1 files changed, 291 insertions, 0 deletions
diff --git a/src/crypto/tls/prf.go b/src/crypto/tls/prf.go
new file mode 100644
index 000000000..fb8b3ab4d
--- /dev/null
+++ b/src/crypto/tls/prf.go
@@ -0,0 +1,291 @@
+// 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"
+	"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(result, secret, label, seed []byte) {
+	labelAndSeed := make([]byte, len(label)+len(seed))
+	copy(labelAndSeed, label)
+	copy(labelAndSeed[len(label):], seed)
+
+	pHash(result, secret, labelAndSeed, sha256.New)
+}
+
+// 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")
+
+func prfForVersion(version uint16) func(result, secret, label, seed []byte) {
+	switch version {
+	case VersionSSL30:
+		return prf30
+	case VersionTLS10, VersionTLS11:
+		return prf10
+	case VersionTLS12:
+		return prf12
+	default:
+		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, 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)(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) {
+	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)(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 {
+	if version >= VersionTLS12 {
+		return finishedHash{sha256.New(), sha256.New(), nil, nil, version}
+	}
+	return finishedHash{sha1.New(), sha1.New(), md5.New(), md5.New(), version}
+}
+
+// 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
+
+	version uint16
+}
+
+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)
+	}
+	return len(msg), nil
+}
+
+// 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.client, masterSecret, ssl3ClientFinishedMagic)
+	}
+
+	out := make([]byte, finishedVerifyLength)
+	if h.version >= VersionTLS12 {
+		seed := h.client.Sum(nil)
+		prf12(out, masterSecret, clientFinishedLabel, seed)
+	} else {
+		seed := make([]byte, 0, md5.Size+sha1.Size)
+		seed = h.clientMD5.Sum(seed)
+		seed = h.client.Sum(seed)
+		prf10(out, masterSecret, clientFinishedLabel, seed)
+	}
+	return out
+}
+
+// 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.server, masterSecret, ssl3ServerFinishedMagic)
+	}
+
+	out := make([]byte, finishedVerifyLength)
+	if h.version >= VersionTLS12 {
+		seed := h.server.Sum(nil)
+		prf12(out, masterSecret, serverFinishedLabel, seed)
+	} else {
+		seed := make([]byte, 0, md5.Size+sha1.Size)
+		seed = h.serverMD5.Sum(seed)
+		seed = h.server.Sum(seed)
+		prf10(out, masterSecret, serverFinishedLabel, seed)
+	}
+	return out
+}
+
+// hashForClientCertificate returns a digest, hash function, and TLS 1.2 hash
+// id suitable for signing by a TLS client certificate.
+func (h finishedHash) hashForClientCertificate(sigType uint8) ([]byte, crypto.Hash, uint8) {
+	if h.version >= VersionTLS12 {
+		digest := h.server.Sum(nil)
+		return digest, crypto.SHA256, hashSHA256
+	}
+	if sigType == signatureECDSA {
+		digest := h.server.Sum(nil)
+		return digest, crypto.SHA1, hashSHA1
+	}
+
+	digest := make([]byte, 0, 36)
+	digest = h.serverMD5.Sum(digest)
+	digest = h.server.Sum(digest)
+	return digest, crypto.MD5SHA1, 0 /* not specified in TLS 1.2. */
+}