1 files changed, 283 insertions, 0 deletions
diff --git a/src/crypto/tls/prf.go b/src/crypto/tls/prf.go
new file mode 100644
index 0000000..13bfa00
--- /dev/null
+++ b/src/crypto/tls/prf.go
@@ -0,0 +1,283 @@
+// 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"
+	"crypto/hmac"
+	"crypto/md5"
+	"crypto/sha1"
+	"crypto/sha256"
+	"crypto/sha512"
+	"errors"
+	"fmt"
+	"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)
+		copy(result[j:], b)
+		j += len(b)
+
+		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)
+	}
+}
+
+const (
+	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")
+
+func prfAndHashForVersion(version uint16, suite *cipherSuite) (func(result, secret, label, seed []byte), crypto.Hash) {
+	switch version {
+	case VersionTLS10, VersionTLS11:
+		return prf10, crypto.Hash(0)
+	case VersionTLS12:
+		if suite.flags&suiteSHA384 != 0 {
+			return prf12(sha512.New384), crypto.SHA384
+		}
+		return prf12(sha256.New), crypto.SHA256
+	default:
+		panic("unknown version")
+	}
+}
+
+func prfForVersion(version uint16, suite *cipherSuite) func(result, secret, label, seed []byte) {
+	prf, _ := prfAndHashForVersion(version, suite)
+	return prf
+}
+
+// masterFromPreMasterSecret generates the master secret from the pre-master
+// secret. See RFC 5246, Section 8.1.
+func masterFromPreMasterSecret(version uint16, suite *cipherSuite, preMasterSecret, clientRandom, serverRandom []byte) []byte {
+	seed := make([]byte, 0, len(clientRandom)+len(serverRandom))
+	seed = append(seed, clientRandom...)
+	seed = append(seed, serverRandom...)
+
+	masterSecret := make([]byte, masterSecretLength)
+	prfForVersion(version, suite)(masterSecret, preMasterSecret, masterSecretLabel, seed)
+	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) {
+	seed := make([]byte, 0, len(serverRandom)+len(clientRandom))
+	seed = append(seed, serverRandom...)
+	seed = append(seed, clientRandom...)
+
+	n := 2*macLen + 2*keyLen + 2*ivLen
+	keyMaterial := make([]byte, n)
+	prfForVersion(version, suite)(keyMaterial, masterSecret, keyExpansionLabel, seed)
+	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 buffer []byte
+	if version >= VersionTLS12 {
+		buffer = []byte{}
+	}
+
+	prf, hash := prfAndHashForVersion(version, cipherSuite)
+	if hash != 0 {
+		return finishedHash{hash.New(), hash.New(), nil, nil, buffer, version, prf}
+	}
+
+	return finishedHash{sha1.New(), sha1.New(), md5.New(), md5.New(), buffer, version, prf}
+}
+
+// A finishedHash calculates the hash of a set of handshake messages suitable
+// for including in a Finished message.
+type finishedHash struct {
+	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, a full buffer is sadly required.
+	buffer []byte
+
+	version uint16
+	prf     func(result, secret, label, seed []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)
+}
+
+// clientSum returns the contents of the verify_data member of a client's
+// Finished message.
+func (h finishedHash) clientSum(masterSecret []byte) []byte {
+	out := make([]byte, finishedVerifyLength)
+	h.prf(out, masterSecret, clientFinishedLabel, h.Sum())
+	return out
+}
+
+// serverSum returns the contents of the verify_data member of a server's
+// Finished message.
+func (h finishedHash) serverSum(masterSecret []byte) []byte {
+	out := make([]byte, finishedVerifyLength)
+	h.prf(out, masterSecret, serverFinishedLabel, h.Sum())
+	return out
+}
+
+// hashForClientCertificate returns the handshake messages so far, pre-hashed if
+// necessary, suitable for signing by a TLS client certificate.
+func (h finishedHash) hashForClientCertificate(sigType uint8, hashAlg crypto.Hash, masterSecret []byte) []byte {
+	if (h.version >= VersionTLS12 || sigType == signatureEd25519) && h.buffer == nil {
+		panic("tls: handshake hash for a client certificate requested after discarding the handshake buffer")
+	}
+
+	if sigType == signatureEd25519 {
+		return h.buffer
+	}
+
+	if h.version >= VersionTLS12 {
+		hash := hashAlg.New()
+		hash.Write(h.buffer)
+		return hash.Sum(nil)
+	}
+
+	if sigType == signatureECDSA {
+		return h.server.Sum(nil)
+	}
+
+	return h.Sum()
+}
+
+// discardHandshakeBuffer is called when there is no more need to
+// buffer the entirety of the handshake messages.
+func (h *finishedHash) discardHandshakeBuffer() {
+	h.buffer = nil
+}
+
+// noExportedKeyingMaterial is used as a value of
+// ConnectionState.ekm when renegotiation is enabled and thus
+// we wish to fail all key-material export requests.
+func noExportedKeyingMaterial(label string, context []byte, length int) ([]byte, error) {
+	return nil, errors.New("crypto/tls: ExportKeyingMaterial is unavailable when renegotiation is enabled")
+}
+
+// ekmFromMasterSecret generates exported keying material as defined in RFC 5705.
+func ekmFromMasterSecret(version uint16, suite *cipherSuite, masterSecret, clientRandom, serverRandom []byte) func(string, []byte, int) ([]byte, error) {
+	return func(label string, context []byte, length int) ([]byte, error) {
+		switch label {
+		case "client finished", "server finished", "master secret", "key expansion":
+			// These values are reserved and may not be used.
+			return nil, fmt.Errorf("crypto/tls: reserved ExportKeyingMaterial label: %s", label)
+		}
+
+		seedLen := len(serverRandom) + len(clientRandom)
+		if context != nil {
+			seedLen += 2 + len(context)
+		}
+		seed := make([]byte, 0, seedLen)
+
+		seed = append(seed, clientRandom...)
+		seed = append(seed, serverRandom...)
+
+		if context != nil {
+			if len(context) >= 1<<16 {
+				return nil, fmt.Errorf("crypto/tls: ExportKeyingMaterial context too long")
+			}
+			seed = append(seed, byte(len(context)>>8), byte(len(context)))
+			seed = append(seed, context...)
+		}
+
+		keyMaterial := make([]byte, length)
+		prfForVersion(version, suite)(keyMaterial, masterSecret, []byte(label), seed)
+		return keyMaterial, nil
+	}
+}