327 linhas
8.4 KiB
Go
327 linhas
8.4 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 trs
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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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"errors"
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"io"
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)
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// A SessionTicketSealer provides a way to securely encapsulate
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// session state for storage on the client. All methods are safe for
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// concurrent use.
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type SessionTicketSealer interface {
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// Seal returns a session ticket value that can be later passed to Unseal
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// to recover the content, usually by encrypting it. The ticket will be sent
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// to the client to be stored, and will be sent back in plaintext, so it can
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// be read and modified by an attacker.
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Seal(cs *ConnectionState, content []byte) (ticket []byte, err error)
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// Unseal returns a session ticket contents. The ticket can't be safely
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// assumed to have been generated by Seal.
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// If unable to unseal the ticket, the connection will proceed with a
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// complete handshake.
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Unseal(chi *ClientHelloInfo, ticket []byte) (content []byte, success bool)
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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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usedEMS bool
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masterSecret []byte
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certificates [][]byte
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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 (s *sessionState) equal(i interface{}) bool {
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s1, ok := i.(*sessionState)
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if !ok {
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return false
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}
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if s.vers != s1.vers ||
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s.usedEMS != s1.usedEMS ||
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s.cipherSuite != s1.cipherSuite ||
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!bytes.Equal(s.masterSecret, s1.masterSecret) {
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return false
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}
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if len(s.certificates) != len(s1.certificates) {
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return false
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}
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for i := range s.certificates {
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if !bytes.Equal(s.certificates[i], s1.certificates[i]) {
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return false
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}
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}
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return true
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}
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func (s *sessionState) marshal() []byte {
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length := 2 + 2 + 2 + len(s.masterSecret) + 2
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for _, cert := range s.certificates {
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length += 4 + len(cert)
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}
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ret := make([]byte, length)
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x := ret
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was_used := byte(0)
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if s.usedEMS {
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was_used = byte(0x80)
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}
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x[0] = byte(s.vers>>8) | byte(was_used)
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x[1] = byte(s.vers)
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x[2] = byte(s.cipherSuite >> 8)
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x[3] = byte(s.cipherSuite)
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x[4] = byte(len(s.masterSecret) >> 8)
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x[5] = byte(len(s.masterSecret))
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x = x[6:]
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copy(x, s.masterSecret)
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x = x[len(s.masterSecret):]
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x[0] = byte(len(s.certificates) >> 8)
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x[1] = byte(len(s.certificates))
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x = x[2:]
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for _, cert := range s.certificates {
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x[0] = byte(len(cert) >> 24)
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x[1] = byte(len(cert) >> 16)
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x[2] = byte(len(cert) >> 8)
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x[3] = byte(len(cert))
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copy(x[4:], cert)
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x = x[4+len(cert):]
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}
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return ret
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}
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func (s *sessionState) unmarshal(data []byte) alert {
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if len(data) < 8 {
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return alertDecodeError
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}
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s.vers = (uint16(data[0])<<8 | uint16(data[1])) & 0x7fff
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s.cipherSuite = uint16(data[2])<<8 | uint16(data[3])
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s.usedEMS = (data[0] & 0x80) == 0x80
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masterSecretLen := int(data[4])<<8 | int(data[5])
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data = data[6:]
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if len(data) < masterSecretLen {
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return alertDecodeError
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}
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s.masterSecret = data[:masterSecretLen]
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data = data[masterSecretLen:]
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if len(data) < 2 {
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return alertDecodeError
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}
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numCerts := int(data[0])<<8 | int(data[1])
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data = data[2:]
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s.certificates = make([][]byte, numCerts)
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for i := range s.certificates {
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if len(data) < 4 {
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return alertDecodeError
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}
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certLen := int(data[0])<<24 | int(data[1])<<16 | int(data[2])<<8 | int(data[3])
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data = data[4:]
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if certLen < 0 {
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return alertDecodeError
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}
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if len(data) < certLen {
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return alertDecodeError
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}
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s.certificates[i] = data[:certLen]
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data = data[certLen:]
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}
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if len(data) != 0 {
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return alertDecodeError
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}
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return alertSuccess
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}
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type sessionState13 struct {
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vers uint16
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suite uint16
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ageAdd uint32
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createdAt uint64
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maxEarlyDataLen uint32
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pskSecret []byte
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alpnProtocol string
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SNI string
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}
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func (s *sessionState13) equal(i interface{}) bool {
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s1, ok := i.(*sessionState13)
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if !ok {
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return false
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}
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return s.vers == s1.vers &&
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s.suite == s1.suite &&
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s.ageAdd == s1.ageAdd &&
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s.createdAt == s1.createdAt &&
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s.maxEarlyDataLen == s1.maxEarlyDataLen &&
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subtle.ConstantTimeCompare(s.pskSecret, s1.pskSecret) == 1 &&
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s.alpnProtocol == s1.alpnProtocol &&
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s.SNI == s1.SNI
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}
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func (s *sessionState13) marshal() []byte {
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length := 2 + 2 + 4 + 8 + 4 + 2 + len(s.pskSecret) + 2 + len(s.alpnProtocol) + 2 + len(s.SNI)
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x := make([]byte, length)
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x[0] = byte(s.vers >> 8)
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x[1] = byte(s.vers)
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x[2] = byte(s.suite >> 8)
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x[3] = byte(s.suite)
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x[4] = byte(s.ageAdd >> 24)
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x[5] = byte(s.ageAdd >> 16)
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x[6] = byte(s.ageAdd >> 8)
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x[7] = byte(s.ageAdd)
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x[8] = byte(s.createdAt >> 56)
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x[9] = byte(s.createdAt >> 48)
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x[10] = byte(s.createdAt >> 40)
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x[11] = byte(s.createdAt >> 32)
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x[12] = byte(s.createdAt >> 24)
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x[13] = byte(s.createdAt >> 16)
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x[14] = byte(s.createdAt >> 8)
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x[15] = byte(s.createdAt)
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x[16] = byte(s.maxEarlyDataLen >> 24)
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x[17] = byte(s.maxEarlyDataLen >> 16)
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x[18] = byte(s.maxEarlyDataLen >> 8)
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x[19] = byte(s.maxEarlyDataLen)
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x[20] = byte(len(s.pskSecret) >> 8)
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x[21] = byte(len(s.pskSecret))
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copy(x[22:], s.pskSecret)
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z := x[22+len(s.pskSecret):]
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z[0] = byte(len(s.alpnProtocol) >> 8)
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z[1] = byte(len(s.alpnProtocol))
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copy(z[2:], s.alpnProtocol)
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z = z[2+len(s.alpnProtocol):]
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z[0] = byte(len(s.SNI) >> 8)
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z[1] = byte(len(s.SNI))
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copy(z[2:], s.SNI)
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return x
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}
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func (s *sessionState13) unmarshal(data []byte) alert {
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if len(data) < 24 {
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return alertDecodeError
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}
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s.vers = uint16(data[0])<<8 | uint16(data[1])
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s.suite = uint16(data[2])<<8 | uint16(data[3])
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s.ageAdd = uint32(data[4])<<24 | uint32(data[5])<<16 | uint32(data[6])<<8 | uint32(data[7])
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s.createdAt = uint64(data[8])<<56 | uint64(data[9])<<48 | uint64(data[10])<<40 | uint64(data[11])<<32 |
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uint64(data[12])<<24 | uint64(data[13])<<16 | uint64(data[14])<<8 | uint64(data[15])
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s.maxEarlyDataLen = uint32(data[16])<<24 | uint32(data[17])<<16 | uint32(data[18])<<8 | uint32(data[19])
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l := int(data[20])<<8 | int(data[21])
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if len(data) < 22+l+2 {
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return alertDecodeError
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}
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s.pskSecret = data[22 : 22+l]
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z := data[22+l:]
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l = int(z[0])<<8 | int(z[1])
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if len(z) < 2+l+2 {
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return alertDecodeError
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}
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s.alpnProtocol = string(z[2 : 2+l])
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z = z[2+l:]
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l = int(z[0])<<8 | int(z[1])
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if len(z) != 2+l {
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return alertDecodeError
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}
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s.SNI = string(z[2 : 2+l])
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return alertSuccess
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}
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func (c *Conn) encryptTicket(serialized []byte) ([]byte, error) {
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encrypted := make([]byte, ticketKeyNameLen+aes.BlockSize+len(serialized)+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.config.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:], serialized)
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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) (serialized []byte, usedOldKey bool) {
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if c.config.SessionTicketsDisabled ||
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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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keys := c.config.ticketKeys()
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keyIndex := -1
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for i, candidateKey := range keys {
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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 := &keys[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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ciphertext := encrypted[ticketKeyNameLen+aes.BlockSize : len(encrypted)-sha256.Size]
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plaintext := 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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