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ticket.go
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ticket.go
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// Copyright 2012 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 qtls
import (
"bytes"
"crypto/aes"
"crypto/cipher"
"crypto/hmac"
"crypto/sha256"
"crypto/subtle"
"errors"
"io"
)
// A SessionTicketSealer provides a way to securely encapsulate
// session state for storage on the client. All methods are safe for
// concurrent use.
type SessionTicketSealer interface {
// Seal returns a session ticket value that can be later passed to Unseal
// to recover the content, usually by encrypting it. The ticket will be sent
// to the client to be stored, and will be sent back in plaintext, so it can
// be read and modified by an attacker.
Seal(cs *ConnectionState, content []byte) (ticket []byte, err error)
// Unseal returns a session ticket contents. The ticket can't be safely
// assumed to have been generated by Seal.
// If unable to unseal the ticket, the connection will proceed with a
// complete handshake.
Unseal(chi *ClientHelloInfo, ticket []byte) (content []byte, success bool)
}
// sessionState contains the information that is serialized into a session
// ticket in order to later resume a connection.
type sessionState struct {
vers uint16
cipherSuite uint16
usedEMS bool
masterSecret []byte
certificates [][]byte
// usedOldKey is true if the ticket from which this session came from
// was encrypted with an older key and thus should be refreshed.
usedOldKey bool
}
func (s *sessionState) equal(i interface{}) bool {
s1, ok := i.(*sessionState)
if !ok {
return false
}
if s.vers != s1.vers ||
s.usedEMS != s1.usedEMS ||
s.cipherSuite != s1.cipherSuite ||
!bytes.Equal(s.masterSecret, s1.masterSecret) {
return false
}
if len(s.certificates) != len(s1.certificates) {
return false
}
for i := range s.certificates {
if !bytes.Equal(s.certificates[i], s1.certificates[i]) {
return false
}
}
return true
}
func (s *sessionState) marshal() []byte {
length := 2 + 2 + 2 + len(s.masterSecret) + 2
for _, cert := range s.certificates {
length += 4 + len(cert)
}
ret := make([]byte, length)
x := ret
was_used := byte(0)
if s.usedEMS {
was_used = byte(0x80)
}
x[0] = byte(s.vers>>8) | byte(was_used)
x[1] = byte(s.vers)
x[2] = byte(s.cipherSuite >> 8)
x[3] = byte(s.cipherSuite)
x[4] = byte(len(s.masterSecret) >> 8)
x[5] = byte(len(s.masterSecret))
x = x[6:]
copy(x, s.masterSecret)
x = x[len(s.masterSecret):]
x[0] = byte(len(s.certificates) >> 8)
x[1] = byte(len(s.certificates))
x = x[2:]
for _, cert := range s.certificates {
x[0] = byte(len(cert) >> 24)
x[1] = byte(len(cert) >> 16)
x[2] = byte(len(cert) >> 8)
x[3] = byte(len(cert))
copy(x[4:], cert)
x = x[4+len(cert):]
}
return ret
}
func (s *sessionState) unmarshal(data []byte) alert {
if len(data) < 8 {
return alertDecodeError
}
s.vers = (uint16(data[0])<<8 | uint16(data[1])) & 0x7fff
s.cipherSuite = uint16(data[2])<<8 | uint16(data[3])
s.usedEMS = (data[0] & 0x80) == 0x80
masterSecretLen := int(data[4])<<8 | int(data[5])
data = data[6:]
if len(data) < masterSecretLen {
return alertDecodeError
}
s.masterSecret = data[:masterSecretLen]
data = data[masterSecretLen:]
if len(data) < 2 {
return alertDecodeError
}
numCerts := int(data[0])<<8 | int(data[1])
data = data[2:]
s.certificates = make([][]byte, numCerts)
for i := range s.certificates {
if len(data) < 4 {
return alertDecodeError
}
certLen := int(data[0])<<24 | int(data[1])<<16 | int(data[2])<<8 | int(data[3])
data = data[4:]
if certLen < 0 {
return alertDecodeError
}
if len(data) < certLen {
return alertDecodeError
}
s.certificates[i] = data[:certLen]
data = data[certLen:]
}
if len(data) != 0 {
return alertDecodeError
}
return alertSuccess
}
type sessionState13 struct {
vers uint16
suite uint16
ageAdd uint32
createdAt uint64
maxEarlyDataLen uint32
pskSecret []byte
alpnProtocol string
SNI string
}
func (s *sessionState13) equal(i interface{}) bool {
s1, ok := i.(*sessionState13)
if !ok {
return false
}
return s.vers == s1.vers &&
s.suite == s1.suite &&
s.ageAdd == s1.ageAdd &&
s.createdAt == s1.createdAt &&
s.maxEarlyDataLen == s1.maxEarlyDataLen &&
subtle.ConstantTimeCompare(s.pskSecret, s1.pskSecret) == 1 &&
s.alpnProtocol == s1.alpnProtocol &&
s.SNI == s1.SNI
}
func (s *sessionState13) marshal() []byte {
length := 2 + 2 + 4 + 8 + 4 + 2 + len(s.pskSecret) + 2 + len(s.alpnProtocol) + 2 + len(s.SNI)
x := make([]byte, length)
x[0] = byte(s.vers >> 8)
x[1] = byte(s.vers)
x[2] = byte(s.suite >> 8)
x[3] = byte(s.suite)
x[4] = byte(s.ageAdd >> 24)
x[5] = byte(s.ageAdd >> 16)
x[6] = byte(s.ageAdd >> 8)
x[7] = byte(s.ageAdd)
x[8] = byte(s.createdAt >> 56)
x[9] = byte(s.createdAt >> 48)
x[10] = byte(s.createdAt >> 40)
x[11] = byte(s.createdAt >> 32)
x[12] = byte(s.createdAt >> 24)
x[13] = byte(s.createdAt >> 16)
x[14] = byte(s.createdAt >> 8)
x[15] = byte(s.createdAt)
x[16] = byte(s.maxEarlyDataLen >> 24)
x[17] = byte(s.maxEarlyDataLen >> 16)
x[18] = byte(s.maxEarlyDataLen >> 8)
x[19] = byte(s.maxEarlyDataLen)
x[20] = byte(len(s.pskSecret) >> 8)
x[21] = byte(len(s.pskSecret))
copy(x[22:], s.pskSecret)
z := x[22+len(s.pskSecret):]
z[0] = byte(len(s.alpnProtocol) >> 8)
z[1] = byte(len(s.alpnProtocol))
copy(z[2:], s.alpnProtocol)
z = z[2+len(s.alpnProtocol):]
z[0] = byte(len(s.SNI) >> 8)
z[1] = byte(len(s.SNI))
copy(z[2:], s.SNI)
return x
}
func (s *sessionState13) unmarshal(data []byte) alert {
if len(data) < 24 {
return alertDecodeError
}
s.vers = uint16(data[0])<<8 | uint16(data[1])
s.suite = uint16(data[2])<<8 | uint16(data[3])
s.ageAdd = uint32(data[4])<<24 | uint32(data[5])<<16 | uint32(data[6])<<8 | uint32(data[7])
s.createdAt = uint64(data[8])<<56 | uint64(data[9])<<48 | uint64(data[10])<<40 | uint64(data[11])<<32 |
uint64(data[12])<<24 | uint64(data[13])<<16 | uint64(data[14])<<8 | uint64(data[15])
s.maxEarlyDataLen = uint32(data[16])<<24 | uint32(data[17])<<16 | uint32(data[18])<<8 | uint32(data[19])
l := int(data[20])<<8 | int(data[21])
if len(data) < 22+l+2 {
return alertDecodeError
}
s.pskSecret = data[22 : 22+l]
z := data[22+l:]
l = int(z[0])<<8 | int(z[1])
if len(z) < 2+l+2 {
return alertDecodeError
}
s.alpnProtocol = string(z[2 : 2+l])
z = z[2+l:]
l = int(z[0])<<8 | int(z[1])
if len(z) != 2+l {
return alertDecodeError
}
s.SNI = string(z[2 : 2+l])
return alertSuccess
}
func (c *Conn) encryptTicket(serialized []byte) ([]byte, error) {
encrypted := make([]byte, ticketKeyNameLen+aes.BlockSize+len(serialized)+sha256.Size)
keyName := encrypted[:ticketKeyNameLen]
iv := encrypted[ticketKeyNameLen : ticketKeyNameLen+aes.BlockSize]
macBytes := encrypted[len(encrypted)-sha256.Size:]
if _, err := io.ReadFull(c.config.rand(), iv); err != nil {
return nil, err
}
key := c.config.ticketKeys()[0]
copy(keyName, key.keyName[:])
block, err := aes.NewCipher(key.aesKey[:])
if err != nil {
return nil, errors.New("tls: failed to create cipher while encrypting ticket: " + err.Error())
}
cipher.NewCTR(block, iv).XORKeyStream(encrypted[ticketKeyNameLen+aes.BlockSize:], serialized)
mac := hmac.New(sha256.New, key.hmacKey[:])
mac.Write(encrypted[:len(encrypted)-sha256.Size])
mac.Sum(macBytes[:0])
return encrypted, nil
}
func (c *Conn) decryptTicket(encrypted []byte) (serialized []byte, usedOldKey bool) {
if c.config.SessionTicketsDisabled ||
len(encrypted) < ticketKeyNameLen+aes.BlockSize+sha256.Size {
return nil, false
}
keyName := encrypted[:ticketKeyNameLen]
iv := encrypted[ticketKeyNameLen : ticketKeyNameLen+aes.BlockSize]
macBytes := encrypted[len(encrypted)-sha256.Size:]
keys := c.config.ticketKeys()
keyIndex := -1
for i, candidateKey := range keys {
if bytes.Equal(keyName, candidateKey.keyName[:]) {
keyIndex = i
break
}
}
if keyIndex == -1 {
return nil, false
}
key := &keys[keyIndex]
mac := hmac.New(sha256.New, key.hmacKey[:])
mac.Write(encrypted[:len(encrypted)-sha256.Size])
expected := mac.Sum(nil)
if subtle.ConstantTimeCompare(macBytes, expected) != 1 {
return nil, false
}
block, err := aes.NewCipher(key.aesKey[:])
if err != nil {
return nil, false
}
ciphertext := encrypted[ticketKeyNameLen+aes.BlockSize : len(encrypted)-sha256.Size]
plaintext := ciphertext
cipher.NewCTR(block, iv).XORKeyStream(plaintext, ciphertext)
return plaintext, keyIndex > 0
}