369 lines
11 KiB
Go
369 lines
11 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package tls
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import (
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"crypto"
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"crypto/hmac"
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"crypto/md5"
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"crypto/sha1"
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"crypto/sha256"
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"crypto/sha512"
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"errors"
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"hash"
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)
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// Split a premaster secret in two as specified in RFC 4346, section 5.
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func splitPreMasterSecret(secret []byte) (s1, s2 []byte) {
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s1 = secret[0 : (len(secret)+1)/2]
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s2 = secret[len(secret)/2:]
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return
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}
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// pHash implements the P_hash function, as defined in RFC 4346, section 5.
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func pHash(result, secret, seed []byte, hash func() hash.Hash) {
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h := hmac.New(hash, secret)
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h.Write(seed)
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a := h.Sum(nil)
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j := 0
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for j < len(result) {
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h.Reset()
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h.Write(a)
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h.Write(seed)
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b := h.Sum(nil)
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todo := len(b)
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if j+todo > len(result) {
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todo = len(result) - j
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}
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copy(result[j:j+todo], b)
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j += todo
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h.Reset()
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h.Write(a)
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a = h.Sum(nil)
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}
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}
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// prf10 implements the TLS 1.0 pseudo-random function, as defined in RFC 2246, section 5.
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func prf10(result, secret, label, seed []byte) {
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hashSHA1 := sha1.New
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hashMD5 := md5.New
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labelAndSeed := make([]byte, len(label)+len(seed))
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copy(labelAndSeed, label)
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copy(labelAndSeed[len(label):], seed)
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s1, s2 := splitPreMasterSecret(secret)
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pHash(result, s1, labelAndSeed, hashMD5)
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result2 := make([]byte, len(result))
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pHash(result2, s2, labelAndSeed, hashSHA1)
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for i, b := range result2 {
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result[i] ^= b
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}
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}
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// prf12 implements the TLS 1.2 pseudo-random function, as defined in RFC 5246, section 5.
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func prf12(hashFunc func() hash.Hash) func(result, secret, label, seed []byte) {
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return func(result, secret, label, seed []byte) {
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labelAndSeed := make([]byte, len(label)+len(seed))
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copy(labelAndSeed, label)
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copy(labelAndSeed[len(label):], seed)
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pHash(result, secret, labelAndSeed, hashFunc)
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}
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}
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// prf30 implements the SSL 3.0 pseudo-random function, as defined in
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// www.mozilla.org/projects/security/pki/nss/ssl/draft302.txt section 6.
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func prf30(result, secret, label, seed []byte) {
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hashSHA1 := sha1.New()
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hashMD5 := md5.New()
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done := 0
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i := 0
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// RFC 5246 section 6.3 says that the largest PRF output needed is 128
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// bytes. Since no more ciphersuites will be added to SSLv3, this will
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// remain true. Each iteration gives us 16 bytes so 10 iterations will
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// be sufficient.
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var b [11]byte
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for done < len(result) {
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for j := 0; j <= i; j++ {
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b[j] = 'A' + byte(i)
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}
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hashSHA1.Reset()
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hashSHA1.Write(b[:i+1])
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hashSHA1.Write(secret)
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hashSHA1.Write(seed)
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digest := hashSHA1.Sum(nil)
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hashMD5.Reset()
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hashMD5.Write(secret)
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hashMD5.Write(digest)
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done += copy(result[done:], hashMD5.Sum(nil))
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i++
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}
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}
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const (
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tlsRandomLength = 32 // Length of a random nonce in TLS 1.1.
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masterSecretLength = 48 // Length of a master secret in TLS 1.1.
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finishedVerifyLength = 12 // Length of verify_data in a Finished message.
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)
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var masterSecretLabel = []byte("master secret")
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var keyExpansionLabel = []byte("key expansion")
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var clientFinishedLabel = []byte("client finished")
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var serverFinishedLabel = []byte("server finished")
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func prfAndHashForVersion(version uint16, suite *cipherSuite) (func(result, secret, label, seed []byte), crypto.Hash) {
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switch version {
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case VersionSSL30:
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return prf30, crypto.Hash(0)
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case VersionTLS10, VersionTLS11:
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return prf10, crypto.Hash(0)
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case VersionTLS12:
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if suite.flags&suiteSHA384 != 0 {
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return prf12(sha512.New384), crypto.SHA384
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}
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return prf12(sha256.New), crypto.SHA256
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default:
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panic("unknown version")
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}
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}
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func prfForVersion(version uint16, suite *cipherSuite) func(result, secret, label, seed []byte) {
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prf, _ := prfAndHashForVersion(version, suite)
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return prf
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}
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// masterFromPreMasterSecret generates the master secret from the pre-master
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// secret. See http://tools.ietf.org/html/rfc5246#section-8.1
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func masterFromPreMasterSecret(version uint16, suite *cipherSuite, preMasterSecret, clientRandom, serverRandom []byte) []byte {
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seed := make([]byte, 0, len(clientRandom)+len(serverRandom))
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seed = append(seed, clientRandom...)
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seed = append(seed, serverRandom...)
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masterSecret := make([]byte, masterSecretLength)
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prfForVersion(version, suite)(masterSecret, preMasterSecret, masterSecretLabel, seed)
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return masterSecret
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}
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// keysFromMasterSecret generates the connection keys from the master
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// secret, given the lengths of the MAC key, cipher key and IV, as defined in
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// RFC 2246, section 6.3.
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func keysFromMasterSecret(version uint16, suite *cipherSuite, masterSecret, clientRandom, serverRandom []byte, macLen, keyLen, ivLen int) (clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV []byte) {
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seed := make([]byte, 0, len(serverRandom)+len(clientRandom))
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seed = append(seed, serverRandom...)
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seed = append(seed, clientRandom...)
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n := 2*macLen + 2*keyLen + 2*ivLen
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keyMaterial := make([]byte, n)
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prfForVersion(version, suite)(keyMaterial, masterSecret, keyExpansionLabel, seed)
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clientMAC = keyMaterial[:macLen]
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keyMaterial = keyMaterial[macLen:]
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serverMAC = keyMaterial[:macLen]
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keyMaterial = keyMaterial[macLen:]
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clientKey = keyMaterial[:keyLen]
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keyMaterial = keyMaterial[keyLen:]
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serverKey = keyMaterial[:keyLen]
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keyMaterial = keyMaterial[keyLen:]
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clientIV = keyMaterial[:ivLen]
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keyMaterial = keyMaterial[ivLen:]
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serverIV = keyMaterial[:ivLen]
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return
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}
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// lookupTLSHash looks up the corresponding crypto.Hash for a given
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// TLS hash identifier.
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func lookupTLSHash(hash uint8) (crypto.Hash, error) {
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switch hash {
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case hashSHA1:
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return crypto.SHA1, nil
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case hashSHA256:
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return crypto.SHA256, nil
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case hashSHA384:
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return crypto.SHA384, nil
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default:
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return 0, errors.New("tls: unsupported hash algorithm")
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}
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}
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func newFinishedHash(version uint16, cipherSuite *cipherSuite) finishedHash {
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var buffer []byte
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if version == VersionSSL30 || version >= VersionTLS12 {
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buffer = []byte{}
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}
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prf, hash := prfAndHashForVersion(version, cipherSuite)
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if hash != 0 {
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return finishedHash{hash.New(), hash.New(), nil, nil, buffer, version, prf}
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}
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return finishedHash{sha1.New(), sha1.New(), md5.New(), md5.New(), buffer, version, prf}
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}
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// A finishedHash calculates the hash of a set of handshake messages suitable
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// for including in a Finished message.
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type finishedHash struct {
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client hash.Hash
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server hash.Hash
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// Prior to TLS 1.2, an additional MD5 hash is required.
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clientMD5 hash.Hash
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serverMD5 hash.Hash
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// In TLS 1.2, a full buffer is sadly required.
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buffer []byte
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version uint16
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prf func(result, secret, label, seed []byte)
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}
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func (h *finishedHash) Write(msg []byte) (n int, err error) {
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h.client.Write(msg)
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h.server.Write(msg)
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if h.version < VersionTLS12 {
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h.clientMD5.Write(msg)
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h.serverMD5.Write(msg)
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}
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if h.buffer != nil {
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h.buffer = append(h.buffer, msg...)
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}
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return len(msg), nil
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}
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func (h finishedHash) Sum() []byte {
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if h.version >= VersionTLS12 {
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return h.client.Sum(nil)
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}
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out := make([]byte, 0, md5.Size+sha1.Size)
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out = h.clientMD5.Sum(out)
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return h.client.Sum(out)
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}
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// finishedSum30 calculates the contents of the verify_data member of a SSLv3
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// Finished message given the MD5 and SHA1 hashes of a set of handshake
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// messages.
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func finishedSum30(md5, sha1 hash.Hash, masterSecret []byte, magic []byte) []byte {
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md5.Write(magic)
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md5.Write(masterSecret)
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md5.Write(ssl30Pad1[:])
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md5Digest := md5.Sum(nil)
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md5.Reset()
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md5.Write(masterSecret)
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md5.Write(ssl30Pad2[:])
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md5.Write(md5Digest)
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md5Digest = md5.Sum(nil)
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sha1.Write(magic)
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sha1.Write(masterSecret)
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sha1.Write(ssl30Pad1[:40])
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sha1Digest := sha1.Sum(nil)
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sha1.Reset()
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sha1.Write(masterSecret)
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sha1.Write(ssl30Pad2[:40])
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sha1.Write(sha1Digest)
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sha1Digest = sha1.Sum(nil)
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ret := make([]byte, len(md5Digest)+len(sha1Digest))
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copy(ret, md5Digest)
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copy(ret[len(md5Digest):], sha1Digest)
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return ret
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}
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var ssl3ClientFinishedMagic = [4]byte{0x43, 0x4c, 0x4e, 0x54}
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var ssl3ServerFinishedMagic = [4]byte{0x53, 0x52, 0x56, 0x52}
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// clientSum returns the contents of the verify_data member of a client's
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// Finished message.
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func (h finishedHash) clientSum(masterSecret []byte) []byte {
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if h.version == VersionSSL30 {
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return finishedSum30(h.clientMD5, h.client, masterSecret, ssl3ClientFinishedMagic[:])
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}
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out := make([]byte, finishedVerifyLength)
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h.prf(out, masterSecret, clientFinishedLabel, h.Sum())
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return out
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}
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// serverSum returns the contents of the verify_data member of a server's
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// Finished message.
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func (h finishedHash) serverSum(masterSecret []byte) []byte {
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if h.version == VersionSSL30 {
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return finishedSum30(h.serverMD5, h.server, masterSecret, ssl3ServerFinishedMagic[:])
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}
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out := make([]byte, finishedVerifyLength)
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h.prf(out, masterSecret, serverFinishedLabel, h.Sum())
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return out
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}
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// selectClientCertSignatureAlgorithm returns a signatureAndHash to sign a
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// client's CertificateVerify with, or an error if none can be found.
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func (h finishedHash) selectClientCertSignatureAlgorithm(serverList []signatureAndHash, sigType uint8) (signatureAndHash, error) {
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if h.version < VersionTLS12 {
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// Nothing to negotiate before TLS 1.2.
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return signatureAndHash{signature: sigType}, nil
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}
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for _, v := range serverList {
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if v.signature == sigType && isSupportedSignatureAndHash(v, supportedSignatureAlgorithms) {
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return v, nil
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}
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}
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return signatureAndHash{}, errors.New("tls: no supported signature algorithm found for signing client certificate")
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}
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// hashForClientCertificate returns a digest, hash function, and TLS 1.2 hash
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// id suitable for signing by a TLS client certificate.
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func (h finishedHash) hashForClientCertificate(signatureAndHash signatureAndHash, masterSecret []byte) ([]byte, crypto.Hash, error) {
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if (h.version == VersionSSL30 || h.version >= VersionTLS12) && h.buffer == nil {
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panic("a handshake hash for a client-certificate was requested after discarding the handshake buffer")
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}
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if h.version == VersionSSL30 {
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if signatureAndHash.signature != signatureRSA {
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return nil, 0, errors.New("tls: unsupported signature type for client certificate")
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}
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md5Hash := md5.New()
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md5Hash.Write(h.buffer)
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sha1Hash := sha1.New()
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sha1Hash.Write(h.buffer)
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return finishedSum30(md5Hash, sha1Hash, masterSecret, nil), crypto.MD5SHA1, nil
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}
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if h.version >= VersionTLS12 {
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hashAlg, err := lookupTLSHash(signatureAndHash.hash)
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if err != nil {
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return nil, 0, err
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}
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hash := hashAlg.New()
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hash.Write(h.buffer)
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return hash.Sum(nil), hashAlg, nil
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}
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if signatureAndHash.signature == signatureECDSA {
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return h.server.Sum(nil), crypto.SHA1, nil
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}
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return h.Sum(), crypto.MD5SHA1, nil
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}
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// discardHandshakeBuffer is called when there is no more need to
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// buffer the entirety of the handshake messages.
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func (h *finishedHash) discardHandshakeBuffer() {
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h.buffer = nil
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}
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