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// Copyright 2010 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 (
"crypto"
"crypto/aes"
"crypto/cipher"
"crypto/des"
"crypto/hmac"
"crypto/rc4"
"crypto/sha1"
"crypto/sha256"
"crypto/x509"
"golang.org/x/crypto/chacha20poly1305"
"hash"
)
// a keyAgreement implements the client and server side of a TLS key agreement
// protocol by generating and processing key exchange messages.
type keyAgreement interface {
// On the server side, the first two methods are called in order.
// In the case that the key agreement protocol doesn't use a
// ServerKeyExchange message, generateServerKeyExchange can return nil,
// nil.
generateServerKeyExchange(*Config, *Certificate, *clientHelloMsg, *serverHelloMsg) (*serverKeyExchangeMsg, error)
processClientKeyExchange(*Config, *Certificate, *clientKeyExchangeMsg, uint16) ([]byte, error)
// On the client side, the next two methods are called in order.
// This method may not be called if the server doesn't send a
// ServerKeyExchange message.
processServerKeyExchange(*Config, *clientHelloMsg, *serverHelloMsg, *x509.Certificate, *serverKeyExchangeMsg) error
generateClientKeyExchange(*Config, *clientHelloMsg, *x509.Certificate) ([]byte, *clientKeyExchangeMsg, error)
}
const (
// suiteECDH indicates that the cipher suite involves elliptic curve
// Diffie-Hellman. This means that it should only be selected when the
// client indicates that it supports ECC with a curve and point format
// that we're happy with.
suiteECDHE = 1 << iota
// suiteECDSA indicates that the cipher suite involves an ECDSA
// signature and therefore may only be selected when the server's
// certificate is ECDSA. If this is not set then the cipher suite is
// RSA based.
suiteECDSA
// suiteTLS12 indicates that the cipher suite should only be advertised
// and accepted when using TLS 1.2.
suiteTLS12
// suiteSHA384 indicates that the cipher suite uses SHA384 as the
// handshake hash.
suiteSHA384
// suiteDefaultOff indicates that this cipher suite is not included by
// default.
suiteDefaultOff
)
// A cipherSuite is a specific combination of key agreement, cipher and MAC function.
type cipherSuite struct {
id uint16
// the lengths, in bytes, of the key material needed for each component.
keyLen int
macLen int
ivLen int
ka func(version uint16) keyAgreement
// flags is a bitmask of the suite* values, above.
flags int
cipher func(key, iv []byte, isRead bool) interface{}
mac func(version uint16, macKey []byte) macFunction
aead func(key, fixedNonce []byte) aead
}
var cipherSuites = []*cipherSuite{
// Ciphersuite order is chosen so that ECDHE comes before plain RSA and
// AEADs are the top preference.
{TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305, 32, 0, 12, ecdheRSAKA, suiteECDHE | suiteTLS12, nil, nil, aeadChaCha20Poly1305},
{TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305, 32, 0, 12, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12, nil, nil, aeadChaCha20Poly1305},
{TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12, nil, nil, aeadAESGCM},
{TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12, nil, nil, aeadAESGCM},
{TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM},
{TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM},
{TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, ecdheRSAKA, suiteECDHE | suiteTLS12 | suiteDefaultOff, cipherAES, macSHA256, nil},
{TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil},
{TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12 | suiteDefaultOff, cipherAES, macSHA256, nil},
{TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA, cipherAES, macSHA1, nil},
{TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil},
{TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA, cipherAES, macSHA1, nil},
{TLS_RSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, rsaKA, suiteTLS12, nil, nil, aeadAESGCM},
{TLS_RSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, rsaKA, suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM},
{TLS_RSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, rsaKA, suiteTLS12 | suiteDefaultOff, cipherAES, macSHA256, nil},
{TLS_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil},
{TLS_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil},
{TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, ecdheRSAKA, suiteECDHE, cipher3DES, macSHA1, nil},
{TLS_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, rsaKA, 0, cipher3DES, macSHA1, nil},
// RC4-based cipher suites are disabled by default.
{TLS_RSA_WITH_RC4_128_SHA, 16, 20, 0, rsaKA, suiteDefaultOff, cipherRC4, macSHA1, nil},
{TLS_ECDHE_RSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheRSAKA, suiteECDHE | suiteDefaultOff, cipherRC4, macSHA1, nil},
{TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteDefaultOff, cipherRC4, macSHA1, nil},
}
// A cipherSuiteTLS13 defines only the pair of the AEAD algorithm and hash
// algorithm to be used with HKDF. See RFC 8446, Appendix B.4.
type cipherSuiteTLS13 struct {
id uint16
keyLen int
aead func(key, fixedNonce []byte) aead
hash crypto.Hash
}
var cipherSuitesTLS13 = []*cipherSuiteTLS13{
{TLS_AES_128_GCM_SHA256, 16, aeadAESGCMTLS13, crypto.SHA256},
{TLS_CHACHA20_POLY1305_SHA256, 32, aeadChaCha20Poly1305, crypto.SHA256},
{TLS_AES_256_GCM_SHA384, 32, aeadAESGCMTLS13, crypto.SHA384},
}
func cipherRC4(key, iv []byte, isRead bool) interface{} {
cipher, _ := rc4.NewCipher(key)
return cipher
}
func cipher3DES(key, iv []byte, isRead bool) interface{} {
block, _ := des.NewTripleDESCipher(key)
if isRead {
return cipher.NewCBCDecrypter(block, iv)
}
return cipher.NewCBCEncrypter(block, iv)
}
func cipherAES(key, iv []byte, isRead bool) interface{} {
block, _ := aes.NewCipher(key)
if isRead {
return cipher.NewCBCDecrypter(block, iv)
}
return cipher.NewCBCEncrypter(block, iv)
}
// macSHA1 returns a macFunction for the given protocol version.
func macSHA1(version uint16, key []byte) macFunction {
if version == VersionSSL30 {
mac := ssl30MAC{
h: sha1.New(),
key: make([]byte, len(key)),
}
copy(mac.key, key)
return mac
}
return tls10MAC{h: hmac.New(newConstantTimeHash(sha1.New), key)}
}
// macSHA256 returns a SHA-256 based MAC. These are only supported in TLS 1.2
// so the given version is ignored.
func macSHA256(version uint16, key []byte) macFunction {
return tls10MAC{h: hmac.New(sha256.New, key)}
}
type macFunction interface {
// Size returns the length of the MAC.
Size() int
// MAC appends the MAC of (seq, header, data) to out. The extra data is fed
// into the MAC after obtaining the result to normalize timing. The result
// is only valid until the next invocation of MAC as the buffer is reused.
MAC(seq, header, data, extra []byte) []byte
}
type aead interface {
cipher.AEAD
// explicitNonceLen returns the number of bytes of explicit nonce
// included in each record. This is eight for older AEADs and
// zero for modern ones.
explicitNonceLen() int
}
const (
aeadNonceLength = 12
noncePrefixLength = 4
)
// prefixNonceAEAD wraps an AEAD and prefixes a fixed portion of the nonce to
// each call.
type prefixNonceAEAD struct {
// nonce contains the fixed part of the nonce in the first four bytes.
nonce [aeadNonceLength]byte
aead cipher.AEAD
}
func (f *prefixNonceAEAD) NonceSize() int { return aeadNonceLength - noncePrefixLength }
func (f *prefixNonceAEAD) Overhead() int { return f.aead.Overhead() }
func (f *prefixNonceAEAD) explicitNonceLen() int { return f.NonceSize() }
func (f *prefixNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte {
copy(f.nonce[4:], nonce)
return f.aead.Seal(out, f.nonce[:], plaintext, additionalData)
}
func (f *prefixNonceAEAD) Open(out, nonce, ciphertext, additionalData []byte) ([]byte, error) {
copy(f.nonce[4:], nonce)
return f.aead.Open(out, f.nonce[:], ciphertext, additionalData)
}
// xoredNonceAEAD wraps an AEAD by XORing in a fixed pattern to the nonce
// before each call.
type xorNonceAEAD struct {
nonceMask [aeadNonceLength]byte
aead cipher.AEAD
}
func (f *xorNonceAEAD) NonceSize() int { return 8 } // 64-bit sequence number
func (f *xorNonceAEAD) Overhead() int { return f.aead.Overhead() }
func (f *xorNonceAEAD) explicitNonceLen() int { return 0 }
func (f *xorNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte {
for i, b := range nonce {
f.nonceMask[4+i] ^= b
}
result := f.aead.Seal(out, f.nonceMask[:], plaintext, additionalData)
for i, b := range nonce {
f.nonceMask[4+i] ^= b
}
return result
}
func (f *xorNonceAEAD) Open(out, nonce, ciphertext, additionalData []byte) ([]byte, error) {
for i, b := range nonce {
f.nonceMask[4+i] ^= b
}
result, err := f.aead.Open(out, f.nonceMask[:], ciphertext, additionalData)
for i, b := range nonce {
f.nonceMask[4+i] ^= b
}
return result, err
}
func aeadAESGCM(key, noncePrefix []byte) aead {
if len(noncePrefix) != noncePrefixLength {
panic("tls: internal error: wrong nonce length")
}
aes, err := aes.NewCipher(key)
if err != nil {
panic(err)
}
aead, err := cipher.NewGCM(aes)
if err != nil {
panic(err)
}
ret := &prefixNonceAEAD{aead: aead}
copy(ret.nonce[:], noncePrefix)
return ret
}
func aeadAESGCMTLS13(key, nonceMask []byte) aead {
if len(nonceMask) != aeadNonceLength {
panic("tls: internal error: wrong nonce length")
}
aes, err := aes.NewCipher(key)
if err != nil {
panic(err)
}
aead, err := cipher.NewGCM(aes)
if err != nil {
panic(err)
}
ret := &xorNonceAEAD{aead: aead}
copy(ret.nonceMask[:], nonceMask)
return ret
}
func aeadChaCha20Poly1305(key, nonceMask []byte) aead {
if len(nonceMask) != aeadNonceLength {
panic("tls: internal error: wrong nonce length")
}
aead, err := chacha20poly1305.New(key)
if err != nil {
panic(err)
}
ret := &xorNonceAEAD{aead: aead}
copy(ret.nonceMask[:], nonceMask)
return ret
}
// ssl30MAC implements the SSLv3 MAC function, as defined in
// www.mozilla.org/projects/security/pki/nss/ssl/draft302.txt section 5.2.3.1
type ssl30MAC struct {
h hash.Hash
key []byte
buf []byte
}
func (s ssl30MAC) Size() int {
return s.h.Size()
}
var ssl30Pad1 = [48]byte{0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36}
var ssl30Pad2 = [48]byte{0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c}
// MAC does not offer constant timing guarantees for SSL v3.0, since it's deemed
// useless considering the similar, protocol-level POODLE vulnerability.
func (s ssl30MAC) MAC(seq, header, data, extra []byte) []byte {
padLength := 48
if s.h.Size() == 20 {
padLength = 40
}
s.h.Reset()
s.h.Write(s.key)
s.h.Write(ssl30Pad1[:padLength])
s.h.Write(seq)
s.h.Write(header[:1])
s.h.Write(header[3:5])
s.h.Write(data)
s.buf = s.h.Sum(s.buf[:0])
s.h.Reset()
s.h.Write(s.key)
s.h.Write(ssl30Pad2[:padLength])
s.h.Write(s.buf)
return s.h.Sum(s.buf[:0])
}
type constantTimeHash interface {
hash.Hash
ConstantTimeSum(b []byte) []byte
}
// cthWrapper wraps any hash.Hash that implements ConstantTimeSum, and replaces
// with that all calls to Sum. It's used to obtain a ConstantTimeSum-based HMAC.
type cthWrapper struct {
h constantTimeHash
}
func (c *cthWrapper) Size() int { return c.h.Size() }
func (c *cthWrapper) BlockSize() int { return c.h.BlockSize() }
func (c *cthWrapper) Reset() { c.h.Reset() }
func (c *cthWrapper) Write(p []byte) (int, error) { return c.h.Write(p) }
func (c *cthWrapper) Sum(b []byte) []byte { return c.h.ConstantTimeSum(b) }
func newConstantTimeHash(h func() hash.Hash) func() hash.Hash {
return func() hash.Hash {
return &cthWrapper{h().(constantTimeHash)}
}
}
// tls10MAC implements the TLS 1.0 MAC function. RFC 2246, Section 6.2.3.
type tls10MAC struct {
h hash.Hash
buf []byte
}
func (s tls10MAC) Size() int {
return s.h.Size()
}
// MAC is guaranteed to take constant time, as long as
// len(seq)+len(header)+len(data)+len(extra) is constant. extra is not fed into
// the MAC, but is only provided to make the timing profile constant.
func (s tls10MAC) MAC(seq, header, data, extra []byte) []byte {
s.h.Reset()
s.h.Write(seq)
s.h.Write(header)
s.h.Write(data)
res := s.h.Sum(s.buf[:0])
if extra != nil {
s.h.Write(extra)
}
return res
}
func rsaKA(version uint16) keyAgreement {
return rsaKeyAgreement{}
}
func ecdheECDSAKA(version uint16) keyAgreement {
return &ecdheKeyAgreement{
isRSA: false,
version: version,
}
}
func ecdheRSAKA(version uint16) keyAgreement {
return &ecdheKeyAgreement{
isRSA: true,
version: version,
}
}
// mutualCipherSuite returns a cipherSuite given a list of supported
// ciphersuites and the id requested by the peer.
func mutualCipherSuite(have []uint16, want uint16) *cipherSuite {
for _, id := range have {
if id == want {
return cipherSuiteByID(id)
}
}
return nil
}
func cipherSuiteByID(id uint16) *cipherSuite {
for _, cipherSuite := range utlsSupportedCipherSuites {
if cipherSuite.id == id {
return cipherSuite
}
}
return nil
}
func mutualCipherSuiteTLS13(have []uint16, want uint16) *cipherSuiteTLS13 {
for _, id := range have {
if id == want {
return cipherSuiteTLS13ByID(id)
}
}
return nil
}
func cipherSuiteTLS13ByID(id uint16) *cipherSuiteTLS13 {
for _, cipherSuite := range cipherSuitesTLS13 {
if cipherSuite.id == id {
return cipherSuite
}
}
return nil
}
// A list of cipher suite IDs that are, or have been, implemented by this
// package.
//
// Taken from https://www.iana.org/assignments/tls-parameters/tls-parameters.xml
const (
// TLS 1.0 - 1.2 cipher suites.
TLS_RSA_WITH_RC4_128_SHA uint16 = 0x0005
TLS_RSA_WITH_3DES_EDE_CBC_SHA uint16 = 0x000a
TLS_RSA_WITH_AES_128_CBC_SHA uint16 = 0x002f
TLS_RSA_WITH_AES_256_CBC_SHA uint16 = 0x0035
TLS_RSA_WITH_AES_128_CBC_SHA256 uint16 = 0x003c
TLS_RSA_WITH_AES_128_GCM_SHA256 uint16 = 0x009c
TLS_RSA_WITH_AES_256_GCM_SHA384 uint16 = 0x009d
TLS_ECDHE_ECDSA_WITH_RC4_128_SHA uint16 = 0xc007
TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA uint16 = 0xc009
TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA uint16 = 0xc00a
TLS_ECDHE_RSA_WITH_RC4_128_SHA uint16 = 0xc011
TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA uint16 = 0xc012
TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA uint16 = 0xc013
TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA uint16 = 0xc014
TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 uint16 = 0xc023
TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 uint16 = 0xc027
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 uint16 = 0xc02f
TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 uint16 = 0xc02b
TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 uint16 = 0xc030
TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 uint16 = 0xc02c
TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305 uint16 = 0xcca8
TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305 uint16 = 0xcca9
// TLS 1.3 cipher suites.
TLS_AES_128_GCM_SHA256 uint16 = 0x1301
TLS_AES_256_GCM_SHA384 uint16 = 0x1302
TLS_CHACHA20_POLY1305_SHA256 uint16 = 0x1303
// TLS_FALLBACK_SCSV isn't a standard cipher suite but an indicator
// that the client is doing version fallback. See RFC 7507.
TLS_FALLBACK_SCSV uint16 = 0x5600
)
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