// Copyright 2010 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/aes"
"crypto/cipher"
"crypto/des"
"crypto/hmac"
"crypto/rc4"
"crypto/sha1"
"crypto/x509"
"hash"
)
// a keyAgreement implements the client and server side of a TLS key agreement
// protocol by generating and processing key exchange messages.
type keyAgreement interface {
// On the server side, the first two methods are called in order.
// In the case that the key agreement protocol doesn't use a
// ServerKeyExchange message, generateServerKeyExchange can return nil,
// nil.
generateServerKeyExchange(*Config, *Certificate, *clientHelloMsg, *serverHelloMsg) (*serverKeyExchangeMsg, error)
processClientKeyExchange(*Config, *Certificate, *clientKeyExchangeMsg, uint16) ([]byte, error)
// On the client side, the next two methods are called in order.
// This method may not be called if the server doesn't send a
// ServerKeyExchange message.
processServerKeyExchange(*Config, *clientHelloMsg, *serverHelloMsg, *x509.Certificate, *serverKeyExchangeMsg) error
generateClientKeyExchange(*Config, *clientHelloMsg, *x509.Certificate) ([]byte, *clientKeyExchangeMsg, error)
}
const (
// suiteECDH indicates that the cipher suite involves elliptic curve
// Diffie-Hellman. This means that it should only be selected when the
// client indicates that it supports ECC with a curve and point format
// that we're happy with.
suiteECDHE = 1 << iota
// suiteECDSA indicates that the cipher suite involves an ECDSA
// signature and therefore may only be selected when the server's
// certificate is ECDSA. If this is not set then the cipher suite is
// RSA based.
suiteECDSA
// suiteTLS12 indicates that the cipher suite should only be advertised
// and accepted when using TLS 1.2.
suiteTLS12
// suiteSHA384 indicates that the cipher suite uses SHA384 as the
// handshake hash.
suiteSHA384
// suiteDefaultOff indicates that this cipher suite is not included by
// default.
suiteDefaultOff
)
// A cipherSuite is a specific combination of key agreement, cipher and MAC
// function. All cipher suites currently assume RSA key agreement.
type cipherSuite struct {
id uint16
// the lengths, in bytes, of the key material needed for each component.
keyLen int
macLen int
ivLen int
ka func(version uint16) keyAgreement
// flags is a bitmask of the suite* values, above.
flags int
cipher func(key, iv []byte, isRead bool) interface{}
mac func(version uint16, macKey []byte) macFunction
aead func(key, fixedNonce []byte) cipher.AEAD
}
var cipherSuites = []*cipherSuite{
// Ciphersuite order is chosen so that ECDHE comes before plain RSA
// and RC4 comes before AES (because of the Lucky13 attack).
{TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12, nil, nil, aeadAESGCM},
{TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, 16, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12, nil, nil, aeadAESGCM},
{TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheRSAKA, suiteECDHE | suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM},
{TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, 32, 0, 4, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12 | suiteSHA384, nil, nil, aeadAESGCM},
{TLS_ECDHE_RSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheRSAKA, suiteECDHE | suiteDefaultOff, cipherRC4, macSHA1, nil},
{TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteDefaultOff, cipherRC4, macSHA1, nil},
{TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil},
{TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA, cipherAES, macSHA1, nil},
{TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheRSAKA, suiteECDHE, cipherAES, macSHA1, nil},
{TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheECDSAKA, suiteECDHE | suiteECDSA, cipherAES, macSHA1, nil},
{TLS_RSA_WITH_RC4_128_SHA, 16, 20, 0, rsaKA, suiteDefaultOff, cipherRC4, macSHA1, nil},
{TLS_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil},
{TLS_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, rsaKA, 0, cipherAES, macSHA1, nil},
{TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, ecdheRSAKA, suiteECDHE, cipher3DES, macSHA1, nil},
{TLS_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, rsaKA, 0, cipher3DES, macSHA1, nil},
}
func cipherRC4(key, iv []byte, isRead bool) interface{} {
cipher, _ := rc4.NewCipher(key)
return cipher
}
func cipher3DES(key, iv []byte, isRead bool) interface{} {
block, _ := des.NewTripleDESCipher(key)
if isRead {
return cipher.NewCBCDecrypter(block, iv)
}
return cipher.NewCBCEncrypter(block, iv)
}
func cipherAES(key, iv []byte, isRead bool) interface{} {
block, _ := aes.NewCipher(key)
if isRead {
return cipher.NewCBCDecrypter(block, iv)
}
return cipher.NewCBCEncrypter(block, iv)
}
// macSHA1 returns a macFunction for the given protocol version.
func macSHA1(version uint16, key []byte) macFunction {
if version == VersionSSL30 {
mac := ssl30MAC{
h: sha1.New(),
key: make([]byte, len(key)),
}
copy(mac.key, key)
return mac
}
return tls10MAC{hmac.New(sha1.New, key)}
}
type macFunction interface {
Size() int
MAC(digestBuf, seq, header, data []byte) []byte
}
// fixedNonceAEAD wraps an AEAD and prefixes a fixed portion of the nonce to
// each call.
type fixedNonceAEAD struct {
// sealNonce and openNonce are buffers where the larger nonce will be
// constructed. Since a seal and open operation may be running
// concurrently, there is a separate buffer for each.
sealNonce, openNonce []byte
aead cipher.AEAD
}
func (f *fixedNonceAEAD) NonceSize() int { return 8 }
func (f *fixedNonceAEAD) Overhead() int { return f.aead.Overhead() }
func (f *fixedNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte {
copy(f.sealNonce[len(f.sealNonce)-8:], nonce)
return f.aead.Seal(out, f.sealNonce, plaintext, additionalData)
}
func (f *fixedNonceAEAD) Open(out, nonce, plaintext, additionalData []byte) ([]byte, error) {
copy(f.openNonce[len(f.openNonce)-8:], nonce)
return f.aead.Open(out, f.openNonce, plaintext, additionalData)
}
func aeadAESGCM(key, fixedNonce []byte) cipher.AEAD {
aes, err := aes.NewCipher(key)
if err != nil {
panic(err)
}
aead, err := cipher.NewGCM(aes)
if err != nil {
panic(err)
}
nonce1, nonce2 := make([]byte, 12), make([]byte, 12)
copy(nonce1, fixedNonce)
copy(nonce2, fixedNonce)
return &fixedNonceAEAD{nonce1, nonce2, aead}
}
// ssl30MAC implements the SSLv3 MAC function, as defined in
// www.mozilla.org/projects/security/pki/nss/ssl/draft302.txt section 5.2.3.1
type ssl30MAC struct {
h hash.Hash
key []byte
}
func (s ssl30MAC) Size() int {
return s.h.Size()
}
var ssl30Pad1 = [48]byte{0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36}
var ssl30Pad2 = [48]byte{0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c}
func (s ssl30MAC) MAC(digestBuf, seq, header, data []byte) []byte {
padLength := 48
if s.h.Size() == 20 {
padLength = 40
}
s.h.Reset()
s.h.Write(s.key)
s.h.Write(ssl30Pad1[:padLength])
s.h.Write(seq)
s.h.Write(header[:1])
s.h.Write(header[3:5])
s.h.Write(data)
digestBuf = s.h.Sum(digestBuf[:0])
s.h.Reset()
s.h.Write(s.key)
s.h.Write(ssl30Pad2[:padLength])
s.h.Write(digestBuf)
return s.h.Sum(digestBuf[:0])
}
// tls10MAC implements the TLS 1.0 MAC function. RFC 2246, section 6.2.3.
type tls10MAC struct {
h hash.Hash
}
func (s tls10MAC) Size() int {
return s.h.Size()
}
func (s tls10MAC) MAC(digestBuf, seq, header, data []byte) []byte {
s.h.Reset()
s.h.Write(seq)
s.h.Write(header)
s.h.Write(data)
return s.h.Sum(digestBuf[:0])
}
func rsaKA(version uint16) keyAgreement {
return rsaKeyAgreement{}
}
func ecdheECDSAKA(version uint16) keyAgreement {
return &ecdheKeyAgreement{
sigType: signatureECDSA,
version: version,
}
}
func ecdheRSAKA(version uint16) keyAgreement {
return &ecdheKeyAgreement{
sigType: signatureRSA,
version: version,
}
}
// mutualCipherSuite returns a cipherSuite given a list of supported
// ciphersuites and the id requested by the peer.
func mutualCipherSuite(have []uint16, want uint16) *cipherSuite {
for _, id := range have {
if id == want {
for _, suite := range cipherSuites {
if suite.id == want {
return suite
}
}
return nil
}
}
return nil
}
// A list of the possible cipher suite ids. Taken from
// http://www.iana.org/assignments/tls-parameters/tls-parameters.xml
const (
TLS_RSA_WITH_RC4_128_SHA uint16 = 0x0005
TLS_RSA_WITH_3DES_EDE_CBC_SHA uint16 = 0x000a
TLS_RSA_WITH_AES_128_CBC_SHA uint16 = 0x002f
TLS_RSA_WITH_AES_256_CBC_SHA uint16 = 0x0035
TLS_ECDHE_ECDSA_WITH_RC4_128_SHA uint16 = 0xc007
TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA uint16 = 0xc009
TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA uint16 = 0xc00a
TLS_ECDHE_RSA_WITH_RC4_128_SHA uint16 = 0xc011
TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA uint16 = 0xc012
TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA uint16 = 0xc013
TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA uint16 = 0xc014
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 uint16 = 0xc02f
TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 uint16 = 0xc02b
TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 uint16 = 0xc030
TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 uint16 = 0xc02c
// TLS_FALLBACK_SCSV isn't a standard cipher suite but an indicator
// that the client is doing version fallback. See
// https://tools.ietf.org/html/draft-ietf-tls-downgrade-scsv-00.
TLS_FALLBACK_SCSV uint16 = 0x5600
)