cipher_suites.go

// Copyright (c) 2019 The BFE Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// 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 bfe_tls

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/des"
	"crypto/hmac"
	"crypto/rc4"
	"crypto/sha1"
	"crypto/x509"
	"fmt"
	"hash"
)

import (
	"golang.org/x/crypto/chacha20poly1305"

	"github.com/tjfoc/gmsm/sm3"
	"github.com/tjfoc/gmsm/sm4"
)

// 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
	// suiteRC4 indicates that the cipher suite involves RC4 cipher.
	suiteRC4
	// suiteChacha20 indicates that the cipher suite involves chacha20-poly1305
	// cipher.
	suiteChacha20
)

// 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).

	// Note: chacha20 and poly1305 are built into an AEAD algorithm called AEAD_CHACHA20_POLY1305.
	// it requires a 256 bit key and a 96-bit nonce.
	// See RFC 7905: Chacha20-Poly1305 Cipher Suites for TLS
	{TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256, 32, 0, 12, ecdheRSAKA, suiteECDHE | suiteTLS12 | suiteChacha20, nil, nil, aeadChaCha20Poly1305},
	{TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256, 32, 0, 12, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteTLS12 | suiteChacha20, nil, nil, aeadChaCha20Poly1305},

	{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_RC4_128_SHA, 16, 20, 0, ecdheRSAKA, suiteECDHE | suiteRC4, cipherRC4, macSHA1, nil},
	{TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, 16, 20, 0, ecdheECDSAKA, suiteECDHE | suiteECDSA | suiteRC4, 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, suiteRC4, 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},
	{TLS_RSA_WITH_SM4_SM3, 16, 32, 16, rsaKA, 0, cipherSM4, macSM3, nil},
}

// CheckSuiteRSA checks whether cipher suite using RSA key argreement
func CheckSuiteRSA(id uint16) bool {
	switch id {
	case TLS_RSA_WITH_RC4_128_SHA:
		return true
	case TLS_RSA_WITH_AES_128_CBC_SHA:
		return true
	case TLS_RSA_WITH_AES_256_CBC_SHA:
		return true
	case TLS_RSA_WITH_3DES_EDE_CBC_SHA:
		return true
	case TLS_RSA_WITH_SM4_SM3:
		return true
	}
	return false
}

func CheckSuiteECDHE(id uint16) bool {
	switch id {
	case TLS_ECDHE_ECDSA_WITH_RC4_128_SHA:
		return true
	case TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA:
		return true
	case TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA:
		return true
	case TLS_ECDHE_RSA_WITH_RC4_128_SHA:
		return true
	case TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA:
		return true
	case TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA:
		return true
	case TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA:
		return true
	case TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256:
		return true
	case TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256:
		return true
	case TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256:
		return true
	case TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256:
		return true
	}
	return false
}

func CheckSuitePseudo(suite uint16) bool {
	switch suite {
	case TLS_FALLBACK_SCSV:
		return true
	case TLS_EMPTY_RENEGOTIATION_INFO_SCSV:
		return true
	}
	return false
}

// Note: http2 implementation should not use any of the cipher suite in black list.
// See RFC 7540 Appendix A. TLS 1.2 Cipher Suite Black List
func checkCipherSuiteHttp2Accepted(suite uint16) bool {
	switch suite {
	case TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256:
		return true
	case TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256:
		return true
	case TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256:
		return true
	case TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256:
		return true
	default:
		return false
	}
}

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)
}

func cipherSM4(key, iv []byte, isRead bool) interface{} {
	block, _ := sm4.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)}
}

func macSM3(version uint16, key []byte) macFunction {
	return sm3MAC{hmac.New(sm3.New, key)}
}

type macFunction interface {
	Size() int
	MAC(digestBuf, seq, header, data []byte) []byte
}

// aead wraps cipher.AEAD
type aead interface {
	cipher.AEAD

	// explicitIVLen returns the number of bytes used by the explicit nonce
	// that is included in the record. This is eight for older AEADs and
	// zero for modern ones.
	explicitNonceLen() int
}

// 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) explicitNonceLen() int { return 8 }

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)
}

// xoredNonceAEAD wraps an AEAD and XOR in a fixed pattern to the nonce
// before each call.
type xorNonceAEAD 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 *xorNonceAEAD) NonceSize() int        { return 8 }
func (f *xorNonceAEAD) Overhead() int         { return f.aead.Overhead() }
func (f *xorNonceAEAD) explicitNonceLen() int { return 0 }

func (f *xorNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte {
	// Note: The 96-bit nonce for Chacha20-Poly1305 is constructed from the record sequence number
	// and the shared IV. (The record sequence number is the second input parameter *nonce*,
	// and the shared IV is stored in nonceMask)
	//
	// Nonce for Chacha20-Poly1305 is formed as follows:
	// 1. the 64-bit record sequence number is serialized as an 8-byte big-endian value
	// 2. the sequence number is XORed with the last 8-byte of the shared IV
	//
	// See RFC 7905: ChaCha20-Poly1305 for tls
	for i, b := range nonce {
		f.sealNonce[4+i] ^= b
	}
	result := f.aead.Seal(out, f.sealNonce[:], plaintext, additionalData)
	for i, b := range nonce {
		f.sealNonce[4+i] ^= b
	}

	return result
}

func (f *xorNonceAEAD) Open(out, nonce, plaintext, additionalData []byte) ([]byte, error) {
	for i, b := range nonce {
		f.openNonce[4+i] ^= b
	}
	result, err := f.aead.Open(out, f.openNonce[:], plaintext, additionalData)
	for i, b := range nonce {
		f.openNonce[4+i] ^= b
	}

	return result, err
}

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}
}

func aeadChaCha20Poly1305(key, fixedNonce []byte) cipher.AEAD {
	aead, err := chacha20poly1305.New(key)
	if err != nil {
		panic(err)
	}

	nonce1, nonce2 := make([]byte, 12), make([]byte, 12)
	copy(nonce1, fixedNonce)
	copy(nonce2, fixedNonce)

	return &xorNonceAEAD{nonce1, nonce2, aead}
}

type sm3MAC struct {
	h hash.Hash
}

func (s sm3MAC) Size() int {
	return s.h.Size()
}

func (s sm3MAC) MAC(digestBuf, seq, header, data []byte) []byte {
	s.h.Reset()
	s.h.Write(seq)
	s.h.Write(header)
	s.h.Write(data)
	res := s.h.Sum(digestBuf[:0])
	return res
}

// 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_CHACHA20_POLY1305_SHA256   uint16 = 0xcca8
	TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256 uint16 = 0xcca9
	TLS_RSA_WITH_SM4_SM3                          uint16 = 0xe019

	// 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

	// TLS_EMPTY_RENEGOTIATION_INFO_SCSV isn't a true cipher suite, it has
	// the same semantics as an empty "renegotiation info" extension. See
	// https://tools.ietf.org/html/rfc5746#section-3.3
	TLS_EMPTY_RENEGOTIATION_INFO_SCSV = 0x00ff
)

var cipherSuiteTextMap = map[uint16]string{
	TLS_RSA_WITH_RC4_128_SHA:                      "TLS_RSA_WITH_RC4_128_SHA",
	TLS_RSA_WITH_3DES_EDE_CBC_SHA:                 "TLS_RSA_WITH_3DES_EDE_CBC_SHA",
	TLS_RSA_WITH_AES_128_CBC_SHA:                  "TLS_RSA_WITH_AES_128_CBC_SHA",
	TLS_RSA_WITH_AES_256_CBC_SHA:                  "TLS_RSA_WITH_AES_256_CBC_SHA",
	TLS_ECDHE_ECDSA_WITH_RC4_128_SHA:              "TLS_ECDHE_ECDSA_WITH_RC4_128_SHA",
	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA:          "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA",
	TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA:          "TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA",
	TLS_ECDHE_RSA_WITH_RC4_128_SHA:                "TLS_ECDHE_RSA_WITH_RC4_128_SHA",
	TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA:           "TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA",
	TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA:            "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA",
	TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA:            "TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA",
	TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256:         "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256",
	TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256:       "TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256",
	TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256:   "TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256",
	TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256: "TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256",
	TLS_RSA_WITH_SM4_SM3:                          "TLS_RSA_WITH_SM4_SM3",
}

func CipherSuiteText(suite uint16) string {
	if text, ok := cipherSuiteTextMap[suite]; ok {
		return text
	}
	return fmt.Sprintf("TLS_CIPHER_SUITE_%x", suite)
}

// cipher suite names in OpenSSL
// See: https://www.openssl.org/docs/man1.0.2/apps/ciphers.html
var cipherSuiteTextMapForOpenSSL = map[uint16]string{
	TLS_RSA_WITH_RC4_128_SHA:                      "RC4-SHA",
	TLS_RSA_WITH_3DES_EDE_CBC_SHA:                 "DES-CBC3-SHA",
	TLS_RSA_WITH_AES_128_CBC_SHA:                  "AES128-SHA",
	TLS_RSA_WITH_AES_256_CBC_SHA:                  "AES256-SHA",
	TLS_ECDHE_ECDSA_WITH_RC4_128_SHA:              "ECDHE-ECDSA-RC4-SHA",
	TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA:          "ECDHE-ECDSA-AES128-SHA",
	TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA:          "ECDHE-ECDSA-AES256-SHA",
	TLS_ECDHE_RSA_WITH_RC4_128_SHA:                "ECDHE-RSA-RC4-SHA",
	TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA:           "ECDHE-RSA-DES-CBC3-SHA",
	TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA:            "ECDHE-RSA-AES128-SHA",
	TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA:            "ECDHE-RSA-AES256-SHA",
	TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256:         "ECDHE-RSA-AES128-GCM-SHA256",
	TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256:       "ECDHE-ECDSA-AES128-GCM-SHA256",
	TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256:   "ECDHE-RSA-CHACHA20-POLY1305",
	TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256: "ECDHE-ECDSA-CHACHA20-POLY1305",
}

func CipherSuiteTextForOpenSSL(suite uint16) string {
	if text, ok := cipherSuiteTextMapForOpenSSL[suite]; ok {
		return text
	}
	return fmt.Sprintf("TLS_CIPHER_SUITE_%x", suite)
}

type CipherFilter func(id uint16) bool

func FilterCiphers(cipherSuites []uint16, filter CipherFilter) ([]uint16, []uint16) {
	// only cipher suites filter accepted
	acceptedCipherSuites := make([]uint16, 0)

	// cipher suites filter rejected
	rejectedCipherSuites := make([]uint16, 0)

	for _, cipher := range cipherSuites {
		if filter(cipher) {
			acceptedCipherSuites = append(acceptedCipherSuites, cipher)
			continue
		}
		rejectedCipherSuites = append(rejectedCipherSuites, cipher)
	}

	return acceptedCipherSuites, rejectedCipherSuites
}