275 lines
8.0 KiB
Go
275 lines
8.0 KiB
Go
// Copyright 2012 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package qtls
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import (
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"bytes"
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"crypto/aes"
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"crypto/cipher"
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"crypto/hmac"
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"crypto/sha256"
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"crypto/subtle"
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"encoding/binary"
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"errors"
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"io"
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"time"
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"golang.org/x/crypto/cryptobyte"
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)
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// sessionState contains the information that is serialized into a session
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// ticket in order to later resume a connection.
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type sessionState struct {
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vers uint16
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cipherSuite uint16
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createdAt uint64
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masterSecret []byte // opaque master_secret<1..2^16-1>;
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// struct { opaque certificate<1..2^24-1> } Certificate;
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certificates [][]byte // Certificate certificate_list<0..2^24-1>;
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// usedOldKey is true if the ticket from which this session came from
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// was encrypted with an older key and thus should be refreshed.
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usedOldKey bool
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}
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func (m *sessionState) marshal() []byte {
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var b cryptobyte.Builder
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b.AddUint16(m.vers)
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b.AddUint16(m.cipherSuite)
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addUint64(&b, m.createdAt)
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b.AddUint16LengthPrefixed(func(b *cryptobyte.Builder) {
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b.AddBytes(m.masterSecret)
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})
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b.AddUint24LengthPrefixed(func(b *cryptobyte.Builder) {
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for _, cert := range m.certificates {
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b.AddUint24LengthPrefixed(func(b *cryptobyte.Builder) {
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b.AddBytes(cert)
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})
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}
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})
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return b.BytesOrPanic()
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}
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func (m *sessionState) unmarshal(data []byte) bool {
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*m = sessionState{usedOldKey: m.usedOldKey}
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s := cryptobyte.String(data)
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if ok := s.ReadUint16(&m.vers) &&
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s.ReadUint16(&m.cipherSuite) &&
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readUint64(&s, &m.createdAt) &&
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readUint16LengthPrefixed(&s, &m.masterSecret) &&
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len(m.masterSecret) != 0; !ok {
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return false
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}
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var certList cryptobyte.String
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if !s.ReadUint24LengthPrefixed(&certList) {
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return false
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}
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for !certList.Empty() {
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var cert []byte
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if !readUint24LengthPrefixed(&certList, &cert) {
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return false
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}
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m.certificates = append(m.certificates, cert)
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}
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return s.Empty()
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}
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// sessionStateTLS13 is the content of a TLS 1.3 session ticket. Its first
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// version (revision = 0) doesn't carry any of the information needed for 0-RTT
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// validation and the nonce is always empty.
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// version (revision = 1) carries the max_early_data_size sent in the ticket.
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// version (revision = 2) carries the ALPN sent in the ticket.
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type sessionStateTLS13 struct {
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// uint8 version = 0x0304;
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// uint8 revision = 2;
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cipherSuite uint16
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createdAt uint64
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resumptionSecret []byte // opaque resumption_master_secret<1..2^8-1>;
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certificate Certificate // CertificateEntry certificate_list<0..2^24-1>;
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maxEarlyData uint32
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alpn string
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appData []byte
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}
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func (m *sessionStateTLS13) marshal() []byte {
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var b cryptobyte.Builder
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b.AddUint16(VersionTLS13)
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b.AddUint8(2) // revision
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b.AddUint16(m.cipherSuite)
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addUint64(&b, m.createdAt)
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b.AddUint8LengthPrefixed(func(b *cryptobyte.Builder) {
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b.AddBytes(m.resumptionSecret)
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})
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marshalCertificate(&b, m.certificate)
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b.AddUint32(m.maxEarlyData)
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b.AddUint8LengthPrefixed(func(b *cryptobyte.Builder) {
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b.AddBytes([]byte(m.alpn))
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})
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b.AddUint16LengthPrefixed(func(b *cryptobyte.Builder) {
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b.AddBytes(m.appData)
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})
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return b.BytesOrPanic()
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}
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func (m *sessionStateTLS13) unmarshal(data []byte) bool {
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*m = sessionStateTLS13{}
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s := cryptobyte.String(data)
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var version uint16
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var revision uint8
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var alpn []byte
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ret := s.ReadUint16(&version) &&
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version == VersionTLS13 &&
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s.ReadUint8(&revision) &&
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revision == 2 &&
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s.ReadUint16(&m.cipherSuite) &&
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readUint64(&s, &m.createdAt) &&
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readUint8LengthPrefixed(&s, &m.resumptionSecret) &&
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len(m.resumptionSecret) != 0 &&
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unmarshalCertificate(&s, &m.certificate) &&
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s.ReadUint32(&m.maxEarlyData) &&
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readUint8LengthPrefixed(&s, &alpn) &&
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readUint16LengthPrefixed(&s, &m.appData) &&
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s.Empty()
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m.alpn = string(alpn)
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return ret
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}
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func (c *Conn) encryptTicket(state []byte) ([]byte, error) {
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if len(c.ticketKeys) == 0 {
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return nil, errors.New("tls: internal error: session ticket keys unavailable")
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}
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encrypted := make([]byte, ticketKeyNameLen+aes.BlockSize+len(state)+sha256.Size)
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keyName := encrypted[:ticketKeyNameLen]
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iv := encrypted[ticketKeyNameLen : ticketKeyNameLen+aes.BlockSize]
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macBytes := encrypted[len(encrypted)-sha256.Size:]
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if _, err := io.ReadFull(c.config.rand(), iv); err != nil {
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return nil, err
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}
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key := c.ticketKeys[0]
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copy(keyName, key.keyName[:])
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block, err := aes.NewCipher(key.aesKey[:])
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if err != nil {
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return nil, errors.New("tls: failed to create cipher while encrypting ticket: " + err.Error())
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}
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cipher.NewCTR(block, iv).XORKeyStream(encrypted[ticketKeyNameLen+aes.BlockSize:], state)
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mac := hmac.New(sha256.New, key.hmacKey[:])
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mac.Write(encrypted[:len(encrypted)-sha256.Size])
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mac.Sum(macBytes[:0])
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return encrypted, nil
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}
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func (c *Conn) decryptTicket(encrypted []byte) (plaintext []byte, usedOldKey bool) {
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if len(encrypted) < ticketKeyNameLen+aes.BlockSize+sha256.Size {
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return nil, false
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}
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keyName := encrypted[:ticketKeyNameLen]
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iv := encrypted[ticketKeyNameLen : ticketKeyNameLen+aes.BlockSize]
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macBytes := encrypted[len(encrypted)-sha256.Size:]
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ciphertext := encrypted[ticketKeyNameLen+aes.BlockSize : len(encrypted)-sha256.Size]
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keyIndex := -1
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for i, candidateKey := range c.ticketKeys {
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if bytes.Equal(keyName, candidateKey.keyName[:]) {
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keyIndex = i
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break
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}
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}
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if keyIndex == -1 {
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return nil, false
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}
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key := &c.ticketKeys[keyIndex]
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mac := hmac.New(sha256.New, key.hmacKey[:])
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mac.Write(encrypted[:len(encrypted)-sha256.Size])
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expected := mac.Sum(nil)
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if subtle.ConstantTimeCompare(macBytes, expected) != 1 {
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return nil, false
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}
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block, err := aes.NewCipher(key.aesKey[:])
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if err != nil {
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return nil, false
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}
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plaintext = make([]byte, len(ciphertext))
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cipher.NewCTR(block, iv).XORKeyStream(plaintext, ciphertext)
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return plaintext, keyIndex > 0
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}
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func (c *Conn) getSessionTicketMsg(appData []byte) (*newSessionTicketMsgTLS13, error) {
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m := new(newSessionTicketMsgTLS13)
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var certsFromClient [][]byte
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for _, cert := range c.peerCertificates {
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certsFromClient = append(certsFromClient, cert.Raw)
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}
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state := sessionStateTLS13{
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cipherSuite: c.cipherSuite,
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createdAt: uint64(c.config.time().Unix()),
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resumptionSecret: c.resumptionSecret,
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certificate: Certificate{
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Certificate: certsFromClient,
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OCSPStaple: c.ocspResponse,
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SignedCertificateTimestamps: c.scts,
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},
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appData: appData,
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alpn: c.clientProtocol,
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}
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if c.extraConfig != nil {
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state.maxEarlyData = c.extraConfig.MaxEarlyData
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}
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var err error
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m.label, err = c.encryptTicket(state.marshal())
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if err != nil {
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return nil, err
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}
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m.lifetime = uint32(maxSessionTicketLifetime / time.Second)
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// ticket_age_add is a random 32-bit value. See RFC 8446, section 4.6.1
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// The value is not stored anywhere; we never need to check the ticket age
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// because 0-RTT is not supported.
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ageAdd := make([]byte, 4)
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_, err = c.config.rand().Read(ageAdd)
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if err != nil {
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return nil, err
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}
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m.ageAdd = binary.LittleEndian.Uint32(ageAdd)
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// ticket_nonce, which must be unique per connection, is always left at
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// zero because we only ever send one ticket per connection.
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if c.extraConfig != nil {
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m.maxEarlyData = c.extraConfig.MaxEarlyData
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}
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return m, nil
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}
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// GetSessionTicket generates a new session ticket.
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// It should only be called after the handshake completes.
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// It can only be used for servers, and only if the alternative record layer is set.
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// The ticket may be nil if config.SessionTicketsDisabled is set,
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// or if the client isn't able to receive session tickets.
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func (c *Conn) GetSessionTicket(appData []byte) ([]byte, error) {
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if c.isClient || !c.handshakeComplete() || c.extraConfig == nil || c.extraConfig.AlternativeRecordLayer == nil {
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return nil, errors.New("GetSessionTicket is only valid for servers after completion of the handshake, and if an alternative record layer is set.")
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}
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if c.config.SessionTicketsDisabled {
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return nil, nil
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}
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m, err := c.getSessionTicketMsg(appData)
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if err != nil {
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return nil, err
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}
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return m.marshal(), nil
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}
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