github.com/zmap/zcrypto@v0.0.0-20240512203510-0fef58d9a9db/tls/prf.go (about)

     1  // Copyright 2009 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/hmac"
    10  	"crypto/md5"
    11  	"crypto/sha1"
    12  	"crypto/sha256"
    13  	"crypto/sha512"
    14  	"errors"
    15  	"hash"
    16  )
    17  
    18  // Split a premaster secret in two as specified in RFC 4346, section 5.
    19  func splitPreMasterSecret(secret []byte) (s1, s2 []byte) {
    20  	s1 = secret[0 : (len(secret)+1)/2]
    21  	s2 = secret[len(secret)/2:]
    22  	return
    23  }
    24  
    25  // pHash implements the P_hash function, as defined in RFC 4346, section 5.
    26  func pHash(result, secret, seed []byte, hash func() hash.Hash) {
    27  	h := hmac.New(hash, secret)
    28  	h.Write(seed)
    29  	a := h.Sum(nil)
    30  
    31  	j := 0
    32  	for j < len(result) {
    33  		h.Reset()
    34  		h.Write(a)
    35  		h.Write(seed)
    36  		b := h.Sum(nil)
    37  		todo := len(b)
    38  		if j+todo > len(result) {
    39  			todo = len(result) - j
    40  		}
    41  		copy(result[j:j+todo], b)
    42  		j += todo
    43  
    44  		h.Reset()
    45  		h.Write(a)
    46  		a = h.Sum(nil)
    47  	}
    48  }
    49  
    50  // prf10 implements the TLS 1.0 pseudo-random function, as defined in RFC 2246, section 5.
    51  func prf10(result, secret, label, seed []byte) {
    52  	hashSHA1 := sha1.New
    53  	hashMD5 := md5.New
    54  
    55  	labelAndSeed := make([]byte, len(label)+len(seed))
    56  	copy(labelAndSeed, label)
    57  	copy(labelAndSeed[len(label):], seed)
    58  
    59  	s1, s2 := splitPreMasterSecret(secret)
    60  	pHash(result, s1, labelAndSeed, hashMD5)
    61  	result2 := make([]byte, len(result))
    62  	pHash(result2, s2, labelAndSeed, hashSHA1)
    63  
    64  	for i, b := range result2 {
    65  		result[i] ^= b
    66  	}
    67  }
    68  
    69  // prf12 implements the TLS 1.2 pseudo-random function, as defined in RFC 5246, section 5.
    70  func prf12(hashFunc func() hash.Hash) func(result, secret, label, seed []byte) {
    71  	return func(result, secret, label, seed []byte) {
    72  		labelAndSeed := make([]byte, len(label)+len(seed))
    73  		copy(labelAndSeed, label)
    74  		copy(labelAndSeed[len(label):], seed)
    75  
    76  		pHash(result, secret, labelAndSeed, hashFunc)
    77  	}
    78  }
    79  
    80  // prf30 implements the SSL 3.0 pseudo-random function, as defined in
    81  // www.mozilla.org/projects/security/pki/nss/ssl/draft302.txt section 6.
    82  func prf30(result, secret, label, seed []byte) {
    83  	hashSHA1 := sha1.New()
    84  	hashMD5 := md5.New()
    85  
    86  	done := 0
    87  	i := 0
    88  	// RFC5246 section 6.3 says that the largest PRF output needed is 128
    89  	// bytes. Since no more ciphersuites will be added to SSLv3, this will
    90  	// remain true. Each iteration gives us 16 bytes so 10 iterations will
    91  	// be sufficient.
    92  	var b [11]byte
    93  	for done < len(result) {
    94  		for j := 0; j <= i; j++ {
    95  			b[j] = 'A' + byte(i)
    96  		}
    97  
    98  		hashSHA1.Reset()
    99  		hashSHA1.Write(b[:i+1])
   100  		hashSHA1.Write(secret)
   101  		hashSHA1.Write(seed)
   102  		digest := hashSHA1.Sum(nil)
   103  
   104  		hashMD5.Reset()
   105  		hashMD5.Write(secret)
   106  		hashMD5.Write(digest)
   107  
   108  		done += copy(result[done:], hashMD5.Sum(nil))
   109  		i++
   110  	}
   111  }
   112  
   113  func exportPRF30(result, secret, label, seed []byte) {
   114  	hash := md5.New()
   115  	hash.Write(secret)
   116  	hash.Write(seed)
   117  	copy(result, hash.Sum(nil))
   118  }
   119  
   120  const (
   121  	tlsRandomLength      = 32 // Length of a random nonce in TLS 1.1.
   122  	masterSecretLength   = 48 // Length of a master secret in TLS 1.1.
   123  	finishedVerifyLength = 12 // Length of verify_data in a Finished message.
   124  )
   125  
   126  var masterSecretLabel = []byte("master secret")
   127  var extendedMasterSecretLabel = []byte("extended master secret")
   128  var keyExpansionLabel = []byte("key expansion")
   129  var clientFinishedLabel = []byte("client finished")
   130  var serverFinishedLabel = []byte("server finished")
   131  var clientFinalKeyLabel = []byte("client write key")
   132  var serverFinalKeyLabel = []byte("server write key")
   133  var finalIVLabel = []byte("IV block")
   134  
   135  func prfForVersion(version uint16, suite *cipherSuite) func(result, secret, label, seed []byte) {
   136  	switch version {
   137  	case VersionSSL30:
   138  		return prf30
   139  	case VersionTLS10, VersionTLS11:
   140  		return prf10
   141  	case VersionTLS12:
   142  		if suite.flags&suiteSHA384 != 0 {
   143  			return prf12(sha512.New384)
   144  		}
   145  		return prf12(sha256.New)
   146  	default:
   147  		panic("unknown version")
   148  	}
   149  }
   150  
   151  // masterFromPreMasterSecret generates the master secret from the pre-master
   152  // secret. See http://tools.ietf.org/html/rfc5246#section-8.1
   153  func masterFromPreMasterSecret(version uint16, suite *cipherSuite, preMasterSecret, clientRandom, serverRandom []byte) []byte {
   154  	seed := make([]byte, len(clientRandom)+len(serverRandom))
   155  	copy(seed[0:len(clientRandom)], clientRandom)
   156  	copy(seed[len(clientRandom):], serverRandom)
   157  	masterSecret := make([]byte, masterSecretLength)
   158  	prfForVersion(version, suite)(masterSecret, preMasterSecret, masterSecretLabel, seed[0:])
   159  	return masterSecret
   160  }
   161  
   162  // extendedMasterFromPreMasterSecret generates the master secret from the
   163  // pre-master secret when the Triple Handshake fix is in effect. See
   164  // https://tools.ietf.org/html/draft-ietf-tls-session-hash-01
   165  func extendedMasterFromPreMasterSecret(version uint16, suite *cipherSuite, preMasterSecret []byte, h finishedHash) []byte {
   166  	masterSecret := make([]byte, masterSecretLength)
   167  	prfForVersion(version, suite)(masterSecret, preMasterSecret, extendedMasterSecretLabel, h.Sum())
   168  	return masterSecret
   169  }
   170  
   171  // keysFromMasterSecret generates the connection keys from the master
   172  // secret, given the lengths of the MAC key, cipher key and IV, as defined in
   173  // RFC 2246, section 6.3.
   174  func keysFromMasterSecret(version uint16, suite *cipherSuite, masterSecret, clientRandom, serverRandom []byte, macLen, keyLen, ivLen int) (clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV []byte) {
   175  	if suite.flags&suiteExport > 0 {
   176  		return exportKeysFromMasterSecret(version, suite, masterSecret, clientRandom, serverRandom, macLen, keyLen, ivLen)
   177  	}
   178  	var seed [tlsRandomLength * 2]byte
   179  	copy(seed[0:len(clientRandom)], serverRandom)
   180  	copy(seed[len(serverRandom):], clientRandom)
   181  
   182  	n := 2*macLen + 2*keyLen + 2*ivLen
   183  	keyMaterial := make([]byte, n)
   184  	prfForVersion(version, suite)(keyMaterial, masterSecret, keyExpansionLabel, seed[0:])
   185  	clientMAC = keyMaterial[:macLen]
   186  	keyMaterial = keyMaterial[macLen:]
   187  	serverMAC = keyMaterial[:macLen]
   188  	keyMaterial = keyMaterial[macLen:]
   189  	clientKey = keyMaterial[:keyLen]
   190  	keyMaterial = keyMaterial[keyLen:]
   191  	serverKey = keyMaterial[:keyLen]
   192  	keyMaterial = keyMaterial[keyLen:]
   193  	clientIV = keyMaterial[:ivLen]
   194  	keyMaterial = keyMaterial[ivLen:]
   195  	serverIV = keyMaterial[:ivLen]
   196  	return
   197  }
   198  
   199  // The crypto wars must have been the worst
   200  func exportKeysFromMasterSecret30(version uint16, suite *cipherSuite, masterSecret, clientRandom, serverRandom []byte, macLen, keyLen, ivLen int) (clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV []byte) {
   201  	var seed [tlsRandomLength * 2]byte
   202  	copy(seed[0:len(clientRandom)], serverRandom)
   203  	copy(seed[len(serverRandom):], clientRandom)
   204  	n := 2*macLen + 2*keyLen
   205  	keyMaterial := make([]byte, n)
   206  	prf30(keyMaterial, masterSecret, keyExpansionLabel, seed[0:])
   207  	clientMAC = keyMaterial[:macLen]
   208  	keyMaterial = keyMaterial[macLen:]
   209  	serverMAC = keyMaterial[:macLen]
   210  	keyMaterial = keyMaterial[macLen:]
   211  	clientKey = keyMaterial[:keyLen]
   212  	keyMaterial = keyMaterial[keyLen:]
   213  	serverKey = keyMaterial[:keyLen]
   214  	var exportSeed [tlsRandomLength * 2]byte
   215  	copy(exportSeed[0:len(serverRandom)], clientRandom)
   216  	copy(exportSeed[len(clientRandom):], serverRandom)
   217  	expandedKeyLen := suite.expandedKeyLen
   218  	finalKeyBlock := make([]byte, 2*expandedKeyLen)
   219  	exportPRF30(finalKeyBlock[:expandedKeyLen], clientKey, clientFinalKeyLabel, exportSeed[0:])
   220  	clientKey = finalKeyBlock[:expandedKeyLen]
   221  	finalKeyBlock = finalKeyBlock[expandedKeyLen:]
   222  	exportPRF30(finalKeyBlock[:expandedKeyLen], serverKey, serverFinalKeyLabel, seed[0:])
   223  	serverKey = finalKeyBlock[:expandedKeyLen]
   224  	ivBlock := make([]byte, 2*ivLen)
   225  	clientIV = ivBlock[:ivLen]
   226  	exportPRF30(clientIV, []byte{}, finalIVLabel, exportSeed[0:])
   227  	ivBlock = ivBlock[ivLen:]
   228  	serverIV = ivBlock[:ivLen]
   229  	exportPRF30(serverIV, []byte{}, finalIVLabel, seed[0:])
   230  	return
   231  }
   232  
   233  // If a cryptographer kills me in the night, let it be known I was sorry
   234  func exportKeysFromMasterSecretTLS(version uint16, suite *cipherSuite, masterSecret, clientRandom, serverRandom []byte, macLen, keyLen, ivLen int) (clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV []byte) {
   235  	var seed [tlsRandomLength * 2]byte
   236  	copy(seed[0:len(clientRandom)], serverRandom)
   237  	copy(seed[len(serverRandom):], clientRandom)
   238  	n := 2*macLen + 2*keyLen
   239  	keyMaterial := make([]byte, n)
   240  	prf := prfForVersion(version, suite)
   241  	prf(keyMaterial, masterSecret, keyExpansionLabel, seed[0:])
   242  	clientMAC = keyMaterial[:macLen]
   243  	keyMaterial = keyMaterial[macLen:]
   244  	serverMAC = keyMaterial[:macLen]
   245  	keyMaterial = keyMaterial[macLen:]
   246  	clientKey = keyMaterial[:keyLen]
   247  	keyMaterial = keyMaterial[keyLen:]
   248  	serverKey = keyMaterial[:keyLen]
   249  	expandedKeyLen := suite.expandedKeyLen
   250  	finalKeyBlock := make([]byte, 2*expandedKeyLen)
   251  	var exportSeed [tlsRandomLength * 2]byte
   252  	copy(exportSeed[0:len(serverRandom)], clientRandom)
   253  	copy(exportSeed[len(clientRandom):], serverRandom)
   254  	prf(finalKeyBlock[:expandedKeyLen], clientKey, clientFinalKeyLabel, exportSeed[0:])
   255  	clientKey = finalKeyBlock[:expandedKeyLen]
   256  	finalKeyBlock = finalKeyBlock[expandedKeyLen:]
   257  	prf(finalKeyBlock[:expandedKeyLen], serverKey, serverFinalKeyLabel, exportSeed[0:])
   258  	serverKey = finalKeyBlock[:expandedKeyLen]
   259  	ivBlock := make([]byte, 2*ivLen)
   260  	prf(ivBlock, []byte{}, finalIVLabel, exportSeed[0:])
   261  	clientIV = ivBlock[:ivLen]
   262  	ivBlock = ivBlock[ivLen:]
   263  	serverIV = ivBlock[:ivLen]
   264  	return
   265  }
   266  
   267  func exportKeysFromMasterSecret(version uint16, suite *cipherSuite, masterSecret, clientRandom, serverRandom []byte, macLen, keyLen, ivLen int) (clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV []byte) {
   268  	switch version {
   269  	case VersionSSL30:
   270  		return exportKeysFromMasterSecret30(version, suite, masterSecret, clientRandom, serverRandom, macLen, keyLen, ivLen)
   271  	case VersionTLS10, VersionTLS11, VersionTLS12:
   272  		return exportKeysFromMasterSecretTLS(version, suite, masterSecret, clientRandom, serverRandom, macLen, keyLen, ivLen)
   273  	default:
   274  		panic("unknown version")
   275  	}
   276  }
   277  
   278  // lookupTLSHash looks up the corresponding crypto.Hash for a given
   279  // TLS hash identifier.
   280  func lookupTLSHash(hash uint8) (crypto.Hash, error) {
   281  	switch hash {
   282  	case hashMD5:
   283  		return crypto.MD5, nil
   284  	case hashSHA1:
   285  		return crypto.SHA1, nil
   286  	case hashSHA224:
   287  		return crypto.SHA224, nil
   288  	case hashSHA256:
   289  		return crypto.SHA256, nil
   290  	case hashSHA384:
   291  		return crypto.SHA384, nil
   292  	case hashSHA512:
   293  		return crypto.SHA512, nil
   294  	default:
   295  		return 0, errors.New("tls: unsupported hash algorithm")
   296  	}
   297  }
   298  
   299  func newFinishedHash(version uint16, cipherSuite *cipherSuite) finishedHash {
   300  	if version >= VersionTLS12 {
   301  		newHash := sha256.New
   302  		if cipherSuite != nil && cipherSuite.flags&suiteSHA384 != 0 {
   303  			newHash = sha512.New384
   304  		}
   305  
   306  		return finishedHash{newHash(), newHash(), nil, nil, []byte{}, version, prf12(newHash)}
   307  	}
   308  	return finishedHash{sha1.New(), sha1.New(), md5.New(), md5.New(), []byte{}, version, prf10}
   309  }
   310  
   311  // A finishedHash calculates the hash of a set of handshake messages suitable
   312  // for including in a Finished message.
   313  type finishedHash struct {
   314  	client hash.Hash
   315  	server hash.Hash
   316  
   317  	// Prior to TLS 1.2, an additional MD5 hash is required.
   318  	clientMD5 hash.Hash
   319  	serverMD5 hash.Hash
   320  
   321  	// In TLS 1.2 (and SSL 3 for implementation convenience), a
   322  	// full buffer is required.
   323  	buffer []byte
   324  
   325  	version uint16
   326  	prf     func(result, secret, label, seed []byte)
   327  }
   328  
   329  func (h *finishedHash) Write(msg []byte) (n int, err error) {
   330  	h.client.Write(msg)
   331  	h.server.Write(msg)
   332  
   333  	if h.version < VersionTLS12 {
   334  		h.clientMD5.Write(msg)
   335  		h.serverMD5.Write(msg)
   336  	}
   337  
   338  	if h.buffer != nil {
   339  		h.buffer = append(h.buffer, msg...)
   340  	}
   341  
   342  	return len(msg), nil
   343  }
   344  
   345  func (h finishedHash) Sum() []byte {
   346  	if h.version >= VersionTLS12 {
   347  		return h.client.Sum(nil)
   348  	}
   349  
   350  	out := make([]byte, 0, md5.Size+sha1.Size)
   351  	out = h.clientMD5.Sum(out)
   352  	return h.client.Sum(out)
   353  }
   354  
   355  // finishedSum30 calculates the contents of the verify_data member of a SSLv3
   356  // Finished message given the MD5 and SHA1 hashes of a set of handshake
   357  // messages.
   358  func finishedSum30(md5, sha1 hash.Hash, masterSecret []byte, magic []byte) []byte {
   359  	md5.Write(magic)
   360  	md5.Write(masterSecret)
   361  	md5.Write(ssl30Pad1[:])
   362  	md5Digest := md5.Sum(nil)
   363  
   364  	md5.Reset()
   365  	md5.Write(masterSecret)
   366  	md5.Write(ssl30Pad2[:])
   367  	md5.Write(md5Digest)
   368  	md5Digest = md5.Sum(nil)
   369  
   370  	sha1.Write(magic)
   371  	sha1.Write(masterSecret)
   372  	sha1.Write(ssl30Pad1[:40])
   373  	sha1Digest := sha1.Sum(nil)
   374  
   375  	sha1.Reset()
   376  	sha1.Write(masterSecret)
   377  	sha1.Write(ssl30Pad2[:40])
   378  	sha1.Write(sha1Digest)
   379  	sha1Digest = sha1.Sum(nil)
   380  
   381  	ret := make([]byte, len(md5Digest)+len(sha1Digest))
   382  	copy(ret, md5Digest)
   383  	copy(ret[len(md5Digest):], sha1Digest)
   384  	return ret
   385  }
   386  
   387  var ssl3ClientFinishedMagic = [4]byte{0x43, 0x4c, 0x4e, 0x54}
   388  var ssl3ServerFinishedMagic = [4]byte{0x53, 0x52, 0x56, 0x52}
   389  
   390  // clientSum returns the contents of the verify_data member of a client's
   391  // Finished message.
   392  func (h finishedHash) clientSum(masterSecret []byte) []byte {
   393  	if h.version == VersionSSL30 {
   394  		return finishedSum30(h.clientMD5, h.client, masterSecret, ssl3ClientFinishedMagic[:])
   395  	}
   396  
   397  	out := make([]byte, finishedVerifyLength)
   398  	h.prf(out, masterSecret, clientFinishedLabel, h.Sum())
   399  	return out
   400  }
   401  
   402  // serverSum returns the contents of the verify_data member of a server's
   403  // Finished message.
   404  func (h finishedHash) serverSum(masterSecret []byte) []byte {
   405  	if h.version == VersionSSL30 {
   406  		return finishedSum30(h.serverMD5, h.server, masterSecret, ssl3ServerFinishedMagic[:])
   407  	}
   408  
   409  	out := make([]byte, finishedVerifyLength)
   410  	h.prf(out, masterSecret, serverFinishedLabel, h.Sum())
   411  	return out
   412  }
   413  
   414  // selectClientCertSignatureAlgorithm returns a SigAndHash to sign a
   415  // client's CertificateVerify with, or an error if none can be found.
   416  func (h finishedHash) selectClientCertSignatureAlgorithm(serverList, clientList []SigAndHash, sigType uint8) (SigAndHash, error) {
   417  	if h.version < VersionTLS12 {
   418  		// Nothing to negotiate before TLS 1.2.
   419  		return SigAndHash{Signature: sigType}, nil
   420  	}
   421  
   422  	for _, v := range serverList {
   423  		if v.Signature == sigType && isSupportedSignatureAndHash(v, clientList) {
   424  			return v, nil
   425  		}
   426  	}
   427  	return SigAndHash{}, errors.New("tls: no supported signature algorithm found for signing client certificate")
   428  }
   429  
   430  // hashForClientCertificate returns a digest, hash function, and TLS 1.2 hash
   431  // id suitable for signing by a TLS client certificate.
   432  func (h finishedHash) hashForClientCertificate(signatureAndHash SigAndHash, masterSecret []byte) ([]byte, crypto.Hash, error) {
   433  	if h.version == VersionSSL30 {
   434  		if signatureAndHash.Signature != signatureRSA {
   435  			return nil, 0, errors.New("tls: unsupported signature type for client certificate")
   436  		}
   437  
   438  		md5Hash := md5.New()
   439  		md5Hash.Write(h.buffer)
   440  		sha1Hash := sha1.New()
   441  		sha1Hash.Write(h.buffer)
   442  		return finishedSum30(md5Hash, sha1Hash, masterSecret, nil), crypto.MD5SHA1, nil
   443  	}
   444  	if h.version >= VersionTLS12 {
   445  		hashAlg, err := lookupTLSHash(signatureAndHash.Hash)
   446  		if err != nil {
   447  			return nil, 0, err
   448  		}
   449  		hash := hashAlg.New()
   450  		hash.Write(h.buffer)
   451  		return hash.Sum(nil), hashAlg, nil
   452  	}
   453  	if signatureAndHash.Signature == signatureECDSA {
   454  		return h.server.Sum(nil), crypto.SHA1, nil
   455  	}
   456  
   457  	return h.Sum(), crypto.MD5SHA1, nil
   458  }