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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, *clientHelloMsg, *serverHelloMsg) (*serverKeyExchangeMsg, error)

        processClientKeyExchange(*Config, *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_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},

}

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_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

)