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747 |
jeremybenn |
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package tls
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import (
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"crypto"
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"crypto/rsa"
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"crypto/subtle"
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"crypto/x509"
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"errors"
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"io"
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)
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func (c *Conn) serverHandshake() error {
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config := c.config
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msg, err := c.readHandshake()
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if err != nil {
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return err
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}
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clientHello, ok := msg.(*clientHelloMsg)
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if !ok {
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return c.sendAlert(alertUnexpectedMessage)
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}
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vers, ok := mutualVersion(clientHello.vers)
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if !ok {
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return c.sendAlert(alertProtocolVersion)
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}
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c.vers = vers
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c.haveVers = true
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finishedHash := newFinishedHash(vers)
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finishedHash.Write(clientHello.marshal())
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hello := new(serverHelloMsg)
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supportedCurve := false
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Curves:
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for _, curve := range clientHello.supportedCurves {
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switch curve {
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case curveP256, curveP384, curveP521:
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supportedCurve = true
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break Curves
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}
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}
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supportedPointFormat := false
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for _, pointFormat := range clientHello.supportedPoints {
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if pointFormat == pointFormatUncompressed {
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supportedPointFormat = true
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break
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}
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}
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ellipticOk := supportedCurve && supportedPointFormat
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var suite *cipherSuite
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FindCipherSuite:
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for _, id := range clientHello.cipherSuites {
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for _, supported := range config.cipherSuites() {
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if id == supported {
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suite = nil
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for _, s := range cipherSuites {
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if s.id == id {
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suite = s
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break
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}
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}
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if suite == nil {
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continue
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}
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// Don't select a ciphersuite which we can't
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// support for this client.
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if suite.elliptic && !ellipticOk {
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continue
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}
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break FindCipherSuite
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}
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}
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}
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foundCompression := false
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// We only support null compression, so check that the client offered it.
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for _, compression := range clientHello.compressionMethods {
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if compression == compressionNone {
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foundCompression = true
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break
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}
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}
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if suite == nil || !foundCompression {
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return c.sendAlert(alertHandshakeFailure)
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}
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hello.vers = vers
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hello.cipherSuite = suite.id
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t := uint32(config.time().Unix())
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hello.random = make([]byte, 32)
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hello.random[0] = byte(t >> 24)
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hello.random[1] = byte(t >> 16)
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hello.random[2] = byte(t >> 8)
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hello.random[3] = byte(t)
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_, err = io.ReadFull(config.rand(), hello.random[4:])
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if err != nil {
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return c.sendAlert(alertInternalError)
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}
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hello.compressionMethod = compressionNone
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if clientHello.nextProtoNeg {
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hello.nextProtoNeg = true
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hello.nextProtos = config.NextProtos
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}
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if clientHello.ocspStapling && len(config.Certificates[0].OCSPStaple) > 0 {
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hello.ocspStapling = true
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}
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finishedHash.Write(hello.marshal())
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c.writeRecord(recordTypeHandshake, hello.marshal())
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if len(config.Certificates) == 0 {
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return c.sendAlert(alertInternalError)
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}
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certMsg := new(certificateMsg)
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if len(clientHello.serverName) > 0 {
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c.serverName = clientHello.serverName
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certMsg.certificates = config.getCertificateForName(clientHello.serverName).Certificate
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} else {
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certMsg.certificates = config.Certificates[0].Certificate
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}
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finishedHash.Write(certMsg.marshal())
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c.writeRecord(recordTypeHandshake, certMsg.marshal())
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if hello.ocspStapling {
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certStatus := new(certificateStatusMsg)
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certStatus.statusType = statusTypeOCSP
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certStatus.response = config.Certificates[0].OCSPStaple
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finishedHash.Write(certStatus.marshal())
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c.writeRecord(recordTypeHandshake, certStatus.marshal())
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}
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keyAgreement := suite.ka()
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skx, err := keyAgreement.generateServerKeyExchange(config, clientHello, hello)
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if err != nil {
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c.sendAlert(alertHandshakeFailure)
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return err
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}
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if skx != nil {
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finishedHash.Write(skx.marshal())
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c.writeRecord(recordTypeHandshake, skx.marshal())
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}
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if config.ClientAuth >= RequestClientCert {
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// Request a client certificate
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certReq := new(certificateRequestMsg)
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certReq.certificateTypes = []byte{certTypeRSASign}
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// An empty list of certificateAuthorities signals to
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// the client that it may send any certificate in response
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// to our request. When we know the CAs we trust, then
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// we can send them down, so that the client can choose
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// an appropriate certificate to give to us.
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if config.ClientCAs != nil {
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certReq.certificateAuthorities = config.ClientCAs.Subjects()
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}
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finishedHash.Write(certReq.marshal())
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c.writeRecord(recordTypeHandshake, certReq.marshal())
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}
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helloDone := new(serverHelloDoneMsg)
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finishedHash.Write(helloDone.marshal())
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c.writeRecord(recordTypeHandshake, helloDone.marshal())
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var pub *rsa.PublicKey // public key for client auth, if any
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msg, err = c.readHandshake()
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if err != nil {
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return err
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}
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// If we requested a client certificate, then the client must send a
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// certificate message, even if it's empty.
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if config.ClientAuth >= RequestClientCert {
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if certMsg, ok = msg.(*certificateMsg); !ok {
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return c.sendAlert(alertHandshakeFailure)
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}
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finishedHash.Write(certMsg.marshal())
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if len(certMsg.certificates) == 0 {
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// The client didn't actually send a certificate
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switch config.ClientAuth {
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case RequireAnyClientCert, RequireAndVerifyClientCert:
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c.sendAlert(alertBadCertificate)
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return errors.New("tls: client didn't provide a certificate")
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}
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}
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certs := make([]*x509.Certificate, len(certMsg.certificates))
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for i, asn1Data := range certMsg.certificates {
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if certs[i], err = x509.ParseCertificate(asn1Data); err != nil {
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c.sendAlert(alertBadCertificate)
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return errors.New("tls: failed to parse client certificate: " + err.Error())
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}
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}
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if c.config.ClientAuth >= VerifyClientCertIfGiven && len(certs) > 0 {
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opts := x509.VerifyOptions{
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Roots: c.config.ClientCAs,
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CurrentTime: c.config.time(),
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Intermediates: x509.NewCertPool(),
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}
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for i, cert := range certs {
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if i == 0 {
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continue
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}
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opts.Intermediates.AddCert(cert)
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}
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chains, err := certs[0].Verify(opts)
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if err != nil {
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c.sendAlert(alertBadCertificate)
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return errors.New("tls: failed to verify client's certificate: " + err.Error())
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}
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ok := false
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for _, ku := range certs[0].ExtKeyUsage {
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if ku == x509.ExtKeyUsageClientAuth {
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ok = true
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break
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}
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}
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if !ok {
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c.sendAlert(alertHandshakeFailure)
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return errors.New("tls: client's certificate's extended key usage doesn't permit it to be used for client authentication")
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}
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c.verifiedChains = chains
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}
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if len(certs) > 0 {
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if pub, ok = certs[0].PublicKey.(*rsa.PublicKey); !ok {
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return c.sendAlert(alertUnsupportedCertificate)
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}
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c.peerCertificates = certs
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}
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msg, err = c.readHandshake()
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if err != nil {
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return err
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}
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}
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// Get client key exchange
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ckx, ok := msg.(*clientKeyExchangeMsg)
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if !ok {
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return c.sendAlert(alertUnexpectedMessage)
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}
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finishedHash.Write(ckx.marshal())
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// If we received a client cert in response to our certificate request message,
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// the client will send us a certificateVerifyMsg immediately after the
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// clientKeyExchangeMsg. This message is a MD5SHA1 digest of all preceding
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// handshake-layer messages that is signed using the private key corresponding
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// to the client's certificate. This allows us to verify that the client is in
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// possession of the private key of the certificate.
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if len(c.peerCertificates) > 0 {
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msg, err = c.readHandshake()
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if err != nil {
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return err
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}
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certVerify, ok := msg.(*certificateVerifyMsg)
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if !ok {
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return c.sendAlert(alertUnexpectedMessage)
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}
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| 277 |
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digest := make([]byte, 0, 36)
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digest = finishedHash.serverMD5.Sum(digest)
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digest = finishedHash.serverSHA1.Sum(digest)
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err = rsa.VerifyPKCS1v15(pub, crypto.MD5SHA1, digest, certVerify.signature)
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if err != nil {
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c.sendAlert(alertBadCertificate)
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return errors.New("could not validate signature of connection nonces: " + err.Error())
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| 284 |
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}
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| 285 |
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| 286 |
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finishedHash.Write(certVerify.marshal())
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| 287 |
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}
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| 288 |
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| 289 |
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preMasterSecret, err := keyAgreement.processClientKeyExchange(config, ckx, c.vers)
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| 290 |
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if err != nil {
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| 291 |
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c.sendAlert(alertHandshakeFailure)
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| 292 |
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return err
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| 293 |
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}
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| 294 |
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| 295 |
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masterSecret, clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV :=
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| 296 |
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keysFromPreMasterSecret(c.vers, preMasterSecret, clientHello.random, hello.random, suite.macLen, suite.keyLen, suite.ivLen)
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| 297 |
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| 298 |
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clientCipher := suite.cipher(clientKey, clientIV, true /* for reading */ )
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| 299 |
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clientHash := suite.mac(c.vers, clientMAC)
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| 300 |
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c.in.prepareCipherSpec(c.vers, clientCipher, clientHash)
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| 301 |
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c.readRecord(recordTypeChangeCipherSpec)
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| 302 |
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if err := c.error(); err != nil {
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| 303 |
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return err
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| 304 |
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}
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| 305 |
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| 306 |
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if hello.nextProtoNeg {
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| 307 |
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msg, err = c.readHandshake()
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| 308 |
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if err != nil {
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| 309 |
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return err
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| 310 |
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}
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| 311 |
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nextProto, ok := msg.(*nextProtoMsg)
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| 312 |
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if !ok {
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| 313 |
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return c.sendAlert(alertUnexpectedMessage)
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| 314 |
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}
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| 315 |
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finishedHash.Write(nextProto.marshal())
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| 316 |
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c.clientProtocol = nextProto.proto
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| 317 |
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}
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| 318 |
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| 319 |
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msg, err = c.readHandshake()
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| 320 |
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if err != nil {
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| 321 |
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return err
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| 322 |
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}
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| 323 |
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clientFinished, ok := msg.(*finishedMsg)
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| 324 |
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if !ok {
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| 325 |
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return c.sendAlert(alertUnexpectedMessage)
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| 326 |
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}
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| 327 |
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| 328 |
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verify := finishedHash.clientSum(masterSecret)
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| 329 |
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if len(verify) != len(clientFinished.verifyData) ||
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| 330 |
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subtle.ConstantTimeCompare(verify, clientFinished.verifyData) != 1 {
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| 331 |
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return c.sendAlert(alertHandshakeFailure)
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| 332 |
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}
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| 333 |
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| 334 |
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finishedHash.Write(clientFinished.marshal())
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| 335 |
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| 336 |
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serverCipher := suite.cipher(serverKey, serverIV, false /* not for reading */ )
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| 337 |
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serverHash := suite.mac(c.vers, serverMAC)
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| 338 |
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c.out.prepareCipherSpec(c.vers, serverCipher, serverHash)
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| 339 |
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c.writeRecord(recordTypeChangeCipherSpec, []byte{1})
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| 340 |
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| 341 |
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finished := new(finishedMsg)
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| 342 |
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finished.verifyData = finishedHash.serverSum(masterSecret)
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| 343 |
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c.writeRecord(recordTypeHandshake, finished.marshal())
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| 344 |
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| 345 |
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c.handshakeComplete = true
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| 346 |
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c.cipherSuite = suite.id
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| 347 |
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| 348 |
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return nil
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| 349 |
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}
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