| // 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" |
| "os" |
| ) |
| |
| // 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() |
| |
| j := 0 |
| for j < len(result) { |
| h.Reset() |
| h.Write(a) |
| h.Write(seed) |
| b := h.Sum() |
| 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() |
| } |
| } |
| |
| // 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 |
| } |
| } |
| |
| 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") |
| |
| // keysFromPreMasterSecret generates the connection keys from the pre master |
| // secret, given the lengths of the MAC key, cipher key and IV, as defined in |
| // RFC 2246, section 6.3. |
| func keysFromPreMasterSecret10(preMasterSecret, clientRandom, serverRandom []byte, macLen, keyLen, ivLen int) (masterSecret, clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV []byte) { |
| var seed [tlsRandomLength * 2]byte |
| copy(seed[0:len(clientRandom)], clientRandom) |
| copy(seed[len(clientRandom):], serverRandom) |
| masterSecret = make([]byte, masterSecretLength) |
| pRF10(masterSecret, preMasterSecret, masterSecretLabel, seed[0:]) |
| |
| copy(seed[0:len(clientRandom)], serverRandom) |
| copy(seed[len(serverRandom):], clientRandom) |
| |
| n := 2*macLen + 2*keyLen + 2*ivLen |
| keyMaterial := make([]byte, n) |
| pRF10(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 |
| } |
| |
| // 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 |
| } |
| |
| func newFinishedHash() finishedHash { |
| return finishedHash{md5.New(), sha1.New(), md5.New(), sha1.New()} |
| } |
| |
| func (h finishedHash) Write(msg []byte) (n int, err os.Error) { |
| h.clientMD5.Write(msg) |
| h.clientSHA1.Write(msg) |
| h.serverMD5.Write(msg) |
| h.serverSHA1.Write(msg) |
| return len(msg), nil |
| } |
| |
| // finishedSum calculates the contents of the verify_data member of a Finished |
| // message given the MD5 and SHA1 hashes of a set of handshake messages. |
| func finishedSum(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 |
| } |
| |
| // clientSum returns the contents of the verify_data member of a client's |
| // Finished message. |
| func (h finishedHash) clientSum(masterSecret []byte) []byte { |
| md5 := h.clientMD5.Sum() |
| sha1 := h.clientSHA1.Sum() |
| return finishedSum(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 { |
| md5 := h.serverMD5.Sum() |
| sha1 := h.serverSHA1.Sum() |
| return finishedSum(md5, sha1, serverFinishedLabel, masterSecret) |
| } |