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Source file src/crypto/tls/cipher_suites.go

  // Copyright 2010 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  package tls
  
  import (
  	"crypto/aes"
  	"crypto/cipher"
  	"crypto/des"
  	"crypto/hmac"
  	"crypto/rc4"
  	"crypto/sha1"
  	"crypto/sha256"
  	"crypto/x509"
  	"hash"
  
  	"golang_org/x/crypto/chacha20poly1305"
  )
  
  // a keyAgreement implements the client and server side of a TLS key agreement
  // protocol by generating and processing key exchange messages.
  type keyAgreement interface {
  	// On the server side, the first two methods are called in order.
  
  	// In the case that the key agreement protocol doesn't use a
  	// ServerKeyExchange message, generateServerKeyExchange can return nil,
  	// nil.
  	generateServerKeyExchange(*Config, *Certificate, *clientHelloMsg, *serverHelloMsg) (*serverKeyExchangeMsg, error)
  	processClientKeyExchange(*Config, *Certificate, *clientKeyExchangeMsg, uint16) ([]byte, error)
  
  	// On the client side, the next two methods are called in order.
  
  	// This method may not be called if the server doesn't send a
  	// ServerKeyExchange message.
  	processServerKeyExchange(*Config, *clientHelloMsg, *serverHelloMsg, *x509.Certificate, *serverKeyExchangeMsg) error
  	generateClientKeyExchange(*Config, *clientHelloMsg, *x509.Certificate) ([]byte, *clientKeyExchangeMsg, error)
  }
  
  const (
  	// suiteECDH indicates that the cipher suite involves elliptic curve
  	// Diffie-Hellman. This means that it should only be selected when the
  	// client indicates that it supports ECC with a curve and point format
  	// that we're happy with.
  	suiteECDHE = 1 << iota
  	// suiteECDSA indicates that the cipher suite involves an ECDSA
  	// signature and therefore may only be selected when the server's
  	// certificate is ECDSA. If this is not set then the cipher suite is
  	// RSA based.
  	suiteECDSA
  	// suiteTLS12 indicates that the cipher suite should only be advertised
  	// and accepted when using TLS 1.2.
  	suiteTLS12
  	// suiteSHA384 indicates that the cipher suite uses SHA384 as the
  	// handshake hash.
  	suiteSHA384
  	// suiteDefaultOff indicates that this cipher suite is not included by
  	// default.
  	suiteDefaultOff
  )
  
  // A cipherSuite is a specific combination of key agreement, cipher and MAC
  // function. All cipher suites currently assume RSA key agreement.
  type cipherSuite struct {
  	id uint16
  	// the lengths, in bytes, of the key material needed for each component.
  	keyLen int
  	macLen int
  	ivLen  int
  	ka     func(version uint16) keyAgreement
  	// flags is a bitmask of the suite* values, above.
  	flags  int
  	cipher func(key, iv []byte, isRead bool) interface{}
  	mac    func(version uint16, macKey []byte) macFunction
  	aead   func(key, fixedNonce []byte) cipher.AEAD
  }
  
  var cipherSuites = []*cipherSuite{
  	// Ciphersuite order is chosen so that ECDHE comes before plain RSA and
  	// AEADs are the top preference.
  	{TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305, 32, 0, 12, ecdheRSAKA, suiteECDHE | suiteTLS12, nil, nil, aeadChaCha20Poly1305},
  	{TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305, 32, 0, 12, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12, nil, nil, aeadChaCha20Poly1305},
  	{TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12, nil, nil, aeadAESGCM},
  	{TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12, nil, nil, aeadAESGCM},
  	{TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM},
  	{TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM},
  	{TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, ecdheRSAKA, suiteECDHE | suiteTLS12 | suiteDefaultOff, cipherAES, macSHA256, nil},
  	{TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil},
  	{TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12 | suiteDefaultOff, cipherAES, macSHA256, nil},
  	{TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA, cipherAES, macSHA1, nil},
  	{TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil},
  	{TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA, cipherAES, macSHA1, nil},
  	{TLS_RSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, rsaKA, suiteTLS12, nil, nil, aeadAESGCM},
  	{TLS_RSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, rsaKA, suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM},
  	{TLS_RSA_WITH_AES_128_CBC_SHA256, 16, 32, 16, rsaKA, suiteTLS12 | suiteDefaultOff, cipherAES, macSHA256, nil},
  	{TLS_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil},
  	{TLS_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil},
  	{TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, ecdheRSAKA, suiteECDHE, cipher3DES, macSHA1, nil},
  	{TLS_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, rsaKA, 0, cipher3DES, macSHA1, nil},
  
  	// RC4-based cipher suites are disabled by default.
  	{TLS_RSA_WITH_RC4_128_SHA, 16, 20, 0, rsaKA, suiteDefaultOff, cipherRC4, macSHA1, nil},
  	{TLS_ECDHE_RSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheRSAKA, suiteECDHE | suiteDefaultOff, cipherRC4, macSHA1, nil},
  	{TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteDefaultOff, cipherRC4, macSHA1, nil},
  }
  
  func cipherRC4(key, iv []byte, isRead bool) interface{} {
  	cipher, _ := rc4.NewCipher(key)
  	return cipher
  }
  
  func cipher3DES(key, iv []byte, isRead bool) interface{} {
  	block, _ := des.NewTripleDESCipher(key)
  	if isRead {
  		return cipher.NewCBCDecrypter(block, iv)
  	}
  	return cipher.NewCBCEncrypter(block, iv)
  }
  
  func cipherAES(key, iv []byte, isRead bool) interface{} {
  	block, _ := aes.NewCipher(key)
  	if isRead {
  		return cipher.NewCBCDecrypter(block, iv)
  	}
  	return cipher.NewCBCEncrypter(block, iv)
  }
  
  // macSHA1 returns a macFunction for the given protocol version.
  func macSHA1(version uint16, key []byte) macFunction {
  	if version == VersionSSL30 {
  		mac := ssl30MAC{
  			h:   sha1.New(),
  			key: make([]byte, len(key)),
  		}
  		copy(mac.key, key)
  		return mac
  	}
  	return tls10MAC{hmac.New(newConstantTimeHash(sha1.New), key)}
  }
  
  // macSHA256 returns a SHA-256 based MAC. These are only supported in TLS 1.2
  // so the given version is ignored.
  func macSHA256(version uint16, key []byte) macFunction {
  	return tls10MAC{hmac.New(sha256.New, key)}
  }
  
  type macFunction interface {
  	Size() int
  	MAC(digestBuf, seq, header, data, extra []byte) []byte
  }
  
  type aead interface {
  	cipher.AEAD
  
  	// explicitIVLen returns the number of bytes used by the explicit nonce
  	// that is included in the record. This is eight for older AEADs and
  	// zero for modern ones.
  	explicitNonceLen() int
  }
  
  // fixedNonceAEAD wraps an AEAD and prefixes a fixed portion of the nonce to
  // each call.
  type fixedNonceAEAD struct {
  	// nonce contains the fixed part of the nonce in the first four bytes.
  	nonce [12]byte
  	aead  cipher.AEAD
  }
  
  func (f *fixedNonceAEAD) NonceSize() int        { return 8 }
  func (f *fixedNonceAEAD) Overhead() int         { return f.aead.Overhead() }
  func (f *fixedNonceAEAD) explicitNonceLen() int { return 8 }
  
  func (f *fixedNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte {
  	copy(f.nonce[4:], nonce)
  	return f.aead.Seal(out, f.nonce[:], plaintext, additionalData)
  }
  
  func (f *fixedNonceAEAD) Open(out, nonce, plaintext, additionalData []byte) ([]byte, error) {
  	copy(f.nonce[4:], nonce)
  	return f.aead.Open(out, f.nonce[:], plaintext, additionalData)
  }
  
  // xoredNonceAEAD wraps an AEAD by XORing in a fixed pattern to the nonce
  // before each call.
  type xorNonceAEAD struct {
  	nonceMask [12]byte
  	aead      cipher.AEAD
  }
  
  func (f *xorNonceAEAD) NonceSize() int        { return 8 }
  func (f *xorNonceAEAD) Overhead() int         { return f.aead.Overhead() }
  func (f *xorNonceAEAD) explicitNonceLen() int { return 0 }
  
  func (f *xorNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte {
  	for i, b := range nonce {
  		f.nonceMask[4+i] ^= b
  	}
  	result := f.aead.Seal(out, f.nonceMask[:], plaintext, additionalData)
  	for i, b := range nonce {
  		f.nonceMask[4+i] ^= b
  	}
  
  	return result
  }
  
  func (f *xorNonceAEAD) Open(out, nonce, plaintext, additionalData []byte) ([]byte, error) {
  	for i, b := range nonce {
  		f.nonceMask[4+i] ^= b
  	}
  	result, err := f.aead.Open(out, f.nonceMask[:], plaintext, additionalData)
  	for i, b := range nonce {
  		f.nonceMask[4+i] ^= b
  	}
  
  	return result, err
  }
  
  func aeadAESGCM(key, fixedNonce []byte) cipher.AEAD {
  	aes, err := aes.NewCipher(key)
  	if err != nil {
  		panic(err)
  	}
  	aead, err := cipher.NewGCM(aes)
  	if err != nil {
  		panic(err)
  	}
  
  	ret := &fixedNonceAEAD{aead: aead}
  	copy(ret.nonce[:], fixedNonce)
  	return ret
  }
  
  func aeadChaCha20Poly1305(key, fixedNonce []byte) cipher.AEAD {
  	aead, err := chacha20poly1305.New(key)
  	if err != nil {
  		panic(err)
  	}
  
  	ret := &xorNonceAEAD{aead: aead}
  	copy(ret.nonceMask[:], fixedNonce)
  	return ret
  }
  
  // ssl30MAC implements the SSLv3 MAC function, as defined in
  // www.mozilla.org/projects/security/pki/nss/ssl/draft302.txt section 5.2.3.1
  type ssl30MAC struct {
  	h   hash.Hash
  	key []byte
  }
  
  func (s ssl30MAC) Size() int {
  	return s.h.Size()
  }
  
  var ssl30Pad1 = [48]byte{0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36}
  
  var ssl30Pad2 = [48]byte{0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c}
  
  // MAC does not offer constant timing guarantees for SSL v3.0, since it's deemed
  // useless considering the similar, protocol-level POODLE vulnerability.
  func (s ssl30MAC) MAC(digestBuf, seq, header, data, extra []byte) []byte {
  	padLength := 48
  	if s.h.Size() == 20 {
  		padLength = 40
  	}
  
  	s.h.Reset()
  	s.h.Write(s.key)
  	s.h.Write(ssl30Pad1[:padLength])
  	s.h.Write(seq)
  	s.h.Write(header[:1])
  	s.h.Write(header[3:5])
  	s.h.Write(data)
  	digestBuf = s.h.Sum(digestBuf[:0])
  
  	s.h.Reset()
  	s.h.Write(s.key)
  	s.h.Write(ssl30Pad2[:padLength])
  	s.h.Write(digestBuf)
  	return s.h.Sum(digestBuf[:0])
  }
  
  type constantTimeHash interface {
  	hash.Hash
  	ConstantTimeSum(b []byte) []byte
  }
  
  // cthWrapper wraps any hash.Hash that implements ConstantTimeSum, and replaces
  // with that all calls to Sum. It's used to obtain a ConstantTimeSum-based HMAC.
  type cthWrapper struct {
  	h constantTimeHash
  }
  
  func (c *cthWrapper) Size() int                   { return c.h.Size() }
  func (c *cthWrapper) BlockSize() int              { return c.h.BlockSize() }
  func (c *cthWrapper) Reset()                      { c.h.Reset() }
  func (c *cthWrapper) Write(p []byte) (int, error) { return c.h.Write(p) }
  func (c *cthWrapper) Sum(b []byte) []byte         { return c.h.ConstantTimeSum(b) }
  
  func newConstantTimeHash(h func() hash.Hash) func() hash.Hash {
  	return func() hash.Hash {
  		return &cthWrapper{h().(constantTimeHash)}
  	}
  }
  
  // tls10MAC implements the TLS 1.0 MAC function. RFC 2246, section 6.2.3.
  type tls10MAC struct {
  	h hash.Hash
  }
  
  func (s tls10MAC) Size() int {
  	return s.h.Size()
  }
  
  // MAC is guaranteed to take constant time, as long as
  // len(seq)+len(header)+len(data)+len(extra) is constant. extra is not fed into
  // the MAC, but is only provided to make the timing profile constant.
  func (s tls10MAC) MAC(digestBuf, seq, header, data, extra []byte) []byte {
  	s.h.Reset()
  	s.h.Write(seq)
  	s.h.Write(header)
  	s.h.Write(data)
  	res := s.h.Sum(digestBuf[:0])
  	if extra != nil {
  		s.h.Write(extra)
  	}
  	return res
  }
  
  func rsaKA(version uint16) keyAgreement {
  	return rsaKeyAgreement{}
  }
  
  func ecdheECDSAKA(version uint16) keyAgreement {
  	return &ecdheKeyAgreement{
  		sigType: signatureECDSA,
  		version: version,
  	}
  }
  
  func ecdheRSAKA(version uint16) keyAgreement {
  	return &ecdheKeyAgreement{
  		sigType: signatureRSA,
  		version: version,
  	}
  }
  
  // mutualCipherSuite returns a cipherSuite given a list of supported
  // ciphersuites and the id requested by the peer.
  func mutualCipherSuite(have []uint16, want uint16) *cipherSuite {
  	for _, id := range have {
  		if id == want {
  			for _, suite := range cipherSuites {
  				if suite.id == want {
  					return suite
  				}
  			}
  			return nil
  		}
  	}
  	return nil
  }
  
  // A list of cipher suite IDs that are, or have been, implemented by this
  // package.
  //
  // Taken from http://www.iana.org/assignments/tls-parameters/tls-parameters.xml
  const (
  	TLS_RSA_WITH_RC4_128_SHA                uint16 = 0x0005
  	TLS_RSA_WITH_3DES_EDE_CBC_SHA           uint16 = 0x000a
  	TLS_RSA_WITH_AES_128_CBC_SHA            uint16 = 0x002f
  	TLS_RSA_WITH_AES_256_CBC_SHA            uint16 = 0x0035
  	TLS_RSA_WITH_AES_128_CBC_SHA256         uint16 = 0x003c
  	TLS_RSA_WITH_AES_128_GCM_SHA256         uint16 = 0x009c
  	TLS_RSA_WITH_AES_256_GCM_SHA384         uint16 = 0x009d
  	TLS_ECDHE_ECDSA_WITH_RC4_128_SHA        uint16 = 0xc007
  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA    uint16 = 0xc009
  	TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA    uint16 = 0xc00a
  	TLS_ECDHE_RSA_WITH_RC4_128_SHA          uint16 = 0xc011
  	TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA     uint16 = 0xc012
  	TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA      uint16 = 0xc013
  	TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA      uint16 = 0xc014
  	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 uint16 = 0xc023
  	TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256   uint16 = 0xc027
  	TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256   uint16 = 0xc02f
  	TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 uint16 = 0xc02b
  	TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384   uint16 = 0xc030
  	TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 uint16 = 0xc02c
  	TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305    uint16 = 0xcca8
  	TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305  uint16 = 0xcca9
  
  	// TLS_FALLBACK_SCSV isn't a standard cipher suite but an indicator
  	// that the client is doing version fallback. See
  	// https://tools.ietf.org/html/rfc7507.
  	TLS_FALLBACK_SCSV uint16 = 0x5600
  )
  

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