Source file src/crypto/tls/cipher_suites.go

Documentation: crypto/tls

     1  // Copyright 2010 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package tls
     6  
     7  import (
     8  	"crypto"
     9  	"crypto/aes"
    10  	"crypto/cipher"
    11  	"crypto/des"
    12  	"crypto/hmac"
    13  	"crypto/rc4"
    14  	"crypto/sha1"
    15  	"crypto/sha256"
    16  	"crypto/x509"
    17  	"golang.org/x/crypto/chacha20poly1305"
    18  	"hash"
    19  )
    20  
    21  // a keyAgreement implements the client and server side of a TLS key agreement
    22  // protocol by generating and processing key exchange messages.
    23  type keyAgreement interface {
    24  	// On the server side, the first two methods are called in order.
    25  
    26  	// In the case that the key agreement protocol doesn't use a
    27  	// ServerKeyExchange message, generateServerKeyExchange can return nil,
    28  	// nil.
    29  	generateServerKeyExchange(*Config, *Certificate, *clientHelloMsg, *serverHelloMsg) (*serverKeyExchangeMsg, error)
    30  	processClientKeyExchange(*Config, *Certificate, *clientKeyExchangeMsg, uint16) ([]byte, error)
    31  
    32  	// On the client side, the next two methods are called in order.
    33  
    34  	// This method may not be called if the server doesn't send a
    35  	// ServerKeyExchange message.
    36  	processServerKeyExchange(*Config, *clientHelloMsg, *serverHelloMsg, *x509.Certificate, *serverKeyExchangeMsg) error
    37  	generateClientKeyExchange(*Config, *clientHelloMsg, *x509.Certificate) ([]byte, *clientKeyExchangeMsg, error)
    38  }
    39  
    40  const (
    41  	// suiteECDH indicates that the cipher suite involves elliptic curve
    42  	// Diffie-Hellman. This means that it should only be selected when the
    43  	// client indicates that it supports ECC with a curve and point format
    44  	// that we're happy with.
    45  	suiteECDHE = 1 << iota
    46  	// suiteECSign indicates that the cipher suite involves an ECDSA or
    47  	// EdDSA signature and therefore may only be selected when the server's
    48  	// certificate is ECDSA or EdDSA. If this is not set then the cipher suite
    49  	// is RSA based.
    50  	suiteECSign
    51  	// suiteTLS12 indicates that the cipher suite should only be advertised
    52  	// and accepted when using TLS 1.2.
    53  	suiteTLS12
    54  	// suiteSHA384 indicates that the cipher suite uses SHA384 as the
    55  	// handshake hash.
    56  	suiteSHA384
    57  	// suiteDefaultOff indicates that this cipher suite is not included by
    58  	// default.
    59  	suiteDefaultOff
    60  )
    61  
    62  // A cipherSuite is a specific combination of key agreement, cipher and MAC function.
    63  type cipherSuite struct {
    64  	id uint16
    65  	// the lengths, in bytes, of the key material needed for each component.
    66  	keyLen int
    67  	macLen int
    68  	ivLen  int
    69  	ka     func(version uint16) keyAgreement
    70  	// flags is a bitmask of the suite* values, above.
    71  	flags  int
    72  	cipher func(key, iv []byte, isRead bool) interface{}
    73  	mac    func(version uint16, macKey []byte) macFunction
    74  	aead   func(key, fixedNonce []byte) aead
    75  }
    76  
    77  var cipherSuites = []*cipherSuite{
    78  	// Ciphersuite order is chosen so that ECDHE comes before plain RSA and
    79  	// AEADs are the top preference.
    80  	{TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305, 32, 0, 12, ecdheRSAKA, suiteECDHE | suiteTLS12, nil, nil, aeadChaCha20Poly1305},
    81  	{TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305, 32, 0, 12, ecdheECDSAKA, suiteECDHE | suiteECSign | suiteTLS12, nil, nil, aeadChaCha20Poly1305},
    82  	{TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12, nil, nil, aeadAESGCM},
    83  	{TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECSign | suiteTLS12, nil, nil, aeadAESGCM},
    84  	{TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM},
    85  	{TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECSign | suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM},
    86  	{TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, ecdheRSAKA, suiteECDHE | suiteTLS12 | suiteDefaultOff, cipherAES, macSHA256, nil},
    87  	{TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil},
    88  	{TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, ecdheECDSAKA, suiteECDHE | suiteECSign | suiteTLS12 | suiteDefaultOff, cipherAES, macSHA256, nil},
    89  	{TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECSign, cipherAES, macSHA1, nil},
    90  	{TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil},
    91  	{TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECSign, cipherAES, macSHA1, nil},
    92  	{TLS_RSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, rsaKA, suiteTLS12, nil, nil, aeadAESGCM},
    93  	{TLS_RSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, rsaKA, suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM},
    94  	{TLS_RSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, rsaKA, suiteTLS12 | suiteDefaultOff, cipherAES, macSHA256, nil},
    95  	{TLS_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil},
    96  	{TLS_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil},
    97  	{TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, ecdheRSAKA, suiteECDHE, cipher3DES, macSHA1, nil},
    98  	{TLS_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, rsaKA, 0, cipher3DES, macSHA1, nil},
    99  
   100  	// RC4-based cipher suites are disabled by default.
   101  	{TLS_RSA_WITH_RC4_128_SHA, 16, 20, 0, rsaKA, suiteDefaultOff, cipherRC4, macSHA1, nil},
   102  	{TLS_ECDHE_RSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheRSAKA, suiteECDHE | suiteDefaultOff, cipherRC4, macSHA1, nil},
   103  	{TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheECDSAKA, suiteECDHE | suiteECSign | suiteDefaultOff, cipherRC4, macSHA1, nil},
   104  }
   105  
   106  // A cipherSuiteTLS13 defines only the pair of the AEAD algorithm and hash
   107  // algorithm to be used with HKDF. See RFC 8446, Appendix B.4.
   108  type cipherSuiteTLS13 struct {
   109  	id     uint16
   110  	keyLen int
   111  	aead   func(key, fixedNonce []byte) aead
   112  	hash   crypto.Hash
   113  }
   114  
   115  var cipherSuitesTLS13 = []*cipherSuiteTLS13{
   116  	{TLS_AES_128_GCM_SHA256, 16, aeadAESGCMTLS13, crypto.SHA256},
   117  	{TLS_CHACHA20_POLY1305_SHA256, 32, aeadChaCha20Poly1305, crypto.SHA256},
   118  	{TLS_AES_256_GCM_SHA384, 32, aeadAESGCMTLS13, crypto.SHA384},
   119  }
   120  
   121  func cipherRC4(key, iv []byte, isRead bool) interface{} {
   122  	cipher, _ := rc4.NewCipher(key)
   123  	return cipher
   124  }
   125  
   126  func cipher3DES(key, iv []byte, isRead bool) interface{} {
   127  	block, _ := des.NewTripleDESCipher(key)
   128  	if isRead {
   129  		return cipher.NewCBCDecrypter(block, iv)
   130  	}
   131  	return cipher.NewCBCEncrypter(block, iv)
   132  }
   133  
   134  func cipherAES(key, iv []byte, isRead bool) interface{} {
   135  	block, _ := aes.NewCipher(key)
   136  	if isRead {
   137  		return cipher.NewCBCDecrypter(block, iv)
   138  	}
   139  	return cipher.NewCBCEncrypter(block, iv)
   140  }
   141  
   142  // macSHA1 returns a macFunction for the given protocol version.
   143  func macSHA1(version uint16, key []byte) macFunction {
   144  	if version == VersionSSL30 {
   145  		mac := ssl30MAC{
   146  			h:   sha1.New(),
   147  			key: make([]byte, len(key)),
   148  		}
   149  		copy(mac.key, key)
   150  		return mac
   151  	}
   152  	return tls10MAC{h: hmac.New(newConstantTimeHash(sha1.New), key)}
   153  }
   154  
   155  // macSHA256 returns a SHA-256 based MAC. These are only supported in TLS 1.2
   156  // so the given version is ignored.
   157  func macSHA256(version uint16, key []byte) macFunction {
   158  	return tls10MAC{h: hmac.New(sha256.New, key)}
   159  }
   160  
   161  type macFunction interface {
   162  	// Size returns the length of the MAC.
   163  	Size() int
   164  	// MAC appends the MAC of (seq, header, data) to out. The extra data is fed
   165  	// into the MAC after obtaining the result to normalize timing. The result
   166  	// is only valid until the next invocation of MAC as the buffer is reused.
   167  	MAC(seq, header, data, extra []byte) []byte
   168  }
   169  
   170  type aead interface {
   171  	cipher.AEAD
   172  
   173  	// explicitNonceLen returns the number of bytes of explicit nonce
   174  	// included in each record. This is eight for older AEADs and
   175  	// zero for modern ones.
   176  	explicitNonceLen() int
   177  }
   178  
   179  const (
   180  	aeadNonceLength   = 12
   181  	noncePrefixLength = 4
   182  )
   183  
   184  // prefixNonceAEAD wraps an AEAD and prefixes a fixed portion of the nonce to
   185  // each call.
   186  type prefixNonceAEAD struct {
   187  	// nonce contains the fixed part of the nonce in the first four bytes.
   188  	nonce [aeadNonceLength]byte
   189  	aead  cipher.AEAD
   190  }
   191  
   192  func (f *prefixNonceAEAD) NonceSize() int        { return aeadNonceLength - noncePrefixLength }
   193  func (f *prefixNonceAEAD) Overhead() int         { return f.aead.Overhead() }
   194  func (f *prefixNonceAEAD) explicitNonceLen() int { return f.NonceSize() }
   195  
   196  func (f *prefixNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte {
   197  	copy(f.nonce[4:], nonce)
   198  	return f.aead.Seal(out, f.nonce[:], plaintext, additionalData)
   199  }
   200  
   201  func (f *prefixNonceAEAD) Open(out, nonce, ciphertext, additionalData []byte) ([]byte, error) {
   202  	copy(f.nonce[4:], nonce)
   203  	return f.aead.Open(out, f.nonce[:], ciphertext, additionalData)
   204  }
   205  
   206  // xoredNonceAEAD wraps an AEAD by XORing in a fixed pattern to the nonce
   207  // before each call.
   208  type xorNonceAEAD struct {
   209  	nonceMask [aeadNonceLength]byte
   210  	aead      cipher.AEAD
   211  }
   212  
   213  func (f *xorNonceAEAD) NonceSize() int        { return 8 } // 64-bit sequence number
   214  func (f *xorNonceAEAD) Overhead() int         { return f.aead.Overhead() }
   215  func (f *xorNonceAEAD) explicitNonceLen() int { return 0 }
   216  
   217  func (f *xorNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte {
   218  	for i, b := range nonce {
   219  		f.nonceMask[4+i] ^= b
   220  	}
   221  	result := f.aead.Seal(out, f.nonceMask[:], plaintext, additionalData)
   222  	for i, b := range nonce {
   223  		f.nonceMask[4+i] ^= b
   224  	}
   225  
   226  	return result
   227  }
   228  
   229  func (f *xorNonceAEAD) Open(out, nonce, ciphertext, additionalData []byte) ([]byte, error) {
   230  	for i, b := range nonce {
   231  		f.nonceMask[4+i] ^= b
   232  	}
   233  	result, err := f.aead.Open(out, f.nonceMask[:], ciphertext, additionalData)
   234  	for i, b := range nonce {
   235  		f.nonceMask[4+i] ^= b
   236  	}
   237  
   238  	return result, err
   239  }
   240  
   241  func aeadAESGCM(key, noncePrefix []byte) aead {
   242  	if len(noncePrefix) != noncePrefixLength {
   243  		panic("tls: internal error: wrong nonce length")
   244  	}
   245  	aes, err := aes.NewCipher(key)
   246  	if err != nil {
   247  		panic(err)
   248  	}
   249  	aead, err := cipher.NewGCM(aes)
   250  	if err != nil {
   251  		panic(err)
   252  	}
   253  
   254  	ret := &prefixNonceAEAD{aead: aead}
   255  	copy(ret.nonce[:], noncePrefix)
   256  	return ret
   257  }
   258  
   259  func aeadAESGCMTLS13(key, nonceMask []byte) aead {
   260  	if len(nonceMask) != aeadNonceLength {
   261  		panic("tls: internal error: wrong nonce length")
   262  	}
   263  	aes, err := aes.NewCipher(key)
   264  	if err != nil {
   265  		panic(err)
   266  	}
   267  	aead, err := cipher.NewGCM(aes)
   268  	if err != nil {
   269  		panic(err)
   270  	}
   271  
   272  	ret := &xorNonceAEAD{aead: aead}
   273  	copy(ret.nonceMask[:], nonceMask)
   274  	return ret
   275  }
   276  
   277  func aeadChaCha20Poly1305(key, nonceMask []byte) aead {
   278  	if len(nonceMask) != aeadNonceLength {
   279  		panic("tls: internal error: wrong nonce length")
   280  	}
   281  	aead, err := chacha20poly1305.New(key)
   282  	if err != nil {
   283  		panic(err)
   284  	}
   285  
   286  	ret := &xorNonceAEAD{aead: aead}
   287  	copy(ret.nonceMask[:], nonceMask)
   288  	return ret
   289  }
   290  
   291  // ssl30MAC implements the SSLv3 MAC function, as defined in
   292  // www.mozilla.org/projects/security/pki/nss/ssl/draft302.txt section 5.2.3.1
   293  type ssl30MAC struct {
   294  	h   hash.Hash
   295  	key []byte
   296  	buf []byte
   297  }
   298  
   299  func (s ssl30MAC) Size() int {
   300  	return s.h.Size()
   301  }
   302  
   303  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}
   304  
   305  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}
   306  
   307  // MAC does not offer constant timing guarantees for SSL v3.0, since it's deemed
   308  // useless considering the similar, protocol-level POODLE vulnerability.
   309  func (s ssl30MAC) MAC(seq, header, data, extra []byte) []byte {
   310  	padLength := 48
   311  	if s.h.Size() == 20 {
   312  		padLength = 40
   313  	}
   314  
   315  	s.h.Reset()
   316  	s.h.Write(s.key)
   317  	s.h.Write(ssl30Pad1[:padLength])
   318  	s.h.Write(seq)
   319  	s.h.Write(header[:1])
   320  	s.h.Write(header[3:5])
   321  	s.h.Write(data)
   322  	s.buf = s.h.Sum(s.buf[:0])
   323  
   324  	s.h.Reset()
   325  	s.h.Write(s.key)
   326  	s.h.Write(ssl30Pad2[:padLength])
   327  	s.h.Write(s.buf)
   328  	return s.h.Sum(s.buf[:0])
   329  }
   330  
   331  type constantTimeHash interface {
   332  	hash.Hash
   333  	ConstantTimeSum(b []byte) []byte
   334  }
   335  
   336  // cthWrapper wraps any hash.Hash that implements ConstantTimeSum, and replaces
   337  // with that all calls to Sum. It's used to obtain a ConstantTimeSum-based HMAC.
   338  type cthWrapper struct {
   339  	h constantTimeHash
   340  }
   341  
   342  func (c *cthWrapper) Size() int                   { return c.h.Size() }
   343  func (c *cthWrapper) BlockSize() int              { return c.h.BlockSize() }
   344  func (c *cthWrapper) Reset()                      { c.h.Reset() }
   345  func (c *cthWrapper) Write(p []byte) (int, error) { return c.h.Write(p) }
   346  func (c *cthWrapper) Sum(b []byte) []byte         { return c.h.ConstantTimeSum(b) }
   347  
   348  func newConstantTimeHash(h func() hash.Hash) func() hash.Hash {
   349  	return func() hash.Hash {
   350  		return &cthWrapper{h().(constantTimeHash)}
   351  	}
   352  }
   353  
   354  // tls10MAC implements the TLS 1.0 MAC function. RFC 2246, Section 6.2.3.
   355  type tls10MAC struct {
   356  	h   hash.Hash
   357  	buf []byte
   358  }
   359  
   360  func (s tls10MAC) Size() int {
   361  	return s.h.Size()
   362  }
   363  
   364  // MAC is guaranteed to take constant time, as long as
   365  // len(seq)+len(header)+len(data)+len(extra) is constant. extra is not fed into
   366  // the MAC, but is only provided to make the timing profile constant.
   367  func (s tls10MAC) MAC(seq, header, data, extra []byte) []byte {
   368  	s.h.Reset()
   369  	s.h.Write(seq)
   370  	s.h.Write(header)
   371  	s.h.Write(data)
   372  	res := s.h.Sum(s.buf[:0])
   373  	if extra != nil {
   374  		s.h.Write(extra)
   375  	}
   376  	return res
   377  }
   378  
   379  func rsaKA(version uint16) keyAgreement {
   380  	return rsaKeyAgreement{}
   381  }
   382  
   383  func ecdheECDSAKA(version uint16) keyAgreement {
   384  	return &ecdheKeyAgreement{
   385  		isRSA:   false,
   386  		version: version,
   387  	}
   388  }
   389  
   390  func ecdheRSAKA(version uint16) keyAgreement {
   391  	return &ecdheKeyAgreement{
   392  		isRSA:   true,
   393  		version: version,
   394  	}
   395  }
   396  
   397  // mutualCipherSuite returns a cipherSuite given a list of supported
   398  // ciphersuites and the id requested by the peer.
   399  func mutualCipherSuite(have []uint16, want uint16) *cipherSuite {
   400  	for _, id := range have {
   401  		if id == want {
   402  			return cipherSuiteByID(id)
   403  		}
   404  	}
   405  	return nil
   406  }
   407  
   408  func cipherSuiteByID(id uint16) *cipherSuite {
   409  	for _, cipherSuite := range cipherSuites {
   410  		if cipherSuite.id == id {
   411  			return cipherSuite
   412  		}
   413  	}
   414  	return nil
   415  }
   416  
   417  func mutualCipherSuiteTLS13(have []uint16, want uint16) *cipherSuiteTLS13 {
   418  	for _, id := range have {
   419  		if id == want {
   420  			return cipherSuiteTLS13ByID(id)
   421  		}
   422  	}
   423  	return nil
   424  }
   425  
   426  func cipherSuiteTLS13ByID(id uint16) *cipherSuiteTLS13 {
   427  	for _, cipherSuite := range cipherSuitesTLS13 {
   428  		if cipherSuite.id == id {
   429  			return cipherSuite
   430  		}
   431  	}
   432  	return nil
   433  }
   434  
   435  // A list of cipher suite IDs that are, or have been, implemented by this
   436  // package.
   437  //
   438  // Taken from https://www.iana.org/assignments/tls-parameters/tls-parameters.xml
   439  const (
   440  	// TLS 1.0 - 1.2 cipher suites.
   441  	TLS_RSA_WITH_RC4_128_SHA                uint16 = 0x0005
   442  	TLS_RSA_WITH_3DES_EDE_CBC_SHA           uint16 = 0x000a
   443  	TLS_RSA_WITH_AES_128_CBC_SHA            uint16 = 0x002f
   444  	TLS_RSA_WITH_AES_256_CBC_SHA            uint16 = 0x0035
   445  	TLS_RSA_WITH_AES_128_CBC_SHA256         uint16 = 0x003c
   446  	TLS_RSA_WITH_AES_128_GCM_SHA256         uint16 = 0x009c
   447  	TLS_RSA_WITH_AES_256_GCM_SHA384         uint16 = 0x009d
   448  	TLS_ECDHE_ECDSA_WITH_RC4_128_SHA        uint16 = 0xc007
   449  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA    uint16 = 0xc009
   450  	TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA    uint16 = 0xc00a
   451  	TLS_ECDHE_RSA_WITH_RC4_128_SHA          uint16 = 0xc011
   452  	TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA     uint16 = 0xc012
   453  	TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA      uint16 = 0xc013
   454  	TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA      uint16 = 0xc014
   455  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 uint16 = 0xc023
   456  	TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256   uint16 = 0xc027
   457  	TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256   uint16 = 0xc02f
   458  	TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 uint16 = 0xc02b
   459  	TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384   uint16 = 0xc030
   460  	TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 uint16 = 0xc02c
   461  	TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305    uint16 = 0xcca8
   462  	TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305  uint16 = 0xcca9
   463  
   464  	// TLS 1.3 cipher suites.
   465  	TLS_AES_128_GCM_SHA256       uint16 = 0x1301
   466  	TLS_AES_256_GCM_SHA384       uint16 = 0x1302
   467  	TLS_CHACHA20_POLY1305_SHA256 uint16 = 0x1303
   468  
   469  	// TLS_FALLBACK_SCSV isn't a standard cipher suite but an indicator
   470  	// that the client is doing version fallback. See RFC 7507.
   471  	TLS_FALLBACK_SCSV uint16 = 0x5600
   472  )
   473  

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