- // Copyright 2009 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/hmac"
- "crypto/md5"
- "crypto/sha1"
- "hash"
- )
-
- // Split a premaster secret in two as specified in RFC 4346, section 5.
- func splitPreMasterSecret(secret []byte) (s1, s2 []byte) {
- s1 = secret[0 : (len(secret)+1)/2]
- s2 = secret[len(secret)/2:]
- return
- }
-
- // pHash implements the P_hash function, as defined in RFC 4346, section 5.
- func pHash(result, secret, seed []byte, hash func() hash.Hash) {
- h := hmac.New(hash, secret)
- h.Write(seed)
- a := h.Sum(nil)
-
- j := 0
- for j < len(result) {
- h.Reset()
- h.Write(a)
- h.Write(seed)
- b := h.Sum(nil)
- todo := len(b)
- if j+todo > len(result) {
- todo = len(result) - j
- }
- copy(result[j:j+todo], b)
- j += todo
-
- h.Reset()
- h.Write(a)
- a = h.Sum(nil)
- }
- }
-
- // pRF10 implements the TLS 1.0 pseudo-random function, as defined in RFC 2246, section 5.
- func pRF10(result, secret, label, seed []byte) {
- hashSHA1 := sha1.New
- hashMD5 := md5.New
-
- labelAndSeed := make([]byte, len(label)+len(seed))
- copy(labelAndSeed, label)
- copy(labelAndSeed[len(label):], seed)
-
- s1, s2 := splitPreMasterSecret(secret)
- pHash(result, s1, labelAndSeed, hashMD5)
- result2 := make([]byte, len(result))
- pHash(result2, s2, labelAndSeed, hashSHA1)
-
- for i, b := range result2 {
- result[i] ^= b
- }
- }
-
- // pRF30 implements the SSL 3.0 pseudo-random function, as defined in
- // www.mozilla.org/projects/security/pki/nss/ssl/draft302.txt section 6.
- func pRF30(result, secret, label, seed []byte) {
- hashSHA1 := sha1.New()
- hashMD5 := md5.New()
-
- done := 0
- i := 0
- // RFC5246 section 6.3 says that the largest PRF output needed is 128
- // bytes. Since no more ciphersuites will be added to SSLv3, this will
- // remain true. Each iteration gives us 16 bytes so 10 iterations will
- // be sufficient.
- var b [11]byte
- for done < len(result) {
- for j := 0; j <= i; j++ {
- b[j] = 'A' + byte(i)
- }
-
- hashSHA1.Reset()
- hashSHA1.Write(b[:i+1])
- hashSHA1.Write(secret)
- hashSHA1.Write(seed)
- digest := hashSHA1.Sum(nil)
-
- hashMD5.Reset()
- hashMD5.Write(secret)
- hashMD5.Write(digest)
-
- done += copy(result[done:], hashMD5.Sum(nil))
- i++
- }
- }
-
- const (
- tlsRandomLength = 32 // Length of a random nonce in TLS 1.1.
- masterSecretLength = 48 // Length of a master secret in TLS 1.1.
- finishedVerifyLength = 12 // Length of verify_data in a Finished message.
- )
-
- var masterSecretLabel = []byte("master secret")
- var keyExpansionLabel = []byte("key expansion")
- var clientFinishedLabel = []byte("client finished")
- var serverFinishedLabel = []byte("server finished")
-
- // masterFromPreMasterSecret generates the master secret from the pre-master
- // secret. See http://tools.ietf.org/html/rfc5246#section-8.1
- func masterFromPreMasterSecret(version uint16, preMasterSecret, clientRandom, serverRandom []byte) []byte {
- prf := pRF10
- if version == versionSSL30 {
- prf = pRF30
- }
-
- var seed [tlsRandomLength * 2]byte
- copy(seed[0:len(clientRandom)], clientRandom)
- copy(seed[len(clientRandom):], serverRandom)
- masterSecret := make([]byte, masterSecretLength)
- prf(masterSecret, preMasterSecret, masterSecretLabel, seed[0:])
- return masterSecret
- }
-
- // keysFromMasterSecret generates the connection keys from the master
- // secret, given the lengths of the MAC key, cipher key and IV, as defined in
- // RFC 2246, section 6.3.
- func keysFromMasterSecret(version uint16, masterSecret, clientRandom, serverRandom []byte, macLen, keyLen, ivLen int) (clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV []byte) {
- prf := pRF10
- if version == versionSSL30 {
- prf = pRF30
- }
-
- var seed [tlsRandomLength * 2]byte
- copy(seed[0:len(clientRandom)], serverRandom)
- copy(seed[len(serverRandom):], clientRandom)
-
- n := 2*macLen + 2*keyLen + 2*ivLen
- keyMaterial := make([]byte, n)
- prf(keyMaterial, masterSecret, keyExpansionLabel, seed[0:])
- clientMAC = keyMaterial[:macLen]
- keyMaterial = keyMaterial[macLen:]
- serverMAC = keyMaterial[:macLen]
- keyMaterial = keyMaterial[macLen:]
- clientKey = keyMaterial[:keyLen]
- keyMaterial = keyMaterial[keyLen:]
- serverKey = keyMaterial[:keyLen]
- keyMaterial = keyMaterial[keyLen:]
- clientIV = keyMaterial[:ivLen]
- keyMaterial = keyMaterial[ivLen:]
- serverIV = keyMaterial[:ivLen]
- return
- }
-
- func newFinishedHash(version uint16) finishedHash {
- return finishedHash{md5.New(), sha1.New(), md5.New(), sha1.New(), version}
- }
-
- // A finishedHash calculates the hash of a set of handshake messages suitable
- // for including in a Finished message.
- type finishedHash struct {
- clientMD5 hash.Hash
- clientSHA1 hash.Hash
- serverMD5 hash.Hash
- serverSHA1 hash.Hash
- version uint16
- }
-
- func (h finishedHash) Write(msg []byte) (n int, err error) {
- h.clientMD5.Write(msg)
- h.clientSHA1.Write(msg)
- h.serverMD5.Write(msg)
- h.serverSHA1.Write(msg)
- return len(msg), nil
- }
-
- // finishedSum10 calculates the contents of the verify_data member of a TLSv1
- // Finished message given the MD5 and SHA1 hashes of a set of handshake
- // messages.
- func finishedSum10(md5, sha1, label, masterSecret []byte) []byte {
- seed := make([]byte, len(md5)+len(sha1))
- copy(seed, md5)
- copy(seed[len(md5):], sha1)
- out := make([]byte, finishedVerifyLength)
- pRF10(out, masterSecret, label, seed)
- return out
- }
-
- // finishedSum30 calculates the contents of the verify_data member of a SSLv3
- // Finished message given the MD5 and SHA1 hashes of a set of handshake
- // messages.
- func finishedSum30(md5, sha1 hash.Hash, masterSecret []byte, magic [4]byte) []byte {
- md5.Write(magic[:])
- md5.Write(masterSecret)
- md5.Write(ssl30Pad1[:])
- md5Digest := md5.Sum(nil)
-
- md5.Reset()
- md5.Write(masterSecret)
- md5.Write(ssl30Pad2[:])
- md5.Write(md5Digest)
- md5Digest = md5.Sum(nil)
-
- sha1.Write(magic[:])
- sha1.Write(masterSecret)
- sha1.Write(ssl30Pad1[:40])
- sha1Digest := sha1.Sum(nil)
-
- sha1.Reset()
- sha1.Write(masterSecret)
- sha1.Write(ssl30Pad2[:40])
- sha1.Write(sha1Digest)
- sha1Digest = sha1.Sum(nil)
-
- ret := make([]byte, len(md5Digest)+len(sha1Digest))
- copy(ret, md5Digest)
- copy(ret[len(md5Digest):], sha1Digest)
- return ret
- }
-
- var ssl3ClientFinishedMagic = [4]byte{0x43, 0x4c, 0x4e, 0x54}
- var ssl3ServerFinishedMagic = [4]byte{0x53, 0x52, 0x56, 0x52}
-
- // clientSum returns the contents of the verify_data member of a client's
- // Finished message.
- func (h finishedHash) clientSum(masterSecret []byte) []byte {
- if h.version == versionSSL30 {
- return finishedSum30(h.clientMD5, h.clientSHA1, masterSecret, ssl3ClientFinishedMagic)
- }
-
- md5 := h.clientMD5.Sum(nil)
- sha1 := h.clientSHA1.Sum(nil)
- return finishedSum10(md5, sha1, clientFinishedLabel, masterSecret)
- }
-
- // serverSum returns the contents of the verify_data member of a server's
- // Finished message.
- func (h finishedHash) serverSum(masterSecret []byte) []byte {
- if h.version == versionSSL30 {
- return finishedSum30(h.serverMD5, h.serverSHA1, masterSecret, ssl3ServerFinishedMagic)
- }
-
- md5 := h.serverMD5.Sum(nil)
- sha1 := h.serverSHA1.Sum(nil)
- return finishedSum10(md5, sha1, serverFinishedLabel, masterSecret)
- }
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