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/internal/boring"
    14  	"crypto/rc4"
    15  	"crypto/sha1"
    16  	"crypto/sha256"
    17  	"fmt"
    18  	"hash"
    19  	"internal/cpu"
    20  	"runtime"
    21  
    22  	"golang.org/x/crypto/chacha20poly1305"
    23  )
    24  
    25  // CipherSuite is a TLS cipher suite. Note that most functions in this package
    26  // accept and expose cipher suite IDs instead of this type.
    27  type CipherSuite struct {
    28  	ID   uint16
    29  	Name string
    30  
    31  	// Supported versions is the list of TLS protocol versions that can
    32  	// negotiate this cipher suite.
    33  	SupportedVersions []uint16
    34  
    35  	// Insecure is true if the cipher suite has known security issues
    36  	// due to its primitives, design, or implementation.
    37  	Insecure bool
    38  }
    39  
    40  var (
    41  	supportedUpToTLS12 = []uint16{VersionTLS10, VersionTLS11, VersionTLS12}
    42  	supportedOnlyTLS12 = []uint16{VersionTLS12}
    43  	supportedOnlyTLS13 = []uint16{VersionTLS13}
    44  )
    45  
    46  // CipherSuites returns a list of cipher suites currently implemented by this
    47  // package, excluding those with security issues, which are returned by
    48  // [InsecureCipherSuites].
    49  //
    50  // The list is sorted by ID. Note that the default cipher suites selected by
    51  // this package might depend on logic that can't be captured by a static list,
    52  // and might not match those returned by this function.
    53  func CipherSuites() []*CipherSuite {
    54  	return []*CipherSuite{
    55  		{TLS_AES_128_GCM_SHA256, "TLS_AES_128_GCM_SHA256", supportedOnlyTLS13, false},
    56  		{TLS_AES_256_GCM_SHA384, "TLS_AES_256_GCM_SHA384", supportedOnlyTLS13, false},
    57  		{TLS_CHACHA20_POLY1305_SHA256, "TLS_CHACHA20_POLY1305_SHA256", supportedOnlyTLS13, false},
    58  
    59  		{TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA", supportedUpToTLS12, false},
    60  		{TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, "TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA", supportedUpToTLS12, false},
    61  		{TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA, "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA", supportedUpToTLS12, false},
    62  		{TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA, "TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA", supportedUpToTLS12, false},
    63  		{TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, "TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256", supportedOnlyTLS12, false},
    64  		{TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, "TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384", supportedOnlyTLS12, false},
    65  		{TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256", supportedOnlyTLS12, false},
    66  		{TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384, "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384", supportedOnlyTLS12, false},
    67  		{TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256, "TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256", supportedOnlyTLS12, false},
    68  		{TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256, "TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256", supportedOnlyTLS12, false},
    69  	}
    70  }
    71  
    72  // InsecureCipherSuites returns a list of cipher suites currently implemented by
    73  // this package and which have security issues.
    74  //
    75  // Most applications should not use the cipher suites in this list, and should
    76  // only use those returned by [CipherSuites].
    77  func InsecureCipherSuites() []*CipherSuite {
    78  	// This list includes RC4, CBC_SHA256, and 3DES cipher suites. See
    79  	// cipherSuitesPreferenceOrder for details.
    80  	return []*CipherSuite{
    81  		{TLS_RSA_WITH_RC4_128_SHA, "TLS_RSA_WITH_RC4_128_SHA", supportedUpToTLS12, true},
    82  		{TLS_RSA_WITH_3DES_EDE_CBC_SHA, "TLS_RSA_WITH_3DES_EDE_CBC_SHA", supportedUpToTLS12, true},
    83  		{TLS_RSA_WITH_AES_128_CBC_SHA, "TLS_RSA_WITH_AES_128_CBC_SHA", supportedUpToTLS12, true},
    84  		{TLS_RSA_WITH_AES_256_CBC_SHA, "TLS_RSA_WITH_AES_256_CBC_SHA", supportedUpToTLS12, true},
    85  		{TLS_RSA_WITH_AES_128_CBC_SHA256, "TLS_RSA_WITH_AES_128_CBC_SHA256", supportedOnlyTLS12, true},
    86  		{TLS_RSA_WITH_AES_128_GCM_SHA256, "TLS_RSA_WITH_AES_128_GCM_SHA256", supportedOnlyTLS12, true},
    87  		{TLS_RSA_WITH_AES_256_GCM_SHA384, "TLS_RSA_WITH_AES_256_GCM_SHA384", 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) any
   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  var cipherSuitesPreferenceOrder = []uint16{
   271  	// AEADs w/ ECDHE
   272  	TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
   273  	TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
   274  	TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305, TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
   275  
   276  	// CBC w/ ECDHE
   277  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
   278  	TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
   279  
   280  	// AEADs w/o ECDHE
   281  	TLS_RSA_WITH_AES_128_GCM_SHA256,
   282  	TLS_RSA_WITH_AES_256_GCM_SHA384,
   283  
   284  	// CBC w/o ECDHE
   285  	TLS_RSA_WITH_AES_128_CBC_SHA,
   286  	TLS_RSA_WITH_AES_256_CBC_SHA,
   287  
   288  	// 3DES
   289  	TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA,
   290  	TLS_RSA_WITH_3DES_EDE_CBC_SHA,
   291  
   292  	// CBC_SHA256
   293  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256, TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,
   294  	TLS_RSA_WITH_AES_128_CBC_SHA256,
   295  
   296  	// RC4
   297  	TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, TLS_ECDHE_RSA_WITH_RC4_128_SHA,
   298  	TLS_RSA_WITH_RC4_128_SHA,
   299  }
   300  
   301  var cipherSuitesPreferenceOrderNoAES = []uint16{
   302  	// ChaCha20Poly1305
   303  	TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305, TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
   304  
   305  	// AES-GCM w/ ECDHE
   306  	TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
   307  	TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
   308  
   309  	// The rest of cipherSuitesPreferenceOrder.
   310  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
   311  	TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
   312  	TLS_RSA_WITH_AES_128_GCM_SHA256,
   313  	TLS_RSA_WITH_AES_256_GCM_SHA384,
   314  	TLS_RSA_WITH_AES_128_CBC_SHA,
   315  	TLS_RSA_WITH_AES_256_CBC_SHA,
   316  	TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA,
   317  	TLS_RSA_WITH_3DES_EDE_CBC_SHA,
   318  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256, TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,
   319  	TLS_RSA_WITH_AES_128_CBC_SHA256,
   320  	TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, TLS_ECDHE_RSA_WITH_RC4_128_SHA,
   321  	TLS_RSA_WITH_RC4_128_SHA,
   322  }
   323  
   324  // disabledCipherSuites are not used unless explicitly listed in Config.CipherSuites.
   325  var disabledCipherSuites = map[uint16]bool{
   326  	// CBC_SHA256
   327  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256: true,
   328  	TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256:   true,
   329  	TLS_RSA_WITH_AES_128_CBC_SHA256:         true,
   330  
   331  	// RC4
   332  	TLS_ECDHE_ECDSA_WITH_RC4_128_SHA: true,
   333  	TLS_ECDHE_RSA_WITH_RC4_128_SHA:   true,
   334  	TLS_RSA_WITH_RC4_128_SHA:         true,
   335  }
   336  
   337  // rsaKexCiphers contains the ciphers which use RSA based key exchange,
   338  // which we also disable by default unless a GODEBUG is set.
   339  var rsaKexCiphers = map[uint16]bool{
   340  	TLS_RSA_WITH_RC4_128_SHA:        true,
   341  	TLS_RSA_WITH_3DES_EDE_CBC_SHA:   true,
   342  	TLS_RSA_WITH_AES_128_CBC_SHA:    true,
   343  	TLS_RSA_WITH_AES_256_CBC_SHA:    true,
   344  	TLS_RSA_WITH_AES_128_CBC_SHA256: true,
   345  	TLS_RSA_WITH_AES_128_GCM_SHA256: true,
   346  	TLS_RSA_WITH_AES_256_GCM_SHA384: true,
   347  }
   348  
   349  var defaultCipherSuites []uint16
   350  var defaultCipherSuitesWithRSAKex []uint16
   351  
   352  func init() {
   353  	defaultCipherSuites = make([]uint16, 0, len(cipherSuitesPreferenceOrder))
   354  	defaultCipherSuitesWithRSAKex = make([]uint16, 0, len(cipherSuitesPreferenceOrder))
   355  	for _, c := range cipherSuitesPreferenceOrder {
   356  		if disabledCipherSuites[c] {
   357  			continue
   358  		}
   359  		if !rsaKexCiphers[c] {
   360  			defaultCipherSuites = append(defaultCipherSuites, c)
   361  		}
   362  		defaultCipherSuitesWithRSAKex = append(defaultCipherSuitesWithRSAKex, c)
   363  	}
   364  }
   365  
   366  // defaultCipherSuitesTLS13 is also the preference order, since there are no
   367  // disabled by default TLS 1.3 cipher suites. The same AES vs ChaCha20 logic as
   368  // cipherSuitesPreferenceOrder applies.
   369  var defaultCipherSuitesTLS13 = []uint16{
   370  	TLS_AES_128_GCM_SHA256,
   371  	TLS_AES_256_GCM_SHA384,
   372  	TLS_CHACHA20_POLY1305_SHA256,
   373  }
   374  
   375  var defaultCipherSuitesTLS13NoAES = []uint16{
   376  	TLS_CHACHA20_POLY1305_SHA256,
   377  	TLS_AES_128_GCM_SHA256,
   378  	TLS_AES_256_GCM_SHA384,
   379  }
   380  
   381  var (
   382  	hasGCMAsmAMD64 = cpu.X86.HasAES && cpu.X86.HasPCLMULQDQ
   383  	hasGCMAsmARM64 = cpu.ARM64.HasAES && cpu.ARM64.HasPMULL
   384  	// Keep in sync with crypto/aes/cipher_s390x.go.
   385  	hasGCMAsmS390X = cpu.S390X.HasAES && cpu.S390X.HasAESCBC && cpu.S390X.HasAESCTR &&
   386  		(cpu.S390X.HasGHASH || cpu.S390X.HasAESGCM)
   387  
   388  	hasAESGCMHardwareSupport = runtime.GOARCH == "amd64" && hasGCMAsmAMD64 ||
   389  		runtime.GOARCH == "arm64" && hasGCMAsmARM64 ||
   390  		runtime.GOARCH == "s390x" && hasGCMAsmS390X
   391  )
   392  
   393  var aesgcmCiphers = map[uint16]bool{
   394  	// TLS 1.2
   395  	TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256:   true,
   396  	TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384:   true,
   397  	TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256: true,
   398  	TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384: true,
   399  	// TLS 1.3
   400  	TLS_AES_128_GCM_SHA256: true,
   401  	TLS_AES_256_GCM_SHA384: true,
   402  }
   403  
   404  // aesgcmPreferred returns whether the first known cipher in the preference list
   405  // is an AES-GCM cipher, implying the peer has hardware support for it.
   406  func aesgcmPreferred(ciphers []uint16) bool {
   407  	for _, cID := range ciphers {
   408  		if c := cipherSuiteByID(cID); c != nil {
   409  			return aesgcmCiphers[cID]
   410  		}
   411  		if c := cipherSuiteTLS13ByID(cID); c != nil {
   412  			return aesgcmCiphers[cID]
   413  		}
   414  	}
   415  	return false
   416  }
   417  
   418  func cipherRC4(key, iv []byte, isRead bool) any {
   419  	cipher, _ := rc4.NewCipher(key)
   420  	return cipher
   421  }
   422  
   423  func cipher3DES(key, iv []byte, isRead bool) any {
   424  	block, _ := des.NewTripleDESCipher(key)
   425  	if isRead {
   426  		return cipher.NewCBCDecrypter(block, iv)
   427  	}
   428  	return cipher.NewCBCEncrypter(block, iv)
   429  }
   430  
   431  func cipherAES(key, iv []byte, isRead bool) any {
   432  	block, _ := aes.NewCipher(key)
   433  	if isRead {
   434  		return cipher.NewCBCDecrypter(block, iv)
   435  	}
   436  	return cipher.NewCBCEncrypter(block, iv)
   437  }
   438  
   439  // macSHA1 returns a SHA-1 based constant time MAC.
   440  func macSHA1(key []byte) hash.Hash {
   441  	h := sha1.New
   442  	// The BoringCrypto SHA1 does not have a constant-time
   443  	// checksum function, so don't try to use it.
   444  	if !boring.Enabled {
   445  		h = newConstantTimeHash(h)
   446  	}
   447  	return hmac.New(h, key)
   448  }
   449  
   450  // macSHA256 returns a SHA-256 based MAC. This is only supported in TLS 1.2 and
   451  // is currently only used in disabled-by-default cipher suites.
   452  func macSHA256(key []byte) hash.Hash {
   453  	return hmac.New(sha256.New, key)
   454  }
   455  
   456  type aead interface {
   457  	cipher.AEAD
   458  
   459  	// explicitNonceLen returns the number of bytes of explicit nonce
   460  	// included in each record. This is eight for older AEADs and
   461  	// zero for modern ones.
   462  	explicitNonceLen() int
   463  }
   464  
   465  const (
   466  	aeadNonceLength   = 12
   467  	noncePrefixLength = 4
   468  )
   469  
   470  // prefixNonceAEAD wraps an AEAD and prefixes a fixed portion of the nonce to
   471  // each call.
   472  type prefixNonceAEAD struct {
   473  	// nonce contains the fixed part of the nonce in the first four bytes.
   474  	nonce [aeadNonceLength]byte
   475  	aead  cipher.AEAD
   476  }
   477  
   478  func (f *prefixNonceAEAD) NonceSize() int        { return aeadNonceLength - noncePrefixLength }
   479  func (f *prefixNonceAEAD) Overhead() int         { return f.aead.Overhead() }
   480  func (f *prefixNonceAEAD) explicitNonceLen() int { return f.NonceSize() }
   481  
   482  func (f *prefixNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte {
   483  	copy(f.nonce[4:], nonce)
   484  	return f.aead.Seal(out, f.nonce[:], plaintext, additionalData)
   485  }
   486  
   487  func (f *prefixNonceAEAD) Open(out, nonce, ciphertext, additionalData []byte) ([]byte, error) {
   488  	copy(f.nonce[4:], nonce)
   489  	return f.aead.Open(out, f.nonce[:], ciphertext, additionalData)
   490  }
   491  
   492  // xorNonceAEAD wraps an AEAD by XORing in a fixed pattern to the nonce
   493  // before each call.
   494  type xorNonceAEAD struct {
   495  	nonceMask [aeadNonceLength]byte
   496  	aead      cipher.AEAD
   497  }
   498  
   499  func (f *xorNonceAEAD) NonceSize() int        { return 8 } // 64-bit sequence number
   500  func (f *xorNonceAEAD) Overhead() int         { return f.aead.Overhead() }
   501  func (f *xorNonceAEAD) explicitNonceLen() int { return 0 }
   502  
   503  func (f *xorNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte {
   504  	for i, b := range nonce {
   505  		f.nonceMask[4+i] ^= b
   506  	}
   507  	result := f.aead.Seal(out, f.nonceMask[:], plaintext, additionalData)
   508  	for i, b := range nonce {
   509  		f.nonceMask[4+i] ^= b
   510  	}
   511  
   512  	return result
   513  }
   514  
   515  func (f *xorNonceAEAD) Open(out, nonce, ciphertext, additionalData []byte) ([]byte, error) {
   516  	for i, b := range nonce {
   517  		f.nonceMask[4+i] ^= b
   518  	}
   519  	result, err := f.aead.Open(out, f.nonceMask[:], ciphertext, additionalData)
   520  	for i, b := range nonce {
   521  		f.nonceMask[4+i] ^= b
   522  	}
   523  
   524  	return result, err
   525  }
   526  
   527  func aeadAESGCM(key, noncePrefix []byte) aead {
   528  	if len(noncePrefix) != noncePrefixLength {
   529  		panic("tls: internal error: wrong nonce length")
   530  	}
   531  	aes, err := aes.NewCipher(key)
   532  	if err != nil {
   533  		panic(err)
   534  	}
   535  	var aead cipher.AEAD
   536  	if boring.Enabled {
   537  		aead, err = boring.NewGCMTLS(aes)
   538  	} else {
   539  		boring.Unreachable()
   540  		aead, err = cipher.NewGCM(aes)
   541  	}
   542  	if err != nil {
   543  		panic(err)
   544  	}
   545  
   546  	ret := &prefixNonceAEAD{aead: aead}
   547  	copy(ret.nonce[:], noncePrefix)
   548  	return ret
   549  }
   550  
   551  func aeadAESGCMTLS13(key, nonceMask []byte) aead {
   552  	if len(nonceMask) != aeadNonceLength {
   553  		panic("tls: internal error: wrong nonce length")
   554  	}
   555  	aes, err := aes.NewCipher(key)
   556  	if err != nil {
   557  		panic(err)
   558  	}
   559  	aead, err := cipher.NewGCM(aes)
   560  	if err != nil {
   561  		panic(err)
   562  	}
   563  
   564  	ret := &xorNonceAEAD{aead: aead}
   565  	copy(ret.nonceMask[:], nonceMask)
   566  	return ret
   567  }
   568  
   569  func aeadChaCha20Poly1305(key, nonceMask []byte) aead {
   570  	if len(nonceMask) != aeadNonceLength {
   571  		panic("tls: internal error: wrong nonce length")
   572  	}
   573  	aead, err := chacha20poly1305.New(key)
   574  	if err != nil {
   575  		panic(err)
   576  	}
   577  
   578  	ret := &xorNonceAEAD{aead: aead}
   579  	copy(ret.nonceMask[:], nonceMask)
   580  	return ret
   581  }
   582  
   583  type constantTimeHash interface {
   584  	hash.Hash
   585  	ConstantTimeSum(b []byte) []byte
   586  }
   587  
   588  // cthWrapper wraps any hash.Hash that implements ConstantTimeSum, and replaces
   589  // with that all calls to Sum. It's used to obtain a ConstantTimeSum-based HMAC.
   590  type cthWrapper struct {
   591  	h constantTimeHash
   592  }
   593  
   594  func (c *cthWrapper) Size() int                   { return c.h.Size() }
   595  func (c *cthWrapper) BlockSize() int              { return c.h.BlockSize() }
   596  func (c *cthWrapper) Reset()                      { c.h.Reset() }
   597  func (c *cthWrapper) Write(p []byte) (int, error) { return c.h.Write(p) }
   598  func (c *cthWrapper) Sum(b []byte) []byte         { return c.h.ConstantTimeSum(b) }
   599  
   600  func newConstantTimeHash(h func() hash.Hash) func() hash.Hash {
   601  	boring.Unreachable()
   602  	return func() hash.Hash {
   603  		return &cthWrapper{h().(constantTimeHash)}
   604  	}
   605  }
   606  
   607  // tls10MAC implements the TLS 1.0 MAC function. RFC 2246, Section 6.2.3.
   608  func tls10MAC(h hash.Hash, out, seq, header, data, extra []byte) []byte {
   609  	h.Reset()
   610  	h.Write(seq)
   611  	h.Write(header)
   612  	h.Write(data)
   613  	res := h.Sum(out)
   614  	if extra != nil {
   615  		h.Write(extra)
   616  	}
   617  	return res
   618  }
   619  
   620  func rsaKA(version uint16) keyAgreement {
   621  	return rsaKeyAgreement{}
   622  }
   623  
   624  func ecdheECDSAKA(version uint16) keyAgreement {
   625  	return &ecdheKeyAgreement{
   626  		isRSA:   false,
   627  		version: version,
   628  	}
   629  }
   630  
   631  func ecdheRSAKA(version uint16) keyAgreement {
   632  	return &ecdheKeyAgreement{
   633  		isRSA:   true,
   634  		version: version,
   635  	}
   636  }
   637  
   638  // mutualCipherSuite returns a cipherSuite given a list of supported
   639  // ciphersuites and the id requested by the peer.
   640  func mutualCipherSuite(have []uint16, want uint16) *cipherSuite {
   641  	for _, id := range have {
   642  		if id == want {
   643  			return cipherSuiteByID(id)
   644  		}
   645  	}
   646  	return nil
   647  }
   648  
   649  func cipherSuiteByID(id uint16) *cipherSuite {
   650  	for _, cipherSuite := range cipherSuites {
   651  		if cipherSuite.id == id {
   652  			return cipherSuite
   653  		}
   654  	}
   655  	return nil
   656  }
   657  
   658  func mutualCipherSuiteTLS13(have []uint16, want uint16) *cipherSuiteTLS13 {
   659  	for _, id := range have {
   660  		if id == want {
   661  			return cipherSuiteTLS13ByID(id)
   662  		}
   663  	}
   664  	return nil
   665  }
   666  
   667  func cipherSuiteTLS13ByID(id uint16) *cipherSuiteTLS13 {
   668  	for _, cipherSuite := range cipherSuitesTLS13 {
   669  		if cipherSuite.id == id {
   670  			return cipherSuite
   671  		}
   672  	}
   673  	return nil
   674  }
   675  
   676  // A list of cipher suite IDs that are, or have been, implemented by this
   677  // package.
   678  //
   679  // See https://www.iana.org/assignments/tls-parameters/tls-parameters.xml
   680  const (
   681  	// TLS 1.0 - 1.2 cipher suites.
   682  	TLS_RSA_WITH_RC4_128_SHA                      uint16 = 0x0005
   683  	TLS_RSA_WITH_3DES_EDE_CBC_SHA                 uint16 = 0x000a
   684  	TLS_RSA_WITH_AES_128_CBC_SHA                  uint16 = 0x002f
   685  	TLS_RSA_WITH_AES_256_CBC_SHA                  uint16 = 0x0035
   686  	TLS_RSA_WITH_AES_128_CBC_SHA256               uint16 = 0x003c
   687  	TLS_RSA_WITH_AES_128_GCM_SHA256               uint16 = 0x009c
   688  	TLS_RSA_WITH_AES_256_GCM_SHA384               uint16 = 0x009d
   689  	TLS_ECDHE_ECDSA_WITH_RC4_128_SHA              uint16 = 0xc007
   690  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA          uint16 = 0xc009
   691  	TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA          uint16 = 0xc00a
   692  	TLS_ECDHE_RSA_WITH_RC4_128_SHA                uint16 = 0xc011
   693  	TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA           uint16 = 0xc012
   694  	TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA            uint16 = 0xc013
   695  	TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA            uint16 = 0xc014
   696  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256       uint16 = 0xc023
   697  	TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256         uint16 = 0xc027
   698  	TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256         uint16 = 0xc02f
   699  	TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256       uint16 = 0xc02b
   700  	TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384         uint16 = 0xc030
   701  	TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384       uint16 = 0xc02c
   702  	TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256   uint16 = 0xcca8
   703  	TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256 uint16 = 0xcca9
   704  
   705  	// TLS 1.3 cipher suites.
   706  	TLS_AES_128_GCM_SHA256       uint16 = 0x1301
   707  	TLS_AES_256_GCM_SHA384       uint16 = 0x1302
   708  	TLS_CHACHA20_POLY1305_SHA256 uint16 = 0x1303
   709  
   710  	// TLS_FALLBACK_SCSV isn't a standard cipher suite but an indicator
   711  	// that the client is doing version fallback. See RFC 7507.
   712  	TLS_FALLBACK_SCSV uint16 = 0x5600
   713  
   714  	// Legacy names for the corresponding cipher suites with the correct _SHA256
   715  	// suffix, retained for backward compatibility.
   716  	TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305   = TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
   717  	TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305 = TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256
   718  )
   719
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