Imported Upstream version 1.4upstream/1.4

1 files changed, 685 insertions, 0 deletions

diff --git a/src/crypto/tls/handshake_server.go b/src/crypto/tls/handshake_server.go
new file mode 100644
index 000000000..0d907656c
--- /dev/null
+++ b/src/crypto/tls/handshake_server.go
@@ -0,0 +1,685 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tls
+
+import (
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/rsa"
+	"crypto/subtle"
+	"crypto/x509"
+	"encoding/asn1"
+	"errors"
+	"fmt"
+	"io"
+)
+
+// serverHandshakeState contains details of a server handshake in progress.
+// It's discarded once the handshake has completed.
+type serverHandshakeState struct {
+	c               *Conn
+	clientHello     *clientHelloMsg
+	hello           *serverHelloMsg
+	suite           *cipherSuite
+	ellipticOk      bool
+	ecdsaOk         bool
+	sessionState    *sessionState
+	finishedHash    finishedHash
+	masterSecret    []byte
+	certsFromClient [][]byte
+	cert            *Certificate
+}
+
+// serverHandshake performs a TLS handshake as a server.
+func (c *Conn) serverHandshake() error {
+	config := c.config
+
+	// If this is the first server handshake, we generate a random key to
+	// encrypt the tickets with.
+	config.serverInitOnce.Do(config.serverInit)
+
+	hs := serverHandshakeState{
+		c: c,
+	}
+	isResume, err := hs.readClientHello()
+	if err != nil {
+		return err
+	}
+
+	// For an overview of TLS handshaking, see https://tools.ietf.org/html/rfc5246#section-7.3
+	if isResume {
+		// The client has included a session ticket and so we do an abbreviated handshake.
+		if err := hs.doResumeHandshake(); err != nil {
+			return err
+		}
+		if err := hs.establishKeys(); err != nil {
+			return err
+		}
+		if err := hs.sendFinished(c.firstFinished[:]); err != nil {
+			return err
+		}
+		if err := hs.readFinished(nil); err != nil {
+			return err
+		}
+		c.didResume = true
+	} else {
+		// The client didn't include a session ticket, or it wasn't
+		// valid so we do a full handshake.
+		if err := hs.doFullHandshake(); err != nil {
+			return err
+		}
+		if err := hs.establishKeys(); err != nil {
+			return err
+		}
+		if err := hs.readFinished(c.firstFinished[:]); err != nil {
+			return err
+		}
+		if err := hs.sendSessionTicket(); err != nil {
+			return err
+		}
+		if err := hs.sendFinished(nil); err != nil {
+			return err
+		}
+	}
+	c.handshakeComplete = true
+
+	return nil
+}
+
+// readClientHello reads a ClientHello message from the client and decides
+// whether we will perform session resumption.
+func (hs *serverHandshakeState) readClientHello() (isResume bool, err error) {
+	config := hs.c.config
+	c := hs.c
+
+	msg, err := c.readHandshake()
+	if err != nil {
+		return false, err
+	}
+	var ok bool
+	hs.clientHello, ok = msg.(*clientHelloMsg)
+	if !ok {
+		c.sendAlert(alertUnexpectedMessage)
+		return false, unexpectedMessageError(hs.clientHello, msg)
+	}
+	c.vers, ok = config.mutualVersion(hs.clientHello.vers)
+	if !ok {
+		c.sendAlert(alertProtocolVersion)
+		return false, fmt.Errorf("tls: client offered an unsupported, maximum protocol version of %x", hs.clientHello.vers)
+	}
+	c.haveVers = true
+
+	hs.finishedHash = newFinishedHash(c.vers)
+	hs.finishedHash.Write(hs.clientHello.marshal())
+
+	hs.hello = new(serverHelloMsg)
+
+	supportedCurve := false
+	preferredCurves := config.curvePreferences()
+Curves:
+	for _, curve := range hs.clientHello.supportedCurves {
+		for _, supported := range preferredCurves {
+			if supported == curve {
+				supportedCurve = true
+				break Curves
+			}
+		}
+	}
+
+	supportedPointFormat := false
+	for _, pointFormat := range hs.clientHello.supportedPoints {
+		if pointFormat == pointFormatUncompressed {
+			supportedPointFormat = true
+			break
+		}
+	}
+	hs.ellipticOk = supportedCurve && supportedPointFormat
+
+	foundCompression := false
+	// We only support null compression, so check that the client offered it.
+	for _, compression := range hs.clientHello.compressionMethods {
+		if compression == compressionNone {
+			foundCompression = true
+			break
+		}
+	}
+
+	if !foundCompression {
+		c.sendAlert(alertHandshakeFailure)
+		return false, errors.New("tls: client does not support uncompressed connections")
+	}
+
+	hs.hello.vers = c.vers
+	hs.hello.random = make([]byte, 32)
+	_, err = io.ReadFull(config.rand(), hs.hello.random)
+	if err != nil {
+		c.sendAlert(alertInternalError)
+		return false, err
+	}
+	hs.hello.secureRenegotiation = hs.clientHello.secureRenegotiation
+	hs.hello.compressionMethod = compressionNone
+	if len(hs.clientHello.serverName) > 0 {
+		c.serverName = hs.clientHello.serverName
+	}
+
+	if len(hs.clientHello.alpnProtocols) > 0 {
+		if selectedProto, fallback := mutualProtocol(hs.clientHello.alpnProtocols, c.config.NextProtos); !fallback {
+			hs.hello.alpnProtocol = selectedProto
+			c.clientProtocol = selectedProto
+		}
+	} else {
+		// Although sending an empty NPN extension is reasonable, Firefox has
+		// had a bug around this. Best to send nothing at all if
+		// config.NextProtos is empty. See
+		// https://code.google.com/p/go/issues/detail?id=5445.
+		if hs.clientHello.nextProtoNeg && len(config.NextProtos) > 0 {
+			hs.hello.nextProtoNeg = true
+			hs.hello.nextProtos = config.NextProtos
+		}
+	}
+
+	if len(config.Certificates) == 0 {
+		c.sendAlert(alertInternalError)
+		return false, errors.New("tls: no certificates configured")
+	}
+	hs.cert = &config.Certificates[0]
+	if len(hs.clientHello.serverName) > 0 {
+		chi := &ClientHelloInfo{
+			CipherSuites:    hs.clientHello.cipherSuites,
+			ServerName:      hs.clientHello.serverName,
+			SupportedCurves: hs.clientHello.supportedCurves,
+			SupportedPoints: hs.clientHello.supportedPoints,
+		}
+		if hs.cert, err = config.getCertificate(chi); err != nil {
+			c.sendAlert(alertInternalError)
+			return false, err
+		}
+	}
+
+	_, hs.ecdsaOk = hs.cert.PrivateKey.(*ecdsa.PrivateKey)
+
+	if hs.checkForResumption() {
+		return true, nil
+	}
+
+	var preferenceList, supportedList []uint16
+	if c.config.PreferServerCipherSuites {
+		preferenceList = c.config.cipherSuites()
+		supportedList = hs.clientHello.cipherSuites
+	} else {
+		preferenceList = hs.clientHello.cipherSuites
+		supportedList = c.config.cipherSuites()
+	}
+
+	for _, id := range preferenceList {
+		if hs.suite = c.tryCipherSuite(id, supportedList, c.vers, hs.ellipticOk, hs.ecdsaOk); hs.suite != nil {
+			break
+		}
+	}
+
+	if hs.suite == nil {
+		c.sendAlert(alertHandshakeFailure)
+		return false, errors.New("tls: no cipher suite supported by both client and server")
+	}
+
+	// See https://tools.ietf.org/html/draft-ietf-tls-downgrade-scsv-00.
+	for _, id := range hs.clientHello.cipherSuites {
+		if id == TLS_FALLBACK_SCSV {
+			// The client is doing a fallback connection.
+			if hs.clientHello.vers < c.config.MaxVersion {
+				c.sendAlert(alertInappropriateFallback)
+				return false, errors.New("tls: client using inppropriate protocol fallback")
+			}
+			break
+		}
+	}
+
+	return false, nil
+}
+
+// checkForResumption returns true if we should perform resumption on this connection.
+func (hs *serverHandshakeState) checkForResumption() bool {
+	c := hs.c
+
+	if c.config.SessionTicketsDisabled {
+		return false
+	}
+
+	var ok bool
+	if hs.sessionState, ok = c.decryptTicket(hs.clientHello.sessionTicket); !ok {
+		return false
+	}
+
+	if hs.sessionState.vers > hs.clientHello.vers {
+		return false
+	}
+	if vers, ok := c.config.mutualVersion(hs.sessionState.vers); !ok || vers != hs.sessionState.vers {
+		return false
+	}
+
+	cipherSuiteOk := false
+	// Check that the client is still offering the ciphersuite in the session.
+	for _, id := range hs.clientHello.cipherSuites {
+		if id == hs.sessionState.cipherSuite {
+			cipherSuiteOk = true
+			break
+		}
+	}
+	if !cipherSuiteOk {
+		return false
+	}
+
+	// Check that we also support the ciphersuite from the session.
+	hs.suite = c.tryCipherSuite(hs.sessionState.cipherSuite, c.config.cipherSuites(), hs.sessionState.vers, hs.ellipticOk, hs.ecdsaOk)
+	if hs.suite == nil {
+		return false
+	}
+
+	sessionHasClientCerts := len(hs.sessionState.certificates) != 0
+	needClientCerts := c.config.ClientAuth == RequireAnyClientCert || c.config.ClientAuth == RequireAndVerifyClientCert
+	if needClientCerts && !sessionHasClientCerts {
+		return false
+	}
+	if sessionHasClientCerts && c.config.ClientAuth == NoClientCert {
+		return false
+	}
+
+	return true
+}
+
+func (hs *serverHandshakeState) doResumeHandshake() error {
+	c := hs.c
+
+	hs.hello.cipherSuite = hs.suite.id
+	// We echo the client's session ID in the ServerHello to let it know
+	// that we're doing a resumption.
+	hs.hello.sessionId = hs.clientHello.sessionId
+	hs.finishedHash.Write(hs.hello.marshal())
+	c.writeRecord(recordTypeHandshake, hs.hello.marshal())
+
+	if len(hs.sessionState.certificates) > 0 {
+		if _, err := hs.processCertsFromClient(hs.sessionState.certificates); err != nil {
+			return err
+		}
+	}
+
+	hs.masterSecret = hs.sessionState.masterSecret
+
+	return nil
+}
+
+func (hs *serverHandshakeState) doFullHandshake() error {
+	config := hs.c.config
+	c := hs.c
+
+	if hs.clientHello.ocspStapling && len(hs.cert.OCSPStaple) > 0 {
+		hs.hello.ocspStapling = true
+	}
+
+	hs.hello.ticketSupported = hs.clientHello.ticketSupported && !config.SessionTicketsDisabled
+	hs.hello.cipherSuite = hs.suite.id
+	hs.finishedHash.Write(hs.hello.marshal())
+	c.writeRecord(recordTypeHandshake, hs.hello.marshal())
+
+	certMsg := new(certificateMsg)
+	certMsg.certificates = hs.cert.Certificate
+	hs.finishedHash.Write(certMsg.marshal())
+	c.writeRecord(recordTypeHandshake, certMsg.marshal())
+
+	if hs.hello.ocspStapling {
+		certStatus := new(certificateStatusMsg)
+		certStatus.statusType = statusTypeOCSP
+		certStatus.response = hs.cert.OCSPStaple
+		hs.finishedHash.Write(certStatus.marshal())
+		c.writeRecord(recordTypeHandshake, certStatus.marshal())
+	}
+
+	keyAgreement := hs.suite.ka(c.vers)
+	skx, err := keyAgreement.generateServerKeyExchange(config, hs.cert, hs.clientHello, hs.hello)
+	if err != nil {
+		c.sendAlert(alertHandshakeFailure)
+		return err
+	}
+	if skx != nil {
+		hs.finishedHash.Write(skx.marshal())
+		c.writeRecord(recordTypeHandshake, skx.marshal())
+	}
+
+	if config.ClientAuth >= RequestClientCert {
+		// Request a client certificate
+		certReq := new(certificateRequestMsg)
+		certReq.certificateTypes = []byte{
+			byte(certTypeRSASign),
+			byte(certTypeECDSASign),
+		}
+		if c.vers >= VersionTLS12 {
+			certReq.hasSignatureAndHash = true
+			certReq.signatureAndHashes = supportedClientCertSignatureAlgorithms
+		}
+
+		// An empty list of certificateAuthorities signals to
+		// the client that it may send any certificate in response
+		// to our request. When we know the CAs we trust, then
+		// we can send them down, so that the client can choose
+		// an appropriate certificate to give to us.
+		if config.ClientCAs != nil {
+			certReq.certificateAuthorities = config.ClientCAs.Subjects()
+		}
+		hs.finishedHash.Write(certReq.marshal())
+		c.writeRecord(recordTypeHandshake, certReq.marshal())
+	}
+
+	helloDone := new(serverHelloDoneMsg)
+	hs.finishedHash.Write(helloDone.marshal())
+	c.writeRecord(recordTypeHandshake, helloDone.marshal())
+
+	var pub crypto.PublicKey // public key for client auth, if any
+
+	msg, err := c.readHandshake()
+	if err != nil {
+		return err
+	}
+
+	var ok bool
+	// If we requested a client certificate, then the client must send a
+	// certificate message, even if it's empty.
+	if config.ClientAuth >= RequestClientCert {
+		if certMsg, ok = msg.(*certificateMsg); !ok {
+			c.sendAlert(alertUnexpectedMessage)
+			return unexpectedMessageError(certMsg, msg)
+		}
+		hs.finishedHash.Write(certMsg.marshal())
+
+		if len(certMsg.certificates) == 0 {
+			// The client didn't actually send a certificate
+			switch config.ClientAuth {
+			case RequireAnyClientCert, RequireAndVerifyClientCert:
+				c.sendAlert(alertBadCertificate)
+				return errors.New("tls: client didn't provide a certificate")
+			}
+		}
+
+		pub, err = hs.processCertsFromClient(certMsg.certificates)
+		if err != nil {
+			return err
+		}
+
+		msg, err = c.readHandshake()
+		if err != nil {
+			return err
+		}
+	}
+
+	// Get client key exchange
+	ckx, ok := msg.(*clientKeyExchangeMsg)
+	if !ok {
+		c.sendAlert(alertUnexpectedMessage)
+		return unexpectedMessageError(ckx, msg)
+	}
+	hs.finishedHash.Write(ckx.marshal())
+
+	// If we received a client cert in response to our certificate request message,
+	// the client will send us a certificateVerifyMsg immediately after the
+	// clientKeyExchangeMsg.  This message is a digest of all preceding
+	// handshake-layer messages that is signed using the private key corresponding
+	// to the client's certificate. This allows us to verify that the client is in
+	// possession of the private key of the certificate.
+	if len(c.peerCertificates) > 0 {
+		msg, err = c.readHandshake()
+		if err != nil {
+			return err
+		}
+		certVerify, ok := msg.(*certificateVerifyMsg)
+		if !ok {
+			c.sendAlert(alertUnexpectedMessage)
+			return unexpectedMessageError(certVerify, msg)
+		}
+
+		switch key := pub.(type) {
+		case *ecdsa.PublicKey:
+			ecdsaSig := new(ecdsaSignature)
+			if _, err = asn1.Unmarshal(certVerify.signature, ecdsaSig); err != nil {
+				break
+			}
+			if ecdsaSig.R.Sign() <= 0 || ecdsaSig.S.Sign() <= 0 {
+				err = errors.New("ECDSA signature contained zero or negative values")
+				break
+			}
+			digest, _, _ := hs.finishedHash.hashForClientCertificate(signatureECDSA)
+			if !ecdsa.Verify(key, digest, ecdsaSig.R, ecdsaSig.S) {
+				err = errors.New("ECDSA verification failure")
+				break
+			}
+		case *rsa.PublicKey:
+			digest, hashFunc, _ := hs.finishedHash.hashForClientCertificate(signatureRSA)
+			err = rsa.VerifyPKCS1v15(key, hashFunc, digest, certVerify.signature)
+		}
+		if err != nil {
+			c.sendAlert(alertBadCertificate)
+			return errors.New("could not validate signature of connection nonces: " + err.Error())
+		}
+
+		hs.finishedHash.Write(certVerify.marshal())
+	}
+
+	preMasterSecret, err := keyAgreement.processClientKeyExchange(config, hs.cert, ckx, c.vers)
+	if err != nil {
+		c.sendAlert(alertHandshakeFailure)
+		return err
+	}
+	hs.masterSecret = masterFromPreMasterSecret(c.vers, preMasterSecret, hs.clientHello.random, hs.hello.random)
+
+	return nil
+}
+
+func (hs *serverHandshakeState) establishKeys() error {
+	c := hs.c
+
+	clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV :=
+		keysFromMasterSecret(c.vers, hs.masterSecret, hs.clientHello.random, hs.hello.random, hs.suite.macLen, hs.suite.keyLen, hs.suite.ivLen)
+
+	var clientCipher, serverCipher interface{}
+	var clientHash, serverHash macFunction
+
+	if hs.suite.aead == nil {
+		clientCipher = hs.suite.cipher(clientKey, clientIV, true /* for reading */)
+		clientHash = hs.suite.mac(c.vers, clientMAC)
+		serverCipher = hs.suite.cipher(serverKey, serverIV, false /* not for reading */)
+		serverHash = hs.suite.mac(c.vers, serverMAC)
+	} else {
+		clientCipher = hs.suite.aead(clientKey, clientIV)
+		serverCipher = hs.suite.aead(serverKey, serverIV)
+	}
+
+	c.in.prepareCipherSpec(c.vers, clientCipher, clientHash)
+	c.out.prepareCipherSpec(c.vers, serverCipher, serverHash)
+
+	return nil
+}
+
+func (hs *serverHandshakeState) readFinished(out []byte) error {
+	c := hs.c
+
+	c.readRecord(recordTypeChangeCipherSpec)
+	if err := c.in.error(); err != nil {
+		return err
+	}
+
+	if hs.hello.nextProtoNeg {
+		msg, err := c.readHandshake()
+		if err != nil {
+			return err
+		}
+		nextProto, ok := msg.(*nextProtoMsg)
+		if !ok {
+			c.sendAlert(alertUnexpectedMessage)
+			return unexpectedMessageError(nextProto, msg)
+		}
+		hs.finishedHash.Write(nextProto.marshal())
+		c.clientProtocol = nextProto.proto
+	}
+
+	msg, err := c.readHandshake()
+	if err != nil {
+		return err
+	}
+	clientFinished, ok := msg.(*finishedMsg)
+	if !ok {
+		c.sendAlert(alertUnexpectedMessage)
+		return unexpectedMessageError(clientFinished, msg)
+	}
+
+	verify := hs.finishedHash.clientSum(hs.masterSecret)
+	if len(verify) != len(clientFinished.verifyData) ||
+		subtle.ConstantTimeCompare(verify, clientFinished.verifyData) != 1 {
+		c.sendAlert(alertHandshakeFailure)
+		return errors.New("tls: client's Finished message is incorrect")
+	}
+
+	hs.finishedHash.Write(clientFinished.marshal())
+	copy(out, verify)
+	return nil
+}
+
+func (hs *serverHandshakeState) sendSessionTicket() error {
+	if !hs.hello.ticketSupported {
+		return nil
+	}
+
+	c := hs.c
+	m := new(newSessionTicketMsg)
+
+	var err error
+	state := sessionState{
+		vers:         c.vers,
+		cipherSuite:  hs.suite.id,
+		masterSecret: hs.masterSecret,
+		certificates: hs.certsFromClient,
+	}
+	m.ticket, err = c.encryptTicket(&state)
+	if err != nil {
+		return err
+	}
+
+	hs.finishedHash.Write(m.marshal())
+	c.writeRecord(recordTypeHandshake, m.marshal())
+
+	return nil
+}
+
+func (hs *serverHandshakeState) sendFinished(out []byte) error {
+	c := hs.c
+
+	c.writeRecord(recordTypeChangeCipherSpec, []byte{1})
+
+	finished := new(finishedMsg)
+	finished.verifyData = hs.finishedHash.serverSum(hs.masterSecret)
+	hs.finishedHash.Write(finished.marshal())
+	c.writeRecord(recordTypeHandshake, finished.marshal())
+
+	c.cipherSuite = hs.suite.id
+	copy(out, finished.verifyData)
+
+	return nil
+}
+
+// processCertsFromClient takes a chain of client certificates either from a
+// Certificates message or from a sessionState and verifies them. It returns
+// the public key of the leaf certificate.
+func (hs *serverHandshakeState) processCertsFromClient(certificates [][]byte) (crypto.PublicKey, error) {
+	c := hs.c
+
+	hs.certsFromClient = certificates
+	certs := make([]*x509.Certificate, len(certificates))
+	var err error
+	for i, asn1Data := range certificates {
+		if certs[i], err = x509.ParseCertificate(asn1Data); err != nil {
+			c.sendAlert(alertBadCertificate)
+			return nil, errors.New("tls: failed to parse client certificate: " + err.Error())
+		}
+	}
+
+	if c.config.ClientAuth >= VerifyClientCertIfGiven && len(certs) > 0 {
+		opts := x509.VerifyOptions{
+			Roots:         c.config.ClientCAs,
+			CurrentTime:   c.config.time(),
+			Intermediates: x509.NewCertPool(),
+			KeyUsages:     []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth},
+		}
+
+		for _, cert := range certs[1:] {
+			opts.Intermediates.AddCert(cert)
+		}
+
+		chains, err := certs[0].Verify(opts)
+		if err != nil {
+			c.sendAlert(alertBadCertificate)
+			return nil, errors.New("tls: failed to verify client's certificate: " + err.Error())
+		}
+
+		ok := false
+		for _, ku := range certs[0].ExtKeyUsage {
+			if ku == x509.ExtKeyUsageClientAuth {
+				ok = true
+				break
+			}
+		}
+		if !ok {
+			c.sendAlert(alertHandshakeFailure)
+			return nil, errors.New("tls: client's certificate's extended key usage doesn't permit it to be used for client authentication")
+		}
+
+		c.verifiedChains = chains
+	}
+
+	if len(certs) > 0 {
+		var pub crypto.PublicKey
+		switch key := certs[0].PublicKey.(type) {
+		case *ecdsa.PublicKey, *rsa.PublicKey:
+			pub = key
+		default:
+			c.sendAlert(alertUnsupportedCertificate)
+			return nil, fmt.Errorf("tls: client's certificate contains an unsupported public key of type %T", certs[0].PublicKey)
+		}
+		c.peerCertificates = certs
+		return pub, nil
+	}
+
+	return nil, nil
+}
+
+// tryCipherSuite returns a cipherSuite with the given id if that cipher suite
+// is acceptable to use.
+func (c *Conn) tryCipherSuite(id uint16, supportedCipherSuites []uint16, version uint16, ellipticOk, ecdsaOk bool) *cipherSuite {
+	for _, supported := range supportedCipherSuites {
+		if id == supported {
+			var candidate *cipherSuite
+
+			for _, s := range cipherSuites {
+				if s.id == id {
+					candidate = s
+					break
+				}
+			}
+			if candidate == nil {
+				continue
+			}
+			// Don't select a ciphersuite which we can't
+			// support for this client.
+			if (candidate.flags&suiteECDHE != 0) && !ellipticOk {
+				continue
+			}
+			if (candidate.flags&suiteECDSA != 0) != ecdsaOk {
+				continue
+			}
+			if version < VersionTLS12 && candidate.flags&suiteTLS12 != 0 {
+				continue
+			}
+			return candidate
+		}
+	}
+
+	return nil
+}