blob: c5be2b760f40aacf4967be6e465edf0f3ca53894 [file] [log] [blame]
// 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 runner
import (
"bytes"
"crypto"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rsa"
"crypto/subtle"
"crypto/x509"
"errors"
"fmt"
"io"
"math/big"
"net"
"strconv"
"time"
)
type clientHandshakeState struct {
c *Conn
serverHello *serverHelloMsg
hello *clientHelloMsg
suite *cipherSuite
finishedHash finishedHash
keyShares map[CurveID]ecdhCurve
masterSecret []byte
session *ClientSessionState
finishedBytes []byte
}
func (c *Conn) clientHandshake() error {
if c.config == nil {
c.config = defaultConfig()
}
if len(c.config.ServerName) == 0 && !c.config.InsecureSkipVerify {
return errors.New("tls: either ServerName or InsecureSkipVerify must be specified in the tls.Config")
}
c.sendHandshakeSeq = 0
c.recvHandshakeSeq = 0
nextProtosLength := 0
for _, proto := range c.config.NextProtos {
if l := len(proto); l > 255 {
return errors.New("tls: invalid NextProtos value")
} else {
nextProtosLength += 1 + l
}
}
if nextProtosLength > 0xffff {
return errors.New("tls: NextProtos values too large")
}
minVersion := c.config.minVersion(c.isDTLS)
maxVersion := c.config.maxVersion(c.isDTLS)
hello := &clientHelloMsg{
isDTLS: c.isDTLS,
vers: versionToWire(maxVersion, c.isDTLS),
compressionMethods: []uint8{compressionNone},
random: make([]byte, 32),
ocspStapling: true,
sctListSupported: true,
serverName: c.config.ServerName,
supportedCurves: c.config.curvePreferences(),
supportedPoints: []uint8{pointFormatUncompressed},
nextProtoNeg: len(c.config.NextProtos) > 0,
secureRenegotiation: []byte{},
alpnProtocols: c.config.NextProtos,
duplicateExtension: c.config.Bugs.DuplicateExtension,
channelIDSupported: c.config.ChannelID != nil,
npnLast: c.config.Bugs.SwapNPNAndALPN,
extendedMasterSecret: maxVersion >= VersionTLS10,
srtpProtectionProfiles: c.config.SRTPProtectionProfiles,
srtpMasterKeyIdentifier: c.config.Bugs.SRTPMasterKeyIdentifer,
customExtension: c.config.Bugs.CustomExtension,
}
disableEMS := c.config.Bugs.NoExtendedMasterSecret
if c.cipherSuite != nil {
disableEMS = c.config.Bugs.NoExtendedMasterSecretOnRenegotiation
}
if disableEMS {
hello.extendedMasterSecret = false
}
if c.config.Bugs.NoSupportedCurves {
hello.supportedCurves = nil
}
if c.config.Bugs.SendCompressionMethods != nil {
hello.compressionMethods = c.config.Bugs.SendCompressionMethods
}
if len(c.clientVerify) > 0 && !c.config.Bugs.EmptyRenegotiationInfo {
if c.config.Bugs.BadRenegotiationInfo {
hello.secureRenegotiation = append(hello.secureRenegotiation, c.clientVerify...)
hello.secureRenegotiation[0] ^= 0x80
} else {
hello.secureRenegotiation = c.clientVerify
}
}
if c.noRenegotiationInfo() {
hello.secureRenegotiation = nil
}
var keyShares map[CurveID]ecdhCurve
if maxVersion >= VersionTLS13 {
keyShares = make(map[CurveID]ecdhCurve)
hello.hasKeyShares = true
hello.trailingKeyShareData = c.config.Bugs.TrailingKeyShareData
curvesToSend := c.config.defaultCurves()
for _, curveID := range hello.supportedCurves {
if !curvesToSend[curveID] {
continue
}
curve, ok := curveForCurveID(curveID)
if !ok {
continue
}
publicKey, err := curve.offer(c.config.rand())
if err != nil {
return err
}
if c.config.Bugs.SendCurve != 0 {
curveID = c.config.Bugs.SendCurve
}
if c.config.Bugs.InvalidECDHPoint {
publicKey[0] ^= 0xff
}
hello.keyShares = append(hello.keyShares, keyShareEntry{
group: curveID,
keyExchange: publicKey,
})
keyShares[curveID] = curve
if c.config.Bugs.DuplicateKeyShares {
hello.keyShares = append(hello.keyShares, hello.keyShares[len(hello.keyShares)-1])
}
}
if c.config.Bugs.MissingKeyShare {
hello.hasKeyShares = false
}
}
possibleCipherSuites := c.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 maxVersion < VersionTLS12 && suite.flags&suiteTLS12 != 0 {
continue
}
// Don't advertise non-DTLS cipher suites in DTLS.
if c.isDTLS && suite.flags&suiteNoDTLS != 0 {
continue
}
hello.cipherSuites = append(hello.cipherSuites, suiteId)
continue NextCipherSuite
}
}
if c.config.Bugs.AdvertiseAllConfiguredCiphers {
hello.cipherSuites = possibleCipherSuites
}
if c.config.Bugs.SendRenegotiationSCSV {
hello.cipherSuites = append(hello.cipherSuites, renegotiationSCSV)
}
if c.config.Bugs.SendFallbackSCSV {
hello.cipherSuites = append(hello.cipherSuites, fallbackSCSV)
}
_, err := io.ReadFull(c.config.rand(), hello.random)
if err != nil {
c.sendAlert(alertInternalError)
return errors.New("tls: short read from Rand: " + err.Error())
}
if maxVersion >= VersionTLS12 && !c.config.Bugs.NoSignatureAlgorithms {
hello.signatureAlgorithms = c.config.verifySignatureAlgorithms()
}
var session *ClientSessionState
var cacheKey string
sessionCache := c.config.ClientSessionCache
if sessionCache != nil {
hello.ticketSupported = !c.config.SessionTicketsDisabled
// Try to resume a previously negotiated TLS session, if
// available.
cacheKey = clientSessionCacheKey(c.conn.RemoteAddr(), c.config)
// TODO(nharper): Support storing more than one session
// ticket for TLS 1.3.
candidateSession, ok := sessionCache.Get(cacheKey)
if ok {
ticketOk := !c.config.SessionTicketsDisabled || candidateSession.sessionTicket == nil
// Check that the ciphersuite/version used for the
// previous session are still valid.
cipherSuiteOk := false
for _, id := range hello.cipherSuites {
if id == candidateSession.cipherSuite {
cipherSuiteOk = true
break
}
}
versOk := candidateSession.vers >= minVersion &&
candidateSession.vers <= maxVersion
if ticketOk && versOk && cipherSuiteOk {
session = candidateSession
}
}
}
if session != nil && c.config.time().Before(session.ticketExpiration) {
ticket := session.sessionTicket
if c.config.Bugs.CorruptTicket && len(ticket) > 0 {
ticket = make([]byte, len(session.sessionTicket))
copy(ticket, session.sessionTicket)
offset := 40
if offset >= len(ticket) {
offset = len(ticket) - 1
}
ticket[offset] ^= 0x40
}
if session.vers >= VersionTLS13 || c.config.Bugs.SendBothTickets {
// TODO(nharper): Support sending more
// than one PSK identity.
psk := pskIdentity{
keModes: []byte{pskDHEKEMode},
authModes: []byte{pskAuthMode},
ticket: ticket,
}
if len(c.config.Bugs.SendPSKKeyExchangeModes) != 0 {
psk.keModes = c.config.Bugs.SendPSKKeyExchangeModes
}
if len(c.config.Bugs.SendPSKAuthModes) != 0 {
psk.authModes = c.config.Bugs.SendPSKAuthModes
}
hello.pskIdentities = []pskIdentity{psk}
}
if session.vers < VersionTLS13 || c.config.Bugs.SendBothTickets {
if ticket != nil {
hello.sessionTicket = ticket
// A random session ID is used to detect when the
// server accepted the ticket and is resuming a session
// (see RFC 5077).
sessionIdLen := 16
if c.config.Bugs.OversizedSessionId {
sessionIdLen = 33
}
hello.sessionId = make([]byte, sessionIdLen)
if _, err := io.ReadFull(c.config.rand(), hello.sessionId); err != nil {
c.sendAlert(alertInternalError)
return errors.New("tls: short read from Rand: " + err.Error())
}
} else {
hello.sessionId = session.sessionId
}
}
}
if maxVersion == VersionTLS13 && !c.config.Bugs.OmitSupportedVersions {
if hello.vers >= VersionTLS13 {
hello.vers = VersionTLS12
}
for version := maxVersion; version >= minVersion; version-- {
hello.supportedVersions = append(hello.supportedVersions, versionToWire(version, c.isDTLS))
}
}
if len(c.config.Bugs.SendSupportedVersions) > 0 {
hello.supportedVersions = c.config.Bugs.SendSupportedVersions
}
if c.config.Bugs.SendClientVersion != 0 {
hello.vers = c.config.Bugs.SendClientVersion
}
var helloBytes []byte
if c.config.Bugs.SendV2ClientHello {
// Test that the peer left-pads random.
hello.random[0] = 0
v2Hello := &v2ClientHelloMsg{
vers: hello.vers,
cipherSuites: hello.cipherSuites,
// No session resumption for V2ClientHello.
sessionId: nil,
challenge: hello.random[1:],
}
helloBytes = v2Hello.marshal()
c.writeV2Record(helloBytes)
} else {
helloBytes = hello.marshal()
if c.config.Bugs.PartialClientFinishedWithClientHello {
// Include one byte of Finished. We can compute it
// without completing the handshake. This assumes we
// negotiate TLS 1.3 with no HelloRetryRequest or
// CertificateRequest.
toWrite := make([]byte, 0, len(helloBytes)+1)
toWrite = append(toWrite, helloBytes...)
toWrite = append(toWrite, typeFinished)
c.writeRecord(recordTypeHandshake, toWrite)
} else {
c.writeRecord(recordTypeHandshake, helloBytes)
}
}
c.flushHandshake()
if err := c.simulatePacketLoss(nil); err != nil {
return err
}
msg, err := c.readHandshake()
if err != nil {
return err
}
if c.isDTLS {
helloVerifyRequest, ok := msg.(*helloVerifyRequestMsg)
if ok {
if helloVerifyRequest.vers != VersionTLS10 {
// Per RFC 6347, the version field in
// HelloVerifyRequest SHOULD be always DTLS
// 1.0. Enforce this for testing purposes.
return errors.New("dtls: bad HelloVerifyRequest version")
}
hello.raw = nil
hello.cookie = helloVerifyRequest.cookie
helloBytes = hello.marshal()
c.writeRecord(recordTypeHandshake, helloBytes)
c.flushHandshake()
if err := c.simulatePacketLoss(nil); err != nil {
return err
}
msg, err = c.readHandshake()
if err != nil {
return err
}
}
}
var serverWireVersion uint16
switch m := msg.(type) {
case *helloRetryRequestMsg:
serverWireVersion = m.vers
case *serverHelloMsg:
serverWireVersion = m.vers
default:
c.sendAlert(alertUnexpectedMessage)
return fmt.Errorf("tls: received unexpected message of type %T when waiting for HelloRetryRequest or ServerHello", msg)
}
serverVersion, ok := wireToVersion(serverWireVersion, c.isDTLS)
if ok {
ok = c.config.isSupportedVersion(serverVersion, c.isDTLS)
}
if !ok {
c.sendAlert(alertProtocolVersion)
return fmt.Errorf("tls: server selected unsupported protocol version %x", c.vers)
}
c.vers = serverVersion
c.haveVers = true
helloRetryRequest, haveHelloRetryRequest := msg.(*helloRetryRequestMsg)
var secondHelloBytes []byte
if haveHelloRetryRequest {
var hrrCurveFound bool
if c.config.Bugs.MisinterpretHelloRetryRequestCurve != 0 {
helloRetryRequest.selectedGroup = c.config.Bugs.MisinterpretHelloRetryRequestCurve
}
group := helloRetryRequest.selectedGroup
for _, curveID := range hello.supportedCurves {
if group == curveID {
hrrCurveFound = true
break
}
}
if !hrrCurveFound || keyShares[group] != nil {
c.sendAlert(alertHandshakeFailure)
return errors.New("tls: received invalid HelloRetryRequest")
}
curve, ok := curveForCurveID(group)
if !ok {
return errors.New("tls: Unable to get curve requested in HelloRetryRequest")
}
publicKey, err := curve.offer(c.config.rand())
if err != nil {
return err
}
keyShares[group] = curve
hello.keyShares = append(hello.keyShares, keyShareEntry{
group: group,
keyExchange: publicKey,
})
if c.config.Bugs.SecondClientHelloMissingKeyShare {
hello.hasKeyShares = false
}
hello.hasEarlyData = false
hello.earlyDataContext = nil
hello.raw = nil
secondHelloBytes = hello.marshal()
c.writeRecord(recordTypeHandshake, secondHelloBytes)
c.flushHandshake()
msg, err = c.readHandshake()
if err != nil {
return err
}
}
serverHello, ok := msg.(*serverHelloMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(serverHello, msg)
}
if serverWireVersion != serverHello.vers {
c.sendAlert(alertProtocolVersion)
return fmt.Errorf("tls: server sent non-matching version %x vs %x", serverWireVersion, serverHello.vers)
}
// Check for downgrade signals in the server random, per
// draft-ietf-tls-tls13-14, section 6.3.1.2.
if c.vers <= VersionTLS12 && c.config.maxVersion(c.isDTLS) >= VersionTLS13 {
if bytes.Equal(serverHello.random[len(serverHello.random)-8:], downgradeTLS13) {
c.sendAlert(alertProtocolVersion)
return errors.New("tls: downgrade from TLS 1.3 detected")
}
}
if c.vers <= VersionTLS11 && c.config.maxVersion(c.isDTLS) >= VersionTLS12 {
if bytes.Equal(serverHello.random[len(serverHello.random)-8:], downgradeTLS12) {
c.sendAlert(alertProtocolVersion)
return errors.New("tls: downgrade from TLS 1.2 detected")
}
}
suite := mutualCipherSuite(hello.cipherSuites, serverHello.cipherSuite)
if suite == nil {
c.sendAlert(alertHandshakeFailure)
return fmt.Errorf("tls: server selected an unsupported cipher suite")
}
if haveHelloRetryRequest && (helloRetryRequest.cipherSuite != serverHello.cipherSuite || helloRetryRequest.selectedGroup != serverHello.keyShare.group) {
c.sendAlert(alertHandshakeFailure)
return errors.New("tls: ServerHello parameters did not match HelloRetryRequest")
}
hs := &clientHandshakeState{
c: c,
serverHello: serverHello,
hello: hello,
suite: suite,
finishedHash: newFinishedHash(c.vers, suite),
keyShares: keyShares,
session: session,
}
hs.writeHash(helloBytes, hs.c.sendHandshakeSeq-1)
if haveHelloRetryRequest {
hs.writeServerHash(helloRetryRequest.marshal())
hs.writeClientHash(secondHelloBytes)
}
hs.writeServerHash(hs.serverHello.marshal())
if c.vers >= VersionTLS13 {
if err := hs.doTLS13Handshake(); err != nil {
return err
}
} else {
if c.config.Bugs.EarlyChangeCipherSpec > 0 {
hs.establishKeys()
c.writeRecord(recordTypeChangeCipherSpec, []byte{1})
}
if hs.serverHello.compressionMethod != compressionNone {
c.sendAlert(alertUnexpectedMessage)
return errors.New("tls: server selected unsupported compression format")
}
err = hs.processServerExtensions(&serverHello.extensions)
if err != nil {
return err
}
isResume, err := hs.processServerHello()
if err != nil {
return err
}
if isResume {
if c.config.Bugs.EarlyChangeCipherSpec == 0 {
if err := hs.establishKeys(); err != nil {
return err
}
}
if err := hs.readSessionTicket(); err != nil {
return err
}
if err := hs.readFinished(c.firstFinished[:]); err != nil {
return err
}
if err := hs.sendFinished(nil, isResume); 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.firstFinished[:], isResume); err != nil {
return err
}
// Most retransmits are triggered by a timeout, but the final
// leg of the handshake is retransmited upon re-receiving a
// Finished.
if err := c.simulatePacketLoss(func() {
c.sendHandshakeSeq--
c.writeRecord(recordTypeHandshake, hs.finishedBytes)
c.flushHandshake()
}); err != nil {
return err
}
if err := hs.readSessionTicket(); err != nil {
return err
}
if err := hs.readFinished(nil); err != nil {
return err
}
}
if sessionCache != nil && hs.session != nil && session != hs.session {
if c.config.Bugs.RequireSessionTickets && len(hs.session.sessionTicket) == 0 {
return errors.New("tls: new session used session IDs instead of tickets")
}
sessionCache.Put(cacheKey, hs.session)
}
c.didResume = isResume
c.exporterSecret = hs.masterSecret
}
c.handshakeComplete = true
c.cipherSuite = suite
copy(c.clientRandom[:], hs.hello.random)
copy(c.serverRandom[:], hs.serverHello.random)
return nil
}
func (hs *clientHandshakeState) doTLS13Handshake() error {
c := hs.c
// Once the PRF hash is known, TLS 1.3 does not require a handshake
// buffer.
hs.finishedHash.discardHandshakeBuffer()
zeroSecret := hs.finishedHash.zeroSecret()
// Resolve PSK and compute the early secret.
//
// TODO(davidben): This will need to be handled slightly earlier once
// 0-RTT is implemented.
var psk []byte
if hs.serverHello.hasPSKIdentity {
if hs.serverHello.useCertAuth || !hs.serverHello.hasKeyShare {
c.sendAlert(alertUnsupportedExtension)
return errors.New("tls: server omitted KeyShare or included SignatureAlgorithms on resumption.")
}
// We send at most one PSK identity.
if hs.session == nil || hs.serverHello.pskIdentity != 0 {
c.sendAlert(alertUnknownPSKIdentity)
return errors.New("tls: server sent unknown PSK identity")
}
if hs.session.cipherSuite != hs.suite.id {
c.sendAlert(alertHandshakeFailure)
return errors.New("tls: server sent invalid cipher suite")
}
psk = deriveResumptionPSK(hs.suite, hs.session.masterSecret)
hs.finishedHash.setResumptionContext(deriveResumptionContext(hs.suite, hs.session.masterSecret))
c.didResume = true
} else {
if !hs.serverHello.useCertAuth || !hs.serverHello.hasKeyShare {
c.sendAlert(alertUnsupportedExtension)
return errors.New("tls: server omitted KeyShare and SignatureAlgorithms on non-resumption.")
}
psk = zeroSecret
hs.finishedHash.setResumptionContext(zeroSecret)
}
earlySecret := hs.finishedHash.extractKey(zeroSecret, psk)
// Resolve ECDHE and compute the handshake secret.
var ecdheSecret []byte
if !c.config.Bugs.MissingKeyShare && !c.config.Bugs.SecondClientHelloMissingKeyShare {
curve, ok := hs.keyShares[hs.serverHello.keyShare.group]
if !ok {
c.sendAlert(alertHandshakeFailure)
return errors.New("tls: server selected an unsupported group")
}
c.curveID = hs.serverHello.keyShare.group
var err error
ecdheSecret, err = curve.finish(hs.serverHello.keyShare.keyExchange)
if err != nil {
return err
}
} else {
ecdheSecret = zeroSecret
}
// Compute the handshake secret.
handshakeSecret := hs.finishedHash.extractKey(earlySecret, ecdheSecret)
// Switch to handshake traffic keys.
handshakeTrafficSecret := hs.finishedHash.deriveSecret(handshakeSecret, handshakeTrafficLabel)
c.out.useTrafficSecret(c.vers, hs.suite, handshakeTrafficSecret, handshakePhase, clientWrite)
c.in.useTrafficSecret(c.vers, hs.suite, handshakeTrafficSecret, handshakePhase, serverWrite)
msg, err := c.readHandshake()
if err != nil {
return err
}
encryptedExtensions, ok := msg.(*encryptedExtensionsMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(encryptedExtensions, msg)
}
hs.writeServerHash(encryptedExtensions.marshal())
err = hs.processServerExtensions(&encryptedExtensions.extensions)
if err != nil {
return err
}
var chainToSend *Certificate
var certReq *certificateRequestMsg
if !hs.serverHello.useCertAuth {
if encryptedExtensions.extensions.ocspResponse != nil {
c.sendAlert(alertUnsupportedExtension)
return errors.New("tls: server sent OCSP response without a certificate")
}
if encryptedExtensions.extensions.sctList != nil {
c.sendAlert(alertUnsupportedExtension)
return errors.New("tls: server sent SCT list without a certificate")
}
// Copy over authentication from the session.
c.peerCertificates = hs.session.serverCertificates
c.sctList = hs.session.sctList
c.ocspResponse = hs.session.ocspResponse
} else {
c.ocspResponse = encryptedExtensions.extensions.ocspResponse
c.sctList = encryptedExtensions.extensions.sctList
msg, err := c.readHandshake()
if err != nil {
return err
}
var ok bool
certReq, ok = msg.(*certificateRequestMsg)
if ok {
if len(certReq.requestContext) != 0 {
return errors.New("tls: non-empty certificate request context sent in handshake")
}
if c.config.Bugs.IgnorePeerSignatureAlgorithmPreferences {
certReq.signatureAlgorithms = c.config.signSignatureAlgorithms()
}
hs.writeServerHash(certReq.marshal())
chainToSend, err = selectClientCertificate(c, certReq)
if err != nil {
return err
}
msg, err = c.readHandshake()
if err != nil {
return err
}
}
certMsg, ok := msg.(*certificateMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(certMsg, msg)
}
hs.writeServerHash(certMsg.marshal())
if err := hs.verifyCertificates(certMsg); err != nil {
return err
}
leaf := c.peerCertificates[0]
msg, err = c.readHandshake()
if err != nil {
return err
}
certVerifyMsg, ok := msg.(*certificateVerifyMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(certVerifyMsg, msg)
}
c.peerSignatureAlgorithm = certVerifyMsg.signatureAlgorithm
input := hs.finishedHash.certificateVerifyInput(serverCertificateVerifyContextTLS13)
err = verifyMessage(c.vers, leaf.PublicKey, c.config, certVerifyMsg.signatureAlgorithm, input, certVerifyMsg.signature)
if err != nil {
return err
}
hs.writeServerHash(certVerifyMsg.marshal())
}
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(handshakeTrafficSecret)
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.writeServerHash(serverFinished.marshal())
// The various secrets do not incorporate the client's final leg, so
// derive them now before updating the handshake context.
masterSecret := hs.finishedHash.extractKey(handshakeSecret, zeroSecret)
trafficSecret := hs.finishedHash.deriveSecret(masterSecret, applicationTrafficLabel)
if certReq != nil && !c.config.Bugs.SkipClientCertificate {
certMsg := &certificateMsg{
hasRequestContext: true,
requestContext: certReq.requestContext,
}
if chainToSend != nil {
certMsg.certificates = chainToSend.Certificate
}
hs.writeClientHash(certMsg.marshal())
c.writeRecord(recordTypeHandshake, certMsg.marshal())
if chainToSend != nil {
certVerify := &certificateVerifyMsg{
hasSignatureAlgorithm: true,
}
// Determine the hash to sign.
privKey := chainToSend.PrivateKey
var err error
certVerify.signatureAlgorithm, err = selectSignatureAlgorithm(c.vers, privKey, c.config, certReq.signatureAlgorithms)
if err != nil {
c.sendAlert(alertInternalError)
return err
}
input := hs.finishedHash.certificateVerifyInput(clientCertificateVerifyContextTLS13)
certVerify.signature, err = signMessage(c.vers, privKey, c.config, certVerify.signatureAlgorithm, input)
if err != nil {
c.sendAlert(alertInternalError)
return err
}
if c.config.Bugs.SendSignatureAlgorithm != 0 {
certVerify.signatureAlgorithm = c.config.Bugs.SendSignatureAlgorithm
}
hs.writeClientHash(certVerify.marshal())
c.writeRecord(recordTypeHandshake, certVerify.marshal())
}
}
// Send a client Finished message.
finished := new(finishedMsg)
finished.verifyData = hs.finishedHash.clientSum(handshakeTrafficSecret)
if c.config.Bugs.BadFinished {
finished.verifyData[0]++
}
hs.writeClientHash(finished.marshal())
if c.config.Bugs.PartialClientFinishedWithClientHello {
// The first byte has already been sent.
c.writeRecord(recordTypeHandshake, finished.marshal()[1:])
} else {
c.writeRecord(recordTypeHandshake, finished.marshal())
}
if c.config.Bugs.SendExtraFinished {
c.writeRecord(recordTypeHandshake, finished.marshal())
}
c.flushHandshake()
// Switch to application data keys.
c.out.useTrafficSecret(c.vers, hs.suite, trafficSecret, applicationPhase, clientWrite)
c.in.useTrafficSecret(c.vers, hs.suite, trafficSecret, applicationPhase, serverWrite)
c.exporterSecret = hs.finishedHash.deriveSecret(masterSecret, exporterLabel)
c.resumptionSecret = hs.finishedHash.deriveSecret(masterSecret, resumptionLabel)
return nil
}
func (hs *clientHandshakeState) doFullHandshake() error {
c := hs.c
var leaf *x509.Certificate
if hs.suite.flags&suitePSK == 0 {
msg, err := c.readHandshake()
if err != nil {
return err
}
certMsg, ok := msg.(*certificateMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(certMsg, msg)
}
hs.writeServerHash(certMsg.marshal())
if err := hs.verifyCertificates(certMsg); err != nil {
return err
}
leaf = c.peerCertificates[0]
}
if hs.serverHello.extensions.ocspStapling {
msg, err := c.readHandshake()
if err != nil {
return err
}
cs, ok := msg.(*certificateStatusMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(cs, msg)
}
hs.writeServerHash(cs.marshal())
if cs.statusType == statusTypeOCSP {
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.writeServerHash(skx.marshal())
err = keyAgreement.processServerKeyExchange(c.config, hs.hello, hs.serverHello, leaf, skx)
if err != nil {
c.sendAlert(alertUnexpectedMessage)
return err
}
if ecdhe, ok := keyAgreement.(*ecdheKeyAgreement); ok {
c.curveID = ecdhe.curveID
}
c.peerSignatureAlgorithm = keyAgreement.peerSignatureAlgorithm()
msg, err = c.readHandshake()
if err != nil {
return err
}
}
var chainToSend *Certificate
var certRequested bool
certReq, ok := msg.(*certificateRequestMsg)
if ok {
certRequested = true
if c.config.Bugs.IgnorePeerSignatureAlgorithmPreferences {
certReq.signatureAlgorithms = c.config.signSignatureAlgorithms()
}
hs.writeServerHash(certReq.marshal())
chainToSend, err = selectClientCertificate(c, certReq)
if err != nil {
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.writeServerHash(shd.marshal())
// If the server requested a certificate then we have to send a
// Certificate message in TLS, even if it's empty because we don't have
// a certificate to send. In SSL 3.0, skip the message and send a
// no_certificate warning alert.
if certRequested {
if c.vers == VersionSSL30 && chainToSend == nil {
c.sendAlert(alertNoCertficate)
} else if !c.config.Bugs.SkipClientCertificate {
certMsg := new(certificateMsg)
if chainToSend != nil {
certMsg.certificates = chainToSend.Certificate
}
hs.writeClientHash(certMsg.marshal())
c.writeRecord(recordTypeHandshake, certMsg.marshal())
}
}
preMasterSecret, ckx, err := keyAgreement.generateClientKeyExchange(c.config, hs.hello, leaf)
if err != nil {
c.sendAlert(alertInternalError)
return err
}
if ckx != nil {
if c.config.Bugs.EarlyChangeCipherSpec < 2 {
hs.writeClientHash(ckx.marshal())
}
c.writeRecord(recordTypeHandshake, ckx.marshal())
}
if hs.serverHello.extensions.extendedMasterSecret && c.vers >= VersionTLS10 {
hs.masterSecret = extendedMasterFromPreMasterSecret(c.vers, hs.suite, preMasterSecret, hs.finishedHash)
c.extendedMasterSecret = true
} else {
if c.config.Bugs.RequireExtendedMasterSecret {
return errors.New("tls: extended master secret required but not supported by peer")
}
hs.masterSecret = masterFromPreMasterSecret(c.vers, hs.suite, preMasterSecret, hs.hello.random, hs.serverHello.random)
}
if chainToSend != nil {
certVerify := &certificateVerifyMsg{
hasSignatureAlgorithm: c.vers >= VersionTLS12,
}
// Determine the hash to sign.
privKey := c.config.Certificates[0].PrivateKey
if certVerify.hasSignatureAlgorithm {
certVerify.signatureAlgorithm, err = selectSignatureAlgorithm(c.vers, privKey, c.config, certReq.signatureAlgorithms)
if err != nil {
c.sendAlert(alertInternalError)
return err
}
}
if c.vers > VersionSSL30 {
certVerify.signature, err = signMessage(c.vers, privKey, c.config, certVerify.signatureAlgorithm, hs.finishedHash.buffer)
if err == nil && c.config.Bugs.SendSignatureAlgorithm != 0 {
certVerify.signatureAlgorithm = c.config.Bugs.SendSignatureAlgorithm
}
} else {
// SSL 3.0's client certificate construction is
// incompatible with signatureAlgorithm.
rsaKey, ok := privKey.(*rsa.PrivateKey)
if !ok {
err = errors.New("unsupported signature type for client certificate")
} else {
digest := hs.finishedHash.hashForClientCertificateSSL3(hs.masterSecret)
if c.config.Bugs.InvalidSignature {
digest[0] ^= 0x80
}
certVerify.signature, err = rsa.SignPKCS1v15(c.config.rand(), rsaKey, crypto.MD5SHA1, digest)
}
}
if err != nil {
c.sendAlert(alertInternalError)
return errors.New("tls: failed to sign handshake with client certificate: " + err.Error())
}
hs.writeClientHash(certVerify.marshal())
c.writeRecord(recordTypeHandshake, certVerify.marshal())
}
// flushHandshake will be called in sendFinished.
hs.finishedHash.discardHandshakeBuffer()
return nil
}
func (hs *clientHandshakeState) verifyCertificates(certMsg *certificateMsg) error {
c := hs.c
if len(certMsg.certificates) == 0 {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: no certificates sent")
}
certs := make([]*x509.Certificate, len(certMsg.certificates))
for i, asn1Data := range certMsg.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
}
}
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
}
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(c.vers))
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(c.vers, clientKey, clientIV)
serverCipher = hs.suite.aead(c.vers, serverKey, serverIV)
}
c.in.prepareCipherSpec(c.vers, serverCipher, serverHash)
c.out.prepareCipherSpec(c.vers, clientCipher, clientHash)
return nil
}
func (hs *clientHandshakeState) processServerExtensions(serverExtensions *serverExtensions) error {
c := hs.c
if c.vers < VersionTLS13 {
if c.config.Bugs.RequireRenegotiationInfo && serverExtensions.secureRenegotiation == nil {
return errors.New("tls: renegotiation extension missing")
}
if len(c.clientVerify) > 0 && !c.noRenegotiationInfo() {
var expectedRenegInfo []byte
expectedRenegInfo = append(expectedRenegInfo, c.clientVerify...)
expectedRenegInfo = append(expectedRenegInfo, c.serverVerify...)
if !bytes.Equal(serverExtensions.secureRenegotiation, expectedRenegInfo) {
c.sendAlert(alertHandshakeFailure)
return fmt.Errorf("tls: renegotiation mismatch")
}
}
} else if serverExtensions.secureRenegotiation != nil {
return errors.New("tls: renegotiation info sent in TLS 1.3")
}
if expected := c.config.Bugs.ExpectedCustomExtension; expected != nil {
if serverExtensions.customExtension != *expected {
return fmt.Errorf("tls: bad custom extension contents %q", serverExtensions.customExtension)
}
}
clientDidNPN := hs.hello.nextProtoNeg
clientDidALPN := len(hs.hello.alpnProtocols) > 0
serverHasNPN := serverExtensions.nextProtoNeg
serverHasALPN := len(serverExtensions.alpnProtocol) > 0
if !clientDidNPN && serverHasNPN {
c.sendAlert(alertHandshakeFailure)
return errors.New("server advertised unrequested NPN extension")
}
if !clientDidALPN && serverHasALPN {
c.sendAlert(alertHandshakeFailure)
return errors.New("server advertised unrequested ALPN extension")
}
if serverHasNPN && serverHasALPN {
c.sendAlert(alertHandshakeFailure)
return errors.New("server advertised both NPN and ALPN extensions")
}
if serverHasALPN {
c.clientProtocol = serverExtensions.alpnProtocol
c.clientProtocolFallback = false
c.usedALPN = true
}
if serverHasNPN && c.vers >= VersionTLS13 {
c.sendAlert(alertHandshakeFailure)
return errors.New("server advertised NPN over TLS 1.3")
}
if !hs.hello.channelIDSupported && serverExtensions.channelIDRequested {
c.sendAlert(alertHandshakeFailure)
return errors.New("server advertised unrequested Channel ID extension")
}
if serverExtensions.channelIDRequested && c.vers >= VersionTLS13 {
c.sendAlert(alertHandshakeFailure)
return errors.New("server advertised Channel ID over TLS 1.3")
}
if serverExtensions.extendedMasterSecret && c.vers >= VersionTLS13 {
return errors.New("tls: server advertised extended master secret over TLS 1.3")
}
if serverExtensions.ticketSupported && c.vers >= VersionTLS13 {
return errors.New("tls: server advertised ticket extension over TLS 1.3")
}
if serverExtensions.srtpProtectionProfile != 0 {
if serverExtensions.srtpMasterKeyIdentifier != "" {
return errors.New("tls: server selected SRTP MKI value")
}
found := false
for _, p := range c.config.SRTPProtectionProfiles {
if p == serverExtensions.srtpProtectionProfile {
found = true
break
}
}
if !found {
return errors.New("tls: server advertised unsupported SRTP profile")
}
c.srtpProtectionProfile = serverExtensions.srtpProtectionProfile
}
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 hs.serverResumedSession() {
// For test purposes, assert that the server never accepts the
// resumption offer on renegotiation.
if c.cipherSuite != nil && c.config.Bugs.FailIfResumeOnRenego {
return false, errors.New("tls: server resumed session on renegotiation")
}
if hs.serverHello.extensions.sctList != nil {
return false, errors.New("tls: server sent SCT extension on session resumption")
}
if hs.serverHello.extensions.ocspStapling {
return false, errors.New("tls: server sent OCSP extension on session resumption")
}
// Restore masterSecret and peerCerts from previous state
hs.masterSecret = hs.session.masterSecret
c.peerCertificates = hs.session.serverCertificates
c.extendedMasterSecret = hs.session.extendedMasterSecret
c.sctList = hs.session.sctList
c.ocspResponse = hs.session.ocspResponse
hs.finishedHash.discardHandshakeBuffer()
return true, nil
}
if hs.serverHello.extensions.sctList != nil {
c.sctList = hs.serverHello.extensions.sctList
}
return false, nil
}
func (hs *clientHandshakeState) readFinished(out []byte) error {
c := hs.c
c.readRecord(recordTypeChangeCipherSpec)
if err := c.in.error(); 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)
}
if c.config.Bugs.EarlyChangeCipherSpec == 0 {
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")
}
}
c.serverVerify = append(c.serverVerify[:0], serverFinished.verifyData...)
copy(out, serverFinished.verifyData)
hs.writeServerHash(serverFinished.marshal())
return nil
}
func (hs *clientHandshakeState) readSessionTicket() error {
c := hs.c
// Create a session with no server identifier. Either a
// session ID or session ticket will be attached.
session := &ClientSessionState{
vers: c.vers,
cipherSuite: hs.suite.id,
masterSecret: hs.masterSecret,
handshakeHash: hs.finishedHash.server.Sum(nil),
serverCertificates: c.peerCertificates,
sctList: c.sctList,
ocspResponse: c.ocspResponse,
ticketExpiration: c.config.time().Add(time.Duration(7 * 24 * time.Hour)),
}
if !hs.serverHello.extensions.ticketSupported {
if c.config.Bugs.ExpectNewTicket {
return errors.New("tls: expected new ticket")
}
if hs.session == nil && len(hs.serverHello.sessionId) > 0 {
session.sessionId = hs.serverHello.sessionId
hs.session = session
}
return nil
}
if c.vers == VersionSSL30 {
return errors.New("tls: negotiated session tickets in SSL 3.0")
}
msg, err := c.readHandshake()
if err != nil {
return err
}
sessionTicketMsg, ok := msg.(*newSessionTicketMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(sessionTicketMsg, msg)
}
session.sessionTicket = sessionTicketMsg.ticket
hs.session = session
hs.writeServerHash(sessionTicketMsg.marshal())
return nil
}
func (hs *clientHandshakeState) sendFinished(out []byte, isResume bool) error {
c := hs.c
var postCCSMsgs [][]byte
seqno := hs.c.sendHandshakeSeq
if hs.serverHello.extensions.nextProtoNeg {
nextProto := new(nextProtoMsg)
proto, fallback := mutualProtocol(c.config.NextProtos, hs.serverHello.extensions.nextProtos)
nextProto.proto = proto
c.clientProtocol = proto
c.clientProtocolFallback = fallback
nextProtoBytes := nextProto.marshal()
hs.writeHash(nextProtoBytes, seqno)
seqno++
postCCSMsgs = append(postCCSMsgs, nextProtoBytes)
}
if hs.serverHello.extensions.channelIDRequested {
channelIDMsg := new(channelIDMsg)
if c.config.ChannelID.Curve != elliptic.P256() {
return fmt.Errorf("tls: Channel ID is not on P-256.")
}
var resumeHash []byte
if isResume {
resumeHash = hs.session.handshakeHash
}
r, s, err := ecdsa.Sign(c.config.rand(), c.config.ChannelID, hs.finishedHash.hashForChannelID(resumeHash))
if err != nil {
return err
}
channelID := make([]byte, 128)
writeIntPadded(channelID[0:32], c.config.ChannelID.X)
writeIntPadded(channelID[32:64], c.config.ChannelID.Y)
writeIntPadded(channelID[64:96], r)
writeIntPadded(channelID[96:128], s)
if c.config.Bugs.InvalidChannelIDSignature {
channelID[64] ^= 1
}
channelIDMsg.channelID = channelID
c.channelID = &c.config.ChannelID.PublicKey
channelIDMsgBytes := channelIDMsg.marshal()
hs.writeHash(channelIDMsgBytes, seqno)
seqno++
postCCSMsgs = append(postCCSMsgs, channelIDMsgBytes)
}
finished := new(finishedMsg)
if c.config.Bugs.EarlyChangeCipherSpec == 2 {
finished.verifyData = hs.finishedHash.clientSum(nil)
} else {
finished.verifyData = hs.finishedHash.clientSum(hs.masterSecret)
}
copy(out, finished.verifyData)
if c.config.Bugs.BadFinished {
finished.verifyData[0]++
}
c.clientVerify = append(c.clientVerify[:0], finished.verifyData...)
hs.finishedBytes = finished.marshal()
hs.writeHash(hs.finishedBytes, seqno)
postCCSMsgs = append(postCCSMsgs, hs.finishedBytes)
if c.config.Bugs.FragmentAcrossChangeCipherSpec {
c.writeRecord(recordTypeHandshake, postCCSMsgs[0][:5])
postCCSMsgs[0] = postCCSMsgs[0][5:]
} else if c.config.Bugs.SendUnencryptedFinished {
c.writeRecord(recordTypeHandshake, postCCSMsgs[0])
postCCSMsgs = postCCSMsgs[1:]
}
c.flushHandshake()
if !c.config.Bugs.SkipChangeCipherSpec &&
c.config.Bugs.EarlyChangeCipherSpec == 0 {
ccs := []byte{1}
if c.config.Bugs.BadChangeCipherSpec != nil {
ccs = c.config.Bugs.BadChangeCipherSpec
}
c.writeRecord(recordTypeChangeCipherSpec, ccs)
}
if c.config.Bugs.AppDataAfterChangeCipherSpec != nil {
c.writeRecord(recordTypeApplicationData, c.config.Bugs.AppDataAfterChangeCipherSpec)
}
if c.config.Bugs.AlertAfterChangeCipherSpec != 0 {
c.sendAlert(c.config.Bugs.AlertAfterChangeCipherSpec)
return errors.New("tls: simulating post-CCS alert")
}
if !c.config.Bugs.SkipFinished {
for _, msg := range postCCSMsgs {
c.writeRecord(recordTypeHandshake, msg)
}
if c.config.Bugs.SendExtraFinished {
c.writeRecord(recordTypeHandshake, finished.marshal())
}
c.flushHandshake()
}
return nil
}
func (hs *clientHandshakeState) writeClientHash(msg []byte) {
// writeClientHash is called before writeRecord.
hs.writeHash(msg, hs.c.sendHandshakeSeq)
}
func (hs *clientHandshakeState) writeServerHash(msg []byte) {
// writeServerHash is called after readHandshake.
hs.writeHash(msg, hs.c.recvHandshakeSeq-1)
}
func (hs *clientHandshakeState) writeHash(msg []byte, seqno uint16) {
if hs.c.isDTLS {
// This is somewhat hacky. DTLS hashes a slightly different format.
// First, the TLS header.
hs.finishedHash.Write(msg[:4])
// Then the sequence number and reassembled fragment offset (always 0).
hs.finishedHash.Write([]byte{byte(seqno >> 8), byte(seqno), 0, 0, 0})
// Then the reassembled fragment (always equal to the message length).
hs.finishedHash.Write(msg[1:4])
// And then the message body.
hs.finishedHash.Write(msg[4:])
} else {
hs.finishedHash.Write(msg)
}
}
// selectClientCertificate selects a certificate for use with the given
// certificate, or none if none match. It may return a particular certificate or
// nil on success, or an error on internal error.
func selectClientCertificate(c *Conn, certReq *certificateRequestMsg) (*Certificate, error) {
// RFC 4346 on the certificateAuthorities field:
// A list of the distinguished names of acceptable certificate
// authorities. These distinguished names may specify a desired
// distinguished name for a root CA or for a subordinate CA; thus, this
// message can be used to describe both known roots and a desired
// authorization space. If the certificate_authorities list is empty
// then the client MAY send any certificate of the appropriate
// ClientCertificateType, unless there is some external arrangement to
// the contrary.
var rsaAvail, ecdsaAvail bool
if !certReq.hasRequestContext {
for _, certType := range certReq.certificateTypes {
switch certType {
case CertTypeRSASign:
rsaAvail = true
case CertTypeECDSASign:
ecdsaAvail = true
}
}
}
// We need to search our list of client certs for one
// where SignatureAlgorithm is RSA and the Issuer is in
// certReq.certificateAuthorities
findCert:
for i, chain := range c.config.Certificates {
if !certReq.hasRequestContext && !rsaAvail && !ecdsaAvail {
continue
}
// Ensure the private key supports one of the advertised
// signature algorithms.
if certReq.hasSignatureAlgorithm {
if _, err := selectSignatureAlgorithm(c.vers, chain.PrivateKey, c.config, certReq.signatureAlgorithms); err != nil {
continue
}
}
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 client certificate #" + strconv.Itoa(i) + ": " + err.Error())
}
}
if !certReq.hasRequestContext {
switch {
case rsaAvail && x509Cert.PublicKeyAlgorithm == x509.RSA:
case ecdsaAvail && x509Cert.PublicKeyAlgorithm == x509.ECDSA:
default:
continue findCert
}
}
if len(certReq.certificateAuthorities) == 0 {
// They gave us an empty list, so just take the
// first certificate of valid type from
// c.config.Certificates.
return &chain, nil
}
for _, ca := range certReq.certificateAuthorities {
if bytes.Equal(x509Cert.RawIssuer, ca) {
return &chain, nil
}
}
}
}
return nil, 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
}
// writeIntPadded writes x into b, padded up with leading zeros as
// needed.
func writeIntPadded(b []byte, x *big.Int) {
for i := range b {
b[i] = 0
}
xb := x.Bytes()
copy(b[len(b)-len(xb):], xb)
}