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u_tls_extensions.go
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u_tls_extensions.go
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// Copyright 2017 Google Inc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package tls
import (
"errors"
"io"
"strings"
"golang.org/x/crypto/cryptobyte"
)
// ExtensionIDToExtension returns a TLSExtension for the given extension ID.
func ExtensionIDToExtension(id uint16) TLSExtensionWriter {
// deep copy
switch id {
case extensionServerName:
return &SNIExtension{}
case extensionStatusRequest:
return &StatusRequestExtension{}
case extensionSupportedCurves:
return &SupportedCurvesExtension{}
case extensionSupportedPoints:
return &SupportedPointsExtension{}
case extensionSignatureAlgorithms:
return &SignatureAlgorithmsExtension{}
case extensionALPN:
return &ALPNExtension{}
case extensionStatusRequestV2:
return &StatusRequestV2Extension{}
case extensionSCT:
return &SCTExtension{}
case utlsExtensionPadding:
return &UtlsPaddingExtension{}
case utlsExtensionExtendedMasterSecret:
return &UtlsExtendedMasterSecretExtension{}
case fakeExtensionTokenBinding:
return &FakeTokenBindingExtension{}
case utlsExtensionCompressCertificate:
return &UtlsCompressCertExtension{}
case fakeExtensionDelegatedCredentials:
return &FakeDelegatedCredentialsExtension{}
case extensionSessionTicket:
return &SessionTicketExtension{}
case fakeExtensionPreSharedKey:
return &FakePreSharedKeyExtension{}
// case extensionEarlyData:
// return &EarlyDataExtension{}
case extensionSupportedVersions:
return &SupportedVersionsExtension{}
// case extensionCookie:
// return &CookieExtension{}
case extensionPSKModes:
return &PSKKeyExchangeModesExtension{}
// case extensionCertificateAuthorities:
// return &CertificateAuthoritiesExtension{}
case extensionSignatureAlgorithmsCert:
return &SignatureAlgorithmsCertExtension{}
case extensionKeyShare:
return &KeyShareExtension{}
case extensionNextProtoNeg:
return &NPNExtension{}
case utlsExtensionApplicationSettings:
return &ApplicationSettingsExtension{}
case fakeOldExtensionChannelID:
return &FakeChannelIDExtension{true}
case fakeExtensionChannelID:
return &FakeChannelIDExtension{}
case fakeRecordSizeLimit:
return &FakeRecordSizeLimitExtension{}
case extensionRenegotiationInfo:
return &RenegotiationInfoExtension{}
default:
if isGREASEUint16(id) {
return &UtlsGREASEExtension{}
}
return nil // not returning GenericExtension, it should be handled by caller
}
}
type TLSExtension interface {
writeToUConn(*UConn) error
Len() int // includes header
// Read reads up to len(p) bytes into p.
// It returns the number of bytes read (0 <= n <= len(p)) and any error encountered.
Read(p []byte) (n int, err error) // implements io.Reader
}
// TLSExtensionWriter is an interface allowing a TLS extension to be
// auto-constucted/recovered by reading in a byte stream.
type TLSExtensionWriter interface {
TLSExtension
// Write writes up to len(b) bytes from b.
// It returns the number of bytes written (0 <= n <= len(b)) and any error encountered.
Write(b []byte) (n int, err error)
}
type NPNExtension struct {
NextProtos []string
}
func (e *NPNExtension) writeToUConn(uc *UConn) error {
uc.config.NextProtos = e.NextProtos
uc.HandshakeState.Hello.NextProtoNeg = true
return nil
}
func (e *NPNExtension) Len() int {
return 4
}
func (e *NPNExtension) Read(b []byte) (int, error) {
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
b[0] = byte(extensionNextProtoNeg >> 8)
b[1] = byte(extensionNextProtoNeg & 0xff)
// The length is always 0
return e.Len(), io.EOF
}
// Write is a no-op for NPNExtension. NextProtos are not included in the
// ClientHello.
func (e *NPNExtension) Write(_ []byte) (int, error) {
return 0, nil
}
type SNIExtension struct {
ServerName string // not an array because go crypto/tls doesn't support multiple SNIs
}
func (e *SNIExtension) writeToUConn(uc *UConn) error {
uc.config.ServerName = e.ServerName
hostName := hostnameInSNI(e.ServerName)
uc.HandshakeState.Hello.ServerName = hostName
return nil
}
func (e *SNIExtension) Len() int {
// Literal IP addresses, absolute FQDNs, and empty strings are not permitted as SNI values.
// See RFC 6066, Section 3.
hostName := hostnameInSNI(e.ServerName)
if len(hostName) == 0 {
return 0
}
return 4 + 2 + 1 + 2 + len(hostName)
}
func (e *SNIExtension) Read(b []byte) (int, error) {
// Literal IP addresses, absolute FQDNs, and empty strings are not permitted as SNI values.
// See RFC 6066, Section 3.
hostName := hostnameInSNI(e.ServerName)
if len(hostName) == 0 {
return 0, io.EOF
}
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
// RFC 3546, section 3.1
b[0] = byte(extensionServerName >> 8)
b[1] = byte(extensionServerName)
b[2] = byte((len(hostName) + 5) >> 8)
b[3] = byte(len(hostName) + 5)
b[4] = byte((len(hostName) + 3) >> 8)
b[5] = byte(len(hostName) + 3)
// b[6] Server Name Type: host_name (0)
b[7] = byte(len(hostName) >> 8)
b[8] = byte(len(hostName))
copy(b[9:], []byte(hostName))
return e.Len(), io.EOF
}
// Write is a no-op for StatusRequestExtension.
// SNI should not be fingerprinted and is user controlled.
func (e *SNIExtension) Write(b []byte) (int, error) {
fullLen := len(b)
extData := cryptobyte.String(b)
// RFC 6066, Section 3
var nameList cryptobyte.String
if !extData.ReadUint16LengthPrefixed(&nameList) || nameList.Empty() {
return fullLen, errors.New("unable to read server name extension data")
}
var serverName string
for !nameList.Empty() {
var nameType uint8
var serverNameBytes cryptobyte.String
if !nameList.ReadUint8(&nameType) ||
!nameList.ReadUint16LengthPrefixed(&serverNameBytes) ||
serverNameBytes.Empty() {
return fullLen, errors.New("unable to read server name extension data")
}
if nameType != 0 {
continue
}
if len(serverName) != 0 {
return fullLen, errors.New("multiple names of the same name_type in server name extension are prohibited")
}
serverName = string(serverNameBytes)
if strings.HasSuffix(serverName, ".") {
return fullLen, errors.New("SNI value may not include a trailing dot")
}
}
// clientHelloSpec.Extensions = append(clientHelloSpec.Extensions, &SNIExtension{}) // gaukas moved this line out from the loop.
// don't copy SNI from ClientHello to ClientHelloSpec!
return fullLen, nil
}
type StatusRequestExtension struct {
}
func (e *StatusRequestExtension) writeToUConn(uc *UConn) error {
uc.HandshakeState.Hello.OcspStapling = true
return nil
}
func (e *StatusRequestExtension) Len() int {
return 9
}
func (e *StatusRequestExtension) Read(b []byte) (int, error) {
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
// RFC 4366, section 3.6
b[0] = byte(extensionStatusRequest >> 8)
b[1] = byte(extensionStatusRequest)
b[2] = 0
b[3] = 5
b[4] = 1 // OCSP type
// Two zero valued uint16s for the two lengths.
return e.Len(), io.EOF
}
// Write is a no-op for StatusRequestExtension. No data for this extension.
func (e *StatusRequestExtension) Write(b []byte) (int, error) {
fullLen := len(b)
extData := cryptobyte.String(b)
// RFC 4366, Section 3.6
var statusType uint8
var ignored cryptobyte.String
if !extData.ReadUint8(&statusType) ||
!extData.ReadUint16LengthPrefixed(&ignored) ||
!extData.ReadUint16LengthPrefixed(&ignored) {
return fullLen, errors.New("unable to read status request extension data")
}
if statusType != statusTypeOCSP {
return fullLen, errors.New("status request extension statusType is not statusTypeOCSP(1)")
}
return fullLen, nil
}
type StatusRequestV2Extension struct {
}
func (e *StatusRequestV2Extension) writeToUConn(uc *UConn) error {
uc.HandshakeState.Hello.OcspStapling = true
return nil
}
func (e *StatusRequestV2Extension) Len() int {
return 13
}
func (e *StatusRequestV2Extension) Read(b []byte) (int, error) {
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
// RFC 4366, section 3.6
b[0] = byte(extensionStatusRequestV2 >> 8)
b[1] = byte(extensionStatusRequestV2)
b[2] = 0
b[3] = 9
b[4] = 0
b[5] = 7
b[6] = 2 // OCSP type
b[7] = 0
b[8] = 4
// Two zero valued uint16s for the two lengths.
return e.Len(), io.EOF
}
// Write is a no-op for StatusRequestV2Extension. No data for this extension.
func (e *StatusRequestV2Extension) Write(b []byte) (int, error) {
fullLen := len(b)
extData := cryptobyte.String(b)
// RFC 4366, Section 3.6
var statusType uint8
var ignored cryptobyte.String
if !extData.ReadUint16LengthPrefixed(&ignored) ||
!extData.ReadUint8(&statusType) ||
!extData.ReadUint16LengthPrefixed(&ignored) ||
!extData.ReadUint16LengthPrefixed(&ignored) ||
!extData.ReadUint16LengthPrefixed(&ignored) {
return fullLen, errors.New("unable to read status request v2 extension data")
}
if statusType != statusV2TypeOCSP {
return fullLen, errors.New("status request v2 extension statusType is not statusV2TypeOCSP(2)")
}
return fullLen, nil
}
type SupportedCurvesExtension struct {
Curves []CurveID
}
func (e *SupportedCurvesExtension) writeToUConn(uc *UConn) error {
uc.config.CurvePreferences = e.Curves
uc.HandshakeState.Hello.SupportedCurves = e.Curves
return nil
}
func (e *SupportedCurvesExtension) Len() int {
return 6 + 2*len(e.Curves)
}
func (e *SupportedCurvesExtension) Read(b []byte) (int, error) {
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
// http://tools.ietf.org/html/rfc4492#section-5.5.1
b[0] = byte(extensionSupportedCurves >> 8)
b[1] = byte(extensionSupportedCurves)
b[2] = byte((2 + 2*len(e.Curves)) >> 8)
b[3] = byte(2 + 2*len(e.Curves))
b[4] = byte((2 * len(e.Curves)) >> 8)
b[5] = byte(2 * len(e.Curves))
for i, curve := range e.Curves {
b[6+2*i] = byte(curve >> 8)
b[7+2*i] = byte(curve)
}
return e.Len(), io.EOF
}
func (e *SupportedCurvesExtension) Write(b []byte) (int, error) {
fullLen := len(b)
extData := cryptobyte.String(b)
// RFC 4492, sections 5.1.1 and RFC 8446, Section 4.2.7
var curvesBytes cryptobyte.String
if !extData.ReadUint16LengthPrefixed(&curvesBytes) || curvesBytes.Empty() {
return 0, errors.New("unable to read supported curves extension data")
}
curves := []CurveID{}
for !curvesBytes.Empty() {
var curve uint16
if !curvesBytes.ReadUint16(&curve) {
return 0, errors.New("unable to read supported curves extension data")
}
curves = append(curves, CurveID(unGREASEUint16(curve)))
}
e.Curves = curves
return fullLen, nil
}
type SupportedPointsExtension struct {
SupportedPoints []uint8
}
func (e *SupportedPointsExtension) writeToUConn(uc *UConn) error {
uc.HandshakeState.Hello.SupportedPoints = e.SupportedPoints
return nil
}
func (e *SupportedPointsExtension) Len() int {
return 5 + len(e.SupportedPoints)
}
func (e *SupportedPointsExtension) Read(b []byte) (int, error) {
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
// http://tools.ietf.org/html/rfc4492#section-5.5.2
b[0] = byte(extensionSupportedPoints >> 8)
b[1] = byte(extensionSupportedPoints)
b[2] = byte((1 + len(e.SupportedPoints)) >> 8)
b[3] = byte(1 + len(e.SupportedPoints))
b[4] = byte(len(e.SupportedPoints))
for i, pointFormat := range e.SupportedPoints {
b[5+i] = pointFormat
}
return e.Len(), io.EOF
}
func (e *SupportedPointsExtension) Write(b []byte) (int, error) {
fullLen := len(b)
extData := cryptobyte.String(b)
// RFC 4492, Section 5.1.2
supportedPoints := []uint8{}
if !readUint8LengthPrefixed(&extData, &supportedPoints) ||
len(supportedPoints) == 0 {
return 0, errors.New("unable to read supported points extension data")
}
e.SupportedPoints = supportedPoints
return fullLen, nil
}
type SignatureAlgorithmsExtension struct {
SupportedSignatureAlgorithms []SignatureScheme
}
func (e *SignatureAlgorithmsExtension) writeToUConn(uc *UConn) error {
uc.HandshakeState.Hello.SupportedSignatureAlgorithms = e.SupportedSignatureAlgorithms
return nil
}
func (e *SignatureAlgorithmsExtension) Len() int {
return 6 + 2*len(e.SupportedSignatureAlgorithms)
}
func (e *SignatureAlgorithmsExtension) Read(b []byte) (int, error) {
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
// https://tools.ietf.org/html/rfc5246#section-7.4.1.4.1
b[0] = byte(extensionSignatureAlgorithms >> 8)
b[1] = byte(extensionSignatureAlgorithms)
b[2] = byte((2 + 2*len(e.SupportedSignatureAlgorithms)) >> 8)
b[3] = byte(2 + 2*len(e.SupportedSignatureAlgorithms))
b[4] = byte((2 * len(e.SupportedSignatureAlgorithms)) >> 8)
b[5] = byte(2 * len(e.SupportedSignatureAlgorithms))
for i, sigAndHash := range e.SupportedSignatureAlgorithms {
b[6+2*i] = byte(sigAndHash >> 8)
b[7+2*i] = byte(sigAndHash)
}
return e.Len(), io.EOF
}
func (e *SignatureAlgorithmsExtension) Write(b []byte) (int, error) {
fullLen := len(b)
extData := cryptobyte.String(b)
// RFC 5246, Section 7.4.1.4.1
var sigAndAlgs cryptobyte.String
if !extData.ReadUint16LengthPrefixed(&sigAndAlgs) || sigAndAlgs.Empty() {
return 0, errors.New("unable to read signature algorithms extension data")
}
supportedSignatureAlgorithms := []SignatureScheme{}
for !sigAndAlgs.Empty() {
var sigAndAlg uint16
if !sigAndAlgs.ReadUint16(&sigAndAlg) {
return 0, errors.New("unable to read signature algorithms extension data")
}
supportedSignatureAlgorithms = append(
supportedSignatureAlgorithms, SignatureScheme(sigAndAlg))
}
e.SupportedSignatureAlgorithms = supportedSignatureAlgorithms
return fullLen, nil
}
type SignatureAlgorithmsCertExtension struct {
SupportedSignatureAlgorithms []SignatureScheme
}
func (e *SignatureAlgorithmsCertExtension) writeToUConn(uc *UConn) error {
uc.HandshakeState.Hello.SupportedSignatureAlgorithms = e.SupportedSignatureAlgorithms
return nil
}
func (e *SignatureAlgorithmsCertExtension) Len() int {
return 6 + 2*len(e.SupportedSignatureAlgorithms)
}
func (e *SignatureAlgorithmsCertExtension) Read(b []byte) (int, error) {
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
// https://tools.ietf.org/html/rfc5246#section-7.4.1.4.1
b[0] = byte(extensionSignatureAlgorithmsCert >> 8)
b[1] = byte(extensionSignatureAlgorithmsCert)
b[2] = byte((2 + 2*len(e.SupportedSignatureAlgorithms)) >> 8)
b[3] = byte(2 + 2*len(e.SupportedSignatureAlgorithms))
b[4] = byte((2 * len(e.SupportedSignatureAlgorithms)) >> 8)
b[5] = byte(2 * len(e.SupportedSignatureAlgorithms))
for i, sigAndHash := range e.SupportedSignatureAlgorithms {
b[6+2*i] = byte(sigAndHash >> 8)
b[7+2*i] = byte(sigAndHash)
}
return e.Len(), io.EOF
}
// Write implementation copied from SignatureAlgorithmsExtension.Write
//
// Warning: not tested.
func (e *SignatureAlgorithmsCertExtension) Write(b []byte) (int, error) {
fullLen := len(b)
extData := cryptobyte.String(b)
// RFC 8446, Section 4.2.3
var sigAndAlgs cryptobyte.String
if !extData.ReadUint16LengthPrefixed(&sigAndAlgs) || sigAndAlgs.Empty() {
return 0, errors.New("unable to read signature algorithms extension data")
}
supportedSignatureAlgorithms := []SignatureScheme{}
for !sigAndAlgs.Empty() {
var sigAndAlg uint16
if !sigAndAlgs.ReadUint16(&sigAndAlg) {
return 0, errors.New("unable to read signature algorithms extension data")
}
supportedSignatureAlgorithms = append(
supportedSignatureAlgorithms, SignatureScheme(sigAndAlg))
}
e.SupportedSignatureAlgorithms = supportedSignatureAlgorithms
return fullLen, nil
}
type RenegotiationInfoExtension struct {
// Renegotiation field limits how many times client will perform renegotiation: no limit, once, or never.
// The extension still will be sent, even if Renegotiation is set to RenegotiateNever.
Renegotiation RenegotiationSupport
}
func (e *RenegotiationInfoExtension) writeToUConn(uc *UConn) error {
uc.config.Renegotiation = e.Renegotiation
switch e.Renegotiation {
case RenegotiateOnceAsClient:
fallthrough
case RenegotiateFreelyAsClient:
uc.HandshakeState.Hello.SecureRenegotiationSupported = true
case RenegotiateNever:
default:
}
return nil
}
func (e *RenegotiationInfoExtension) Len() int {
return 5
}
func (e *RenegotiationInfoExtension) Read(b []byte) (int, error) {
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
var extInnerBody []byte // inner body is empty
innerBodyLen := len(extInnerBody)
extBodyLen := innerBodyLen + 1
b[0] = byte(extensionRenegotiationInfo >> 8)
b[1] = byte(extensionRenegotiationInfo & 0xff)
b[2] = byte(extBodyLen >> 8)
b[3] = byte(extBodyLen)
b[4] = byte(innerBodyLen)
copy(b[5:], extInnerBody)
return e.Len(), io.EOF
}
func (e *RenegotiationInfoExtension) Write(_ []byte) (int, error) {
e.Renegotiation = RenegotiateOnceAsClient
return 0, nil
}
type ALPNExtension struct {
AlpnProtocols []string
}
func (e *ALPNExtension) writeToUConn(uc *UConn) error {
uc.config.NextProtos = e.AlpnProtocols
uc.HandshakeState.Hello.AlpnProtocols = e.AlpnProtocols
return nil
}
func (e *ALPNExtension) Len() int {
bLen := 2 + 2 + 2
for _, s := range e.AlpnProtocols {
bLen += 1 + len(s)
}
return bLen
}
func (e *ALPNExtension) Read(b []byte) (int, error) {
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
b[0] = byte(extensionALPN >> 8)
b[1] = byte(extensionALPN & 0xff)
lengths := b[2:]
b = b[6:]
stringsLength := 0
for _, s := range e.AlpnProtocols {
l := len(s)
b[0] = byte(l)
copy(b[1:], s)
b = b[1+l:]
stringsLength += 1 + l
}
lengths[2] = byte(stringsLength >> 8)
lengths[3] = byte(stringsLength)
stringsLength += 2
lengths[0] = byte(stringsLength >> 8)
lengths[1] = byte(stringsLength)
return e.Len(), io.EOF
}
func (e *ALPNExtension) Write(b []byte) (int, error) {
fullLen := len(b)
extData := cryptobyte.String(b)
// RFC 7301, Section 3.1
var protoList cryptobyte.String
if !extData.ReadUint16LengthPrefixed(&protoList) || protoList.Empty() {
return 0, errors.New("unable to read ALPN extension data")
}
alpnProtocols := []string{}
for !protoList.Empty() {
var proto cryptobyte.String
if !protoList.ReadUint8LengthPrefixed(&proto) || proto.Empty() {
return 0, errors.New("unable to read ALPN extension data")
}
alpnProtocols = append(alpnProtocols, string(proto))
}
e.AlpnProtocols = alpnProtocols
return fullLen, nil
}
// ApplicationSettingsExtension represents the TLS ALPS extension.
// At the time of this writing, this extension is currently a draft:
// https://datatracker.ietf.org/doc/html/draft-vvv-tls-alps-01
type ApplicationSettingsExtension struct {
SupportedProtocols []string
}
func (e *ApplicationSettingsExtension) writeToUConn(uc *UConn) error {
return nil
}
func (e *ApplicationSettingsExtension) Len() int {
bLen := 2 + 2 + 2 // Type + Length + ALPS Extension length
for _, s := range e.SupportedProtocols {
bLen += 1 + len(s) // Supported ALPN Length + actual length of protocol
}
return bLen
}
func (e *ApplicationSettingsExtension) Read(b []byte) (int, error) {
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
// Read Type.
b[0] = byte(utlsExtensionApplicationSettings >> 8) // hex: 44 dec: 68
b[1] = byte(utlsExtensionApplicationSettings & 0xff) // hex: 69 dec: 105
lengths := b[2:] // get the remaining buffer without Type
b = b[6:] // set the buffer to the buffer without Type, Length and ALPS Extension Length (so only the Supported ALPN list remains)
stringsLength := 0
for _, s := range e.SupportedProtocols {
l := len(s) // Supported ALPN Length
b[0] = byte(l) // Supported ALPN Length in bytes hex: 02 dec: 2
copy(b[1:], s) // copy the Supported ALPN as bytes to the buffer
b = b[1+l:] // set the buffer to the buffer without the Supported ALPN Length and Supported ALPN (so we can continue to the next protocol in this loop)
stringsLength += 1 + l // Supported ALPN Length (the field itself) + Supported ALPN Length (the value)
}
lengths[2] = byte(stringsLength >> 8) // ALPS Extension Length hex: 00 dec: 0
lengths[3] = byte(stringsLength) // ALPS Extension Length hex: 03 dec: 3
stringsLength += 2 // plus ALPS Extension Length field length
lengths[0] = byte(stringsLength >> 8) // Length hex:00 dec: 0
lengths[1] = byte(stringsLength) // Length hex: 05 dec: 5
return e.Len(), io.EOF
}
// Write implementation copied from ALPNExtension.Write
func (e *ApplicationSettingsExtension) Write(b []byte) (int, error) {
fullLen := len(b)
extData := cryptobyte.String(b)
// https://datatracker.ietf.org/doc/html/draft-vvv-tls-alps-01
var protoList cryptobyte.String
if !extData.ReadUint16LengthPrefixed(&protoList) || protoList.Empty() {
return 0, errors.New("unable to read ALPN extension data")
}
alpnProtocols := []string{}
for !protoList.Empty() {
var proto cryptobyte.String
if !protoList.ReadUint8LengthPrefixed(&proto) || proto.Empty() {
return 0, errors.New("unable to read ALPN extension data")
}
alpnProtocols = append(alpnProtocols, string(proto))
}
e.SupportedProtocols = alpnProtocols
return fullLen, nil
}
type SCTExtension struct {
}
func (e *SCTExtension) writeToUConn(uc *UConn) error {
uc.HandshakeState.Hello.Scts = true
return nil
}
func (e *SCTExtension) Len() int {
return 4
}
func (e *SCTExtension) Read(b []byte) (int, error) {
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
// https://tools.ietf.org/html/rfc6962#section-3.3.1
b[0] = byte(extensionSCT >> 8)
b[1] = byte(extensionSCT)
// zero uint16 for the zero-length extension_data
return e.Len(), io.EOF
}
func (e *SCTExtension) Write(_ []byte) (int, error) {
return 0, nil
}
type SessionTicketExtension struct {
Session *ClientSessionState
}
func (e *SessionTicketExtension) writeToUConn(uc *UConn) error {
if e.Session != nil {
uc.HandshakeState.Session = e.Session
uc.HandshakeState.Hello.SessionTicket = e.Session.sessionTicket
}
return nil
}
func (e *SessionTicketExtension) Len() int {
if e.Session != nil {
return 4 + len(e.Session.sessionTicket)
}
return 4
}
func (e *SessionTicketExtension) Read(b []byte) (int, error) {
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
extBodyLen := e.Len() - 4
b[0] = byte(extensionSessionTicket >> 8)
b[1] = byte(extensionSessionTicket)
b[2] = byte(extBodyLen >> 8)
b[3] = byte(extBodyLen)
if extBodyLen > 0 {
copy(b[4:], e.Session.sessionTicket)
}
return e.Len(), io.EOF
}
func (e *SessionTicketExtension) Write(_ []byte) (int, error) {
// RFC 5077, Section 3.2
return 0, nil
}
// GenericExtension allows to include in ClientHello arbitrary unsupported extensions.
type GenericExtension struct {
Id uint16
Data []byte
}
func (e *GenericExtension) writeToUConn(uc *UConn) error {
return nil
}
func (e *GenericExtension) Len() int {
return 4 + len(e.Data)
}
func (e *GenericExtension) Read(b []byte) (int, error) {
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
b[0] = byte(e.Id >> 8)
b[1] = byte(e.Id)
b[2] = byte(len(e.Data) >> 8)
b[3] = byte(len(e.Data))
if len(e.Data) > 0 {
copy(b[4:], e.Data)
}
return e.Len(), io.EOF
}
type UtlsExtendedMasterSecretExtension struct {
}
// TODO: update when this extension is implemented in crypto/tls
// but we probably won't have to enable it in Config
func (e *UtlsExtendedMasterSecretExtension) writeToUConn(uc *UConn) error {
uc.HandshakeState.Hello.Ems = true
return nil
}
func (e *UtlsExtendedMasterSecretExtension) Len() int {
return 4
}
func (e *UtlsExtendedMasterSecretExtension) Read(b []byte) (int, error) {
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
// https://tools.ietf.org/html/rfc7627
b[0] = byte(utlsExtensionExtendedMasterSecret >> 8)
b[1] = byte(utlsExtensionExtendedMasterSecret)
// The length is 0
return e.Len(), io.EOF
}
func (e *UtlsExtendedMasterSecretExtension) Write(_ []byte) (int, error) {
// https://tools.ietf.org/html/rfc7627
return 0, nil
}
var extendedMasterSecretLabel = []byte("extended master secret")
// extendedMasterFromPreMasterSecret generates the master secret from the pre-master
// secret and session hash. See https://tools.ietf.org/html/rfc7627#section-4
func extendedMasterFromPreMasterSecret(version uint16, suite *cipherSuite, preMasterSecret []byte, sessionHash []byte) []byte {
masterSecret := make([]byte, masterSecretLength)
prfForVersion(version, suite)(masterSecret, preMasterSecret, extendedMasterSecretLabel, sessionHash)
return masterSecret
}
// GREASE stinks with dead parrots, have to be super careful, and, if possible, not include GREASE
// https://github.com/google/boringssl/blob/1c68fa2350936ca5897a66b430ebaf333a0e43f5/ssl/internal.h
const (
ssl_grease_cipher = iota
ssl_grease_group
ssl_grease_extension1
ssl_grease_extension2
ssl_grease_version
ssl_grease_ticket_extension
ssl_grease_last_index = ssl_grease_ticket_extension
)
// it is responsibility of user not to generate multiple grease extensions with same value
type UtlsGREASEExtension struct {
Value uint16
Body []byte // in Chrome first grease has empty body, second grease has a single zero byte
}
func (e *UtlsGREASEExtension) writeToUConn(uc *UConn) error {
return nil
}
// will panic if ssl_grease_last_index[index] is out of bounds.
func GetBoringGREASEValue(greaseSeed [ssl_grease_last_index]uint16, index int) uint16 {
// GREASE value is back from deterministic to random.
// https://github.com/google/boringssl/blob/a365138ac60f38b64bfc608b493e0f879845cb88/ssl/handshake_client.c#L530
ret := uint16(greaseSeed[index])
/* This generates a random value of the form 0xωaωa, for all 0 ≤ ω < 16. */
ret = (ret & 0xf0) | 0x0a
ret |= ret << 8
return ret
}
func (e *UtlsGREASEExtension) Len() int {
return 4 + len(e.Body)
}
func (e *UtlsGREASEExtension) Read(b []byte) (int, error) {
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
b[0] = byte(e.Value >> 8)
b[1] = byte(e.Value)
b[2] = byte(len(e.Body) >> 8)
b[3] = byte(len(e.Body))
if len(e.Body) > 0 {
copy(b[4:], e.Body)
}
return e.Len(), io.EOF
}
func (e *UtlsGREASEExtension) Write(b []byte) (int, error) {
e.Value = GREASE_PLACEHOLDER
e.Body = make([]byte, len(b))
n := copy(e.Body, b)
return n, nil
}
type UtlsPaddingExtension struct {
PaddingLen int
WillPad bool // set to false to disable extension
// Functor for deciding on padding length based on unpadded ClientHello length.
// If willPad is false, then this extension should not be included.
GetPaddingLen func(clientHelloUnpaddedLen int) (paddingLen int, willPad bool)
}
func (e *UtlsPaddingExtension) writeToUConn(uc *UConn) error {
return nil
}
func (e *UtlsPaddingExtension) Len() int {
if e.WillPad {
return 4 + e.PaddingLen
} else {
return 0
}
}
func (e *UtlsPaddingExtension) Update(clientHelloUnpaddedLen int) {
if e.GetPaddingLen != nil {
e.PaddingLen, e.WillPad = e.GetPaddingLen(clientHelloUnpaddedLen)
}
}
func (e *UtlsPaddingExtension) Read(b []byte) (int, error) {
if !e.WillPad {
return 0, io.EOF
}
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
// https://tools.ietf.org/html/rfc7627
b[0] = byte(utlsExtensionPadding >> 8)
b[1] = byte(utlsExtensionPadding)
b[2] = byte(e.PaddingLen >> 8)
b[3] = byte(e.PaddingLen)
return e.Len(), io.EOF
}
func (e *UtlsPaddingExtension) Write(_ []byte) (int, error) {
e.GetPaddingLen = BoringPaddingStyle
return 0, nil
}
// https://github.com/google/boringssl/blob/7d7554b6b3c79e707e25521e61e066ce2b996e4c/ssl/t1_lib.c#L2803
func BoringPaddingStyle(unpaddedLen int) (int, bool) {
if unpaddedLen > 0xff && unpaddedLen < 0x200 {
paddingLen := 0x200 - unpaddedLen
if paddingLen >= 4+1 {
paddingLen -= 4
} else {
paddingLen = 1
}
return paddingLen, true
}
return 0, false
}
// UtlsCompressCertExtension is only implemented client-side, for server certificates. Alternate
// certificate message formats (https://datatracker.ietf.org/doc/html/rfc7250) are not supported.
//
// See https://datatracker.ietf.org/doc/html/rfc8879#section-3
type UtlsCompressCertExtension struct {
Algorithms []CertCompressionAlgo
}
func (e *UtlsCompressCertExtension) writeToUConn(uc *UConn) error {
uc.certCompressionAlgs = e.Algorithms
return nil
}
func (e *UtlsCompressCertExtension) Len() int {
return 4 + 1 + (2 * len(e.Algorithms))
}
func (e *UtlsCompressCertExtension) Read(b []byte) (int, error) {
if len(b) < e.Len() {
return 0, io.ErrShortBuffer
}
b[0] = byte(utlsExtensionCompressCertificate >> 8)
b[1] = byte(utlsExtensionCompressCertificate & 0xff)
extLen := 2 * len(e.Algorithms)
if extLen > 255 {
return 0, errors.New("too many certificate compression methods")
}
// Extension data length.
b[2] = byte((extLen + 1) >> 8)
b[3] = byte((extLen + 1) & 0xff)
// Methods length.
b[4] = byte(extLen)
i := 5
for _, compMethod := range e.Algorithms {
b[i] = byte(compMethod >> 8)
b[i+1] = byte(compMethod)
i += 2
}
return e.Len(), io.EOF
}