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// 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 runner
import (
"crypto"
"crypto/hmac"
"crypto/md5"
"crypto/sha1"
"crypto/sha256"
"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
}
}
// prf12 implements the TLS 1.2 pseudo-random function, as defined in RFC 5246, section 5.
func prf12(hashFunc func() hash.Hash) func(result, secret, label, seed []byte) {
return func(result, secret, label, seed []byte) {
labelAndSeed := make([]byte, len(label)+len(seed))
copy(labelAndSeed, label)
copy(labelAndSeed[len(label):], seed)
pHash(result, secret, labelAndSeed, hashFunc)
}
}
// 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 extendedMasterSecretLabel = []byte("extended master secret")
var keyExpansionLabel = []byte("key expansion")
var clientFinishedLabel = []byte("client finished")
var serverFinishedLabel = []byte("server finished")
var finishedLabel = []byte("finished")
var channelIDLabel = []byte("TLS Channel ID signature\x00")
var channelIDResumeLabel = []byte("Resumption\x00")
func prfForVersion(version uint16, suite *cipherSuite) func(result, secret, label, seed []byte) {
switch version {
case VersionSSL30:
return prf30
case VersionTLS10, VersionTLS11:
return prf10
case VersionTLS12:
return prf12(suite.hash().New)
}
panic("unknown version")
}
// masterFromPreMasterSecret generates the master secret from the pre-master
// secret. See http://tools.ietf.org/html/rfc5246#section-8.1
func masterFromPreMasterSecret(version uint16, suite *cipherSuite, preMasterSecret, clientRandom, serverRandom []byte) []byte {
var seed [tlsRandomLength * 2]byte
copy(seed[0:len(clientRandom)], clientRandom)
copy(seed[len(clientRandom):], serverRandom)
masterSecret := make([]byte, masterSecretLength)
prfForVersion(version, suite)(masterSecret, preMasterSecret, masterSecretLabel, seed[0:])
return masterSecret
}
// extendedMasterFromPreMasterSecret generates the master secret from the
// pre-master secret when the Triple Handshake fix is in effect. See
// https://tools.ietf.org/html/rfc7627
func extendedMasterFromPreMasterSecret(version uint16, suite *cipherSuite, preMasterSecret []byte, h finishedHash) []byte {
masterSecret := make([]byte, masterSecretLength)
prfForVersion(version, suite)(masterSecret, preMasterSecret, extendedMasterSecretLabel, h.Sum())
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, suite *cipherSuite, masterSecret, clientRandom, serverRandom []byte, macLen, keyLen, ivLen int) (clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV []byte) {
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)
prfForVersion(version, suite)(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, cipherSuite *cipherSuite) finishedHash {
var ret finishedHash
if version >= VersionTLS12 {
ret.hash = cipherSuite.hash()
ret.client = ret.hash.New()
ret.server = ret.hash.New()
if version == VersionTLS12 {
ret.prf = prf12(ret.hash.New)
} else {
ret.secret = make([]byte, ret.hash.Size())
}
} else {
ret.hash = crypto.MD5SHA1
ret.client = sha1.New()
ret.server = sha1.New()
ret.clientMD5 = md5.New()
ret.serverMD5 = md5.New()
ret.prf = prf10
}
ret.buffer = []byte{}
ret.version = version
return ret
}
// A finishedHash calculates the hash of a set of handshake messages suitable
// for including in a Finished message.
type finishedHash struct {
hash crypto.Hash
client hash.Hash
server hash.Hash
// Prior to TLS 1.2, an additional MD5 hash is required.
clientMD5 hash.Hash
serverMD5 hash.Hash
// In TLS 1.2 (and SSL 3 for implementation convenience), a
// full buffer is required.
buffer []byte
version uint16
prf func(result, secret, label, seed []byte)
// secret, in TLS 1.3, is the running input secret.
secret []byte
}
func (h *finishedHash) Write(msg []byte) (n int, err error) {
h.client.Write(msg)
h.server.Write(msg)
if h.version < VersionTLS12 {
h.clientMD5.Write(msg)
h.serverMD5.Write(msg)
}
if h.buffer != nil {
h.buffer = append(h.buffer, msg...)
}
return len(msg), nil
}
func (h finishedHash) Sum() []byte {
if h.version >= VersionTLS12 {
return h.client.Sum(nil)
}
out := make([]byte, 0, md5.Size+sha1.Size)
out = h.clientMD5.Sum(out)
return h.client.Sum(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 []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(baseKey []byte) []byte {
if h.version == VersionSSL30 {
return finishedSum30(h.clientMD5, h.client, baseKey, ssl3ClientFinishedMagic[:])
}
if h.version < VersionTLS13 {
out := make([]byte, finishedVerifyLength)
h.prf(out, baseKey, clientFinishedLabel, h.Sum())
return out
}
clientFinishedKey := hkdfExpandLabel(h.hash, baseKey, finishedLabel, nil, h.hash.Size())
finishedHMAC := hmac.New(h.hash.New, clientFinishedKey)
finishedHMAC.Write(h.appendContextHashes(nil))
return finishedHMAC.Sum(nil)
}
// serverSum returns the contents of the verify_data member of a server's
// Finished message.
func (h finishedHash) serverSum(baseKey []byte) []byte {
if h.version == VersionSSL30 {
return finishedSum30(h.serverMD5, h.server, baseKey, ssl3ServerFinishedMagic[:])
}
if h.version < VersionTLS13 {
out := make([]byte, finishedVerifyLength)
h.prf(out, baseKey, serverFinishedLabel, h.Sum())
return out
}
serverFinishedKey := hkdfExpandLabel(h.hash, baseKey, finishedLabel, nil, h.hash.Size())
finishedHMAC := hmac.New(h.hash.New, serverFinishedKey)
finishedHMAC.Write(h.appendContextHashes(nil))
return finishedHMAC.Sum(nil)
}
// hashForClientCertificateSSL3 returns the hash to be signed for client
// certificates in SSL 3.0.
func (h finishedHash) hashForClientCertificateSSL3(masterSecret []byte) []byte {
md5Hash := md5.New()
md5Hash.Write(h.buffer)
sha1Hash := sha1.New()
sha1Hash.Write(h.buffer)
return finishedSum30(md5Hash, sha1Hash, masterSecret, nil)
}
// hashForChannelID returns the hash to be signed for TLS Channel
// ID. If a resumption, resumeHash has the previous handshake
// hash. Otherwise, it is nil.
func (h finishedHash) hashForChannelID(resumeHash []byte) []byte {
hash := sha256.New()
hash.Write(channelIDLabel)
if resumeHash != nil {
hash.Write(channelIDResumeLabel)
hash.Write(resumeHash)
}
hash.Write(h.Sum())
return hash.Sum(nil)
}
// discardHandshakeBuffer is called when there is no more need to
// buffer the entirety of the handshake messages.
func (h *finishedHash) discardHandshakeBuffer() {
h.buffer = nil
}
// zeroSecretTLS13 returns the default all zeros secret for TLS 1.3, used when a
// given secret is not available in the handshake. See draft-ietf-tls-tls13-16,
// section 7.1.
func (h *finishedHash) zeroSecret() []byte {
return make([]byte, h.hash.Size())
}
// addEntropy incorporates ikm into the running TLS 1.3 secret with HKDF-Expand.
func (h *finishedHash) addEntropy(ikm []byte) {
h.secret = hkdfExtract(h.hash.New, h.secret, ikm)
}
// hkdfExpandLabel implements TLS 1.3's HKDF-Expand-Label function, as defined
// in section 7.1 of draft-ietf-tls-tls13-16.
func hkdfExpandLabel(hash crypto.Hash, secret, label, hashValue []byte, length int) []byte {
if len(label) > 255 || len(hashValue) > 255 {
panic("hkdfExpandLabel: label or hashValue too long")
}
hkdfLabel := make([]byte, 3+9+len(label)+1+len(hashValue))
x := hkdfLabel
x[0] = byte(length >> 8)
x[1] = byte(length)
x[2] = byte(9 + len(label))
x = x[3:]
copy(x, []byte("TLS 1.3, "))
x = x[9:]
copy(x, label)
x = x[len(label):]
x[0] = byte(len(hashValue))
copy(x[1:], hashValue)
return hkdfExpand(hash.New, secret, hkdfLabel, length)
}
// appendContextHashes returns the concatenation of the handshake hash and the
// resumption context hash, as used in TLS 1.3.
func (h *finishedHash) appendContextHashes(b []byte) []byte {
b = h.client.Sum(b)
return b
}
// The following are labels for traffic secret derivation in TLS 1.3.
var (
externalPSKBinderLabel = []byte("external psk binder key")
resumptionPSKBinderLabel = []byte("resumption psk binder key")
earlyTrafficLabel = []byte("client early traffic secret")
clientHandshakeTrafficLabel = []byte("client handshake traffic secret")
serverHandshakeTrafficLabel = []byte("server handshake traffic secret")
clientApplicationTrafficLabel = []byte("client application traffic secret")
serverApplicationTrafficLabel = []byte("server application traffic secret")
applicationTrafficLabel = []byte("application traffic secret")
exporterLabel = []byte("exporter master secret")
resumptionLabel = []byte("resumption master secret")
)
// deriveSecret implements TLS 1.3's Derive-Secret function, as defined in
// section 7.1 of draft ietf-tls-tls13-16.
func (h *finishedHash) deriveSecret(label []byte) []byte {
return hkdfExpandLabel(h.hash, h.secret, label, h.appendContextHashes(nil), h.hash.Size())
}
// The following are context strings for CertificateVerify in TLS 1.3.
var (
clientCertificateVerifyContextTLS13 = []byte("TLS 1.3, client CertificateVerify")
serverCertificateVerifyContextTLS13 = []byte("TLS 1.3, server CertificateVerify")
channelIDContextTLS13 = []byte("TLS 1.3, Channel ID")
)
// certificateVerifyMessage returns the input to be signed for CertificateVerify
// in TLS 1.3.
func (h *finishedHash) certificateVerifyInput(context []byte) []byte {
const paddingLen = 64
b := make([]byte, paddingLen, paddingLen+len(context)+1+2*h.hash.Size())
for i := 0; i < paddingLen; i++ {
b[i] = 32
}
b = append(b, context...)
b = append(b, 0)
b = h.appendContextHashes(b)
return b
}
type trafficDirection int
const (
clientWrite trafficDirection = iota
serverWrite
)
var (
keyTLS13 = []byte("key")
ivTLS13 = []byte("iv")
)
// deriveTrafficAEAD derives traffic keys and constructs an AEAD given a traffic
// secret.
func deriveTrafficAEAD(version uint16, suite *cipherSuite, secret []byte, side trafficDirection) interface{} {
key := hkdfExpandLabel(suite.hash(), secret, keyTLS13, nil, suite.keyLen)
iv := hkdfExpandLabel(suite.hash(), secret, ivTLS13, nil, suite.ivLen(version))
return suite.aead(version, key, iv)
}
func updateTrafficSecret(hash crypto.Hash, secret []byte) []byte {
return hkdfExpandLabel(hash, secret, applicationTrafficLabel, nil, hash.Size())
}
func computePSKBinder(psk, label []byte, cipherSuite *cipherSuite, transcript, truncatedHello []byte) []byte {
finishedHash := newFinishedHash(VersionTLS13, cipherSuite)
finishedHash.addEntropy(psk)
binderKey := finishedHash.deriveSecret(label)
finishedHash.Write(transcript)
finishedHash.Write(truncatedHello)
return finishedHash.clientSum(binderKey)
}