Source file src/crypto/tls/cipher_suites.go

     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  	"fmt"
    17  	"hash"
    18  	"internal/cpu"
    19  	"runtime"
    20  
    21  	"golang.org/x/crypto/chacha20poly1305"
    22  )
    23  
    24  // CipherSuite is a TLS cipher suite. Note that most functions in this package
    25  // accept and expose cipher suite IDs instead of this type.
    26  type CipherSuite struct {
    27  	ID   uint16
    28  	Name string
    29  
    30  	// Supported versions is the list of TLS protocol versions that can
    31  	// negotiate this cipher suite.
    32  	SupportedVersions []uint16
    33  
    34  	// Insecure is true if the cipher suite has known security issues
    35  	// due to its primitives, design, or implementation.
    36  	Insecure bool
    37  }
    38  
    39  var (
    40  	supportedUpToTLS12 = []uint16{VersionTLS10, VersionTLS11, VersionTLS12}
    41  	supportedOnlyTLS12 = []uint16{VersionTLS12}
    42  	supportedOnlyTLS13 = []uint16{VersionTLS13}
    43  )
    44  
    45  // CipherSuites returns a list of cipher suites currently implemented by this
    46  // package, excluding those with security issues, which are returned by
    47  // InsecureCipherSuites.
    48  //
    49  // The list is sorted by ID. Note that the default cipher suites selected by
    50  // this package might depend on logic that can't be captured by a static list,
    51  // and might not match those returned by this function.
    52  func CipherSuites() []*CipherSuite {
    53  	return []*CipherSuite{
    54  		{TLS_RSA_WITH_AES_128_CBC_SHA, "TLS_RSA_WITH_AES_128_CBC_SHA", supportedUpToTLS12, false},
    55  		{TLS_RSA_WITH_AES_256_CBC_SHA, "TLS_RSA_WITH_AES_256_CBC_SHA", supportedUpToTLS12, false},
    56  		{TLS_RSA_WITH_AES_128_GCM_SHA256, "TLS_RSA_WITH_AES_128_GCM_SHA256", supportedOnlyTLS12, false},
    57  		{TLS_RSA_WITH_AES_256_GCM_SHA384, "TLS_RSA_WITH_AES_256_GCM_SHA384", supportedOnlyTLS12, false},
    58  
    59  		{TLS_AES_128_GCM_SHA256, "TLS_AES_128_GCM_SHA256", supportedOnlyTLS13, false},
    60  		{TLS_AES_256_GCM_SHA384, "TLS_AES_256_GCM_SHA384", supportedOnlyTLS13, false},
    61  		{TLS_CHACHA20_POLY1305_SHA256, "TLS_CHACHA20_POLY1305_SHA256", supportedOnlyTLS13, false},
    62  
    63  		{TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA", supportedUpToTLS12, false},
    64  		{TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, "TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA", supportedUpToTLS12, false},
    65  		{TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA, "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA", supportedUpToTLS12, false},
    66  		{TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA, "TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA", supportedUpToTLS12, false},
    67  		{TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, "TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256", supportedOnlyTLS12, false},
    68  		{TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, "TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384", supportedOnlyTLS12, false},
    69  		{TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256", supportedOnlyTLS12, false},
    70  		{TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384, "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384", supportedOnlyTLS12, false},
    71  		{TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256, "TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256", supportedOnlyTLS12, false},
    72  		{TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256, "TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256", supportedOnlyTLS12, false},
    73  	}
    74  }
    75  
    76  // InsecureCipherSuites returns a list of cipher suites currently implemented by
    77  // this package and which have security issues.
    78  //
    79  // Most applications should not use the cipher suites in this list, and should
    80  // only use those returned by CipherSuites.
    81  func InsecureCipherSuites() []*CipherSuite {
    82  	// This list includes RC4, CBC_SHA256, and 3DES cipher suites. See
    83  	// cipherSuitesPreferenceOrder for details.
    84  	return []*CipherSuite{
    85  		{TLS_RSA_WITH_RC4_128_SHA, "TLS_RSA_WITH_RC4_128_SHA", supportedUpToTLS12, true},
    86  		{TLS_RSA_WITH_3DES_EDE_CBC_SHA, "TLS_RSA_WITH_3DES_EDE_CBC_SHA", supportedUpToTLS12, true},
    87  		{TLS_RSA_WITH_AES_128_CBC_SHA256, "TLS_RSA_WITH_AES_128_CBC_SHA256", supportedOnlyTLS12, true},
    88  		{TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, "TLS_ECDHE_ECDSA_WITH_RC4_128_SHA", supportedUpToTLS12, true},
    89  		{TLS_ECDHE_RSA_WITH_RC4_128_SHA, "TLS_ECDHE_RSA_WITH_RC4_128_SHA", supportedUpToTLS12, true},
    90  		{TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA, "TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA", supportedUpToTLS12, true},
    91  		{TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256, "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256", supportedOnlyTLS12, true},
    92  		{TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256, "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256", supportedOnlyTLS12, true},
    93  	}
    94  }
    95  
    96  // CipherSuiteName returns the standard name for the passed cipher suite ID
    97  // (e.g. "TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256"), or a fallback representation
    98  // of the ID value if the cipher suite is not implemented by this package.
    99  func CipherSuiteName(id uint16) string {
   100  	for _, c := range CipherSuites() {
   101  		if c.ID == id {
   102  			return c.Name
   103  		}
   104  	}
   105  	for _, c := range InsecureCipherSuites() {
   106  		if c.ID == id {
   107  			return c.Name
   108  		}
   109  	}
   110  	return fmt.Sprintf("0x%04X", id)
   111  }
   112  
   113  const (
   114  	// suiteECDHE indicates that the cipher suite involves elliptic curve
   115  	// Diffie-Hellman. This means that it should only be selected when the
   116  	// client indicates that it supports ECC with a curve and point format
   117  	// that we're happy with.
   118  	suiteECDHE = 1 << iota
   119  	// suiteECSign indicates that the cipher suite involves an ECDSA or
   120  	// EdDSA signature and therefore may only be selected when the server's
   121  	// certificate is ECDSA or EdDSA. If this is not set then the cipher suite
   122  	// is RSA based.
   123  	suiteECSign
   124  	// suiteTLS12 indicates that the cipher suite should only be advertised
   125  	// and accepted when using TLS 1.2.
   126  	suiteTLS12
   127  	// suiteSHA384 indicates that the cipher suite uses SHA384 as the
   128  	// handshake hash.
   129  	suiteSHA384
   130  )
   131  
   132  // A cipherSuite is a TLS 1.0–1.2 cipher suite, and defines the key exchange
   133  // mechanism, as well as the cipher+MAC pair or the AEAD.
   134  type cipherSuite struct {
   135  	id uint16
   136  	// the lengths, in bytes, of the key material needed for each component.
   137  	keyLen int
   138  	macLen int
   139  	ivLen  int
   140  	ka     func(version uint16) keyAgreement
   141  	// flags is a bitmask of the suite* values, above.
   142  	flags  int
   143  	cipher func(key, iv []byte, isRead bool) interface{}
   144  	mac    func(key []byte) hash.Hash
   145  	aead   func(key, fixedNonce []byte) aead
   146  }
   147  
   148  var cipherSuites = []*cipherSuite{ // TODO: replace with a map, since the order doesn't matter.
   149  	{TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305, 32, 0, 12, ecdheRSAKA, suiteECDHE | suiteTLS12, nil, nil, aeadChaCha20Poly1305},
   150  	{TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305, 32, 0, 12, ecdheECDSAKA, suiteECDHE | suiteECSign | suiteTLS12, nil, nil, aeadChaCha20Poly1305},
   151  	{TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12, nil, nil, aeadAESGCM},
   152  	{TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECSign | suiteTLS12, nil, nil, aeadAESGCM},
   153  	{TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM},
   154  	{TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECSign | suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM},
   155  	{TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, ecdheRSAKA, suiteECDHE | suiteTLS12, cipherAES, macSHA256, nil},
   156  	{TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil},
   157  	{TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, ecdheECDSAKA, suiteECDHE | suiteECSign | suiteTLS12, cipherAES, macSHA256, nil},
   158  	{TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECSign, cipherAES, macSHA1, nil},
   159  	{TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil},
   160  	{TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECSign, cipherAES, macSHA1, nil},
   161  	{TLS_RSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, rsaKA, suiteTLS12, nil, nil, aeadAESGCM},
   162  	{TLS_RSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, rsaKA, suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM},
   163  	{TLS_RSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, rsaKA, suiteTLS12, cipherAES, macSHA256, nil},
   164  	{TLS_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil},
   165  	{TLS_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil},
   166  	{TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, ecdheRSAKA, suiteECDHE, cipher3DES, macSHA1, nil},
   167  	{TLS_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, rsaKA, 0, cipher3DES, macSHA1, nil},
   168  	{TLS_RSA_WITH_RC4_128_SHA, 16, 20, 0, rsaKA, 0, cipherRC4, macSHA1, nil},
   169  	{TLS_ECDHE_RSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheRSAKA, suiteECDHE, cipherRC4, macSHA1, nil},
   170  	{TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheECDSAKA, suiteECDHE | suiteECSign, cipherRC4, macSHA1, nil},
   171  }
   172  
   173  // selectCipherSuite returns the first TLS 1.0–1.2 cipher suite from ids which
   174  // is also in supportedIDs and passes the ok filter.
   175  func selectCipherSuite(ids, supportedIDs []uint16, ok func(*cipherSuite) bool) *cipherSuite {
   176  	for _, id := range ids {
   177  		candidate := cipherSuiteByID(id)
   178  		if candidate == nil || !ok(candidate) {
   179  			continue
   180  		}
   181  
   182  		for _, suppID := range supportedIDs {
   183  			if id == suppID {
   184  				return candidate
   185  			}
   186  		}
   187  	}
   188  	return nil
   189  }
   190  
   191  // A cipherSuiteTLS13 defines only the pair of the AEAD algorithm and hash
   192  // algorithm to be used with HKDF. See RFC 8446, Appendix B.4.
   193  type cipherSuiteTLS13 struct {
   194  	id     uint16
   195  	keyLen int
   196  	aead   func(key, fixedNonce []byte) aead
   197  	hash   crypto.Hash
   198  }
   199  
   200  var cipherSuitesTLS13 = []*cipherSuiteTLS13{ // TODO: replace with a map.
   201  	{TLS_AES_128_GCM_SHA256, 16, aeadAESGCMTLS13, crypto.SHA256},
   202  	{TLS_CHACHA20_POLY1305_SHA256, 32, aeadChaCha20Poly1305, crypto.SHA256},
   203  	{TLS_AES_256_GCM_SHA384, 32, aeadAESGCMTLS13, crypto.SHA384},
   204  }
   205  
   206  // cipherSuitesPreferenceOrder is the order in which we'll select (on the
   207  // server) or advertise (on the client) TLS 1.0–1.2 cipher suites.
   208  //
   209  // Cipher suites are filtered but not reordered based on the application and
   210  // peer's preferences, meaning we'll never select a suite lower in this list if
   211  // any higher one is available. This makes it more defensible to keep weaker
   212  // cipher suites enabled, especially on the server side where we get the last
   213  // word, since there are no known downgrade attacks on cipher suites selection.
   214  //
   215  // The list is sorted by applying the following priority rules, stopping at the
   216  // first (most important) applicable one:
   217  //
   218  //   - Anything else comes before RC4
   219  //
   220  //       RC4 has practically exploitable biases. See https://www.rc4nomore.com.
   221  //
   222  //   - Anything else comes before CBC_SHA256
   223  //
   224  //       SHA-256 variants of the CBC ciphersuites don't implement any Lucky13
   225  //       countermeasures. See http://www.isg.rhul.ac.uk/tls/Lucky13.html and
   226  //       https://www.imperialviolet.org/2013/02/04/luckythirteen.html.
   227  //
   228  //   - Anything else comes before 3DES
   229  //
   230  //       3DES has 64-bit blocks, which makes it fundamentally susceptible to
   231  //       birthday attacks. See https://sweet32.info.
   232  //
   233  //   - ECDHE comes before anything else
   234  //
   235  //       Once we got the broken stuff out of the way, the most important
   236  //       property a cipher suite can have is forward secrecy. We don't
   237  //       implement FFDHE, so that means ECDHE.
   238  //
   239  //   - AEADs come before CBC ciphers
   240  //
   241  //       Even with Lucky13 countermeasures, MAC-then-Encrypt CBC cipher suites
   242  //       are fundamentally fragile, and suffered from an endless sequence of
   243  //       padding oracle attacks. See https://eprint.iacr.org/2015/1129,
   244  //       https://www.imperialviolet.org/2014/12/08/poodleagain.html, and
   245  //       https://blog.cloudflare.com/yet-another-padding-oracle-in-openssl-cbc-ciphersuites/.
   246  //
   247  //   - AES comes before ChaCha20
   248  //
   249  //       When AES hardware is available, AES-128-GCM and AES-256-GCM are faster
   250  //       than ChaCha20Poly1305.
   251  //
   252  //       When AES hardware is not available, AES-128-GCM is one or more of: much
   253  //       slower, way more complex, and less safe (because not constant time)
   254  //       than ChaCha20Poly1305.
   255  //
   256  //       We use this list if we think both peers have AES hardware, and
   257  //       cipherSuitesPreferenceOrderNoAES otherwise.
   258  //
   259  //   - AES-128 comes before AES-256
   260  //
   261  //       The only potential advantages of AES-256 are better multi-target
   262  //       margins, and hypothetical post-quantum properties. Neither apply to
   263  //       TLS, and AES-256 is slower due to its four extra rounds (which don't
   264  //       contribute to the advantages above).
   265  //
   266  //   - ECDSA comes before RSA
   267  //
   268  //       The relative order of ECDSA and RSA cipher suites doesn't matter,
   269  //       as they depend on the certificate. Pick one to get a stable order.
   270  //
   271  var cipherSuitesPreferenceOrder = []uint16{
   272  	// AEADs w/ ECDHE
   273  	TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
   274  	TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
   275  	TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305, TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
   276  
   277  	// CBC w/ ECDHE
   278  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
   279  	TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
   280  
   281  	// AEADs w/o ECDHE
   282  	TLS_RSA_WITH_AES_128_GCM_SHA256,
   283  	TLS_RSA_WITH_AES_256_GCM_SHA384,
   284  
   285  	// CBC w/o ECDHE
   286  	TLS_RSA_WITH_AES_128_CBC_SHA,
   287  	TLS_RSA_WITH_AES_256_CBC_SHA,
   288  
   289  	// 3DES
   290  	TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA,
   291  	TLS_RSA_WITH_3DES_EDE_CBC_SHA,
   292  
   293  	// CBC_SHA256
   294  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256, TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,
   295  	TLS_RSA_WITH_AES_128_CBC_SHA256,
   296  
   297  	// RC4
   298  	TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, TLS_ECDHE_RSA_WITH_RC4_128_SHA,
   299  	TLS_RSA_WITH_RC4_128_SHA,
   300  }
   301  
   302  var cipherSuitesPreferenceOrderNoAES = []uint16{
   303  	// ChaCha20Poly1305
   304  	TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305, TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
   305  
   306  	// AES-GCM w/ ECDHE
   307  	TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
   308  	TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
   309  
   310  	// The rest of cipherSuitesPreferenceOrder.
   311  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
   312  	TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
   313  	TLS_RSA_WITH_AES_128_GCM_SHA256,
   314  	TLS_RSA_WITH_AES_256_GCM_SHA384,
   315  	TLS_RSA_WITH_AES_128_CBC_SHA,
   316  	TLS_RSA_WITH_AES_256_CBC_SHA,
   317  	TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA,
   318  	TLS_RSA_WITH_3DES_EDE_CBC_SHA,
   319  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256, TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,
   320  	TLS_RSA_WITH_AES_128_CBC_SHA256,
   321  	TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, TLS_ECDHE_RSA_WITH_RC4_128_SHA,
   322  	TLS_RSA_WITH_RC4_128_SHA,
   323  }
   324  
   325  // disabledCipherSuites are not used unless explicitly listed in
   326  // Config.CipherSuites. They MUST be at the end of cipherSuitesPreferenceOrder.
   327  var disabledCipherSuites = []uint16{
   328  	// CBC_SHA256
   329  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256, TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,
   330  	TLS_RSA_WITH_AES_128_CBC_SHA256,
   331  
   332  	// RC4
   333  	TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, TLS_ECDHE_RSA_WITH_RC4_128_SHA,
   334  	TLS_RSA_WITH_RC4_128_SHA,
   335  }
   336  
   337  var (
   338  	defaultCipherSuitesLen = len(cipherSuitesPreferenceOrder) - len(disabledCipherSuites)
   339  	defaultCipherSuites    = cipherSuitesPreferenceOrder[:defaultCipherSuitesLen]
   340  )
   341  
   342  // defaultCipherSuitesTLS13 is also the preference order, since there are no
   343  // disabled by default TLS 1.3 cipher suites. The same AES vs ChaCha20 logic as
   344  // cipherSuitesPreferenceOrder applies.
   345  var defaultCipherSuitesTLS13 = []uint16{
   346  	TLS_AES_128_GCM_SHA256,
   347  	TLS_AES_256_GCM_SHA384,
   348  	TLS_CHACHA20_POLY1305_SHA256,
   349  }
   350  
   351  var defaultCipherSuitesTLS13NoAES = []uint16{
   352  	TLS_CHACHA20_POLY1305_SHA256,
   353  	TLS_AES_128_GCM_SHA256,
   354  	TLS_AES_256_GCM_SHA384,
   355  }
   356  
   357  var (
   358  	hasGCMAsmAMD64 = cpu.X86.HasAES && cpu.X86.HasPCLMULQDQ
   359  	hasGCMAsmARM64 = cpu.ARM64.HasAES && cpu.ARM64.HasPMULL
   360  	// Keep in sync with crypto/aes/cipher_s390x.go.
   361  	hasGCMAsmS390X = cpu.S390X.HasAES && cpu.S390X.HasAESCBC && cpu.S390X.HasAESCTR &&
   362  		(cpu.S390X.HasGHASH || cpu.S390X.HasAESGCM)
   363  
   364  	hasAESGCMHardwareSupport = runtime.GOARCH == "amd64" && hasGCMAsmAMD64 ||
   365  		runtime.GOARCH == "arm64" && hasGCMAsmARM64 ||
   366  		runtime.GOARCH == "s390x" && hasGCMAsmS390X
   367  )
   368  
   369  var aesgcmCiphers = map[uint16]bool{
   370  	// TLS 1.2
   371  	TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256:   true,
   372  	TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384:   true,
   373  	TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256: true,
   374  	TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384: true,
   375  	// TLS 1.3
   376  	TLS_AES_128_GCM_SHA256: true,
   377  	TLS_AES_256_GCM_SHA384: true,
   378  }
   379  
   380  var nonAESGCMAEADCiphers = map[uint16]bool{
   381  	// TLS 1.2
   382  	TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305:   true,
   383  	TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305: true,
   384  	// TLS 1.3
   385  	TLS_CHACHA20_POLY1305_SHA256: true,
   386  }
   387  
   388  // aesgcmPreferred returns whether the first known cipher in the preference list
   389  // is an AES-GCM cipher, implying the peer has hardware support for it.
   390  func aesgcmPreferred(ciphers []uint16) bool {
   391  	for _, cID := range ciphers {
   392  		if c := cipherSuiteByID(cID); c != nil {
   393  			return aesgcmCiphers[cID]
   394  		}
   395  		if c := cipherSuiteTLS13ByID(cID); c != nil {
   396  			return aesgcmCiphers[cID]
   397  		}
   398  	}
   399  	return false
   400  }
   401  
   402  func cipherRC4(key, iv []byte, isRead bool) interface{} {
   403  	cipher, _ := rc4.NewCipher(key)
   404  	return cipher
   405  }
   406  
   407  func cipher3DES(key, iv []byte, isRead bool) interface{} {
   408  	block, _ := des.NewTripleDESCipher(key)
   409  	if isRead {
   410  		return cipher.NewCBCDecrypter(block, iv)
   411  	}
   412  	return cipher.NewCBCEncrypter(block, iv)
   413  }
   414  
   415  func cipherAES(key, iv []byte, isRead bool) interface{} {
   416  	block, _ := aes.NewCipher(key)
   417  	if isRead {
   418  		return cipher.NewCBCDecrypter(block, iv)
   419  	}
   420  	return cipher.NewCBCEncrypter(block, iv)
   421  }
   422  
   423  // macSHA1 returns a SHA-1 based constant time MAC.
   424  func macSHA1(key []byte) hash.Hash {
   425  	return hmac.New(newConstantTimeHash(sha1.New), key)
   426  }
   427  
   428  // macSHA256 returns a SHA-256 based MAC. This is only supported in TLS 1.2 and
   429  // is currently only used in disabled-by-default cipher suites.
   430  func macSHA256(key []byte) hash.Hash {
   431  	return hmac.New(sha256.New, key)
   432  }
   433  
   434  type aead interface {
   435  	cipher.AEAD
   436  
   437  	// explicitNonceLen returns the number of bytes of explicit nonce
   438  	// included in each record. This is eight for older AEADs and
   439  	// zero for modern ones.
   440  	explicitNonceLen() int
   441  }
   442  
   443  const (
   444  	aeadNonceLength   = 12
   445  	noncePrefixLength = 4
   446  )
   447  
   448  // prefixNonceAEAD wraps an AEAD and prefixes a fixed portion of the nonce to
   449  // each call.
   450  type prefixNonceAEAD struct {
   451  	// nonce contains the fixed part of the nonce in the first four bytes.
   452  	nonce [aeadNonceLength]byte
   453  	aead  cipher.AEAD
   454  }
   455  
   456  func (f *prefixNonceAEAD) NonceSize() int        { return aeadNonceLength - noncePrefixLength }
   457  func (f *prefixNonceAEAD) Overhead() int         { return f.aead.Overhead() }
   458  func (f *prefixNonceAEAD) explicitNonceLen() int { return f.NonceSize() }
   459  
   460  func (f *prefixNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte {
   461  	copy(f.nonce[4:], nonce)
   462  	return f.aead.Seal(out, f.nonce[:], plaintext, additionalData)
   463  }
   464  
   465  func (f *prefixNonceAEAD) Open(out, nonce, ciphertext, additionalData []byte) ([]byte, error) {
   466  	copy(f.nonce[4:], nonce)
   467  	return f.aead.Open(out, f.nonce[:], ciphertext, additionalData)
   468  }
   469  
   470  // xoredNonceAEAD wraps an AEAD by XORing in a fixed pattern to the nonce
   471  // before each call.
   472  type xorNonceAEAD struct {
   473  	nonceMask [aeadNonceLength]byte
   474  	aead      cipher.AEAD
   475  }
   476  
   477  func (f *xorNonceAEAD) NonceSize() int        { return 8 } // 64-bit sequence number
   478  func (f *xorNonceAEAD) Overhead() int         { return f.aead.Overhead() }
   479  func (f *xorNonceAEAD) explicitNonceLen() int { return 0 }
   480  
   481  func (f *xorNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte {
   482  	for i, b := range nonce {
   483  		f.nonceMask[4+i] ^= b
   484  	}
   485  	result := f.aead.Seal(out, f.nonceMask[:], plaintext, additionalData)
   486  	for i, b := range nonce {
   487  		f.nonceMask[4+i] ^= b
   488  	}
   489  
   490  	return result
   491  }
   492  
   493  func (f *xorNonceAEAD) Open(out, nonce, ciphertext, additionalData []byte) ([]byte, error) {
   494  	for i, b := range nonce {
   495  		f.nonceMask[4+i] ^= b
   496  	}
   497  	result, err := f.aead.Open(out, f.nonceMask[:], ciphertext, additionalData)
   498  	for i, b := range nonce {
   499  		f.nonceMask[4+i] ^= b
   500  	}
   501  
   502  	return result, err
   503  }
   504  
   505  func aeadAESGCM(key, noncePrefix []byte) aead {
   506  	if len(noncePrefix) != noncePrefixLength {
   507  		panic("tls: internal error: wrong nonce length")
   508  	}
   509  	aes, err := aes.NewCipher(key)
   510  	if err != nil {
   511  		panic(err)
   512  	}
   513  	aead, err := cipher.NewGCM(aes)
   514  	if err != nil {
   515  		panic(err)
   516  	}
   517  
   518  	ret := &prefixNonceAEAD{aead: aead}
   519  	copy(ret.nonce[:], noncePrefix)
   520  	return ret
   521  }
   522  
   523  func aeadAESGCMTLS13(key, nonceMask []byte) aead {
   524  	if len(nonceMask) != aeadNonceLength {
   525  		panic("tls: internal error: wrong nonce length")
   526  	}
   527  	aes, err := aes.NewCipher(key)
   528  	if err != nil {
   529  		panic(err)
   530  	}
   531  	aead, err := cipher.NewGCM(aes)
   532  	if err != nil {
   533  		panic(err)
   534  	}
   535  
   536  	ret := &xorNonceAEAD{aead: aead}
   537  	copy(ret.nonceMask[:], nonceMask)
   538  	return ret
   539  }
   540  
   541  func aeadChaCha20Poly1305(key, nonceMask []byte) aead {
   542  	if len(nonceMask) != aeadNonceLength {
   543  		panic("tls: internal error: wrong nonce length")
   544  	}
   545  	aead, err := chacha20poly1305.New(key)
   546  	if err != nil {
   547  		panic(err)
   548  	}
   549  
   550  	ret := &xorNonceAEAD{aead: aead}
   551  	copy(ret.nonceMask[:], nonceMask)
   552  	return ret
   553  }
   554  
   555  type constantTimeHash interface {
   556  	hash.Hash
   557  	ConstantTimeSum(b []byte) []byte
   558  }
   559  
   560  // cthWrapper wraps any hash.Hash that implements ConstantTimeSum, and replaces
   561  // with that all calls to Sum. It's used to obtain a ConstantTimeSum-based HMAC.
   562  type cthWrapper struct {
   563  	h constantTimeHash
   564  }
   565  
   566  func (c *cthWrapper) Size() int                   { return c.h.Size() }
   567  func (c *cthWrapper) BlockSize() int              { return c.h.BlockSize() }
   568  func (c *cthWrapper) Reset()                      { c.h.Reset() }
   569  func (c *cthWrapper) Write(p []byte) (int, error) { return c.h.Write(p) }
   570  func (c *cthWrapper) Sum(b []byte) []byte         { return c.h.ConstantTimeSum(b) }
   571  
   572  func newConstantTimeHash(h func() hash.Hash) func() hash.Hash {
   573  	return func() hash.Hash {
   574  		return &cthWrapper{h().(constantTimeHash)}
   575  	}
   576  }
   577  
   578  // tls10MAC implements the TLS 1.0 MAC function. RFC 2246, Section 6.2.3.
   579  func tls10MAC(h hash.Hash, out, seq, header, data, extra []byte) []byte {
   580  	h.Reset()
   581  	h.Write(seq)
   582  	h.Write(header)
   583  	h.Write(data)
   584  	res := h.Sum(out)
   585  	if extra != nil {
   586  		h.Write(extra)
   587  	}
   588  	return res
   589  }
   590  
   591  func rsaKA(version uint16) keyAgreement {
   592  	return rsaKeyAgreement{}
   593  }
   594  
   595  func ecdheECDSAKA(version uint16) keyAgreement {
   596  	return &ecdheKeyAgreement{
   597  		isRSA:   false,
   598  		version: version,
   599  	}
   600  }
   601  
   602  func ecdheRSAKA(version uint16) keyAgreement {
   603  	return &ecdheKeyAgreement{
   604  		isRSA:   true,
   605  		version: version,
   606  	}
   607  }
   608  
   609  // mutualCipherSuite returns a cipherSuite given a list of supported
   610  // ciphersuites and the id requested by the peer.
   611  func mutualCipherSuite(have []uint16, want uint16) *cipherSuite {
   612  	for _, id := range have {
   613  		if id == want {
   614  			return cipherSuiteByID(id)
   615  		}
   616  	}
   617  	return nil
   618  }
   619  
   620  func cipherSuiteByID(id uint16) *cipherSuite {
   621  	for _, cipherSuite := range cipherSuites {
   622  		if cipherSuite.id == id {
   623  			return cipherSuite
   624  		}
   625  	}
   626  	return nil
   627  }
   628  
   629  func mutualCipherSuiteTLS13(have []uint16, want uint16) *cipherSuiteTLS13 {
   630  	for _, id := range have {
   631  		if id == want {
   632  			return cipherSuiteTLS13ByID(id)
   633  		}
   634  	}
   635  	return nil
   636  }
   637  
   638  func cipherSuiteTLS13ByID(id uint16) *cipherSuiteTLS13 {
   639  	for _, cipherSuite := range cipherSuitesTLS13 {
   640  		if cipherSuite.id == id {
   641  			return cipherSuite
   642  		}
   643  	}
   644  	return nil
   645  }
   646  
   647  // A list of cipher suite IDs that are, or have been, implemented by this
   648  // package.
   649  //
   650  // See https://www.iana.org/assignments/tls-parameters/tls-parameters.xml
   651  const (
   652  	// TLS 1.0 - 1.2 cipher suites.
   653  	TLS_RSA_WITH_RC4_128_SHA                      uint16 = 0x0005
   654  	TLS_RSA_WITH_3DES_EDE_CBC_SHA                 uint16 = 0x000a
   655  	TLS_RSA_WITH_AES_128_CBC_SHA                  uint16 = 0x002f
   656  	TLS_RSA_WITH_AES_256_CBC_SHA                  uint16 = 0x0035
   657  	TLS_RSA_WITH_AES_128_CBC_SHA256               uint16 = 0x003c
   658  	TLS_RSA_WITH_AES_128_GCM_SHA256               uint16 = 0x009c
   659  	TLS_RSA_WITH_AES_256_GCM_SHA384               uint16 = 0x009d
   660  	TLS_ECDHE_ECDSA_WITH_RC4_128_SHA              uint16 = 0xc007
   661  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA          uint16 = 0xc009
   662  	TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA          uint16 = 0xc00a
   663  	TLS_ECDHE_RSA_WITH_RC4_128_SHA                uint16 = 0xc011
   664  	TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA           uint16 = 0xc012
   665  	TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA            uint16 = 0xc013
   666  	TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA            uint16 = 0xc014
   667  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256       uint16 = 0xc023
   668  	TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256         uint16 = 0xc027
   669  	TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256         uint16 = 0xc02f
   670  	TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256       uint16 = 0xc02b
   671  	TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384         uint16 = 0xc030
   672  	TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384       uint16 = 0xc02c
   673  	TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256   uint16 = 0xcca8
   674  	TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256 uint16 = 0xcca9
   675  
   676  	// TLS 1.3 cipher suites.
   677  	TLS_AES_128_GCM_SHA256       uint16 = 0x1301
   678  	TLS_AES_256_GCM_SHA384       uint16 = 0x1302
   679  	TLS_CHACHA20_POLY1305_SHA256 uint16 = 0x1303
   680  
   681  	// TLS_FALLBACK_SCSV isn't a standard cipher suite but an indicator
   682  	// that the client is doing version fallback. See RFC 7507.
   683  	TLS_FALLBACK_SCSV uint16 = 0x5600
   684  
   685  	// Legacy names for the corresponding cipher suites with the correct _SHA256
   686  	// suffix, retained for backward compatibility.
   687  	TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305   = TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
   688  	TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305 = TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256
   689  )
   690  

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