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// 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)
}
// 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() keyAgreement
// If elliptic is set, a server will only consider this ciphersuite if
// the ClientHello indicated that the client supports an elliptic curve
// and point format that we can handle.
elliptic bool
cipher func(key, iv []byte, isRead bool) interface{}
mac func(version uint16, macKey []byte) macFunction
}
var cipherSuites = []*cipherSuite{
{TLS_RSA_WITH_RC4_128_SHA, 16, 20, 0, rsaKA, false, cipherRC4, macSHA1},
{TLS_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, rsaKA, false, cipher3DES, macSHA1},
{TLS_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, rsaKA, false, cipherAES, macSHA1},
{TLS_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, rsaKA, false, cipherAES, macSHA1},
{TLS_ECDHE_RSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheRSAKA, true, cipherRC4, macSHA1},
{TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA, 24, 20, 8, ecdheRSAKA, true, cipher3DES, macSHA1},
{TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA, 16, 20, 16, ecdheRSAKA, true, cipherAES, macSHA1},
{TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA, 32, 20, 16, ecdheRSAKA, true, cipherAES, macSHA1},
}
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, data []byte) []byte
}
// 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, record []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(record[:1])
s.h.Write(record[3:5])
s.h.Write(record[recordHeaderLen:])
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, record []byte) []byte {
s.h.Reset()
s.h.Write(seq)
s.h.Write(record)
return s.h.Sum(digestBuf[:0])
}
func rsaKA() keyAgreement {
return rsaKeyAgreement{}
}
func ecdheRSAKA() keyAgreement {
return new(ecdheRSAKeyAgreement)
}
// 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_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
)
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