if err != nil {
 214                 c.sendAlert(alertInternalError)
 215                 return err
 216         }
 217         hs.hello.serverShare = keyShare{group: selectedGroup, data: params.PublicKey()}
 218         hs.sharedKey = params.SharedKey(clientKeyShare.data)
 219         if hs.sharedKey == nil {
 220                 c.sendAlert(alertIllegalParameter)
 221                 return errors.New("tls: invalid client key share")
 222         }
 223
 224         c.serverName = hs.clientHello.serverName
 225         return nil
 226 }
 227
 228 func (hs *serverHandshakeStateTLS13) checkForResumption() error {
 229         c := hs.c
 230
 231         if c.config.SessionTicketsDisabled {
 232                 return nil
 233         }
 234
 235         modeOK := false
 236         for _, mode := range hs.clientHello.pskModes {
 237                 if mode == pskModeDHE {
 238                         modeOK = true
 239                         break
 240                 }
 241         }
 242         if !modeOK {
 243                 return nil
 244         }
 245
 246         if len(hs.clientHello.pskIdentities) != len(hs.clientHello.pskBinders) {
 247                 c.sendAlert(alertIllegalParameter)
 248                 return errors.New("tls: invalid or missing PSK binders")
 249         }
 250         if len(hs.clientHello.pskIdentities) == 0 {
 251                 return nil
 252         }
 253
 254         for i, identity := range hs.clientHello.pskIdentities {
 255                 if i >= maxClientPSKIdentities {
 256                         break
 257                 }
 258
 259                 plaintext, _ := c.decryptTicket(identity.label)
 260                 if plaintext == nil {
 261                         continue
 262                 }
 263                 sessionState := new(sessionStateTLS13)
 264                 if ok := sessionState.unmarshal(plaintext); !ok {
 265                         continue
 266                 }
 267
 268                 createdAt := time.Unix(int64(sessionState.createdAt), 0)
 269                 if c.config.time().Sub(createdAt) > maxSessionTicketLifetime {
 270                         continue
 271                 }
 272
 273                 // We don't check the obfuscated ticket age because it's affected by
 274                 // clock skew and it's only a freshness signal useful for shrinking the
 275                 // window for replay attacks, which don't affect us as we don't do 0-RTT.
 276
 277                 pskSuite := cipherSuiteTLS13ByID(sessionState.cipherSuite)
 278                 if pskSuite == nil || pskSuite.hash != hs.suite.hash {
 279                         continue
 280                 }
 281
 282                 // PSK connections don't re-establish client certificates, but carry
 283                 // them over in the session ticket. Ensure the presence of client certs
 284                 // in the ticket is consistent with the configured requirements.
 285                 sessionHasClientCerts := len(sessionState.certificate.Certificate) != 0
 286                 needClientCerts := requiresClientCert(c.config.ClientAuth)
 287                 if needClientCerts && !sessionHasClientCerts {
 288                         continue
 289                 }
 290                 if sessionHasClientCerts && c.config.ClientAuth == NoClientCert {
 291                         continue
 292                 }
 293
 294                 psk := hs.suite.expandLabel(sessionState.resumptionSecret, "resumption",
 295                         nil, hs.suite.hash.Size())
 296                 hs.earlySecret = hs.suite.extract(psk, nil)
 297                 binderKey := hs.suite.deriveSecret(hs.earlySecret, resumptionBinderLabel, nil)
 298                 // Clone the transcript in case a HelloRetryRequest was recorded.
 299                 transcript := cloneHash(hs.transcript, hs.suite.hash)
 300                 if transcript == nil {
 301                         c.sendAlert(alertInternalError)
 302                         return errors.New("tls: internal error: failed to clone hash")
 303                 }
 304                 transcript.Write(hs.clientHello.marshalWithoutBinders())
 305                 pskBinder := hs.suite.finishedHash(binderKey, transcript)
 306                 if !hmac.Equal(hs.clientHello.pskBinders[i], pskBinder) {
 307                         c.sendAlert(alertDecryptError)
 308                         return errors.New("tls: invalid PSK binder")
 309                 }
 310
 311                 c.didResume = true
 312                 if err := c.processCertsFromClient(sessionState.certificate); err != nil {
 313                         return err
 314                 }
 315
 316                 hs.hello.selectedIdentityPresent = true
 317                 hs.hello.selectedIdentity = uint16(i)
 318                 hs.usingPSK = true
 319                 return nil
 320         }
 321
 322         return nil
 323 }
 324
 325 // cloneHash uses the encoding.BinaryMarshaler and encoding.BinaryUnmarshaler
 326 // interfaces implemented by standard library hashes to clone the state of in
 327 // to a new instance of h. It returns nil if the operation fails.
 328 func cloneHash(in hash.Hash, h crypto.Hash) hash.Hash {
 329         // Recreate the interface to avoid importing encoding.
 330         type binaryMarshaler interface {
 331                 MarshalBinary() (data []byte, err error)
 332                 UnmarshalBinary(data []byte) error
 333         }
 334         marshaler, ok := in.(binaryMarshaler)
 335         if !ok {
 336                 return nil
 337         }
 338         state, err := marshaler.MarshalBinary()
 339         if err != nil {
 340                 return nil
 341         }
 342         out := h.New()
 343         unmarshaler, ok := out.(binaryMarshaler)
 344         if !ok {
 345                 return nil
 346         }
 347         if err := unmarshaler.UnmarshalBinary(state); err != nil {
 348                 return nil
 349         }
 350         return out
 351 }
 352
 353 func (hs *serverHandshakeStateTLS13) pickCertificate() error {
 354         c := hs.c
 355
 356         // Only one of PSK and certificates are used at a time.
 357         if hs.usingPSK {
 358                 return nil
 359         }
 360
 361         // signature_algorithms is required in TLS 1.3. See RFC 8446, Section 4.2.3.
 362         if len(hs.clientHello.supportedSignatureAlgorithms) == 0 {
 363                 return c.sendAlert(alertMissingExtension)
 364         }
 365
 366         certificate, err := c.config.getCertificate(clientHelloInfo(hs.ctx, c, hs.clientHello))
 367         if err != nil {
 368                 if err == errNoCertificates {
 369                         c.sendAlert(alertUnrecognizedName)
 370                 } else {
 371                         c.sendAlert(alertInternalError)
 372                 }
 373                 return err
 374         }
 375         hs.sigAlg, err = selectSignatureScheme(c.vers, certificate, hs.clientHello.supportedSignatureAlgorithms)
 376         if err != nil {
 377                 // getCertificate returned a certificate that is unsupported or
 378                 // incompatible with the client's signature algorithms.
 379                 c.sendAlert(alertHandshakeFailure)
 380                 return err
 381         }
 382         hs.cert = certificate
 383
 384         return nil
 385 }
 386
 387 // sendDummyChangeCipherSpec sends a ChangeCipherSpec record for compatibility
 388 // with middleboxes that didn't implement TLS correctly. See RFC 8446, Appendix D.4.
 389 func (hs *serverHandshakeStateTLS13) sendDummyChangeCipherSpec() error {
 390         if hs.sentDummyCCS {
 391                 return nil
 392         }
 393         hs.sentDummyCCS = true
 394
 395         _, err := hs.c.writeRecord(recordTypeChangeCipherSpec, []byte{1})
 396         return err
 397 }
 398
 399 func (hs *serverHandshakeStateTLS13) doHelloRetryRequest(selectedGroup CurveID) error {
 400         c := hs.c
 401
 402         // The first ClientHello gets double-hashed into the transcript upon a
 403         // HelloRetryRequest. See RFC 8446, Section 4.4.1.
 404         hs.transcript.Write(hs.clientHello.marshal())
 405         chHash := hs.transcript.Sum(nil)
 406         hs.transcript.Reset()
 407         hs.transcript.Write([]byte{typeMessageHash, 0, 0, uint8(len(chHash))})
 408         hs.transcript.Write(chHash)
 409
 410         helloRetryRequest := &serverHelloMsg{
 411                 vers:              hs.hello.vers,
 412                 random:            helloRetryRequestRandom,
 413                 sessionId:         hs.hello.sessionId,
 414                 cipherSuite:       hs.hello.cipherSuite,
 415                 compressionMethod: hs.hello.compressionMethod,
 416                 supportedVersion:  hs.hello.supportedVersion,
 417                 selectedGroup:     selectedGroup,
 418         }
 419
 420         hs.transcript.Write(helloRetryRequest.marshal())
 421         if _, err := c.writeRecord(recordTypeHandshake, helloRetryRequest.marshal()); err != nil {
 422                 return err
 423         }
 424
 425         if err := hs.sendDummyChangeCipherSpec(); err != nil {
 426                 return err
 427         }
 428
 429         msg, err := c.readHandshake()
 430         if err != nil {
 431                 return err
 432         }
 433
 434         clientHello, ok := msg.(*clientHelloMsg)
 435         if !ok {
 436                 c.sendAlert(alertUnexpectedMessage)
 437                 return unexpectedMessageError(clientHello, msg)
 438         }
 439
 440         if len(clientHello.keyShares) != 1 || clientHello.keyShares[0].group != selectedGroup {
 441                 c.sendAlert(alertIllegalParameter)
 442                 return errors.New("tls: client sent invalid key share in second ClientHello")
 443         }
 444
 445         if clientHello.earlyData {
 446                 c.sendAlert(alertIllegalParameter)
 447                 return errors.New("tls: client indicated early data in second ClientHello")
 448         }
 449
 450         if illegalClientHelloChange(clientHello, hs.clientHello) {
 451                 c.sendAlert(alertIllegalParameter)
 452                 return errors.New("tls: client illegally modified second ClientHello")
 453         }
 454
 455         hs.clientHello = clientHello
 456         return nil
 457 }
 458
 459 // illegalClientHelloChange reports whether the two ClientHello messages are
 460 // different, with the exception of the changes allowed before and after a
 461 // HelloRetryRequest. See RFC 8446, Section 4.1.2.
 462 func illegalClientHelloChange(ch, ch1 *clientHelloMsg) bool {
 463         if len(ch.supportedVersions) != len(ch1.supportedVersions) ||
 464                 len(ch.cipherSuites) != len(ch1.cipherSuites) ||
 465                 len(ch.supportedCurves) != len(ch1.supportedCurves) ||
 466                 len(ch.supportedSignatureAlgorithms) != len(ch1.supportedSignatureAlgorithms) ||
 467                 len(ch.supportedSignatureAlgorithmsCert) != len(ch1.supportedSignatureAlgorithmsCert) ||
 468                 len(ch.alpnProtocols) != len(ch1.alpnProtocols) {
 469                 return true
 470         }
 471         for i := range ch.supportedVersions {
 472                 if ch.supportedVersions[i] != ch1.supportedVersions[i] {
 473                         return true
 474                 }
 475         }
 476         for i := range ch.cipherSuites {
 477                 if ch.cipherSuites[i] != ch1.cipherSuites[i] {
 478                         return true
 479                 }
 480         }
 481         for i := range ch.supportedCurves {
 482                 if ch.supportedCurves[i] != ch1.supportedCurves[i] {
 483                         return true
 484                 }
 485         }
 486         for i := range ch.supportedSignatureAlgorithms {
 487                 if ch.supportedSignatureAlgorithms[i] != ch1.supportedSignatureAlgorithms[i] {
 488                         return true
 489                 }
 490         }
 491         for i := range ch.supportedSignatureAlgorithmsCert {
 492                 if ch.supportedSignatureAlgorithmsCert[i] != ch1.supportedSignatureAlgorithmsCert[i] {
 493                         return true
 494                 }
 495         }
 496         for i := range ch.alpnProtocols {
 497                 if ch.alpnProtocols[i] != ch1.alpnProtocols[i] {
 498                         return true
 499                 }
 500         }
 501         return ch.vers != ch1.vers ||
 502                 !bytes.Equal(ch.random, ch1.random) ||
 503                 !bytes.Equal(ch.sessionId, ch1.sessionId) ||
 504                 !bytes.Equal(ch.compressionMethods, ch1.compressionMethods) ||
 505                 ch.serverName != ch1.serverName ||
 506                 ch.ocspStapling != ch1.ocspStapling ||
 507                 !bytes.Equal(ch.supportedPoints, ch1.supportedPoints) ||
 508                 ch.ticketSupported != ch1.ticketSupported ||
 509                 !bytes.Equal(ch.sessionTicket, ch1.sessionTicket) ||
 510                 ch.secureRenegotiationSupported != ch1.secureRenegotiationSupported ||
 511                 !bytes.Equal(ch.secureRenegotiation, ch1.secureRenegotiation) ||
 512                 ch.scts != ch1.scts ||
 513                 !bytes.Equal(ch.cookie, ch1.cookie) ||
 514                 !bytes.Equal(ch.pskModes, ch1.pskModes)
 515 }
 516
 517 func (hs *serverHandshakeStateTLS13) sendServerParameters() error {
 518         c := hs.c
 519
 520         hs.transcript.Write(hs.clientHello.marshal())
 521         hs.transcript.Write(hs.hello.marshal())
 522         if _, err := c.writeRecord(recordTypeHandshake, hs.hello.marshal()); err != nil {
 523                 return err
 524         }
 525
 526         if err := hs.sendDummyChangeCipherSpec(); err != nil {
 527                 return err
 528         }
 529
 530         earlySecret := hs.earlySecret
 531         if earlySecret == nil {
 532                 earlySecret = hs.suite.extract(nil, nil)
 533         }
 534         hs.handshakeSecret = hs.suite.extract(hs.sharedKey,
 535                 hs.suite.deriveSecret(earlySecret, "derived", nil))
 536
 537         clientSecret := hs.suite.deriveSecret(hs.handshakeSecret,
 538                 clientHandshakeTrafficLabel, hs.transcript)
 539         c.in.setTrafficSecret(hs.suite, clientSecret)
 540         serverSecret := hs.suite.deriveSecret(hs.handshakeSecret,
 541                 serverHandshakeTrafficLabel, hs.transcript)
 542         c.out.setTrafficSecret(hs.suite, serverSecret)
 543
 544         err := c.config.writeKeyLog(keyLogLabelClientHandshake, hs.clientHello.random, clientSecret)
 545         if err != nil {
 546                 c.sendAlert(alertInternalError)
 547                 return err
 548         }
 549         err = c.config.writeKeyLog(keyLogLabelServerHandshake, hs.clientHello.random, serverSecret)
 550         if err != nil {
 551                 c.sendAlert(alertInternalError)
 552                 return err
 553         }
 554
 555         encryptedExtensions := new(encryptedExtensionsMsg)
 556
 557         selectedProto, err := negotiateALPN(c.config.NextProtos, hs.clientHello.alpnProtocols)
 558         if err != nil {
 559                 c.sendAlert(alertNoApplicationProtocol)
 560                 return err
 561         }
 562         encryptedExtensions.alpnProtocol = selectedProto
 563         c.clientProtocol = selectedProto
 564
 565         hs.transcript.Write(encryptedExtensions.marshal())
 566         if _, err := c.writeRecord(recordTypeHandshake, encryptedExtensions.marshal()); err != nil {
 567                 return err
 568         }
 569
 570         return nil
 571 }
 572
 573 func (hs *serverHandshakeStateTLS13) requestClientCert() bool {
 574         return hs.c.config.ClientAuth >= RequestClientCert && !hs.usingPSK
 575 }
 576
 577 func (hs *serverHandshakeStateTLS13) sendServerCertificate() error {
 578         c := hs.c
 579
 580         // Only one of PSK and certificates are used at a time.
 581         if hs.usingPSK {
 582                 return nil
 583         }
 584
 585         if hs.requestClientCert() {
 586                 // Request a client certificate
 587                 certReq := new(certificateRequestMsgTLS13)
 588                 certReq.ocspStapling = true
 589                 certReq.scts = true
 590                 certReq.supportedSignatureAlgorithms = supportedSignatureAlgorithms()
 591                 if c.config.ClientCAs != nil {
 592                         certReq.certificateAuthorities = c.config.ClientCAs.Subjects()
 593                 }
 594
 595                 hs.transcript.Write(certReq.marshal())
 596                 if _, err := c.writeRecord(recordTypeHandshake, certReq.marshal()); err != nil {
 597                         return err
 598                 }
 599         }
 600
 601         certMsg := new(certificateMsgTLS13)
 602
 603         certMsg.certificate = *hs.cert
 604         certMsg.scts = hs.clientHello.scts && len(hs.cert.SignedCertificateTimestamps) > 0
 605         certMsg.ocspStapling = hs.clientHello.ocspStapling && len(hs.cert.OCSPStaple) > 0
 606
 607         hs.transcript.Write(certMsg.marshal())
 608         if _, err := c.writeRecord(recordTypeHandshake, certMsg.marshal()); err != nil {
 609                 return err
 610         }
 611
 612         certVerifyMsg := new(certificateVerifyMsg)
 613         certVerifyMsg.hasSignatureAlgorithm = true
 614         certVerifyMsg.signatureAlgorithm = hs.sigAlg
 615
 616         sigType, sigHash, err := typeAndHashFromSignatureScheme(hs.sigAlg)
 617         if err != nil {
 618                 return c.sendAlert(alertInternalError)
 619         }
 620
 621         signed := signedMessage(sigHash, serverSignatureContext, hs.transcript)
 622         signOpts := crypto.SignerOpts(sigHash)
 623         if sigType == signatureRSAPSS {
 624                 signOpts = &rsa.PSSOptions{SaltLength: rsa.PSSSaltLengthEqualsHash, Hash: sigHash}
 625         }
 626         sig, err := hs.cert.PrivateKey.(crypto.Signer).Sign(c.config.rand(), signed, signOpts)
 627         if err != nil {
 628                 public := hs.cert.PrivateKey.(crypto.Signer).Public()
 629                 if rsaKey, ok := public.(*rsa.PublicKey); ok && sigType == signatureRSAPSS &&
 630                         rsaKey.N.BitLen()/8 < sigHash.Size()*2+2 { // key too small for RSA-PSS
 631                         c.sendAlert(alertHandshakeFailure)
 632                 } else {
 633                         c.sendAlert(alertInternalError)
 634                 }
 635                 return errors.New("tls: failed to sign handshake: " + err.Error())
 636         }
 637         certVerifyMsg.signature = sig
 638
 639         hs.transcript.Write(certVerifyMsg.marshal())
 640         if _, err := c.writeRecord(recordTypeHandshake, certVerifyMsg.marshal()); err != nil {
 641                 return err
 642         }
 643
 644         return nil
 645 }
 646
 647 func (hs *serverHandshakeStateTLS13) sendServerFinished() error {
 648         c := hs.c
 649
 650         finished := &finishedMsg{
 651                 verifyData: hs.suite.finishedHash(c.out.trafficSecret, hs.transcript),
 652         }
 653
 654         hs.transcript.Write(finished.marshal())
 655         if _, err := c.writeRecord(recordTypeHandshake, finished.marshal()); err != nil {
 656                 return err
 657         }
 658
 659         // Derive secrets that take context through the server Finished.
 660
 661         hs.masterSecret = hs.suite.extract(nil,
 662                 hs.suite.deriveSecret(hs.handshakeSecret, "derived", nil))
 663
 664         hs.trafficSecret = hs.suite.deriveSecret(hs.masterSecret,
 665                 clientApplicationTrafficLabel, hs.transcript)
 666         serverSecret := hs.suite.deriveSecret(hs.masterSecret,
 667                 serverApplicationTrafficLabel, hs.transcript)
 668         c.out.setTrafficSecret(hs.suite, serverSecret)
 669
 670         err := c.config.writeKeyLog(keyLogLabelClientTraffic, hs.clientHello.random, hs.trafficSecret)
 671         if err != nil {
 672                 c.sendAlert(alertInternalError)
 673                 return err
 674         }
 675         err = c.config.writeKeyLog(keyLogLabelServerTraffic, hs.clientHello.random, serverSecret)
 676         if err != nil {
 677                 c.sendAlert(alertInternalError)
 678                 return err
 679         }
 680
 681         c.ekm = hs.suite.exportKeyingMaterial(hs.masterSecret, hs.transcript)
 682
 683         // If we did not request client certificates, at this point we can
 684         // precompute the client finished and roll the transcript forward to send
 685         // session tickets in our first flight.
 686         if !hs.requestClientCert() {
 687                 if err := hs.sendSessionTickets(); err != nil {
 688                         return err
 689                 }
 690         }
 691
 692         return nil
 693 }
 694
 695 func (hs *serverHandshakeStateTLS13) shouldSendSessionTickets() bool {
 696         if hs.c.config.SessionTicketsDisabled {
 697                 return false
 698         }
 699
 700         // Don't send tickets the client wouldn't use. See RFC 8446, Section 4.2.9.
 701         for _, pskMode := range hs.clientHello.pskModes {
 702                 if pskMode == pskModeDHE {
 703                         return true
 704                 }
 705         }
 706         return false
 707 }
 708
 709 func (hs *serverHandshakeStateTLS13) sendSessionTickets() error {
 710         c := hs.c
 711
 712         hs.clientFinished = hs.suite.finishedHash(c.in.trafficSecret, hs.transcript)
 713         finishedMsg := &finishedMsg{
 714                 verifyData: hs.clientFinished,
 715         }
 716         hs.transcript.Write(finishedMsg.marshal())
 717
 718         if !hs.shouldSendSessionTickets() {
 719                 return nil
 720         }
 721
 722         resumptionSecret := hs.suite.deriveSecret(hs.masterSecret,
 723                 resumptionLabel, hs.transcript)
 724
 725         m := new(newSessionTicketMsgTLS13)
 726
 727         var certsFromClient [][]byte
 728         for _, cert := range c.peerCertificates {
 729                 certsFromClient = append(certsFromClient, cert.Raw)
 730         }
 731         state := sessionStateTLS13{
 732                 cipherSuite:      hs.suite.id,
 733                 createdAt:        uint64(c.config.time().Unix()),
 734                 resumptionSecret: resumptionSecret,
 735                 certificate: Certificate{
 736                         Certificate:                 certsFromClient,
 737                         OCSPStaple:                  c.ocspResponse,
 738                         SignedCertificateTimestamps: c.scts,
 739                 },
 740         }
 741         var err error
 742         m.label, err = c.encryptTicket(state.marshal())
 743         if err != nil {
 744                 return err
 745         }
 746         m.lifetime = uint32(maxSessionTicketLifetime / time.Second)
 747
 748         if _, err := c.writeRecord(recordTypeHandshake, m.marshal()); err != nil {
 749                 return err
 750         }
 751
 752         return nil
 753 }
 754
 755 func (hs *serverHandshakeStateTLS13) readClientCertificate() error {
 756         c := hs.c
 757
 758         if !hs.requestClientCert() {
 759                 // Make sure the connection is still being verified whether or not
 760                 // the server requested a client certificate.
 761                 if c.config.VerifyConnection != nil {
 762                         if err := c.config.VerifyConnection(c.connectionStateLocked()); err != nil {
 763                                 c.sendAlert(alertBadCertificate)
 764                                 return err
 765                         }
 766                 }
 767                 return nil
 768         }
 769
 770         // If we requested a client certificate, then the client must send a
 771         // certificate message. If it's empty, no CertificateVerify is sent.
 772
 773         msg, err := c.readHandshake()
 774         if err != nil {
 775                 return err
 776         }
 777
 778         certMsg, ok := msg.(*certificateMsgTLS13)
 779         if !ok {
 780                 c.sendAlert(alertUnexpectedMessage)
 781                 return unexpectedMessageError(certMsg, msg)
 782         }
 783         hs.transcript.Write(certMsg.marshal())
 784
 785         if err := c.processCertsFromClient(certMsg.certificate); err != nil {
 786                 return err
 787         }
 788
 789         if c.config.VerifyConnection != nil {
 790                 if err := c.config.VerifyConnection(c.connectionStateLocked()); err != nil {
 791                         c.sendAlert(alertBadCertificate)
 792                         return err
 793                 }
 794         }
 795
 796         if len(certMsg.certificate.Certificate) != 0 {
 797                 msg, err = c.readHandshake()
 798                 if err != nil {
 799                         return err
 800                 }
 801
 802                 certVerify, ok := msg.(*certificateVerifyMsg)
 803                 if !ok {
 804                         c.sendAlert(alertUnexpectedMessage)
 805                         return unexpectedMessageError(certVerify, msg)
 806                 }
 807
 808                 // See RFC 8446, Section 4.4.3.
 809                 if !isSupportedSignatureAlgorithm(certVerify.signatureAlgorithm, supportedSignatureAlgorithms()) {
 810                         c.sendAlert(alertIllegalParameter)
 811                         return errors.New("tls: client certificate used with invalid signature algorithm")
 812                 }
 813                 sigType, sigHash, err := typeAndHashFromSignatureScheme(certVerify.signatureAlgorithm)
 814                 if err != nil {
 815                         return c.sendAlert(alertInternalError)
 816                 }
 817                 if sigType == signaturePKCS1v15 || sigHash == crypto.SHA1 {
 818                         c.sendAlert(alertIllegalParameter)
 819                         return errors.New("tls: client certificate used with invalid signature algorithm")
 820                 }
 821                 signed := signedMessage(sigHash, clientSignatureContext, hs.transcript)
 822                 if err := verifyHandshakeSignature(sigType, c.peerCertificates[0].PublicKey,
 823                         sigHash, signed, certVerify.signature); err != nil {
 824                         c.sendAlert(alertDecryptError)
 825                         return errors.New("tls: invalid signature by the client certificate: " + err.Error())
 826                 }
 827
 828                 hs.transcript.Write(certVerify.marshal())
 829         }
 830
 831         // If we waited until the client certificates to send session tickets, we
 832         // are ready to do it now.
 833         if err := hs.sendSessionTickets(); err != nil {
 834                 return err
 835         }
 836
 837         return nil
 838 }
 839
 840 func (hs *serverHandshakeStateTLS13) readClientFinished() error {
 841         c := hs.c
 842
 843         msg, err := c.readHandshake()
 844         if err != nil {
 845                 return err
 846         }
 847
 848         finished, ok := msg.(*finishedMsg)
 849         if !ok {
 850                 c.sendAlert(alertUnexpectedMessage)
 851                 return unexpectedMessageError(finished, msg)
 852         }
 853
 854         if !hmac.Equal(hs.clientFinished, finished.verifyData) {
 855                 c.sendAlert(alertDecryptError)
 856                 return errors.New("tls: invalid client finished hash")
 857         }
 858
 859         c.in.setTrafficSecret(hs.suite, hs.trafficSecret)
 860
 861         return nil
 862 }