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vendor.github.com.refraction-networking.utls.handshake_server.go Maven / Gradle / Ivy
// 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"
"errors"
"fmt"
"io"
"sync/atomic"
)
// 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
rsaDecryptOk bool
rsaSignOk bool
sessionState *sessionState
finishedHash finishedHash
masterSecret []byte
cert *Certificate
}
// serverHandshake performs a TLS handshake as a server.
func (c *Conn) serverHandshake() error {
// If this is the first server handshake, we generate a random key to
// encrypt the tickets with.
c.config.serverInitOnce.Do(func() { c.config.serverInit(nil) })
clientHello, err := c.readClientHello()
if err != nil {
return err
}
if c.vers == VersionTLS13 {
hs := serverHandshakeStateTLS13{
c: c,
clientHello: clientHello,
}
return hs.handshake()
}
hs := serverHandshakeState{
c: c,
clientHello: clientHello,
}
return hs.handshake()
}
func (hs *serverHandshakeState) handshake() error {
c := hs.c
if err := hs.processClientHello(); err != nil {
return err
}
// For an overview of TLS handshaking, see RFC 5246, Section 7.3.
c.buffering = true
if hs.checkForResumption() {
// 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
}
// ticketSupported is set in a resumption handshake if the
// ticket from the client was encrypted with an old session
// ticket key and thus a refreshed ticket should be sent.
if hs.hello.ticketSupported {
if err := hs.sendSessionTicket(); err != nil {
return err
}
}
if err := hs.sendFinished(c.serverFinished[:]); err != nil {
return err
}
if _, err := c.flush(); err != nil {
return err
}
c.clientFinishedIsFirst = false
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.pickCipherSuite(); err != nil {
return err
}
if err := hs.doFullHandshake(); err != nil {
return err
}
if err := hs.establishKeys(); err != nil {
return err
}
if err := hs.readFinished(c.clientFinished[:]); err != nil {
return err
}
c.clientFinishedIsFirst = true
c.buffering = true
if err := hs.sendSessionTicket(); err != nil {
return err
}
if err := hs.sendFinished(nil); err != nil {
return err
}
if _, err := c.flush(); err != nil {
return err
}
}
c.ekm = ekmFromMasterSecret(c.vers, hs.suite, hs.masterSecret, hs.clientHello.random, hs.hello.random)
atomic.StoreUint32(&c.handshakeStatus, 1)
return nil
}
// readClientHello reads a ClientHello message and selects the protocol version.
func (c *Conn) readClientHello() (*clientHelloMsg, error) {
msg, err := c.readHandshake()
if err != nil {
return nil, err
}
clientHello, ok := msg.(*clientHelloMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return nil, unexpectedMessageError(clientHello, msg)
}
if c.config.GetConfigForClient != nil {
chi := clientHelloInfo(c, clientHello)
if newConfig, err := c.config.GetConfigForClient(chi); err != nil {
c.sendAlert(alertInternalError)
return nil, err
} else if newConfig != nil {
newConfig.serverInitOnce.Do(func() { newConfig.serverInit(c.config) })
c.config = newConfig
}
}
clientVersions := clientHello.supportedVersions
if len(clientHello.supportedVersions) == 0 {
clientVersions = supportedVersionsFromMax(clientHello.vers)
}
c.vers, ok = c.config.mutualVersion(false, clientVersions)
if !ok {
c.sendAlert(alertProtocolVersion)
return nil, fmt.Errorf("tls: client offered only unsupported versions: %x", clientVersions)
}
c.haveVers = true
c.in.version = c.vers
c.out.version = c.vers
return clientHello, nil
}
func (hs *serverHandshakeState) processClientHello() error {
c := hs.c
hs.hello = new(serverHelloMsg)
hs.hello.vers = c.vers
supportedCurve := false
preferredCurves := c.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 errors.New("tls: client does not support uncompressed connections")
}
hs.hello.random = make([]byte, 32)
serverRandom := hs.hello.random
// Downgrade protection canaries. See RFC 8446, Section 4.1.3.
maxVers := c.config.maxSupportedVersion(false)
if maxVers >= VersionTLS12 && c.vers < maxVers {
if c.vers == VersionTLS12 {
copy(serverRandom[24:], downgradeCanaryTLS12)
} else {
copy(serverRandom[24:], downgradeCanaryTLS11)
}
serverRandom = serverRandom[:24]
}
_, err := io.ReadFull(c.config.rand(), serverRandom)
if err != nil {
c.sendAlert(alertInternalError)
return err
}
if len(hs.clientHello.secureRenegotiation) != 0 {
c.sendAlert(alertHandshakeFailure)
return errors.New("tls: initial handshake had non-empty renegotiation extension")
}
hs.hello.secureRenegotiationSupported = hs.clientHello.secureRenegotiationSupported
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
// c.config.NextProtos is empty. See
// https://golang.org/issue/5445.
if hs.clientHello.nextProtoNeg && len(c.config.NextProtos) > 0 {
hs.hello.nextProtoNeg = true
hs.hello.nextProtos = c.config.NextProtos
}
}
hs.cert, err = c.config.getCertificate(clientHelloInfo(c, hs.clientHello))
if err != nil {
c.sendAlert(alertInternalError)
return err
}
if hs.clientHello.scts {
hs.hello.scts = hs.cert.SignedCertificateTimestamps
}
if priv, ok := hs.cert.PrivateKey.(crypto.Signer); ok {
switch priv.Public().(type) {
case *ecdsa.PublicKey:
hs.ecdsaOk = true
case *rsa.PublicKey:
hs.rsaSignOk = true
default:
c.sendAlert(alertInternalError)
return fmt.Errorf("tls: unsupported signing key type (%T)", priv.Public())
}
}
if priv, ok := hs.cert.PrivateKey.(crypto.Decrypter); ok {
switch priv.Public().(type) {
case *rsa.PublicKey:
hs.rsaDecryptOk = true
default:
c.sendAlert(alertInternalError)
return fmt.Errorf("tls: unsupported decryption key type (%T)", priv.Public())
}
}
return nil
}
func (hs *serverHandshakeState) pickCipherSuite() error {
c := hs.c
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.setCipherSuite(id, supportedList, c.vers) {
break
}
}
if hs.suite == nil {
c.sendAlert(alertHandshakeFailure)
return errors.New("tls: no cipher suite supported by both client and server")
}
for _, id := range hs.clientHello.cipherSuites {
if id == TLS_FALLBACK_SCSV {
// The client is doing a fallback connection. See RFC 7507.
if hs.clientHello.vers < c.config.maxSupportedVersion(false) {
c.sendAlert(alertInappropriateFallback)
return errors.New("tls: client using inappropriate protocol fallback")
}
break
}
}
return nil
}
// checkForResumption reports whether we should perform resumption on this connection.
func (hs *serverHandshakeState) checkForResumption() bool {
c := hs.c
if c.config.SessionTicketsDisabled {
return false
}
plaintext, usedOldKey := c.decryptTicket(hs.clientHello.sessionTicket)
if plaintext == nil {
return false
}
hs.sessionState = &sessionState{usedOldKey: usedOldKey}
ok := hs.sessionState.unmarshal(plaintext)
if !ok {
return false
}
// Never resume a session for a different TLS version.
if c.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.
if !hs.setCipherSuite(hs.sessionState.cipherSuite, c.config.cipherSuites(), hs.sessionState.vers) {
return false
}
sessionHasClientCerts := len(hs.sessionState.certificates) != 0
needClientCerts := requiresClientCert(c.config.ClientAuth)
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.hello.ticketSupported = hs.sessionState.usedOldKey
hs.finishedHash = newFinishedHash(c.vers, hs.suite)
hs.finishedHash.discardHandshakeBuffer()
hs.finishedHash.Write(hs.clientHello.marshal())
hs.finishedHash.Write(hs.hello.marshal())
if _, err := c.writeRecord(recordTypeHandshake, hs.hello.marshal()); err != nil {
return err
}
if err := c.processCertsFromClient(Certificate{
Certificate: hs.sessionState.certificates,
}); err != nil {
return err
}
hs.masterSecret = hs.sessionState.masterSecret
return nil
}
func (hs *serverHandshakeState) doFullHandshake() error {
c := hs.c
if hs.clientHello.ocspStapling && len(hs.cert.OCSPStaple) > 0 {
hs.hello.ocspStapling = true
}
hs.hello.ticketSupported = hs.clientHello.ticketSupported && !c.config.SessionTicketsDisabled
hs.hello.cipherSuite = hs.suite.id
hs.finishedHash = newFinishedHash(hs.c.vers, hs.suite)
if c.config.ClientAuth == NoClientCert {
// No need to keep a full record of the handshake if client
// certificates won't be used.
hs.finishedHash.discardHandshakeBuffer()
}
hs.finishedHash.Write(hs.clientHello.marshal())
hs.finishedHash.Write(hs.hello.marshal())
if _, err := c.writeRecord(recordTypeHandshake, hs.hello.marshal()); err != nil {
return err
}
certMsg := new(certificateMsg)
certMsg.certificates = hs.cert.Certificate
hs.finishedHash.Write(certMsg.marshal())
if _, err := c.writeRecord(recordTypeHandshake, certMsg.marshal()); err != nil {
return err
}
if hs.hello.ocspStapling {
certStatus := new(certificateStatusMsg)
certStatus.response = hs.cert.OCSPStaple
hs.finishedHash.Write(certStatus.marshal())
if _, err := c.writeRecord(recordTypeHandshake, certStatus.marshal()); err != nil {
return err
}
}
keyAgreement := hs.suite.ka(c.vers)
skx, err := keyAgreement.generateServerKeyExchange(c.config, hs.cert, hs.clientHello, hs.hello)
if err != nil {
c.sendAlert(alertHandshakeFailure)
return err
}
if skx != nil {
hs.finishedHash.Write(skx.marshal())
if _, err := c.writeRecord(recordTypeHandshake, skx.marshal()); err != nil {
return err
}
}
if c.config.ClientAuth >= RequestClientCert {
// Request a client certificate
certReq := new(certificateRequestMsg)
certReq.certificateTypes = []byte{
byte(certTypeRSASign),
byte(certTypeECDSASign),
}
if c.vers >= VersionTLS12 {
certReq.hasSignatureAlgorithm = true
certReq.supportedSignatureAlgorithms = supportedSignatureAlgorithms
}
// 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 c.config.ClientCAs != nil {
certReq.certificateAuthorities = c.config.ClientCAs.Subjects()
}
hs.finishedHash.Write(certReq.marshal())
if _, err := c.writeRecord(recordTypeHandshake, certReq.marshal()); err != nil {
return err
}
}
helloDone := new(serverHelloDoneMsg)
hs.finishedHash.Write(helloDone.marshal())
if _, err := c.writeRecord(recordTypeHandshake, helloDone.marshal()); err != nil {
return err
}
if _, err := c.flush(); err != nil {
return err
}
var pub crypto.PublicKey // public key for client auth, if any
msg, err := c.readHandshake()
if err != nil {
return err
}
// If we requested a client certificate, then the client must send a
// certificate message, even if it's empty.
if c.config.ClientAuth >= RequestClientCert {
certMsg, ok := msg.(*certificateMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(certMsg, msg)
}
hs.finishedHash.Write(certMsg.marshal())
if err := c.processCertsFromClient(Certificate{
Certificate: certMsg.certificates,
}); err != nil {
return err
}
if len(certMsg.certificates) != 0 {
pub = c.peerCertificates[0].PublicKey
}
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())
preMasterSecret, err := keyAgreement.processClientKeyExchange(c.config, hs.cert, ckx, c.vers)
if err != nil {
c.sendAlert(alertHandshakeFailure)
return err
}
hs.masterSecret = masterFromPreMasterSecret(c.vers, hs.suite, preMasterSecret, hs.clientHello.random, hs.hello.random)
if err := c.config.writeKeyLog(keyLogLabelTLS12, hs.clientHello.random, hs.masterSecret); err != nil {
c.sendAlert(alertInternalError)
return err
}
// 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)
}
// Determine the signature type.
_, sigType, hashFunc, err := pickSignatureAlgorithm(pub, []SignatureScheme{certVerify.signatureAlgorithm}, supportedSignatureAlgorithms, c.vers)
if err != nil {
c.sendAlert(alertIllegalParameter)
return err
}
var digest []byte
if digest, err = hs.finishedHash.hashForClientCertificate(sigType, hashFunc, hs.masterSecret); err == nil {
err = verifyHandshakeSignature(sigType, pub, hashFunc, digest, certVerify.signature)
}
if err != nil {
c.sendAlert(alertBadCertificate)
return errors.New("tls: could not validate signature of connection nonces: " + err.Error())
}
hs.finishedHash.Write(certVerify.marshal())
}
hs.finishedHash.discardHandshakeBuffer()
return nil
}
func (hs *serverHandshakeState) establishKeys() error {
c := hs.c
clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV :=
keysFromMasterSecret(c.vers, hs.suite, 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
if err := c.readChangeCipherSpec(); 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 certsFromClient [][]byte
for _, cert := range c.peerCertificates {
certsFromClient = append(certsFromClient, cert.Raw)
}
state := sessionState{
vers: c.vers,
cipherSuite: hs.suite.id,
masterSecret: hs.masterSecret,
certificates: certsFromClient,
}
var err error
m.ticket, err = c.encryptTicket(state.marshal())
if err != nil {
return err
}
hs.finishedHash.Write(m.marshal())
if _, err := c.writeRecord(recordTypeHandshake, m.marshal()); err != nil {
return err
}
return nil
}
func (hs *serverHandshakeState) sendFinished(out []byte) error {
c := hs.c
if _, err := c.writeRecord(recordTypeChangeCipherSpec, []byte{1}); err != nil {
return err
}
finished := new(finishedMsg)
finished.verifyData = hs.finishedHash.serverSum(hs.masterSecret)
hs.finishedHash.Write(finished.marshal())
if _, err := c.writeRecord(recordTypeHandshake, finished.marshal()); err != nil {
return err
}
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 (c *Conn) processCertsFromClient(certificate Certificate) error {
certificates := certificate.Certificate
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 errors.New("tls: failed to parse client certificate: " + err.Error())
}
}
if len(certs) == 0 && requiresClientCert(c.config.ClientAuth) {
c.sendAlert(alertBadCertificate)
return errors.New("tls: client didn't provide a certificate")
}
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 errors.New("tls: failed to verify client's certificate: " + err.Error())
}
c.verifiedChains = chains
}
if c.config.VerifyPeerCertificate != nil {
if err := c.config.VerifyPeerCertificate(certificates, c.verifiedChains); err != nil {
c.sendAlert(alertBadCertificate)
return err
}
}
if len(certs) == 0 {
return nil
}
switch certs[0].PublicKey.(type) {
case *ecdsa.PublicKey, *rsa.PublicKey:
default:
c.sendAlert(alertUnsupportedCertificate)
return fmt.Errorf("tls: client's certificate contains an unsupported public key of type %T", certs[0].PublicKey)
}
c.peerCertificates = certs
c.ocspResponse = certificate.OCSPStaple
c.scts = certificate.SignedCertificateTimestamps
return nil
}
// setCipherSuite sets a cipherSuite with the given id as the serverHandshakeState
// suite if that cipher suite is acceptable to use.
// It returns a bool indicating if the suite was set.
func (hs *serverHandshakeState) setCipherSuite(id uint16, supportedCipherSuites []uint16, version uint16) bool {
for _, supported := range supportedCipherSuites {
if id == supported {
candidate := cipherSuiteByID(id)
if candidate == nil {
continue
}
// Don't select a ciphersuite which we can't
// support for this client.
if candidate.flags&suiteECDHE != 0 {
if !hs.ellipticOk {
continue
}
if candidate.flags&suiteECDSA != 0 {
if !hs.ecdsaOk {
continue
}
} else if !hs.rsaSignOk {
continue
}
} else if !hs.rsaDecryptOk {
continue
}
if version < VersionTLS12 && candidate.flags&suiteTLS12 != 0 {
continue
}
hs.suite = candidate
return true
}
}
return false
}
func clientHelloInfo(c *Conn, clientHello *clientHelloMsg) *ClientHelloInfo {
supportedVersions := clientHello.supportedVersions
if len(clientHello.supportedVersions) == 0 {
supportedVersions = supportedVersionsFromMax(clientHello.vers)
}
return &ClientHelloInfo{
CipherSuites: clientHello.cipherSuites,
ServerName: clientHello.serverName,
SupportedCurves: clientHello.supportedCurves,
SupportedPoints: clientHello.supportedPoints,
SignatureSchemes: clientHello.supportedSignatureAlgorithms,
SupportedProtos: clientHello.alpnProtocols,
SupportedVersions: supportedVersions,
Conn: c.conn,
}
}
