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// 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 (
"bytes"
"crypto"
"crypto/ecdsa"
"crypto/rsa"
"crypto/subtle"
"crypto/x509"
"errors"
"fmt"
"io"
"net"
"strconv"
"strings"
"sync/atomic"
"time"
)
type clientHandshakeState struct {
c *Conn
serverHello *serverHelloMsg
hello *clientHelloMsg
suite *cipherSuite
finishedHash finishedHash
masterSecret []byte
session *ClientSessionState
}
func (c *Conn) makeClientHello() (*clientHelloMsg, ecdheParameters, error) {
config := c.config
if len(config.ServerName) == 0 && !config.InsecureSkipVerify {
return nil, nil, errors.New("tls: either ServerName or InsecureSkipVerify must be specified in the tls.Config")
}
nextProtosLength := 0
for _, proto := range config.NextProtos {
if l := len(proto); l == 0 || l > 255 {
return nil, nil, errors.New("tls: invalid NextProtos value")
} else {
nextProtosLength += 1 + l
}
}
if nextProtosLength > 0xffff {
return nil, nil, errors.New("tls: NextProtos values too large")
}
supportedVersions := config.supportedVersions(true)
if len(supportedVersions) == 0 {
return nil, nil, errors.New("tls: no supported versions satisfy MinVersion and MaxVersion")
}
clientHelloVersion := supportedVersions[0]
// The version at the beginning of the ClientHello was capped at TLS 1.2
// for compatibility reasons. The supported_versions extension is used
// to negotiate versions now. See RFC 8446, Section 4.2.1.
if clientHelloVersion > VersionTLS12 {
clientHelloVersion = VersionTLS12
}
hello := &clientHelloMsg{
vers: clientHelloVersion,
compressionMethods: []uint8{compressionNone},
random: make([]byte, 32),
sessionId: make([]byte, 32),
ocspStapling: true,
scts: true,
serverName: hostnameInSNI(config.ServerName),
supportedCurves: config.curvePreferences(),
supportedPoints: []uint8{pointFormatUncompressed},
nextProtoNeg: len(config.NextProtos) > 0,
secureRenegotiationSupported: true,
alpnProtocols: config.NextProtos,
supportedVersions: supportedVersions,
}
if c.handshakes > 0 {
hello.secureRenegotiation = c.clientFinished[:]
}
possibleCipherSuites := config.cipherSuites()
hello.cipherSuites = make([]uint16, 0, len(possibleCipherSuites))
NextCipherSuite:
for _, suiteId := range possibleCipherSuites {
for _, suite := range cipherSuites {
if suite.id != suiteId {
continue
}
// Don't advertise TLS 1.2-only cipher suites unless
// we're attempting TLS 1.2.
if hello.vers < VersionTLS12 && suite.flags&suiteTLS12 != 0 {
continue
}
hello.cipherSuites = append(hello.cipherSuites, suiteId)
continue NextCipherSuite
}
}
_, err := io.ReadFull(config.rand(), hello.random)
if err != nil {
return nil, nil, errors.New("tls: short read from Rand: " + err.Error())
}
// A random session ID is used to detect when the server accepted a ticket
// and is resuming a session (see RFC 5077). In TLS 1.3, it's always set as
// a compatibility measure (see RFC 8446, Section 4.1.2).
if _, err := io.ReadFull(config.rand(), hello.sessionId); err != nil {
return nil, nil, errors.New("tls: short read from Rand: " + err.Error())
}
if hello.vers >= VersionTLS12 {
hello.supportedSignatureAlgorithms = supportedSignatureAlgorithms
}
var params ecdheParameters
if hello.supportedVersions[0] == VersionTLS13 {
hello.cipherSuites = append(hello.cipherSuites, defaultCipherSuitesTLS13()...)
curveID := config.curvePreferences()[0]
if _, ok := curveForCurveID(curveID); curveID != X25519 && !ok {
return nil, nil, errors.New("tls: CurvePreferences includes unsupported curve")
}
params, err = generateECDHEParameters(config.rand(), curveID)
if err != nil {
return nil, nil, err
}
hello.keyShares = []keyShare{{group: curveID, data: params.PublicKey()}}
}
return hello, params, nil
}
func (c *Conn) clientHandshake() (err error) {
if c.config == nil {
c.config = defaultConfig()
}
// This may be a renegotiation handshake, in which case some fields
// need to be reset.
c.didResume = false
hello, ecdheParams, err := c.makeClientHello()
if err != nil {
return err
}
cacheKey, session, earlySecret, binderKey := c.loadSession(hello)
if cacheKey != "" && session != nil {
defer func() {
// If we got a handshake failure when resuming a session, throw away
// the session ticket. See RFC 5077, Section 3.2.
//
// RFC 8446 makes no mention of dropping tickets on failure, but it
// does require servers to abort on invalid binders, so we need to
// delete tickets to recover from a corrupted PSK.
if err != nil {
c.config.ClientSessionCache.Put(cacheKey, nil)
}
}()
}
if _, err := c.writeRecord(recordTypeHandshake, hello.marshal()); err != nil {
return err
}
msg, err := c.readHandshake()
if err != nil {
return err
}
serverHello, ok := msg.(*serverHelloMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(serverHello, msg)
}
if err := c.pickTLSVersion(serverHello); err != nil {
return err
}
if c.vers == VersionTLS13 {
hs := &clientHandshakeStateTLS13{
c: c,
serverHello: serverHello,
hello: hello,
ecdheParams: ecdheParams,
session: session,
earlySecret: earlySecret,
binderKey: binderKey,
}
// In TLS 1.3, session tickets are delivered after the handshake.
return hs.handshake()
}
hs := &clientHandshakeState{
c: c,
serverHello: serverHello,
hello: hello,
session: session,
}
if err := hs.handshake(); err != nil {
return err
}
// If we had a successful handshake and hs.session is different from
// the one already cached - cache a new one.
if cacheKey != "" && hs.session != nil && session != hs.session {
c.config.ClientSessionCache.Put(cacheKey, hs.session)
}
return nil
}
func (c *Conn) loadSession(hello *clientHelloMsg) (cacheKey string,
session *ClientSessionState, earlySecret, binderKey []byte) {
if c.config.SessionTicketsDisabled || c.config.ClientSessionCache == nil {
return "", nil, nil, nil
}
hello.ticketSupported = true
if hello.supportedVersions[0] == VersionTLS13 {
// Require DHE on resumption as it guarantees forward secrecy against
// compromise of the session ticket key. See RFC 8446, Section 4.2.9.
hello.pskModes = []uint8{pskModeDHE}
}
// Session resumption is not allowed if renegotiating because
// renegotiation is primarily used to allow a client to send a client
// certificate, which would be skipped if session resumption occurred.
if c.handshakes != 0 {
return "", nil, nil, nil
}
// Try to resume a previously negotiated TLS session, if available.
cacheKey = clientSessionCacheKey(c.conn.RemoteAddr(), c.config)
session, ok := c.config.ClientSessionCache.Get(cacheKey)
if !ok || session == nil {
return cacheKey, nil, nil, nil
}
// Check that version used for the previous session is still valid.
versOk := false
for _, v := range hello.supportedVersions {
if v == session.vers {
versOk = true
break
}
}
if !versOk {
return cacheKey, nil, nil, nil
}
// Check that the cached server certificate is not expired, and that it's
// valid for the ServerName. This should be ensured by the cache key, but
// protect the application from a faulty ClientSessionCache implementation.
if !c.config.InsecureSkipVerify {
if len(session.verifiedChains) == 0 {
// The original connection had InsecureSkipVerify, while this doesn't.
return cacheKey, nil, nil, nil
}
serverCert := session.serverCertificates[0]
if c.config.time().After(serverCert.NotAfter) {
// Expired certificate, delete the entry.
c.config.ClientSessionCache.Put(cacheKey, nil)
return cacheKey, nil, nil, nil
}
if err := serverCert.VerifyHostname(c.config.ServerName); err != nil {
return cacheKey, nil, nil, nil
}
}
if session.vers != VersionTLS13 {
// In TLS 1.2 the cipher suite must match the resumed session. Ensure we
// are still offering it.
if mutualCipherSuite(hello.cipherSuites, session.cipherSuite) == nil {
return cacheKey, nil, nil, nil
}
hello.sessionTicket = session.sessionTicket
return
}
// Check that the session ticket is not expired.
if c.config.time().After(session.useBy) {
c.config.ClientSessionCache.Put(cacheKey, nil)
return cacheKey, nil, nil, nil
}
// In TLS 1.3 the KDF hash must match the resumed session. Ensure we
// offer at least one cipher suite with that hash.
cipherSuite := cipherSuiteTLS13ByID(session.cipherSuite)
if cipherSuite == nil {
return cacheKey, nil, nil, nil
}
cipherSuiteOk := false
for _, offeredID := range hello.cipherSuites {
offeredSuite := cipherSuiteTLS13ByID(offeredID)
if offeredSuite != nil && offeredSuite.hash == cipherSuite.hash {
cipherSuiteOk = true
break
}
}
if !cipherSuiteOk {
return cacheKey, nil, nil, nil
}
// Set the pre_shared_key extension. See RFC 8446, Section 4.2.11.1.
ticketAge := uint32(c.config.time().Sub(session.receivedAt) / time.Millisecond)
identity := pskIdentity{
label: session.sessionTicket,
obfuscatedTicketAge: ticketAge + session.ageAdd,
}
hello.pskIdentities = []pskIdentity{identity}
hello.pskBinders = [][]byte{make([]byte, cipherSuite.hash.Size())}
// Compute the PSK binders. See RFC 8446, Section 4.2.11.2.
psk := cipherSuite.expandLabel(session.masterSecret, "resumption",
session.nonce, cipherSuite.hash.Size())
earlySecret = cipherSuite.extract(psk, nil)
binderKey = cipherSuite.deriveSecret(earlySecret, resumptionBinderLabel, nil)
transcript := cipherSuite.hash.New()
transcript.Write(hello.marshalWithoutBinders())
pskBinders := [][]byte{cipherSuite.finishedHash(binderKey, transcript)}
hello.updateBinders(pskBinders)
return
}
func (c *Conn) pickTLSVersion(serverHello *serverHelloMsg) error {
peerVersion := serverHello.vers
if serverHello.supportedVersion != 0 {
peerVersion = serverHello.supportedVersion
}
vers, ok := c.config.mutualVersion(true, []uint16{peerVersion})
if !ok {
c.sendAlert(alertProtocolVersion)
return fmt.Errorf("tls: server selected unsupported protocol version %x", peerVersion)
}
c.vers = vers
c.haveVers = true
c.in.version = vers
c.out.version = vers
return nil
}
// Does the handshake, either a full one or resumes old session. Requires hs.c,
// hs.hello, hs.serverHello, and, optionally, hs.session to be set.
func (hs *clientHandshakeState) handshake() error {
c := hs.c
isResume, err := hs.processServerHello()
if err != nil {
return err
}
hs.finishedHash = newFinishedHash(c.vers, hs.suite)
// No signatures of the handshake are needed in a resumption.
// Otherwise, in a full handshake, if we don't have any certificates
// configured then we will never send a CertificateVerify message and
// thus no signatures are needed in that case either.
if isResume || (len(c.config.Certificates) == 0 && c.config.GetClientCertificate == nil) {
hs.finishedHash.discardHandshakeBuffer()
}
hs.finishedHash.Write(hs.hello.marshal())
hs.finishedHash.Write(hs.serverHello.marshal())
c.buffering = true
if isResume {
if err := hs.establishKeys(); err != nil {
return err
}
if err := hs.readSessionTicket(); err != nil {
return err
}
if err := hs.readFinished(c.serverFinished[:]); err != nil {
return err
}
c.clientFinishedIsFirst = false
if err := hs.sendFinished(c.clientFinished[:]); err != nil {
return err
}
if _, err := c.flush(); err != nil {
return err
}
} else {
if err := hs.doFullHandshake(); err != nil {
return err
}
if err := hs.establishKeys(); err != nil {
return err
}
if err := hs.sendFinished(c.clientFinished[:]); err != nil {
return err
}
if _, err := c.flush(); err != nil {
return err
}
c.clientFinishedIsFirst = true
if err := hs.readSessionTicket(); err != nil {
return err
}
if err := hs.readFinished(c.serverFinished[:]); err != nil {
return err
}
}
c.ekm = ekmFromMasterSecret(c.vers, hs.suite, hs.masterSecret, hs.hello.random, hs.serverHello.random)
c.didResume = isResume
atomic.StoreUint32(&c.handshakeStatus, 1)
return nil
}
func (hs *clientHandshakeState) pickCipherSuite() error {
if hs.suite = mutualCipherSuite(hs.hello.cipherSuites, hs.serverHello.cipherSuite); hs.suite == nil {
hs.c.sendAlert(alertHandshakeFailure)
return errors.New("tls: server chose an unconfigured cipher suite")
}
hs.c.cipherSuite = hs.suite.id
return nil
}
func (hs *clientHandshakeState) doFullHandshake() error {
c := hs.c
msg, err := c.readHandshake()
if err != nil {
return err
}
certMsg, ok := msg.(*certificateMsg)
if !ok || len(certMsg.certificates) == 0 {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(certMsg, msg)
}
hs.finishedHash.Write(certMsg.marshal())
if c.handshakes == 0 {
// If this is the first handshake on a connection, process and
// (optionally) verify the server's certificates.
if err := c.verifyServerCertificate(certMsg.certificates); err != nil {
return err
}
} else {
// This is a renegotiation handshake. We require that the
// server's identity (i.e. leaf certificate) is unchanged and
// thus any previous trust decision is still valid.
//
// See https://mitls.org/pages/attacks/3SHAKE for the
// motivation behind this requirement.
if !bytes.Equal(c.peerCertificates[0].Raw, certMsg.certificates[0]) {
c.sendAlert(alertBadCertificate)
return errors.New("tls: server's identity changed during renegotiation")
}
}
msg, err = c.readHandshake()
if err != nil {
return err
}
cs, ok := msg.(*certificateStatusMsg)
if ok {
// RFC4366 on Certificate Status Request:
// The server MAY return a "certificate_status" message.
if !hs.serverHello.ocspStapling {
// If a server returns a "CertificateStatus" message, then the
// server MUST have included an extension of type "status_request"
// with empty "extension_data" in the extended server hello.
c.sendAlert(alertUnexpectedMessage)
return errors.New("tls: received unexpected CertificateStatus message")
}
hs.finishedHash.Write(cs.marshal())
c.ocspResponse = cs.response
msg, err = c.readHandshake()
if err != nil {
return err
}
}
keyAgreement := hs.suite.ka(c.vers)
skx, ok := msg.(*serverKeyExchangeMsg)
if ok {
hs.finishedHash.Write(skx.marshal())
err = keyAgreement.processServerKeyExchange(c.config, hs.hello, hs.serverHello, c.peerCertificates[0], skx)
if err != nil {
c.sendAlert(alertUnexpectedMessage)
return err
}
msg, err = c.readHandshake()
if err != nil {
return err
}
}
var chainToSend *Certificate
var certRequested bool
certReq, ok := msg.(*certificateRequestMsg)
if ok {
certRequested = true
hs.finishedHash.Write(certReq.marshal())
cri := certificateRequestInfoFromMsg(certReq)
if chainToSend, err = c.getClientCertificate(cri); err != nil {
c.sendAlert(alertInternalError)
return err
}
msg, err = c.readHandshake()
if err != nil {
return err
}
}
shd, ok := msg.(*serverHelloDoneMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(shd, msg)
}
hs.finishedHash.Write(shd.marshal())
// If the server requested a certificate then we have to send a
// Certificate message, even if it's empty because we don't have a
// certificate to send.
if certRequested {
certMsg = new(certificateMsg)
certMsg.certificates = chainToSend.Certificate
hs.finishedHash.Write(certMsg.marshal())
if _, err := c.writeRecord(recordTypeHandshake, certMsg.marshal()); err != nil {
return err
}
}
preMasterSecret, ckx, err := keyAgreement.generateClientKeyExchange(c.config, hs.hello, c.peerCertificates[0])
if err != nil {
c.sendAlert(alertInternalError)
return err
}
if ckx != nil {
hs.finishedHash.Write(ckx.marshal())
if _, err := c.writeRecord(recordTypeHandshake, ckx.marshal()); err != nil {
return err
}
}
if chainToSend != nil && len(chainToSend.Certificate) > 0 {
certVerify := &certificateVerifyMsg{
hasSignatureAlgorithm: c.vers >= VersionTLS12,
}
key, ok := chainToSend.PrivateKey.(crypto.Signer)
if !ok {
c.sendAlert(alertInternalError)
return fmt.Errorf("tls: client certificate private key of type %T does not implement crypto.Signer", chainToSend.PrivateKey)
}
signatureAlgorithm, sigType, hashFunc, err := pickSignatureAlgorithm(key.Public(), certReq.supportedSignatureAlgorithms, hs.hello.supportedSignatureAlgorithms, c.vers)
if err != nil {
c.sendAlert(alertInternalError)
return err
}
// SignatureAndHashAlgorithm was introduced in TLS 1.2.
if certVerify.hasSignatureAlgorithm {
certVerify.signatureAlgorithm = signatureAlgorithm
}
digest, err := hs.finishedHash.hashForClientCertificate(sigType, hashFunc, hs.masterSecret)
if err != nil {
c.sendAlert(alertInternalError)
return err
}
signOpts := crypto.SignerOpts(hashFunc)
if sigType == signatureRSAPSS {
signOpts = &rsa.PSSOptions{SaltLength: rsa.PSSSaltLengthEqualsHash, Hash: hashFunc}
}
certVerify.signature, err = key.Sign(c.config.rand(), digest, signOpts)
if err != nil {
c.sendAlert(alertInternalError)
return err
}
hs.finishedHash.Write(certVerify.marshal())
if _, err := c.writeRecord(recordTypeHandshake, certVerify.marshal()); err != nil {
return err
}
}
if hs.hello.ems && hs.serverHello.ems {
hs.masterSecret = extendedMasterFromPreMasterSecret(c.vers, hs.suite, preMasterSecret, hs.finishedHash)
} else {
hs.masterSecret = masterFromPreMasterSecret(c.vers, hs.suite, preMasterSecret, hs.hello.random, hs.serverHello.random)
}
if err := c.config.writeKeyLog(keyLogLabelTLS12, hs.hello.random, hs.masterSecret); err != nil {
c.sendAlert(alertInternalError)
return errors.New("tls: failed to write to key log: " + err.Error())
}
hs.finishedHash.discardHandshakeBuffer()
return nil
}
func (hs *clientHandshakeState) establishKeys() error {
c := hs.c
clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV :=
keysFromMasterSecret(c.vers, hs.suite, hs.masterSecret, hs.hello.random, hs.serverHello.random, hs.suite.macLen, hs.suite.keyLen, hs.suite.ivLen)
var clientCipher, serverCipher interface{}
var clientHash, serverHash macFunction
if hs.suite.cipher != nil {
clientCipher = hs.suite.cipher(clientKey, clientIV, false /* not for reading */)
clientHash = hs.suite.mac(c.vers, clientMAC)
serverCipher = hs.suite.cipher(serverKey, serverIV, true /* 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, serverCipher, serverHash)
c.out.prepareCipherSpec(c.vers, clientCipher, clientHash)
return nil
}
func (hs *clientHandshakeState) serverResumedSession() bool {
// If the server responded with the same sessionId then it means the
// sessionTicket is being used to resume a TLS session.
return hs.session != nil && hs.hello.sessionId != nil &&
bytes.Equal(hs.serverHello.sessionId, hs.hello.sessionId)
}
func (hs *clientHandshakeState) processServerHello() (bool, error) {
c := hs.c
if err := hs.pickCipherSuite(); err != nil {
return false, err
}
if hs.serverHello.compressionMethod != compressionNone {
c.sendAlert(alertUnexpectedMessage)
return false, errors.New("tls: server selected unsupported compression format")
}
if c.handshakes == 0 && hs.serverHello.secureRenegotiationSupported {
c.secureRenegotiation = true
if len(hs.serverHello.secureRenegotiation) != 0 {
c.sendAlert(alertHandshakeFailure)
return false, errors.New("tls: initial handshake had non-empty renegotiation extension")
}
}
if c.handshakes > 0 && c.secureRenegotiation {
var expectedSecureRenegotiation [24]byte
copy(expectedSecureRenegotiation[:], c.clientFinished[:])
copy(expectedSecureRenegotiation[12:], c.serverFinished[:])
if !bytes.Equal(hs.serverHello.secureRenegotiation, expectedSecureRenegotiation[:]) {
c.sendAlert(alertHandshakeFailure)
return false, errors.New("tls: incorrect renegotiation extension contents")
}
}
clientDidNPN := hs.hello.nextProtoNeg
clientDidALPN := len(hs.hello.alpnProtocols) > 0
serverHasNPN := hs.serverHello.nextProtoNeg
serverHasALPN := len(hs.serverHello.alpnProtocol) > 0
if !clientDidNPN && serverHasNPN {
c.sendAlert(alertHandshakeFailure)
return false, errors.New("tls: server advertised unrequested NPN extension")
}
if !clientDidALPN && serverHasALPN {
c.sendAlert(alertHandshakeFailure)
return false, errors.New("tls: server advertised unrequested ALPN extension")
}
if serverHasNPN && serverHasALPN {
c.sendAlert(alertHandshakeFailure)
return false, errors.New("tls: server advertised both NPN and ALPN extensions")
}
if serverHasALPN {
c.clientProtocol = hs.serverHello.alpnProtocol
c.clientProtocolFallback = false
}
c.scts = hs.serverHello.scts
if !hs.serverResumedSession() {
return false, nil
}
if hs.session.vers != c.vers {
c.sendAlert(alertHandshakeFailure)
return false, errors.New("tls: server resumed a session with a different version")
}
if hs.session.cipherSuite != hs.suite.id {
c.sendAlert(alertHandshakeFailure)
return false, errors.New("tls: server resumed a session with a different cipher suite")
}
// Restore masterSecret and peerCerts from previous state
hs.masterSecret = hs.session.masterSecret
c.peerCertificates = hs.session.serverCertificates
c.verifiedChains = hs.session.verifiedChains
return true, nil
}
func (hs *clientHandshakeState) readFinished(out []byte) error {
c := hs.c
if err := c.readChangeCipherSpec(); err != nil {
return err
}
msg, err := c.readHandshake()
if err != nil {
return err
}
serverFinished, ok := msg.(*finishedMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(serverFinished, msg)
}
verify := hs.finishedHash.serverSum(hs.masterSecret)
if len(verify) != len(serverFinished.verifyData) ||
subtle.ConstantTimeCompare(verify, serverFinished.verifyData) != 1 {
c.sendAlert(alertHandshakeFailure)
return errors.New("tls: server's Finished message was incorrect")
}
hs.finishedHash.Write(serverFinished.marshal())
copy(out, verify)
return nil
}
func (hs *clientHandshakeState) readSessionTicket() error {
if !hs.serverHello.ticketSupported {
return nil
}
c := hs.c
msg, err := c.readHandshake()
if err != nil {
return err
}
sessionTicketMsg, ok := msg.(*newSessionTicketMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(sessionTicketMsg, msg)
}
hs.finishedHash.Write(sessionTicketMsg.marshal())
hs.session = &ClientSessionState{
sessionTicket: sessionTicketMsg.ticket,
vers: c.vers,
cipherSuite: hs.suite.id,
masterSecret: hs.masterSecret,
serverCertificates: c.peerCertificates,
verifiedChains: c.verifiedChains,
receivedAt: c.config.time(),
}
return nil
}
func (hs *clientHandshakeState) sendFinished(out []byte) error {
c := hs.c
if _, err := c.writeRecord(recordTypeChangeCipherSpec, []byte{1}); err != nil {
return err
}
if hs.serverHello.nextProtoNeg {
nextProto := new(nextProtoMsg)
proto, fallback := mutualProtocol(c.config.NextProtos, hs.serverHello.nextProtos)
nextProto.proto = proto
c.clientProtocol = proto
c.clientProtocolFallback = fallback
hs.finishedHash.Write(nextProto.marshal())
if _, err := c.writeRecord(recordTypeHandshake, nextProto.marshal()); err != nil {
return err
}
}
finished := new(finishedMsg)
finished.verifyData = hs.finishedHash.clientSum(hs.masterSecret)
hs.finishedHash.Write(finished.marshal())
if _, err := c.writeRecord(recordTypeHandshake, finished.marshal()); err != nil {
return err
}
copy(out, finished.verifyData)
return nil
}
// verifyServerCertificate parses and verifies the provided chain, setting
// c.verifiedChains and c.peerCertificates or sending the appropriate alert.
func (c *Conn) verifyServerCertificate(certificates [][]byte) error {
certs := make([]*x509.Certificate, len(certificates))
for i, asn1Data := range certificates {
cert, err := x509.ParseCertificate(asn1Data)
if err != nil {
c.sendAlert(alertBadCertificate)
return errors.New("tls: failed to parse certificate from server: " + err.Error())
}
certs[i] = cert
}
if !c.config.InsecureSkipVerify {
opts := x509.VerifyOptions{
Roots: c.config.RootCAs,
CurrentTime: c.config.time(),
DNSName: c.config.ServerName,
Intermediates: x509.NewCertPool(),
}
for i, cert := range certs {
if i == 0 {
continue
}
opts.Intermediates.AddCert(cert)
}
var err error
c.verifiedChains, err = certs[0].Verify(opts)
if err != nil {
c.sendAlert(alertBadCertificate)
return err
}
}
if c.config.VerifyPeerCertificate != nil {
if err := c.config.VerifyPeerCertificate(certificates, c.verifiedChains); err != nil {
c.sendAlert(alertBadCertificate)
return err
}
}
switch certs[0].PublicKey.(type) {
case *rsa.PublicKey, *ecdsa.PublicKey:
break
default:
c.sendAlert(alertUnsupportedCertificate)
return fmt.Errorf("tls: server's certificate contains an unsupported type of public key: %T", certs[0].PublicKey)
}
c.peerCertificates = certs
return nil
}
// tls11SignatureSchemes contains the signature schemes that we synthesise for
// a TLS <= 1.1 connection, based on the supported certificate types.
var (
tls11SignatureSchemes = []SignatureScheme{ECDSAWithP256AndSHA256, ECDSAWithP384AndSHA384, ECDSAWithP521AndSHA512, PKCS1WithSHA256, PKCS1WithSHA384, PKCS1WithSHA512, PKCS1WithSHA1}
tls11SignatureSchemesECDSA = tls11SignatureSchemes[:3]
tls11SignatureSchemesRSA = tls11SignatureSchemes[3:]
)
// certificateRequestInfoFromMsg generates a CertificateRequestInfo from a TLS
// <= 1.2 CertificateRequest, making an effort to fill in missing information.
func certificateRequestInfoFromMsg(certReq *certificateRequestMsg) *CertificateRequestInfo {
var rsaAvail, ecdsaAvail bool
for _, certType := range certReq.certificateTypes {
switch certType {
case certTypeRSASign:
rsaAvail = true
case certTypeECDSASign:
ecdsaAvail = true
}
}
cri := &CertificateRequestInfo{
AcceptableCAs: certReq.certificateAuthorities,
}
if !certReq.hasSignatureAlgorithm {
// Prior to TLS 1.2, the signature schemes were not
// included in the certificate request message. In this
// case we use a plausible list based on the acceptable
// certificate types.
switch {
case rsaAvail && ecdsaAvail:
cri.SignatureSchemes = tls11SignatureSchemes
case rsaAvail:
cri.SignatureSchemes = tls11SignatureSchemesRSA
case ecdsaAvail:
cri.SignatureSchemes = tls11SignatureSchemesECDSA
}
return cri
}
// In TLS 1.2, the signature schemes apply to both the certificate chain and
// the leaf key, while the certificate types only apply to the leaf key.
// See RFC 5246, Section 7.4.4 (where it calls this "somewhat complicated").
// Filter the signature schemes based on the certificate type.
cri.SignatureSchemes = make([]SignatureScheme, 0, len(certReq.supportedSignatureAlgorithms))
for _, sigScheme := range certReq.supportedSignatureAlgorithms {
switch signatureFromSignatureScheme(sigScheme) {
case signatureECDSA:
if ecdsaAvail {
cri.SignatureSchemes = append(cri.SignatureSchemes, sigScheme)
}
case signatureRSAPSS, signaturePKCS1v15:
if rsaAvail {
cri.SignatureSchemes = append(cri.SignatureSchemes, sigScheme)
}
}
}
return cri
}
func (c *Conn) getClientCertificate(cri *CertificateRequestInfo) (*Certificate, error) {
if c.config.GetClientCertificate != nil {
return c.config.GetClientCertificate(cri)
}
// We need to search our list of client certs for one
// where SignatureAlgorithm is acceptable to the server and the
// Issuer is in AcceptableCAs.
for i, chain := range c.config.Certificates {
sigOK := false
for _, alg := range signatureSchemesForCertificate(&chain) {
if isSupportedSignatureAlgorithm(alg, cri.SignatureSchemes) {
sigOK = true
break
}
}
if !sigOK {
continue
}
if len(cri.AcceptableCAs) == 0 {
return &chain, nil
}
for j, cert := range chain.Certificate {
x509Cert := chain.Leaf
// Parse the certificate if this isn't the leaf node, or if
// chain.Leaf was nil.
if j != 0 || x509Cert == nil {
var err error
if x509Cert, err = x509.ParseCertificate(cert); err != nil {
c.sendAlert(alertInternalError)
return nil, errors.New("tls: failed to parse configured certificate chain #" + strconv.Itoa(i) + ": " + err.Error())
}
}
for _, ca := range cri.AcceptableCAs {
if bytes.Equal(x509Cert.RawIssuer, ca) {
return &chain, nil
}
}
}
}
// No acceptable certificate found. Don't send a certificate.
return new(Certificate), nil
}
// clientSessionCacheKey returns a key used to cache sessionTickets that could
// be used to resume previously negotiated TLS sessions with a server.
func clientSessionCacheKey(serverAddr net.Addr, config *Config) string {
if len(config.ServerName) > 0 {
return config.ServerName
}
return serverAddr.String()
}
// mutualProtocol finds the mutual Next Protocol Negotiation or ALPN protocol
// given list of possible protocols and a list of the preference order. The
// first list must not be empty. It returns the resulting protocol and flag
// indicating if the fallback case was reached.
func mutualProtocol(protos, preferenceProtos []string) (string, bool) {
for _, s := range preferenceProtos {
for _, c := range protos {
if s == c {
return s, false
}
}
}
return protos[0], true
}
// hostnameInSNI converts name into an approriate hostname for SNI.
// Literal IP addresses and absolute FQDNs are not permitted as SNI values.
// See RFC 6066, Section 3.
func hostnameInSNI(name string) string {
host := name
if len(host) > 0 && host[0] == '[' && host[len(host)-1] == ']' {
host = host[1 : len(host)-1]
}
if i := strings.LastIndex(host, "%"); i > 0 {
host = host[:i]
}
if net.ParseIP(host) != nil {
return ""
}
for len(name) > 0 && name[len(name)-1] == '.' {
name = name[:len(name)-1]
}
return name
}
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