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crypto/tls: implement X25519MLKEM768

Browse source 
This makes three related changes that work particularly well together
and would require significant extra work to do separately: it replaces
X25519Kyber768Draft00 with X25519MLKEM768, it makes CurvePreferences
ordering crypto/tls-selected, and applies a preference to PQ key
exchange methods over key shares (to mitigate downgrades).

TestHandshakeServerUnsupportedKeyShare was removed because we are not
rejecting unsupported key shares anymore (nor do we select them, and
rejecting them actively is a MAY). It would have been nice to keep the
test to check we still continue successfully, but testClientHelloFailure
is broken in the face of any server-side behavior which requires writing
any other messages back to the client, or reading them.

Updates #69985
Fixes #69393

Change-Id: I58de76f5b8742a9bd4543fd7907c48e038507b19
Reviewed-on: https://go-review.googlesource.com/c/go/+/630775
Reviewed-by: Roland Shoemaker <roland@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Filippo Valsorda <filippo@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
This commit is contained in:
Filippo Valsorda 2024-11-21 21:21:58 +01:00 • committed by Gopher Robot
parent 68e64cfceb
commit 77ea502eee
14 changed files with 177 additions and 206 deletions
Download patch file Download diff file Expand all files Collapse all files

13
bogo_config.json
View file

@ -33,8 +33,14 @@
"TLS-ECH-Server-EarlyData": "Go does not support early (0-RTT) data",
"TLS-ECH-Server-EarlyDataRejected": "Go does not support early (0-RTT) data",
"CurveTest-Client-Kyber-TLS13": "Temporarily disabled since the curve ID is not exposed and it cannot be correctly configured",
"CurveTest-Server-Kyber-TLS13": "Temporarily disabled since the curve ID is not exposed and it cannot be correctly configured",
"MLKEMKeyShareIncludedSecond": "BoGo wants us to order the key shares based on its preference, but we don't support that",
"MLKEMKeyShareIncludedThird": "BoGo wants us to order the key shares based on its preference, but we don't support that",
"PostQuantumNotEnabledByDefaultInClients": "We do enable it by default!",
"*-Kyber-TLS13": "We don't support Kyber, only ML-KEM (BoGo bug ignoring AllCurves?)",
"SendEmptySessionTicket-TLS13": "https://github.com/golang/go/issues/70513",
"*-SignDefault-*": "TODO, partially it encodes BoringSSL defaults, partially we might be missing some implicit behavior of a missing flag",
"SendV2ClientHello*": "We don't support SSLv2",
"*QUIC*": "No QUIC support",
@ -238,6 +244,7 @@
23,
24,
25,
29
29,
4588
]
}

9
bogo_shim_test.go
View file

@ -420,7 +420,7 @@ func TestBogoSuite(t *testing.T) {
if *bogoLocalDir != "" {
bogoDir = *bogoLocalDir
} else {
const boringsslModVer = "v0.0.0-20240523173554-273a920f84e8"
const boringsslModVer = "v0.0.0-20241120195446-5cce3fbd23e1"
bogoDir = cryptotest.FetchModule(t, "boringssl.googlesource.com/boringssl.git", boringsslModVer)
}
@ -473,11 +473,8 @@ func TestBogoSuite(t *testing.T) {
// are present in the output. They are only checked if -bogo-filter
// was not passed.
assertResults := map[string]string{
// TODO: these tests are temporarily disabled, since we don't expose the
// necessary curve ID, and it's currently not possible to correctly
// configure it.
// "CurveTest-Client-Kyber-TLS13": "PASS",
// "CurveTest-Server-Kyber-TLS13": "PASS",
"CurveTest-Client-MLKEM-TLS13": "PASS",
"CurveTest-Server-MLKEM-TLS13": "PASS",
}
for name, result := range results.Tests {

62
common.go
View file

@ -145,17 +145,21 @@ const (
type CurveID uint16
const (
CurveP256 CurveID = 23
CurveP384 CurveID = 24
CurveP521 CurveID = 25
X25519 CurveID = 29
// Experimental codepoint for X25519Kyber768Draft00, specified in
// draft-tls-westerbaan-xyber768d00-03. Not exported, as support might be
// removed in the future.
x25519Kyber768Draft00 CurveID = 0x6399 // X25519Kyber768Draft00
CurveP256 CurveID = 23
CurveP384 CurveID = 24
CurveP521 CurveID = 25
X25519 CurveID = 29
X25519MLKEM768 CurveID = 4588
)
func isTLS13OnlyKeyExchange(curve CurveID) bool {
return curve == X25519MLKEM768
}
func isPQKeyExchange(curve CurveID) bool {
return curve == X25519MLKEM768
}
// TLS 1.3 Key Share. See RFC 8446, Section 4.2.8.
type keyShare struct {
group CurveID
@ -419,9 +423,12 @@ type ClientHelloInfo struct {
// client is using SNI (see RFC 4366, Section 3.1).
ServerName string
// SupportedCurves lists the elliptic curves supported by the client.
// SupportedCurves is set only if the Supported Elliptic Curves
// Extension is being used (see RFC 4492, Section 5.1.1).
// SupportedCurves lists the key exchange mechanisms supported by the
// client. It was renamed to "supported groups" in TLS 1.3, see RFC 8446,
// Section 4.2.7 and [CurveID].
//
// SupportedCurves may be nil in TLS 1.2 and lower if the Supported Elliptic
// Curves Extension is not being used (see RFC 4492, Section 5.1.1).
SupportedCurves []CurveID
// SupportedPoints lists the point formats supported by the client.
@ -761,14 +768,15 @@ type Config struct {
// which is currently TLS 1.3.
MaxVersion uint16
// CurvePreferences contains the elliptic curves that will be used in
// an ECDHE handshake, in preference order. If empty, the default will
// be used. The client will use the first preference as the type for
// its key share in TLS 1.3. This may change in the future.
// CurvePreferences contains a set of supported key exchange mechanisms.
// The name refers to elliptic curves for legacy reasons, see [CurveID].
// The order of the list is ignored, and key exchange mechanisms are chosen
// from this list using an internal preference order. If empty, the default
// will be used.
//
// From Go 1.23, the default includes the X25519Kyber768Draft00 hybrid
// From Go 1.24, the default includes the [X25519MLKEM768] hybrid
// post-quantum key exchange. To disable it, set CurvePreferences explicitly
// or use the GODEBUG=tlskyber=0 environment variable.
// or use the GODEBUG=tlsmlkem=0 environment variable.
CurvePreferences []CurveID
// DynamicRecordSizingDisabled disables adaptive sizing of TLS records.
@ -1176,23 +1184,19 @@ func supportedVersionsFromMax(maxVersion uint16) []uint16 {
func (c *Config) curvePreferences(version uint16) []CurveID {
var curvePreferences []CurveID
if c != nil && len(c.CurvePreferences) != 0 {
curvePreferences = slices.Clone(c.CurvePreferences)
if fips140tls.Required() {
return slices.DeleteFunc(curvePreferences, func(c CurveID) bool {
return !slices.Contains(defaultCurvePreferencesFIPS, c)
})
}
} else if fips140tls.Required() {
if fips140tls.Required() {
curvePreferences = slices.Clone(defaultCurvePreferencesFIPS)
} else {
curvePreferences = defaultCurvePreferences()
}
if version < VersionTLS13 {
return slices.DeleteFunc(curvePreferences, func(c CurveID) bool {
return c == x25519Kyber768Draft00
if c != nil && len(c.CurvePreferences) != 0 {
curvePreferences = slices.DeleteFunc(curvePreferences, func(x CurveID) bool {
return !slices.Contains(c.CurvePreferences, x)
})
}
if version < VersionTLS13 {
curvePreferences = slices.DeleteFunc(curvePreferences, isTLS13OnlyKeyExchange)
}
return curvePreferences
}

6
common_string.go
View file

@ -71,13 +71,13 @@ func _() {
_ = x[CurveP384-24]
_ = x[CurveP521-25]
_ = x[X25519-29]
_ = x[x25519Kyber768Draft00-25497]
_ = x[X25519MLKEM768-4588]
}
const (
_CurveID_name_0 = "CurveP256CurveP384CurveP521"
_CurveID_name_1 = "X25519"
_CurveID_name_2 = "X25519Kyber768Draft00"
_CurveID_name_2 = "X25519MLKEM768"
)
var (
@ -91,7 +91,7 @@ func (i CurveID) String() string {
return _CurveID_name_0[_CurveID_index_0[i]:_CurveID_index_0[i+1]]
case i == 29:
return _CurveID_name_1
case i == 25497:
case i == 4588:
return _CurveID_name_2
default:
return "CurveID(" + strconv.FormatInt(int64(i), 10) + ")"

9
defaults.go
View file

@ -13,14 +13,15 @@ import (
// Defaults are collected in this file to allow distributions to more easily patch
// them to apply local policies.
var tlskyber = godebug.New("tlskyber")
var tlsmlkem = godebug.New("tlsmlkem")
// defaultCurvePreferences is the default set of supported key exchanges, as
// well as the preference order.
func defaultCurvePreferences() []CurveID {
if tlskyber.Value() == "0" {
if tlsmlkem.Value() == "0" {
return []CurveID{X25519, CurveP256, CurveP384, CurveP521}
}
// For now, x25519Kyber768Draft00 must always be followed by X25519.
return []CurveID{x25519Kyber768Draft00, X25519, CurveP256, CurveP384, CurveP521}
return []CurveID{X25519MLKEM768, X25519, CurveP256, CurveP384, CurveP521}
}
// defaultSupportedSignatureAlgorithms contains the signature and hash algorithms that

5
fips_test.go
View file

@ -184,16 +184,13 @@ func TestFIPSServerCipherSuites(t *testing.T) {
func TestFIPSServerCurves(t *testing.T) {
serverConfig := testConfig.Clone()
serverConfig.CurvePreferences = nil
serverConfig.BuildNameToCertificate()
for _, curveid := range defaultCurvePreferences() {
t.Run(fmt.Sprintf("curve=%d", curveid), func(t *testing.T) {
clientConfig := testConfig.Clone()
clientConfig.CurvePreferences = []CurveID{curveid}
if curveid == x25519Kyber768Draft00 {
// x25519Kyber768Draft00 is not supported standalone.
clientConfig.CurvePreferences = append(clientConfig.CurvePreferences, X25519)
}
runWithFIPSDisabled(t, func(t *testing.T) {
if _, _, err := testHandshake(t, clientConfig, serverConfig); err != nil {

25
handshake_client.go
View file

@ -24,6 +24,7 @@ import (
"internal/godebug"
"io"
"net"
"slices"
"strconv"
"strings"
"time"
@ -156,7 +157,9 @@ func (c *Conn) makeClientHello() (*clientHelloMsg, *keySharePrivateKeys, *echCli
}
curveID := hello.supportedCurves[0]
keyShareKeys = &keySharePrivateKeys{curveID: curveID}
if curveID == x25519Kyber768Draft00 {
// Note that if X25519MLKEM768 is supported, it will be first because
// the preference order is fixed.
if curveID == X25519MLKEM768 {
keyShareKeys.ecdhe, err = generateECDHEKey(config.rand(), X25519)
if err != nil {
return nil, nil, nil, err
@ -165,18 +168,20 @@ func (c *Conn) makeClientHello() (*clientHelloMsg, *keySharePrivateKeys, *echCli
if _, err := io.ReadFull(config.rand(), seed); err != nil {
return nil, nil, nil, err
}
keyShareKeys.kyber, err = mlkem.NewDecapsulationKey768(seed)
keyShareKeys.mlkem, err = mlkem.NewDecapsulationKey768(seed)
if err != nil {
return nil, nil, nil, err
}
// For draft-tls-westerbaan-xyber768d00-03, we send both a hybrid
// and a standard X25519 key share, since most servers will only
// support the latter. We reuse the same X25519 ephemeral key for
// both, as allowed by draft-ietf-tls-hybrid-design-09, Section 3.2.
mlkemEncapsulationKey := keyShareKeys.mlkem.EncapsulationKey().Bytes()
x25519EphemeralKey := keyShareKeys.ecdhe.PublicKey().Bytes()
hello.keyShares = []keyShare{
{group: x25519Kyber768Draft00, data: append(keyShareKeys.ecdhe.PublicKey().Bytes(),
keyShareKeys.kyber.EncapsulationKey().Bytes()...)},
{group: X25519, data: keyShareKeys.ecdhe.PublicKey().Bytes()},
{group: X25519MLKEM768, data: append(mlkemEncapsulationKey, x25519EphemeralKey...)},
}
// If both X25519MLKEM768 and X25519 are supported, we send both key
// shares (as a fallback) and we reuse the same X25519 ephemeral
// key, as allowed by draft-ietf-tls-hybrid-design-09, Section 3.2.
if slices.Contains(hello.supportedCurves, X25519) {
hello.keyShares = append(hello.keyShares, keyShare{group: X25519, data: x25519EphemeralKey})
}
} else {
if _, ok := curveForCurveID(curveID); !ok {
@ -711,7 +716,7 @@ func (hs *clientHandshakeState) doFullHandshake() error {
if ok {
err = keyAgreement.processServerKeyExchange(c.config, hs.hello, hs.serverHello, c.peerCertificates[0], skx)
if err != nil {
c.sendAlert(alertUnexpectedMessage)
c.sendAlert(alertIllegalParameter)
return err
}
if len(skx.key) >= 3 && skx.key[0] == 3 /* named curve */ {

29
handshake_client_tls13.go
View file

@ -322,12 +322,11 @@ func (hs *clientHandshakeStateTLS13) processHelloRetryRequest() error {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: server sent an unnecessary HelloRetryRequest key_share")
}
// Note: we don't support selecting X25519Kyber768Draft00 in a HRR,
// because we currently only support it at all when CurvePreferences is
// empty, which will cause us to also send a key share for it.
// Note: we don't support selecting X25519MLKEM768 in a HRR, because it
// is currently first in preference order, so if it's enabled we'll
// always send a key share for it.
//
// This will have to change once we support selecting hybrid KEMs
// without sending key shares for them.
// This will have to change once we support multiple hybrid KEMs.
if _, ok := curveForCurveID(curveID); !ok {
c.sendAlert(alertInternalError)
return errors.New("tls: CurvePreferences includes unsupported curve")
@ -480,12 +479,12 @@ func (hs *clientHandshakeStateTLS13) establishHandshakeKeys() error {
c := hs.c
ecdhePeerData := hs.serverHello.serverShare.data
if hs.serverHello.serverShare.group == x25519Kyber768Draft00 {
if len(ecdhePeerData) != x25519PublicKeySize+mlkem.CiphertextSize768 {
if hs.serverHello.serverShare.group == X25519MLKEM768 {
if len(ecdhePeerData) != mlkem.CiphertextSize768+x25519PublicKeySize {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: invalid server key share")
return errors.New("tls: invalid server X25519MLKEM768 key share")
}
ecdhePeerData = hs.serverHello.serverShare.data[:x25519PublicKeySize]
ecdhePeerData = hs.serverHello.serverShare.data[mlkem.CiphertextSize768:]
}
peerKey, err := hs.keyShareKeys.ecdhe.Curve().NewPublicKey(ecdhePeerData)
if err != nil {
@ -497,17 +496,17 @@ func (hs *clientHandshakeStateTLS13) establishHandshakeKeys() error {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: invalid server key share")
}
if hs.serverHello.serverShare.group == x25519Kyber768Draft00 {
if hs.keyShareKeys.kyber == nil {
if hs.serverHello.serverShare.group == X25519MLKEM768 {
if hs.keyShareKeys.mlkem == nil {
return c.sendAlert(alertInternalError)
}
ciphertext := hs.serverHello.serverShare.data[x25519PublicKeySize:]
kyberShared, err := kyberDecapsulate(hs.keyShareKeys.kyber, ciphertext)
ciphertext := hs.serverHello.serverShare.data[:mlkem.CiphertextSize768]
mlkemShared, err := hs.keyShareKeys.mlkem.Decapsulate(ciphertext)
if err != nil {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: invalid Kyber server key share")
return errors.New("tls: invalid X25519MLKEM768 server key share")
}
sharedKey = append(sharedKey, kyberShared...)
sharedKey = append(mlkemShared, sharedKey...)
}
c.curveID = hs.serverHello.serverShare.group

2
handshake_server.go
View file

@ -705,7 +705,7 @@ func (hs *serverHandshakeState) doFullHandshake() error {
preMasterSecret, err := keyAgreement.processClientKeyExchange(c.config, hs.cert, ckx, c.vers)
if err != nil {
c.sendAlert(alertHandshakeFailure)
c.sendAlert(alertIllegalParameter)
return err
}
if hs.hello.extendedMasterSecret {

16
handshake_server_test.go
View file

@ -939,22 +939,6 @@ func TestHandshakeServerKeySharePreference(t *testing.T) {
runServerTestTLS13(t, test)
}
// TestHandshakeServerUnsupportedKeyShare tests a client that sends a key share
// that's not in the supported groups list.
func TestHandshakeServerUnsupportedKeyShare(t *testing.T) {
pk, _ := ecdh.P384().GenerateKey(rand.Reader)
clientHello := &clientHelloMsg{
vers: VersionTLS12,
random: make([]byte, 32),
supportedVersions: []uint16{VersionTLS13},
cipherSuites: []uint16{TLS_AES_128_GCM_SHA256},
compressionMethods: []uint8{compressionNone},
keyShares: []keyShare{{group: CurveP384, data: pk.PublicKey().Bytes()}},
supportedCurves: []CurveID{CurveP256},
}
testClientHelloFailure(t, testConfig, clientHello, "client sent key share for group it does not support")
}
func TestHandshakeServerALPN(t *testing.T) {
config := testConfig.Clone()
config.NextProtos = []string{"proto1", "proto2"}

89
handshake_server_tls13.go
View file

@ -20,6 +20,7 @@ import (
"internal/byteorder"
"io"
"slices"
"sort"
"time"
)
@ -195,37 +196,45 @@ func (hs *serverHandshakeStateTLS13) processClientHello() error {
hs.hello.cipherSuite = hs.suite.id
hs.transcript = hs.suite.hash.New()
// Pick the key exchange method in server preference order, but give
// priority to key shares, to avoid a HelloRetryRequest round-trip.
var selectedGroup CurveID
var clientKeyShare *keyShare
// First, if a post-quantum key exchange is available, use one. See
// draft-ietf-tls-key-share-prediction-01, Section 4 for why this must be
// first.
//
// Second, if the client sent a key share for a group we support, use that,
// to avoid a HelloRetryRequest round-trip.
//
// Finally, pick in our fixed preference order.
preferredGroups := c.config.curvePreferences(c.vers)
for _, preferredGroup := range preferredGroups {
ki := slices.IndexFunc(hs.clientHello.keyShares, func(ks keyShare) bool {
return ks.group == preferredGroup
})
if ki != -1 {
clientKeyShare = &hs.clientHello.keyShares[ki]
selectedGroup = clientKeyShare.group
if !slices.Contains(hs.clientHello.supportedCurves, selectedGroup) {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: client sent key share for group it does not support")
preferredGroups = slices.DeleteFunc(preferredGroups, func(group CurveID) bool {
return !slices.Contains(hs.clientHello.supportedCurves, group)
})
if len(preferredGroups) == 0 {
c.sendAlert(alertHandshakeFailure)
return errors.New("tls: no key exchanges supported by both client and server")
}
hasKeyShare := func(group CurveID) bool {
for _, ks := range hs.clientHello.keyShares {
if ks.group == group {
return true
}
}
return false
}
sort.SliceStable(preferredGroups, func(i, j int) bool {
return hasKeyShare(preferredGroups[i]) && !hasKeyShare(preferredGroups[j])
})
sort.SliceStable(preferredGroups, func(i, j int) bool {
return isPQKeyExchange(preferredGroups[i]) && !isPQKeyExchange(preferredGroups[j])
})
selectedGroup := preferredGroups[0]
var clientKeyShare *keyShare
for _, ks := range hs.clientHello.keyShares {
if ks.group == selectedGroup {
clientKeyShare = &ks
break
}
}
if selectedGroup == 0 {
for _, preferredGroup := range preferredGroups {
if slices.Contains(hs.clientHello.supportedCurves, preferredGroup) {
selectedGroup = preferredGroup
break
}
}
}
if selectedGroup == 0 {
c.sendAlert(alertHandshakeFailure)
return errors.New("tls: no ECDHE curve supported by both client and server")
}
if clientKeyShare == nil {
ks, err := hs.doHelloRetryRequest(selectedGroup)
if err != nil {
@ -237,13 +246,13 @@ func (hs *serverHandshakeStateTLS13) processClientHello() error {
ecdhGroup := selectedGroup
ecdhData := clientKeyShare.data
if selectedGroup == x25519Kyber768Draft00 {
if selectedGroup == X25519MLKEM768 {
ecdhGroup = X25519
if len(ecdhData) != x25519PublicKeySize+mlkem.EncapsulationKeySize768 {
if len(ecdhData) != mlkem.EncapsulationKeySize768+x25519PublicKeySize {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: invalid Kyber client key share")
return errors.New("tls: invalid X25519MLKEM768 client key share")
}
ecdhData = ecdhData[:x25519PublicKeySize]
ecdhData = ecdhData[mlkem.EncapsulationKeySize768:]
}
if _, ok := curveForCurveID(ecdhGroup); !ok {
c.sendAlert(alertInternalError)
@ -265,14 +274,24 @@ func (hs *serverHandshakeStateTLS13) processClientHello() error {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: invalid client key share")
}
if selectedGroup == x25519Kyber768Draft00 {
ciphertext, kyberShared, err := kyberEncapsulate(clientKeyShare.data[x25519PublicKeySize:])
if selectedGroup == X25519MLKEM768 {
k, err := mlkem.NewEncapsulationKey768(clientKeyShare.data[:mlkem.EncapsulationKeySize768])
if err != nil {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: invalid Kyber client key share")
return errors.New("tls: invalid X25519MLKEM768 client key share")
}
hs.sharedKey = append(hs.sharedKey, kyberShared...)
hs.hello.serverShare.data = append(hs.hello.serverShare.data, ciphertext...)
ciphertext, mlkemSharedSecret := k.Encapsulate()
// draft-kwiatkowski-tls-ecdhe-mlkem-02, Section 3.1.3: "For
// X25519MLKEM768, the shared secret is the concatenation of the ML-KEM
// shared secret and the X25519 shared secret. The shared secret is 64
// bytes (32 bytes for each part)."
hs.sharedKey = append(mlkemSharedSecret, hs.sharedKey...)
// draft-kwiatkowski-tls-ecdhe-mlkem-02, Section 3.1.2: "When the
// X25519MLKEM768 group is negotiated, the server's key exchange value
// is the concatenation of an ML-KEM ciphertext returned from
// encapsulation to the client's encapsulation key, and the server's
// ephemeral X25519 share."
hs.hello.serverShare.data = append(ciphertext, hs.hello.serverShare.data...)
}
selectedProto, err := negotiateALPN(c.config.NextProtos, hs.clientHello.alpnProtocols, c.quic != nil)

36
key_schedule.go
View file

@ -8,7 +8,6 @@ import (
"crypto/ecdh"
"crypto/hmac"
"crypto/internal/fips140/mlkem"
"crypto/internal/fips140/sha3"
"crypto/internal/fips140/tls13"
"errors"
"hash"
@ -53,40 +52,7 @@ func (c *cipherSuiteTLS13) exportKeyingMaterial(s *tls13.MasterSecret, transcrip
type keySharePrivateKeys struct {
curveID CurveID
ecdhe *ecdh.PrivateKey
kyber *mlkem.DecapsulationKey768
}
// kyberDecapsulate implements decapsulation according to Kyber Round 3.
func kyberDecapsulate(dk *mlkem.DecapsulationKey768, c []byte) ([]byte, error) {
K, err := dk.Decapsulate(c)
if err != nil {
return nil, err
}
return kyberSharedSecret(c, K), nil
}
// kyberEncapsulate implements encapsulation according to Kyber Round 3.
func kyberEncapsulate(ek []byte) (c, ss []byte, err error) {
k, err := mlkem.NewEncapsulationKey768(ek)
if err != nil {
return nil, nil, err
}
c, ss = k.Encapsulate()
return c, kyberSharedSecret(c, ss), nil
}
func kyberSharedSecret(c, K []byte) []byte {
// Package mlkem implements ML-KEM, which compared to Kyber removed a
// final hashing step. Compute SHAKE-256(K || SHA3-256(c), 32) to match Kyber.
// See https://words.filippo.io/mlkem768/#bonus-track-using-a-ml-kem-implementation-as-kyber-v3.
h := sha3.NewShake256()
h.Write(K)
ch := sha3.New256()
ch.Write(c)
h.Write(ch.Sum(nil))
out := make([]byte, 32)
h.Read(out)
return out
mlkem *mlkem.DecapsulationKey768
}
const x25519PublicKeySize = 32

19
key_schedule_test.go
View file

@ -6,7 +6,6 @@ package tls
import (
"bytes"
"crypto/internal/fips140/mlkem"
"crypto/internal/fips140/tls13"
"crypto/sha256"
"encoding/hex"
@ -118,21 +117,3 @@ func TestTrafficKey(t *testing.T) {
t.Errorf("cipherSuiteTLS13.trafficKey() gotIV = % x, want % x", gotIV, wantIV)
}
}
func TestKyberEncapsulate(t *testing.T) {
dk, err := mlkem.GenerateKey768()
if err != nil {
t.Fatal(err)
}
ct, ss, err := kyberEncapsulate(dk.EncapsulationKey().Bytes())
if err != nil {
t.Fatal(err)
}
dkSS, err := kyberDecapsulate(dk, ct)
if err != nil {
t.Fatal(err)
}
if !bytes.Equal(ss, dkSS) {
t.Fatalf("got %x, want %x", ss, dkSS)
}
}

63
tls_test.go
View file

@ -1887,26 +1887,21 @@ func testVerifyCertificates(t *testing.T, version uint16) {
}
}
func TestHandshakeKyber(t *testing.T) {
skipFIPS(t) // No Kyber768 in FIPS
if x25519Kyber768Draft00.String() != "X25519Kyber768Draft00" {
t.Fatalf("unexpected CurveID string: %v", x25519Kyber768Draft00.String())
}
func TestHandshakeMLKEM(t *testing.T) {
skipFIPS(t) // No X25519MLKEM768 in FIPS
var tests = []struct {
name string
clientConfig func(*Config)
serverConfig func(*Config)
preparation func(*testing.T)
expectClientSupport bool
expectKyber bool
expectMLKEM bool
expectHRR bool
}{
{
name: "Default",
expectClientSupport: true,
expectKyber: true,
expectMLKEM: true,
expectHRR: false,
},
{
@ -1922,7 +1917,7 @@ func TestHandshakeKyber(t *testing.T) {
config.CurvePreferences = []CurveID{X25519}
},
expectClientSupport: true,
expectKyber: false,
expectMLKEM: false,
expectHRR: false,
},
{
@ -1931,9 +1926,25 @@ func TestHandshakeKyber(t *testing.T) {
config.CurvePreferences = []CurveID{CurveP256}
},
expectClientSupport: true,
expectKyber: false,
expectMLKEM: false,
expectHRR: true,
},
{
name: "ClientMLKEMOnly",
clientConfig: func(config *Config) {
config.CurvePreferences = []CurveID{X25519MLKEM768}
},
expectClientSupport: true,
expectMLKEM: true,
},
{
name: "ClientSortedCurvePreferences",
clientConfig: func(config *Config) {
config.CurvePreferences = []CurveID{CurveP256, X25519MLKEM768}
},
expectClientSupport: true,
expectMLKEM: true,
},
{
name: "ClientTLSv12",
clientConfig: func(config *Config) {
@ -1947,12 +1958,12 @@ func TestHandshakeKyber(t *testing.T) {
config.MaxVersion = VersionTLS12
},
expectClientSupport: true,
expectKyber: false,
expectMLKEM: false,
},
{
name: "GODEBUG",
preparation: func(t *testing.T) {
t.Setenv("GODEBUG", "tlskyber=0")
t.Setenv("GODEBUG", "tlsmlkem=0")
},
expectClientSupport: false,
},
@ -1972,10 +1983,10 @@ func TestHandshakeKyber(t *testing.T) {
test.serverConfig(serverConfig)
}
serverConfig.GetConfigForClient = func(hello *ClientHelloInfo) (*Config, error) {
if !test.expectClientSupport && slices.Contains(hello.SupportedCurves, x25519Kyber768Draft00) {
return nil, errors.New("client supports Kyber768Draft00")
} else if test.expectClientSupport && !slices.Contains(hello.SupportedCurves, x25519Kyber768Draft00) {
return nil, errors.New("client does not support Kyber768Draft00")
if !test.expectClientSupport && slices.Contains(hello.SupportedCurves, X25519MLKEM768) {
return nil, errors.New("client supports X25519MLKEM768")
} else if test.expectClientSupport && !slices.Contains(hello.SupportedCurves, X25519MLKEM768) {
return nil, errors.New("client does not support X25519MLKEM768")
}
return nil, nil
}
@ -1987,19 +1998,19 @@ func TestHandshakeKyber(t *testing.T) {
if err != nil {
t.Fatal(err)
}
if test.expectKyber {
if ss.testingOnlyCurveID != x25519Kyber768Draft00 {
t.Errorf("got CurveID %v (server), expected %v", ss.testingOnlyCurveID, x25519Kyber768Draft00)
if test.expectMLKEM {
if ss.testingOnlyCurveID != X25519MLKEM768 {
t.Errorf("got CurveID %v (server), expected %v", ss.testingOnlyCurveID, X25519MLKEM768)
}
if cs.testingOnlyCurveID != x25519Kyber768Draft00 {
t.Errorf("got CurveID %v (client), expected %v", cs.testingOnlyCurveID, x25519Kyber768Draft00)
if cs.testingOnlyCurveID != X25519MLKEM768 {
t.Errorf("got CurveID %v (client), expected %v", cs.testingOnlyCurveID, X25519MLKEM768)
}
} else {
if ss.testingOnlyCurveID == x25519Kyber768Draft00 {
t.Errorf("got CurveID %v (server), expected not Kyber", ss.testingOnlyCurveID)
if ss.testingOnlyCurveID == X25519MLKEM768 {
t.Errorf("got CurveID %v (server), expected not X25519MLKEM768", ss.testingOnlyCurveID)
}
if cs.testingOnlyCurveID == x25519Kyber768Draft00 {
t.Errorf("got CurveID %v (client), expected not Kyber", cs.testingOnlyCurveID)
if cs.testingOnlyCurveID == X25519MLKEM768 {
t.Errorf("got CurveID %v (client), expected not X25519MLKEM768", cs.testingOnlyCurveID)
}
}
if test.expectHRR {