blob: 44b817ee4532d990dbfcda3febbd623497b4da59 [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/ed25519"
"crypto/elliptic"
"crypto/rsa"
"crypto/subtle"
"crypto/x509"
"errors"
"fmt"
"io"
"math/big"
"time"
)
// serverHandshakeState contains details of a server handshake in progress.
// It's discarded once the handshake has completed.
type serverHandshakeState struct {
c *Conn
clientHello *clientHelloMsg
hello *serverHelloMsg
suite *cipherSuite
ellipticOk bool
ecdsaOk bool
sessionState *sessionState
finishedHash finishedHash
masterSecret []byte
certsFromClient [][]byte
cert *Certificate
finishedBytes []byte
}
// serverHandshake performs a TLS handshake as a server.
func (c *Conn) serverHandshake() error {
config := c.config
// If this is the first server handshake, we generate a random key to
// encrypt the tickets with.
config.serverInitOnce.Do(config.serverInit)
c.sendHandshakeSeq = 0
c.recvHandshakeSeq = 0
hs := serverHandshakeState{
c: c,
}
if err := hs.readClientHello(); err != nil {
return err
}
if c.vers >= VersionTLS13 {
if err := hs.doTLS13Handshake(); err != nil {
return err
}
} else {
isResume, err := hs.processClientHello()
if err != nil {
return err
}
// For an overview of TLS handshaking, see https://tools.ietf.org/html/rfc5246#section-7.3
if isResume {
// The client has included a session ticket and so we do an abbreviated handshake.
if err := hs.doResumeHandshake(); err != nil {
return err
}
if err := hs.establishKeys(); err != nil {
return err
}
if c.config.Bugs.RenewTicketOnResume {
if err := hs.sendSessionTicket(); 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.readFinished(nil, isResume); err != nil {
return err
}
c.didResume = true
} else {
// The client didn't include a session ticket, or it wasn't
// valid so we do a full handshake.
if err := hs.doFullHandshake(); err != nil {
return err
}
if err := hs.establishKeys(); err != nil {
return err
}
if err := hs.readFinished(c.firstFinished[:], isResume); err != nil {
return err
}
if c.config.Bugs.AlertBeforeFalseStartTest != 0 {
c.sendAlert(c.config.Bugs.AlertBeforeFalseStartTest)
}
if c.config.Bugs.ExpectFalseStart {
if err := c.readRecord(recordTypeApplicationData); err != nil {
return fmt.Errorf("tls: peer did not false start: %s", err)
}
}
if err := hs.sendSessionTicket(); err != nil {
return err
}
if err := hs.sendFinished(nil, isResume); err != nil {
return err
}
}
c.exporterSecret = hs.masterSecret
}
c.handshakeComplete = true
copy(c.clientRandom[:], hs.clientHello.random)
copy(c.serverRandom[:], hs.hello.random)
return nil
}
// readClientHello reads a ClientHello message from the client and determines
// the protocol version.
func (hs *serverHandshakeState) readClientHello() error {
config := hs.c.config
c := hs.c
if err := c.simulatePacketLoss(nil); err != nil {
return err
}
msg, err := c.readHandshake()
if err != nil {
return err
}
var ok bool
hs.clientHello, ok = msg.(*clientHelloMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(hs.clientHello, msg)
}
if size := config.Bugs.RequireClientHelloSize; size != 0 && len(hs.clientHello.raw) != size {
return fmt.Errorf("tls: ClientHello record size is %d, but expected %d", len(hs.clientHello.raw), size)
}
if c.isDTLS && !config.Bugs.SkipHelloVerifyRequest {
// Per RFC 6347, the version field in HelloVerifyRequest SHOULD
// be always DTLS 1.0
helloVerifyRequest := &helloVerifyRequestMsg{
vers: VersionDTLS10,
cookie: make([]byte, 32),
}
if _, err := io.ReadFull(c.config.rand(), helloVerifyRequest.cookie); err != nil {
c.sendAlert(alertInternalError)
return errors.New("dtls: short read from Rand: " + err.Error())
}
c.writeRecord(recordTypeHandshake, helloVerifyRequest.marshal())
c.flushHandshake()
if err := c.simulatePacketLoss(nil); err != nil {
return err
}
msg, err := c.readHandshake()
if err != nil {
return err
}
newClientHello, ok := msg.(*clientHelloMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(hs.clientHello, msg)
}
if !bytes.Equal(newClientHello.cookie, helloVerifyRequest.cookie) {
return errors.New("dtls: invalid cookie")
}
// Apart from the cookie, the two ClientHellos must
// match. Note that clientHello.equal compares the
// serialization, so we make a copy.
oldClientHelloCopy := *hs.clientHello
oldClientHelloCopy.raw = nil
oldClientHelloCopy.cookie = nil
newClientHelloCopy := *newClientHello
newClientHelloCopy.raw = nil
newClientHelloCopy.cookie = nil
if !oldClientHelloCopy.equal(&newClientHelloCopy) {
return errors.New("dtls: retransmitted ClientHello does not match")
}
hs.clientHello = newClientHello
}
if config.Bugs.RequireSameRenegoClientVersion && c.clientVersion != 0 {
if c.clientVersion != hs.clientHello.vers {
return fmt.Errorf("tls: client offered different version on renego")
}
}
if config.Bugs.FailIfCECPQ2Offered {
for _, offeredCurve := range hs.clientHello.supportedCurves {
if isPqGroup(offeredCurve) {
return errors.New("tls: CECPQ2 or CECPQ2b was offered")
}
}
}
if expected := config.Bugs.ExpectedKeyShares; expected != nil {
if len(expected) != len(hs.clientHello.keyShares) {
return fmt.Errorf("tls: expected %d key shares, but found %d", len(expected), len(hs.clientHello.keyShares))
}
for i, group := range expected {
if found := hs.clientHello.keyShares[i].group; found != group {
return fmt.Errorf("tls: key share #%d is for group %d, not %d", i, found, group)
}
}
}
if c.config.Bugs.ExpectPQExperimentSignal != hs.clientHello.pqExperimentSignal {
return fmt.Errorf("tls: PQ experiment signal presence (%t) was not what was expected", hs.clientHello.pqExperimentSignal)
}
c.clientVersion = hs.clientHello.vers
// Use the versions extension if supplied, otherwise use the legacy ClientHello version.
if len(hs.clientHello.supportedVersions) == 0 {
if c.isDTLS {
if hs.clientHello.vers <= VersionDTLS12 {
hs.clientHello.supportedVersions = append(hs.clientHello.supportedVersions, VersionDTLS12)
}
if hs.clientHello.vers <= VersionDTLS10 {
hs.clientHello.supportedVersions = append(hs.clientHello.supportedVersions, VersionDTLS10)
}
} else {
if hs.clientHello.vers >= VersionTLS12 {
hs.clientHello.supportedVersions = append(hs.clientHello.supportedVersions, VersionTLS12)
}
if hs.clientHello.vers >= VersionTLS11 {
hs.clientHello.supportedVersions = append(hs.clientHello.supportedVersions, VersionTLS11)
}
if hs.clientHello.vers >= VersionTLS10 {
hs.clientHello.supportedVersions = append(hs.clientHello.supportedVersions, VersionTLS10)
}
if hs.clientHello.vers >= VersionSSL30 {
hs.clientHello.supportedVersions = append(hs.clientHello.supportedVersions, VersionSSL30)
}
}
} else if config.Bugs.ExpectGREASE && !containsGREASE(hs.clientHello.supportedVersions) {
return errors.New("tls: no GREASE version value found")
}
if !c.haveVers {
if config.Bugs.NegotiateVersion != 0 {
c.wireVersion = config.Bugs.NegotiateVersion
} else {
var found bool
for _, vers := range hs.clientHello.supportedVersions {
if _, ok := config.isSupportedVersion(vers, c.isDTLS); ok {
c.wireVersion = vers
found = true
break
}
}
if !found {
c.sendAlert(alertProtocolVersion)
return errors.New("tls: client did not offer any supported protocol versions")
}
}
} else if config.Bugs.NegotiateVersionOnRenego != 0 {
c.wireVersion = config.Bugs.NegotiateVersionOnRenego
}
c.vers, ok = wireToVersion(c.wireVersion, c.isDTLS)
if !ok {
panic("Could not map wire version")
}
c.haveVers = true
clientProtocol, ok := wireToVersion(c.clientVersion, c.isDTLS)
// Reject < 1.2 ClientHellos with signature_algorithms.
if ok && clientProtocol < VersionTLS12 && len(hs.clientHello.signatureAlgorithms) > 0 {
return fmt.Errorf("tls: client included signature_algorithms before TLS 1.2")
}
// Check the client cipher list is consistent with the version.
if ok && clientProtocol < VersionTLS12 {
for _, id := range hs.clientHello.cipherSuites {
if isTLS12Cipher(id) {
return fmt.Errorf("tls: client offered TLS 1.2 cipher before TLS 1.2")
}
}
}
if config.Bugs.ExpectNoTLS12Session {
if len(hs.clientHello.sessionId) > 0 && c.vers >= VersionTLS13 {
return fmt.Errorf("tls: client offered an unexpected session ID")
}
if len(hs.clientHello.sessionTicket) > 0 {
return fmt.Errorf("tls: client offered an unexpected session ticket")
}
}
if config.Bugs.ExpectNoTLS13PSK && len(hs.clientHello.pskIdentities) > 0 {
return fmt.Errorf("tls: client offered unexpected PSK identities")
}
var scsvFound bool
for _, cipherSuite := range hs.clientHello.cipherSuites {
if cipherSuite == fallbackSCSV {
scsvFound = true
break
}
}
if !scsvFound && config.Bugs.FailIfNotFallbackSCSV {
return errors.New("tls: no fallback SCSV found when expected")
} else if scsvFound && !config.Bugs.FailIfNotFallbackSCSV {
return errors.New("tls: fallback SCSV found when not expected")
}
if config.Bugs.ExpectGREASE && !containsGREASE(hs.clientHello.cipherSuites) {
return errors.New("tls: no GREASE cipher suite value found")
}
var greaseFound bool
for _, curve := range hs.clientHello.supportedCurves {
if isGREASEValue(uint16(curve)) {
greaseFound = true
break
}
}
if !greaseFound && config.Bugs.ExpectGREASE {
return errors.New("tls: no GREASE curve value found")
}
if len(hs.clientHello.keyShares) > 0 {
greaseFound = false
for _, keyShare := range hs.clientHello.keyShares {
if isGREASEValue(uint16(keyShare.group)) {
greaseFound = true
break
}
}
if !greaseFound && config.Bugs.ExpectGREASE {
return errors.New("tls: no GREASE curve value found")
}
}
if err := checkRSAPSSSupport(config.Bugs.ExpectRSAPSSSupport, hs.clientHello.signatureAlgorithms, hs.clientHello.signatureAlgorithmsCert); err != nil {
return err
}
applyBugsToClientHello(hs.clientHello, config)
return nil
}
func applyBugsToClientHello(clientHello *clientHelloMsg, config *Config) {
if config.Bugs.IgnorePeerSignatureAlgorithmPreferences {
clientHello.signatureAlgorithms = config.signSignatureAlgorithms()
}
if config.Bugs.IgnorePeerCurvePreferences {
clientHello.supportedCurves = config.curvePreferences()
}
if config.Bugs.IgnorePeerCipherPreferences {
clientHello.cipherSuites = config.cipherSuites()
}
}
func (hs *serverHandshakeState) doTLS13Handshake() error {
c := hs.c
config := c.config
// We've read the ClientHello, so the next record must be preceded with ChangeCipherSpec.
c.expectTLS13ChangeCipherSpec = true
hs.hello = &serverHelloMsg{
isDTLS: c.isDTLS,
vers: c.wireVersion,
sessionId: hs.clientHello.sessionId,
compressionMethod: config.Bugs.SendCompressionMethod,
versOverride: config.Bugs.SendServerHelloVersion,
supportedVersOverride: config.Bugs.SendServerSupportedVersionExtension,
omitSupportedVers: config.Bugs.OmitServerSupportedVersionExtension,
customExtension: config.Bugs.CustomUnencryptedExtension,
unencryptedALPN: config.Bugs.SendUnencryptedALPN,
}
hs.hello.random = make([]byte, 32)
if _, err := io.ReadFull(config.rand(), hs.hello.random); err != nil {
c.sendAlert(alertInternalError)
return err
}
// TLS 1.3 forbids clients from advertising any non-null compression.
if len(hs.clientHello.compressionMethods) != 1 || hs.clientHello.compressionMethods[0] != compressionNone {
return errors.New("tls: client sent compression method other than null for TLS 1.3")
}
// Prepare an EncryptedExtensions message, but do not send it yet.
encryptedExtensions := new(encryptedExtensionsMsg)
encryptedExtensions.empty = config.Bugs.EmptyEncryptedExtensions
if err := hs.processClientExtensions(&encryptedExtensions.extensions); err != nil {
return err
}
// Select the cipher suite.
var preferenceList, supportedList []uint16
if config.PreferServerCipherSuites {
preferenceList = config.cipherSuites()
supportedList = hs.clientHello.cipherSuites
} else {
preferenceList = hs.clientHello.cipherSuites
supportedList = config.cipherSuites()
}
for _, id := range preferenceList {
if hs.suite = c.tryCipherSuite(id, supportedList, c.vers, true, true); hs.suite != nil {
break
}
}
if hs.suite == nil {
c.sendAlert(alertHandshakeFailure)
return errors.New("tls: no cipher suite supported by both client and server")
}
hs.hello.cipherSuite = hs.suite.id
if c.config.Bugs.SendCipherSuite != 0 {
hs.hello.cipherSuite = c.config.Bugs.SendCipherSuite
}
hs.finishedHash = newFinishedHash(c.wireVersion, c.isDTLS, hs.suite)
hs.finishedHash.discardHandshakeBuffer()
hs.writeClientHash(hs.clientHello.marshal())
supportedCurve := false
var selectedCurve CurveID
preferredCurves := config.curvePreferences()
Curves:
for _, curve := range hs.clientHello.supportedCurves {
for _, supported := range preferredCurves {
if supported == curve {
supportedCurve = true
selectedCurve = curve
break Curves
}
}
}
if !supportedCurve {
c.sendAlert(alertHandshakeFailure)
return errors.New("tls: no curve supported by both client and server")
}
pskIdentities := hs.clientHello.pskIdentities
pskKEModes := hs.clientHello.pskKEModes
if len(pskIdentities) == 0 && len(hs.clientHello.sessionTicket) > 0 && c.config.Bugs.AcceptAnySession {
psk := pskIdentity{
ticket: hs.clientHello.sessionTicket,
}
pskIdentities = []pskIdentity{psk}
pskKEModes = []byte{pskDHEKEMode}
}
var pskIndex int
foundKEMode := bytes.IndexByte(pskKEModes, pskDHEKEMode) >= 0
if foundKEMode && !config.SessionTicketsDisabled {
for i, pskIdentity := range pskIdentities {
// TODO(svaldez): Check the obfuscatedTicketAge before accepting 0-RTT.
sessionState, ok := c.decryptTicket(pskIdentity.ticket)
if !ok {
continue
}
if !config.Bugs.AcceptAnySession {
if sessionState.vers != c.vers {
continue
}
if sessionState.ticketExpiration.Before(c.config.time()) {
continue
}
sessionCipher := cipherSuiteFromID(sessionState.cipherSuite)
if sessionCipher == nil || sessionCipher.hash() != hs.suite.hash() {
continue
}
}
clientTicketAge := time.Duration(uint32(pskIdentity.obfuscatedTicketAge-sessionState.ticketAgeAdd)) * time.Millisecond
if config.Bugs.ExpectTicketAge != 0 && clientTicketAge != config.Bugs.ExpectTicketAge {
c.sendAlert(alertHandshakeFailure)
return errors.New("tls: invalid ticket age")
}
hs.sessionState = sessionState
hs.hello.hasPSKIdentity = true
hs.hello.pskIdentity = uint16(i)
pskIndex = i
if config.Bugs.SelectPSKIdentityOnResume != 0 {
hs.hello.pskIdentity = config.Bugs.SelectPSKIdentityOnResume
}
c.didResume = true
break
}
}
if config.Bugs.AlwaysSelectPSKIdentity {
hs.hello.hasPSKIdentity = true
hs.hello.pskIdentity = 0
}
// Verify the PSK binder. Note there may not be a PSK binder if
// AcceptAnyBinder is set. See https://crbug.com/boringssl/115.
if hs.sessionState != nil && !config.Bugs.AcceptAnySession {
binderToVerify := hs.clientHello.pskBinders[pskIndex]
if err := verifyPSKBinder(c.wireVersion, hs.clientHello, hs.sessionState, binderToVerify, []byte{}, []byte{}); err != nil {
return err
}
}
// Resolve PSK and compute the early secret.
if hs.sessionState != nil {
hs.finishedHash.addEntropy(hs.sessionState.masterSecret)
} else {
hs.finishedHash.addEntropy(hs.finishedHash.zeroSecret())
}
hs.hello.hasKeyShare = true
if hs.sessionState != nil && config.Bugs.NegotiatePSKResumption {
hs.hello.hasKeyShare = false
}
if config.Bugs.MissingKeyShare {
hs.hello.hasKeyShare = false
}
firstHelloRetryRequest := true
ResendHelloRetryRequest:
var sendHelloRetryRequest bool
cipherSuite := hs.suite.id
if config.Bugs.SendHelloRetryRequestCipherSuite != 0 {
cipherSuite = config.Bugs.SendHelloRetryRequestCipherSuite
}
helloRetryRequest := &helloRetryRequestMsg{
vers: c.wireVersion,
sessionId: hs.clientHello.sessionId,
cipherSuite: cipherSuite,
compressionMethod: config.Bugs.SendCompressionMethod,
duplicateExtensions: config.Bugs.DuplicateHelloRetryRequestExtensions,
}
if config.Bugs.AlwaysSendHelloRetryRequest {
sendHelloRetryRequest = true
}
if config.Bugs.SendHelloRetryRequestCookie != nil {
sendHelloRetryRequest = true
helloRetryRequest.cookie = config.Bugs.SendHelloRetryRequestCookie
}
if len(config.Bugs.CustomHelloRetryRequestExtension) > 0 {
sendHelloRetryRequest = true
helloRetryRequest.customExtension = config.Bugs.CustomHelloRetryRequestExtension
}
var selectedKeyShare *keyShareEntry
if hs.hello.hasKeyShare {
// Look for the key share corresponding to our selected curve.
for i := range hs.clientHello.keyShares {
if hs.clientHello.keyShares[i].group == selectedCurve {
selectedKeyShare = &hs.clientHello.keyShares[i]
break
}
}
if config.Bugs.ExpectMissingKeyShare && selectedKeyShare != nil {
return errors.New("tls: expected missing key share")
}
if selectedKeyShare == nil {
helloRetryRequest.hasSelectedGroup = true
helloRetryRequest.selectedGroup = selectedCurve
sendHelloRetryRequest = true
}
}
if config.Bugs.SendHelloRetryRequestCurve != 0 {
helloRetryRequest.hasSelectedGroup = true
helloRetryRequest.selectedGroup = config.Bugs.SendHelloRetryRequestCurve
sendHelloRetryRequest = true
}
if config.Bugs.SkipHelloRetryRequest {
sendHelloRetryRequest = false
}
if sendHelloRetryRequest {
if err := hs.finishedHash.UpdateForHelloRetryRequest(); err != nil {
return err
}
oldClientHelloBytes := hs.clientHello.marshal()
hs.writeServerHash(helloRetryRequest.marshal())
c.writeRecord(recordTypeHandshake, helloRetryRequest.marshal())
c.flushHandshake()
if !c.config.Bugs.SkipChangeCipherSpec {
c.writeRecord(recordTypeChangeCipherSpec, []byte{1})
}
if hs.clientHello.hasEarlyData {
c.skipEarlyData = true
}
// Read new ClientHello.
newMsg, err := c.readHandshake()
if err != nil {
return err
}
newClientHello, ok := newMsg.(*clientHelloMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(newClientHello, newMsg)
}
hs.writeClientHash(newClientHello.marshal())
if config.Bugs.ExpectNoTLS13PSKAfterHRR && len(newClientHello.pskIdentities) > 0 {
return fmt.Errorf("tls: client offered unexpected PSK identities after HelloRetryRequest")
}
if newClientHello.hasEarlyData {
return errors.New("tls: EarlyData sent in new ClientHello")
}
applyBugsToClientHello(newClientHello, config)
// Check that the new ClientHello matches the old ClientHello,
// except for relevant modifications.
//
// TODO(davidben): Make this check more precise.
oldClientHelloCopy := *hs.clientHello
oldClientHelloCopy.raw = nil
oldClientHelloCopy.hasEarlyData = false
newClientHelloCopy := *newClientHello
newClientHelloCopy.raw = nil
if helloRetryRequest.hasSelectedGroup {
newKeyShares := newClientHelloCopy.keyShares
if len(newKeyShares) != 1 || newKeyShares[0].group != helloRetryRequest.selectedGroup {
return errors.New("tls: KeyShare from HelloRetryRequest not in new ClientHello")
}
selectedKeyShare = &newKeyShares[0]
newClientHelloCopy.keyShares = oldClientHelloCopy.keyShares
}
if len(helloRetryRequest.cookie) > 0 {
if !bytes.Equal(newClientHelloCopy.tls13Cookie, helloRetryRequest.cookie) {
return errors.New("tls: cookie from HelloRetryRequest not present in new ClientHello")
}
newClientHelloCopy.tls13Cookie = nil
}
// PSK binders and obfuscated ticket age are both updated in the
// second ClientHello.
if len(oldClientHelloCopy.pskIdentities) != len(newClientHelloCopy.pskIdentities) {
newClientHelloCopy.pskIdentities = oldClientHelloCopy.pskIdentities
} else {
if len(oldClientHelloCopy.pskIdentities) != len(newClientHelloCopy.pskIdentities) {
return errors.New("tls: PSK identity count from old and new ClientHello do not match")
}
for i, identity := range oldClientHelloCopy.pskIdentities {
newClientHelloCopy.pskIdentities[i].obfuscatedTicketAge = identity.obfuscatedTicketAge
}
}
newClientHelloCopy.pskBinders = oldClientHelloCopy.pskBinders
newClientHelloCopy.hasEarlyData = oldClientHelloCopy.hasEarlyData
if !oldClientHelloCopy.equal(&newClientHelloCopy) {
return errors.New("tls: new ClientHello does not match")
}
if firstHelloRetryRequest && config.Bugs.SecondHelloRetryRequest {
firstHelloRetryRequest = false
goto ResendHelloRetryRequest
}
// Verify the PSK binder. Note there may not be a PSK binder if
// AcceptAnyBinder is set. See https://crbug.com/115.
if hs.sessionState != nil && !config.Bugs.AcceptAnySession {
binderToVerify := newClientHello.pskBinders[pskIndex]
if err := verifyPSKBinder(c.wireVersion, newClientHello, hs.sessionState, binderToVerify, oldClientHelloBytes, helloRetryRequest.marshal()); err != nil {
return err
}
}
}
// Decide whether or not to accept early data.
if !sendHelloRetryRequest && hs.clientHello.hasEarlyData {
if !config.Bugs.AlwaysRejectEarlyData && hs.sessionState != nil {
if c.clientProtocol == string(hs.sessionState.earlyALPN) || config.Bugs.AlwaysAcceptEarlyData {
encryptedExtensions.extensions.hasEarlyData = true
}
}
if encryptedExtensions.extensions.hasEarlyData {
earlyTrafficSecret := hs.finishedHash.deriveSecret(earlyTrafficLabel)
c.earlyExporterSecret = hs.finishedHash.deriveSecret(earlyExporterLabel)
if err := c.useInTrafficSecret(c.wireVersion, hs.suite, earlyTrafficSecret); err != nil {
return err
}
c.earlyCipherSuite = hs.suite
for _, expectedMsg := range config.Bugs.ExpectEarlyData {
if err := c.readRecord(recordTypeApplicationData); err != nil {
return err
}
msg := c.input.data[c.input.off:]
if !bytes.Equal(msg, expectedMsg) {
return fmt.Errorf("tls: got early data record %x, wanted %x", msg, expectedMsg)
}
c.in.freeBlock(c.input)
c.input = nil
}
} else {
c.skipEarlyData = true
}
}
if config.Bugs.SendEarlyDataExtension {
encryptedExtensions.extensions.hasEarlyData = true
}
// Resolve ECDHE and compute the handshake secret.
if hs.hello.hasKeyShare {
// Once a curve has been selected and a key share identified,
// the server needs to generate a public value and send it in
// the ServerHello.
curve, ok := curveForCurveID(selectedCurve, config)
if !ok {
panic("tls: server failed to look up curve ID")
}
c.curveID = selectedCurve
var peerKey []byte
if config.Bugs.SkipHelloRetryRequest {
// If skipping HelloRetryRequest, use a random key to
// avoid crashing.
curve2, _ := curveForCurveID(selectedCurve, config)
var err error
peerKey, err = curve2.offer(config.rand())
if err != nil {
return err
}
} else {
peerKey = selectedKeyShare.keyExchange
}
publicKey, ecdheSecret, err := curve.accept(config.rand(), peerKey)
if err != nil {
c.sendAlert(alertHandshakeFailure)
return err
}
hs.finishedHash.nextSecret()
hs.finishedHash.addEntropy(ecdheSecret)
hs.hello.hasKeyShare = true
curveID := selectedCurve
if c.config.Bugs.SendCurve != 0 {
curveID = config.Bugs.SendCurve
}
if c.config.Bugs.InvalidECDHPoint {
publicKey[0] ^= 0xff
}
hs.hello.keyShare = keyShareEntry{
group: curveID,
keyExchange: publicKey,
}
if config.Bugs.EncryptedExtensionsWithKeyShare {
encryptedExtensions.extensions.hasKeyShare = true
encryptedExtensions.extensions.keyShare = keyShareEntry{
group: curveID,
keyExchange: publicKey,
}
}
} else {
hs.finishedHash.nextSecret()
hs.finishedHash.addEntropy(hs.finishedHash.zeroSecret())
}
// Send unencrypted ServerHello.
hs.writeServerHash(hs.hello.marshal())
if config.Bugs.PartialEncryptedExtensionsWithServerHello {
helloBytes := hs.hello.marshal()
toWrite := make([]byte, 0, len(helloBytes)+1)
toWrite = append(toWrite, helloBytes...)
toWrite = append(toWrite, typeEncryptedExtensions)
c.writeRecord(recordTypeHandshake, toWrite)
} else {
c.writeRecord(recordTypeHandshake, hs.hello.marshal())
}
c.flushHandshake()
if !c.config.Bugs.SkipChangeCipherSpec && !sendHelloRetryRequest {
c.writeRecord(recordTypeChangeCipherSpec, []byte{1})
}
for i := 0; i < c.config.Bugs.SendExtraChangeCipherSpec; i++ {
c.writeRecord(recordTypeChangeCipherSpec, []byte{1})
}
// Switch to handshake traffic keys.
serverHandshakeTrafficSecret := hs.finishedHash.deriveSecret(serverHandshakeTrafficLabel)
c.useOutTrafficSecret(c.wireVersion, hs.suite, serverHandshakeTrafficSecret)
// Derive handshake traffic read key, but don't switch yet.
clientHandshakeTrafficSecret := hs.finishedHash.deriveSecret(clientHandshakeTrafficLabel)
// Send EncryptedExtensions.
hs.writeServerHash(encryptedExtensions.marshal())
if config.Bugs.PartialEncryptedExtensionsWithServerHello {
// The first byte has already been sent.
c.writeRecord(recordTypeHandshake, encryptedExtensions.marshal()[1:])
} else {
c.writeRecord(recordTypeHandshake, encryptedExtensions.marshal())
}
if hs.sessionState == nil {
if config.ClientAuth >= RequestClientCert {
// Request a client certificate
certReq := &certificateRequestMsg{
vers: c.wireVersion,
hasSignatureAlgorithm: !config.Bugs.OmitCertificateRequestAlgorithms,
hasRequestContext: true,
requestContext: config.Bugs.SendRequestContext,
customExtension: config.Bugs.SendCustomCertificateRequest,
}
if !config.Bugs.NoSignatureAlgorithms {
certReq.signatureAlgorithms = config.verifySignatureAlgorithms()
}
// An empty list of certificateAuthorities signals to
// the client that it may send any certificate in response
// to our request. When we know the CAs we trust, then
// we can send them down, so that the client can choose
// an appropriate certificate to give to us.
if config.ClientCAs != nil {
certReq.certificateAuthorities = config.ClientCAs.Subjects()
}
hs.writeServerHash(certReq.marshal())
c.writeRecord(recordTypeHandshake, certReq.marshal())
}
certMsg := &certificateMsg{
hasRequestContext: true,
}
if !config.Bugs.EmptyCertificateList {
for i, certData := range hs.cert.Certificate {
cert := certificateEntry{
data: certData,
}
if i == 0 {
if hs.clientHello.ocspStapling && !c.config.Bugs.NoOCSPStapling {
cert.ocspResponse = hs.cert.OCSPStaple
}
if hs.clientHello.sctListSupported && !c.config.Bugs.NoSignedCertificateTimestamps {
cert.sctList = hs.cert.SignedCertificateTimestampList
}
cert.duplicateExtensions = config.Bugs.SendDuplicateCertExtensions
cert.extraExtension = config.Bugs.SendExtensionOnCertificate
} else {
if config.Bugs.SendOCSPOnIntermediates != nil {
cert.ocspResponse = config.Bugs.SendOCSPOnIntermediates
}
if config.Bugs.SendSCTOnIntermediates != nil {
cert.sctList = config.Bugs.SendSCTOnIntermediates
}
}
certMsg.certificates = append(certMsg.certificates, cert)
}
}
certMsgBytes := certMsg.marshal()
sentCompressedCertMsg := false
FindCertCompressionAlg:
for candidate, alg := range c.config.CertCompressionAlgs {
for _, id := range hs.clientHello.compressedCertAlgs {
if id == candidate {
if expected := config.Bugs.ExpectedCompressedCert; expected != 0 && expected != id {
return fmt.Errorf("expected to send compressed cert with alg %d, but picked %d", expected, id)
}
if override := config.Bugs.SendCertCompressionAlgId; override != 0 {
id = override
}
uncompressed := certMsgBytes[4:]
uncompressedLen := uint32(len(uncompressed))
if override := config.Bugs.SendCertUncompressedLength; override != 0 {
uncompressedLen = override
}
compressedCertMsgBytes := (&compressedCertificateMsg{
algID: id,
uncompressedLength: uncompressedLen,
compressed: alg.Compress(uncompressed),
}).marshal()
hs.writeServerHash(compressedCertMsgBytes)
c.writeRecord(recordTypeHandshake, compressedCertMsgBytes)
sentCompressedCertMsg = true
break FindCertCompressionAlg
}
}
}
if !sentCompressedCertMsg {
if config.Bugs.ExpectedCompressedCert != 0 {
return errors.New("unexpectedly sent uncompressed certificate")
}
hs.writeServerHash(certMsgBytes)
c.writeRecord(recordTypeHandshake, certMsgBytes)
}
certVerify := &certificateVerifyMsg{
hasSignatureAlgorithm: true,
}
// Determine the hash to sign.
privKey := hs.cert.PrivateKey
var err error
certVerify.signatureAlgorithm, err = selectSignatureAlgorithm(c.vers, privKey, config, hs.clientHello.signatureAlgorithms)
if err != nil {
c.sendAlert(alertInternalError)
return err
}
input := hs.finishedHash.certificateVerifyInput(serverCertificateVerifyContextTLS13)
certVerify.signature, err = signMessage(c.vers, privKey, c.config, certVerify.signatureAlgorithm, input)
if err != nil {
c.sendAlert(alertInternalError)
return err
}
if config.Bugs.SendSignatureAlgorithm != 0 {
certVerify.signatureAlgorithm = config.Bugs.SendSignatureAlgorithm
}
if !config.Bugs.SkipCertificateVerify {
hs.writeServerHash(certVerify.marshal())
c.writeRecord(recordTypeHandshake, certVerify.marshal())
}
} else if hs.sessionState != nil {
// Pick up certificates from the session instead.
if len(hs.sessionState.certificates) > 0 {
if _, err := hs.processCertsFromClient(hs.sessionState.certificates); err != nil {
return err
}
}
}
finished := new(finishedMsg)
finished.verifyData = hs.finishedHash.serverSum(serverHandshakeTrafficSecret)
if config.Bugs.BadFinished {
finished.verifyData[0]++
}
hs.writeServerHash(finished.marshal())
c.writeRecord(recordTypeHandshake, finished.marshal())
if c.config.Bugs.SendExtraFinished {
c.writeRecord(recordTypeHandshake, finished.marshal())
}
c.flushHandshake()
if encryptedExtensions.extensions.hasEarlyData && !c.skipEarlyData {
for _, expectedMsg := range config.Bugs.ExpectLateEarlyData {
if err := c.readRecord(recordTypeApplicationData); err != nil {
return err
}
if !bytes.Equal(c.input.data[c.input.off:], expectedMsg) {
return errors.New("ExpectLateEarlyData: did not get expected message")
}
c.in.freeBlock(c.input)
c.input = nil
}
}
// The various secrets do not incorporate the client's final leg, so
// derive them now before updating the handshake context.
hs.finishedHash.nextSecret()
hs.finishedHash.addEntropy(hs.finishedHash.zeroSecret())
clientTrafficSecret := hs.finishedHash.deriveSecret(clientApplicationTrafficLabel)
serverTrafficSecret := hs.finishedHash.deriveSecret(serverApplicationTrafficLabel)
c.exporterSecret = hs.finishedHash.deriveSecret(exporterLabel)
// Switch to application data keys on write. In particular, any alerts
// from the client certificate are sent over these keys.
c.useOutTrafficSecret(c.wireVersion, hs.suite, serverTrafficSecret)
// Send 0.5-RTT messages.
for _, halfRTTMsg := range config.Bugs.SendHalfRTTData {
if _, err := c.writeRecord(recordTypeApplicationData, halfRTTMsg); err != nil {
return err
}
}
// Read end_of_early_data.
if encryptedExtensions.extensions.hasEarlyData {
msg, err := c.readHandshake()
if err != nil {
return err
}
endOfEarlyData, ok := msg.(*endOfEarlyDataMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(endOfEarlyData, msg)
}
hs.writeClientHash(endOfEarlyData.marshal())
}
// Switch input stream to handshake traffic keys.
if err := c.useInTrafficSecret(c.wireVersion, hs.suite, clientHandshakeTrafficSecret); err != nil {
return err
}
// If we requested a client certificate, then the client must send a
// certificate message, even if it's empty.
if config.ClientAuth >= RequestClientCert {
msg, err := c.readHandshake()
if err != nil {
return err
}
certMsg, ok := msg.(*certificateMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(certMsg, msg)
}
hs.writeClientHash(certMsg.marshal())
if len(certMsg.certificates) == 0 {
// The client didn't actually send a certificate
switch config.ClientAuth {
case RequireAnyClientCert, RequireAndVerifyClientCert:
c.sendAlert(alertCertificateRequired)
return errors.New("tls: client didn't provide a certificate")
}
}
var certs [][]byte
for _, cert := range certMsg.certificates {
certs = append(certs, cert.data)
// OCSP responses and SCT lists are not negotiated in
// client certificates.
if cert.ocspResponse != nil || cert.sctList != nil {
c.sendAlert(alertUnsupportedExtension)
return errors.New("tls: unexpected extensions in the client certificate")
}
}
pub, err := hs.processCertsFromClient(certs)
if err != nil {
return err
}
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)
}
c.peerSignatureAlgorithm = certVerify.signatureAlgorithm
input := hs.finishedHash.certificateVerifyInput(clientCertificateVerifyContextTLS13)
if err := verifyMessage(c.vers, pub, config, certVerify.signatureAlgorithm, input, certVerify.signature); err != nil {
c.sendAlert(alertBadCertificate)
return err
}
hs.writeClientHash(certVerify.marshal())
}
}
if encryptedExtensions.extensions.channelIDRequested {
msg, err := c.readHandshake()
if err != nil {
return err
}
channelIDMsg, ok := msg.(*channelIDMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(channelIDMsg, msg)
}
channelIDHash := crypto.SHA256.New()
channelIDHash.Write(hs.finishedHash.certificateVerifyInput(channelIDContextTLS13))
channelID, err := verifyChannelIDMessage(channelIDMsg, channelIDHash.Sum(nil))
if err != nil {
return err
}
c.channelID = channelID
hs.writeClientHash(channelIDMsg.marshal())
}
// Read the client Finished message.
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(clientHandshakeTrafficSecret)
if len(verify) != len(clientFinished.verifyData) ||
subtle.ConstantTimeCompare(verify, clientFinished.verifyData) != 1 {
c.sendAlert(alertHandshakeFailure)
return errors.New("tls: client's Finished message was incorrect")
}
hs.writeClientHash(clientFinished.marshal())
// Switch to application data keys on read.
if err := c.useInTrafficSecret(c.wireVersion, hs.suite, clientTrafficSecret); err != nil {
return err
}
c.cipherSuite = hs.suite
c.resumptionSecret = hs.finishedHash.deriveSecret(resumptionLabel)
// TODO(davidben): Allow configuring the number of tickets sent for
// testing.
if !c.config.SessionTicketsDisabled && foundKEMode {
ticketCount := 2
for i := 0; i < ticketCount; i++ {
c.SendNewSessionTicket([]byte{byte(i)})
}
}
return nil
}
// processClientHello processes the ClientHello message from the client and
// decides whether we will perform session resumption.
func (hs *serverHandshakeState) processClientHello() (isResume bool, err error) {
config := hs.c.config
c := hs.c
hs.hello = &serverHelloMsg{
isDTLS: c.isDTLS,
vers: c.wireVersion,
versOverride: config.Bugs.SendServerHelloVersion,
compressionMethod: config.Bugs.SendCompressionMethod,
extensions: serverExtensions{
supportedVersion: config.Bugs.SendServerSupportedVersionExtension,
},
omitExtensions: config.Bugs.OmitExtensions,
emptyExtensions: config.Bugs.EmptyExtensions,
}
hs.hello.random = make([]byte, 32)
_, err = io.ReadFull(config.rand(), hs.hello.random)
if err != nil {
c.sendAlert(alertInternalError)
return false, err
}
_, supportsTLS13 := c.config.isSupportedVersion(VersionTLS13, false)
// Signal downgrades in the server random, per RFC 8446, section 4.1.3.
if supportsTLS13 || config.Bugs.SendTLS13DowngradeRandom {
if c.vers <= VersionTLS12 && config.maxVersion(c.isDTLS) >= VersionTLS13 {
copy(hs.hello.random[len(hs.hello.random)-8:], downgradeTLS13)
}
if c.vers <= VersionTLS11 && config.maxVersion(c.isDTLS) == VersionTLS12 {
copy(hs.hello.random[len(hs.hello.random)-8:], downgradeTLS12)
}
}
if config.Bugs.SendJDK11DowngradeRandom {
copy(hs.hello.random[len(hs.hello.random)-8:], downgradeJDK11)
}
if len(hs.clientHello.sessionId) == 0 && c.config.Bugs.ExpectClientHelloSessionID {
return false, errors.New("tls: expected non-empty session ID from client")
}
foundCompression := false
// We only support null compression, so check that the client offered it.
for _, compression := range hs.clientHello.compressionMethods {
if compression == compressionNone {
foundCompression = true
break
}
}
if !foundCompression {
c.sendAlert(alertHandshakeFailure)
return false, errors.New("tls: client does not support uncompressed connections")
}
if err := hs.processClientExtensions(&hs.hello.extensions); err != nil {
return false, err
}
supportedCurve := false
preferredCurves := config.curvePreferences()
Curves:
for _, curve := range hs.clientHello.supportedCurves {
if isPqGroup(curve) && c.vers < VersionTLS13 {
// CECPQ2 and CECPQ2b is TLS 1.3-only.
continue
}
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
_, hs.ecdsaOk = hs.cert.PrivateKey.(*ecdsa.PrivateKey)
// Ed25519 also uses ECDSA certificates.
_, ed25519Ok := hs.cert.PrivateKey.(ed25519.PrivateKey)
hs.ecdsaOk = hs.ecdsaOk || ed25519Ok
// For test purposes, check that the peer never offers a session when
// renegotiating.
if c.cipherSuite != nil && len(hs.clientHello.sessionId) > 0 && c.config.Bugs.FailIfResumeOnRenego {
return false, errors.New("tls: offered resumption on renegotiation")
}
if c.config.Bugs.FailIfSessionOffered && (len(hs.clientHello.sessionTicket) > 0 || len(hs.clientHello.sessionId) > 0) {
return false, errors.New("tls: client offered a session ticket or ID")
}
if hs.checkForResumption() {
return true, nil
}
var preferenceList, supportedList []uint16
if c.config.PreferServerCipherSuites {
preferenceList = c.config.cipherSuites()
supportedList = hs.clientHello.cipherSuites
} else {
preferenceList = hs.clientHello.cipherSuites
supportedList = c.config.cipherSuites()
}
for _, id := range preferenceList {
if hs.suite = c.tryCipherSuite(id, supportedList, c.vers, hs.ellipticOk, hs.ecdsaOk); hs.suite != nil {
break
}
}
if hs.suite == nil {
c.sendAlert(alertHandshakeFailure)
return false, errors.New("tls: no cipher suite supported by both client and server")
}
return false, nil
}
// processClientExtensions processes all ClientHello extensions not directly
// related to cipher suite negotiation and writes responses in serverExtensions.
func (hs *serverHandshakeState) processClientExtensions(serverExtensions *serverExtensions) error {
config := hs.c.config
c := hs.c
if c.vers < VersionTLS13 || config.Bugs.NegotiateRenegotiationInfoAtAllVersions {
if !bytes.Equal(c.clientVerify, hs.clientHello.secureRenegotiation) {
c.sendAlert(alertHandshakeFailure)
return errors.New("tls: renegotiation mismatch")
}
if len(c.clientVerify) > 0 && !c.config.Bugs.EmptyRenegotiationInfo {
serverExtensions.secureRenegotiation = append(serverExtensions.secureRenegotiation, c.clientVerify...)
serverExtensions.secureRenegotiation = append(serverExtensions.secureRenegotiation, c.serverVerify...)
if c.config.Bugs.BadRenegotiationInfo {
serverExtensions.secureRenegotiation[0] ^= 0x80
}
if c.config.Bugs.BadRenegotiationInfoEnd {
serverExtensions.secureRenegotiation[len(serverExtensions.secureRenegotiation)-1] ^= 0x80
}
} else {
serverExtensions.secureRenegotiation = hs.clientHello.secureRenegotiation
}
if c.noRenegotiationInfo() {
serverExtensions.secureRenegotiation = nil
}
}
serverExtensions.duplicateExtension = c.config.Bugs.DuplicateExtension
if len(hs.clientHello.serverName) > 0 {
c.serverName = hs.clientHello.serverName
}
if len(config.Certificates) == 0 {
c.sendAlert(alertInternalError)
return errors.New("tls: no certificates configured")
}
hs.cert = &config.Certificates[0]
if len(hs.clientHello.serverName) > 0 {
hs.cert = config.getCertificateForName(hs.clientHello.serverName)
}
if expected := c.config.Bugs.ExpectServerName; expected != "" && expected != hs.clientHello.serverName {
return errors.New("tls: unexpected server name")
}
if cert := config.Bugs.RenegotiationCertificate; c.cipherSuite != nil && cert != nil {
hs.cert = cert
}
if len(hs.clientHello.alpnProtocols) > 0 {
// We will never offer ALPN as a client on renegotiation
// handshakes.
if len(c.clientVerify) > 0 {
return errors.New("tls: offered ALPN on renegotiation")
}
if proto := c.config.Bugs.ALPNProtocol; proto != nil {
serverExtensions.alpnProtocol = *proto
serverExtensions.alpnProtocolEmpty = len(*proto) == 0
c.clientProtocol = *proto
c.usedALPN = true
} else if selectedProto, fallback := mutualProtocol(hs.clientHello.alpnProtocols, c.config.NextProtos); !fallback {
serverExtensions.alpnProtocol = selectedProto
c.clientProtocol = selectedProto
c.usedALPN = true
}
}
if len(c.config.Bugs.SendALPN) > 0 {
serverExtensions.alpnProtocol = c.config.Bugs.SendALPN
}
if c.vers < VersionTLS13 || config.Bugs.NegotiateNPNAtAllVersions {
if len(hs.clientHello.alpnProtocols) == 0 || c.config.Bugs.NegotiateALPNAndNPN {
// Although sending an empty NPN extension is reasonable, Firefox has
// had a bug around this. Best to send nothing at all if
// config.NextProtos is empty. See
// https://code.google.com/p/go/issues/detail?id=5445.
if hs.clientHello.nextProtoNeg && len(config.NextProtos) > 0 {
serverExtensions.nextProtoNeg = true
serverExtensions.nextProtos = config.NextProtos
serverExtensions.npnAfterAlpn = config.Bugs.SwapNPNAndALPN
}
}
}
if len(hs.clientHello.quicTransportParams) > 0 {
c.quicTransportParams = hs.clientHello.quicTransportParams
serverExtensions.quicTransportParams = c.config.QUICTransportParams
}
if c.vers < VersionTLS13 || config.Bugs.NegotiateEMSAtAllVersions {
disableEMS := config.Bugs.NoExtendedMasterSecret
if c.cipherSuite != nil {
disableEMS = config.Bugs.NoExtendedMasterSecretOnRenegotiation
}
serverExtensions.extendedMasterSecret = c.vers >= VersionTLS10 && hs.clientHello.extendedMasterSecret && !disableEMS
}
if hs.clientHello.channelIDSupported && config.RequestChannelID {
serverExtensions.channelIDRequested = true
}
if config.TokenBindingParams != nil {
if !bytes.Equal(config.ExpectTokenBindingParams, hs.clientHello.tokenBindingParams) {
return errors.New("client did not send expected token binding params")
}
// For testing, blindly send whatever is set in config, even if
// it is invalid.
serverExtensions.tokenBindingParams = config.TokenBindingParams
serverExtensions.tokenBindingVersion = config.TokenBindingVersion
}
if len(hs.clientHello.tokenBindingParams) > 0 && (!hs.clientHello.extendedMasterSecret || hs.clientHello.secureRenegotiation == nil) {
return errors.New("client sent Token Binding without EMS and/or RI")
}
if hs.clientHello.srtpProtectionProfiles != nil {
SRTPLoop:
for _, p1 := range c.config.SRTPProtectionProfiles {
for _, p2 := range hs.clientHello.srtpProtectionProfiles {
if p1 == p2 {
serverExtensions.srtpProtectionProfile = p1
c.srtpProtectionProfile = p1
break SRTPLoop
}
}
}
}
if c.config.Bugs.SendSRTPProtectionProfile != 0 {
serverExtensions.srtpProtectionProfile = c.config.Bugs.SendSRTPProtectionProfile
}
if expected := c.config.Bugs.ExpectedCustomExtension; expected != nil {
if hs.clientHello.customExtension != *expected {
return fmt.Errorf("tls: bad custom extension contents %q", hs.clientHello.customExtension)
}
}
serverExtensions.customExtension = config.Bugs.CustomExtension
if c.config.Bugs.AdvertiseTicketExtension {
serverExtensions.ticketSupported = true
}
if c.config.Bugs.SendSupportedPointFormats != nil {
serverExtensions.supportedPoints = c.config.Bugs.SendSupportedPointFormats
}
if c.config.Bugs.SendServerSupportedCurves {
serverExtensions.supportedCurves = c.config.curvePreferences()
}
if !hs.clientHello.hasGREASEExtension && config.Bugs.ExpectGREASE {
return errors.New("tls: no GREASE extension found")
}
serverExtensions.serverNameAck = c.config.Bugs.SendServerNameAck
serverExtensions.pqExperimentSignal = hs.clientHello.pqExperimentSignal
return nil
}
// checkForResumption returns true if we should perform resumption on this connection.
func (hs *serverHandshakeState) checkForResumption() bool {
c := hs.c
ticket := hs.clientHello.sessionTicket
if len(ticket) == 0 && len(hs.clientHello.pskIdentities) > 0 && c.config.Bugs.AcceptAnySession {
ticket = hs.clientHello.pskIdentities[0].ticket
}
if len(ticket) > 0 {
if c.config.SessionTicketsDisabled {
return false
}
var ok bool
if hs.sessionState, ok = c.decryptTicket(ticket); !ok {
return false
}
} else {
if c.config.ServerSessionCache == nil {
return false
}
var ok bool
sessionId := string(hs.clientHello.sessionId)
if hs.sessionState, ok = c.config.ServerSessionCache.Get(sessionId); !ok {
return false
}
}
if c.config.Bugs.AcceptAnySession {
// Replace the cipher suite with one known to work, to test
// cross-version resumption attempts.
hs.sessionState.cipherSuite = TLS_RSA_WITH_AES_128_CBC_SHA
} else {
// Never resume a session for a different SSL 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.
hs.suite = c.tryCipherSuite(hs.sessionState.cipherSuite, c.config.cipherSuites(), c.vers, hs.ellipticOk, hs.ecdsaOk)
if hs.suite == nil {
return false
}
sessionHasClientCerts := len(hs.sessionState.certificates) != 0
needClientCerts := c.config.ClientAuth == RequireAnyClientCert || c.config.ClientAuth == RequireAndVerifyClientCert
if needClientCerts && !sessionHasClientCerts {
return false
}
if sessionHasClientCerts && c.config.ClientAuth == NoClientCert {
return false
}
return true
}
func (hs *serverHandshakeState) doResumeHandshake() error {
c := hs.c
hs.hello.cipherSuite = hs.suite.id
if c.config.Bugs.SendCipherSuite != 0 {
hs.hello.cipherSuite = c.config.Bugs.SendCipherSuite
}
// 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.extensions.ticketSupported = c.config.Bugs.RenewTicketOnResume
if c.config.Bugs.SendSCTListOnResume != nil {
hs.hello.extensions.sctList = c.config.Bugs.SendSCTListOnResume
}
if c.config.Bugs.SendOCSPResponseOnResume != nil {
// There is no way, syntactically, to send an OCSP response on a
// resumption handshake.
hs.hello.extensions.ocspStapling = true
}
hs.finishedHash = newFinishedHash(c.wireVersion, c.isDTLS, hs.suite)
hs.finishedHash.discardHandshakeBuffer()
hs.writeClientHash(hs.clientHello.marshal())
hs.writeServerHash(hs.hello.marshal())
c.writeRecord(recordTypeHandshake, hs.hello.marshal())
if len(hs.sessionState.certificates) > 0 {
if _, err := hs.processCertsFromClient(hs.sessionState.certificates); err != nil {
return err
}
}
hs.masterSecret = hs.sessionState.masterSecret
c.extendedMasterSecret = hs.sessionState.extendedMasterSecret
return nil
}
func (hs *serverHandshakeState) doFullHandshake() error {
config := hs.c.config
c := hs.c
isPSK := hs.suite.flags&suitePSK != 0
if !isPSK && hs.clientHello.ocspStapling && len(hs.cert.OCSPStaple) > 0 && !c.config.Bugs.NoOCSPStapling {
hs.hello.extensions.ocspStapling = true
}
if hs.clientHello.sctListSupported && len(hs.cert.SignedCertificateTimestampList) > 0 && !c.config.Bugs.NoSignedCertificateTimestamps {
hs.hello.extensions.sctList = hs.cert.SignedCertificateTimestampList
}
if len(c.clientVerify) > 0 && config.Bugs.SendSCTListOnRenegotiation != nil {
hs.hello.extensions.sctList = config.Bugs.SendSCTListOnRenegotiation
}
hs.hello.extensions.ticketSupported = hs.clientHello.ticketSupported && !config.SessionTicketsDisabled && c.vers > VersionSSL30
hs.hello.cipherSuite = hs.suite.id
if config.Bugs.SendCipherSuite != 0 {
hs.hello.cipherSuite = config.Bugs.SendCipherSuite
}
c.extendedMasterSecret = hs.hello.extensions.extendedMasterSecret
// Generate a session ID if we're to save the session.
if !hs.hello.extensions.ticketSupported && config.ServerSessionCache != nil {
hs.hello.sessionId = make([]byte, 32)
if _, err := io.ReadFull(config.rand(), hs.hello.sessionId); err != nil {
c.sendAlert(alertInternalError)
return errors.New("tls: short read from Rand: " + err.Error())
}
}
if config.Bugs.EchoSessionIDInFullHandshake {
hs.hello.sessionId = hs.clientHello.sessionId
}
hs.finishedHash = newFinishedHash(c.wireVersion, c.isDTLS, hs.suite)
hs.writeClientHash(hs.clientHello.marshal())
hs.writeServerHash(hs.hello.marshal())
if config.Bugs.SendSNIWarningAlert {
c.SendAlert(alertLevelWarning, alertUnrecognizedName)
}
c.writeRecord(recordTypeHandshake, hs.hello.marshal())
if !isPSK {
certMsg := new(certificateMsg)
if !config.Bugs.EmptyCertificateList {
for _, certData := range hs.cert.Certificate {
certMsg.certificates = append(certMsg.certificates, certificateEntry{
data: certData,
})
}
}
if !config.Bugs.UnauthenticatedECDH {
certMsgBytes := certMsg.marshal()
hs.writeServerHash(certMsgBytes)
c.writeRecord(recordTypeHandshake, certMsgBytes)
}
}
if hs.hello.extensions.ocspStapling && !c.config.Bugs.SkipCertificateStatus {
certStatus := new(certificateStatusMsg)
certStatus.statusType = statusTypeOCSP
certStatus.response = hs.cert.OCSPStaple
if len(c.clientVerify) > 0 && config.Bugs.SendOCSPResponseOnRenegotiation != nil {
certStatus.response = config.Bugs.SendOCSPResponseOnRenegotiation
}
hs.writeServerHash(certStatus.marshal())
c.writeRecord(recordTypeHandshake, certStatus.marshal())
}
keyAgreement := hs.suite.ka(c.vers)
skx, err := keyAgreement.generateServerKeyExchange(config, hs.cert, hs.clientHello, hs.hello, c.vers)
if err != nil {
c.sendAlert(alertHandshakeFailure)
return err
}
if ecdhe, ok := keyAgreement.(*ecdheKeyAgreement); ok {
c.curveID = ecdhe.curveID
}
if skx != nil && !config.Bugs.SkipServerKeyExchange {
hs.writeServerHash(skx.marshal())
c.writeRecord(recordTypeHandshake, skx.marshal())
}
if config.ClientAuth >= RequestClientCert {
// Request a client certificate
certReq := &certificateRequestMsg{
vers: c.wireVersion,
certificateTypes: config.ClientCertificateTypes,
}
if certReq.certificateTypes == nil {
certReq.certificateTypes = []byte{
byte(CertTypeRSASign),
byte(CertTypeECDSASign),
}
}
if c.vers >= VersionTLS12 {
certReq.hasSignatureAlgorithm = true
if !config.Bugs.NoSignatureAlgorithms {
certReq.signatureAlgorithms = config.verifySignatureAlgorithms()
}
}
// An empty list of certificateAuthorities signals to
// the client that it may send any certificate in response
// to our request. When we know the CAs we trust, then
// we can send them down, so that the client can choose
// an appropriate certificate to give to us.
if config.ClientCAs != nil {
certReq.certificateAuthorities = config.ClientCAs.Subjects()
}
hs.writeServerHash(certReq.marshal())
c.writeRecord(recordTypeHandshake, certReq.marshal())
}
helloDone := new(serverHelloDoneMsg)
hs.writeServerHash(helloDone.marshal())
c.writeRecord(recordTypeHandshake, helloDone.marshal())
c.flushHandshake()
var pub crypto.PublicKey // public key for client auth, if any
if err := c.simulatePacketLoss(nil); err != nil {
return err
}
msg, err := c.readHandshake()
if err != nil {
return err
}
var ok bool
// If we requested a client certificate, then the client must send a
// certificate message, even if it's empty.
if config.ClientAuth >= RequestClientCert {
var certMsg *certificateMsg
var certificates [][]byte
if certMsg, ok = msg.(*certificateMsg); ok {
if c.vers == VersionSSL30 && len(certMsg.certificates) == 0 {
return errors.New("tls: empty certificate message in SSL 3.0")
}
hs.writeClientHash(certMsg.marshal())
for _, cert := range certMsg.certificates {
certificates = append(certificates, cert.data)
}
} else if c.vers == VersionSSL30 {
// In SSL 3.0, no certificate is signaled by a warning
// alert which we translate to ssl3NoCertificateMsg.
if _, ok := msg.(*ssl3NoCertificateMsg); !ok {
return errors.New("tls: client provided neither a certificate nor no_certificate warning alert")
}
} else {
// In TLS, the Certificate message is required. In SSL
// 3.0, the peer skips it when sending no certificates.
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(certMsg, msg)
}
if len(certificates) == 0 {
// The client didn't actually send a certificate
switch config.ClientAuth {
case RequireAnyClientCert, RequireAndVerifyClientCert:
c.sendAlert(alertBadCertificate)
return errors.New("tls: client didn't provide a certificate")
}
}
pub, err = hs.processCertsFromClient(certificates)
if err != nil {
return err
}
msg, err = c.readHandshake()
if err != nil {
return err
}
}
// Get client key exchange
ckx, ok := msg.(*clientKeyExchangeMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(ckx, msg)
}
hs.writeClientHash(ckx.marshal())
preMasterSecret, err := keyAgreement.processClientKeyExchange(config, hs.cert, ckx, c.vers)
if err != nil {
c.sendAlert(alertHandshakeFailure)
return err
}
if c.extendedMasterSecret {
hs.masterSecret = extendedMasterFromPreMasterSecret(c.vers, hs.suite, preMasterSecret, hs.finishedHash)
} 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.clientHello.random, hs.hello.random)
}
// 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.
var sigAlg signatureAlgorithm
if certVerify.hasSignatureAlgorithm {
sigAlg = certVerify.signatureAlgorithm
c.peerSignatureAlgorithm = sigAlg
}
if c.vers > VersionSSL30 {
err = verifyMessage(c.vers, pub, c.config, sigAlg, hs.finishedHash.buffer, certVerify.signature)
} else {
// SSL 3.0's client certificate construction is
// incompatible with signatureAlgorithm.
rsaPub, ok := pub.(*rsa.PublicKey)
if !ok {
err = errors.New("unsupported key type for client certificate")
} else {
digest := hs.finishedHash.hashForClientCertificateSSL3(hs.masterSecret)
err = rsa.VerifyPKCS1v15(rsaPub, crypto.MD5SHA1, digest, certVerify.signature)
}
}
if err != nil {
c.sendAlert(alertBadCertificate)
return errors.New("could not validate signature of connection nonces: " + err.Error())
}
hs.writeClientHash(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(c.vers))
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(c.vers, clientKey, clientIV)
serverCipher = hs.suite.aead(c.vers, serverKey, serverIV)
}
c.in.prepareCipherSpec(c.wireVersion, clientCipher, clientHash)
c.out.prepareCipherSpec(c.wireVersion, serverCipher, serverHash)
return nil
}
func (hs *serverHandshakeState) readFinished(out []byte, isResume bool) error {
c := hs.c
c.readRecord(recordTypeChangeCipherSpec)
if err := c.in.error(); err != nil {
return err
}
if hs.hello.extensions.nextProtoNeg {
msg, err := c.readHandshake()
if err != nil {
return err
}
nextProto, ok := msg.(*nextProtoMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(nextProto, msg)
}
hs.writeClientHash(nextProto.marshal())
c.clientProtocol = nextProto.proto
}
if hs.hello.extensions.channelIDRequested {
msg, err := c.readHandshake()
if err != nil {
return err
}
channelIDMsg, ok := msg.(*channelIDMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(channelIDMsg, msg)
}
var resumeHash []byte
if isResume {
resumeHash = hs.sessionState.handshakeHash
}
channelID, err := verifyChannelIDMessage(channelIDMsg, hs.finishedHash.hashForChannelID(resumeHash))
if err != nil {
return err
}
c.channelID = channelID
hs.writeClientHash(channelIDMsg.marshal())
}
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")
}
c.clientVerify = append(c.clientVerify[:0], clientFinished.verifyData...)
copy(out, clientFinished.verifyData)
hs.writeClientHash(clientFinished.marshal())
return nil
}
func (hs *serverHandshakeState) sendSessionTicket() error {
c := hs.c
state := sessionState{
vers: c.vers,
cipherSuite: hs.suite.id,
masterSecret: hs.masterSecret,
certificates: hs.certsFromClient,
handshakeHash: hs.finishedHash.Sum(),
}
if !hs.hello.extensions.ticketSupported || hs.c.config.Bugs.SkipNewSessionTicket {
if c.config.ServerSessionCache != nil && len(hs.hello.sessionId) != 0 {
c.config.ServerSessionCache.Put(string(hs.hello.sessionId), &state)
}
return nil
}
m := new(newSessionTicketMsg)
m.vers = c.wireVersion
m.isDTLS = c.isDTLS
if c.config.Bugs.SendTicketLifetime != 0 {
m.ticketLifetime = uint32(c.config.Bugs.SendTicketLifetime / time.Second)
}
if !c.config.Bugs.SendEmptySessionTicket {
var err error
m.ticket, err = c.encryptTicket(&state)
if err != nil {
return err
}
}
hs.writeServerHash(m.marshal())
c.writeRecord(recordTypeHandshake, m.marshal())
return nil
}
func (hs *serverHandshakeState) sendFinished(out []byte, isResume bool) error {
c := hs.c
finished := new(finishedMsg)
finished.verifyData = hs.finishedHash.serverSum(hs.masterSecret)
copy(out, finished.verifyData)
if c.config.Bugs.BadFinished {
finished.verifyData[0]++
}
c.serverVerify = append(c.serverVerify[:0], finished.verifyData...)
hs.finishedBytes = finished.marshal()
hs.writeServerHash(hs.finishedBytes)
postCCSBytes := hs.finishedBytes
if c.config.Bugs.FragmentAcrossChangeCipherSpec {
c.writeRecord(recordTypeHandshake, postCCSBytes[:5])
postCCSBytes = postCCSBytes[5:]
} else if c.config.Bugs.SendUnencryptedFinished {
c.writeRecord(recordTypeHandshake, postCCSBytes)
postCCSBytes = nil
}
if !c.config.Bugs.SkipChangeCipherSpec {
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 && len(postCCSBytes) > 0 {
c.writeRecord(recordTypeHandshake, postCCSBytes)
if c.config.Bugs.SendExtraFinished {
c.writeRecord(recordTypeHandshake, finished.marshal())
}
}
if isResume || (!c.config.Bugs.PackHelloRequestWithFinished && !c.config.Bugs.PackAppDataWithHandshake) {
// Defer flushing until Renegotiate() or Write().
c.flushHandshake()
}
c.cipherSuite = hs.suite
return nil
}
// processCertsFromClient takes a chain of client certificates either from a
// Certificates message or from a sessionState and verifies them. It returns
// the public key of the leaf certificate.
func (hs *serverHandshakeState) processCertsFromClient(certificates [][]byte) (crypto.PublicKey, error) {
c := hs.c
hs.certsFromClient = certificates
certs := make([]*x509.Certificate, len(certificates))
var err error
for i, asn1Data := range certificates {
if certs[i], err = x509.ParseCertificate(asn1Data); err != nil {
c.sendAlert(alertBadCertificate)
return nil, errors.New("tls: failed to parse client certificate: " + err.Error())
}
}
if c.config.ClientAuth >= VerifyClientCertIfGiven && len(certs) > 0 {
opts := x509.VerifyOptions{
Roots: c.config.ClientCAs,
CurrentTime: c.config.time(),
Intermediates: x509.NewCertPool(),
KeyUsages: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth},
}
for _, cert := range certs[1:] {
opts.Intermediates.AddCert(cert)
}
chains, err := certs[0].Verify(opts)
if err != nil {
c.sendAlert(alertBadCertificate)
return nil, errors.New("tls: failed to verify client's certificate: " + err.Error())
}
ok := false
for _, ku := range certs[0].ExtKeyUsage {
if ku == x509.ExtKeyUsageClientAuth {
ok = true
break
}
}
if !ok {
c.sendAlert(alertHandshakeFailure)
return nil, errors.New("tls: client's certificate's extended key usage doesn't permit it to be used for client authentication")
}
c.verifiedChains = chains
}
if len(certs) > 0 {
pub := certs[0].PublicKey
switch pub.(type) {
case *ecdsa.PublicKey, *rsa.PublicKey, ed25519.PublicKey:
break
default:
c.sendAlert(alertUnsupportedCertificate)
return nil, fmt.Errorf("tls: client's certificate contains an unsupported public key of type %T", pub)
}
c.peerCertificates = certs
return pub, nil
}
return nil, nil
}
func verifyChannelIDMessage(channelIDMsg *channelIDMsg, channelIDHash []byte) (*ecdsa.PublicKey, error) {
x := new(big.Int).SetBytes(channelIDMsg.channelID[0:32])
y := new(big.Int).SetBytes(channelIDMsg.channelID[32:64])
r := new(big.Int).SetBytes(channelIDMsg.channelID[64:96])
s := new(big.Int).SetBytes(channelIDMsg.channelID[96:128])
if !elliptic.P256().IsOnCurve(x, y) {
return nil, errors.New("tls: invalid channel ID public key")
}
channelID := &ecdsa.PublicKey{Curve: elliptic.P256(), X: x, Y: y}
if !ecdsa.Verify(channelID, channelIDHash, r, s) {
return nil, errors.New("tls: invalid channel ID signature")
}
return channelID, nil
}
func (hs *serverHandshakeState) writeServerHash(msg []byte) {
// writeServerHash is called before writeRecord.
hs.writeHash(msg, hs.c.sendHandshakeSeq)
}
func (hs *serverHandshakeState) writeClientHash(msg []byte) {
// writeClientHash is called after readHandshake.
hs.writeHash(msg, hs.c.recvHandshakeSeq-1)
}
func (hs *serverHandshakeState) 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)
}
}
// tryCipherSuite returns a cipherSuite with the given id if that cipher suite
// is acceptable to use.
func (c *Conn) tryCipherSuite(id uint16, supportedCipherSuites []uint16, version uint16, ellipticOk, ecdsaOk bool) *cipherSuite {
for _, supported := range supportedCipherSuites {
if id == supported {
var candidate *cipherSuite
for _, s := range cipherSuites {
if s.id == id {
candidate = s
break
}
}
if candidate == nil {
continue
}
// Don't select a ciphersuite which we can't
// support for this client.
if version >= VersionTLS13 || candidate.flags&suiteTLS13 != 0 {
if version < VersionTLS13 || candidate.flags&suiteTLS13 == 0 {
continue
}
return candidate
}
if (candidate.flags&suiteECDHE != 0) && !ellipticOk {
continue
}
if (candidate.flags&suiteECDSA != 0) != ecdsaOk {
continue
}
if version < VersionTLS12 && candidate.flags&suiteTLS12 != 0 {
continue
}
return candidate
}
}
return nil
}
func isTLS12Cipher(id uint16) bool {
for _, cipher := range cipherSuites {
if cipher.id != id {
continue
}
return cipher.flags&suiteTLS12 != 0
}
// Unknown cipher.
return false
}
func isGREASEValue(val uint16) bool {
return val&0x0f0f == 0x0a0a && val&0xff == val>>8
}
func verifyPSKBinder(version uint16, clientHello *clientHelloMsg, sessionState *sessionState, binderToVerify, firstClientHello, helloRetryRequest []byte) error {
binderLen := 2
for _, binder := range clientHello.pskBinders {
binderLen += 1 + len(binder)
}
truncatedHello := clientHello.marshal()
truncatedHello = truncatedHello[:len(truncatedHello)-binderLen]
pskCipherSuite := cipherSuiteFromID(sessionState.cipherSuite)
if pskCipherSuite == nil {
return errors.New("tls: Unknown cipher suite for PSK in session")
}
binder := computePSKBinder(sessionState.masterSecret, version, resumptionPSKBinderLabel, pskCipherSuite, firstClientHello, helloRetryRequest, truncatedHello)
if !bytes.Equal(binder, binderToVerify) {
return errors.New("tls: PSK binder does not verify")
}
return nil
}