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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 tls
import (
"bytes"
"crypto/aes"
"crypto/cipher"
"crypto/hmac"
"crypto/sha256"
"crypto/subtle"
"errors"
"io"
"golang.org/x/crypto/cryptobyte"
)
// 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
createdAt uint64
masterSecret []byte // opaque master_secret<1..2^16-1>;
// struct { opaque certificate<1..2^24-1> } Certificate;
certificates [][]byte // Certificate certificate_list<0..2^24-1>;
// 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 (m *sessionState) marshal() []byte {
var b cryptobyte.Builder
b.AddUint16(m.vers)
b.AddUint16(m.cipherSuite)
addUint64(&b, m.createdAt)
b.AddUint16LengthPrefixed(func(b *cryptobyte.Builder) {
b.AddBytes(m.masterSecret)
})
b.AddUint24LengthPrefixed(func(b *cryptobyte.Builder) {
for _, cert := range m.certificates {
b.AddUint24LengthPrefixed(func(b *cryptobyte.Builder) {
b.AddBytes(cert)
})
}
})
return b.BytesOrPanic()
}
func (m *sessionState) unmarshal(data []byte) bool {
*m = sessionState{usedOldKey: m.usedOldKey}
s := cryptobyte.String(data)
if ok := s.ReadUint16(&m.vers) &&
s.ReadUint16(&m.cipherSuite) &&
readUint64(&s, &m.createdAt) &&
readUint16LengthPrefixed(&s, &m.masterSecret) &&
len(m.masterSecret) != 0; !ok {
return false
}
var certList cryptobyte.String
if !s.ReadUint24LengthPrefixed(&certList) {
return false
}
for !certList.Empty() {
var cert []byte
if !readUint24LengthPrefixed(&certList, &cert) {
return false
}
m.certificates = append(m.certificates, cert)
}
return s.Empty()
}
// sessionStateTLS13 is the content of a TLS 1.3 session ticket. Its first
// version (revision = 0) doesn't carry any of the information needed for 0-RTT
// validation and the nonce is always empty.
type sessionStateTLS13 struct {
// uint8 version = 0x0304;
// uint8 revision = 0;
cipherSuite uint16
createdAt uint64
resumptionSecret []byte // opaque resumption_master_secret<1..2^8-1>;
certificate Certificate // CertificateEntry certificate_list<0..2^24-1>;
}
func (m *sessionStateTLS13) marshal() []byte {
var b cryptobyte.Builder
b.AddUint16(VersionTLS13)
b.AddUint8(0) // revision
b.AddUint16(m.cipherSuite)
addUint64(&b, m.createdAt)
b.AddUint8LengthPrefixed(func(b *cryptobyte.Builder) {
b.AddBytes(m.resumptionSecret)
})
marshalCertificate(&b, m.certificate)
return b.BytesOrPanic()
}
func (m *sessionStateTLS13) unmarshal(data []byte) bool {
*m = sessionStateTLS13{}
s := cryptobyte.String(data)
var version uint16
var revision uint8
return s.ReadUint16(&version) &&
version == VersionTLS13 &&
s.ReadUint8(&revision) &&
revision == 0 &&
s.ReadUint16(&m.cipherSuite) &&
readUint64(&s, &m.createdAt) &&
readUint8LengthPrefixed(&s, &m.resumptionSecret) &&
len(m.resumptionSecret) != 0 &&
unmarshalCertificate(&s, &m.certificate) &&
s.Empty()
}
func (c *Conn) encryptTicket(state []byte) ([]byte, error) {
if len(c.ticketKeys) == 0 {
return nil, errors.New("tls: internal error: session ticket keys unavailable")
}
encrypted := make([]byte, ticketKeyNameLen+aes.BlockSize+len(state)+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.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:], state)
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) (plaintext []byte, usedOldKey bool) {
if 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:]
ciphertext := encrypted[ticketKeyNameLen+aes.BlockSize : len(encrypted)-sha256.Size]
keyIndex := -1
for i, candidateKey := range c.ticketKeys {
if bytes.Equal(keyName, candidateKey.keyName[:]) {
keyIndex = i
break
}
}
if keyIndex == -1 {
return nil, false
}
key := &c.ticketKeys[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
}
plaintext = make([]byte, len(ciphertext))
cipher.NewCTR(block, iv).XORKeyStream(plaintext, ciphertext)
return plaintext, keyIndex > 0
}
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