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/aes"
     9  	"crypto/cipher"
    10  	"crypto/des"
    11  	"crypto/hmac"
    12  	"crypto/rc4"
    13  	"crypto/sha1"
    14  	"crypto/sha256"
    15  	"crypto/x509"
    16  	"hash"
    17  
    18  	"golang_org/x/crypto/chacha20poly1305"
    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  	// suiteECDSA indicates that the cipher suite involves an ECDSA
    47  	// signature and therefore may only be selected when the server's
    48  	// certificate is ECDSA. If this is not set then the cipher suite is
    49  	// RSA based.
    50  	suiteECDSA
    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
    63  // function. All cipher suites currently assume RSA key agreement.
    64  type cipherSuite struct {
    65  	id uint16
    66  	// the lengths, in bytes, of the key material needed for each component.
    67  	keyLen int
    68  	macLen int
    69  	ivLen  int
    70  	ka     func(version uint16) keyAgreement
    71  	// flags is a bitmask of the suite* values, above.
    72  	flags  int
    73  	cipher func(key, iv []byte, isRead bool) interface{}
    74  	mac    func(version uint16, macKey []byte) macFunction
    75  	aead   func(key, fixedNonce []byte) cipher.AEAD
    76  }
    77  
    78  var cipherSuites = []*cipherSuite{
    79  	// Ciphersuite order is chosen so that ECDHE comes before plain RSA and
    80  	// AEADs are the top preference.
    81  	{TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305, 32, 0, 12, ecdheRSAKA, suiteECDHE | suiteTLS12, nil, nil, aeadChaCha20Poly1305},
    82  	{TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305, 32, 0, 12, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12, nil, nil, aeadChaCha20Poly1305},
    83  	{TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12, nil, nil, aeadAESGCM},
    84  	{TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12, nil, nil, aeadAESGCM},
    85  	{TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM},
    86  	{TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM},
    87  	{TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, ecdheRSAKA, suiteECDHE | suiteTLS12 | suiteDefaultOff, cipherAES, macSHA256, nil},
    88  	{TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil},
    89  	{TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12 | suiteDefaultOff, cipherAES, macSHA256, nil},
    90  	{TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA, cipherAES, macSHA1, nil},
    91  	{TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil},
    92  	{TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA, cipherAES, macSHA1, nil},
    93  	{TLS_RSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, rsaKA, suiteTLS12, nil, nil, aeadAESGCM},
    94  	{TLS_RSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, rsaKA, suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM},
    95  	{TLS_RSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, rsaKA, suiteTLS12 | suiteDefaultOff, cipherAES, macSHA256, nil},
    96  	{TLS_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil},
    97  	{TLS_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil},
    98  	{TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, ecdheRSAKA, suiteECDHE, cipher3DES, macSHA1, nil},
    99  	{TLS_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, rsaKA, 0, cipher3DES, macSHA1, nil},
   100  
   101  	// RC4-based cipher suites are disabled by default.
   102  	{TLS_RSA_WITH_RC4_128_SHA, 16, 20, 0, rsaKA, suiteDefaultOff, cipherRC4, macSHA1, nil},
   103  	{TLS_ECDHE_RSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheRSAKA, suiteECDHE | suiteDefaultOff, cipherRC4, macSHA1, nil},
   104  	{TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteDefaultOff, cipherRC4, macSHA1, nil},
   105  }
   106  
   107  func cipherRC4(key, iv []byte, isRead bool) interface{} {
   108  	cipher, _ := rc4.NewCipher(key)
   109  	return cipher
   110  }
   111  
   112  func cipher3DES(key, iv []byte, isRead bool) interface{} {
   113  	block, _ := des.NewTripleDESCipher(key)
   114  	if isRead {
   115  		return cipher.NewCBCDecrypter(block, iv)
   116  	}
   117  	return cipher.NewCBCEncrypter(block, iv)
   118  }
   119  
   120  func cipherAES(key, iv []byte, isRead bool) interface{} {
   121  	block, _ := aes.NewCipher(key)
   122  	if isRead {
   123  		return cipher.NewCBCDecrypter(block, iv)
   124  	}
   125  	return cipher.NewCBCEncrypter(block, iv)
   126  }
   127  
   128  // macSHA1 returns a macFunction for the given protocol version.
   129  func macSHA1(version uint16, key []byte) macFunction {
   130  	if version == VersionSSL30 {
   131  		mac := ssl30MAC{
   132  			h:   sha1.New(),
   133  			key: make([]byte, len(key)),
   134  		}
   135  		copy(mac.key, key)
   136  		return mac
   137  	}
   138  	return tls10MAC{hmac.New(newConstantTimeHash(sha1.New), key)}
   139  }
   140  
   141  // macSHA256 returns a SHA-256 based MAC. These are only supported in TLS 1.2
   142  // so the given version is ignored.
   143  func macSHA256(version uint16, key []byte) macFunction {
   144  	return tls10MAC{hmac.New(sha256.New, key)}
   145  }
   146  
   147  type macFunction interface {
   148  	Size() int
   149  	MAC(digestBuf, seq, header, data, extra []byte) []byte
   150  }
   151  
   152  type aead interface {
   153  	cipher.AEAD
   154  
   155  	// explicitIVLen returns the number of bytes used by the explicit nonce
   156  	// that is included in the record. This is eight for older AEADs and
   157  	// zero for modern ones.
   158  	explicitNonceLen() int
   159  }
   160  
   161  // fixedNonceAEAD wraps an AEAD and prefixes a fixed portion of the nonce to
   162  // each call.
   163  type fixedNonceAEAD struct {
   164  	// nonce contains the fixed part of the nonce in the first four bytes.
   165  	nonce [12]byte
   166  	aead  cipher.AEAD
   167  }
   168  
   169  func (f *fixedNonceAEAD) NonceSize() int        { return 8 }
   170  func (f *fixedNonceAEAD) Overhead() int         { return f.aead.Overhead() }
   171  func (f *fixedNonceAEAD) explicitNonceLen() int { return 8 }
   172  
   173  func (f *fixedNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte {
   174  	copy(f.nonce[4:], nonce)
   175  	return f.aead.Seal(out, f.nonce[:], plaintext, additionalData)
   176  }
   177  
   178  func (f *fixedNonceAEAD) Open(out, nonce, plaintext, additionalData []byte) ([]byte, error) {
   179  	copy(f.nonce[4:], nonce)
   180  	return f.aead.Open(out, f.nonce[:], plaintext, additionalData)
   181  }
   182  
   183  // xoredNonceAEAD wraps an AEAD by XORing in a fixed pattern to the nonce
   184  // before each call.
   185  type xorNonceAEAD struct {
   186  	nonceMask [12]byte
   187  	aead      cipher.AEAD
   188  }
   189  
   190  func (f *xorNonceAEAD) NonceSize() int        { return 8 }
   191  func (f *xorNonceAEAD) Overhead() int         { return f.aead.Overhead() }
   192  func (f *xorNonceAEAD) explicitNonceLen() int { return 0 }
   193  
   194  func (f *xorNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte {
   195  	for i, b := range nonce {
   196  		f.nonceMask[4+i] ^= b
   197  	}
   198  	result := f.aead.Seal(out, f.nonceMask[:], plaintext, additionalData)
   199  	for i, b := range nonce {
   200  		f.nonceMask[4+i] ^= b
   201  	}
   202  
   203  	return result
   204  }
   205  
   206  func (f *xorNonceAEAD) Open(out, nonce, plaintext, additionalData []byte) ([]byte, error) {
   207  	for i, b := range nonce {
   208  		f.nonceMask[4+i] ^= b
   209  	}
   210  	result, err := f.aead.Open(out, f.nonceMask[:], plaintext, additionalData)
   211  	for i, b := range nonce {
   212  		f.nonceMask[4+i] ^= b
   213  	}
   214  
   215  	return result, err
   216  }
   217  
   218  func aeadAESGCM(key, fixedNonce []byte) cipher.AEAD {
   219  	aes, err := aes.NewCipher(key)
   220  	if err != nil {
   221  		panic(err)
   222  	}
   223  	aead, err := cipher.NewGCM(aes)
   224  	if err != nil {
   225  		panic(err)
   226  	}
   227  
   228  	ret := &fixedNonceAEAD{aead: aead}
   229  	copy(ret.nonce[:], fixedNonce)
   230  	return ret
   231  }
   232  
   233  func aeadChaCha20Poly1305(key, fixedNonce []byte) cipher.AEAD {
   234  	aead, err := chacha20poly1305.New(key)
   235  	if err != nil {
   236  		panic(err)
   237  	}
   238  
   239  	ret := &xorNonceAEAD{aead: aead}
   240  	copy(ret.nonceMask[:], fixedNonce)
   241  	return ret
   242  }
   243  
   244  // ssl30MAC implements the SSLv3 MAC function, as defined in
   245  // www.mozilla.org/projects/security/pki/nss/ssl/draft302.txt section 5.2.3.1
   246  type ssl30MAC struct {
   247  	h   hash.Hash
   248  	key []byte
   249  }
   250  
   251  func (s ssl30MAC) Size() int {
   252  	return s.h.Size()
   253  }
   254  
   255  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}
   256  
   257  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}
   258  
   259  // MAC does not offer constant timing guarantees for SSL v3.0, since it's deemed
   260  // useless considering the similar, protocol-level POODLE vulnerability.
   261  func (s ssl30MAC) MAC(digestBuf, seq, header, data, extra []byte) []byte {
   262  	padLength := 48
   263  	if s.h.Size() == 20 {
   264  		padLength = 40
   265  	}
   266  
   267  	s.h.Reset()
   268  	s.h.Write(s.key)
   269  	s.h.Write(ssl30Pad1[:padLength])
   270  	s.h.Write(seq)
   271  	s.h.Write(header[:1])
   272  	s.h.Write(header[3:5])
   273  	s.h.Write(data)
   274  	digestBuf = s.h.Sum(digestBuf[:0])
   275  
   276  	s.h.Reset()
   277  	s.h.Write(s.key)
   278  	s.h.Write(ssl30Pad2[:padLength])
   279  	s.h.Write(digestBuf)
   280  	return s.h.Sum(digestBuf[:0])
   281  }
   282  
   283  type constantTimeHash interface {
   284  	hash.Hash
   285  	ConstantTimeSum(b []byte) []byte
   286  }
   287  
   288  // cthWrapper wraps any hash.Hash that implements ConstantTimeSum, and replaces
   289  // with that all calls to Sum. It's used to obtain a ConstantTimeSum-based HMAC.
   290  type cthWrapper struct {
   291  	h constantTimeHash
   292  }
   293  
   294  func (c *cthWrapper) Size() int                   { return c.h.Size() }
   295  func (c *cthWrapper) BlockSize() int              { return c.h.BlockSize() }
   296  func (c *cthWrapper) Reset()                      { c.h.Reset() }
   297  func (c *cthWrapper) Write(p []byte) (int, error) { return c.h.Write(p) }
   298  func (c *cthWrapper) Sum(b []byte) []byte         { return c.h.ConstantTimeSum(b) }
   299  
   300  func newConstantTimeHash(h func() hash.Hash) func() hash.Hash {
   301  	return func() hash.Hash {
   302  		return &cthWrapper{h().(constantTimeHash)}
   303  	}
   304  }
   305  
   306  // tls10MAC implements the TLS 1.0 MAC function. RFC 2246, section 6.2.3.
   307  type tls10MAC struct {
   308  	h hash.Hash
   309  }
   310  
   311  func (s tls10MAC) Size() int {
   312  	return s.h.Size()
   313  }
   314  
   315  // MAC is guaranteed to take constant time, as long as
   316  // len(seq)+len(header)+len(data)+len(extra) is constant. extra is not fed into
   317  // the MAC, but is only provided to make the timing profile constant.
   318  func (s tls10MAC) MAC(digestBuf, seq, header, data, extra []byte) []byte {
   319  	s.h.Reset()
   320  	s.h.Write(seq)
   321  	s.h.Write(header)
   322  	s.h.Write(data)
   323  	res := s.h.Sum(digestBuf[:0])
   324  	if extra != nil {
   325  		s.h.Write(extra)
   326  	}
   327  	return res
   328  }
   329  
   330  func rsaKA(version uint16) keyAgreement {
   331  	return rsaKeyAgreement{}
   332  }
   333  
   334  func ecdheECDSAKA(version uint16) keyAgreement {
   335  	return &ecdheKeyAgreement{
   336  		sigType: signatureECDSA,
   337  		version: version,
   338  	}
   339  }
   340  
   341  func ecdheRSAKA(version uint16) keyAgreement {
   342  	return &ecdheKeyAgreement{
   343  		sigType: signatureRSA,
   344  		version: version,
   345  	}
   346  }
   347  
   348  // mutualCipherSuite returns a cipherSuite given a list of supported
   349  // ciphersuites and the id requested by the peer.
   350  func mutualCipherSuite(have []uint16, want uint16) *cipherSuite {
   351  	for _, id := range have {
   352  		if id == want {
   353  			for _, suite := range cipherSuites {
   354  				if suite.id == want {
   355  					return suite
   356  				}
   357  			}
   358  			return nil
   359  		}
   360  	}
   361  	return nil
   362  }
   363  
   364  // A list of cipher suite IDs that are, or have been, implemented by this
   365  // package.
   366  //
   367  // Taken from http://www.iana.org/assignments/tls-parameters/tls-parameters.xml
   368  const (
   369  	TLS_RSA_WITH_RC4_128_SHA                uint16 = 0x0005
   370  	TLS_RSA_WITH_3DES_EDE_CBC_SHA           uint16 = 0x000a
   371  	TLS_RSA_WITH_AES_128_CBC_SHA            uint16 = 0x002f
   372  	TLS_RSA_WITH_AES_256_CBC_SHA            uint16 = 0x0035
   373  	TLS_RSA_WITH_AES_128_CBC_SHA256         uint16 = 0x003c
   374  	TLS_RSA_WITH_AES_128_GCM_SHA256         uint16 = 0x009c
   375  	TLS_RSA_WITH_AES_256_GCM_SHA384         uint16 = 0x009d
   376  	TLS_ECDHE_ECDSA_WITH_RC4_128_SHA        uint16 = 0xc007
   377  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA    uint16 = 0xc009
   378  	TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA    uint16 = 0xc00a
   379  	TLS_ECDHE_RSA_WITH_RC4_128_SHA          uint16 = 0xc011
   380  	TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA     uint16 = 0xc012
   381  	TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA      uint16 = 0xc013
   382  	TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA      uint16 = 0xc014
   383  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 uint16 = 0xc023
   384  	TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256   uint16 = 0xc027
   385  	TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256   uint16 = 0xc02f
   386  	TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 uint16 = 0xc02b
   387  	TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384   uint16 = 0xc030
   388  	TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 uint16 = 0xc02c
   389  	TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305    uint16 = 0xcca8
   390  	TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305  uint16 = 0xcca9
   391  
   392  	// TLS_FALLBACK_SCSV isn't a standard cipher suite but an indicator
   393  	// that the client is doing version fallback. See
   394  	// https://tools.ietf.org/html/rfc7507.
   395  	TLS_FALLBACK_SCSV uint16 = 0x5600
   396  )
   397
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