libgo/go/crypto/tls/prf.go

   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         "fmt"
  16         "hash"
  17 )
  18
  19 // Split a premaster secret in two as specified in RFC 4346, section 5.
  20 func splitPreMasterSecret(secret []byte) (s1, s2 []byte) {
  21         s1 = secret[0 : (len(secret)+1)/2]
  22         s2 = secret[len(secret)/2:]
  23         return
  24 }
  25
  26 // pHash implements the P_hash function, as defined in RFC 4346, section 5.
  27 func pHash(result, secret, seed []byte, hash func() hash.Hash) {
  28         h := hmac.New(hash, secret)
  29         h.Write(seed)
  30         a := h.Sum(nil)
  31
  32         j := 0
  33         for j < len(result) {
  34                 h.Reset()
  35                 h.Write(a)
  36                 h.Write(seed)
  37                 b := h.Sum(nil)
  38                 copy(result[j:], b)
  39                 j += len(b)
  40
  41                 h.Reset()
  42                 h.Write(a)
  43                 a = h.Sum(nil)
  44         }
  45 }
  46
  47 // prf10 implements the TLS 1.0 pseudo-random function, as defined in RFC 2246, section 5.
  48 func prf10(result, secret, label, seed []byte) {
  49         hashSHA1 := sha1.New
  50         hashMD5 := md5.New
  51
  52         labelAndSeed := make([]byte, len(label)+len(seed))
  53         copy(labelAndSeed, label)
  54         copy(labelAndSeed[len(label):], seed)
  55
  56         s1, s2 := splitPreMasterSecret(secret)
  57         pHash(result, s1, labelAndSeed, hashMD5)
  58         result2 := make([]byte, len(result))
  59         pHash(result2, s2, labelAndSeed, hashSHA1)
  60
  61         for i, b := range result2 {
  62                 result[i] ^= b
  63         }
  64 }
  65
  66 // prf12 implements the TLS 1.2 pseudo-random function, as defined in RFC 5246, section 5.
  67 func prf12(hashFunc func() hash.Hash) func(result, secret, label, seed []byte) {
  68         return func(result, secret, label, seed []byte) {
  69                 labelAndSeed := make([]byte, len(label)+len(seed))
  70                 copy(labelAndSeed, label)
  71                 copy(labelAndSeed[len(label):], seed)
  72
  73                 pHash(result, secret, labelAndSeed, hashFunc)
  74         }
  75 }
  76
  77 // prf30 implements the SSL 3.0 pseudo-random function, as defined in
  78 // www.mozilla.org/projects/security/pki/nss/ssl/draft302.txt section 6.
  79 func prf30(result, secret, label, seed []byte) {
  80         hashSHA1 := sha1.New()
  81         hashMD5 := md5.New()
  82
  83         done := 0
  84         i := 0
  85         // RFC 5246 section 6.3 says that the largest PRF output needed is 128
  86         // bytes. Since no more ciphersuites will be added to SSLv3, this will
  87         // remain true. Each iteration gives us 16 bytes so 10 iterations will
  88         // be sufficient.
  89         var b [11]byte
  90         for done < len(result) {
  91                 for j := 0; j <= i; j++ {
  92                         b[j] = 'A' + byte(i)
  93                 }
  94
  95                 hashSHA1.Reset()
  96                 hashSHA1.Write(b[:i+1])
  97                 hashSHA1.Write(secret)
  98                 hashSHA1.Write(seed)
  99                 digest := hashSHA1.Sum(nil)
 100
 101                 hashMD5.Reset()
 102                 hashMD5.Write(secret)
 103                 hashMD5.Write(digest)
 104
 105                 done += copy(result[done:], hashMD5.Sum(nil))
 106                 i++
 107         }
 108 }
 109
 110 const (
 111         tlsRandomLength      = 32 // Length of a random nonce in TLS 1.1.
 112         masterSecretLength   = 48 // Length of a master secret in TLS 1.1.
 113         finishedVerifyLength = 12 // Length of verify_data in a Finished message.
 114 )
 115
 116 var masterSecretLabel = []byte("master secret")
 117 var keyExpansionLabel = []byte("key expansion")
 118 var clientFinishedLabel = []byte("client finished")
 119 var serverFinishedLabel = []byte("server finished")
 120
 121 func prfAndHashForVersion(version uint16, suite *cipherSuite) (func(result, secret, label, seed []byte), crypto.Hash) {
 122         switch version {
 123         case VersionSSL30:
 124                 return prf30, crypto.Hash(0)
 125         case VersionTLS10, VersionTLS11:
 126                 return prf10, crypto.Hash(0)
 127         case VersionTLS12:
 128                 if suite.flags&suiteSHA384 != 0 {
 129                         return prf12(sha512.New384), crypto.SHA384
 130                 }
 131                 return prf12(sha256.New), crypto.SHA256
 132         default:
 133                 panic("unknown version")
 134         }
 135 }
 136
 137 func prfForVersion(version uint16, suite *cipherSuite) func(result, secret, label, seed []byte) {
 138         prf, _ := prfAndHashForVersion(version, suite)
 139         return prf
 140 }
 141
 142 // masterFromPreMasterSecret generates the master secret from the pre-master
 143 // secret. See https://tools.ietf.org/html/rfc5246#section-8.1
 144 func masterFromPreMasterSecret(version uint16, suite *cipherSuite, preMasterSecret, clientRandom, serverRandom []byte) []byte {
 145         seed := make([]byte, 0, len(clientRandom)+len(serverRandom))
 146         seed = append(seed, clientRandom...)
 147         seed = append(seed, serverRandom...)
 148
 149         masterSecret := make([]byte, masterSecretLength)
 150         prfForVersion(version, suite)(masterSecret, preMasterSecret, masterSecretLabel, seed)
 151         return masterSecret
 152 }
 153
 154 // keysFromMasterSecret generates the connection keys from the master
 155 // secret, given the lengths of the MAC key, cipher key and IV, as defined in
 156 // RFC 2246, section 6.3.
 157 func keysFromMasterSecret(version uint16, suite *cipherSuite, masterSecret, clientRandom, serverRandom []byte, macLen, keyLen, ivLen int) (clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV []byte) {
 158         seed := make([]byte, 0, len(serverRandom)+len(clientRandom))
 159         seed = append(seed, serverRandom...)
 160         seed = append(seed, clientRandom...)
 161
 162         n := 2*macLen + 2*keyLen + 2*ivLen
 163         keyMaterial := make([]byte, n)
 164         prfForVersion(version, suite)(keyMaterial, masterSecret, keyExpansionLabel, seed)
 165         clientMAC = keyMaterial[:macLen]
 166         keyMaterial = keyMaterial[macLen:]
 167         serverMAC = keyMaterial[:macLen]
 168         keyMaterial = keyMaterial[macLen:]
 169         clientKey = keyMaterial[:keyLen]
 170         keyMaterial = keyMaterial[keyLen:]
 171         serverKey = keyMaterial[:keyLen]
 172         keyMaterial = keyMaterial[keyLen:]
 173         clientIV = keyMaterial[:ivLen]
 174         keyMaterial = keyMaterial[ivLen:]
 175         serverIV = keyMaterial[:ivLen]
 176         return
 177 }
 178
 179 // lookupTLSHash looks up the corresponding crypto.Hash for a given
 180 // hash from a TLS SignatureScheme.
 181 func lookupTLSHash(signatureAlgorithm SignatureScheme) (crypto.Hash, error) {
 182         switch signatureAlgorithm {
 183         case PKCS1WithSHA1, ECDSAWithSHA1:
 184                 return crypto.SHA1, nil
 185         case PKCS1WithSHA256, PSSWithSHA256, ECDSAWithP256AndSHA256:
 186                 return crypto.SHA256, nil
 187         case PKCS1WithSHA384, PSSWithSHA384, ECDSAWithP384AndSHA384:
 188                 return crypto.SHA384, nil
 189         case PKCS1WithSHA512, PSSWithSHA512, ECDSAWithP521AndSHA512:
 190                 return crypto.SHA512, nil
 191         default:
 192                 return 0, fmt.Errorf("tls: unsupported signature algorithm: %#04x", signatureAlgorithm)
 193         }
 194 }
 195
 196 func newFinishedHash(version uint16, cipherSuite *cipherSuite) finishedHash {
 197         var buffer []byte
 198         if version == VersionSSL30 || version >= VersionTLS12 {
 199                 buffer = []byte{}
 200         }
 201
 202         prf, hash := prfAndHashForVersion(version, cipherSuite)
 203         if hash != 0 {
 204                 return finishedHash{hash.New(), hash.New(), nil, nil, buffer, version, prf}
 205         }
 206
 207         return finishedHash{sha1.New(), sha1.New(), md5.New(), md5.New(), buffer, version, prf}
 208 }
 209
 210 // A finishedHash calculates the hash of a set of handshake messages suitable
 211 // for including in a Finished message.
 212 type finishedHash struct {
 213         client hash.Hash
 214         server hash.Hash
 215
 216         // Prior to TLS 1.2, an additional MD5 hash is required.
 217         clientMD5 hash.Hash
 218         serverMD5 hash.Hash
 219
 220         // In TLS 1.2, a full buffer is sadly required.
 221         buffer []byte
 222
 223         version uint16
 224         prf     func(result, secret, label, seed []byte)
 225 }
 226
 227 func (h *finishedHash) Write(msg []byte) (n int, err error) {
 228         h.client.Write(msg)
 229         h.server.Write(msg)
 230
 231         if h.version < VersionTLS12 {
 232                 h.clientMD5.Write(msg)
 233                 h.serverMD5.Write(msg)
 234         }
 235
 236         if h.buffer != nil {
 237                 h.buffer = append(h.buffer, msg...)
 238         }
 239
 240         return len(msg), nil
 241 }
 242
 243 func (h finishedHash) Sum() []byte {
 244         if h.version >= VersionTLS12 {
 245                 return h.client.Sum(nil)
 246         }
 247
 248         out := make([]byte, 0, md5.Size+sha1.Size)
 249         out = h.clientMD5.Sum(out)
 250         return h.client.Sum(out)
 251 }
 252
 253 // finishedSum30 calculates the contents of the verify_data member of a SSLv3
 254 // Finished message given the MD5 and SHA1 hashes of a set of handshake
 255 // messages.
 256 func finishedSum30(md5, sha1 hash.Hash, masterSecret []byte, magic []byte) []byte {
 257         md5.Write(magic)
 258         md5.Write(masterSecret)
 259         md5.Write(ssl30Pad1[:])
 260         md5Digest := md5.Sum(nil)
 261
 262         md5.Reset()
 263         md5.Write(masterSecret)
 264         md5.Write(ssl30Pad2[:])
 265         md5.Write(md5Digest)
 266         md5Digest = md5.Sum(nil)
 267
 268         sha1.Write(magic)
 269         sha1.Write(masterSecret)
 270         sha1.Write(ssl30Pad1[:40])
 271         sha1Digest := sha1.Sum(nil)
 272
 273         sha1.Reset()
 274         sha1.Write(masterSecret)
 275         sha1.Write(ssl30Pad2[:40])
 276         sha1.Write(sha1Digest)
 277         sha1Digest = sha1.Sum(nil)
 278
 279         ret := make([]byte, len(md5Digest)+len(sha1Digest))
 280         copy(ret, md5Digest)
 281         copy(ret[len(md5Digest):], sha1Digest)
 282         return ret
 283 }
 284
 285 var ssl3ClientFinishedMagic = [4]byte{0x43, 0x4c, 0x4e, 0x54}
 286 var ssl3ServerFinishedMagic = [4]byte{0x53, 0x52, 0x56, 0x52}
 287
 288 // clientSum returns the contents of the verify_data member of a client's
 289 // Finished message.
 290 func (h finishedHash) clientSum(masterSecret []byte) []byte {
 291         if h.version == VersionSSL30 {
 292                 return finishedSum30(h.clientMD5, h.client, masterSecret, ssl3ClientFinishedMagic[:])
 293         }
 294
 295         out := make([]byte, finishedVerifyLength)
 296         h.prf(out, masterSecret, clientFinishedLabel, h.Sum())
 297         return out
 298 }
 299
 300 // serverSum returns the contents of the verify_data member of a server's
 301 // Finished message.
 302 func (h finishedHash) serverSum(masterSecret []byte) []byte {
 303         if h.version == VersionSSL30 {
 304                 return finishedSum30(h.serverMD5, h.server, masterSecret, ssl3ServerFinishedMagic[:])
 305         }
 306
 307         out := make([]byte, finishedVerifyLength)
 308         h.prf(out, masterSecret, serverFinishedLabel, h.Sum())
 309         return out
 310 }
 311
 312 // hashForClientCertificate returns a digest over the handshake messages so far,
 313 // suitable for signing by a TLS client certificate.
 314 func (h finishedHash) hashForClientCertificate(sigType uint8, hashAlg crypto.Hash, masterSecret []byte) ([]byte, error) {
 315         if (h.version == VersionSSL30 || h.version >= VersionTLS12) && h.buffer == nil {
 316                 panic("a handshake hash for a client-certificate was requested after discarding the handshake buffer")
 317         }
 318
 319         if h.version == VersionSSL30 {
 320                 if sigType != signaturePKCS1v15 {
 321                         return nil, errors.New("tls: unsupported signature type for client certificate")
 322                 }
 323
 324                 md5Hash := md5.New()
 325                 md5Hash.Write(h.buffer)
 326                 sha1Hash := sha1.New()
 327                 sha1Hash.Write(h.buffer)
 328                 return finishedSum30(md5Hash, sha1Hash, masterSecret, nil), nil
 329         }
 330         if h.version >= VersionTLS12 {
 331                 hash := hashAlg.New()
 332                 hash.Write(h.buffer)
 333                 return hash.Sum(nil), nil
 334         }
 335
 336         if sigType == signatureECDSA {
 337                 return h.server.Sum(nil), nil
 338         }
 339
 340         return h.Sum(), nil
 341 }
 342
 343 // discardHandshakeBuffer is called when there is no more need to
 344 // buffer the entirety of the handshake messages.
 345 func (h *finishedHash) discardHandshakeBuffer() {
 346         h.buffer = nil
 347 }
 348
 349 // noExportedKeyingMaterial is used as a value of
 350 // ConnectionState.ekm when renegotation is enabled and thus
 351 // we wish to fail all key-material export requests.
 352 func noExportedKeyingMaterial(label string, context []byte, length int) ([]byte, error) {
 353         return nil, errors.New("crypto/tls: ExportKeyingMaterial is unavailable when renegotiation is enabled")
 354 }
 355
 356 // ekmFromMasterSecret generates exported keying material as defined in
 357 // https://tools.ietf.org/html/rfc5705.
 358 func ekmFromMasterSecret(version uint16, suite *cipherSuite, masterSecret, clientRandom, serverRandom []byte) func(string, []byte, int) ([]byte, error) {
 359         return func(label string, context []byte, length int) ([]byte, error) {
 360                 switch label {
 361                 case "client finished", "server finished", "master secret", "key expansion":
 362                         // These values are reserved and may not be used.
 363                         return nil, fmt.Errorf("crypto/tls: reserved ExportKeyingMaterial label: %s", label)
 364                 }
 365
 366                 seedLen := len(serverRandom) + len(clientRandom)
 367                 if context != nil {
 368                         seedLen += 2 + len(context)
 369                 }
 370                 seed := make([]byte, 0, seedLen)
 371
 372                 seed = append(seed, clientRandom...)
 373                 seed = append(seed, serverRandom...)
 374
 375                 if context != nil {
 376                         if len(context) >= 1<<16 {
 377                                 return nil, fmt.Errorf("crypto/tls: ExportKeyingMaterial context too long")
 378                         }
 379                         seed = append(seed, byte(len(context)>>8), byte(len(context)))
 380                         seed = append(seed, context...)
 381                 }
 382
 383                 keyMaterial := make([]byte, length)
 384                 prfForVersion(version, suite)(keyMaterial, masterSecret, []byte(label), seed)
 385                 return keyMaterial, nil
 386         }
 387 }